Micrometeorological measurements and vapour pressure deficit relations under in-field rainwater harvesting

NASA Astrophysics Data System (ADS)

Tesfuhuney, Weldemichael A.; Walker, Sue; Van Rensburg, Leon D.; Steyn, A. Stephan

2016-08-01

In a cropped field, microclimate and thermal stability conditions depend on the canopy structures and the prevailing weather. The main aim of the study therefore was to characterize the vertical profiles of weather variables within and above a maize (Zea mays L.) canopy and to describe the water vapour pressure deficit (VPD) under different atmospheric and soil surface conditions for both wide and narrow runoff strips with the in-field rainwater harvesting (IRWH) system. Micrometeorological measurements of wind, temperature and relative humidity were performed at eight levels, within canopy (1.8 and 2.1 m), and just above the canopy (2.4, 2.7, 3.0, and 3.3 m) up to reference levels (3.9 and 4.5 m) when the maize reached a maximum height of 2.2 m. Under incomplete canopy cover of the IRWH system, two important factors complicated evapotranspiration estimation, namely the local advection and high temperatures of the bare soil between adjacent plant rows. Diurnal variations of water vapour related to turbulence at each locality and its position in the thermal internal boundary layers. Generally, advection was more pronounced in wide runoff strips than narrow strips. On wide runoff strips the wind was more effective in replacing the air between the rows and maintained a higher driving force for evaporation. The maximum VPD over the narrow strips was observed at reference level during a dry day, at about 2.2 kPa in the afternoon, while wet day VPD reached a maximum of 1.8 kPa. The VPD of the wide runoff strips correlated negatively with wind speed, but showed a fairly positive correlation with some scattered values on wet days after rain. Therefore, profile characteristics within and above plant canopies played a key role in determining the VPD and consequently, could help to explain transpiration rates of crops. Hence, VPD relations enhanced the understanding of the heat energy exchange processes under the heterogeneous nature of maize canopy of the IRWH tillage system.

Urban tree species show the same hydraulic response to vapor pressure deficit across varying tree size and environmental conditions.

PubMed

Chen, Lixin; Zhang, Zhiqiang; Ewers, Brent E

2012-01-01

The functional convergence of tree transpiration has rarely been tested for tree species growing under urban conditions even though it is of significance to elucidate the relationship between functional convergence and species differences of urban trees for establishing sustainable urban forests in the context of forest water relations. We measured sap flux of four urban tree species including Cedrus deodara, Zelkova schneideriana, Euonymus bungeanus and Metasequoia glyptostroboides in an urban park by using thermal dissipation probes (TDP). The concurrent microclimate conditions and soil moisture content were also measured. Our objectives were to examine 1) the influence of tree species and size on transpiration, and 2) the hydraulic control of urban trees under different environmental conditions over the transpiration in response to VPD as represented by canopy conductance. The results showed that the functional convergence between tree diameter at breast height (DBH) and tree canopy transpiration amount (E(c)) was not reliable to predict stand transpiration and there were species differences within same DBH class. Species differed in transpiration patterns to seasonal weather progression and soil water stress as a result of varied sensitivity to water availability. Species differences were also found in their potential maximum transpiration rate and reaction to light. However, a same theoretical hydraulic relationship between G(c) at VPD = 1 kPa (G(cref)) and the G(c) sensitivity to VPD (-dG(c)/dlnVPD) across studied species as well as under contrasting soil water and R(s) conditions in the urban area. We concluded that urban trees show the same hydraulic regulation over response to VPD across varying tree size and environmental conditions and thus tree transpiration could be predicted with appropriate assessment of G(cref).

Response of transpiration to rain pulses for two tree species in a semiarid plantation

NASA Astrophysics Data System (ADS)

Chen, Lixin; Zhang, Zhiqiang; Zeppel, Melanie; Liu, Caifeng; Guo, Junting; Zhu, Jinzhao; Zhang, Xuepei; Zhang, Jianjun; Zha, Tonggang

2014-09-01

Responses of transpiration ( E c) to rain pulses are presented for two semiarid tree species in a stand of Pinus tabulaeformis and Robinia pseudoacacia. Our objectives are to investigate (1) the environmental control over the stand transpiration after rainfall by analyzing the effect of vapor pressure deficit (VPD), soil water condition, and rainfall on the post-rainfall E c development and recovery rate, and (2) the species responses to rain pulses and implications on vegetation coverage under a changing rainfall regime. Results showed that the sensitivity of canopy conductance ( G c) to VPD varied under different incident radiation and soil water conditions, and the two species exhibited the same hydraulic control (-d G c/dlnVPD to G cref ratio) over transpiration. Strengthened physiological control and low sapwood area of the stand contributed to low E c. VPD after rainfall significantly influenced the magnitude and time series of post-rainfall stand E c. The fluctuation of post-rainfall VPD in comparison with the pre-rainfall influenced the E c recovery. Further, the stand E c was significantly related to monthly rainfall, but the recovery was independent of the rainfall event size. E c enhanced with cumulative soil moisture change (ΔVWC) within each dry-wet cycle, yet still was limited in large rainfall months. The two species had different response patterns of post-rainfall E c recovery. E c recovery of P. tabulaeformis was influenced by the pre- and post-rainfall VPD differences and the duration of rainless interval. R. pseudoacacia showed a larger immediate post-rainfall E c increase than P. tabulaeformis did. We, therefore, concluded that concentrated rainfall events do not trigger significant increase of transpiration unless large events penetrate the deep soil and the species differences of E c in response to pulses of rain may shape the composition of semiarid woodlands under future rainfall regimes.

Hysteresis responses of evapotranspiration to meteorological factors at a diel timescale: patterns and causes.

PubMed

Zheng, Han; Wang, Qiufeng; Zhu, Xianjin; Li, Yingnian; Yu, Guirui

2014-01-01

Evapotranspiration (ET) is an important component of the water cycle in terrestrial ecosystems. Understanding the ways in which ET changes with meteorological factors is central to a better understanding of ecological and hydrological processes. In this study, we used eddy covariance measurements of ET from a typical alpine shrubland meadow ecosystem in China to investigate the hysteresis response of ET to environmental variables including air temperature (Ta), vapor pressure deficit (VPD) and net radiation (Rn) at a diel timescale. Meanwhile, the simulated ET by Priestly-Taylor equation was used to interpret the measured ET under well-watered conditions. Pronounced hysteresis was observed in both Ta and VPD response curves of ET. At a similar Ta and VPD, ET was always significantly depressed in the afternoon compared with the morning. But the hysteresis response of ET to Rn was not evident. Similar hysteresis patterns were also observed in the Ta/VPD response curves of simulated ET. The magnitudes of the measured and simulated hysteresis loops showed similar seasonal variation, with relatively smaller values occurring from May to September, which agreed well with the lifetime of plants and the period of rainy season at this site. About 62% and 23% of changes in the strength of measured ET-Ta and ET-VPD loops could be explained by the changes in the strength of simulated loops, respectively. Thus, the time lag between Rn and Ta/VPD is the most important factor generating and modulating the ET-Ta/VPD hysteresis, but plants and water status also contribute to the hysteresis response of ET. Our research confirmed the different hysteresis in the responses of ET to meteorological factors and proved the vital role of Rn in driving the diel course of ET.

Photosynthetic Response of Poplars (Populus) to Climatic Stressors: Investigating Isoprene's Role in Increasing Tolerance to Temperature and Atmospheric Water Stress in Arizona

NASA Astrophysics Data System (ADS)

Pfeiffer, A. W.; Minor, R. L.; Heard, M. M.; Barron-Gafford, G.

2014-12-01

The southwestern United States is expected to become warmer and drier under future climate projections. The way in which plant and ecosystems respond to these changes is valuable for predicting carbon and water cycling, ecosystem resilience, phenology, and future agriculture, including biofuel production. We examined the interacting effects of dominant climate stressors--vapor pressure deficit (VPD) and temperature--on photosynthesis. Specifically, we tested whether or not plant production of the terpene isoprene imparts heat and water-stress tolerance. Within an experimental common garden of poplars (Populus) at University of Arizona's Biosphere 2 we measured four separate genetic lines - two that retained isoprene production capacity and two that had this gene "knocked out". VPD was altered at temperatures of 30, 35, and 40C to present both heat and aridity stresses. Maximum photosynthetic capacity (Amax), the VPD at which Amax occurred (VPDopt), and the VPD range between Amax and ninety percent of Amax (Ω90) were calculated to quantify how VPD differentially affected the lines. Amax was significantly lower in knockout lines than in control lines. Moreover, the difference in Amax between lines increased from 19.3% at 30C to 28.4% at 35C to 39.0% at 40C, indicating that trees without isoprene production are less equipped to handle hot and dry conditions. Ω90 and VPDopt response were not the same, though. Isoprene knockouts had significantly higher VPD optimums (1.9749 kPA vs. 1.6451 kPa) compared to isoprene-producing lines. Although maximum photosynthesis is diminished without isoprene production under water and heat stress, isoprene knockout lines were still fairly active at a high VPD and under a wide range of VPD conditions. Beyond advancing our basic understanding of plant ecophysiology, these results will inform the potential use of poplars as a source of biofuel production across a range of current and projected climate conditions.

Silver and zinc inhibitors influence transpiration rate and aquaporin transcript levels in intact soybean plants

USDA-ARS?s Scientific Manuscript database

Some soybean (Glycine max (L.) Merr.) have been identified that expressed limited transpiration rate (TR) above a threshold vapor pressure deficit (VPD). Restriction of TR at high VPD conditions is considered a water conservation trait that allows water to be retained in the soil to benefit of crop...

Chickpea Genotypes Contrasting for Vigor and Canopy Conductance Also Differ in Their Dependence on Different Water Transport Pathways

PubMed Central

Sivasakthi, Kaliamoorthy; Tharanya, Murugesan; Kholová, Jana; Wangari Muriuki, Ruth; Thirunalasundari, Thiyagarajan; Vadez, Vincent

2017-01-01

Lower plant transpiration rate (TR) under high vapor pressure deficit (VPD) conditions and early plant vigor are proposed as major traits influencing the rate of crop water use and possibly the fitness of chickpea lines to specific terminal drought conditions—this being the major constraint limiting chickpea productivity. The physiological mechanisms underlying difference in TR under high VPD and vigor are still unresolved, and so is the link between vigor and TR. Lower TR is hypothesized to relate to hydraulic conductance differences. Experiments were conducted in both soil (Vertisol) and hydroponic culture. The assessment of the TR response to increasing VPD showed that high vigor genotypes had TR restriction under high VPD, and this was confirmed in the early vigor parent and progeny genotype (ICC 4958 and RIL 211) having lower TR than the late vigor parent and progeny genotype (ICC 1882 and RIL 022). Inhibition of water transport pathways [apoplast and symplast (aquaporins)] in intact plants led to a lower transpiration inhibition in the early vigor/low TR genotypes than in the late vigor/high TR genotypes. De-rooted shoot treatment with an aquaporin inhibitor led to a lower transpiration inhibition in the early vigor/low TR genotypes than in the late vigor/high TR genotypes. Early vigor genotypes had lower root hydraulic conductivity than late vigor/high TR genotypes. Under inhibited conditions (apoplast, symplast), root hydraulic conductivity was reduced more in the late vigor/high TR genotypes than in the early vigor/low TR genotypes. We interpret that early vigor/low TR genotypes have a lower involvement of aquaporins in water transport pathways and may also have a smaller apoplastic pathway than high TR genotypes, which could explain the transpiration restriction under high VPD and would be helpful to conserve soil water under high evaporative demand. These findings open an opportunity for breeding to tailor genotypes with different “dosage” of these traits toward adaptation to varying drought-prone environments. PMID:29085377

Photosynthetic induction and its diffusional, carboxylation and electron transport processes as affected by CO2 partial pressure, temperature, air humidity and blue irradiance.

PubMed

Kaiser, Elias; Kromdijk, Johannes; Harbinson, Jeremy; Heuvelink, Ep; Marcelis, Leo F M

2017-01-01

Plants depend on photosynthesis for growth. In nature, factors such as temperature, humidity, CO 2 partial pressure, and spectrum and intensity of irradiance often fluctuate. Whereas irradiance intensity is most influential and has been studied in detail, understanding of interactions with other factors is lacking. We tested how photosynthetic induction after dark-light transitions was affected by CO 2 partial pressure (20, 40, 80 Pa), leaf temperatures (15·5, 22·8, 30·5 °C), leaf-to-air vapour pressure deficits (VPD leaf-air ; 0·5, 0·8, 1·6, 2·3 kPa) and blue irradiance (0-20 %) in tomato leaves (Solanum lycopersicum). Rates of photosynthetic induction strongly increased with CO 2 partial pressure, due to increased apparent Rubisco activation rates and reduced diffusional limitations. High leaf temperature produced slightly higher induction rates, and increased intrinsic water use efficiency and diffusional limitation. High VPD leaf-air slowed down induction rates and apparent Rubisco activation and (at 2·3 kPa) induced damped stomatal oscillations. Blue irradiance had no effect. Slower apparent Rubisco activation in elevated VPD leaf-air may be explained by low leaf internal CO 2 partial pressure at the beginning of induction. The environmental factors CO 2 partial pressure, temperature and VPD leaf-air had significant impacts on rates of photosynthetic induction, as well as on underlying diffusional, carboxylation and electron transport processes. Furthermore, maximizing Rubisco activation rates would increase photosynthesis by at most 6-8 % in ambient CO 2 partial pressure (across temperatures and humidities), while maximizing rates of stomatal opening would increase photosynthesis by at most 1-3 %. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Diurnal depression in leaf hydraulic conductance at ambient and elevated [CO2] reveals anisohydric water management in field-grown soybean

USDA-ARS?s Scientific Manuscript database

Diurnal cycles of photosynthesis and water use in field-grown soybean (Glycine max) are tied to light intensity and vapor pressure deficit (VPD). At high mid-day VPD, transpiration rates can lead to a decline in leaf water potential if leaf hydraulic conductance is insufficient to supply water to in...

Diurnal depression in leaf hydraulic conductance at ambient and elevated [CO2] and reveals anisohydric water management in field-grown soybean

USDA-ARS?s Scientific Manuscript database

Diurnal cycles of photosynthesis and water use in field-grown soybean (Glycine max) are tied to light intensity and vapor pressure deficit (VPD). At high mid-day VPD, transpiration rates can lead to a decline in leaf water potential ('leaf) if leaf hydraulic conductance (Kleaf) is insufficient to su...

Forest productivity varies with soil moisture more than temperature in a small montane watershed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Liang; Zhou, Hang; Link, Timothy E

Mountainous terrain creates variability in microclimate, including nocturnal cold air drainage and resultant temperature inversions. Driven by the elevational temperature gradient, vapor pressure deficit (VPD) also varies with elevation. Soil depth and moisture availability often increase from ridgetop to valley bottom. These variations complicate predictions of forest productivity and other biological responses. We analyzed spatiotemporal air temperature (T) and VPD variations in a forested, 27-km 2 catchment that varied from 1000 to 1650 m in elevation. Temperature inversions occurred on 76% of mornings in the growing season. The inversion had a clear upper boundary at midslope (~1370 m a.s.l.). Vapormore » pressure was relatively constant across elevations, therefore VPD was mainly controlled by T in the watershed. Here, we assessed the impact of microclimate and soil moisture on tree height, forest productivity, and carbon stable isotopes (δ 13C) using a physiological forest growth model (3-PG). Simulated productivity and tree height were tested against observations derived from lidar data. The effects on photosynthetic gas-exchange of dramatic elevational variations in T and VPD largely cancelled as higher temperature (increasing productivity) accompanies higher VPD (reducing productivity). Although it was not measured, the simulations suggested that realistic elevational variations in soil moisture predicted the observed decline in productivity with elevation. Therefore, in this watershed, the model parameterization should have emphasized soil moisture rather than precise descriptions of temperature inversions.« less

Forest productivity varies with soil moisture more than temperature in a small montane watershed

DOE PAGES

Wei, Liang; Zhou, Hang; Link, Timothy E; ...

2018-05-16

Mountainous terrain creates variability in microclimate, including nocturnal cold air drainage and resultant temperature inversions. Driven by the elevational temperature gradient, vapor pressure deficit (VPD) also varies with elevation. Soil depth and moisture availability often increase from ridgetop to valley bottom. These variations complicate predictions of forest productivity and other biological responses. We analyzed spatiotemporal air temperature (T) and VPD variations in a forested, 27-km 2 catchment that varied from 1000 to 1650 m in elevation. Temperature inversions occurred on 76% of mornings in the growing season. The inversion had a clear upper boundary at midslope (~1370 m a.s.l.). Vapormore » pressure was relatively constant across elevations, therefore VPD was mainly controlled by T in the watershed. Here, we assessed the impact of microclimate and soil moisture on tree height, forest productivity, and carbon stable isotopes (δ 13C) using a physiological forest growth model (3-PG). Simulated productivity and tree height were tested against observations derived from lidar data. The effects on photosynthetic gas-exchange of dramatic elevational variations in T and VPD largely cancelled as higher temperature (increasing productivity) accompanies higher VPD (reducing productivity). Although it was not measured, the simulations suggested that realistic elevational variations in soil moisture predicted the observed decline in productivity with elevation. Therefore, in this watershed, the model parameterization should have emphasized soil moisture rather than precise descriptions of temperature inversions.« less

Urban Tree Species Show the Same Hydraulic Response to Vapor Pressure Deficit across Varying Tree Size and Environmental Conditions

PubMed Central

Chen, Lixin; Zhang, Zhiqiang; Ewers, Brent E.

2012-01-01

Background The functional convergence of tree transpiration has rarely been tested for tree species growing under urban conditions even though it is of significance to elucidate the relationship between functional convergence and species differences of urban trees for establishing sustainable urban forests in the context of forest water relations. Methodology/Principal Findings We measured sap flux of four urban tree species including Cedrus deodara, Zelkova schneideriana, Euonymus bungeanus and Metasequoia glyptostroboides in an urban park by using thermal dissipation probes (TDP). The concurrent microclimate conditions and soil moisture content were also measured. Our objectives were to examine 1) the influence of tree species and size on transpiration, and 2) the hydraulic control of urban trees under different environmental conditions over the transpiration in response to VPD as represented by canopy conductance. The results showed that the functional convergence between tree diameter at breast height (DBH) and tree canopy transpiration amount (E c) was not reliable to predict stand transpiration and there were species differences within same DBH class. Species differed in transpiration patterns to seasonal weather progression and soil water stress as a result of varied sensitivity to water availability. Species differences were also found in their potential maximum transpiration rate and reaction to light. However, a same theoretical hydraulic relationship between G c at VPD = 1 kPa (G cref) and the G c sensitivity to VPD (−dG c/dlnVPD) across studied species as well as under contrasting soil water and R s conditions in the urban area. Conclusions/Significance We concluded that urban trees show the same hydraulic regulation over response to VPD across varying tree size and environmental conditions and thus tree transpiration could be predicted with appropriate assessment of G cref. PMID:23118904

High atmospheric demand for water can limit forest carbon uptake and transpiration as severely as dry soil

Treesearch

Benjamin N. Sulman; Daniel Tyler Roman; Koong Yi; Lixin Wang; Richard P. Phillips; Kimberly A. Novick

2016-01-01

When stressed by low soil water content (SWC) or high vapor pressure deficit (VPD), plants close stomata, reducing transpiration and photosynthesis. However, it has historically been difficult to disentangle the magnitudes of VPD compared to SWC limitations on ecosystem-scale fluxes. We used a 13 year record of eddy covariance measurements from a forest in south...

Expression of ABA synthesis and metabolism genes under different irrigation strategies and atmospheric VPDs is associated with stomatal conductance in grapevine (Vitis vinifera L. cv Cabernet Sauvignon).

PubMed

Speirs, Jim; Binney, Allan; Collins, Marisa; Edwards, Everard; Loveys, Brian

2013-04-01

The influence of different levels of irrigation and of variation in atmospheric vapour pressure deficit (VPD) on the synthesis, metabolism, and transport of abscisic acid (ABA) and the effects on stomatal conductance were examined in field-grown Cabernet Sauvignon grapevines. Xylem sap, leaf tissue, and root tissue were collected at regular intervals during two seasons in conjunction with measurements of leaf water potential (Ψleaf) and stomatal conductance (gs). The different irrigation levels significantly altered the Ψleaf and gs of the vines across both seasons. ABA abundance in the xylem sap was correlated with gs. The expression of genes associated with ABA synthesis, NCED1 and NCED2, was higher in the roots than in the leaves throughout and highest in the roots in mid January, a time when soil moisture declined and VPD was at its highest. Their expression in roots was also inversely related to the levels of irrigation and correlated with ABA abundance in the roots, xylem sap, and leaves. Three genes encoding ABA 8'-hydroxylases were isolated and their identities confirmed by expression in yeast cells. The expression of one of these, Hyd1, was elevated in leaves when VPD was below 2.0-2.5 kPa and minimal at higher VPD levels. The results provide evidence that ABA plays an important role in linking stomatal response to soil moisture status and that changes in ABA catabolism at or near its site of action allows optimization of gas exchange to current environmental conditions.

Relating Stomatal Conductance to Leaf Functional Traits.

PubMed

Kröber, Wenzel; Plath, Isa; Heklau, Heike; Bruelheide, Helge

2015-10-12

Leaf functional traits are important because they reflect physiological functions, such as transpiration and carbon assimilation. In particular, morphological leaf traits have the potential to summarize plants strategies in terms of water use efficiency, growth pattern and nutrient use. The leaf economics spectrum (LES) is a recognized framework in functional plant ecology and reflects a gradient of increasing specific leaf area (SLA), leaf nitrogen, phosphorus and cation content, and decreasing leaf dry matter content (LDMC) and carbon nitrogen ratio (CN). The LES describes different strategies ranging from that of short-lived leaves with high photosynthetic capacity per leaf mass to long-lived leaves with low mass-based carbon assimilation rates. However, traits that are not included in the LES might provide additional information on the species' physiology, such as those related to stomatal control. Protocols are presented for a wide range of leaf functional traits, including traits of the LES, but also traits that are independent of the LES. In particular, a new method is introduced that relates the plants' regulatory behavior in stomatal conductance to vapor pressure deficit. The resulting parameters of stomatal regulation can then be compared to the LES and other plant functional traits. The results show that functional leaf traits of the LES were also valid predictors for the parameters of stomatal regulation. For example, leaf carbon concentration was positively related to the vapor pressure deficit (vpd) at the point of inflection and the maximum of the conductance-vpd curve. However, traits that are not included in the LES added information in explaining parameters of stomatal control: the vpd at the point of inflection of the conductance-vpd curve was lower for species with higher stomatal density and higher stomatal index. Overall, stomata and vein traits were more powerful predictors for explaining stomatal regulation than traits used in the LES.

How does the VPD response of isohydric and anisohydric plants depend on leaf surface particles?

PubMed

Burkhardt, J; Pariyar, S

2016-01-01

Atmospheric vapour pressure deficit (VPD) is the driving force for plant transpiration. Plants have different strategies to respond to this 'atmospheric drought'. Deposited aerosols on leaf surfaces can interact with plant water relations and may influence VPD response. We studied transpiration and water use efficiency of pine, beech and sunflower by measuring sap flow, gas exchange and carbon isotopes, thereby addressing different time scales of plant/atmosphere interaction. Plants were grown (i) outdoors under rainfall exclusion (OD) and in ventilated greenhouses with (ii) ambient air (AA) or (iii) filtered air (FA), the latter containing <1% ambient aerosol concentrations. In addition, some AA plants were sprayed once with 25 mM salt solution of (NH4 )2 SO4 or NaNO3 . Carbon isotope values (δ(13) C) became more negative in the presence of more particles; more negative for AA compared to FA sunflower and more negative for OD Scots pine compared to other growth environments. FA beech had less negative δ(13) C than AA, OD and NaNO3 -treated beech. Anisohydric beech showed linearly increasing sap flow with increasing VPD. The slopes doubled for (NH4 )2 SO4 - and tripled for NaNO3 -sprayed beech compared to control seedlings, indicating decreased ability to resist atmospheric demand. In contrast, isohydric pine showed constant transpiration rates with increasing VPD, independent of growth environment and spray, likely caused by decreasing gs with increasing VPD. Generally, NaNO3 spray had stronger effects on water relations than (NH4 )2 SO4 spray. The results strongly support the role of leaf surface particles as an environmental factor affecting plant water use. Hygroscopic and chaotropic properties of leaf surface particles determine their ability to form wicks across stomata. Such wicks enhance unproductive water loss of anisohydric plant species and decrease CO2 uptake of isohydric plants. They become more relevant with increasing number of fine particles and increasing VPD and are thus related to air pollution and climate change. Wicks cause a deviation from the analogy between CO2 and water pathways through stomata, bringing some principal assumptions of gas exchange theory into question. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

Evidence that Tropical Forest Photosynthesis is Not Directly Limited by High Temperatures

NASA Astrophysics Data System (ADS)

Smith, M.; Taylor, T.; Van Haren, J. L. M.; Rosolem, R.; Restrepo-Coupe, N.; Wu, J.; Oliveira Junior, R. C.; Silva, R. D.; De Araujo, A. C.; Camargo, P. B. D.; Huxman, T. E.; Saleska, S. R.

2016-12-01

Loss of tropical forest biomass under rising temperatures could result in significant feedbacks to global climate. The vulnerability of tropical trees to climate warming depends on the specific physiological mechanisms controlling photosynthetic decline at temperatures above the thermal optimum. High temperatures may negatively impact photosynthetic metabolism (direct effects) (Doughty and Goulden 2008), or leaves may respond to the concomitant increase in vapor pressure deficit (VPD) by closing stomata (indirect effects) (Lloyd and Farquhar 2008). The difference is important because the former reveals a vulnerability of photosynthetic infrastructure to higher temperatures, while the latter is an expected physiological response of healthy leaves. We investigated these contrasting hypotheses in a climate controlled, 0.2 ha artificial tropical forest (the Biosphere 2 tropical forest biome, B2-TF). Typically coupled in nature, VPD and temperature can be varied independently in the controlled environment of the B2-TF, and their effects on photosynthesis distinguished. We found that in the B2-TF, gross ecosystem productivity (GEP) was strongly reduced by increasing VPD, but responded little to temperature. Whereas eddy flux-derived GEP of three natural tropical forest sites in the Amazon of Brazil declined at temperatures above 27°C, GEP in the B2-TF remained stable up to 33°C under both low and high VPD regimes. While either mechanism results in reduced photosynthesis, the impact of VPD is short-lived and may be mitigated by enhanced water use efficiency under elevated atmospheric CO2 concentrations, allowing tropical forests to be more resilient to climate warming.

Further insights into the components of resistance to Ophiostoma novo-ulmi in Ulmus minor: hydraulic conductance, stomatal sensitivity and bark dehydration.

PubMed

Pita, Pilar; Rodríguez-Calcerrada, Jesús; Medel, David; Gil, Luis

2018-02-01

Dutch elm disease (DED) is a vascular disease that has killed over 1 billion elm trees. The pathogen spreads throughout the xylem network triggering vessel blockage, which results in water stress, tissue dehydration and extensive leaf wilting in susceptible genotypes. We investigated the differences between four Ulmus minor Mill. clones of contrasting susceptibility to Ophiostoma novo-ulmi Brasier regarding morphological, anatomical and physiological traits affecting water transport, in order to gain a better understanding of the mechanisms underlying DED susceptibility. We analyzed the differential response to water shortage and increased air vapor pressure deficit (VPD) to investigate whether resistance to water stress might be related to DED tolerance. Sixteen plants per clone, aged 2 years, were grown inside a greenhouse under differential watering. Stomatal conductance was measured under ambient and increased VPD. Growth, bark water content and stem hydraulic and anatomical parameters were measured 22 days after starting differential watering. Vessel lumen area, lumen fraction and hydraulic conductance were highest in susceptible clones. Stomatal conductance was lowest under low VPD and decreased faster under increased VPD in resistant clones. We found a negative relationship between the decrease in stomatal conductance at increased VPD and specific hydraulic conductance, revealing a narrower hydraulic margin for sustaining transpiration in resistant clones. The effect of water shortage was greater on radial stem growth than on leaf area, which could be explained through an extensive use of capacitance water to buffer xylem water potential. Water shortage reduced stomatal conductance and vessel lumen area. Bark water content under conditions of water shortage only decreased in susceptible clones. Higher hydraulic constraints to sap flow in resistant clones may determine higher stomatal sensitivity to VPD and so contribute to DED resistance by limiting pathogen expansion and reducing water loss and metabolic impairment in cells involved in fighting against infection. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Bioenergy Sorghum Crop Model Predicts VPD-Limited Transpiration Traits Enhance Biomass Yield in Water-Limited Environments

PubMed Central

Truong, Sandra K.; McCormick, Ryan F.; Mullet, John E.

2017-01-01

Bioenergy sorghum is targeted for production in water-limited annual cropland therefore traits that improve plant water capture, water use efficiency, and resilience to water deficit are necessary to maximize productivity. A crop modeling framework, APSIM, was adapted to predict the growth and biomass yield of energy sorghum and to identify potentially useful traits for crop improvement. APSIM simulations of energy sorghum development and biomass accumulation replicated results from field experiments across multiple years, patterns of rainfall, and irrigation schemes. Modeling showed that energy sorghum's long duration of vegetative growth increased water capture and biomass yield by ~30% compared to short season crops in a water-limited production region. Additionally, APSIM was extended to enable modeling of VPD-limited transpiration traits that reduce crop water use under high vapor pressure deficits (VPDs). The response of transpiration rate to increasing VPD was modeled as a linear response until a VPD threshold was reached, at which the slope of the response decreases, representing a range of responses to VPD observed in sorghum germplasm. Simulation results indicated that the VPD-limited transpiration trait is most beneficial in hot and dry regions of production where crops are exposed to extended periods without rainfall during the season or to a terminal drought. In these environments, slower but more efficient transpiration increases biomass yield and prevents or delays the exhaustion of soil water and onset of leaf senescence. The VPD-limited transpiration responses observed in sorghum germplasm increased biomass accumulation by 20% in years with lower summer rainfall, and the ability to drastically reduce transpiration under high VPD conditions could increase biomass by 6% on average across all years. This work indicates that the productivity and resilience of bioenergy sorghum grown in water-limited environments could be further enhanced by development of genotypes with optimized VPD-limited transpiration traits and deployment of these crops in water limited growing environments. The energy sorghum model and VPD-limited transpiration trait implementation are made available to simulate performance in other target environments. PMID:28377779

Bioenergy Sorghum Crop Model Predicts VPD-Limited Transpiration Traits Enhance Biomass Yield in Water-Limited Environments.

PubMed

Truong, Sandra K; McCormick, Ryan F; Mullet, John E

2017-01-01

Bioenergy sorghum is targeted for production in water-limited annual cropland therefore traits that improve plant water capture, water use efficiency, and resilience to water deficit are necessary to maximize productivity. A crop modeling framework, APSIM, was adapted to predict the growth and biomass yield of energy sorghum and to identify potentially useful traits for crop improvement. APSIM simulations of energy sorghum development and biomass accumulation replicated results from field experiments across multiple years, patterns of rainfall, and irrigation schemes. Modeling showed that energy sorghum's long duration of vegetative growth increased water capture and biomass yield by ~30% compared to short season crops in a water-limited production region. Additionally, APSIM was extended to enable modeling of VPD-limited transpiration traits that reduce crop water use under high vapor pressure deficits (VPDs). The response of transpiration rate to increasing VPD was modeled as a linear response until a VPD threshold was reached, at which the slope of the response decreases, representing a range of responses to VPD observed in sorghum germplasm. Simulation results indicated that the VPD-limited transpiration trait is most beneficial in hot and dry regions of production where crops are exposed to extended periods without rainfall during the season or to a terminal drought. In these environments, slower but more efficient transpiration increases biomass yield and prevents or delays the exhaustion of soil water and onset of leaf senescence. The VPD-limited transpiration responses observed in sorghum germplasm increased biomass accumulation by 20% in years with lower summer rainfall, and the ability to drastically reduce transpiration under high VPD conditions could increase biomass by 6% on average across all years. This work indicates that the productivity and resilience of bioenergy sorghum grown in water-limited environments could be further enhanced by development of genotypes with optimized VPD-limited transpiration traits and deployment of these crops in water limited growing environments. The energy sorghum model and VPD-limited transpiration trait implementation are made available to simulate performance in other target environments.

Bioenergy sorghum crop model predicts VPD-limited transpiration traits enhance biomass yield in water-limited environments

DOE PAGES

Truong, Sandra K.; McCormick, Ryan F.; Mullet, John E.

2017-03-21

Bioenergy sorghum is targeted for production in water-limited annual cropland therefore traits that improve plant water capture, water use efficiency, and resilience to water deficit are necessary to maximize productivity. A crop modeling framework, APSIM, was adapted to predict the growth and biomass yield of energy sorghum and to identify potentially useful traits for crop improvement. APSIM simulations of energy sorghum development and biomass accumulation replicated results from field experiments across multiple years, patterns of rainfall, and irrigation schemes. Modeling showed that energy sorghum’s long duration of vegetative growth increased water capture and biomass yield by ~30% compared to shortmore » season crops in a water-limited production region. Additionally, APSIM was extended to enable modeling of VPD-limited transpiration traits that reduce crop water use under high vapor pressure deficits (VPDs). The response of transpiration rate to increasing VPD was modeled as a linear response until a VPD threshold was reached, at which the slope of the response decreases, representing a range of responses to VPD observed in sorghum germplasm. Simulation results indicated that the VPD-limited transpiration trait is most beneficial in hot and dry regions of production where crops are exposed to extended periods without rainfall during the season or to a terminal drought. In these environments, slower but more efficient transpiration increases biomass yield and prevents or delays the exhaustion of soil water and onset of leaf senescence. The VPD-limited transpiration responses observed in sorghum germplasm increased biomass accumulation by 20% in years with lower summer rainfall, and the ability to drastically reduce transpiration under high VPD conditions could increase biomass by 6% on average across all years. This work indicates that the productivity and resilience of bioenergy sorghum grown in water-limited environments could be further enhanced by development of genotypes with optimized VPD-limited transpiration traits and deployment of these crops in water limited growing environments. As a result, the energy sorghum model and VPD-limited transpiration trait implementation aremade available to simulate performance in other target environments.« less

Bioenergy sorghum crop model predicts VPD-limited transpiration traits enhance biomass yield in water-limited environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Truong, Sandra K.; McCormick, Ryan F.; Mullet, John E.

Bioenergy sorghum is targeted for production in water-limited annual cropland therefore traits that improve plant water capture, water use efficiency, and resilience to water deficit are necessary to maximize productivity. A crop modeling framework, APSIM, was adapted to predict the growth and biomass yield of energy sorghum and to identify potentially useful traits for crop improvement. APSIM simulations of energy sorghum development and biomass accumulation replicated results from field experiments across multiple years, patterns of rainfall, and irrigation schemes. Modeling showed that energy sorghum’s long duration of vegetative growth increased water capture and biomass yield by ~30% compared to shortmore » season crops in a water-limited production region. Additionally, APSIM was extended to enable modeling of VPD-limited transpiration traits that reduce crop water use under high vapor pressure deficits (VPDs). The response of transpiration rate to increasing VPD was modeled as a linear response until a VPD threshold was reached, at which the slope of the response decreases, representing a range of responses to VPD observed in sorghum germplasm. Simulation results indicated that the VPD-limited transpiration trait is most beneficial in hot and dry regions of production where crops are exposed to extended periods without rainfall during the season or to a terminal drought. In these environments, slower but more efficient transpiration increases biomass yield and prevents or delays the exhaustion of soil water and onset of leaf senescence. The VPD-limited transpiration responses observed in sorghum germplasm increased biomass accumulation by 20% in years with lower summer rainfall, and the ability to drastically reduce transpiration under high VPD conditions could increase biomass by 6% on average across all years. This work indicates that the productivity and resilience of bioenergy sorghum grown in water-limited environments could be further enhanced by development of genotypes with optimized VPD-limited transpiration traits and deployment of these crops in water limited growing environments. As a result, the energy sorghum model and VPD-limited transpiration trait implementation aremade available to simulate performance in other target environments.« less

Expression of ABA synthesis and metabolism genes under different irrigation strategies and atmospheric VPDs is associated with stomatal conductance in grapevine (Vitis vinifera L. cv Cabernet Sauvignon)

PubMed Central

Speirs, Jim; Binney, Allan; Collins, Marisa; Edwards, Everard; Loveys, Brian

2013-01-01

The influence of different levels of irrigation and of variation in atmospheric vapour pressure deficit (VPD) on the synthesis, metabolism, and transport of abscisic acid (ABA) and the effects on stomatal conductance were examined in field-grown Cabernet Sauvignon grapevines. Xylem sap, leaf tissue, and root tissue were collected at regular intervals during two seasons in conjunction with measurements of leaf water potential (Ψleaf) and stomatal conductance (gs). The different irrigation levels significantly altered the Ψleaf and gs of the vines across both seasons. ABA abundance in the xylem sap was correlated with gs. The expression of genes associated with ABA synthesis, NCED1 and NCED2, was higher in the roots than in the leaves throughout and highest in the roots in mid January, a time when soil moisture declined and VPD was at its highest. Their expression in roots was also inversely related to the levels of irrigation and correlated with ABA abundance in the roots, xylem sap, and leaves. Three genes encoding ABA 8’-hydroxylases were isolated and their identities confirmed by expression in yeast cells. The expression of one of these, Hyd1, was elevated in leaves when VPD was below 2.0–2.5 kPa and minimal at higher VPD levels. The results provide evidence that ABA plays an important role in linking stomatal response to soil moisture status and that changes in ABA catabolism at or near its site of action allows optimization of gas exchange to current environmental conditions. PMID:23630325

Atmospheric Humidity Influences Oviposition Rate of Tetranychus urticae (Acari: Tetranychidae) Through Morphological Responses of Host Cucumis sativus Leaves.

PubMed

Shibuya, T; Itagaki, K; Ueyama, S; Hirai, N; Endo, R

2016-02-01

We investigated the effects of morphology of host cucumber, Cucumis sativus L., leaves acclimatized to different atmospheric humidity levels on oviposition by adult females of the twospotted spider mite, Tetranychus urticae Koch. Cucumber seedlings were grown at a vapor pressure deficit (VPD) of 0.4, 1.9, or 3.0 kPa at 28°C (90%, 50%, or 20% relative humidity, respectively) in growth chambers until the second true leaves had expanded. Adult females of T. urticae were released on the adaxial surfaces of leaf squares cut from first and second true leaves in each treatment group, and held in the same humidity condition. Eggs were counted 2 d after release. The lower acclimatization humidity (higher VPD) increased trichome (leaf hair) density of the host leaves and oviposition rate, but the relationship between the trichome and oviposition differed between leaf positions. The leaf mass per area (LMA) was greater in first true leaves than in second true leaves, but was not influenced by VPD. A linear regression model with oviposition rate as the dependent variable and trichome density and LMA as independent variables showed that both variables influenced the oviposition rate approximately equally. We conclude that oviposition was accelerated under low humidity (high VPD) conditions indirectly probably through an increase in the trichome density of host leaves. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Representation of physiological drought at ecosystem level based on model and eddy covariance measurements

NASA Astrophysics Data System (ADS)

Zhang, Y.; Novick, K. A.; Song, C.; Zhang, Q.; Hwang, T.

2017-12-01

Drought and heat waves are expected to increase both in frequency and amplitude, exhibiting a major disturbance to global carbon and water cycles under future climate change. However, how these climate anomalies translate into physiological drought, or ecosystem moisture stress are still not clear, especially under the co-limitations from soil moisture supply and atmospheric demand for water. In this study, we characterized the ecosystem-level moisture stress in a deciduous forest in the southeastern United States using the Coupled Carbon and Water (CCW) model and in-situ eddy covariance measurements. Physiologically, vapor pressure deficit (VPD) as an atmospheric water demand indicator largely controls the openness of leaf stomata, and regulates atmospheric carbon and water exchanges during periods of hydrological stress. Here, we tested three forms of VPD-related moisture scalars, i.e. exponent (K2), hyperbola (K3), and logarithm (K4) to quantify the sensitivity of light-use efficiency to VPD along different soil moisture conditions. The sensitivity indicators of K values were calibrated based on the framework of CCW using Monte Carlo simulations on the hourly scale, in which VPD and soil water content (SWC) are largely decoupled and the full carbon and water exchanging information are held. We found that three K values show similar performances in the predictions of ecosystem-level photosynthesis and transpiration after calibration. However, all K values show consistent gradient changes along SWC, indicating that this deciduous forest is less responsive to VPD as soil moisture decreases, a phenomena of isohydricity in which plants tend to close stomata to keep the leaf water potential constant and reduce the risk of hydraulic failure. Our study suggests that accounting for such isohydric information, or spectrum of moisture stress along different soil moisture conditions in models can significantly improve our ability to predict ecosystem responses to future drought.

Transpiration Response and Growth in Pearl Millet Parental Lines and Hybrids Bred for Contrasting Rainfall Environments

PubMed Central

Medina, Susan; Gupta, S. K.; Vadez, Vincent

2017-01-01

Under conditions of high vapor pressure deficit (VPD) and soil drying, restricting transpiration is an important avenue to gain efficiency in water use. The question we raise in this article is whether breeding for agro-ecological environments that differ for the rainfall have selected for traits that control plant water use. These are measured in pearl millet materials bred for zones varying in rainfall (8 combinations of parent and F1-hybrids, 18 F1-hybrids and then 40 F1-hybrids). In all cases, we found an agro-ecological variation in the slope of the transpiration response to increasing VPD, and parental line variation in the transpiration response to soil drying within hybrids/parent combinations. The hybrids adapted to lower rainfall had higher transpiration response curves than those from the highest rainfall zones, but showed no variation in how transpiration responded to soil drying. The genotypes bred for lower rainfall zones showed lower leaf area, dry matter, thicker leaves, root development, and exudation, than the ones bred for high rainfall zone when grown in the low VPD environment of the greenhouse, but there was no difference in their root length neither on the root/shoot index in these genotypes. By contrast, when grown under high VPD conditions outdoors, the lower rainfall hybrids had the highest leaf, tiller, and biomass development. Finally, under soil drying the genotypes from the lower rainfall accumulated less biomass than the ones from higher rainfall zone, and so did the parental lines compared to the hybrids. These differences in the transpiration response and growth clearly showed that breeding for different agro-ecological zones also bred for different genotype strategies in relation to traits related to plant water use. Highlights: • Variation in transpiration response reflected breeding for agro-ecological zones • Different growth strategies depended on the environmental conditions • Different ideotypes reflected rainfall levels in specific agro-ecological zones PMID:29163578

Transpiration Response and Growth in Pearl Millet Parental Lines and Hybrids Bred for Contrasting Rainfall Environments.

PubMed

Medina, Susan; Gupta, S K; Vadez, Vincent

2017-01-01

Under conditions of high vapor pressure deficit (VPD) and soil drying, restricting transpiration is an important avenue to gain efficiency in water use. The question we raise in this article is whether breeding for agro-ecological environments that differ for the rainfall have selected for traits that control plant water use. These are measured in pearl millet materials bred for zones varying in rainfall (8 combinations of parent and F 1 -hybrids, 18 F 1 -hybrids and then 40 F 1 -hybrids). In all cases, we found an agro-ecological variation in the slope of the transpiration response to increasing VPD, and parental line variation in the transpiration response to soil drying within hybrids/parent combinations. The hybrids adapted to lower rainfall had higher transpiration response curves than those from the highest rainfall zones, but showed no variation in how transpiration responded to soil drying. The genotypes bred for lower rainfall zones showed lower leaf area, dry matter, thicker leaves, root development, and exudation, than the ones bred for high rainfall zone when grown in the low VPD environment of the greenhouse, but there was no difference in their root length neither on the root/shoot index in these genotypes. By contrast, when grown under high VPD conditions outdoors, the lower rainfall hybrids had the highest leaf, tiller, and biomass development. Finally, under soil drying the genotypes from the lower rainfall accumulated less biomass than the ones from higher rainfall zone, and so did the parental lines compared to the hybrids. These differences in the transpiration response and growth clearly showed that breeding for different agro-ecological zones also bred for different genotype strategies in relation to traits related to plant water use. Highlights : • Variation in transpiration response reflected breeding for agro-ecological zones • Different growth strategies depended on the environmental conditions • Different ideotypes reflected rainfall levels in specific agro-ecological zones.

Environmental Humidity Regulates Effects of Experimental Warming on Vegetation Index and Biomass Production in an Alpine Meadow of the Northern Tibet

PubMed Central

Fu, Gang; Shen, Zhen Xi

2016-01-01

Uncertainty about responses of vegetation index, aboveground biomass (AGB) and gross primary production (GPP) limits our ability to predict how climatic warming will influence plant growth in alpine regions. A field warming experiment was conducted in an alpine meadow at a low (4313 m), mid- (4513 m) and high elevation (4693 m) in the Northern Tibet since May 2010. Growing season vapor pressure deficit (VPD), soil temperature (Ts) and air temperature (Ta) decreased with increasing elevation, while growing season precipitation, soil moisture (SM), normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI), AGB and GPP increased with increasing elevation. The growing season Ta, Ts and VPD in 2015 was greater than that in 2014, while the growing season precipitation, SM, NDVI, SAVI, AGB and GPP in 2015 was lower than that in 2014, respectively. Compared to the mean air temperature and precipitation during the growing season in 1963–2015, it was a warmer and wetter year in 2014 and a warmer and drier year in 2015. Experimental warming increased growing season Ts, Ta,VPD, but decreased growing season SM in 2014–2015 at all the three elevations. Experimental warming only reduced growing season NDVI, SAVI, AGB and GPP at the low elevation in 2015. Growing season NDVI, SAVI, AGB and GPP increased with increasing SM and precipitation, but decreased with increasing VPD, indicating vegetation index and biomass production increased with environmental humidity. The VPD explained more variation of growing season NDVI, SAVI, AGB and GPP compared to Ts, Ta and SM at all the three elevations. Therefore, environmental humidity regulated the effect of experimental warming on vegetation index and biomass production in alpine meadows on the Tibetan Plateau. PMID:27798690

Understanding the Spatiotemporal Variability of Inherent Water Use Efficiency

NASA Astrophysics Data System (ADS)

Boese, Sven; Jung, Martin; Carvalhais, Nuno; Reichstein, Markus

2015-04-01

The global carbon and water cycles are coupled via plant physiology. However, the resulting spatial and temporal covariability of both fluxes on a global scale lacks sufficient understanding. This is required to estimate the impact of atmospheric drought on photosynthesis in water-limited ecosystems. Water use efficiency (WUE) is an essential ecosystem diagnostic defined as the ratio between gross primary productivity (GPP) and transpiration (T). WUE is known to vary with vapour-pressure deficit (VPD) and therefore also in time. The inherent water use efficiency (iWUE) accounts for the VPD effect on WUE and aims at representing a largely time-invariant ecosystem property. However, different ways of describing the functional response of iWUE to VPD are found in the literature. One established iWUE definition was proposed by Beer et al. (2009) and takes the form of iWUE = GPP--VPD- . T (1) A similar definition can be derived from stomatal conductance theories such as Katul et al. (2010) and takes the form of √ -- GPP---VPD- iWUE = T . (2) Here, we use eddy covariance measurements from the FLUXNET database to evaluate both approaches for a globally representative set of biomes including tropical, temperate and semi-arid ecosystems. Testing both definitions in a model-data fusion setup indicated that (2) is more consistent with FLUXNET observations than (1). However, there still remains considerable temporal variability of iWUE which is linked to seasonal changes in VPD. To explore up to which extent the temporal variability of iWUE may be related to the prescribed functional responses to VPD, we treated the exponent of VPD as a global parameter, here termed γ. When γ = 1 the functional response is equivalent to (1), while when γ = 0.5 it corresponds to formulation of model (2)). The global estimate was found to be significantly lower than 0.5, which would have been expected from stomatal conductance theory at leaf level. We assessed whether adding γ as site-specific parameter could be justified. The additional model complexity was warranted by an increased goodness-of-fit as quantified by the Akaike information criterion. However, temporal variations in iWUE persist. The structural adequacy of the models was assessed via the correlation structure of the residuals. Ultimately, changing γ in the definition impacts the between-site variability of iWUE. The iWUE estimates with γ = 1.0 were only weakly correlated with those with γ = 0.5. This has crucial implications for spatial analyses on the drought response of water-limited ecosystems. We discuss uncertainties involved in the analysis and highlight possible mechanisms responsible for the remaining temporal variability of iWUE. The consequences of differing iWUE definitions for the analysis of global carbon and water cycles are explored.

Satellite Estimation of Daily Land Surface Water Vapor Pressure Deficit from AMSR- E

NASA Astrophysics Data System (ADS)

Jones, L. A.; Kimball, J. S.; McDonald, K. C.; Chan, S. K.; Njoku, E. G.; Oechel, W. C.

2007-12-01

Vapor pressure deficit (VPD) is a key variable for monitoring land surface water and energy exchanges, and estimating plant water stress. Multi-frequency day/night brightness temperatures from the Advanced Microwave Scanning Radiometer on EOS Aqua (AMSR-E) were used to estimate daily minimum and average near surface (2 m) air temperatures across a North American boreal-Arctic transect. A simple method for determining daily mean VPD (Pa) from AMSR-E air temperature retrievals was developed and validated against observations across a regional network of eight study sites ranging from boreal grassland and forest to arctic tundra. The method assumes that the dew point and minimum daily air temperatures tend to equilibrate in areas with low night time temperatures and relatively moist conditions. This assumption was tested by comparing the VPD algorithm results derived from site daily temperature observations against results derived from AMSR-E retrieved temperatures alone. An error analysis was conducted to determine the amount of error introduced in VPD estimates given known levels of error in satellite retrieved temperatures. Results indicate that the assumption generally holds for the high latitude study sites except for arid locations in mid-summer. VPD estimates using the method with AMSR-E retrieved temperatures compare favorably with site observations. The method can be applied to land surface temperature retrievals from any sensor with day and night surface or near-surface thermal measurements and shows potential for inferring near-surface wetness conditions where dense vegetation may hinder surface soil moisture retrievals from low-frequency microwave sensors. This work was carried out at The University of Montana, at San Diego State University, and at the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration.

[Net photosynthesis and its affecting factors in a tropical seasonal rainforest ecosystem in southwest China].

PubMed

Song, Qing-hai; Zhang, Yi-ping; Tan, Zheng-hong; Zhang, Lei-ming; Yang, Zhen; Zhao, Shuang-ju; Sun, Xiao-min

2010-12-01

By using eddy covariance technique, this paper quantitatively analyzed the photosynthetic characteristics of tropical seasonal rainforest ecosystem and related environmental controlling factors in Xishuangbanna in 2003-2006. In the study period, less interannual difference was observed in the net photosynthesis of the ecosystem, with the maximum photosynthesis rate (P(eco,opt)), respiration at daytime (R(eco,d)), and apparent quantum yield (alpha) averaged by 0.813 mg x m(-2) x s(-1), 0.238 mg x m(-2) x s(-1), and 0.0023 mg x micromol(-1), respectively. As affected by the interaction of air temperature (Ta) and vapor pressure deficit (VPD), the photosynthetic characteristics had some seasonal differences. In rainy season, the ecosystem had the strongest photosynthetic capacity because of the higher precipitation and warmer air temperature; in foggy and cool season, fog drip played an important role in the water relations of plants, and thereby, the ecosystem photosynthetic capacity was still higher; in dry and hot season, due to the limited precipitation and high temperature, the Ta and VPD increased, inducing a decrease of ecosystem alpha and P(eco,opt). The net CO2 exchange of the ecosystem strongly depended on the Ta above 20 degrees C and the VPD above 1 kPa.

Seasonal changes in Cyclobalanopsis glauca transpiration and canopy stomatal conductance and their dependence on subterranean water and climatic factors in rocky karst terrain

NASA Astrophysics Data System (ADS)

Huang, Yuqing; Li, Xiankun; Zhang, Zhongfeng; He, Chengxin; Zhao, Ping; You, Yeming; Mo, Ling

2011-05-01

SummaryThe presence of forest on south China karst is presumed to increase perennial epikarst spring flow, partly because there is adequate storage in bedrock fractures underlying the shallow soil in the forest. If true, transpiration of the ecosystem would not be strongly reduced by temperate drought if trees develop deep roots to reach the perched epikarst water. Therefore, in karst ecosystem the epikarst-soil-plant-atmosphere continuum (ESPAC) would be different from the SPAC in non-karst system. We measured transpiration and canopy conductance from a Cyclobalanopsis glauca (syn. Quercus glauca) stand on a rocky hill slope in South China during 2006-2007 by using the Granier's sap-flow method. Annual stand transpiration (836 mm y -1) accounted for 48.7% of the rainfall during the experimental year. Per month, daily stand transpiration ( E c) maximums varied between 2.1 mm d -1 in January (cool season) to 5.1 mm d -1 in July (hot season). In the driest months, September and October, E c of C. glauca was still high with maximum E c 3.82 mm d -1 and 2.96 mm d -1 respectively. Solar radiation ( PAR), vapor pressure deficiency ( VPD), and air temperature were simple influences on transpiration of C. glauca, which contributed to a quadratic power model, while soil water content ( SWC) moisture influence on transpiration was complicated, which SWC influenced E c greatly under higher VPD, but did not influence E c under low VPD. High stomatal openness occurred in C. glauca in the early morning and declined throughout the day. The relation coefficient between canopy stomatal conductance ( G c) and E c was high when VPD was more than 1.0 kPa, moderate when 0.5 kPa < VPD < 1.0 kPa, and low with VPD of less than 0.5 kPa. Under high VPD, stomatal control of transpiration is high. The pattern of seasonal change of transpiration and canopy stomatal conductance of the plant in karst regions is different from that in non-karst regions, with the stand transpiration and canopy stomatal conductance being high even during the dry season in the karst region because karst plants obtain water partially from the epikarst. With high stand transpiration and canopy stomatal conductance, karst vegetation is presumed to be the most important "pathway" for ESPAC.

Large-scale drought-induced vegetation die-off: expanding the ecohydrological emphasis more explicitly on atmospheric demand. (Invited)

NASA Astrophysics Data System (ADS)

Breshears, D. D.; Adams, H. D.; Eamus, D.; McDowell, N. G.; Law, D. J.; Will, R. E.; Williams, P.; Zou, C.

2013-12-01

Ecohydrology focuses on the interactions of water availability, ecosystem productivity, and biogeochemical cycles via ecological-hydrological connections. These connections can be particularly pronounced and socially relevant when there are large-scale rapid changes in vegetation. One such key change, vegetation mortality, can be triggered by drought and is projected to become more frequent and/or extensive in the future under changing climate. Recent research on drought-induced vegetation die-off has focused primarily on direct drought effects, such as soil moisture deficit, and, to a much lesser degree, the potential for warmer temperatures to exacerbate stress and accelerate mortality. However, temperature is tightly interrelated with atmospheric demand (vapor pressure deficit, VPD) but the latter has rarely been considered explicitly relative to die-off events. Here we highlight the importance of VPD in addition to soil moisture deficit and warmer temperature as an important driver of future die-off. Recent examples highlighting the importance of VPD include mortality patterns corresponding to VPD drivers, a strong dependence of forest growth on VPD, patterns of observed mortality along an environmental gradient, an experimentally-determined climate envelope for mortality, and a suite of modeling simulations segregating the drought effects of VPD from those of temperature. The vast bulk of evidence suggests that atmospheric demand needs to be considered in addition to temperature and soil moisture deficit in predicting risk of future vegetation die-off and associated ecohydrological transformations.

Direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning revealed by a prolonged drought at a temperate forest site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Lianhong; Meyers, T. P.; Pallardy, Stephen G.

2006-01-01

The purpose of this paper is to examine the mechanism that controls the variation of surface energy partitioning between latent and sensible heat fluxes at a temperate deciduous forest site in central Missouri, USA. Taking advantage of multiple micrometeorological and ecophysiological measurements and a prolonged drought in the middle of the 2005 growing season at this site, we studied how soil moisture, atmospheric vapor pressure deficit (VPD), and net radiation affected surface energy partitioning. We stratified these factors to minimize potential confounding effects of correlation among them. We found that all three factors had direct effects on surface energy partitioning,more » but more important, all three factors also had crucial indirect effects. The direct effect of soil moisture was characterized by a rapid decrease in Bowen ratio with increasing soil moisture when the soil was dry and by insensitivity of Bowen ratio to variations in soil moisture when the soil was wet. However, the rate of decrease in Bowen ratio when the soil was dry and the level of soil moisture above which Bowen ratio became insensitive to changes in soil moisture depended on atmospheric conditions. The direct effect of increased net radiation was to increase Bowen ratio. The direct effect of VPD was very nonlinear: Increased VPD decreased Bowen ratio at low VPD but increased Bowen ratio at high VPD. The indirect effects were much more complicated. Reduced soil moisture weakened the influence of VPD but enhanced the influence of net adiation on surface energy partitioning. Soil moisture also controlled how net radiation influenced the relationship between surface energy partitioning and VPD and how VPD affected the relationship between surface energy partitioning and net radiation. Furthermore, both increased VPD and increased net radiation enhanced the sensitivity of Bowen ratio to changes in soil moisture and the effect of drought on surface energy partitioning. The direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning identified in this paper provide a target for testing atmospheric general circulation models in their representation of land-atmosphere coupling.« less

Tree water dynamics in a drying and warming world: Future tree water dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grossiord, Charlotte; Sevanto, Sanna; Borrego, Isaac

Disentangling the relative impacts of precipitation reduction and vapour pressure deficit (VPD) on plant water dynamics and determining whether acclimation may influence these patterns in the future is an important challenge. Here, we report sap flux density (FD), stomatal conductance (Gs), hydraulic conductivity (KL) and xylem anatomy in piñon pine (Pinus edulis) and juniper (Juniperus monosperma) trees subjected to five years of precipitation reduction, atmospheric warming (elevated VPD) and their combined effects. No acclimation occurred under precipitation reduction: lower Gs and FD were found for both species compared to ambient conditions. Warming reduced the sensibility of stomata to VPD formore » both species but resulted in the maintenance of Gs and FD to ambient levels only for piñon. For juniper, reduced soil moisture under warming negated benefits of stomatal adjustments and resulted in reduced FD, Gs and KL. Although reduced stomatal sensitivity to VPD also occurred under combined stresses, reductions in Gs, FD and KL took place to similar levels as under single stresses for both species. Our results show that stomatal conductance adjustments to high VPD could minimize but not entirely prevent additive effects of warming and drying on water use and carbon acquisition of trees in semi-arid regions.« less

Tree water dynamics in a drying and warming world

DOE PAGES

Grossiord, Charlotte; Sevanto, Sanna Annika; Borrego, Isaac Anthony; ...

2017-05-26

Disentangling the relative impacts of precipitation reduction and vapour pressure deficit ( VPD) on plant water dynamics and determining whether acclimation may influence these patterns in the future is an important challenge. Here, we report sap flux density ( FD), stomatal conductance ( Gs), hydraulic conductivity ( KL) and xylem anatomy in piñon pine ( Pinus edulis) and juniper ( Juniperus monosperma) trees subjected to five years of precipitation reduction, atmospheric warming (elevated VPD) and their combined effects. No acclimation occurred under precipitation reduction: lower Gs and FD were found for both species compared to ambient conditions. Warming reduced themore » sensibility of stomata to VPD for both species but resulted in the maintenance of Gs and FD to ambient levels only for piñon. For juniper, reduced soil moisture under warming negated benefits of stomatal adjustments and resulted in reduced FD, Gs and KL. Although reduced stomatal sensitivity to VPD also occurred under combined stresses, reductions in Gs, FD and KL took place to similar levels as under single stresses for both species. Here our results show that stomatal conductance adjustments to high VPD could minimize but not entirely prevent additive effects of warming and drying on water use and carbon acquisition of trees in semi-arid regions.« less

Tree water dynamics in a drying and warming world

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grossiord, Charlotte; Sevanto, Sanna Annika; Borrego, Isaac Anthony

Disentangling the relative impacts of precipitation reduction and vapour pressure deficit ( VPD) on plant water dynamics and determining whether acclimation may influence these patterns in the future is an important challenge. Here, we report sap flux density ( FD), stomatal conductance ( Gs), hydraulic conductivity ( KL) and xylem anatomy in piñon pine ( Pinus edulis) and juniper ( Juniperus monosperma) trees subjected to five years of precipitation reduction, atmospheric warming (elevated VPD) and their combined effects. No acclimation occurred under precipitation reduction: lower Gs and FD were found for both species compared to ambient conditions. Warming reduced themore » sensibility of stomata to VPD for both species but resulted in the maintenance of Gs and FD to ambient levels only for piñon. For juniper, reduced soil moisture under warming negated benefits of stomatal adjustments and resulted in reduced FD, Gs and KL. Although reduced stomatal sensitivity to VPD also occurred under combined stresses, reductions in Gs, FD and KL took place to similar levels as under single stresses for both species. Here our results show that stomatal conductance adjustments to high VPD could minimize but not entirely prevent additive effects of warming and drying on water use and carbon acquisition of trees in semi-arid regions.« less

Increased water deficit decreases Douglas fir growth throughout western US forests.

PubMed

Restaino, Christina M; Peterson, David L; Littell, Jeremy

2016-08-23

Changes in tree growth rates can affect tree mortality and forest feedbacks to the global carbon cycle. As air temperature increases, evaporative demand also increases, increasing effective drought in forest ecosystems. Using a spatially comprehensive network of Douglas fir (Pseudotsuga menziesii) chronologies from 122 locations that represent distinct climate environments in the western United States, we show that increased temperature decreases growth via vapor pressure deficit (VPD) across all latitudes. Using an ensemble of global circulation models, we project an increase in both the mean VPD associated with the lowest growth extremes and the probability of exceeding these VPD values. As temperature continues to increase in future decades, we can expect deficit-related stress to increase and consequently Douglas fir growth to decrease throughout its US range.

Increased water deficit decreases Douglas fir growth throughout western US forests

PubMed Central

Restaino, Christina M.; Peterson, David L.; Littell, Jeremy

2016-01-01

Changes in tree growth rates can affect tree mortality and forest feedbacks to the global carbon cycle. As air temperature increases, evaporative demand also increases, increasing effective drought in forest ecosystems. Using a spatially comprehensive network of Douglas fir (Pseudotsuga menziesii) chronologies from 122 locations that represent distinct climate environments in the western United States, we show that increased temperature decreases growth via vapor pressure deficit (VPD) across all latitudes. Using an ensemble of global circulation models, we project an increase in both the mean VPD associated with the lowest growth extremes and the probability of exceeding these VPD values. As temperature continues to increase in future decades, we can expect deficit-related stress to increase and consequently Douglas fir growth to decrease throughout its US range. PMID:27503880

Measurement of transpiration in Pinus taeda L. and Liquidambar styraciflua L. in an environmental chamber using tritiated water

NASA Technical Reports Server (NTRS)

Levy, G. F.; Sonenshine, D. E.; Czoch, J. K.

1976-01-01

Transpiration rates of loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) were measured at two different atmospheric water vapor pressure deficits (V.P.D.) in a controlled environment growth chamber using tritiated water as a tracer. The trees were maintained in a sealed plant bed containing a hydroponic nutrient solution into which labeled water (spike) was introduced. Samples of leaves, chamber air, spiked nutrient solution and control water were assayed for ratio-activity using liquid scintillation techniques to determine transpiration rates. The transpiration rate of sweetgum in ml./hr./gm. (4.95) was found to be 5 times greater than that of loblolly pine (1.03) at 1.84 V.P.D. and 8 times greater at 6.74 V.P.D. (15.99 for sweetgum vs. 2.19 for pine). Transpiration (based on measurements of leaf radioactivity) in both species rose with increasing deficit; however sweetgum increased its output by 3 times while pine only doubled its rate. Cyclical changes in transpiration rates were noted in both species; the sweetgum cycle required a 6 hour interval whereas the pine cycle required a 9 hour interval.

Evaluation of Water Use Efficiency of Short Rotation Poplar Coppice at Bohemian-Moravian Highlands

NASA Astrophysics Data System (ADS)

Hlaváčová, Marcela; Fischer, Milan; Mani Tripathi, Abhishek; Orság, Matěj; Trnka, Miroslav

2015-04-01

The water availability of the locality constitutes one of the main constraint for short rotation coppices grown on arable land. As a convenient characteristic assessing how the water use is coupled with the biomass yields, so called water use efficiency (WUE) is proposed. One method of water use efficiency determination is presented within this study. The study was carried out at short rotation poplar coppice (poplar clone J-105) at the Test Station Domanínek, Ltd. at Bohemian-Moravian Highlands during the growing season 2013. Diameters at breast height (DBH) were measured for 16 sample trees where sap flow measuring systems (Granier's Thermal Dissipation Probe, TDP) were installed. TDP outputs are expressed as temperature differences (ΔT) between the heated and non-heated probes. Estimation of sap flux density (Fd) by the Granier method relies on the measurement of temperature difference (ΔT). Determination of maximum temperature difference (ΔTmax) is fundamental for sap flux density (Fd) calculation. Although ΔTmax can be theoretically defined as ΔT at Fd = 0, many factors may prevent the occurrence of the zero flow state, such as night-time water movement for new growth (vegetative or reproductive) or water loss from the canopy due to high vapour pressure deficit (VPD). Therefore, the VPD condition was established for determination of ΔTmax. VPD condition was established as follows: VPD reaching values 0.2 at least 6 hours during night (from 21 p. m. to 3 a. m. and when the condition was fullfilled, the value at 3 a. m. was taken) because it is a supposed time after that the tree has no transpiration. The programmable part of Mini 32 software (www.emsbrno.cz) was used for application of the script establishing ΔTmax values under this VPD condition. Nevertheless, another script was applied on ΔT data set to determination of ΔTmax values for every night at 3 a. m. (as this is when ΔT should be at its daily maximum) without VPD condition restriction for comparison of both approaches. Since application of the two mentioned scripts led to two sets of resulting values, calculations of Fd and consequent sap flow values were computed for both variants of ΔTmaxvalues. The sample trees were divided into 3 diameter classes according to DBH values at the beginning of regular measurements (April 24, 2013). Allometry was carried out on February 20, 2014 to calculation of aboveground woody biomass. The input data for calculations of WUE of aboveground woody biomass productivity was biomass increments and monthly totals of sap flow for 16 sample trees. The total WUE for 16 measured trees reached 4.93 g kg-1 (when calculated with data set without VPD condition) and 4.63 g kg-1 (when calculated with data set under VPD condition). This study was funded by project "Building up a multidisciplinary scientific team focused on drought" No. CZ.1.07/2.3.00/20.0248 and LD130030 supporting COST Action ES1106.

Tree ring δ18O reveals no long-term change of atmospheric water demand since 1800 in the northern Great Hinggan Mountains, China

NASA Astrophysics Data System (ADS)

Liu, Xiaohong; Zhang, Xuanwen; Zhao, Liangju; Xu, Guobao; Wang, Lixin; Sun, Weizhen; Zhang, Qiuliang; Wang, Wenzhi; Zeng, Xiaomin; Wu, Guoju

2017-07-01

Global warming will significantly increase transpirational water demand, which could dramatically affect plant physiology and carbon and water budgets. Tree ring δ18O is a potential index of the leaf-to-air vapor-pressure deficit (VPD) and therefore has great potential for long-term climatic reconstruction. Here we developed δ18O chronologies of two dominant native trees, Dahurian larch (Larix gmelinii Rupr.) and Mongolian pine (Pinus sylvestris var. mongolica), from a permafrost region in the Great Hinggan Mountains of northeastern China. We found that the July-August VPD and relative humidity were the dominant factors that controlled tree ring δ18O in the study region, indicating strong regulation of stomatal conductance. Based on the larch and pine tree ring δ18O chronologies, we developed a reliable summer (July-August) VPD reconstruction since 1800. Warming growing season temperatures increase transpiration and enrich cellulose 18O, but precipitation seemed to be the most important influence on VPD changes in this cold region. Periods with stronger transpirational demand occurred around the 1850s, from 1914 to 1925, and from 2005 to 2010. However, we found no overall long-term increasing or decreasing trends for VPD since 1800, suggesting that despite the increasing temperatures and thawing permafrost throughout the region, forest transpirational demand has not increased significantly during the past two centuries. Under current climatic conditions, VPD did not limit growth of larch and pine, even during extremely drought years. Our findings will support more realistic evaluations and reliable predictions of the potential influences of ongoing climatic change on carbon and water cycles and on forest dynamics in permafrost regions.

Stomatal dynamics are limited by leaf hydraulics in ferns and conifers: results from simultaneous measurements of liquid and vapour fluxes in leaves.

PubMed

Martins, Samuel C V; McAdam, Scott A M; Deans, Ross M; DaMatta, Fábio M; Brodribb, Tim J

2016-03-01

Stomatal responsiveness to vapour pressure deficit (VPD) results in continuous regulation of daytime gas-exchange directly influencing leaf water status and carbon gain. Current models can reasonably predict steady-state stomatal conductance (gs ) to changes in VPD but the gs dynamics between steady-states are poorly known. Here, we used a diverse sample of conifers and ferns to show that leaf hydraulic architecture, in particular leaf capacitance, has a major role in determining the gs response time to perturbations in VPD. By using simultaneous measurements of liquid and vapour fluxes into and out of leaves, the in situ fluctuations in leaf water balance were calculated and appeared to be closely tracked by changes in gs thus supporting a passive model of stomatal control. Indeed, good agreement was found between observed and predicted gs when using a hydropassive model based on hydraulic traits. We contend that a simple passive hydraulic control of stomata in response to changes in leaf water status provides for efficient stomatal responses to VPD in ferns and conifers, leading to closure rates as fast or faster than those seen in most angiosperms. © 2015 John Wiley & Sons Ltd.

Renal, metabolic, and hormonal responses to proteins of different origin in normotensive, nonproteinuric type I diabetic patients.

PubMed

Kontessis, P A; Bossinakou, I; Sarika, L; Iliopoulou, E; Papantoniou, A; Trevisan, R; Roussi, D; Stipsanelli, K; Grigorakis, S; Souvatzoglou, A

1995-09-01

Whether the differences in renal function found in vegetarian compared with omnivorous subjects are related to quantity or quality of the protein is unknown. We have studied the renal function of nine normotensive, nonproteinuric type I diabetic patients who were fed in random order for 4 weeks either an animal protein diet (APD) (protein intake 1.1 g . kg-1 . day-1) or a vegetable protein diet VPD (protein intake 0.95 g . kg-1 . day-1). The two diets were isocaloric. In a crossover study, we measured glomerular filtration rate (GFR) (inulin clearance), renal plasma flow (RPF) (p-aminohippurate clearance), plasma amino acids, growth hormone, glucagon, insulin-like growth factor I-(IGF-I), and microalbuminuria. GFR and RPF were lower with the VPD than with the APD (89.9 +/- 4.1 vs. 105.6 +/- 5.1 ml . min-1 . 1.73 m-2, P < 0.05, and 425.7 +/- 22.2 vs. 477.8 +/- 32.2 ml . min-1 1.73m-2, P < 0.05, respectively). Renal vascular resistance (RVR) was higher with the VPD than with the APD (101 +/- 25 vs. 91 +/- 10 mmHg . min-1 . ml-1, P < 0.05). Filtration fraction (FF) remained unchanged after either diet. Fractional clearance of albumin fell with the VPD to 2.0 +/- 0.65 from 3.4 +/- 1.15 x 10-6 (P < 0.05). At the end of the APD and VPD, the plasma levels of growth hormone and glucagon did not differ significantly. Plasma levels of IGF-I were higher with the APD than with the VPD (1.1 +/- 0.6 vs. 0.9 +/- 0.13 U/ml, P < 0.05). Plasma concentrations of valine and lysine were significantly higher with the APD than with the VPD (234.6 +/- 30.3 vs. 164.5 +/- 25.4 mm1/1, P < 0.05, and 565 +/- 45.1 vs. 430 +/- 56.1 mmol/l, P < 0.05, respectively), whereas plasma valine was strongly correlated to the GFR (r = 0.832, P < 0.01). No differences were found in other amino acids. A VPD has significantly different renal effects from an APD equal in protein intake in normotensive type I diabetic patients. This could be explained partly by differences in plasma concentrations of amino acids and IGF-I.

Cephalometric findings among children with velopharyngeal dysfunction following adenoidectomy-A retrospective study.

PubMed

Kassem, F; Ebner, Y; Nageris, B; Watted, N; DeRowe, A; Nachmani, A

2017-12-01

To characterise the craniofacial structure by cephalometry, especially the skull base and nasopharyngeal space, in children who underwent adenoidectomy and developed persistent velopharyngeal dysfunction (VPD). Retrospective study. Speech and swallowing clinic of a single academic hospital. Thirty-nine children with persistent VPD following adenoidectomy (mean age 8.0±3.6 years) and a control group of 80 healthy children. Cephalometric landmarks were chosen; craniofacial linear and angular dimensions were measured and analysed. The linear dimensions of the nasopharyngeal area were shorter in the VPD group, S-Ba (41.6±4.2 mm, P<.05) and S-Ptm (42.4±5.1 mm, P<.05). The anterior skull base, N-S, was similar (68.1 mm±6.8). The velum length, Ptm-P was significantly shorter in the VPD group (27.8±4.3 mm, P<.001). The Ba-S-Ptm angle was significantly larger in the VPD group (63.5±5.6°, P<.001). There was no significant difference in cranial base angle (CBA), Ba-S-N, between the two groups. Cephalometry may provide information regarding persistent postoperative VPD. The nasopharyngeal space angle and velar length appear to be risk factors for persistent VPD after adenoidectomy. © 2017 John Wiley & Sons Ltd.

Photosynthesis, Transpiration, Leaf Temperature, and Stomatal Activity of Cotton Plants under Varying Water Potentials

PubMed Central

Pallas, J. E.; Michel, B. E.; Harris, D. G.

1967-01-01

Cotton plants, Gossypium hirsutum L. were grown in a growth room under incident radiation levels of 65, 35, and 17 Langleys per hour to determine the effects of vapor pressure deficits (VPD's) of 2, 9, and 17 mm Hg at high soil water potential, and the effects of decreasing soil water potential and reirrigation on transpiration, leaf temperature, stomatal activity, photosynthesis, and respiration at a VPD of 9 mm Hg. Transpiration was positively correlated with radiation level, air VPD and soil water potential. Reirrigation following stress led to slow recovery, which may be related to root damage occurring during stress. Leaf water potential decreased with, but not as fast as, soil water potential. Leaf temperature was usually positively correlated with light intensity and negatively correlated with transpiration, air VPD, and soil water. At high soil water, leaf temperatures ranged from a fraction of 1 to a few degrees above ambient, except at medium and low light and a VPD of 19 mm Hg when they were slightly below ambient, probably because of increased transpirational cooling. During low soil water leaf temperatures as high as 3.4° above ambient were recorded. Reirrigation reduced leaf temperature before appreciably increasing transpiration. The upper leaf surface tended to be warmer than the lower at the beginning of the day and when soil water was adequate; otherwise there was little difference or the lower surface was warmer. This pattern seemed to reflect transpiration cooling and leaf position effects. Although stomata were more numerous in the lower than the upper epidermis, most of the time a greater percentage of the upper were open. With sufficient soil water present, stomata opened with light and closed with darkness. Fewer stomata opened under low than high light intensity and under even moderate, as compared with high soil water. It required several days following reirrigation for stomata to regain original activity levels. Apparent photosynthesis of cotton leaves occasionally oscillated with variable amplitude and frequency. When soil water was adequate, photosynthesis was nearly proportional to light intensity, with some indication of higher rates at higher VPD's. As soil water decreased, photosynthesis first increased and then markedly decreased. Following reirrigation, photosynthesis rapidly recovered. Respiration was slowed moderately by decreasing soil water but increased before watering. Respiration slowed with increasing leaf age only on leaves that were previously under high light intensity. PMID:16656488

Environmental and physiological effects on grouping of drought-tolerant and susceptible rice varieties related to rice (Oryza sativa) root hydraulics under drought

PubMed Central

Henry, Amelia; Wehler, Regina; Grondin, Alexandre; Franke, Rochus; Quintana, Marinell

2016-01-01

Background and Aims Root hydraulic limitations (i.e. intra-plant restrictions to water movement) may be related to crop performance under drought, and groupings in the hydraulic function of drought-tolerant and drought-susceptible rice (Oryza sativa) varieties have been previously reported. This study aimed to better understand the environmental and physiological relationships with rice root hydraulics under drought. Methods Xylem sap bleeding rates in the field (gsap g–1 shoot) were measured on seasonal and diurnal time frames, during which time environmental conditions were monitored and physiological measurements were conducted. Complementary experiments on the effects of vapour pressure deficit (VPD) on root hydraulic conductivity and on transpiration rates of de-rooted tillers were conducted in growth chambers. Key Results The diurnal effects on bleeding rate were more closely related to irradiance than VPD, and VPD effects on root hydraulic conductivity measured on 21-day-old plants were due to effects on plant growth including root surface area, maximum root depth and root:shoot ratio. Leaf osmotic potential was related to the grouping of drought-tolerant and drought-susceptible varieties in rice root hydraulics, and these groupings were independent of differences in phenology. Low single-tiller bleeding rates were observed under high evapo-transpirational demand, higher bleeding rates were observed at more negative leaf osmotic potentials in drought-susceptible varieties, and drought-tolerant and susceptible varieties differed in the VPD-induced increase in transpiration rates of de-rooted tillers. Low root suberin amounts in some of the drought-susceptible varieties may have resulted in higher ion transport, as evidenced by higher sap K+ concentration and higher bleeding rates in those varieties. Conclusions These results provide evidence of the environmental effects on shoots that can influence root hydraulics. The consistent groupings of drought-tolerant and susceptible varieties suggest that traits affecting plant osmotic status may regulate root hydraulic response to drought in rice. PMID:27192712

Vapor Pressure Deficit and Sap Velocity Dynamic Coupling in Canopy Dominant Trees in the Amazon basin

NASA Astrophysics Data System (ADS)

Chambers, J. Q.; Gimenez, B.; Jardine, K.; Negron Juarez, R. I.; Cobello, L. O.; Fontes, C.; Dawson, T. E.; Higuchi, N.

2017-12-01

In order to improve our ability to predict terrestrial water fluxes, an understanding of the interactions between plant physiology and environmental conditions is necessary, especially in tropical forests which recycle large fluxes of water to the atmosphere. This need has become more relevant due to observed records in global temperature. In this study we show a strong temporal correlation between sap velocity and leaf-to-air vapor pressure deficit (VPD) in canopy dominant trees in two primary rainforest sites in the Amazon basin (Santarém and Manaus, Brazil). As VPDs in the upper canopy (20-30 m) varied throughout the day and night, basal sap velocity (1.5 m) responded rapidly without an observable delay (< 15 min). Sap velocity showed a sigmoidal dependence on VPDs including an exponential increase, an inflection point, and a plateau, in all observed trees. Moreover, a clear diurnal hysteresis in sap velocity, stomatal conductance, and leaf water potential was evident with morning periods showing higher sensitivities to VPD than afternoon and night periods. Diurnal leaf gas exchange observations revealed a morning to midday peak in stomatal conductance, but midday to afternoon peak in transpiration and VPD. Thus, our study confirms that the temporal lag between the Gs peak and VPD peak are the major regulators of the hysteresis phenomenon as previously described by other studies. Moreover, out study provide direct evidence for the role of decreased stomatal conductance in the warm afternoon periods to reduce transpiration and allow for the partial recovery of leaf water potential to less negative values. Our results suggests the possibility of predicting evapotranspiration fluxes from ecosystem to regional scales using remote sensing of vegetation temperature from, for example, thermal images of satellites and drones.

Manipulative experiments demonstrate how long-term soil moisture changes alter controls of plant water use

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grossiord, Charlotte; Sevanto, Sanna Annika; Limousin, Jean -Marc

Tree transpiration depends on biotic and abiotic factors that might change in the future, including precipitation and soil moisture status. Although short-term sap flux responses to soil moisture and evaporative demand have been the subject of attention before, the relative sensitivity of sap flux to these two factors under long-term changes in soil moisture conditions has rarely been determined experimentally. We tested how long-term artificial change in soil moisture affects the sensitivity of tree-level sap flux to daily atmospheric vapor pressure deficit ( VPD) and soil moisture variations, and the generality of these effects across forest types and environments usingmore » four manipulative sites in mature forests. Exposure to relatively long-term (two to six years) soil moisture reduction decreases tree sap flux sensitivity to daily VPD and relative extractable water ( REW) variations, leading to lower sap flux even under high soil moisture and optimal VPD. Inversely, trees subjected to long-term irrigation showed a significant increase in their sensitivity to daily VPD and REW, but only at the most water-limited site. The ratio between the relative change in soil moisture manipulation and the relative change in sap flux sensitivity to VPD and REW variations was similar across sites suggesting common adjustment mechanisms to long-term soil moisture status across environments for evergreen tree species. Altogether, our results show that long-term changes in soil water availability, and subsequent adjustments to these novel conditions, could play a critical and increasingly important role in controlling forest water use in the future.« less

Manipulative experiments demonstrate how long-term soil moisture changes alter controls of plant water use

DOE PAGES

Grossiord, Charlotte; Sevanto, Sanna Annika; Limousin, Jean -Marc; ...

2017-12-14

Tree transpiration depends on biotic and abiotic factors that might change in the future, including precipitation and soil moisture status. Although short-term sap flux responses to soil moisture and evaporative demand have been the subject of attention before, the relative sensitivity of sap flux to these two factors under long-term changes in soil moisture conditions has rarely been determined experimentally. We tested how long-term artificial change in soil moisture affects the sensitivity of tree-level sap flux to daily atmospheric vapor pressure deficit ( VPD) and soil moisture variations, and the generality of these effects across forest types and environments usingmore » four manipulative sites in mature forests. Exposure to relatively long-term (two to six years) soil moisture reduction decreases tree sap flux sensitivity to daily VPD and relative extractable water ( REW) variations, leading to lower sap flux even under high soil moisture and optimal VPD. Inversely, trees subjected to long-term irrigation showed a significant increase in their sensitivity to daily VPD and REW, but only at the most water-limited site. The ratio between the relative change in soil moisture manipulation and the relative change in sap flux sensitivity to VPD and REW variations was similar across sites suggesting common adjustment mechanisms to long-term soil moisture status across environments for evergreen tree species. Altogether, our results show that long-term changes in soil water availability, and subsequent adjustments to these novel conditions, could play a critical and increasingly important role in controlling forest water use in the future.« less

Manipulative experiments demonstrate how long-term soil moisture changes alter controls of plant water use

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grossiord, Charlotte; Sevanto, Sanna; Limousin, Jean-Marc

Tree transpiration depends on biotic and abiotic factors that might change in the future, including precipitation and soil moisture status. Although short-term sap flux responses to soil moisture and evaporative demand have been the subject of attention before, the relative sensitivity of sap flux to these two factors under long-term changes in soil moisture conditions has rarely been determined experimentally. We tested how long-term artificial change in soil moisture affects the sensitivity of tree-level sap flux to daily atmospheric vapor pressure deficit (VPD) and soil moisture variations, and the generality of these effects across forest types and environments using fourmore » manipulative sites in mature forests. Exposure to relatively long-term (two to six years) soil moisture reduction decreases tree sap flux sensitivity to daily VPD and relative extractable water (REW) variations, leading to lower sap flux even under high soil moisture and optimal VPD. Inversely, trees subjected to long-term irrigation showed a significant increase in their sensitivity to daily VPD and REW, but only at the most water-limited site. The ratio between the relative change in soil moisture manipulation and the relative change in sap flux sensitivity to VPD and REW variations was similar across sites suggesting common adjustment mechanisms to long-term soil moisture status across environments for evergreen tree species. Overall, our results show that long-term changes in soil water availability, and subsequent adjustments to these novel conditions, could play a critical and increasingly important role in controlling forest water use in the future.« less

Effects of nitrogen and vapour pressure deficit on phytomer growth and development in a C4 grass.

PubMed

Yang, Fang; Gong, Xiao Ying; Liu, Hai Tao; Schäufele, Rudi; Schnyder, Hans

2016-01-01

Phytomers are basic morphological units of plants. Knowledge of phytomer development is essential for understanding morphological plasticity, functional-structural modelling of plant growth and the usage of leaf characteristics to indicate growth conditions at the time of production (e.g. stable isotope signals). Yet, systematic analysis on the process of phytomer development is unavailable for wild or perennial C 4 grasses. Also, effects of environmental factors, such as nitrogen nutrition or vapour pressure deficit (VPD), on coordination events of developmental processes of C 4 grasses have not been studied. This study investigates phytomer growth and development in Cleistogenes squarrosa, a predominant C 4 grass in the Eurasian steppe, grown at low (0.63 kPa) or high (1.58 kPa) VPD with low or high nitrogen supply in controlled environments. Elongation of phytomers on marked tillers was measured daily for 13 days. Then lengths of immature and mature phytomer components (blade, sheath and internode) of all phytomers were measured following dissection. Nitrogen nutrition and VPD had no effects on coordination of growth within and between phytomers: phytomer tips emerged when phytomers reached 26 % of their final length, coincident with the acceleration phase of its elongation; blade elongation stopped when phytomers reached ∼75 % of their final length and elongation of the preceding phytomer was confined to the internode. The relationship between fraction of final phytomer length and days after tip emergence for all treatments was well described by a sigmoidal function: y = 1/{1 + exp[(1.82 - x)/1.81]}. C. squarrosa exhibited little morphological plasticity at phytomer-level in response to nitrogen supply and VPD, but a clear increase in tillering under high N supply. Also, the invariant coordination of elongation within and between phytomers was a stable developmental feature, thus the quantitative coordination rules are applicable for predicting morphological development of C. squarrosa under contrasting levels of nitrogen nutrition or VPD. © The Authors 2016. Published by Oxford University Press on behalf of the Annals of Botany Company.

Impact of water use efficiency on eddy covariance flux partitioning using correlation structure analysis

NASA Astrophysics Data System (ADS)

Anderson, Ray; Skaggs, Todd; Alfieri, Joseph; Kustas, William; Wang, Dong; Ayars, James

2016-04-01

Partitioned land surfaces fluxes (e.g. evaporation, transpiration, photosynthesis, and ecosystem respiration) are needed as input, calibration, and validation data for numerous hydrological and land surface models. However, one of the most commonly used techniques for measuring land surface fluxes, Eddy Covariance (EC), can directly measure net, combined water and carbon fluxes (evapotranspiration and net ecosystem exchange/productivity). Analysis of the correlation structure of high frequency EC time series (hereafter flux partitioning or FP) has been proposed to directly partition net EC fluxes into their constituent components using leaf-level water use efficiency (WUE) data to separate stomatal and non-stomatal transport processes. FP has significant logistical and spatial representativeness advantages over other partitioning approaches (e.g. isotopic fluxes, sap flow, microlysimeters), but the performance of the FP algorithm is reliant on the accuracy of the intercellular CO2 (ci) concentration used to parameterize WUE for each flux averaging interval. In this study, we tested several parameterizations for ci as a function of atmospheric CO2 (ca), including (1) a constant ci/ca ratio for C3 and C4 photosynthetic pathway plants, (2) species-specific ci/ca-Vapor Pressure Deficit (VPD) relationships (quadratic and linear), and (3) generalized C3 and C4 photosynthetic pathway ci/ca-VPD relationships. We tested these ci parameterizations at three agricultural EC towers from 2011-present in C4 and C3 crops (sugarcane - Saccharum officinarum L. and peach - Prunus persica), and validated again sap-flow sensors installed at the peach site. The peach results show that the species-specific parameterizations driven FP algorithm came to convergence significantly more frequently (~20% more frequently) than the constant ci/ca ratio or generic C3-VPD relationship. The FP algorithm parameterizations with a generic VPD relationship also had slightly higher transpiration (5 Wm-2 difference) than the constant ci/ca ratio. However, photosynthesis and respiration fluxes over sugarcane were ~15% lower with a VPD-ci/ca relationship than a constant ci/ca ratio. The results illustrate the importance of combining leaf-level physiological observations with EC to improve the performance of the FP algorithm.

The effect of nasopharyngoscopic biofeedback in patients with cleft palate and velopharyngeal dysfunction.

PubMed

Brunner, Monika; Stellzig-Eisenhauer, Angelika; Pröschel, Ute; Verres, Rolf; Komposch, Gerda

2005-11-01

To evaluate the immediate, long-term, and carry-over effects of nasopharyngoscopic biofeedback therapy in patients with cleft palate who exhibit velopharyngeal dysfunction (VPD). Pre- versus posttreatment and follow-up comparisons. Cleft palate center of the Heidelberg University Hospital, Heidelberg, Germany. Eleven patients with VPD who had received conventional speech therapy without showing significant improvement. A four-stage feedback procedure. The patients watched and evaluated their velopharyngeal (VP) valving during speech by an endoscopic image displayed on a video monitor. Two feedback sessions took place for every target sound. Mean occurrence of VP closure during speech sound production on different linguistic levels. Patients' self-perception was assessed by a questionnaire and speech diary. Significant improvement and stability of VP closure was noted. Mean occurrence of VP closure was 5% before therapy, 91% after two biofeedback sessions, and 86% in the follow-up after 6 months. Velopharyngeal dysfunction associated with compensatory articulation proved to be equally well trained as VPD on sounds with good articulatory placement. No significant difference was observed in the degree of improvement between phoneme-specific VPD and generalized VPD. The transfer to the level of words and sentences was successful and showed significant stability. The stability of VP closure for vowels was less than the stability for fricatives and stop sounds. Patients gained improved auditory and kinesthetic self-perception of their articulation. Nasopharyngoscopic biofeedback therapy proves to be a quick and effective method to change VPD. It shows stable results and carry-over effects.

The importance of radiation for semiempirical water-use efficiency models

NASA Astrophysics Data System (ADS)

Boese, Sven; Jung, Martin; Carvalhais, Nuno; Reichstein, Markus

2017-06-01

Water-use efficiency (WUE) is a fundamental property for the coupling of carbon and water cycles in plants and ecosystems. Existing model formulations predicting this variable differ in the type of response of WUE to the atmospheric vapor pressure deficit of water (VPD). We tested a representative WUE model on the ecosystem scale at 110 eddy covariance sites of the FLUXNET initiative by predicting evapotranspiration (ET) based on gross primary productivity (GPP) and VPD. We found that introducing an intercept term in the formulation increases model performance considerably, indicating that an additional factor needs to be considered. We demonstrate that this intercept term varies seasonally and we subsequently associate it with radiation. Replacing the constant intercept term with a linear function of global radiation was found to further improve model predictions of ET. Our new semiempirical ecosystem WUE formulation indicates that, averaged over all sites, this radiation term accounts for up to half (39-47 %) of transpiration. These empirical findings challenge the current understanding of water-use efficiency on the ecosystem scale.

Turning over a new 'leaf': multiple functional significances of leaves versus phyllodes in Hawaiian Acacia koa.

PubMed

Pasquet-Kok, Jessica; Creese, Christine; Sack, Lawren

2010-12-01

Hawaiian endemic tree Acacia koa is a model for heteroblasty with bipinnately compound leaves and phyllodes. Previous studies suggested three hypotheses for their functional differentiation: an advantage of leaves for early growth or shade tolerance, and an advantage of phyllodes for drought tolerance. We tested the ability of these hypotheses to explain differences between leaf types for potted plants in 104 physiological and morphological traits, including gas exchange, structure and composition, hydraulic conductance, and responses to varying light, intercellular CO(2) , vapour pressure deficit (VPD) and drought. Leaf types were similar in numerous traits including stomatal pore area per leaf area, leaf area-based gas exchange rates and cuticular conductance. Each hypothesis was directly supported by key differences in function. Leaves had higher mass-based gas exchange rates, while the water storage tissue in phyllodes contributed to greater capacitance per area; phyllodes also showed stronger stomatal closure at high VPD, and higher maximum hydraulic conductance per area, with stronger decline during desiccation and recovery with rehydration. While no single hypothesis completely explained the differences between leaf types, together the three hypotheses explained 91% of differences. These findings indicate that the heteroblasty confers multiple benefits, realized across different developmental stages and environmental contexts. © 2010 Blackwell Publishing Ltd.

Craniofacial structure variations in patients with palatal anomalies and velopharyngeal dysfunction.

PubMed

Nachmani, Ariela; Aizenbud, Dror; Nageris, Ben; Emodi, Omri; Kassem, Firas

2017-02-01

Cephalometric evaluation of craniofacial and craniopharyngeal morphology is important for understanding the factors affecting velopharyngeal dysfunction (VPD) in patients with palatal anomalies. In this study, 366 patients with VPD were retrospectively stratified into cleft lip and palate (CLP), cleft palate (CP), submucous cleft palate (SMCP), occult submucous cleft palate (OSMCP), and non-CP groups. Lateral cephalometrics were used to assess craniofacial, craniopharyngeal, and velopharyngeal anatomy. The average craniofacial morphology in patients with VPD differed significantly according to the type of palatal anomaly. The non-CP and OSMCP groups differed from the CLP, CP, and SMCP groups in nasopharyngeal size and shape as depicted by a larger ANS-Ptm-Ve angle, a smaller S-N-Ba and NBa-PP angles, and a shorter linear value of S-Ar in the non-CP group. The CLP and CP groups had shorter ANS-Ptm, shorter Ptm-P, and smaller SNA and SNB angles. VPD patients with overt clefts have different skeletal and nasopharyngeal shapes compared to non-CP and OSMCP. Velopharyngeal function assessment should include the size and shape of the nasopharyngeal space in addition to the size and the activity of the velum and posterior and lateral walls of the nasopharynx. This should enable a more precise understanding of VPD pathology, and lead to improvements in the posterior pharyngeal flap technique in order to obtain better postoperative speech outcomes after surgical management of velopharyngeal dysfunction. Copyright © 2016 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Acclimation of Biochemical and Diffusive Components of Photosynthesis in Rice, Wheat, and Maize to Heat and Water Deficit: Implications for Modeling Photosynthesis

PubMed Central

Perdomo, Juan A.; Carmo-Silva, Elizabete; Hermida-Carrera, Carmen; Flexas, Jaume; Galmés, Jeroni

2016-01-01

The impact of the combined effects of heat stress, increased vapor pressure deficit (VPD) and water deficit on the physiology of major crops needs to be better understood to help identifying the expected negative consequences of climate change and heat waves on global agricultural productivity. To address this issue, rice, wheat, and maize plants were grown under control temperature (CT, 25°C, VPD 1.8 kPa), and a high temperature (HT, 38°C, VPD 3.5 kPa), both under well-watered (WW) and water deficit (WD) conditions. Gas-exchange measurements showed that, in general, WD conditions affected the leaf conductance to CO2, while growth at HT had a more marked effect on the biochemistry of photosynthesis. When combined, HT and WD had an additive effect in limiting photosynthesis. The negative impacts of the imposed treatments on the processes governing leaf gas-exchange were species-dependent. Wheat presented a higher sensitivity while rice and maize showed a higher acclimation potential to increased temperature. Rubisco and PEPC kinetic constants determined in vitro at 25°C and 38°C were used to estimate Vcmax, Jmax, and Vpmax in the modeling of C3 and C4 photosynthesis. The results here obtained reiterate the need to use species-specific and temperature-specific values for Rubisco and PEPC kinetic constants for a precise parameterization of the photosynthetic response to changing environmental conditions in different crop species. PMID:27920782

Environmental and physiological effects on grouping of drought-tolerant and susceptible rice varieties related to rice (Oryza sativa) root hydraulics under drought.

PubMed

Henry, Amelia; Wehler, Regina; Grondin, Alexandre; Franke, Rochus; Quintana, Marinell

2016-05-02

Root hydraulic limitations (i.e. intra-plant restrictions to water movement) may be related to crop performance under drought, and groupings in the hydraulic function of drought-tolerant and drought-susceptible rice (Oryza sativa) varieties have been previously reported. This study aimed to better understand the environmental and physiological relationships with rice root hydraulics under drought. Xylem sap bleeding rates in the field (g sap g -1 shoot ) were measured on seasonal and diurnal time frames, during which time environmental conditions were monitored and physiological measurements were conducted. Complementary experiments on the effects of vapour pressure deficit (VPD) on root hydraulic conductivity and on transpiration rates of de-rooted tillers were conducted in growth chambers. The diurnal effects on bleeding rate were more closely related to irradiance than VPD, and VPD effects on root hydraulic conductivity measured on 21-day-old plants were due to effects on plant growth including root surface area, maximum root depth and root:shoot ratio. Leaf osmotic potential was related to the grouping of drought-tolerant and drought-susceptible varieties in rice root hydraulics, and these groupings were independent of differences in phenology. Low single-tiller bleeding rates were observed under high evapo-transpirational demand, higher bleeding rates were observed at more negative leaf osmotic potentials in drought-susceptible varieties, and drought-tolerant and susceptible varieties differed in the VPD-induced increase in transpiration rates of de-rooted tillers. Low root suberin amounts in some of the drought-susceptible varieties may have resulted in higher ion transport, as evidenced by higher sap K + concentration and higher bleeding rates in those varieties. These results provide evidence of the environmental effects on shoots that can influence root hydraulics. The consistent groupings of drought-tolerant and susceptible varieties suggest that traits affecting plant osmotic status may regulate root hydraulic response to drought in rice. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Analysis of vegetation dynamics and climatic variability impacts on greenness across Canada using remotely sensed data from 2000 to 2009

NASA Astrophysics Data System (ADS)

Fang, Xiuqin; Zhu, Qiuan; Chen, Huai; Ma, Zhihai; Wang, Weifeng; Song, Xinzhang; Zhao, Pengxiang; Peng, Changhui

2014-01-01

Using time series of moderate-resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) data from 2000 to 2009, we assessed decadal vegetation dynamics across Canada and examined the relationship between NDVI and climatic variables (precipitation and temperature). The Palmer drought severity index and vapor pressure difference (VPD) were used to relate the vegetation changes to the climate, especially in cases of drought. Results indicated that MODIS NDVI measurements provided a dynamic picture of interannual variation in Canadian vegetation patterns. Greenness declined in 2000, 2002, and 2009 and increased in 2005, 2006, and 2008. Vegetation dynamics varied across regions during the period. Most forest land shows little change, while vegetation in the ecozone of Pacific Maritime, Prairies, and Taiga Shield shows more dynamics than in the others. Significant correlations were found between NDVI and the climatic variables. The variation of NDVI resulting from climatic variability was more highly correlated to temperature than to precipitation in most ecozones. Vegetation grows better with higher precipitation and temperature in almost all ecozones. However, vegetation grows worse under higher temperature in the Prairies ecozone. The annual changes in NDVI corresponded well with the change in VPD in most ecozones.

Drivers of radial growth and carbon isotope discrimination of bur oak (Quercus macrocarpa Michx.) across continental gradients in precipitation, vapour pressure deficit and irradiance.

PubMed

Voelker, Steven L; Meinzer, Frederick C; Lachenbruch, Barbara; Brooks, J Renée; Guyette, Richard P

2014-03-01

Tree-ring characteristics are commonly used to reconstruct climate variables, but divergence from the assumption of a single biophysical control may reduce the accuracy of these reconstructions. Here, we present data from bur oaks (Quercus macrocarpa Michx.) sampled within and beyond the current species bioclimatic envelope to identify the primary environmental controls on ring-width indices (RWIs) and carbon stable isotope discrimination (Δ(13) C) in tree-ring cellulose. Variation in Δ(13) C and RWI was more strongly related to leaf-to-air vapour pressure deficit (VPD) at the centre and western edge of the range compared with the northern and wettest regions. Among regions, Δ(13) C of tree-ring cellulose was closely predicted by VPD and light responses of canopy-level Δ(13) C estimated using a model driven by eddy flux and meteorological measurements (R(2)  = 0.96, P = 0.003). RWI and Δ(13) C were positively correlated in the drier regions, while they were negatively correlated in the wettest region. The strength and direction of the correlations scaled with regional VPD or the ratio of precipitation to evapotranspiration. Therefore, the correlation strength between RWI and Δ(13) C may be used to infer past wetness or aridity from paleo wood by determining the degree to which carbon gain and growth have been more limited by moisture or light. © 2013 John Wiley & Sons Ltd.

The importance of radiation for semiempirical water-use efficiency models

DOE PAGES

Boese, Sven; Jung, Martin; Carvalhais, Nuno; ...

2017-06-22

Water-use efficiency (WUE) is a fundamental property for the coupling of carbon and water cycles in plants and ecosystems. Existing model formulations predicting this variable differ in the type of response of WUE to the atmospheric vapor pressure deficit of water (VPD). We tested a representative WUE model on the ecosystem scale at 110 eddy covariance sites of the FLUXNET initiative by predicting evapotranspiration (ET) based on gross primary productivity (GPP) and VPD. We found that introducing an intercept term in the formulation increases model performance considerably, indicating that an additional factor needs to be considered. We demonstrate that thismore » intercept term varies seasonally and we subsequently associate it with radiation. Replacing the constant intercept term with a linear function of global radiation was found to further improve model predictions of ET. Our new semiempirical ecosystem WUE formulation indicates that, averaged over all sites, this radiation term accounts for up to half (39–47 %) of transpiration. These empirical findings challenge the current understanding of water-use efficiency on the ecosystem scale.« less

Irrigation scheduling based on crop canopy temperature for humid environments

USDA-ARS?s Scientific Manuscript database

The use of infrared thermometers (IR) to measure canopy temperatures for irrigation scheduling has been successfully applied in arid environments. Functionality of this technique in humid areas has been limited due to the presence of low vapor pressure deficits (VPD) and intermittent cloud cover. T...

Regulation of Vapor Pressure Deficit by Greenhouse Micro-Fog Systems Improved Growth and Productivity of Tomato via Enhancing Photosynthesis during Summer Season

PubMed Central

Zhang, Dalong; Zhang, Zhongdian; Li, Jianming; Chang, Yibo; Du, Qingjie; Pan, Tonghua

2015-01-01

The role of a proposed micro-fog system in regulating greenhouse environments and enhancing tomato (Solanum lycopersicum L.) productivity during summer season was studied. Experiments were carried out in a multi-span glass greenhouse, which was divided into two identical compartments involving different environments: (1) without environment control and (2) with a micro-fog system operating when the air vapor pressure deficit (VPD) of greenhouse was higher than 0.5 KPa. The micro-fog system effectively alleviated heat stress and evaporative demand in the greenhouse during summer season. The physiologically favourable environment maintained by micro-fog treatment significantly enhanced elongation of leaf and stem, which contributed to a substantial elevation of final leaf area and shoot biomass. These improvements in physiological and morphological traits resulted in around 12.3% increase of marketable tomato yield per plant. Relative growth rate (RGR) of micro-fog treatment was also significantly higher than control plants, which was mainly determined by the substantial elevation in net assimilation rate (NAR), and to a lesser extent caused by leaf area ratio (LAR). Measurement of leaf gas exchange parameters also demonstrated that micro-fog treatment significantly enhanced leaf photosynthesis capacity. Taken together, manipulation of VPD in greenhouses by micro-fog systems effectively enhanced tomato growth and productivity via improving photosynthesis during summer season. PMID:26221726

Does vapor pressure deficit drive the seasonality of δ 13 C of the net land-atmosphere CO 2 exchange across the United States?: The Influence of VPD on δ 13 C of NEE

DOE PAGES

Raczka, B.; Biraud, S. C.; Ehleringer, J. R.; ...

2017-08-10

The seasonal pattern of the carbon isotope content (δ 13C) of atmospheric CO 2 depends on local and nonlocal land-atmosphere exchange and atmospheric transport. Previous studies suggested that the δ13C of the net land-atmosphere CO 2 flux (δsource) varies seasonally as stomatal conductance of plants responds to vapor pressure deficit of air (VPD). We studied the variation of δ source at seven sites across the United States representing forests, grasslands, and an urban center. Using a two-part mixing model, we calculated the seasonal δsource for each site after removing background influence and, when possible, removing δ 13C variation of nonlocalmore » sources. Compared to previous analyses, we found a reduced seasonal (March–September) variation in δ source at the forest sites (0.5‰variation). We did not find a consistent seasonal relationship between VPD and δ source across forest (or other) sites, providing evidence that stomatal response to VPD was not the cause of the global, coherent seasonal pattern in δsource. In contrast to the forest sites, grassland and urban sites had a larger seasonal variation in δ source (5‰) dominated by seasonal transitions in C 3/C 4 grass productivity and in fossil fuel emissions, respectively. Our findings were sensitive to the location used to account for atmospheric background variation within the mixing model method that determined δsource. Special consideration should be given to background location depending on whether the intent is to understand site level dynamics or regional scale impacts of land-atmosphere exchange. The seasonal amplitude in δ 13C of land-atmosphere CO 2 exchange (δ source) varied across land cover types and was not driven by seasonal changes in vapor pressure deficit. The largest seasonal amplitudes of δsource were at grassland and urban sites, driven by changes in C 3/C 4 grass productivity and fossil fuel emissions, respectively. Mixing model approaches may incorrectly calculate δs ource when background atmospheric observations are remote and/or prone to anthropogenic influence.« less

Does vapor pressure deficit drive the seasonality of δ 13 C of the net land-atmosphere CO 2 exchange across the United States?: The Influence of VPD on δ 13 C of NEE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raczka, B.; Biraud, S. C.; Ehleringer, J. R.

The seasonal pattern of the carbon isotope content (δ 13C) of atmospheric CO 2 depends on local and nonlocal land-atmosphere exchange and atmospheric transport. Previous studies suggested that the δ13C of the net land-atmosphere CO 2 flux (δsource) varies seasonally as stomatal conductance of plants responds to vapor pressure deficit of air (VPD). We studied the variation of δ source at seven sites across the United States representing forests, grasslands, and an urban center. Using a two-part mixing model, we calculated the seasonal δsource for each site after removing background influence and, when possible, removing δ 13C variation of nonlocalmore » sources. Compared to previous analyses, we found a reduced seasonal (March–September) variation in δ source at the forest sites (0.5‰variation). We did not find a consistent seasonal relationship between VPD and δ source across forest (or other) sites, providing evidence that stomatal response to VPD was not the cause of the global, coherent seasonal pattern in δsource. In contrast to the forest sites, grassland and urban sites had a larger seasonal variation in δ source (5‰) dominated by seasonal transitions in C 3/C 4 grass productivity and in fossil fuel emissions, respectively. Our findings were sensitive to the location used to account for atmospheric background variation within the mixing model method that determined δsource. Special consideration should be given to background location depending on whether the intent is to understand site level dynamics or regional scale impacts of land-atmosphere exchange. The seasonal amplitude in δ 13C of land-atmosphere CO 2 exchange (δ source) varied across land cover types and was not driven by seasonal changes in vapor pressure deficit. The largest seasonal amplitudes of δsource were at grassland and urban sites, driven by changes in C 3/C 4 grass productivity and fossil fuel emissions, respectively. Mixing model approaches may incorrectly calculate δs ource when background atmospheric observations are remote and/or prone to anthropogenic influence.« less

Biophysical regulation of carbon fluxes over an alpine meadow ecosystem in the eastern Tibetan Plateau.

PubMed

Wang, Shaoying; Zhang, Yu; Lü, Shihua; Su, Peixi; Shang, Lunyu; Li, Zhaoguo

2016-06-01

The eddy covariance method was used to measure net ecosystem CO2 exchange (NEE) between atmosphere and an alpine meadow ecosystem in the eastern Tibetan Plateau of China in 2010. Our results show that photosynthesis was reduced under low air temperature (T a), high vapor pressure deficit (VPD), and medium soil water content (SWC) conditions, when compared to that under other T a (i.e., medium and high), VPD (i.e., low and medium), and SWC (i.e., low and high) conditions. The apparent temperature sensitivity of ecosystem respiration (Q 10) declined with progressing phenology during the growing season and decreased with an increase of soil temperature (T s) during the non-growing season. Increased ecosystem respiration (R eco) was measured during spring soil thawing. By the path analysis, T a, T s, and VPD were the main control factors of CO2 exchange at 30-min scale in this alpine meadow. Integrated NEE, gross primary production (GPP), and R eco over the measured year were -156.4, 1164.3, and 1007.9 g C m(-2), respectively. Zoige alpine meadow was a medium carbon sink based on published data for grassland ecosystems.

Extreme mid-winter drought weakens tree hydraulic-carbohydrate systems and slows growth.

PubMed

Earles, J Mason; Stevens, Jens T; Sperling, Or; Orozco, Jessica; North, Malcolm P; Zwieniecki, Maciej A

2018-07-01

Rising temperatures and extended periods of drought compromise tree hydraulic and carbohydrate systems, threatening forest health globally. Despite winter's biological significance to many forests, the effects of warmer and dryer winters on tree hydraulic and carbohydrate status have largely been overlooked. Here we report a sharp and previously unknown decline in stem water content of three conifer species during California's anomalous 2015 mid-winter drought that was followed by dampened spring starch accumulation. Recent precipitation and seasonal vapor pressure deficit (VPD) anomaly, not absolute VPD, best predicted the hydraulic patterns observed. By linking relative water content and hydraulic conductivity (K h ), we estimated that stand-level K h declined by 52% during California's 2015 mid-winter drought, followed by a 50% reduction in spring starch accumulation. Further examination of tree increment records indicated a concurrent decline of growth with rising mid-winter, but not summer, VPD anomaly. Thus, our findings suggest a seasonality to tree hydraulic and carbohydrate declines, with consequences for annual growth rates, raising novel physiological and ecological questions about how rising winter temperatures will affect forest vitality as climate changes. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Resource use and efficiency, and stomatal responses to environmental drivers of oak and pine species in an Atlantic Coastal Plain forest.

PubMed

Renninger, Heidi J; Carlo, Nicholas J; Clark, Kenneth L; Schäfer, Karina V R

2015-01-01

Pine-oak ecosystems are globally distributed even though differences in anatomy and leaf habit between many co-occurring oaks and pines suggest different strategies for resource use, efficiency and stomatal behavior. The New Jersey Pinelands contain sandy soils with low water- and nutrient-holding capacity providing an opportunity to examine trade-offs in resource uptake and efficiency. Therefore, we compared resource use in terms of transpiration rates and leaf nitrogen content and resource-use efficiency including water-use efficiency (WUE) via gas exchange and leaf carbon isotopes and photosynthetic nitrogen-use efficiency (PNUE) between oaks (Quercus alba, Q. prinus, Q. velutina) and pines (Pinus rigida, P. echinata). We also determined environmental drivers [vapor pressure deficit (VPD), soil moisture, solar radiation] of canopy stomatal conductance (GS) estimated via sap flow and stomatal sensitivity to light and soil moisture. Net assimilation rates were similar between genera, but oak leaves used about 10% more water and pine foliage contained about 20% more N per unit leaf area. Therefore, oaks exhibited greater PNUE while pines had higher WUE based on gas exchange, although WUE from carbon isotopes was not significantly different. For the environmental drivers of GS, oaks had about 10% lower stomatal sensitivity to VPD normalized by reference stomatal conductance compared with pines. Pines exhibited a significant positive relationship between shallow soil moisture and GS, but only GS in Q. velutina was positively related to soil moisture. In contrast, stomatal sensitivity to VPD was significantly related to solar radiation in all oak species but only pines at one site. Therefore, oaks rely more heavily on groundwater resources but have lower WUE, while pines have larger leaf areas and nitrogen acquisition but lower PNUE demonstrating a trade-off between using water and nitrogen efficiently in a resource-limited ecosystem.

Resource use and efficiency, and stomatal responses to environmental drivers of oak and pine species in an Atlantic Coastal Plain forest

PubMed Central

Renninger, Heidi J.; Carlo, Nicholas J.; Clark, Kenneth L.; Schäfer, Karina V. R.

2015-01-01

Pine-oak ecosystems are globally distributed even though differences in anatomy and leaf habit between many co-occurring oaks and pines suggest different strategies for resource use, efficiency and stomatal behavior. The New Jersey Pinelands contain sandy soils with low water- and nutrient-holding capacity providing an opportunity to examine trade-offs in resource uptake and efficiency. Therefore, we compared resource use in terms of transpiration rates and leaf nitrogen content and resource-use efficiency including water-use efficiency (WUE) via gas exchange and leaf carbon isotopes and photosynthetic nitrogen-use efficiency (PNUE) between oaks (Quercus alba, Q. prinus, Q. velutina) and pines (Pinus rigida, P. echinata). We also determined environmental drivers [vapor pressure deficit (VPD), soil moisture, solar radiation] of canopy stomatal conductance (GS) estimated via sap flow and stomatal sensitivity to light and soil moisture. Net assimilation rates were similar between genera, but oak leaves used about 10% more water and pine foliage contained about 20% more N per unit leaf area. Therefore, oaks exhibited greater PNUE while pines had higher WUE based on gas exchange, although WUE from carbon isotopes was not significantly different. For the environmental drivers of GS, oaks had about 10% lower stomatal sensitivity to VPD normalized by reference stomatal conductance compared with pines. Pines exhibited a significant positive relationship between shallow soil moisture and GS, but only GS in Q. velutina was positively related to soil moisture. In contrast, stomatal sensitivity to VPD was significantly related to solar radiation in all oak species but only pines at one site. Therefore, oaks rely more heavily on groundwater resources but have lower WUE, while pines have larger leaf areas and nitrogen acquisition but lower PNUE demonstrating a trade-off between using water and nitrogen efficiently in a resource-limited ecosystem. PMID:25999966

The role of cephalometry in assessing velopharyngeal dysfunction in velocardiofacial syndrome.

PubMed

Veerapandiyan, Aravindhan; Blalock, David; Ghosh, Srija; Ip, Edward; Barnes, Craig; Shashi, Vandana

2011-04-01

To report our experience with cephalometry in evaluating velopharyngeal dysfunction (VPD) in velocardiofacial syndrome (VCFS) and its utility in assessing the role of cervical spine abnormalities in VPD, prior to surgical correction of VPD. Clinical charts and cephalometric radiographs done prior to surgery for VPD were retrospectively analyzed to ascertain velopharyngeal measurements and cervical spine abnormalities. Twenty-six patients (age: 6-23 years) with molecularly confirmed VCFS. Wake Forest University Health Sciences (1997-2005). Cranial base angle, nasopharyngeal depth, velum length, and Need ratio at rest, velar dimple location, and velopharyngeal length during phonation; information on presence/absence of submucous cleft palate and cervical spine abnormalities were also obtained. The relationship between C1 anterior arch abnormalities and Need ratio was examined. Seventy-three percent of the VCFS patients had excessive nasopharyngeal depth, 80% had an abnormal Need ratio, 50% had a short velum, 81% had a submucous or occult submucous cleft palate, 90.5% had a cervical spine abnormality (C1 anterior arch abnormalities in 38%) and 11.5% had platybasia. There was a significant difference in the Need ratio between patients with and without C1 anterior arch abnormalities. Cephalometry can be used to delineate factors such as C1 vertebral abnormalities, excessive pharyngeal depth, and short velum that contribute to VPD in VCFS. This would help otolaryngologists better understand the anatomy prior to surgical treatment of VPD. This is the first study to highlight the frequent occurrence of C1 anterior arch abnormalities in VCFS. Copyright © 2011 The American Laryngological, Rhinological, and Otological Society, Inc., Rhinological, and Otological Society, Inc.

Direct and Indirect Effects of Tides on Ecosystem-Scale CO2 Exchange in a Brackish Tidal Marsh in Northern California

NASA Astrophysics Data System (ADS)

Knox, S. H.; Windham-Myers, L.; Anderson, F.; Sturtevant, C.; Bergamaschi, B.

2018-03-01

We investigated the direct and indirect influence of tides on net ecosystem exchange (NEE) of carbon dioxide (CO2) in a temperate brackish tidal marsh. NEE displayed a tidally driven pattern with obvious characteristics at the multiday scale, with greater net CO2 uptake during spring tides than neap tides. Based on the relative mutual information between NEE and biophysical variables, this was driven by a combination of higher water table depth (WTD), cooler air temperature, and lower vapor pressure deficit (VPD) during spring tides relative to neap tides, as the fortnightly tidal cycle not only influenced water levels but also strongly modulated water and air temperature and VPD. Tides also influenced NEE at shorter timescales, with a reduction in nighttime fluxes during growing season spring tides when the higher of the two semidiurnal tides caused inundation at the site. WTD significantly influenced ecosystem respiration (Reco), with lower Reco during spring tides than neap tides. While WTD did not appear to affect ecosystem photosynthesis (gross ecosystem production, GPP) directly, the impact of tides on temperature and VPD influenced GPP, with higher daily light-use efficiency and photosynthetic activity during spring tides than neap tides when temperature and VPD were lower. The strong direct and indirect influence of tides on NEE across the diel and multiday timescales has important implications for modeling NEE in tidal wetlands and can help inform the timing and frequency of chamber measurements as annual or seasonal net CO2 uptake may be underestimated if measurements are only taken during nonflooded periods.

Testing Earth System Models with Earth System Data: using C isotopes in atmospheric CO2 to probe stomatal response to future climate change

NASA Astrophysics Data System (ADS)

Ballantyne, A. P.; Miller, J. B.; Bowling, D. R.; Tans, P. P.; Baker, I. T.

2013-12-01

The global cycles of water and carbon are inextricably linked through photosynthesis. This link is largely governed by stomatal conductance that regulates water loss to the atmosphere and carbon gain to the biosphere. Although extensive research has focused on the response of stomatal conductance to increased atmospheric CO2, much less research has focused on the response of stomatal conductance to concomitant climate change. Here we make use of intensive and extensive measurements of C isotopes in source CO2 to the atmosphere (del-bio) to make inferences about stomatal response to climatic factors at a single forest site and across a network of global observation sites. Based on intensive observations at the Niwot Ridge Ameriflux site we discover that del-bio is an excellent physical proxy of stomatal response during the growing season and this response is highly sensitive to atmospheric water vapor pressure deficit (VPD). We use these intensive single forest site observations to inform our analysis of the global observation network, focusing in on the growing season across an array of terrestrial sites. We find that stomatal response across most of these terrestrial sites is also highly sensitive to VPD. Lastly, we simulate the response of future climate change on stomatal response and discover that future increases in VPD may limit the biosphere's capacity to assimilate future CO2 emissions. These results have direct implications for the benchmarking of Earth System Models as stomatal conductance in many of these models does not vary as a function of VPD.

Understanding moisture stress on light-use efficiency based on MODIS and global flux tower data

NASA Astrophysics Data System (ADS)

Zhang, Y.; Song, C.; Sun, G.

2014-12-01

Gross primary productivity (GPP) is a key indicator of terrestrial ecosystem functions and global carbon balance. However, accurately estimating GPP is still one of the major challenges in global change study. Compared with other prognostic models, remote-sensing-based light-use efficiency (LUE) modes are considered to have the most potential to characterize the spatial-temporal dynamics of GPP. However, the environmental regulations on LUE, especially from water stress, have relatively large uncertainties, which reversely constrained the applications of LUE models. Here, we used MODIS and global flux tower data to investigate the moisture stress on LUE for different biomes on daily, 8-day and monthly scales. Three groups of moisture stress indicators were adopted in our study, including atmosphere (i.e. precipitation and daytime vapor pressure deficit (VPD)), soil (i.e. soil water content (SWC) and scaled SWC (SWCs) by field capacity and wilting point) , and plant indicators (i.e. land surface wetness index (LSWI) and the ratio of latent heat to the sum of latent and sensible heat (L/(L+H)). We applied a series of steps to eliminate the effects of high/low temperature and diffuse radiation effects on observed LUE. Our analysis showed that there were great variations in moisture stress effects on LUE between and within biomes. Generally, the moisture stress effects on LUE are ranked as plant indicator (i.e. L/(L+H) & LSWI) > atmosphere indicator (i.e. VPD) > soil indicator (i.e. SWC/SWCs). Precipitation has the poorest relationship with observed LUE and doesn't show any significant lag effects. For deep-root biomes (e.g. forest), LUE shows higher sensitivity in VPD than SWC; but for short-root biomes (e.g. grass), LUE is more sensitive to SWC than VPD. Most indicators (except SWC/SWCs) are more effective in affecting LUE at the daily/8-day scale than at the monthly scale probably because the observed LUE becomes more stable as temporal scale increases. SWC do not show close relationship with LUE, suggesting that the current measured SWC in the top-soil layer may not be sufficient to capture the moisture effects on LUE for biomes with different root distributions. Our study highlights the complexity of moisture stress on observed LUE, and provides useful guidance for developing more reliable LUE models to estimate GPP.

Overstory and Understory CO2 and Energy Fluxes of a Black Spruce Forest in Interior Alaska

NASA Astrophysics Data System (ADS)

Ikawa, H.; Nakai, T.; Busey, R.; Kim, Y.; Kobayashi, H.; Nagai, S.; Ueyama, M.; Saito, K.; Suzuki, R.; Hinzman, L. D.

2014-12-01

Eddy covariance techniques were used to quantify understory contributions to carbon and energy balances, and to evaluate the environmental responses of the overstory and understory at a black spruce forest in interior Alaska. Net ecosystem productivity (NEP), gross primary productivity (GPP), ecosystem respiration (RE), sensible heat flux (H), and latent heat flux (LE) were estimated for the ecosystem (subscripted by 'eco'), canopy (subscripted by 'cano') and forest floor (subscripted by 'floor') based on canopy gap fraction and footprint analyses for 3 years, 2011 - 2013. Fluxes per unit land surface area of black spruce overstory (subscripted by 'b') and that of understory (subscripted by 'u') were also evaluated their ecophysiological responses to micrometeorological environments. Overall, NEPfloor, GPPfloor, REfloor and LEfloor represented 60 (37, growing season in parenthesis) %, 47 (51) %, 47 (54) %, and 75 (76) % of NEPeco, GPPeco, REeco, and LEeco, respectively with the average canopy gap fraction of 0.52 (± 0.073 SD). The year, 2013 was characterized by high air temperature and vapor pressure deficit (VPD) during the growing season. The high temperature and VPD particularly reduced understory NEP and their growth inferred by low green excessive index (GEI), which was correlated to GPPu more strongly than GPPb. LEu linearly increased with vapor pressure deficit (VPD) whereas LEb was insensitive to VPD. Future warming and drying expected in the boreal forest will increase understory evapotranspiration disproportionately to that of black spruce and likely decrease the production of the current understory community. Acknowledgments This study was supported by the Japan Aerospace Exploration Agency (JAXA) and the JAMSTEC-IARC Collaboration Study, with funding provided by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) to the International Arctic Research Center (IARC). The Polar Geospatial Center, University of Minnesota provided the Quick Bird Image as a support for the NSF grand number 1107524. HI acknowledges J. H. Matthes for helping the footprint algorism, R. Hirata, D. McGuire, and E. Euskirchen for fruitful discussion, and Y. Harazono and H. Nagano for providing parts of meteorological data. We thank N. Bauer for editing.

The photosynthetic response of tobacco plants overexpressing ice plant aquaporin McMIPB to a soil water deficit and high vapor pressure deficit.

PubMed

Kawase, Miki; Hanba, Yuko T; Katsuhara, Maki

2013-07-01

We investigated the photosynthetic capacity and plant growth of tobacco plants overexpressing ice plant (Mesembryanthemum crystallinum L.) aquaporin McMIPB under (1) a well-watered growth condition, (2) a well-watered and temporal higher vapor pressure deficit (VPD) condition, and (3) a soil water deficit growth condition to investigate the effect of McMIPB on photosynthetic responses under moderate soil and atmospheric humidity and water deficit conditions. Transgenic plants showed a significantly higher photosynthesis rate (by 48 %), higher mesophyll conductance (by 52 %), and enhanced growth under the well-watered growth condition than those of control plants. Decreases in the photosynthesis rate and stomatal conductance from ambient to higher VPD were slightly higher in transgenic plants than those in control plants. When plants were grown under the soil water deficit condition, decreases in the photosynthesis rate and stomatal conductance were less significant in transgenic plants than those in control plants. McMIPB is likely to work as a CO2 transporter, as well as control the regulation of stomata to water deficits.

Quantum-mechanical approach to predissociation of water dimers in the vibrational adiabatic representation: Importance of channel interactions.

PubMed

Mineo, H; Niu, Y L; Kuo, J L; Lin, S H; Fujimura, Y

2015-08-28

The results of application of the quantum-mechanical adiabatic theory to vibrational predissociation (VPD) of water dimers, (H2O)2 and (D2O)2, are presented. We consider the VPD processes including the totally symmetric OH mode of the dimer and the bending mode of the fragment. The VPD in the adiabatic representation is induced by breakdown of the vibrational adiabatic approximation, and two types of nonadiabatic coupling matrix elements are involved: one provides the VPD induced by the low-frequency dissociation mode and the other provides the VPD through channel interactions induced by the low-frequency modes. The VPD rate constants were calculated using the Fermi golden rule expression. A closed form for the nonadiabatic transition matrix element between the discrete and continuum states was derived in the Morse potential model. All of the parameters used were obtained from the potential surfaces of the water dimers, which were calculated by the density functional theory procedures. The VPD rate constants for the two processes were calculated in the non-Condon scheme beyond the so-called Condon approximation. The channel interactions in and between the initial and final states were taken into account, and those are found to increase the VPD rates by 3(1) orders of magnitude for the VPD processes in (H2O)2 ((D2O)2). The fraction of the bending-excited donor fragments is larger than that of the bending-excited acceptor fragments. The results obtained by quantum-mechanical approach are compared with both experimental and quasi-classical trajectory calculation results.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mineo, H.; Kuo, J. L.; Niu, Y. L.

The results of application of the quantum-mechanical adiabatic theory to vibrational predissociation (VPD) of water dimers, (H{sub 2}O){sub 2} and (D{sub 2}O){sub 2}, are presented. We consider the VPD processes including the totally symmetric OH mode of the dimer and the bending mode of the fragment. The VPD in the adiabatic representation is induced by breakdown of the vibrational adiabatic approximation, and two types of nonadiabatic coupling matrix elements are involved: one provides the VPD induced by the low-frequency dissociation mode and the other provides the VPD through channel interactions induced by the low-frequency modes. The VPD rate constants weremore » calculated using the Fermi golden rule expression. A closed form for the nonadiabatic transition matrix element between the discrete and continuum states was derived in the Morse potential model. All of the parameters used were obtained from the potential surfaces of the water dimers, which were calculated by the density functional theory procedures. The VPD rate constants for the two processes were calculated in the non-Condon scheme beyond the so-called Condon approximation. The channel interactions in and between the initial and final states were taken into account, and those are found to increase the VPD rates by 3(1) orders of magnitude for the VPD processes in (H{sub 2}O){sub 2} ((D{sub 2}O){sub 2}). The fraction of the bending-excited donor fragments is larger than that of the bending-excited acceptor fragments. The results obtained by quantum-mechanical approach are compared with both experimental and quasi-classical trajectory calculation results.« less

Carbon stable isotopic composition of soluble sugars in Tillandsia epiphytes varies in response to shifts in habitat.

PubMed

Goode, Laurel K; Erhardt, Erik B; Santiago, Louis S; Allen, Michael F

2010-07-01

We studied C stable isotopic composition (delta(13)C) of bulk leaf tissue and extracted sugars of four epiphytic Tillandsia species to investigate flexibility in the use of crassulacean acid metabolism (CAM) and C(3) photosynthetic pathways. Plants growing in two seasonally dry tropical forest reserves in Mexico that differ in annual precipitation were measured during wet and dry seasons, and among secondary, mature, and wetland forest types within each site. Dry season sugars were more enriched in (13)C than wet season sugars, but there was no seasonal difference in bulk tissues. Bulk tissue delta(13)C differed by species and by forest type, with values from open-canopied wetlands more enriched in (13)C than mature or secondary forest types. The shifts within forest habitat were related to temporal and spatial changes in vapor pressure deficits (VPD). Modeling results estimate a possible 4% increase in the proportional contribution of the C(3) pathway during the wet season, emphasizing that any seasonal or habitat-mediated variation in photosynthetic pathway appears to be quite moderate and within the range of isotopic effects caused by variation in stomatal conductance during assimilation through the C(3) pathway and environmental variation in VPD. C isotopic analysis of sugars together with bulk leaf tissue offers a useful approach for incorporating short- and long-term measurements of C isotope discrimination during photosynthesis.

Carbon stable isotopic composition of soluble sugars in Tillandsia epiphytes varies in response to shifts in habitat

PubMed Central

Erhardt, Erik B.; Santiago, Louis S.; Allen, Michael F.

2010-01-01

We studied C stable isotopic composition (δ13C) of bulk leaf tissue and extracted sugars of four epiphytic Tillandsia species to investigate flexibility in the use of crassulacean acid metabolism (CAM) and C3 photosynthetic pathways. Plants growing in two seasonally dry tropical forest reserves in Mexico that differ in annual precipitation were measured during wet and dry seasons, and among secondary, mature, and wetland forest types within each site. Dry season sugars were more enriched in 13C than wet season sugars, but there was no seasonal difference in bulk tissues. Bulk tissue δ13C differed by species and by forest type, with values from open-canopied wetlands more enriched in 13C than mature or secondary forest types. The shifts within forest habitat were related to temporal and spatial changes in vapor pressure deficits (VPD). Modeling results estimate a possible 4% increase in the proportional contribution of the C3 pathway during the wet season, emphasizing that any seasonal or habitat-mediated variation in photosynthetic pathway appears to be quite moderate and within the range of isotopic effects caused by variation in stomatal conductance during assimilation through the C3 pathway and environmental variation in VPD. C isotopic analysis of sugars together with bulk leaf tissue offers a useful approach for incorporating short- and long-term measurements of C isotope discrimination during photosynthesis. PMID:20155286

Within-catchment variation in regulation of water use by eucalypts, and the roles of stomatal anatomy and physiology

NASA Astrophysics Data System (ADS)

Gharun, Mana; Turnbull, Tarryn; Adams, Mark

2014-05-01

Understanding how environmental cues impact water use of forested catchments is crucial for accurate calculation of water balance and effective catchment management in terrestrial ecosystems. We characterised structural and physiological properties of leaves and canopies of Eucalyptus delegatensis, E. pauciflora and E. radiata, the most common species in high-country catchments in temperate Australia. These properties were related to whole-tree water transport to assess differences in water use strategies among the three species. Stomatal conductance, instantaneous transpiration efficiency, stomatal occlusion (through cuticular ledges) and leaf area index differed significantly among species. Whole-tree water use of all species was strongly coupled to changes in vapour pressure deficit (VPD) and photosynthetically active radiation (Q), yet stomatal closure reduced water transport at VPD > 1 kPa in all species, even when soil water was not limiting. The observed differences in leaf traits and related water use strategies reflect species-specific adaptations to dominant environmental conditions within the landscape matrix of catchments. The generalist E. radiata seems to follow an opportunistic, while the two more spatially restricted species have adopted a pessimistic water use strategy. Catchment-scale models of carbon and water fluxes will need to reflect such variation in structure and function, if they are to fully capture species effects on water balance and yield.

[Dynamics of sap flow density in stems of typical desert shrub Calligonum mongolicum and its responses to environmental variables].

PubMed

Xu, Shi-qin; Ji, Xi-bin; Jin, Bo-wen

2016-02-01

Independent measurements of stem sap flow in stems of Calligonum mongolicum and environmental variables using commercial sap flow gauges and a micrometeorological monitoring system, respectively, were made to simulate the variation of sap flow density in the middle range of Hexi Corridor, Northwest China during June to September, 2014. The results showed that the diurnal process of sap flow density in C. mongolicum showed a broad unimodal change, and the maximum sap flow density reached about 30 minutes after the maximum of photosynthetically active radiation (PAR) , while about 120 minutes before the maximum of temperature and vapor pressure deficit (VPD). During the studying period, sap flow density closely related with atmosphere evapor-transpiration demand, and mainly affected by PAR, temperature and VPD. The model was developed which directly linked the sap flow density with climatic variables, and good correlation between measured and simulated sap flow density was observed in different climate conditions. The accuracy of simulation was significantly improved if the time-lag effect was taken into consideration, while this model underestimated low and nighttime sap flow densities, which was probably caused by plant physiological characteristics.

Drought-Tolerant Corn Hybrids Yield More in Drought-Stressed Environments with No Penalty in Non-stressed Environments

PubMed Central

Adee, Eric; Roozeboom, Kraig; Balboa, Guillermo R.; Schlegel, Alan; Ciampitti, Ignacio A.

2016-01-01

The potential benefit of drought-tolerant (DT) corn (Zea mays L.) hybrids may depend on drought intensity, duration, crop growth stage (timing), and the array of drought tolerance mechanisms present in selected hybrids. We hypothesized that corn hybrids containing DT traits would produce more consistent yields compared to non-DT hybrids in the presence of drought stress. The objective of this study was to define types of production environments where DT hybrids have a yield advantage compared to non-DT hybrids. Drought tolerant and non-DT hybrid pairs of similar maturity were planted in six site-years with different soil types, seasonal evapotranspiration (ET), and vapor pressure deficit (VPD), representing a range of macro-environments. Irrigation regimes and seeding rates were used to create several micro-environments within each macro-environment. Hybrid response to the range of macro and micro-environmental stresses were characterized in terms of water use efficiency, grain yield, and environmental index. Yield advantage of DT hybrids was positively correlated with environment ET and VPD. Drought tolerant hybrids yielded 5 to 7% more than non-DT hybrids in high and medium ET environments (>430 mm ET), corresponding to seasonal VPD greater than 1200 Pa. Environmental index analysis confirmed that DT hybrids were superior in stressful environments. Yield advantage for DT hybrids appeared as yield dropped below 10.8 Mg ha-1 and averaged as much as 0.6–1 Mg ha-1 at the low yield range. Hybrids with DT technology can offer a degree of buffering against drought stress by minimizing yield reduction, but also maintaining a comparable yield potential in high yielding environments. Further studies should focus on the physiological mechanisms presented in the commercially available corn drought tolerant hybrids. PMID:27790237

Diurnal and seasonal changes in stem increment and water use by yellow poplar trees in response to environmental stress.

PubMed

McLaughlin, Samuel B; Wullschleger, Stan D; Nosal, Miloslav

2003-11-01

To evaluate indicators of whole-tree physiological responses to climate stress, we determined seasonal, daily and diurnal patterns of growth and water use in 10 yellow poplar (Liriodendron tulipifera L.) trees in a stand recently released from competition. Precise measurements of stem increment and sap flow made with automated electronic dendrometers and thermal dissipation probes, respectively, indicated close temporal linkages between water use and patterns of stem shrinkage and swelling during daily cycles of water depletion and recharge of extensible outer-stem tissues. These cycles also determined net daily basal area increment. Multivariate regression models based on a 123-day data series showed that daily diameter increments were related negatively to vapor pressure deficit (VPD), but positively to precipitation and temperature. The same model form with slight changes in coefficients yielded coefficients of determination of about 0.62 (0.57-0.66) across data subsets that included widely variable growth rates and VPDs. Model R2 was improved to 0.75 by using 3-day running mean daily growth data. Rapid recovery of stem diameter growth following short-term, diurnal reductions in VPD indicated that water stored in extensible stem tissues was part of a fast recharge system that limited hydration changes in the cambial zone during periods of water stress. There were substantial differences in the seasonal dynamics of growth among individual trees, and analyses indicated that faster-growing trees were more positively affected by precipitation, solar irradiance and temperature and more negatively affected by high VPD than slower-growing trees. There were no negative effects of ozone on daily growth rates in a year of low ozone concentrations.

Quantifying soil moisture impacts on light use efficiency across biomes.

PubMed

Stocker, Benjamin D; Zscheischler, Jakob; Keenan, Trevor F; Prentice, I Colin; Peñuelas, Josep; Seneviratne, Sonia I

2018-06-01

Terrestrial primary productivity and carbon cycle impacts of droughts are commonly quantified using vapour pressure deficit (VPD) data and remotely sensed greenness, without accounting for soil moisture. However, soil moisture limitation is known to strongly affect plant physiology. Here, we investigate light use efficiency, the ratio of gross primary productivity (GPP) to absorbed light. We derive its fractional reduction due to soil moisture (fLUE), separated from VPD and greenness changes, using artificial neural networks trained on eddy covariance data, multiple soil moisture datasets and remotely sensed greenness. This reveals substantial impacts of soil moisture alone that reduce GPP by up to 40% at sites located in sub-humid, semi-arid or arid regions. For sites in relatively moist climates, we find, paradoxically, a muted fLUE response to drying soil, but reduced fLUE under wet conditions. fLUE identifies substantial drought impacts that are not captured when relying solely on VPD and greenness changes and, when seasonally recurring, are missed by traditional, anomaly-based drought indices. Counter to common assumptions, fLUE reductions are largest in drought-deciduous vegetation, including grasslands. Our results highlight the necessity to account for soil moisture limitation in terrestrial primary productivity data products, especially for drought-related assessments. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Environmental controls on sap flow in black locust forest in Loess Plateau, China.

PubMed

Ma, Changkun; Luo, Yi; Shao, Mingan; Li, Xiangdong; Sun, Lin; Jia, Xiaoxu

2017-10-13

Black locust accounts for over 90% of artificial forests in China's Loess Plateau region. However, water use of black locust is an uphill challenge for this semi-arid region. To accurately quantify tree water use and to explain the related hydrological processes, it is important to collect reliable data for application in the estimation of sap flow and its response to environmental factors. This study measured sap flow in black locust in the 2015 and 2016 growth seasons using the thermal dissipation probes technique and laboratory-calibrated Granier's equation. The study showed that the laboratory calibrated coefficient α was much larger than the original value presented by Granier, while the coefficient β was similar to the original one. The average daily transpiration was 2.1 mm day -1 for 2015 and 1.6 mm day -1 for 2016. Net solar radiation (Rn) was the key meteorological factor controlling sap flow, followed by vapor pressure deficit (VPD) and then temperature (T). VPD had a threshold control on sap flow at threshold values of 1.9 kPa for 2015 and 1.6 kPa for 2016. The effects of diurnal hysteresis of Rn, VPD and T on sap flow were evident, indicating that black locust water use was conservative.

The Sap Flow Dynamics and Response of Hedysarum scoparium to Environmental Factors in Semiarid Northwestern China.

PubMed

Deng, Jifeng; Ding, Guodong; Gao, Guanglei; Wu, Bin; Zhang, Yuqing; Qin, Shugao; Fan, Wenhui

2015-01-01

Hedysarum scoparium is an important, fast-growing and drought-resistant shrub that has been extensively used for grassland restoration and preventing desertification in semiarid regions of northwestern China. The primary objective of this study was to investigate the diurnal and seasonal variations in stem sap flow (Js) and its relation to environmental factors. The stem heat balance method was applied to plants that were approximately 17 years old (with diameters of 25, 16, 13, and 9 mm at ground level and heights of 3.1, 1.8, 1.7 and 1.4 m) and growing under natural conditions. The vertical soil temperature profile (ST), soil surface heat flux (SoilG), volumetric soil moisture content (SWC) and meteorological variables such as solar radiation (Rn), air temperature (Ta), vapour pressure deficit (VPD), wind speed (Ws) relative humidity (RH) and precipitation (P) were simultaneously measured at a meteorological station on site. Results indicated that Js varied regularly during the diurnal and seasonal term. The nocturnal Js was substantial, with a seasonal variation similar to the patterns of daytime Js. The magnitude of Js changed considerably between sunny and rainy days. Redundancy (RDA) and Kendall's tau analysis suggested that daily Js in large plants was more sensitive to environmental factors, and the variation in daily Js during the growing season could be described by a multiple linear regression against environmental variables including Ta, VPD, Ws, RH, ST, and SoilG. While the nocturnal Js in smaller plants was more sensitive to meteorological factors. Ta, VPD, and Ws were significantly correlated with nighttime Js. The hourly nighttime sap flow rate of H. scoparium corresponded closely to Ta and VPD following a non-linear pattern. The results of this study can be used to estimate the transpiration of H. scoparium.

Water cycles in closed ecological systems: effects of atmospheric pressure.

PubMed

Rygalov, Vadim Y; Fowler, Philip A; Metz, Joannah M; Wheeler, Raymond M; Bucklin, Ray A

2002-01-01

In bioregenerative life support systems that use plants to generate food and oxygen, the largest mass flux between the plants and their surrounding environment will be water. This water cycle is a consequence of the continuous change of state (evaporation-condensation) from liquid to gas through the process of transpiration and the need to transfer heat (cool) and dehumidify the plant growth chamber. Evapotranspiration rates for full plant canopies can range from ~1 to 10 L m-2 d-1 (~1 to 10 mm m-2 d-1), with the rates depending primarily on the vapor pressure deficit (VPD) between the leaves and the air inside the plant growth chamber. VPD in turn is dependent on the air temperature, leaf temperature, and current value of relative humidity (RH). Concepts for developing closed plant growth systems, such as greenhouses for Mars, have been discussed for many years and the feasibility of such systems will depend on the overall system costs and reliability. One approach for reducing system costs would be to reduce the operating pressure within the greenhouse to reduce structural mass and gas leakage. But managing plant growth environments at low pressures (e.g., controlling humidity and heat exchange) may be difficult, and the effects of low-pressure environments on plant growth and system water cycling need further study. We present experimental evidence to show that water saturation pressures in air under isothermal conditions are only slightly affected by total pressure, but the overall water flux from evaporating surfaces can increase as pressure decreases. Mathematical models describing these observations are presented, along with discussion of the importance for considering "water cycles" in closed bioregenerative life support systems.

Water cycles in closed ecological systems: effects of atmospheric pressure

NASA Technical Reports Server (NTRS)

Rygalov, Vadim Y.; Fowler, Philip A.; Metz, Joannah M.; Wheeler, Raymond M.; Bucklin, Ray A.; Sager, J. C. (Principal Investigator)

2002-01-01

In bioregenerative life support systems that use plants to generate food and oxygen, the largest mass flux between the plants and their surrounding environment will be water. This water cycle is a consequence of the continuous change of state (evaporation-condensation) from liquid to gas through the process of transpiration and the need to transfer heat (cool) and dehumidify the plant growth chamber. Evapotranspiration rates for full plant canopies can range from 1 to 10 L m-2 d-1 (1 to 10 mm m-2 d-1), with the rates depending primarily on the vapor pressure deficit (VPD) between the leaves and the air inside the plant growth chamber. VPD in turn is dependent on the air temperature, leaf temperature, and current value of relative humidity (RH). Concepts for developing closed plant growth systems, such as greenhouses for Mars, have been discussed for many years and the feasibility of such systems will depend on the overall system costs and reliability. One approach for reducing system costs would be to reduce the operating pressure within the greenhouse to reduce structural mass and gas leakage. But managing plant growth environments at low pressures (e.g., controlling humidity and heat exchange) may be difficult, and the effects of low-pressure environments on plant growth and system water cycling need further study. We present experimental evidence to show that water saturation pressures in air under isothermal conditions are only slightly affected by total pressure, but the overall water flux from evaporating surfaces can increase as pressure decreases. Mathematical models describing these observations are presented, along with discussion of the importance for considering "water cycles" in closed bioregenerative life support systems.

Soil Moisture (SMAP) and Vapor Pressure Deficit Controls on Evaporative Fraction over the Continental U.S.

NASA Astrophysics Data System (ADS)

Salvucci, G.; Rigden, A. J.; Gianotti, D.; Entekhabi, D.

2017-12-01

We analyze the control over evapotranspiration (ET) imposed by soil moisture limitations and stomatal closure due to vapor pressure deficit (VPD) across the United States using estimates of satellite-derived soil moisture from SMAP and a meteorological, data-driven ET estimate over a two year period at over 1000 locations. The ET data are developed independent of soil moisture using the emergent relationship between the diurnal cycle of the relative humidity profile and ET based on ETRHEQ (Salvucci and Gentine (2013), PNAS, 110(16): 6287-6291, Rigden and Salvucci, 2015, WRR, 51(4): 2951-2973; Rigden and Salvucci, 2017, GCB, 23(3) 1140-1151). The key advantage of using this approach to estimate ET is that no measurements of surface limiting factors (soil moisture, leaf area, canopy conductance) are required; instead, ET is estimated from only meteorological data. The combination of these two independent datasets allows for a unique spatial analysis of the control on ET imposed by the availability of soil moisture vs. VPD. Spatial patterns of limitations are inferred by fitting the ETRHEQ-inferred surface conductance to a weighted sum of a Jarvis type stomatal conductance model and bare soil evaporation conductance model, with separate moisture-dependent evaporation efficiency relations for bare soil and vegetation. Spatial patterns are visualized by mapping the optimal curve fitting coefficients and by conducting sensitivity analyses of the resulting fitted model across the Unites States. Results indicate regional variations in rate-limiting factors, and suggest that in some areas the VPD effect on stomatal closure is strong enough to induce a decrease in ET under projected climate change, despite an increase in atmospheric drying (and thus evaporative demand).

Water Use Patterns of Four Tropical Bamboo Species Assessed with Sap Flux Measurements.

PubMed

Mei, Tingting; Fang, Dongming; Röll, Alexander; Niu, Furong; Hendrayanto; Hölscher, Dirk

2015-01-01

Bamboos are grasses (Poaceae) that are widespread in tropical and subtropical regions. We aimed at exploring water use patterns of four tropical bamboo species (Bambusa vulgaris, Dendrocalamus asper, Gigantochloa atroviolacea, and G. apus) with sap flux measurement techniques. Our approach included three experimental steps: (1) a pot experiment with a comparison of thermal dissipation probes (TDPs), the stem heat balance (SHB) method and gravimetric readings using potted B. vulgaris culms, (2) an in situ calibration of TDPs with the SHB method for the four bamboo species, and (3) field monitoring of sap flux of the four bamboo species along with three tropical tree species (Gmelina arborea, Shorea leprosula, and Hevea brasiliensis) during a dry and a wet period. In the pot experiment, it was confirmed that the SHB method is well suited for bamboos but that TDPs need to be calibrated. In situ, species-specific parameters for such calibration formulas were derived. During field monitoring we found that some bamboo species reached high maximum sap flux densities. Across bamboo species, maximal sap flux density increased with decreasing culm diameter. In the diurnal course, sap flux densities in bamboos peaked much earlier than radiation and vapor pressure deficit (VPD), and also much earlier than sap flux densities in trees. There was a pronounced hysteresis between sap flux density and VPD in bamboos, which was less pronounced in trees. Three of the four bamboo species showed reduced sap flux densities at high VPD values during the dry period, which was associated with a decrease in soil moisture content. Possible roles of internal water storage, root pressure and stomatal sensitivity are discussed.

Water Use Patterns of Four Tropical Bamboo Species Assessed with Sap Flux Measurements

PubMed Central

Mei, Tingting; Fang, Dongming; Röll, Alexander; Niu, Furong; Hendrayanto; Hölscher, Dirk

2016-01-01

Bamboos are grasses (Poaceae) that are widespread in tropical and subtropical regions. We aimed at exploring water use patterns of four tropical bamboo species (Bambusa vulgaris, Dendrocalamus asper, Gigantochloa atroviolacea, and G. apus) with sap flux measurement techniques. Our approach included three experimental steps: (1) a pot experiment with a comparison of thermal dissipation probes (TDPs), the stem heat balance (SHB) method and gravimetric readings using potted B. vulgaris culms, (2) an in situ calibration of TDPs with the SHB method for the four bamboo species, and (3) field monitoring of sap flux of the four bamboo species along with three tropical tree species (Gmelina arborea, Shorea leprosula, and Hevea brasiliensis) during a dry and a wet period. In the pot experiment, it was confirmed that the SHB method is well suited for bamboos but that TDPs need to be calibrated. In situ, species-specific parameters for such calibration formulas were derived. During field monitoring we found that some bamboo species reached high maximum sap flux densities. Across bamboo species, maximal sap flux density increased with decreasing culm diameter. In the diurnal course, sap flux densities in bamboos peaked much earlier than radiation and vapor pressure deficit (VPD), and also much earlier than sap flux densities in trees. There was a pronounced hysteresis between sap flux density and VPD in bamboos, which was less pronounced in trees. Three of the four bamboo species showed reduced sap flux densities at high VPD values during the dry period, which was associated with a decrease in soil moisture content. Possible roles of internal water storage, root pressure and stomatal sensitivity are discussed. PMID:26779233

Surface vapor conductance derived from the ETRHEQ: Dependence on environmental variables and similarity to Oren's stomatal stress model for vapor pressure deficit

NASA Astrophysics Data System (ADS)

Salvucci, G.; Rigden, A. J.

2015-12-01

Daily time series of evapotranspiration and surface conductance to water vapor were estimated using the ETRHEQ method (Evapotranspiration from Relative Humidity at Equilibrium). ETRHEQ has been previously compared with ameriflux site-level measurements of ET at daily and seasonal time scales, with watershed water balance estimates, and with various benchmark ET data sets. The ETRHEQ method uses meteorological data collected at common weather stations and estimates the surface conductance by minimizing the vertical variance of the calculated relative humidity profile averaged over the day. The key advantage of the ETRHEQ method is that it does not require knowledge of the surface state (soil moisture, stomatal conductance, leaf are index, etc.) or site-specific calibration. The daily estimates of conductance from 229 weather stations for 53 years were analyzed for dependence on environmental variables known to impact stomatal conductance and soil diffusivity: surface temperature, surface vapor pressure deficit, solar radiation, antecedent precipitation (as a surrogate for soil moisture), and a seasonal vegetation greenness index. At each site the summertime (JJAS) conductance values estimated from ETRHEQ were fitted to a multiplicate Jarvis-type stress model. Functional dependence was not proscribed, but instead fitted using flexible piecewise-linear splines. The resulting stress functions reproduce the time series of conductance across a wide range of ecosystems and climates. The VPD stress term resembles that proposed by Oren (i.e., 1-m*log(VPD) ), with VPD measured in kilopascals. The equivalent value of m derived from our spline-fits at each station varied over a remarkably small range of 0.58 to 0.62, in agreement with Oren's original analysis based on leaf and tree-level measurements.

Identification and Validation of Reference Genes and Their Impact on Normalized Gene Expression Studies across Cultivated and Wild Cicer Species

PubMed Central

Reddy, Palakolanu Sudhakar; Sri Cindhuri, Katamreddy; Sivaji Ganesh, Adusumalli; Sharma, Kiran Kumar

2016-01-01

Quantitative Real-Time PCR (qPCR) is a preferred and reliable method for accurate quantification of gene expression to understand precise gene functions. A total of 25 candidate reference genes including traditional and new generation reference genes were selected and evaluated in a diverse set of chickpea samples. The samples used in this study included nine chickpea genotypes (Cicer spp.) comprising of cultivated and wild species, six abiotic stress treatments (drought, salinity, high vapor pressure deficit, abscisic acid, cold and heat shock), and five diverse tissues (leaf, root, flower, seedlings and seed). The geNorm, NormFinder and RefFinder algorithms used to identify stably expressed genes in four sample sets revealed stable expression of UCP and G6PD genes across genotypes, while TIP41 and CAC were highly stable under abiotic stress conditions. While PP2A and ABCT genes were ranked as best for different tissues, ABCT, UCP and CAC were most stable across all samples. This study demonstrated the usefulness of new generation reference genes for more accurate qPCR based gene expression quantification in cultivated as well as wild chickpea species. Validation of the best reference genes was carried out by studying their impact on normalization of aquaporin genes PIP1;4 and TIP3;1, in three contrasting chickpea genotypes under high vapor pressure deficit (VPD) treatment. The chickpea TIP3;1 gene got significantly up regulated under high VPD conditions with higher relative expression in the drought susceptible genotype, confirming the suitability of the selected reference genes for expression analysis. This is the first comprehensive study on the stability of the new generation reference genes for qPCR studies in chickpea across species, different tissues and abiotic stresses. PMID:26863232

Identification and Validation of Reference Genes and Their Impact on Normalized Gene Expression Studies across Cultivated and Wild Cicer Species.

PubMed

Reddy, Dumbala Srinivas; Bhatnagar-Mathur, Pooja; Reddy, Palakolanu Sudhakar; Sri Cindhuri, Katamreddy; Sivaji Ganesh, Adusumalli; Sharma, Kiran Kumar

2016-01-01

Quantitative Real-Time PCR (qPCR) is a preferred and reliable method for accurate quantification of gene expression to understand precise gene functions. A total of 25 candidate reference genes including traditional and new generation reference genes were selected and evaluated in a diverse set of chickpea samples. The samples used in this study included nine chickpea genotypes (Cicer spp.) comprising of cultivated and wild species, six abiotic stress treatments (drought, salinity, high vapor pressure deficit, abscisic acid, cold and heat shock), and five diverse tissues (leaf, root, flower, seedlings and seed). The geNorm, NormFinder and RefFinder algorithms used to identify stably expressed genes in four sample sets revealed stable expression of UCP and G6PD genes across genotypes, while TIP41 and CAC were highly stable under abiotic stress conditions. While PP2A and ABCT genes were ranked as best for different tissues, ABCT, UCP and CAC were most stable across all samples. This study demonstrated the usefulness of new generation reference genes for more accurate qPCR based gene expression quantification in cultivated as well as wild chickpea species. Validation of the best reference genes was carried out by studying their impact on normalization of aquaporin genes PIP1;4 and TIP3;1, in three contrasting chickpea genotypes under high vapor pressure deficit (VPD) treatment. The chickpea TIP3;1 gene got significantly up regulated under high VPD conditions with higher relative expression in the drought susceptible genotype, confirming the suitability of the selected reference genes for expression analysis. This is the first comprehensive study on the stability of the new generation reference genes for qPCR studies in chickpea across species, different tissues and abiotic stresses.

GWAS reveals loci associated with velopharyngeal dysfunction.

PubMed

Chernus, Jonathan; Roosenboom, Jasmien; Ford, Matthew; Lee, Myoung Keun; Emanuele, Beth; Anderton, Joel; Hecht, Jacqueline T; Padilla, Carmencita; Deleyiannis, Frederic W B; Buxo, Carmen J; Feingold, Eleanor; Leslie, Elizabeth J; Shaffer, John R; Weinberg, Seth M; Marazita, Mary L

2018-05-31

Velopharyngeal dysfunction (VPD) occurs when the muscular soft palate (velum) and lateral pharyngeal walls are physically unable to separate the oral and nasal cavities during speech production leading to hypernasality and abnormal speech reduction. Because VPD is often associated with overt or submucous cleft palate, it could be present as a subclinical phenotype in families with a history of orofacial clefting. A key assumption to this model is that the overt and subclinical manifestations of the orofacial cleft phenotype exist on a continuum and therefore share common etiological factors. We performed a genome-wide association study in 976 unaffected relatives of isolated CP probands, 54 of whom had VPD. Five loci were significantly (p < 5 × 10 -8 ) associated with VPD: 3q29, 9p21.1, 12q21.31, 16p12.3 and 16p13.3. An additional 15 loci showing suggestive evidence of association with VPD were observed. Several genes known to be involved in orofacial clefting and craniofacial development are located in these regions, such as TFRC, PCYT1A, BNC2 and FREM1. Although further research is necessary, this could be an indication for a potential shared genetic architecture between VPD and cleft palate, and supporting the hypothesis that VPD is a subclinical phenotype of orofacial clefting.

Stomatal structure and physiology do not explain differences in water use among montane eucalypts.

PubMed

Gharun, Mana; Turnbull, Tarryn L; Pfautsch, Sebastian; Adams, Mark A

2015-04-01

Understanding the regulation of water use at the whole-tree scale is critical to advancing the utility of physiological ecology, for example in its role in predictive hydrology of forested catchments. For three eucalypt species that dominate high-elevation catchments in south-eastern Australia, we examined if whole-tree water use could be related to three widely discussed regulators of water use: stomatal anatomy, sensitivity of stomata [i.e. stomatal conductance (g(s))] to environmental influences, and sapwood area. While daily tree water use varied sixfold among species, sap velocity and sapwood area varied in parallel. Combined, stomatal structure and physiology could not explain differences in species-specific water use. Species which exhibited the fastest (Eucalyptus delegatensis) and slowest (Eucalyptus pauciflora) rates of water use both exhibited greater capacity for physiological control of g(s) [indicated by sensitivity to vapour pressure deficit (VPD)] and a reduced capacity to limit g(s) anatomically [indicated by greater potential g(s) (g(max))]. Conversely, g(s) was insensitive to VPD and g(max) was lowest for Eucalyptus radiata, the species showing intermediate rates of water use. Improved knowledge of stomatal anatomy will help us to understand the capacity of species to regulate leaf-level water loss, but seems likely to remain of limited use for explaining rates of whole-tree water use in montane eucalypts at the catchment scale.

Increased leaf area dominates carbon flux response to elevated CO2 in stands of Populus deltoides (Bartr.)

Treesearch

Ramesh Murthy; Greg Barron-Gafford; Philip M. Dougherty; Victor c. Engels; Katie Grieve; Linda Handley; Christie Klimas; Mark J. Postosnaks; Stanley J. Zarnoch; Jianwei Zhang

2005-01-01

We examined the effects of atmospheric vapor pressure deficit (VPD) and soil moisture stress (SMS) on leaf- and stand-level CO2 exchange in model 3-year-old coppiced cottonwood (Populus deltoides Bartr.) plantations using the large-scale, controlled environments of the Biosphere 2 Laboratory. A short-term experiment was imposed...

Field evidences for the positive effects of aerosols on tree growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xin; Wu, Jin; Chen, Min

Theoretical and eddy-covariance studies demonstrate that aerosol-loading stimulates canopy photosynthesis, but field evidence for the aerosol effect on tree growth is limited. For this study, we measured in-situ daily stem growth rates of aspen trees under a wide range of aerosol-loading in China. The results showed that daily stem growth rates were positively correlated with aerosol-loading, even at exceptionally high aerosol levels. Using structural equation modelling analysis, we showed that variations in stem growth rates can be largely attributed to two environmental variables co-varying with aerosol loading: diffuse fraction of radiation and vapor pressure deficit (VPD). Furthermore, we found thatmore » these two factors influence stem growth by influencing photosynthesis from different parts of canopy. By using field observations and a mechanistic photosynthesis model, we demonstrate that photosynthetic rates of both sun and shade leaves increased under high aerosol-loading conditions but for different reasons. For sun leaves, the photosynthetic increase was primarily attributed to the concurrent lower VPD; for shade leaves, the positive aerosol effect was tightly connected with increased diffuse light. Overall, our study provides the first field-evidence of increased tree growth under high aerosol loading. We highlight the importance of understanding biophysical mechanisms of aerosol-meteorology interactions, and incorporating the different pathways of aerosol effects into earth system models to improve the prediction of large-scale aerosol impacts, and the associated vegetation-mediated climate feedbacks.« less

Field evidences for the positive effects of aerosols on tree growth

DOE PAGES

Wang, Xin; Wu, Jin; Chen, Min; ...

2018-06-01

Theoretical and eddy-covariance studies demonstrate that aerosol-loading stimulates canopy photosynthesis, but field evidence for the aerosol effect on tree growth is limited. For this study, we measured in-situ daily stem growth rates of aspen trees under a wide range of aerosol-loading in China. The results showed that daily stem growth rates were positively correlated with aerosol-loading, even at exceptionally high aerosol levels. Using structural equation modelling analysis, we showed that variations in stem growth rates can be largely attributed to two environmental variables co-varying with aerosol loading: diffuse fraction of radiation and vapor pressure deficit (VPD). Furthermore, we found thatmore » these two factors influence stem growth by influencing photosynthesis from different parts of canopy. By using field observations and a mechanistic photosynthesis model, we demonstrate that photosynthetic rates of both sun and shade leaves increased under high aerosol-loading conditions but for different reasons. For sun leaves, the photosynthetic increase was primarily attributed to the concurrent lower VPD; for shade leaves, the positive aerosol effect was tightly connected with increased diffuse light. Overall, our study provides the first field-evidence of increased tree growth under high aerosol loading. We highlight the importance of understanding biophysical mechanisms of aerosol-meteorology interactions, and incorporating the different pathways of aerosol effects into earth system models to improve the prediction of large-scale aerosol impacts, and the associated vegetation-mediated climate feedbacks.« less

[Sap flux density in response to rainfall pulses for Pinus tabuliformis and Hippophae rhamnoides from mixed plantation in hilly Loess Plateau].

PubMed

Lu, Sen Bao; Chen, Yun Ming; Tang, Ya Kun; Wu, Xu; Wen, Jie

2017-11-01

Thermal dissipation probe (TDP) was used to continuously measure the sap flux density (F d ) of Pinus tabuliformis and Hippophae rhamnoides individuals in hilly Loess Plateau, from June to October 2015, and the environmental factors, i.e., photosynthetic active radiation (PAR), water vapor pressure deficit (VPD), and soil water content (SWC), were simultaneously monitored to clarify the difference of rainfall utilization between the two tree species in a mixed plantation. Using the methods of a Threshold-delay model, stepwise multiple regression analyses, and partial correlation analyses, this paper studied the process of F d in these two species in response to the rainfall pulses and then determined the effects of environmental factors on F d . The results showed that, with the increase of rainfall, the response percentages of F d in both P. tabuliformis and H. rhamnoides increased at first but then decreased; specifically, in the range of 0-1 mm rainfall, the F d of P. tabuliformis (-16.3%) and H. rhamnoides (-6.3%) clearly decreased; in the range of 1-5 mm rainfall, the F d of P. tabuliformis decreased (-0.4%), whereas that of H. rhamnoides significantly increased (9.0%). The lower rainfall thresholds (R L ) of F d for P. tabuliformis and H. rhamnoides were 6.4 and 1.9 mm, respectively, with a corresponding time-lag (τ) of 1.96 and 1.67 days. In the pre-rainfall period, the peak time of F d of P. tabuliformis converged upon 12:00-12:30 (70%), while the F d of H. rhamnoides peaked twice, between 10:30 and 12:00 (48%) and again between 16:00 and 16:30 (30%). In the post-rainfall period, the peak time of F d of P. tabuliformis converged upon 11:00-13:00 (40%), while that of H. rhamnoides peaked twice, between 12:00 and 13:00 (52%) and again between 16:30 and 17:00 (24%). Among the environmental factors, the rank order of factors associated with the F d of both P. tabuliformis and H. rhamnoides was PAR>VPD, before rainfall. However, the rank order of factors influencing the F d of P. tabuliformis was PAR>VPD>0-20 cm SWC (SWC 0-20 ), whereas this order was different for H. rhamnoides: SWC 0-20 >PAR >VPD, after rainfall. This mixed plantation of P. tabuliformis and H. rhamnoides trees had a high stability of water utilization.

Temporal and Spatial Variations of Energy Balance Closure across FLUXNET Research Sites

NASA Astrophysics Data System (ADS)

Chui, T. F. M.; CUI, W.

2017-12-01

The surface energy balance at most measurement sites is not closed and the reason behind the discrepancy between available energy and output energy is always under debate. Based on the FLUXNET database and MODIS product, this study analyzed the energy balance closure (EBC) of around 100 sites covering nine vegetation types in different latitudes and explored the possible relationships between EBC and environmental variables. The results showed that EBC is closely related with precipitation, friction velocity, vapor pressure deficit (VPD) and enhanced vegetation index (EVI). The EBC, computed at 30-min intervals, of different land covers increased with the friction velocity and was highest when the air temperature was between 10 and 20 and the VPD was less than 5 hPa. There was no obvious difference in the seasonal variation of EBC among different land covers. However, for most land covers in the boreal region, the worst EBC usually occurred in November, December and January when EVI was minimum, and the best closure occurred in June and July when EVI was maximum. Moreover, the EBC in the lower latitude was better than that in higher latitude, which could be related with the large uncertainty in ground heat flux measurement due to soil freezing and thawing in the high latitude. This study evaluated the temporal and spatial variations of EBC and investigated the physical explanation behind the energy imbalance based on vegetation growth and climates in different latitudes. It shed some insights regarding the energy imbalance issue and the energy flux between the atmosphere and land surface.

An evolutionary attractor model for sapwood cross section in relation to leaf area.

PubMed

Westoby, Mark; Cornwell, William K; Falster, Daniel S

2012-06-21

Sapwood cross-sectional area per unit leaf area (SA:LA) is an influential trait that plants coordinate with physical environment and with other traits. We develop theory for SA:LA and also for root surface area per leaf area (RA:LA) on the premise that plants maximizing the surplus of revenue over costs should have competitive advantage. SA:LA is predicted to increase in water-relations environments that reduce photosynthetic revenue, including low soil water potential, high water vapor pressure deficit (VPD), and low atmospheric CO(2). Because sapwood has costs, SA:LA adjustment does not completely offset difficult water relations. Where sapwood costs are large, as in tall plants, optimal SA:LA may actually decline with (say) high VPD. Large soil-to-root resistance caps the benefits that can be obtained from increasing SA:LA. Where a plant can adjust water-absorbing surface area of root per leaf area (RA:LA) as well as SA:LA, optimal RA:SA is not affected by VPD, CO(2) or plant height. If selection favours increased height more so than increased revenue-minus-cost, then height is predicted to rise substantially under improved water-relations environments such as high-CO(2) atmospheres. Evolutionary-attractor theory for SA:LA and RA:LA complements models that take whole-plant conductivity per leaf area as a parameter. Copyright © 2012 Elsevier Ltd. All rights reserved.

Factors affecting articulation skills in children with velocardiofacial syndrome and children with cleft palate or velopharyngeal dysfunction: A preliminary report

PubMed Central

Baylis, Adriane L.; Munson, Benjamin; Moller, Karlind T.

2010-01-01

Objective To examine the influence of speech perception, cognition, and implicit phonological learning on articulation skills of children with Velocardiofacial syndrome (VCFS) and children with cleft palate or velopharyngeal dysfunction (VPD). Design Cross-sectional group experimental design. Participants 8 children with VCFS and 5 children with non-syndromic cleft palate or VPD. Methods and Measures All children participated in a phonetic inventory task, speech perception task, implicit priming nonword repetition task, conversational sample, nonverbal intelligence test, and hearing screening. Speech tasks were scored for percentage of phonemes correctly produced. Group differences and relations among measures were examined using nonparametric statistics. Results Children in the VCFS group demonstrated significantly poorer articulation skills and lower standard scores of nonverbal intelligence compared to the children with cleft palate or VPD. There were no significant group differences in speech perception skills. For the implicit priming task, both groups of children were more accurate in producing primed nonwords than unprimed nonwords. Nonverbal intelligence and severity of velopharyngeal inadequacy for speech were correlated with articulation skills. Conclusions In this study, children with VCFS had poorer articulation skills compared to children with cleft palate or VPD. Articulation difficulties seen in the children with VCFS did not appear to be associated with speech perception skills or the ability to learn new phonological representations. Future research should continue to examine relationships between articulation, cognition, and velopharyngeal dysfunction in a larger sample of children with cleft palate and VCFS. PMID:18333642

Daily changes in VPD during leaf development in high air humidity increase the stomatal responsiveness to darkness and dry air.

PubMed

Arve, Louise E; Kruse, Ole Mathis Opstad; Tanino, Karen K; Olsen, Jorunn E; Futsæther, Cecilia; Torre, Sissel

2017-04-01

Previous studies have shown that plants developed under high relative air humidity (RH>85%) develop malfunctioning stomata and therefor have increased transpiration and reduced desiccation tolerance when transferred to lower RH conditions and darkness. In this study, plants developed at high RH were exposed to daily VPD fluctuations created by changes in temperature and/or RH to evaluate the potential improvements in stomatal functioning. Daily periods with an 11°C temperature increase and consequently a VPD increase (vpd: 0.36-2.37KPa) reduced the stomatal apertures and improved the stomatal functionality and desiccation tolerance of the rosette plant Arabidopsis thaliana. A similar experiment was performed with only a 4°C temperature increase and/or a RH decrease on tomato. The results showed that a daily change in VPD (vpd: 0.36-1.43KPa) also resulted in improved stomatal responsiveness and decreased water usage during growth. In tomato, the most effective treatment to increase the stomatal responsiveness to darkness as a signal for closure was daily changes in RH without a temperature increase. Copyright © 2017 Elsevier GmbH. All rights reserved.

Effects of Weather Variables on Ascospore Discharge from Fusarium graminearum Perithecia

PubMed Central

Manstretta, Valentina; Rossi, Vittorio

2015-01-01

Fusarium graminearum is a predominant component of the Fusarium head blight (FHB) complex of small grain cereals. Ascosporic infection plays a relevant role in the spread of the disease. A 3-year study was conducted on ascospore discharge. To separate the effect of weather on discharge from the effect of weather on the production and maturation of ascospores in perithecia, discharge was quantified with a volumetric spore sampler placed near maize stalk residues bearing perithecia with mature ascospores; the residues therefore served as a continuous source of ascospores. Ascospores were discharged from perithecia on 70% of 154 days. Rain (R) and vapor pressure deficit (VPD) were the variables that most affected ascospore discharge, with 84% of total discharges occurring on days with R≥0.2 mm or VPD≤11 hPa, and with 70% of total ascospore discharge peaks (≥ 30 ascospores/m3 air per day) occurring on days with R≥0.2 mm and VPD≤6.35 hPa. An ROC analysis using these criteria for R and VPD provided True Positive Proportion (TPP) = 0.84 and True Negative Proportion (TNP) = 0.63 for occurrence of ascospore discharge, and TPP = 0.70 and TNP = 0.89 for occurrence of peaks. Globally, 68 ascospores (2.5% of the total ascospores sampled) were trapped on the 17 days when no ascospores were erroneously predicted. When a discharge occurred, the numbers of F. graminearum ascospores sampled were predicted by a multiple regression model with R2 = 0.68. This model, which includes average and maximum temperature and VPD as predicting variables, slightly underestimated the real data and especially ascospore peaks. Numbers of ascospores in peaks were best predicted by wetness duration of the previous day, minimum temperature, and VPD, with R2 = 0.71. These results will help refine the epidemiological models used as decision aids in FHB management programs. PMID:26402063

Response of sap flow to environmental factors in the headwater catchment of Miyun Reservoir in subhumid North China

NASA Astrophysics Data System (ADS)

Tie, Qiang; Hu, Hongchang; Tian, Fuqiang; Liu, Yaping; Xu, Ran

2015-04-01

Since the headwater catchment of Miyun Reservoir is the main drinking water conservation area of Beijing, its water cycle is of importance for the regional water resource. Transpiration is an important component of water cycle, which can be estimated by sap flow. In this study, the dynamics of sap flow and its response to environmental factors and relationship with leaf area index (LAI) were analyzed. The field study was conducted in the Xitaizi Experimental Catchment, located in the headwater catchment of Miyun Reservoir in subhumid North China. The Aspen (Populus davidiana) and Epinette (Larix gmelinii) are the two dominant tree species. Sap flow in 15 Aspen (Populus davidiana) trees was monitored using thermal dissipation probes (TDP) during the growing season of 2013 and 2014, and sap flow in another 3 Epinette (Larix gmelinii) trees was also monitored during September and October in 2014 for comparative analysis. Physiological and biometric parameters of the selected trees and the environmental factors, including meteorological variables, soil moisture content and groundwater table depth were measured. Vapor pressure deficit (VPD), variable of transpiration (VT) and reference crop evapotranspiration (ET0) were calculated using the measured environmental factors. The LAI, which is used to characterize phenophase, was calculated using the Moderate Resolution Imaging Spectroradiometer (MODIS) LAI product (MCD15A3). Correlation analysis for daily sap flow and air temperature, relative humidity, precipitation, wind speed, solar radiation, VPD, VT and ET0 under different soil moisture and groundwater table depth conditions was performed. Diurnal course and hysteresis of sap flow were analyzed as a function of air temperature, solar radiation, VPD and VT on the typical sunny, cloudy and rainy days under different soil moisture conditions. Correlation analysis between daily sap flow and LAI showed that LAI and phenophase significantly influence sap flow and restrict the maximum value of sap flow. The sap flow and its response to environmental factors were compared between Aspen and Epinette. The result could make contributions to improve empirical transpiration modeling for efficient water resource management in the headwater catchment of subhumid region.

Compounding nonlinearities in the climate and wildfire system contribute to high uncertainty in estimates of future burned area in the western United State

NASA Astrophysics Data System (ADS)

Williams, P.

2015-12-01

Ecological studies are increasingly recognizing the importance of atmospheric vapor-pressure deficit (VPD) as a driver of forest drought stress and disturbance processes such as wildfire. Because of the nonlinear Clausius-Clapeyron relationship between temperature and saturation vapor pressure, small variations in temperature can have large impacts on VPD, and therefore drought, particularly in warm, dry areas and particularly during the warm season. It is also clear that VPD and drought affect forest fire nonlinearly, as incremental drying leads to increasingly large burned areas. Forest fire is also affected by fuel amount and connectivity, which are promoted by vegetation growth in previous years, which is in turn promoted by lack of drought, highlighting the importance of nuances in the sequencing of natural interannual climate variations in modulating the impacts of drought on wildfire. The many factors affecting forest fire, and the nonlinearities embedded within the climate and wildfire systems, cause interannual variability in forest-fire area and frequency to be wildly variable and strongly affected by internal climate variability. In addition, warming over the past century has produced a background increase in forest fire frequency and area in many regions. In this talk I focus on the western United States and will explore whether the relationships between internal climate variability on forest fire area have been amplified by the effects of warming as a result of the compounding nonlinearities described above. I will then explore what this means for future burned area in the western United States and make the case that uncertainties in the future global greenhouse gas emissions trajectory, model projections of mean temperatures, model projections of precipitation, and model projections of natural climate variability translate to very large uncertainties in the effects of future climate variability on forest fire area in the United States and globally.

Drivers and implications of recent large fire years in boreal North America

NASA Astrophysics Data System (ADS)

Veraverbeke, S.; Rogers, B. M.; Goulden, M.; Jandt, R.; Miller, C. E.; Wiggins, E. B.; Randerson, J. T.

2016-12-01

High latitude ecosystems are rapidly transforming because of climate change. Boreal North America recently experienced two exceptionally large fire years: 2014 in the Northwest Territories, Canada, and 2015 in Alaska, USA. We used geospatial climate, lightning, fire, and vegetation datasets to assess the mechanisms contributing to these recent extreme years and to the causes of recent decadal-scale changes in fire dynamics. We found that the two events had a record number of lightning ignitions and unusually high levels of burning near the boreal treeline, contributing to emissions of 164 ± 32 Tg C in the Northwest Territories and 65 ± 13 Tg C in Interior Alaska. The annual number ignitions in both regions displayed a significant increasing trend since 1975, driven by an increase in lightning ignitions. We found that vapor pressure deficit (VPD) in June, lightning, and ignition events were significantly correlated on interannual timescales. Future climate-driven increases in VPD and lightning near the treeline ecotone may enable northward forest expansion within tundra ecosystems.

The critical amplifying role of increasing atmospheric moisture demand on tree mortality and associated regional die-off

DOE PAGES

Breshears, David D.; Adams, Henry D.; Eamus, Derek; ...

2013-08-02

Drought-induced tree mortality, including large-scale die-off events and increases in background rates of mortality, is a global phenomenon (Allen et al., 2010) that can directly impact numerous earth system properties and ecosystem goods and services (Adams et al., 2010; Breshears et al., 2011; Anderegg et al., 2013). Tree mortality is particularly of concern because of the likelihood that it will increase in frequency and extent with climate change (McDowell et al., 2008, 2011; Adams et al., 2009; McDowell, 2011; Williams et al., 2013). Recent plant science advances related to drought have focused on understanding the physiological mechanisms that not onlymore » affect plant growth and associated carbon metabolism, but also the more challenging issue of predicting plant mortality thresholds (McDowell et al., 2013). Although some advances related to mechanisms of mortality have been made and have increased emphasis on interrelationships between carbon metabolism and plant hydraulics (McDowell et al., 2011), notably few studies have specifically evaluated effects of increasing atmospheric demand for moisture (i.e., vapour pressure deficit; VPD) on rates of tree death. In this opinion article we highlight the importance of considering the key risks of future large-scale tree die-off and other mortality events arising from increased VPD. Here we focus on mortality of trees, but our point about the importance of VPD is also relevant to other vascular plants.« less

Vaccine-preventable diseases: the role of the European Centre for Disease Prevention and Control.

PubMed

Kramarz, P; Lopalco, P L; Huitric, E; Pastore Celentano, L

2014-05-01

The role of the European Centre for Disease Prevention and Control (ECDC) is to strengthen the capacity of the European Union (EU) Member States to protect human health through the prevention and control of infectious diseases. The main objective of the programme on vaccine-preventable diseases and invasive bacterial infections (VPD) is to provide robust evidence and high-quality technical support to the EU Member States to help them in their efforts to prevent and control VPD. Since the establishment of ECDC, several existing VPD surveillance networks have been transferred to ECDC, namely EU-IBIS, DIPNET and EUVAC. In addition to surveillance of diseases, ECDC is collecting information and monitoring other parameters that are of crucial importance for a well-functioning immunization system, including vaccination coverage. The VPD programme also provides independent scientific opinions in the area of immunization and initiates and coordinates scientific studies in the area of vaccination to answer specific questions of public health importance, including risk perception and analysis of behaviour in different population groups. One of the overall ECDC priorities over recent years is the Centre's involvement in measles elimination. The 'Message' tool and the 'Measles Atlas' are examples of work aiming at supporting the efforts of Member States in the elimination phase. © 2013 The Authors Clinical Microbiology and Infection © 2013 European Society of Clinical Microbiology and Infectious Diseases.

Value added by Spirulina platensis in two different diets on growth performance, gut microbiota, and meat quality of Japanese quails.

PubMed

Yusuf, Mohamed S; Hassan, Marwa A; Abdel-Daim, Mohamed M; Nabtiti, Adel S El; Ahmed, Ali Meawad; Moawed, Sherief A; El-Sayed, Ahmed Kamel; Cui, Hengmi

2016-11-01

The growth promoting effect of the blue-green filamentous alga Spirulina platensis (SP) was observed on meat type Japanese quail with antibiotic growth promoter alternative and immune enhancing power. This study was conducted on 180 Japanese quail chicks for 4 weeks to find out the effect of diet type (vegetarian protein diet [VPD] and fish meal protein diet [FMPD])- Spirulina dose interaction (1 or 2 g/kg diet) on growth performance, gut microbiota, and sensory meat quality of growing Japanese quails (1-5 weeks old). Data revealed improvement (p<0.05) of weight gain, feed conversion ratio and European efficiency index due to 1, 2 g (SP)/kg VPD, and 2 g (SP)/kg FMPD, respectively. There was a significant decrease of ileum mean pH value by 1 g (SP)/kg VPD. Concerning gut microbiota, there was a trend toward an increase in Lactobacilli count in both 1; 2 g (SP)/kg VPD and 2 g (SP)/kg FMPD. It was concluded that 1 or 2 g (SP)/kg vegetarian diet may enhance parameters of performance without obvious effect on both meat quality and gut microbiota. Moreover, 1 and/or 2 g (SP) may not be invited to share fish meal based diet for growing Japanese quails. Using of SP will support the profitable production of Japanese quails fed vegetable protein diet.

The enigma of effective path length for (18) O enrichment in leaf water of conifers.

PubMed

Roden, John; Kahmen, Ansgar; Buchmann, Nina; Siegwolf, Rolf

2015-12-01

The Péclet correction is often used to predict leaf evaporative enrichment and requires an estimate of effective path length (L). Studies to estimate L in conifer needles have produced unexpected patterns based on Péclet theory and leaf anatomy. We exposed seedlings of six conifer species to different vapour pressure deficits (VPD) in controlled climate chambers to produce steady-state leaf water enrichment (in (18) O). We measured leaf gas exchange, stable oxygen isotopic composition (δ(18) O) of input and plant waters as well as leaf anatomical characteristics. Variation in bulk needle water δ(18) O was strongly related to VPD. Conifer needles had large amounts of water within the vascular strand that was potentially unenriched (up to 40%). Both standard Craig-Gordon and Péclet models failed to accurately predict conifer leaf water δ(18) O without taking into consideration the unenriched water in the vascular strand and variable L. Although L was linearly related to mesophyll thickness, large within-species variation prevented the development of generalizations that could allow a broader use of the Péclet effect in predictive models. Our results point to the importance of within needle water pools and isolating mechanisms that need further investigation in order to integrate Péclet corrections with 'two compartment' leaf water concepts. © 2015 John Wiley & Sons Ltd.

Velopharyngeal Dysfunction Evaluation and Treatment.

PubMed

Meier, Jeremy D; Muntz, Harlan R

2016-11-01

Velopharyngeal dysfunction (VPD) can significantly impair a child's quality of life and may have lasting consequences if inadequately treated. This article reviews the work-up and management options for patients with VPD. An accurate perceptual speech analysis, nasometry, and nasal endoscopy are helpful to appropriately evaluate patients with VPD. Treatment options include nonsurgical management with speech therapy or a speech bulb and surgical approaches including double-opposing Z-plasty, sphincter pharyngoplasty, pharyngeal flap, or posterior wall augmentation. Copyright © 2016 Elsevier Inc. All rights reserved.

Assessment of stenosis severity: Correlation of angiography, T1-201 scintigraphy, and intracoronary pressure gradients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bateman, T.; Raymond, M.; Czer, L.

1984-01-01

To clarify the relationship between angiographic and hemodynamic stenosis severity and the appearance during stress-redistribution myocardial T1-201 scintigraphy (Ex-T1) of a visual (V) or quantitative (Q) perfusion defect (PD) or washout (WO) abnormality, 24 pts with CAD underwent intracoronary pressure gradient study at bypass surgery (CABG). All had pre-CABG Ex-T1 without interval deterioration. The mean diastolic pressure gradient (MDG) measured at reproducible hyperemic flow rates was determined for 34 stenoses (13 LAD, 7 LCX, 14 RCA) and compared with the results of Ex-T1 in subtended myocardial regions (LAD=anterior; LCX=posterolateral; RCA=inferior). Fourteen stenoses (50-99% diameter narrowing) were unassociated with VPD despitemore » maximal exercise: MDG was 9 +- 5mmHg, with MDG/mean aortic diastolic pressure (ADP) ratio of 0.12 +- 0.07. QPD and QWO analysis detected 8 of these. Thirteen stenoses (90-100% severity) led to reversible VPD: MDG was 36 +- 11 mm Hg, MDG/ADP ratio was 0.52 +- 0.17, and Q analysis was abnormal in 12/13. Seven stenoses (90-100% severity) subtended infarcted myocardium: MDG was 42 +- 21 mm Hg, MDG/ADP ratio was 0.52 +- 0.18, and V and Q analyses were abnormal in all. From this study, the authors derive the following conclusion: 1) Ex-T1 correlates better with hemodynamic severity of stenoses than does angiography; 2) V abnormalities identify stenoses of major angiographic and hemodynamic severity, while Q analysis detects some (57% in this study) stenoses of lesser severity; and 3) stenoses causing reversible Ex-T1 abnormalities present similar hemodynamic impediments to those causing myocardial infarcts.« less

Gross primary production of a semiarid grassland is enhanced by six years of exposure to elevated atmospheric CO2, warming, and irrigation.

NASA Astrophysics Data System (ADS)

Ryan, E.; Ogle, K.; Peltier, D.; Williams, D. G.; Pendall, E.

2014-12-01

The goal of this study was to quantify interannual variation of gross primary production (GPP) and evaluate potential drivers of GPP with global change using the Prairie Heating and CO2 Enrichment (PHACE) experiment in semiarid grassland in southeastern Wyoming. PHACE consists of the treatments: control, warming only, elevated CO2 (eCO2) only, eCO2 and warming, and irrigation only. We expected that GPP would be most strongly influenced by interannual variability in precipitation under all PHACE treatments, soil water availability under eCO2, and nitrogen availability. GPP data were obtained from paired measurements of net ecosystem exchange (NEE) and ecosystem respiration (Reco; GPP = Reco - NEE) made on 2-4 week intervals over six growing seasons (2007-2012). Soil temperature (T), soil water content (SWC), vapor pressure deficit (VPD), and photosynthetically active radiation (PAR) were continuously recorded at the plot (T, SWC) and site (VPD, PAR) scales. Annual, plot-level aboveground plant nitrogen content (N) was measured during peak biomass. We fit a non-linear light-response model to the GPP data within a Bayesian framework, and modeled the maximum GPP rate (Gmax) and canopy light-use efficiency (Q) as functions of N and current and antecedent SWC, T, and VPD. The model fit the GPP data well (R2 = 0.64), and regardless of the PHACE treatment the most important drivers of GPP were N (for Gmax), VPD (Gmax and Q), antecedent T (Gmax), and antecedent VPD (Q). Model simulations predicted that annual GPP increased on average by about 16% with eCO2, 14% with warming, 12% with eCO2 and warming, and 23% with irrigation. For four of the six years, annual GPP was significantly affected by either eCO2 alone or when combined with warming. The increase in annual GPP under irrigation was similar to the increase under eCO2 during a dry year (2012), but irrigation stimulated GPP to a greater degree than eCO2 during wet years (2008, 2009). Hence, increases in GPP under eCO2 appear to be indirectly due to increases in SWC, especially under dry conditions. These results suggest that future climate scenarios will lead to more productive grasslands in semiarid regions, but the overall response of the C cycle and the potential for these systems to sequester greater C will depend on the magnitude and direction of both the Reco and GPP responses.

Value added by Spirulina platensis in two different diets on growth performance, gut microbiota, and meat quality of Japanese quails

PubMed Central

Yusuf, Mohamed S.; Hassan, Marwa A.; Abdel-Daim, Mohamed M.; Nabtiti, Adel S. El; Ahmed, Ali Meawad; Moawed, Sherief A.; El-Sayed, Ahmed Kamel; Cui, Hengmi

2016-01-01

Aim: The growth promoting effect of the blue-green filamentous alga Spirulina platensis (SP) was observed on meat type Japanese quail with antibiotic growth promoter alternative and immune enhancing power. Materials and Methods: This study was conducted on 180 Japanese quail chicks for 4 weeks to find out the effect of diet type (vegetarian protein diet [VPD] and fish meal protein diet [FMPD])- Spirulina dose interaction (1 or 2 g/kg diet) on growth performance, gut microbiota, and sensory meat quality of growing Japanese quails (1-5 weeks old). Results: Data revealed improvement (p<0.05) of weight gain, feed conversion ratio and European efficiency index due to 1, 2 g (SP)/kg VPD, and 2 g (SP)/kg FMPD, respectively. There was a significant decrease of ileum mean pH value by 1 g (SP)/kg VPD. Concerning gut microbiota, there was a trend toward an increase in Lactobacilli count in both 1; 2 g (SP)/kg VPD and 2 g (SP)/kg FMPD. It was concluded that 1 or 2 g (SP)/kg vegetarian diet may enhance parameters of performance without obvious effect on both meat quality and gut microbiota. Moreover, 1 and/or 2 g (SP) may not be invited to share fish meal based diet for growing Japanese quails. Conclusion: Using of SP will support the profitable production of Japanese quails fed vegetable protein diet. PMID:27956783

Predicting Individual Tree and Shrub Species Distributions with Empirically Derived Microclimate Surfaces in a Complex Mountain Ecosystem in Northern Idaho, USA

NASA Astrophysics Data System (ADS)

Holden, Z.; Cushman, S.; Evans, J.; Littell, J. S.

2009-12-01

The resolution of current climate interpolation models limits our ability to adequately account for temperature variability in complex mountainous terrain. We empirically derive 30 meter resolution models of June-October day and nighttime temperature and April nighttime Vapor Pressure Deficit (VPD) using hourly data from 53 Hobo dataloggers stratified by topographic setting in mixed conifer forests near Bonners Ferry, ID. 66%, of the variability in average June-October daytime temperature is explained by 3 variables (elevation, relative slope position and topographic roughness) derived from 30 meter digital elevation models. 69% of the variability in nighttime temperatures among stations is explained by elevation, relative slope position and topographic dissection (450 meter window). 54% of variability in April nighttime VPD is explained by elevation, soil wetness and the NDVIc derived from Landsat. We extract temperature and VPD predictions at 411 intensified Forest Inventory and Analysis plots (FIA). We use these variables with soil wetness and solar radiation indices derived from a 30 meter DEM to predict the presence and absence of 10 common forest tree species and 25 shrub species. Classification accuracies range from 87% for Pinus ponderosa , to > 97% for most other tree species. Shrub model accuracies are also high with greater than 90% accuracy for the majority of species. Species distribution models based on the physical variables that drive species occurrence, rather than their topographic surrogates, will eventually allow us to predict potential future distributions of these species with warming climate at fine spatial scales.

Circadian patterns of xylem sap properties and their covariation with plant hydraulic traits in hybrid aspen.

PubMed

Meitern, Annika; Õunapuu-Pikas, Eele; Sellin, Arne

2017-06-01

Physiological processes taking place in plants are subject to diverse circadian patterns but some of them are poorly documented in natural conditions. The daily dynamics of physico-chemical properties of xylem sap and their covariation with tree hydraulic traits were investigated in hybrid aspen (Populus tremula L.×P. tremuloides Michx) in field conditions in order to clarify which environmental drivers govern the daily variation in these parameters. K + concentration ([K + ]), electrical conductivity (σ sap ), osmolality (Osm) and pH of the xylem sap, as well as branch hydraulic traits, were measured in the field over 24-h cycles. All studied xylem sap properties and hydraulic characteristics including whole-branch (K wb ), leaf blade (K lb ) and petiole hydraulic conductances (K P ) showed clear daily dynamics. Air temperature (T A ) and photosynthetic photon flux density (PPFD), but also water vapour pressure deficit (VPD) and relative humidity (RH), had significant impacts on K wb K lb , K P , [K + ] and σ sap . Osm varied only with light intensity, while K B varied depending on atmospheric evaporative demand expressed as T A , VPD or RH. Xylem sap pH depended inversely on soil water potential (Ψ S ) and during daylight also on VPD. Although soil water content was close to saturation during the study period, Ψ S influenced also [K + ] and σ sap . The present study presents evidence of coupling between circadian patterns of xylem sap properties and plant hydraulic conductance providing adequate water supply to foliage under environmental conditions characterised by diurnal variation. Copyright © 2017 Elsevier GmbH. All rights reserved.

Spatial and temporal patterns of xylem sap pH derived from stems and twigs of Populus deltoides L.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aubrey, Doug P.; Boyles, Justin G.; Krysinsky, Laura S.

2011-02-12

Xylem sap pH (pHX) is critical in determining the quantity of inorganic carbon dissolved in xylem solution from gaseous [CO2] measurements. Studies of internal carbon transport have generally assumed that pHX derived from stems and twigs is similar and that pHX remains constant through time; however, no empirical studies have investigated these assumptions. If any of these assumptions are violated, potentially large errors can be introduced into calculations of dissolved CO 2 in xylem and resulting estimates of internal carbon transport.Wetested the validity of assumptions related to pHX in Populus deltoides L. with a series of non-manipulative experiments. The pHXmore » derived from stems and twigs was generally similar and remained relatively constant through a diel period. The only exception was that pHX derived from lower stem sections at night was higher than that derived from twigs. The pHX derived from stems was similar on clear days when solar radiation and vapor pressure deficit (VPD) were similar, but higher on an overcast day when solar radiation and VPD were lower. Similarly, cloudy conditions immediately before an afternoon thunderstorm increased pHX derived from twigs. The pHX derived from twigs remained similar when measured on sunny afternoons between July and October. Our results suggest that common assumptions of pHX used in studies of internal carbon transport appear valid for P. deltoides and further suggest pHX is influenced by environmental factors, such as solar radiation and VPD that affect transpiration rates.« less

Precipitation thresholds and drought-induced tree die-off: insights from patterns of Pinus edulis mortality along an environmental stress gradient.

PubMed

Clifford, Michael J; Royer, Patrick D; Cobb, Neil S; Breshears, David D; Ford, Paulette L

2013-10-01

Recent regional tree die-off events appear to have been triggered by a combination of drought and heat - referred to as 'global-change-type drought'. To complement experiments focused on resolving mechanisms of drought-induced tree mortality, an evaluation of how patterns of tree die-off relate to highly spatially variable precipitation is needed. Here, we explore precipitation relationships with a die-off event of pinyon pine (Pinus edulis Engelm.) in southwestern North America during the 2002-2003 global-change-type drought. Pinyon die-off and its relationship with precipitation was quantified spatially along a precipitation gradient in north-central New Mexico with standard field plot measurements of die-off combined with canopy cover derived from normalized burn ratio (NBR) from Landsat imagery. Pinyon die-off patterns revealed threshold responses to precipitation (cumulative 2002-2003) and vapor pressure deficit (VPD), with little to no mortality (< 10%) above 600 mm and below warm season VPD of c. 1.7 kPa. [Correction added after online publication 17 June 2013; in the preceding sentence, the word 'below' has been inserted.] Our results refine how precipitation patterns within a region influence pinyon die-off, revealing a precipitation and VPD threshold for tree mortality and its uncertainty band where other factors probably come into play - a response type that influences stand demography and landscape heterogeneity and is of general interest, yet has not been documented. © 2013 No claim to US Government works. New Phytologist © 2013 New Phytologist Trust.

Shift in potential evapotranspiration and its implications for dryness/wetness over Southwest China

NASA Astrophysics Data System (ADS)

Sun, Shanlei; Chen, Haishan; Wang, Guojie; Li, Jinjian; Mu, Mengyuan; Yan, Guixia; Xu, Bei; Huang, Jin; Wang, Jie; Zhang, Fangmin; Zhu, Siguang

2016-08-01

During 1961-2012, the regional average annual potential evapotranspiration (PET) of Southwest China (SWC) and the four subregions (named as SR1, SR2, SR3, and SR4) showed different decreases (excluding SR3); while the breakpoint analysis suggested that PET changes (i.e., sign and magnitude) have shifted. Based on a group of sensitivity experiments with Penman-Monteith equation and a new separating method, the contributions of each climate factor alone (i.e., net radiation, Rn; mean temperature, Tave; wind speed, Wnd; and vapor pressure deficit, Vpd) to PET changes were calculated. Results showed that declined Wnd in SR1, reduced Rn in SR2, SR4, and SWC, and increased Vpd in SR3 were responsible for the PET changes during 1961-2012. However, the determinant factor for each subregion and SWC varied in different segmented periods, which were identified using the breakpoint analysis. The impacts of PET shifts on SWC dryness/wetness (reflected by the 3 month Standardized Precipitation-Evapotranspiration index, SPEI-3) during 1961-2012 were then quantified. Briefly, SPEI-3 changes in SR3, SR4, and SWC had the determinant factor of PET in the first one or two period(s), and precipitation in the last period; while they were attributed to PET (precipitation) in SR1 (SR2) for each segmented period. It is found that PET and precipitation had comparable contributions to the variations in SWC dryness/wetness. Our findings have suggested that more attentions should be paid to the impacts of PET changes and shifts in future studies of dryness/wetness or drought.

Increased vapor pressure deficit due to higher temperature leads to greater transpiration and faster mortality during drought for tree seedlings common to the forest-grassland ecotone.

PubMed

Will, Rodney E; Wilson, Stuart M; Zou, Chris B; Hennessey, Thomas C

2013-10-01

Tree species growing along the forest-grassland ecotone are near the moisture limit of their range. Small increases in temperature can increase vapor pressure deficit (VPD) which may increase tree water use and potentially hasten mortality during severe drought. We tested a 40% increase in VPD due to an increase in growing temperature from 30 to 33°C (constant dewpoint 21°C) on seedlings of 10 tree species common to the forest-grassland ecotone in the southern Great Plains, USA. Measurement at 33 vs 30°C during reciprocal leaf gas exchange measurements, that is, measurement of all seedlings at both growing temperatures, increased transpiration for seedlings grown at 30°C by 40% and 20% for seedlings grown at 33°C. Higher initial transpiration of seedlings in the 33°C growing temperature treatment resulted in more negative xylem water potentials and fewer days until transpiration decreased after watering was withheld. The seedlings grown at 33°C died 13% (average 2 d) sooner than seedlings grown at 30°C during terminal drought. If temperature and severity of droughts increase in the future, the forest-grassland ecotone could shift because low seedling survival rate may not sufficiently support forest regeneration and migration. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Velo-pharyngeal dysfunction: Evaluation and management

PubMed Central

Marsh, Jeffrey L.

2009-01-01

Separation of the nasal and oral cavities by dynamic closure of the velo-pharyngeal port is necessary for normal speech and swallowing. Velo-pharyngeal dysfunction (VPD) may either follow repair of a cleft palate or be independent of clefting. While the diagnosis of VPD is made by audiologic perceptual evaluation of speech, identification of the mechanism of the dysfunction requires instrumental visualization of the velo-pharyngeal port during specific speech tasks. Matching the specific intervention for management of VPD with the type of dysfunction, i.e. differential management for differential diagnosis, maximizes the result while minimizing the morbidity of the intervention. PMID:19884668

Environmental Controls on the Carbon Isotope Composition of Ecosystem Respired Carbon Dioxide in Contrasting Forest Ecosystems in Canada and USA

NASA Astrophysics Data System (ADS)

Alstad, K.; Lai, C.; Flanagan, L. B.; Ehleringer, J. R.

2006-12-01

Our objective was to compare the carbon isotope composition of respired CO2 (δ13CR) from 11 forest ecosystems in Canada and USA and to examine differences among forests in their response to seasonal variation in photosynthetic photon flux density (PPFD), soil and air temperature, vapor pressure deficit (VPD), precipitation, and soil moisture during May-October 2004. We proposed that variations in δ13CR can be used as a proxy for short-term changes in photosynthetic discrimination and associated shifts in integrated ecosystem-level ci/ca. Our analyses included comparisons of δ13CR responses for three functional groups: deciduous, boreal, and coastal forests. The δ13CR values were well predicted for each group based on the six environmental variables considered, where the highest R2 values determined for the coastal, deciduous, and boreal groups were 0.81, 0.80, and 0.56, respectively. Consistent with several previous studies, the highest correlations between δ13CR and shifts in environmental conditions were achieved when the environmental variables were averaged for 2-, 3- or 4-days previous to δ13CR sample collection. The relationships we observed between δ13CR and environmental factors were consistent with known leaf-level responses, and this was especially apparent within each functional group. However, there were differences among the functional groups for the strength and/or significance of the relationships between δ13CR and particular environmental factors. For example, while VPD and soil temperature were significant determinants of variation in δ13CR in the boreal group, PPFD was not a significant factor and there was only a weak relationship observed between δ13CR and changes in soil moisture. By contrast, in the coastal group, variation in δ13CR was very strongly correlated with changes in PPFD, and there was no significant relationship with VPD. At a single site comparisons made between years suggested the potential application of δ13CR values to assess year-to-year variation in ecosystem physiological responses to changing environmental conditions, but also showed that all environmental factors influencing carbon isotope discrimination during photosynthetic gas exchange need to be considered in such an analysis.

Measuring canopy loss and climatic thresholds from an extreme drought along a fivefold precipitation gradient across Texas.

PubMed

Schwantes, Amanda M; Swenson, Jennifer J; González-Roglich, Mariano; Johnson, Daniel M; Domec, Jean-Christophe; Jackson, Robert B

2017-12-01

Globally, trees are increasingly dying from extreme drought, a trend that is expected to increase with climate change. Loss of trees has significant ecological, biophysical, and biogeochemical consequences. In 2011, a record drought caused widespread tree mortality in Texas. Using remotely sensed imagery, we quantified canopy loss during and after the drought across the state at 30-m spatial resolution, from the eastern pine/hardwood forests to the western shrublands, a region that includes the boundaries of many species ranges. Canopy loss observations in ~200 multitemporal fine-scale orthophotos (1-m) were used to train coarser Landsat imagery (30-m) to create 30-m binary statewide canopy loss maps. We found that canopy loss occurred across all major ecoregions of Texas, with an average loss of 9.5%. The drought had the highest impact in post oak woodlands, pinyon-juniper shrublands and Ashe juniper woodlands. Focusing on a 100-km by ~1,000-km transect spanning the State's fivefold east-west precipitation gradient (~1,500 to ~300 mm), we compared spatially explicit 2011 climatic anomalies to our canopy loss maps. Much of the canopy loss occurred in areas that passed specific climatic thresholds: warm season anomalies in mean temperature (+1.6°C) and vapor pressure deficit (VPD, +0.66 kPa), annual percent deviation in precipitation (-38%), and 2011 difference between precipitation and potential evapotranspiration (-1,206 mm). Although similarly low precipitation occurred during the landmark 1950s drought, the VPD and temperature anomalies observed in 2011 were even greater. Furthermore, future climate data under the representative concentration pathway 8.5 trajectory project that average values will surpass the 2011 VPD anomaly during the 2070-2099 period and the temperature anomaly during the 2040-2099 period. Identifying vulnerable ecological systems to drought stress and climate thresholds associated with canopy loss will aid in predicting how forests will respond to a changing climate and how ecological landscapes will change in the near term. © 2017 John Wiley & Sons Ltd.

Unexpected Connections between Humidity and Ion Transport Discovered Using a Model to Bridge Guard Cell-to-Leaf Scales.

PubMed

Wang, Yizhou; Hills, Adrian; Vialet-Chabrand, Silvere; Papanatsiou, Maria; Griffiths, Howard; Rogers, Simon; Lawson, Tracy; Lew, Virgilio L; Blatt, Michael R

2017-11-01

Stomatal movements depend on the transport and metabolism of osmotic solutes that drive reversible changes in guard cell volume and turgor. These processes are defined by a deep knowledge of the identities of the key transporters and of their biophysical and regulatory properties, and have been modeled successfully with quantitative kinetic detail at the cellular level. Transpiration of the leaf and canopy, by contrast, is described by quasilinear, empirical relations for the inputs of atmospheric humidity, CO 2 , and light, but without connection to guard cell mechanics. Until now, no framework has been available to bridge this gap and provide an understanding of their connections. Here, we introduce OnGuard2, a quantitative systems platform that utilizes the molecular mechanics of ion transport, metabolism, and signaling of the guard cell to define the water relations and transpiration of the leaf. We show that OnGuard2 faithfully reproduces the kinetics of stomatal conductance in Arabidopsis thaliana and its dependence on vapor pressure difference (VPD) and on water feed to the leaf. OnGuard2 also predicted with VPD unexpected alterations in K + channel activities and changes in stomatal conductance of the slac1 Cl - channel and ost2 H + -ATPase mutants, which we verified experimentally. OnGuard2 thus bridges the micro-macro divide, offering a powerful tool with which to explore the links between guard cell homeostasis, stomatal dynamics, and foliar transpiration. © 2017 American Society of Plant Biologists. All rights reserved.

On the theory relating changes in area-average and pan evaporation (Invited)

NASA Astrophysics Data System (ADS)

Shuttleworth, W.; Serrat-Capdevila, A.; Roderick, M. L.; Scott, R.

2009-12-01

Theory relating changes in area-average evaporation with changes in the evaporation from pans or open water is developed. Such changes can arise by Type (a) processes related to large-scale changes in atmospheric concentrations and circulation that modify surface evaporation rates in the same direction, and Type (b) processes related to coupling between the surface and atmospheric boundary layer (ABL) at the landscape scale that usually modify area-average evaporation and pan evaporation in different directions. The interrelationship between evaporation rates in response to Type (a) changes is derived. They have the same sign and broadly similar magnitude but the change in area-average evaporation is modified by surface resistance. As an alternative to assuming the complementary evaporation hypothesis, the results of previous modeling studies that investigated surface-atmosphere coupling are parameterized and used to develop a theoretical description of Type (b) coupling via vapor pressure deficit (VPD) in the ABL. The interrelationship between appropriately normalized pan and area-average evaporation rates is shown to vary with temperature and wind speed but, on average, the Type (b) changes are approximately equal and opposite. Long-term Australian pan evaporation data are analyzed to demonstrate the simultaneous presence of Type (a) and (b) processes, and observations from three field sites in southwestern USA show support for the theory describing Type (b) coupling via VPD. England's victory over Australia in 2009 Ashes cricket test match series will not be mentioned.

The TOFp/pVPD time-of-flight system for STAR

NASA Astrophysics Data System (ADS)

Llope, W. J.; Geurts, F.; Mitchell, J. W.; Liu, Z.; Adams, N.; Eppley, G.; Keane, D.; Li, J.; Liu, F.; Liu, L.; Mutchler, G. S.; Nussbaum, T.; Bonner, B.; Sappenfield, P.; Zhang, B.; Zhang, W.-M.

2004-04-01

A time-of-flight system was constructed for the STAR Experiment for the direct identification of hadrons produced in 197Au+ 197Au collisions at RHIC. The system consists of two separate detector subsystems, one called the Pseudo Vertex Position Detector (pVPD, the "start" detector) and the other called the Time of Flight Patch (TOFp, the "stop" detector). Each detector is based on conventional scintillator/phototube technology and includes custom high-performance front-end electronics and a common CAMAC-based digitization and read-out. The design of the system and its performance during the 2001 RHIC run will be described. The start resolution attained by the pVPD was 24 ps, implying a pVPD single-detector resolution of 58 ps. The total time resolution of the system averaged over all detector channels was 87 ps, allowing direct π/ K/ p discrimination for momenta up to ˜1.8 GeV/ c, and direct ( π+ K)/ p discrimination up to ˜3 GeV/ c.

Ambipolar Graphene-Quantum Dot Hybrid Vertical Photodetector with a Graphene Electrode.

PubMed

Che, Yongli; Zhang, Yating; Cao, Xiaolong; Zhang, Haiting; Song, Xiaoxian; Cao, Mingxuan; Yu, Yu; Dai, Haitao; Yang, Junbo; Zhang, Guizhong; Yao, Jianquan

2017-09-20

A strategy to fabricate an ambipolar near-infrared vertical photodetector (VPD) by sandwiching a photoactive material as a channel film between the bottom graphene and top metal electrodes was developed. The channel length in the vertical architecture was determined by the channel layer thickness, which can provide an ultrashort channel length without the need for a high-precision manufacturing process. The performance of VPDs with two types of semiconductor layers, a graphene-PbS quantum dot hybrid (GQDH) and PbS quantum dots (QDs), was measured. The GQDH VPD showed better photoelectric properties than the QD VPD because of the high mobility of graphene doped in the channel. The GQDH VPD exhibited excellent photoresponse properties with a responsivity of 1.6 × 10 4 A/W in the p-type regime and a fast response speed with a rise time of 8 ms. The simple manufacture and the promising photoresponse of the GQDH VPDs reveal that an easy and effective way to fabricate high-performance ambipolar photodetectors was developed.

Response of Quercus velutina growth and water use efficiency to climate variability and nitrogen fertilization in a temperate deciduous forest in the northeastern USA.

PubMed

Jennings, Katie A; Guerrieri, Rossella; Vadeboncoeur, Matthew A; Asbjornsen, Heidi

2016-04-01

Nitrogen (N) deposition and changing climate patterns in the northeastern USA can influence forest productivity through effects on plant nutrient relations and water use. This study evaluates the combined effects of N fertilization, climate and rising atmospheric CO2on tree growth and ecophysiology in a temperate deciduous forest. Tree ring widths and stable carbon (δ(13)C) and oxygen (δ(18)O) isotopes were used to assess tree growth (basal area increment, BAI) and intrinsic water use efficiency (iWUE) ofQuercus velutinaLamb., the dominant tree species in a 20+ year N fertilization experiment at Harvard Forest (MA, USA). We found that fertilized trees exhibited a pronounced and sustained growth enhancement relative to control trees, with the low- and high-N treatments responding similarly. All treatments exhibited improved iWUE over the study period (1984-2011). Intrinsic water use efficiency trends in the control trees were primarily driven by changes in stomatal conductance, while a stimulation in photosynthesis, supported by an increase in foliar %N, contributed to enhancing iWUE in fertilized trees. All treatments were predominantly influenced by growing season vapor pressure deficit (VPD), with BAI responding most strongly to early season VPD and iWUE responding most strongly to late season VPD. Nitrogen fertilization increasedQ. velutinasensitivity to July temperature and precipitation. Combined, these results suggest that ambient N deposition in N-limited northeastern US forests has enhanced tree growth over the past 30 years, while rising ambient CO2has improved iWUE, with N fertilization and CO2having synergistic effects on iWUE. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Manipulation of the apoplastic pH of intact plants mimics stomatal and growth responses to water availability and microclimatic variation.

PubMed

Wilkinson, Sally; Davies, William J

2008-01-01

The apoplastic pH of intact Forsythiaxintermedia (cv. Lynwood) and tomato (Solanum lycopersicum) plants has been manipulated using buffered foliar sprays, and thereby stomatal conductance (g(s)), leaf growth rate, and plant water loss have been controlled. The more alkaline the pH of the foliar spray, the lower the g(s) and/or leaf growth rate subsequently measured. The most alkaline pH that was applied corresponds to that measured in sap extracted from shoots of tomato and Forsythia plants experiencing, respectively, soil drying or a relatively high photon flux density (PFD), vapour pressure deficit (VPD), and temperature in the leaf microclimate. The negative correlation between PFD/VPD/temperature and g(s) determined in well-watered Forsythia plants exposed to a naturally varying summer microclimate was eliminated by spraying the plants with relatively alkaline but not acidic buffers, providing evidence for a novel pH-based signalling mechanism linking the aerial microclimate with stomatal aperture. Increasing the pH of the foliar spray only reduced g(s) in plants of the abscisic acid (ABA)-deficient flacca mutant of tomato when ABA was simultaneously sprayed onto leaves or injected into stems. In well-watered Forsythia plants exposed to a naturally varying summer microclimate (variable PFD, VPD, and temperature), xylem pH and leaf ABA concentration fluctuated but were positively correlated. Manipulation of foliar apoplastic pH also affected the response of g(s) and leaf growth to ABA injected into stems of intact Forsythia plants. The techniques used here to control physiology and water use in intact growing plants could easily be applied in a horticultural context.

Are winter-active species vulnerable to climate warming? A case study with the wintergreen terrestrial orchid, Tipularia discolor.

PubMed

Marchin, Renée M; Dunn, Robert R; Hoffmann, William A

2014-12-01

In the eastern United States, winter temperature has been increasing nearly twice as fast as summer temperature, but studies of warming effects on plants have focused on species that are photosynthetically active in summer. The terrestrial orchid Tipularia discolor is leafless in summer and acquires C primarily in winter. The optimum temperature for photosynthesis in T. discolor is higher than the maximum temperature throughout most of its growing season, and therefore growth can be expected to increase with warming. Contrary to this hypothesis, experimental warming negatively affected reproductive fitness (number of flowering stalks, flowers, fruits) and growth (change in leaf area from 2010 to 2012) in T. discolor. Temperature in June-July was critical for flowering, and mean July temperature greater than 29 °C (i.e., 2.5 °C above ambient) eliminated reproduction. Warming of 1.2 °C delayed flowering by an average of 10 days and fruiting by an average of 5 days. Warming of 4.4 °C reduced relative growth rates by about 60%, which may have been partially caused by the direct effects of temperature on photosynthesis and respiration. Warming indirectly increased vapor pressure deficit (VPD) by 0.2-0.5 kPa, and leaf-to-air VPD over 1.3 kPa restricted stomatal conductance of T. discolor to 10-40% of maximum conductance. These results highlight the need to account for changes in VPD when estimating temperature responses of plant species under future warming scenarios. Increasing temperature in the future will likely be an important limiting factor to the distribution of T. discolor, especially along the southern edge of its range.

Evapotranspiration Measurement and Crop Coefficient Estimation over a Spring Wheat Farmland Ecosystem in the Loess Plateau

PubMed Central

Yang, Fulin; Zhang, Qiang; Wang, Runyuan; Zhou, Jing

2014-01-01

Evapotranspiration (ET) is an important component of the surface energy balance and hydrological cycle. In this study, the eddy covariance technique was used to measure ET of the semi-arid farmland ecosystem in the Loess Plateau during 2010 growing season (April to September). The characteristics and environmental regulations of ET and crop coefficient (Kc) were investigated. The results showed that the diurnal variation of latent heat flux (LE) was similar to single-peak shape for each month, with the largest peak value of LE occurring in August (151.4 W m−2). The daily ET rate of the semi-arid farmland in the Loess Plateau also showed clear seasonal variation, with the maximum daily ET rate of 4.69 mm day−1. Cumulative ET during 2010 growing season was 252.4 mm, and lower than precipitation. Radiation was the main driver of farmland ET in the Loess Plateau, which explained 88% of the variances in daily ET (p<0.001). The farmland Kc values showed the obvious seasonal fluctuation, with the average of 0.46. The correlation analysis between daily Kc and its major environmental factors indicated that wind speed (Ws), relative humidity (RH), soil water content (SWC), and atmospheric vapor pressure deficit (VPD) were the major environmental regulations of daily Kc. The regression analysis results showed that Kc exponentially decreased with Ws increase, an exponentially increased with RH, SWC increase, and a linearly decreased with VPD increase. An experiential Kc model for the semi-arid farmland in the Loess Plateau, driven by Ws, RH, SWC and VPD, was developed, showing a good consistency between the simulated and the measured Kc values. PMID:24941017

Evapotranspiration measurement and crop coefficient estimation over a spring wheat Farmland ecosystem in the Loess Plateau.

PubMed

Yang, Fulin; Zhang, Qiang; Wang, Runyuan; Zhou, Jing

2014-01-01

Evapotranspiration (ET) is an important component of the surface energy balance and hydrological cycle. In this study, the eddy covariance technique was used to measure ET of the semi-arid farmland ecosystem in the Loess Plateau during 2010 growing season (April to September). The characteristics and environmental regulations of ET and crop coefficient (Kc) were investigated. The results showed that the diurnal variation of latent heat flux (LE) was similar to single-peak shape for each month, with the largest peak value of LE occurring in August (151.4 W m(-2)). The daily ET rate of the semi-arid farmland in the Loess Plateau also showed clear seasonal variation, with the maximum daily ET rate of 4.69 mm day(-1). Cumulative ET during 2010 growing season was 252.4 mm, and lower than precipitation. Radiation was the main driver of farmland ET in the Loess Plateau, which explained 88% of the variances in daily ET (p<0.001). The farmland Kc values showed the obvious seasonal fluctuation, with the average of 0.46. The correlation analysis between daily Kc and its major environmental factors indicated that wind speed (Ws), relative humidity (RH), soil water content (SWC), and atmospheric vapor pressure deficit (VPD) were the major environmental regulations of daily Kc. The regression analysis results showed that Kc exponentially decreased with Ws increase, an exponentially increased with RH, SWC increase, and a linearly decreased with VPD increase. An experiential Kc model for the semi-arid farmland in the Loess Plateau, driven by Ws, RH, SWC and VPD, was developed, showing a good consistency between the simulated and the measured Kc values.

Quantification issues of trace metal contaminants on silicon wafers by means of TOF-SIMS, ICP-MS, and TXRF

NASA Astrophysics Data System (ADS)

Rostam-Khani, P.; Hopstaken, M. J. P.; Vullings, P.; Noij, G.; O'Halloran, O.; Claassen, W.

2004-06-01

Measurement of surface metal contamination on silicon wafers is essential for yield enhancement in IC manufacturing. Vapor phase decomposition coupled with either inductively coupled plasma mass spectrometry (VPD-ICP-MS), or total reflection X-ray fluorescence (VPD-TXRF), TXRF and more recently time of flight secondary ion mass spectrometry (TOF-SIMS) are used to monitor surface metal contamination. These techniques complement each other in their respective strengths and weaknesses. For reliable and accurate quantification, so-called relative sensitivity factors (RSF) are required for TOF-SIMS analysis. For quantification purposes in VPD, the collection efficiency (CE) is important to ensure complete collection of contamination. A standard procedure has been developed that combines the determination of these RSFs as well as the collection efficiency using all the analytical techniques mentioned above. Therefore, sample wafers were intentionally contaminated and analyzed (by TOF-SIMS) directly after preparation. After VPD-ICP-MS, several scanned surfaces were analyzed again by TOF-SIMS. Comparing the intensities of the specific metals before and after the VPD-DC procedure on the scanned surface allows the determination of so-called removing efficiency (RE). In general, very good agreement was obtained comparing the four analytical techniques after updating the RSFs for TOF-SIMS. Progress has been achieved concerning the CE evaluation as well as determining the RSFs more precisely for TOF-SIMS.

Stand-level variation in evapotranspiration in non-water-limited eucalypt forests

NASA Astrophysics Data System (ADS)

Benyon, Richard G.; Nolan, Rachael H.; Hawthorn, Sandra N. D.; Lane, Patrick N. J.

2017-08-01

To better understand water and energy cycles in forests over years to decades, measurements of spatial and long-term temporal variability in evapotranspiration (Ea) are needed. In mountainous terrain, plot-level measurements are important to achieving this. Forest inventory data including tree density and size measurements, often collected repeatedly over decades, sample the variability occurring within the geographic and topographic range of specific forest types. Using simple allometric relationships, tree stocking and size data can be used to estimate variables including sapwood area index (SAI), which may be strongly correlated with annual Ea. This study analysed plot-level variability in SAI and its relationship with overstorey and understorey transpiration, interception and evaporation over a 670 m elevation gradient, in non-water-limited, even-aged stands of Eucalyptus regnans F. Muell. to determine how well spatial variation in annual Ea from forests can be mapped using SAI. Over the 3 year study, mean sap velocity in five E. regnans stands was uncorrelated with overstorey sapwood area index (SAI) or elevation: annual transpiration was predicted well by SAI (R2 0.98). Overstorey and total annual interception were positively correlated with SAI (R2 0.90 and 0.75). Ea from the understorey was strongly correlated with vapour pressure deficit (VPD) and net radiation (Rn) measured just above the understorey, but relationships between understorey Ea and VPD and Rn differed between understorey types and understorey annual Ea was not correlated with SAI. Annual total Ea was also strongly correlated with SAI: the relationship being similar to two previous studies in the same region, despite differences in stand age and species. Thus, spatial variation in annual Ea can be reliably mapped using measurements of SAI.

In Search of the Optimal Surgical Treatment for Velopharyngeal Dysfunction in 22q11.2 Deletion Syndrome: A Systematic Review

PubMed Central

Spruijt, Nicole E.; ReijmanHinze, Judith; Hens, Greet; Vander Poorten, Vincent; Mink van der Molen, Aebele B.

2012-01-01

Background Patients with the 22q11.2 deletion syndrome (22qDS) and velopharyngeal dysfunction (VPD) tend to have residual VPD following surgery. This systematic review seeks to determine whether a particular surgical procedure results in superior speech outcome or less morbidity. Methodology/ Principal Findings A combined computerized and hand-search yielded 70 studies, of which 27 were deemed relevant for this review, reporting on a total of 525 patients with 22qDS and VPD undergoing surgery for VPD. All studies were levels 2c or 4 evidence. The methodological quality of these studies was assessed using criteria based on the Cochrane Collaboration's tool for assessing risk of bias. Heterogeneous groups of patients were reported on in the studies. The surgical procedure was often tailored to findings on preoperative imaging. Overall, 50% of patients attained normal resonance, 48% attained normal nasal emissions scores, and 83% had understandable speech postoperatively. However, 5% became hyponasal, 1% had obstructive sleep apnea (OSA), and 17% required further surgery. There were no significant differences in speech outcome between patients who underwent a fat injection, Furlow or intravelar veloplasty, pharyngeal flap pharyngoplasty, Honig pharyngoplasty, or sphincter pharyngoplasty or Hynes procedures. There was a trend that a lower percentage of patients attained normal resonance after a fat injection or palatoplasty than after the more obstructive pharyngoplasties (11–18% versus 44–62%, p = 0.08). Only patients who underwent pharyngeal flaps or sphincter pharyngoplasties incurred OSA, yet this was not statistically significantly more often than after other procedures (p = 0.25). More patients who underwent a palatoplasty needed further surgery than those who underwent a pharyngoplasty (50% versus 7–13%, p = 0.03). Conclusions/ Significance In the heterogeneous group of patients with 22qDS and VPD, a grade C recommendation can be made to minimize the morbidity of further surgery by choosing to perform a pharyngoplasty directly instead of only a palatoplasty. PMID:22470558

Soil moisture and wild olive tree transpiration relationship in a water-limited Mediterranean ecosystem.

NASA Astrophysics Data System (ADS)

Curreli, M.; Montaldo, N.; Oren, R.

2016-12-01

Typically, during the dry summers, Mediterranean ecosystems are characterized by a simple dual PFTs system with strong-resistant woody vegetation and bare soil, since grass died. In these conditions the combined use of sap flow measurements, based on Granier's thermo-dissipative probes, eddy covariance technique and soil water content measurements provides a robust estimation of evapotranspiration (ET). An eddy covariance micrometeorological tower, thermo-dissipative probes based on the Granier technique and TDR sensors have been installed in the Orroli site in Sardinia (Italy). The site landscape is a mixture of Mediterranean patchy vegetation types: wild olives, different shrubs and herbaceous species, which died during the summer. 33 sap flow sensors have been installed at the Orroli site into 15 wild olives clumps with different characteristics (tree size, exposition to wind, solar radiation and soil depth). Sap flow measurements show the significantly impacts on transpiration of soil moisture, radiation and vapor pressure deficit (VPD). In addition ET is strongly influenced by the tree position into the clump. Results show a significant difference in sap flow rate for the south exposed trees compared to inside clump and north exposed trees. Using an innovative scaling procedure, the transpiration calculated from sap flow measurements have been compared to the eddy covariance ET. Sap flow measurements show night time uptake allows the recharge of the stem capacity, depleted during the day before due to transpiration. The night uptake increases with increasing VPD and transpiration but surprisingly it is independent to soil water content. Soil moisture probes allow monitoring spatial and temporal dynamics of water content at different soil depth and distance to the trees, and estimating its correlation with hydraulic lift. During the light hours soil moisture is depleted by roots to provide the water for transpiration and during night time the lateral roots transfer water from pasture in conjunction whit deep roots uptake to recharge water in the stem.

Sea breezes and advective effects in southwest James Bay

NASA Technical Reports Server (NTRS)

Mckendry, Ian; Roulet, Nigel

1994-01-01

Observations from a transect extending 100 km inland during the Northern Wetlands Study (NOWES) in 1990 show that the sea breeze develops on approximately 25% of days during summer and may penetrate up to 100 km inland on occasions. The sea breeze exhibits a marked diurnal clockwise rotation as a result of the Coriolis effect along the unobstructed coastline. The marine advective effect is shown to depend on gradient wind direction. With northwesterly upper level flow the sea breeze tends to be northeasterly in direction and is associated with decreased temperatures and vapor pressure deficits (VPD). With southwesterly upper level flow the sea breeze tends to have a southeasterly direction and less effect on temperatures and VPD. This is attributed to shorter residence times of air parcels over water. For two cases, Colorado State University mesoscale model simulations show good agreement with surface wind observations and suggest that under northwesterly gradient flow, Bowen ratios are increased in the onshore flow along western James Bay, while during southwesterly gradient flow these effects are negligible. These results have implications for the interpretation of local climate, ecology, and hydrology as well as land-based and airborne turbulent flux measurements made during NOWES.

Leaf age affects the responses of foliar injury and gas exchange to tropospheric ozone in Prunus serotina seedlings.

PubMed

Zhang, Jianwei; Schaub, Marcus; Ferdinand, Jonathan A; Skelly, John M; Steiner, Kim C; Savage, James E

2010-08-01

We investigated the effect of leaf age on the response of net photosynthesis (A), stomatal conductance (g(wv)), foliar injury, and leaf nitrogen concentration (N(L)) to tropospheric ozone (O(3)) on Prunus serotina seedlings grown in open-plots (AA) and open-top chambers, supplied with either carbon-filtered or non-filtered air. We found significant variation in A, g(wv), foliar injury, and N(L) (P < 0.05) among O(3) treatments. Seedlings in AA showed the highest A and g(wv) due to relatively low vapor pressure deficit (VPD). Older leaves showed significantly lower A, g(wv), N(L), and higher foliar injury (P < 0.001) than younger leaves. Leaf age affected the response of A, g(wv), and foliar injury to O(3). Both VPD and N(L) had a strong influence on leaf gas exchange. Foliar O(3)-induced injury appeared when cumulative O(3) uptake reached 8-12 mmol m(-2), depending on soil water availability. The mechanistic assessment of O(3)-induced injury is a valuable approach for a biologically relevant O(3) risk assessment for forest trees. Published by Elsevier Ltd.

A limited-angle intrafraction verification (LIVE) system for radiation therapy.

PubMed

Ren, Lei; Zhang, You; Yin, Fang-Fang

2014-02-01

Currently, no 3D or 4D volumetric x-ray imaging techniques are available for intrafraction verification of target position during actual treatment delivery or in-between treatment beams, which is critical for stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) treatments. This study aims to develop a limited-angle intrafraction verification (LIVE) system to use prior information, deformation models, and limited angle kV-MV projections to verify target position intrafractionally. The LIVE system acquires limited-angle kV projections simultaneously during arc treatment delivery or in-between static 3D/IMRT treatment beams as the gantry moves from one beam to the next. Orthogonal limited-angle MV projections are acquired from the beam's eye view (BEV) exit fluence of arc treatment beam or in-between static beams to provide additional anatomical information. MV projections are converted to kV projections using a linear conversion function. Patient prior planning CT at one phase is used as the prior information, and the on-board patient volume is considered as a deformation of the prior images. The deformation field is solved using the data fidelity constraint, a breathing motion model extracted from the planning 4D-CT based on principal component analysis (PCA) and a free-form deformation (FD) model. LIVE was evaluated using a 4D digital extended cardiac torso phantom (XCAT) and a CIRS 008A dynamic thoracic phantom. In the XCAT study, patient breathing pattern and tumor size changes were simulated from CT to treatment position. In the CIRS phantom study, the artificial target in the lung region experienced both size change and position shift from CT to treatment position. Varian Truebeam research mode was used to acquire kV and MV projections simultaneously during the delivery of a dynamic conformal arc plan. The reconstruction accuracy was evaluated by calculating the 3D volume percentage difference (VPD) and the center of mass (COM) difference of the tumor in the true on-board images and reconstructed images. In both simulation and phantom studies, LIVE achieved substantially better reconstruction accuracy than reconstruction using PCA or FD deformation model alone. In the XCAT study, the average VPD and COM differences among different patient scenarios for LIVE system using orthogonal 30° scan angles were 4.3% and 0.3 mm when using kV+BEV MV. Reducing scan angle to 15° increased the average VPD and COM differences to 15.1% and 1.7 mm. In the CIRS phantom study, the VPD and COM differences for the LIVE system using orthogonal 30° scan angles were 6.4% and 1.4 mm. Reducing scan angle to 15° increased the VPD and COM differences to 51.9% and 3.8 mm. The LIVE system has the potential to substantially improve intrafraction target localization accuracy by providing volumetric verification of tumor position simultaneously during arc treatment delivery or in-between static treatment beams. With this improvement, LIVE opens up a new avenue for margin reduction and dose escalation in both fractionated treatments and SRS and SBRT treatments.

A limited-angle intrafraction verification (LIVE) system for radiation therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Lei, E-mail: lei.ren@duke.edu; Yin, Fang-Fang; Zhang, You

Purpose: Currently, no 3D or 4D volumetric x-ray imaging techniques are available for intrafraction verification of target position during actual treatment delivery or in-between treatment beams, which is critical for stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) treatments. This study aims to develop a limited-angle intrafraction verification (LIVE) system to use prior information, deformation models, and limited angle kV-MV projections to verify target position intrafractionally. Methods: The LIVE system acquires limited-angle kV projections simultaneously during arc treatment delivery or in-between static 3D/IMRT treatment beams as the gantry moves from one beam to the next. Orthogonal limited-angle MV projectionsmore » are acquired from the beam's eye view (BEV) exit fluence of arc treatment beam or in-between static beams to provide additional anatomical information. MV projections are converted to kV projections using a linear conversion function. Patient prior planning CT at one phase is used as the prior information, and the on-board patient volume is considered as a deformation of the prior images. The deformation field is solved using the data fidelity constraint, a breathing motion model extracted from the planning 4D-CT based on principal component analysis (PCA) and a free-form deformation (FD) model. LIVE was evaluated using a 4D digital extended cardiac torso phantom (XCAT) and a CIRS 008A dynamic thoracic phantom. In the XCAT study, patient breathing pattern and tumor size changes were simulated from CT to treatment position. In the CIRS phantom study, the artificial target in the lung region experienced both size change and position shift from CT to treatment position. Varian Truebeam research mode was used to acquire kV and MV projections simultaneously during the delivery of a dynamic conformal arc plan. The reconstruction accuracy was evaluated by calculating the 3D volume percentage difference (VPD) and the center of mass (COM) difference of the tumor in the true on-board images and reconstructed images. Results: In both simulation and phantom studies, LIVE achieved substantially better reconstruction accuracy than reconstruction using PCA or FD deformation model alone. In the XCAT study, the average VPD and COM differences among different patient scenarios for LIVE system using orthogonal 30° scan angles were 4.3% and 0.3 mm when using kV+BEV MV. Reducing scan angle to 15° increased the average VPD and COM differences to 15.1% and 1.7 mm. In the CIRS phantom study, the VPD and COM differences for the LIVE system using orthogonal 30° scan angles were 6.4% and 1.4 mm. Reducing scan angle to 15° increased the VPD and COM differences to 51.9% and 3.8 mm. Conclusions: The LIVE system has the potential to substantially improve intrafraction target localization accuracy by providing volumetric verification of tumor position simultaneously during arc treatment delivery or in-between static treatment beams. With this improvement, LIVE opens up a new avenue for margin reduction and dose escalation in both fractionated treatments and SRS and SBRT treatments.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Lei, E-mail: lei.ren@duke.edu; Yin, Fang-Fang; Zhang, You

Purpose: Currently, no 3D or 4D volumetric x-ray imaging techniques are available for intrafraction verification of target position during actual treatment delivery or in-between treatment beams, which is critical for stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) treatments. This study aims to develop a limited-angle intrafraction verification (LIVE) system to use prior information, deformation models, and limited angle kV-MV projections to verify target position intrafractionally. Methods: The LIVE system acquires limited-angle kV projections simultaneously during arc treatment delivery or in-between static 3D/IMRT treatment beams as the gantry moves from one beam to the next. Orthogonal limited-angle MV projectionsmore » are acquired from the beam's eye view (BEV) exit fluence of arc treatment beam or in-between static beams to provide additional anatomical information. MV projections are converted to kV projections using a linear conversion function. Patient prior planning CT at one phase is used as the prior information, and the on-board patient volume is considered as a deformation of the prior images. The deformation field is solved using the data fidelity constraint, a breathing motion model extracted from the planning 4D-CT based on principal component analysis (PCA) and a free-form deformation (FD) model. LIVE was evaluated using a 4D digital extended cardiac torso phantom (XCAT) and a CIRS 008A dynamic thoracic phantom. In the XCAT study, patient breathing pattern and tumor size changes were simulated from CT to treatment position. In the CIRS phantom study, the artificial target in the lung region experienced both size change and position shift from CT to treatment position. Varian Truebeam research mode was used to acquire kV and MV projections simultaneously during the delivery of a dynamic conformal arc plan. The reconstruction accuracy was evaluated by calculating the 3D volume percentage difference (VPD) and the center of mass (COM) difference of the tumor in the true on-board images and reconstructed images. Results: In both simulation and phantom studies, LIVE achieved substantially better reconstruction accuracy than reconstruction using PCA or FD deformation model alone. In the XCAT study, the average VPD and COM differences among different patient scenarios for LIVE system using orthogonal 30° scan angles were 4.3% and 0.3 mm when using kV+BEV MV. Reducing scan angle to 15° increased the average VPD and COM differences to 15.1% and 1.7 mm. In the CIRS phantom study, the VPD and COM differences for the LIVE system using orthogonal 30° scan angles were 6.4% and 1.4 mm. Reducing scan angle to 15° increased the VPD and COM differences to 51.9% and 3.8 mm. Conclusions: The LIVE system has the potential to substantially improve intrafraction target localization accuracy by providing volumetric verification of tumor position simultaneously during arc treatment delivery or in-between static treatment beams. With this improvement, LIVE opens up a new avenue for margin reduction and dose escalation in both fractionated treatments and SRS and SBRT treatments.« less

Multi-temporal Scale Analysis of Environmental Control on Net Ecosystem Exchange of CO2 in Forest Ecosystems

NASA Astrophysics Data System (ADS)

Zhang, Mi; Yu, Guirui; Zhuang, Jie; Gentry, Randy; Koirala, Shesh; Zhang, Leiming; Sun, Xiaomin; Han, Shijie; Yan, Junhua

2013-04-01

Multi-temporal scale analysis of environmental control on forest ecosystem carbon budget is a basis for understanding the responses and adaptation of forest carbon cycle to climate change. In this study, we chose two typical forest ecosystems, Changbaishan temperate mixed forest (CBS) in northeastern China and Dinghushan subtropical evergreen broad-leaved forest (DHS) in southern China to identify the changes in environmental control on net ecosystem exchange of carbon dioxide (NEE) with the temporal scales. The analysis was made based on the flux and routine meteorological data measured during the period from 2005 to 2008. These time series data were analyzed using wavelet and cross wavelet transform. The results showed that NEE had significant daily and annual periodic variation in the two types of forest ecosystem. NEE at CBS and DHS showed semi-annual (176 days) and seasonal (88-104 days) periodic variations, respectively. Photosynthetically active radiation (PAR), vapor pressure deficient (VPD), air temperature (Ta), soil temperature (Ts, at 5-cm depth) controlled daily variation of NEE as indicated by the significant high common power of cross wavelet transform spectrums between NEE and these factors. Similarly, Ta, VPD, and precipitation (P) controlled annual variation of NEE at CBS. However, Ta, PAR, and soil water content (SWC, at 5-cm depth) dominated the annual variation of NEE at DHS. An anti-phase between NEE and PAR at daily scale in the two forest ecosystems demonstrated an agreement of the variation of NEE with PAR, with rising sunlight corresponding with increased net carbon uptake. At annual scale, phase angles between NEE and Ta and between NEE and P were -170° and 176°, respectively at CBS. At DHS, phase angle between NEE and VPD was smallest at annual scale. The results indicated that the peak of net carbon uptake seasonal variation and the peaks of P and Ta seasonal variations occurred at the same month at CBS. But, at DHS, seasonal variation of net carbon uptake was in agreement with that of VPD at annual scale. This study showed that wavelet analysis was an effective approach to identifying the temporal pattern of environmental control on carbon exchange between ecosystem and the atmosphere.

Quantity of protein deposited on hydrogel contact lenses and its relation to visible protein deposits.

PubMed

Myers, R I; Larsen, D W; Tsao, M; Castellano, C; Becherer, L D; Fontana, F; Ghormley, N R; Meier, G

1991-10-01

The purposes of this study were to determine if the quantity of protein deposited (QPD) upon hydrogel lenses was affected by enzymatic cleaning and to test the potential relation between QPD and visible protein deposition (VPD) and change. Seventy-four contact lens patients classified as "heavy depositors" wore new lenses for an average of 80 (SD = 32) days. Cleaning and disinfection solutions varied. One lens was cleaned weekly by a papain enzymatic treatment. The distribution of QPD measurements was bimodal and was related to the FDA material for nonionic, low water content lenses (FDA Materials Group no. 1). The mean deposition was 45 micrograms/cm2 (N = 112) compared with that of ionic, high water content lenses (FDA Materials Group no. 4), which was 1010 micrograms/cm2 (N = 30). VPD distributions were the same for the FDA Group no. 1 and no. 4 lenses. Enzymatic treatment did not significantly reduce QPD; however, enzymatic treatment did reduce VPD. Thus QPD and VPD are independent phenomena and possible reasons for this are given.

CO2 uptake and ecophysiological parameters of the grain crops of midcontinent North America: estimates from flux tower measurements

USGS Publications Warehouse

Gilmanov, Tagir; Wylie, Bruce; Tieszen, Larry; Meyers, Tilden P.; Baron, Vern S.; Bernacchi, Carl J.; Billesbach, David P.; Burba, George G.; Fischer, Marc L.; Glenn, Aaron J.; Hanan, Niall P.; Hatfield, Jerry L.; Heuer, Mark W.; Hollinger, Steven E.; Howard, Daniel M.; Matamala, Roser; Prueger, John H.; Tenuta, Mario; Young, David G.

2013-01-01

We analyzed net CO2 exchange data from 13 flux tower sites with 27 site-years of measurements over maize and wheat fields across midcontinent North America. A numerically robust “light-soil temperature-VPD”-based method was used to partition the data into photosynthetic assimilation and ecosystem respiration components. Year-round ecosystem-scale ecophysiological parameters of apparent quantum yield, photosynthetic capacity, convexity of the light response, respiration rate parameters, ecological light-use efficiency, and the curvature of the VPD-response of photosynthesis for maize and wheat crops were numerically identified and interpolated/extrapolated. This allowed us to gap-fill CO2 exchange components and calculate annual totals and budgets. VPD-limitation of photosynthesis was systematically observed in grain crops of the region (occurring from 20 to 120 days during the growing season, depending on site and year), determined by the VPD regime and the numerical value of the curvature parameter of the photosynthesis-VPD-response, σVPD. In 78% of the 27 site-years of observations, annual gross photosynthesis in these crops significantly exceeded ecosystem respiration, resulting in a net ecosystem production of up to 2100 g CO2 m−2 year−1. The measurement-based photosynthesis, respiration, and net ecosystem production data, as well as the estimates of the ecophysiological parameters, provide an empirical basis for parameterization and validation of mechanistic models of grain crop production in this economically and ecologically important region of North America.

Cost analysis of an integrated vaccine-preventable disease surveillance system in Costa Rica.

PubMed

Toscano, C M; Vijayaraghavan, M; Salazar-Bolaños, H M; Bolaños-Acuña, H M; Ruiz-González, A I; Barrantes-Solis, T; Fernández-Vargas, I; Panero, M S; de Oliveira, L H; Hyde, T B

2013-07-02

Following World Health Organization recommendations set forth in the Global Framework for Immunization Monitoring and Surveillance, Costa Rica in 2009 became the first country to implement integrated vaccine-preventable disease (iVPD) surveillance, with support from the U.S. Centers for Disease Control and Prevention (CDC) and the Pan American Health Organization (PAHO). As surveillance for diseases prevented by new vaccines is integrated into existing surveillance systems, these systems could cost more than routine surveillance for VPDs targeted by the Expanded Program on Immunization. We estimate the costs associated with establishing and subsequently operating the iVPD surveillance system at a pilot site in Costa Rica. We retrospectively collected data on costs incurred by the institutions supporting iVPD surveillance during the preparatory (January 2007 through August 2009) and implementation (September 2009 through August 2010) phases of the iVPD surveillance project in Costa Rica. These data were used to estimate costs for personnel, meetings, infrastructure, office equipment and supplies, transportation, and laboratory facilities. Costs incurred by each of the collaborating institutions were also estimated. During the preparatory phase, the estimated total cost was 128,000 U.S. dollars (US$), including 64% for personnel costs. The preparatory phase was supported by CDC and PAHO. The estimated cost for 1 year of implementation was US$ 420,000, including 58% for personnel costs, 28% for laboratory costs, and 14% for meeting, infrastructure, office, and transportation costs combined. The national reference laboratory and the PAHO Costa Rica office incurred 64% of total costs, and other local institutions supporting iVPD surveillance incurred the remaining 36%. Countries planning to implement iVPD surveillance will require adequate investments in human resources, laboratories, data management, reporting, and investigation. Our findings will be valuable for decision makers and donors planning and implementing similar strategies in other countries. Copyright © 2013 Elsevier Ltd. All rights reserved.

Cost analysis of an integrated vaccine-preventable disease surveillance system in Costa Rica✩

PubMed Central

Toscano, C.M.; Vijayaraghavan, M.; Salazar-Bolaños, H.M.; Bolaños-Acuña, H.M.; Ruiz-González, A.I.; Barrantes-Solis, T.; Fernández-Vargas, I.; Panero, M.S.; de Oliveira, L.H.; Hyde, T.B.

2015-01-01

Introduction Following World Health Organization recommendations set forth in the Global Framework for Immunization Monitoring and Surveillance, Costa Rica in 2009 became the first country to implement integrated vaccine-preventable disease (iVPD) surveillance, with support from the U.S. Centers for Disease Control and Prevention (CDC) and the Pan American Health Organization (PAHO). As surveillance for diseases prevented by new vaccines is integrated into existing surveillance systems, these systems could cost more than routine surveillance for VPDs targeted by the Expanded Program on Immunization. Objectives We estimate the costs associated with establishing and subsequently operating the iVPD surveillance system at a pilot site in Costa Rica. Methods We retrospectively collected data on costs incurred by the institutions supporting iVPD surveillance during the preparatory (January 2007 through August 2009) and implementation (September 2009 through August 2010) phases of the iVPD surveillance project in Costa Rica. These data were used to estimate costs for personnel, meetings, infrastructure, office equipment and supplies, transportation, and laboratory facilities. Costs incurred by each of the collaborating institutions were also estimated. Results During the preparatory phase, the estimated total cost was 128,000 U.S. dollars (US$), including 64% for personnel costs. The preparatory phase was supported by CDC and PAHO. The estimated cost for 1 year of implementation was US$ 420,000, including 58% for personnel costs, 28% for laboratory costs, and 14% for meeting, infrastructure, office, and transportation costs combined. The national reference laboratory and the PAHO Costa Rica office incurred 64% of total costs, and other local institutions supporting iVPD surveillance incurred the remaining 36%. Conclusions Countries planning to implement iVPD surveillance will require adequate investments in human resources, laboratories, data management, reporting, and investigation. Our findings will be valuable for decision makers and donors planning and implementing similar strategies in other countries. PMID:23777698

Climatic limits on foliar growth during major droughts in the Southwestern U.S.A.

USGS Publications Warehouse

Weiss, Jeremy L.; Betancourt, Julio L.; Overpeck, Jonathan T.

2012-01-01

Pronounced droughts during the 1950s and 2000s in the Southwestern U.S.A. (SW) provide an opportunity to compare mesoscale ecosystem responses to anomalously dry conditions before and during the regional warming that started in the late 1970s. This year-round warming has produced fewer cool season freezes, losses in regional snowpack, an 8-10 day advance in spring onset, and hotter summers, all of which should affect vegetation differently across seasons and elevations. Here, we examine indices that represent climatic limits on foliar growth for both drought periods, and evaluate these indices for areas that experienced tree mortality during the 2000s drought. Relative to the 1950s drought, warmer conditions during the 2000s drought decreased the occurrence of temperatures too low for foliar growth at lower elevations in winter and higher elevations in summer. Higher vapor pressure deficits (VPDs) largely driven by warmer temperatures in the more recent drought were more limiting to foliar growth from spring through summer at lower and middle elevations. At many locations where tree mortality occurred during the 2000s drought, low-temperature constraints on foliar growth were extremely unlimiting, whereas VPD constraints were extremely limiting from early spring through late autumn. Our analysis shows that in physiographically complex regions like the SW, seasonality and elevational gradients are important for understanding vegetative responses to warming. It also suggests that continued warming will increase the degree to which VPD limits foliar growth during future droughts, and expand its reach to higher elevations and other seasons.

Low-dose mitomycin C, etoposide, and cisplatin for invasive vulvar Paget's disease.

PubMed

Watanabe, Yoh; Hoshiai, H; Ueda, H; Nakai, H; Obata, K; Noda, K

2002-01-01

We report the effect of low-dose mitomycin C, etoposide, and cisplatin (low-dose MEP) therapy for three patients with invasive vulvar Paget's disease (invasive VPD) who declined radical vulvectomy and skin grafting. One patient achieved a complete response, while the other two showed partial responses (PR) without grade 3 or 4 adverse effects. The two patients with PR were undergone partial vulvectomy and inguinal lymph node dissection. All patients have no sign of recurrence for 10 months after chemotherapy. Our present results suggest that low-dose MEP is an effective and safe chemotherapy for invasive VPD and low-dose MEP may significantly improve postoperative quality of life in patients with invasive VPD by avoiding extensive vulvar resection and skin grafting.

Different sources of soil CO2 respiration from a drained spruce forest and their dependence on environmental factors

NASA Astrophysics Data System (ADS)

Nousratpour, A.

2011-12-01

The annual CO2 emission from soils corresponds to a large portion of the global carbon cycle and equals 10 percent of the total atmospheric carbon pool. The total forest soil CO2 loss equals the sum of contribution from autotrophic and heterotrophic organisms. The autotrophic respiration is derived from recent photosynthates from the forest canopy and exudates via the roots. The heterotrophic respiration is less directly dependent on root presence and recently assimilated photosynthates, which points to the possibility of separate mechanisms governing the CO2 emissions. The variation of the CO2 flux from these some-what overlapping sources in the soil i.e. rhizospheric and non-rhizosperically is still not fully understood. Soil temperature and water availability in particular have often been used to explain the variation of soil CO2 efflux by using regression methods. In this experiment around 1000 hours of soil CO2-emission rates from a drained spruce forest was collected from 6 plots, among which 3 were previously root excluded. The emission rates were collected during 5 campaigns throughout the growing season along with continuous above ground and below ground temperature and water properties such as precipitation and VPD (vapor pressure deficit). The resulting matrix was analyzed using multivariate statistical model PLSr (Partial Least Squares regression). This operation reduces the dimensionality of large datasets with probable multicollinearity and helps clarify the dependence of a response factor on x- variables. In addition a time series analysis is applied to the dataset to address the time lag between below ground temperature and water properties to the above ground weather conditions such as VPD and air temperature. Mean carbon emission from the control plots (428 mg Carbon m-2 hr-1) was significantly larger than that from the root excluded plots (136 mg Carbon m-2 hr-1). During the growing season more than 2/3 of the total CO2 release was estimated to be root contribution. The results show that the activity in the rhizosphere increased with rising soil temperature, VPD and ground water depletion until a certain point. When the level of ground water depth was deeper than about 0.5 m the dependence was reversed. This effect was either the opposite or lacking in the root excluded plots, which reflects the involvement of the tree roots and the separate factors controlling the different sources of CO2.

Video Game Rehabilitation of Velopharyngeal Dysfunction: A Case Series.

PubMed

Cler, Gabriel J; Mittelman, Talia; Braden, Maia N; Woodnorth, Geralyn Harvey; Stepp, Cara E

2017-06-22

Video games provide a promising platform for rehabilitation of speech disorders. Although video games have been used to train speech perception in foreign language learners and have been proposed for aural rehabilitation, their use in speech therapy has been limited thus far. We present feasibility results from at-home use in a case series of children with velopharyngeal dysfunction (VPD) using an interactive video game that provided real-time biofeedback to facilitate appropriate nasalization. Five participants were recruited across a range of ages, VPD severities, and VPD etiologies. Participants completed multiple weeks of individual game play with a video game that provides feedback on nasalization measured via nasal accelerometry. Nasalization was assessed before and after training by using nasometry, aerodynamic measures, and expert perceptual judgments. Four participants used the game at home or school, with the remaining participant unwilling to have the nasal accelerometer secured to his nasal skin, perhaps due to his young age. The remaining participants showed a tendency toward decreased nasalization after training, particularly for the words explicitly trained in the video game. Results suggest that video game-based systems may provide a useful rehabilitation platform for providing real-time feedback of speech nasalization in VPD. https://doi.org/10.23641/asha.5116828.

Drivers of variability in water use of two co-occurring species in a subalpine forest in Jiuzhaigou Valley, Southwest of China

NASA Astrophysics Data System (ADS)

Yan, C.; Zhao, W.; Wang, Y.; Zhang, Q.; Qiu, G. Y.

2016-12-01

Co-occur species with different sensitivity to soil water may be particularly useful in evaluating water use by different forest stands as well as the response of species distribution, forest structure and stand composition to soil water availability in water-limited area. To clarify the species-specific water use strategy and provide insights into the possible succession trend, variations in sap flow and environmental conditions were investigated for two co-occur species (Betula albo-sinensis and Pinus tabulaeformis) in a mixed forest in Jiuzhaigou Valley in 2014. Sap flow was measured by Granier-type thermal dissipation probes and soil water content was measured by time-domain reflectometry probes for a successive period. Pinus tabulaeformis and Betua albo-sinensis species showed different responses to meteorological factors under different soil water conditions. Despite that whole tree water use was much higher for Pinus tabulaeformis due to greater sapwood area, sap flux density of the other co-occurring species Betua albo-sinensis was higher throughout the growing season. Normalized sap flux density (Fd) could be mostly well fitted to solar radiation (Rs), vapor pressure deficit (VPD), or the variable of transpiration (VT) by the exponential saturation function. Much better fitted curves were found for Fd -VPD and Fd - VT datasets than Fd - Rs datasets. For most datasets, normalized Fd increased rapidly when the environmental factors were below their threshold values, but reached an asymptote thereafter. Based on the species' differences in fitting parameters and the average maximum sap flow level under different soil water conditions, it was concluded that Pinus tabulaeformis was sensitive to soil water conditions and tolerant of low soil water availability, while Betua albo-sinensis was insensitive to soil moisture and needed to access to similarly high amount of soil water in the growing season after leaf expansion. These results indicated possible successful succession for Pinus tabulaeformis rather than Betua albo-sinensis. Our results may be useful for proper reforestation practices and sustainable forest management in water-limited regions.

Partitioning Evapotranspiration for Three Typical Ecosystems in the Heihe River Basin, Northwestern China

NASA Astrophysics Data System (ADS)

Zhou, S.; Yu, B.; Zhang, Y.; Huang, Y.; Wang, G.

2017-12-01

It is crucial to improve water use efficiency (WUE) and the transpiration fraction of evapotranspiration (T/ET) for water conservation in arid regions. As a link between carbon and water cycling, WUE is defined as the ratio of gross primary productivity (GPP) and ET at the ecosystem scale. By incorporating the effect of vapor pressure deficit (VPD), two underlying WUE (uWUE) formulations, i.e. a potential uWUE (uWUEp=GPP·VPD0.5/T) and an apparent uWUE (uWUEa=GPP·VPD0.5/ET), were proposed. uWUEp is nearly constant for a given vegetation type, while uWUEa varies with T/ET. The ratio of uWUEa and uWUEp was then used to estimate T/ET. This new method for ET partitioning was applied to three typical ecosystems in the Heihe River Basin. Growing season T/ET at the Daman site (0.63) was higher than that at the Arou and Huyanglin sites (0.55) due to the application of plastic film mulching. The effect of leaf area index (LAI) on seasonal variations in T/ET was strong for Arou (R2=0.74) and Daman (R2=0.76) sites, but weak for Huyanglin (R2=0.44) site. Daily T/ET derived using the uWUE method agreed with that using the isotope and lysimeter/eddy covariance methods during the peak growth season at the Daman site. The estimated T using the uWUE method showed consistent seasonal and diurnal patterns and magnitudes with that using the sap flow method at the Huyanglin site. In addition, the uWUE method is scale-independent, and can effectively capture T/ET variations in relation to LAI changes and the abrupt T/ET changes in response to individual irrigation events. These advantages make the uWUE method more effective for ET partitioning at the ecosystem scale, and can be used for water resources management by predicting seasonal pattern of irrigation water requirements in arid regions.

Weather and Prey Predict Mammals' Visitation to Water.

PubMed

Harris, Grant; Sanderson, James G; Erz, Jon; Lehnen, Sarah E; Butler, Matthew J

2015-01-01

Throughout many arid lands of Africa, Australia and the United States, wildlife agencies provide water year-round for increasing game populations and enhancing biodiversity, despite concerns that water provisioning may favor species more dependent on water, increase predation, and reduce biodiversity. In part, understanding the effects of water provisioning requires identifying why and when animals visit water. Employing this information, by matching water provisioning with use by target species, could assist wildlife management objectives while mitigating unintended consequences of year-round watering regimes. Therefore, we examined if weather variables (maximum temperature, relative humidity [RH], vapor pressure deficit [VPD], long and short-term precipitation) and predator-prey relationships (i.e., prey presence) predicted water visitation by 9 mammals. We modeled visitation as recorded by trail cameras at Sevilleta National Wildlife Refuge, New Mexico, USA (June 2009 to September 2014) using generalized linear modeling. For 3 native ungulates, elk (Cervus Canadensis), mule deer (Odocoileus hemionus), and pronghorn (Antilocapra americana), less long-term precipitation and higher maximum temperatures increased visitation, including RH for mule deer. Less long-term precipitation and higher VPD increased oryx (Oryx gazella) and desert cottontail rabbits (Sylvilagus audubonii) visitation. Long-term precipitation, with RH or VPD, predicted visitation for black-tailed jackrabbits (Lepus californicus). Standardized model coefficients demonstrated that the amount of long-term precipitation influenced herbivore visitation most. Weather (especially maximum temperature) and prey (cottontails and jackrabbits) predicted bobcat (Lynx rufus) visitation. Mule deer visitation had the largest influence on coyote (Canis latrans) visitation. Puma (Puma concolor) visitation was solely predicted by prey visitation (elk, mule deer, oryx). Most ungulate visitation peaked during May and June. Coyote, elk and puma visitation was relatively consistent throughout the year. Within the diel-period, activity patterns for predators corresponded with prey. Year-round water management may favor species with consistent use throughout the year, and facilitate predation. Providing water only during periods of high use by target species may moderate unwanted biological costs.

Midday depression of leaf CO2 exchange within the crown of Dipterocarpus sublamellatus in a lowland dipterocarp forest in Peninsular Malaysia.

PubMed

Kosugi, Yoshiko; Takanashi, Satoru; Matsuo, Naoko; Nik, Abdul Rahim

2009-04-01

We observed diurnal and seasonal patterns of leaf-scale gas exchange within the crown of a Dipterocarpus sublamellatus Foxw. tree growing in a lowland dipterocarp forest at Pasoh, Peninsular Malaysia. Observations were carried out nine times over 6 years, from September 2002 to December 2007. Observation periods included both wet and mild-dry periods, and natural and saturated photosynthetic photon flux density (PPFD) light conditions. In situ measurements of the diurnal change in net photosynthetic rate and in stomatal conductance were carried out on canopy leaves of a 40-m-tall D. sublamellatus tree, which was accessed from a canopy corridor. A diurnal change in electron transport rate was observed under saturated PPFD conditions. The maximum net assimilation rate was approximately 10 micromol m(-2) s(-1). There was a clear inhibition of the net assimilation rate coupled with stomatal closure after late morning and this inhibition occurred year-round. Although the electron transport rate decreased alongside this inhibition, it sometimes followed on. Numerical analysis showed that the main factor in the inhibition of the net assimilation rate was patchy bimodal stomatal closure, which occurred in both mild-dry and wet periods. The midday depression occurred year-round, though there are fluctuations in soil moisture during the mild-dry and wet periods. The magnitude of the inhibition was not related to soil water content but was related to vapor pressure deficit (VPD): that is, whether the days were sunny and hot or cloudy and cool. On cloudy, cool days in the wet period, the net photosynthesis was only moderately inhibited, but it still decreased in the afternoon and was coupled with patchy stomatal closure, even in quite moderate VPD, leaf temperature and PPFD conditions. Our results suggest that patchy stomatal closure signaled by the increase in VPD, in transpiration and by circadian rhythms, was the key factor in constraining midday leaf gas exchange of the D. sublamellatus canopy leaves.

Weather and Prey Predict Mammals’ Visitation to Water

PubMed Central

Harris, Grant; Sanderson, James G.; Erz, Jon; Lehnen, Sarah E.; Butler, Matthew J.

2015-01-01

Throughout many arid lands of Africa, Australia and the United States, wildlife agencies provide water year-round for increasing game populations and enhancing biodiversity, despite concerns that water provisioning may favor species more dependent on water, increase predation, and reduce biodiversity. In part, understanding the effects of water provisioning requires identifying why and when animals visit water. Employing this information, by matching water provisioning with use by target species, could assist wildlife management objectives while mitigating unintended consequences of year-round watering regimes. Therefore, we examined if weather variables (maximum temperature, relative humidity [RH], vapor pressure deficit [VPD], long and short-term precipitation) and predator-prey relationships (i.e., prey presence) predicted water visitation by 9 mammals. We modeled visitation as recorded by trail cameras at Sevilleta National Wildlife Refuge, New Mexico, USA (June 2009 to September 2014) using generalized linear modeling. For 3 native ungulates, elk (Cervus Canadensis), mule deer (Odocoileus hemionus), and pronghorn (Antilocapra americana), less long-term precipitation and higher maximum temperatures increased visitation, including RH for mule deer. Less long-term precipitation and higher VPD increased oryx (Oryx gazella) and desert cottontail rabbits (Sylvilagus audubonii) visitation. Long-term precipitation, with RH or VPD, predicted visitation for black-tailed jackrabbits (Lepus californicus). Standardized model coefficients demonstrated that the amount of long-term precipitation influenced herbivore visitation most. Weather (especially maximum temperature) and prey (cottontails and jackrabbits) predicted bobcat (Lynx rufus) visitation. Mule deer visitation had the largest influence on coyote (Canis latrans) visitation. Puma (Puma concolor) visitation was solely predicted by prey visitation (elk, mule deer, oryx). Most ungulate visitation peaked during May and June. Coyote, elk and puma visitation was relatively consistent throughout the year. Within the diel-period, activity patterns for predators corresponded with prey. Year-round water management may favor species with consistent use throughout the year, and facilitate predation. Providing water only during periods of high use by target species may moderate unwanted biological costs. PMID:26560518

Desiccation resistance in tropical insects: causes and mechanisms underlying variability in a Panama ant community.

PubMed

Bujan, Jelena; Yanoviak, Stephen P; Kaspari, Michael

2016-09-01

Desiccation resistance, the ability of an organism to reduce water loss, is an essential trait in arid habitats. Drought frequency in tropical regions is predicted to increase with climate change, and small ectotherms are often under a strong desiccation risk. We tested hypotheses regarding the underexplored desiccation potential of tropical insects. We measured desiccation resistance in 82 ant species from a Panama rainforest by recording the time ants can survive desiccation stress. Species' desiccation resistance ranged from 0.7 h to 97.9 h. We tested the desiccation adaptation hypothesis, which predicts higher desiccation resistance in habitats with higher vapor pressure deficit (VPD) - the drying power of the air. In a Panama rainforest, canopy microclimates averaged a VPD of 0.43 kPa, compared to a VPD of 0.05 kPa in the understory. Canopy ants averaged desiccation resistances 2.8 times higher than the understory ants. We tested a number of mechanisms to account for desiccation resistance. Smaller insects should desiccate faster given their higher surface area to volume ratio. Desiccation resistance increased with ant mass, and canopy ants averaged 16% heavier than the understory ants. A second way to increase desiccation resistance is to carry more water. Water content was on average 2.5% higher in canopy ants, but total water content was not a good predictor of ant desiccation resistance or critical thermal maximum (CT max), a measure of an ant's thermal tolerance. In canopy ants, desiccation resistance and CT max were inversely related, suggesting a tradeoff, while the two were positively correlated in understory ants. This is the first community level test of desiccation adaptation hypothesis in tropical insects. Tropical forests do contain desiccation-resistant species, and while we cannot predict those simply based on their body size, high levels of desiccation resistance are always associated with the tropical canopy.

Climate-resilient agroforestry: physiological responses to climate change and engineering of crassulacean acid metabolism (CAM) as a mitigation strategy.

PubMed

Borland, Anne M; Wullschleger, Stan D; Weston, David J; Hartwell, James; Tuskan, Gerald A; Yang, Xiaohan; Cushman, John C

2015-09-01

Global climate change threatens the sustainability of agriculture and agroforestry worldwide through increased heat, drought, surface evaporation and associated soil drying. Exposure of crops and forests to warmer and drier environments will increase leaf:air water vapour-pressure deficits (VPD), and will result in increased drought susceptibility and reduced productivity, not only in arid regions but also in tropical regions with seasonal dry periods. Fast-growing, short-rotation forestry (SRF) bioenergy crops such as poplar (Populus spp.) and willow (Salix spp.) are particularly susceptible to hydraulic failure following drought stress due to their isohydric nature and relatively high stomatal conductance. One approach to sustaining plant productivity is to improve water-use efficiency (WUE) by engineering crassulacean acid metabolism (CAM) into C3 crops. CAM improves WUE by shifting stomatal opening and primary CO2 uptake and fixation to the night-time when leaf:air VPD is low. CAM members of the tree genus Clusia exemplify the compatibility of CAM performance within tree species and highlight CAM as a mechanism to conserve water and maintain carbon uptake during drought conditions. The introduction of bioengineered CAM into SRF bioenergy trees is a potentially viable path to sustaining agroforestry production systems in the face of a globally changing climate. © 2014 John Wiley & Sons Ltd.

Detection efficiency vs. cathode and anode separation in cylindrical vacuum photodiodes used for measuring x-rays from plasma focus device.

PubMed

Borthakur, T K; Talukdar, N; Neog, N K; Rao, C V S; Shyam, A

2011-10-01

A qualitative study on the performance of cylindrical vacuum photodiodes (VPDs) for x-ray detection in plasma focus device has been carried out. Various parameters of VPD such as electrode's diameter, electrode's separation, and its sensitivity are experimentally tested in plasma focus environment. For the first time it is found experimentally that the electrode-separation in the lateral direction of the two coaxial electrodes of cylindrical VPD also plays an important role to increase the efficiency of the detector. The efficiency is found to be highest for the detector with smaller cathode-anode lateral gap (1.5 mm) with smaller photo cathode diameter (10 mm). A comparison between our VPD with PIN (BPX-65) diode as an x-ray detector has also been made.

Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

NASA Astrophysics Data System (ADS)

Gao, Yao; Markkanen, Tiina; Aurela, Mika; Mammarella, Ivan; Thum, Tea; Tsuruta, Aki; Yang, Huiyi; Aalto, Tuula

2017-09-01

The influence of drought on plant functioning has received considerable attention in recent years, however our understanding of the response of carbon and water coupling to drought in terrestrial ecosystems still needs to be improved. A severe soil moisture drought occurred in southern Finland in the late summer of 2006. In this study, we investigated the response of water use efficiency to summer drought in a boreal Scots pine forest (Pinus sylvestris) on the daily time scale mainly using eddy covariance flux data from the Hyytiälä (southern Finland) flux site. In addition, simulation results from the JSBACH land surface model were evaluated against the observed results. Based on observed data, the ecosystem level water use efficiency (EWUE; the ratio of gross primary production, GPP, to evapotranspiration, ET) showed a decrease during the severe soil moisture drought, while the inherent water use efficiency (IWUE; a quantity defined as EWUE multiplied with mean daytime vapour pressure deficit, VPD) increased and the underlying water use efficiency (uWUE, a metric based on IWUE and a simple stomatal model, is the ratio of GPP multiplied with a square root of VPD to ET) was unchanged during the drought. The decrease in EWUE was due to the stronger decline in GPP than in ET. The increase in IWUE was because of the decreased stomatal conductance under increased VPD. The unchanged uWUE indicates that the trade-off between carbon assimilation and transpiration of the boreal Scots pine forest was not disturbed by this drought event at the site. The JSBACH simulation showed declines of both GPP and ET under the severe soil moisture drought, but to a smaller extent compared to the observed GPP and ET. Simulated GPP and ET led to a smaller decrease in EWUE but a larger increase in IWUE because of the severe soil moisture drought in comparison to observations. As in the observations, the simulated uWUE showed no changes in the drought event. The model deficiencies exist mainly due to the lack of the limiting effect of increased VPD on stomatal conductance during the low soil moisture condition. Our study provides a deeper understanding of the coupling of carbon and water cycles in the boreal Scots pine forest ecosystem and suggests possible improvements to land surface models, which play an important role in the prediction of biosphere-atmosphere feedbacks in the climate system.

Changes in whole-tree water relations during ontogeny of Pinus flexilis and Pinus ponderosa in a high-elevation meadow.

PubMed

Fischer, Dylan G; Kolb, Thomas E; DeWald, Laura E

2002-07-01

We measured sap flux in Pinus ponderosa Laws. and Pinus flexilis James trees in a high-elevation meadow in northern Arizona that has been invaded by conifers over the last 150 years. Sap flux and environmental data were collected from July 1 to September 1, 2000, and used to estimate leaf specific transpiration rate (El), canopy conductance (Gc) and whole-plant hydraulic conductance (Kh). Leaf area to sapwood area ratio (LA/SA) increased with increasing tree size in P. flexilis, but decreased with increasing tree size in P. ponderosa. Both Gc and Kh decreased with increasing tree size in P. flexilis, and showed no clear trends with tree size in P. ponderosa. For both species, Gc was lower in the summer dry season than in the summer rainy season, but El did not change between wet and dry summer seasons. Midday water potential (Psi(mid)) did not change across seasons for either species, whereas predawn water potential (Psi(pre)) tracked variation in soil water content across seasons. Pinus flexilis showed greater stomatal response to vapor pressure deficit (VPD) and maintained higher Psi(mid) than P. ponderosa. Both species showed greater sensitivity to VPD at high photosynthetically active radiation (PAR; > 2500 micromol m-2 s-1) than at low PAR (< 2500 micromol m-2 s-1). We conclude that the direction of change in Gc and Kh with increasing tree size differed between co-occurring Pinus species, and was influenced by changes in LA/SA. Whole-tree water use and El were similar between wet and dry summer seasons, possibly because of tight stomatal control over water loss. 2002 Heron Publishing--Victoria, Canada

Video Game Rehabilitation of Velopharyngeal Dysfunction: A Case Series

PubMed Central

Mittelman, Talia; Braden, Maia N.; Woodnorth, Geralyn Harvey; Stepp, Cara E.

2017-01-01

Purpose Video games provide a promising platform for rehabilitation of speech disorders. Although video games have been used to train speech perception in foreign language learners and have been proposed for aural rehabilitation, their use in speech therapy has been limited thus far. We present feasibility results from at-home use in a case series of children with velopharyngeal dysfunction (VPD) using an interactive video game that provided real-time biofeedback to facilitate appropriate nasalization. Method Five participants were recruited across a range of ages, VPD severities, and VPD etiologies. Participants completed multiple weeks of individual game play with a video game that provides feedback on nasalization measured via nasal accelerometry. Nasalization was assessed before and after training by using nasometry, aerodynamic measures, and expert perceptual judgments. Results Four participants used the game at home or school, with the remaining participant unwilling to have the nasal accelerometer secured to his nasal skin, perhaps due to his young age. The remaining participants showed a tendency toward decreased nasalization after training, particularly for the words explicitly trained in the video game. Conclusion Results suggest that video game–based systems may provide a useful rehabilitation platform for providing real-time feedback of speech nasalization in VPD. Supplemental Material https://doi.org/10.23641/asha.5116828 PMID:28655049

Gross primary production responses to warming, elevated CO2 , and irrigation: quantifying the drivers of ecosystem physiology in a semiarid grassland.

PubMed

Ryan, Edmund M; Ogle, Kiona; Peltier, Drew; Walker, Anthony P; De Kauwe, Martin G; Medlyn, Belinda E; Williams, David G; Parton, William; Asao, Shinichi; Guenet, Bertrand; Harper, Anna B; Lu, Xingjie; Luus, Kristina A; Zaehle, Sönke; Shu, Shijie; Werner, Christian; Xia, Jianyang; Pendall, Elise

2017-08-01

Determining whether the terrestrial biosphere will be a source or sink of carbon (C) under a future climate of elevated CO 2 (eCO 2 ) and warming requires accurate quantification of gross primary production (GPP), the largest flux of C in the global C cycle. We evaluated 6 years (2007-2012) of flux-derived GPP data from the Prairie Heating and CO 2 Enrichment (PHACE) experiment, situated in a grassland in Wyoming, USA. The GPP data were used to calibrate a light response model whose basic formulation has been successfully used in a variety of ecosystems. The model was extended by modeling maximum photosynthetic rate (A max ) and light-use efficiency (Q) as functions of soil water, air temperature, vapor pressure deficit, vegetation greenness, and nitrogen at current and antecedent (past) timescales. The model fits the observed GPP well (R 2  = 0.79), which was confirmed by other model performance checks that compared different variants of the model (e.g. with and without antecedent effects). Stimulation of cumulative 6-year GPP by warming (29%, P = 0.02) and eCO 2 (26%, P = 0.07) was primarily driven by enhanced C uptake during spring (129%, P = 0.001) and fall (124%, P = 0.001), respectively, which was consistent across years. Antecedent air temperature (Tair ant ) and vapor pressure deficit (VPD ant ) effects on A max (over the past 3-4 days and 1-3 days, respectively) were the most significant predictors of temporal variability in GPP among most treatments. The importance of VPD ant suggests that atmospheric drought is important for predicting GPP under current and future climate; we highlight the need for experimental studies to identify the mechanisms underlying such antecedent effects. Finally, posterior estimates of cumulative GPP under control and eCO 2 treatments were tested as a benchmark against 12 terrestrial biosphere models (TBMs). The narrow uncertainties of these data-driven GPP estimates suggest that they could be useful semi-independent data streams for validating TBMs. © 2017 John Wiley & Sons Ltd.

Net ecosystem carbon dioxide exchange in tropical rainforests - sensitivity to environmental drivers and flux measurement methodology

NASA Astrophysics Data System (ADS)

Fu, Z.; Stoy, P. C.

2017-12-01

Tropical rainforests play a central role in the Earth system services of carbon metabolism, climate regulation, biodiversity maintenance, and more. They are under threat by direct anthropogenic effects including deforestation and indirect anthropogenic effects including climate change. A synthesis of the factors that determine the net ecosystem exchange of carbon dioxide (NEE) across multiple time scales in different tropical rainforests has not been undertaken to date. Here, we study NEE and its components, gross primary productivity (GPP) and ecosystem respiration (RE), across thirteen tropical rainforest research sites with 63 total site-years of eddy covariance data. Results reveal that the five ecosystems that have greater carbon uptakes (with the magnitude of GPP greater than 3000 g C m-2 y-1) sequester less carbon - or even lose it - on an annual basis at the ecosystem scale. This counterintuitive result is because high GPP is compensated by similar magnitudes of RE. Sites that provided subcanopy CO2 storage observations had higher average magnitudes of GPP and RE and consequently lower NEE, highlighting the importance of measurement methodology for understanding carbon dynamics in tropical rainforests. Vapor pressure deficit (VPD) constrained GPP at all sites, but to differing degrees. Many environmental variables are significantly related to NEE at time scales greater than one year, and NEE at a rainforest in Malaysia is significantly related to soil moisture variability at seasonal time scales. Climate projections from 13 general circulation models (CMIP5) under representative concentration pathway (RCP) 8.5 suggest that many current tropical rainforest sites on the cooler end of the current temperature range are likely to reach a climate space similar to present-day warmer sites by the year 2050, and warmer sites will reach a climate space not currently experienced. Results demonstrate the need to quantify if mature tropical trees acclimate to heat and VPD, and to further develop flux-partitioning and gap-filling algorithms for defensible estimates of carbon exchange in tropical rainforests.

Leaf functional plasticity decreases the water consumption without further consequences for carbon uptake in Quercus coccifera L. under Mediterranean conditions

PubMed Central

Peguero-Pina, José Javier; Sisó, Sergio; Fernández-Marín, Beatriz; Flexas, Jaume; Galmés, Jeroni; García-Plazaola, Jose Ignacio; Niinemets, Ülo; Sancho-Knapik, Domingo; Gil-Pelegrín, Eustaquio

2016-01-01

The accumulation of epicuticular waxes over stomata in Quercus coccifera L. contributes to a severe reduction in maximum stomatal conductance (gs,max) under Mediterranean (MED) conditions. However, this phenomenon was not observed in this species under temperate (TEM) conditions, which could lead to differences in the ability to assimilate CO2 between the sites. We hypothesise that the overall importance of such a reduction in gs,max on photosynthesis is modulated by other factors affecting carbon gain, mainly mesophyll conductance to CO2 (gm), through a plastic response to changes in environmental conditions (i.e., vapour pressure deficit, VPD, and mean daily quantum flux density, Qint). The results reveal that leaves grown at the TEM site did not show an increased ability for net CO2 assimilation (AN), mainly due to an equal gm at both sites. This fact is explained by a trade-off between an increased conductance of the gas phase (gias) and a reduced conductance of the liquid phase (gliq) at the TEM site compared with the MED site. In spite of the reduction in gs,max at the MED site, transpiration (E) did not diminish during midsummer to the levels of the TEM site due to a higher VPD found at the MED site, yielding a higher water use efficiency (AN/E) at the TEM site. Moreover, photosynthetic nitrogen use efficiency was also higher at the TEM site, indicating these leaves can reach similar values of AN with lower nitrogen investment that those at the MED site. These results suggest that Q. coccifera does not always use the main resources (water and nutrients) at leaf level as efficiently as possible. Moreover, the different patterns of resource use (in particular N), together with the functional plasticity, cannot overcome the morpho-functional constraints that limit photosynthetic activity, even under potentially favourable conditions. PMID:26705310

Investigating the Contribution of Climate Variables to Estimates of Net Primary Productivity in a Tropical Ecosystem in India

NASA Astrophysics Data System (ADS)

Tripathi, P.; Behera, M. D.; Behera, S. K.; Sahu, N.

2016-12-01

Investigating the impact of climate variables on net primary productivity is crucial to evaluate the ecosystem health and the status of forest type response to climate change. The objective of this paper is (1) to analyze the spatio-temporal pattern of net primary productivity (NPP) in a tropical forest ecosystem situated along the Himalayan foothills in India and (2) to investigate the continuous and delayed effects of climatic variables. Weapplied simple Monteith equation based Light use efficiency model for two dominant plant functional types; sal (Shorea robusta) forest and teak (Tectona grandis) plantation to estimate the NPP for a decadal period from 2001 to 2010. The impact of climate variables on NPP for these 10 years was seen by applying two correlation analyses; generalized linear modelling (GLM) and time lag correlation approach.The impact of different climate variables was observed to vary throughout the study period.A decline in mean NPP during 2002-2003, 2005 and 2008 to 2010 could be attributed to drought, increased vapour pressure deficit, and decreased humidity and solar radiation. In time lag correlation analysis, precipitation and humidity were observed to be the major variables affecting NPP; whereas combination of temperature, humidity and VPD showed dominant effect on NPP in GLM. Shorea robusta forest showed slightly higher NPP than that of Tectona grandis plantation throughout the study period. Highest decrease in NPP was observed during 2010,pertaining to lower solar radiation, humidity and precipitation along with increased VPD.Higher gains in NPP by sal during all years indicates their better adaptability to climate compared to teak. Contribution of different climatic variables through some link process is revealed in statistical analysis clearly indicates the co-dominance of all the variables in explaining NPP. Lacking of site specific meteorological observations and microclimate put constraint on broad level analyses.

Transpiration and stomatal conductance in a young secondary tropical montane forest: contrasts between native trees and invasive understorey shrubs.

PubMed

Ghimire, Chandra Prasad; Bruijnzeel, L Adrian; Lubczynski, Maciek W; Zwartendijk, Bob W; Odongo, Vincent Omondi; Ravelona, Maafaka; van Meerveld, H J Ilja

2018-04-21

It has been suggested that vigorous secondary tropical forests can have very high transpiration rates, but sap flow and stomatal conductance dynamics of trees and shrubs in these forests are understudied. In an effort to address this knowledge gap, sap flow (thermal dissipation method, 12 trees) and stomatal conductance (porometry, six trees) were measured for young (5-7 years) Psiadia altissima (DC.) Drake trees, a widely occurring species dominating young regrowth following abandonment of swidden agriculture in upland eastern Madagascar. In addition, stomatal conductance (gs) was determined for three individuals of two locally common invasive shrubs (Lantana camara L. and Rubus moluccanus L.) during three periods with contrasting soil moisture conditions. Values of gs for the three investigated species were significantly higher and more sensitive to climatic conditions during the wet period compared with the dry period. Further, gs of the understorey shrubs was much more sensitive to soil moisture content than that of the trees. Tree transpiration rates (Ec) were relatively stable during the dry season and were only affected somewhat by soil water content at the end of the dry season, suggesting the trees had continued access to soil water despite drying out of the topsoil. The Ec exhibited a plateau-shaped relation with vapour pressure deficit (VPD), which was attributed to stomatal closure at high VPD. Vapour pressure deficit was the major driver of variation in Ec, during both the wet and the dry season. Overall water use of the trees was modest, possibly reflecting low site fertility after three swidden cultivation cycles. The observed contrast in gs response to soil water and climatic conditions for the trees and shrubs underscores the need to take root distributions into account when modelling transpiration from regenerating tropical forests.

Utilizing Chamber Data for Developing and Validating Climate Change Models

NASA Technical Reports Server (NTRS)

Monje, Oscar

2012-01-01

Controlled environment chambers (e.g. growth chambers, SPAR chambers, or open-top chambers) are useful for measuring plant ecosystem responses to climatic variables and CO2 that affect plant water relations. However, data from chambers was found to overestimate responses of C fluxes to CO2 enrichment. Chamber data may be confounded by numerous artifacts (e.g. sidelighting, edge effects, increased temperature and VPD, etc) and this limits what can be measured accurately. Chambers can be used to measure canopy level energy balance under controlled conditions and plant transpiration responses to CO2 concentration can be elucidated. However, these measurements cannot be used directly in model development or validation. The response of stomatal conductance to CO2 will be the same as in the field, but the measured response must be recalculated in such a manner to account for differences in aerodynamic conductance, temperature and VPD between the chamber and the field.

Sensitivity of Photosynthetic Gas Exchange and Growth of Lodgepole Pine to Climate Variability Depends on the Age of Pleistocene Glacial Surfaces

NASA Astrophysics Data System (ADS)

Osborn, B.; Chapple, W.; Ewers, B. E.; Williams, D. G.

2014-12-01

The interaction between soil conditions and climate variability plays a central role in the ecohydrological functions of montane conifer forests. Although soil moisture availability to trees is largely dependent on climate, the depth and texture of soil exerts a key secondary influence. Multiple Pleistocene glacial events have shaped the landscape of the central Rocky Mountains creating a patchwork of soils differing in age and textural classification. This mosaic of soil conditions impacts hydrological properties, and montane conifer forests potentially respond to climate variability quite differently depending on the age of glacial till and soil development. We hypothesized that the age of glacial till and associated soil textural changes exert strong control on growth and photosynthetic gas exchange of lodgepole pine. We examined physiological and growth responses of lodgepole pine to interannual variation in maximum annual snow water equivalence (SWEmax) of montane snowpack and growing season air temperature (Tair) and vapor pressure deficit (VPD) across a chronosequence of Pleistocene glacial tills ranging in age from 700k to 12k years. Soil textural differences across the glacial tills illustrate the varying degrees of weathering with the most well developed soils with highest clay content on the oldest till surfaces. We show that sensitivity of growth and carbon isotope discrimination, an integrated measure of canopy gas exchange properties, to interannual variation SWEmax , Tair and VPD is greatest on young till surfaces, whereas trees on old glacial tills with well-developed soils are mostly insensitive to these interannual climate fluctuations. Tree-ring widths were most sensitive to changes in SWEmax on young glacial tills (p < 0.01), and less sensitive on the oldest till (p < 0.05). Tair correlates strongly with δ13C values on the oldest and youngest tills sites, but shows no significant relationship on the middle aged glacial till. It is clear that growth and photosynthetic gas exchange parameters are sensitive to glacial till surfaces, which is evident by the different responses to SWEmax and Tair across sites.

Climate-resilient agroforestry: physiological responses to climate change and engineering of crassulacean acid metabolism (CAM) as a mitigation strategy: CAM engineering in trees

DOE PAGES

Borland, Anne M.; Wullschleger, Stan D.; Weston, David J.; ...

2014-12-15

We know that global climate change threatens the sustainability of agriculture and agroforestry worldwide through increased heat, drought, surface evaporation and associated soil drying. Exposure of crops and forests to warmer and drier environments will increase leaf:air water vapour–pressure deficits (VPD), and will result in increased drought susceptibility and reduced productivity, not only in arid regions but also in tropical regions with seasonal dry periods. Fast-growing, short-rotation forestry (SRF) bioenergy crops such as poplar (Populus spp.) and willow (Salix spp.) are particularly susceptible to hydraulic failure following drought stress due to their isohydric nature and relatively high stomatal conductance. Onemore » approach to sustaining plant productivity is to improve water-use efficiency (WUE) by engineering crassulacean acid metabolism (CAM) into C3 crops. CAM improves WUE by shifting stomatal opening and primary CO 2 uptake and fixation to the night-time when leaf:air VPD is low. CAMmembers of the tree genus Clusia exemplify the compatibility of CAM performance within tree species and highlight CAM as a mechanism to conserve water and maintain carbon uptake during drought conditions. Moreover, the introduction of bioengineered CAM into SRF bioenergy trees is a potentially viable path to sustaining agroforestry production systems in the face of a globally changing climate.« less

Climate-resilient agroforestry: physiological responses to climate change and engineering of crassulacean acid metabolism (CAM) as a mitigation strategy: CAM engineering in trees

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borland, Anne M.; Wullschleger, Stan D.; Weston, David J.

We know that global climate change threatens the sustainability of agriculture and agroforestry worldwide through increased heat, drought, surface evaporation and associated soil drying. Exposure of crops and forests to warmer and drier environments will increase leaf:air water vapour–pressure deficits (VPD), and will result in increased drought susceptibility and reduced productivity, not only in arid regions but also in tropical regions with seasonal dry periods. Fast-growing, short-rotation forestry (SRF) bioenergy crops such as poplar (Populus spp.) and willow (Salix spp.) are particularly susceptible to hydraulic failure following drought stress due to their isohydric nature and relatively high stomatal conductance. Onemore » approach to sustaining plant productivity is to improve water-use efficiency (WUE) by engineering crassulacean acid metabolism (CAM) into C3 crops. CAM improves WUE by shifting stomatal opening and primary CO 2 uptake and fixation to the night-time when leaf:air VPD is low. CAMmembers of the tree genus Clusia exemplify the compatibility of CAM performance within tree species and highlight CAM as a mechanism to conserve water and maintain carbon uptake during drought conditions. Moreover, the introduction of bioengineered CAM into SRF bioenergy trees is a potentially viable path to sustaining agroforestry production systems in the face of a globally changing climate.« less

Elevated CO2 reduces sap flux in mature deciduous forest trees.

PubMed

Cech, Patrick G; Pepin, Steeve; Körner, Christian

2003-10-01

We enriched in CO2 the canopy of 14 broad-leaved trees in a species-rich, ca. 30-m-tall forest in NW Switzerland to test whether elevated CO2 reduces water use in mature forest trees. Measurements of sap flux density (JS) were made prior to CO2 enrichment (summer 2000) and throughout the first whole growing season of CO2 exposure (2001) using the constant heat-flow technique. The short-term responses of sap flux to brief (1.5-3 h) interruptions of CO2 enrichment were also examined. There were no significant a priori differences in morphological and physiological traits between trees which were later exposed to elevated CO2 (n=14) and trees later used as controls (n=19). Over the entire growing season, CO2 enrichment resulted in an average 10.7% reduction in mean daily JS across all species compared to control trees. Responses were most pronounced in Carpinus, Acer, Prunus and Tilia, smaller in Quercus and close to zero in Fagus trees. The JS of treated trees significantly increased by 7% upon transient exposure to ambient CO2 concentrations at noon. Hence, responses of the different species were, in the short term, similar in magnitude to those observed over the whole season (though opposite because of the reversed treatment). The reductions in mean JS of CO2-enriched trees were high (22%) under conditions of low evaporative demand (vapour pressure deficit, VPD <5 hPa) and small (2%) when mean daily VPD was greater than 10 hPa. During a relatively dry period, the effect of elevated CO2 on JS even appeared to be reversed. These results suggest that daily water savings by CO2-enriched trees may have accumulated to a significantly improved water status by the time when control trees were short of soil moisture. Our data indicate that the magnitude of CO2 effects on stand transpiration will depend on rainfall regimes and the relative abundance of the different species, being more pronounced under humid conditions and in stands dominated by species such as Carpinus and negligible in mono-specific Fagus forests.

Are we there yet? Assessing achievement of vaccine-preventable disease goals in WHO's Western Pacific Region.

PubMed

Hennessey, Karen; Schluter, W William; Wang, Xiaojun; Boualam, Liliane; Jee, Youngmee; Mendoza-Aldana, Jorge; Roesel, Sigrun; Diorditsa, Sergey; Ehrenberg, John

2014-07-23

Accelerated disease control goals have long been appreciated for their role in galvanizing commitment and bringing a sense of urgency for disease prevention. WHO's Western Pacific Region has 14 on-going communicable disease reduction goals including 1 targeting eradication, 10 targeting elimination, and 3 control initiatives. These goals cover mother-to-child transmission of HIV, congenital syphilis, tuberculosis, leprosy, five parasitic diseases and four vaccine-preventable diseases (VPD). The initiatives have distinct objectives, approaches, and means in which to measure achievement of the goals. Given the long history and experience with VPD initiatives in the Western Pacific Region, this manuscript focuses on the Region's following initiatives: (1) smallpox eradication, (2) polio eradication, (3) measles elimination, (4) maternal and neonatal tetanus elimination (MNTE), and (5) hepatitis B control. There is good consistency across the Region's VPD initiatives yet a pattern of more robust and representative data requirements, stricter evaluation criteria, and more formal evaluation bodies are linked to the intensity of the goal - with eradication being the peak. On the other end of this spectrum, the Regional hepatitis B control initiative has established efficient and low-cost approaches for measuring impact and evaluating if the goals have been met. Even within the confines of VPD initiatives there are some deviations in use of terminology and comparisons across other disease control initiatives in the Region are provided. Copyright © 2014 World Health Organization. Published by Elsevier Ltd.. All rights reserved.

Insensitivity of evapotranspiration to seasonal rainfall distribution directs climate change impacts at water yield

NASA Astrophysics Data System (ADS)

Montaldo, N.; Oren, R.

2017-12-01

Over the past century, climate change is affecting precipitation regimes across the world. In the Mediterranean regions there is a persistent trend of precipitation and runoff decreases, generating a desertification process. Given the past winter precipitation shifts, the impacts on evapotranspiration (ET) need to be carefully evaluated, and the compelling question is what will be the impact of future climate change scenarios (predicting changes of precipitation and vapor pressure deficit, VPD) on evapotranspiration and water yield? Looking for the key elements of the climate change that are impacting annual ET, we investigate main climate conditions (e.g. precipitation and VPD) and basin physiographic properties contributing to annual ET. We propose a simplified model for annual ET predictions that accounts for the strong meteo seasonality typical of Mediterranean climates, using the steady state assumption of the basin water balance at mean annual scale. We investigate the Sardinia case study because the position of the island of Sardinia in the center of the western Mediterranean Sea basin and its low urbanization and human activity make Sardinia a perfect reference laboratory for Mediterranean hydrologic studies. Sardinian runoff decreased drastically over the 1975-2010 period, with mean yearly runoff reduced by more than 40% compared to the previous 1922-1974 period, and most yearly runoff in the Sardinian basins (70% on average) is produced by winter precipitation due to the seasonality typical of the Mediterranean climate regime. The use of our proposed model allows to predict future ET and water yield using future climate scenarios. We use the future climate scenarios predicted by Global climate models (GCM) in the Fifth Assessment report of the Intergovernmental Panel on Climate Change (IPCC), and we select most reliable models testing the past GCM predictions with historical data. Contrasting shifts of precipitation (both positive and negative) are predicted in the future scenarios by GCMs but these changes will produce significant changes (level of significance > 90%) only in runoff and not in ET. Surprisingly, we show that ET is insensitive to intra-annual rainfall distribution changes, and is insensitive to VPD scenario changes.

The significant impact of framing coils on long-term outcomes in endovascular coiling for intracranial aneurysms: how to select an appropriate framing coil.

PubMed

Ishida, Wataru; Sato, Masayuki; Amano, Tatsuo; Matsumaru, Yuji

2016-09-01

OBJECTIVE The importance of a framing coil (FC)-the first coil inserted into an aneurysm during endovascular coiling, also called a lead coil or a first coil-is recognized, but its impact on long-term outcomes, including recanalization and retreatment, is not well established. The purposes of this study were to test the hypothesis that the FC is a significant factor for aneurysmal recurrence and to provide some insights on appropriate FC selection. METHODS The authors retrospectively reviewed endovascular coiling for 280 unruptured intracranial aneurysms and gathered data on age, sex, aneurysm location, aneurysm morphology, maximal size, neck width, adjunctive techniques, recanalization, retreatment, follow-up periods, total volume packing density (VPD), volume packing density of the FC, and framing coil percentage (FCP; the percentage of FC volume in total coil volume) to clarify the associated factors for aneurysmal recurrence. RESULTS Of 236 aneurysms included in this study, 33 (14.0%) had recanalization, and 18 (7.6%) needed retreatment during a mean follow-up period of 37.7 ± 16.1 months. In multivariate analysis, aneurysm size (odds ratio [OR] = 1.29, p < 0.001), FCP < 32% (OR 3.54, p = 0.009), and VPD < 25% (OR 2.96, p = 0.015) were significantly associated with recanalization, while aneurysm size (OR 1.25, p < 0.001) and FCP < 32% (OR 6.91, p = 0.017) were significant predictors of retreatment. VPD as a continuous value or VPD with any cutoff value could not predict retreatment with statistical significance in multivariate analysis. CONCLUSIONS FCP, which is equal to the FC volume as a percentage of the total coil volume and is unaffected by the morphology of the aneurysm or the measurement error in aneurysm length, width, or height, is a novel predictor of recanalization and retreatment and is more significantly predictive of retreatment than VPD. To select FCs large enough to meet the condition of FCP ≥ 32% is a potential relevant factor for better long-term outcomes. These findings support our hypothesis that the FC is a significant factor for aneurysmal recurrence.

Photosynthetic responses to altitude: an explanation based on optimality principles

NASA Astrophysics Data System (ADS)

Wang, Han; Prenticce, Iain Colin; Davis, Tyler; Keenan, Trevor; Wright, Ian; Peng, Changhui

2017-04-01

Increasing altitude is commonly accompanied by a declining ratio of leaf-internal to ambient CO2 partial pressures (ci:ca; hereafter, χ) and an increase in carboxylation capacity (Vcmax), while carbon assimilation (A) shows little to no change. Here we provide a consistent, quantitative explanation for these responses based on the 'least-cost hypothesis' for the regulation of χ and the 'co-ordination hypothesis' for the regulation of Vcmax. With leaf temperature held constant, our analysis predicts that the cost of maintaining water transport capacity increases with altitude (due to declining atmospheric pressure and increasing vapour pressure deficit, VPD) while the cost of maintaining carboxylation capacity decreases (due to the enhanced affinity of Rubisco for CO2 at low O2 partial pressures). Both effects favour investment in carboxylation capacity rather than water transport capacity. The response of A then reflects the competing effects of stronger CO2 limitation at low ci versus increased radiation penetration through a thinner atmosphere. These effects of atmospheric pressure are expected to be most strongly expressed in herbaceous plants that can maintain leaf temperatures in a narrow range. In leaves closely coupled to the atmosphere additional effects of declining temperature on photosynthesis are expected to modify but not obliterate those of pressure.

Seasonal and interannual variability of climate and vegetation indices across the Amazon.

PubMed

Brando, Paulo M; Goetz, Scott J; Baccini, Alessandro; Nepstad, Daniel C; Beck, Pieter S A; Christman, Mary C

2010-08-17

Drought exerts a strong influence on tropical forest metabolism, carbon stocks, and ultimately the flux of carbon to the atmosphere. Satellite-based studies have suggested that Amazon forests green up during droughts because of increased sunlight, whereas field studies have reported increased tree mortality during severe droughts. In an effort to reconcile these apparently conflicting findings, we conducted an analysis of climate data, field measurements, and improved satellite-based measures of forest photosynthetic activity. Wet-season precipitation and plant-available water (PAW) decreased over the Amazon Basin from 1996-2005, and photosynthetically active radiation (PAR) and air dryness (expressed as vapor pressure deficit, VPD) increased from 2002-2005. Using improved enhanced vegetation index (EVI) measurements (2000-2008), we show that gross primary productivity (expressed as EVI) declined with VPD and PAW in regions of sparse canopy cover across a wide range of environments for each year of the study. In densely forested areas, no climatic variable adequately explained the Basin-wide interannual variability of EVI. Based on a site-specific study, we show that monthly EVI was relatively insensitive to leaf area index (LAI) but correlated positively with leaf flushing and PAR measured in the field. These findings suggest that production of new leaves, even when unaccompanied by associated changes in LAI, could play an important role in Basin-wide interannual EVI variability. Because EVI variability was greatest in regions of lower PAW, we hypothesize that drought could increase EVI by synchronizing leaf flushing via its effects on leaf bud development.

Fir Decline and Mortality in the Southern Siberian Mountains

NASA Technical Reports Server (NTRS)

Kharuk, Viacheslav I.; Im, Sergei T.; Petrov, Ilya A.; Dvinskaya, Mariya, L.; Fedotova, Elena V.; Ranson, Kenneth J.

2016-01-01

Increased dieback and mortality of dark needle conifer (DNC) stands (composed of fir (Abies sibirica),Siberian pine (Pinus sibirica) and spruce (Picea obovata))were documented in Russia during recent decades. Here we analyzed spatial and temporal patterns of fir decline and mortality in the southern Siberian Mountains based on satellite, in situ and dendrochronological data. The studied stands are located within the boundary between DNC taiga to the north and forest-steppe to the south. Fir decline and mortality were observed to originate where topographic features contributed to maximal water-stress risk, i.e., steep (1825),convex, south-facing slopes with a shallow well-drained root zone. Fir regeneration survived droughts and increased stem radial growth, while upper canopy trees died. Tree ring width(TRW) growth negatively correlated with vapor pressure deficit (VPD), drought index and occurrence of late frosts, and positively with soil water content. Previous year growth conditions (i.e., drought index, VPD, soil water anomalies)have a high impact on current TRW (r 0.600.74). Fir mortality was induced by increased water stress and severe droughts (as a primary factor) in synergy with bark-beetles and fungi attacks (as secondary factors). Dendrochronology data indicated that fir mortality is a periodic process. In a future climate with increased aridity and drought frequency, fir (and Siberian pine) may disappear from portions of its current range (primarily within the boundary with the forest steppe)and is likely to be replaced by drought-tolerant species such as Pinus sylvestris and Larix sibirica.

Converting Paddy Rice Field to Urban Use Dramatically Altered the Water and Energy Balances in Southern China

NASA Astrophysics Data System (ADS)

Hao, L.; Sun, G.; Liu, Y.; Qin, M.; Huang, X.; Fang, D.

2017-12-01

Paddy rice wetlands are the main land use type across southern China, which impact the regional environments by affecting evapotranspiration (ET) and other water and energy related processes. Our study focuses on the effects of land-cover change on water and energy processes in the Qinhuai River Basin, a typical subtropical humid region that is under rapid ecological and economical transformations. This study integrates multiple methods and techniques including remote sensing, water and energy balance model (i.e., Surface Energy Balance Algorithm for Land, SEBAL), ecohydrological model (i.e., Soil and Water Assessment Tool, SWAT), and ground observation (Eddy Covariance measurement, etc.). We found that conversion of paddy rice field to urban use led to rise in vapor pressure deficit (VPD) and reduction in ET, and thus resulted in changes in local and regional water and heat balance. The effects of the land-use change on ET and VPD overwhelmed the effects of regional climate warming and climate variability. We conclude that the ongoing large-scale urbanization of the rice paddy-dominated regions in humid southern China and East Asia will likely exacerbate environmental consequences (e.g., elevated storm-flow volume, aggravated flood risks, and intensified urban heat island and urban dry island effects). The potential role of vegetated land cover in moderating water and energy balances and maintaining a stable climate should be considered in massive urban planning and global change impact assessment in southern China.

[Environmental responses of four urban tree species transpiration in northern China].

PubMed

Chen, Li-xin; Li, Zhan-dong; Zhang, Zhi-qiang; Zhang, Wen-juan; Zhang, Xiao-fang; Dong, Ke-yu; Wang, Guo-yu

2009-12-01

By using thermal dissipation probes (TDP), this paper monitored the sap flow of four tree species (Cedrus deodara, Zelkova schneideriana, Euonymus bungeanus, and Metasequoia glyptostroboides) at the Laodong Park in Dalian City from June to August 2008, and the soil moisture content and micrometeorological variables were mehsured simultaneously. Due to the absence of water-stress in the habitat, the sap flow of all sampled trees had no significant correlation with soil moisture content (R2 < 0.050, P > 0.211, n=1296). The correlation coefficient between solar radiation and sap flow reached 0.624-0.773 (P = 0.00, n=1296) despite the existing hysteresis. Solar radiation had major effect (R2 > 0.700, P < 0.05) during early morning (5:00-8:00) and late afternoon (18:00-20:00) when undergoing dramatic changes. As the main factor determining nighttime sap flow (R2 > 0.660, P < 0.05, n=1872), vapor pressure deficit (VPD) had a correlation coefficient as high as 0.650-0.823 (P = 0.00, n=1296) with the sap flow in whole-day scale. Meanwhile, the models constructed on the basis of VPD were able to explain 90% of daily sap flow change (P = 0.00). The correlation coefficient between sap flow and wind speed was relatively smaller than the previous two (R2 < 0.380, P = 0.00, n=1296), though showing significant correlation in affecting sap flow. Observations also detected the saturation phenomenon of sap flow to the environmental demands.

The Implications of Nasal Substitutions in the Early Phonology of Toddlers With Repaired Cleft Palate.

PubMed

Hardin-Jones, Mary A; Chapman, Kathy L

2018-01-01

To examine the implications of nasal substitutions in the early words of toddlers with cleft palate. Retrospective. Thirty-four toddlers with nonsyndromic cleft palate and 20 noncleft toddlers, followed from ages 13 to 39 months. The groups were compared for the percentage of toddlers who produced nasal substitutions in their early words. The percentage of toddlers with repaired cleft palate who produced nasal substitutions and were later suspected of having velopharyngeal dysfunction (VPD) was also examined. Seventy-six percent of the toddlers in the cleft group (n = 26) and 35% of toddlers in the noncleft group (n = 7) produced nasal substitutions on one or more of their early words. Only 38% (10/26) of the toddlers with cleft palate who produced nasal substitutions in their early words were later diagnosed as having moderate-severe hypernasality and suspected VPD. The presence of nasal substitutions following palatal surgery was not always an early sign of VPD. These substitutions were present in the early lexicon of children with and without cleft palate.

Impacts of prescribed fire on Pinus rigida Mill. in upland forests of the Atlantic Coastal Plain.

PubMed

Carlo, Nicholas J; Renninger, Heidi J; Clark, Kenneth L; Schäfer, Karina V R

2016-08-01

A comparative analysis of the impacts of prescribed fire on three upland forest stands in the Northeastern Atlantic Plain, NJ, USA, was conducted. Effects of prescribed fire on water use and gas exchange of overstory pines were estimated via sap-flux rates and photosynthetic measurements on Pinus rigida Mill. Each study site had two sap-flux plots, one experiencing prescribed fire and one control (unburned) plot for comparison before and after the fire. We found that photosynthetic capacity in terms of Rubisco-limited carboxylation rate and intrinsic water-use efficiency was unaffected, while light compensation point and dark respiration rate were significantly lower in the burned vs control plots post-fire. Furthermore, quantum yield in pines in the pine-dominated stands was less affected than pines in the mixed oak/pine stand, as there was an increase in quantum yield in the oak/pine stand post-fire compared with the control (unburned) plot. We attribute this to an effect of forest type but not fire per se. Average daily sap-flux rates of the pine trees increased compared with control (unburned) plots in pine-dominated stands and decreased in the oak/pine stand compared with control (unburned) plots, potentially due to differences in fuel consumption and pre-fire sap-flux rates. Finally, when reference canopy stomatal conductance was analyzed, pines in the pine-dominated stands were more sensitive to changes in vapor pressure deficit (VPD), while stomatal responses of pines in the oak/pine stand were less affected by VPD. Therefore, prescribed fire affects physiological functioning and water use of pines, but the effects may be modulated by forest stand type and fuel consumption pattern, which suggests that these factors may need to be taken into account for forest management in fire-dominated systems. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Impacts of cloud immersion on microclimate, photosynthesis and water relations of Abies fraseri (Pursh.) Poiret in a temperate mountain cloud forest.

PubMed

Reinhardt, Keith; Smith, William K

2008-11-01

The red spruce-Fraser fir ecosystem [Picea rubens Sarg.-Abies fraseri (Pursh) Poir.] of the southern Appalachian mountains, USA, is a temperate zone cloud forest immersed in clouds for 30-40% of a typical summer day, and experiencing immersion on about 65% of all days annually. We compared the microclimate, photosynthetic gas exchange, and water relations of Fraser fir trees in open areas during cloud-immersed, low-cloud, or sunny periods. In contrast to sunny periods, cloud immersion reduced instantaneous sunlight irradiance by 10-50%, and midday atmospheric vapor pressure deficit (VPD) was 85% lower. Needle surfaces were wet for up to 16 h per day during cloud-immersed days compared to <1 h for clear days. Shoot-level light-saturated photosynthesis (A (sat)) on both cloud-immersed (16.0 micromol m(-2) s(-1)) and low-cloud (17.9 micromol m(-2) s(-1)) days was greater than A (sat) on sunny days (14.4 micromol m(-2) s(-1)). Daily mean A was lowest on cloud-immersed days due to reduced sunlight levels, while leaf conductance (g) was significantly higher, with a mean value of 0.30 mol m(-2) s(-1). These g values were greater than commonly reported for conifer tree species with needle-like leaves, and declined exponentially with increasing leaf-to-air VPD. Daily mean transpiration (E) on immersed days was 43 and 20% lower compared to sunny and low-cloud days, respectively. As a result, daily mean water use efficiency (A/E) was lowest on cloud-immersed days due to light limitation of A, and high humidity resulted in greater uncoupling of A from g. Thus, substantial differences in photosynthetic CO2 uptake, and corresponding water relations, were strongly associated with cloud conditions that occur over substantial periods of the summer growth season.

Comparisons of xylem sap flow and water vapour flux at the stand level and derivation of canopy conductance for Scots pine

NASA Astrophysics Data System (ADS)

Granier, A.; Biron, P.; Köstner, B.; Gay, L. W.; Najjar, G.

1996-03-01

Simultaneous measurements of xylem sap flow and water vapour flux over a Scots pine ( Pinus sylvestris) forest (Hartheim, Germany), were carried out during the Hartheim Experiment (HartX), an intensive observation campaign of the international programme REKLIP. Sap flow was measured every 30 min using both radial constant heating (Granier, 1985) and two types of Cermak sap flowmeters installed on 24 trees selected to cover a wide range of the diameter classes of the stand (min 8 cm; max 17.5 cm). Available energy was high during the observation period (5.5 to 6.9 mm.day-1), and daily cumulated sap flow on a ground area basis varied between 2.0 and 2.7 mm day-1 depending on climate conditions. Maximum hourly values of sap flow reached 0.33 mm h-1, i.e., 230 W m-2. Comparisons of sap flow with water vapour flux as measured with two OPEC (One Propeller Eddy Correlation, University of Arizona) systems showed a time lag between the two methods, sap flow lagging about 90 min behind vapour flux. After taking into account this time lag in the sap flow data set, a good agreement was found between both methods: sap flow = 0.745* vapour flux, r 2 = 0.86. The difference between the two estimates was due to understory transpiration. Canopy conductance ( g c ) was calculated from sap flow measurements using the reverse form of Penman-Monteith equation and climatic data measured 4 m above the canopy. Variations of g c were well correlated ( r 2 = 0.85) with global radiation ( R) and vapour pressure deficit ( vpd). The quantitative expression for g c = f ( R, vpd) was very similar to that previously found with maritime pine ( Pinus pinaster) in the forest of Les Landes, South Western France.

Patterns and variability in seedling carbon assimilation: implications for tree recruitment under climate change.

PubMed

Peltier, Drew M P; Ibáñez, Inés

2015-01-01

Predicting future forests' structure and functioning is a critical goal for ecologists, thus information on seedling recruitment will be crucial in determining the composition and structure of future forest ecosystems. In particular, seedlings' photosynthetic response to a changing environment will be a key component determining whether particular species establish enough individuals to maintain populations, as growth is a major determinant of survival. We quantified photosynthetic responses of sugar maple (Acer saccharum Marsh.), pignut hickory (Carya glabra Mill.), northern red oak (Quercus rubra L.) and eastern black oak (Quercus velutina Lam.) seedlings to environmental conditions including light habitat, temperature, soil moisture and vapor pressure deficit (VPD) using extensive in situ gas exchange measurements spanning an entire growing season. We estimated the parameters in a hierarchical Bayesian version of the Farquhar model of photosynthesis, additionally informed by soil moisture and VPD, and found that maximum Rubisco carboxylation (V(cmax)) and electron transport (J(max)) rates showed significant seasonal variation, but not the peaked patterns observed in studies of adult trees. Vapor pressure deficit and soil moisture limited J(max) and V(cmax) for all four species. Predictions indicate large declines in summer carbon assimilation rates under a 3 °C increase in mean annual temperature projected by climate models, while spring and fall assimilation rates may increase. Our model predicts decreases in summer assimilation rates in gap habitats with at least 90% probability, and with 20-99.9% probability in understory habitats depending on species. Predictions also show 70% probability of increases in fall and 52% probability in spring in understory habitats. All species were impacted, but our findings suggest that oak species may be favored in northeastern North America under projected increases in temperature due to superior assimilation rates under these conditions, though as growing seasons become longer, the effects of climate change on seedling photosynthesis may be complex. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Canopy structure and atmospheric flows in relation to the δ13C of respired CO2 in a subalpine coniferous forest

USGS Publications Warehouse

Schaeffer, Sean M.; Anderson, Dean E.; Burns, Sean P.; Monson, Russell K.; Sun, Jielun; Bowling, David R.

2008-01-01

Stable isotopes provide insight into ecosystem carbon cycling, plant physiological processes, atmospheric boundary-layer dynamics, and are useful for the integration of processes over multiple scales. Of particular interest is the carbon isotope content (δ13C) of nocturnal ecosystem-respired CO2 (δR). Recent advances in technology have made it possible to continuously examine the variation in δR within a forest canopy over relatively long time-scales (months–years). We used tunable diode laser spectroscopy to examine δR at within- and below-canopy spatial locations in a Colorado subalpine forest (the Niwot Ridge AmeriFlux site). We found a systematic pattern of increased δR within the forest canopy (δR-c) compared to that near the ground (δR-g). Values of δR-c were weakly correlated with the previous day's mean maximum daytime vapor pressure deficit (VPD). Conversely, there was a negative but still weak correlation between δR-g and time-lagged (0–5 days) daily mean soil moisture. The topography and presence of sustained nightly drainage flows at the Niwot Ridge forest site suggests that, on nights with stable atmospheric conditions, there is little mixing of air near the ground with that in the canopy. Atmospheric stability was assessed using thresholds of friction velocity, stability above the canopy, and bulk Richardson number within the canopy. When we selectively calculated δR-g and δR-c by removing time periods when ground and canopy air were well mixed, we found stronger correlations between δR-c and VPD, and δR-g and soil moisture. This suggests that there may be fundamental differences in the environmental controls on δR at sub-canopy spatial scales. These results may help explain the wide variance observed in the correlation of δR with different environmental parameters in other studies.

Estimation of Mangrove Net Primary Production and Carbon Sequestration service using Light Use Efficiency model in the Sunderban Biosphere region, India

NASA Astrophysics Data System (ADS)

Sannigrahi, Srikanta; Sen, Somnath; Paul, Saikat

2016-04-01

Net Primary Production (NPP) of mangrove ecosystem and its capacity to sequester carbon from the atmosphere may be used to quantify the regulatory ecosystem services. Three major group of parameters has been set up as BioClimatic Parameters (BCP): (Photosynthetically Active Radiation (PAR), Absorbed PAR (APAR), Fraction of PAR (FPAR), Photochemical Reflectance Index (PRI), Light Use Efficiency (LUE)), BioPhysical Parameters (BPP) :(Normalize Difference Vegetation Index (NDVI), scaled NDVI, Enhanced Vegetation Index (EVI), scaled EVI, Optimised and Modified Soil Adjusted Vegetation Index (OSAVI, MSAVI), Leaf Area Index (LAI)), and Environmental Limiting Parameters (ELP) (Temperature Stress (TS), Land Surface Water Index (LSWI), Normalize Soil Water Index (NSWI), Water Stress Scalar (WS), Inversed WS (iWS) Land Surface Temperature (LST), scaled LST, Vapor Pressure Deficit (VPD), scaled VPD, and Soil Water Deficit Index (SWDI)). Several LUE models namely Carnegie Ames Stanford Approach (CASA), Eddy Covariance - LUE (EC-LUE), Global Production Efficiency Model (GloPEM), Vegetation Photosynthesis Model (VPM), MOD NPP model, Temperature and Greenness Model (TG), Greenness and Radiation model (GR) and MOD17 was adopted in this study to assess the spatiotemporal nature of carbon fluxes. Above and Below Ground Biomass (AGB & BGB) was calculated using field based estimation of OSAVI and NDVI. Microclimatic zonation has been set up to assess the impact of coastal climate on environmental limiting factors. MODerate Resolution Imaging Spectroradiometer (MODIS) based yearly Gross Primary Production (GPP) and NPP product MOD17 was also tested with LUE based results with standard model validation statistics: Root Mean Square of Error (RMSE), Mean Absolute Error (MEA), Bias, Coefficient of Variation (CV) and Coefficient of Determination (R2). The performance of CASA NPP was tested with the ground based NPP with R2 = 0.89 RMSE = 3.28 P = 0.01. Among the all adopted models, EC-LUE and VPM models has explained the maximum variances (>80%) in comparison to the other model. Study result has also showed that the BPP has explained the maximum model variances (>93%) followed by BCP (>65%) and ELP (>50%). Scaled WS, iWS, LST, VPD, NDVI was performed better in a minimum ELP condition whereas surface moisture and wetness was highly correlated with the AGB and NPP (R2 = 0.86 RMSE = 1.83). During this study period (2000-2013), it was found that there was a significantly declining trend (R2 = 0.32 P = 0.05) of annual NPP and the maximum decrease was found in the eastern part where built-up area was mainly accounted for reduction of NPP. BCP are explained higher variances (>80%) in the optimum climatic condition exist along the coastal stretches in comparison to the landward extent (>45%).

Velopharyngeal Anatomy in 22q11.2 Deletion Syndrome: A Three-Dimensional Cephalometric Analysis

PubMed Central

Ruotolo, Rachel A.; Veitia, Nestor A.; Corbin, Aaron; McDonough, Joseph; Solot, Cynthia B.; McDonald-McGinn, Donna; Zackai, Elaine H.; Emanuel, Beverly S.; Cnaan, Avital; LaRossa, Don; Arens, Raanan; Kirschner, Richard E.

2010-01-01

Objective 22q11.2 deletion syndrome is the most common genetic cause of velopharyngeal dysfunction (VPD). Magnetic resonance imaging (MRI) is a promising method for noninvasive, three-dimensional (3D) assessment of velopharyngeal (VP) anatomy. The purpose of this study was to assess VP structure in patients with 22q11.2 deletion syndrome by using 3D MRI analysis. Design This was a retrospective analysis of magnetic resonance images obtained in patients with VPD associated with a 22q11.2 deletion compared with a normal control group. Setting This study was conducted at The Children’s Hospital of Philadelphia, a pediatric tertiary care center. Patients, Participants The study group consisted of 5 children between the ages of 2.9 and 7.9 years, with 22q11.2 deletion syndrome confirmed by fluorescence in situ hybridization analysis. All had VPD confirmed by nasendoscopy or videofluoroscopy. The control population consisted of 123 unaffected patients who underwent MRI for reasons other than VP assessment. Interventions Axial and sagittal T1- and T2-weighted magnetic resonance images with 3-mm slice thickness were obtained from the orbit to the larynx in all patients by using a 1.5T Siemens Visions system. Outcome Measures Linear, angular, and volumetric measurements of VP structures were obtained from the magnetic resonance images with VIDA image- processing software. Results The study group demonstrated greater anterior and posterior cranial base and atlanto-dental angles. They also demonstrated greater pharyngeal cavity volume and width and lesser tonsillar and adenoid volumes. Conclusion Patients with a 22q11.2 deletion demonstrate significant alterations in VP anatomy that may contribute to VPD. PMID:16854203

Association between symptoms of sleep-disordered breathing and speech in children with craniofacial malformations.

PubMed

Moraleda-Cibrián, Marta; Berger, Mary; Edwards, Sean P; Kasten, Steven J; Buchman, Steven R; O'Brien, Louise M

2014-06-15

Sleep-disordered breathing (SDB) and speech difficulties are common problems in children with craniofacial malformations (CFM). The present study was designed to investigate whether resonance issues identified during speech assessment are associated with parental report of SDB symptoms in children with CFM. Children aged 2-18 years with congenital CFM attending at the Craniofacial Anomalies Program from March 2007 to April 2011 were screened for SDB symptoms using the Sleep-Related Breathing Disturbance Scale of the Pediatric Sleep Questionnaire. Speech evaluation, based on the Pittsburgh Weighted Speech Scale score, was the tool used to investigate velopharyngeal dysfunction (VPD) based on speech perceptual assessment. A total of 488 children with congenital CFM were included. Overall 81% were Caucasian and 24% were overweight/obese. Twenty-four percent of children screened positive for SDB and 35% had VPD. Children with VPD were no more likely to screen positive for SDB than children without VPD (26% vs. 23%, p = 0.38). However, children with previous sphincter pharyngoplasty (SP) were more likely to have hyponasality (51% vs. 12%, p = 0.0001) and reduced or absent nasal emission (33% vs. 16%, p = 0.008). In a logistic regression, the adjusted odds ratio for SDB for those with hyponasality was 2.10 (95%CI 1.21-3.61, p = 0.008) and for those with reduced or absent nasal emission was 1.75 (95%CI 1.06-2.88, p = 0.028). Symptoms of sleep disordered breathing are common in children with craniofacial malformations especially if they have undergone sphincter pharyngoplasty; many of these children can be identified by measures of resonance on routine speech evaluation.

SU-F-J-162: Is Bulky Electron Density Assignment Appropriatefor MRI-Only Based Treatment Planning for Lung Cancer?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prior, P; Chen, X; Johnstone, C

Purpose: To assess the appropriateness of bulky electron density assisment for MRI-only treatment planning for lung cancer via comparing dosimetric difference between MRI- and CT-based plans. Methods: Planning 4DCTs acquired for six representative lung cancer patients were used to generate CT-based IMRT plans. To avoid the effect of anatomic difference between CT and MRI, MRI-based plans were generated using CTs by forcing the relative electron density (rED) of organ specific values from ICRU report 46 and using the mean rED value of the internal target volume (ITV) of the patient for the ITV. Both CT and “MRI” plans were generatedmore » using a research planning system (Monaco, Elekta) employing Monte Carlo dose calculation the following dose-volume-parameters (DVPs): D99 – dose delivered to 99% of the ITV/PTV volume; D95; D5; D1; Vpd –volume receiving the prescription dose; V5 – volume of normal lung irradiated > 5 Gy; and V20. The percent point difference and dose difference was used for comparison for Vpd-V5-V20 and D99-D1, respectively. Four additional plans per patient were calculated with rEDITV = 0.6 and 1.0 and rEDlung = 0.1 and 0.5. Results: Noticeable differences in the ITV and PTV point doses and DVPs were observed. Variations in Vpd ranged from 0.0–6.4% and 0.32–18.3% for the ITV and PTV, respectively. The ITV and PTV variations in D99, D95, D5 and D1 were 0.15–3.2 Gy. The normal lung V5 & V20 variations were no larger than 1.9%. In some instances, varying the rEDITV between rEDmean, 0.6 and 1.0 resulted in D95 increases ranging from 3.9–6.3%. Uniform rED assignment on normal lung affected DVPs of ITV and PTV by 4.0–9.8% and 0.3–19.6%, respectively. Conclusion: The commonly-used uniform rED assignment in MRI-only based planning may not be appropriate for lung-cancer. A voxel based method, e.g. synthetic CT generated from MRI data, is required. This work was partially funded by Elekta, Inc.« less

High sensitivity of broadleaf trees to water availability in northeastern United States

NASA Astrophysics Data System (ADS)

Levesque, Mathieu; Andreu-Hayles, Laia; Pederson, Neil

2016-04-01

Broadleaf dominated forests of eastern US cover more than one million km2 and provide ecosystem services to millions of people. High species diversity and a varied sensitivity to drought make it uncertain whether these forests will be carbon sinks or sources under climate change. Ongoing climate change, increased in atmospheric CO2 concentration (ca) and strong reductions in acidic depositions are expected to alter growth and gas exchange of trees, and ultimately forest productivity. Still, the magnitude of these effects is unclear. A better comprehension of the species-specific responses to environmental changes will better inform models and managers on the vulnerability and resiliency of these forests. Here, we combined tree-ring width data with δ13C and δ18O measurements to investigate growth and physiological responses of red oak (Quercus rubra L.) and tulip poplar (Liriodendron tulipifera L.) in northeastern US to changes in water availability, ca and acidic depositions for the period 1950-2014. Based on structural equation modeling approaches, we found that summer water availability (June-August) is the main environmental variable driving growth, water-use efficiency and δ18O of broadleaf trees whereas ca and acidic depositions have little effects. This high sensitivity to moisture availability was also supported by the very strong correlations found between summer vapor pressure deficit (VPD) and tree-ring δ13C (r = 0.67 and 0.71), and δ18O series (r = 0.62 and 0.72), for red oak and tulip poplar, respectively. In contrast, tree-ring width was less sensitive to summer VPD (r = -0.44 and-0.31). Since the mid 1980s, pluvial conditions occurring in northeastern US have increased stomatal conductance, carbon uptake, and growth of both species. Further, the strong spatial field correlations found between the tree-ring δ13C and δ18O and summer VPD indicate a greater sensitivity of eastern US broadleaf forests to moisture availability than previously known. This appears especially true since much of the calibration period looks wet in a multi-centennial perspective. Overall, our findings indicate a great potential for the use of tree-ring stable isotopes in large-scale hydroclimatic reconstructions studies in eastern US.

Seasonal and interannual variability of climate and vegetation indices across the Amazon

PubMed Central

Brando, Paulo M.; Goetz, Scott J.; Baccini, Alessandro; Nepstad, Daniel C.; Beck, Pieter S. A.; Christman, Mary C.

2010-01-01

Drought exerts a strong influence on tropical forest metabolism, carbon stocks, and ultimately the flux of carbon to the atmosphere. Satellite-based studies have suggested that Amazon forests green up during droughts because of increased sunlight, whereas field studies have reported increased tree mortality during severe droughts. In an effort to reconcile these apparently conflicting findings, we conducted an analysis of climate data, field measurements, and improved satellite-based measures of forest photosynthetic activity. Wet-season precipitation and plant-available water (PAW) decreased over the Amazon Basin from 1996−2005, and photosynthetically active radiation (PAR) and air dryness (expressed as vapor pressure deficit, VPD) increased from 2002–2005. Using improved enhanced vegetation index (EVI) measurements (2000–2008), we show that gross primary productivity (expressed as EVI) declined with VPD and PAW in regions of sparse canopy cover across a wide range of environments for each year of the study. In densely forested areas, no climatic variable adequately explained the Basin-wide interannual variability of EVI. Based on a site-specific study, we show that monthly EVI was relatively insensitive to leaf area index (LAI) but correlated positively with leaf flushing and PAR measured in the field. These findings suggest that production of new leaves, even when unaccompanied by associated changes in LAI, could play an important role in Basin-wide interannual EVI variability. Because EVI variability was greatest in regions of lower PAW, we hypothesize that drought could increase EVI by synchronizing leaf flushing via its effects on leaf bud development. PMID:20679201

Influence of overstory density on ecophysiology of red oak (Quercus rubra) and sugar maple (Acer saccharum) seedlings in central Ontario shelterwoods.

PubMed

Parker, William C; Dey, Daniel C

2008-05-01

A field experiment was established in a second-growth hardwood forest dominated by red oak (Quercus rubra L.) to examine the effects of shelterwood overstory density on leaf gas exchange and seedling water status of planted red oak, naturally regenerated red oak and sugar maple (Acer saccharum Marsh.) seedlings during the first growing season following harvest. Canopy cover of uncut control stands and moderate and light shelterwoods averaged 97, 80 and 49%, respectively. Understory light and vapor pressure deficit (VPD) strongly influenced gas exchange responses to overstory reduction. Increased irradiance beneath the shelterwoods significantly increased net photosynthesis (P(n)) and leaf conductance to water vapor (G(wv)) of red oak and maple seedlings; however, P(n) and G(wv) of planted and naturally regenerated red oak seedlings were two to three times higher than those of sugar maple seedlings in both partial harvest treatments, due in large part to decreased stomatal limitation of gas exchange in red oak as a result of increased VPD in the shelterwoods. In both species, seedling water status was higher in the partial harvest treatments, as reflected by the higher predawn leaf water potential and seedling water-use efficiency in seedlings in shelterwoods than in uncut stands. Within a treatment, planted and natural red oak seedlings exhibited similar leaf gas exchange rates and water status, indicating little adverse physiological effect of transplanting. We conclude that the use of shelterwoods favors photosynthetic potential of red oak over sugar maple, and should improve red oak regeneration in Ontario.

Leaf temperature and stomatal influences on sap velocity diurnal hysteresis in the Amazon rainforest

NASA Astrophysics Data System (ADS)

Jardine, K.; Gimenez, B.; Negron Juarez, R. I.; Koven, C.; Powell, T.; Higuchi, N.; Chambers, J.; Varadharajan, C.

2016-12-01

In order to improve our ability to predict terrestrial evapotranspiration fluxes, an understanding of the interactions between plant physiology and environmental conditions is necessary, but remains poorly characterized, especially in tropical ecosystems. In this study we show a tight positive correlation between sap velocity (at 1 m of height) and leaf surface temperature (LST, 20-30 m of height) in canopy dominant trees in two primary rainforest sites in the Amazon basin (Santarém and Manaus, Brazil). As leaf temperatures varied throughout the day, sap velocity responded with little delay (<15 min). Positive sap velocity was often observed at night, but also closely followed night time LSTs. When plotted versus LST, sap velocity showed an exponential increase before reaching a reflection point and a plateau and is characterized as a sigmoidal curve, in all observed trees. Moreover, a clear diurnal hysteresis in sap velocity was evident with morning periods showing higher temperature sensitivities than afternoon and night periods. Diurnal leaf observations showed a morning peak in stomatal conductance ( 10:00-10:30), but a mid-day to afternoon peak in transpiration and leaf temperature (12:00-14:00). Our observations suggest the sap velocity-LST hysteresis pattern arises due to the temporal offset between stomatal conductance and vapor pressure deficits (VPD) and demonstrates the dominating effect of VPD over stomatal conductance in maintaining high transpiration/sap flow rates under elevated temperatures. Our results have important implications for modeling tropical forest transpiration and suggests the possibility of predicting evapotranspiration fluxes at the ecosystem to regional scales based on remote sensed vegetation temperature.

Higher absorbed solar radiation partly offset the negative effects of water stress on the photosynthesis of Amazon forests during the 2015 drought

NASA Astrophysics Data System (ADS)

Li, Xing; Xiao, Jingfeng; He, Binbin

2018-04-01

Amazon forests play an important role in the global carbon cycle and Earth’s climate. The vulnerability of Amazon forests to drought remains highly controversial. Here we examine the impacts of the 2015 drought on the photosynthesis of Amazon forests to understand how solar radiation and precipitation jointly control forest photosynthesis during the severe drought. We use a variety of gridded vegetation and climate datasets, including solar-induced chlorophyll fluorescence (SIF), photosynthetic active radiation (PAR), the fraction of absorbed PAR (APAR), leaf area index (LAI), precipitation, soil moisture, cloud cover, and vapor pressure deficit (VPD) in our analysis. Satellite-derived SIF observations provide a direct diagnosis of plant photosynthesis from space. The decomposition of SIF to SIF yield (SIFyield) and APAR (the product of PAR and fPAR) reveals the relative effects of precipitation and solar radiation on photosynthesis. We found that the drought significantly reduced SIFyield, the emitted SIF per photon absorbed. The higher APAR resulting from lower cloud cover and higher LAI partly offset the negative effects of water stress on the photosynthesis of Amazon forests, leading to a smaller reduction in SIF than in SIFyield and precipitation. We further found that SIFyield anomalies were more sensitive to precipitation and VPD anomalies in the southern regions of the Amazon than in the central and northern regions. Our findings shed light on the relative and combined effects of precipitation and solar radiation on photosynthesis, and can improve our understanding of the responses of Amazon forests to drought.

Fir Decline and Mortality in the Southern Siberian Mountains

NASA Technical Reports Server (NTRS)

Kharuk, Viacheslav I.; Im, Sergei T.; Petrov, Ilya A.; Dvinskaya, Mariya, L.; Fedotova, Elena V.; Ranson, Kenneth J.

2016-01-01

Increased dieback and mortality of dark needle conifer (DNC) stands (composed of fir (Abies sibirica),Siberian pine (Pinus sibirica) and spruce (Picea obovata)) were documented in Russia during recent decades. Here we analyzed spatial and temporal patterns of fir decline and mortality in the southern Siberian Mountains based on satellite, in situ and dendrochronological data. The studied stands are located within the boundary between DNC taiga to the north and forest-steppe to the south. Fir decline and mortality were observed to originate where topographic features contributed to maximal water-stress risk, i.e., steep (18 deg to 25 deg), convex, south-facing slopes with a shallow well-drained root zone. Fir regeneration survived droughts and increased stem radial growth, while upper canopy trees died. Tree ring width (TRW) growth negatively correlated with vapor pressure deficit (VPD), drought index and occurrence of late frosts, and positively with soil water content. Previous year growth conditions (i.e., drought index, VPD, soil water anomalies) have a high impact on current TRW (r = 0.60 to 0.74). Fir mortality was induced by increased water stress and severe droughts (as a primary factor) in synergy with bark-beetles and fungi attacks (as secondary factors). Dendrochronology data indicated that fir mortality is a periodic process. In a future climate with increased aridity and drought frequency, fir (and Siberian pine) may disappear from portions of its current range (primarily within the boundary with the forest- steppe) and is likely to be replaced by drought-tolerant species such as Pinus sylvestris and Larix sibirica.

Video copy protection and detection framework (VPD) for e-learning systems

NASA Astrophysics Data System (ADS)

ZandI, Babak; Doustarmoghaddam, Danial; Pour, Mahsa R.

2013-03-01

This Article reviews and compares the copyright issues related to the digital video files, which can be categorized as contended based and Digital watermarking copy Detection. Then we describe how to protect a digital video by using a special Video data hiding method and algorithm. We also discuss how to detect the copy right of the file, Based on expounding Direction of the technology of the video copy detection, and Combining with the own research results, brings forward a new video protection and copy detection approach in terms of plagiarism and e-learning systems using the video data hiding technology. Finally we introduce a framework for Video protection and detection in e-learning systems (VPD Framework).

Diurnal patterns in Scots pine stem oleoresin pressure in a boreal forest.

PubMed

Rissanen, K; Hölttä, T; Vanhatalo, A; Aalto, J; Nikinmaa, E; Rita, H; Bäck, J

2016-03-01

Coniferous tree stems contain large amounts of oleoresin under positive pressure in the resin ducts. Studies in North-American pines indicated that the stem oleoresin exudation pressure (OEP) correlates negatively with transpiration rate and soil water content. However, it is not known how the OEP changes affect the emissions of volatile vapours from the trees. We measured the OEP, xylem diameter changes indicating changes in xylem water potential and monoterpene emissions under field conditions in mature Scots pine (Pinus sylvestris L.) trees in southern Finland. Contrary to earlier reports, the diurnal OEP changes were positively correlated with temperature and transpiration rate. OEP was lowest at the top part of the stem, where water potentials were also more negative, and often closely linked to ambient temperature and stem monoterpene emissions. However, occasionally OEP was affected by sudden changes in vapour pressure deficit (VPD), indicating the importance of xylem water potential on OEP as well. We conclude that the oleoresin storage pools in tree stems are in a dynamic relationship with ambient temperature and xylem water potential, and that the canopy monoterpene emission rates may therefore be also regulated by whole tree processes and not only by the conditions prevailing in the upper canopy. © 2015 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.

Association between Symptoms of Sleep-Disordered Breathing and Speech in Children with Craniofacial Malformations

PubMed Central

Moraleda-Cibrián, Marta; Berger, Mary; Edwards, Sean P.; Kasten, Steven J.; Buchman, Steven R.; O'Brien, Louise M.

2014-01-01

Study Objective: Sleep-disordered breathing (SDB) and speech difficulties are common problems in children with craniofacial malformations (CFM). The present study was designed to investigate whether resonance issues identified during speech assessment are associated with parental report of SDB symptoms in children with CFM. Methods: Children aged 2-18 years with congenital CFM attending at the Craniofacial Anomalies Program from March 2007 to April 2011 were screened for SDB symptoms using the Sleep-Related Breathing Disturbance Scale of the Pediatric Sleep Questionnaire. Speech evaluation, based on the Pittsburgh Weighted Speech Scale score, was the tool used to investigate velopharyngeal dysfunction (VPD) based on speech perceptual assessment. Results: A total of 488 children with congenital CFM were included. Overall 81% were Caucasian and 24% were overweight/obese. Twenty-four percent of children screened positive for SDB and 35% had VPD. Children with VPD were no more likely to screen positive for SDB than children without VPD (26% vs. 23%, p = 0.38). However, children with previous sphincter pharyngoplasty (SP) were more likely to have hyponasality (51% vs. 12%, p = 0.0001) and reduced or absent nasal emission (33% vs. 16%, p = 0.008). In a logistic regression, the adjusted odds ratio for SDB for those with hyponasality was 2.10 (95%CI 1.21-3.61, p = 0.008) and for those with reduced or absent nasal emission was 1.75 (95%CI 1.06-2.88, p = 0.028). Conclusion: Symptoms of sleep disordered breathing are common in children with craniofacial malformations especially if they have undergone sphincter pharyngoplasty; many of these children can be identified by measures of resonance on routine speech evaluation. Citation: Moraleda-Cibrián M, Berger M, Edwards SP, Kasten SJ, Buchman SR, O'Brien LM. Association between symptoms of sleep-disordered breathing and speech in children with craniofacial malformations. J Clin Sleep Med 2014;10(6):671-676. PMID:24932148

Event Water Balance and Recharge at the Panola Mountain Research Watershed, Georgia, U.S.A.

NASA Astrophysics Data System (ADS)

Riley, J. W.; Aulenbach, B. T.

2016-12-01

Investigating catchment storage and runoff pathways allows a better mechanistic understanding of stream flow generation processes. This information can be used to elucidate processes such as those influencing baseflow that support human consumption and ecological needs. Here we describe storm runoff water budgets from 483 rain events to determine the conditions under which precipitation infiltrates to deeper storage that supports baseflow. Further, we examine the storage and recharge behavior of different storm characteristics and antecedent conditions. We use a simple water budget approach to achieve this in which Deep Recharge = (Precipitation) - (Storm Runoff) - (Event Change in Soil Storage). Hydrograph separation was used to determine the storm periods and split storm runoff into baseflow and quickflow. Quickflow was assumed to account for the event water lost to the stream. Data from volumetric water content sensors were used to calculate the soil profile water storage and the change in water storage over the course of an event. The remaining water after these two components was assumed to represent water available for deeper recharge. The median event quickflow:precipitation ratio was 11.8%. Event soil moisture recharge in the top one meter of soil accounted for a median of 65.3% of precipitation. Quickflow and shallow soil moisture recharge accounted for a median of 77.1% of the precipitation delivered to the watershed. Water budgets indicated that 43% of the events provided water for deeper recharge. Of these events, however, only 28% provided 50 mm or more of deep recharge. Because the focus was on events, when humidity was high and the vapor pressure deficit (VPD) was low, we ignored the role of evapotranspiration. However, interception, which was not accounted for, would have resulted in less storm precipitation than was measured at the watershed rain gage. Furthermore, transpiration may have altered the post-storm water balance when VPD increased and before excess water was able to infiltrate to deeper storage. While uncertainty remains, this study provided insight into the partitioning of incoming precipitation and the conditions under which water was likely available for deeper recharge.

Long-term effects of drought on tree-ring growth and carbon isotope variability in Scots pine in a dry environment.

PubMed

Timofeeva, Galina; Treydte, Kerstin; Bugmann, Harald; Rigling, Andreas; Schaub, Marcus; Siegwolf, Rolf; Saurer, Matthias

2017-08-01

Drought frequency is increasing in many parts of the world and may enhance tree decline and mortality. The underlying physiological mechanisms are poorly understood, however, particularly regarding chronic effects of long-term drought and the response to increasing temperature and vapor pressure deficit (VPD). We combined analyses of radial growth and stable carbon isotope ratios (δ13C) in tree rings in a mature Scots pine (Pinus sylvestris L.) forest over the 20th century to elucidate causes of tree mortality in one of the driest parts of the European Alps (Pfynwald, Switzerland). We further compared trees that have recently died with living trees in a 10-year irrigation experiment, where annual precipitation was doubled. We found a sustained growth increase and immediate depletion of δ13C values for irrigated trees, indicating higher stomatal conductance and thus indeed demonstrating that water is a key limiting factor for growth. Growth of the now-dead trees started declining in the mid-1980s, when both mean temperature and VPD increased strongly. But growth of these trees was reduced to some extent already several decades earlier, while intrinsic water-use efficiency derived from δ13C values was higher. This indicates a more conservative water-use strategy compared with surviving trees, possibly at the cost of low carbon uptake and long-term reduction of the needle mass. We observed reduced climatic sensitivity of raw tree-ring δ13C for the now-dead in contrast to surviving trees, indicating impaired stomatal regulation, although this difference between the tree groups was smaller after detrending the data. Higher autocorrelation and a lower inter-annual δ13C variability of the now-dead trees further indicates a strong dependence on (low) carbon reserves. We conclude that the recent increase in atmospheric moisture demand in combination with insufficient soil water supply was the main trigger for mortality of those trees that were weakened by long-term reduced carbon uptake. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Using eco-physiological traits to understand the realized niche: the role of desiccation tolerance in Chagas disease vectors.

PubMed

de la Vega, Gerardo J; Schilman, Pablo E

2017-12-01

Small ectotherms, such as insects, with high surface area-to-volume ratios are usually at risk of dehydration in arid environments. We hypothesize that desiccation tolerance in insects could be reflected in their distribution, which is limited by areas with high relative values of water vapor pressure deficit (VPD) (e.g., hot and dry). The main goal of this study was to explore whether incorporation of eco-physiological traits such as desiccation tolerance in arid environments can improve our understanding of species distribution models (SDM). We use a novel eco-physiological approach to understand the distribution and the potential overlap with their fundamental niche in triatomine bugs, Chagas disease vectors. The desiccation dimension for T. infestans, T. delpontei, T. dimidiata, and T. sordida niches seems to extend to very dry areas. For T. vitticeps, xeric areas seem to limit the geographical range of their realized niche. The maximum VPD limits the western and southern distributions of T. vitticeps, T. delpontei, and T. patagonica. All species showed high tolerance to desiccation with survival times (35 °C-RH ~ 15%) ranging from 24 to 38 days, except for T. dimidiata (9 days), which can be explained by a higher water-loss rate, due to a higher cuticular permeability along with a higher critical water content. This approach indicates that most of these triatomine bugs could be exploiting the dryness dimension of their fundamental niche. Incorporating such species-specific traits in studies of distribution, range, and limits under scenarios of changing climate could enhance predictions of movement of disease-causing vectors into novel regions.

Contrasting precipitation seasonality influences evapotranspiration dynamics in water-limited shrublands

NASA Astrophysics Data System (ADS)

Villarreal, Samuel; Vargas, Rodrigo; Yepez, Enrico A.; Acosta, Jose S.; Castro, Angel; Escoto-Rodriguez, Martin; Lopez, Eulogio; Martínez-Osuna, Juan; Rodriguez, Julio C.; Smith, Stephen V.; Vivoni, Enrique R.; Watts, Christopher J.

2016-02-01

Water-limited ecosystems occupy nearly 30% of the Earth, but arguably, the controls on their ecosystem processes remain largely uncertain. We analyzed six site years of eddy covariance measurements of evapotranspiration (ET) from 2008 to 2010 at two water-limited shrublands: one dominated by winter precipitation (WP site) and another dominated by summer precipitation (SP site), but with similar solar radiation patterns in the Northern Hemisphere. We determined how physical forcing factors (i.e., net radiation (Rn), soil water content (SWC), air temperature (Ta), and vapor pressure deficit (VPD)) influence annual and seasonal variability of ET. Mean annual ET at SP site was 455 ± 91 mm yr-1, was mainly influenced by SWC during the dry season, by Rn during the wet season, and was highly sensitive to changes in annual precipitation (P). Mean annual ET at WP site was 363 ± 52 mm yr-1, had less interannual variability, but multiple variables (i.e., SWC, Ta, VPD, and Rn) were needed to explain ET among years and seasons. Wavelet coherence analysis showed that ET at SP site has a consistent temporal coherency with Ta and P, but this was not the case for ET at WP site. Our results support the paradigm that SWC is the main control of ET in water-limited ecosystems when radiation and temperature are not the limiting factors. In contrast, when P and SWC are decoupled from available energy (i.e., radiation and temperature), then ET is controlled by an interaction of multiple variables. Our results bring attention to the need for better understanding how climate and soil dynamics influence ET across these globally distributed ecosystems.

Soil moisture control of sap-flow response to biophysical factors in a desert-shrub species, Artemisia ordosica

NASA Astrophysics Data System (ADS)

Zha, Tianshan; Qian, Duo; Jia, Xin; Bai, Yujie; Tian, Yun; Bourque, Charles P.-A.; Ma, Jingyong; Feng, Wei; Wu, Bin; Peltola, Heli

2017-10-01

The current understanding of acclimation processes in desert-shrub species to drought stress in dryland ecosystems is still incomplete. In this study, we measured sap flow in Artemisia ordosica and associated environmental variables throughout the growing seasons of 2013 and 2014 (May-September period of each year) to better understand the environmental controls on the temporal dynamics of sap flow. We found that the occurrence of drought in the dry year of 2013 during the leaf-expansion and leaf-expanded periods caused sap flow per leaf area (Js) to decline significantly, resulting in transpiration being 34 % lower in 2013 than in 2014. Sap flow per leaf area correlated positively with radiation (Rs), air temperature (T), and water vapor pressure deficit (VPD) when volumetric soil water content (VWC) was greater than 0.10 m3 m-3. Diurnal Js was generally ahead of Rs by as much as 6 hours. This time lag, however, decreased with increasing VWC. The relative response of Js to the environmental variables (i.e., Rs, T, and VPD) varied with VWC, Js being more strongly controlled by plant-physiological processes during periods of dryness indicated by a low decoupling coefficient and low sensitivity to the environmental variables. According to this study, soil moisture is shown to control sap-flow (and, therefore, plant-transpiration) response in Artemisia ordosica to diurnal variations in biophysical factors. This species escaped (acclimated to) water limitations by invoking a water-conservation strategy with the regulation of stomatal conductance and advancement of Js peaking time, manifesting in a hysteresis effect. The findings of this study add to the knowledge of acclimation processes in desert-shrub species under drought-associated stress. This knowledge is essential in modeling desert-shrub-ecosystem functioning under changing climatic conditions.

Harnessing long-term flux records to better understand ecosystem response to drought

NASA Astrophysics Data System (ADS)

Novick, K. A.; Ficklin, D. L.; Stoy, P. C.; Williams, C. A.; Bohrer, G.; Oishi, A. C.; Papuga, S. A.; Blanken, P.; Noormets, A.; Scott, R. L.; Wang, L.; Roman, D. T.; Yi, K.; Sulman, B. N.; Phillips, R.

2016-12-01

While ongoing climate change affects a number of meteorological drivers relevant to plant functioning, the predicted increase in the frequency and severity of droughts may ultimately have the biggest impact on ecosystem carbon cycling. Because it is difficult to experimentally manipulate all of the meteorological drivers that change during drought (including precipitation, light, temperature, and humidity), our understanding of the mechanisms by which plants respond to drought is generally limited to an understanding of how plants respond to variable soil moisture. As flux tower records grow in length and number, they permit us to harness natural spatial and temporal variability in hydrologic condition to better understand how ecosystems respond to the full suite of meteorological drivers that change during drought stress. Here, a series of case studies are presented that illustrate how long term flux data can be used to disentangle limitations to ecosystem functioning imposed by declining soil moisture as compared to rising atmospheric demand for water during drought. At the site-level, we pair observations from the Morgan-Monroe State Forest Ameriflux tower (active since 1999) with eco-physiological datasets collected during the severe 2012 Midwestern drought. We show that vapor pressure deficit (VPD) limits ecosystem carbon uptake and transpiration as much as soil moisture, but that individual species vary in their sensitivity to these drivers. We then present results from two cross-site Ameriflux syntheses that quantify how VPD as compared to soil moisture limitations to carbon and water cycling vary across broad climate gradients spanning semi-arid to mesic biomes. Informed by these results, we end by highlighting ways that flux network data may be leveraged together with other eco-physiological networks and databases to further expand our understanding of the mechanisms determining ecosystem response to drought.

Separating heat stress from moisture stress: analyzing yield response to high temperature in irrigated maize

NASA Astrophysics Data System (ADS)

Carter, Elizabeth K.; Melkonian, Jeff; Riha, Susan J.; Shaw, Stephen B.

2016-09-01

Several recent studies have indicated that high air temperatures are limiting maize (Zea mays L.) yields in the US Corn Belt and project significant yield losses with expected increases in growing season temperatures. Further work has suggested that high air temperatures are indicative of high evaporative demand, and that decreases in maize yields which correlate to high temperatures and vapor pressure deficits (VPD) likely reflect underlying soil moisture limitations. It remains unclear whether direct high temperature impacts on yields, independent of moisture stress, can be observed under current temperature regimes. Given that projected high temperature and moisture may not co-vary the same way as they have historically, quantitative analyzes of direct temperature impacts are critical for accurate yield projections and targeted mitigation strategies under shifting temperature regimes. To evaluate yield response to above optimum temperatures independent of soil moisture stress, we analyzed climate impacts on irrigated maize yields obtained from the National Corn Growers Association (NCGA) corn yield contests for Nebraska, Kansas and Missouri. In irrigated maize, we found no evidence of a direct negative impact on yield by daytime air temperature, calculated canopy temperature, or VPD when analyzed seasonally. Solar radiation was the primary yield-limiting climate variable. Our analyses suggested that elevated night temperature impacted yield by increasing rates of phenological development. High temperatures during grain-fill significantly interacted with yields, but this effect was often beneficial and included evidence of acquired thermo-tolerance. Furthermore, genetics and management—information uniquely available in the NCGA contest data—explained more yield variability than climate, and significantly modified crop response to climate. Thermo-acclimation, improved genetics and changes to management practices have the potential to partially or completely offset temperature-related yield losses in irrigated maize.

Short- and Long-Term Feedbacks on Vegetation Water Use: Unifying Evidence from Observations and Modeling

NASA Astrophysics Data System (ADS)

Mackay, D. S.

2001-05-01

Recent efforts to measure and model the interacting influences of climate, soil, and vegetation on soil water and nutrient dynamics have identified numerous important feedbacks that produce nonlinear responses. In particular, plant physiological factors that control rates of transpiration respond to soil water deficits and vapor pressure deficits (VPD) in the short-term, and to climate, nutrient cycling and disturbance in the long-term. The starting point of this presentation is the observation that in many systems, in particular forest ecosystems, conservative water use emerges as a result of short-term closure of stomata in response to high evaporative demand, and long-term vegetative canopy development under nutrient limiting conditions. Evidence for important short-term controls is presented from sap flux measurements of stand transpiration, remote sensing, and modeling of transpiration through a combination of physically-based modeling and Monte Carlo analysis. A common result is a strong association between stomatal conductance (gs) and the negative evaporative gain (∂ gs/∂ VPD) associated with the sensitivity of stomatal closure to rates of water loss. The importance of this association from the standpoint of modeling transpiration depends on the degree of canopy-atmosphere coupling. This suggests possible simplifications to future canopy component models for use in watershed and larger-scale hydrologic models for short-term processes. However, further results are presented from theoretical modeling, which suggest that feedbacks between hydrology and vegetation in current long-term (inter-annual to century) models may be too simple, as they do not capture the spatially variable nature of slow nutrient cycling in response to soil water dynamics and site history. Memory effects in the soil nutrient pools can leave lasting effects on more rapid processes associated with soil, vegetation, atmosphere coupling.

Large net CO2 loss from a grass-dominated tropical savanna in south-central Brazil in response to seasonal and interannual drought

NASA Astrophysics Data System (ADS)

Zanella De Arruda, Paulo Henrique; Vourlitis, George Louis; Santanna, Franciele Bomfiglio; Pinto, Osvaldo Borges, Jr.; De Almeida Lobo, Francisco; De Souza Nogueira, José

2016-08-01

The savanna vegetation of Brazil (Cerrado) accounts for 20-25% of the land cover of Brazil and is the second largest ecosystem following Amazonian forest; however, Cerrado mass and energy exchange is still highly uncertain. We used eddy covariance to measure the net ecosystem CO2 exchange (NEE) of grass-dominated Cerrado (campo sujo) over 3 years. We hypothesized that soil water availability would be a key control over the seasonal and interannual variations in NEE. Multiple regression indicated that gross primary production (GPP) was positively correlated (Pearson's r = 0.69; p < 0.001) with soil water content, radiation, and the Moderate Resolution Imaging Spectroradiometer (MODIS)-derived enhanced vegetation index (EVI) but negatively correlated with the vapor pressure deficit (VPD), indicating that drier conditions increased water limitations on GPP. Similarly, ecosystem respiration (Reco) was positively correlated (Pearson's r = 0.78; p < 0.001) with the EVI, radiation, soil water content, and temperature but slightly negatively correlated with rainfall and the VPD. While the NEE responded rapidly to temporal variations in soil water availability, the grass-dominated Cerrado stand was a net source of CO2 to the atmosphere during the study period, which was drier compared to the long-term average rainfall. Cumulative NEE was approximately 842 gC m-2, varying from 357 gC m-2 in 2011 to 242 gC m-2 in 2012. Our results indicate that grass-dominated Cerrado may be an important regional CO2 source in response to the warming and drying that is expected to occur in the southern Amazon Basin under climate change.

Surviving a Dry Future: Abscisic Acid (ABA)-Mediated Plant Mechanisms for Conserving Water under Low Humidity

PubMed Central

McAdam, Scott A. M.

2017-01-01

Angiosperms are able to respond rapidly to the first sign of dry conditions, a decrease in air humidity, more accurately described as an increase in the vapor pressure deficit between the leaf and the atmosphere (VPD), by abscisic acid (ABA)-mediated stomatal closure. The genes underlying this response offer valuable candidates for targeted selection of crop varieties with improved drought tolerance, a critical goal for current plant breeding programs, to maximize crop production in drier and increasingly marginalized environments, and meet the demands of a growing population in the face of a changing climate. Here, we review current understanding of the genetic mechanisms underpinning ABA-mediated stomatal closure, a key means for conserving water under dry conditions, examine how these mechanisms evolved, and discuss what remains to be investigated. PMID:29113039

SU-G-JeP3-04: Estimating 4D CBCT from Prior Information and Extremely Limited Angle Projections Using Structural PCA and Weighted Free-Form Deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, W; Yin, F; Zhang, Y

Purpose: To investigate the feasibility of using structure-based principal component analysis (PCA) motion-modeling and weighted free-form deformation to estimate on-board 4D-CBCT using prior information and extremely limited angle projections for potential 4D target verification of lung radiotherapy. Methods: A technique for lung 4D-CBCT reconstruction has been previously developed using a deformation field map (DFM)-based strategy. In the previous method, each phase of the 4D-CBCT was generated by deforming a prior CT volume. The DFM was solved by a motion-model extracted by global PCA and a free-form deformation (GMM-FD) technique, using data fidelity constraint and the deformation energy minimization. In thismore » study, a new structural-PCA method was developed to build a structural motion-model (SMM) by accounting for potential relative motion pattern changes between different anatomical structures from simulation to treatment. The motion model extracted from planning 4DCT was divided into two structures: tumor and body excluding tumor, and the parameters of both structures were optimized together. Weighted free-form deformation (WFD) was employed afterwards to introduce flexibility in adjusting the weightings of different structures in the data fidelity constraint based on clinical interests. XCAT (computerized patient model) simulation with a 30 mm diameter lesion was simulated with various anatomical and respirational changes from planning 4D-CT to onboard volume. The estimation accuracy was evaluated by the Volume-Percent-Difference (VPD)/Center-of-Mass-Shift (COMS) between lesions in the estimated and “ground-truth” on board 4D-CBCT. Results: Among 6 different XCAT scenarios corresponding to respirational and anatomical changes from planning CT to on-board using single 30° on-board projections, the VPD/COMS for SMM-WFD was reduced to 10.64±3.04%/1.20±0.45mm from 21.72±9.24%/1.80±0.53mm for GMM-FD. Using 15° orthogonal projections, the VPD/COMS was further reduced to 1.91±0.86%/0.31±0.42mm based on SMM-WFD. Conclusion: Compared to GMM-FD technique, the SMM-WFD technique can substantially improve the 4D-CBCT estimation accuracy using extremely small scan angles to provide ultra-fast 4D verification. This work was supported by the National Institutes of Health under Grant No. R01-CA184173 and a research grant from Varian Medical Systems.« less

(BOREAS) BOREAS TE-7 Sap Flow Data

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Hogg, E. H.; Hurdle, P. A.

2000-01-01

The BOREAS TE-7 team collected data sets in support of its efforts to characterize and interpret information on the sap flow of boreal vegetation. The heat pulse method was used to monitor sap flow and to estimate rates of transpiration from aspen, black spruce, and mixed wood forests at the SSAOA, MIX, SSA-OBS. and Batoche sites in Saskatchewan, Canada. Measurements were made at the various sites from May to October 1994, May to October 1995, and April to October 1996. A scaling procedure was used to estimate canopy transpiration rates from the sap flow measurements. The data were stored in tabular ASCII files. Analyses to date show a tendency for sap flow in aspen to remain remarkably constant over a wide range of environmental conditions VPD from 1.0 to 4.8 kPa and solar radiation less than 400 W/sq m). For forests with high aerodynamic conductance, the results would indicate an inverse relationship between stomatal conductance and VPD, for VPD greater than 1 kPa. A possible interpretation is that stomata are operating to maintain leaf water potentials above a critical minimum value, which in turn places a maximum value on the rate of sap flow that can be sustained by the tree. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distrobuted Activity Archive Center (DAAC).

A technique for estimating 4D-CBCT using prior knowledge and limited-angle projections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, You; Yin, Fang-Fang; Ren, Lei

2013-12-15

Purpose: To develop a technique to estimate onboard 4D-CBCT using prior information and limited-angle projections for potential 4D target verification of lung radiotherapy.Methods: Each phase of onboard 4D-CBCT is considered as a deformation from one selected phase (prior volume) of the planning 4D-CT. The deformation field maps (DFMs) are solved using a motion modeling and free-form deformation (MM-FD) technique. In the MM-FD technique, the DFMs are estimated using a motion model which is extracted from planning 4D-CT based on principal component analysis (PCA). The motion model parameters are optimized by matching the digitally reconstructed radiographs of the deformed volumes tomore » the limited-angle onboard projections (data fidelity constraint). Afterward, the estimated DFMs are fine-tuned using a FD model based on data fidelity constraint and deformation energy minimization. The 4D digital extended-cardiac-torso phantom was used to evaluate the MM-FD technique. A lung patient with a 30 mm diameter lesion was simulated with various anatomical and respirational changes from planning 4D-CT to onboard volume, including changes of respiration amplitude, lesion size and lesion average-position, and phase shift between lesion and body respiratory cycle. The lesions were contoured in both the estimated and “ground-truth” onboard 4D-CBCT for comparison. 3D volume percentage-difference (VPD) and center-of-mass shift (COMS) were calculated to evaluate the estimation accuracy of three techniques: MM-FD, MM-only, and FD-only. Different onboard projection acquisition scenarios and projection noise levels were simulated to investigate their effects on the estimation accuracy.Results: For all simulated patient and projection acquisition scenarios, the mean VPD (±S.D.)/COMS (±S.D.) between lesions in prior images and “ground-truth” onboard images were 136.11% (±42.76%)/15.5 mm (±3.9 mm). Using orthogonal-view 15°-each scan angle, the mean VPD/COMS between the lesion in estimated and “ground-truth” onboard images for MM-only, FD-only, and MM-FD techniques were 60.10% (±27.17%)/4.9 mm (±3.0 mm), 96.07% (±31.48%)/12.1 mm (±3.9 mm) and 11.45% (±9.37%)/1.3 mm (±1.3 mm), respectively. For orthogonal-view 30°-each scan angle, the corresponding results were 59.16% (±26.66%)/4.9 mm (±3.0 mm), 75.98% (±27.21%)/9.9 mm (±4.0 mm), and 5.22% (±2.12%)/0.5 mm (±0.4 mm). For single-view scan angles of 3°, 30°, and 60°, the results for MM-FD technique were 32.77% (±17.87%)/3.2 mm (±2.2 mm), 24.57% (±18.18%)/2.9 mm (±2.0 mm), and 10.48% (±9.50%)/1.1 mm (±1.3 mm), respectively. For projection angular-sampling-intervals of 0.6°, 1.2°, and 2.5° with the orthogonal-view 30°-each scan angle, the MM-FD technique generated similar VPD (maximum deviation 2.91%) and COMS (maximum deviation 0.6 mm), while sparser sampling yielded larger VPD/COMS. With equal number of projections, the estimation results using scattered 360° scan angle were slightly better than those using orthogonal-view 30°-each scan angle. The estimation accuracy of MM-FD technique declined as noise level increased.Conclusions: The MM-FD technique substantially improves the estimation accuracy for onboard 4D-CBCT using prior planning 4D-CT and limited-angle projections, compared to the MM-only and FD-only techniques. It can potentially be used for the inter/intrafractional 4D-localization verification.« less

Variation of NEE and its affecting factors in a vineyard of arid region of northwest China

NASA Astrophysics Data System (ADS)

Guo, W. H.; Kang, S. Z.; Li, F. S.; Li, S. E.

2014-02-01

To understand the variation of net ecosystem CO2 exchange (NEE) in orchard ecosystem and it's affecting factors, carbon flux was measured using eddy covariance system in a wine vineyard in arid northwest China during 2008-2010. Results show that vineyard NEE was positive value at the early growth stage, higher negative value at the mid-growth stage, and lower negative value at the later growth stage. Diurnal variation of NEE was "W" shaped curve in sunny day, but "U" shaped curve in cloudy day. Irrigation and pruning did not affect diurnal variation shape of NEE, however, irrigation reduced the difference between maximal and minimal value of NEE and pruning reduced the carbon sink capacity. The main factors affecting hourly NEE were canopy conductance (gc) and net radiation (Rn). The hourly NEE increased with the increase of gc or Rn when gc was less than 0.02 m·s-1 or Rn was between 0 and 200 W·m-2. The main factors affecting both daily and seasonal NEE were gc, air temperature (Ta), atmospheric CO2 density, vapour pressure deficit (VPD) and soil moisture content.

Does canopy mean N concentration explain differences in light use efficiency in 14 eddy-covariance sites?

NASA Astrophysics Data System (ADS)

Peltoniemi, Mikko; Pulkkinen, Minna; Kolari, Pasi; Mäkelä, Annikki

2010-05-01

Production efficiency models aim at explaining variation of vegetation productivity with climatic input and information on vegetation cover often obtained from satellite observations. It has been acknowledged that different plant species differ in their potential to assimilate carbon dioxide per unit of PAR (i.e light use efficiency, LUE). Subsequently, some LUE-based models apply different LUE-coefficients for different plant functional types. Leaf N concentrations differ between plant species, and related differences in light saturated photosynthesis rate (A_max) have been detected. How much these differences affect the ecosystem production or LUE is more obscure. Canopies acclimate to prevailing environmental conditions, which causes variation e.g. in the proportion of leaves exposed to direct sunlight, leaf morphology, structure,orientation, and vertical N distibution. Furthermore, a fair proportion of photosynthesis occurs during cloudy days, in which case high A_max is unessential, and number of these days differs by location. We studied if canopy mean N concentration could explain differences in LUE derived for 14 forest sites using eddy-covariance measurements. The largest actual LUE was estimated for each site directly as an upper percentile of the ratio of Gross Primary Production (GPP) to absorbed PAR. Potential LUE for each site, on the other hand, was estimated by parameterising a LUE-based production efficiency model (Prelued), which accounts for daily changes in weather (temperature, VPD, PAR). In this model structure, the LUE-parameter for each site, can be interpreted as the potential LUE under optimal environmental conditions, i.e when the environment is not limiting production at all. Averages of the largest actual LUE and potential LUE were higher in deciduous sites than in conifer sites. Canopy mean N correlated weakly with both the largest actual and potential LUE, and the correlation was also significant in conifer subset in the former case. Mean growing season VPD was the only climatic variable which correlated significantly with the largest actual LUE; none of them correlated with potential LUE. Inclusion of nitrogen in the Prelued-model structure did not improve the goodness of fit of the model. According to our results LUE correlates with mean canopy N concentration. The correlation of mean VPD with the largest actual LUE can also be explained with the model accounting for daily variation in climate, as was made with Prelued-model for the potential LUE. Further studies utilising seasonal values of canopy N are called upon. *Acknowledgements: Eero Nikinmaa, Pertti Hari, Timo Vesala, Tuomas Laurila, Fredrik Lagergren, Meelis Mölder, Anders Lindroth, Thomas Grünwald, Christian Bernhofer, Denis Loustau, Paul Berbigier, Beverly Law, Alison Dunn, Steve Wofsy, Torbjörn Johansson, Torben Christensen, Terry Callaghan, Hans Verbeeck, Remko Duursma, Leonardo Montagnani, Dario Papale, Andreas Ibrom, Ebba Dellwik, Kim Pilegaard, Kentaro Takagi, Eva van Gorsel, Heather Keith, Sonia Wharton, Matthias Falk, Kya Tha Paw U, Matt Schroeder, Jon Lloyd

Influence of crop load on almond tree water status and its importance in irrigation scheduling

NASA Astrophysics Data System (ADS)

Puerto Conesa, Pablo; Domingo Miguel, Rafael; Torres Sánchez, Roque; Pérez Pastor, Alejandro

2014-05-01

In the Mediterranean area water is the main factor limiting crop production and therefore irrigation is essential to achieve economically viable yields. One of the fundamental techniques to ensure that irrigation water is managed efficiently with maximum productivity and minimum environmental impact is irrigation scheduling. The fact that the plant water status integrates atmospheric demand and soil water content conditions encourages the use of plant-based water status indicators. Some researchers have successfully scheduled irrigation in certain fruit trees by maintaining the maximum daily trunk diameter shrinkage (MDS) signal intensity at threshold values to generate (or not) water stress. However MDS not only depends on the climate and soil water content, but may be affected by tree factors such as age, size, phenological stage and fruit load. There is therefore a need to quantify the influence of these factors on MDS. The main objective of this work was to study the effects of crop load on tree water relations for scheduling purposes. We particularly focused on MDS vs VPD10-15 (mean air vapor pressure deficit during the period 10.00-15.00 h solar time) for different loads and phenological phases under non-limiting soil water conditions. The experiment was carried out in 2011 in a 1 ha plot in SE Spain with almond trees (Prunus dulcis (Mill.) D.A. Webb cv. 'Marta'). Three crop load treatments were studied according to three crop load levels, i) T100, high crop load, characteristic crop load, ii) T50, medium crop load, in which 50% of the fruits were removed and iii) T0, practically without fruits. Fruits were manually thinned. Each treatment, randomly distributed in blocks, was run in triplicate. Plant water status was assessed from midday stem water potential (Ψs), MDS, daily trunk growth rate (TGR), leaf turgor potential Ψp, fruit water potential (Ψf), stomatal conductance (gs) and photosynthesis (Pn) and transpiration rates (E). Yield, pruning weights and reserve sugar concentration were also evaluated. Trees were drip irrigated in order to satisfy the maximum crop water requirements. Variations in MDS were compared with changes in Ψs and VPD10-15 in the three treatments at the end of fruit growth stage (stage III), kernel filling stage (stage IV) and postharvest (stage V). Our results highlighted that crop load affects almond tree water status. We observed a greater effect of crop load on MDS and TGR than on Ψs. In T0 trees, Ψs was 16% higher than in T50 and T100. MDS was 36% and 49% lower in the low (T50) and almost nil-cropping trees (T0) than in the high-cropping trees (T100). The slope of MDS vs VPD10-15 forced to the origin increased with crop load, suggesting that different relationships are needed to estimate tree water status. TGR was 33% higher in T0 than in the cropping trees. In the same way, the presence of fruits, as reflected by the source/sink relationship, increased gas exchange parameters. Also pruning weights reflected competition between fruits and shoots for photoassimilates. Nevertheless the reserve sugar concentration at the base of the main branches was unaffected by the crop load. All this implies that it is necessary to consider the crop load in irrigation scheduling based on MDS signal intensity.

Interannual variations in needle and sapwood traits of Pinus edulis branches under an experimental drought

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guerin, Marceau; Martin-Benito, Dario; von Arx, Georg

In recent years, widespread forest mortality in response to drought has been documented worldwide (Allen, Breshears & McDowell 2015). An example of widespread and rapid increase in drought-induced mortality, or die-off, was observed for Pinus edulis Engelm. across the Southwestern USA in response to several years of reduced rainfall and high vapor pressure deficits (VPD) (Breshears et al. 2009; Allen et al. 2010; Williams et al. 2013). Although stomatal closure under drought has been hypothesized to increase mortality through carbon starvation (McDowell et al. 2008; Breshears et al. 2009), more evidences exist for mortality being caused by hydraulic failure (Plautmore » et al. 2012; McDowell et al. 2013; Sevanto et al. 2014; Garcia-Forner et al. 2016). Regardless of the mechanism of drought-induced decline, maintaining a positive supply of water to the foliage is critical for tree functioning and survival.« less

Interannual variations in needle and sapwood traits of Pinus edulis branches under an experimental drought

DOE PAGES

Guerin, Marceau; Martin-Benito, Dario; von Arx, Georg; ...

2018-01-05

In recent years, widespread forest mortality in response to drought has been documented worldwide (Allen, Breshears & McDowell 2015). An example of widespread and rapid increase in drought-induced mortality, or die-off, was observed for Pinus edulis Engelm. across the Southwestern USA in response to several years of reduced rainfall and high vapor pressure deficits (VPD) (Breshears et al. 2009; Allen et al. 2010; Williams et al. 2013). Although stomatal closure under drought has been hypothesized to increase mortality through carbon starvation (McDowell et al. 2008; Breshears et al. 2009), more evidences exist for mortality being caused by hydraulic failure (Plautmore » et al. 2012; McDowell et al. 2013; Sevanto et al. 2014; Garcia-Forner et al. 2016). Regardless of the mechanism of drought-induced decline, maintaining a positive supply of water to the foliage is critical for tree functioning and survival.« less

[Multi-temporal scale analysis of impacts of extreme high temperature on net carbon uptake in subtropical coniferous plantation.

PubMed

Zhang, Mi; Wen, Xue Fa; Zhang, Lei Ming; Wang, Hui Min; Guo, Yi Wen; Yu, Gui Rui

2018-02-01

Extreme high temperature is one of important extreme weathers that impact forest ecosystem carbon cycle. In this study, applying CO 2 flux and routine meteorological data measured during 2003-2012, we examined the impacts of extreme high temperature and extreme high temperature event on net carbon uptake of subtropical coniferous plantation in Qianyanzhou. Combining with wavelet analysis, we analyzed environmental controls on net carbon uptake at different temporal scales, when the extreme high temperature and extreme high temperature event happened. The results showed that mean daily cumulative NEE decreased by 51% in the days with daily maximum air temperature range between 35 ℃ and 40 ℃, compared with that in the days with the range between 30 ℃ and 34 ℃. The effects of the extreme high temperature and extreme high temperature event on monthly NEE and annual NEE related to the strength and duration of extreme high tempe-rature event. In 2003, when strong extreme high temperature event happened, the sum of monthly cumulative NEE in July and August was only -11.64 g C·m -2 ·(2 month) -1 . The value decreased by 90%, compared with multi-year average value. At the same time, the relative variation of annual NEE reached -6.7%. In July and August, when the extreme high temperature and extreme high temperature event occurred, air temperature (T a ) and vapor press deficit (VPD) were the dominant controller for the daily variation of NEE. The coherency between NEE T a and NEE VPD was 0.97 and 0.95, respectively. At 8-, 16-, and 32-day periods, T a , VPD, soil water content at 5 cm depth (SWC), and precipitation (P) controlled NEE. The coherency between NEE SWC and NEE P was higher than 0.8 at monthly scale. The results indicated that atmospheric water deficit impacted NEE at short temporal scale, when the extreme high temperature and extreme high temperature event occurred, both of atmospheric water deficit and soil drought stress impacted NEE at long temporal scales in this ecosystem.

Contrasting trait syndromes in angiosperms and conifers are associated with different responses of tree growth to temperature on a large scale.

PubMed

Carnicer, Jofre; Barbeta, Adrià; Sperlich, Dominik; Coll, Marta; Peñuelas, Josep

2013-01-01

Recent large-scale studies of tree growth in the Iberian Peninsula reported contrasting positive and negative effects of temperature in Mediterranean angiosperms and conifers. Here we review the different hypotheses that may explain these trends and propose that the observed contrasting responses of tree growth to temperature in this region could be associated with a continuum of trait differences between angiosperms and conifers. Angiosperm and conifer trees differ in the effects of phenology in their productivity, in their growth allometry, and in their sensitivity to competition. Moreover, angiosperms and conifers significantly differ in hydraulic safety margins, sensitivity of stomatal conductance to vapor-pressure deficit (VPD), xylem recovery capacity or the rate of carbon transfer. These differences could be explained by key features of the xylem such as non-structural carbohydrate content (NSC), wood parenchymal fraction or wood capacitance. We suggest that the reviewed trait differences define two contrasting ecophysiological strategies that may determine qualitatively different growth responses to increased temperature and drought. Improved reciprocal common garden experiments along altitudinal or latitudinal gradients would be key to quantify the relative importance of the different hypotheses reviewed. Finally, we show that warming impacts in this area occur in an ecological context characterized by the advance of forest succession and increased dominance of angiosperm trees over extensive areas. In this context, we examined the empirical relationships between the responses of tree growth to temperature and hydraulic safety margins in angiosperm and coniferous trees. Our findings suggest a future scenario in Mediterranean forests characterized by contrasting demographic responses in conifer and angiosperm trees to both temperature and forest succession, with increased dominance of angiosperm trees, and particularly negative impacts in pines.

Contrasting trait syndromes in angiosperms and conifers are associated with different responses of tree growth to temperature on a large scale

PubMed Central

Carnicer, Jofre; Barbeta, Adrià; Sperlich, Dominik; Coll, Marta; Peñuelas, Josep

2013-01-01

Recent large-scale studies of tree growth in the Iberian Peninsula reported contrasting positive and negative effects of temperature in Mediterranean angiosperms and conifers. Here we review the different hypotheses that may explain these trends and propose that the observed contrasting responses of tree growth to temperature in this region could be associated with a continuum of trait differences between angiosperms and conifers. Angiosperm and conifer trees differ in the effects of phenology in their productivity, in their growth allometry, and in their sensitivity to competition. Moreover, angiosperms and conifers significantly differ in hydraulic safety margins, sensitivity of stomatal conductance to vapor-pressure deficit (VPD), xylem recovery capacity or the rate of carbon transfer. These differences could be explained by key features of the xylem such as non-structural carbohydrate content (NSC), wood parenchymal fraction or wood capacitance. We suggest that the reviewed trait differences define two contrasting ecophysiological strategies that may determine qualitatively different growth responses to increased temperature and drought. Improved reciprocal common garden experiments along altitudinal or latitudinal gradients would be key to quantify the relative importance of the different hypotheses reviewed. Finally, we show that warming impacts in this area occur in an ecological context characterized by the advance of forest succession and increased dominance of angiosperm trees over extensive areas. In this context, we examined the empirical relationships between the responses of tree growth to temperature and hydraulic safety margins in angiosperm and coniferous trees. Our findings suggest a future scenario in Mediterranean forests characterized by contrasting demographic responses in conifer and angiosperm trees to both temperature and forest succession, with increased dominance of angiosperm trees, and particularly negative impacts in pines. PMID:24146668

Expansion of Vaccination Services and Strengthening Vaccine-Preventable Diseases Surveillance in Haiti, 2010–2016

PubMed Central

Tohme, Rania A.; Francois, Jeannot; Cavallaro, Kathleen F.; Paluku, Gilson; Yalcouye, Idrissa; Jackson, Ernsley; Wright, Tracie; Adrien, Paul; Katz, Mark A.; Hyde, Terri B.; Faye, Pape; Kimanuka, Francine; Dietz, Vance; Vertefeuille, John; Lowrance, David; Dahl, Benjamin; Patel, Roopal

2017-01-01

Abstract. Following the 2010 earthquake, Haiti was at heightened risk for vaccine-preventable diseases (VPDs) outbreaks due to the exacerbation of long-standing gaps in the vaccination program and subsequent risk of VPD importation from other countries. Therefore, partners supported the Haitian Ministry of Health and Population to improve vaccination services and VPD surveillance. During 2010–2016, three polio, measles, and rubella vaccination campaigns were implemented, achieving a coverage > 90% among children and maintaining Haiti free of those VPDs. Furthermore, Haiti is on course to eliminate maternal and neonatal tetanus, with 70% of communes achieving tetanus vaccine two-dose coverage > 80% among women of childbearing age. In addition, the vaccine cold chain storage capacity increased by 91% at the central level and 285% at the department level, enabling the introduction of three new vaccines (pentavalent, rotavirus, and pneumococcal conjugate vaccines) that could prevent an estimated 5,227 deaths annually. Haiti moved from the fourth worst performing country in the Americas in 2012 to the sixth best performing country in 2015 for adequate investigation of suspected measles/rubella cases. Sentinel surveillance sites for rotavirus diarrhea and meningococcal meningitis were established to estimate baseline rates of those diseases prior to vaccine introduction and to evaluate the impact of vaccination in the future. In conclusion, Haiti significantly improved vaccination services and VPD surveillance. However, high dependence on external funding and competing vaccination program priorities are potential threats to sustaining the improvements achieved thus far. Political commitment and favorable economic and legal environments are needed to maintain these gains. PMID:29064356

A whole-tree chamber system for examining tree-level physiological responses of field-grown trees to environmental variation and climate change.

PubMed

Medhurst, Jane; Parsby, Jan; Linder, Sune; Wallin, Göran; Ceschia, Eric; Slaney, Michelle

2006-09-01

A whole-tree chamber (WTC) system was installed at Flakaliden in northern Sweden to examine the long-term physiological responses of field-grown 40-year-old Norway spruce trees [Picea abies (L.) Karst.] to climate change. The WTCs were designed as large cuvettes to allow the net tree-level CO(2) and water fluxes to be measured on a continuous basis. A total of 12 WTCs were used to impose combinations of atmospheric carbon dioxide concentration, [CO(2)], and air temperature treatments. The air inside the ambient and elevated [CO(2)] WTCs was maintained at 365 and 700 micromol mol(-1), respectively. The air temperature inside the ambient temperature WTCs tracked air temperature outside the WTCs. Elevated temperatures were altered on a monthly time-step and ranged between +2.8 and +5.6 degrees C above ambient temperature. The system allowed continuous, long-term measurement of whole-tree photosynthesis, night-time respiration and transpiration. The performance of the WTCs was assessed using winter and spring data sets. The ability of the WTC system to measure tree-level physiological responses is demonstrated. All WTCs displayed a high level of control over tracking of air temperatures. The set target of 365 micromol mol(-1) in the ambient [CO(2)] chambers was too low to be maintained during winter because of tree dormancy and the high natural increase in [CO(2)] over winter at high latitudes such as the Flakaliden site. Accurate control over [CO(2)] in the ambient [CO(2)] chambers was restored during the spring and the system maintained the elevated [CO(2)] target of 700 micromol mol(-1) for both measurement periods. Air water vapour deficit (VPD) was accurately tracked in ambient temperature WTCs. However, as water vapour pressure in all 12 WTCs was maintained at the level of non-chambered (reference) air, VPD of elevated temperature WTCs was increased.

Characterization of land surface energy fluxes in a tropical lowland rice paddy

NASA Astrophysics Data System (ADS)

Chatterjee, Dibyendu; Tripathi, Rahul; Chatterjee, Sumanta; Debnath, Manish; Shahid, Mohammad; Bhattacharyya, Pratap; Swain, Chinmaya Kumar; Tripathy, Rojalin; Bhattacharya, Bimal K.; Nayak, Amaresh Kumar

2018-04-01

A field experiment was conducted in 2015 to study the land surface energy fluxes from tropical lowland rice paddy in eastern India with an objective to determine the mass, momentum, and energy exchange rates between rice paddies and the atmosphere. All the land surface energy fluxes were measured by eddy covariance (EC) system (make Campbell Scientific) in dry season (DS, 1-125 Julian days), dry fallow (DF, 126-181 Julian days), wet season (WS, 182-324 Julian days), and wet fallow (WF, 325-365 Julian days). The rice was cultivated in dry season (January-May) and wet season (July-November) in low wet lands and the ground is kept fallow during the remainder of the year. Results showed that albedo varied from 0.09 to 0.24 and showed positive value from morning 6:00 h until evening 18:00 h. Mean soil temperature (T g) was highest in DF, while the skin temperature (T s) was highest in WS. Average Bowen ratio (B) ranged from 0.21 to 0.64 and large variation in B was observed during the fallow periods as compared to the cropping seasons. The magnitude of aerodynamic, canopy, and climatological resistances increased with the progress of cropping season and their magnitudes decreased during the end of both cropping seasons and found minimum during the fallow periods. At a constant vapor pressure deficit (VPD) at 0.16, 0.18, 0.15, and 0.43 kPa, latent heat flux (LE) initially increased, but later it tended to level off with an increase in VPD. The actual evapotranspiration (ETa) during both the cropping seasons was higher than the fallow period. This study can be used as a source of default values for many land surface energy fluxes which are required in various meteorological or air-quality models for rice paddies. A larger imbalance of energy was observed during the wet season as the energy is stored and perhaps advected in the fresh water.

Historical effects of CO2 and climate trends on global crop water demand

NASA Astrophysics Data System (ADS)

Urban, Daniel W.; Sheffield, Justin; Lobell, David B.

2017-12-01

A critical question for agricultural production and food security is how water demand for staple crops will respond to climate and carbon dioxide (CO2) changes1, especially in light of the expected increases in extreme heat exposure2. To quantify the trade-offs between the effects of climate and CO2 on water demand, we use a `sink-strength' model of demand3,4 which relies on the vapour-pressure deficit (VPD), incident radiation and the efficiencies of canopy-radiation use and canopy transpiration; the latter two are both dependent on CO2. This model is applied to a global data set of gridded monthly weather data over the cropping regions of maize, soybean, wheat and rice during the years 1948-2013. We find that this approach agrees well with Penman-Monteith potential evapotranspiration (PM) for the C3 crops of soybean, wheat and rice, where the competing CO2 effects largely cancel each other out, but that water demand in maize is significantly overstated by a demand measure that does not include CO2, such as the PM. We find the largest changes in wheat, for which water demand has increased since 1981 over 86% of the global cropping area and by 2.3-3.6 percentage points per decade in different regions.

Measles, rubella, and varicella among the crew of a cruise ship sailing from Florida, United States, 2006.

PubMed

Mitruka, Kiren; Felsen, Christina B; Tomianovic, Danitza; Inman, Barry; Street, Karen; Yambor, Phyllis; Reef, Susan E

2012-07-01

Cruise ship outbreaks of vaccine-preventable diseases (VPD) such as rubella and varicella have been previously associated with introduction and spread among susceptible crew members originating from countries with endemic transmission of these diseases. During February to April 2006, we investigated a cluster of rash illnesses due to measles, rubella, or varicella on a cruise ship sailing from Florida to the Caribbean. Case-finding measures included review of medical logs, active surveillance for rash illness among crew members, and passive surveillance for rash illness in the ship's infirmary lasting two incubation periods from the last case of measles. Passengers with potential exposure to these VPD were notified by letters. All susceptible crew members with potential exposure were administered the measles, mumps, and rubella vaccine after informed consent. A total of 16 cases were identified only among crew members: 1 rubella, 3 measles (two-generation spread), 11 varicella (three-generation spread), and 1 unknown diagnosis. Of 1,197 crew members evaluated, 4 had proof of immunity to measles and rubella. Based on passive surveillance, no cases were identified among passengers, the majority of whom resided in the United States. The international makeup of the population aboard cruise ships combined with their semi-enclosed environment has the potential to facilitate introduction and spread of VPD such as measles, rubella, and varicella onboard and into communities. Cruise lines should ensure crew members have evidence of immunity to these diseases. Passengers should be up to date with all vaccinations, including those that are travel-specific, prior to embarking on cruise travel. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

Interannual and seasonal variability of water use efficiency in a tropical rainforest: Results from a 9 year eddy flux time series

NASA Astrophysics Data System (ADS)

Tan, Zheng-Hong; Zhang, Yi-Ping; Deng, Xiao-Bao; Song, Qing-Hai; Liu, Wen-Jie; Deng, Yun; Tang, Jian-Wei; Liao, Zhi-Yong; Zhao, Jun-Fu; Song, Liang; Yang, Lian-Yan

2015-01-01

used a continuous 9 year (2003-2011) eddy flux time series with 30 min resolution to examine water use efficiency in a tropical rainforest and determine its environmental controls. The multiyear mean water use efficiency (Wue) of this rainforest was 3.16 ± 0.33 gC per kg H2O, which is close to that of boreal forests, but higher than subtropical forests, and lower than temperate forests. The water vapor deficit (VPD) had a strong impact on instantaneous Wue, in the manner predicted by stomatal optimization theory. At the seasonal scale, temperature was the dominant controller of Wue. The negative correlation between temperature and Wue was probably caused by high continuous photosynthesis during low-temperature periods. The VPD did not correlate with Wue at the interannual scale. No interannual trend was detected in Wue or inherent water use efficiency (Wei), either annually or seasonally. The fact that no increasing trend of Wei was found in the studied tropical rainforest, along with other evidence of CO2 stimulation in tropical rainforests, requires special attention and data validation. There was no significant difference between Wue during a drought and the 9 year mean values in the forest we studied, but we found that dry season transpiration (Tr) was consistently lower during the drought compared to the mean values. Finally, whether Wue increases or decreases during a drought is determined by the drought sensitivity of gross primary production (GPP).

Photodissociation Dynamics of Vinyl Cyanide Studied by Chirped-Pulse Millimeter-Wave Spectroscopy of HCN and HNC Products

NASA Astrophysics Data System (ADS)

Prozument, Kirill; Shaver, Rachel G.; Baraban, Joshua H.; Park, G. Barratt; Suits, Arthur G.; Muenter, John S.; Field, Robert W.

2013-06-01

Vinyl cyanide 193 nm photodissociation has been studied using Chirped-Pulse Millimeter-Wave (CPmmW) spectroscopy. J = 0 - 1 transitions of more than 30 vibrationally excited states of the HCN and HNC products have been recorded and assigned within the 7 GHz wide chirp range. Bending excitations of HCN up to v_2 = 14, leading toward the HCN leftrightarrow HNC isomerization transition state, are detected and interpreted in terms of their electric quadrupole, (eQq)_{N}, and rotational, B_v, constants. The photolysis reaction transition states were probed using both normal vinyl cyanide, CH_2=CHCN, and its singly-deuterated isotopologue, CH_2=CDCN. The observed difference in the vibrational population distribution (VPD) obtained from the integrated intensities of the HCN and DCN products from the CH_2=CHCN vs. CH_2=CDCN photolysis reactions, suggests the relative unimportance of the three-center elimination mechanism for HCN production. On the other hand, the similarity in the observed VPD and overall intensities of HCN from CH_2=CHCN and CH_2=CDCN photolysis suggests four-center elimination as the major mechanism leading to the HCN product. Additional J - (J + 1) transitions would be required to characterize both the vibrational and the rotational state distributions of the products, which would permit more complete characterization of the transition state(s). The authors thank the Department of Energy, and KP thanks the ACS Petroleum Research Fund for their support of this work.

Net Ecosystem Production (NEP) of the Great Plains, United States

USGS Publications Warehouse

Howard, Daniel; Gilmanov, Tagir; Gu, Yingxin; Wylie, Bruce; Zhang, Li

2012-01-01

Flux tower networks, such as AmeriFlux and FLUXNET, consist of a growing number of eddy covariance flux tower sites that provide a synoptic record of the exchange of carbon, water, and energy between the ecosystem and atmosphere at various temporal frequencies. These towers also detect and measure certain site characteristics, such as wind, temperature, precipitation, humidity, atmospheric pressure, soil features, and phenological progressions. Efforts are continuous to combine flux tower network data with remote sensing data to upscale the conditions observed at specific sites to a regional and, ultimately, worldwide scale. Data-driven regression tree models have the ability to incorporate flux tower records and remote sensing data to quantify exchanges of carbon with the atmosphere (Wylie and others, 2007; Xiao and others, 2010; Zhang and others, 2010; Zhang and others, 2011). Previous study results demonstrated the dramatic effect weather has on NEP and revealed specific ecoregions and times acting as carbon sinks or sources. As of 2012, more than 100 site-years of flux tower measurements, represented by more than 50 individual cropland or grassland sites throughout the Great Plains and surrounding area, have been acquired, quality controlled, and partitioned into gross photosynthesis (Pg) and ecosystem Re using detailed light-response, soil temperature, and vapor pressure deficit (VPD) based analysis.

Infectious Disease Risk and Vaccination in Northern Syria after 5 Years of Civil War: The MSF Experience.

PubMed

de Lima Pereira, Alan; Southgate, Rosamund; Ahmed, Hikmet; O'Connor, Penelope; Cramond, Vanessa; Lenglet, Annick

2018-02-02

In 2015, following an influx of population into Kobanê in northern Syria, Médecins Sans Frontières (MSF) in collaboration with the Kobanê Health Administration (KHA) initiated primary healthcare activities. A vaccination coverage survey and vaccine-preventable disease (VPD) risk analysis were undertaken to clarify the VPD risk and vaccination needs. This was followed by a measles Supplementary Immunization Activity (SIA). We describe the methods and results used for this prioritisation activity around vaccination in Kobanê in 2015. We implemented a pre-SIA survey in 135 randomly-selected households in Kobanê using a vaccination history questionnaire for all children <5 years. We conducted a VPD Risk Analysis using MSF 'Preventive Vaccination in Humanitarian Emergencies' guidance to prioritize antigens with the highest public health threat for mass vaccination activities. A Measles SIA was then implemented and followed by vaccine coverage survey in 282 randomly-selected households targeting children <5 years. The pre-SIA survey showed that 168/212 children (79.3%; 95%CI=72.7-84.6%) had received one vaccine or more in their lifetime. Forty-three children (20.3%; 95%CI: 15.1-26.6%) had received all vaccines due by their age; only one was <12 months old and this child had received all vaccinations outside of Syria. The VPD Risk Analysis prioritised measles, Haemophilus Influenza type B (Hib) and Pneumococcus vaccinations. In the measles SIA, 3410 children aged 6-59 months were vaccinated. The use of multiple small vaccination sites to reduce risks associated with crowds in this active conflict setting was noted as a lesson learnt. The post-SIA survey estimated 82% (95%CI: 76.9-85.9%; n=229/280) measles vaccination coverage in children 6-59 months. As a result of the conflict in Syria, the progressive collapse of the health care system in Kobanê has resulted in low vaccine coverage rates, particularly in younger age groups. The repeated displacements of the population, attacks on health institutions and exodus of healthcare workers, challenge the resumption of routine immunization in this conflict setting and limit the use of SIAs to ensure sustainable immunity to VPDs. We have shown that the risk for several VPDs in Kobanê remains high. We call on all health actors and the international community to work towards re-establishment of routine immunisation activities as a priority to ensure that children who have had no access to vaccination in the last five years are adequately protected for VPDs as soon as possible.

The enigma of effective pathlength for 18O enrichment in leaf water of conifers

NASA Astrophysics Data System (ADS)

Roden, J. S.; Kahmen, A.; Buchmann, N. C.; Siegwolf, R. T.

2013-12-01

The stable isotopes of oxygen (δ18O) in tree ring cellulose provide valuable proxy information about past environments and climate. Mechanistic models have been used to clarify the important drivers of isotope fractionation and help interpret δ18O variation in tree rings. A critical component to these models is an estimate of leaf water enrichment. However, standard models seldom accurately predict 18O enrichment in conifer needles and Péclet corrections often require effective pathlengths (L) that seem unreasonable from the perspective of needle morphology (>0.5 m). To analyze the potential role of path length on the Péclet effect in conifers we carried out experiments in controlled environment chambers. We exposed seedlings of six species of conifer (Abies alba, Larix decidua, Picea abies, Pinus cembra, P. sylvestris, Taxus bacata), that differ in needle morphology, to four different vapor pressure deficits (VPD), in order to modify transpiration rates (E) and leaf water 18O enrichment. Environmental and δ18O data (leaf, stem and chamber water vapor) were collected to parameterize leaf water models. Cross-sections of needles were sampled for an analysis of needle anatomy. Conifer needles have a single strand of vascular tissue making pathlength determinations through anatomical assessments possible. The six species differed in mesophyll distance (measured from endodermis to epidermis) and cell number, with Pinus and Picea species having the shortest distance and Abies and Taxus the longest (flat needle morphology). Other anatomical measures (transfusion distance, cell size etc.) did not differ significantly. A suberized strip was apparent in the endodermis of all species except Taxus and Abies. Conifer needles have a large proportion (from 0.2 to 0.4) of needle cross-sectional area in vascular tissues that may not be subject to evaporative enrichment. As expected, leaf water δ18O and E responded strongly to VPD and standard models (Craig-Gordon) overestimated leaf water δ18O. A single species-specific value for L could not be determined as the fractional difference between modeled and measured leaf water δ18O did not increase with E as theory predicts. Accounting for potentially unenriched water in vascular and transfusion tissues as well as a Péclet correction that allows the value for L to change with E (as in Song et al., 2013) produced accurate predictions of leaf water δ18O. Estimates of L (for a given E) were positively correlated with mean mesophyll thickness, which to our knowledge is the first time L has been related to a leaf anatomical measure. We repeated the experiment using young needles with much higher values for E, and found a continuing trend of reduced fractional difference with E, implying that Péclet corrections may need to be modified to predict conifer needle water over the range of needle phenology and physiology. Our study will help to better quantify effective pathlength and needle water δ18O in conifers, which are some of the most important organisms used for paleoclimate reconstruction.

Process and Outcome Study of Multidisciplinary Prosthetic Treatment for Velopharyngeal Dysfunction

ERIC Educational Resources Information Center

Sell, Debbie; Mars, Michael; Worrell, Emma

2006-01-01

Background: A prosthetic approach to velopharyngeal dysfunction (VPD) is not new. However, a collaborative interdisciplinary team approach by a speech-and-language therapist, dental specialist and maxillofacial technician, including accurate fitting using nasendoscopy, has provided an opportunity to define the clinical care pathway, and audit the…

Clinical and radiographic evaluation of Bio-Gen with biocollagen compared with Bio-Gen with connective tissue in the treatment of class II furcation defects: a randomized clinical trial

PubMed Central

JENABIAN, Niloofar; HAGHANIFAR, Sina; MABOUDI, Avideh; BIJANI, Ali

2013-01-01

Objective Treatment of furcation defects are thought to be challenging. The purpose of this study was to evaluate the clinical and radiographic parameters of Bio-Gen with Biocollagen compared with Bio-Gen with connective tissue in the treatment of Class II furcation defects. Material and Methods In this clinical trial, 24 patients with Class II furcation defect on a buccal or lingual mandibular molar were recruited. After oral hygiene instruction, scaling and root planing and achievement of acceptable plaque control, the patients were randomly chosen to receive either connective tissue and Bio-Gen (case group) or Biocollagen and Bio-Gen (control group). The following parameters were recorded before the first and re-entry surgery (six months later): vertical clinical attachment level (VCAL), gingival index (GI), plaque index (PI), horizontal probing depth (HPD), vertical probing depth (VPD), gingival recession (GR), furcation vertical component (FVC), furcation to alveolar crest (FAC), fornix to base of defect (FBD), and furcation horizontal component (FHC) were calculated at the time of first surgery and during re-entry. A digital periapical radiograph was taken in parallel before first surgery and re-entry. The radiographs were then analyzed by digital subtraction. The differences with p value <0.05 were considered significant. Results Only the mean changes of FAC, FHC, mean of FHC, FBD in re-entry revealed statistically significant differences between the two groups. HPD, VPD, FBD, FAC, and FHC showed statistically significant differences after 6 months in the case group. However, in the control group, statistically significant differences were found in GR and HPD. We did not observe any significant difference in radiographic changes among the two groups. Conclusion The results of this trial indicate that better clinical outcomes can be obtained with connective tissue grafts in combination with bone material compared with a resorbable barrier with bone material. The differences in radiographic changes between the two groups, however, were not statistically significant. PMID:24212988

Photosynthetic capacity and water use efficiency in Ricinus communis (L.) under drought stress in semi-humid and semi-arid areas.

PubMed

Santos, Claudiana M Dos; Endres, Laurício; Ferreira, Vilma M; Silva, José V; Rolim, Eduardo V; Wanderley, Humberto C L

2017-01-01

Castor bean is one of the crops with potential to provide raw material for production of oils for biodiesel. This species possess adaptive mechanisms for maintaining the water status when subjected to drought stress. A better understanding these mechanisms under field conditions can unravel the survival strategies used by this species. This study aimed to compare the physiological adaptations of Ricinus communis (L.) in two regions with different climates, the semi-arid and semi-humid subject to water stress. The plants showed greater vapor pressure deficit during the driest hours of the day, which contributed to higher values of the leaf temperature and leaf transpiration, however, the VPD(leaf-air) had the greatest effect on plants in the semi-arid region. In both regions, between 12:00 p.m. and 2:00 p.m., the plants presented reduction in the rates of photosynthesis and intracellular CO2 concentration in response to stomatal closure. During the dry season in the semi-arid region, photoinhibition occurred in the leaves of castor bean between 12:00 p.m. and 2:00 p.m. These results suggest that castor bean plants possess compensatory mechanisms for drought tolerance, such as: higher stomatal control and maintenance of photosynthetic capacity, allowing the plant to survive well in soil with low water availability.

WE-G-BRF-03: A Quasi-Cine CBCT Reconstruction Technique for Real-Time On- Board Target Tracking of Lung Cancer Treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Y; Yin, F; Ren, L

2014-06-15

Purpose: To develop a quasi-cine CBCT reconstruction technique that uses extremely-small angle (∼3°) projections to generate real-time high-quality lung CBCT images. Method: 4D-CBCT is obtained at the beginning and used as prior images. This study uses extremely-small angle (∼3°) on-board projections acquired at a single respiratory phase to reconstruct the CBCT image at this phase. An adaptive constrained free-form deformation (ACFD) method is developed to deform the prior 4D-CBCT volume at the same phase to reconstruct the new CBCT. Quasi-cine CBCT images are obtained by continuously reconstructing CBCT images at subsequent phases every 3° angle (∼0.5s). Note that the priormore » 4D-CBCT images are dynamically updated using the latest CBCT images. The 4D digital extended-cardiac-torso (XCAT) phantom was used to evaluate the efficacy of ACFD. A lung patient was simulated with a tumor baseline shift of 2mm along superior-inferior (SI) direction after every respiratory cycle for 5 cycles. Limited-angle projections were simulated for each cycle. The 4D-CBCT reconstructed by these projections were compared with the ground-truth generated in XCAT.Volume-percentage-difference (VPD) and center-of-mass-shift (COMS) were calculated between the reconstructed and the ground-truth tumors to evaluate their geometric differences.The ACFD was also compared to a principal-component-analysis based motion-modeling (MM) method. Results: Using orthogonal-view 3° projections, the VPD/COMS values for tumor baseline shifts of 2mm, 4mm, 6mm, 8mm, 10mm were 11.0%/0.3mm, 25.3%/2.7mm, 22.4%/2.9mm, 49.5%/5.4mm, 77.2%/8.1mm for the MM method, and 2.9%/0.7mm, 3.9%/0.8mm, 6.2%/1mm, 7.9%/1.2mm, 10.1%/1.1mm for the ACFD method. Using orthogonal-view 0° projections (1 projection only), the ACFD method yielded VPD/COMS results of 5.0%/0.9mm, 10.5%/1.2mm, 15.1%/1.4mm, 20.9%/1.6mm and 24.8%/1.6mm. Using single-view instead of orthogonal-view projections yielded less accurate results for ACFD. Conclusion: The ACFD method accurately reconstructs snapshot CBCT images using orthogonal-view 3° projections. It has a great potential to provide real-time quasi-cine CBCT images for verification in lung radiation therapy. The research is supported by grant from Varian Medical Systems.« less

Policing ‘Vancouver’s Mental Health Crisis’: A Critical Discourse Analysis

PubMed Central

Boyd, Jade; Kerr, Thomas

2016-01-01

In Canada and other western nations there has been an unprecedented expansion of criminal justice systems and a well documented increase of contact between people with mental illness and the police. Canadian police, especially in Vancouver, British Columbia, have been increasingly at the forefront of discourse and regulation specific to mental health. Drawing on critical discourse analysis, this paper explores this claim through a case study of four Vancouver Police Department (VPD) policy reports on “Vancouver’s mental health crisis” from 2008–2013, which include recommendations for action. Analyzed is the VPD’s role in framing issues of mental health in one urban space. This study is the first analysis to critically examine the VPD reports on mental health in Vancouver, B.C. The reports reproduce negative discourses about deinstitutionalization, mental illness and dangerousness that may contribute to further stigma and discrimination of persons with mental illness. Policing reports are widely drawn upon, thus critical analyses are particularly significant for policy makers and public health professionals in and outside of Canada. PMID:28496294

Adverse weather impacts on arable cropping systems

NASA Astrophysics Data System (ADS)

Gobin, Anne

2016-04-01

Damages due to extreme or adverse weather strongly depend on crop type, crop stage, soil conditions and management. The impact is largest during the sensitive periods of the farming calendar, and requires a modelling approach to capture the interactions between the crop, its environment and the occurrence of the meteorological event. The hypothesis is that extreme and adverse weather events can be quantified and subsequently incorporated in current crop models. Since crop development is driven by thermal time and photoperiod, a regional crop model was used to examine the likely frequency, magnitude and impacts of frost, drought, heat stress and waterlogging in relation to the cropping season and crop sensitive stages. Risk profiles and associated return levels were obtained by fitting generalized extreme value distributions to block maxima for air humidity, water balance and temperature variables. The risk profiles were subsequently confronted with yields and yield losses for the major arable crops in Belgium, notably winter wheat, winter barley, winter oilseed rape, sugar beet, potato and maize at the field (farm records) to regional scale (statistics). The average daily vapour pressure deficit (VPD) and reference evapotranspiration (ET0) during the growing season is significantly lower (p < 0.001) and has a higher variability before 1988 than after 1988. Distribution patterns of VPD and ET0 have relevant impacts on crop yields. The response to rising temperatures depends on the crop's capability to condition its microenvironment. Crops short of water close their stomata, lose their evaporative cooling potential and ultimately become susceptible to heat stress. Effects of heat stress therefore have to be combined with moisture availability such as the precipitation deficit or the soil water balance. Risks of combined heat and moisture deficit stress appear during the summer. These risks are subsequently related to crop damage. The methodology of defining meteorological risks and subsequently relating the risk to the cropping calendar will be demonstrated for major arable crops in Belgium. Physically based crop models assist in understanding the links between adverse weather events, sensitive crop stages and crop damage. Financial support was obtained from Belspo under research contract SD/RI/03A.

Analysing surface energy balance closure and partitioning over a semi-arid savanna FLUXNET site in Skukuza, Kruger National Park, South Africa

NASA Astrophysics Data System (ADS)

Majozi, Nobuhle P.; Mannaerts, Chris M.; Ramoelo, Abel; Mathieu, Renaud; Nickless, Alecia; Verhoef, Wouter

2017-07-01

Flux towers provide essential terrestrial climate, water, and radiation budget information needed for environmental monitoring and evaluation of climate change impacts on ecosystems and society in general. They are also intended for calibration and validation of satellite-based Earth observation and monitoring efforts, such as assessment of evapotranspiration from land and vegetation surfaces using surface energy balance approaches. In this paper, 15 years of Skukuza eddy covariance data, i.e. from 2000 to 2014, were analysed for surface energy balance closure (EBC) and partitioning. The surface energy balance closure was evaluated using the ordinary least squares regression (OLS) of turbulent energy fluxes (sensible (H) and latent heat (LE)) against available energy (net radiation (Rn) less soil heat (G)), and the energy balance ratio (EBR). Partitioning of the surface energy during the wet and dry seasons was also investigated, as well as how it is affected by atmospheric vapour pressure deficit (VPD), and net radiation. After filtering years with low-quality data (2004-2008), our results show an overall mean EBR of 0.93. Seasonal variations of EBR also showed the wet season with 1.17 and spring (1.02) being closest to unity, with the dry season (0.70) having the highest imbalance. Nocturnal surface energy closure was very low at 0.26, and this was linked to low friction velocity during night-time, with results showing an increase in closure with increase in friction velocity. The energy partition analysis showed that sensible heat flux is the dominant portion of net radiation, especially between March and October, followed by latent heat flux, and lastly the soil heat flux, and during the wet season where latent heat flux dominated sensible heat flux. An increase in net radiation was characterized by an increase in both LE and H, with LE showing a higher rate of increase than H in the wet season, and the reverse happening during the dry season. An increase in VPD is correlated with a decrease in LE and increase in H during the wet season, and an increase in both fluxes during the dry season.

Forecasting Brassica rapa: Merging climate models with genotype specific process models for evaluation whole species response to climate change.

NASA Astrophysics Data System (ADS)

Pleban, J. R.; Mackay, D. S.; Ewers, B. E.; Weinig, C.; Guadagno, C. L.

2016-12-01

Human society has modified agriculture management practices and utilized a variety of breeding approaches to adapt to changing environments. Presently a dual pronged challenge has emerged as environmental change is occurring more rapidly while the demand of population growth on food supply is rising. Knowledge of how current agricultural practices will respond to these challenges can be informed through crafted prognostic modeling approaches. Amongst the uncertainties associated with forecasting agricultural production in a changing environment is evaluation of the responses across the existing genotypic diversity of crop species. Mechanistic models of plant productivity provide a means of genotype level parameterization allowing for a prognostic evaluation of varietal performance under changing climate. Brassica rapa represents an excellent species for this type of investigation because of its wide cultivation as well as large morphological and physiological diversity. We incorporated genotypic parameterization of B. rapa genotypes based on unique CO2 assimilation strategies, vulnerabilities to cavitation, and root to leaf area relationships into the TREES model. Three climate drivers, following the "business-as-usual" greenhouse gas emissions scenario (RCP 8.5) from Coupled Model Intercomparison Project, Phase 5 (CMIP5) were considered: temperature (T) along with associated changes in vapor pressure deficit (VPD), increasing CO2, as well as alternatives in irrigation regime across a temporal scale of present day to 2100. Genotypic responses to these drivers were evaluated using net primary productivity (NPP) and percent loss hydraulic conductance (PLC) as a measure of tolerance for a particular watering regime. Genotypic responses to T were witnessed as water demand driven by increases in VPD at 2050 and 2100 drove some genotypes to greater PLC and in a subset of these saw periodic decreases in NPP during a growing season. Genotypes able to withstand the greater water demand showed lower NPP yields relative to hydraulically aggressive genotypes but saw limited PLC. Expansion of this analysis to large recombinant inbred populations may inform breeders in identification of trait combinations needed to meet the coupled challenge of rapid environmental change and increase food demand.

Estimating 4D CBCT from prior information and extremely limited angle projections using structural PCA and weighted free-form deformation for lung radiotherapy

PubMed Central

Harris, Wendy; Zhang, You; Yin, Fang-Fang; Ren, Lei

2017-01-01

Purpose To investigate the feasibility of using structural-based principal component analysis (PCA) motion-modeling and weighted free-form deformation to estimate on-board 4D-CBCT using prior information and extremely limited angle projections for potential 4D target verification of lung radiotherapy. Methods A technique for lung 4D-CBCT reconstruction has been previously developed using a deformation field map (DFM)-based strategy. In the previous method, each phase of the 4D-CBCT was generated by deforming a prior CT volume. The DFM was solved by a motion-model extracted by global PCA and free-form deformation (GMM-FD) technique, using a data fidelity constraint and deformation energy minimization. In this study, a new structural-PCA method was developed to build a structural motion-model (SMM) by accounting for potential relative motion pattern changes between different anatomical structures from simulation to treatment. The motion model extracted from planning 4DCT was divided into two structures: tumor and body excluding tumor, and the parameters of both structures were optimized together. Weighted free-form deformation (WFD) was employed afterwards to introduce flexibility in adjusting the weightings of different structures in the data fidelity constraint based on clinical interests. XCAT (computerized patient model) simulation with a 30 mm diameter lesion was simulated with various anatomical and respirational changes from planning 4D-CT to onboard volume to evaluate the method. The estimation accuracy was evaluated by the Volume-Percent-Difference (VPD)/Center-of-Mass-Shift (COMS) between lesions in the estimated and “ground-truth” on board 4D-CBCT. Different onboard projection acquisition scenarios and projection noise levels were simulated to investigate their effects on the estimation accuracy. The method was also evaluated against 3 lung patients. Results The SMM-WFD method achieved substantially better accuracy than the GMM-FD method for CBCT estimation using extremely small scan angles or projections. Using orthogonal 15° scanning angles, the VPD/COMS were 3.47±2.94% and 0.23±0.22mm for SMM-WFD and 25.23±19.01% and 2.58±2.54mm for GMM-FD among all 8 XCAT scenarios. Compared to GMM-FD, SMM-WFD was more robust against reduction of the scanning angles down to orthogonal 10° with VPD/COMS of 6.21±5.61% and 0.39±0.49mm, and more robust against reduction of projection numbers down to only 8 projections in total for both orthogonal-view 30° and orthogonal-view 15° scan angles. SMM-WFD method was also more robust than the GMM-FD method against increasing levels of noise in the projection images. Additionally, the SMM-WFD technique provided better tumor estimation for all three lung patients compared to the GMM-FD technique. Conclusion Compared to the GMM-FD technique, the SMM-WFD technique can substantially improve the 4D-CBCT estimation accuracy using extremely small scan angles and low number of projections to provide fast low dose 4D target verification. PMID:28079267

Dan Goldin Presentation: Pathway to the Future

NASA Technical Reports Server (NTRS)

1999-01-01

In the "Path to the Future" presentation held at NASA's Langley Center on March 31, 1999, NASA's Administrator Daniel S. Goldin outlined the future direction and strategies of NASA in relation to the general space exploration enterprise. NASA's Vision, Future System Characteristics, Evolutions of Engineering, and Revolutionary Changes are the four main topics of the presentation. In part one, the Administrator talks in detail about NASA's vision in relation to the NASA Strategic Activities that are Space Science, Earth Science, Human Exploration, and Aeronautics & Space Transportation. Topics discussed in this section include: space science for the 21st century, flying in mars atmosphere (mars plane), exploring new worlds, interplanetary internets, earth observation and measurements, distributed information-system-in-the-sky, science enabling understanding and application, space station, microgravity, science and exploration strategies, human mars mission, advance space transportation program, general aviation revitalization, and reusable launch vehicles. In part two, he briefly talks about the future system characteristics. He discusses major system characteristics like resiliencey, self-sufficiency, high distribution, ultra-efficiency, and autonomy and the necessity to overcome any distance, time, and extreme environment barriers. Part three of Mr. Goldin's talk deals with engineering evolution, mainly evolution in the Computer Aided Design (CAD)/Computer Aided Engineering (CAE) systems. These systems include computer aided drafting, computerized solid models, virtual product development (VPD) systems, networked VPD systems, and knowledge enriched networked VPD systems. In part four, the last part, the Administrator talks about the need for revolutionary changes in communication and networking areas of a system. According to the administrator, the four major areas that need cultural changes in the creativity process are human-centered computing, an infrastructure for distributed collaboration, rapid synthesis and simulation tools, and life-cycle integration and validation. Mr. Goldin concludes his presentation with the following maxim "Collaborate, Integrate, Innovate or Stagnate and Evaporate." He also answers some questions after the presentation.

Immunity against measles, mumps, rubella, varicella, diphtheria, tetanus, polio, hepatitis A and hepatitis B among adult asylum seekers in the Netherlands, 2016.

PubMed

Freidl, Gudrun S; Tostmann, Alma; Curvers, Moud; Ruijs, Wilhelmina L M; Smits, Gaby; Schepp, Rutger; Duizer, Erwin; Boland, Greet; de Melker, Hester; van der Klis, Fiona R M; Hautvast, Jeannine L A; Veldhuijzen, Irene K

2018-03-14

Asylum seekers are a vulnerable population for contracting infectious diseases. Outbreaks occur among children and adults. In the Netherlands, asylum seeker children are offered vaccination according to the National Immunization Program. Little is known about protection against vaccine-preventable diseases (VPD) in adult asylum seekers. In this 2016 study, we assessed the immunity of adult asylum seekers against nine VPD to identify groups that might benefit from additional vaccinations. We invited asylum seekers from Syria, Iran, Iraq, Afghanistan, Eritrea and Ethiopia to participate in a serosurvey. Participants provided informed consent and a blood sample, and completed a questionnaire. We measured prevalence of protective antibodies to measles, mumps, rubella, varicella, diphtheria, tetanus, polio type 1-3 and hepatitis A and B, stratified them by country of origin and age groups. The median age of the 622 participants was 28 years (interquartile range: 23-35), 81% were male and 48% originated from Syria. Overall, seroprotection was 88% for measles (range between countries: 83-93%), 91% for mumps (81-95%), 94% for rubella (84-98%), 96% for varicella (92-98%), 82% for diphtheria (65-88%), 98% for tetanus (86-100%), 91% (88-94%) for polio type 1, 95% (90-98%) for polio type 2, 82% (76-86%) for polio type 3, 84% (54-100%) for hepatitis A and 27% for hepatitis B (anti-HBs; 8-42%). Our results indicate insufficient protection against certain VPD in some subgroups. For all countries except Eritrea, measles seroprotection was below the 95% threshold required for elimination. Measles seroprevalence was lowest among adults younger than 25 years. In comparison, seroprevalence in the Dutch general population was 96% in 2006/07. The results of this study can help prioritizing vaccination of susceptible subgroups of adult asylum seekers, in general and in outbreak situations. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Characterizing uncertainties in recent trends of global terrestrial net primary production through ensemble modeling

NASA Astrophysics Data System (ADS)

Wang, W.; Hashimoto, H.; Ganguly, S.; Votava, P.; Nemani, R. R.; Myneni, R. B.

2010-12-01

Large uncertainties exist in our understanding of the trends and variability in global net primary production (NPP) and its controls. This study attempts to address this question through a multi-model ensemble experiment. In particular, we drive ecosystem models including CASA, LPJ, Biome-BGC, TOPS-BGC, and BEAMS with a long-term climate dataset (i.e., CRU-NCEP) to estimate global NPP from 1901 to 2009 at a spatial resolution of 0.5 x 0.5 degree. We calculate the trends of simulated NPP during different time periods and test their sensitivities to climate variables of solar radiation, air temperature, precipitation, vapor pressure deficit (VPD), and atmospheric CO2 levels. The results indicate a large diversity among the simulated NPP trends over the past 50 years, ranging from nearly no trend to an increasing trend of ~0.1 PgC/yr. Spatial patterns of the NPP generally show positive trends in boreal forests, induced mainly by increasing temperatures in these regions; they also show negative trends in the tropics, although the spatial patterns are more diverse. These diverse trends result from different climatic sensitivities of NPP among the tested models. Depending the ecological processes (e.g., photosynthesis or respiration) a model emphasizes, it can be more or less responsive to changes in solar radiation, temperatures, water, or atmospheric CO2 levels. Overall, these results highlight the limit of current ecosystem models in simulating NPP, which cannot be easily observed. They suggest that the traditional single-model approach is not ideal for characterizing trends and variability in global carbon cycling.

Infectious Disease Risk and Vaccination in Northern Syria after 5 Years of Civil War: The MSF Experience

PubMed Central

de Lima Pereira, Alan; Southgate, Rosamund; Ahmed, Hikmet; O’Connor, Penelope; Cramond, Vanessa; Lenglet, Annick

2018-01-01

Introduction: In 2015, following an influx of population into Kobanê in northern Syria, Médecins Sans Frontières (MSF) in collaboration with the Kobanê Health Administration (KHA) initiated primary healthcare activities. A vaccination coverage survey and vaccine-preventable disease (VPD) risk analysis were undertaken to clarify the VPD risk and vaccination needs. This was followed by a measles Supplementary Immunization Activity (SIA). We describe the methods and results used for this prioritisation activity around vaccination in Kobanê in 2015. Methods: We implemented a pre-SIA survey in 135 randomly-selected households in Kobanê using a vaccination history questionnaire for all children <5 years. We conducted a VPD Risk Analysis using MSF ‘Preventive Vaccination in Humanitarian Emergencies’ guidance to prioritize antigens with the highest public health threat for mass vaccination activities. A Measles SIA was then implemented and followed by vaccine coverage survey in 282 randomly-selected households targeting children <5 years. Results: The pre-SIA survey showed that 168/212 children (79.3%; 95%CI=72.7-84.6%) had received one vaccine or more in their lifetime. Forty-three children (20.3%; 95%CI: 15.1-26.6%) had received all vaccines due by their age; only one was <12 months old and this child had received all vaccinations outside of Syria. The VPD Risk Analysis prioritised measles, Haemophilus Influenza type B (Hib) and Pneumococcus vaccinations. In the measles SIA, 3410 children aged 6-59 months were vaccinated. The use of multiple small vaccination sites to reduce risks associated with crowds in this active conflict setting was noted as a lesson learnt. The post-SIA survey estimated 82% (95%CI: 76.9-85.9%; n=229/280) measles vaccination coverage in children 6-59 months. Discussion: As a result of the conflict in Syria, the progressive collapse of the health care system in Kobanê has resulted in low vaccine coverage rates, particularly in younger age groups. The repeated displacements of the population, attacks on health institutions and exodus of healthcare workers, challenge the resumption of routine immunization in this conflict setting and limit the use of SIAs to ensure sustainable immunity to VPDs. We have shown that the risk for several VPDs in Kobanê remains high. Conclusion: We call on all health actors and the international community to work towards re-establishment of routine immunisation activities as a priority to ensure that children who have had no access to vaccination in the last five years are adequately protected for VPDs as soon as possible. PMID:29511602

Fast Uncooled Low Density FPA of VPD PbSe for Applications in Hyperspectral Imagery

DTIC Science & Technology

2009-10-01

Marañosa (ITM-CIDA). Area de Optronica y Acustica Unidad de Sensores y Micro-Nano Tecnologia Arturo Soria, 289 E-28033 Madrid, Spain ABSTRACT...ADDRESS(ES) Instituto Tecnologico de la Marañosa (ITM-CIDA). Area de Optronica y Acustica Unidad de Sensores y Micro-Nano Tecnologia Arturo Soria, 289

Recovery of Physiological Traits in Saplings of Invasive Bischofia Tree Compared with Three Species Native to the Bonin Islands under Successive Drought and Irrigation Cycles

PubMed Central

Yazaki, Kenichi; Kuroda, Katsushi; Nakano, Takashi; Kitao, Mitsutoshi; Tobita, Hiroyuki; Ogasa, Mayumi Y.; Ishida, Atsushi

2015-01-01

Partial leaf shedding induced by hydraulic failure under prolonged drought can prevent excess water consumption, resulting in delayed recovery of carbon productivity following rainfall. To understand the manner of water use of invasive species in oceanic island forests under a fluctuating water regime, leaf shedding, multiple physiological traits, and the progress of embolism in the stem xylem under repeated drought-irrigation cycles were examined in the potted saplings of an invasive species, Bischofia javanica Blume, and three endemic native species, Schima mertensiana (Sieb. Et Zucc,) Koitz., Hibiscus glaber Matsum, and Distylium lepidotum Nakai, from the Bonin Islands, Japan. The progress of xylem embolism was observed by cryo-scanning electron microscopy. The samples exhibited different processes of water saving and drought tolerance based on the different combinations of partial leaf shedding involved in embolized conduits following repeated de-rehydration. Predawn leaf water potential largely decreased with each successive drought-irrigation cycle for all tree species, except for B. javanica. B. javanica shed leaves conspicuously under drought and showed responsive stomatal conductance to VPD, which contributed to recover leaf gas exchange in the remaining leaves, following a restored water supply. In contrast, native tree species did not completely recover photosynthetic rates during the repeated drought-irrigation cycles. H. glaber and D. lepidotum preserved water in vessels and adjusted leaf osmotic rates but did not actively shed leaves. S. mertensiana exhibited partial leaf shedding during the first cycle with an osmotic adjustment, but they showed less responsive stomatal conductance to VPD. Our data indicate that invasive B. javanica saplings can effectively use water supplied suddenly under drought conditions. We predict that fluctuating precipitation in the future may change tree distributions even in mesic or moist sites in the Bonin Islands. PMID:26291326

Recovery of Physiological Traits in Saplings of Invasive Bischofia Tree Compared with Three Species Native to the Bonin Islands under Successive Drought and Irrigation Cycles.

PubMed

Yazaki, Kenichi; Kuroda, Katsushi; Nakano, Takashi; Kitao, Mitsutoshi; Tobita, Hiroyuki; Ogasa, Mayumi Y; Ishida, Atsushi

2015-01-01

Partial leaf shedding induced by hydraulic failure under prolonged drought can prevent excess water consumption, resulting in delayed recovery of carbon productivity following rainfall. To understand the manner of water use of invasive species in oceanic island forests under a fluctuating water regime, leaf shedding, multiple physiological traits, and the progress of embolism in the stem xylem under repeated drought-irrigation cycles were examined in the potted saplings of an invasive species, Bischofia javanica Blume, and three endemic native species, Schima mertensiana (Sieb. Et Zucc,) Koitz., Hibiscus glaber Matsum, and Distylium lepidotum Nakai, from the Bonin Islands, Japan. The progress of xylem embolism was observed by cryo-scanning electron microscopy. The samples exhibited different processes of water saving and drought tolerance based on the different combinations of partial leaf shedding involved in embolized conduits following repeated de-rehydration. Predawn leaf water potential largely decreased with each successive drought-irrigation cycle for all tree species, except for B. javanica. B. javanica shed leaves conspicuously under drought and showed responsive stomatal conductance to VPD, which contributed to recover leaf gas exchange in the remaining leaves, following a restored water supply. In contrast, native tree species did not completely recover photosynthetic rates during the repeated drought-irrigation cycles. H. glaber and D. lepidotum preserved water in vessels and adjusted leaf osmotic rates but did not actively shed leaves. S. mertensiana exhibited partial leaf shedding during the first cycle with an osmotic adjustment, but they showed less responsive stomatal conductance to VPD. Our data indicate that invasive B. javanica saplings can effectively use water supplied suddenly under drought conditions. We predict that fluctuating precipitation in the future may change tree distributions even in mesic or moist sites in the Bonin Islands.

Ecosystem-level water-use efficiency inferred from eddy covariance data: definitions, patterns and spatial up-scaling

NASA Astrophysics Data System (ADS)

Reichstein, M.; Beer, C.; Kuglitsch, F.; Papale, D.; Soussana, J. A.; Janssens, I.; Ciais, P.; Baldocchi, D.; Buchmann, N.; Verbeeck, H.; Ceulemans, R.; Moors, E.; Köstner, B.; Schulze, D.; Knohl, A.; Law, B. E.

2007-12-01

In this presentation we discuss ways to infer and to interpret water-use efficiency at ecosystem level (WUEe) from eddy covariance flux data and possibilities for scaling these patterns to regional and continental scale. In particular we convey the following: WUEe may be computed as a ratio of integrated fluxes or as the slope of carbon versus water fluxes offering different chances for interpretation. If computed from net ecosystem exchange and evapotranspiration on has to take of counfounding effects of respiration and soil evaporation. WUEe time-series at diurnal and seasonal scale is a valuable ecosystem physiological diagnostic for example about ecosystem-level responses to drought. Most often WUEe decreases during dry periods. The mean growing season ecosystem water-use efficiency of gross carbon uptake (WUEGPP) is highest in temperate broad-leaved deciduous forests, followed by temperate mixed forests, temperate evergreen conifers, Mediterranean broad-leaved deciduous forests, Mediterranean broad-leaved evergreen forests and Mediterranean evergreen conifers and boreal, grassland and tundra ecosystems. Water-use efficiency exhibits a temporally quite conservative relation with atmospheric water vapor pressure deficit (VPD) that is modified between sites by leaf area index (LAI) and soil quality, such that WUEe increases with LAI and soil water holding capacity which is related to texture. This property and tight coupling between carbon and water cycles is used to estimate catchment-scale water-use efficiency and primary productivity by integration of space-borne earth observation and river discharge data.

Differential responses of carbon and water vapor fluxes to climate among evergreen needleleaf forests in the USA

DOE PAGES

Wagle, Pradeep; Xiao, Xiangming; Kolb, Thomas E.; ...

2016-05-31

Here, understanding the differences in carbon and water vapor fluxes of spatially distributed evergreen needleleaf forests (ENFs) is crucial for accurately estimating regional or global carbon and water budgets and when predicting the responses of ENFs to current and future climate. We compared the fluxes of ten AmeriFlux ENF sites to investigate cross-site variability in net ecosystem exchange of carbon (NEE), gross primary production (GPP), and evapotranspiration (ET). We used wavelet cross-correlation analysis to examine responses of NEE and ET to common climatic drivers over multiple timescales and also determined optimum values of air temperature (T a) and vapor pressuremore » deficit (VPD) for NEE and ET.« less

Differential responses of carbon and water vapor fluxes to climate among evergreen needleleaf forests in the USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagle, Pradeep; Xiao, Xiangming; Kolb, Thomas E.

Here, understanding the differences in carbon and water vapor fluxes of spatially distributed evergreen needleleaf forests (ENFs) is crucial for accurately estimating regional or global carbon and water budgets and when predicting the responses of ENFs to current and future climate. We compared the fluxes of ten AmeriFlux ENF sites to investigate cross-site variability in net ecosystem exchange of carbon (NEE), gross primary production (GPP), and evapotranspiration (ET). We used wavelet cross-correlation analysis to examine responses of NEE and ET to common climatic drivers over multiple timescales and also determined optimum values of air temperature (T a) and vapor pressuremore » deficit (VPD) for NEE and ET.« less

Estimating 4D-CBCT from prior information and extremely limited angle projections using structural PCA and weighted free-form deformation for lung radiotherapy.

PubMed

Harris, Wendy; Zhang, You; Yin, Fang-Fang; Ren, Lei

2017-03-01

To investigate the feasibility of using structural-based principal component analysis (PCA) motion-modeling and weighted free-form deformation to estimate on-board 4D-CBCT using prior information and extremely limited angle projections for potential 4D target verification of lung radiotherapy. A technique for lung 4D-CBCT reconstruction has been previously developed using a deformation field map (DFM)-based strategy. In the previous method, each phase of the 4D-CBCT was generated by deforming a prior CT volume. The DFM was solved by a motion model extracted by a global PCA and free-form deformation (GMM-FD) technique, using a data fidelity constraint and deformation energy minimization. In this study, a new structural PCA method was developed to build a structural motion model (SMM) by accounting for potential relative motion pattern changes between different anatomical structures from simulation to treatment. The motion model extracted from planning 4DCT was divided into two structures: tumor and body excluding tumor, and the parameters of both structures were optimized together. Weighted free-form deformation (WFD) was employed afterwards to introduce flexibility in adjusting the weightings of different structures in the data fidelity constraint based on clinical interests. XCAT (computerized patient model) simulation with a 30 mm diameter lesion was simulated with various anatomical and respiratory changes from planning 4D-CT to on-board volume to evaluate the method. The estimation accuracy was evaluated by the volume percent difference (VPD)/center-of-mass-shift (COMS) between lesions in the estimated and "ground-truth" on-board 4D-CBCT. Different on-board projection acquisition scenarios and projection noise levels were simulated to investigate their effects on the estimation accuracy. The method was also evaluated against three lung patients. The SMM-WFD method achieved substantially better accuracy than the GMM-FD method for CBCT estimation using extremely small scan angles or projections. Using orthogonal 15° scanning angles, the VPD/COMS were 3.47 ± 2.94% and 0.23 ± 0.22 mm for SMM-WFD and 25.23 ± 19.01% and 2.58 ± 2.54 mm for GMM-FD among all eight XCAT scenarios. Compared to GMM-FD, SMM-WFD was more robust against reduction of the scanning angles down to orthogonal 10° with VPD/COMS of 6.21 ± 5.61% and 0.39 ± 0.49 mm, and more robust against reduction of projection numbers down to only 8 projections in total for both orthogonal-view 30° and orthogonal-view 15° scan angles. SMM-WFD method was also more robust than the GMM-FD method against increasing levels of noise in the projection images. Additionally, the SMM-WFD technique provided better tumor estimation for all three lung patients compared to the GMM-FD technique. Compared to the GMM-FD technique, the SMM-WFD technique can substantially improve the 4D-CBCT estimation accuracy using extremely small scan angles and low number of projections to provide fast low dose 4D target verification. © 2017 American Association of Physicists in Medicine.

Hydrodynamic Trait Coordination and Cost-Benefit Tradeoffs throughout the Isohydric-Anisohydric Continuum in Trees

NASA Astrophysics Data System (ADS)

Mirfenderesgi, G.; Matheny, A. M.; Bohrer, G.

2017-12-01

Whole-plant hydraulic performance depends on the integrated function of complexes of traits, such as embolism resistance and xylem anatomy, stomatal closure mechanisms, hydraulic architecture, and root properties. The diversity of such traits produces a wide range of response strategies to both short-term variation of soil moisture and VPD, and to long-term changes to climate and hydrological cycles which affect water availability. This study aims to assess the role of different hydraulic trait combinations in trees' vulnerability to limitations in soil water availability. We use a quantitative hydrodynamic modeling framework which allows studying the influence of each suits of plant hydraulic traits independently, and assess how the different trait groups interact with each other to form viable hydraulic strategies in response to reduced soil moisture availability. We utilize the advanced plant hydrodynamic model, FETCH2, which resolves plant functional hydrodynamics, using parameters that represent emergent physiological traits at the root, stem and leaf levels. FETCH2 simulates the integrated plant-level transpiration and water capacitance, provided hydraulic traits and environmental forcing. We define a multi-dimensional hydraulic "trait space" by considering a broad continuum of hydraulic traits at each of the leaf, stem, and root levels. We test the consequences of different strategies under a range of environmental conditions, representing typical wet, intermediate, and dry conditions, based on as observations in a research forest in Northern Michigan, USA. We evaluate the degree to which simulated trees suffer hydraulic failure due to cavitation, resulting in loss of xylem conductivity, or carbon starvation, through leaf water-potential-driven reduction of stomatal conductance. Our result demonstrated that risk-prone leaf strategy when combined with risk-adverse xylem traits may expose plant to the risk of hydraulic failure due to declining water potential during period of low soil moisture and high VPD. However, if this strategy is coupled with deep roots, the plant is less likely to experience water stress even during periods of low soil water availability and high evaporative demand.

Evaluating the Community Land Model (CLM4.5) at a coniferous forest site in northwestern United States using flux and carbon-isotope measurements

DOE PAGES

Duarte, Henrique F.; Raczka, Brett M.; Ricciuto, Daniel M.; ...

2017-09-28

Droughts in the western United States are expected to intensify with climate change. Thus, an adequate representation of ecosystem response to water stress in land models is critical for predicting carbon dynamics. The goal of this study was to evaluate the performance of the Community Land Model (CLM) version 4.5 against observations at an old-growth coniferous forest site in the Pacific Northwest region of the United States (Wind River AmeriFlux site), characterized by a Mediterranean climate that subjects trees to water stress each summer. CLM was driven by site-observed meteorology and calibrated primarily using parameter values observed at the site ormore » at similar stands in the region. Key model adjustments included parameters controlling specific leaf area and stomatal conductance. Default values of these parameters led to significant underestimation of gross primary production, overestimation of evapotranspiration, and consequently overestimation of photosynthetic 13C discrimination, reflected in reduced 13C: 12C ratios of carbon fluxes and pools. Adjustments in soil hydraulic parameters within CLM were also critical, preventing significant underestimation of soil water content and unrealistic soil moisture stress during summer. After calibration, CLM was able to simulate energy and carbon fluxes, leaf area index, biomass stocks, and carbon isotope ratios of carbon fluxes and pools in reasonable agreement with site observations. Overall, the calibrated CLM was able to simulate the observed response of canopy conductance to atmospheric vapor pressure deficit (VPD) and soil water content, reasonably capturing the impact of water stress on ecosystem functioning. Both simulations and observations indicate that stomatal response from water stress at Wind River was primarily driven by VPD and not soil moisture. The calibration of the Ball–Berry stomatal conductance slope ( m bb) at Wind River aligned with findings from recent CLM experiments at sites characterized by the same plant functional type (needleleaf evergreen temperate forest), despite significant differences in stand composition and age and climatology, suggesting that CLM could benefit from a revised m bb value of 6, rather than the default value of 9, for this plant functional type. Conversely, Wind River required a unique calibration of the hydrology submodel to simulate soil moisture, suggesting that the default hydrology has a more limited applicability. Here, this study demonstrates that carbon isotope data can be used to constrain stomatal conductance and intrinsic water use efficiency in CLM, as an alternative to eddy covariance flux measurements. It also demonstrates that carbon isotopes can expose structural weaknesses in the model and provide a key constraint that may guide future model development.« less

Evaluating the Community Land Model (CLM4.5) at a coniferous forest site in northwestern United States using flux and carbon-isotope measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duarte, Henrique F.; Raczka, Brett M.; Ricciuto, Daniel M.

Droughts in the western United States are expected to intensify with climate change. Thus, an adequate representation of ecosystem response to water stress in land models is critical for predicting carbon dynamics. The goal of this study was to evaluate the performance of the Community Land Model (CLM) version 4.5 against observations at an old-growth coniferous forest site in the Pacific Northwest region of the United States (Wind River AmeriFlux site), characterized by a Mediterranean climate that subjects trees to water stress each summer. CLM was driven by site-observed meteorology and calibrated primarily using parameter values observed at the site ormore » at similar stands in the region. Key model adjustments included parameters controlling specific leaf area and stomatal conductance. Default values of these parameters led to significant underestimation of gross primary production, overestimation of evapotranspiration, and consequently overestimation of photosynthetic 13C discrimination, reflected in reduced 13C: 12C ratios of carbon fluxes and pools. Adjustments in soil hydraulic parameters within CLM were also critical, preventing significant underestimation of soil water content and unrealistic soil moisture stress during summer. After calibration, CLM was able to simulate energy and carbon fluxes, leaf area index, biomass stocks, and carbon isotope ratios of carbon fluxes and pools in reasonable agreement with site observations. Overall, the calibrated CLM was able to simulate the observed response of canopy conductance to atmospheric vapor pressure deficit (VPD) and soil water content, reasonably capturing the impact of water stress on ecosystem functioning. Both simulations and observations indicate that stomatal response from water stress at Wind River was primarily driven by VPD and not soil moisture. The calibration of the Ball–Berry stomatal conductance slope ( m bb) at Wind River aligned with findings from recent CLM experiments at sites characterized by the same plant functional type (needleleaf evergreen temperate forest), despite significant differences in stand composition and age and climatology, suggesting that CLM could benefit from a revised m bb value of 6, rather than the default value of 9, for this plant functional type. Conversely, Wind River required a unique calibration of the hydrology submodel to simulate soil moisture, suggesting that the default hydrology has a more limited applicability. Here, this study demonstrates that carbon isotope data can be used to constrain stomatal conductance and intrinsic water use efficiency in CLM, as an alternative to eddy covariance flux measurements. It also demonstrates that carbon isotopes can expose structural weaknesses in the model and provide a key constraint that may guide future model development.« less

Improvement of satellite-based gross primary production through incorporation of high resolution input data over east asia

NASA Astrophysics Data System (ADS)

Park, Haemi; Im, Jungho; Kim, Miae

2016-04-01

Photosynthesis of plants is the main mechanism of carbon absorption from the atmosphere into the terrestrial ecosystem and it contributes to remove greenhouse gases such as carbon dioxide. Annually, 120 Gt of C is supposed to be assimilated through photosynthetic activity of plants as the gross primary production (GPP) over global land area. In terms of climate change, GPP modelling is essential to understand carbon cycle and the balance of carbon budget over various ecosystems. One of the GPP modelling approaches uses light use efficiency that each vegetation type has a specific efficiency for consuming solar radiation related with temperature and humidity. Satellite data can be used to measure various meteorological and biophysical factors over vast areas, which can be used to quantify GPP. NASA Earth Observing System (EOS) program provides Moderate Resolution Imaging Spectroradiometer (MODIS)-derived global GPP product, namely MOD17A2H, on a daily basis. However, significant underestimation of MOD17A2H has been reported in Eastern Asia due to its dense forest distribution and humid condition during monsoon rainy season in summer. The objective of this study was to improve underestimation of MODIS GPP (MOD17A2H) by incorporating meteorological data-temperature, relative humidity, and solar radiation-of higher spatial resolution than data used in MOD17A2H. Landsat-based land cover maps of finer resolution observation and monitoring - global land cover (FROM-GLC) at 30m resolution were used for selection of light use efficiency (LUE). GPP (eq1. GPP = APAR×LUE) is computed by multiplication of APAR (IPAR×fPAR) and LUE (ɛ= ɛmax×T(°C)scalar×VPD(Pa)scalar, where, T is temperature, VPD is vapour pressure deficit) in this study. Meteorological data of Japanese 55-year Reanalysis (JRA-55, 0.56° grid, 3hr) were used for calculation of GPP in East Asia, including Eastern part of China, Korean peninsula, and Japan. Results were validated using flux tower-observed GPP data of AsiaFlux. Results showed that about 40% of underestimation of monthly average of MOD17A2H is confirmed and underestimation of MOD17A2 was improved from 42.3% and 60.4% to 8.3% and -26.2% for two flux tower sites (API site in Japan and GCK site in Korea), respectively. These improvements suggest that correction of LUE by finer land cover classification and/or better frequency of solar radiation data is effective where MOD17A2H does not work well. Further research will include evaluation of the proposed approach over areas in different climate conditions and environments.

Evaluating the Community Land Model (CLM4.5) at a coniferous forest site in northwestern United States using flux and carbon-isotope measurements

NASA Astrophysics Data System (ADS)

Duarte, Henrique F.; Raczka, Brett M.; Ricciuto, Daniel M.; Lin, John C.; Koven, Charles D.; Thornton, Peter E.; Bowling, David R.; Lai, Chun-Ta; Bible, Kenneth J.; Ehleringer, James R.

2017-09-01

Droughts in the western United States are expected to intensify with climate change. Thus, an adequate representation of ecosystem response to water stress in land models is critical for predicting carbon dynamics. The goal of this study was to evaluate the performance of the Community Land Model (CLM) version 4.5 against observations at an old-growth coniferous forest site in the Pacific Northwest region of the United States (Wind River AmeriFlux site), characterized by a Mediterranean climate that subjects trees to water stress each summer. CLM was driven by site-observed meteorology and calibrated primarily using parameter values observed at the site or at similar stands in the region. Key model adjustments included parameters controlling specific leaf area and stomatal conductance. Default values of these parameters led to significant underestimation of gross primary production, overestimation of evapotranspiration, and consequently overestimation of photosynthetic 13C discrimination, reflected in reduced 13C : 12C ratios of carbon fluxes and pools. Adjustments in soil hydraulic parameters within CLM were also critical, preventing significant underestimation of soil water content and unrealistic soil moisture stress during summer. After calibration, CLM was able to simulate energy and carbon fluxes, leaf area index, biomass stocks, and carbon isotope ratios of carbon fluxes and pools in reasonable agreement with site observations. Overall, the calibrated CLM was able to simulate the observed response of canopy conductance to atmospheric vapor pressure deficit (VPD) and soil water content, reasonably capturing the impact of water stress on ecosystem functioning. Both simulations and observations indicate that stomatal response from water stress at Wind River was primarily driven by VPD and not soil moisture. The calibration of the Ball-Berry stomatal conductance slope (mbb) at Wind River aligned with findings from recent CLM experiments at sites characterized by the same plant functional type (needleleaf evergreen temperate forest), despite significant differences in stand composition and age and climatology, suggesting that CLM could benefit from a revised mbb value of 6, rather than the default value of 9, for this plant functional type. Conversely, Wind River required a unique calibration of the hydrology submodel to simulate soil moisture, suggesting that the default hydrology has a more limited applicability. This study demonstrates that carbon isotope data can be used to constrain stomatal conductance and intrinsic water use efficiency in CLM, as an alternative to eddy covariance flux measurements. It also demonstrates that carbon isotopes can expose structural weaknesses in the model and provide a key constraint that may guide future model development.

Modeling soybean canopy resistance from micrometeorological and plant variables for estimating evapotranspiration using one-step Penman-Monteith approach

NASA Astrophysics Data System (ADS)

Irmak, Suat; Mutiibwa, Denis; Payero, Jose; Marek, Thomas; Porter, Dana

2013-12-01

Canopy resistance (rc) is one of the most important variables in evapotranspiration, agronomy, hydrology and climate change studies that link vegetation response to changing environmental and climatic variables. This study investigates the concept of generalized nonlinear/linear modeling approach of rc from micrometeorological and plant variables for soybean [Glycine max (L.) Merr.] canopy at different climatic zones in Nebraska, USA (Clay Center, Geneva, Holdrege and North Platte). Eight models estimating rc as a function of different combination of micrometeorological and plant variables are presented. The models integrated the linear and non-linear effects of regulating variables (net radiation, Rn; relative humidity, RH; wind speed, U3; air temperature, Ta; vapor pressure deficit, VPD; leaf area index, LAI; aerodynamic resistance, ra; and solar zenith angle, Za) to predict hourly rc. The most complex rc model has all regulating variables and the simplest model has only Rn, Ta and RH. The rc models were developed at Clay Center in the growing season of 2007 and applied to other independent sites and years. The predicted rc for the growing seasons at four locations were then used to estimate actual crop evapotranspiration (ETc) as a one-step process using the Penman-Monteith model and compared to the measured data at all locations. The models were able to account for 66-93% of the variability in measured hourly ETc across locations. Models without LAI generally underperformed and underestimated due to overestimation of rc, especially during full canopy cover stage. Using vapor pressure deficit or relative humidity in the models had similar effect on estimating rc. The root squared error (RSE) between measured and estimated ETc was about 0.07 mm h-1 for most of the models at Clay Center, Geneva and Holdrege. At North Platte, RSE was above 0.10 mm h-1. The results at different sites and different growing seasons demonstrate the robustness and consistency of the models in estimating soybean rc, which is encouraging towards the general application of one-step estimation of soybean canopy ETc in practice using the Penman-Monteith model and could aid in enhancing the utilization of the approach by irrigation and water management community.

Biophysical control of whole tree transpiration under an urban environment in Northern China

NASA Astrophysics Data System (ADS)

Chen, Lixin; Zhang, Zhiqiang; Li, Zhandong; Tang, Jianwu; Caldwell, Peter; Zhang, Wenjuan

2011-05-01

SummaryUrban reforestation in China has led to increasing debate about the impact of urban trees and forests on water resources. Although transpiration is the largest water flux leaving terrestrial ecosystems, little is known regarding whole tree transpiration in urban environments. In this study, we quantified urban tree transpiration at various temporal scales and examined the biophysical control of the transpiration pattern under different water conditions to understand how trees survive in an urban environment. Concurrent with microclimate and soil moisture measurements, transpiration from C edrus deodara(Roxb)Loud ., Zelkova schneideriana Hend.-Mazz., Euonymus bungeanus Maxim., and Metasequoia glyptostroboides Hu et cheng was measured over a 2-year period using thermal dissipation probe (TDP) techniques. The average monthly transpiration rates reached 12.78 ± 0.73 (S.E.) mm, 1.79 ± 0.16 mm, 10.18 ± 0.55 mm and 19.28 ± 2.24 mm for C. deodara, Z.schneideriana, E. bungeanus and M. glyptostroboides, respectively. Transpiration rates from M. glyptostroboides reported here may need further study as this species showed much higher sap flows and greater transpiration fluctuation under different environmental conditions than other species. Because of deep soil moisture supply, summer dry spells did not reduce transpiration rates even when tree transpiration exceeded rainfall. While vapor pressure deficit ( VPD) was the dominant environmental factor on transpiration, trees controlled canopy conductance effectively to limit transpiration in times of water stress. Our results provide evidence that urban trees could adopt strong physiological control over transpiration under high evaporative demands to avoid dehydration and can make use of water in deeper soil layers to survive summer dry spells. Moreover, urban trees have the ability to make the best use of precipitation when it is limited, and are sensitive to soil and air dryness.

Virtually There--Transforming Gifted Education through New Technologies, Trends and Practices in Learning, International Communication and Global Education

ERIC Educational Resources Information Center

Eriksson, Gillian

2012-01-01

"It is the year 2025 and I am compiling this article for an instant VPD (videopod) that is streamed over the world. An EESR (Educational Expert Service Request) came from an empathetic computer HIAS (Hi, I am Sam) that matched my qualifications with a quest by online activists SFT (Searching for Truth) to examine global interactions in…

Influence of Gap-Filling to Generate Continuous Datasets on Process Network Analysis

NASA Astrophysics Data System (ADS)

Yun, J.; Kim, J.; Kim, S.; Chun, J.

2013-12-01

The interplay of environmental conditions, energy, matter, and information defines the context and constraints for the set of processes and structures that may emerge during self-organization in complex ecosystems. Following Ruddell and Kumar (2009), we have evaluated statistical measures of characterizing the organization of the information flow in ecohydrological process networks in a deciduous forest ecosystem. We used the time series data obtained in 2008 (normal year) from the KoFlux forest tower site in central Korea. The 30-minute averages of eddy fluxes of energy, water and CO2 were measured at 40m above an oak-dominated old deciduous forest along with other micrometeorological variables. In this analysis, we selected 13 variables: atmospheric pressure (Pa), net ecosystem CO2 exchange (NEE), gross primary productivity (GPP), ecosystem respiration (RE), latent heat flux (LE), precipitation (Precip), solar radiation (Rg), air temperature (T), vapor pressure deficit (VPD), sensible heat flux (H), canopy temperature (Tc), wind direction (WD), and wind speed (WS). Our results support that a process network approach can be used to formally resolve feedback, time scales, and subsystems that define the complex ecosystem's organization by considering mutual information and transfer entropy simultaneously. We also observed that the turbulent and atmospheric boundary layer subsystems are coupled through feedback loops, and form a regional self-organizing subsystem in August when the forest is in healthy environment. In particular, we noted that the observed feedback loops in the process network disappeared when the time series data were artificially gap-filled for missing data, which is a common practice in post-data processing. In this presentation, we report the influence of gap-filling on the process network analysis by artificially assigning different sizes and periods of missing data and discuss the implication of our results on validation and calibration of ecosystem models. Acknowledgment. This research was supported by the Korea Meteorological Administration Research and Development Program under Grant CATER 2013-3030.

Virtual Sensors for Designing Irrigation Controllers in Greenhouses

PubMed Central

Sánchez, Jorge Antonio; Rodríguez, Francisco; Guzmán, José Luis; Arahal, Manuel R

2012-01-01

Monitoring the greenhouse transpiration for control purposes is currently a difficult task. The absence of affordable sensors that provide continuous transpiration measurements motivates the use of estimators. In the case of tomato crops, the availability of estimators allows the design of automatic fertirrigation (irrigation + fertilization) schemes in greenhouses, minimizing the dispensed water while fulfilling crop needs. This paper shows how system identification techniques can be applied to obtain nonlinear virtual sensors for estimating transpiration. The greenhouse used for this study is equipped with a microlysimeter, which allows one to continuously sample the transpiration values. While the microlysimeter is an advantageous piece of equipment for research, it is also expensive and requires maintenance. This paper presents the design and development of a virtual sensor to model the crop transpiration, hence avoiding the use of this kind of expensive sensor. The resulting virtual sensor is obtained by dynamical system identification techniques based on regressors taken from variables typically found in a greenhouse, such as global radiation and vapor pressure deficit. The virtual sensor is thus based on empirical data. In this paper, some effort has been made to eliminate some problems associated with grey-box models: advance phenomenon and overestimation. The results are tested with real data and compared with other approaches. Better results are obtained with the use of nonlinear Black-box virtual sensors. This sensor is based on global radiation and vapor pressure deficit (VPD) measurements. Predictive results for the three models are developed for comparative purposes. PMID:23202208

TH-EF-BRA-08: A Novel Technique for Estimating Volumetric Cine MRI (VC-MRI) From Multi-Slice Sparsely Sampled Cine Images Using Motion Modeling and Free Form Deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, W; Yin, F; Wang, C

Purpose: To develop a technique to estimate on-board VC-MRI using multi-slice sparsely-sampled cine images, patient prior 4D-MRI, motion-modeling and free-form deformation for real-time 3D target verification of lung radiotherapy. Methods: A previous method has been developed to generate on-board VC-MRI by deforming prior MRI images based on a motion model(MM) extracted from prior 4D-MRI and a single-slice on-board 2D-cine image. In this study, free-form deformation(FD) was introduced to correct for errors in the MM when large anatomical changes exist. Multiple-slice sparsely-sampled on-board 2D-cine images located within the target are used to improve both the estimation accuracy and temporal resolution ofmore » VC-MRI. The on-board 2D-cine MRIs are acquired at 20–30frames/s by sampling only 10% of the k-space on Cartesian grid, with 85% of that taken at the central k-space. The method was evaluated using XCAT(computerized patient model) simulation of lung cancer patients with various anatomical and respirational changes from prior 4D-MRI to onboard volume. The accuracy was evaluated using Volume-Percent-Difference(VPD) and Center-of-Mass-Shift(COMS) of the estimated tumor volume. Effects of region-of-interest(ROI) selection, 2D-cine slice orientation, slice number and slice location on the estimation accuracy were evaluated. Results: VCMRI estimated using 10 sparsely-sampled sagittal 2D-cine MRIs achieved VPD/COMS of 9.07±3.54%/0.45±0.53mm among all scenarios based on estimation with ROI-MM-ROI-FD. The FD optimization improved estimation significantly for scenarios with anatomical changes. Using ROI-FD achieved better estimation than global-FD. Changing the multi-slice orientation to axial, coronal, and axial/sagittal orthogonal reduced the accuracy of VCMRI to VPD/COMS of 19.47±15.74%/1.57±2.54mm, 20.70±9.97%/2.34±0.92mm, and 16.02±13.79%/0.60±0.82mm, respectively. Reducing the number of cines to 8 enhanced temporal resolution of VC-MRI by 25% while maintaining the estimation accuracy. Estimation using slices sampled uniformly through the tumor achieved better accuracy than slices sampled non-uniformly. Conclusions: Preliminary studies showed that it is feasible to generate VC-MRI from multi-slice sparsely-sampled 2D-cine images for real-time 3D-target verification. This work was supported by the National Institutes of Health under Grant No. R01-CA184173 and a research grant from Varian Medical Systems.« less

Diurnal and Seasonal Variations in the Net Ecosystem CO2 Exchange of a Pasture in the Three-River Source Region of the Qinghai−Tibetan Plateau

PubMed Central

Wang, Bin; Jin, Haiyan; Li, Qi; Chen, Dongdong; Zhao, Liang; Tang, Yanhong; Kato, Tomomichi; Gu, Song

2017-01-01

Carbon dioxide (CO2) exchange between the atmosphere and grassland ecosystems is very important for the global carbon balance. To assess the CO2 flux and its relationship to environmental factors, the eddy covariance method was used to evaluate the diurnal cycle and seasonal pattern of the net ecosystem CO2 exchange (NEE) of a cultivated pasture in the Three-River Source Region (TRSR) on the Qinghai−Tibetan Plateau from January 1 to December 31, 2008. The diurnal variations in the NEE and ecosystem respiration (Re) during the growing season exhibited single-peak patterns, the maximum and minimum CO2 uptake observed during the noon hours and night; and the maximum and minimum Re took place in the afternoon and early morning, respectively. The minimum hourly NEE rate and the maximum hourly Re rate were −7.89 and 5.03 μmol CO2 m−2 s−1, respectively. The NEE and Re showed clear seasonal variations, with lower values in winter and higher values in the peak growth period. The highest daily values for C uptake and Re were observed on August 12 (−2.91 g C m−2 d−1) and July 28 (5.04 g C m−2 day−1), respectively. The annual total NEE and Re were −140.01 and 403.57 g C m−2 year−1, respectively. The apparent quantum yield (α) was −0.0275 μmol μmol−1 for the entire growing period, and the α values for the pasture’s light response curve varied with the leaf area index (LAI), air temperature (Ta), soil water content (SWC) and vapor pressure deficit (VPD). Piecewise regression results indicated that the optimum Ta and VPD for the daytime NEE were 14.1°C and 0.65 kPa, respectively. The daytime NEE decreased with increasing SWC, and the temperature sensitivity of respiration (Q10) was 3.0 during the growing season, which was controlled by the SWC conditions. Path analysis suggested that the soil temperature at a depth of 5 cm (Tsoil) was the most important environmental factor affecting daily variations in NEE during the growing season, and the photosynthetic photon flux density (PPFD) was the major limiting factor for this cultivated pasture. PMID:28129406

Net ecosystem exchange of CO2 and H2O fluxes from irrigated grain sorghum and maize in the Texas High Plains.

PubMed

Wagle, Pradeep; Gowda, Prasanna H; Moorhead, Jerry E; Marek, Gary W; Brauer, David K

2018-05-08

Net ecosystem exchange (NEE) of carbon dioxide (CO 2 ) and water vapor (H 2 O) fluxes from irrigated grain sorghum (Sorghum bicolor L. Moench) and maize (Zea mays L.) fields in the Texas High Plains were quantified using the eddy covariance (EC) technique during 2014-2016 growing seasons and examined in terms of relevant controlling climatic variables. Eddy covariance measured evapotranspiration (ET EC ) was also compared against lysimeter measured ET (ET Lys ). Daily peak (7-day averages) NEE reached approximately -12 g C m -2 for sorghum and -14.78 g C m -2 for maize. Daily peak (7-day averages) ET EC reached approximately 6.5 mm for sorghum and 7.3 mm for maize. Higher leaf area index (5.7 vs 4-4.5 m 2  m -2 ) and grain yield (14 vs 8-9 t ha -1 ) of maize compared to sorghum caused larger magnitudes of NEE and ET EC in maize. Comparisons of ET EC and ET Lys showed a strong agreement (R 2  = 0.93-0.96), while the EC system underestimated ET by 15-24% as compared to lysimeter without any corrections or energy balance adjustments. Both NEE and ET EC were not inhibited by climatic variables during peak photosynthetic period even though diurnal peak values (~2-weeks average) of photosynthetic photon flux density (PPFD), air temperature (T a ), and vapor pressure deficit (VPD) had reached over 2000 μmol m -2  s -1 , 30 °C, and 2.5 kPa, respectively, indicating well adaptation of both C 4 crops in the Texas High Plains under irrigation. However, more sensitivity of NEE and H 2 O fluxes beyond threshold T a and VPD for maize than for sorghum indicated higher adaptability of sorghum for the region. These findings provide baseline information on CO 2 fluxes and ET for a minimally studied grain sorghum and offer a robust geographic comparison for maize outside the United States Corn Belt. However, longer-term measurements are required for assessing carbon and water dynamics of these globally important agro-ecosystems. Copyright © 2018. Published by Elsevier B.V.

Analyzing energy-water exchange dynamics in the Thar desert

NASA Astrophysics Data System (ADS)

Raja, P.; Singh, Nilendu; Srinivas, C. V.; Singhal, Mohit; Chauhan, Pankaj; Singh, Maharaj; Sinha, N. K.

2017-07-01

Regions of strong land-atmosphere coupling will be more susceptible to the hydrological impacts in the intensifying hydrological cycle. In this study, micrometeorological experiments were performed to examine the land-atmosphere coupling strength over a heat low region (Thar desert, NW India), known to influence the Indian summer monsoon (ISM). Within the vortex of Thar desert heat low, energy-water exchange and coupling behavior were studied for 4 consecutive years (2011-2014) based on sub-hourly measurements of radiative-convective flux, state parameters and sub-surface thermal profiles using lead-lag analysis between various E-W balance components. Results indicated a strong (0.11-0.35) but variable monsoon season (July-September) land-atmosphere coupling events. Coupling strength declined with time, becomes negative beyond 10-day lag. Evapotranspiration (LE) influences rainfall at the monthly time-scale (20-40 days). Highly correlated monthly rainfall and LE anomalies (r = 0.55, P < 0.001) suggested a large precipitation memory linked to the local land surface state. Sensible heating (SH) during March and April are more strongly (r = 0.6-0.7) correlated to ISM rainfall than heating during May or June (r = 0.16-0.36). Analyses show strong and weak couplings among net radiation (Rn)-vapour pressure deficit (VPD), LE-VPD and Rn-LE switching between energy-limited to water-limited conditions. Consistently, +ve and -ve residual energy [(dE) = (Rn - G) - (SH + LE)] were associated with regional wet and dry spells respectively with a lead of 10-40 days. Dew deposition (18.8-37.9 mm) was found an important component in the annual surface water balance. Strong association of variation of LE and rainfall was found during monsoon at local-scale and with regional-scale LE (MERRA 2D) but with a lag which was more prominent at local-scale than at regional-scale. Higher pre-monsoon LE at local-scale as compared to low and monotonous variation in regional-scale LE led to hypothesize that excess energy and water vapour brought through advection caused by pre-monsoon rainfall might have been recycled through rainfall to compensate for early part of monsoon rainfall at local-scale. However, long-term measurements and isotope analysis would be able to strengthen this hypothesis. This study would fill the key gaps in the global flux studies and improve understanding on local E-W exchange pathways, responses and feedbacks.

Environmental impacts on the evapotranspiration of an water limited and heterogeneous Mediterranean ecosystem.

NASA Astrophysics Data System (ADS)

Mackay, D. S.; Ewers, B. E.; Sperry, J. S.; Frank, J. M.; Reed, D. E.

2014-12-01

Mediterranean water limited ecosystems are characterized by an heterogeneous spatial distribution of different plant functional types (PFT), such as grass and trees, competing for water use. Typically, during the dry summers, these ecosystems are characterized by a simple dual PFTs system with strong-resistant woody vegetation and bare soil, since grass died. The coupled use of sap flow measurements and eddy covariance technique is essential to estimate Evapotransiration (ET) in an heterogeneous ecosystem. An eddy covariance - micrometeorological tower has been installed since 2003 and 33 thermo-dissipation probes based on the Granier technique have installed at the Orroli site in Sardinia (Italy). The site landscape is a mixture of Mediterranean patchy vegetation types: wild olives, different shrubs and herbaceous species, which died during the summer. The sensors have been installed at the Orroli site into 15 wild olives clumps with different characteristics in terms of tree size, exposition to wind and solar radiation and soil depth. A network of 30 soil moisture sensors has also been installed for monitoring soil moisture spatial and temporal dynamics and their correlation with trees. Sap flow measurements show the significantly impacts on ET of soil moisture, radiation, vapor pressure deficit (VPD) and interestingly of tree position into the clump, showing double rates for the trees inside the wild olive clumps. The sap flow sensor outputs are analyzed for estimating innovative allometric relationships between sapwood area, diameter, canopy cover area, which are needed for the correct upscale of the local tree measurements to the site plot larger scale. Finally using an innovative scaling procedure, the sap-flow transpiration at field scale have been compared to the eddy covariance ET, showing the approximation of the eddy covariance technique. Finally the impact of environmental factors on ET for different soil depth and tree position is demonstrated.

Environmental impacts on the evapotranspiration of an water limited and heterogeneous Mediterranean ecosystem.

NASA Astrophysics Data System (ADS)

Montaldo, N.; Curreli, M.; Corona, R.; Oren, R.

2015-12-01

Mediterranean water limited ecosystems are characterized by an heterogeneous spatial distribution of different plant functional types (PFT), such as grass and trees, competing for water use. Typically, during the dry summers, these ecosystems are characterized by a simple dual PFTs system with strong-resistant woody vegetation and bare soil, since grass died. The coupled use of sap flow measurements and eddy covariance technique is essential to estimate Evapotransiration (ET) in an heterogeneous ecosystem. An eddy covariance - micrometeorological tower has been installed since 2003 and 33 thermo-dissipation probes based on the Granier technique have installed at the Orroli site in Sardinia (Italy). The site landscape is a mixture of Mediterranean patchy vegetation types: wild olives, different shrubs and herbaceous species, which died during the summer. The sensors have been installed at the Orroli site into 15 wild olives clumps with different characteristics in terms of tree size, exposition to wind and solar radiation and soil depth. A network of 30 soil moisture sensors has also been installed for monitoring soil moisture spatial and temporal dynamics and their correlation with trees. Sap flow measurements show the significantly impacts on ET of soil moisture, radiation, vapor pressure deficit (VPD) and interestingly of tree position into the clump, showing double rates for the trees inside the wild olive clumps. The sap flow sensor outputs are analyzed for estimating innovative allometric relationships between sapwood area, diameter, canopy cover area, which are needed for the correct upscale of the local tree measurements to the site plot larger scale. Finally using an innovative scaling procedure, the sap-flow transpiration at field scale have been compared to the eddy covariance ET, showing the approximation of the eddy covariance technique. Finally the impact of environmental factors on ET for different soil depth and tree position is demonstrated.

Research frontiers for improving our understanding of drought‐induced tree and forest mortality

USGS Publications Warehouse

Hartmann, Henrik; Moura, Catarina; Anderegg, William R. L.; Ruehr, Nadine; Salmon, Yann; Allen, Craig D.; Arndt, Stefan K.; Breshears, David D.; Davi, Hendrik; Galbraith, David; Ruthrof, Katinka X.; Wunder, Jan; Adams, Henry D.; Bloemen, Jasper; Cailleret, Maxime; Cobb, Richard; Gessler, Arthur; Grams, Thorsten E. E.; Jansen, Steven; Kautz, Markus; Lloret, Francisco; O’Brien, Michael

2018-01-01

Accumulating evidence highlights increased mortality risks for trees during severe drought, particularly under warmer temperatures and increasing vapour pressure deficit (VPD). Resulting forest die‐off events have severe consequences for ecosystem services, biophysical and biogeochemical land–atmosphere processes. Despite advances in monitoring, modelling and experimental studies of the causes and consequences of tree death from individual tree to ecosystem and global scale, a general mechanistic understanding and realistic predictions of drought mortality under future climate conditions are still lacking. We update a global tree mortality map and present a roadmap to a more holistic understanding of forest mortality across scales. We highlight priority research frontiers that promote: (1) new avenues for research on key tree ecophysiological responses to drought; (2) scaling from the tree/plot level to the ecosystem and region; (3) improvements of mortality risk predictions based on both empirical and mechanistic insights; and (4) a global monitoring network of forest mortality. In light of recent and anticipated large forest die‐off events such a research agenda is timely and needed to achieve scientific understanding for realistic predictions of drought‐induced tree mortality. The implementation of a sustainable network will require support by stakeholders and political authorities at the international level.

Integration of Multiplex Bead Assays for Parasitic Diseases into a National, Population-Based Serosurvey of Women 15-39 Years of Age in Cambodia

PubMed Central

Priest, Jeffrey W.; Jenks, M. Harley; Moss, Delynn M.; Mao, Bunsoth; Buth, Sokhal; Wannemuehler, Kathleen; Soeung, Sann Chan; Lucchi, Naomi W.; Udhayakumar, Venkatachalam; Gregory, Christopher J.; Huy, Rekol; Muth, Sinuon; Lammie, Patrick J.

2016-01-01

Collection of surveillance data is essential for monitoring and evaluation of public health programs. Integrated collection of household-based health data, now routinely carried out in many countries through demographic health surveys and multiple indicator surveys, provides critical measures of progress in health delivery. In contrast, biomarker surveys typically focus on single or related measures of malaria infection, HIV status, vaccination coverage, or immunity status for vaccine-preventable diseases (VPD). Here we describe an integrated biomarker survey based on use of a multiplex bead assay (MBA) to simultaneously measure antibody responses to multiple parasitic diseases of public health importance as part of a VPD serological survey in Cambodia. A nationally-representative cluster-based survey was used to collect serum samples from women of child-bearing age. Samples were tested by MBA for immunoglobulin G antibodies recognizing recombinant antigens from Plasmodium falciparum and P. vivax, Wuchereria bancrofti, Toxoplasma gondii, Taenia solium, and Strongyloides stercoralis. Serologic IgG antibody results were useful both for generating national prevalence estimates for the parasitic diseases of interest and for confirming the highly focal distributions of some of these infections. Integrated surveys offer an opportunity to systematically assess the status of multiple public health programs and measure progress toward Millennium Development Goals. PMID:27136913

Multistakeholder partnerships with the Democratic Peoples' Republic of Korea to improve childhood immunisation: A perspective from global health equity and political determinants of health equity.

PubMed

Kim, Hani; Marks, Florian; Novakovic, Uros; Hotez, Peter J; Black, Robert E

2016-08-01

To examine the current partnerships to improve the childhood immunisation programme in the Democratic Peoples' Republic of Korea (DPRK) in the context of the political determinants of health equity. A literature search was conducted to identify public health collaborations with the DPRK government. Based on the amount of publicly accessible data and a shared approach in health system strengthening among the partners in immunisation programmes, the search focused on these partnerships. The efforts by WHO, UNICEF, GAVI and IVI with the DPRK government improved the delivery of childhood vaccines (e.g. pentavalent vaccines, inactivated polio vaccine, two-dose measles vaccine and Japanese encephalitis vaccine) and strengthened the DPRK health system by equipping health centres, and training all levels of public health personnel for VPD surveillance and immunisation service delivery. The VPD-focused programmatic activities in the DPRK have improved the delivery of childhood immunisation and have created dialogue and contact with the people of the DPRK. These efforts are likely to ameliorate the political isolation of the people of the DPRK and potentially improve global health equity. © 2016 The Authors. Tropical Medicine & International Health Published by John Wiley & Sons Ltd.

Visually Coupled Systems (VCS): The Virtual Panoramic Display (VPD) System

NASA Technical Reports Server (NTRS)

Kocian, Dean F.

1992-01-01

The development and impact is described of new visually coupled system (VCS) equipment designed to support engineering and human factors research in the military aircraft cockpit environment. VCS represents an advanced man-machine interface (MMI). Its potential to improve aircrew situational awareness seems enormous, but its superiority over the conventional cockpit MMI has not been established in a conclusive and rigorous fashion. What has been missing is a 'systems' approach to technology advancement that is comprehensive enough to produce conclusive results concerning the operational viability of the VCS concept and verify any risk factors that might be involved with its general use in the cockpit. The advanced VCS configuration described here, was ruggedized for use in military aircraft environments and was dubbed the Virtual Panoramic Display (VPD). It was designed to answer the VCS portion of the systems problem, and is implemented as a modular system whose performance can be tailored to specific application requirements. The overall system concept and the design of the two most important electronic subsystems that support the helmet mounted parts, a new militarized version of the magnetic helmet mounted sight and correspondingly similar helmet display electronics, are discussed in detail. Significant emphasis is given to illustrating how particular design features in the hardware improve overall system performance and support research activities.

Reducing scan angle using adaptive prior knowledge for a limited-angle intrafraction verification (LIVE) system for conformal arc radiotherapy.

PubMed

Zhang, Yawei; Yin, Fang-Fang; Zhang, You; Ren, Lei

2017-05-07

The purpose of this study is to develop an adaptive prior knowledge guided image estimation technique to reduce the scan angle needed in the limited-angle intrafraction verification (LIVE) system for 4D-CBCT reconstruction. The LIVE system has been previously developed to reconstruct 4D volumetric images on-the-fly during arc treatment for intrafraction target verification and dose calculation. In this study, we developed an adaptive constrained free-form deformation reconstruction technique in LIVE to further reduce the scanning angle needed to reconstruct the 4D-CBCT images for faster intrafraction verification. This technique uses free form deformation with energy minimization to deform prior images to estimate 4D-CBCT based on kV-MV projections acquired in extremely limited angle (orthogonal 3°) during the treatment. Note that the prior images are adaptively updated using the latest CBCT images reconstructed by LIVE during treatment to utilize the continuity of the respiratory motion. The 4D digital extended-cardiac-torso (XCAT) phantom and a CIRS 008A dynamic thoracic phantom were used to evaluate the effectiveness of this technique. The reconstruction accuracy of the technique was evaluated by calculating both the center-of-mass-shift (COMS) and 3D volume-percentage-difference (VPD) of the tumor in reconstructed images and the true on-board images. The performance of the technique was also assessed with varied breathing signals against scanning angle, lesion size, lesion location, projection sampling interval, and scanning direction. In the XCAT study, using orthogonal-view of 3° kV and portal MV projections, this technique achieved an average tumor COMS/VPD of 0.4  ±  0.1 mm/5.5  ±  2.2%, 0.6  ±  0.3 mm/7.2  ±  2.8%, 0.5  ±  0.2 mm/7.1  ±  2.6%, 0.6  ±  0.2 mm/8.3  ±  2.4%, for baseline drift, amplitude variation, phase shift, and patient breathing signal variation, respectively. In the CIRS phantom study, this technique achieved an average tumor COMS/VPD of 0.7  ±  0.1 mm/7.5  ±  1.3% for a 3 cm lesion and 0.6  ±  0.2 mm/11.4  ±  1.5% for a 2 cm lesion in the baseline drift case. The average tumor COMS/VPD were 0.5  ±  0.2 mm/10.8  ±  1.4%, 0.4  ±  0.3 mm/7.3  ±  2.9%, 0.4  ±  0.2 mm/7.4  ±  2.5%, 0.4  ±  0.2 mm/7.3  ±  2.8% for the four real patient breathing signals, respectively. Results demonstrated that the adaptive prior knowledge guided image estimation technique with LIVE system is robust against scanning angle, lesion size, location and scanning direction. It can estimate on-board images accurately with as little as 6 projections in orthogonal-view 3° angle. In conclusion, adaptive prior knowledge guided image reconstruction technique accurately estimates 4D-CBCT images using extremely-limited angle and projections. This technique greatly improves the efficiency and accuracy of LIVE system for ultrafast 4D intrafraction verification of lung SBRT treatments.

Field-acclimated Gossypium hirsutum cultivars exhibit genotypic and seasonal differences in photosystem II thermostability.

PubMed

Snider, John L; Oosterhuis, Derrick M; Collins, Guy D; Pilon, Cristiane; Fitzsimons, Toby R

2013-03-15

Previous investigations have demonstrated that photosystem II (PSII) thermostability acclimates to prior exposure to heat and drought, but contrasting results have been reported for cotton (Gossypium hirsutum). We hypothesized that PSII thermotolerance in G. hirsutum would acclimate to environmental conditions during the growing season and that there would be differences in PSII thermotolerance between commercially-available U.S. cultivars. To this end, three cotton cultivars were grown under dryland conditions in Tifton Georgia, and two under irrigated conditions in Marianna Arkansas. At Tifton, measurements included PSII thermotolerance (T15, the temperature causing a 15% decline in maximum quantum yield), leaf temperatures, air temperatures, midday (1200 to 1400h) leaf water potentials (ΨMD), leaf-air vapor pressure deficit (VPD), actual quantum yield (ΦPSII) and electron transport rate through PSII (ETR) on three sample dates. At Marianna, T15 was measured on two sample dates. Optimal air and leaf temperatures were observed on all sample dates in Tifton, but PSII thermotolerance increased with water deficit conditions (ΨMD=-3.1MPa), and ETR was either unaffected or increased under water-stress. Additionally, T15 for PHY 499 was ∼5°C higher than for the other cultivars examined (DP 0912 and DP 1050). The Marianna site experienced more extreme high temperature conditions (20-30 days Tmax≥35°C), and showed an increase in T15 with higher average Tmax. When average T15 values for each location and sample date were plotted versus average daily Tmax, strong, positive relationships (r(2) from .954 to .714) were observed between Tmax and T15. For all locations T15 was substantially higher than actual field temperature conditions. We conclude that PSII thermostability in G. hirsutum acclimates to pre-existing environmental conditions; PSII is extremely tolerant to high temperature and water-deficit stress; and differences in PSII thermotolerance exist between commercially-available cultivars. Copyright © 2012 Elsevier GmbH. All rights reserved.

Shoot development in grapevine (Vitis vinifera) is affected by the modular branching pattern of the stem and intra- and inter-shoot trophic competition.

PubMed

Lebon, Eric; Pellegrino, Anne; Tardieu, Francois; Lecoeur, Jeremie

2004-03-01

Shoot architecture variability in grapevine (Vitis vinifera) was analysed using a generic modelling approach based on thermal time developed for annual herbaceous species. The analysis of shoot architecture was based on various levels of shoot organization, including pre-existing and newly formed parts of the stem, and on the modular structure of the stem, which consists of a repeated succession of three phytomers (P0-P1-P2). Four experiments were carried out using the cultivar 'Grenache N': two on potted vines (one of which was carried out in a glasshouse) and two on mature vines in a vineyard. These experiments resulted in a broad diversity of environmental conditions, but none of the plants experienced soil water deficit. Development of the main axis was highly dependent on air temperature, being linearly related to thermal time for all stages of leaf development from budbreak to veraison. The stable progression of developmental stages along the main stem resulted in a thermal-time based programme of leaf development. Leaf expansion rate varied with trophic competition (shoot and cluster loads) and environmental conditions (solar radiation, VPD), accounting for differences in final leaf area. Branching pattern was highly variable. Classification of the branches according to ternary modular structure increased the accuracy of the quantitative analysis of branch development. The rate and duration of leaf production were higher for branches derived from P0 phytomers than for branches derived from P1 or P2 phytomers. Rates of leaf production, expressed as a -function of thermal time, were not stable and depended on trophic competition and environmental conditions such as solar radiation or VPD. The application to grapevine of a generic model developed in annual plants made it possible to identify constants in main stem development and to determine the hierarchical structure of branches with respect to the modular structure of the stem in response to intra- and inter-shoot trophic competition.

Measles, Rubella and Varicella IgG Seroprevalence in a Large Refugee Cohort in Germany in 2015: A Cross-Sectional Study.

PubMed

Jablonka, Alexandra; Happle, Christine; Wetzke, Martin; Dopfer, Christian; Merkesdal, Sonja; Schmidt, Reinhold E; Behrens, Georg M N; Solbach, Philipp

2017-12-01

The current extent of migration to the European continent is associated with exceptional humanitarian challenges. In 2015, Western Europe faced an enormous immigration of refugees with largely unknown protection status against communicable diseases. To adapt vaccination strategies, we aimed at assessing seroprevalences against three of the most relevant vaccine preventable diseases (VPD) in a large representative cohort. IgG seroprevalences for rubella, varicella (n = 554) and measles (n = 552) were analyzed in inhabitants of a Northern German refugee camp in the summer of 2015. Of the refugees, 77.9% were male (mean age 27.4 years for male and 26.8 years for female migrants). Most refugees came from the Eastern Mediterranean region (83.4%), followed by immigrants from Eastern Europe (7.4%), Africa (4.6%), or other regions (4.5%). The vast majority of migrants were protected against the three VPD: overall IgG seropositivity was 88.5% for measles, 77.9% for rubella and 95.9% for varicella. However, seroprevalences showed age- and origin-dependent differences. Varicella immunity, for example, was lowest in the youngest age group of both genders (10.1% of male/4.5% of female seronegative refugees <18 years vs. 100% seropositivity in men and women >49 years of age), and Sudanese migrants displayed particularly low rates of protection against varicella. In accordance with previous studies, our analyses show an overall satisfactory seropositivity against measles, rubella, and varicella in refugees entering Europe during the current exodus. However, this rate is not sufficient for preventing transmission. For example, the rate of 12.9-17.9% female refugees at reproductive age unprotected against measles and the low protection levels against varicella in minors observed in our cohort emphasizes the need for stringent vaccination strategies in refugees coming to Europe during the current crisis.

Interannual variations in needle and sapwood traits of Pinus edulis branches under an experimental drought.

PubMed

Guérin, Marceau; Martin-Benito, Dario; von Arx, Georg; Andreu-Hayles, Laia; Griffin, Kevin L; Hamdan, Rayann; McDowell, Nate G; Muscarella, Robert; Pockman, William; Gentine, Pierre

2018-02-01

In the southwestern USA, recent large-scale die-offs of conifers raise the question of their resilience and mortality under droughts. To date, little is known about the interannual structural response to droughts. We hypothesized that piñon pines ( Pinus edulis ) respond to drought by reducing the drop of leaf water potential in branches from year to year through needle morphological adjustments. We tested our hypothesis using a 7-year experiment in central New Mexico with three watering treatments (irrigated, normal, and rain exclusion). We analyzed how variation in "evaporative structure" (needle length, stomatal diameter, stomatal density, stomatal conductance) responded to watering treatment and interannual climate variability. We further analyzed annual functional adjustments by comparing yearly addition of needle area (LA) with yearly addition of sapwood area (SA) and distance to tip ( d ), defining the yearly ratios SA:LA and SA:LA/ d . Needle length ( l ) increased with increasing winter and monsoon water supply, and showed more interannual variability when the soil was drier. Stomatal density increased with dryness, while stomatal diameter was reduced. As a result, anatomical maximal stomatal conductance was relatively invariant across treatments. SA:LA and SA:LA/ d showed significant differences across treatments and contrary to our expectation were lower with reduced water input. Within average precipitation ranges, the response of these ratios to soil moisture was similar across treatments. However, when extreme soil drought was combined with high VPD, needle length, SA:LA and SA:LA/ d became highly nonlinear, emphasizing the existence of a response threshold of combined high VPD and dry soil conditions. In new branch tissues, the response of annual functional ratios to water stress was immediate (same year) and does not attempt to reduce the drop of water potential. We suggest that unfavorable evaporative structural response to drought is compensated by dynamic stomatal control to maximize photosynthesis rates.

Auditing the management of vaccine-preventable disease outbreaks: the need for a tool.

PubMed

Torner, Nuria; Carnicer-Pont, Dolors; Castilla, Jesus; Cayla, Joan; Godoy, Pere; Dominguez, Angela

2011-01-13

Public health activities, especially infectious disease control, depend on effective teamwork. We present the results of a pilot audit questionnaire aimed at assessing the quality of public health services in the management of VPD outbreaks. Audit questionnaire with three main areas indicators (structure, process and results) was developed. Guidelines were set and each indicator was assessed by three auditors. Differences in indicator scores according to median size of outbreaks were determined by ANOVA (significance at p≤0.05). Of 154 outbreaks; eighteen indicators had a satisfactory mean score, indicator "updated guidelines" and "timely reporting" had a poor mean score (2.84±106 and 2.44±1.67, respectively). Statistically significant differences were found according to outbreak size, in the indicators "availability of guidelines/protocol updated less than 3 years ago" (p = 0.03) and "days needed for outbreak control" (p = 0.04). Improving availability of updated guidelines, enhancing timely reporting and adequate recording of control procedures taken is needed to allow for management assessment and improvement.

Variability in carbon dioxide fluxes among six winter wheat paddocks managed under different tillage and grazing practices

NASA Astrophysics Data System (ADS)

Wagle, Pradeep; Gowda, Prasanna H.; Northup, Brian K.; Turner, Kenneth E.; Neel, James P. S.; Manjunatha, Priyanka; Zhou, Yuting

2018-07-01

Carbon dioxide (CO2) fluxes from six winter wheat (Triticum aestivum L.) paddocks (grain only, graze-grain, and graze-out) managed under conventional till (CT) and no-till (NT) systems were synthesized for the 2016-2017 growing season to compare the magnitudes and seasonal dynamics of CO2 fluxes and to investigate among-site variability of CO2 fluxes. Large variations in CO2 fluxes were observed among paddocks. Maximum daily (7-day averages) net ecosystem CO2 exchange (NEE) ranged from -3.39 to -8.68 g C m-2, gross primary production (GPP) ranged from 7.33 to 16.92 g C m-2, and ecosystem respiration (ER) ranged from 5.85 to 9.98 g C m-2. Seasonal sums of NEE ranged from -137 to -542 g C m-2. Optimum photosynthetically active radiation (PAR), air temperature (Ta), and vapor pressure deficit (VPD) for NEE were approximately 1700 μmol m-2 s-1, 22 °C, and 1.25 kPa, respectively. Across-site analysis showed percent of canopy cover (Canopy%) was strongly correlated with NEE (R2 = 0.76) and ecosystem light use efficiency (ELUE, R2 = 0.76). Integration of PAR with leaf area index (LAI) and integration of Ta with dry biomass weight (DW) explained 81% and 74% of variations in GPP and ER, respectively. Remotely-sensed enhanced vegetation index (EVI) explained 66% and normalized difference vegetation index (NDVI) explained 69% of the variations in NEE. Integration of PAR with NDVI or EVI explained ∼80% of variations in GPP, while NDVI × Ta explained 58% of variations in ER. Results illustrated that differences in wheat canopies related to paddock management, as indicated by differences in DW, LAI, Canopy%, NDVI, and EVI, must be accounted for explaining among-site variability of CO2 fluxes. Long-term measurements from our clustered and paired eddy covariance towers will provide insights into the effects of tillage and different grazing practices on CO2 dynamics in winter wheat.

Evaluation of hydrologic equilibrium in a mountainous watershed: incorporating forest canopy spatial adjustment to soil biogeochemical processes

NASA Astrophysics Data System (ADS)

Mackay, D. Scott

Hydrologic equilibrium theory has been used to describe both short-term regulation of gas exchange and long-term adjustment of forest canopy density. However, by focusing on water and atmospheric conditions alone a hydrologic equilibrium may impose an oversimplification of the growth of forests adjusted to hydrology. In this study nitrogen is incorporated as a third regulation of catchment level forest dynamics and gas exchange. This was examined with an integrated distributed hydrology and forest growth model in a central Sierra Nevada watershed covered primarily by old-growth coniferous forest. Water and atmospheric conditions reasonably reproduced daily latent heat flux, and predicted the expected catenary trend of leaf area index (LAI). However, it was not until the model was provided a spatially detailed description of initial soil carbon and nitrogen pools that spatial patterns of LAI were generated. This latter problem was attributed to a lack of soil history or memory in the initialization of the simulations. Finally, by reducing stomatal sensitivity to vapor pressure deficit (VPD) the canopy density increased when water and nitrogen limitations were not present. The results support a three-control hydrologic equilibrium in the Sierra Nevada watershed. This has implications for modeling catchment level soil-vegetation-atmospheric interactions over interannual, decade, and century time-scales.

Multiple mechanisms of Amazonian forest biomass losses in three dynamic global vegetation models under climate change.

PubMed

Galbraith, David; Levy, Peter E; Sitch, Stephen; Huntingford, Chris; Cox, Peter; Williams, Mathew; Meir, Patrick

2010-08-01

*The large-scale loss of Amazonian rainforest under some future climate scenarios has generally been considered to be driven by increased drying over Amazonia predicted by some general circulation models (GCMs). However, the importance of rainfall relative to other drivers has never been formally examined. *Here, we conducted factorial simulations to ascertain the contributions of four environmental drivers (precipitation, temperature, humidity and CO(2)) to simulated changes in Amazonian vegetation carbon (C(veg)), in three dynamic global vegetation models (DGVMs) forced with climate data based on HadCM3 for four SRES scenarios. *Increased temperature was found to be more important than precipitation reduction in causing losses of Amazonian C(veg) in two DGVMs (Hyland and TRIFFID), and as important as precipitation reduction in a third DGVM (LPJ). Increases in plant respiration, direct declines in photosynthesis and increases in vapour pressure deficit (VPD) all contributed to reduce C(veg) under high temperature, but the contribution of each mechanism varied greatly across models. Rising CO(2) mitigated much of the climate-driven biomass losses in the models. *Additional work is required to constrain model behaviour with experimental data under conditions of high temperature and drought. Current models may be overly sensitive to long-term elevated temperatures as they do not account for physiological acclimation.

Simulation of semi-arid biomass plantations and irrigation using the WRF-NOAH model - a comparison with observations from Israel

NASA Astrophysics Data System (ADS)

Branch, O.; Warrach-Sagi, K.; Wulfmeyer, V.; Cohen, S.

2014-05-01

A 10 × 10 km irrigated biomass plantation was simulated in an arid region of Israel to simulate diurnal energy balances during the summer of 2012 (JJA). The goal is to examine daytime horizontal flux gradients between plantation and desert. Simulations were carried out within the coupled WRF-NOAH atmosphere/land surface model. MODIS land surface data was adjusted by prescribing tailored land surface and soil/plant parameters, and by adding a controllable sub-surface irrigation scheme to NOAH. Two model cases studies were compared - Impact and Control. Impact simulates the irrigated plantation. Control simulates the existing land surface, where the predominant land surface is bare desert soil. Central to the study is parameter validation against land surface observations from a desert site and from a 400 ha Simmondsia chinensis (jojoba) plantation. Control was validated with desert observations, and Impact with Jojoba observations. Model evapotranspiration was validated with two Penman-Monteith estimates based on the observations. Control simulates daytime desert conditions with a maximum deviation for surface 2 m air temperatures (T2) of 0.2 °C, vapour pressure deficit (VPD) of 0.25 hPa, wind speed (U) of 0.5 m s-1, surface radiation (Rn) of 25 W m-2, soil heat flux (G) of 30 W m-2 and 5 cm soil temperatures (ST5) of 1.5 °C. Impact simulates irrigated vegetation conditions with a maximum deviation for T2 of 1-1.5 °C, VPD of 0.5 hPa, U of 0.5 m s-1, Rn of 50 W m-5, G of 40 W m-2 and ST5 of 2 °C. Latent heat curves in Impact correspond closely with Penman-Monteith estimates, and magnitudes of 160 W m-2 over the plantation are usual. Sensible heat fluxes, are around 450 W m-2 and are at least 100-110 W m-2 higher than the surrounding desert. This surplus is driven by reduced albedo and high surface resistance, and demonstrates that high evaporation rates may not occur over Jojoba if irrigation is optimized. Furthermore, increased daytime T2 over plantations highlight the need for hourly as well as daily mean statistics. Daily mean statistics alone may imply an overall cooling effect due to surplus nocturnal cooling, when in fact a daytime warming effect is observed.

An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM4.5)

NASA Astrophysics Data System (ADS)

Raczka, Brett; Duarte, Henrique F.; Koven, Charles D.; Ricciuto, Daniel; Thornton, Peter E.; Lin, John C.; Bowling, David R.

2016-09-01

Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. We distinguished between isotopic behavior in response to a decrease of δ13C within atmospheric CO2 (Suess effect) vs. photosynthetic discrimination (Δcanopy), by creating a site-customized atmospheric CO2 and δ13C of CO2 time series. We implemented a seasonally varying Vcmax model calibration that best matched site observations of net CO2 carbon exchange, latent heat exchange, and biomass. The model accurately simulated observed δ13C of needle and stem tissue, but underestimated the δ13C of bulk soil carbon by 1-2 ‰. The model overestimated the multiyear (2006-2012) average Δcanopy relative to prior data-based estimates by 2-4 ‰. The amplitude of the average seasonal cycle of Δcanopy (i.e., higher in spring/fall as compared to summer) was correctly modeled but only when using a revised, fully coupled An - gs (net assimilation rate, stomatal conductance) version of the model in contrast to the partially coupled An - gs version used in the default model. The model attributed most of the seasonal variation in discrimination to An, whereas interannual variation in simulated Δcanopy during the summer months was driven by stomatal response to vapor pressure deficit (VPD). The model simulated a 10 % increase in both photosynthetic discrimination and water-use efficiency (WUE) since 1850 which is counter to established relationships between discrimination and WUE. The isotope observations used here to constrain CLM suggest (1) the model overestimated stomatal conductance and (2) the default CLM approach to representing nitrogen limitation (partially coupled model) was not capable of reproducing observed trends in discrimination. These findings demonstrate that isotope observations can provide important information related to stomatal function driven by environmental stress from VPD and nitrogen limitation. Future versions of CLM that incorporate carbon isotope discrimination are likely to benefit from explicit inclusion of mesophyll conductance.

Helmet Mounted Eye Tracking for Virtual Panoramic Displays. Volume 1: Review of Current Eye Movement Measurement Technology

DTIC Science & Technology

1989-08-01

paths for integration with the off-aperture and dual-mirror VPD designs. PREFACE The goal of this work was to explore integration of an eye line-of- gaze ...Relationship in one plane between point-of- gaze on a flat scene and relative eye, detector, and scene positions...and eye line-of- gaze measurement. As a first step towards the design of an appropriate eye trac.<ing system for interface with the virtual cockpit

Retrieval of Mid-tropospheric CO2 Directly from AIRS Measurements

NASA Technical Reports Server (NTRS)

Olsen, Edward T.; Chahine, Moustafa T.; Chen, Luke L.; Pagano, Thomas S.

2008-01-01

We apply the method of Vanishing Partial Derivatives (VPD) to AIRS spectra to retrieve daily the global distribution of CO2 at a nadir geospatial resolution of 90 km x 90 km without requiring a first-guess input beyond the global average. Our retrievals utilize the 15 (micro)m band radiances, a complex spectral region. This method may be of value in other applications, in which spectral signatures of multiple species are not well isolated spectrally from one another.

Simulation of carbon isotope discrimination of the terrestrial biosphere

NASA Astrophysics Data System (ADS)

Suits, N. S.; Denning, A. S.; Berry, J. A.; Still, C. J.; Kaduk, J.; Miller, J. B.; Baker, I. T.

2005-03-01

We introduce a multistage model of carbon isotope discrimination during C3 photosynthesis and global maps of C3/C4 plant ratios to an ecophysiological model of the terrestrial biosphere (SiB2) in order to predict the carbon isotope ratios of terrestrial plant carbon globally at a 1° resolution. The model is driven by observed meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), constrained by satellite-derived Normalized Difference Vegetation Index (NDVI) and run for the years 1983-1993. Modeled mean annual C3 discrimination during this period is 19.2‰; total mean annual discrimination by the terrestrial biosphere (C3 and C4 plants) is 15.9‰. We test simulation results in three ways. First, we compare the modeled response of C3 discrimination to changes in physiological stress, including daily variations in vapor pressure deficit (vpd) and monthly variations in precipitation, to observed changes in discrimination inferred from Keeling plot intercepts. Second, we compare mean δ13C ratios from selected biomes (Broadleaf, Temperate Broadleaf, Temperate Conifer, and Boreal) to the observed values from Keeling plots at these biomes. Third, we compare simulated zonal δ13C ratios in the Northern Hemisphere (20°N to 60°N) to values predicted from high-frequency variations in measured atmospheric CO2 and δ13C from terrestrially dominated sites within the NOAA-Globalview flask network. The modeled response to changes in vapor pressure deficit compares favorably to observations. Simulated discrimination in tropical forests of the Amazon basin is less sensitive to changes in monthly precipitation than is suggested by some observations. Mean model δ13C ratios for Broadleaf, Temperate Broadleaf, Temperate Conifer, and Boreal biomes compare well with the few measurements available; however, there is more variability in observations than in the simulation, and modeled δ13C values for tropical forests are heavy relative to observations. Simulated zonal δ13C ratios in the Northern Hemisphere capture patterns of zonal δ13C inferred from atmospheric measurements better than previous investigations. Finally, there is still a need for additional constraints to verify that carbon isotope models behave as expected.

Growth maximization trumps maintenance of leaf conductance in the tallest angiosperm.

PubMed

Koch, George W; Sillett, Stephen C; Antoine, Marie E; Williams, Cameron B

2015-02-01

Structural and physiological changes that occur as trees grow taller are associated with increased hydraulic constraints on leaf gas exchange, yet it is unclear if leaf-level constraints influence whole-tree growth as trees approach their maximum size. We examined variation in leaf physiology, leaf area to sapwood area ratio (L/S), and annual aboveground growth across a range of tree heights in Eucalyptus regnans. Leaf photosynthetic capacity did not differ among upper crown leaves of individuals 61.1-92.4 m tall. Maximum daily and integrated diurnal stomatal conductance (g s) averaged 36 and 34% higher, respectively, in upper crown leaves of ~60-m-tall, 80-year-old trees than in ~90-m-tall, 300-year-old trees, with larger differences observed on days with a high vapor pressure deficit (VPD). Greater stomatal regulation in taller trees resulted in similar minimum daily leaf water potentials (Ψ L) in shorter and taller trees over a broad range of VPDs. The long-term stomatal limitation on photosynthesis, as inferred from leaf δ (13)C composition, was also greater in taller trees. The δ (13)C of wood indicated that the bulk of photosynthesis used to fuel wood production in the main trunk and branches occurred in the upper crown. L/S increased with tree height, especially after accounting for size-independent variation in crown structure across 27 trees up to 99.8 m tall. Despite greater stomatal limitation of leaf photosynthesis in taller trees, total L explained 95% of the variation in annual aboveground biomass growth among 15 trees measured for annual biomass growth increment in 2006. Our results support a theoretical model proposing that, in the face of increasing hydraulic constraints with height, whole-tree growth is maximized by a resource trade-off that increases L to maximize light capture rather than by reducing L/S to sustain g s.

Controlling factors of evaporation and CO2 flux over an open water lake in southeastern margin of Tibetan Plateau

NASA Astrophysics Data System (ADS)

Du, Q.; Liu, H.; Liu, Y.; Wang, L.; Xu, L.

2017-12-01

Erhai lake is located in the southeastern margin of Tibetan Plateau. Based on the 4 years measurement over Erhai lake with eddy covariance technique (EC) from 2012 to 2015, the diurnal and seasonal variations of latent and sensible heat and CO2 fluxes, and their controlling factors over different time scales were analyzed. The diurnal average LE ranged from 31 to 171 Wm-2, while Hs ranged from -31 to 21 Wm-2. Bowen ratio was larger during January and May and smaller during June and October. The lake continued storing heat during January and June, and releasing heat since July. The diurnal average CO2 fluxes during nighttime were higher than the daytime, and carbon uptake was almost observed during the midday time of the day for the whole study period. The annual carbon budget fluctuated from 117.5 to 161.7 g C m-2 a-1, while annual total evaporation (ET) from 1120.8 to 1228.5 mm for the four-years period. The Erhai Lake behaved as a net carbon source over the whole period but carbon uptake was observed during the middle time of each year. The difference between water surface and air temperature (DeltaT) and the product of DeltaT and wind speed were the main controlling factors for Hs from halfhourly to monthly scale. There was significant relationship between wind speed, the product of wind speed and vapor pressure deficit (VPD) and LE on halfhourly and daily scales. The total cloud amount and net radiation (Rn) had a large effect on monthly variation of LE. Photosynthetic active radiation (PAR) and wind speed was mainly responsible for the variation of halfhourly and daily CO2 fluxes, respectively. The total cloud amount was the most important factors controlling for annual total ET. The annual rainfall, water surface temperature was observed to be negatively related with annual CO2 fluxes.

Leaf morphology of 40 evergreen and deciduous broadleaved subtropical tree species and relationships to functional ecophysiological traits.

PubMed

Kröber, W; Heklau, H; Bruelheide, H

2015-03-01

We explored potential of morphological and anatomical leaf traits for predicting ecophysiological key functions in subtropical trees. We asked whether the ecophysiological parameters stomatal conductance and xylem cavitation vulnerability could be predicted from microscopy leaf traits. We investigated 21 deciduous and 19 evergreen subtropical tree species, using individuals of the same age and from the same environment in the Biodiversity-Ecosystem Functioning experiment at Jiangxi (BEF-China). Information-theoretic linear model selection was used to identify the best combination of morphological and anatomical predictors for ecophysiological functions. Leaf anatomy and morphology strongly depended on leaf habit. Evergreen species tended to have thicker leaves, thicker spongy and palisade mesophyll, more palisade mesophyll layers and a thicker subepidermis. Over 50% of all evergreen species had leaves with multi-layered palisade parenchyma, while only one deciduous species (Koelreuteria bipinnata) had this. Interactions with leaf habit were also included in best multi-predictor models for stomatal conductance (gs ) and xylem cavitation vulnerability. In addition, maximum gs was positively related to log ratio of palisade to spongy mesophyll thickness. Vapour pressure deficit (vpd) for maximum gs increased with the log ratio of palisade to spongy mesophyll thickness in species having leaves with papillae. In contrast, maximum specific hydraulic conductivity and xylem pressure at which 50% loss of maximum specific xylem hydraulic conductivity occurred (Ψ50 ) were best predicted by leaf habit and density of spongy parenchyma. Evergreen species had lower Ψ50 values and lower maximum xylem hydraulic conductivities. As hydraulic leaf and wood characteristics were reflected in structural leaf traits, there is high potential for identifying further linkages between morphological and anatomical leaf traits and ecophysiological responses. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

Immunity to polio, measles and rubella in women of child-bearing age and estimated congenital rubella syndrome incidence, Cambodia, 2012.

PubMed

Mao, B; Chheng, K; Wannemuehler, K; Vynnycky, E; Buth, S; Soeung, S C; Reef, S; Weldon, W; Quick, L; Gregory, C J

2015-07-01

Significant gaps in immunity to polio, measles, and rubella may exist in adults in Cambodia and threaten vaccine-preventable disease (VPD) elimination and control goals, despite high childhood vaccination coverage. We conducted a nationwide serological survey during November-December 2012 of 2154 women aged 15-39 years to assess immunity to polio, measles, and rubella and to estimate congenital rubella syndrome (CRS) incidence. Measles and rubella antibodies were detected by IgG ELISA and polio antibodies by microneutralization testing. Age-structured catalytic models were fitted to rubella serological data to predict CRS cases. Overall, 29.8% of women lacked immunity to at least one poliovirus (PV); seroprevalence to PV1, PV2 and PV3 was 85.9%, 93.4% and 83.3%, respectively. Rubella and measles antibody seroprevalence was 73.3% and 95.9%, respectively. In the 15-19 years age group, 48.2% [95% confidence interval (CI) 42.4-54.1] were susceptible to either PV1 or PV3, and 40.3% (95% CI 33.0-47.5) to rubella virus. Based on rubella antibody seroprevalence, we estimate that >600 infants are born with CRS in Cambodia annually. Significant numbers of Cambodian women are still susceptible to polio and rubella, especially those aged 15-19 years, emphasizing the need to include adults in VPD surveillance and a potential role for vaccination strategies targeted at adults.

Analysis of gas exchange, stomatal behaviour and micronutrients uncovers dynamic response and adaptation of tomato plants to monochromatic light treatments.

PubMed

O'Carrigan, Andrew; Babla, Mohammad; Wang, Feifei; Liu, Xiaohui; Mak, Michelle; Thomas, Richard; Bellotti, Bill; Chen, Zhong-Hua

2014-09-01

Light spectrum affects the yield and quality of greenhouse tomato, especially over a prolonged period of monochromatic light treatments. Physiological and chemical analysis was employed to investigate the influence of light spectral (blue, green and red) changes on growth, photosynthesis, stomatal behaviour, leaf pigment, and micronutrient levels. We found that plants are less affected under blue light treatment, which was evident by the maintenance of higher A, gs, Tr, and stomatal parameters and significantly lower VPD and Tleaf as compared to those plants grown in green and red light treatments. Green and red light treatments led to significantly larger increase in the accumulation of Fe, B, Zn, and Cu than blue light. Moreover, guard cell length, width, and volume all showed highly significant positive correlations to gs, Tr and negative links to VPD. There was negative impact of monochromatic lights-induced accumulation of Mn, Cu, and Zn on photosynthesis, leaf pigments and plant growth. Furthermore, most of the light-induced significant changes of the physiological traits were partially recovered at the end of experiment. A high degree of morphological and physiological plasticity to blue, green and red light treatments suggested that tomato plants may have developed mechanisms to adapt to the light treatments. Thus, understanding the optimization of light spectrum for photosynthesis and growth is one of the key components for greenhouse tomato production. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

WE-DE-BRA-01: SCIENCE COUNCIL JUNIOR INVESTIGATOR COMPETITION WINNER: Acceleration of a Limited-Angle Intrafraction Verification (LIVE) System Using Adaptive Prior Knowledge Based Image Estimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Y; Yin, F; Ren, L

Purpose: To develop an adaptive prior knowledge based image estimation method to reduce the scan angle needed in the LIVE system to reconstruct 4D-CBCT for intrafraction verification. Methods: The LIVE system has been previously proposed to reconstructs 4D volumetric images on-the-fly during arc treatment for intrafraction target verification and dose calculation. This system uses limited-angle beam’s eye view (BEV) MV cine images acquired from the treatment beam together with the orthogonally acquired limited-angle kV projections to reconstruct 4D-CBCT images for target verification during treatment. In this study, we developed an adaptive constrained free-form deformation reconstruction technique in LIVE to furthermore » reduce the scanning angle needed to reconstruct the CBCT images. This technique uses free form deformation with energy minimization to deform prior images to estimate 4D-CBCT based on projections acquired in limited angle (orthogonal 6°) during the treatment. Note that the prior images are adaptively updated using the latest CBCT images reconstructed by LIVE during treatment to utilize the continuity of patient motion.The 4D digital extended-cardiac-torso (XCAT) phantom was used to evaluate the efficacy of this technique with LIVE system. A lung patient was simulated with different scenario, including baseline drifts, amplitude change and phase shift. Limited-angle orthogonal kV and beam’s eye view (BEV) MV projections were generated for each scenario. The CBCT reconstructed by these projections were compared with the ground-truth generated in XCAT.Volume-percentage-difference (VPD) and center-of-mass-shift (COMS) were calculated between the reconstructed and the ground-truth tumors to evaluate the reconstruction accuracy. Results: Using orthogonal-view of 6° kV and BEV- MV projections, the VPD/COMS values were 12.7±4.0%/0.7±0.5 mm, 13.0±5.1%/0.8±0.5 mm, and 11.4±5.4%/0.5±0.3 mm for the three scenarios, respectively. Conclusion: The technique enables LIVE to accurately reconstruct 4D-CBCT images using only orthogonal 6° angle, which greatly improves the efficiency and reduces dose of LIVE for intrafraction verification.« less

A Technique for Generating Volumetric Cine-Magnetic Resonance Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, Wendy; Ren, Lei, E-mail: lei.ren@duke.edu; Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina

Purpose: The purpose of this study was to develop a techique to generate on-board volumetric cine-magnetic resonance imaging (VC-MRI) using patient prior images, motion modeling, and on-board 2-dimensional cine MRI. Methods and Materials: One phase of a 4-dimensional MRI acquired during patient simulation is used as patient prior images. Three major respiratory deformation patterns of the patient are extracted from 4-dimensional MRI based on principal-component analysis. The on-board VC-MRI at any instant is considered as a deformation of the prior MRI. The deformation field is represented as a linear combination of the 3 major deformation patterns. The coefficients of themore » deformation patterns are solved by the data fidelity constraint using the acquired on-board single 2-dimensional cine MRI. The method was evaluated using both digital extended-cardiac torso (XCAT) simulation of lung cancer patients and MRI data from 4 real liver cancer patients. The accuracy of the estimated VC-MRI was quantitatively evaluated using volume-percent-difference (VPD), center-of-mass-shift (COMS), and target tracking errors. Effects of acquisition orientation, region-of-interest (ROI) selection, patient breathing pattern change, and noise on the estimation accuracy were also evaluated. Results: Image subtraction of ground-truth with estimated on-board VC-MRI shows fewer differences than image subtraction of ground-truth with prior image. Agreement between normalized profiles in the estimated and ground-truth VC-MRI was achieved with less than 6% error for both XCAT and patient data. Among all XCAT scenarios, the VPD between ground-truth and estimated lesion volumes was, on average, 8.43 ± 1.52% and the COMS was, on average, 0.93 ± 0.58 mm across all time steps for estimation based on the ROI region in the sagittal cine images. Matching to ROI in the sagittal view achieved better accuracy when there was substantial breathing pattern change. The technique was robust against noise levels up to SNR = 20. For patient data, average tracking errors were less than 2 mm in all directions for all patients. Conclusions: Preliminary studies demonstrated the feasibility of generating real-time VC-MRI for on-board localization of moving targets in radiation therapy.« less

Biosphere-atmosphere Exchange of CO2 in a Subtropical Mangrove Wetland in Hong Kong

NASA Astrophysics Data System (ADS)

Liu, J.; Neogi, S.; Lai, D. Y. F.

2017-12-01

Mangrove ecosystems play an important role in the global carbon cycle due to their high primary productivity, carbon-rich sediment, and sensitivity to climate change. Yet, there is currently a paucity of studies that quantify the biosphere-atmosphere exchange of GHGs in mangrove wetlands continuously at the ecosystem level. In this study, the temporal variability of net ecosystem CO2 exchange (NEE) between the Kandelia obovata mangrove and the atmosphere was determined in the Mai Po Marshes Nature Reserve of subtropical Hong Kong using an eddy covariance system between February 2016 and January 2017. The daytime half-hourly NEE ranged between -5.0 and +3.3 µmol m-2 s-1, while the maximum nighttime NEE could reach +5.0 µmol m-2 s-1 during the wet, warm season. Temperature, photosynthetic photon flux density (PPFD), vapor pressure deficit (VPD), and surface water salinity were some key physical and hydrological controls of NEE. Tidal activity could also exert profound influence on CO2 fluxes in this mangrove ecosystem by exporting dissolved carbon to adjacent estuary and inhibiting soil respiration during the inundation period. Overall, this coastal mangrove was a net sink of atmospheric CO2. Our results suggest that the ability of subtropical mangrove ecosystems in sequestering CO2 could be highly dependent on future changes in temperature, precipitation, and salinity.

Predicting moisture dynamics of fine understory fuels in a moist tropical rainforest system: results of a pilot study undertaken to identify proxy variables useful for rating fire danger.

PubMed

Ray, David; Nepstad, Dan; Brando, Paulo

2010-08-01

*The use of fire as a land management tool in the moist tropics often has the unintended consequence of degrading adjacent forest, particularly during severe droughts. Reliable models of fire danger are needed to help mitigate these impacts. *Here, we studied the moisture dynamics of fine understory fuels in the east-central Brazilian Amazon during the 2003 dry season. Drying stations established under varying amounts of canopy cover (leaf area index (LAI) = 0 - 5.3) were subjected to a range of water inputs (5-15 mm) and models were developed to forecast litter moisture content (LMC). Predictions were then compared with independent field data. *A multiple linear regression relating litter moisture content to forest structure (LAI), ambient vapor pressure deficit (VPD(M)) and an index of elapsed time since a precipitation event (d(-1)) was identified as the best-fit model (adjusted R(2) = 0.89). Relative to the independent observations, model predictions were relatively unbiased when the LMC was

Color vision deficiency compensation for Visual Processing Disorder using Hardy-Rand-Rittler test and color transformation

NASA Astrophysics Data System (ADS)

Balbin, Jessie R.; Pinugu, Jasmine Nadja J.; Bautista, Joshua Ian C.; Nebres, Pauline D.; Rey Hipolito, Cipriano M.; Santella, Jose Anthony A.

2017-06-01

Visual processing skill is used to gather visual information from environment however, there are cases that Visual Processing Disorder (VPD) occurs. The so called visual figure-ground discrimination is a type of VPD where color is one of the factors that contributes on this type. In line with this, color plays a vital role in everyday living, but individuals that have limited and inaccurate color perception suffers from Color Vision Deficiency (CVD) and still not aware on their case. To resolve this case, this study focuses on the design of KULAY, a Head-Mounted Display (HMD) device that can assess whether a user has a CVD or not thru the standard Hardy-Rand-Rittler (HRR) test. This test uses pattern recognition in order to evaluate the user. In addition, color vision deficiency simulation and color correction thru color transformation is also a concern of this research. This will enable people with normal color vision to know how color vision deficient perceives and vice-versa. For the accuracy of the simulated HRR assessment, its results were validated thru an actual assessment done by a doctor. Moreover, for the preciseness of color transformation, Structural Similarity Index Method (SSIM) was used to compare the simulated CVD images and the color corrected images to other reference sources. The output of the simulated HRR assessment and color transformation shows very promising results indicating effectiveness and efficiency of the study. Thus, due to its form factor and portability, this device is beneficial in the field of medicine and technology.

Ten-year variability in ecosystem water use efficiency in an oak-dominated temperate forest under a warming climate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Jing; Chen, Jiquan; Sun, Ge

The impacts of extreme weather events on water-carbon (C) coupling and ecosystem-scale water use efficiency (WUE) over a long term are poorly understood. We analyzed the changes in ecosystem water use efficiency (WUE) from 10 years of eddy-covariance measurements (2004-2013) over an oak-dominated temperate forest in Ohio, USA. The aim was to investigate the long-term response of ecosystem WUE to measured changes in site-biophysical conditions and ecosystem attributes. The oak forest produced new plant biomass of 2.5 +/- 0.2 gC kg(-1) of water loss annually. Monthly evapotranspiration (ET) and gross ecosystem production (GEP) were tightly coupled over the 10-year studymore » period (R-2=0.94). Daily WUE had a linear relationship with air temperature (T-a) in low-temperature months and a unimodal relationship with T-a in high-temperature months during the growing season. On average, daily WUE ceased to increase when T-a exceeded 22 degrees C in warm months for both wet and dry years. Monthly WUE had a strong positive linear relationship with leaf area index (LAI), net radiation (R-n), and T-a and weak logarithmic relationship with water vapor pressure deficit (VPD) and precipitation (P) on a growing-season basis. When exploring the regulatory mechanisms on WUE within each season, spring LAI and P, summer R-n and T-a, and autumnal VPD and R-n were found to be the main explanatory variables for seasonal variation in WUE. The model developed in this study was able to capture 78% of growing-season variation in WUE on a monthly basis. The negative correlation between WUE and A in spring was mainly due to the high precipitation amounts in spring, decreasing GEP and WUE when LAI was still small, adding ET being observed to increase with high levels of evaporation as a result of high SWC in spring. Summer WUE had a significant decreasing trend across the 10 years mainly due to the combined effect of seasonal drought and increasing potential and available energy increasing ET, but decreasing GEP in summer. We concluded that seasonal dynamics of the interchange between precipitation and drought status of the system was an important variable in controlling seasonal WUE in wet years. In contrast, despite the negative impacts of unfavorable warming, available groundwater and an early start of the growing season were important contributing variables in high seasonal GEP, and thus, high seasonal WUE in dry years. (C) 2015 Elsevier B.V. All rights reserved.« less

An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM4.5)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raczka, Brett; Duarte, Henrique F.; Koven, Charles D.

Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO 2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. Wemore » distinguished between isotopic behavior in response to a decrease of δ 13C within atmospheric CO 2 (Suess effect) vs. photosynthetic discrimination (Δ canopy), by creating a site-customized atmospheric CO 2 and δ 13C of CO 2 time series. We implemented a seasonally varying V cmax model calibration that best matched site observations of net CO 2 carbon exchange, latent heat exchange, and biomass. The model accurately simulated observed δ 13C of needle and stem tissue, but underestimated the δ 13C of bulk soil carbon by 1–2 ‰. The model overestimated the multiyear (2006–2012) average Δ canopy relative to prior data-based estimates by 2–4 ‰. The amplitude of the average seasonal cycle of Δ canopy (i.e., higher in spring/fall as compared to summer) was correctly modeled but only when using a revised, fully coupled A n- g s (net assimilation rate, stomatal conductance) version of the model in contrast to the partially coupled A n- g s version used in the default model. The model attributed most of the seasonal variation in discrimination to A n, whereas interannual variation in simulated Δ canopy during the summer months was driven by stomatal response to vapor pressure deficit (VPD). The model simulated a 10 % increase in both photosynthetic discrimination and water-use efficiency (WUE) since 1850 which is counter to established relationships between discrimination and WUE. The isotope observations used here to constrain CLM suggest (1) the model overestimated stomatal conductance and (2) the default CLM approach to representing nitrogen limitation (partially coupled model) was not capable of reproducing observed trends in discrimination. These findings demonstrate that isotope observations can provide important information related to stomatal function driven by environmental stress from VPD and nitrogen limitation. Future versions of CLM that incorporate carbon isotope discrimination are likely to benefit from explicit inclusion of mesophyll conductance.« less

An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM4.5)

DOE PAGES

Raczka, Brett; Duarte, Henrique F.; Koven, Charles D.; ...

2016-09-19

Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO 2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. Wemore » distinguished between isotopic behavior in response to a decrease of δ 13C within atmospheric CO 2 (Suess effect) vs. photosynthetic discrimination (Δ canopy), by creating a site-customized atmospheric CO 2 and δ 13C of CO 2 time series. We implemented a seasonally varying V cmax model calibration that best matched site observations of net CO 2 carbon exchange, latent heat exchange, and biomass. The model accurately simulated observed δ 13C of needle and stem tissue, but underestimated the δ 13C of bulk soil carbon by 1–2 ‰. The model overestimated the multiyear (2006–2012) average Δ canopy relative to prior data-based estimates by 2–4 ‰. The amplitude of the average seasonal cycle of Δ canopy (i.e., higher in spring/fall as compared to summer) was correctly modeled but only when using a revised, fully coupled A n- g s (net assimilation rate, stomatal conductance) version of the model in contrast to the partially coupled A n- g s version used in the default model. The model attributed most of the seasonal variation in discrimination to A n, whereas interannual variation in simulated Δ canopy during the summer months was driven by stomatal response to vapor pressure deficit (VPD). The model simulated a 10 % increase in both photosynthetic discrimination and water-use efficiency (WUE) since 1850 which is counter to established relationships between discrimination and WUE. The isotope observations used here to constrain CLM suggest (1) the model overestimated stomatal conductance and (2) the default CLM approach to representing nitrogen limitation (partially coupled model) was not capable of reproducing observed trends in discrimination. These findings demonstrate that isotope observations can provide important information related to stomatal function driven by environmental stress from VPD and nitrogen limitation. Future versions of CLM that incorporate carbon isotope discrimination are likely to benefit from explicit inclusion of mesophyll conductance.« less

Ten-year variability in ecosystem water use efficiency in an oak-dominated temperate forest under a warming climate

DOE PAGES

Xie, Jing; Chen, Jiquan; Sun, Ge; ...

2016-01-07

The impacts of extreme weather events on water-carbon (C) coupling and ecosystem-scale water use efficiency (WUE) over a long term are poorly understood. We analyzed the changes in ecosystem water use efficiency (WUE) from 10 years of eddy-covariance measurements (2004-2013) over an oak-dominated temperate forest in Ohio, USA. The aim was to investigate the long-term response of ecosystem WUE to measured changes in site-biophysical conditions and ecosystem attributes. The oak forest produced new plant biomass of 2.5 +/- 0.2 gC kg(-1) of water loss annually. Monthly evapotranspiration (ET) and gross ecosystem production (GEP) were tightly coupled over the 10-year studymore » period (R-2=0.94). Daily WUE had a linear relationship with air temperature (T-a) in low-temperature months and a unimodal relationship with T-a in high-temperature months during the growing season. On average, daily WUE ceased to increase when T-a exceeded 22 degrees C in warm months for both wet and dry years. Monthly WUE had a strong positive linear relationship with leaf area index (LAI), net radiation (R-n), and T-a and weak logarithmic relationship with water vapor pressure deficit (VPD) and precipitation (P) on a growing-season basis. When exploring the regulatory mechanisms on WUE within each season, spring LAI and P, summer R-n and T-a, and autumnal VPD and R-n were found to be the main explanatory variables for seasonal variation in WUE. The model developed in this study was able to capture 78% of growing-season variation in WUE on a monthly basis. The negative correlation between WUE and A in spring was mainly due to the high precipitation amounts in spring, decreasing GEP and WUE when LAI was still small, adding ET being observed to increase with high levels of evaporation as a result of high SWC in spring. Summer WUE had a significant decreasing trend across the 10 years mainly due to the combined effect of seasonal drought and increasing potential and available energy increasing ET, but decreasing GEP in summer. We concluded that seasonal dynamics of the interchange between precipitation and drought status of the system was an important variable in controlling seasonal WUE in wet years. In contrast, despite the negative impacts of unfavorable warming, available groundwater and an early start of the growing season were important contributing variables in high seasonal GEP, and thus, high seasonal WUE in dry years. (C) 2015 Elsevier B.V. All rights reserved.« less

International Workshop on Condensed Matter Theories (13th) Held in Campos do Jordao, Brazil on August 1989

DTIC Science & Technology

1990-01-01

Pdc(rlr 2 r)][Pc-(r’) + Pdco (rr.rl)] (2) The two- and three-point irreducible exchange functions Paf, and Pa.- are clas- sified according to the...r, r2r’) l(ri rI )PdCI(rI r~r’) + Perde(r r2r’ ) + PVdc(r r’ ) grter,) - VPd(rl r2 r’ ) Pdco (r’ r 2 ri) - vPCC(r)Pdc.(r’r2r,) - vPc(r’)Pdc(r~r2r’)I

A technique for estimating 4D-CBCT using prior knowledge and limited-angle projections.

PubMed

Zhang, You; Yin, Fang-Fang; Segars, W Paul; Ren, Lei

2013-12-01

To develop a technique to estimate onboard 4D-CBCT using prior information and limited-angle projections for potential 4D target verification of lung radiotherapy. Each phase of onboard 4D-CBCT is considered as a deformation from one selected phase (prior volume) of the planning 4D-CT. The deformation field maps (DFMs) are solved using a motion modeling and free-form deformation (MM-FD) technique. In the MM-FD technique, the DFMs are estimated using a motion model which is extracted from planning 4D-CT based on principal component analysis (PCA). The motion model parameters are optimized by matching the digitally reconstructed radiographs of the deformed volumes to the limited-angle onboard projections (data fidelity constraint). Afterward, the estimated DFMs are fine-tuned using a FD model based on data fidelity constraint and deformation energy minimization. The 4D digital extended-cardiac-torso phantom was used to evaluate the MM-FD technique. A lung patient with a 30 mm diameter lesion was simulated with various anatomical and respirational changes from planning 4D-CT to onboard volume, including changes of respiration amplitude, lesion size and lesion average-position, and phase shift between lesion and body respiratory cycle. The lesions were contoured in both the estimated and "ground-truth" onboard 4D-CBCT for comparison. 3D volume percentage-difference (VPD) and center-of-mass shift (COMS) were calculated to evaluate the estimation accuracy of three techniques: MM-FD, MM-only, and FD-only. Different onboard projection acquisition scenarios and projection noise levels were simulated to investigate their effects on the estimation accuracy. For all simulated patient and projection acquisition scenarios, the mean VPD (±S.D.)∕COMS (±S.D.) between lesions in prior images and "ground-truth" onboard images were 136.11% (±42.76%)∕15.5 mm (±3.9 mm). Using orthogonal-view 15°-each scan angle, the mean VPD∕COMS between the lesion in estimated and "ground-truth" onboard images for MM-only, FD-only, and MM-FD techniques were 60.10% (±27.17%)∕4.9 mm (±3.0 mm), 96.07% (±31.48%)∕12.1 mm (±3.9 mm) and 11.45% (±9.37%)∕1.3 mm (±1.3 mm), respectively. For orthogonal-view 30°-each scan angle, the corresponding results were 59.16% (±26.66%)∕4.9 mm (±3.0 mm), 75.98% (±27.21%)∕9.9 mm (±4.0 mm), and 5.22% (±2.12%)∕0.5 mm (±0.4 mm). For single-view scan angles of 3°, 30°, and 60°, the results for MM-FD technique were 32.77% (±17.87%)∕3.2 mm (±2.2 mm), 24.57% (±18.18%)∕2.9 mm (±2.0 mm), and 10.48% (±9.50%)∕1.1 mm (±1.3 mm), respectively. For projection angular-sampling-intervals of 0.6°, 1.2°, and 2.5° with the orthogonal-view 30°-each scan angle, the MM-FD technique generated similar VPD (maximum deviation 2.91%) and COMS (maximum deviation 0.6 mm), while sparser sampling yielded larger VPD∕COMS. With equal number of projections, the estimation results using scattered 360° scan angle were slightly better than those using orthogonal-view 30°-each scan angle. The estimation accuracy of MM-FD technique declined as noise level increased. The MM-FD technique substantially improves the estimation accuracy for onboard 4D-CBCT using prior planning 4D-CT and limited-angle projections, compared to the MM-only and FD-only techniques. It can potentially be used for the inter/intrafractional 4D-localization verification.

Factors Related to Pertussis and Tetanus Vaccination Status Among Foreign-Born Adults Living in the United States.

PubMed

Sánchez-González, Liliana; Rodriguez-Lainz, Alfonso; O'Halloran, Alissa; Rowhani-Rahbar, Ali; Liang, Jennifer L; Lu, Peng-Jun; Houck, Peter M; Verguet, Stephane; Williams, Walter W

2017-06-01

Pertussis is a common vaccine-preventable disease (VPD) worldwide. Its reported incidence has increased steadily in the United States, where it is endemic. Tetanus is a rare but potentially fatal VPD. Foreign-born adults have lower tetanus-diphtheria-pertussis (Tdap) and tetanus-diphtheria (Td) vaccination coverage than do U.S.-born adults. We studied the association of migration-related, socio-demographic, and access-to-care factors with Tdap and Td vaccination among foreign-born adults living in the United States. The 2012 and 2013 National Health Interview Survey data for foreign-born respondents were analyzed. Multivariable logistic regression was conducted to calculate prevalence ratios and 95% confidence intervals, and to identify variables independently associated with Tdap and Td vaccination among foreign-born adults. Tdap and Td vaccination status was available for 9316 and 12,363 individuals, respectively. Overall vaccination coverage was 9.1% for Tdap and 49.8% for Td. Younger age, higher education, having private health insurance (vs. public insurance or uninsured), having visited a doctor in the previous year, and region of residence were independently associated with Tdap and Td vaccination. Among those reporting a doctor visit, two-thirds had not received Tdap. This study provides further evidence of the need to enhance access to health care and immunization services and reduce missed opportunities for Tdap and Td vaccination for foreign-born adults in the United States. These findings apply to all foreign-born, irrespective of their birthplace, citizenship, language and years of residence in the United States. Addressing vaccination disparities among the foreign-born will help achieve national vaccination goals and protect all communities in the United States.

Diagnosing subtle palatal anomalies: Validation of video-analysis and assessment protocol for diagnosing occult submucous cleft palate.

PubMed

Rourke, Ryan; Weinberg, Seth M; Marazita, Mary L; Jabbour, Noel

2017-09-01

Submucous cleft palate (SMCP) classically involves bifid uvula, zona pellucida, and notched hard palate. However, patients may present with more subtle anatomic abnormalities. The ability to detect these abnormalities is important for surgeons managing velopharyngeal dysfunction (VPD) or considering adenoidectomy. Validate an assessment protocol for diagnosis of occult submucous cleft palate (OSMCP) and identify physical examination features present in patients with OSMCP in the relaxed and activated palate positions. Study participants included patients referred to a pediatric VPD clinic with concern for hypernasality or SMCP. Using an appropriately encrypted iPod touch, transoral video was obtained for each patient with the palate in the relaxed and activated positions. The videos were reviewed by two otolaryngologists in normal speed and slow-motion, as needed, and a questionnaire was completed by each reviewer pertaining to the anatomy and function of the palate. 47 patients, with an average age of 4.6 years, were included in the study over a one-year period. Four videos were unusable due to incomplete view of the palate. The most common palatal abnormality noted was OSMCP, diagnosed by each reviewer in 26/43 and 30/43 patients respectively. Using the assessment protocol, agreement on palatal diagnosis was 83.7% (kappa = 0.68), indicating substantial agreement, with the most prevalent anatomic features being vaulted palate elevation (96%) and visible notching of hard palate (75%). The diagnosis of subtle palatal anomalies is difficult and can be subjective. Using the proposed video-analysis method and assessment protocol may improve reliability of diagnosis of OSMCP. Copyright © 2017 Elsevier B.V. All rights reserved.

Productivity and CO2 exchange of Great Plains ecoregions. I. Shortgrass steppe: Flux tower estimates

USGS Publications Warehouse

Gilmanov, Tagir G.; Morgan, Jack A.; Hanan, Niall P.; Wylie, Bruce K.; Rajan, Nithya; Smith, David P.; Howard, Daniel M.

2017-01-01

The shortgrass steppe (SGS) occupies the southwestern part of the Great Plains. Half of the land is cultivated, but significant areas remain under natural vegetation. Despite previous studies of the SGS carbon cycle, not all aspects have been completely addressed, including gross productivity, ecosystem respiration, and ecophysiological parameters. Our analysis of 1998 − 2007 flux tower measurements at five Bowen ratio–energy balance (BREB) and three eddy covariance (EC) sites characterized seasonal and interannual variability of gross photosynthesis and ecosystem respiration. Identification of the nonrectangular hyperbolic equation for the diurnal CO2 exchange, with vapor pressure deficit (VPD) limitation and exponential temperature response, quantified quantum yield α, photosynthetic capacity Amax, and respiration rate rd with variation ranges (19 \\< α \\< 51 mmol mol− 1, 0.48 \\< Amax \\< 2.1 mg CO2 m− 2 s− 1, 0.15 \\< rd \\< 0.49 mg CO2 m− 2 s− 1). Gross photosynthesis varied from 1 100 to 2 700 g CO2 m− 2 yr− 1, respiration from 900 to 3,000 g CO2 m− 2 yr− 1, and net ecosystem production from − 900 to + 700 g CO2 m− 2 yr− 1, indicating that SGS may switch from a sink to a source depending on weather. Comparison of the 2004 − 2006 measurements at two BREB and two parallel EC flux towers located at comparable SGS sites showed moderately higher photosynthesis, lower respiration, and higher net production at the BREB than EC sites. However, the difference was not related only to methodologies, as the normalized difference vegetation index at the BREB sites was higher than at the EC sites. Overall magnitudes and seasonal patterns at the BREB and the EC sites during the 3-yr period were similar, with trajectories within the ± 1.5 standard deviation around the mean of the four sites and mostly reflecting the effects of meteorology.

Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico

NASA Astrophysics Data System (ADS)

Brienen, Roel J. W.; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

2013-12-01

Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ18Otr). Interannual variation in δ18Otr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ13C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ18Otr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18O-depleted rain in the region and seem to have affected the δ18Otr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ18Otr of M. acantholoba can be used as a proxy for source water δ18O and that interannual variation in δ18Oprec is caused by a regional amount effect. This contrasts with δ18O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in disentangling the processes influencing precipitation δ18O.

Preliminary Modelling of Mass Flux at the Surface of Plant Leaves within the MELiSSA Higher Plant Compartments

NASA Astrophysics Data System (ADS)

Holmberg, Madeleine; Paille, Christel; Lasseur, Christophe

The ESA project Micro Ecological Life Support System Alternative (MELiSSA) is an ecosystem of micro-organisms and higher plants, constructed with the objective of being operated as a tool to understand artificial ecosystems to be used for a long-term or permanent manned planetary base (e.g. Moon or Mars). The purpose of such a system is to provide for generation of food, water recycling, atmospheric regeneration and waste management within defined standards of quality and reliability. As MELiSSA consists of individual compartments which are connected to each other, the robustness of the system is fully dependent on the control of each compartment, as well as the flow management between them. Quality of consumables and reliability of the ecosystem rely on the knowledge, understanding and control of each of the components. This includes the full understanding of all processes related to the higher plants. To progress in that direction, this paper focuses on the mechanical processes driving the gas and liquid exchanges between the plant leaf and its environment. The process responsible for the mass transfer on the surface of plant leaves is diffusion. The diffusion flux is dependent on the behaviour of the stoma of the leaf and also on the leaf boundary layer (BL). In this paper, the physiology of the leaf is briefly examined in order to relate parameters such as light quality, light quantity, CO2 concentration, temperature, leaf water potential, humidity, vapour pressure deficit (VPD) gradients and pollutants to the opening or closing of stomata. The diffusion process is described theoretically and the description is compared to empirical approaches. The variables of the BL are examined and the effect airflow in the compartment has on the BL is investigated. Also presented is the impact changes in different environmental parameters may have on the fluid exchanges. Finally, some tests, to evaluate the accuracy of the concluded model, are suggested.

Clover as a tool for bioindication of phytotoxic ozone--5 years of experience from southern Sweden--consequences for the short-term critical levels.

PubMed

Karlsson, Gunilla Pihl; Karlsson, Per Erik; Danielsson, Helena; Pleijel, Håkan

2003-01-01

Critical levels (CLs) for ozone effects on plants in Europe have been defined within the UN-ECE Convention on Long-Range Transboundary Air Pollution, CLRTAP. The purpose of the short-term CLs is to ensure protection of all crops to acute ozone injury. The currently used CLs are based on the ozone exposure of the plants during daylight hours expressed as AOT40 (Accumulated exposure Over the Threshold 40 nmol mol(-1) ozone). The aims of this study were: to test the performance of the current short-term CLs, to test alternative ozone exposure indices and to test if changes in the ozone cut-off concentration, the inclusion of a lag-period (LP) between exposure and identification of visible ozone injury or the duration of the ozone integration period improved the performance of the exposure index. The analysis was based on 38 different datasets from experiments with subterranean clover, Trifolium subterraneum in southern Sweden. AOT indices generally performed better than averaged ozone concentrations or SUM (Sum of ozone concentrations when a threshold is exceeded) indices. Regression analysis showed that the current short-term CL, AOT40 with a VPD (water vapour pressure deficit) threshold of 1.5 kPa, explained 56% of the variation in visible injury. A longer exposure period and the introduction of a LP, admitting visible ozone injury time to develop after exposure, improved the performance of the exposure index. AOT30 accumulated over 10 days before harvest, excluding a LP of 3 days before injury observation, performed best and explained 88% of the variation in visible injury. AOT40 indices left a rather large amount of visible injury unexplained indicating that a lower cut-off concentration for ozone is preferable. The results of the investigation indicated that a visible injury threshold of 10% improved the distinction between harmful and less harmful exposure. Copyright 2002 Elsevier Science B.V.

Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico

PubMed Central

Brienen, Roel J W; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

2013-01-01

[1] Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ18Otr). Interannual variation in δ18Otr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ13C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ18Otr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18O-depleted rain in the region and seem to have affected the δ18Otr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ18Otr of M. acantholoba can be used as a proxy for source water δ18O and that interannual variation in δ18Oprec is caused by a regional amount effect. This contrasts with δ18O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in disentangling the processes influencing precipitation δ18O. PMID:26213660

Vegetation canopy and physiological control of GPP decline during drought and heat wave

NASA Astrophysics Data System (ADS)

Zhang, Y.; Xiao, X.; Zhou, S.; McCarthy, H. R.; Ciais, P.; Luo, Y.

2015-12-01

Different vegetation indices derived from satellites were often used as a proxy of vegetation activity to monitor and evaluate the impacts of drought and heat wave on ecosystem carbon fluxes (gross primary production, respiration) through the production efficiency models (PEMs). However, photosynthesis is also regulated by a series of physiological processes which cannot be directly observed through satellites. In this study, we analyzed the response of drought and heat wave induced GPP and climate anomaly from 15 Euroflux sites and the corresponding vegetation indices from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. Correlation analysis suggests that the vegetation indices are more responsive to GPP variation in grasslands and open shrublands, but less responsive in forest ecosystems. Physiology control can be up to 20% of the total GPP during the drought period without changing the canopy structure. At temporal scale for each site, VPD and vegetation indices can be used to track the GPP for forest and non-forest, respectively. However, different stand characteristics should be taken into consideration for forest ecosystems. Based on the above findings, a conceptual model is built to illuminate the physiological and canopy control on the GPP during the drought period. Improvement for future PEMs should incorporate better indicators to deal with drought conditions for different ecosystems.

Cadmium sulfide solar cells

NASA Technical Reports Server (NTRS)

Stanley, A. G.

1975-01-01

Development, fabrication and applications of CdS solar cells are reviewed in detail. The suitability of CdS cells for large solar panels and microcircuitry, and their low cost, are emphasized. Developments are reviewed by manufacturer-developer. Vapor phase deposition of thin-film solar cells, doping and co-evaporation, sputtering, chemical spray, and sintered layers are reviewed, in addition to spray deposition, monograin layer structures, and silk screening. Formation of junctions by electroplating, evaporation, brushing, CuCl dip, and chemiplating are discussed, along with counterelectrode fabrication, VPD film structures, the Cu2S barrier layer, and various photovoltaic effects (contact photovoltage, light intensity variation, optical enhancement), and various other CdS topics.

TU-AB-BRA-09: A Novel Method of Generating Ultrafast Volumetric Cine MRI (VC-MRI) Using Prior 4D-MRI and On-Board Phase-Skipped Encoding Acquisition for Radiotherapy Target Localization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, C; Yin, F; Harris, W

Purpose: To develop a technique generating ultrafast on-board VC-MRI using prior 4D-MRI and on-board phase-skipped encoding k-space acquisition for real-time 3D target tracking of liver and lung radiotherapy. Methods: The end-of-expiration (EOE) volume in 4D-MRI acquired during the simulation was selected as the prior volume. 3 major respiratory deformation patterns were extracted through the principal component analysis of the deformation field maps (DFMs) generated between EOE and all other phases. The on-board VC-MRI at each instant was considered as a deformation of the prior volume, and the deformation was modeled as a linear combination of the extracted 3 major deformationmore » patterns. To solve the weighting coefficients of the 3 major patterns, a 2D slice was extracted from VC-MRI volume to match with the 2D on-board sampling data, which was generated by 8-fold phase skipped-encoding k-space acquisition (i.e., sample 1 phase-encoding line out of every 8 lines) to achieve an ultrafast 16–24 volumes/s frame rate. The method was evaluated using XCAT digital phantom to simulate lung cancer patients. The 3D volume of end-ofinhalation (EOI) phase at the treatment day was used as ground-truth onboard VC-MRI with simulated changes in 1) breathing amplitude and 2) breathing amplitude/phase change from the simulation day. A liver cancer patient case was evaluated for in-vivo feasibility demonstration. Results: The comparison between ground truth and estimated on-board VC-MRI shows good agreements. In XCAT study with changed breathing amplitude, the volume-percent-difference(VPD) between ground-truth and estimated tumor volumes at EOI was 6.28% and the Center-of-Mass-Shift(COMS) was 0.82mm; with changed breathing amplitude and phase, the VPD was 8.50% and the COMS was 0.54mm. The study of liver patient case also demonstrated a promising in vivo feasibility of the proposed method Conclusion: Preliminary results suggest the feasibility to estimate ultrafast VC-MRI for on-board target localization with phase skipped-encoding k-space acquisition. Research grant from NIH R01-184173.« less

Canopy transpiration of two black locust (Robinia pseudoacacia) plantations with different ages in semi-arid Loess Plateau, China

NASA Astrophysics Data System (ADS)

Jiao, L.

2015-12-01

Black locust (Robinia pseudoacacia) was widely planted to control soil erosion and restore degraded ecosystem in Loess Plateau. The water use of the plantations was concerned due to its potential effects on hydrological cycle and regional water resource. Although some studies estimated canopy transpiration (Ec) of the mature black locust plantation, variation in Ec in plantations with different ages was not clear. In this study, we selected two plantations with different ages (12 years and 27 years, denoted as young stand and mature stand, respectively) in similar topographical conditions in Yangjuangou catchment in the central of Loess Plateau. Sap flux density (Fd) and tree biometrics were measured in each stand during the growing season in 2014. Soil water content (SWC) in each plot and meteorological variables in the catchment were simultaneously monitored. Tree transpiration (Et) was derived from Fd and tree sapwood area (As). Canopy transpiration (Ec) was estimated by a product of mean stand sap flux density (Js) and stand total sapwood area (AST). The mean Fd of mature trees was 2-fold larger than that of young trees.However, tree-to-tree variation in Fd among sampled trees within mature stand was evident compared to that within young stand. Mean Et in mature stand was higher than that in young stand. Ec in mature stand was significant higher than that in young stand,with cumulative value of 54 mm and 27 mm respectively. This is attributed to higher Js in mature stand although AST in young is slightly higher than that in mature stand. The patterns of daily Ec during the growing season were similar in both stands during the study period. A exponential saturation model can explain the responses of Ec to vapor deficit pressure (VPD) and solar radiation (Rs) in both stands.The relationship between Ec and SWC was not detected. Our finding suggested that stand age should be taken into consideration when estimated vegetation water use in this region. Further researches on variations in Ec of black locust plantations along a chronosequence and responses of Ec to drought should be conducted to provide useful information on water resource and forest managements in this region.

Transpirational water use and its regulation in the mountainous terrain of S. Korea

NASA Astrophysics Data System (ADS)

Otieno Dennis, O.; Eunyoung, J.; Sinkyu, K.; Tenhunen, J. D.

2009-12-01

Quantifying water use by forests growing on complex mountainous terrain is difficult and understanding of controls on water use by these forests a challenge. Yet mountains are crucial as water towers and better understanding of their hydrology and ecology is critical for sustainable management. Consequently, there is a growing need for new research approaches designed with attention to the particular needs and constraints of large-scale studies and that have the potential to generate reliable and accurate data. The use of a combination of different sapflow-measurement techniques provides a unique opportunity to monitor water use by the understory and canopy forest tree species at micro-scale, allowing for accurate estimation of total forest water use. The obtained data, in conjunction with intensively measured climatic variables, allow for better understanding and interpretation of transpiration results. A research initiative under the International Training Group: Complex Terrain and Ecological Heterogeneity (TERRECO) seeks to address pertinent issues related to forest water use and production in complex terrain. Stem Heat balance (SHB) and Heat Dissipation techniques have been employed to measure sapflow in the understory woody plants and tree branches and on stems of canopy trees respectively. Measurements have been stratified to account for differences in tree sizes and species diversity. To better understand the data, we are intensively monitoring soil moisture at 5, 10 and 30 cm depths, in addition to a range of micrometeorology sensors that have been set up below, within and above the canopy. These measurements have been planned, taking into account altitudinal/elevation gradient, aspect and within site differences in species composition and tree sizes and to generate data for large-scale modeling of the entire catchment. A total of 70 trees from 9 species growing in six different locations at varying elevations and aspects are being monitored. Peak daily water use by trees during mid summer amounts to 45 kg d-1 but varies significantly with sapwood area. Within a species, there is a consistent relationship between tree size (DBH) and sapwood area irrespective of elevation. We have also established a common trend in the relationship between wood density and sap flux density (Js) that transcends the boundaries of species differences. These initial findings are critical for our planned upscaling of water use by the forest catchment. In addition to soil moisture, vapor pressure deficit (VPD) and light play a crucial regulatory role on forest water use. We are at the stage of establishing a common link that brings together micrometeorology and transpiration that will allow for large scale modeling of forest water use.

Polycrystalline lead selenide: the resurgence of an old infrared detector

NASA Astrophysics Data System (ADS)

Vergara, G.; Montojo, M. T.; Torquemada, M. C.; Rodrigo, M. T.; Sánchez, F. J.; Gómez, L. J.; Almazán, R. M.; Verdú, M.; Rodríguez, P.; Villamayor, V.; Álvarez, M.; Diezhandino, J.; Plaza, J.; Catalán, I.

2007-06-01

The existing technology for uncooled MWIR photon detectors based on polycrystalline lead salts is stigmatized for being a 50-year-old technology. It has been traditionally relegated to single-element detectors and relatively small linear arrays due to the limitations imposed by its standard manufacture process based on a chemical bath deposition technique (CBD) developed more than 40 years ago. Recently, an innovative method for processing detectors, based on a vapour phase deposition (VPD) technique, has allowed manufacturing the first 2D array of polycrystalline PbSe with good electro optical characteristics. The new method of processing PbSe is an all silicon technology and it is compatible with standard CMOS circuitry. In addition to its affordability, VPD PbSe constitutes a perfect candidate to fill the existing gap in the photonic and uncooled IR imaging detectors sensitive to the MWIR photons. The perspectives opened are numerous and very important, converting the old PbSe detector in a serious alternative to others uncooled technologies in the low cost IR detection market. The number of potential applications is huge, some of them with high commercial impact such as personal IR imagers, enhanced vision systems for automotive applications and other not less important in the security/defence domain such as sensors for active protection systems (APS) or low cost seekers. Despite the fact, unanimously accepted, that uncooled will dominate the majority of the future IR detection applications, today, thermal detectors are the unique plausible alternative. There is plenty of room for photonic uncooled and complementary alternatives are needed. This work allocates polycrystalline PbSe in the current panorama of the uncooled IR detectors, underlining its potentiality in two areas of interest, i.e., very low cost imaging IR detectors and MWIR fast uncooled detectors for security and defence applications. The new method of processing again converts PbSe into an emerging technology.

Observations Illustrating the Use of Health Informatics to Link Public Health Immunization Registries and Pharmacies to Increase Adult Immunization Rates and Improve Population Health Outcomes.

PubMed

Popovich, Michael; Altstadter, Brandy; Popovich, Lara Hargraves

2016-01-01

The Health Information Technology for Economic and Clinical Health (HITECH) Act encourages health information exchange between clinical care and public health through Meaningful Use measures. Meaningful Use specifically identifies objectives to support a number of public health programs including immunizations, cancer registries, syndromic surveillance, and disease case reports. The objective is to improve public and population health. Stage 2 of Meaningful Use focused on compliance to sending of information to public health. The next phase focuses on bi-directional information exchange to support immunization intelligence and to empower providers, pharmacists, and the consumer. The HITECH Act Stage 2 initiative provided incentive and motivation for healthcare providers to encourage their Electronic Medical Record (EMR) vendors to implement data exchanges with public health, with the expected result being timely awareness of health risks. The empowerment nugget in the HITECH Act is not in the compliance reporting to public health. The nugget is the ability for a provider to receive relevant information on the patient or consumer currently in front of them or to those they will connect to through their outreach efforts. The ability for public health to retain current immunization records of individuals from a variety of providers supports their program goals to increase immunization rates and mitigate the risk of vaccine-preventable disease (VPD). The ability for providers to receive at the point of service more complete immunization histories integrated with decision support enhances their delivery of care, thereby reducing the risk of VPD to their patients. Indirectly payers benefit through healthcare cost savings and when the focus is expanded from a health model to a business model, there are significant return on investment (ROI) opportunities that exponentially increase the value of a bi-directional immunization data exchange. This paper will provide descriptions of case examples to demonstrate the value of electronic data exchanges when pharmacy immunization providers and public health work together.

Expanding poliomyelitis and measles surveillance networks to establish surveillance for acute meningitis and encephalitis syndromes--Bangladesh, China, and India, 2006-2008.

PubMed

2012-12-14

Quality surveillance is critical to the control and elimination of vaccine-preventable diseases (VPDs). A key strategy for enhancing VPD surveillance, outlined in the World Health Organization (WHO) Global Framework for Immunization Monitoring and Surveillance (GFIMS), is to expand and link existing VPD surveillance systems (particularly those developed for polio eradication and measles elimination) to include other priority VPDs. Since the launch of the Global Polio Eradication Initiative in 1988, the incidence of polio has decrease by 99% worldwide. A cornerstone of this success is a sensitive surveillance system based on the rapid and timely reporting of all acute flaccid paralysis (AFP) cases in children aged <15 years, with confirmatory diagnostic testing performed by laboratories that are part of a global network. As countries achieve polio-free status, many have expanded syndromic surveillance to include persons with rash and fever, and have built measles diagnostic capacity in existing polio reference laboratories. Acute meningitis/encephalitis syndrome (AMES) and acute encephalitis syndrome (AES) are candidates for expanded surveillance because they are most often caused by VPDs of public health importance for which confirmatory laboratory tests exist. Vaccine-preventable cases of encephalitis include approximately 68,000 Japanese encephalitis (JE) cases, resulting in 13,000-20,000 deaths each year in Asia. Moreover, although bacterial meningitis incidence in Asia is not as well-documented, pneumococcal and meningococcal meningitis outbreaks have been reported in Bangladesh and China, and the incidence of Haemophilus influenzae type b (Hib) meningitis in children aged <5 years in India has been estimated to be 7.1 per 100,000 population, similar to that in European countries before the introduction of vaccine. This report describes a prototype for expanding existing polio and measles surveillance networks in Bangladesh, China, and India to include surveillance for viral and bacterial vaccine-preventable causes of AMES and AES and presents data from 2006-2008.

Differences in estimating terrestrial water flux from three satellite-based Priestley-Taylor algorithms

NASA Astrophysics Data System (ADS)

Yao, Yunjun; Liang, Shunlin; Yu, Jian; Zhao, Shaohua; Lin, Yi; Jia, Kun; Zhang, Xiaotong; Cheng, Jie; Xie, Xianhong; Sun, Liang; Wang, Xuanyu; Zhang, Lilin

2017-04-01

Accurate estimates of terrestrial latent heat of evaporation (LE) for different biomes are essential to assess energy, water and carbon cycles. Different satellite- based Priestley-Taylor (PT) algorithms have been developed to estimate LE in different biomes. However, there are still large uncertainties in LE estimates for different PT algorithms. In this study, we evaluated differences in estimating terrestrial water flux in different biomes from three satellite-based PT algorithms using ground-observed data from eight eddy covariance (EC) flux towers of China. The results reveal that large differences in daily LE estimates exist based on EC measurements using three PT algorithms among eight ecosystem types. At the forest (CBS) site, all algorithms demonstrate high performance with low root mean square error (RMSE) (less than 16 W/m2) and high squared correlation coefficient (R2) (more than 0.9). At the village (HHV) site, the ATI-PT algorithm has the lowest RMSE (13.9 W/m2), with bias of 2.7 W/m2 and R2 of 0.66. At the irrigated crop (HHM) site, almost all models algorithms underestimate LE, indicating these algorithms may not capture wet soil evaporation by parameterization of the soil moisture. In contrast, the SM-PT algorithm shows high values of R2 (comparable to those of ATI-PT and VPD-PT) at most other (grass, wetland, desert and Gobi) biomes. There are no obvious differences in seasonal LE estimation using MODIS NDVI and LAI at most sites. However, all meteorological or satellite-based water-related parameters used in the PT algorithm have uncertainties for optimizing water constraints. This analysis highlights the need to improve PT algorithms with regard to water constraints.

Irrigated plantations and their effect on energy fluxes in a semi-arid region of Israel - a validated 3-D model simulation

NASA Astrophysics Data System (ADS)

Branch, O.; Warrach-Sagi, K.; Wulfmeyer, V.; Cohen, S.

2013-11-01

A large irrigated biomass plantation was simulated in an arid region of Israel within the WRF-NOAH coupled atmospheric/land surface model in order to assess land surface atmosphere feedbacks. Simulations were carried out for the 2012 summer season (JJA). The irrigated plantations were simulated by prescribing tailored land surface and soil/plant parameters, and by implementing a newly devised, controllable sub-surface irrigation scheme within NOAH. Two model cases studies were considered and compared - Impact and Control. Impact simulates a hypothetical 10 km × 10 km irrigated plantation. Control represents a baseline and uses the existing land surface data, where the predominant land surface type in the area is bare desert soil. Central to the study is model validation against observations collected for the study over the same period. Surface meteorological and soil observations were made at a desert site and from a 400 ha Simmondsia chinensis (Jojoba) plantation. Control was validated with data from the desert, and Impact from the Jojoba. Finally, estimations were made of the energy balance, applying two Penman-Monteith based methods along with observed meteorological data. These estimations were compared with simulated energy fluxes. Control simulates the daytime desert surface 2 m air temperatures (T2) with less than 0.2 °C deviation and the vapour pressure deficit (VPD) to within 0.25 hPa. Desert wind speed (U) is simulated to within 0.5 m s-1 and the net surface radiation (Rn) to 25 W m-2. Soil heat flux (G) is not so accurately simulated by Control (up to 30 W m-2 deviation) and 5 cm soil temperatures (ST5) are simulated to within 1.5 °C. Impact simulates daytime T2 over irrigated vegetation to within 1-1.5 °C, the VPD to 0.5 hPa, Rn to 50 W m-2 and ST5 to within 2 °C. Simulated Impact G deviates up to 40 W m-2, highlighting a need for re-parameterisation or better soil classification, but the overall contribution to the energy balance is small (5-6%). During the night, significant T2 and ST5 cold biases of 2-4 °C are present. Diurnal latent heat values from WRF Impact correspond closely with Penman-Monteith estimation curves, and latent heat magnitudes of 160 W m-2 over the plantation are usual. Simulated plantation sensible heat fluxes are high (450 W m-2) - around 100-110 W m-2 higher than over the surrounding desert. The high relative HFX over the vegetation, driven by high Rn and high surface resistances, indicate that low Bowen ratios should not necessarily be assumed when irrigated plantations are implemented in, and optimized for arid regions. Furthermore, the high plantation T2 magnitudes highlight the importance of considering diurnal dynamics, which drive the evolution of boundary layers, rather than only on daily mean statistics which often indicate an irrigation cooling effect.

Sap flux-scaled transpiration by tamarisk (Tamarix spp.) before, during and after episodic defoliation by the saltcedar leaf beetle (Diorhabda carinulata)

USGS Publications Warehouse

Hultine, K.R.; Nagler, P.L.; Morino, K.; Bush, S.E.; Burtch, K.G.; Dennison, P.E.; Glenn, E.P.; Ehleringer, J.R.

2010-01-01

The release of the saltcedar beetle (Diorhabda carinulata) has resulted in the periodic defoliation of tamarisk (Tamarix spp.) along more than 1000 river km in the upper Colorado River Basin and is expected to spread along many other river reaches throughout the upper basin, and possibly into the lower Colorado River Basin. Identifying the impacts of these release programs on tamarisk water use and subsequent water cycling in arid riparian systems are largely unknown, due in part to the difficulty of measuring water fluxes in these systems. We used lab-calibrated, modified heat-dissipation sap flux sensors to monitor tamarisk water use (n=20 trees) before, during and after defoliation by the saltcedar leaf beetle during the 2008 and 2009 growing seasons (May-October) in southeastern Utah. We incorporated a simple model that related mean stem sap flux density (Js) with atmospheric vapor pressure deficit (vpd) before the onset of defoliation in 2008. The model was used to calculate differences between predicted Js and Js measured throughout the two growing seasons. Episodic defoliation resulted in a 16% reduction in mean annual rates of Js in both 2008 and 2009, with decreases occurring only during the periods in which the trees were defoliated (about 6-8 weeks per growing season). In other words, rates of Js rebounded to values predicted by the model when the trees produced new leaves after defoliation. Sap flux data were scaled to stand water use by constructing a tamarisk-specific allometric equation to relate conducting sapwood area to stem diameter, and by measuring the size distribution of stems within the stand. Total water use in both years was 0.224m, representing a reduction of about 0.04myr-1. Results showed that repeated defoliation/refoliation cycles did not result in a progressive decrease in either leaf production or water use over the duration of the study. This investigation improves ground-based estimates of tamarisk water use, and will support future efforts to characterize impacts of the beetle on basin-wide hydrologic processes. ?? 2010 Elsevier B.V.

Gap-filling methods to impute eddy covariance flux data by preserving variance.

NASA Astrophysics Data System (ADS)

Kunwor, S.; Staudhammer, C. L.; Starr, G.; Loescher, H. W.

2015-12-01

To represent carbon dynamics, in terms of exchange of CO2 between the terrestrial ecosystem and the atmosphere, eddy covariance (EC) data has been collected using eddy flux towers from various sites across globe for more than two decades. However, measurements from EC data are missing for various reasons: precipitation, routine maintenance, or lack of vertical turbulence. In order to have estimates of net ecosystem exchange of carbon dioxide (NEE) with high precision and accuracy, robust gap-filling methods to impute missing data are required. While the methods used so far have provided robust estimates of the mean value of NEE, little attention has been paid to preserving the variance structures embodied by the flux data. Preserving the variance of these data will provide unbiased and precise estimates of NEE over time, which mimic natural fluctuations. We used a non-linear regression approach with moving windows of different lengths (15, 30, and 60-days) to estimate non-linear regression parameters for one year of flux data from a long-leaf pine site at the Joseph Jones Ecological Research Center. We used as our base the Michaelis-Menten and Van't Hoff functions. We assessed the potential physiological drivers of these parameters with linear models using micrometeorological predictors. We then used a parameter prediction approach to refine the non-linear gap-filling equations based on micrometeorological conditions. This provides us an opportunity to incorporate additional variables, such as vapor pressure deficit (VPD) and volumetric water content (VWC) into the equations. Our preliminary results indicate that improvements in gap-filling can be gained with a 30-day moving window with additional micrometeorological predictors (as indicated by lower root mean square error (RMSE) of the predicted values of NEE). Our next steps are to use these parameter predictions from moving windows to gap-fill the data with and without incorporation of potential driver variables of the parameters traditionally used. Then, comparisons of the predicted values from these methods and 'traditional' gap-filling methods (using 12 fixed monthly windows) will be assessed to show the scale of preserving variance. Further, this method will be applied to impute artificially created gaps for analyzing if variance is preserved.

Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico.

PubMed

Brienen, Roel J W; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

2013-12-01

[1] Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings ( δ 18 O tr ). Interannual variation in δ 18 O tr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ 13 C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ 18 O tr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18 O-depleted rain in the region and seem to have affected the δ 18 O tr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ 18 O tr of M . acantholoba can be used as a proxy for source water δ 18 O and that interannual variation in δ 18 O prec is caused by a regional amount effect. This contrasts with δ 18 O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in disentangling the processes influencing precipitation δ 18 O.

The effect of fluoroalkylsilanes on tribological properties and wettability of Si-DLC coatings

NASA Astrophysics Data System (ADS)

Bystrzycka, E.; Prowizor, M.; Piwoński, I.; Kisielewska, A.; Batory, D.; Jędrzejczak, A.; Dudek, M.; Kozłowski, W.; Cichomski, M.

2018-03-01

Silicon-containing diamond-like carbon (Si-DLC) coatings were prepared on silicon wafers by Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) method using methane/hexamethyl-disiloxane atmosphere. Herein, we report that Si-DLC coatings can be effectively modified by fluoroalkylsilanes which results in significant enhancement of frictional and wettability properties. Two types of fluoroalkylsilanes differing in the length of fluorocarbon chains were deposited on Si-DLC coatings with the use of Vapor Phase Deposition (VPD) method. The chemical composition of Si-DLC coatings and effectiveness of modification with fluoroalkylsilanes were confirmed by Fourier Transform Infrared Spectroscopy (FTIR) and x-ray Photoelectron Spectroscopy (XPS). Frictional properties in microscale were investigated with the use of ball-on-flat apparatus operating at millinewton (mN) load range. It was found that the presence of silicon enhances the chemisorption of fluoroalkylsilanes on Si-DLC coatings by creating adsorption anchoring centers. In consequence, a decrease of adhesion and an increase of hydrophobicity along with a decrease of coefficient of friction were observed. Experimental results indicate, that tribological properties are correlated with dispersive and acid-base components of the surface free energy as well as with the work of adhesion.

A comparison of coupled biogeophysical and biogeochemical dynamics across a precipitation gradient in Oregon using data assimilation

NASA Astrophysics Data System (ADS)

Pettijohn, J. C.; Law, B. E.; Williams, M. D.; Stoekli, R.; Thornton, P. E.; Thomas, C. K.; Hudiburg, T. W.; Martin, J.

2010-12-01

We present results from our coupled biophysical - biochemical model data fusion (MDF) analysis across a climatic gradient in Oregon, USA, using data from a coast-range Douglas-fir (US-Fir; 2006-2008) and a semi-arid ponderosa pine (US-Me2; 2002-2008) AmeriFlux site. Our MDF scheme couples the Ensemble Kalman Filter (EnKF) with the National Center for Atmospheric Research (NCAR) Community Land Model with Carbon-Nitrogen coupling (CLM-CN, version 3.5). Assimilated data includes continuous eddy covariance measurements of forest-atmosphere CO2 (NEE, net ecosystem exchange) and water vapor fluxes (λE, latent heat flux), chamber-based soil respiratory flux, soil moisture and temperature, snow depth (US-Me2), MODIS-derived 8 day LAI, and carbon and nitrogen pools. We quantify the ecosystem carbon and nitrogen budgets, partition NEE and λE fluxes, and thus increase confidence in multi-scale controls on CO2 and water vapor exchange. The MDF did a better job predicting NEE than λE at both sites (r2 = 0.86 for NEE at both sites; λE r2 = 0.65 and 0.63 at the US-ME2 and US-Fir sites, respectively) partly due to a weighting scheme we prescribed for NEE. The distribution of carbon and nitrogen differed significantly between sites, with total ecosystem carbon (vegetation, detritus, soil) of the US-Fir site being about 1.4 times higher than the US-Me2 site (35 kg C m-2 vs. 25 kg C m-2). Mean NEE over overlapping water years ‘07-‘08 was -495 gC m-2 at the US-Me2 site as opposed to -809 gC m-2 at the US-Fir site, nearly a two-fold difference in C uptake across this precipitation gradient. Average GPP and ecosystem respiration (Re) over these two water years were both ~1.7x greater at the US-Fir site, with 1712 gC m^-2 and 1217 gC m-2, respectively, at the US-Me2 site vs. 2841 gC m-2 and 2032 gC m-2 at the US-Fir. Autotrophic respiration contributed 79% and 72% to the Re flux at the US-Me2 and US-Fir sites, respectively, with total soil respiration contributing 53% and 58% to Re. While a comparison of observed and MDF environmental response functions suggests both root-zone soil moisture and leaf-to-air VPD photosynthetic controls at both sites, the MDF did not impose CLM-CN’s soil stress upon photosynthesis at the US-Fir site, suggesting the apparent soil moisture response arises from correlations with other driving variables such as VPD. In summary, we demonstrate that MDF analysis can help constrain coupled ecosystem carbon and water dynamics by combining long-term ecosystem measurements by incorporating necessary measurement and model uncertainties.

Responses of ecosystem water use efficiency to spring snow and summer water addition with or without nitrogen addition in a temperate steppe

PubMed Central

Zhai, Penghui; Huang, Jianhui; Zhao, Xiang; Dong, Kuanhu

2018-01-01

Water use efficiency (WUE) is an important indicator of ecosystem functioning but how ecosystem WUE responds to climate change including precipitation and nitrogen (N) deposition increases is still unknown. To investigate such responses, an experiment with a randomized block design with water (spring snowfall or summer water addition) and nitrogen addition was conducted in a temperate steppe of northern China. We investigated net ecosystem CO2 production (NEP), gross ecosystem production (GEP) and evapotranspiration (ET) to calculate ecosystem WUE (WUEnep = NEP/ET or WUEgep = GEP/ET) under spring snow and summer water addition with or without N addition from 2011 to 2013. The results showed that spring snow addition only had significant effect on ecosystem WUE in 2013 and summer water addition showed positive effect on ecosystem WUE in 2011 and 2013, as their effects on NEP and GEP is stronger than ET. N addition increased ecosystem WUE in 2012 and 2013 both in spring snow addition and summer water addition for its increasing effects on NEP and GEP but no effect on ET. Summer water addition had less but N addition had greater increasing effects on ecosystem WUE as natural precipitation increase indicating that natural precipitation regulates ecosystem WUE responses to water and N addition. Moreover, WUE was tightly related with atmospheric vapor-pressure deficit (VPD), photosynthetic active radiation (PAR), precipitation and soil moisture indicating the regulation of climate drivers on ecosystem WUE. In addition, it also was affected by aboveground net primary production (ANPP). The study suggests that ecosystem WUE responses to water and N addition is determined by the change in carbon process rather than that in water process, which are regulated by climate change in the temperate steppe of northern China. PMID:29529082

Responses of ecosystem water use efficiency to spring snow and summer water addition with or without nitrogen addition in a temperate steppe.

PubMed

Zhang, Xiaolin; Zhai, Penghui; Huang, Jianhui; Zhao, Xiang; Dong, Kuanhu

2018-01-01

Water use efficiency (WUE) is an important indicator of ecosystem functioning but how ecosystem WUE responds to climate change including precipitation and nitrogen (N) deposition increases is still unknown. To investigate such responses, an experiment with a randomized block design with water (spring snowfall or summer water addition) and nitrogen addition was conducted in a temperate steppe of northern China. We investigated net ecosystem CO2 production (NEP), gross ecosystem production (GEP) and evapotranspiration (ET) to calculate ecosystem WUE (WUEnep = NEP/ET or WUEgep = GEP/ET) under spring snow and summer water addition with or without N addition from 2011 to 2013. The results showed that spring snow addition only had significant effect on ecosystem WUE in 2013 and summer water addition showed positive effect on ecosystem WUE in 2011 and 2013, as their effects on NEP and GEP is stronger than ET. N addition increased ecosystem WUE in 2012 and 2013 both in spring snow addition and summer water addition for its increasing effects on NEP and GEP but no effect on ET. Summer water addition had less but N addition had greater increasing effects on ecosystem WUE as natural precipitation increase indicating that natural precipitation regulates ecosystem WUE responses to water and N addition. Moreover, WUE was tightly related with atmospheric vapor-pressure deficit (VPD), photosynthetic active radiation (PAR), precipitation and soil moisture indicating the regulation of climate drivers on ecosystem WUE. In addition, it also was affected by aboveground net primary production (ANPP). The study suggests that ecosystem WUE responses to water and N addition is determined by the change in carbon process rather than that in water process, which are regulated by climate change in the temperate steppe of northern China.

Climate impact on the tree growth, vigor and productivity in Siberia

NASA Astrophysics Data System (ADS)

Kharuk, V.; Im, S.; Petrov, I.; Dvinskaya, M.

2017-12-01

Changing climate has an impact on the Siberian taiga forests. We analyzed GPP and NPP trends, growth index, and stands mortality within the Central Siberia (48°- 75°N/80°-115°E). Considered forests included larch-dominant (Larix sibirica, L. dahurica) and "dark needle conifer" (DNC: Abies sibirica, Pinus sibirica, Picea obovata) stands. GPP and NPP trends calculated based on the Terra/MODIS products. Growth index calculations based on dendrochronology data. Water stress analysis based on the gravimetric and microwave satellite data and MERRA-2 database. Analyzed variables included precipitation, air temperature, VPD, drought index SPEI, and root zone wetness. We found positive GPP trends within majority (>90%) of larch-dominant and DNC ranges, whereas NPP trends are positive on the <40% territory. Negative NPP trends correlated with growth index within key-sites. Siberian pine and fir growth index increase since late 1970th, turning to depression since late 1980th. Within permafrost zone larch growth correlated with sum of positive (t>+10C°) temperatures and vegetation period length. During recent years larch experience water stress in the beginning of vegetation period. Tree decline and mortality observed within DNC stands, and that phenomenon regularly coincided with zones of negative NPP trends. Mortality correlated with VPD, SPEI, and root zone moisture content. Bark beetles (including aggressive species Polygraphus proximus, similar to Dendroctonus ponderosae in American forests) attacked water-stressed trees. Geographically, mortality began on the margins of the DNC range (e.g., within the forest-steppe ecotone) and on terrain features with maximal water stress risk (narrow-shaped hilltops, convex steep south facing slopes, shallow well-drained soils). Currently, Siberian pine and fir decline observed within southern range of these species. In addition, air temperature and aridity increase promotes Siberian silkmoth (Dendrolimus sibiricus) outbreak that occurred about one degree northward of formerly range. Observing and predicting aridity increase will lead to the replacement of Siberian pine and fir within southern range of these species with more tolerant species (e.g., Pinus sylvestris, Larix spp.).

Declining trends in exposures to harmful policing among people who inject drugs in Vancouver, Canada.

PubMed

Landsberg, Adina; Kerr, Thomas; Milloy, Michael-John; Dong, Huiru; Nguyen, Paul; Wood, Evan; Hayashi, Kanna

2016-01-01

In 2006, the Vancouver Police Department (VPD) developed an organization-wide drug policy approach, which included endorsing harm reduction strategies for people who inject drugs (PWID). We sought to examine rates of potentially harmful policing exposures and associated HIV risk behaviour among PWID in Vancouver, Canada before and after the VPD policy change. Data were derived from two prospective cohort studies of PWID. Multivariable generalized estimating equation models were used to examine changes in the risk of confiscation of drug use paraphernalia and physical violence by the police, as well as changes in the relationship between exposures to the two policing practices and sharing of drug use paraphernalia, before and after the policy change. Among 2193 participants, including 757 (34.5%) women, the rates of experiencing police confiscation of drug use paraphernalia declined from 22.3% in 2002 to 2.8% in 2014, and the rates of reporting experiencing physical violence by the police also declined from 14.1% in 2004 to 2.9% in 2014. In multivariable analyses, the post-policy change period remained independently and negatively associated with reports of confiscation of drug use paraphernalia (adjusted odds ratio (AOR): 0.25; 95% confidence interval (CI): 0.21 to 0.31) and reported physical violence by the police (AOR: 0.76; 95% CI: 0.63 to 0.91). However, experiencing both confiscation of drug use paraphernalia and physical violence by the police (AOR: 1.92; 95% CI: 1.10 to 3.33) and experiencing only confiscation of drug use paraphernalia (AOR: 1.71; 95% CI: 1.34 to 2.19) remained independently and positively associated with sharing of drug use paraphernalia during the post-policy change period. In our study, two policing practices known to increase HIV risk among PWID have declined significantly since the local police launched an evidence-based drug policy approach. However, these practices remained independently associated with elevated HIV risk after the post-policy change. Although there remains a continued need to ensure that policing activities do not undermine public health efforts, these findings demonstrate that a major shift towards a public health approach to policing is possible for a municipal police force.

Synergistic Ecoclimate Teleconnections from Forest Loss in Different Regions Structure Global Ecological Responses.

PubMed

Garcia, Elizabeth S; Swann, Abigail L S; Villegas, Juan C; Breshears, David D; Law, Darin J; Saleska, Scott R; Stark, Scott C

2016-01-01

Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates of deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia's GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. Our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change.

A framework for incorporating the effects of hydrodynamic stresses on forest photosynthesis and evaporation

NASA Astrophysics Data System (ADS)

Matheny, A. M.; Bohrer, G.; Thompsen, J.; Frasson, R.; Frasson, C. D.; Ivanov, V. Y.

2012-12-01

Hydraulic limitations are known to control transpiration in forest ecosystems when the soil is drying or when the vapor pressure deficit between the air and stomata (VPD) is very large, but they can also impact stomatal apertures under conditions of adequate soil moisture and lower evaporative demand. We use the NACP flux measurements and models dataset for multiple site/model intercomparisons to evaluate the degree to which currently un-resolved high-frequency (sub-daily) hydrodynamic stresses affect the error in model prediction of latent heat flux. We find that many site-model combinations are characterized by a typical pattern of overestimation of afternoon flux and a corresponding underestimation of pre-noon flux. We hypothesize that this pattern is a result of un-resolved afternoon stomata closure due to hydrodynamic stresses. In a forest plot at the University of Michigan Biological Station, we use measurements of leaf-level stomata conductance and water potential to demonstrate that trees of similar type - mid-late successional deciduous trees - have very different hydrodynamic strategies that lead to differences in their temporal patterns of stomata conductance. We found that red oak trees continue transpiring despite a large stem-water deficit while red maple trees regulate stomata to maintain a high water potential. Red oaks, which are ring porous, are also able to access more soil water, assumingly from deeper ground layers and have higher conductivity, compared with the maples, which are diffuse porous. These differences will lead to large differences in stomata conductance and water use based on the species composition of the forest. We also demonstrate that the size and shape of the tree stem-branch system may lead to differences in the extent of hydrodynamic stress, which may change the forest respiration patterns as the forest grows and ages. We propose a framework to resolve tree hydrodynamics in global and regional models. It is based on the Finite-Elements Tree-Crown Hydrodynamics model (FETCH) combined with a statistical functional-type/hydraulic-type/size representation of the trees in the forest. Lidar and multi-spectral images of the forest can be used to obtain numerical distributions of species and size of individual tree crowns needed to initialize such simulations. FETCH simulates water flow through the tree as a simplified system of porous media conduits. It explicitly resolves spatiotemporal hydraulic stresses throughout the tree's hydraulic system that cannot be easily represented using other stomatal-conductance models. It uses a physical representation of water flow in a 3-D tree-stem-branch system assuming the xylem is a porous media. Empirical equations relate water potential at the branch-tips to stomata conductance at leaves connected to these branches. FETCH calculates the hydrodynamic stress related closure of stomata, provided the atmospheric and biological variables from the global model, and could replace the current empirical formulation for stomata adjustment based on soil moisture.

Expansion of Surveillance for Vaccine-preventable Diseases: Building on the Global Polio Laboratory Network and the Global Measles and Rubella Laboratory Network Platforms.

PubMed

Mulders, Mick N; Serhan, Fatima; Goodson, James L; Icenogle, Joseph; Johnson, Barbara W; Rota, Paul A

2017-07-01

Laboratory networks were established to provide accurate and timely laboratory confirmation of infections, an essential component of disease surveillance systems. The World Health Organization (WHO) coordinates global laboratory surveillance of vaccine-preventable diseases (VPDs), including polio, measles and rubella, yellow fever, Japanese encephalitis, rotavirus, and invasive bacterial diseases. In addition to providing high-quality laboratory surveillance data to help guide disease control, elimination, and eradication programs, these global networks provide capacity-building and an infrastructure for public health laboratories. There are major challenges with sustaining and expanding the global laboratory surveillance capacity: limited resources and the need for expansion to meet programmatic goals. Here, we describe the WHO-coordinated laboratory networks supporting VPD surveillance and present a plan for the further development of these networks. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America.

Fast uncooled module 32×32 array of polycrystalline PbSe used for muzzle flash detection

NASA Astrophysics Data System (ADS)

Kastek, Mariusz; Dulski, Rafał; Trzaskawka, Piotr; Bieszczad, Grzegorz

2011-06-01

The paper presents some aspects of muzzle flash detection using low resolution polycrystalline PbSe uncooled 32×32 detectors array. This system for muzzle flash detection works in MWIR (3 - 5 microns) region and it is based on VPD (Vapor Phase Deposition) technology. The low density uncooled 32×32 array is suitable for being used in low cost IR imagers sensitive in the MWIR band with frame rates exceeding 1.000 Hz. The FPA detector, read-out electronics and processing electronics (allowing the implementation of some algorithms for muzzle flash detection) has been presented. The system has been tested at field test ground. Results of detection range measurement with two types of optical systems (wide and narrow field of view) have been shown. The initial results of testing of some algorithms for muzzle flash detection have been also presented.

Image acquisition optimization of a limited-angle intrafraction verification (LIVE) system for lung radiotherapy.

PubMed

Zhang, Yawei; Deng, Xinchen; Yin, Fang-Fang; Ren, Lei

2018-01-01

Limited-angle intrafraction verification (LIVE) has been previously developed for four-dimensional (4D) intrafraction target verification either during arc delivery or between three-dimensional (3D)/IMRT beams. Preliminary studies showed that LIVE can accurately estimate the target volume using kV/MV projections acquired over orthogonal view 30° scan angles. Currently, the LIVE imaging acquisition requires slow gantry rotation and is not clinically optimized. The goal of this study is to optimize the image acquisition parameters of LIVE for different patient respiratory periods and gantry rotation speeds for the effective clinical implementation of the system. Limited-angle intrafraction verification imaging acquisition was optimized using a digital anthropomorphic phantom (XCAT) with simulated respiratory periods varying from 3 s to 6 s and gantry rotation speeds varying from 1°/s to 6°/s. LIVE scanning time was optimized by minimizing the number of respiratory cycles needed for the four-dimensional scan, and imaging dose was optimized by minimizing the number of kV and MV projections needed for four-dimensional estimation. The estimation accuracy was evaluated by calculating both the center-of-mass-shift (COMS) and three-dimensional volume-percentage-difference (VPD) between the tumor in estimated images and the ground truth images. The robustness of LIVE was evaluated with varied respiratory patterns, tumor sizes, and tumor locations in XCAT simulation. A dynamic thoracic phantom (CIRS) was used to further validate the optimized imaging schemes from XCAT study with changes of respiratory patterns, tumor sizes, and imaging scanning directions. Respiratory periods, gantry rotation speeds, number of respiratory cycles scanned and number of kV/MV projections acquired were all positively correlated with the estimation accuracy of LIVE. Faster gantry rotation speed or longer respiratory period allowed less respiratory cycles to be scanned and less kV/MV projections to be acquired to estimate the target volume accurately. Regarding the scanning time minimization, for patient respiratory periods of 3-4 s, gantry rotation speeds of 1°/s, 2°/s, 3-6°/s required scanning of five, four, and three respiratory cycles, respectively. For patient respiratory periods of 5-6 s, the corresponding respiratory cycles required in the scan changed to four, three, and two cycles, respectively. Regarding the imaging dose minimization, for patient respiratory periods of 3-4 s, gantry rotation speeds of 1°/s, 2-4°/s, 5-6°/s required acquiring of 7, 5, 4 kV and MV projections, respectively. For patient respiratory periods of 5-6 s, 5 kV and 5 MV projections are sufficient for all gantry rotation speeds. The optimized LIVE system was robust against breathing pattern, tumor size and tumor location changes. In the CIRS study, the optimized LIVE system achieved the average center-of-mass-shift (COMS)/volume-percentage-difference (VPD) of 0.3 ± 0.1 mm/7.7 ± 2.0% for the scanning time priority case, 0.2 ± 0.1 mm/6.1 ± 1.2% for the imaging dose priority case, respectively, among all gantry rotation speeds tested. LIVE was robust against different scanning directions investigated. The LIVE system has been preliminarily optimized for different patient respiratory periods and treatment gantry rotation speeds using digital and physical phantoms. The optimized imaging parameters, including number of respiratory cycles scanned and kV/MV projection numbers acquired, provide guidelines for optimizing the scanning time and imaging dose of the LIVE system for its future evaluations and clinical implementations through patient studies. © 2017 American Association of Physicists in Medicine.

Declining trends in exposures to harmful policing among people who inject drugs in Vancouver, Canada

PubMed Central

Landsberg, Adina; Kerr, Thomas; Milloy, Michael-John; Dong, Huiru; Nguyen, Paul; Wood, Evan; Hayashi, Kanna

2016-01-01

Introduction In 2006, the Vancouver Police Department (VPD) developed an organization-wide drug policy approach, which included endorsing harm reduction strategies for people who inject drugs (PWID). We sought to examine rates of potentially harmful policing exposures and associated HIV risk behaviour among PWID in Vancouver, Canada before and after the VPD policy change. Methods Data were derived from two prospective cohort studies of PWID. Multivariable generalized estimating equation models were used to examine changes in the risk of confiscation of drug use paraphernalia and physical violence by the police, as well as changes in the relationship between exposures to the two policing practices and sharing of drug use paraphernalia, before and after the policy change. Results Among 2193 participants, including 757 (34.5%) women, the rates of experiencing police confiscation of drug use paraphernalia declined from 22.3% in 2002 to 2.8% in 2014, and the rates of reporting experiencing physical violence by the police also declined from 14.1% in 2004 to 2.9% in 2014. In multivariable analyses, the post-policy change period remained independently and negatively associated with reports of confiscation of drug use paraphernalia (adjusted odds ratio (AOR): 0.25; 95% confidence interval (CI): 0.21 to 0.31) and reported physical violence by the police (AOR: 0.76; 95% CI: 0.63 to 0.91). However, experiencing both confiscation of drug use paraphernalia and physical violence by the police (AOR: 1.92; 95% CI: 1.10 to 3.33) and experiencing only confiscation of drug use paraphernalia (AOR: 1.71; 95% CI: 1.34 to 2.19) remained independently and positively associated with sharing of drug use paraphernalia during the post-policy change period. Conclusions In our study, two policing practices known to increase HIV risk among PWID have declined significantly since the local police launched an evidence-based drug policy approach. However, these practices remained independently associated with elevated HIV risk after the post-policy change. Although there remains a continued need to ensure that policing activities do not undermine public health efforts, these findings demonstrate that a major shift towards a public health approach to policing is possible for a municipal police force. PMID:27435707

Under-vaccinated groups in Europe and their beliefs, attitudes and reasons for non-vaccination; two systematic reviews.

PubMed

Fournet, N; Mollema, L; Ruijs, W L; Harmsen, I A; Keck, F; Durand, J Y; Cunha, M P; Wamsiedel, M; Reis, R; French, J; Smit, E G; Kitching, A; van Steenbergen, J E

2018-01-30

Despite effective national immunisation programmes in Europe, some groups remain incompletely or un-vaccinated ('under-vaccinated'), with underserved minorities and certain religious/ideological groups repeatedly being involved in outbreaks of vaccine preventable diseases (VPD). Gaining insight into factors regarding acceptance of vaccination of 'under-vaccinated groups' (UVGs) might give opportunities to communicate with them in a trusty and reliable manner that respects their belief system and that, maybe, increase vaccination uptake. We aimed to identify and describe UVGs in Europe and to describe beliefs, attitudes and reasons for non-vaccination in the identified UVGs. We defined a UVG as a group of persons who share the same beliefs and/or live in socially close-knit communities in Europe and who have/had historically low vaccination coverage and/or experienced outbreaks of VPDs since 1950. We searched MEDLINE, EMBASE and PsycINFO databases using specific search term combinations. For the first systematic review, studies that described a group in Europe with an outbreak or low vaccination coverage for a VPD were selected and for the second systematic review, studies that described possible factors that are associated with non-vaccination in these groups were selected. We selected 48 articles out of 606 and 13 articles out of 406 from the first and second search, respectively. Five UVGs were identified in the literature: Orthodox Protestant communities, Anthroposophists, Roma, Irish Travellers, and Orthodox Jewish communities. The main reported factors regarding vaccination were perceived non-severity of traditional "childhood" diseases, fear of vaccine side-effects, and need for more information about for example risk of vaccination. Within each UVG identified, there are a variety of health beliefs and objections to vaccination. In addition, similar factors are shared by several of these groups. Communication strategies regarding these similar factors such as educating people about the risks associated with being vaccinated versus not being vaccinated, addressing their concerns, and countering vaccination myths present among members of a specific UVG through a trusted source, can establish a reliable relationship with these groups and increase their vaccination uptake. Furthermore, other interventions such as improving access to health care could certainly increase vaccination uptake in Roma and Irish travellers.

Accelerating volumetric cine MRI (VC-MRI) using undersampling for real-time 3D target localization/tracking in radiation therapy: a feasibility study

NASA Astrophysics Data System (ADS)

Harris, Wendy; Yin, Fang-Fang; Wang, Chunhao; Zhang, You; Cai, Jing; Ren, Lei

2018-01-01

Purpose. To accelerate volumetric cine MRI (VC-MRI) using undersampled 2D-cine MRI to provide real-time 3D guidance for gating/target tracking in radiotherapy. Methods. 4D-MRI is acquired during patient simulation. One phase of the prior 4D-MRI is selected as the prior images, designated as MRIprior. The on-board VC-MRI at each time-step is considered a deformation of the MRIprior. The deformation field map is represented as a linear combination of the motion components extracted by principal component analysis from the prior 4D-MRI. The weighting coefficients of the motion components are solved by matching the corresponding 2D-slice of the VC-MRI with the on-board undersampled 2D-cine MRI acquired. Undersampled Cartesian and radial k-space acquisition strategies were investigated. The effects of k-space sampling percentage (SP) and distribution, tumor sizes and noise on the VC-MRI estimation were studied. The VC-MRI estimation was evaluated using XCAT simulation of lung cancer patients and data from liver cancer patients. Volume percent difference (VPD) and Center of Mass Shift (COMS) of the tumor volumes and tumor tracking errors were calculated. Results. For XCAT, VPD/COMS were 11.93  ±  2.37%/0.90  ±  0.27 mm and 11.53  ±  1.47%/0.85  ±  0.20 mm among all scenarios with Cartesian sampling (SP  =  10%) and radial sampling (21 spokes, SP  =  5.2%), respectively. When tumor size decreased, higher sampling rate achieved more accurate VC-MRI than lower sampling rate. VC-MRI was robust against noise levels up to SNR  =  20. For patient data, the tumor tracking errors in superior-inferior, anterior-posterior and lateral (LAT) directions were 0.46  ±  0.20 mm, 0.56  ±  0.17 mm and 0.23  ±  0.16 mm, respectively, for Cartesian-based sampling with SP  =  20% and 0.60  ±  0.19 mm, 0.56  ±  0.22 mm and 0.42  ±  0.15 mm, respectively, for radial-based sampling with SP  =  8% (32 spokes). Conclusions. It is feasible to estimate VC-MRI from a single undersampled on-board 2D cine MRI. Phantom and patient studies showed that the temporal resolution of VC-MRI can potentially be improved by 5-10 times using a 2D cine image acquired with 10-20% k-space sampling.

Synergistic Ecoclimate Teleconnections from Forest Loss in Different Regions Structure Global Ecological Responses

PubMed Central

Garcia, Elizabeth S.; Swann, Abigail L. S.; Villegas, Juan C.; Breshears, David D.; Law, Darin J.; Saleska, Scott R.; Stark, Scott C.

2016-01-01

Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates of deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia’s GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. Our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change. PMID:27851740

Habitat moisture is an important driver of patterns of sap flow and water balance in tropical montane cloud forest epiphytes.

PubMed

Darby, Alexander; Draguljić, Danel; Glunk, Andrew; Gotsch, Sybil G

2016-10-01

Microclimate in the tropical montane cloud forest (TMCF) is variable on both spatial and temporal scales and can lead to large fluctuations in both leaf-level transpiration and whole plant water use. While variation in transpiration has been found in TMCFs, the influence of different microclimatic drivers on plant water relations in this ecosystem has been relatively understudied. Within the TMCF, epiphytes may be particularly affected by natural variation in microclimate due to their partial or complete disassociation from soil resources. In this study, we examined the effects of seasonal microclimate on whole plant water balance in epiphytes in both an observational and a manipulative experiment. We also evaluated the effects of different microclimatic drivers using three hierarchical linear (mixed) models. On average, 31 % of total positive sap flow was recovered via foliar water uptake (FWU) over the course of the study. We found that precipitation was the greatest driver of foliar water uptake and nighttime sap flow in our study species and that both VPD and precipitation were important drivers to daytime sap flow. We also found that despite adaptations to withstand seasonal drought, an extended dry period caused severe desiccation in most plants despite a large reduction in leaf-level and whole plant transpiration. Our results indicate that the epiphytes studied rely on FWU to maintain positive water balance in the dry season and that increases in dry periods in the TMCF may be detrimental to these common members of the epiphyte community.

Synergistic Ecoclimate Teleconnections from Forest Loss in Different Regions Structure Global Ecological Responses

DOE PAGES

Garcia, Elizabeth S.; Swann, Abigail L. S.; Villegas, Juan C.; ...

2016-11-16

Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates ofmore » deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia's GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. In conclusion, our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change.« less

Synergistic Ecoclimate Teleconnections from Forest Loss in Different Regions Structure Global Ecological Responses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia, Elizabeth S.; Swann, Abigail L. S.; Villegas, Juan C.

Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates ofmore » deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia's GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. In conclusion, our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change.« less

Dynamic analysis of pan evaporation variations in the Huai River Basin, a climate transition zone in eastern China.

PubMed

Li, Meng; Chu, Ronghao; Shen, Shuanghe; Islam, Abu Reza Md Towfiqul

2018-06-01

Pan evaporation (E pan ), which we examine in this study to better understand atmospheric evaporation demand, represents a pivotal indicator of the terrestrial ecosystem and hydrological cycle, particularly in the Huai River Basin (HRB) in eastern China, where high potential risks of drought and flooding are commonly observed. In this study, we examine the spatiotemporal trend patterns of climatic factors and E pan by using the Mann-Kendall test and the Theil-Sen estimator based on a daily meteorological dataset from 89 weather stations during 1965-2013 in the HRB. Furthermore, the PenPan model is employed to estimate E pan at a monthly time scale, and a differential equation method is applied to quantify contributions from four meteorological variables to E pan trends. The results show that E pan significantly decreased (P<0.001) at an average rate of -8.119mm·a -2 at annual time scale in the whole HRB, with approximately 90% of stations occupied. Meanwhile, the generally higher E pan values were detected in the northern HRB. The values of the aerodynamic components in the PenPan model were much greater than those of the radiative components, which were responsible for the variations in the E pan trend. The significantly decreasing wind speed (u 2 ) was the most dominant factor that controlled the decreasing E pan trend at each time scale, followed by the notable decreasing net radiation (R n ) at the annual time scale also in growing season and summer. However, the second dominant factor shifted to the mean temperature (T a ) during the spring and winter and the vapor pressure deficit (vpd) during the autumn. These phenomena demonstrated a positive link between the significance of climate variables and their control over the E pan trend. Copyright © 2017 Elsevier B.V. All rights reserved.

Environmental signals in tree-ring δ18O from a temperate catchment in Switzerland

NASA Astrophysics Data System (ADS)

Oertel, Annika; Treydte, Kerstin; Michel, Dominik; Tschumi, Elisabeth; Kahmen, Ansgar; Frank, David; Seneviratne, Sonia Isabelle

2017-04-01

Oxygen isotopes (δ18O) in tree rings are a valuable proxy for past environmental conditions. Yet, the contribution of source water δ18O versus signals generated at the leaf level as well as the influence of tree-physiological responses on tree-ring δ18O differences between individual trees at a site remain uncertain. To address this topic, we conducted a study at a catchment research site in northeastern Switzerland. Its unique long-term sampling design allowed for bi-weekly δ18O measurements of precipitation and creek water for the 2002 to 2014 period. Four ash trees (Fraxinus sp.) situated at a creek and four on a nearby steep slope were selected for δ18O measurements of tree-ring cellulose for the same 13 year period. δ18O of soil water as well as cryogenically extracted stem and twig xylem water were determined for three days within the 2016 vegetation period for comparison of xylem and soil water δ18O between the slope and the creek site. Gas exchange measurements with a LI-COR (Li-6400) allowed for comparison of transpiration rate, stomatal conductance and productivity between sites. We calculated correlations to environmental variables and applied the mechanistic Péclet-modified-Craig-Gordon (PMCG) model to simulate observed δ18O cellulose values while varying the parameterization of physiological and environmental variables according to the measured values. Mean inter-series correlations between the tree-level δ18O time series are similarly high at the slope and the creek locations, and both site-chronologies are tightly correlated (r=0.9) although offset by 0.9 ‰ on average. Both chronologies contain a similarly strong summer VPD/RH signal, but we find correlations to precipitation and creek discharge δ18O are just as high. Our results suggest that i) both leaf-level and source water signals are imprinted in cellulose δ18O, and ii) in addition to leaf-level evaporative enrichment the VPD signal at least partly results from its correlation to precipitation δ18O (r=0.57). The cellulose δ18O values are on average 0.9 ‰ higher at the slope site compared to the creek site despite similar stem xylem and soil water δ18O. Although it is commonly assumed that no fractionation occurs during transport from the roots to the twigs, we find that twig xylem δ18O is about 1 ‰ higher than stem xylem δ18O. Simulations with the PMCG model (which captured the overall behaviour in the δ18O time series well) with varying parameterization for stomatal conductance and twig xylem δ18O according to measured values show that about 50 % of the 0.9 ‰ offset between creek and slope is explained. We conclude that i) it is unlikely that differences in source water δ18O cause the 0.9 ‰ offset between both sites alone, ii) despite the proximity of both sites the transpiration rate and productivity of trees at the creek site is higher, and iii) according to the PMCG model tree physiological responses are important for site internal tree-ring δ18O variability although interannual variations are only slightly affected.

A guide to phylogenetic metrics for conservation, community ecology and macroecology.

PubMed

Tucker, Caroline M; Cadotte, Marc W; Carvalho, Silvia B; Davies, T Jonathan; Ferrier, Simon; Fritz, Susanne A; Grenyer, Rich; Helmus, Matthew R; Jin, Lanna S; Mooers, Arne O; Pavoine, Sandrine; Purschke, Oliver; Redding, David W; Rosauer, Dan F; Winter, Marten; Mazel, Florent

2017-05-01

The use of phylogenies in ecology is increasingly common and has broadened our understanding of biological diversity. Ecological sub-disciplines, particularly conservation, community ecology and macroecology, all recognize the value of evolutionary relationships but the resulting development of phylogenetic approaches has led to a proliferation of phylogenetic diversity metrics. The use of many metrics across the sub-disciplines hampers potential meta-analyses, syntheses, and generalizations of existing results. Further, there is no guide for selecting the appropriate metric for a given question, and different metrics are frequently used to address similar questions. To improve the choice, application, and interpretation of phylo-diversity metrics, we organize existing metrics by expanding on a unifying framework for phylogenetic information. Generally, questions about phylogenetic relationships within or between assemblages tend to ask three types of question: how much; how different; or how regular? We show that these questions reflect three dimensions of a phylogenetic tree: richness, divergence, and regularity. We classify 70 existing phylo-diversity metrics based on their mathematical form within these three dimensions and identify 'anchor' representatives: for α-diversity metrics these are PD (Faith's phylogenetic diversity), MPD (mean pairwise distance), and VPD (variation of pairwise distances). By analysing mathematical formulae and using simulations, we use this framework to identify metrics that mix dimensions, and we provide a guide to choosing and using the most appropriate metrics. We show that metric choice requires connecting the research question with the correct dimension of the framework and that there are logical approaches to selecting and interpreting metrics. The guide outlined herein will help researchers navigate the current jungle of indices. © 2016 The Authors. Biological Reviews published by John Wiley © Sons Ltd on behalf of Cambridge Philosophical Society.

A guide to phylogenetic metrics for conservation, community ecology and macroecology

PubMed Central

Cadotte, Marc W.; Carvalho, Silvia B.; Davies, T. Jonathan; Ferrier, Simon; Fritz, Susanne A.; Grenyer, Rich; Helmus, Matthew R.; Jin, Lanna S.; Mooers, Arne O.; Pavoine, Sandrine; Purschke, Oliver; Redding, David W.; Rosauer, Dan F.; Winter, Marten; Mazel, Florent

2016-01-01

ABSTRACT The use of phylogenies in ecology is increasingly common and has broadened our understanding of biological diversity. Ecological sub‐disciplines, particularly conservation, community ecology and macroecology, all recognize the value of evolutionary relationships but the resulting development of phylogenetic approaches has led to a proliferation of phylogenetic diversity metrics. The use of many metrics across the sub‐disciplines hampers potential meta‐analyses, syntheses, and generalizations of existing results. Further, there is no guide for selecting the appropriate metric for a given question, and different metrics are frequently used to address similar questions. To improve the choice, application, and interpretation of phylo‐diversity metrics, we organize existing metrics by expanding on a unifying framework for phylogenetic information. Generally, questions about phylogenetic relationships within or between assemblages tend to ask three types of question: how much; how different; or how regular? We show that these questions reflect three dimensions of a phylogenetic tree: richness, divergence, and regularity. We classify 70 existing phylo‐diversity metrics based on their mathematical form within these three dimensions and identify ‘anchor’ representatives: for α‐diversity metrics these are PD (Faith's phylogenetic diversity), MPD (mean pairwise distance), and VPD (variation of pairwise distances). By analysing mathematical formulae and using simulations, we use this framework to identify metrics that mix dimensions, and we provide a guide to choosing and using the most appropriate metrics. We show that metric choice requires connecting the research question with the correct dimension of the framework and that there are logical approaches to selecting and interpreting metrics. The guide outlined herein will help researchers navigate the current jungle of indices. PMID:26785932

Readability of online patient education materials for velopharyngeal insufficiency.

PubMed

Xie, Deborah X; Wang, Ray Y; Chinnadurai, Sivakumar

2018-01-01

Evaluate the readability of online and mobile application health information about velopharyngeal insufficiency (VPI). Top website and mobile application results for search terms "velopharyngeal insufficiency", "velopharyngeal dysfunction", "VPI", and "VPD" were analyzed. Readability was determined using 10 algorithms with Readability Studio Professional Edition (Oleander Software Ltd; Vandalia, OH). Subgroup analysis was performed based on search term and article source - academic hospital, general online resource, peer-reviewed journal, or professional organization. 18 unique articles were identified. Overall mean reading grade level was a 12.89 ± 2.9. The highest reading level among these articles was 15.47-approximately the level of a college senior. Articles from "velopharyngeal dysfunction" had the highest mean reading level (13.73 ± 2.11), above "velopharyngeal insufficiency" (12.30 ± 1.56) and "VPI" (11.66 ± 1.70). Articles from peer-reviewed journals had the highest mean reading level (15.35 ± 2.79), while articles from academic hospitals had the lowest (12.81 ± 1.66). There were statistically significant differences in reading levels between the different search terms (P < 0.01) and article source types (P < 0.05). Only one mobile application was identified with VPI information, with a readability of 10.68. Despite published reading level guidelines, online patient education materials for VPI are disseminated with language too complex for most readers. There is also a lack of VPI-related mobile application data available for patients. Patients will benefit if future updates to websites and disseminated patient information are undertaken with health literacy in mind. Future studies will investigate patient comprehension of these materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Net primary productivity of China's terrestrial ecosystems from a process model driven by remote sensing.

PubMed

Feng, X; Liu, G; Chen, J M; Chen, M; Liu, J; Ju, W M; Sun, R; Zhou, W

2007-11-01

The terrestrial carbon cycle is one of the foci in global climate change research. Simulating net primary productivity (NPP) of terrestrial ecosystems is important for carbon cycle research. In this study, China's terrestrial NPP was simulated using the Boreal Ecosystem Productivity Simulator (BEPS), a carbon-water coupled process model based on remote sensing inputs. For these purposes, a national-wide database (including leaf area index, land cover, meteorology, vegetation and soil) at a 1 km resolution and a validation database were established. Using these databases and BEPS, daily maps of NPP for the entire China's landmass in 2001 were produced, and gross primary productivity (GPP) and autotrophic respiration (RA) were estimated. Using the simulated results, we explore temporal-spatial patterns of China's terrestrial NPP and the mechanisms of its responses to various environmental factors. The total NPP and mean NPP of China's landmass were 2.235 GtC and 235.2 gCm(-2)yr(-1), respectively; the total GPP and mean GPP were 4.418 GtC and 465 gCm(-2)yr(-1); and the total RA and mean RA were 2.227 GtC and 234 gCm(-2)yr(-1), respectively. On average, NPP was 50.6% of GPP. In addition, statistical analysis of NPP of different land cover types was conducted, and spatiotemporal patterns of NPP were investigated. The response of NPP to changes in some key factors such as LAI, precipitation, temperature, solar radiation, VPD and AWC are evaluated and discussed.

Variable filter array spectrometer of VPD PbSe

NASA Astrophysics Data System (ADS)

Linares-Herrero, R.; Vergara, G.; Gutiérrez-Álvarez, R.; Fernández-Montojo, C.; Gómez, L. J.; Villamayor, V.; Baldasano-Ramírez, A.; Montojo, M. T.

2012-06-01

MWIR spectroscopy shows a large potential in the current IR devices market, due to its multiple applications (gas detection, chemical analysis, industrial monitoring, combustion and flame characterization, food packaging etc) and its outstanding performance (good sensitivity, NDT method, velocity of response, among others), opening this technique to very diverse fields of application, such as industrial monitoring and control, agriculture, medicine and environmental monitoring. However, even though a big interest on MWIR spectroscopy technique has been present in the last years, two major barriers have held it back from its widespread use outside the laboratory: the complexity and delicateness of some popular techniques such as Fourier-transform IR (FT-IR) spectrometers, and the lack of affordable specific key elements such a MWIR light sources and low cost (real uncooled) detectors. Recent developments in electrooptical components are helping to overcome these drawbacks. The need for simpler solutions for analytical measurements has prompted the development of better and more affordable uncooled MWIR detectors, electronics and optics. In this paper a new MWIR spectrometry device is presented. Based on linear arrays of different geometries (64, 128 and 256 elements), NIT has developed a MWIR Variable Filter Array Spectrometer (VFAS). This compact device, with no moving parts, based on a rugged and affordable detector, is suitable to be used in applications which demand high sensitivity, good spectral discrimination, reliability and compactness, and where an alternative to the traditional scanning instrument is desired. Some measurements carried out for several industries will be also presented.

Immunisation coverage and its determinants among children aged 12-23 months in Atakumosa-west district, Osun State Nigeria: a cross-sectional study.

PubMed

Adedire, Elizabeth B; Ajayi, Ikeoluwapo; Fawole, Olufunmilayo I; Ajumobi, Olufemi; Kasasa, Simon; Wasswa, Peter; Nguku, Patrick

2016-08-30

Routine immunisation (RI) contributes immensely to reduction in mortality from vaccine preventable diseases (VPD) among children. The Nigerian Demographic and Health Survey, 2008 revealed that only 58 % of children in Osun State had received all recommended vaccines, which is far below World Health Organization (WHO) target of 80 %. We therefore, assessed RI uptake and its determinants among children in Atakumosa-west district of Osun State. Atakumosa-west district has an estimated population of 90,525 inhabitants. We enrolled 750 mothers of children aged 12-23 months in this cross-sectional study. Semi-structured questionnaires were used to obtain data on socio-demographic characteristics, knowledge of mothers on RI, history of RI in children and factors associated with full RI uptake. A fully-immunised child was defined as a child who had received one dose of Bacillus-Calmette-Guerin, three doses of Oral-Polio-Vaccine, three doses of Diptheria-Pertusis-Tetanus vaccine and one dose of measles vaccine by 12 months of age. We tested for the association between immunisation uptake and its likely determinants using multivariable logistic regression at 0.05 level of significance and 95 % confidence Interval (CI). Mean ± (SD) age of the mothers and children were 27.9 ± 6.1 years and 17.2 ± 4.0 months, respectively. About 94 % (703/750) of mothers had received antenatal care (ANC) and 63.3 % (475) of the children possessed vaccination cards. Seventy-six percent (571/750) had good knowledge of RI and VPD. About 58 % (275/475) of children who possessed vaccination card were fully-immunised. Mothers antenatal care attendance (aOR = 3.3, 95 % CI = 1.1-8.3), maternal tetanus toxoid immunisation (aOR = 3.2, 95 % CI = 1.1-10.0) access to immunisation information (aOR = 1.8, 95 % CI = 1.1-2.5) and mothers having good knowledge of immunisation (aOR = 2.4, 95 % CI = 1.6-3.8) were significant determinants of full immunisation. Routine immunisation uptake was still below WHO target in the study area. Encouraging mothers to attend antenatal care and educational interventions targeted at rural mothers are recommended to improve vaccination status of children in the rural communities.

Calibration of the maximum carboxylation velocity (vcmax) for the Caatinga for use in dynamic global vegetation models (DGVMs)

NASA Astrophysics Data System (ADS)

Rezende, L. C.; Arenque, B.; von Randow, C.; Moura, M. S.; Aidar, S. D.; Buckeridge, M. S.; Menezes, R.; Souza, L. S.; Ometto, J. P.

2013-12-01

The Caatinga biome in the semi-arid region of northeastern Brazil is extremely important due to its biodiversity and endemism. This biome, which is under high anthropogenic influences, presents high levels of environmental degradation, land use being among the main causes of such degradation. The simulations of land cover and the vegetation dynamic under different climate scenarios are important features for prediction of environmental risks and determination of sustainable pathways for the planet in the future. Modeling of the vegetation can be performed by use of dynamic global vegetation models (DGVMs). The DGVMs simulate the surface processes (e.g. transfer of energy, water, CO2 and momentum); plant physiology (e.g. photosynthesis, stomatal conductance) phenology; gross and net primary productivity, respiration, plant species classified by functional traits; competition for light, water and nutrients, soil characteristics and processes (e.g. nutrients, heterotrophic respiration). Currently, most of the parameters used in DGVMs are static pre-defined values, and the lack of observational information to aid choosing the most adequate values for these parameters is particularly critical for the semi-arid regions in the world. Through historical meteorological data and measurements of carbon assimilation we aim to calibrate the maximum carboxylation velocity (Vcmax), for the native species Poincianella microphylla, abundant in the Caatinga region. The field data (collected at Lat: 90 2' S, Lon: 40019' W) displayed two contrasting meteorological conditions, with precipitations of 16 mm and 104 mm prior to the sampling campaigns (April 9-13, 2012 and February 4-8, 2013; respectively). Calibration (obtaining values of Vcmax more suitable for vegetation of Caatinga) has been performed through an algorithm of pattern recognition: Classification And Regression Tree (CART) and calculation of the vapor pressure deficit (VPD), which was used as attribute for discrimination of data. CART can be utilized for classification or regression, being used in the context of this work for non-linear regression. Our results show that CART algorithm correctly classified data according to the two contrasting periods (i.e. correctly distinguished assimilation data measured during drier or rainy periods), and suggest average Vcmax values of 14.2 μmol CO2 m-2 s-1 for the drier period and of 102.5 μmol CO2 m-2 s-1 for the rainy period. Comparing the values obtained in this work with values obtained through a traditional parameter optimization technique, it is possible to gauge pros and cons of such a combination of field measurements and machine learning technique.

Does increasing intrinsic water use efficiency (iWUE) stimulate tree growth at natural alpine timberline on the southeastern Tibetan Plateau?

NASA Astrophysics Data System (ADS)

Huang, Ru; Zhu, Haifeng; Liu, Xiaohong; Liang, Eryuan; Grießinger, Jussi; Wu, Guoju; Li, Xiaoxia; Bräuning, Achim

2017-01-01

Little is known about whether increasing iWUE (intrinsic water use efficiency) can stimulate tree growth in the temperature-limited natural timberlines. Here, we presented the basal area increment (BAI) and iWUE chronologies of Smith fir (Abies georgei var. smithii) from 1900 to 2006 at a high-elevation (ca. 4400 m a.s.l.) timberline in the humid Sygera Mountains, southeastern Tibetan Plateau (TP). The commonality analysis model was applied to investigate the relationships among BAI, temperatures, atmospheric CO2 concentration (Ca) and iWUE during 1961-2006, taking into account of both pure and joint effects. As illustrated by the commonality analysis model, the pure effect of Ca (39.15%) had more stronger influence on iWUE than that of the Tmean (annul mean temperature, 0.12%), but the joint effect between Ca and Tmean (49.79%) on iWUE was stronger than any pure effect for the raw data with an increasing trend. For the first-difference data with year-to-year variations, the pure effect of Ca (7.72%) on iWUE was stronger than that of Tmean (0.59%) and the joint effect between them (0.59%). All above imply the Ca is the dominant factor for iWUE both for the 46-year trend and interannual variations. In addition, as showed by the commonality analysis model, the pure effect of iWUE (17.57%) played a much more important role on BAI than that of temperatures (smt, mean temperature during June, July, August of current year, 5.92%; amt, mean temperature during September, October, November of previous year, 3.04%), while joint effects of iWUE and temperatures contributed more (27.96%; 13.90%; 16.47%) to the BAI than their pure effects for the raw data with an increasing linear trend. For the first-difference data with interannual variations, the pure effect of smt (12.45%) had much more effect on BAI than that of iWUE (5.49%), at the same time the joint iWUE and temperatures contributed less (3.56%; 1.9%; 1.31%) to the BAI than their pure effects. These results suggest that an increasing iWUE could enhance 46-year increasing tree growth trend at humid and high-elevation timberlines, supporting the CO2 fertilization hypothesis, while temperatures dominate the interannual variations of tree growth. Background about the sample plot in the timberline Comparison among iWUE series under different scenarios (Ci = constant, Ci/Ca = constant, Ca-Ci = constant, and method mentioned in Silva et al. 2013) The representative of our chronology for tree growth during the past century Vapor Pressure Deficit (VPD) Corrected carbon isotopes series and their climatic signal Methods for removing climate signal from iWUE Information about uncertainties of calculating iWUE in our study The 30-year moving correlations among BAI, iWUE, smt,Ca Results of the commonality analysis are shown from a perspective of set theories Raw data and first-difference data used for the commonality analysis.

Prevalence of inter-arm blood pressure difference among clinical out-patients.

PubMed

Sharma, Balkishan; Ramawat, Pramila

2016-04-01

An increased inter-arm blood pressure difference is an easily determined physical finding, may use as an indicator of cardio vascular event and other sever diseases. Authors evaluated 477 patients to determine the prevalence and significance of inter-arm blood pressure difference. 477 routine outdoor patients selected to observe the inter-arm blood pressure difference. Age, height, weight, body mass index, history of disease and blood pressure recorded. The prevalence of ≥10 mmHg systolic inter-arm blood pressure difference was 5.0% was more as compared to 3.8% had diastolic inter-arm blood pressure difference. The prevalence of systolic and diastolic inter-arm difference between 6 to 10 mmHg was 31.4% and 27.9% respectively. Mean systolic inter-arm blood pressure difference was significantly higher among those patients had a multisystem disorder (10.57±0.98 mmHg) and followed by patients with cardiovascular disease (10.22±0.67 mmHg) as compared to healthy patients (2.71±0.96 mmHg). Various diseases highly influenced the increase in blood pressure irrespective of systolic or diastolic was confirmed strongly significant (p<0.001) at different inter arm blood pressure difference levels. This study supports the view of inter-arm blood pressure difference as an alarming stage of increased disease risk that incorporated to investigate potential problems at an early diagnostic stage. A significant mean difference between left and right arm blood pressure recorded for many diseases.

Prevalence of inter-arm blood pressure difference among clinical out-patients

PubMed Central

Sharma, Balkishan; Ramawat, Pramila

2016-01-01

Objectives An increased inter-arm blood pressure difference is an easily determined physical finding, may use as an indicator of cardio vascular event and other sever diseases. Authors evaluated 477 patients to determine the prevalence and significance of inter-arm blood pressure difference. Methodology 477 routine outdoor patients selected to observe the inter-arm blood pressure difference. Age, height, weight, body mass index, history of disease and blood pressure recorded. Results The prevalence of ≥10 mmHg systolic inter-arm blood pressure difference was 5.0% was more as compared to 3.8% had diastolic inter-arm blood pressure difference. The prevalence of systolic and diastolic inter-arm difference between 6 to 10 mmHg was 31.4% and 27.9% respectively. Mean systolic inter-arm blood pressure difference was significantly higher among those patients had a multisystem disorder (10.57±0.98 mmHg) and followed by patients with cardiovascular disease (10.22±0.67 mmHg) as compared to healthy patients (2.71±0.96 mmHg). Various diseases highly influenced the increase in blood pressure irrespective of systolic or diastolic was confirmed strongly significant (p<0.001) at different inter arm blood pressure difference levels. Conclusion This study supports the view of inter-arm blood pressure difference as an alarming stage of increased disease risk that incorporated to investigate potential problems at an early diagnostic stage. A significant mean difference between left and right arm blood pressure recorded for many diseases. PMID:27103905

Leaf physiological responses of mature Norway Spruce trees exposed to elevated carbon dioxide and temperature

NASA Astrophysics Data System (ADS)

Lamba, Shubhangi; Uddling, Johan; Räntfors, Mats; Hall, Marianne; Wallin, Göran

2014-05-01

Leaf photosynthesis, respiration and stomatal conductance exert strong control over the exchange of carbon, water and energy between the terrestrial biosphere and the atmosphere. As such, leaf physiological responses to rising atmospheric CO2 concentration ([CO2]) and temperature have important implications for the global carbon cycle and rate of ongoing global warming, as well as for local and regional hydrology and evaporative cooling. It is therefore critical to improve the understanding of plant physiological responses to elevated [CO2] and temperature, in particular for boreal and tropical ecosystems. In order to do so, we examined physiological responses of mature boreal Norway spruce trees (ca 40-years old) exposed to elevated [CO2] and temperature inside whole-tree chambers at Flakaliden research site, Northern Sweden. The trees were exposed to a factorial combination of two levels of [CO2] (ambient and doubled) and temperature (ambient and +2.8 degree C in summer and +5.6 degree C in winter). Three replicates in each of the four treatments were used. It was found that photosynthesis was increased considerably in elevated [CO2], but was not affected by the warming treatment. The maximum rate of photosynthetic carboxylation was reduced in the combined elevated [CO2] and elevated temperature treatment, but not in single factor treatments. Elevated [CO2] also strongly increased the base rate of respiration and to a lesser extent reduced the temperature sensitivity (Q10 value) of respiration; responses which may be important for the carbon balance of these trees which have a large proportion of shaded foliage. Stomatal conductance at a given VPD was reduced by elevated temperature treatment, to a degree that mostly offset the higher vapour pressure deficit in warmed air with respect to transpiration. Elevated [CO2] did not affect stomatal conductance, and thus increased the ratio of leaf internal to external [CO2]. These results indicate that the large elevated [CO2]-induced increase in CO2 uptake is partly counteracted by substantial increases in autotrophic respiration in boreal spruce. Furthermore, stomatal results suggest conservative leaf-level water use of spruce under rising [CO2] and temperature.

Evaluation and comparison of gross primary production estimates for the Northern Great Plains grasslands

USGS Publications Warehouse

Zhang, Li; Wylie, Bruce K.; Loveland, Thomas R.; Fosnight, Eugene A.; Tieszen, Larry L.; Ji, Lei; Gilmanov, Tagir

2007-01-01

Two spatially-explicit estimates of gross primary production (GPP) are available for the Northern Great Plains. An empirical piecewise regression (PWR) GPP model was developed from flux tower measurements to map carbon flux across the region. The Moderate Resolution Imaging Spectrometer (MODIS) GPP model is a process-based model that uses flux tower data to calibrate its parameters. Verification and comparison of the regional PWR GPP and the global MODIS GPP are important for the modeling of grassland carbon flux. This study compared GPP estimates from PWR and MODIS models with five towers in the grasslands. Among them, PWR GPP and MODIS GPP showed a good agreement with tower-based GPP at three towers. The global MODIS GPP, however, did not agree well with tower-based GPP at two other towers, probably because of the insensitivity of MODIS model to regional ecosystem and climate change and extreme soil moisture conditions. Cross-validation indicated that the PWR model is relatively robust for predicting regional grassland GPP. However, the PWR model should include a wide variety of flux tower data as the training data sets to obtain more accurate results.In addition, GPP maps based on the PWR and MODIS models were compared for the entire region. In the northwest and south, PWR GPP was much higher than MODIS GPP. These areas were characterized by the higher water holding capacity with a lower proportion of C4 grasses in the northwest and a higher proportion of C4 grasses in the south. In the central and southeastern regions, PWR GPP was much lower than MODIS GPP under complicated conditions with generally mixed C3/C4 grasses. The analysis indicated that the global MODIS GPP model has some limitations on detecting moisture stress, which may have been caused by the facts that C3 and C4 grasses are not distinguished, water stress is driven by vapor pressure deficit (VPD) from coarse meteorological data, and MODIS land cover data are unable to differentiate the sub-pixel cropland components.

Evidence of hydraulic lift for pre-rainy season leaf out and dry-season stem water enrichment in Sclerocarya birrea, a tropical agroforestry tree

NASA Astrophysics Data System (ADS)

Ceperley, Natalie; Mande, Theophile; Rinaldo, Andrea; Parlange, Marc B.

2014-05-01

We use stable isotopes of water as tracers to follow water use by five Sclerocarya birrea trees in a catchment in South Eastern Burkina Faso interspersed with millet fields, gallery forest, Sudanian savanna, and fallow fields. Isotopic ratios were determined from water extracted from stems of the trees and sub-canopy soil of two of them, while nearby ground water, precipitation, and surface water was sampled weekly. A unique configuration of sensors connected with a wireless sensor network of meteorological stations measured sub-canopy shading, the temperature and humidity in the canopy, through-fall, and soil moisture under two of the trees. Both water extracted from sap and water extracted from soil is extremely enriched in the dry season, but drop to levels close to the ground water in February or March, which coincides with the growth of leaves. Dates of leaf out were confirmed by changes in δDH and δO18 concentrations of water, photographic documentation & pixel analysis, and analysis of sub-canopy radiation and proceeded the rise in humidity and flow that was later detected in the sub-canopy soil, the trunk of the tree (sap-flow), and atmosphere (canopy VPD). Examination of the isotopic signature suggests that size of tree plays an important role in duration and timing of this leaf-out as well as the degree of enrichment during the peak of the dry season. Further examination of the isotopic signatures of the roots suggested that the trees are performing hydraulic redistribution, or lifting the ground water and "sharing it" with the soil in the rooting zone in the dry season. The enriched level of xylem in this case is a product of water loss, and enrichment, along the travel path of the water from the roots to the tip of the stem, as evidenced by the variation according to size of tree. Vapor pressure deficit, soil water, and soil moisture interactions support this picture of interacting controls, separate from hydrologic triggers on the water movement in the tree.

Modeling the health and productivity of Oak Savannas in central USA

NASA Astrophysics Data System (ADS)

Nightingale, J. M.; Hill, M. J.

2012-12-01

Oak species have a long history of domination in eastern North America and their present distribution in various regions exceeds that recorded in the original forests at the time of European settlement. The increase in oak during the late 18th and 19th centuries can be attributed to historical changes in disturbance regimes in the eastern biome. The expansion in oak distribution has occurred on xeric or nutrient-poor sites, which indicates the stress tolerance capabilities of many oak species. The aim of this research is to assess the health and productivity of the fragmented oak savannas that span from Texas north to the Canada border using statewide GAP, climate and MODIS data and the 3PGS (Physiological Principles Predicting Growth using satellite data) ecosystem process model. 3-PGS is a simple big-leaf productivity model that sets upper limits on monthly gross primary productivity (GPP) by determining the amount of photosynthetically active radiation absorbed (APAR) by vegetation and the photosynthetic capacity (LUE) of the canopy. The utilized portion of APAR is calculated by reducing total PAR by an amount determined by the most constraining of a series of environmental modifiers that affect gas exchange through stomata. These include: (a) high daytime atmospheric VPD; (b) soil water availability; and (c) the frequency of sub-freezing temperatures (<-2 °C). Climate data including day length, precipitation, average temperature and vapor pressure deficit are obtained from the Daymet daily gridded surface data from Oak Ridge National Laboratory (ORNL). The fraction of APAR is obtained from the MODIS terra/aqua combined product. Monthly surfaces were derived for the study period 2003-2008 spanning available MODIS and Climate datasets. Soil properties for the entire U.S.A., derived from luster analysis of STATSGO soil parameters, terrain and climate observations were obtained from ORNL. Oak savannas within this region are identified using the statewide Gap Analysis Program data provided by USGS. Several landsat scenes selected across the study region provided an estimate of the seasonal variation in fPAR and distinction between the tree and understory grass signals.

Oscillometric blood pressure devices and simulators: measurements of repeatability and differences between models.

PubMed

Sims, A J; Reay, C A; Bousfield, D R; Menes, J A; Murray, A

2005-01-01

To measure the repeatability and pressure pulse envelope of simulators used for testing oscillometric non-invasive blood pressure (NIBP) devices; to study the effect of different envelopes on NIBP devices, and to measure the difference between NIBP devices due to different oscillometric algorithms. Three different models of NIBP simulator and 18 different patient monitors with NIBP function were studied. We developed a pressure measurement system (accuracy 0.048?mmHg) to measure the repeatability of simulators. The effect of changing the envelope was measured by using three simulators with one NIBP device. Differences between 18 NIBP devices were measured using one simulator at seven blood pressure settings. Simulators generate repeatable pressure pulse envelopes (< 0.2 mmHg) but the magnitude and shape depends on the model of simulator. Oscillometric NIBP devices are highly repeatable (< 2 mmHg) when presented with a repeatable pressure pulse envelope, but different devices employ different algorithms and give different results. For a simulated standard blood pressure setting of 120/80 mmHg, estimates of systolic pressure ranged from 112.6 to 126.6 mmHg (sd of 3.0 mmHg), and diastolic pressure ranged from 74.8 to 86.9 mmHg (sd of 3.5 mmHg). Simulators and NIBP devices are sufficiently repeatable for clinical use, but further systematic clinical studies are required to better characterize the pressure pulse envelope for different patient groups.

Generation, cryopreservation, function and in vivo persistence of ex-vivo expanded cynomolgus monkey regulatory T cells

PubMed Central

Guo, Hao; Zhang, Hong; Lu, Lien; Ezzelarab, Mohamed B.; Thomson, Angus W.

2015-01-01

We expanded flow-sorted Foxp3+ cynomolgus monkey regulatory T cells (Treg) >1000-fold after three rounds of stimulation with anti-CD3 mAb-loaded artificial antigen-presenting cells, rapamycin (first round only) and IL-2. The expanded Treg maintained their expression of Treg signature markers, CD25, CD27, CD39, Foxp3, Helios, and CTLA-4, as well as CXCR3, which plays an important role in T cell migration to sites of inflammation. In contrast to expanded effector T cells (Teff), expanded Treg produced minimal IFN-γ and IL-17 and no IL-2 and potently suppressed Teff proliferation. Following cryopreservation, thawed Treg were less viable than their freshly-expanded counterparts, although no significant changes in phenotype or suppressive ability were observed. Additional rounds of stimulation/expansion restored maximal viability. Furthermore, adoptively-transferred autologous Treg expanded from cryopreserved second round stocks and labeled with CFSE or VPD450 were detected in blood and secondary lymphoid tissues of normal or immunosuppressed recipients at least two months after their systemic infusion. PMID:25732601

Estimating meningitis hospitalization rates for sentinel hospitals conducting invasive bacterial vaccine-preventable diseases surveillance.

PubMed

2013-10-04

The World Health Organization (WHO)-coordinated Global Invasive Bacterial Vaccine-Preventable Diseases (IB-VPD) sentinel hospital surveillance network provides data for decision making regarding use of pneumococcal conjugate vaccine and Haemophilus influenzae type b (Hib) vaccine, both recommended for inclusion in routine childhood immunization programs worldwide. WHO recommends that countries conduct sentinel hospital surveillance for meningitis among children aged <5 years, including collection of cerebrospinal fluid (CSF) for laboratory detection of bacterial etiologies. Surveillance for pneumonia and sepsis are recommended at selected hospitals with well-functioning laboratories where meningitis surveillance consistently meets process indicators (e.g., surveillance performance indicators). To use sentinel hospital surveillance for meningitis to estimate meningitis hospitalization rates, WHO developed a rapid method to estimate the number of children at-risk for meningitis in a sentinel hospital catchment area. Monitoring changes in denominators over time using consistent methods is essential for interpreting changes in sentinel surveillance incidence data and for assessing the effect of vaccine introduction on disease epidemiology. This report describes the method and its use in The Gambia and Senegal.

The systolic blood pressure difference between arms and cardiovascular disease in the Framingham Heart Study.

PubMed

Weinberg, Ido; Gona, Philimon; O'Donnell, Christopher J; Jaff, Michael R; Murabito, Joanne M

2014-03-01

An increased interarm systolic blood pressure difference is an easily determined physical examination finding. The relationship between interarm systolic blood pressure difference and risk of future cardiovascular disease is uncertain. We described the prevalence and risk factor correlates of interarm systolic blood pressure difference in the Framingham Heart Study (FHS) original and offspring cohorts and examined the association between interarm systolic blood pressure difference and incident cardiovascular disease and all-cause mortality. An increased interarm systolic blood pressure difference was defined as ≥ 10 mm Hg using the average of initial and repeat blood pressure measurements obtained in both arms. Participants were followed through 2010 for incident cardiovascular disease events. Multivariable Cox proportional hazards regression analyses were performed to investigate the effect of interarm systolic blood pressure difference on incident cardiovascular disease. We examined 3390 (56.3% female) participants aged 40 years and older, free of cardiovascular disease at baseline, mean age of 61.1 years, who attended a FHS examination between 1991 and 1994 (original cohort) and from 1995 to 1998 (offspring cohort). The mean absolute interarm systolic blood pressure difference was 4.6 mm Hg (range 0-78). Increased interarm systolic blood pressure difference was present in 317 (9.4%) participants. The median follow-up time was 13.3 years, during which time 598 participants (17.6%) experienced a first cardiovascular event, including 83 (26.2%) participants with interarm systolic blood pressure difference ≥ 10 mm Hg. Compared with those with normal interarm systolic blood pressure difference, participants with an elevated interarm systolic blood pressure difference were older (63.0 years vs 60.9 years), had a greater prevalence of diabetes mellitus (13.3% vs 7.5%,), higher systolic blood pressure (136.3 mm Hg vs 129.3 mm Hg), and a higher total cholesterol level (212.1 mg/dL vs 206.5 mg/dL). Interarm systolic blood pressure difference was associated with a significantly increased hazard of incident cardiovascular events in the multivariable adjusted model (hazard ratio 1.38; 95% CI, 1.09-1.75). For each 1-SD-unit increase in absolute interarm systolic blood pressure difference, the hazard ratio for incident cardiovascular events was 1.07 (95% CI, 1.00-1.14) in the fully adjusted model. There was no such association with mortality (hazard ratio 1.02; 95% CI 0.76-1.38). In this community-based cohort, an interarm systolic blood pressure difference is common and associated with a significant increased risk for future cardiovascular events, even when the absolute difference in arm systolic blood pressure is modest. These findings support research to expand clinical use of this simple measurement. Copyright © 2014 Elsevier Inc. All rights reserved.

[Measuring the blood pressure in both arms is of little use; longitudinal study into blood pressure differences between both arms and its reproducibility in patients with diabetes mellitus type 2].

PubMed

Kleefstra, N; Houweling, S T; Meyboom-de Jong, B; Bilo, H J G

2007-07-07

To determine the prevalence of inter-arm blood pressure differences > 10 mmHg in patients with diabetes mellitus type 2 (DM2) and to determine whether these differences are consistent over time. Descriptive. In an evaluation study of 169 DM2 patients from 5 general practices in 2003 and 2004, different methods of oscillatory measurement were used to investigate inter-arm blood pressure differences > 10 mmHg systolic or diastolic. These methods were: one measurement in each arm non-simultaneously (method A), one measurement simultaneously (B) and the mean of two simultaneous measurements (C). With method A an inter-arm blood pressure difference was found in 33% of patients. This percentage diminished to 9 with method C. In 44% (n = 7) of the patients in whom method C detected a relevant blood pressure difference, this difference was not found with method A. In 79% of patients the inter-arm blood pressure difference was not reproduced after one year. In daily practice, one non-simultaneous blood pressure measurement in each arm (method A) was of little value for identification of patients with inter-arm blood pressure differences. The reproducibility was poor one year later. Bilateral blood pressure measurement is therefore of little value.

Ideal resuscitation pressure for uncontrolled hemorrhagic shock in different ages and sexes of rats

PubMed Central

2013-01-01

Introduction Our previous studies demonstrated that 50-60 mmHg mean arterial blood pressure was the ideal target hypotension for uncontrolled hemorrhagic shock during the active hemorrhage in sexually mature rats. The ideal target resuscitation pressure for immature and older rats has not been determined. Methods To elucidate this issue, using uncontrolled hemorrhagic-shock rats of different ages and sexes (6 weeks, 14 weeks and 1.5 years representing pre-adult, adult and older rats, respectively), the resuscitation effects of different target pressures (40, 50, 60, 70 and 80 mmHg) on uncontrolled hemorrhagic shock during active hemorrhage and the age and sex differences were observed. Results Different target resuscitation pressures had different resuscitation outcomes for the same age and sex of rats. The optimal target resuscitation pressures for 6-week-old, 14-week-old and 1.5-year-old rats were 40 to 50 mmHg, 50 to 60 mmHg and 70 mmHg respectively. Ideal target resuscitation pressures were significantly superior to other resuscitation pressures in improving the hemodynamics, blood perfusion, organ function and animal survival of uncontrolled hemorrhagic-shock rats (P < 0.01). For same target resuscitation pressures, the beneficial effect on hemorrhagic shock had a significant age difference (P < 0.01) but no sex difference (P > 0.05). Different resuscitation pressures had no effect on coagulation function. Conclusion Hemorrhagic-shock rats at different ages have different target resuscitation pressures during active hemorrhage. The ideal target resuscitation hypotension for 6-week-old, 14-week-old and 1.5-year-old rats was 40 to 50 mmHg, 50 to 60 mmHg and 70 mmHg, respectively. Their resuscitation effects have significant age difference but had no sex difference. PMID:24020401

Age-related differences in tongue-palate pressures for strength and swallowing tasks.

PubMed

Fei, Tiffany; Polacco, Rebecca Cliffe; Hori, Sarah E; Molfenter, Sonja M; Peladeau-Pigeon, Melanie; Tsang, Clemence; Steele, Catriona M

2013-12-01

The tongue plays a key role in the generation of pressures for transporting liquids and foods through the mouth in swallowing. Recent studies suggest that there is an age-related decline in tongue strength in healthy adults. However, whether age-related changes occur in tongue pressures generated for the purpose of swallowing remains unclear. Prior literature in this regard does not clearly explore the influence of task on apparent age-related differences in tongue pressure amplitudes. Furthermore, differences attributable to variations across individuals in strength, independent of age, have not clearly been elucidated. In this study, our goal was to clarify whether older adults have reduced tongue-palate pressures during maximum isometric, saliva swallowing, and water swallowing tasks, while controlling for individual variations in strength. Data were collected from 40 healthy younger adults (under age 40) and 38 healthy mature adults (over age 60). As a group, the mature participants had significantly lower maximum isometric pressures (MIPs). Swallowing pressures differed significantly by task, with higher pressures seen in saliva swallows than in water swallows. Age-group differences were not seen in swallowing pressures. Consideration of MIP as a covariate in the analysis of swallowing pressures revealed significant correlations between strength and swallowing pressures in the older participant group. Age-group differences were evident only when strength was considered in the model, suggesting that apparent age-related differences are, in fact, explained by differences in strength, which tends to be lower in healthy older adults. Our results show no evidence of independent differences in swallowing pressures attributable to age.

Canopy Defoliation has More Impact on Carbohydrate Availability than on Hydraulic Function in Declining Scots Pine Populations

NASA Astrophysics Data System (ADS)

Poyatos, R.; Aguadé, D.; Gómez, M.; Mencuccini, M.; Martínez-Vilalta, J.

2013-12-01

Drought-induced defoliation has recently been associated with depletion of carbohydrate reserves and increased mortality risk in Scots pine (Pinus sylvestris L.) at its dry limit. Are defoliated pines hydraulically impaired compared to non-defoliated pines? Moreover, how do defoliated pines cope with potentially lethal droughts, as compared to non-defoliated pines in the same population? In order to address these questions, we measured the seasonal dynamics of sap flow and needle water potentials (2010-2012), hydraulic function and non-structural carbohydrates (NSC) (2012) in healthy and defoliated pines in the Prades mountains (NE Spain). The summer drought was mild in 2010, intense in 2012 and extremely long in 2011. Defoliated Scots pines showed higher sap flow per unit leaf area during spring, but they were more sensitive to summer drought (Figure 1). This pattern was associated with a steeper decline in soil-to-leaf hydraulic conductance, which could not be explained by differences in branch vulnerability to embolism across defoliation classes. Accordingly, the native loss of xylem conductivity in branches, measured in 2012, remained similar across defoliation classes and reached >65% at the peak of the drought. However, a steeper vulnerability curve was observed for root xylem of defoliated pines. Xylem diameter variations (2011-2012) will be used to further investigate possible differences in the aboveground/belowground partitioning of hydraulic resistance across defoliation classes. NSC levels varied across tree organs (leaves>branches>roots>trunk) and strongly declined with drought. Defoliated pines displayed reduced NSC levels throughout the study period, despite enhanced water transport capacity and increased gas exchange rates during spring. Overall, the defoliated vs. healthy status seems to be more associated to differences in carbohydrate storage and dynamics than to hydraulic differences per se. However, starch conversion to soluble sugars during drought also suggests that NSC may be actively involved in the maintenance of xylem and phloem transport. These results highlight the close connection between carbon and water relations in declining Scots pines. Seasonal course (2010-2012) of VPD (upper panel), soil moisture (mid panel) and sap flow per unit leaf area of defoliated and non defoliated Scots pines (lower panel).

Muscular subaortic stenosis: the initial left ventricular inflow tract pressure as evidence of outflow tract obstruction.

PubMed

Wigle, E D; Auger, P; Marquis, Y

1966-10-15

Two types of intraventricular pressure differences within the left ventricle of man are described. The first is encountered in cases of muscular (or fibrous) subaortic stenosis, in which the outflow tract pressure distal to the stenosis (and proximal to the aortic valve) is low, whereas all pressures recorded in the left ventricle proximal to the stenosis, including that just inside the mitral valve (the initial inflow tract pressure) are high.The second type of intraventricular pressure difference may be recorded in patients without muscular subaortic stenosis when a heart catheter is advanced to the left ventricular wall in such a manner that it becomes imbedded or entrapped by cardiac muscle in systole. Such an entrapped catheter records a high intraventricular pressure that is believed to reflect intramyocardial tissue pressure, which normally exceeds intracavitary pressure. In such cases the initial inflow tract pressure is not high and is precisely equal to the outflow tract systolic pressure, i.e. both are recording intracavity pressure. This type of intramyocardial to intracavitary pressure difference may also be encountered in the left ventricle of dogs.The recent suggestion that intraventricular pressure differences in the left ventricle of cases of muscular subaortic stenosis are due to catheter entrapment by cardiac muscle is refuted by using the initial inflow tract pressure as the means of differentiation between the two types of intraventricular pressure differences outlined.

Assessing Pharmacy Students’ Ability to Accurately Measure Blood Pressure Using a Blood Pressure Simulator Arm

PubMed Central

Bryant, Ginelle A.; Haack, Sally L.; North, Andrew M.

2013-01-01

Objective. To compare student accuracy in measuring normal and high blood pressures using a simulator arm. Methods. In this prospective, single-blind, study involving third-year pharmacy students, simulator arms were programmed with prespecified normal and high blood pressures. Students measured preset normal and high diastolic and systolic blood pressure using a crossover design. Results. One hundred sixteen students completed both blood pressure measurements. There was a significant difference between the accuracy of high systolic blood pressure (HSBP) measurement and normal systolic blood pressure (NSBP) measurement (mean HSBP difference 8.4 ± 10.9 mmHg vs NSBP 3.6 ± 6.4 mmHg; p<0.001). However, there was no difference between the accuracy of high diastolic blood pressure (HDBP) measurement and normal diastolic blood pressure (NDBP) measurement (mean HDBP difference 6.8 ± 9.6 mmHg vs. mean NDBP difference 4.6 ± 4.5 mmHg; p=0.089). Conclusions. Pharmacy students may need additional instruction and experience with taking high blood pressure measurements to ensure they are able to accurately assess this important vital sign. PMID:23788809

Assessing pharmacy students' ability to accurately measure blood pressure using a blood pressure simulator arm.

PubMed

Bottenberg, Michelle M; Bryant, Ginelle A; Haack, Sally L; North, Andrew M

2013-06-12

To compare student accuracy in measuring normal and high blood pressures using a simulator arm. In this prospective, single-blind, study involving third-year pharmacy students, simulator arms were programmed with prespecified normal and high blood pressures. Students measured preset normal and high diastolic and systolic blood pressure using a crossover design. One hundred sixteen students completed both blood pressure measurements. There was a significant difference between the accuracy of high systolic blood pressure (HSBP) measurement and normal systolic blood pressure (NSBP) measurement (mean HSBP difference 8.4 ± 10.9 mmHg vs NSBP 3.6 ± 6.4 mmHg; p<0.001). However, there was no difference between the accuracy of high diastolic blood pressure (HDBP) measurement and normal diastolic blood pressure (NDBP) measurement (mean HDBP difference 6.8 ± 9.6 mmHg vs. mean NDBP difference 4.6 ± 4.5 mmHg; p=0.089). Pharmacy students may need additional instruction and experience with taking high blood pressure measurements to ensure they are able to accurately assess this important vital sign.

Spool-Valve Pressure-Difference Regulator

NASA Technical Reports Server (NTRS)

Grasso, A. P.

1983-01-01

Valves maintain preset pressure difference between gas flows. Two spool valves connected by shaft move back and forth in response to changes in pressure in oxygen and hydrogen chambers. Spool-valve assembly acts to restore pressures to preset difference. By eliminating diaphragms, pressure exerted directly on external end of spool valve; however, forces and therefore sensitivity of assembly are reduced.

The Systolic Blood Pressure Difference Between Arms and Cardiovascular Disease in the Framingham Heart Study

PubMed Central

Weinberg, Ido; Gona, Philimon; O’Donnell, Christopher J.; Jaff, Michael R.; Murabito, Joanne M.

2014-01-01

Background An increased inter-arm systolic blood pressure difference is an easily determined physical examination finding. The relationship between inter-arm systolic blood pressure difference and risk of future cardiovascular disease is uncertain. We described the prevalence and risk factor correlates of inter-arm systolic blood pressure difference in the Framingham Heart Study (FHS) original and offspring cohorts and examined the association between inter-arm systolic blood pressure difference and incident cardiovascular disease and all-cause mortality. Methods An increased inter-arm systolic blood pressure difference was defined as ≥10mmHg using the average of initial and repeat blood pressure measurements obtained in both arms. Participants were followed through 2010 for incident cardiovascular disease events. Multivariable Cox proportional hazards regression analyses were performed to investigate the effect of inter-arm systolic blood pressure difference on incident cardiovascular disease. Results We examined 3,390 (56.3% female) participants aged 40 years and older, free of cardiovascular disease at baseline, mean age of 61.1 years, who attended a FHS examination between 1991 and 1994 (original cohort) and from 1995 to 1998 (offspring cohort). The mean absolute inter-arm systolic blood pressure difference was 4.6 mmHg (range 0 to 78). Increased inter-arm systolic blood pressure difference was present in 317 (9.4%) participants. The median follow-up time was 13.3 years, during which time 598 participants (17.6%) experienced a first cardiovascular event including 83 (26.2%) participants with inter-arm systolic blood pressure difference ≥10 mmHg. Compared to those with normal inter-arm systolic blood pressure difference, participants with an elevated inter-arm systolic blood pressure difference were older (63.0 years vs. 60.9 years), had a greater prevalence of diabetes mellitus (13.3% vs. 7.5%,), higher systolic blood pressure (136.3 mmHg vs. 129.3 mmHg), and a higher total cholesterol level (212.1 mg/dL vs. 206.5 mg/dL). Inter-arm systolic blood pressure difference was associated with a significantly increased hazard of incident cardiovascular events in the multivariable adjusted model (hazard ratio 1.38, 95% CI, 1.09 to 1.75). For each 1-standard deviation unit increase in absolute interarm systolic blood pressure difference, the hazard ratio for incident cardiovascular events was 1.07 (CI, 1.00 to 1.14) in the fully-adjusted model. There was no such association with mortality (hazard ratio 1.02, 95% CI 0.76 to 1.38). Conclusions In this community-based cohort, an inter-arm systolic blood pressure difference is common and associated with a significant increased risk for future cardiovascular events, even when the absolute difference in arm systolic blood pressure is modest. These findings support research to expand clinical use of this simple measurement. PMID:24287007

Introversion associated with large differences between screening blood pressure and home blood pressure measurement: The Ohasama study.

PubMed

Hozawa, Atsushi; Ohkubo, Takayoshi; Obara, Taku; Metoki, Hirohito; Kikuya, Masahiro; Asayama, Kei; Totsune, Kazuhito; Hashimoto, Junichiro; Hoshi, Haruhisa; Arai, Yumiko; Satoh, Hiroshi; Hosokawa, Toru; Imai, Yutaka

2006-11-01

To explore the effect of personality on screening blood pressures measured in clinical settings and home blood pressure measurements. From 1997 to 1999, 699 participants underwent screening and home blood pressure measurements and completed the Japanese version of the short-form Eysenck personality questionnaire. An increased screening blood pressure was defined as screening blood pressure > or = 140/90 mmHg and an increased home blood pressure was defined as home blood pressure > or = 135/85 mmHg. Participants with lower extroversion scores (i.e., introversion) showed a greater difference between screening and home systolic blood pressure. The association between introversion and differences was statistically significant, even after adjustment for other possible factors (younger age, female, wide screening pulse pressure, never smoked, and no antihypertensive medication). The adjusted means of SBP differences were 7.3 and 4.4 mmHg among the lowest and highest extroversion quartiles, respectively (P for trend = 0.02). Other personality scores (psychoticism or neuroticism) were not associated with screening and home blood pressure differences. The incorporation of an extroversion score in the basic model consisting of the above factors that affected the difference between screening and home blood pressure slightly improved the prediction of a high home blood pressure. The area under the receiver operating characteristic curve increased by 0.037 among participants with high screening blood pressure and 0.006 for those with normal screening blood pressure compared with the basic model. Physicians may need to be aware of 'introverted' patients who have high blood pressure in clinic settings, because they have the potential for 'white-coat' hypertension.

Muscular Subaortic Stenosis

PubMed Central

Wigle, E. Douglas; Auger, Pierre; Marquis, Yves

1966-01-01

Two types of intraventricular pressure differences within the left ventricle of man are described. The first is encountered in cases of muscular (or fibrous) subaortic stenosis, in which the outflow tract pressure distal to the stenosis (and proximal to the aortic valve) is low, whereas all pressures recorded in the left ventricle proximal to the stenosis, including that just inside the mitral valve (the initial inflow tract pressure) are high. The second type of intraventricular pressure difference may be recorded in patients without muscular subaortic stenosis when a heart catheter is advanced to the left ventricular wall in such a manner that it becomes imbedded or entrapped by cardiac muscle in systole. Such an entrapped catheter records a high intraventricular pressure that is believed to reflect intramyocardial tissue pressure, which normally exceeds intracavitary pressure. In such cases the initial inflow tract pressure is not high and is precisely equal to the outflow tract systolic pressure, i.e. both are recording intracavity pressure. This type of intramyocardial to intracavitary pressure difference may also be encountered in the left ventricle of dogs. The recent suggestion that intraventricular pressure differences in the left ventricle of cases of muscular subaortic stenosis are due to catheter entrapment by cardiac muscle is refuted by using the initial inflow tract pressure as the means of differentiation between the two types of intraventricular pressure differences outlined. PMID:5951625

High vacuum measurements and calibrations, molecular flow fluid transient effects

DOE PAGES

Leishear, Robert A.; Gavalas, Nickolas A.

2015-04-29

High vacuum pressure measurements and calibrations below 1 × 10 -8 Torr are problematic. Specifically, measurement accuracies change drastically for vacuum gauges when pressures are suddenly lowered in vacuum systems. How can gauges perform like this? A brief system description is first required to answer this question. Calibrations were performed using a vacuum calibration chamber with attached vacuum gauges. To control chamber pressures, vacuum pumps decreased the chamber pressure while nitrogen tanks increased the chamber pressure. By balancing these opposing pressures, equilibrium in the chamber was maintained at selected set point pressures to perform calibrations. When pressures were suddenly decreasedmore » during set point adjustments, a sudden rush of gas from the chamber also caused a surge of gas from the gauges to decrease the pressures in those gauges. Gauge pressures did not return to equilibrium as fast as chamber pressures due to the sparse distribution of gas molecules in the system. This disparity in the rate of pressure changes caused the pressures in different gauges to be different than expected. This discovery was experimentally proven to show that different gauge designs return to equilibrium at different rates, and that gauge accuracies vary for different gauge designs due to fluid transients in molecular flow.« less

Experimental Investigation of Oscillatory Flow Pressure and Pressure Drop Through Complex Geometries

NASA Technical Reports Server (NTRS)

Ibrahim, Mounir B.; Wang, Meng; Gedeon, David

2005-01-01

A series of experiments have been performed to investigate the oscillatory flow pressure and pressure drop through complex geometries. These experiments were conducted at the CSU-SLRE facility which is a horizontally opposed, two-piston, single-acting engine with a split crankshaft driving mechanism. Flow through a rectangular duct, with no insert (obstruction), was studied first. Then four different inserts were examined: Abrupt, Manifold, Diverging Short and Diverging Long. The inserts were mounted in the center of the rectangular duct to represent different type of geometries that could be encountered in Stirling machines. The pressure and pressure drop of the oscillating flow was studied for: 1) different inserts, 2) different phase angle between the two pistons of the engine (zero, 90 lead, 180, and 90 lag), and 3) for different piston frequencies (5, 10, 15, and 20 Hz). It was found that the pressure drop of the oscillatory flow increases with increasing Reynolds number. The pressure drop was shown to be mainly due to the gas inertia for the case of oscillatory flow through a rectangular duct with no insert. On the other hand, for the cases with different inserts into the rectangular duct, the pressure drop has three sources: inertia, friction, and local losses. The friction pressure drop is only a small fraction of the total pressure drop. It was also shown that the dimensionless pressure drop decreases with increasing kinetic Reynolds number.

Effect of Coronary Anatomy and Hydrostatic Pressure on Intracoronary Indices of Stenosis Severity.

PubMed

Härle, Tobias; Luz, Mareike; Meyer, Sven; Kronberg, Kay; Nickau, Britta; Escaned, Javier; Davies, Justin; Elsässer, Albrecht

2017-04-24

The authors sought to analyze height differences within the coronary artery tree in patients in a supine position and to quantify the impact of hydrostatic pressure on intracoronary pressure measurements in vitro. Although pressure equalization of the pressure sensor and the systemic pressure at the catheter tip is mandatory in intracoronary pressure measurements, subsequent measurements may be influenced by hydrostatic pressure related to the coronary anatomy in the supine position. Outlining and quantifying this phenomenon is important to interpret routine and pullback pressure measurements within the coronary tree. Coronary anatomy was analyzed in computed tomography angiographies of 70 patients to calculate height differences between the catheter tip and different coronary segments in the supine position. Using a dynamic pressure simulator, the effect of the expected hydrostatic pressure resulting from such height differences on indices stenosis severity was assessed. In all patients, the left anterior and right posterior descending arteries are the highest points of the coronary tree with a mean height difference of -4.9 ± 1.6 cm and -3.8 ± 1.0 cm; whereas the circumflex artery and right posterolateral branches are the lowest points, with mean height differences of 3.9 ± 0.9 cm and 2.6 ± 1.6 cm compared with the according ostium. In vitro measurements demonstrated a correlation of the absolute pressure differences with height differences (r = 0.993; p < 0.0001) and the slope was 0.77 mm Hg/cm. The Pd/Pa ratio and instantaneous wave-free ratio correlated also with the height difference (fractional flow reserve r = 0.98; p < 0.0001; instantaneous wave-free ratio r = 0.97; p < 0.0001), but both were influenced by the systemic pressure level. Hydrostatic pressure variations resulting from normal coronary anatomy in a supine position influence intracoronary pressure measurements and may affect their interpretation during stenosis severity assessment. Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Microcirculatory responses of sacral tissue in healthy individuals and inpatients on different pressure-redistribution mattresses.

PubMed

Bergstrand, S; Källman, U; Ek, A-C; Engström, M; Lindgren, M

2015-08-01

The aim of this study was to explore the interaction between interface pressure, pressure-induced vasodilation, and reactive hyperaemia with different pressure-redistribution mattresses. A cross-sectional study was performed with a convenience sample of healthy young individuals, and healthy older individuals and inpatients, at a university hospital in Sweden. Blood flow was measured at depths of 1mm, 2mm, and 10mm using laser Doppler flowmetry and photoplethysmography. The blood flow, interface pressure and skin temperature were measured in the sacral tissue before, during, and after load while lying on one standard hospital mattress and three different pressure-redistribution mattresses. There were significant differences between the average sacral pressure, peak sacral pressure, and local probe pressure on the three pressure-redistribution mattresses, the lowest values found were with the visco-elastic foam/air mattress (23.5 ± 2.5mmHg, 49.3 ± 11.1mmHg, 29.2 ± 14.0mmHg, respectively). Blood flow, measured as pressure-induced vasodilation, was most affected in the visco-elastic foam/air group compared to the alternating pressure mattress group at tissue depths of 2mm (39.0% and 20.0%, respectively), and 10mm (56.9 % and 35.1%, respectively). Subjects in all three groups, including healthy 18-65 year olds, were identified with no pressure-induced vasodilation or reactive hyperaemia on any mattress (n=11), which is considered a high-risk blood flow response. Interface pressure magnitudes considered not harmful during pressure-exposure on different pressure-redistribution mattresses can affect the microcirculation in different tissue structures. Despite having the lowest pressure values compared with the other mattresses, the visco-elastic foam/air mattress had the highest proportion of subjects with decreased blood flow. Healthy young individuals were identified with the high-risk blood flow response, suggesting an innate vulnerability to pressure exposure. Furthermore, the evaluation of pressure-redistribution support surfaces in terms of mean blood flow during and after tissue exposure is not feasible, but assessment of pressure-induced vasodilation and reactive hyperaemia could be a new way to assess individualised physiological measurements of mechanisms known to be related to pressure ulcer development.

Inter-arm blood pressure differences compared with ambulatory monitoring: a manifestation of the ‘white-coat’ effect?

PubMed Central

Martin, Una; Holder, Roger; Hodgkinson, James; McManus, Richard

2013-01-01

Background Inter-arm difference in blood pressure of >10 mmHg is associated with peripheral vascular disease, but it is unclear how much of the difference in sequential right and left arm blood pressure measurements might be due to a ‘white-coat’ effect. Aim To use ambulatory blood pressure monitoring (ABPM) to better understand the clinical significance of inter-arm differences in blood pressure. Design and setting Retrospective study in a teaching hospital in Birmingham. Method Anonymised clinical data collected from 784 patients attending a single hospital-based hypertension clinic were retrospectively analysed. Each participant had blood pressure measured sequentially in both arms, followed by ABPM over the subsequent 24 hours. Result Data were available for 710 (91%) patients, of whom 39.3% (279) had a blood pressure difference of 10 mmHg or more between each arm. Compared to daytime systolic ABPM, the difference was 25.1 mmHg using the arm with the highest reading, but only 15.5 mmHg if the lower reading was taken (mean difference 9.6 mmHg (95% confidence interval [CI] = 9.0 mmHg to 10.3 mmHg)). However, differences between mean right (20.7 mmHg) or left (19.9 mmHg) arm blood pressure and daytime systolic ABPM were very similar. Conclusion Compared with ABPM, use of the higher of the left and right arm readings measured sequentially appears to overestimate true mean blood pressure. As there is no significant difference in the extent of disparity with ABPM by left or right arm, this is unlikely to be due to arm dominance and may be due to the ‘white-coat’ effect reducing blood pressure on repeated measurement. Where a large inter-arm blood pressure difference is detected with sequential measurement, healthcare professionals should re-measure the blood pressure in the original arm. PMID:23561681

Inter-arm blood pressure differences compared with ambulatory monitoring: a manifestation of the 'white-coat' effect?

PubMed

Martin, Una; Holder, Roger; Hodgkinson, James; McManus, Richard

2013-02-01

Inter-arm difference in blood pressure of >10 mmHg is associated with peripheral vascular disease, but it is unclear how much of the difference in sequential right and left arm blood pressure measurements might be due to a 'white-coat' effect. To use ambulatory blood pressure monitoring (ABPM) to better understand the clinical significance of inter-arm differences in blood pressure. Retrospective study in a teaching hospital in Birmingham. Anonymised clinical data collected from 784 patients attending a single hospital-based hypertension clinic were retrospectively analysed. Each participant had blood pressure measured sequentially in both arms, followed by ABPM over the subsequent 24 hours. Data were available for 710 (91%) patients, of whom 39.3% (279) had a blood pressure difference of 10 mmHg or more between each arm. Compared to daytime systolic ABPM, the difference was 25.1 mmHg using the arm with the highest reading, but only 15.5 mmHg if the lower reading was taken (mean difference 9.6 mmHg (95% confidence interval [CI] = 9.0 mmHg to 10.3 mmHg)). However, differences between mean right (20.7 mmHg) or left (19.9 mmHg) arm blood pressure and daytime systolic ABPM were very similar. Compared with ABPM, use of the higher of the left and right arm readings measured sequentially appears to overestimate true mean blood pressure. As there is no significant difference in the extent of disparity with ABPM by left or right arm, this is unlikely to be due to arm dominance and may be due to the 'white-coat' effect reducing blood pressure on repeated measurement. Where a large inter-arm blood pressure difference is detected with sequential measurement, healthcare professionals should re-measure the blood pressure in the original arm.

Vaccination Coverage Among Children Aged 2 Years - U.S. Affiliated Pacific Islands, April-October, 2016.

PubMed

Tippins, Ashley; Murthy, Neil; Meghani, Mehreen; Solsman, Amy; Apaisam, Carter; Basilius, Merlyn; Eckert, Maribeth; Judicpa, Peter; Masunu, Yolanda; Pistotnik, Kelsey; Pedro, Daisy; Sasamoto, Jeremy; Underwood, J Michael

2018-05-25

Vaccine-preventable diseases (VPDs) cause substantial morbidity and mortality in the United States Affiliated Pacific Islands (USAPI).* CDC collaborates with USAPI immunization programs to monitor vaccination coverage. In 2016, † USAPI immunization programs and CDC piloted a method for estimating up-to-date status among children aged 2 years using medical record abstraction to ascertain regional vaccination coverage. This was the first concurrent assessment of childhood vaccination coverage across five USAPI jurisdictions (American Samoa; Chuuk State, Federated States of Micronesia [FSM]; Commonwealth of the Northern Mariana Islands [CNMI]; Republic of the Marshall Islands [RMI]; and Republic of Palau). § Differences in vaccination coverage between main and outer islands ¶ were assessed for two jurisdictions where data were adequate.** Series coverage in this report includes the following doses of vaccines: ≥4 doses of diphtheria and tetanus toxoids and acellular pertussis vaccine (DTaP); ≥3 doses of inactivated poliovirus vaccine (IPV); ≥1 dose of measles, mumps, and rubella vaccine (MMR); ≥3 doses of Haemophilus influenzae type B (Hib) vaccine; ≥3 doses of hepatitis B (HepB) vaccine; and ≥4 doses of pneumococcal conjugate vaccine (PCV); i.e., 4:3:1:3:3:4. Coverage with ≥3 doses of rotavirus vaccine was also assessed. Completion of the recommended series of each of these vaccines †† was <90% in all jurisdictions except Palau. Coverage with the full recommended six-vaccine series (4:3:1:3:3:4) ranged from 19.5% (Chuuk) to 69.1% (Palau). In RMI and Chuuk, coverage was lower in the outer islands than in the main islands for most vaccines, with differences ranging from 0.9 to 66.8 percentage points. Medical record abstraction enabled rapid vaccination coverage assessment and timely dissemination of results to guide programmatic decision-making. Effectively monitoring vaccination coverage, coupled with implementation of data-driven interventions, is essential to maintain protection from VPD outbreaks in the region and the mainland United States.

Alterations to throughfall water and solute flux by Tillandsias usneoides L. (Spanish moss) cover in a maritime live oak forest

NASA Astrophysics Data System (ADS)

Gay, T. E.; Van Stan, J. T., II; Reichard, J. S.; Moore, L. D.; Lewis, E. S.

2014-12-01

Alterations to forest canopy structures can have a direct effect on hydrological and biogeochemical cycles in forest ecosystems. Epiphytes act as additional canopy biomass intercepting water, effecting pathways under different micrometeorological conditions and alternating nutrient uptake/releases. Most studies on epiphyte cover have focused on non-vascular epiphytes (e.g., lichen and bryophyte mosses), leaving vascular epiphytes like Tillandsia usneoides L. (Spanish moss) relatively understudied. To fill this gap, we characterized alterations to throughfall water and dissolved ion enrichment/flux to soils by T. usneoides in a Quercus Virginiana Mill. (southern live oak) stand on St. Catherine's Island. Specifically, we compare throughfall generated from heavy T. usneoides coverage, bare canopy, and a continuum of T. usneoides cover percentages (~400 water & 210 chemistry observations over ~40 storms for each canopy cover category). Findings show T.usneoides acts as a significant water storage agent, significantly reducing throughfall. However, under certain meteorological conditions T. usneoides can become saturated and act as a funneling "hotspot." Tillandsia usneoides coverage enriched throughfall with primarily dry deposited ions (Na+,Cl-, SO42-, Li+), leached greater Mg2+, Ca2+, reduced NO3- and increased NH4+ concentrations. Dry deposited ion enrichment is likely a result of the moss' greater surface roughness. It has been shown that epiphytes prefer to leach Mg2+ and Ca2+. Increased NH4+ suggests that the saturated T. usneoides mat likely hosts microbial decomposition of leaf, branch, and bark biomass ensnared in the plant itself. K-means cluster analysis on the storms revealed 4 storm types of the differing meteorological conditions (windy/calm, dry/wet [high/low VPD], high/low intensity, intermittent/consistent), and these throughfall dynamics varied between these storm types. Discussion of future research questions regarding how these throughfall variations may impact ecological communities in the litter, soil, or understory vegetation is also provided.

Reproducibility of repeated measurements with the Kikuhime pressure sensor under pressure garments in burn scar treatment.

PubMed

Van den Kerckhove, Eric; Fieuws, Steffen; Massagé, Patrick; Hierner, Robert; Boeckx, Willy; Deleuze, Jean-Paul; Laperre, Jan; Anthonissen, Mieke

2007-08-01

This study investigated the reproducibility of repeated measurements with the Kikuhime pressure sensor under two different types of pressure garments used in the treatment and prevention of scars after burns. Also efficiency of garments was assessed in clinical circumstances by assessing pressure loss and residual pressure after 1 month. Intra- and inter-observer reproducibility and repeated measurements with 1-month time lapse were examined on 55 sites in 26 subjects by means of intra-class correlation coefficients and standard error of measurements. Results showed good to excellent ICC and low SEMs in the two conditions. There was a significant difference in pressure after 1 month between elastic tricot and weft knit garments, although evolution of pressure loss after 1 month was similar. Concerning different locations, there was a significant difference in pressure loss after 1 month between gloves and sleeves with the largest pressure loss for sleeves. Considering these results we concluded that the Kikuhime pressure sensor provides valid and reliable information and can be used in comparative clinical trials to evaluate pressure garments used in burn scar treatment. Secondly, elastic tricot garments in our study tended to have higher clinical pressures but both types of garments had similar pressure loss over time.

Emergence of ethnic differences in blood pressure in adolescence: the determinants of adolescent social well-being and health study.

PubMed

Harding, Seeromanie; Whitrow, Melissa; Lenguerrand, Erik; Maynard, Maria; Teyhan, Alison; Cruickshank, J Kennedy; Der, Geoff

2010-04-01

The cause of ethnic differences in cardiovascular disease remains a scientific challenge. Blood pressure tracks from late childhood to adulthood. We examined ethnic differences in changes in blood pressure between early and late adolescence in the United Kingdom. Longitudinal measures of blood pressure, height, weight, leg length, smoking, and socioeconomic circumstances were obtained from London, United Kingdom, schoolchildren of White British (n=692), Black Caribbean (n=670), Black African (n=772), Indian (n=384), and Pakistani and Bangladeshi (n=402) ethnicity at 11 to 13 years and 14 to 16 years. Predicted age- and ethnic-specific means of blood pressure, adjusted for anthropometry and social exposures, were derived using mixed models. Among boys, systolic blood pressure did not differ by ethnicity at 12 years, but the greater increase among Black Africans than Whites led to higher systolic blood pressure at 16 years (+2.9 mm Hg). Among girls, ethnic differences in mean systolic blood pressure were not significant at any age, but while systolic blood pressure hardly changed with age among White girls, it increased among Black Caribbeans and Black Africans. Ethnic differences in diastolic blood pressure were more marked than those for systolic blood pressure. Body mass index, height, and leg length were independent predictors of blood pressure, with few ethnic-specific effects. Socioeconomic disadvantage had a disproportionate effect on blood pressure for girls in minority groups. The findings suggest that ethnic divergences in blood pressure begin in adolescence and are particularly striking for boys. They signal the need for early prevention of adverse cardiovascular disease risks in later life.

Inter-arm blood pressure difference in type 2 diabetes: a barrier to effective management?

PubMed Central

Clark, Christopher E; Greaves, Colin J; Evans, Philip H; Dickens, Andy; Campbell, John L

2009-01-01

Background Previous studies have identified a substantial prevalence of a blood pressure difference between arms in various populations, but not patients with type 2 diabetes. Recognition of such a difference would be important as a potential cause of underestimation of blood pressure. Aim To measure prevalence of an inter-arm blood pressure difference in patients with type 2 diabetes, and to estimate how frequently blood pressure measurements could be erroneously underestimated if an inter-arm difference is unrecognised. Design of study Cross-sectional study. Setting Five surgeries covered by three general practices, Devon, England. Method Patients with type 2 diabetes underwent bilateral simultaneous blood pressure measurements using a validated protocol. Mean blood pressures were calculated for each arm to derive mean systolic and diastolic differences, and to estimate point prevalence of predefined magnitudes of difference. Results A total of 101 participants were recruited. Mean age was 66 years (standard deviation [SD] = 13.9 years); 59% were male, and mean blood pressure was 138/79 mmHg (SD = 15/10 mmHg). Ten participants (10%; 95% confidence interval [CI] = 4 to 16) had a systolic inter-arm difference ≥10 mmHg; 29 (29%; 95% CI = 20 to 38) had a diastolic difference ≥5 mmHg; and three (3%; 95% CI = 0 to 6) a diastolic difference ≥10 mmHg. No confounding variable was observed to account for the magnitude of an inter-arm difference. Conclusion A systolic inter-arm difference ≥10 mmHg was observed in 10% of patients with diabetes. Failure to recognise this would misclassify half of these as normotensive rather than hypertensive using the lower-reading arm. New patients with type 2 diabetes should be screened for an inter-arm blood pressure difference. PMID:19520026

Inter-arm blood pressure difference in type 2 diabetes: a barrier to effective management?

PubMed

Clark, Christopher E; Greaves, Colin J; Evans, Philip H; Dickens, Andy; Campbell, John L

2009-06-01

Previous studies have identified a substantial prevalence of a blood pressure difference between arms in various populations, but not patients with type 2 diabetes. Recognition of such a difference would be important as a potential cause of underestimation of blood pressure. To measure prevalence of an inter-arm blood pressure difference in patients with type 2 diabetes, and to estimate how frequently blood pressure measurements could be erroneously underestimated if an inter-arm difference is unrecognised. Cross-sectional study. Five surgeries covered by three general practices, Devon, England. Patients with type 2 diabetes underwent bilateral simultaneous blood pressure measurements using a validated protocol. Mean blood pressures were calculated for each arm to derive mean systolic and diastolic differences, and to estimate point prevalence of predefined magnitudes of difference. A total of 101 participants were recruited. Mean age was 66 years (standard deviation [SD] = 13.9 years); 59% were male, and mean blood pressure was 138/79 mmHg (SD = 15/10 mmHg). Ten participants (10%; 95% confidence interval [CI] = 4 to 16) had a systolic inter-arm difference > or =10 mmHg; 29 (29%; 95% CI = 20 to 38) had a diastolic difference >/=5 mmHg; and three (3%; 95% CI = 0 to 6) a diastolic difference > or =10 mmHg. No confounding variable was observed to account for the magnitude of an inter-arm difference. A systolic inter-arm difference > or =10 mmHg was observed in 10% of patients with diabetes. Failure to recognise this would misclassify half of these as normotensive rather than hypertensive using the lower-reading arm. New patients with type 2 diabetes should be screened for an inter-arm blood pressure difference.

The effects of confining pressure and stress difference on static fatigue of granite

NASA Technical Reports Server (NTRS)

Kranz, R. L.

1979-01-01

Samples of Barre granite were creep tested at room temperature at confining pressures up to 2 kilobars. The time to fracture increased with decreasing stress difference at every pressure, but the rate of change of fracture time with respect to the stress difference increased with pressure. At 87% of the short-term fracture strength, the time to fracture increased from about 4 minutes at atmospheric pressure to longer than one day at 2 Kb of pressure. The inelastic volumetric strain at the onset of tertiary creep, delta, was constant within 25% at any particular pressure but increased with pressure in a manner analogous to the increase of strength with pressure. At the onset of tertiary creep, the number of cracks and their average length increased with pressure. The crack angle and crack length spectra were quite similar, however, at each pressure at the onset of tertiary creep.

Comparative evaluation of pressure generated on a simulated maxillary oral analog by impression materials in custom trays of different spacer designs: An in vitro study.

PubMed

Chopra, Sakshi; Gupta, Narendra Kumar; Tandan, Amrit; Dwivedi, Ravi; Gupta, Swati; Agarwal, Garima

2016-01-01

Literature reveals that masticatory load on denture bearing tissues through complete dentures should be maximum on primary stress bearing areas and least on relief area in accordance with the histology of underlying tissues. A study to validate the existing beliefs was planned to compare the pressure on mucosa using selective pressure technique and minimal pressure technique, with the incorporation of two different impression materials utilizing the pressure sensors during secondary impression procedure. The study was performed using a maxillary analog. Three pressure sensors were imbedded in the oral analog, one in the mid palatine area and the other two in the right and left ridge crest. Custom trays of two different configurations were fabricated. The two impression materials tested were light body and zinc oxide eugenol. A total of 40 impressions were made. A constant weight of 1 kg was placed, and the pressure was recorded as initial and end pressures. A significant difference in the pressure produced using different impression materials was found (P < 0.001). Light body vinyl polysiloxane produced significantly lesser pressure than zinc oxide eugenol impression materials. The presence of relief did affect the magnitude of pressure at various locations. All impression materials produced pressure during maxillary edentulous impression making. Tray modification is an important factor in changing the amount of pressure produced. The impression materials used also had a significant role to play on the pressures acting on the tissues during impression procedure. Light body VPS impression material may be recommended to achieve minimal pressure on the denture bearing tissues in both selective as well as minimal pressure techniques.

Inter-Arm Difference in Brachial Blood Pressure in the General Population of Koreans.

PubMed

Song, Bo Mi; Kim, Hyeon Chang; Shim, Jee-Seon; Lee, Myung Ha; Choi, Dong Phil

2016-05-01

We investigated the inter-arm difference in blood pressure of the general Korean population to identify associated factors. A total of 806 participants aged 30 to 64 years without history of major cardiovascular disease were analyzed in this cross-sectional study. They participated in the Cardiovascular and Metabolic Disease Etiology Research Center cohort study that began in 2013. Brachial blood pressure was measured simultaneously for both arms using an automated oscillometric device equipped with two cuffs in seated position. After five minutes of rest, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured three times. The average of the three measurements was used for analysis. Multivariate logistic regression models were used to identify factors associated with inter-arm differences in blood pressure. The mean inter-arm difference was 3.3 mmHg for SBP and 2.0 mmHg for DBP. Large inter-arm differences (≥10 mmHg) in SBP and in DBP were found in 3.7% and 0.9% of subjects, respectively. A large inter-arm difference in SBP was associated with mean SBP (p=0.002) and C-reactive protein (p=0.014) while a large inter-arm different in DBP was only associated with body mass index (p=0.015). Sex, age, and anti-hypertensive medication use were not associated with differences in inter-arm blood pressure. Large inter-arm difference in blood pressure is only present in a small portion of healthy Korean adults. Our findings suggest that high SBP, chronic inflammation, and obesity may be associated with larger difference in inter-arm blood pressure.

Evaluation of Pressure Generated by Resistors From Different Positive Expiratory Pressure Devices.

PubMed

Fagevik Olsén, Monika; Carlsson, Maria; Olsén, Erik; Westerdahl, Elisabeth

2015-10-01

Breathing exercises with positive expiratory pressure (PEP) are used to improve pulmonary function and airway clearance. Different PEP devices are available, but there have been no studies that describe the pressure generated by different resistors. The purpose of this study was to compare pressures generated from the proprietary resistor components of 4 commercial flow-dependent PEP valves with all other parameters kept constant. Resistors from 4 flow-regulated PEP devices (Pep/Rmt system, Wellspect HealthCare; Pipe P breathing exerciser, Koo Medical Equipment; Mini-PEP, Philips Respironics [including resistors by Rüsch]; and 15-mm endo-adapter, VBM Medizintechnik) were tested randomly by a blinded tester at constant flows of 10 and 18 L/min from an external gas system. All resistors were tested 3 times. Resistors with a similar diameter produced statistically significant different pressures at the same flow. The differences were smaller when the flow was 10 L/min compared with 18 L/min. The differences were also smaller when the diameter of the resistor was increased. The pressures produced by the 4 resistors of the same size were all significantly different when measuring 1.5- and 2.0-mm resistors at a flow of 10 L/min and 2.0-mm resistors at a flow of 18 L/min (P < .001). There were no significant differences between any of the resistors when testing sizes of 4.5 and 5.0 mm at either flow. The Mini-PEP and adapter resistors gave the highest pressures. Pressures generated by the different proprietary resistor components of 4 commercial PEP devices were not comparable, even though the diameter of the resistors is reported to be the same. The pressures generated were significantly different, particularly when using small-diameter resistors at a high flow. Therefore, the resistors may not be interchangeable. This is important information for clinicians, particularly when considering PEP for patients who do not tolerate higher pressures. Copyright © 2015 by Daedalus Enterprises.

The child-adolescent blood pressure study: I. Distribution of blood pressure levels in Seventh-Day-Adventist (SDA) and non-SDA children.

PubMed

Harris, R D; Phillips, R L; Williams, P M; Kuzma, J W; Fraser, G E

1981-12-01

Distribution of systolic and diastolic blood pressures (measured with an automated blood pressure recorder) of two large groups of children-3,159 from Seventh-Day Adventist (SDA) schools and 4,681 from non-SDA schools-are reported. They boys and girls were from four different ethnic groups and attended grades one through 10 in 29 Southern California schools. The analysis of the data failed to show significant differences in mean blood pressure levels between the two groups of children at all ages, despite marked differences in life-style between the two groups, and despite the fact that adults from the two population groups have marked differences in mortality from diseases associated with elevated blood pressure. A comparison between boys and girls showed significantly higher trends in mean systolic blood pressure for boys after age 12. Inter-ethnic comparisons of blood pressure revealed that Black children of both sexes had slightly higher mean blood pressure levels at all ages.

The child-adolescent blood pressure study: I. Distribution of blood pressure levels in Seventh-Day-Adventist (SDA) and non-SDA children.

PubMed Central

Harris, R D; Phillips, R L; Williams, P M; Kuzma, J W; Fraser, G E

1981-01-01

Distribution of systolic and diastolic blood pressures (measured with an automated blood pressure recorder) of two large groups of children-3,159 from Seventh-Day Adventist (SDA) schools and 4,681 from non-SDA schools-are reported. They boys and girls were from four different ethnic groups and attended grades one through 10 in 29 Southern California schools. The analysis of the data failed to show significant differences in mean blood pressure levels between the two groups of children at all ages, despite marked differences in life-style between the two groups, and despite the fact that adults from the two population groups have marked differences in mortality from diseases associated with elevated blood pressure. A comparison between boys and girls showed significantly higher trends in mean systolic blood pressure for boys after age 12. Inter-ethnic comparisons of blood pressure revealed that Black children of both sexes had slightly higher mean blood pressure levels at all ages. PMID:7315999

Measurements of the Exerted Pressure by Pelvic Circumferential Compression Devices

PubMed Central

Knops, Simon P; van Riel, Marcel P.J.M; Goossens, Richard H.M; van Lieshout, Esther M.M; Patka, Peter; Schipper, Inger B

2010-01-01

Background: Data on the efficacy and safety of non-invasive Pelvic Circumferential Compression Devices (PCCDs) is limited. Tissue damage may occur if a continuous pressure on the skin exceeding 9.3 kPa is sustained for more than two or three hours. The aim of this study was to gain insight into the pressure build-up at the interface, by measuring the PCCD-induced pressure when applying pulling forces to three different PCCDs (Pelvic Binder® , SAM-Sling ® and T-POD® ) in a simplified model. Methods: The resulting exerted pressures were measured at four ‘anatomical’ locations (right, left, posterior and anterior) in a model using a pressure measurement system consisting of pressure cuffs. Results: The exerted pressure varied substantially between the locations as well as between the PCCDs. Maximum pressures ranged from 18.9-23.3 kPa and from 19.2-27.5 kPa at the right location and left location, respectively. Pressures at the posterior location stayed below 18 kPa. At the anterior location pressures varied markedly between the different PCCDs. Conclusion: The circumferential compression by the different PCCDs showed high pressures measured at the four locations using a simplified model. Difference in design and functional characteristics of the PCCDs resulted in different pressure build-up at the four locations. When following the manufacturer’s instructions, the exerted pressure of all three PCCDs tested exceeded the tissue damaging level (9.3 kPa). In case of prolonged use in a clinical situation this might put patients at risk for developing tissue damage. PMID:20361001

Effect of pressure on the sorption correction to stainless steel, platinum/iridium and silicon mass artefacts

NASA Astrophysics Data System (ADS)

Berry, James; Davidson, Stuart

2014-04-01

This paper reports work undertaken to evaluate the change in mass of platinum/iridium, stainless steel and silicon artefacts measured at atmospheric pressure and in vacuum at a range of pressures typical of those used in vacuum mass comparators and watt balances and for x-ray crystal density (XRCD) measurements. The sets of platinum/iridium, stainless steel and silicon artefacts used in this work have different surface areas and the effect of transferring them between atmospheric pressure and different levels of vacuum was evaluated by measuring the relative changes in mass between them. Reversible variations in the mass differences between the artefacts were found over the pressure range from 0.1 Pa to 100 000 Pa (atmospheric pressure). At lower pressures (0.001 Pa to 0.1 Pa) the mass differences between all the artefacts were stable and no evidence for hysteresis over this range was found when going down in pressure compared with increasing pressure. Therefore consistent results between watt balance, XRCD measurements and vacuum mass measurements can be realized providing the measurements are performed within this pressure range.

[Effects of long time different negative pressures on osteogenic differentiation of rabbit bone mesenchymal stem cells].

PubMed

Zhao, Bowen; Zhang, Hongwei; Xu, Qiang; Ge, Quanhu; Li, Bolong; Peng, Xinyu; Wu, Xiangwei

2017-05-01

To investigate the effects of long time different negative pressures on osteogenic diffe-rentiation of rabbit bone mesenchymal stem cells (BMSCs). The rabbit BMSCs were isolated and cultured by density gradient centrifugation. Flow cytometry was used to analyze expression of surface markers. The third passage cells cultured under condition of osteogenic induction and under different negative pressure of 0 mm Hg (control group), 75 mm Hg (low negative pressure group), and 150 mm Hg (high negative pressure group) (1 mm Hg=0.133 kPa), and the negative pressure time was 30 min/h. Cell growth was observed under phase contrast microscopy, and the growth curve was drawn; alkaline phosphatase (ALP) activity was detected by ELISA after induced for 3, 7, and 14 days. The mRNA and protein expressions of collagen type I (COL-I) and osteocalcin (OC) in BMSCs were analyzed by real-time fluorescence quantitative PCR and Western blot. The cultured cells were identified as BMSCs by flow cytometry. The third passage BMSCs exhibited typical long shuttle and irregular shape. Cell proliferation was inhibited with the increase of negative pressure. After induced for 4 days, the cell number of high negative pressure group was significantly less than that in control group and low negative pressure group ( P <0.05), but there was no significant difference between the low negative pressure group and the control group ( P >0.05); at 5-7 days, the cell number showed significant difference between 3 groups ( P <0.05). The greater the negative pressure was, the greater the inhibition of cell proliferation was. There was no significant difference in ALP activity between groups at 3 days after induction ( P >0.05); the ALP activity showed significant difference ( P <0.05) between the high negative pressure group and the control group at 7 days after induction; and significant difference was found in the ALP activity between 3 groups at 14 days after induction ( P <0.05). The greater the negative pressure was, the higher the ALP activity was. Real-time fluorescence quantitative PCR and Western blot detection showed that the mRNA and protein expressions of COL-I and OC protein were significantly higher in low negative pressure group and high negative pressure group than control group ( P <0.05), and in the high negative pressure group than the low negative pressure group ( P <0.05). With the increase of the negative pressure, the osteogenic differentiation ability of BMSCs increases gradually, but the cell proliferation is inhibited.

Clinical response to dorsal duct drainage via the minor papilla in refractory obstructing chronic calcific pancreatitis

PubMed Central

Kwon, Chang-Il; Gromski, Mark A.; Sherman, Stuart; El Hajj, Ihab I.; Easler, Jeffrey J.; Watkins, James; McHenry, Lee; Lehman, Glen A.; Fogel, Evan L.

2017-01-01

Background and study aims Complete stone removal from the main pancreatic duct might not be achieved in all patients with obstructive chronic calcific pancreatitis. We report our results for endoscopic dorsal pancreatic duct (DPD) bypass of obstructing stones in the ventral pancreatic duct (VPD). Patients and methods 16 patients with obstructive chronic calcific pancreatitis were treated with a DPD bypass. Clinical success was defined as significant pain relief and no hospital admissions for pain management during the ongoing treatment period. Results Among 16 patients meeting entry criteria, 10 (62.5%) had a history of unsuccessful endoscopic therapy, and 8 had failed extracorporeal shockwave lithotripsy (ESWL). Clinical success was achieved in 12 patients (75 %). Among these responders, 10 patients (83.3 %) had markedly improved or complete pain relief after the first stent placement, which persisted throughout the follow-up period; 11 patients (91.7 %) were able to discontinue their daily analgesics. Conclusions In selected patients with obstructive chronic calcific pancreatitis, the DPD bypass may be considered as a rescue endoscopic therapy, potentially obviating the need for surgery when standard endoscopic methods and ESWL fail. PMID:28201840

Measurement of bite force variables related to human discrimination of left-right hardness differences of silicone rubber samples placed between the incisors.

PubMed

Dan, Haruka; Azuma, Teruaki; Hayakawa, Fumiyo; Kohyama, Kaoru

2005-05-01

This study was designed to examine human subjects' ability to discriminate between spatially different bite pressures. We measured actual bite pressure distribution when subjects simultaneously bit two silicone rubber samples with different hardnesses using their right and left incisors. They were instructed to compare the hardness of these two rubber samples and indicate which was harder (right or left). The correct-answer rates were statistically significant at P < 0.05 for all pairs of different right and left silicone rubber hardnesses. Simultaneous bite measurements using a multiple-point sheet sensor demonstrated that the bite force, active pressure and maximum pressure point were greater for the harder silicone rubber sample. The difference between the left and right was statistically significant (P < 0.05) for all pairs with different silicone rubber hardnesses. We demonstrated for the first time that subjects could perceive and discriminate between spatially different bite pressures during a single bite with incisors. Differences of the bite force, pressure and the maximum pressure point between the right and left silicone samples should be sensory cues for spatial hardness discrimination.

Virtual directions in paleomagnetism: A global and rapid approach to evaluate the NRM components.

NASA Astrophysics Data System (ADS)

Ramón, Maria J.; Pueyo, Emilio L.; Oliva-Urcia, Belén; Larrasoaña, Juan C.

2017-02-01

We introduce a method and software to process demagnetization data for a rapid and integrative estimation of characteristic remanent magnetization (ChRM) components. The virtual directions (VIDI) of a paleomagnetic site are “all” possible directions that can be calculated from a given demagnetization routine of “n” steps (being m the number of specimens in the site). If the ChRM can be defined for a site, it will be represented in the VIDI set. Directions can be calculated for successive steps using principal component analysis, both anchored to the origin (resultant virtual directions RVD; m * (n2+n)/2) and not anchored (difference virtual directions DVD; m * (n2-n)/2). The number of directions per specimen (n2) is very large and will enhance all ChRM components with noisy regions where two components were fitted together (mixing their unblocking intervals). In the same way, resultant and difference virtual circles (RVC, DVC) are calculated. Virtual directions and circles are a global and objective approach to unravel different natural remanent magnetization (NRM) components for a paleomagnetic site without any assumption. To better constrain the stable components, some filters can be applied, such as establishing an upper boundary to the MAD, removing samples with anomalous intensities, or stating a minimum number of demagnetization steps (objective filters) or selecting a given unblocking interval (subjective but based on the expertise). On the other hand, the VPD program also allows the application of standard approaches (classic PCA fitting of directions a circles) and other ancillary methods (stacking routine, linearity spectrum analysis) giving an objective, global and robust idea of the demagnetization structure with minimal assumptions. Application of the VIDI method to natural cases (outcrops in the Pyrenees and u-channel data from a Roman dam infill in northern Spain) and their comparison to other approaches (classic end-point, demagnetization circle analysis, stacking routine and linearity spectrum analysis) allows validation of this technique. The VIDI is a global approach and it is especially useful for large data sets and rapid estimation of the NRM components.

Change in terrestrial ecosystem water-use efficiency over the last three decades.

PubMed

Huang, Mengtian; Piao, Shilong; Sun, Yan; Ciais, Philippe; Cheng, Lei; Mao, Jiafu; Poulter, Ben; Shi, Xiaoying; Zeng, Zhenzhong; Wang, Yingping

2015-06-01

Defined as the ratio between gross primary productivity (GPP) and evapotranspiration (ET), ecosystem-scale water-use efficiency (EWUE) is an indicator of the adjustment of vegetation photosynthesis to water loss. The processes controlling EWUE are complex and reflect both a slow evolution of plants and plant communities as well as fast adjustments of ecosystem functioning to changes of limiting resources. In this study, we investigated EWUE trends from 1982 to 2008 using data-driven models derived from satellite observations and process-oriented carbon cycle models. Our findings suggest positive EWUE trends of 0.0056, 0.0007 and 0.0001 g C m(-2)  mm(-1)  yr(-1) under the single effect of rising CO2 ('CO2 '), climate change ('CLIM') and nitrogen deposition ('NDEP'), respectively. Global patterns of EWUE trends under different scenarios suggest that (i) EWUE-CO2 shows global increases, (ii) EWUE-CLIM increases in mainly high latitudes and decreases at middle and low latitudes, (iii) EWUE-NDEP displays slight increasing trends except in west Siberia, eastern Europe, parts of North America and central Amazonia. The data-driven MTE model, however, shows a slight decline of EWUE during the same period (-0.0005 g C m(-2)  mm(-1)  yr(-1) ), which differs from process-model (0.0064 g C m(-2)  mm(-1)  yr(-1) ) simulations with all drivers taken into account. We attribute this discrepancy to the fact that the nonmodeled physiological effects of elevated CO2 reducing stomatal conductance and transpiration (TR) in the MTE model. Partial correlation analysis between EWUE and climate drivers shows similar responses to climatic variables with the data-driven model and the process-oriented models across different ecosystems. Change in water-use efficiency defined from transpiration-based WUEt (GPP/TR) and inherent water-use efficiency (IWUEt , GPP×VPD/TR) in response to rising CO2 , climate change, and nitrogen deposition are also discussed. Our analyses will facilitate mechanistic understanding of the carbon-water interactions over terrestrial ecosystems under global change. © 2015 John Wiley & Sons Ltd.

Pressure Venting Tests of Phenolic Impregnated Carbon Ablator (PICA)

NASA Technical Reports Server (NTRS)

Blosser, Max L.; Knutson, Jeffrey R.

2015-01-01

A series of tests was devised to investigate the pressure venting behavior of one of the candidate ablators for the Orion capsule heat shield. Three different specimens of phenolic impregnated carbon ablator (PICA) were instrumented with internal pressure taps and subjected to rapid pressure changes from near vacuum to one atmosphere and simulated Orion ascent pressure histories. The specimens vented rapidly to ambient pressure and sustained no detectable damage during testing. Peak pressure differences through the thickness of a 3-inch-thick specimen were less than 1 psi during a simulated ascent pressure history.

Numerical simulation of rock fragmentation during cutting by conical picks under confining pressure

NASA Astrophysics Data System (ADS)

Li, Xuefeng; Wang, Shibo; Ge, Shirong; Malekian, Reza; Li, Zhixiong

2017-12-01

In this article, the effect of confining pressure on rock fragmentation process during cutting was investigated by numerical simulation with a discrete element method (DEM). Four kinds of sandstones with different physical properties were simulated in the rock cutting models under different confining pressures. The rock fragmentation process, the cutting force, and the specific energy under different confining pressures were analyzed. With the increase in confining pressure and rock strength, the vertical propagation of cracks was restrained. Rock samples were compacted and strengthened by confining pressure resulting in the increase of the cutting force. The specific energy of rock cutting linearly increased with the increase of the confining pressure ratio.

Inter-Arm Difference in Brachial Blood Pressure in the General Population of Koreans

PubMed Central

Song, Bo Mi; Shim, Jee-Seon; Lee, Myung Ha; Choi, Dong Phil

2016-01-01

Background and Objectives We investigated the inter-arm difference in blood pressure of the general Korean population to identify associated factors. Subjects and Methods A total of 806 participants aged 30 to 64 years without history of major cardiovascular disease were analyzed in this cross-sectional study. They participated in the Cardiovascular and Metabolic Disease Etiology Research Center cohort study that began in 2013. Brachial blood pressure was measured simultaneously for both arms using an automated oscillometric device equipped with two cuffs in seated position. After five minutes of rest, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured three times. The average of the three measurements was used for analysis. Multivariate logistic regression models were used to identify factors associated with inter-arm differences in blood pressure. Results The mean inter-arm difference was 3.3 mmHg for SBP and 2.0 mmHg for DBP. Large inter-arm differences (≥10 mmHg) in SBP and in DBP were found in 3.7% and 0.9% of subjects, respectively. A large inter-arm difference in SBP was associated with mean SBP (p=0.002) and C-reactive protein (p=0.014) while a large inter-arm different in DBP was only associated with body mass index (p=0.015). Sex, age, and anti-hypertensive medication use were not associated with differences in inter-arm blood pressure. Conclusion Large inter-arm difference in blood pressure is only present in a small portion of healthy Korean adults. Our findings suggest that high SBP, chronic inflammation, and obesity may be associated with larger difference in inter-arm blood pressure. PMID:27275174

Comparison between gradient-dependent hydraulic conductivities of roots using the root pressure probe: the role of pressure propagations and implications for the relative roles of parallel radial pathways.

PubMed

Bramley, Helen; Turner, Neil C; Turner, David W; Tyerman, Stephen D

2007-07-01

Hydrostatic pressure relaxations with the root pressure probe are commonly used for measuring the hydraulic conductivity (Lp(r)) of roots. We compared the Lp(r) of roots from species with different root hydraulic properties (Lupinus angustifolius L. 'Merrit', Lupinus luteus L. 'Wodjil', Triticum aestivum L. 'Kulin' and Zea mays L. 'Pacific DK 477') using pressure relaxations, a pressure clamp and osmotic gradients to induce water flow across the root. Only the pressure clamp measures water flow under steady-state conditions. Lp(r) determined by pressure relaxations was two- to threefold greater than Lp(r) from pressure clamps and was independent of the direction of water flow. Lp(r) (pressure clamp) was two- to fourfold higher than for Lp(r) (osmotic) for all species except Triticum aestivum where Lp(r) (pressure clamp) and Lp(r) (osmotic) were not significantly different. A novel technique was developed to measure the propagation of pressure through roots to investigate the cause of the differences in Lp(r). Root segments were connected between two pressure probes so that when root pressure (P(r)) was manipulated by one probe, the other probe recorded changes in P(r). Pressure relaxations did not induce the expected kinetics in pressure in the probe at the other end of the root when axial hydraulic conductance, and probe and root capacitances were accounted for. An electric circuit model of the root was constructed that included an additional capacitance in the root loaded by a series of resistances. This accounted for the double exponential kinetics for intact roots in pressure relaxation experiments as well as the reduced response observed with the double probe experiments. Although there were potential errors with all the techniques, we considered that the measurement of Lp(r) using the pressure clamp was the most unambiguous for small pressure changes, and provided that sufficient time was allowed for pressure propagation through the root. The differences in Lp(r) from different methods of measurement have implications for the models describing water transport through roots and the potential role of aquaporins.

High hydrostatic pressures in traumatic joints require elevated synovial capillary pressure probably associated with arteriolar vasodilatation.

PubMed

Ahlqvist, J; Harilainen, A; Aalto, K; Sarna, S; Lalla, M; Osterlund, K

1994-11-01

Three out of the four Starling pressures were determined at arthroscopy of traumatic effusions of the knee. The range of the joint fluid hydrostatic pressure Pjoint was 5-83 cmH2O (0.5-8.1 kPa, 4-61 mmHg), that of the colloid osmotic pressure difference COPplasma-COPjoint 0-21.7 cmH2O. In 11 of 15 cases the sum Pjoint+COP difference exceeded 32.6 cmH2O (3.19 kPa, 24 mmHg), a high estimate of average capillary pressure at the level of the heart. The number of 'exceeding' cases was 8/15 if only 80% of the COP difference was considered effective. Pjoint and the COP difference oppose filtration of fluid from plasma into joints, indicating that mean capillary pressure, the only Starling pressure not determined, was elevated unless the effusions were being resorbed back into the blood. The findings can be explained by tamponade compensated by arteriolar vasodilatation, suspected to be metabolically mediated.

Elevation correction factor for absolute pressure measurements

NASA Technical Reports Server (NTRS)

Panek, Joseph W.; Sorrells, Mark R.

1996-01-01

With the arrival of highly accurate multi-port pressure measurement systems, conditions that previously did not affect overall system accuracy must now be scrutinized closely. Errors caused by elevation differences between pressure sensing elements and model pressure taps can be quantified and corrected. With multi-port pressure measurement systems, the sensing elements are connected to pressure taps that may be many feet away. The measurement system may be at a different elevation than the pressure taps due to laboratory space or test article constraints. This difference produces a pressure gradient that is inversely proportional to height within the interface tube. The pressure at the bottom of the tube will be higher than the pressure at the top due to the weight of the tube's column of air. Tubes with higher pressures will exhibit larger absolute errors due to the higher air density. The above effect is well documented but has generally been taken into account with large elevations only. With error analysis techniques, the loss in accuracy from elevation can be easily quantified. Correction factors can be applied to maintain the high accuracies of new pressure measurement systems.

Effect of holding pressure on microstructure and fracture behavior of low-pressure die cast A356-T6 alloy

NASA Astrophysics Data System (ADS)

Wu, Xiaoyan; Yun, Ying; Zhang, Huarui; Ma, Zhen; Jia, Lina; Tao, Tongxiang; Zhang, Hu

2017-12-01

The effect of different holding pressures on microstructure, tensile properties and fracture behavior of A356-T6 aluminum alloy was investigated. It was observed that the ultimate strength, yield strength and elongation of A356-T6 aluminum alloy increased with the increasing of holding pressure from 85 kPa to 300 kPa. This was attributed to the finer microstructure and the elimination of porosity defects caused by high holding pressure. The fractographs of specimens obtained under lower holding pressure displayed mixed quasi-cleavage and dimple type morphology with flat dimples and large amount of porosities. However, the fractographs of specimens obtained under high holding pressure of 300 kPa clearly exhibited a dimple morphology with small and deep dimples. The differences in the tensile fracture were attributed to the different shape of eutectic Si particle and different amount of porosity defects.

[Effect of sustained inflation with different degrees of negative pressure for sputum aspiration in patients with acute respiratory distress syndrome on lung recruitment].

PubMed

Huang, Xia; Cui, Jiwen

2015-07-01

To investigate the effect of different degrees of pressure of sustained inflation (SI) in patients with acute respiratory distress syndrome (ARDS) after lung recruitment as the result of different negative pressure for sputum aspiration. A prospective single-blind randomized controlled trial was conducted. The factorial analysis of variance was adopted. 150 patients with ARDS admitted to the emergency intensive care unit (ICU) of Chongqing Three Gorges Central Hospital from January 2012 to December 2014 were enrolled, and they were randomly divided into S1, S2, S3 group, with 50 patients in each group, suction pressure varying from 150, 175, to 200 mmHg (1 mmHg=0.133 kPa) was respectively used in each group. Then the patients of each group were randomly subdivided into five subgroups of P0, P1, P2, P3, P4, with 10 patients in each group, and 0, 30, 35, 40, and 45 cmH2O (1 cmH2O=0.098 kPa) were used for control pulmonary inflation pressure, respectively. The respiratory mechanics and the hemodynamic parameters were recorded, and they were compared before and after the sputum aspiration as well as lung recruitment with sustained inflation. The lung recruitment volume (mL: 87.56±28.47 vs. 109.38±34.63, t=3.573, P=0.001) and lung static compliance [Cst (mL/cmH2O): 27.69±13.25 vs. 35.87±17.47, t=2.814, P=0.004] after sputum aspiration in the 150 patients were significantly lower than those before the sputum aspiration, and peak airway pressure [PIP (cmH2O): 24.16±8.28 vs. 18.63±6.67, t=2.957, P=0.005], airway plateau pressure [Pplat (cmH2O): 21.28±9.14 vs. 17.47±7.26, t=2.089, P=0.032], and mean airway pressure [Pm (cmH2O): 13.26±4.65 vs. 10.41±3.54, t=3.271, P=0.001] were significantly higher than those before the treatment. There were no significant differences in the lung recruitment volume, Cst, PIP, Pplat and Pm between groups with different negative pressure for sputum aspiration (F value was 0.809, 0.986, 1.121, 0.910, 1.043, and P value was 0.452, 0.381, 0.335, 0.410, 0.361), but statistical significance was found among different groups of different lung recruitment pressures (F value was 3.581, 5.028, 3.064, 3.036, 4.050, and P value was 0.013, 0.002, 0.026, 0.027, 0.007). There was no interaction between the two factors. After pairwise comparison, under the same negative pressure for sputum aspiration, lung recruitment volume and Cst in different lung recruitment pressures subgroups (P1, P2, P3, P4) were significantly higher than those of P0 subgroup, and PIP, Pplat, and Pm were significantly lower than those of P0 subgroup. There was no significant difference among P1, P2, P3 and P4 groups. There were no significant differences in mean arterial pressure (MAP) and pulmonary arterial pressure (PAP) among different groups with negative pressures for sputum aspiration and different lung recruitment pressures (negative pressure for sputum aspiration: F=0.586, P=0.561, F=1.373, P=0.264; lung recruitment pressure: F=1.313, P=0.280, F=1.621, P=0.186), there was no interaction between the two factors (F=0.936, P=0.497, F=1.391, P=0.227). The difference of heart rate (HR) in different negative pressure for sputum aspiration groups was not significant (F=1.144, P=0.328), and there were significant differences in different lung recruitment pressure groups (F=3.297, P=0.019), there was no interaction between the two factors (F=1.277, P=0.280). After pairwise comparison, under the same negative pressure for sputum aspiration, HR in P3 and P4 subgroups was significantly higher than that in P0, P1, and P2 subgroups (all P<0.05). 30 cmH2O and 35 cmH2O were the suitable pressure for SI in ARDS patients, and they were not affected by different negative pressure for sputum aspiration.

Pulse pressure and diabetes treatments: Blood pressure and pulse pressure difference among glucose lowering modality groups in type 2 diabetes.

PubMed

Alemi, Hamid; Khaloo, Pegah; Mansournia, Mohammad Ali; Rabizadeh, Soghra; Salehi, Salome Sadat; Mirmiranpour, Hossein; Meftah, Neda; Esteghamati, Alireza; Nakhjavani, Manouchehr

2018-02-01

Type 2 diabetes is associated with higher pulse pressure. In this study, we assessed and compared effects of classic diabetes treatments on pulse pressure (PP), systolic blood pressure (SBP), and diastolic blood pressure (DBP) in patients with type 2 diabetes.In a retrospective cohort study, 718 non-hypertensive patients with type 2 diabetes were selected and divided into 4 groups including metformin, insulin, glibenclamide+metformin, and metformin+insulin. They were followed for 4 consecutive visits lasting about 45.5 months. Effects of drug regimens on pulse and blood pressure over time were assessed separately and compared in regression models with generalized estimating equation method and were adjusted for age, duration of diabetes, sex, smoking, and body mass index (BMI).Studied groups had no significant change in PP, SBP, and DBP over time. No significant difference in PP and DBP among studied groups was observed (PP:P = 0.090; DBP:P = 0.063). Pairwise comparisons of PP, SBP, and DBP showed no statistically significant contrast between any 2 studied groups. Interactions of time and treatment were not different among groups.Our results demonstrate patients using metformin got higher PP and SBP over time. Averagely, pulse and blood pressure among groups were not different. Trends of variation in pulse and blood pressure were not different among studied diabetes treatments.

Prediction of Three-Dimensional Downward Flame Spread Characteristics over Poly(methyl methacrylate) Slabs in Different Pressure Environments.

PubMed

Zhao, Kun; Zhou, Xiao-Dong; Liu, Xue-Qiang; Lu, Lei; Wu, Zhi-Bo; Peng, Fei; Ju, Xiao-Yu; Yang, Li-Zhong

2016-11-22

The present study is aimed at predicting downward flame spread characteristics over poly(methyl methacrylate) (PMMA) with different sample dimensions in different pressure environments. Three-dimensional (3-D) downward flame spread experiments on free PMMA slabs were conducted at five locations with different altitudes, which provide different pressures. Pressure effects on the flame spread rate, profile of pyrolysis front and flame height were analyzed at all altitudes. The flame spread rate in the steady-state stage was calculated based on the balance on the fuel surface and fuel properties. Results show that flame spread rate increases exponentially with pressure, and the exponent of pressure further shows an increasing trend with the thickness of the sample. The angle of the pyrolysis front emerged on sample residue in the width direction, which indicates a steady-burning stage, varies clearly with sample thicknesses and ambient pressures. A global non-dimensional equation was proposed to predict the variation tendency of the angle of the pyrolysis front with pressure and was found to fit well with the measured results. In addition, the dependence of average flame height on mass burning rate, sample dimension and pressure was proposed based on laminar diffusion flame theory. The fitted exponent of experimental data is 1.11, which is close to the theoretical value.

Acute tamponade alters subendo- and subepicardial pressure-flow relations differently during vasodilation.

PubMed

Kingma, J G; Martin, J; Rouleau, J R

1994-07-01

Instantaneous diastolic left coronary artery pressure-flow relations (PFR) shift during acute tamponade as pressure surrounding the heart increases. Coronary pressure at zero flow (Pf = 0) on the linear portion of the PFR is the weighted mean of the different myocardial waterfall pressures, the distribution of which varies across the left ventricular wall during diastole. However, instantaneous PFR measured in large epicardial coronary arteries cannot be used to estimate Pf = 0 in the different myocardial tissue layers. During coronary vasodilatation in a capacitance-free model, myocardial PFR differs from subendocardium to subepicardium. Therefore, we studied the effects of acute tamponade during maximal pharmacology induced coronary vasodilatation on myocardial PFR in in situ anesthetized dogs. Tamponade reduced cardiac output, aortic pressure, and coronary blood flow. Results demonstrate that different mechanisms influence distribution of myocardial blood flow during tamponade. Subepicardial vascular resistance is unchanged and the extrapolated Pf = 0 is increased, thereby shifting PFR to a higher intercept on the pressure axis. Subendocardial vascular resistance is increased while the extrapolated Pf = 0 remains unchanged. Results indicate that in the setting of acute tamponade with coronary vasodilatation different mechanisms regulate the distribution of myocardial blood flow: in the subepicardium only outflow pressure increases, whereas in the subendocardium only vascular resistance increases.

Generational Differences in Resistance to Peer Pressure among Mexican-Origin Adolescents.

ERIC Educational Resources Information Center

Umana-Taylor, Adriana J.; Bamaca-Gomez, Mayra Y.

2003-01-01

Examined whether Mexican origin adolescents who varied by generational status would differ in their resistance to peer pressure. After controlling for gender, resistance to peer pressure varied significantly by generational status. Adolescents with no familial births in the United States were significantly more resistant to peer pressure than…

Changes of contact pressure and area in patellofemoral joint after different meniscectomies.

PubMed

Bai, Bo; Shun, Hui; Yin, Zhi Xun; Liao, Zhuang-Wen; Chen, Ni

2012-05-01

We investigated the contact pressure and area of the patellofemoral joint both before and after different meniscectomies to provide a biomechanical basis for selecting meniscectomy and its clinical application for meniscus injuries. Six fresh cadaveric knees were used in the study. Using Staubli robots and an ultra-low-min-type pressure-sensitive tablet, changes in contact area and stress in the patellofemoral joint were measured at various flexion angles following different parts and degrees of meniscectomy. The patellofemoral contact area enlarged with the increase of knee flexion angle. From the values obtained from contact areas and average contact pressure of the patellofemoral joint, we found no significant difference between partial meniscectomy and intact knees, but a significant difference was found between total meniscectomy and intact knees. The contact area after lateral meniscectomy was statistically less than that of intact knees. The mean patellofemoral contact pressure after lateral meniscectomy was larger than in intact knees at each angle of flexion. No significant difference in contact area was observed between intact knees and medial meniscectomy. The average patellofemoral contact pressure after medial meniscectomy was larger than in intact knees from 0° ~ 30° of knee flexion, and no significant differences were found between intact knees and medial meniscectomy while knee bending from 60° to 90°. Different meniscectomies result in high contact pressure or disordered distribution of contact pressure, which may be the cause of postoperative patellofemoral degenerative arthrosis.

Detection of non-natural springtime precipitation change over northern South America

NASA Astrophysics Data System (ADS)

Barkhordarian, A.; Behrangi, A.; Mechoso, C. R.

2017-12-01

Here we determine whether the climate over South America has changed as a result of human activity since the beginning of the industrial revolution. To this end, we assess whether the observed changes are likely to have been due to natural (internal) variability alone, and if not, whether they are consistent with what models simulate as response to anthropogenic and natural forcing. Internal variability is estimated using 12,000-year control runs derived from CMIP5 archive. Results indicate that, in the past decades, trends in springtime (ASO, August-October) precipitation over South America have a magnitude that is beyond the estimated range due to natural (internal) variability or natural forcings alone. Evidence for the presence of an external driving factor is clearly detectable in the observed precipitation record (with less than 5% risk of error). The regression results illustrate the concerted emergence of an anthropogenic signal consistent with greenhouse gas (GHG) in observed decreasing 30-year trends of precipitation ending in 1998 and later on. In addition, the fingerprint of land-use-change signal is detectable in the observed precipitation decrease over 1983-2012. While the influence of GHG signal is detectable in precipitation, an observed decrease up to 10 mm/decade drying over the Amazon region, is much larger than the changes simulated by global and regional climate models as response to GHG forcing. We further show that the projected increasing trend of vapor pressure deficit (VPD), an indicator of background aridity, by the climate models with GHG forcing is much smaller than that observed over the Amazon rainforest. This may imply that models may underestimate the resulting reductions in forest CO2 uptake that could function as a positive feedback to rising temperature and reducing precipitation. Taking the ensemble of 23 IPCC models as a crude metric of probabilities, we further show that with 19 out of 24 models the effect of GS signal (greenhouse gas and anthropogenic aerosols) based on RCP4.5 scenario has already a detectable influence in the observed drying over Amazon region. This may imply that the observed drier air conditions plus higher surface air temperature during austral spring serve as an illustration of plausible future expected change in the region.

Effects of long-term low atmospheric pressure on gas exchange and growth of lettuce

NASA Astrophysics Data System (ADS)

Tang, Yongkang; Guo, Shuangsheng; Dong, Wenping; Qin, Lifeng; Ai, Weidang; Lin, Shan

2010-09-01

The objectives of this research were to determine photosynthesis, evapotranspiration and growth of lettuce at long-term low atmospheric pressure. Lettuce ( Lactuca sativa L . cv. Youmaicai) plants were grown at 40 kPa total pressure (8.4 kPa p) or 101 kPa total pressure (20.9 kPa p) from seed to harvest for 35 days. Germination rate of lettuce seeds decreased by 7.6% at low pressure, although this was not significant. There was no significant difference in crop photosynthetic rate between hypobaria and ambient pressure during the 35-day study. The crop evapotranspiration rate was significantly lower at low pressure than that at ambient pressure from 20 to 30 days after planting (DAP), but it had no significant difference before 20 DAP or after 30 DAP. The growth cycle of lettuce plants at low pressure was delayed. At low pressure, lettuce leaves were curly at the seedling stage and this disappeared gradually as the plants grew. Ambient lettuce plants were yellow and had an epinastic growth at harvest. The shoot height, leaf number, leaf length and shoot/root ratio were lower at low pressure than those at ambient pressure, while leaf area and root growth increased. Total biomass of lettuce plants grown at two pressures had no significant difference. Ethylene production at low pressure decreased significantly by 38.8% compared with ambient pressure. There was no significant difference in microelements, nutritional phytochemicals and nitrate concentrations at the two treatments. This research shows that lettuce can be grown at long-term low pressure (40 kPa) without significant adverse effects on seed germination, gas exchange and plant growth. Furthermore, ethylene release was reduced in hypobaria.

An ex vivo porcine skin model to evaluate pressure-reducing devices of different mechanical properties used for pressure ulcer prevention.

PubMed

Yeung, Ching-Yan C; Holmes, David F; Thomason, Helen A; Stephenson, Christian; Derby, Brian; Hardman, Matthew J

2016-11-01

Pressure ulcers are complex wounds caused by pressure- and shear-induced trauma to skin and underlying tissues. Pressure-reducing devices, such as dressings, have been shown to successfully reduce pressure ulcer incidence, when used in adjunct to pressure ulcer preventative care. While pressure-reducing devices are available in a range of materials, with differing mechanical properties, understanding of how a material's mechanical properties will influence clinical efficacy remains limited. The aim of this study was to establish a standardized ex vivo model to allow comparison of the cell protection potential of two gel-like pressure-reducing devices with differing mechanical properties (elastic moduli of 77 vs. 35 kPa). The devices also displayed differing energy dissipation under compressive loading, and resisted strain differently under constant load in compressive creep tests. To evaluate biological efficacy we employed a new ex vivo porcine skin model, with a confirmed elastic moduli closely matching that of human skin (113 vs. 119 kPa, respectively). Static loads up to 20 kPa were applied to porcine skin ex vivo with subsequent evaluation of pressure-induced cell death and cytokine release. Pressure application alone increased the percentage of epidermal apoptotic cells from less than 2% to over 40%, and increased cellular secretion of the pro-inflammatory cytokine TNF-alpha. Co-application of a pressure-reducing device significantly reduced both cellular apoptosis and cytokine production, protecting against cellular damage. These data reveal new insight into the relationship between mechanical properties of pressure-reducing devices and their biological effects. After appropriate validation of these results in clinical pressure ulcer prevention with all tissue layers present between the bony prominence and external surface, this ex vivo porcine skin model could be widely employed to optimize design and evaluation of devices aimed at reducing pressure-induced skin damage. © 2016 The Authors Wound Repair and Regeneration published by Wiley Periodicals, Inc. on behalf of The Wound Healing Society.

Student measurement of blood pressure using a simulator arm compared with a live subject's arm.

PubMed

Lee, Jennifer J; Sobieraj, Diana M; Kuti, Effie L

2010-06-15

To compare accuracy of blood pressure measurements using a live subject and a simulator arm, and to determine students' preferences regarding measurement. This was a crossover study comparing blood pressure measurements from a live subject and a simulator arm. Students completed an anonymous survey instrument defining opinions on ease of measurement. Fifty-seven students completed blood pressure measurements on live subjects while 72 students completed blood pressure measurements using the simulator arm. There were no significant systematic differences between the 2 measurement techniques. Systolic blood pressure measurements from a live subject arm were less likely to be within 4 mm Hg compared with measurements of a simulator arm. Diastolic blood pressure measurements were not significantly different between the 2 techniques. Accuracy of student measurement of blood pressure using a simulator arm was similar to the accuracy with a live subject. There was no difference in students' preferences regarding measurement techniques.

Pressure monitoring during lipofilling procedures.

PubMed

Klein, S M; Prantl, L; Geis, S; Eisenmann-Klein, M; Dolderer, J; Felthaus, O; Loibl, M; Heine, N

2014-01-01

Grafting of autologous lipoaspirate for various clinical applications has become a common procedure in clinical practice. With an estimated mortality rate of 10-15 percent, fat embolism is among the most severe complications to be expected after lipofilling therapies. The aim of this study was to determine the level of interstitial pressure after the injection of defined volumes of lipoaspirate into the subcutaneous tissue of female breasts. It was hypothesized, that interstitial pressure levels exceed the physiologic capillary pressure during lipofilling procedures and hence increase the potential risk for fat embolism. Further it was investigated if external tissue expansion has the potential to significantly reduce interstitial tissue pressure. Interstitial pressure was monitored in 36 female patients, that underwent autologous fat injections into the breast. Measurements were conducted with a sensor needle connected to a pressure transducer (LogiCal Pressure Monitoring Kit, Smiths medical int. Ltd., UK). Patients were divided into 4 subcohorts differing in their pre-treatment regimen or local tissue conditions. Pre-treatment consisted of tissue expansion, achieved with the Brava™ (Brava LLC Miami, Fla., USA) vacuum-chamber. The increase in interstitial pressure after injection volumes of 100 ml (p = 0.006), 200 ml (p = 0.000) and between 100 ml and 200 ml (p = 0.004) respectively, were significant in non-mastectomized patients without pre-treatment. Patients pre-treated with Brava™ did not show such statistically significant differences in interstitial pressures before and after the injection of 100 ml and 200 ml of lipoaspirate (p = 0.178). The difference in interstitial pressure in mastectomized patients between 0 ml and 100 ml (p = 0.003), as well as 0 ml and 200 ml (p = 0.028) was significant. The difference in pressures between pre-treated patients and patients without pre-treatment did not differ significantly in the mastectomized patient cohort. During lipofilling procedures interstitial pressures are reached that exceed pressure limits defined as hazardous for fat embolism. To date it is unknown what pressure levels need to be considered critical for complications in soft tissue interventions. Further the results indicate higher interstitial pressures for patients that had undergone mastectomy, whereas pre-treatment with external tissue expansion seemed to diminish pressure values.

Confounding compression: the effects of posture, sizing and garment type on measured interface pressure in sports compression clothing.

PubMed

Brophy-Williams, Ned; Driller, Matthew William; Shing, Cecilia Mary; Fell, James William; Halson, Shona Leigh; Halson, Shona Louise

2015-01-01

The purpose of this investigation was to measure the interface pressure exerted by lower body sports compression garments, in order to assess the effect of garment type, size and posture in athletes. Twelve national-level boxers were fitted with sports compression garments (tights and leggings), each in three different sizes (undersized, recommended size and oversized). Interface pressure was assessed across six landmarks on the lower limb (ranging from medial malleolus to upper thigh) as athletes assumed sitting, standing and supine postures. Sports compression leggings exerted a significantly higher mean pressure than sports compression tights (P < 0.001). Oversized tights applied significantly less pressure than manufacturer-recommended size or undersized tights (P < 0.001), yet no significant differences were apparent between different-sized leggings. Standing posture resulted in significantly higher mean pressure application than a seated posture for both tights and leggings (P < 0.001 and P = 0.002, respectively). Pressure was different across landmarks, with analyses revealing a pressure profile that was neither strictly graduated nor progressive in nature. The pressure applied by sports compression garments is significantly affected by garment type, size and posture assumed by the wearer.

The position of the arm during blood pressure measurement in sitting position.

PubMed

Adiyaman, Ahmet; Verhoeff, Rutger; Lenders, Jacques W M; Deinum, Jaap; Thien, Theo

2006-12-01

Determining the influence of the position of the arm on blood pressure measurement in the sitting position. Blood pressure of 128 individuals (the majority being treated hypertensive patients) visiting the outpatient clinic was measured simultaneously on both arms with arms in two different positions. First, both arms were placed at the chair support level and blood pressure was measured three times on both arms after 10 min of rest. Subsequently, while still remaining in the same sitting position, five blood pressure measurements were made simultaneously at both arms with one arm placed on the desk and one arm placed and supported at heart level (mid-sternal). The arm placed at heart level served as the reference arm. The choice of which arm was placed at desk level and which arm was placed at heart level was randomized. Both at desk level and at chair support level, mean (+/-SD) systolic and diastolic blood pressures were higher than blood pressure at heart level by 6.1/5.7+/-4.6/3.1 and 9.3/9.4+/-5.4/3.4 mmHg, respectively. The effect of the height differences between the arm positions on the blood pressure readings was smaller than predicted (0.49 mmHg/cm systolic and 0.47 mmHg/cm diastolic). No significant correlation was found between blood pressure difference in the different arm positions (desk and heart level) and age, sex, weight or baseline blood pressure. Different arm positions below heart level have significant effects on blood pressure readings. The leading guidelines about arm position during blood pressure measurement are not in accordance with the arm position used in the Framingham study, the most frequently used study for risk estimations.

Exercise capacity in young adults with hypertension and systolic blood pressure difference between right arm and leg after repair of coarctation of the aorta.

PubMed

Instebø, Arne; Norgård, Gunnar; Helgheim, Vegard; Røksund, Ola Drange; Segadal, Leidulf; Greve, Gottfried

2004-10-01

Coarctation of the aorta represents 5-7% of congenital heart defects. Symptoms and prognosis depend on the degree of stenosis, age at surgery, surgical method and the presence of other heart defects. Postoperative complications are hypertension, restenosis and an abnormal blood pressure response during exercise. This study includes 41 patients, 15-40 years old, operated in the period 1975-1996. All were exercised on a treadmill until maximal oxygen consumption was achieved. Blood pressure was measured in the right arm and leg before and immediately after exercise, and in the right arm during exercise. Oxygen consumption was monitored and we defined an aerobic phase, an isocapnic buffering phase and a hypocapnic hyperventilation phase. The resting systolic blood pressure correlates with the resting systolic blood pressure difference between right arm and leg. A resting systolic blood pressure difference between the right arm and leg of 0.13 kPa (1 mmHg) to 2.67 kPa (20 mmHg) corresponds with a slight increase in resting systolic blood pressure. This rise in blood pressure increases the aerobic phase of the exercise test, helping the patients to achieve higher maximal oxygen consumption. A resting systolic blood pressure difference of more than 2.67 kPa (20 mmHg) corresponds with severe hypertension and causes reduction in the aerobic phase and maximal oxygen consumption. Resting systolic blood pressure and resting systolic blood pressure difference between the right arm and leg are not indicators for blood pressure response during exercise. Exercise testing is important to reveal exercise-induced hypertension and to monitor changes in transition from aerobic to anaerobic exercise and limitation to exercise capacity.

[Features of arterial blood pressure in elderly persons of different ethnic groups in Yakutsk].

PubMed

Nikitin, Iu P; Tatarinova, O V; Neustroeva, V N; Shcherbakova, L V; Sidorov, A S

2013-01-01

The differences in arterial blood pressure in the sample of population in the age of 60 and older of different ethnic groups in Yakutsk, as well as its connection with the other cardiovascular diseases risk factors have been analyzed. It was shown that the average values of systolic and diastolic blood pressure in subsample of the Yakuts appeared to be lower than in Caucasoid gerontic persons. The average values of systolic arterial blood pressure both in the Yakuts and in the Caucasoids were detected higher than normal values in all age-dependent subgroups. The average values of diastolic blood pressure in both ethnic groups were within the limits of high normal level. From 60 to 90 years and older the decrease in systolic and diastolic arterial blood pressure was detected; it was more marked in Caucasoid gerontic persons. The average values of pulse pressure in the Yakuts and in the Caucasoids appeared to be higher than the existing standard and didn't have any differences in ethnic groups. In both ethnical subsamples, pulse pressure values increase was observed in persons of 60-89 years old and its decrease after 90. Persons with overweight, obesity, central (abdominal) obesity, dyslypoproteidemias irrespective of belonging to ethnical group were characterized as having higher levels of arterial blood pressure. Statistically significant differences in the levels of arterial blood pressure in the Yakuts and in the Caucasoids depending on hyperglycemia, smoking, the presence of burdened anamnesis, educational level, marital status was not detected.

Effect of different pressure magnitudes on hypertrophic scar in a Chinese population.

PubMed

Candy, Lai Hoi Yan; Cecilia, Li-Tsang Wai Ping; Ping, Zheng Yong

2010-12-01

This study aimed to investigate the effect of different pressure magnitudes on treatment outcomes of hypertrophic scars, and determine pressure loss over time. A randomized clinical trial was adopted. 53 hypertrophic scar samples from 17 Chinese participants were recruited and randomly assigned into a high pressure group (20-25 mmHg) and low pressure group (10-15 mmHg) for a five-month intervention program. The scars were assessed objectively before intervention and monthly after intervention for thickness, color (redness, yellowness and lightness) and scar pliability. Pressure magnitude at each assessment was also measured. Two-way repeated ANOVA was used to compare for differences between groups. The results showed that both levels of pressure produced reduction in scar thickness and redness, but the improvement in the high pressure group was statistically better than that of the counterpart (both p<0.05). Monthly pressure measurement revealed that pressure loss in the high pressure group was more severe. However, no major changes in other color parameters and pliability were observed for both the groups. High pressure was demonstrated to be more effective for scar management, but it was also more prone to higher pressure loss. Pressure therapy integrated with regular monitoring of the interface pressure is suggested to improve its therapeutic efficacy. Copyright © 2010 Elsevier Ltd and ISBI. All rights reserved.

Office blood pressure or ambulatory blood pressure for the prediction of cardiovascular events.

PubMed

Mortensen, Rikke Nørmark; Gerds, Thomas Alexander; Jeppesen, Jørgen Lykke; Torp-Pedersen, Christian

2017-11-21

To determine the added value of (i) 24-h ambulatory blood pressure relative to office blood pressure and (ii) night-time ambulatory blood pressure relative to daytime ambulatory blood pressure for 10-year person-specific absolute risks of fatal and non-fatal cardiovascular events. A total of 7927 participants were included from the International Database on Ambulatory blood pressure monitoring in relation to Cardiovascular Outcomes. We used cause-specific Cox regression to predict 10-year person-specific absolute risks of fatal and non-fatal cardiovascular events. Discrimination of 10-year outcomes was assessed by time-dependent area under the receiver operating characteristic curve (AUC). No differences in predicted risks were observed when comparing office blood pressure and ambulatory blood pressure. The median difference in 10-year risks (1st; 3rd quartile) was -0.01% (-0.3%; 0.1%) for cardiovascular mortality and -0.1% (-1.1%; 0.5%) for cardiovascular events. The difference in AUC (95% confidence interval) was 0.65% (0.22-1.08%) for cardiovascular mortality and 1.33% (0.83-1.84%) for cardiovascular events. Comparing daytime and night-time blood pressure, the median difference in 10-year risks was 0.002% (-0.1%; 0.1%) for cardiovascular mortality and -0.01% (-0.5%; 0.2%) for cardiovascular events. The difference in AUC was 0.10% (-0.08 to 0.29%) for cardiovascular mortality and 0.15% (-0.06 to 0.35%) for cardiovascular events. Ten-year predictions obtained from ambulatory blood pressure are similar to predictions from office blood pressure. Night-time blood pressure does not improve 10-year predictions obtained from daytime measurements. For an otherwise healthy population sufficient prognostic accuracy of cardiovascular risks can be achieved with office blood pressure. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For permissions, please email: journals.permissions@oup.com.

Variability and repeatability analysis of plantar pressure during gait in older people.

PubMed

Franco, Pedro S; Silva, Caio Borella P da; Rocha, Emmanuel S da; Carpes, Felipe P

2015-01-01

Repeatability and variability of the plantar pressure during walking are important components in the clinical assessment of the elderly. However, there is a lack of information on the uniformity of plantar pressure patterns in the elderly. To analyze the repeatability and variability in plantar pressure considering mean, peak and asymmetries during aged gait. Plantar pressure was monitored in four different days for ten elderly subjects (5 female), with mean±standard-deviation age of 73±6 years, walking barefoot at preferred speed. Data were compared between steps for each day and between different days. Mean and peak plantar pressure values were similar between the different days of evaluation. Asymmetry indexes were similar between the different days evaluated. Plantar pressure presented a consistent pattern in the elderly. However, the asymmetry indexes observed suggest that the elderly are exposed to repetitive asymmetric loading during locomotion. Such result requires further investigation, especially concerning the role of these asymmetries for development of articular injuries. Copyright © 2015 Elsevier Editora Ltda. All rights reserved.

Influence of phase type and solute structure on changes in retention with pressure in reversed-phase high performance liquid chromatography.

PubMed

Fallas, Morgane M; Tanaka, Nobuo; Buckenmaier, Stephan M C; McCalley, David V

2013-07-05

The influence of pressure on the retention of several types of solute, including acids, bases and neutrals, was studied by the use of restriction capillaries added to the end of various monomeric and polymeric octadecylsilyl-modified 5μm particle size columns. Although it appeared that certain polymeric columns could give somewhat greater increases in retention with pressure, differences in behaviour between these different C18 columns were rather small. Differences in solute molecular size were most important in determining increases in retention with pressure. However, solute structure such as polarity and planarity were also influential. A prototype C30 column gave interesting selectivity changes between planar and non-planar solutes as a function of pressure. Considerable selectivity differences with pressure were shown when diverse mixtures of solutes were analysed. For the solutes studied, only minor effects of increased pressure on column efficiency and peak shape were noted. Copyright © 2013 Elsevier B.V. All rights reserved.

High pressure phase transformations revisited

NASA Astrophysics Data System (ADS)

Levitas, Valery I.

2018-04-01

High pressure phase transformations play an important role in the search for new materials and material synthesis, as well as in geophysics. However, they are poorly characterized, and phase transformation pressure and pressure hysteresis vary drastically in experiments of different researchers, with different pressure transmitting media, and with different material suppliers. Here we review the current state, challenges in studying phase transformations under high pressure, and the possible ways in overcoming the challenges. This field is critically compared with fields of phase transformations under normal pressure in steels and shape memory alloys, as well as plastic deformation of materials. The main reason for the above mentioned discrepancy is the lack of understanding that there is a fundamental difference between pressure-induced transformations under hydrostatic conditions, stress-induced transformations under nonhydrostatic conditions below yield, and strain-induced transformations during plastic flow. Each of these types of transformations has different mechanisms and requires a completely different thermodynamic and kinetic description and experimental characterization. In comparison with other fields the following challenges are indicated for high pressure phase transformation: (a) initial and evolving microstructure is not included in characterization of transformations; (b) continuum theory is poorly developed; (c) heterogeneous stress and strain fields in experiments are not determined, which leads to confusing material transformational properties with a system behavior. Some ways to advance the field of high pressure phase transformations are suggested. The key points are: (a) to take into account plastic deformations and microstructure evolution during transformations; (b) to formulate phase transformation criteria and kinetic equations in terms of stress and plastic strain tensors (instead of pressure alone); (c) to develop multiscale continuum theories, and (d) to couple experimental, theoretical, and computational studies of the behavior of a tested sample to extract information about fields of stress and strain tensors and concentration of high pressure phase, transformation criteria and kinetics. The ideal characterization should contain complete information which is required for simulation of the same experiments.

Influence of hydrostatic pressure on intracoronary indices of stenosis severity in vivo.

PubMed

Härle, Tobias; Luz, Mareike; Meyer, Sven; Vahldiek, Felix; van der Harst, Pim; van Dijk, Randy; Ties, Daan; Escaned, Javier; Davies, Justin; Elsässer, Albrecht

2018-03-01

An influence of hydrostatic pressure on intracoronary indices of stenosis severity in vitro was recently reported. We sought to analyze the influence of hydrostatic pressure, caused by the height difference between the distal and proximal pressure sensor after guidewire positioning in the interrogated vessel, on intracoronary pressure measurements in vivo. In 30 coronary stenoses, intracoronary pressure measurements were performed in supine, left, and right lateral patient position. Height differences between the distal and proximal pressure sensor were measured by blinded observers. Measurement results of the position with the highest ("high") and lowest height difference ("low") were compared. In group "high", all measured indices were higher: mean difference of fractional flow reserve (FFR) 0.045 (SD 0.033, 95% CI 0.033-0.057, p < 0.0001), of instantaneous wave-free ratio (iFR) 0.043 (SD 0.04, 95% CI 0.029-0.057, p < 0.0001), and of resting Pd/Pa 0.037 (SD 0.034, 95% CI 0.025-0.049, p < 0.0001). Addition of the physically expectable hydrostatic pressure to the distal coronary pressures of the control group abolished the differences: corrected ∆FFR - 0.006 (SD 0.027, 95% CI - 0.015 to 0.004, p = 0.26), corrected ∆Pd/Pa - 0.008 (SD 0.03, 95% CI - 0.019 to 0.003, p = 0.18). Adjustment for hydrostatic pressure of FFR values in a standard supine position increased all values in anterior vessels and decreased all values in posterior vessels. The mean changes of FFR due to adjustment were: LAD - 0.048 (SD 0.016), CX 0.02 (SD 0.009), RCA 0.02 (SD 0.021). Dichotomous severity classification changed in 12.9% of stenoses. The study demonstrates a relevant influence of hydrostatic pressure on intracoronary indices of stenosis severity in vivo, caused by the height differences between distal and proximal pressure sensor.

High pressure phase transformations revisited.

PubMed

Levitas, Valery I

2018-04-25

High pressure phase transformations play an important role in the search for new materials and material synthesis, as well as in geophysics. However, they are poorly characterized, and phase transformation pressure and pressure hysteresis vary drastically in experiments of different researchers, with different pressure transmitting media, and with different material suppliers. Here we review the current state, challenges in studying phase transformations under high pressure, and the possible ways in overcoming the challenges. This field is critically compared with fields of phase transformations under normal pressure in steels and shape memory alloys, as well as plastic deformation of materials. The main reason for the above mentioned discrepancy is the lack of understanding that there is a fundamental difference between pressure-induced transformations under hydrostatic conditions, stress-induced transformations under nonhydrostatic conditions below yield, and strain-induced transformations during plastic flow. Each of these types of transformations has different mechanisms and requires a completely different thermodynamic and kinetic description and experimental characterization. In comparison with other fields the following challenges are indicated for high pressure phase transformation: (a) initial and evolving microstructure is not included in characterization of transformations; (b) continuum theory is poorly developed; (c) heterogeneous stress and strain fields in experiments are not determined, which leads to confusing material transformational properties with a system behavior. Some ways to advance the field of high pressure phase transformations are suggested. The key points are: (a) to take into account plastic deformations and microstructure evolution during transformations; (b) to formulate phase transformation criteria and kinetic equations in terms of stress and plastic strain tensors (instead of pressure alone); (c) to develop multiscale continuum theories, and (d) to couple experimental, theoretical, and computational studies of the behavior of a tested sample to extract information about fields of stress and strain tensors and concentration of high pressure phase, transformation criteria and kinetics. The ideal characterization should contain complete information which is required for simulation of the same experiments.

Comparison of endotracheal tube cuff pressure values before and after training seminar.

PubMed

Özcan, Ayça Tuba Dumanlı; Döğer, Cihan; But, Abdülkadir; Kutlu, Işık; Aksoy, Şemsi Mustafa

2018-06-01

It is recommended that endotracheal cuff (ETTc) pressure be between 20 and 30 cm H 2 O. In this present study, we intend to observe average cuff pressure values in our clinic and the change in these values after the training seminar. The cuff pressure values of 200 patients intubated following general anesthesia induction in the operating theatre were measured following intubation. One hundred patients whose values were measured before the training seminar held for all physician assistants, and 100 patients whose values were measured after the training seminar were regarded as Group 1 and Group 2, respectively. Cuff pressures of both groups were recorded, and the difference between them was shown. Moreover, cuff pressure values were explored according to the working period of the physician assistants. There was no significant difference between the groups in terms of age, gender and tube diameters. Statistically significant difference was found between cuff pressure values before and after the training (p < 0.001). Average pressure measure for Group I was 54 cm H 2 O, while average pressure in Group II declined to 33 cm H 2 O. It was observed that as the working period and experience of physician assistants increased, cuff pressure values decreased, however no statistically significant different was found (p < 0.375). We believe that clinical experience does not have significant effects on cuff pressure and that training seminars held at intervals would prevent high cuff pressure values and potential complications.

The difference in blood pressure readings between arms and survival: primary care cohort study.

PubMed

Clark, Christopher E; Taylor, Rod S; Shore, Angela C; Campbell, John L

2012-03-20

To determine whether a difference in systolic blood pressure readings between arms can predict a reduced event free survival after 10 years. Cohort study. Rural general practice in Devon, United Kingdom. 230 people receiving treatment for hypertension in primary care. Bilateral blood pressure measurements recorded at three successive surgery attendances. Cardiovascular events and deaths from all causes during a median follow-up of 9.8 years. At recruitment 24% (55/230) of participants had a mean interarm difference in systolic blood pressure of 10 mm Hg or more and 9% (21/230) of 15 mm Hg or more; these differences were associated with an increased risk of all cause mortality (adjusted hazard ratio 3.6, 95% confidence interval 2.0 to 6.5 and 3.1, 1.6 to 6.0, respectively). The risk of death was also increased in 183 participants without pre-existing cardiovascular disease with an interarm difference in systolic blood pressure of 10 mm Hg or more or 15 mm Hg or more (2.6, 1.4 to 4.8 and 2.7, 1.3 to 5.4). An interarm difference in diastolic blood pressure of 10 mm Hg or more was weakly associated with an increased risk of cardiovascular events or death. Differences in systolic blood pressure between arms can predict an increased risk of cardiovascular events and all cause mortality over 10 years in people with hypertension. This difference could be a valuable indicator of increased cardiovascular risk. Bilateral blood pressure measurements should become a routine part of cardiovascular assessment in primary care.

Randomized trial of low versus high carbon dioxide insufflation pressures in posterior retroperitoneoscopic adrenalectomy.

PubMed

Fraser, Sheila; Norlén, Olov; Bender, Kyle; Davidson, Joanne; Bajenov, Sonya; Fahey, David; Li, Shawn; Sidhu, Stan; Sywak, Mark

2018-05-01

Posterior retroperitoneoscopic adrenalectomy has gained widespread acceptance for the removal of benign adrenal tumors. Higher insufflation pressures using carbon dioxide (CO 2 ) are required, although the ideal starting pressure is unclear. This prospective, randomized, single-blinded, study aims to compare physiologic differences with 2 different CO 2 insufflation pressures during posterior retroperitoneoscopic adrenalectomy. Participants were randomly assigned to a starting insufflation pressure of 20 mm Hg (low pressure) or 25 mm Hg (high pressure). The primary outcome measure was partial pressure of arterial CO 2 at 60 minutes. Secondary outcomes included end-tidal CO 2 , arterial pH, blood pressure, and peak airway pressure. Breaches of protocol to change insufflation pressure were permitted if required and were recorded. A prospective randomized trial including 31 patients (low pressure: n = 16; high pressure: n = 15) was undertaken. At 60 minutes, the high pressure group had greater mean partial pressure of arterial CO 2 (64 vs 50 mm Hg, P = .003) and end-tidal CO 2 (54 vs 45 mm Hg, P = .008) and a lesser pH (7.21 vs 7.29, P = .0005). There were no significant differences in base excess, peak airway pressure, operative time, or duration of hospital stay. Clinically indicated protocol breaches were more common in the low pressure than the high pressure group (8 vs 3, P = .03). In posterior retroperitoneoscopic adrenalectomy, greater insufflation pressures are associated with greater partial pressure of arterial CO 2 and end-tidal CO 2 and lesser pH at 60 minutes, be significant. Commencing with lesser CO 2 insufflation pressures decreases intraoperative acidosis. Copyright © 2017 Elsevier Inc. All rights reserved.

Apparatus and method for depositing coating onto porous substrate

DOEpatents

Isenberg, Arnold O.; Zymboly, Gregory E.

1986-01-01

Disclosed is an apparatus for forming a chemically vapor deposited coating on a porous substrate where oxygen from a first gaseous reactant containing a source of oxygen permeates through the pores of the substrate to react with a second gaseous reactant that is present on the other side of the substrate. The apparatus includes means for controlling the pressure and flow rate of each gaseous reactant, a manometer for measuring the difference in pressure between the gaseous reactants on each side of the substrate, and means for changing the difference in pressure between the gaseous reactants. Also disclosed is a method of detecting and closing cracks in the coating by reducing the pressure difference between the two gaseous reactants whenever the pressure difference falls suddenly after gradually rising, then again increasing the pressure difference on the two gases. The attack by the by-products of the reaction on the substrate are reduced by maintaining the flow rate of the first reactant through the pores of the substrate.

Non-invasive pressure difference estimation from PC-MRI using the work-energy equation

PubMed Central

Donati, Fabrizio; Figueroa, C. Alberto; Smith, Nicolas P.; Lamata, Pablo; Nordsletten, David A.

2015-01-01

Pressure difference is an accepted clinical biomarker for cardiovascular disease conditions such as aortic coarctation. Currently, measurements of pressure differences in the clinic rely on invasive techniques (catheterization), prompting development of non-invasive estimates based on blood flow. In this work, we propose a non-invasive estimation procedure deriving pressure difference from the work-energy equation for a Newtonian fluid. Spatial and temporal convergence is demonstrated on in silico Phase Contrast Magnetic Resonance Image (PC-MRI) phantoms with steady and transient flow fields. The method is also tested on an image dataset generated in silico from a 3D patient-specific Computational Fluid Dynamics (CFD) simulation and finally evaluated on a cohort of 9 subjects. The performance is compared to existing approaches based on steady and unsteady Bernoulli formulations as well as the pressure Poisson equation. The new technique shows good accuracy, robustness to noise, and robustness to the image segmentation process, illustrating the potential of this approach for non-invasive pressure difference estimation. PMID:26409245

Ethnic differences in blood pressure, pulse rate, and related characteristics in young adults. The CARDIA study.

PubMed

Liu, K; Ballew, C; Jacobs, D R; Sidney, S; Savage, P J; Dyer, A; Hughes, G; Blanton, M M

1989-08-01

This study examined ethnic differences in blood pressure and pulse rate in young adults to see whether the differences, if they exist, can be explained by differences in body mass index, lifestyle, psychological, and socioeconomic characteristics. Data used were from the baseline examination of the Coronary Artery Risk Development in (Young) Adults Study (CARDIA). CARDIA is a longitudinal study of lifestyle and evolution of cardiovascular disease risk factors in 5,116 young adults, black and white, men and women, aged 18-30 years, of varying socioeconomic status. Young black adults had higher mean systolic blood pressure and slightly higher mean diastolic blood pressure than young white adults. For both men and women, the blood pressure differences between blacks and whites tended to be greater for the age group 25-30 than for the age group 18-24 years. Among the variables studied, body mass index, duration of exercise on the treadmill, number of cigarettes smoked per day, and number of alcoholic drinks per week were consistently associated with blood pressure. The blood pressure differences were greatly reduced after adjusting for these variables. Black participants had lower mean pulse rate than white participants. The differences tended to be greater for the age group 18-24 than for the age group 25-30 years. Among the variables studied, only duration on treadmill and number of cigarettes smoked per day were consistently correlated with pulse rate. With adjustment for duration on treadmill, the differences in pulse rate increased. These results suggest that differences in ethnic pattern of blood pressures and pulse rate with age may be due in part to obesity, physical fitness, alcohol consumption, and cigarette smoking.

[Pressure control in medical gas distribution systems].

PubMed

Bourgain, J L; Benayoun, L; Baguenard, P; Haré, G; Puizillout, J M; Billard, V

1997-01-01

To assess whether the pressure gauges at the downstream part of pressure regulators are accurate enough to ensure that pressure in O2 pipeline is always higher than in Air pipeline and that pressure in the latter is higher than pressure in N2O pipeline. A pressure difference of at least 0.4 bar between two medical gas supply systems is recommended to avoid the reflow of either N2O or Air into the O2 pipeline, through a faulty mixer or proportioning device. Prospective technical comparative study. Readings of 32 Bourdon gauges were compared with data obtained with a calibrated reference transducer. Two sets of measurements were performed at a one month interval. Pressure differences between Bourdon gauges and reference transducer were 8% (0.28 bar) in average for a theoretical maximal error less than 2.5%. During the first set of measurements, Air pressure was higher than O2 pressure in one place and N2O pressure higher than Air pressure in another. After an increase in the O2 pipeline pressure and careful setting of pressure regulators, this problem was not observed at the second set of measurements. Actual accuracy of Bourdon gauges was not convenient enough to ensure that O2 pressure was always above Air pressure. Regular controls of these pressure gauges are therefore essential. Replacement of the faulty Bourdon gauges by more accurate transducers should be considered. As an alternative, the increase in pressure difference between O2 and Air pipelines to at least 0.6 bar is recommended.

Follow-up of Antihypertensive Therapy Improves Blood Pressure Control: Results of HYT (HYperTension survey) Follow-up.

PubMed

Fici, F; Seravalle, G; Koylan, N; Nalbantgil, I; Cagla, N; Korkut, Y; Quarti-Trevano, F; Makel, W; Grassi, G

2017-09-01

Although improved during the past few years, blood pressure control remains sub optimal. The impact of follow-up assessment on blood pressure control was evaluated in a group of patients of the HYT (HYperTension survey), treated with a combination of different dihydropyridine calcium-channel blockers (CCBs regimen) and inhibitors of renin-angiotensin-aldosterone system (RAAS) and with uncontrolled blood pressure. This was obtained assessing (a) the rate of blood pressure control at 3 and 6 months of follow-up in the whole group of patients, (b) the rate of blood pressure control and the average blood pressure values in subjects treated with different DHP-CCBs regimen. From the 4993 patients with uncontrolled blood pressure, (BP ≥ 140/90 or ≥140/85 in patients with diabetes), 3729 (mean age 61.2 ± 11.5 years), maintained CCBs regimen combined wih RAAS blockers and were evaluated at 3 and 6 months follow-up. At each visit BP (semiautomatic device, Omron-M6, 3 measurements), heart rate, adverse events and treatment persistence were collected. At 1st and 2nd follow-up the rate of controlled BP was 63.5 and 72.8% respectively (p < 0.05 vs 35.3% at baseline), whereas in diabetes was 32.5 and 37.9% respectively (p < 0.05 vs 20% at baseline). No differences in heart rate were observed. No differences in control rate were observed between the different CCBs regimen. The incidence of drugs related adverse events was 3.6%. These findings provide evidence that: (a) the follow-up of hypertensive patients under therapy increase the rate of blood pressure control; (b) there is no significant difference in the antihypertensive effect between different CCBs regimen; (c) lipophilic CCBs induce less ankle edema.

Lower limb intracast pressures generated by different types of immobilisation casts.

PubMed

Chaudhury, Salma; Hazlerigg, Alexandra; Vusirikala, Anuhya; Nguyen, Joseph; Matthews, Stuart

2017-02-18

To determine if complete, split casts and backslabs [plaster of Paris (POP) and fiberglass] generate different intracast pressures and pain. Increased swelling within casts was modeled by a closed water system attached to an expandable bag placed directly under different types of casts applied to a healthy lower limb. Complete fiberglass and POP casts, split casts and backslabs were applied. Twenty-five milliliter aliquots of saline were injected into the system and the generated intracast pressures were measured using a sphygmomanometer. The subject was blinded to the pressure scores to avoid bias. All casts were applied to the same right limb on the same subject to avoid the effects of variations in anatomy or physiology on intracast pressures. Pain levels were evaluated using the Visual Analogue Score after each sequential saline injection. Each type of cast was reapplied four times and the measurements were repeated on four separate occasions. Sample sizes were determined by a pre-study 90% power calculation to detect a 20% difference in intracast pressures between cast groups. A significant difference between the various types of casts was noted when the saline volume was greater than 100 mL ( P = 0.009). The greatest intracast pressure was generated by complete fiberglass casts, which were significantly higher than complete POP casts or backslabs ( P = 0.018 and P = 0.008 respectively) at intracast saline volumes of 100 mL and higher. Backslabs produced a significantly lower intracast pressure compared to complete POP only once the saline volume within casts exceeded 225 mL ( P = 0.009). Intracast pressures were significantly lower in split casts ( P = 0.003). Split POP and fiberglass casts produced the lowest intracast pressures, even compared to backslabs ( P = 0.009). Complete fiberglass casts generated the highest pain levels at manometer pressures of 75 mmHg and greater ( P = 0.001). Split fiberglass casts had significantly reduced pain levels ( P = 0.001). In contrast, a split complete POP cast did not produce significantly reduced pain levels at pressures between 25-150 mmHg. There was no difference in pain generated by complete POP and backslabs at manometer pressures of 200 mmHg and lower. Fibreglass casts generate significantly higher intracast pressures and pain than POP casts. Split casts cause lower intracast pressures regardless of material, than complete casts and backslabs.

The values of intrapleural pressure before the removal of chest tube in non-complicated pulmonary lobectomies.

PubMed

Refai, Majed; Brunelli, Alessandro; Varela, Gonzalo; Novoa, Nuria; Pompili, Cecilia; Jimenez, Marcelo F; Aranda, José Luis; Sabbatini, Armando

2012-04-01

Digitalized chest drainage systems allow for quantification of air leak and measurement of intrapleural pressure. Little is known about the value of intrapleural pressure during the postoperative phase and its role in the recovering process after pulmonary resection. The objective of this investigation was to measure the values of pleural pressure immediately before the removal of chest tube after different types of pulmonary lobectomy. Prospective observational analysis on 203 consecutive patients submitted to pulmonary lobectomy during a 12-month period at two centres. Multiple measurements were recorded in the last hour before the removal of chest tube and averaged for the analysis. All patients were seated in bed in a 45° up-right position or in a chair, had a single chest tube and were not connected to suction during the evaluation period. Analysis of variance (ANOVA) was used to assess the differences in pleural pressure between different types of lobectomies. The average maximum, minimum and differential pressures were -6.1, -19.5 and 13.3 cmH(2)O, respectively. The average pressures were similar in all types of lobectomies (ANOVA, P = 0.2) and ranged from -11 to -13 cmH(2)O, with the exception of right upper bilobectomy (-20 cmH(2)O, all P-values vs. other types of lobectomies <0.05). Similar values were also recorded for maximum pressures (range -4.4 to -8.4 cmH(2)O) and minimum pressures (-31.6 cmH(2)O vs. ranged from -15.4 to -20.5 cmH(2)O, all P-values <0.01). The average pleural pressure was not associated with FEV1 (P = 0.9), DLCO (P = 0.2) or FEV1/FVC ratio (P = 0.6), when tested with linear regression. Similarly, the average pleural pressure was similar in patients with and without COPD (-12.1 vs. -13.0 cmH(2)O, P = 0.4). The ANOVA test was used to assess differences in pressures between different lobectomies. The so-called water seal status may actually correspond to intrapleural pressures ranging from -13 to -20 cmH(2)O. Modern electronic chest drainage devices allow a stable control of the intrapleural pressure. Thus, the values found in this study may be used as target pressures for different types of lobectomies, in order to favour lung recovery after surgery.

Simultaneously Measured Interarm Blood Pressure Difference and Stroke: An Individual Participants Data Meta-Analysis.

PubMed

Tomiyama, Hirofumi; Ohkuma, Toshiaki; Ninomiya, Toshiharu; Mastumoto, Chisa; Kario, Kazuomi; Hoshide, Satoshi; Kita, Yoshikuni; Inoguchi, Toyoshi; Maeda, Yasutaka; Kohara, Katsuhiko; Tabara, Yasuharu; Nakamura, Motoyuki; Ohkubo, Takayoshi; Watada, Hirotaka; Munakata, Masanori; Ohishi, Mitsuru; Ito, Norihisa; Nakamura, Michinari; Shoji, Tetsuo; Vlachopoulos, Charalambos; Yamashina, Akira

2018-06-01

We conducted individual participant data meta-analysis to examine the validity of interarm blood pressure difference in simultaneous measurement as a marker to identify subjects with ankle-brachial pressure index <0.90 and to predict future cardiovascular events. We collected individual participant data on 13 317 Japanese subjects from 10 cohorts (general population-based cohorts, cohorts of patients with past history of cardiovascular events, and those with cardiovascular risk factors). Binary logistic regression analysis with adjustments identified interarm blood pressure difference >5 mm Hg as being associated with a significant odds ratio for the presence of ankle-brachial pressure index <0.90 (odds ratio, 2.19; 95% confidence interval, 1.60-3.03; P <0.01). Among 11 726 subjects without a past history of cardiovascular disease, 249 developed stroke during the average follow-up period of 7.4 years. Interarm blood pressure difference >15 mm Hg was associated with a significant Cox stratified adjusted hazard ratio for subsequent stroke (hazard ratio, 2.42; 95% confidence interval, 1.27-4.60; P <0.01). Therefore, interarm blood pressure differences, measured simultaneously in both arms, may be associated with vascular damage in the systemic arterial tree. These differences may be useful for identifying subjects with an ankle-brachial pressure index of <0.90 in the overall study population, and also a reliable predictor of future stroke in subjects without a past history of cardiovascular disease. These findings support the recommendation to measure blood pressure in both arms at the first visit. © 2018 American Heart Association, Inc.

Effect of breast feeding in infancy on blood pressure in later life: systematic review and meta-analysis.

PubMed

Owen, Christopher G; Whincup, Peter H; Gilg, Julie A; Cook, Derek G

2003-11-22

To determine whether breast feeding in infancy compared with bottle feeding formula milk is associated with lower mean blood pressure at different ages. Systematic review. Embase, Medline, and Web of Science databases. Studies showing the effects of feeding in infancy on blood pressure at different ages. Pooled mean differences in blood pressure between breast fed infants and those bottle fed formula milk, based on random effects models. The pooled mean difference in systolic blood pressure was -1.10 mm Hg (95% confidence interval -1.79 to -0.42 mm Hg) but with significant heterogeneity between estimates (P < 0.001). The difference was largest in studies of < 300 participants (-2.05 mm Hg, -3.30 to -0.80 mm Hg), intermediate in studies of 300-1000 participants (1.13 mm Hg, -2.53 to 0.27 mm Hg), and smallest in studies of > 1000 participants (-0.16 mm Hg, -0.60 to 0.28 mm Hg). An Egger test but not Begg test was statistically significant for publication bias. The difference was unaltered by adjustment for current size and was independent of age at measurement of blood pressure and year of birth. Diastolic blood pressure was not significantly related to type of feeding in infancy. Selective publication of small studies with positive findings may have exaggerated claims that breast feeding in infancy reduces systolic blood pressure in later life. The results of larger studies suggest that feeding in infancy has at most a modest effect on blood pressure, which is of limited clinical or public health importance.

Get a Grip: Substrate Orientation and Digital Grasping Pressures in Strepsirrhines.

PubMed

Congdon, Kimberly A; Ravosa, Matthew J

2016-01-01

Skeletal functional morphology in primates underlies many fossil interpretations. Understanding the functional correlates of arboreal grasping is central to identifying locomotor signatures in extinct primates. We tested 3 predictions linking substrate orientation and digital grasping pressures: (1) below-branch pressures are greater than above-branch and vertical-branch pressures; (2) there is no difference in pressure exerted across digits within autopods at any substrate orientation, and (3) there is no difference in pressure exerted between homologous digits across autopods at any substrate orientation. Adult males and females from 3 strepsirrhine species crossed an artificial arboreal substrate oriented for above-, below- and vertical-branch locomotion. We compared digital pressures within and across behaviors via ANOVA and Tukey's Honest Significant Difference test. Results show limited support for all predictions: below-branch pressures exceeded vertical-branch pressures and above-branch pressures for some digits and species (prediction 1), lateral digits often exerted greater pressures than medial digits (prediction 2), and pedal digits occasionally exerted greater pressures than manual digits during above-branch and vertical orientations but less often for below-branch locomotion (prediction 3). We observed functional variability across autopods, substrate and species that could underlie morphological variation within and across primates. Future work should consider the complexity of arboreality when inferring locomotor modes in fossils. © 2016 S. Karger AG, Basel.

Influence of the Pressure Difference and Door Swing on Heavy Contaminants Migration between Rooms

PubMed Central

Hendiger, Jacek; Chludzińska, Marta; Ziętek, Piotr

2016-01-01

This paper presents the results of investigations whose aim was to describe the influence of the pressure difference level on the ability of contaminants migration between neighbouring rooms in dynamic conditions associated with door swing. The analysis was based on airflow visualization made with cold smoke, which simulated the heavy contaminants. The test room was pressurized to a specific level and then the door was opened to observe the trail of the smoke plume in the plane of the door. The door was opened in both directions: to the positively and negatively pressurized room. This study focuses on the visualization of smoke plume discharge and an uncertainty analysis is not applicable. Unlike other studies which focus on the analysis of pressure difference, the present study looks at the contaminants which are heavier than air and on “pumping out” the contaminants by means of door swing. Setting the proper level of pressure difference between the contaminated room and the neighbouring rooms can prove instrumental in ensuring protection against toxic contaminants migration. This study helped to establish the threshold of pressure difference necessary to reduce migration of heavy contaminants to neighbouring rooms. PMID:27171260

Influence of the Pressure Difference and Door Swing on Heavy Contaminants Migration between Rooms.

PubMed

Hendiger, Jacek; Chludzińska, Marta; Ziętek, Piotr

2016-01-01

This paper presents the results of investigations whose aim was to describe the influence of the pressure difference level on the ability of contaminants migration between neighbouring rooms in dynamic conditions associated with door swing. The analysis was based on airflow visualization made with cold smoke, which simulated the heavy contaminants. The test room was pressurized to a specific level and then the door was opened to observe the trail of the smoke plume in the plane of the door. The door was opened in both directions: to the positively and negatively pressurized room. This study focuses on the visualization of smoke plume discharge and an uncertainty analysis is not applicable. Unlike other studies which focus on the analysis of pressure difference, the present study looks at the contaminants which are heavier than air and on "pumping out" the contaminants by means of door swing. Setting the proper level of pressure difference between the contaminated room and the neighbouring rooms can prove instrumental in ensuring protection against toxic contaminants migration. This study helped to establish the threshold of pressure difference necessary to reduce migration of heavy contaminants to neighbouring rooms.

An ultrasound-based liquid pressure measurement method in small diameter pipelines considering the installation and temperature.

PubMed

Li, Xue; Song, Zhengxiang

2015-04-09

Liquid pressure is a key parameter for detecting and judging faults in hydraulic mechanisms, but traditional measurement methods have many deficiencies. An effective non-intrusive method using an ultrasound-based technique to measure liquid pressure in small diameter (less than 15 mm) pipelines is presented in this paper. The proposed method is based on the principle that the transmission speed of an ultrasonic wave in a Kneser liquid correlates with liquid pressure. Liquid pressure was calculated using the variation of ultrasonic propagation time in a liquid under different pressures: 0 Pa and X Pa. In this research the time difference was obtained by an electrical processing approach and was accurately measured to the nanosecond level through a high-resolution time measurement module. Because installation differences and liquid temperatures could influence the measurement accuracy, a special type of circuit called automatic gain control (AGC) circuit and a new back propagation network (BPN) model accounting for liquid temperature were employed to improve the measurement results. The corresponding pressure values were finally obtained by utilizing the relationship between time difference, transient temperature and liquid pressure. An experimental pressure measurement platform was built and the experimental results confirm that the proposed method has good measurement accuracy.

A novel method for calculating the dynamic capillary force and correcting the pressure error in micro-tube experiment.

PubMed

Wang, Shuoliang; Liu, Pengcheng; Zhao, Hui; Zhang, Yuan

2017-11-29

Micro-tube experiment has been implemented to understand the mechanisms of governing microcosmic fluid percolation and is extensively used in both fields of micro electromechanical engineering and petroleum engineering. The measured pressure difference across the microtube is not equal to the actual pressure difference across the microtube. Taking into account the additional pressure losses between the outlet of the micro tube and the outlet of the entire setup, we propose a new method for predicting the dynamic capillary pressure using the Level-set method. We first demonstrate it is a reliable method for describing microscopic flow by comparing the micro-model flow-test results against the predicted results using the Level-set method. In the proposed approach, Level-set method is applied to predict the pressure distribution along the microtube when the fluids flow along the microtube at a given flow rate; the microtube used in the calculation has the same size as the one used in the experiment. From the simulation results, the pressure difference across a curved interface (i.e., dynamic capillary pressure) can be directly obtained. We also show that dynamic capillary force should be properly evaluated in the micro-tube experiment in order to obtain the actual pressure difference across the microtube.

Tourniquet pressures: strap width and tensioning system widths.

PubMed

Wall, Piper L; Coughlin, Ohmar; Rometti, Mary; Birkholz, Sarah; Gildemaster, Yvonne; Grulke, Lisa; Sahr, Sheryl; Buising, Charisse M

2014-01-01

Pressure distribution over tourniquet width is a determinant of pressure needed for arterial occlusion. Different width tensioning systems could result in arterial occlusion pressure differences among nonelastic strap designs of equal width. Ratcheting Medical Tourniquets (RMTs; m2 inc., http://www.ratcheting buckles.com) with a 1.9 cm-wide (Tactical RMT) or 2.3 cm-wide (Mass Casualty RMT) ladder were directly compared (16 recipients, 16 thighs and 16 upper arms for each tourniquetx2). Then, RMTs were retrospectively compared with the windlass Combat Application Tourniquet (C-A-T ["CAT"], http://combattourniquet.com) with a 2.5 cm-wide internal tensioning strap. Pressure was measured with an air-filled No. 1 neonatal blood pressure cuff under each 3.8 cm-wide tourniquet. RMT circumferential pressure distribution was not uniform. Tactical RMT pressures were not higher, and there were no differences between the RMTs in the effectiveness, ease of use ("97% easy"), or discomfort. However, a difference did occur regarding tooth skipping of the pawl during ratchet advancement: it occurred in 1 of 64 Tactical RMT applications versus 27 of 64 Mass Casualty RMT applications. CAT and RMT occlusion pressures were frequently over 300 mmHg. RMT arm occlusion pressures (175-397 mmHg), however, were lower than RMT thigh occlusion pressures (197-562 mmHg). RMT effectiveness was better with 99% reached occlusion and 1% lost occlusion over 1 minute versus the CAT with 95% reached occlusion and 28% lost occlusion over 1 minute. RMT muscle tension changes (up to 232 mmHg) and pressure losses over 1 minute (24±11 mmHg arm under strap to 40±12 mmHg thigh under ladder) suggest more occlusion losses may have occurred if tourniquet duration was extended. The narrower tensioning system Tactical RMT has better performance characteristics than the Mass Casualty RMT. The 3.8 cm-wide RMTs have some pressure and effectiveness similarities and differences compared with the CAT. Clinically significant pressure changes occur under nonelastic strap tourniquets with muscle tension changes and over time periods as short as 1 minute. An examination of pressure and occlusion changes beyond 1 minute would be of interest. 2014.

Arterial Pressure Gradients during Upright Posture and 30 deg Head Down Tilt

NASA Technical Reports Server (NTRS)

Sanchez, E. R; William, J. M.; Ueno, T.; Ballard, R. E.; Hargens, A. R.; Holton, Emily M. (Technical Monitor)

1997-01-01

Gravity alters local blood pressure within the body so that arterial pressures in the head and foot are lower and higher, respectively, than that at heart level. Furthermore, vascular responses to local alterations of arterial pressure are probably important to maintain orthostatic tolerance upon return to the Earth after space flight. However, it has been difficult to evaluate the body's arterial pressure gradient due to the lack of noninvasive technology. This study was therefore designed to investigate whether finger arterial pressure (FAP), measured noninvasively, follows a normal hydrostatic pressure gradient above and below heart level during upright posture and 30 deg head down tilt (HDT). Seven healthy subjects gave informed consent and were 19 to 52 years old with a height range of 158 to 181 cm. A Finapres device measured arterial pressure at different levels of the body by moving the hand from 36 cm below heart level (BH) to 72 cm above heart level (AH) in upright posture and from 36 cm BH to 48 cm AH during HDT in increments of 12 cm. Mean FAP creased by 85 mmHg transitioning from BH to AH in upright posture, and the pressure gradient calculated from hydrostatic pressure difference (rho(gh)) was 84 mmHg. In HDT, mean FAP decreased by 65 mmHg from BH to AH, and the calculated pressure gradient was also 65 mmHg. There was no significant difference between the measured FAP gradient and the calculated pressure gradient, although a significant (p = 0.023) offset was seen for absolute arterial pressure in upright posture. These results indicate that arterial pressure at various levels can be obtained from the blood pressure at heart level by calculating rho(gh) + an offset. The offset equals the difference between heart level and the site of measurement. In summary, we conclude that local blood pressure gradients can be measured by noninvasive studies of FAP.

Differences in blood pressure control in a large population-based sample of older African Americans and non-Hispanic whites.

PubMed

Delgado, Jose; Jacobs, Elizabeth A; Lackland, Daniel T; Evans, Denis A; de Leon, Carlos F Mendes

2012-11-01

Cardiovascular disease is the main cause of death in older adults. Uncontrolled blood pressure is an important risk factor for cardiovascular disease. African Americans have poorer blood pressure control than non-Hispanic whites. Little is known about whether this difference persists in older ages or the factors that contribute to this racial gap. Data were obtained from participants of the Chicago Health and Aging Program. Blood pressure control was defined according to JNC-7 criteria. Univariate chi-square analyses were used to determine racial differences in hypertension and blood pressure control, whereas sequential multivariate logistic regression models were used to determine the effect of race on blood pressure control. African Americans had a higher prevalence of hypertension (74% vs 63%; p < .001), higher awareness of hypertension (81% vs 72%; p < .001), and poorer blood pressure control (45% vs 51%, p < .001) than non-Hispanic whites. Racial differences in blood pressure control persisted after adjustment for socioeconomic status, medical conditions, obesity, and use of antihypertensive medications (odds ratio = 0.84, 95% confidence interval = 0.70-0.94). From 1993 to 2008, blood pressure control improved more among non-Hispanic whites than among African Americans. Racial differences in blood pressure control in older adults were not explained by socioeconomic status. The racial disparity in the prevalence and control of hypertension remained consistent for older hypertensive individuals eligible for Medicare. Although the rates of hypertension control improved for both racial groups, the improvement was greater among whites, thus widening the gap in this older population at high risk for cardiovascular disease.

Intra-abdominal pressure during swimming.

PubMed

Moriyama, S; Ogita, F; Huang, Z; Kurobe, K; Nagira, A; Tanaka, T; Takahashi, H; Hirano, Y

2014-02-01

The present study aimed to determine the intra-abdominal pressure during front crawl swimming at different velocities in competitive swimmers and to clarify the relationships between stroke indices and changes in intra-abdominal pressure. The subjects were 7 highly trained competitive collegiate male swimmers. Intra-abdominal pressure was measured during front crawl swimming at 1.0, 1.2 and 1.4 m · s(-1) and during the Valsalva maneuver. Intra-abdominal pressure was taken as the difference between minimum and maximum values, and the mean of 6 stable front crawl stroke cycles was used. Stroke rate and stroke length were also measured as stroke indices. There were significant differences in stroke rate among all velocities (P < 0.05). However, there was no significant difference in stroke length by velocity. Significant within-subject correlations between intra-abdominal pressure and stroke rate or stroke length (P < 0.01) were observed, although there were no significant correlations between intra-abdominal pressure and stroke indices when controlling for swimming velocity. These findings do not appear to support the effectiveness of trunk training performed by competitive swimmers aimed at increasing intra-abdominal pressure. © Georg Thieme Verlag KG Stuttgart · New York.

Do Arthroscopic Fluid Pumps Display True Surgical Site Pressure During Hip Arthroscopy?

PubMed

Ross, Jeremy A; Marland, Jennifer D; Payne, Brayden; Whiting, Daniel R; West, Hugh S

2018-01-01

To report on the accuracy of 5 commercially available arthroscopic fluid pumps to measure fluid pressure at the surgical site during hip arthroscopy. Patients undergoing hip arthroscopy for femoroacetabular impingement were block randomized to the use of 1 of 5 arthroscopic fluid pumps. A spinal needle inserted into the operative field was used to measure surgical site pressure. Displayed pump pressures and surgical site pressures were recorded at 30-second intervals for the duration of the case. Mean differences between displayed pump pressures and surgical site pressures were obtained for each pump group. Of the 5 pumps studied, 3 (Crossflow, 24K, and Continuous Wave III) reflected the operative field fluid pressure within 11 mm Hg of the pressure readout. In contrast, 2 of the 5 pumps (Double Pump RF and FMS/DUO+) showed a difference of greater than 59 mm Hg between the operative field fluid pressure and the pressure readout. Joint-calibrated pumps more closely reflect true surgical site pressure than gravity-equivalent pumps. With a basic understanding of pump design, either type of pump can be used safely and efficiently. The risk of unfamiliarity with these differences is, on one end, the possibility of pump underperformance and, on the other, potentially dangerously high operating pressures. Level II, prospective block-randomized study. Copyright © 2017. Published by Elsevier Inc.

Deviation of tracheal pressure from airway opening pressure during high-frequency oscillatory ventilation in a porcine lung model.

PubMed

Johannes, Amélie; Zollhoefer, Bernd; Eujen, Ulrike; Kredel, Markus; Rauch, Stefan; Roewer, Norbert; Muellenbach, Ralf M

2013-04-01

Oxygenation during high-frequency oscillatory ventilation is secured by a high level of mean airway pressure. Our objective was to identify a pressure difference between the airway opening of the respiratory circuit and the trachea during application of different oscillatory frequencies. Six female Pietrain pigs (57.1 ± 3.6 kg) were first ventilated in a conventional mechanical ventilation mode. Subsequently, the animals were switched to high-frequency oscillatory ventilation by setting mean airway opening pressure 5 cmH(2)O above the one measured during controlled mechanical ventilation. Measurements at the airway opening and at tracheal levels were performed in healthy lungs and after induction of acute lung injury by surfactant depletion. During high-frequency oscillatory ventilation, the airway opening pressure was set at a constant level. The pressure amplitude was fixed at 90 cmH(2)O. Starting from an oscillatory frequency of 3 Hz, the frequency was increased in steps of 3 Hz to 15 Hz and then decreased accordingly. At each frequency, measurements were performed in the trachea through a side-lumen of the endotracheal tube and the airway opening pressure was recorded. The pressure difference was calculated. At every oscillatory frequency, a pressure loss towards the trachea could be shown. This pressure difference increased with higher oscillatory frequencies (3 Hz 2.2 ± 2.1 cmH(2)O vs. 15 Hz 7.5 ± 1.8 cmH(2)O). The results for healthy and injured lungs were similar. Tracheal pressures decreased with higher oscillatory frequencies. This may lead to pulmonary derecruitment. This has to be taken into consideration when increasing oscillatory frequencies and differentiated pressure settings are mandatory.

Overweight, high blood pressure and impaired fasting glucose in Uyghur, Han, and Kazakh Chinese children and adolescents.

PubMed

Yan, W L; Li, X S; Wang, Q; Huang, Y D; Zhang, W G; Zhai, X H; Wang, C C; Lee, J H

2015-01-01

To investigate whether the levels of blood pressure and fasting glucose differ among Chinese children of three different ethnicities (i.e., Uyghurs, Kazakhs, and Hans) and whether the differences are explained by childhood obesity. A school-based cross-sectional study was conducted in a large three ethnic pediatric population (n = 6633), whose ages ranged from 7 to 18 years. Anthropometrics and blood pressure were measured using standard protocols. Fasting glucose was measured in a subset of children (n = 2295) who were randomly selected based on ethnicity and age. The age-sex stratified Chinese national cut-offs were used to define obesity and high blood pressure (HBP). The prevalence of HBP, impaired fasting glucose (IFG), mean levels of blood pressure, and glucose were compared among three ethnic groups. 2142 Uyghurs, 2078 Han, and 1997 Kazakhs were analyzed. After adjusting for age and body mass index (BMI), the mean blood pressure for Uyghurs was on average, 2-4 mm Hg lower than those for Hans and Kazakhs. Kazakhs had the lowest mean fasting glucose compared with Hans and Uyghurs (4.5 vs. 5.0 vs. 4.8 mmol/L, respectively). The differences in blood pressure and fasting glucose persisted even after adjusting for age and BMI, and the differences among ethnic groups in blood pressure levels and fasting glucose levels were observed as early as 7-9 years of age. The prevalence of HBP and IFG differed significantly among Uyghurs, Hans, and Kazakhs, and the ethnic differences observed in childhood were consistent with those observed in adults from the same region. While childhood obesity is a significant risk factor for hypertension and elevated glucose, the differences among ethnic groups were not explained by obesity alone.

The difference in blood pressure readings between arms and survival: primary care cohort study

PubMed Central

Taylor, Rod S; Shore, Angela C; Campbell, John L

2012-01-01

Objective To determine whether a difference in systolic blood pressure readings between arms can predict a reduced event free survival after 10 years. Design Cohort study. Setting Rural general practice in Devon, United Kingdom. Participants 230 people receiving treatment for hypertension in primary care. Intervention Bilateral blood pressure measurements recorded at three successive surgery attendances. Main outcome measures Cardiovascular events and deaths from all causes during a median follow-up of 9.8 years. Results At recruitment 24% (55/230) of participants had a mean interarm difference in systolic blood pressure of 10 mm Hg or more and 9% (21/230) of 15 mm Hg or more; these differences were associated with an increased risk of all cause mortality (adjusted hazard ratio 3.6, 95% confidence interval 2.0 to 6.5 and 3.1, 1.6 to 6.0, respectively). The risk of death was also increased in 183 participants without pre-existing cardiovascular disease with an interarm difference in systolic blood pressure of 10 mm Hg or more or 15 mm Hg or more (2.6, 1.4 to 4.8 and 2.7, 1.3 to 5.4). An interarm difference in diastolic blood pressure of 10 mm Hg or more was weakly associated with an increased risk of cardiovascular events or death. Conclusions Differences in systolic blood pressure between arms can predict an increased risk of cardiovascular events and all cause mortality over 10 years in people with hypertension. This difference could be a valuable indicator of increased cardiovascular risk. Bilateral blood pressure measurements should become a routine part of cardiovascular assessment in primary care. PMID:22433975

Influence of everyday bolus consistencies in different body positions on high-resolution esophageal pressure topography (HREPT) parameters.

PubMed

Hasan, Y; Go, J; Hashmi, S M; Valestin, J; Schey, R

2015-04-01

The standard protocol for esophageal manometry involves placing the patient in the supine position with head turned to left (supine head left [SHL]) while evaluating liquid bolus swallows. Routinely, semisolid or solid boluses are not evaluated. Currently, the daily American diet includes up to 40% solid or semisolid texture. Thus far, the data on the effect of different bolus on high-resolution esophageal pressure topography (HREPT) parameters are scarce. This study aims to evaluate the effect of every day bolus consistencies in different body positions on HREPT variables. HREPT was performed on healthy volunteers with a modified protocol including liquid swallows in the SHL position followed by applesauce (semisolid), cracker (solid), and marshmallow (soft solid) in three different positions (SHL, sitting, and standing). A total of 38 healthy adult subjects (22 males and 16 females, median age = 27, and mean body mass index = 25) were evaluated. The resting upper esophageal sphincter pressure was significantly different while subjects swallowed crackers, applesauce, and marshmallows in most positions compared with liquid SHL (P < 0.05). The lower esophageal sphincter, contractile front velocity, and distal contractile integral pressures did not differ in all different consistencies compared with SHL. The integrated relaxation period was significantly higher with solid bolus compared with liquid bolus only in SHL position. The intrabolus pressure was significantly different with solid and soft solid boluses in all postures compared to liquid SHL. The American diet consistency affects upper esophageal sphincter pressure and partially integrated relaxation period and intrabolus pressure in various positions. Semisolid bolus swallows do not cause substantial pressure changes and are safe for evaluation and maintaining adequate caloric intake in patients with dysphagia who cannot tolerate solids. © 2014 International Society for Diseases of the Esophagus.

HOPG/ZnO/HOPG pressure sensor

NASA Astrophysics Data System (ADS)

Jahangiri, Mojtaba; Yousefiazari, Ehsan; Ghalamboran, Milad

2017-12-01

Pressure sensor is one of the most commonly used sensors in the research laboratories and industries. These are generally categorized in three different classes of absolute pressure sensors, gauge pressure sensors, and differential pressure sensors. In this paper, we fabricate and assess the pressure sensitivity of the current vs. voltage diagrams in a graphite/ZnO/graphite structure. Zinc oxide layers are deposited on highly oriented pyrolytic graphite (HOPG) substrates by sputtering a zinc target under oxygen plasma. The top electrode is also a slice of HOPG which is placed on the ZnO layer and connected to the outside electronic circuits. By recording the I-V characteristics of the device under different forces applied to the top HOPG electrode, the pressure sensitivity is demonstrated; at the optimum biasing voltage, the device current changes 10 times upon changing the pressure level on the top electrode by 20 times. Repeatability and reproducibility of the observed effect is studied on the same and different samples. All the materials used for the fabrication of this pressure sensor are biocompatible, the fabricated device is anticipated to find potential applications in biomedical engineering.

Influence of a Binder Layer on the Response Time of Pressure-Sensitive Coatings

NASA Astrophysics Data System (ADS)

Zharkova, G. M.; Khachaturyan, V. M.; Malov, A. N.; Lopatkina, A. A.

2002-07-01

The present work describes an experimental study of pressure-sensitive luminescent coatings containing phosphors prepared on different substrates. Data are presented concerning measurements of luminescence intensity and luminescence decay kinetics at different pressures and temperatures.

The pressure distribution for biharmonic transmitting array: theoretical study

NASA Astrophysics Data System (ADS)

Baranowska, A.

2005-03-01

The aim of the paper is theoretical analysis of the finite amplitude waves interaction problem for the biharmonic transmitting array. We assume that the array consists of 16 circular pistons of the same dimensions that regrouped in two sections. Two different arrangements of radiating elements were considered. In this situation the radiating surface is non-continuous without axial symmetry. The mathematical model was built on the basis of the Khokhlov - Zabolotskaya - Kuznetsov (KZK) equation. To solve the problem the finite-difference method was applied. On-axis pressure amplitude for different frequency waves as a function of distance from the source, transverse pressure distribution of these waves at fixed distances from the source and pressure amplitude distribution for them at fixed planes were examined. Especially changes of normalized pressure amplitude for difference frequency were studied. The paper presents mathematical model and some results of theoretical investigations obtained for different values of source parameters.

Acute baroreflex resetting: differential control of pressure and nerve activity.

PubMed

Drummond, H A; Seagard, J L

1996-03-01

This study evaluated acute resetting of carotid baroreflex control of arterial blood pressure and renal or thoracic sympathetic nerve activity in thiopental-anesthetized mongrel dogs with the use of a vascularly isolated carotid sinus preparation, the experimental model used previously to characterize acute resetting in carotid baroreceptor afferent fibers. Carotid baroreceptors were conditioned with a pulsatile pressure for 20 minutes at three pressure ranges: low (50 to 75 mm Hg), mid (100 to 125), or high (150 to 175). Blood pressure and nerve activity were recorded in response to slow ramp increases in sinus pressure; nonlinear regression and best-fit analyses were used for determination of curve fit parameters of the blood pressure and nerve activity versus sinus pressure response curves. Carotid sinus pressure thresholds for blood pressure and renal nerve activity responses at all conditioning pressures were significantly different; however, only the pressure threshold for thoracic nerve activity at the low conditioning pressure was significantly different from the responses at other conditioning pressures. Average renal activity resetting (0.506 +/- 0.072) was significantly greater than blood pressure resetting (0.335 +/- 0.046) in the same dogs, and thoracic activity (0.200 +/- 0.057) was not different from blood pressure resetting (0.194 +/- 0.031) in the same dogs. In a previous investigation, our laboratory had demonstrated that type 1 carotid baroreceptors acutely reset at a value of about 0.15. These results indicate that (1) renal and thoracic nerve activities and blood pressure acutely reset to a greater degree than type 1 carotid baroreceptors and that (2) renal activity acutely resets to a greater degree than blood pressure and thoracic nerve activity.

Evaluation of the impact of atmospheric pressure in different seasons on blood pressure in patients with arterial hypertension.

PubMed

Kamiński, Marek; Cieślik-Guerra, Urszula I; Kotas, Rafał; Mazur, Piotr; Marańda, Witold; Piotrowicz, Maciej; Sakowicz, Bartosz; Napieralski, Andrzej; Trzos, Ewa; Uznańska-Loch, Barbara; Rechciński, Tomasz; Kurpesa, Małgorzata

2016-01-01

Atmospheric pressure is the most objective weather factor because regardless of if outdoors or indoors it affects all objects in the same way. The majority of previous studies have used the average daily values of atmospheric pressure in a bioclimatic analysis and have found no correlation with blood pressure changes. The main objective of our research was to assess the relationship between atmospheric pressure recorded with a frequency of 1 measurement per minute and the results of 24-h blood pressure monitoring in patients with treated hypertension in different seasons in the moderate climate of the City of Łódź (Poland). The study group consisted of 1662 patients, divided into 2 equal groups (due to a lower and higher average value of atmospheric pressure). Comparisons between blood pressure values in the 2 groups were performed using the Mann-Whitney U test. We observed a significant difference in blood pressure recorded during the lower and higher range of atmospheric pressure: on the days of the spring months systolic (p = 0.043) and diastolic (p = 0.005) blood pressure, and at nights of the winter months systolic blood pressure (p = 0.013). A significant inverse relationship between atmospheric pressure and blood pressure during the spring days and, only for systolic blood pressure, during winter nights was observed. Int J Occup Med Environ Health 2016;29(5):783-792. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

Inter-arm blood pressure differences in pregnant women.

PubMed

Poon, L C Y; Kametas, N; Strobl, I; Pachoumi, C; Nicolaides, K H

2008-08-01

To determine the prevalence of blood pressure inter-arm difference (IAD) in early pregnancy and to investigate its possible association with maternal characteristics. A cross-sectional observational study. Routine antenatal visit in a university hospital. A total of 5435 pregnant women at 11-14 weeks of gestation. Blood pressure was taken from both arms simultaneously with a validated automated device. The presence of inter-arm blood pressure difference of 10 mmHg or more. The IAD in systolic and diastolic blood pressure was 10 mmHg or more in 8.3 and 2.3% of the women, respectively. Systolic IAD was found to be significantly related to systolic blood pressure and pulse pressure, and diastolic IAD was found to be significantly related to maternal age, diastolic blood pressure and pulse pressure. The systolic and diastolic IAD were higher in the hypertensive group compared with the normotensive group and absolute IAD increased with increasing blood pressure. About 31.0 and 23.9% of cases of hypertension would have been underreported if the left arm and the right arm were used, respectively, in measuring the blood pressure. There is a blood pressure IAD in a significant proportion of the pregnant population, and its prevalence increases with increasing blood pressure. By measuring blood pressure only on one arm, there is a one in three chance of underreporting hypertension. Therefore, it would be prudent that during the booking visit blood pressure should be taken in both arms and thus provide guidance for subsequent blood pressure measurements during the course of pregnancy.

Gender Differences in Behavioral and Neural Responses to Unfairness Under Social Pressure.

PubMed

Zheng, Li; Ning, Reipeng; Li, Lin; Wei, Chunli; Cheng, Xuemei; Zhou, Chu; Guo, Xiuyan

2017-10-18

Numerous studies have revealed the key role of social pressure on individuals' decision-making processes. However, the impact of social pressure on unfairness-related decision-making processes remains unclear. In the present study, we investigated how social pressure modulated men's and women's responses in an ultimatum game. Twenty women and eighteen men played the ultimatum game as responders in the scanner, where fair and unfair offers were tendered by proposers acting alone (low pressure) or by proposers endorsed by three supporters (high pressure). Results showed that men rejected more, whereas women accepted more unfair offers in the high versus low pressure context. Neurally, pregenual anterior cingulate cortex activation in women positively predicted their acceptance rate difference between contexts. In men, stronger right anterior insula activation and increased connectivity between right anterior insula and dorsal anterior cingulate cortex were observed when they receiving unfair offers in the high than low pressure context. Furthermore, more bilateral anterior insula and left dorsolateral prefrontal cortex activations were found when men rejected (relative to accepted) unfair offers in the high than low pressure context. These findings highlighted gender differences in the modulation of behavioral and neural responses to unfairness by social pressure.

Modeling the pyrolysis study of non-charring polymers under reduced pressure environments

NASA Astrophysics Data System (ADS)

Zong, Ruowen; Kang, Ruxue; Hu, Yanghui; Zhi, Youran

2018-04-01

In order to study the pyrolysis of non-charring polymers under reduced pressure environments, a series of experiments based on black acrylonitrile butadiene styrene (ABS) was conducted in a reduced pressure chamber under different external heat fluxes. The temperatures of the top surface and the bottom of the sample and the mass loss during the whole process were measured in real time. A one-dimensional numerical model was developed to predict the top surface and the bottom surface temperatures of ABS during the pyrolysis at different reduced pressures and external heat fluxes, and the model was validated by the experimental data. The results of the study indicate that the profiles of the top surface and the bottom surface temperatures are different at different pressures and heat fluxes. The temperature and the mass loss rate of the sample under a lower heat flux decreased significantly as the pressure was increased. However, under a higher heat flux, the temperature and the mass loss rate showed little sensitivity to the pressure. The simulated results fitted the experimental results better at the higher heat flux than at the lower heat flux.

Regional pressure and temperature variations across the injured human brain: comparisons between paired intraparenchymal and ventricular measurements.

PubMed

Childs, Charmaine; Shen, Liang

2015-06-23

Intraparenchymal, multimodality sensors are commonly used in the management of patients with severe traumatic brain injury (TBI). The 'gold standard', based on accuracy, reliability and cost for intracranial pressure (ICP) monitoring is within the cerebral ventricle (external strain gauge). There are no standards yet for intracerebral temperature monitoring and little is known of temperature differences between brain tissue and ventricle. The aim of the study therefore was to determine pressure and temperature differences at intraparenchymal and ventricular sites during five days of continuous neuromonitoring. Patients with severe TBI requiring emergency surgery. patients who required ICP monitoring were eligible for recruitment. Two intracerebral probe types were used: a) intraventricular, dual parameter sensor (measuring pressure, temperature) with inbuilt catheter for CSF drainage: b) multiparameter intraparenchymal sensor measuring pressure, temperature and oxygen partial pressure. All sensors were inserted during surgery and under aseptic conditions. Seventeen patients, 12 undergoing neurosurgery (decompressive craniectomy n = 8, craniotomy n = 4) aged 21-78 years were studied. Agreement of measures for 9540 brain tissue-ventricular temperature 'pairs' and 10,291 brain tissue-ventricular pressure 'pairs' were determined using mixed model to compare mean temperature and pressure for longitudinal data. There was no significant overall difference for mean temperature (p = 0.92) or mean pressure readings (p = 0.379) between tissue and ventricular sites. With 95.8 % of paired temperature readings within 2SD (-0.4 to 0.4 °C) differences in temperature between brain tissue and ventricle were clinically insignificant. For pressure, 93.5 % of readings pairs fell within the 2SD range (-9.4756 to 7.8112 mmHg). However, for individual patients, agreement for mean tissue-ventricular pressure differences was poor on occasions. There is good overall agreement between paired temperature measurements obtained from deep white matter and brain ventricle in patients with and without early neurosurgery. For paired ICP measurements, 93.5 % of readings were within 2SD of mean difference. Whilst the majority of paired readings were comparable (within 10 mmHg) clinically relevant tissue-ventricular dissociations were noted. Further work is required to unravel the events responsible for short intervals of pressure dissociation before tissue pressure readings can be definitively accepted as a reliable surrogate for ventricular pressure.

Evaluation of films for packaging applications in high pressure processing

NASA Astrophysics Data System (ADS)

Largeteau, A.; Angulo, I.; Coulet, J. P.; Demazeau, G.

2010-03-01

Food treatments implying high pressures used pre-packaging systems; consequently it appeared necessary to validate different packaging films able to be used in such processes. Two different packaging films from AMCOR FLEXIBLES have been evaluated: VIROFLEXAL: BOLSA 80 MICRAS, coextrusion PA/PE (20/60μm) RILTHENE: SEMI 20/60 MICRAS, laminate PA/PE (20/60μm) Three different physico-chemical characterizations have been developed for the evaluation of films behaviour after High Hydrostatic Pressure (HHP): (i) Mechanical properties (tensile strength and sealing strength), (ii) Oxygen permeability, (iii) Migration, through the contact with four food simulating liquids FSLs (water, acetic acid 3%, ethyl alcohol 10%, iso-octane). Two different pressures values (P = 400MPa and 500MPa) have been tested, with a duration of 15 min, at ambient temperature (+20°C) and only one pressure (P = 200MPa) for the experiments at low temperature (T = -20°C) with the same duration (15min). The selection of such values can be justified taking into account that experimental conditions as a temperature close to +20°C and a pressure between 400 and 500MPa are appropriated to inactivate bacteria and different others micro-organisms. Due to the efficiency of the association of hydrostatic pressure processing and low temperature (HHP/LT) [1, 2], the same films have been tested under high pressure processing (200MPa) but at negative temperature (-20°C).

Hydraulic safety margins and embolism reversal in stems and leaves: Why are conifers and angiosperms so different?

Treesearch

Daniel M. Johnson; Katherine A. McCulloh; David R. Woodruff; Frederick C. Meinzer

2012-01-01

Angiosperm and coniferous tree species utilize a continuum of hydraulic strategies. Hydraulic safety margins (defined as differences between naturally occurring xylem pressures and pressures that would cause hydraulic dysfunction, or differences between pressures resulting in loss of hydraulic function in adjacent organs (e.g., stems vs. leaves) tend to be much greater...

Effects of thermal loading and hydrostatic pressure on reflecting wavelengths of double-coated fiber Bragg grating with different coating-layer thickness

NASA Astrophysics Data System (ADS)

Seraji, Faramarz E.; Toutian, Golnoush

2017-10-01

Fiber Bragg grating (FBG) of different configurations used as sensing devices are vulnerable to environmental factors, such as static pressures and thermal loading, which cause their characteristic Bragg reflecting wavelengths to up/down-shift. In this paper, by considering double-coated FBG with different primary and secondary coating materials, the effects of thermal loading and hydrostatic pressure on FBG with different coating-layer thicknesses are analyzed to find design criteria for controlling the Bragg wavelength shift. The obtained results of the analysis may be employed as criteria to design pressure and temperature sensors when using double-coated FBGs.

Preliminary investigation of foot pressure distribution variation in men and women adults while standing.

PubMed

Periyasamy, R; Mishra, A; Anand, Sneh; Ammini, A C

2011-09-01

Women and men are anatomically and physiologically different in a number of ways. They differ in both shape and size. These differences could potentially mean foot pressure distribution variation in men and women. The purpose of this study was to analyze standing foot pressure image to obtain the foot pressure distribution parameter - power ratio variation between men and women using image processing in frequency domain. We examined 28 healthy adult subjects (14 men and 14 women) aged between 20 and 45 years was recruited for our study. Foot pressure distribution patterns while standing are obtained by using a PedoPowerGraph plantar pressure measurement system for foot image formation, a digital camera for image capturing, a TV tuner PC-add on card, a WinDvr software for still capture and Matlab software with dedicated image processing algorithms have been developed. Various PedoPowerGraphic parameters such as percentage medial impulse (PMI), fore foot to hind foot pressure distribution ratio (F/H), big toe to fore foot pressure distribution ratio (B/F) and power ratio (PR) were evaluated. In men, contact area was significantly larger in all regions of the foot compared with women. There were significant differences in plantar pressure distribution but there was no significant difference in F/H and B/F ratio. Mean PR value was significantly greater in men than women under the hind foot and fore foot. PMI value was greater in women than men. As compared to men, women have maximum PR variations in the mid foot. Hence there is significant difference at level p<0.05 in medial mid foot and mid foot PR of women as compared to men. There was variation in plantar pressure distribution because the contact area of the men foot was larger than that of women foot. Hence knowledge of pressure distributions variation of both feet can provide suitable guidelines to biomedical engineers and doctor for designing orthotic devices for reliving the area of excessively high pressure. Copyright © 2011 Elsevier Ltd. All rights reserved.

The significance of visitors' pressure for soil status in an urban park in Tel-Aviv

NASA Astrophysics Data System (ADS)

Zhevelev, Helena; Sarah, Pariente; Oz, Atar

2010-05-01

A park is one of the most important elements of sustainable development and optimization of the urban environment. The equilibrium within the complex of natural and anthropogenic factors defines the status of a park's ecosystem. The seasonal dynamics and spatial variations of soil properties in areas under differing levels of visitors' pressure were studied in a park in Tel-Aviv. Soil was sampled twice a year, in wet (March) and dry (July) seasons, from three types of areas, subjected to differing levels of visitors' pressure: high, low and none (control). In each type of area samples were taken from two depths (0-2 cm and 5-10 cm), at 14-39 points. In total, 268 soil samples were taken. Before the soil sampling, penetration depth was determined at each point. In addition, the numbers of barbecue fires in each of the three areas were counted. Gravimetric soil moisture, organic matter, pH, electrical conductivity, and soluble ions were measured in 1:1 water extraction. Penetration depth and electrical conductivity, and organic matter, sodium, potassium and chlorite contents differed under differing levels of visitors' pressure, whereas soil moisture, pH and calcium content exhibited only minor differences. Soil moisture, electrical conductivity, and magnesium and chlorite contents exhibited strong seasonal changes, whereas the organic matter, potassium and pH levels were unaffected by seasonal dynamics. Calcium, organic matter, magnesium and chlorite contents, and electrical conductivity were significantly affected by the depth of soil sampling, whereas pH was not so affected. The seasonal changes in soil properties in the area subjected to high visitors' pressure were higher than in the one under low visitors' pressure. In most cases, visitors' pressure led to increases in variance and coefficient of variation. Different soil properties were differently affected by visitors' pressure, seasonal dynamics and soil depth. The surface of the soil was more sensitive to both seasonal dynamics and visitors' pressure, than the deeper layer. Visitors' pressure increased seasonal changes in the studied soil properties, and also increased the spatial heterogeneity of the soil. The differences in organic matter, electrical conductivity and soluble ions among the areas under differing visitors' pressure are attributed to anthropogenic additions, which accompanied the recreational activities in the urban parks: remnants of barbecue fires and meals, and excreta of urban animals. Addition of urban dust, enriched in CaCO3, minimized the effect of visitors' pressure on soil calcium content. All the above anthropogenic additions enhance the differentiation in soil layers. The notable effect of visitors' pressure on variations in soil properties highlighted its high significance for urban parks.

Medial stabilized and posterior stabilized TKA affect patellofemoral kinematics and retropatellar pressure distribution differently.

PubMed

Glogaza, Alexander; Schröder, Christian; Woiczinski, Matthias; Müller, Peter; Jansson, Volkmar; Steinbrück, Arnd

2018-06-01

Patellofemoral kinematics and retropatellar pressure distribution change after total knee arthroplasty (TKA). It was hypothesized that different TKA designs will show altered retropatellar pressure distribution patterns and different patellofemoral kinematics according to their design characteristics. Twelve fresh-frozen knee specimens were tested dynamically in a knee rig. Each specimen was measured native, after TKA with a posterior stabilized design (PS) and after TKA with a medial stabilized design (MS). Retropatellar pressure distribution was measured using a pressure sensitive foil which was subdivided into three areas (lateral and medial facet and patellar ridge). Patellofemoral kinematics were measured by an ultrasonic-based three-dimensional motion system (Zebris CMS20, Isny Germany). Significant changes in patellofemoral kinematics and retropatellar pressure distribution were found in both TKA types when compared to the native situation. Mean retropatellar contact areas were significantly smaller after TKA (native: 241.1 ± 75.6 mm 2 , MS: 197.7 ± 74.5 mm 2 , PS: 181.2 ± 56.7 mm 2 , native vs. MS p < 0.001; native vs. PS p < 0.001). The mean peak pressures were significantly higher after TKA. The increased peak pressures were however seen in different areas: medial and lateral facet in the PS-design (p < 0.001), ridge in the MS design (p < 0.001). Different patellofemoral kinematics were found in both TKA designs when compared to the native knee during flexion and extension with a more medial patella tracking. Patellofemoral kinematics and retropatellar pressure change after TKA in different manner depending on the type of TKA used. Surgeons should be aware of influencing the risks of patellofermoral complications by the choice of the prosthesis design.

Effect of breast feeding in infancy on blood pressure in later life: systematic review and meta-analysis

PubMed Central

Owen, Christopher G; Whincup, Peter H; Gilg, Julie A; Cook, Derek G

2003-01-01

Objective To determine whether breast feeding in infancy compared with bottle feeding formula milk is associated with lower mean blood pressure at different ages. Design Systematic review. Data sources Embase, Medline, and Web of Science databases. Study selection Studies showing the effects of feeding in infancy on blood pressure at different ages. Data extraction Pooled mean differences in blood pressure between breast fed infants and those bottle fed formula milk, based on random effects models. Data synthesis The pooled mean difference in systolic blood pressure was -1.10 mm Hg (95% confidence interval -1.79 to -0.42 mm Hg) but with significant heterogeneity between estimates (P < 0.001). The difference was largest in studies of < 300 participants (-2.05 mm Hg, -3.30 to -0.80 mm Hg), intermediate in studies of 300-1000 participants (1.13 mm Hg, -2.53 to 0.27 mm Hg), and smallest in studies of > 1000 participants (-0.16 mm Hg, -0.60 to 0.28 mm Hg). An Egger test but not Begg test was statistically significant for publication bias. The difference was unaltered by adjustment for current size and was independent of age at measurement of blood pressure and year of birth. Diastolic blood pressure was not significantly related to type of feeding in infancy. Conclusions Selective publication of small studies with positive findings may have exaggerated claims that breast feeding in infancy reduces systolic blood pressure in later life. The results of larger studies suggest that feeding in infancy has at most a modest effect on blood pressure, which is of limited clinical or public health importance. PMID:14630752

The effect of continuous nursing intervention guided by chronotherapeutics on ambulatory blood pressure of older hypertensive patients in the community.

PubMed

Cheng, Mei; Cheng, Shu-Ling; Zhang, Qing; Jiang, He; Cong, Ji-Yan; Zang, Xiao-Ying; Zhao, Yue

2014-08-01

To explore the effect of continuous nursing intervention guided by chronotherapeutics so as to provide the easy, noninvasive, effective and acceptable intervention for older hypertensive patients in the community. Many researchers studied the effect of administration at different times on blood pressure control and circadian rhythm. However, the individual administrative time was set ambiguously in previous studies. A semi-experimental study. In the study, 90 eligible patients were recruited and separated into three groups randomly, which were the control group, intervention group A (behaviour and chronotherapy intervention) and intervention group B (behaviour intervention). At 6 and 12 months after the study, the intervention groups were measured 24-hour ambulatory blood pressure monitoring. There were significant differences in ambulatory blood pressure monitoring parameters of the two intervention groups at different measurement times, and there were interaction between measurement time and different groups. The number of patients with dipper increased and reverse dipper decreased in group A as the intervention applied. There were statistical differences between two groups. The number of patients with morning surge in group A decreased more, and there were statistical differences between two groups at six months after the intervention. The behaviour and chronotherapy intervention based on the patients' ambulatory blood pressure monitoring can control casual blood pressure much better and last longer, which can also improve patients' indexes of ambulatory blood pressure monitoring better than behaviour intervention only. The behaviour and chronotherapy intervention can increase patients' nocturnal blood pressure drop, increase the number of patients with dipper and decrease reverse dipper, and improve blood pressure surge in the morning. Nurses can use continuous nursing intervention guided by chronotherapeutics to help improve hypertension of older patients better in the community. © 2014 John Wiley & Sons Ltd.

EXTRASOLAR STORMS: PRESSURE-DEPENDENT CHANGES IN LIGHT-CURVE PHASE IN BROWN DWARFS FROM SIMULTANEOUS HST AND SPITZER OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Hao; Apai, Dániel; Karalidi, Theodora

We present Spitzer /Infrared Array Camera Ch1 and Ch2 monitoring of six brown dwarfs during eight different epochs over the course of 20 months. For four brown dwarfs, we also obtained simulataneous Hubble Space Telescope ( HST )/WFC3 G141 grism spectra during two epochs and derived light curves in five narrowband filters. Probing different pressure levels in the atmospheres, the multiwavelength light curves of our six targets all exhibit variations, and the shape of the light curves evolves over the timescale of a rotation period, ranging from 1.4 to 13 hr. We compare the shapes of the light curves andmore » estimate the phase shifts between the light curves observed at different wavelengths by comparing the phase of the primary Fourier components. We use state-of-the-art atmosphere models to determine the flux contribution of different pressure layers to the observed flux in each filter. We find that the light curves that probe higher pressures are similar and in phase, but are offset and often different from the light curves that probe lower pressures. The phase differences between the two groups of light curves suggest that the modulations seen at lower and higher pressures may be introduced by different cloud layers.« less

Foot pressures during gait: a comparison of techniques for reducing pressure points.

PubMed

Lawless, M W; Reveal, G T; Laughlin, R T

2001-07-01

Various methods have been used to redistribute plantar surface foot pressure in patients with foot ulcers. This study was conducted to determine the effectiveness of four modalities (fracture walker, fracture walker with insert, and open and closed toe total contact casts) in reducing plantar foot pressure. Ten healthy, normal volunteer subjects had an F-scan sensor (ultra thin shoe insert pressure monitor) placed under the right foot. They then ambulated on a flat surface, maintaining their normal gait. Dynamic plantar pressures were averaged over 10 steps at four different sites (plantar surface of great toe, first metatarsal head, base of fifth metatarsal, and plantar heel). All subjects repeated this sequence under five different testing conditions (barefoot, with a fracture walker, fracture walker with arch support insert, open and closed toe total contact cast). Each subject's barefoot pressures were then compared with the pressures during the different modalities. All four treatment modalities significantly reduced (p < 0.05) plantar pressure at the first metatarsal head (no method was superior). The fracture walker, fracture walker with insert, and open toe total contact cast significantly reduced pressure at the heel. Pressures at the base of the fifth metatarsal and great toe were not significantly reduced with any treatment form. The fracture walker, with and without arch support, and total contact cast can effectively reduce plantar pressure at the heel and first metatarsal head.

Impact of State Public Health Spending on Disease Incidence in the United States from 1980 to 2009.

PubMed

Verma, Reetu; Clark, Samantha; Leider, Jonathon; Bishai, David

2017-02-01

To understand the relationship between state-level spending by public health departments and the incidence of three vaccine preventable diseases (VPDs): mumps, pertussis, and rubella in the United States from 1980 to 2009. This study uses state-level public health spending data from The Census Bureau and annual mumps, pertussis, and rubella incidence counts from the University of Pittsburgh's project Tycho. Ordinary least squares (OLS), fixed effects, and random effects regression models were tested, with results indicating that a fixed effects model would be most appropriate model for this analysis. Model output suggests a statistically significant, negative relationship between public health spending and mumps and rubella incidence. Lagging outcome variables indicate that public health spending actually has the greatest impact on VPD incidence in subsequent years, rather than the year in which the spending occurred. Results were robust to models with lagged spending variables, national time trends, and state time trends, as well as models with and without Medicaid and hospital spending. Our analysis indicates that there is evidence of a significant, negative relationship between a state's public health spending and the incidence of two VPDs, mumps and rubella, in the United States. © Health Research and Educational Trust.

Technology of uncooled fast polycrystalline PbSe focal plane arrays in systems for muzzle flash detection

NASA Astrophysics Data System (ADS)

Kastek, Mariusz; PiÄ tkowski, Tadeusz; Polakowski, Henryk; Barela, Jaroslaw; Firmanty, Krzysztof; Trzaskawka, Piotr; Vergara, German; Linares, Rodrigo; Gutierrez, Raul; Fernandez, Carlos; Montojo Supervielle, Maria Teresa

2014-05-01

The paper presents some aspects of muzzle flash detection using low resolution polycrystalline PbSe 32×32 and 80×80 detectors FPA operating at room temperature (uncooled performance). These sensors, which detect in MWIR (3 - 5 microns region) and are manufactured using proprietary technology from New Infrared Technologies (VPD PbSe - Vapor Phase Deposition of polycrystalline PbSe), can be applied to muzzle flash detection. The system based in the uncooled 80×80 FPA monolithically integrated with the CMOS readout circuitry has allowed image recording with frame rates over 2000 Hz (true snapshot acquisition), whereas the lower density, uncooled 32×32 FPA is suitable for being used in low cost infrared imagers sensitive in the MWIR band with frame rates above 1000 Hz. The FPA detector, read-out electronics and processing electronics (allows the implementation of some algorithms for muzzle flash detection) of both systems are presented. The systems have been tested at field test ground. Results of detection range measurement with two types of optical systems (wide and narrow field of view) have been shown. The theoretical analysis of possibility detection of muzzle flash and initial results of testing of some algorithms for muzzle flash detection have been presented too.

A closer look at travellers' infections abroad: Finnish nationwide data with incidences, 2010 to 2012.

PubMed

Siikamäki, Heli; Kivelä, Pia; Fotopoulos, Mikael; Kantele, Anu

Although infections represent the most common health problem of travellers abroad, data on morbidity and incidences of various infections are scarce. Data on infections of Finnish travellers during 2010-2012 were retrieved from the database of SOS International, an assistance organization covering 95% of Finns requiring aid abroad. The study included 30,086 cases. For incidence calculation, the data were linked to the numbers of Finns visiting these regions during the same period as recorded by the Official Statistics of Finland. The incidence of infections was particularly high in Africa, southern Europe plus the eastern Mediterranean, and Asia plus Oceania. The most frequent diagnoses were acute gastroenteritis (38.0%) and respiratory-tract infections (RTI) (34.5%), followed by infections of the ear (12.6%), skin or subcutaneous tissue (5.1%), urogenital tract (4.2%), eye (3.1%), and systemic febrile infections (2.2%). Vaccine-preventable diseases (VPD) accounted for 0.8% of cases, with varicella as most (49%) and influenza as second-most (27%) common. Incidence of infections was higher in southern than in eastern and western Europe. Gastroenteritis and RTI proved the most frequent diagnoses, whereas systemic febrile infections were uncommon. Despite pre-travel immunizations, VPDs still occurred; pre-travel consultation should cover both varicella and influenza. Copyright © 2016 Elsevier Ltd. All rights reserved.

Development and validation of a numerical model of the swine head subjected to open-field blasts

NASA Astrophysics Data System (ADS)

Kalra, A.; Zhu, F.; Feng, K.; Saif, T.; Kallakuri, S.; Jin, X.; Yang, K.; King, A.

2017-11-01

A finite element model of the head of a 55-kg Yucatan pig was developed to calculate the incident pressure and corresponding intracranial pressure due to the explosion of 8 lb (3.63 kg) of C4 at three different distances. The results from the model were validated by comparing findings with experimentally obtained data from five pigs at three different blast overpressure levels: low (150 kPa), medium (275 kPa), and high (400 kPa). The peak values of intracranial pressures from numerical model at different locations of the brain such as the frontal, central, left temporal, right temporal, parietal, and occipital regions were compared with experimental values. The model was able to predict the peak pressure with reasonable percentage differences. The differences for peak incident and intracranial pressure values between the simulation results and the experimental values were found to be less than 2.2 and 29.3%, respectively, at all locations other than the frontal region. Additionally, a series of parametric studies shows that the intracranial pressure was very sensitive to sensor locations, the presence of air bubbles, and reflections experienced during the experiments. Further efforts will be undertaken to correlate the different biomechanical response parameters, such as the intracranial pressure gradient, stress, and strain results obtained from the validated model with injured brain locations once the histology data become available.

Investigation of peak pressure index parameters for people with spinal cord injury using wheelchair tilt-in-space and recline: methodology and preliminary report.

PubMed

Lung, Chi-Wen; Yang, Tim D; Crane, Barbara A; Elliott, Jeannette; Dicianno, Brad E; Jan, Yih-Kuen

2014-01-01

The purpose of this study was to determine the effect of the sensel window's location and size when calculating the peak pressure index (PPI) of pressure mapping with varying degrees of wheelchair tilt-in-space (tilt) and recline in people with spinal cord injury (SCI). Thirteen power wheelchair users were recruited into this study. Six combinations of wheelchair tilt (15°, 25°, and 35°) and recline (10° and 30°) were used by the participants in random order. Displacements of peak pressure and center of pressure were extracted from the left side of the mapping system. Normalized PPI was computed for three sensel window dimensions (3 sensels × 3 sensels, 5 × 5, and 7 × 7). At least 3.33 cm of Euclidean displacement of peak pressures was observed in the tilt and recline. For every tilt angle, peak pressure displacement was not significantly different between 10° and 30° recline, while center of pressure displacement was significantly different (P < .05). For each recline angle, peak pressure displacement was not significantly different between pairs of 15°, 25°, and 35° tilt, while center of pressure displacement was significantly different between 15° versus 35° and 25° versus 35°. Our study showed that peak pressure displacement occurs in response to wheelchair tilt and recline, suggesting that the selected sensel window locations used to calculate PPI should be adjusted during changes in wheelchair configuration.

Application of intermittent negative pressure on the lower extremity and its effect on macro- and microcirculation in the foot of healthy volunteers.

PubMed

Sundby, Øyvind H; Høiseth, Lars Øivind; Mathiesen, Iacob; Jørgensen, Jørgen J; Weedon-Fekjær, Harald; Hisdal, Jonny

2016-09-01

Intermittent negative pressure (INP) applied to the lower leg and foot may increase peripheral circulation. However, it is not clear how different patterns of INP affect macro- and microcirculation in the foot. The aim of this study was therefore to determine the effect of different patterns of negative pressure on foot perfusion in healthy volunteers. We hypothesized that short periods with INP would elicit an increase in foot perfusion compared to no negative pressure. In 23 healthy volunteers, we continuously recorded blood flow velocity in a distal foot artery, skin blood flow, heart rate, and blood pressure during application of different patterns of negative pressure (-40 mmHg) to the lower leg. Each participant had their right leg inside an airtight chamber connected to an INP generator. After a baseline period at atmospheric pressure, we applied four different 120 sec sequences with either constant negative pressure or different INP patterns, in a randomized order. The results showed corresponding fluctuations in blood flow velocity and skin blood flow throughout the INP sequences. Blood flow velocity reached a maximum at 4 sec after the onset of negative pressure (average 44% increase above baseline, P < 0.001). Skin blood flow and skin temperature increased during all INP sequences (P < 0.001). During constant negative pressure, average blood flow velocity, skin blood flow, and skin temperature decreased (P < 0.001). In conclusion, we observed increased foot perfusion in healthy volunteers after the application of INP on the lower limb. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

Intramedullary pressure changes in rats after spinal cord injury.

PubMed

Dong, X; Yang, D; Li, J; Liu, C; Yang, M; Du, L; Gu, R; Hu, A; Zhang, H

2016-11-01

The objectives of this study were to explore the change of intramedullary pressure over time in rats after different degrees of spinal cord contusion injury and to verify the hypothesis that the more serious the injury, the higher the intramedullary pressure. The control group rats underwent laminectomy only, whereas the rats in the three experimental groups were subjected to mild, moderate or severe 10th thoracic cord (T10) contusion injury after laminectomy. In addition, an intramedullary pressure of T10 was measured by a Millar Mikro-Tip pressure catheter (Millar Incorporated Company, Houston, TX, USA) immediately in the control group or at different time points after injury in the experimental groups. The average intramedullary pressure of the rats in the control group was 6.88±1.67 mm Hg, whereas that of the rats in any injury group was significantly higher (P=0.000). There was statistical difference among the different time points in the mild or moderate injury group (P=0.007/0.017), but no in the severe (P=0.374). The curves of intramedullary pressure over time in the mild and moderate injury group were bimodal, peaking at 1 and 48 h after the injury. The intramedullary pressure after injury was positively correlated with the injury degree (r=0.438, P=0.000). The intramedullary pressure of the rats increased after traumatic spinal cord injury. If the injury was not serious, the intramedullary pressure fluctuated with time and peaked at 1 and 48 h after injury. If the injury was serious, the intramedullary pressure remained high. The more serious the injury, the higher the intramedullary pressure.

Performance of different PEEP valves and helmet outlets at increasing gas flow rates: a bench top study.

PubMed

Isgrò, S; Zanella, A; Giani, M; Abd El Aziz El Sayed Deab, S; Pesenti, A; Patroniti, N

2012-10-01

Aim of the paper was to assess the performance of different expiratory valves and the resistance of helmet outlet ports at increasing gas flow rates. A gas flow-meter was connected to 10 different expiratory peep valves: 1 water-seal valve, 4 precalibrated fixed PEEP valves and 5 adjustable PEEP valves. Three new valves of each brand, set at different pressure levels (5-7.5-10-12.5-15 cmH(2)O, if available), were tested at increasing gas flow rates (from 30 to 150 L/min). We measured the pressure generated just before the valves. Three different helmets sealed on a mock head were connected at the inlet port with a gas flow-meter while the outlet was left clear. We measured the pressure generated inside the helmet (due to the flow-resistance of the outlet port) at increasing gas flow rates. Adjustable valves showed a variable degree flow-dependency (increasing difference between the measured and the expected pressure at increasing flow rates), while pre-calibrated valves revealed a flow-independent behavior. Water seal valve showed low degree flow-dependency. The pressures generated by the outlet port of the tested helmets ranged from 0.02 to 2.29 cmH(2)O at the highest gas flow rate. Adjustable PEEP valves are not suggested for continuous-flow CPAP systems as their flow-dependency can lead to pressures higher than expected. Precalibrated and water seal valves exhibit the best performance. Different helmet outlet ports do not significantly affect the pressure generated during helmet CPAP. In order to avoid iatrogenic complications gas flow and pressure delivered during helmet CPAP must always be monitored.

Comparison of noninvasive blood pressure measurement techniques via the coccygeal artery in anesthetized cheetahs (Acinonyx jubatus).

PubMed

Sadler, Ryan A; Hall, Natalie H; Kass, Philip H; Citino, Scott B

2013-12-01

Two indirect blood pressure measurement techniques, Doppler (DOP) sphygmomanometry and oscillometry, applied at the ventral coccygeal artery were compared with simultaneous direct blood pressure measurements at the dorsal pedal artery in 10 anesthetized, captive cheetahs (Acinonyx jubatus). The DOP method was moderately accurate, with relatively little bias (mean difference 3.8 mmHg) and 88.6% of the DOP systolic arterial pressure measurements being within 10 mmHg of the direct systolic arterial measurement. With the oscillometric (OM) method, 89.2% of the mean arterial pressure measurements were within 10 mmHg of the direct measurement and had the least bias (mean difference 2.3 mmHg), 80.7% of the systolic measurements were within 10 mmHg of the direct measurement and had the second least bias (mean difference 2.3 mmHg), and 59% of the diastolic measurements were within 10 mmHg of the direct measurement and had significant bias (mean difference 7.3 mmHg). However, DOP showed relatively poor precision (SD 11.2 mmHg) compared with OM systolic (SD 8.0 mmHg), diastolic (SD 8.6 mmHg), and mean (SD 5.7 mmHg). Both techniques showed a linear relationship with the direct technique measurements over a wide range of blood pressures. The DOP method tended to underestimate systolic measurements below 160 mmHg and overestimate systolic measurements above 160 mmHg. The OM method tended to underestimate mean pressures below 160 mm Hg, overestimate mean pressures above 160 mmHg, underestimate systolic pressures below 170 mmHg, overestimate systolic pressures above 170 mmHg, and underestimate diastolic pressures throughout the measured blood pressure range. Indirect blood pressure measurement using the ventral coccygeal artery, particularly when using an OM device for mean and systolic arterial pressure, may be useful in the clinical assessment of cheetahs when monitoring trends over time, but caution should be taken when interpreting individual values.