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Sample records for contrasting seasonal dynamics

  1. 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.

  2. Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River basin

    NASA Astrophysics Data System (ADS)

    Zuijdgeest, A. L.; Zurbrügg, R.; Blank, N.; Fulcri, R.; Senn, D. B.; Wehrli, B.

    2015-12-01

    Floodplains are important biogeochemical reactors during fluvial transport of carbon and nutrient species towards the oceans. In the tropics and subtropics, pronounced rainfall seasonality results in highly dynamic floodplain biogeochemistry. The massive construction of dams, however, has significantly altered the hydrography and chemical characteristics of many (sub)tropical rivers. In this study, we compare organic-matter and nutrient biogeochemistry of two large, contrasting floodplains in the Zambezi River basin in southern Africa: the Barotse Plains and the Kafue Flats. Both systems are of comparable size but differ in anthropogenic influence: while the Barotse Plains are still in large parts pristine, the Kafue Flats are bordered by two hydropower dams. The two systems exhibit different flooding dynamics, with a larger contribution of floodplain-derived water in the Kafue Flats and a stronger peak flow in the Barotse Plains. Distinct seasonal differences have been observed in carbon and nutrient concentrations, loads, and export and retention behavior in both systems. The simultaneous retention of particulate carbon and nitrogen and the net export of dissolved organic and inorganic carbon and nitrogen suggested that degradation of particulate organic matter was the dominant process influencing the river biogeochemistry during the wet season in the Barotse Plains and during the dry season in the Kafue Flats. Reverse trends during the dry season indicated that primary production was important in the Barotse Plains, whereas the Kafue Flats seemed to have both primary production and respiration occurring during the wet season, potentially occurring spatially separated in the main channel and on the floodplain. Carbon-to-nitrogen ratios of particulate organic matter showed that soil-derived material was dominant year-round in the Barotse Plains, whereas the Kafue Flats transported particulate organic matter that had been produced in the upstream reservoir during

  3. Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River Basin

    NASA Astrophysics Data System (ADS)

    Zuijdgeest, A. L.; Zurbrügg, R.; Blank, N.; Fulcri, R.; Senn, D. B.; Wehrli, B.

    2015-07-01

    Floodplains are important biogeochemical reactors during fluvial transport of carbon and nutrient species towards the oceans. In the tropics and subtropics pronounced rainfall seasonality results in highly dynamic floodplain biogeochemistry. Massive construction of hydropower dams, however, has significantly altered the hydrography and chemical characteristics of many (sub)tropical rivers. In this study, we compare organic matter and nutrient biogeochemistry of two large, contrasting floodplains in the Zambezi River Basin in Southern Africa, the Barotse Plains and the Kafue Flats. Both systems are of comparable size, but differ in anthropogenic influence: while the Barotse Plains are still relatively pristine, the Kafue Flats are bordered by two hydropower dams. While the Barotse Plains retain particles during the wet season, annual yields of particulate organic carbon and nitrogen are higher than previously reported for the Zambezi and other tropical rivers. Enhanced wet-season runoff adds soil-derived dissolved organic carbon and nitrogen to the Zambezi River, with a corresponding increase in the Barotse Plains. Soil-derived organic matter dominates the particulate phase year-round in the Barotse Plains, and a varying influence of C3- and C4-plant vegetation can be observed throughout the year. In contrast to the Barotse Plains, net export of particulate matter from the Kafue Flats has been observed during the wet season, but over an annual cycle, the Kafue Flats are effectively accumulating dissolved carbon and nutrients. In the Kafue Flats, the runoff-induced increase in dissolved organic carbon and nitrogen concentrations is delayed by the upstream dam operation. The dam reservoir also causes a shift in the source of the particulate organic matter - from soil-derived during the dry season to aquatically produced in the wet season - in the downstream Kafue Flats. Spatial zonation in vegetation and temporal flooding dynamics in the Kafue Flats result in mostly C

  4. Contrasting spin dynamics

    SciTech Connect

    Ning, F. L.; Ahilan, K.; Imai, T.; Sefat, A. S.; McGuire, Michael A; Sales, Brian C; Mandrus, David; Cheng, P.; Shen, B.; Wen, H.-H.

    2010-01-01

    We report the first NMR investigation of spin dynamics in the overdoped nonsuperconducting regime of Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} up to x=0.26. We demonstrate that the absence of interband transitions with large momentum transfer Q{sub AF}-({pi}/a,0) between the hole and electron Fermi surfaces results in complete suppression of antiferromagnetic spin fluctuations for x {ge} 0.15. Our experimental results provide direct evidence for a correlation between T{sub c} and the strength of Q{sub AF} antiferromagnetic spin fluctuations.

  5. Contrasting Strategies of Tree Function in a Seasonal Amazon Rainforest

    NASA Astrophysics Data System (ADS)

    Ivanov, V. Y.; Oliveira, R.; Agee, E.; Brum, M., Jr.; Saleska, S. R.; Fatichi, S.; Ewing, G.

    2015-12-01

    The increased frequency and severity of drought conditions in the Amazon Basin region have emphasized the question of rainforest vulnerability and resilience to heat and drought-induced stresses. However, what emerges from much research is that the impacts of droughts, essential controlling factors of the rainforest function, and variability of tree-scale strategies are yet to be fully understood. We present here a preliminary analysis of hydraulic relations of a seasonal Amazon rainforest using a set of ecohydrologic data collected through the GoAmazon project over dry and wet seasons. Expressions of different hydraulic strategies are identified that convey different implications for tree resilience during short- (diurnal) and longer-term (seasonal) stress periods. These hydraulic strategies appear to be inter-related with the tree growth and non-structural carbohydrate dynamics, contributing to the understanding of trait coordination at the whole-plant scale. Integration of individual responses is conducted over a range of wood density and exposure conditions. The results of this research thus shed light on the implication of variations in the rainforest function for future stresses, vital for predictive models of ecosystem dynamics of next generation.

  6. Contrasting seasonal niche separation between rare and abundant taxa conceals the extent of protist diversity.

    PubMed

    Nolte, Viola; Pandey, Ram Vinay; Jost, Steffen; Medinger, Ralph; Ottenwälder, Birgit; Boenigk, Jens; Schlötterer, Christian

    2010-07-01

    With the advent of molecular methods, it became clear that microbial biodiversity had been vastly underestimated. Since then, species abundance patterns were determined for several environments, but temporal changes in species composition were not studied to the same level of resolution. Using massively parallel sequencing on the 454 GS FLX platform we identified a highly dynamic turnover of the seasonal abundance of protists in the Austrian lake Fuschlsee. We show that seasonal abundance patterns of protists closely match their biogeographic distribution. The stable predominance of few highly abundant taxa, which previously led to the suggestion of a low global protist species richness, is contrasted by a highly dynamic turnover of rare species. We suggest that differential seasonality of rare and abundant protist taxa explains the--so far--conflicting evidence in the 'everything is everywhere' dispute. Consequently temporal sampling is basic for adequate diversity and species richness estimates. PMID:20609083

  7. Optical imaging with dynamic contrast agents.

    PubMed

    Wei, Qingshan; Wei, Alexander

    2011-01-24

    Biological imaging applications often employ molecular probes or nanoparticles for enhanced contrast. However, resolution and detection are still often limited by the intrinsic heterogeneity of the sample, which can produce high levels of background that obscure the signals of interest. Herein, we describe approaches to overcome this obstacle based on the concept of dynamic contrast: a strategy for elucidating signals by the suppression or removal of background noise. Dynamic contrast mechanisms can greatly reduce the loading requirement of contrast agents, and may be especially useful for single-probe imaging. Dynamic contrast modalities are also platform-independent, and can enhance the performance of sophisticated biomedical imaging systems or simple optical microscopes alike. Dynamic contrast is performed in two stages: 1) a signal modulation scheme to introduce time-dependent changes in amplitude or phase, and 2) a demodulation step for signal recovery. Optical signals can be coupled with magnetic nanoparticles, photoswitchable probes, or plasmon-resonant nanostructures for modulation by magnetomotive, photonic, or photothermal mechanisms, respectively. With respect to image demodulation, many of the strategies developed for signal processing in electronics and communication technologies can also be applied toward the editing of digital images. The image-processing step can be as simple as differential imaging, or may involve multiple reference points for deconvolution by using cross-correlation algorithms. Periodic signals are particularly amenable to image demodulation strategies based on Fourier transform; the contrast of the demodulated signal increases with acquisition time, and modulation frequencies in the kHz range are possible. Dynamic contrast is an emerging topic with considerable room for development, both with respect to molecular or nanoscale probes for signal modulation, and also to methods for more efficient image processing and editing. PMID

  8. Seasonal Population Dynamics of Three Potato Pests in Washington State.

    PubMed

    D'Auria, Elizabeth M; Wohleb, Carrie H; Waters, Timothy D; Crowder, David W

    2016-08-01

    Pest phenology models allow producers to anticipate pest outbreaks and deploy integrated pest management (IPM) strategies. Phenology models are particularly useful for cropping systems with multiple economically damaging pests throughout a season. Potato (Solanum tuberosum L.) crops of Washington State, USA, are attacked by many insect pests including the potato tuberworm (Phthorimaea operculella Zeller), the beet leafhopper (Circulifer tenellus Baker), and the green peach aphid (Myzus persicae Sulzer). Each of these pests directly damages potato foliage or tubers; C. tenellus and M. persicae also transmit pathogens that can drastically reduce potato yields. We monitored the seasonal population dynamics of these pests by conducting weekly sampling on a network of commercial farms from 2007 to 2014. Using these data, we developed phenology models to characterize the seasonal population dynamics of each pest based on accumulated degree-days (DD). All three pests exhibited consistent population dynamics across seasons that were mediated by temperature. Of the three pests, C. tenellus was generally the first detected in potato crops, with 90% of adults captured by 936 DD. In contrast, populations of P. operculella and M. persicae built up more slowly over the course of the season, with 90% cumulative catch by 1,590 and 2,634 DD, respectively. Understanding these seasonal patterns could help potato producers plan their IPM strategies while allowing them to move away from calendar-based applications of insecticides. More broadly, our results show how long-term monitoring studies that explore dynamics of multiple pest species can aid in developing IPM strategies in crop systems. PMID:27271946

  9. Seasonal Contrasts in the Surface Energy Balance of the Sahel

    SciTech Connect

    Miller, Ron; Slingo, A.; Barnard, James C.; Kassianov, Evgueni I.

    2009-03-14

    Over most of the world ocean, heating of the surface by sunlight is balanced predominately by evaporative cooling. Even over land, moisture for evaporation is available from vegetation or the soil reservoir. However, at the ARM Mobile Facility in Niamey, Niger, soil moisture is so depleted that evaporation makes a significant contribution to the surface energy balance only at the height of the rainy season, when precipitation has replenished the soil reservoir. Using observations at the Mobile Facility from late 2005 to early 2007, we describe how the surface balances radiative forcing. How the surface compensates time-averaged solar heating varies with seasonal changes in atmospheric water vapor, which modulates the greenhouse effect and the ability of the surface to radiate thermal energy directly to space. During the dry season, sunlight is balanced mainly by longwave radiation and the turbulent flux of sensible heat. The ability of longwave radiation to cool the surface drops after the onset of the West African summer monsoon, when moist, oceanic air flows onshore, increasing local column moisture and atmospheric opacity at these wavelengths. After the monsoon onset, but prior to significant rainfall, solar heating is compensated mainly by the sensible heat flux. During the rainy season, the magnitude of evaporation is initially controlled by the supply of moisture from precipitation. However, by the height of the rainy season, sufficient precipitation has accumulated at the surface that evaporation is related to the flux demanded by solar radiation, and radiative forcing of the surface is balanced comparably by the latent, sensible, and longwave fluxes. Radiative forcing of the surface also varies on a subseasonal time scale due to fluctuations in water vapor, clouds, and aerosol concentration. Except at the height of the rainy season, subseasonal forcing is balanced mainly by sensible heating and longwave anomalies. The efficacy of the sensible heat flux

  10. Contrasting patterns of litterfall seasonality and seasonal changes in litter decomposability in a tropical rainforest region

    NASA Astrophysics Data System (ADS)

    Parsons, S. A.; Valdez-Ramirez, V.; Congdon, R. A.; Williams, S. E.

    2014-09-01

    The seasonality of litter inputs in forests has important implications for understanding ecosystem processes and biogeochemical cycles. We quantified the drivers of seasonality in litterfall and leaf decomposability using plots throughout the Australian wet tropical region. Litter fell mostly in the summer (wet, warm) months in the region, but other peaks occurred throughout the year. Litterfall seasonality was modelled well with the level of deciduousness of the site (plots with more deciduous species had lower seasonality than evergreen plots), temperature (higher seasonality in the uplands), disturbance (lower seasonality with more early secondary species) and soil fertility (higher seasonality with higher N : P/P limitation) (SL total litterfall model 1 = deciduousness + soil N : P + early secondary sp.: r2 = 0.63, n = 30; model 2 = temperature + early secondary sp. + soil N : P: r2 = 0.54, n = 30; SL leaf = temperature + early secondary sp. + rainfall seasonality: r2 = 0.39, n = 30). Leaf litter decomposability was lower in the dry season than in the wet season, driven by higher phenolic concentrations in the dry, with the difference exacerbated particularly by lower dry season moisture. Our results are contrary to the global trend for tropical rainforests; in that seasonality of litterfall input was generally higher in wetter, cooler, evergreen forests, compared to generally drier, warmer, semi-deciduous sites that had more uniform monthly inputs. We consider this due to more diverse litter shedding patterns in semi-deciduous and raingreen rainforest sites, and an important consideration for ecosystem modellers. Seasonal changes in litter quality are likely to have impacts on decomposition and biogeochemical cycles in these forests due to the litter that falls in the dry season being more recalcitrant to decay.

  11. Contrasting patterns of litterfall seasonality and seasonal changes in litter decomposability in a tropical rainforest region

    NASA Astrophysics Data System (ADS)

    Parsons, S. A.; Valdez-Ramirez, V.; Congdon, R. A.; Williams, S. E.

    2014-06-01

    The seasonality of litter inputs in forests has important implications for understanding ecosystem processes and biogeochemical cycles. We quantified the drivers of seasonality in litterfall and leaf decomposability, using plots throughout the Australian wet tropical region. Litter fell mostly in the summer (wet, warm) months in the region, but other peaks occurred throughout the year. Litterfall seasonality was modelled well with the level of deciduousness of the site (plots with more deciduous species had lower seasonality than evergreen plots), temperature (higher seasonality in the uplands), disturbance (lower seasonality with more early secondary species) and soil fertility (higher seasonality with higher N : P/P limitation) (SL total litterfall model 1 = deciduousness + soil N : P + early secondary sp: r2 = 0.63, n = 30 plots; model 2 = temperature + early secondary sp. + soil N : P: r2 = 0.54, n = 30; SL leaf = temperature + early secondary sp. + rainfall seasonality: r2 = 0.39, n = 30). Leaf litter decomposability was lower in the dry season than in the wet season, driven by higher phenolic concentrations in the dry, with the difference exacerbated particularly by lower dry season moisture. Our results are contrary to the global trend for tropical rainforests; in that seasonality of litterfall inputs were generally higher in wetter, cooler, evergreen forests, compared to generally drier, warmer, semi-deciduous sites that had more uniform monthly inputs. We consider this due to more diverse litter shedding patterns in semi-deciduous and raingreen rainforest sites, and an important consideration for ecosystem modellers. Seasonal changes in litter quality are likely to have impacts on decomposition and biogeochemical cycles in these forests due to the litter that falls in the dry being more recalcitrant to decay.

  12. Contrasting the epidemiological and evolutionary dynamics of influenza spatial transmission

    PubMed Central

    Viboud, Cécile; Nelson, Martha I.; Tan, Yi; Holmes, Edward C.

    2013-01-01

    In the past decade, rapid increases in the availability of high-resolution molecular and epidemiological data, combined with developments in statistical and computational methods to simulate and infer migration patterns, have provided key insights into the spatial dynamics of influenza A viruses in humans. In this review, we contrast findings from epidemiological and molecular studies of influenza virus transmission at different spatial scales. We show that findings are broadly consistent in large-scale studies of inter-regional or inter-hemispheric spread in temperate regions, revealing intense epidemics associated with multiple viral introductions, followed by deep troughs driven by seasonal bottlenecks. However, aspects of the global transmission dynamics of influenza viruses are still debated, especially with respect to the existence of tropical source populations experiencing high levels of genetic diversity and the extent of prolonged viral persistence between epidemics. At the scale of a country or community, epidemiological studies have revealed spatially structured diffusion patterns in seasonal and pandemic outbreaks, which were not identified in molecular studies. We discuss the role of sampling issues in generating these conflicting results, and suggest strategies for future research that may help to fully integrate the epidemiological and evolutionary dynamics of influenza virus over space and time. PMID:23382422

  13. Seasonal dynamics in an SIR epidemic system.

    PubMed

    Augeraud-Véron, E; Sari, N

    2014-02-01

    We consider a seasonally forced SIR epidemic model where periodicity occurs in the contact rate. This periodical forcing represents successions of school terms and holidays. The epidemic dynamics are described by a switched system. Numerical studies in such a model have shown the existence of periodic solutions. First, we analytically prove the existence of an invariant domain D containing all periodic (harmonic and subharmonic) orbits. Then, using different scales in time and variables, we rewrite the SIR model as a slow-fast dynamical system and we establish the existence of a macroscopic attractor domain K, included in D, for the switched dynamics. The existence of a unique harmonic solution is also proved for any value of the magnitude of the seasonal forcing term which can be interpreted as an annual infection. Subharmonic solutions can be seen as epidemic outbreaks. Our theoretical results allow us to exhibit quantitative characteristics about epidemics, such as the maximal period between major outbreaks and maximal prevalence. PMID:23404038

  14. Monitoring and modeling growing season dynamics

    NASA Astrophysics Data System (ADS)

    White, Michael Aaron

    Phenology, the study of recurring biological cycles and their connection to climate, is a growing field of global change research. Vegetation phenology exerts a strong control over carbon cycles, weather, and global radiation partitioning between sensible and latent heat fluxes. Phenological monitors of the timing and length of the growing season can also be used as barometers of vegetation responses to climatic variability. In the following chapters, I present research investigating the monitoring and interpretation of growing season dynamics. Ecological modeling is limited more by data availability than by model theory. In particular, the description of vegetation functional types (biomes) for distributed modeling has been lacking. In chapter 1, I present a documented description and sensitivity analysis of the 34 parameters used in the ecosystem model, BIOME-BGC, for major temperate biomes. I applied BIOME-BGC in the eastern U.S. deciduous broad leaf forest and found that minor phenological variation created large impacts on simulated net ecosystem exchange of carbon (chapter 2). In addition to simulating the effects of growing season variability, it is also important to develop accurate field monitoring techniques, both as a means of testing modeling activities and as a validation of satellite remote sensing estimates. I conducted an intercomparison of field techniques that could be used to monitor phenological dynamics in and ecosystems (chapter 3). I found that methodological barriers to rapid, low cost monitoring were severe, but that a digital camera with both visible and near-infrared channels was a viable option. Satellite remote sensing provides the only means of obtaining consistent estimates of phenological variation at a global scale, yet our understanding of these data has been limited by a lack of ground observations. To address this problem, I proposed, developed, and wrote a phenology measurement protocol for the Global Learning and Observations

  15. Diversity and seasonal dynamics of airborne archaea

    NASA Astrophysics Data System (ADS)

    Fröhlich-Nowoisky, J.; Ruzene Nespoli, C.; Pickersgill, D. A.; Galand, P. E.; Müller-Germann, I.; Nunes, T.; Gomes Cardoso, J.; Almeida, S. M.; Pio, C.; Andreae, M. O.; Conrad, R.; Pöschl, U.; Després, V. R.

    2014-11-01

    Archaea are widespread and abundant in many terrestrial and aquatic environments, and are thus outside extreme environments, accounting for up to ~10% of the prokaryotes. Compared to bacteria and other microorganisms, however, very little is known about the abundance, diversity, and dispersal of archaea in the atmosphere. By means of DNA analysis and Sanger sequencing targeting the 16S rRNA (435 sequences) and amoA genes in samples of air particulate matter collected over 1 year at a continental sampling site in Germany, we obtained first insights into the seasonal dynamics of airborne archaea. The detected archaea were identified as Thaumarchaeota or Euryarchaeota, with soil Thaumarchaeota (group I.1b) being present in all samples. The normalized species richness of Thaumarchaeota correlated positively with relative humidity and negatively with temperature. This together with an increase in bare agricultural soil surfaces may explain the diversity peaks observed in fall and winter. The detected Euryarchaeota were mainly predicted methanogens with a low relative frequency of occurrence. A slight increase in their frequency during spring may be linked to fertilization processes in the surrounding agricultural fields. Comparison with samples from the Cape Verde islands (72 sequences) and from other coastal and continental sites indicates that the proportions of Euryarchaeota are enhanced in coastal air, which is consistent with their suggested abundance in marine surface waters. We conclude that air transport may play an important role in the dispersal of archaea, including assumed ammonia-oxidizing Thaumarchaeota and methanogens.

  16. Diversity and seasonal dynamics of airborne Archaea

    NASA Astrophysics Data System (ADS)

    Fröhlich-Nowoisky, J.; Ruzene Nespoli, C.; Pickersgill, D. A.; Galand, P. E.; Müller-Germann, I.; Nunes, T.; Gomes Cardoso, J.; Marta Almeida, S.; Pio, C.; Andreae, M. O.; Conrad, R.; Pöschl, U.; Després, V. R.

    2014-05-01

    Archaea are widespread and abundant in many terrestrial and aquatic environments, accounting for up to ∼10% of the prokaryotes. Compared to Bacteria and other microorganisms, however, very little is known about the abundance, diversity, and dispersal of Archaea in the atmosphere. By DNA analysis targeting the 16S rRNA and amoA genes in samples of air particulate matter collected over one year at a continental sampling site in Germany, we obtained first insights into the seasonal dynamics of airborne Archaea. The detected Archaea were identified as Thaumarchaeota or Euryarchaeota, with soil Thaumarchaeota (group I.1b) being present in all samples. The normalized species richness of Thaumarchaeota correlated positively with relative humidity and negatively with temperature. This together with an increase of bare agricultural soil surfaces may explain the diversity peaks observed in fall and winter. The detected Euryarchaeota were mainly methanogens with a low relative frequency of occurrence. A slight increase in their frequency during spring may be linked to fertilization processes in the surrounding agricultural fields. Comparison with samples from the Cape Verde islands and from other coastal and continental sites indicates that the proportions of Euryarchaeota are enhanced in coastal air, which is consistent with their suggested abundance in marine surface waters. We conclude that air transport may play an important role for the dispersal of Archaea, including ammonia-oxidizing Thaumarchaeota and methanogens. Also, anthropogenic activities might influence the atmospheric abundance and diversity of Archaea.

  17. Hormonal dynamics contributes to divergence in seasonal stomatal behaviour in a monsoonal plant community.

    PubMed

    McAdam, Scott A M; Brodribb, Timothy J

    2015-03-01

    The plant hormone abscisic acid (ABA) is a primary regulator of plant transpiration, but its influence in determining seasonal stomatal behaviour in natural plant communities is poorly understood. We examined distantly related vascular plants growing together in a seasonally dry, monsoonal environment to determine whether ABA dynamics contributed to contrasting water use patterns in this natural setting. Regular sampling of angiosperm, cycad, conifer and fern species revealed characteristic seasonal patterns in ABA production, but these were highly distinct among species. Although no general relationship was observed between ABA levels, plant hydration or stomatal conductance among species, the seasonal dynamics in stomatal behaviour within species were predictable functions of either ABA or leaf water potential. Strong divergence in the seasonal role of ABA among species suggests that modification in ABA-stomatal interactions represents an important evolutionary pathway for adaptation in plant water use. PMID:24995884

  18. Modeling seasonal interactions in the population dynamics of migratory birds

    USGS Publications Warehouse

    Runge, M.C.; Marra, P.P.

    2005-01-01

    Understanding the population dynamics of migratory birds requires understanding the relevant biological events that occur during breeding, migratory, and overwintering periods. The few available population models for passerine birds focus on breeding-season events, disregard or oversimplify events during nonbreeding periods, and ignore interactions that occur between periods of the annual cycle. Identifying and explicitly incorporating seasonal interactions into population models for migratory birds could provide important insights about when population limitation actually occurs in the annual cycle. We present a population model for the annual cycle of a migratory bird, based on the American Redstart (Setophaga ruticilla) but more generally applicable, that examines the importance of seasonal interactions by incorporating: (1) density dependence during the breeding and winter seasons, (2) a carry-over effect of winter habitat on breeding-season productivity, and (3) the effects of behavioral dominance on seasonal and habitat specific demographic rates. First, we show that habitat availability on both the wintering and breeding grounds can strongly affect equilibrium population size and sex ratio. Second, sex ratio dynamics, as mediated by behavioral dominance, can affect all other aspects of population dynamics. Third, carry-over effects can be strong, especially when winter events are limiting. These results suggest that understanding the population dynamics of migratory birds may require more consideration of the seasonal interactions induced by carry-over effects and density dependence in multiple seasons. This model provides a framework in which to explore more fully these seasonal dynamics and a context for estimation of life history parameters.

  19. Seasonal hyporheic temperature dynamics over riffle bedforms

    NASA Astrophysics Data System (ADS)

    Hannah, D. M.; Malcolm, I. A.; Bradley, C.

    2009-04-01

    There is growing interest in riverbed temperature due to the ecological and biogeochemical significance of the hyporheic zone, and its potential to moderate river temperature. Riffles exhibit complex thermal behaviour, hypothesised to be caused by local alteration of groundwater-surface water (GW-SW) interactions; but hitherto most research has been in upland/ gravel-bed/ hard rock catchments. Accordingly, this article aims: (1) to characterise spatio- temporal variability in hyporheic temperature over two riffles (R1 and R2) in a lowland river basin (Tern, Shropshire, UK) underlain by sandstone; and (2) to explain thermal dynamics by inferring hyporheic processes and the influence of GW-SW interactions. Hyporheic [riffle head, crest and tail at 0.1, 0.2 and 0.4 m], water column, spring water and air temperature were collected at 15 min resolution over 22 months and used to explore seasonal variations. Borehole water levels and temperature provide insight into groundwater variability over a hydrological year. Hyporheic temperature is cooler (warmer) than water column in summer (winter), with convergence in spring and autumn. Riffle heads and R2 crest yield small thermal gradients; and R1 tail larger vertical difference. R1 crest temperature is similar and attenuated (cf. water column) at all depths. R2 tail temperature differs markedly from surface water. Thus, hyporheic temperature varies temporally across and between riffles, reflecting: (1) hydroclimatological controls on river and groundwater temperature, and (2) hydrological, local morphological and sedimentary controls on surface water and groundwater flux. This research demonstrates the utility of depth-related riverbed temperature time-series in understanding hyporheic zone processes and groundwater-surface water interactions.

  20. Motility Contrast Imaging and Tissue Dynamics Spectroscopy

    NASA Astrophysics Data System (ADS)

    Nolte, David D.; An, Ran; Turek, John

    Motion is the defining physiological characteristic of living matter. If we are interested in how things function, then the way they move is most informative. Motion provides an endogenous and functional suite of biomarkers that are sensitive to subtle changes that occur under applied pharmacological doses or cellular stresses. This chapter reviews the application of biodynamic imaging to measure cellular dynamics in three-dimensional tissue culture for drug screening applications. Nanoscale and microscale motions are detected through statistical fluctuations in dynamic speckle across an ensemble of cells within each resolution voxel. Tissue dynamics spectroscopy generates drug-response spectrograms that serve as phenotypic fingerprints of drug action and can differentiate responses from heterogeneous regions of tumor tissue.

  1. Modelling Seasonal Carbon Dynamics on Fen Peatlands

    NASA Astrophysics Data System (ADS)

    Giebels, Michael; Beyer, Madlen; Augustin, Jürgen; Roppel, Mario; Juszczak, Radoszlav; Serba, Tomasz

    2010-05-01

    In Germany more than 99 % of fens have lost their carbon and nutrient sink function due to heavy drainage and agricultural land use especially during the last decades and thus resulted in compression and heavy peat loss (CHARMAN 2002; JOOSTEN & CLARKE 2002; SUCCOW & JOOSTEN 2001; AUGUSTIN et al. 1996; KUNTZE 1993). Therefore fen peatlands play an important part (4-5 %) in the national anthropogenic trace gas budget. But only a small part of drained and agricultural used fens in NE Germany can be restored. Knowledge of the influence of land use to trace gas exchange is important for mitigation of the climate impact of the anthropogenic peatland use. We study carbon exchanges between soil and atmosphere on several fen peatland use areas at different sites in NE-Germany. Our research covers peatlands of supposed strongly climate forcing land use (cornfield and intensive pasture) and of probably less forcing, alternative types (meadow and extensive pasture) as well as rewetted (formerly drained) areas and near-natural sites like a low-degraded fen and a wetted alder woodland. We measured trace gas fluxes with manual and automatic chambers in periodic routines since spring 2007. The used chamber technique bases on DROESLER (2005). In total we now do research at 22 sites situated in 5 different locations covering agricultural, varying states of rewetted and near-natural treatments. We present results of at least 2 years of measurements on our site of varying types of agricultural land use. There we found significant differences in the annual carbon balances depending on the genesis of the observed sites and the seasonal dynamics. Annual balances were constructed by applying single respiration and photosynthesis CO2 models for each measurement campaign. These models were based on LLOYD-TAYLOR (1994) and Michaelis-Menten-Kinetics respectively. Crosswise comparison of different site treatments combined with the seasonal environmental observations give good hints for the

  2. Contrasts in Sea Ice Deformation and Production in the Arctic Seasonal and Perennial Ice Zones

    NASA Technical Reports Server (NTRS)

    Kwok, K.

    2006-01-01

    Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the sea ice deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) ice zones. Ice production is of seasonal ice in openings during the winter. Three-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the midwinter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is seen in the SIZ north of coastal Alaska. Both ice deformation and production are higher in the SIZ: deformation-related ice production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m): this is connected to ice strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal ice growth in ice fractures accounts for approx.25-40% of the total ice production of the Arctic Ocean. Uncertainties in these estimates are discussed. By itself, this deformation-ice production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on ice production in the face of increasing seasonal and thinner/weaker ice coverage could be modified by local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and the upwelling of the pynocline associated with increased occurrence of large shear motion in sea ice. Divergence is shown to be negligibly correlated to cyclonic motion in summer and winter in both ice zones.

  3. Contrasts in Sea Ice Formation and Production in the Arctic Seasonal and Perennial Ice Zones

    NASA Technical Reports Server (NTRS)

    Kwok, R.

    2006-01-01

    Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the sea ice deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) ice zones. Ice production is of seasonal ice in openings during the winter. 3-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the mid-winter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is in the SIZ north of coastal Alaska. Both ice deformation and production are higher in the SIZ: deformation-related ice production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m) - this is connected to ice strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal ice growth in ice fractures accounts for approx.25-40% of the total ice production of the Arctic Ocean. By itself, this deformation-ice production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on ice production in the face of increasing seasonal and thinner/weaker ice coverage could be modified by: local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and, the upwelling of the pynocline associated with increased occurrence of large shear motion in sea ice.

  4. Number size distribution measurements of biological aerosols under contrasting environments and seasons from southern tropical India

    NASA Astrophysics Data System (ADS)

    Valsan, Aswathy; Cv, Biju; Krishna, Ravi; Huffman, Alex; Poschl, Ulrich; Gunthe, Sachin

    2016-04-01

    Biological aerosols constitute a wide range of dead and alive biological materials and structures that are suspended in the atmosphere. They play an important role in the atmospheric physical, chemical and biological processes and health of living being by spread of diseases among humans, plants, and, animals. The atmospheric abundance, sources, physical properties of PBAPs as compared to non-biological aerosols, however, is poorly characterized. Though omnipresent, their concentration and composition exhibit large spatial and temporal variations depending up on their sources, land-use, and local meteorology. The Indian tropical region, which constitutes approximately 18% of the world's total population exhibits vast geographical extend and experiences a distinctive meteorological phenomenon by means of Indian Summer Monsoon (IMS). Thus, the sources, properties and characteristics of biological aerosols are also expected to have significant variations over the Indian subcontinent depending upon the location and seasons. Here we present the number concentration and size distribution of Fluorescent Biological Aerosol Particles (FBAP) from two contrasting locations in Southern tropical India measured during contrasting seasons using Ultra Violet Aerodynamic Particle Sizer (UV-APS). Measurements were carried out at a pristine high altitude continental site, Munnar (10.09 N, 77.06 E; 1605 m asl) during two contrasting seasons, South-West Monsoon (June-August, 2014) and winter (Jan - Feb, 2015) and in Chennai, a coastal urban area, during July - November 2015. FBAP concentrations at both the locations showed large variability with higher concentrations occurring at Chennai. Apart from regional variations, the FBAP concentrations also exhibited variations over two different seasons under the same environmental condition. In Munnar the FBAP concentration increased by a factor of four from South-West Monsoon to winter season. The average size distribution of FBAP at both

  5. Carbon dynamics of contrasting agricultural practices

    NASA Astrophysics Data System (ADS)

    Ghee, Claire; Hallett, Paul; Neilson, Roy; Robinson, David; Paterson, Eric

    2013-04-01

    Application of organic amendments can improve soil quality and provide crop nutrients. To optimise these agricultural benefits from organic applications, the capacity of microbe-driven nutrient and carbon cycling must be understood and exploited. Consideration is therefore required of the complex interactions between the rhizosphere, microbial biomass and organic amendment. We hypothesise that the labile C present in root exudates of plants increases the mineralisation of organic matter in soil, constituting a mechanism to promote nutrient acquisition. This mechanism is known as the 'priming effect', but is poorly understood in the context of agricultural carbon and nutrient management. Field data from the Centre of Sustainable Cropping (CSC) research platform (Dundee, Scotland, UK) are utilised to build an understanding of soil C and N fluxes between contrasting agricultural practices. The field site uses a split-plot design to compare (i) compost amended soils with reduced tillage and chemical inputs and (ii) conventionally managed soils, reflective of current UK commercial arable practice. Significant differences (p= <0.001) were identified between compost amended and conventionally managed soils at field-scale with respect to soil microbial biomass (SMB), total organic carbon (TOC) and mineral nitrogen. Investigation into the priming effect within compost amended soils was subsequently undertaken under laboratory conditions. Stable isotope analysis and measurements of soil biotic parameters were used to quantify priming resulting from Spring Barley (Hordeum vulgare cv. Optic) cultivation for (i) unamended and (ii) municipal compost incorporated soils. Compost treatments comprised amendments of 25, 50 and 150 t/Ha and planted soils were compared with unplanted controls. Soil mesocosms were maintained under controlled environmental conditions within labelling chambers supplied continuously with 13C-depleted CO2. Throughout a 41-day incubation period, soil CO2

  6. [MRI with dynamic contrast enhancement in brain tumors].

    PubMed

    Panfilenko, A F; Iakovlev, S A; Pozdniakov, A V; Tiumin, L A; Shcherbuk, A Iu

    2013-01-01

    Magnetic resonance imaging (MRI) is the leading method of radiation diagnosis of brain tumors. In conditions of the artificial contrast enhancement there are more clearly differentiated the boundaries of the tumor node on the back of peritumorous edema and identified structural features of the tumor. The purpose of this study was to examine indicators of the dynamics of accumulation and removal of contrast agents by brain tumors in MRI technique with dynamic contrast and identify opportunities of this method in the differential diagnosis of various types of tumors. PMID:23814831

  7. Identifying seasonal patterns of phosphorus storm dynamics with dynamic time warping

    NASA Astrophysics Data System (ADS)

    Dupas, Rémi; Tavenard, Romain; Fovet, Ophélie; Gilliet, Nicolas; Grimaldi, Catherine; Gascuel-Odoux, Chantal

    2015-11-01

    Phosphorus (P) transfer during storm events represents a significant part of annual P loads in streams and contributes to eutrophication in downstream water bodies. To improve understanding of P storm dynamics, automated or semiautomated methods are needed to extract meaningful information from ever-growing water quality measurement data sets. In this paper, seasonal patterns of P storm dynamics are identified in two contrasting watersheds (arable and grassland) through Dynamic Time Warping (DTW) combined with k-means clustering. DTW was used to align discharge time series of different lengths and with differences in phase, which allowed robust application of a k-means clustering algorithm on rescaled P time series. In the arable watershed, the main storm pattern identified from autumn to winter displayed distinct export dynamics for particulate and dissolved P, which suggests independent transport mechanisms for both P forms. Conversely, the main storm pattern identified in spring displayed synchronized export of particulate and dissolved P. In the grassland watershed, the occurrence of synchronized export of dissolved and particulate P forms was not related to the season, but rather to the amplitude of storm events. Differences between the seasonal distributions of the patterns identified for the two watersheds were interpreted in terms of P sources and transport pathways. The DTW-based clustering algorithm used in this study proved useful for identifying common patterns in water quality time series and for isolating unusual events. It will open new possibilities for interpreting the high-frequency and multiparameter water quality time series that are currently acquired worldwide.

  8. Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin

    NASA Astrophysics Data System (ADS)

    Sobrinho, R. L.; Bernardes, M. C.; Abril, G.; Kim, J.-H.; Zell, C. I.; Mortillaro, J.-M.; Meziane, T.; Moreira-Turcq, P.; Sinninghe Damsté, J. S.

    2015-06-01

    In this study, we investigated the seasonal and spatial pattern of sedimentary organic matter (SOM) in five floodplain lakes of the central Amazon basin (Cabaliana, Janauaca, Canaçari, Miratuba, and Curuai) which have different morphologies, hydrodynamics and vegetation coverages. Surface sediments were collected in four hydrological seasons: low water (LW), rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010. We investigated commonly used bulk geochemical tracers such as the C : N ratio and the stable isotopic composition of organic carbon (δ13Corg). These results were compared with lignin-phenol parameters as an indicator of vascular plant detritus and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to trace the input of soil organic matter (OM) from land to the aquatic settings. We also applied the isoprenoid GDGT (iGDGT) crenarchaeol as an indicator of riverine suspended particulate organic matter (SPOM). Our data showed that during the RW and FW seasons, the surface sediments were enriched in lignin and brGDGTs in comparison to other seasons. Our study also indicated that floodplain lake sediments primarily consisted of allochthonous, C3 plant-derived OM. However, a downstream increase in C4 macrophyte derived OM contribution was observed along the gradient of increasing open waters, i.e. from upstream to downstream. Accordingly, we attribute temporal and spatial difference in SOM composition to the hydrological dynamics between the floodplain lakes and the surrounding flooded forests.

  9. Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin

    NASA Astrophysics Data System (ADS)

    Sobrinho, R. L.; Bernardes, M. C.; Abril, G.; Kim, J.-H.; Zell, C. I.; Mortillaro, J.-M.; Meziane, T.; Moreira-Turcq, P.; Sinninghe Damsté, J. S.

    2016-01-01

    In this study, we investigated the seasonal and spatial pattern of sedimentary organic matter (SOM) in five floodplain lakes of the central Amazon basin (Cabaliana, Janauaca, Canaçari, Mirituba and Curuai) which have different morphologies, hydrodynamics and vegetation coverages. Surface sediments were collected in four hydrological seasons: low water (LW), rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010. We investigated commonly used bulk geochemical tracers such as the C : N ratio and the stable isotopic composition of organic carbon (δ13Corg). These results were compared with lignin phenol parameters as an indicator of vascular plant detritus and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to trace the input of soil organic matter (OM) from land to the aquatic settings. We also applied the crenarchaeol as an indicator of aquatic (rivers and lakes) OM. Our data showed that during the RW and FW seasons, the surface sediments were enriched in lignin and brGDGTs in comparison to other seasons. Our study also indicated that floodplain lake sediments primarily consisted of allochthonous, C3 plant-derived OM. However, a downstream increase in C4 macrophyte-derived OM contribution was observed along the gradient of increasing open waters - i.e., from upstream to downstream. Accordingly, we attribute the temporal and spatial difference in SOM composition to the hydrological dynamics between the floodplain lakes and the surrounding flooded forests.

  10. Seasonally forced disease dynamics explored as switching between attractors

    NASA Astrophysics Data System (ADS)

    Keeling, Matt J.; Rohani, Pejman; Grenfell, Bryan T.

    2001-01-01

    Biological phenomena offer a rich diversity of problems that can be understood using mathematical techniques. Three key features common to many biological systems are temporal forcing, stochasticity and nonlinearity. Here, using simple disease models compared to data, we examine how these three factors interact to produce a range of complicated dynamics. The study of disease dynamics has been amongst the most theoretically developed areas of mathematical biology; simple models have been highly successful in explaining the dynamics of a wide variety of diseases. Models of childhood diseases incorporate seasonal variation in contact rates due to the increased mixing during school terms compared to school holidays. This ‘binary’ nature of the seasonal forcing results in dynamics that can be explained as switching between two nonlinear spiral sinks. Finally, we consider the stability of the attractors to understand the interaction between the deterministic dynamics and demographic and environmental stochasticity. Throughout attention is focused on the behaviour of measles, whooping cough and rubella.

  11. Tumor Characterization with Dynamic Contrast Enhanced Magnetic Resonance Imaging and Biodegradable Macromolecular Contrast Agents in Mice

    PubMed Central

    Wu, Xueming; Feng, Yi; Jeong, Eun-Kee; Emerson, Lyska; Lu, Zheng-Rong

    2009-01-01

    Purpose To investigate the efficacy of polydisulfide-based biodegradable macromolecular contrast agents of different degradability and molecular weight for tumor characterization based on angiogenesis using dynamic contrast enhanced MRI (DCE-MRI). Methods Biodegradable macromolecular MRI contrast agents, GDCC and GDCP, with molecular weight of 20 and 70 KDa were evaluated for tumor characterization. The DCE-MRI studies were performed in nude mice bearing MDA PCa 2b and PC-3 human prostate tumor xenografts. Tumor angiogenic kinetic parameters, endothelium transfer coefficient (Ktrans) and fractional tumor plasma volume (fPV), were calculated from the DCE-MRI data using a two-compartment model. Results There was no significant difference in the fPV values between two tumor models estimated with the same agent except for GDCC-70. The Ktrans values in both tumor models decreased with increasing molecular weight of the agents. GDCC-70 showed a higher Ktrans values than GDCP-70 due to high degradability of the former in both tumor models (p < 0.05). The Ktrans values of MDA PCa 2b tumors were significantly higher than those of PC-3 tumors estimated by Gd(DTPA-BMA), GDCC-20, GDCC-70, GDCP-70, and albumin-(Gd-DTPA) (p < 0.05). Conclusions The polydisulfide based biodegradable macromolecular MRI contrast agents are promising in tumor characterization with dynamic contrast enhanced MRI. PMID:19597972

  12. Optimal contrast enhancement liquid for dynamic MRI of swallowing.

    PubMed

    Ohkubo, M; Higaki, T; Nishikawa, K; Otonari-Yamamoto, M; Sugiyama, T; Ishida, R; Wakoh, M

    2016-09-01

    Several dynamic magnetic resonance imaging (MRI) techniques to observe swallowing and their parameters have been reported. Although these studies used several contrast enhancement liquids, no studies were conducted to investigate the most suitable liquids. The purpose of this study was to identify the optimal contrast enhancement liquid for dynamic MRI of swallowing. MRI was performed using a new sequence consisting of true fast imaging with steady-state precession, generalised auto-calibrating partially parallel acquisition and a keyhole imaging technique. Seven liquids were studied, including pure distilled water, distilled water with thickener at 10, 20 and 30 mg mL(-1) concentrations and oral MRI contrast medium at 1, 2 or 3 mg mL(-1) . Distilled water showed the highest signal intensity. There were statistically significant differences among the following contrast media: distilled water with thickener at 20 mg mL(-1) and the oral MRI contrast medium at 2 mg mL(-1) and 1 mg mL(-1) . It can be concluded that the optimal liquid for dynamic MRI of swallowing is a water-based substance that allows variations in viscosity. PMID:27328011

  13. Seasonality Impact on the Transmission Dynamics of Tuberculosis

    PubMed Central

    2016-01-01

    The statistical data of monthly pulmonary tuberculosis (TB) incidence cases from January 2004 to December 2012 show the seasonality fluctuations in Shaanxi of China. A seasonality TB epidemic model with periodic varying contact rate, reactivation rate, and disease-induced death rate is proposed to explore the impact of seasonality on the transmission dynamics of TB. Simulations show that the basic reproduction number of time-averaged autonomous systems may underestimate or overestimate infection risks in some cases, which may be up to the value of period. The basic reproduction number of the seasonality model is appropriately given, which determines the extinction and uniform persistence of TB disease. If it is less than one, then the disease-free equilibrium is globally asymptotically stable; if it is greater than one, the system at least has a positive periodic solution and the disease will persist. Moreover, numerical simulations demonstrate these theorem results. PMID:27042199

  14. Nonlinear dynamic phase contrast microscopy for microfluidic and microbiological applications

    NASA Astrophysics Data System (ADS)

    Denz, C.; Holtmann, F.; Woerdemann, M.; Oevermann, M.

    2008-08-01

    In live sciences, the observation and analysis of moving living cells, molecular motors or motion of micro- and nano-objects is a current field of research. At the same time, microfluidic innovations are needed for biological and medical applications on a micro- and nano-scale. Conventional microscopy techniques are reaching considerable limits with respect to these issues. A promising approach for this challenge is nonlinear dynamic phase contrast microscopy. It is an alternative full field approach that allows to detect motion as well as phase changes of living unstained micro-objects in real-time, thereby being marker free, without contact and non destructive, i.e. fully biocompatible. The generality of this system allows it to be combined with several other microscope techniques such as conventional bright field or fluorescence microscopy. In this article we will present the dynamic phase contrast technique and its applications in analysis of micro organismic dynamics, micro flow velocimetry and micro-mixing analysis.

  15. Hydrology and seasonality determine distinct DOC export mechanisms in contrasting upland catchments in Scotland

    NASA Astrophysics Data System (ADS)

    Dawson, J. J. C.; Soulsby, C.; Tetzlaff, D.; Hrachowitz, M.; Dunn, S. M.; Malcolm, I. A.

    2009-04-01

    How climate variability influences soil processes, production and export of DOC are important in understanding hydrologically mediated carbon losses from soils and its affect on stream and river water quality. This necessitates understanding both biogeochemical and hydrological factors that control the quantity and timing of carbon availability for export from soils to the drainage network. Long-term records of DOC concentrations at upland catchments with contrasting climatic characteristics in Scotland were investigated for intra-annual relationships to evaluate potential long-term seasonal as well as inter-annual patterns. Catchments in West-Central Scotland (>2000 mm/yr rainfall) with high rainfall-runoff ratios, short transit times and well-connected responsive soils show a distinct annual periodicity in DOC concentrations throughout the long-term datasets. Increased DOC concentrations occurred between June and November with correspondingly lower DOC concentrations from December to May. This appears unrelated to discharge, and is dependent mainly on higher temperatures driving biological activity, increasing decomposition of available organic matter for rapid export. Relatively drier catchments (ca. 1000 mm/yr) have lower rainfall-runoff ratios, longer transit times and annual drying-wetting regimes linked to changing connectivity of soils. These are characterised by seasonal DOC concentration-discharge relationships with an autumnal flush of DOC. Temperature influences the availability of organic matter for eventual DOC transport producing a high DOC concentration-discharge relationship in summer/autumn and low DOC concentration-discharge relationship in winter/spring. These two distinct modes of seasonal DOC transport have important implications for understanding changes in DOC concentrations and export brought about by climate changes (temperature, rainfall and deposition patterns) and modeling of aquatic carbon losses from soil-types under different

  16. Land surface phenologies viewed in the middle infrared: seasonal contrasts between vegetation, soils, and impervious surfaces

    NASA Astrophysics Data System (ADS)

    Henebry, G. M.; Krehbiel, C.; Kovalskyy, V.

    2012-12-01

    The middle infrared (MIR) region of the electromagnetic spectrum spans 3-5 microns. It is the mixing zone between reflected sunlight and emitted earthlight in roughly equal proportions. This region has received very little attention in terrestrial remote sensing. Yet the MIR merits exploration of how it could be used for monitoring land surface phenologies (LSP) and seasonalities due to five characteristics. First, green vegetation is MIR-dark, reflecting just 2-5% of the incident radiation. Second, soils are MIR-bright, reflecting up to one-third of the incident radiation. Third, impervious surfaces, such as concretes, asphalts, and other building and paving materials are also MIR-bright. Fourth, the resulting seasonal contrast in MIR between vegetated and non-vegetated surfaces lets urbanized areas emerge from the vegetated landscape. Fifth, MIR wavelengths penetrate anthropogenic haze and smoke because the particle radii are smaller. Here we use MODIS (MYD02) image time series to illustrate the temporal progressions of MIR at various wavelengths and how they compare to and diverge from the more familiar NDVI and derived LSP metrics.IR portrait of the USA east of W98: maximum value composite of Aqua MODIS MIR band 23 during DOY 219-233 of 2010.

  17. The hydrological behaviour of a forested catchment during two contrasting summer monsoon seasons

    NASA Astrophysics Data System (ADS)

    Payeur-Poirier, Jean-Lionel; Hopp, Luisa; Peiffer, Stefan

    2015-04-01

    The climate of South Korea is strongly influenced by the East Asian summer monsoon. It is hypothesized that the high precipitation regime of the summer monsoon causes significant changes in the hydrological behaviour of forested catchments, namely in water quantity, quality and flow paths. We conducted high frequency hydrometric, isotopic, hydrochemical and meteorological measurements in a forested catchment before, during and after two contrasting summer monsoon seasons. The catchment is located within the Lake Soyang watershed, where recent trends of increasing eutrophication, sediment load and organic carbon load have been observed. We studied the temporal variability of catchment runoff in relation with the spatial and temporal variability of water flow paths. The 2013 and 2014 summer monsoon seasons were, respectively, the longest and shortest that occurred in this region since 1973 and accounted for 206% and 32% of the average precipitation for the summer monsoon since 1973. For the period from June through August, the precipitation of 2014 was the lowest on record since 1973. Catchment runoff for the summer monsoon totalled 559 mm and 12 mm for 2013 and 2014, respectively. The Q50 of the flow duration curve for 2014 was more than four times lower than that for 2013. A total of 18 storm events were monitored, ranging between 13 mm and 126 mm in precipitation. A principal component analysis (PCA) and an end-member mixing analysis (EMMA) were performed in order to quantify the contribution of different end-members to catchment runoff and highlight the differences between both years. The combination of the hydrometric, isotopic and hydrochemical approaches allowed us to test our hypothesis and to shed light on the hydrological behaviour of the catchment under contrasting environmental conditions. The findings of this study could be useful for the estimation of the water balance of the Lake Soyang watershed as well as for the management of Lake Soyang.

  18. Model averaging methods to merge operational statistical and dynamic seasonal streamflow forecasts in Australia

    NASA Astrophysics Data System (ADS)

    Schepen, Andrew; Wang, Q. J.

    2015-03-01

    The Australian Bureau of Meteorology produces statistical and dynamic seasonal streamflow forecasts. The statistical and dynamic forecasts are similarly reliable in ensemble spread; however, skill varies by catchment and season. Therefore, it may be possible to optimize forecasting skill by weighting and merging statistical and dynamic forecasts. Two model averaging methods are evaluated for merging forecasts for 12 locations. The first method, Bayesian model averaging (BMA), applies averaging to forecast probability densities (and thus cumulative probabilities) for a given forecast variable value. The second method, quantile model averaging (QMA), applies averaging to forecast variable values (quantiles) for a given cumulative probability (quantile fraction). BMA and QMA are found to perform similarly in terms of overall skill scores and reliability in ensemble spread. Both methods improve forecast skill across catchments and seasons. However, when both the statistical and dynamical forecasting approaches are skillful but produce, on special occasions, very different event forecasts, the BMA merged forecasts for these events can have unusually wide and bimodal distributions. In contrast, the distributions of the QMA merged forecasts for these events are narrower, unimodal and generally more smoothly shaped, and are potentially more easily communicated to and interpreted by the forecast users. Such special occasions are found to be rare. However, every forecast counts in an operational service, and therefore the occasional contrast in merged forecasts between the two methods may be more significant than the indifference shown by the overall skill and reliability performance.

  19. Skill improvement of dynamical seasonal Arctic sea ice forecasts

    NASA Astrophysics Data System (ADS)

    Krikken, Folmer; Schmeits, Maurice; Vlot, Willem; Guemas, Virginie; Hazeleger, Wilco

    2016-05-01

    We explore the error and improve the skill of the outcome from dynamical seasonal Arctic sea ice reforecasts using different bias correction and ensemble calibration methods. These reforecasts consist of a five-member ensemble from 1979 to 2012 using the general circulation model EC-Earth. The raw model reforecasts show large biases in Arctic sea ice area, mainly due to a differently simulated seasonal cycle and long term trend compared to observations. This translates very quickly (1-3 months) into large biases. We find that (heteroscedastic) extended logistic regressions are viable ensemble calibration methods, as the forecast skill is improved compared to standard bias correction methods. Analysis of regional skill of Arctic sea ice shows that the Northeast Passage and the Kara and Barents Sea are most predictable. These results show the importance of reducing model error and the potential for ensemble calibration in improving skill of seasonal forecasts of Arctic sea ice.

  20. Dynamic Studies of Lung Fluid Clearance with Phase Contrast Imaging

    NASA Astrophysics Data System (ADS)

    Kitchen, Marcus J.; Lewis, Rob A.; Hooper, Stuart B.; Wallace, Megan J.; Siu, Karen K. W.; Williams, Ivan; Irvine, Sarah C.; Morgan, Michael J.; Paganin, David M.; Pavlov, Konstantin; Yagi, Naoto; Uesugi, Kentaro

    2007-01-01

    Clearance of liquid from the airways at birth is a poorly understood process, partly due to the difficulties of observing and measuring the distribution of air within the lung. Imaging dynamic processes within the lung in vivo with high contrast and spatial resolution is therefore a major challenge. However, phase contrast X-ray imaging is able to exploit inhaled air as a contrast agent, rendering the lungs of small animals visible due to the large changes in the refractive index at air/tissue interfaces. In concert with the high spatial resolution afforded by X-ray imaging systems (<100 μm), propagation-based phase contrast imaging is ideal for studying lung development. To this end we have utilized intense, monochromatic synchrotron radiation, together with a fast readout CCD camera, to study fluid clearance from the lungs of rabbit pups at birth. Local rates of fluid clearance have been measured from the dynamic sequences using a single image phase retrieval algorithm.

  1. Dynamic Studies of Lung Fluid Clearance with Phase Contrast Imaging

    SciTech Connect

    Kitchen, Marcus J.; Williams, Ivan; Irvine, Sarah C.; Morgan, Michael J.; Paganin, David M.; Lewis, Rob A.; Pavlov, Konstantin; Hooper, Stuart B.; Wallace, Megan J.; Siu, Karen K. W.; Yagi, Naoto; Uesugi, Kentaro

    2007-01-19

    Clearance of liquid from the airways at birth is a poorly understood process, partly due to the difficulties of observing and measuring the distribution of air within the lung. Imaging dynamic processes within the lung in vivo with high contrast and spatial resolution is therefore a major challenge. However, phase contrast X-ray imaging is able to exploit inhaled air as a contrast agent, rendering the lungs of small animals visible due to the large changes in the refractive index at air/tissue interfaces. In concert with the high spatial resolution afforded by X-ray imaging systems (<100 {mu}m), propagation-based phase contrast imaging is ideal for studying lung development. To this end we have utilized intense, monochromatic synchrotron radiation, together with a fast readout CCD camera, to study fluid clearance from the lungs of rabbit pups at birth. Local rates of fluid clearance have been measured from the dynamic sequences using a single image phase retrieval algorithm.

  2. Seasonal soil moisture patterns in contrasting habitats in the Willamette Valley, Oregon

    EPA Science Inventory

    Changing seasonal soil moisture regimes caused by global warming may alter plant community composition in sensitive habitats such as wetlands and oak savannas. To evaluate such changes, an understanding of typical seasonal soil moisture regimes is necessary. The primary objective...

  3. Seasonal plankton dynamics along a cross-shelf gradient

    PubMed Central

    Stenseth, Nils Chr; Llope, Marcos; Anadón, Ricardo; Ciannelli, Lorenzo; Chan, Kung-Sik; Hjermann, Dag Ø; Bagøien, Espen; Ottersen, Geir

    2006-01-01

    Much interest has recently been devoted to reconstructing the dynamic structure of ecological systems on the basis of time-series data. Using 10 years of monthly data on phyto- and zooplankton abundance from the Bay of Biscay (coastal to shelf-break sites), we demonstrate that the interaction between these two plankton components is approximately linear, whereas the effects of environmental factors (nutrients, temperature, upwelling and photoperiod) on these two plankton population growth rates are nonlinear. With the inclusion of the environmental factors, the main observed seasonal and inter-annual dynamic patterns within the studied plankton assemblage also indicate the prevalence of bottom-up regulatory control. PMID:17015313

  4. Seasonal nutrient dynamics in three stream types in SE Alaska

    NASA Astrophysics Data System (ADS)

    Edwards, R. T.; Norberg, E.; Fellman, J.

    2005-05-01

    The Tongass National Forest encompasses over 5,000 salmon streams draining a wide variety of lithologies, microclimates and landforms. To predict management outcomes and responses to climate change, managers need an understanding of how ecosystem processes in streams vary over large spatial scales and with major controlling landscape variables. We measured forms of N, P and DOM in three common stream types: glacial, brownwater and clearwater near Juneau, AK. Glacial and clearwater streams showed strong seasonal trends in nitrate and total nitrogen related to snow melt and summer uptake, whereas brownwater streams were variable but not highly seasonal. Total nitrogen concentrations were dominated by inorganic forms in clearwater streams, organic forms in brownwater streams and varied seasonally between organic and inorganic forms in glacial streams. DOC concentrations were low in clearwater and glacial streams and varied little seasonally. Brownwater stream DOC values were high, variable and varied with discharge, with an increasing trend during summer. The Tongass NF recently classified SE Alaska forest lands into ecological subsections based on large-scale geophysical factors such as lithology and surficial geology. Partitioning Tongass streams using this approach may lead to better management predictions by more accurately incorporating natural variation in baseline stream dynamics.

  5. Evaluation of microbubble contrast agents for dynamic imaging with x-ray phase contrast

    PubMed Central

    Millard, T. P.; Endrizzi, M.; Everdell, N.; Rigon, L.; Arfelli, F.; Menk, R. H.; Stride, E.; Olivo, A.

    2015-01-01

    X-rays are commonly used as a means to image the inside of objects opaque to visible light, as their short wavelength allows penetration through matter and the formation of high spatial resolution images. This physical effect has found particular importance in medicine where x-ray based imaging is routinely used as a diagnostic tool. Increasingly, however, imaging modalities that provide functional as well as morphological information are required. In this study the potential to use x-ray phase based imaging as a functional modality through the use of microbubbles that can be targeted to specific biological processes is explored. We show that the concentration of a microbubble suspension can be monitored quantitatively whilst in flow using x-ray phase contrast imaging. This could provide the basis for a dynamic imaging technique that combines the tissue penetration, spatial resolution, and high contrast of x-ray phase based imaging with the functional information offered by targeted imaging modalities. PMID:26219661

  6. [Population dynamics of thrushes and seasonal resource partition].

    PubMed

    Burskiĭ, O V; Demidova, E Iu; Morkovin, A A

    2014-01-01

    We studied seasonal population dynamics in birds using four thrush species from the Yenisei middle taiga region as an example. Long-term data on bird route censuses, capture-mark-recapture, and nest observa- tions were incorporated in the analysis. Particularly, methodological problems that complicate a direct comparison between assessed numbers at different phases of the annual cycle are considered. The integrated analysis of the results allowed comparing changes in numbers, energy expenditure, age structure, migrating status, and density distribution of selected populations during the snowless period and relating them to seasonal changes in food resource abundance. Thrush population numbers within the breeding range, and their energy consumption in the Yenisei middle taiga proportionately reflect the seasonal change in abundance of food resources. The compliance between resource intake and carrying capacity of the environment is attained by: timing of arrival and departure regarding to the species' range of tolerance; change in numbers as a result of reproduction and mortality; change in numbers due to habitat changes and long-distance movements; increasing energetic expenditures during reproduction and molt; timing, intensity and replication of nesting attempts; timing of molt and proportion of molting individuals in a population; individual variations of the annual cycle. Reproductive growth of local bird populations is not fast enough to catch up with seasonal growth of ecosystems productivity. Superabundance of invertebrates at the peak of the season offers a temporal niche which, on the one hand, is suitable for species capable of diet switching, while, on the other hand, may be used by specialized consumers, namely tropical migrants for whom, at high resource level, a shortened breeding period suffices. PMID:25786310

  7. Image fusion for dynamic contrast enhanced magnetic resonance imaging

    PubMed Central

    Twellmann, Thorsten; Saalbach, Axel; Gerstung, Olaf; Leach, Martin O; Nattkemper, Tim W

    2004-01-01

    Background Multivariate imaging techniques such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) have been shown to provide valuable information for medical diagnosis. Even though these techniques provide new information, integrating and evaluating the much wider range of information is a challenging task for the human observer. This task may be assisted with the use of image fusion algorithms. Methods In this paper, image fusion based on Kernel Principal Component Analysis (KPCA) is proposed for the first time. It is demonstrated that a priori knowledge about the data domain can be easily incorporated into the parametrisation of the KPCA, leading to task-oriented visualisations of the multivariate data. The results of the fusion process are compared with those of the well-known and established standard linear Principal Component Analysis (PCA) by means of temporal sequences of 3D MRI volumes from six patients who took part in a breast cancer screening study. Results The PCA and KPCA algorithms are able to integrate information from a sequence of MRI volumes into informative gray value or colour images. By incorporating a priori knowledge, the fusion process can be automated and optimised in order to visualise suspicious lesions with high contrast to normal tissue. Conclusion Our machine learning based image fusion approach maps the full signal space of a temporal DCE-MRI sequence to a single meaningful visualisation with good tissue/lesion contrast and thus supports the radiologist during manual image evaluation. PMID:15494072

  8. Seasonality directs contrasting food collection behavior and nutrient regulation strategies of ants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Long-lived animals, including social insects, often display seasonal shifts in foraging behavior. Foraging is ultimately a nutrient consumption exercise, but the effect of seasonality per se on changes in foraging behavior, particularly as it relates to nutrient regulation, is poorly understood. H...

  9. Seasonal Phytoplankton Dynamics in the Eastern Tropical Atlantic

    NASA Technical Reports Server (NTRS)

    Monger, Bruce; McClain, Charles; Murtugudde, Ragu

    1997-01-01

    The coastal zone color scanner (CZCS) that operated aboard the Nimbus 7 satellite provided extensive coverage of phytoplankton pigment concentrations in the surface waters of the eastern tropical Atlantic (ETA) from March 1979 to February 1980 and coincided with four major research cruises to this region. Total primary production within the ETA (5 deg N-10 deg S, 25 deg W-10 deg E) was determined from CZCS pigment estimates and an empirical algorithm derived from concurrent in situ data taken along 4 deg W that relates near-surface chlorophyll concentration and integrated primary production. We estimated an average annual production for the ETA of 2.3 Gt C/yr with an associated 3.5-fold seasonal variation in the magnitude of this production. We describe the principal physical mechanisms controlling seasonal phytoplankton dynamics within the ETA and propose that in addition to seasonal change in the thermocline depth, one must also consider changes in the depth of the equatorial under current. An extensive validation effort indicates that the standard CZCS global products are a conservative estimate of pigment concentrations in ETA surface waters. Significant underestimates by the CZCS global products were observed in June and July which we attributed, in part, to aerosol correction errors and, more importantly, to errors caused by a significant reduction in the concentration of near-surface dissolved organic matter that resulted from strong equatorial upwelling.

  10. Diversity and seasonal dynamics of bacterial community in indoor environment

    PubMed Central

    Rintala, Helena; Pitkäranta, Miia; Toivola, Mika; Paulin, Lars; Nevalainen, Aino

    2008-01-01

    Background We spend most of our lives in indoor environments and are exposed to microbes present in these environments. Hence, knowledge about this exposure is important for understanding how it impacts on human health. However, the bacterial flora in indoor environments has been only fragmentarily explored and mostly using culture methods. The application of molecular methods previously utilised in other environments has resulted in a substantial increase in our awareness of microbial diversity. Results The composition and dynamics of indoor dust bacterial flora were investigated in two buildings over a period of one year. Four samples were taken in each building, corresponding to the four seasons, and 16S rDNA libraries were constructed. A total of 893 clones were analysed and 283 distinct operational taxonomic units (OTUs) detected among them using 97% sequence similarity as the criterion. All libraries were dominated by Gram-positive sequences, with the most abundant phylum being Firmicutes. Four OTUs having high similarity to Corynebacterium-, Propionibacterium-, Streptococcus- and Staphylococcus- sequences were present in all samples. The most abundant of the Gram-negative OTUs were members of the family Sphingomonadaceae, followed by Oxalobacteraceae, Comamonadaceae, Neisseriaceae and Rhizobiaceae. The relative abundance of alpha- and betaproteobacteria increased slightly towards summer at the expense of firmicutes. The proportion of firmicutes and gammaproteobacteria of the total diversity was highest in winter and that of actinobacteria, alpha- and betaproteobacteria in spring or summer, whereas the diversity of bacteroidetes peaked in fall. A statistical comparison of the libraries revealed that the bacterial flora of the two buildings differed during all seasons except spring, but differences between seasons within one building were not that clear, indicating that differences between the buildings were greater than the differences between seasons

  11. Seasonal statistical-dynamical forecasts of droughts over Western Iberia

    NASA Astrophysics Data System (ADS)

    Ribeiro, Andreia; Pires, Carlos

    2015-04-01

    The Standard Precipitation Index (SPI) has been used here as a drought predictand in order to assess seasonal drought predictability over the western Iberia. Hybrid (statistical-dynamical) long-range forecasts of the drought index SPI are estimated with lead-times up to 6 months, over the period of 1987-2008. Operational forecasts of geopotential height and total precipitation from the UK Met Office operational forecasting system are considered. Past ERA-Interim reanalysis data, prior to the forecast launching, are used for the purpose of build a set of SPI predictors, integrating recent past observations. Then, a two-step hybridization procedure is adopted: in the first-step both forecasted and observational large-scale fields are subjected to a Principal Component Analysis (PCA) and forecasted PCs and persistent PCs are used as predictors. The second hybridization step consists on a statistical/hybrid downscaling to the regional scale based on regression techniques, after the selection of the statistically significant predictors. The large-scale filter predictors from past observations and operational forecasts are used to downscale SPI and the advantage of combining predictors with both dynamical and statistical background in the prediction of drought conditions at different lags is evaluated. The SPI estimations and the added value of combining dynamical and statistical methods are evaluated in cross-validation mode. Results show that winter is the most predictable season, and most of the predictive power is on the large-scale fields and at the shorter lead-times. The hybridization improves forecasting drought skill in comparison to purely dynamical forecasts, since the persistence of large-scale patterns displays the main role in the long-range predictability of precipitation. These findings provide clues about the predictability of the SPI, particularly in Portugal, and may contribute to the predictability of crops yields and to some guidance on users (such

  12. Role of seasonality on predator-prey-subsidy population dynamics.

    PubMed

    Levy, Dorian; Harrington, Heather A; Van Gorder, Robert A

    2016-05-01

    The role of seasonality on predator-prey interactions in the presence of a resource subsidy is examined using a system of non-autonomous ordinary differential equations (ODEs). The problem is motivated by the Arctic, inhabited by the ecological system of arctic foxes (predator), lemmings (prey), and seal carrion (subsidy). We construct two nonlinear, nonautonomous systems of ODEs named the Primary Model, and the n-Patch Model. The Primary Model considers spatial factors implicitly, and the n-Patch Model considers space explicitly as a "Stepping Stone" system. We establish the boundedness of the dynamics, as well as the necessity of sufficiently nutritional food for the survival of the predator. We investigate the importance of including the resource subsidy explicitly in the model, and the importance of accounting for predator mortality during migration. We find a variety of non-equilibrium dynamics for both systems, obtaining both limit cycles and chaotic oscillations. We were then able to discuss relevant implications for biologically interesting predator-prey systems including subsidy under seasonal effects. Notably, we can observe the extinction or persistence of a species when the corresponding autonomous system might predict the opposite. PMID:26916622

  13. The response of ecosystem carbon fluxes to LAI and environmental drivers in a maize crop grown in two contrasting seasons

    NASA Astrophysics Data System (ADS)

    Vitale, Luca; Di Tommasi, Paul; D'Urso, Guido; Magliulo, Vincenzo

    2016-03-01

    The eddy correlation technique was used to investigate the influence of biophysical variables and crop phenological phases on the behaviour of ecosystem carbon fluxes of a maize crop, in two contrasting growing seasons. In 2009, the reduced water supply during the early growing stage limited leaf area expansion, thus negatively affecting canopy photosynthesis. The variability of gross primary production (GPP) and ecosystem respiration ( R eco) was mainly explained by seasonal variation of leaf area index (LAI). The seasonal variation of R eco was positively influenced by soil temperatures ( T soil) in 2008 but not in 2009. In 2008, a contribution of both autotrophic and heterotrophic components to total R eco could be hypothesized, while during 2009, autotrophic respiration is supposed to be the most important component. Crop phenological phases affected the response of ecosystem fluxes to biophysical drivers.

  14. Seasonal contrasts in the response of coffee ants to agroforestry shade-tree management.

    PubMed

    Teodoro, A V; Sousa-Souto, L; Klein, A-M; Tscharntke, T

    2010-12-01

    In many tropical landscapes, agroforestry systems are the last forested ecosystems, providing shade, having higher humidity, mitigating potential droughts, and possessing more species than any other crop system. Here, we tested the hypothesis that higher levels of shade and associated humidity in agroforestry enhance coffee ant richness more during the dry than rainy season, comparing ant richness in 22 plots of three coffee agroforestry types in coastal Ecuador: simple-shade agroforests (intensively managed with low tree species diversity), complex-shade agroforests (extensively managed with intermediate tree species diversity) and abandoned coffee agroforests (abandoned for 10-15 yr and resembling secondary forests). Seasonality affected responses of ant richness but not composition to agroforestry management, in that most species were observed in abandoned coffee agroforests in the dry season. In the rainy season, however, most species were found in simple-shade agroforests, and complex agroforestry being intermediate. Foraging coffee ants species composition did not change differently according to agroforestry type and season. Results show that shade appears to be most important in the dry seasons, while a mosaic of different land-use types may provide adequate environmental conditions to ant species, maximizing landscape-wide richness throughout the year. PMID:22182538

  15. Contrasting "Fish" Diversity Dynamics between Marine and Freshwater Environments.

    PubMed

    Guinot, Guillaume; Cavin, Lionel

    2015-08-31

    Two theoretical models have been proposed to describe long-term dynamics of diversification: the equilibrium model considers the Earth as a closed system with a fixed maximum biological carrying capacity, whereas the expansion model hypothesizes a continuously increasing diversification of life. Based on the analysis of the fossil record of all organisms, Benton suggested contrasting models of diversity dynamics between marine and continental realms. Diversity in marine environments is characterized by phases of rapid diversification followed by plateaux, i.e., an equilibrium model directly derived from insular biogeography theories, whereas diversity in continental environments is characterized by exponential growth. Previous studies that aimed at testing these models with empirical data were based on datasets extracted directly from the reading of the vagaries of the raw fossil record, without correcting for common fossil record biases (preservation and sampling). Although correction of datasets for the incompleteness of the fossil record is now commonly performed for addressing long-term biodiversity variations, only a few attempts have been made to produce diversity curves corrected by phylogenetic data from extant and extinct taxa. Here we show that phylogenetically corrected diversity curves for "fish" (actinopterygians and elasmobranchs) during the last 200 million years fit an equilibrium model in the marine realm and an expansion model in the freshwater realm. These findings demonstrate that the rate of diversification has decreased for marine fish over the Cenozoic but is in sharp expansion for freshwater fish. PMID:26279235

  16. Seasonal dynamics of insecticide resistance, multiple resistance, and morphometric variation in field populations of Culex pipiens.

    PubMed

    Taskin, Belgin Gocmen; Dogaroglu, Taylan; Kilic, Sercan; Dogac, Ersin; Taskin, Vatan

    2016-05-01

    Resistance to insecticides that impairs nervous transmission has been widely investigated in mosquito populations as insecticides are crucial to effective insect control. The development of insecticide resistance is also of special interest to evolutionary biologists since it represents the opportunity to observe the genetic consequences of a well-characterized alteration in the environment. Although the frequencies of resistance alleles in Culex pipiens populations against different groups of insecticides have been reported, no detailed information is available on the relative change in these allele frequencies over time. In this study, we collected mosquitoes of the Cx. pipiens complex from six locations in three seasons in the Aegean region of Turkey and examined the i) seasonal variations in resistance to four different chemical classes of insecticides, ii) seasonal fluctuations in frequencies of resistance-associated target-site mutations of the three genes (ace-1, kdr, and Rdl), and iii) potential seasonal variations in wing morphometric characters that may be modified in resistant mosquitoes. Our bioassay results indicated the presence of different levels of resistance to all tested insecticides for all three seasons in all locations. The results of the PCR-based molecular analysis revealed low frequencies of mutations in ace-1 and Rdl that are associated with resistance to malathion, bendiocarb, and dieldrin and no obvious seasonal changes. In contrast, we detected high frequencies and striking seasonal changes for two kdr mutations associated with resistance to DDT and pyrethroids. In addition, the evaluation of the field populations from all seasons in terms of the combinations of polymorphisms at four resistance-associated mutations did not reveal the presence of insects that are resistant to all pesticides. Results from the morphological analysis displayed a similar pattern for both wings and did not show a clear separation among the samples from the

  17. Impact of seasonality upon the dynamics of a novel pathogen in a seabird colony

    NASA Astrophysics Data System (ADS)

    O'Regan, S. M.

    2008-11-01

    A seasonally perturbed variant of the basic Susceptible-Infected-Recovered (SIR) model in epidemiology is considered in this paper. The effect of seasonality on an IR system of ordinary differential equations describing the dynamics of a novel pathogen, e.g., highly pathogenic avian influenza, in a seabird colony is investigated. The method of Lyapunov functions is used to determine the long-term behaviour of this system. Numerical simulations of the seasonally perturbed IR system indicate that the system exhibits complex dynamics as the amplitude of the seasonal perturbation term is increased. These findings suggest that seasonality may exert a considerable effect on the dynamics of epidemics in a seabird colony.

  18. Seasonal dynamics of turbidity maximum in the Muthupet estuary, India

    NASA Astrophysics Data System (ADS)

    Priya, K. L.; Jegathambal, P.; James, E. J.

    2015-10-01

    Results are presented of the longitudinal and vertical profiling of salinity and suspended particulate matter (SPM) at the Muthupet estuary, India, during a one year period under widely varying freshwater flow conditions. Freshwater flow was available during post-monsoon and monsoon. An up-estuary shift in the location of estuarine turbidity maxima (ETM) was observed during the transition from post-monsoon to pre-monsoon and further it shifted downstream during the transition from pre-monsoon to monsoon, thereby exhibiting a pronounced seasonal cycle. The salinity intrusion was dependent on the freshwater discharge and was expressed as a power function of freshwater flow, explaining 97% of the variance. The formation of a salt plug in Muthupet estuary and its seasonal dynamics were observed, which is not an identified feature of any of the Indian estuaries studied so far. The geographical positions of salt plug and ETM core were more or less the same during their formation. The occurrence of two ETM during the LW of post-monsoon and the absence of ETM during monsoon explains the strong seasonal variation in the formation of ETM. The primary factor affecting the formation of ETM was identified as the freshwater flow over an annual cycle; the resuspension of sediments by tidal current affecting the formation on a flood/ebb cycle was secondary. The extent of shift of ETM was found to be an inverse logarithmic function of the freshwater discharge. The separation between ETM intrusion and salinity intrusion increased two fold with the increase in ETM intrusion.

  19. Integrated monitoring of nitrogen dynamics in contrasting catchments

    NASA Astrophysics Data System (ADS)

    Schwientek, M.; Fleischer, M.

    2012-04-01

    The research institute WESS (Water & Earth System Science) is monitoring three adjacent meso-scale catchments (72 - 140 km2) in southwest Germany with respect to water quantity and quality. Due to their spatial proximity, the studied catchments are similar regarding climatic conditions and water balance. Geology is characterized by sedimentary rocks which are partly karstified. The catchments contrast strongly in land use and show a range from predominantly agriculture to almost exclusively forestry. In this context, a special focus of our research is the distinction of matter coming from the catchment area versus substances stemming from urban point sources. One important compound representing inputs from the catchment area is nitrogen. Nitrogen is an essential nutrient governing plant growth. If available in excess it leads to eutrophication and is therefore one of the globally most widespread contaminants in aquatic ecosystems. Transport of human-derived nitrogen through landscapes including urban areas to the oceans predominantly occurs via river network systems. Hence, monitoring of nitrogen fluxes in streams and rivers reveals mechanisms and dynamics of its transport and gives also insight into hydrologic processes which influence the mobilization of nitrogen. Presently, the catchments are equipped with online probes enabling high resolution monitoring of nitrate concentrations and other parameters. We found that average nitrate concentrations in stream water perfectly reflect the portion of fertilized arable land. The dynamics of N transport, however, largely depends on the hydrologic system and is driven by the dominating runoff generation processes. The interplay between different hydrological storages, which eventually also act as N pools, turns out to be decisive for the temporal variability of N concentrations in stream discharge. Inversely, the study of N transport dynamics can be used to infer the hydrologic mechanisms responsible for N mobilization

  20. Seasonal coastal sea level prediction using a dynamical model

    NASA Astrophysics Data System (ADS)

    McIntosh, Peter C.; Church, John A.; Miles, Elaine R.; Ridgway, Ken; Spillman, Claire M.

    2015-08-01

    Sea level varies on a range of time scales from tidal to decadal and centennial change. To date, little attention has been focussed on the prediction of interannual sea level anomalies. Here we demonstrate that forecasts of coastal sea level anomalies from the dynamical Predictive Ocean Atmosphere Model for Australia (POAMA) have significant skill throughout the equatorial Pacific and along the eastern boundaries of the Pacific and Indian Oceans at lead times out to 8 months. POAMA forecasts for the western Pacific generally have greater skill than persistence, particularly at longer lead times. POAMA also has comparable or greater skill than previously published statistical forecasts from both a Markov model and canonical correlation analysis. Our results indicate the capability of physically based models to address the challenge of providing skillful forecasts of seasonal sea level fluctuations for coastal communities over a broad area and at a range of lead times.

  1. Seasonal meridional energy balance and thermal structure of the atmosphere of Uranus - A radiative-convective-dynamical model

    NASA Technical Reports Server (NTRS)

    Friedson, James; Ingersoll, Andrew P.

    1987-01-01

    A model is presented for the thermodynamics of the seasonal meridional energy balance and thermal structure of the Uranian atmosphere. The model considers radiation and small-scale convection, and dynamical heat fluxes due to large-scale baroclinic eddies. Phase oscillations with a period of 0.5 Uranian year are discerned in the total internal power and global enthalpy storage. The variations in the identity of the main transport agent with the magnitude of the internal heat source are discussed. It is shown that meridional heat transport in the atmosphere is sufficient to lower seasonal horizontal temperature contrasts below those predicted with radiative-convection models.

  2. Quantifying Groundwater Recharge During Dynamic Seasonality in Cold Climates

    NASA Astrophysics Data System (ADS)

    Pasha, E.; Rudolph, D. L.

    2015-12-01

    Estimating groundwater recharge in cold climates, during periods of dynamic seasonality such as winter and spring freshets is challenging due to subsurface heterogeneities and the complexity of vadose zone processes under partially frozen conditions. In order to obtain robust recharge estimates, numerical models simulating these complex processes need to be based on reliable parameter estimates and closely calibrated to field observations. This study focuses on quantifying recharge under an ephemeral stream that develops in the vicinity of a municipal well field during spring and winter freshets at a site in Southern Ontario. Temperature and moisture content profiles in the vadose zone were obtained during the 2015 spring melt at three different locations, using a variety of hydrogeological instruments. Temperature thermisters and Tid-Bit transducers were both installed at 15-30 cm spacings to the depth of the water table in order to compare and calibrate the results. Similarly, Time Domain Reflectometry probes were placed to the depth of the water table and the results were calibrated to daily moisture content readings taken with a Neutron Probe. Water table fluctuations were monitored and regular water samples were taken for analysis of geochemistry and isotope fractionation. This data provided the boundary conditions for the numerical model (Hydrus 1D) and allowed for its calibration and validation. Regions of rapid infiltration were observed at the site, as well as steep temperature gradients that could be used as a tracer for estimating recharge in cold climates. The geochemistry and isotope fractionation results provided support of surface water groundwater interaction within event based time periods predicted by the numerical models. Furthermore, the surface water samples were found to have high concentrations of microbial indicator species, and therefore the intense recharge phenomena observed at the site has significant implications to groundwater

  3. Dynamic Contrast-Enhanced CT in Patients with Pancreatic Cancer.

    PubMed

    Eriksen, Rie Ø; Strauch, Louise S; Sandgaard, Michael; Kristensen, Thomas S; Nielsen, Michael B; Lauridsen, Carsten A

    2016-01-01

    The aim of this systematic review is to provide an overview of the use of Dynamic Contrast-enhanced Computed Tomography (DCE-CT) in patients with pancreatic cancer. This study was composed according to the PRISMA guidelines 2009. The literature search was conducted in PubMed, Cochrane Library, EMBASE, and Web of Science databases to identify all relevant publications. The QUADAS-2 tool was implemented to assess the risk of bias and applicability concerns of each included study. The initial literature search yielded 483 publications. Thirteen articles were included. Articles were categorized into three groups: nine articles concerning primary diagnosis or staging, one article about tumor response to treatment, and three articles regarding scan techniques. In exocrine pancreatic tumors, measurements of blood flow in eight studies and blood volume in seven studies were significantly lower in tumor tissue, compared with measurements in pancreatic tissue outside of tumor, or normal pancreatic tissue in control groups of healthy volunteers. The studies were heterogeneous in the number of patients enrolled and scan protocols. Perfusion parameters measured and analyzed by DCE-CT might be useful in the investigation of characteristic vascular patterns of exocrine pancreatic tumors. Further clinical studies are desired for investigating the potential of DCE-CT in pancreatic tumors. PMID:27608045

  4. Dynamic Susceptibility Contrast MRI with Localized Arterial Input Functions

    PubMed Central

    Lee, J.J.; Bretthorst, G.L.; Derdeyn, C.P.; Powers, W.J.; Videen, T.O.; Snyder, A.Z.; Markham, J.; Shimony, J.S.

    2010-01-01

    Compared to gold-standard measurements of cerebral perfusion with positron emission tomography (PET) using H2[15O] tracers, measurements with dynamic susceptibility contrast (DSC) MR are more accessible, less expensive and less invasive. However, existing methods for analyzing and interpreting data from DSC MR have characteristic disadvantages that include sensitivity to incorrectly modeled delay and dispersion in a single, global arterial input function (AIF). We describe a model of tissue microcirculation derived from tracer kinetics which estimates for each voxel a unique, localized AIF (LAIF). Parameters of the model were estimated using Bayesian probability theory and Markov-chain Monte Carlo, circumventing difficulties arising from numerical deconvolution. Applying the new method to imaging studies from a cohort of fourteen patients with chronic, atherosclerotic, occlusive disease showed strong correlations between perfusion measured by DSC MR with LAIF and perfusion measured by quantitative PET with H2[15O]. Regression to PET measurements enabled conversion of DSC MR to a physiological scale. Regression analysis for LAIF gave estimates of a scaling factor for quantitation which described perfusion accurately in patients with substantial variability in hemodynamic impairment. PMID:20432301

  5. Seasonal Variation in the Fate of Seeds under Contrasting Logging Regimes

    PubMed Central

    Fleury, Marina; Rodrigues, Ricardo R.; do Couto, Hilton T. Z.; Galetti, Mauro

    2014-01-01

    Seed predators and dispersers may drive the speed and structure of forest regeneration in natural ecosystems. Rodents and ants prey upon and disperse seeds, yet empirical studies on the magnitude of these effects are lacking. Here, we examined the role of ants and rodents on seed predation in 4 plant species in a successional gradient on a tropical rainforest island. We found that (1) seeds are mostly consumed rather than dispersed; (2) rates of seed predation vary by habitat, season, and species; (3) seed size, shape, and hardness do not affect the probability of being depredated. Rodents were responsible for 70% of seed predation and were negligible (0.14%) seed dispersers, whereas ants were responsible for only 2% of seed predation and for no dispersal. We detected seasonal and habitat effects on seed loss, with higher seed predation occurring during the wet season and in old-growth forests. In the absence of predators regulating seed-consumer populations, the densities of these resilient animals explode to the detriment of natural regeneration and may reduce diversity and carrying capacity for consumers and eventually lead to ecological meltdown. PMID:24614500

  6. Disentangling seasonal bacterioplankton population dynamics by high-frequency sampling.

    PubMed

    Lindh, Markus V; Sjöstedt, Johanna; Andersson, Anders F; Baltar, Federico; Hugerth, Luisa W; Lundin, Daniel; Muthusamy, Saraladevi; Legrand, Catherine; Pinhassi, Jarone

    2015-07-01

    Multiyear comparisons of bacterioplankton succession reveal that environmental conditions drive community shifts with repeatable patterns between years. However, corresponding insight into bacterioplankton dynamics at a temporal resolution relevant for detailed examination of variation and characteristics of specific populations within years is essentially lacking. During 1 year, we collected 46 samples in the Baltic Sea for assessing bacterial community composition by 16S rRNA gene pyrosequencing (nearly twice weekly during productive season). Beta-diversity analysis showed distinct clustering of samples, attributable to seemingly synchronous temporal transitions among populations (populations defined by 97% 16S rRNA gene sequence identity). A wide spectrum of bacterioplankton dynamics was evident, where divergent temporal patterns resulted both from pronounced differences in relative abundance and presence/absence of populations. Rates of change in relative abundance calculated for individual populations ranged from 0.23 to 1.79 day(-1) . Populations that were persistently dominant, transiently abundant or generally rare were found in several major bacterial groups, implying evolution has favoured a similar variety of life strategies within these groups. These findings suggest that high temporal resolution sampling allows constraining the timescales and frequencies at which distinct populations transition between being abundant or rare, thus potentially providing clues about physical, chemical or biological forcing on bacterioplankton community structure. PMID:25403576

  7. Seasonal dynamics of the flower head infestation of Smallanthus maculatus by two nonfrugivorous tephritids.

    PubMed

    Dzul-Cauich, José F; Hernández-Ortiz, Vicente; Parra-Tabla, Victor; Rico-Gray, Victor

    2014-01-01

    Seasonal dynamics of the capitula infested by Dictyotrypeta sp. and Rhynencina spilogaster (Steyskal) (Diptera: Tephritidae) was evaluated throughout the flowering cycle of their host plant the sunflower, Smallanthus maculatus (Cavanilles) Robinson (Asterales: Asteraceae). In central Veracruz, Mexico, along 16 consecutive weeks, a total of 1,017 mature capitula were collected, recording the presence and abundance of immature stages (larvae and pupae) and their related parasitoids. Both fly species were present throughout the entire season, with overall infestation of 51.5% of the capitula examined. However, Dictyotrypeta sp. infested 11.3%, representing about one-fifth of them, and R. spilogaster was most abundant infesting four times as many capitula (42.9%), whereas both species were found together in only 2.6% of the capitula examined. Based on the temporal occurrence of larvae and pupae into flower heads as well as their associated parasitoids and times of emergence, Dictyotrypeta sp. had two yearly generations, and it seems that the second generation could enter a seasonal diapause; in contrast, R. spilogaster was a univoltine species that entered diapause that lasted until the next year. PMID:25368091

  8. Dynamic contrast-enhanced MRI evaluation of cerebral cavernous malformations.

    PubMed

    Hart, Blaine L; Taheri, Saeid; Rosenberg, Gary A; Morrison, Leslie A

    2013-10-01

    The aim of this study is to quantitatively evaluate the behavior of CNS cavernous malformations (CCMs) using a dynamic contrast-enhanced MRI (DCEMRI) technique sensitive for slow transfer rates of gadolinium. The prospective study was approved by the institutional review board and was HIPPA compliant. Written informed consent was obtained from 14 subjects with familial CCMs (4 men and 10 women, ages 22-76 years, mean 48.1 years). Following routine anatomic MRI of the brain, DCEMRI was performed for six slices, using T1 mapping with partial inversion recovery (TAPIR) to calculate T1 values, following administration of 0.025 mmol/kg gadolinium DTPA. The transfer rate (Ki) was calculated using the Patlak model, and Ki within CCMs was compared to normal-appearing white matter as well as to 17 normal control subjects previously studied. All subjects had typical MRI appearance of CCMs. Thirty-nine CCMs were studied using DCEMRI. Ki was low or normal in 12 lesions and elevated from 1.4 to 12 times higher than background in the remaining 27 lesions. Ki ranged from 2.1E-6 to 9.63E-4 min(-1), mean 3.55E-4. Normal-appearing white matter in the CCM patients had a mean Ki of 1.57E-4, not statistically different from mean WM Ki of 1.47E-4 in controls. TAPIR-based DCEMRI technique permits quantifiable assessment of CCMs in vivo and reveals considerable differences not seen with conventional MRI. Potential applications include correlation with biologic behavior such as lesion growth or hemorrage, and measurement of drug effects. PMID:24323376

  9. Dynamic manipulation of magnetic contrast agents in photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Jia, Congxian; Xia, Jinjun; Pelivanov, Ivan M.; Seo, Chi Hyung; Hu, Xiaoge; Jin, Yongdong; Gao, Xiaohu; O'Donnell, Matthew

    2011-03-01

    Magnetic nanoparticles (MNPs) have been used extensively ex vivo for cellular and molecular separations. We recently showed that a coupled nanoparticle combining a superparamagnetic core with a thin, isolated gold shell providing strong absorption in the near infrared can be used for magnetomotive photoacoustic imaging (mmPA), a new technique in which magnetic manipulation of the particle during PA imaging greatly enhances molecular contrast specificity. This particle can also be biologically targeted for in vivo applications, where mmPA imaging provides a spatially localized readout of magnetic manipulations. As an initial test of potential in vivo molecular assays and integrated molecular therapeutics using magnetic manipulation of nanoparticles, we present experiments demonstrating PA readout of trapped magnetic particles in a flow field. An aqueous solution containing a concentration of 0.05-mg/ml 10-μM superparamagnetic iron oxide particles flowed in a 1.65-mm diameter Zeus PTFE (Teflon) sublite wall tubing at three velocities of 0.8, 1.5 and 3.0-mm/s. Opposed permanent magnets separated by 40-mm were positioned on both sides of the tube. As expected, the targeted objects can be magnetically captured and accumulated locally. By translating the magnets, a dynamic magnetic field (0.1-0.3-T) was alternately generated on the side of the tube closest to one of the magnets and created a synchronous PA motion from accumulated targeted objects. This synchronized motion can be used to differentiate the stationary background or other PA sources moving asynchronously with magnetic manipulations (e.g., moving blood) from targeted cells moving synchronously with the magnetic field. This technology can potentially provide sensitive molecular assays of cellular targets travelling in the vasculature (e.g., metastatic tumor cells).

  10. Influence of Hydrology and Seasonality on DOC Exports from 3 Contrasting Upland Catchments

    NASA Astrophysics Data System (ADS)

    Dawson, J. J.; Soulsby, C.; Tetzlaff, D.; Hrachowitz, M.; Dunn, S. M.; Malcolm, I. A.

    2008-12-01

    How climate variability influences soil processes, production and export of DOC are important in understanding hydrologically mediated carbon losses from soils and its affect on water quality. This necessitates understanding factors controlling the quantity and timing of carbon availability for export from soils to the drainage network. Long-term records (1987-2006) of DOC concentrations at 6 catchments (0.44- 10.0 km2) across a climatic transect in Scotland were investigated for intra-annual relationships to evaluate potential long-term seasonal as well as inter-annual patterns. Catchments in wetter Central Scotland with high rainfall-runoff ratios, short transit times and well-connected responsive soils show a distinct annual periodicity in DOC concentrations throughout the long-term datasets. Increased DOC concentrations occurred between June and November with correspondingly lower DOC concentrations from December to May. This appears unrelated to discharge, and is dependent mainly on higher temperatures driving biological activity, increasing decomposition of available organic matter and solubility of DOC. The drier eastern catchments have lower rainfall-runoff ratios, longer transit times and annual drying-wetting regimes linked to changing connectivity of soils. These are characterised by seasonal DOC concentration- discharge relationships with an autumnal flush of DOC. Temperature influences the availability of organic matter for subsequent DOC transport producing a high DOC concentration-discharge relationship in summer/autumn and low DOC concentration-discharge relationship in winter/spring. These two distinct modes of seasonal DOC transport have important implications for understanding changes in DOC concentrations and export brought about by climate changes (temperature and precipitation) and modeling of aquatic carbon losses from soil-types under different hydrological regimes.

  11. Contrasting seasonal leaf habits of canopy trees between tropical dry-deciduous and evergreen forests in Thailand.

    PubMed

    Ishida, Atsushi; Diloksumpun, Sapit; Ladpala, Phanumard; Staporn, Duriya; Panuthai, Samreong; Gamo, Minoru; Yazaki, Kenichi; Ishizuka, Moriyoshi; Puangchit, Ladawan

    2006-05-01

    We compared differences in leaf properties, leaf gas exchange and photochemical properties between drought-deciduous and evergreen trees in tropical dry forests, where soil nutrients differed but rainfall was similar. Three canopy trees (Shorea siamensis Miq., Xylia xylocarpa (Roxb.) W. Theob. and Vitex peduncularis Wall. ex Schauer) in a drought-deciduous forest and a canopy tree (Hopea ferrea Lanessan) in an evergreen forest were selected. Soil nutrient availability is lower in the evergreen forest than in the deciduous forest. Compared with the evergreen tree, the deciduous trees had shorter leaf life spans, lower leaf masses per area, higher leaf mass-based nitrogen (N) contents, higher leaf mass-based photosynthetic rates (mass-based P(n)), higher leaf N-based P(n), higher daily maximum stomatal conductance (g(s)) and wider conduits in wood xylem. Mass-based P(n) decreased from the wet to the dry season for all species. Following onset of the dry season, daily maximum g(s) and sensitivity of g(s) to leaf-to-air vapor pressure deficit remained relatively unchanged in the deciduous trees, whereas both properties decreased in the evergreen tree during the dry season. Photochemical capacity and non-photochemical quenching (NPQ) of photosystem II (PSII) also remained relatively unchanged in the deciduous trees even after the onset of the dry season. In contrast, photochemical capacity decreased and NPQ increased in the evergreen tree during the dry season, indicating that the leaves coped with prolonged drought by down-regulating PSII. Thus, the drought-avoidant deciduous species were characterized by high N allocation for leaf carbon assimilation, high water use and photoinhibition avoidance, whereas the drought-tolerant evergreen was characterized by low N allocation for leaf carbon assimilation, conservative water use and photoinhibition tolerance. PMID:16452078

  12. Sediment dynamics during the rainy season in tropical highland catchments of central Mexico using fallout radionuclides

    NASA Astrophysics Data System (ADS)

    Evrard, Olivier; Némery, Julien; Gratiot, Nicolas; Duvert, Clément; Ayrault, Sophie; Lefèvre, Irène; Poulenard, Jérôme; Prat, Christian; Bonté, Philippe; Esteves, Michel

    2010-12-01

    Tropical regions are affected by intense soil erosion associated with deforestation, overgrazing, and cropping intensification. This land degradation leads to important on-site (e.g., decrease in soil fertility) and off-site (e.g., reservoir siltation and water pollution) impacts. This study determined the mean soil particle and sediment residence times in soils and rivers of three subcatchments (3-12 km 2) with contrasted land uses (i.e., cropland, forests, and rangelands) draining to a reservoir located in highlands of the transvolcanic Mexican belt. Calculations were based on rainfall amount and river discharges as well as on fallout radionuclide measurements (Be-7, Cs-137, and Pb-210) conducted on rainfall precipitated samples, soil sampled in the catchments, and suspended sediment collected by automatic samplers in the river during most storms recorded throughout the 2009 rainy season. Calculations using a radionuclide two-box balance model showed that the mean residence time of particles in soils ranged between 5000 ± 1500 and 23,300 ± 7000 years. In contrast, sediment residence time in rivers was much shorter, fluctuating between 50 ± 30 and 200 ± 70 days. The shortest mean residence times were measured in a hilly catchment dominated by cropland and rangelands, whereas they were the longest in an undulating catchment dominated by forests and cropland. Calculation of the Be-7/excess-Pb-210 in both rainfall and sediment allowed gaining insight on sediment dynamics throughout the rainy season. The first heavy storms of the year exported the bulk of the sediment stock accumulated in the river channel during the previous year. Then, during the rainy season, the two steeper catchments dominated by cropland and rangelands reacted strongly to rainfall. Sediment was indeed eroded and exported from both catchments during single heavy storms on several occasions in 2009. In contrast, the agro-forested catchment with gentler slopes exported sediment at a constant

  13. Use of computational fluid dynamics in the design of dynamic contrast enhanced imaging phantoms.

    PubMed

    Hariharan, Prasanna; Freed, Melanie; Myers, Matthew R

    2013-09-21

    Phantoms for dynamic contrast enhanced (DCE) imaging modalities such as DCE computed tomography (DCE-CT) and DCE magnetic resonance imaging (DCE-MRI) are valuable tools for evaluating and comparing imaging systems. It is important for the contrast-agent distribution within the phantom to possess a time dependence that replicates a curve observed clinically, known as the 'tumor-enhancement curve'. It is also important for the concentration field within the lesion to be as uniform as possible. This study demonstrates how computational fluid dynamics (CFD) can be applied to achieve these goals within design constraints. The distribution of the contrast agent within the simulated phantoms was investigated in relation to the influence of three factors of the phantom design. First, the interaction between the inlets and the uniformity of the contrast agent within the phantom was modeled. Second, pumps were programmed using a variety of schemes and the resultant dynamic uptake curves were compared to tumor-enhancement curves obtained from clinical data. Third, the effectiveness of pulsing the inlet flow rate to produce faster equilibration of the contrast-agent distribution was quantified. The models employed a spherical lesion and design constraints (lesion diameter, inlet-tube size and orientation, contrast-agent flow rates and fluid properties) taken from a recently published DCE-MRI phantom study. For DCE-MRI in breast cancer detection, where the target tumor-enhancement curve varies on the scale of hundreds of seconds, optimizing the number of inlet tubes and their orientation was found to be adequate for attaining concentration uniformity and reproducing the target tumor-enhancement curve. For DCE-CT in liver tumor detection, where the tumor-enhancement curve varies on a scale of tens of seconds, the use of an iterated inlet condition (programmed into the pump) enabled the phantom to reproduce the target tumor-enhancement curve within a few per cent beyond about 6

  14. Use of computational fluid dynamics in the design of dynamic contrast enhanced imaging phantoms

    NASA Astrophysics Data System (ADS)

    Hariharan, Prasanna; Freed, Melanie; Myers, Matthew R.

    2013-09-01

    Phantoms for dynamic contrast enhanced (DCE) imaging modalities such as DCE computed tomography (DCE-CT) and DCE magnetic resonance imaging (DCE-MRI) are valuable tools for evaluating and comparing imaging systems. It is important for the contrast-agent distribution within the phantom to possess a time dependence that replicates a curve observed clinically, known as the ‘tumor-enhancement curve’. It is also important for the concentration field within the lesion to be as uniform as possible. This study demonstrates how computational fluid dynamics (CFD) can be applied to achieve these goals within design constraints. The distribution of the contrast agent within the simulated phantoms was investigated in relation to the influence of three factors of the phantom design. First, the interaction between the inlets and the uniformity of the contrast agent within the phantom was modeled. Second, pumps were programmed using a variety of schemes and the resultant dynamic uptake curves were compared to tumor-enhancement curves obtained from clinical data. Third, the effectiveness of pulsing the inlet flow rate to produce faster equilibration of the contrast-agent distribution was quantified. The models employed a spherical lesion and design constraints (lesion diameter, inlet-tube size and orientation, contrast-agent flow rates and fluid properties) taken from a recently published DCE-MRI phantom study. For DCE-MRI in breast cancer detection, where the target tumor-enhancement curve varies on the scale of hundreds of seconds, optimizing the number of inlet tubes and their orientation was found to be adequate for attaining concentration uniformity and reproducing the target tumor-enhancement curve. For DCE-CT in liver tumor detection, where the tumor-enhancement curve varies on a scale of tens of seconds, the use of an iterated inlet condition (programmed into the pump) enabled the phantom to reproduce the target tumor-enhancement curve within a few per cent beyond about

  15. Seasonal and spatial contrasts of sedimentary organic carbon in floodplain lakes of the central Amazon basin.

    NASA Astrophysics Data System (ADS)

    Sobrinho, Rodrigo; Kim, Jung-Hyun; Abril, Gwenaël; Zell, Claudia; Moreira-Turcq, Patricia; Mortillaro, Jean-Michel; Meziane, Tarik; Damsté, Jaap; Bernardes, Marcelo

    2014-05-01

    Three-quarters of the area of flooded land in the world are temporary wetlands (Downing, 2009), which play a significant role in the global carbon cycle(Einsele et al., 2001; Cole et al., 2007; Battin et al., 2009; Abril et al., 2013). Previous studies of the Amazonian floodplain lakes (várzeas), one important compartment of wetlands, showed that the sedimentation of organic carbon (OC) in the floodplain lakes is strongly linked to the periodical floods and to the biogeography from upstream to downstream(Victoria et al., 1992; Martinelli et al., 2003). However, the main sources of sedimentary OC remain uncertain. Hence, the study of the sources of OC buried in floodplain lake sediments can enhance our understanding of the carbon balance of the Amazon ecosystems. In this study, we investigated the seasonal and spatial pattern of sedimentary organic matter in five floodplain lakes of the central Amazon basin (Cabaliana, Janauaca, Canaçari, Miratuba, and Curuai) which have different morphologies, hydrodynamics and vegetation coverage. Surface sediments were collected in four hydrological seasons: low water (LW), rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010. We investigated commonly used bulk geochemical tracers such as C:N ratio and stable isotopic composition of organic carbon (δ13COC). These results were compared with lignin-phenol parameters as an indicator of vascular plant detritus (Hedges and Ertel, 1982) and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to trace the soil OC from land to the aquatic settings (Hopmans et al., 2004). Our data showed that during the RW and FW seasons, the concentration of lignin and brGDGTs were higher in comparison to other seasons. Our study also indicated that floodplain lake sediments primarily consisted of a mixture of C3 plant detritus and soil OC. However, a downstream increase in C4 plant-derived OC contribution was observed along the gradient of increasingly open waters, i

  16. Dynamic contrast-enhanced diffuse optical tomography (DCE-DOT): experimental validation with a dynamic phantom

    PubMed Central

    Unlu, Mehmet Burcin; Lin, Yuting; Gulsen, Gultekin

    2010-01-01

    Dynamic contrast-enhanced diffuse optical tomography (DCE-DOT) can provide spatially resolved enhancement kinetics of an optical contrast agent. We undertook a systematic phantom study to evaluate the effects of the geometrical parameters such as the depth and size of the inclusion as well as the optical parameters of the background on the recovered enhancement kinetics of the most commonly used optical contrast agent, indocyanine green (ICG). For this purpose a computer-controlled dynamic phantom was constructed. An ICG–intralipid–water mixture was circulated through the inclusions while the DCE-DOT measurements were acquired with a temporal resolution of 16 s. The same dynamic study was repeated using inclusions of different sizes located at different depths. In addition to this, the effect of non-scattering regions was investigated by placing a second inclusion filled with water in the background. The phantom studies confirmed that although the peak enhancement varied substantially for each case, the recovered injection and dilution rates obtained from the percentage enhancement maps agreed within 15% independent of not only the depth and the size of the inclusion but also the presence of a non-scattering region in the background. Although no internal structural information was used in these phantom studies, it may be necessary to use it for small objects buried deep in tissue. However, the different contrast mechanisms of optical and other imaging modalities as well as imperfect co-registration between both modalities may lead to potential errors in the structural a priori. Therefore, the effect of erroneous selection of structural priors was investigated as the final step. Again, the injection and dilution rates obtained from the percentage enhancement maps were also immune to the systematic errors introduced by erroneous selection of the structural priors, e.g. choosing the diameter of the inclusion 20% smaller increased the peak enhancement 60% but

  17. Hydrological niche separation explains seasonal and inter-annual variations of vegetation dynamics in seasonally dry tropical forests

    NASA Astrophysics Data System (ADS)

    Xu, X.; Medvigy, D.; Powers, J. S.; Becknell, J. M.; Guan, K.

    2015-12-01

    Despite ample water supply, vegetation dynamics are subject to seasonal water stress in large fraction of tropical forests. These seasonally dry tropical forests (SDTFs) account for over 40% of tropical forests, harbor high biodiversity, have large potential carbon sink due to forest recovery from human disturbance and also play a critical role in global carbon budget and inter-annual variations. Plants in this biome display notably diverse responses to seasonal and inter-annual variations of water availability, especially inter-specific variations in canopy seasonality and biomass growth. Current process-based dynamic vegetation models cannot represent these diversities and are shown to perform poorly on simulating drought responses of tropical forests, calling into question of their ability to accurately simulate future changes in SDTFs. Accumulated field observations, suggest that hydrological niche separation driven by coordinated plant functional traits is associated with plants' performance under drought. Yet, it remains not clear whether the physiology-level hydrological niche separation can explain the ecosystem-level diversity observed in SDTFs. Here, we test the theory with a model-data fusion approach. We implemented a new plant hydrodynamic module that is able to track leaf water potential at sub-daily scale in ED2 model. We further incorporated a hydrological niche separation scheme based on a meta-data analysis of key functional traits in SDTFs. Simulated ecological patterns with and without hydrological niche separation were then compared with remote-sensing and long-term field observations from an SDTF site in Palo Verde, Costa Rica. Using several numerical experiments, we specifically examine the following questions: (i) Whether hydrological niche separation can explain the diversity in canopy seasonality and biomass growth? (ii) How important are the yet uncertain belowground functional traits, especially root profile in determining canopy

  18. Ocean time-series reveals recurring seasonal patterns of virioplankton dynamics in the northwestern Sargasso Sea.

    PubMed

    Parsons, Rachel J; Breitbart, Mya; Lomas, Michael W; Carlson, Craig A

    2012-02-01

    There are an estimated 10(30) virioplankton in the world oceans, the majority of which are phages (viruses that infect bacteria). Marine phages encompass enormous genetic diversity, affect biogeochemical cycling of elements, and partially control aspects of prokaryotic production and diversity. Despite their importance, there is a paucity of data describing virioplankton distributions over time and depth in oceanic systems. A decade of high-resolution time-series data collected from the upper 300 m in the northwestern Sargasso Sea revealed recurring temporal and vertical patterns of virioplankton abundance in unprecedented detail. An annual virioplankton maximum developed between 60 and 100 m during periods of summer stratification and eroded during winter convective mixing. The timing and vertical positioning of this seasonal pattern was related to variability in water column stability and the dynamics of specific picophytoplankton and heterotrophic bacterioplankton lineages. Between 60 and 100 m, virioplankton abundance was negatively correlated to the dominant heterotrophic bacterioplankton lineage SAR11, as well as the less abundant picophytoplankton, Synechococcus. In contrast, virioplankton abundance was positively correlated to the dominant picophytoplankton lineage Prochlorococcus, and the less abundant alpha-proteobacteria, Rhodobacteraceae. Seasonally, virioplankton abundances were highly synchronous with Prochlorococcus distributions and the virioplankton to Prochlorococcus ratio remained remarkably constant during periods of water column stratification. The data suggest that a significant fraction of viruses in the mid-euphotic zone of the subtropical gyres may be cyanophages and patterns in their abundance are largely determined by Prochlorococcus dynamics in response to water column stability. This high-resolution, decadal survey of virioplankton abundance provides insight into the possible controls of virioplankton dynamics in the open ocean. PMID

  19. Contrasting Metabolism in Perenniating Structures of Upland and Lowland Switchgrass Plants Late in the Growing Season

    PubMed Central

    Tobias, Christian M.; Twigg, Paul; Xia, Yuannan; Vogel, Kenneth P.; Madhavan, Soundararajan; Sattler, Scott E.; Sarath, Gautam

    2014-01-01

    Background Switchgrass (Panicum virgatum L.) is being developed as a bioenergy crop for many temperate regions of the world. One way to increase biomass yields is to move southern adapted lowland cultivars to more northern latitudes. However, many southerly adapted switchgrass germplasm can suffer significant winter kill in northerly climes. Materials and Methods Here, we have applied next-generation sequencing in combination with biochemical analyses to query the metabolism of crowns and rhizomes obtained from two contrasting switchgrass cultivars. Crowns and rhizomes from field-grown lowland (cv Kanlow) and upland (cv Summer) switchgrass cultivars were collected from three randomly selected post-flowering plants. Summer plants were senescing, whereas Kanlow plants were not at this harvest date. Results Principal component analysis (PCA) differentiated between both the Summer and Kanlow transcriptomes and metabolomes. Significant differences in transcript abundances were detected for 8,050 genes, including transcription factors such as WRKYs and those associated with phenylpropanoid biosynthesis. Gene-set enrichment analyses showed that a number of pathways were differentially up-regulated in the two populations. For both populations, protein levels and enzyme activities agreed well with transcript abundances for genes involved in the phenylpropanoid pathway that were up-regulated in Kanlow crowns and rhizomes. The combination of these datasets suggests that dormancy-related mechanisms had been triggered in the crowns and rhizomes of the Summer plants, whereas the crowns and rhizomes of Kanlow plants had yet to enter dormancy. Conclusions Delayed establishment of dormancy at more northerly latitudes could be one factor that reduces winter-survival in the high-yielding Kanlow plants. Understanding the cellular signatures that accompany the transition to dormancy can be used in the future to select plants with improved winter hardiness. PMID:25133804

  20. Dynamic contrast-based quantization for lossy wavelet image compression.

    PubMed

    Chandler, Damon M; Hemami, Sheila S

    2005-04-01

    This paper presents a contrast-based quantization strategy for use in lossy wavelet image compression that attempts to preserve visual quality at any bit rate. Based on the results of recent psychophysical experiments using near-threshold and suprathreshold wavelet subband quantization distortions presented against natural-image backgrounds, subbands are quantized such that the distortions in the reconstructed image exhibit root-mean-squared contrasts selected based on image, subband, and display characteristics and on a measure of total visual distortion so as to preserve the visual system's ability to integrate edge structure across scale space. Within a single, unified framework, the proposed contrast-based strategy yields images which are competitive in visual quality with results from current visually lossless approaches at high bit rates and which demonstrate improved visual quality over current visually lossy approaches at low bit rates. This strategy operates in the context of both nonembedded and embedded quantization, the latter of which yields a highly scalable codestream which attempts to maintain visual quality at all bit rates; a specific application of the proposed algorithm to JPEG-2000 is presented. PMID:15825476

  1. Seasonal population dynamics of Zeuxapta seriolae (Monogenea: Heteraxinidae) parasitising Seriola dumerili (Carangidae) in the Western Mediterranean.

    PubMed

    Repullés-Albelda, Aigües; Kostadinova, Aneta; Raga, Juan Antonio; Montero, Francisco E

    2013-03-31

    We examined the seasonal and yearly population dynamics of the monogenean pathogen Zeuxapta seriolae on juvenile fish from wild populations of Seriola dumerili. The study is based on bimonthly monitoring between April, 2005 and April, 2007 off Majorca, and newly obtained monogenean population data for juvenile fish from three additional localities in the Western Mediterranean (off Alicante, Corsica and Sardinia). We documented the highest intensities and abundances of Z. seriolae, with mean abundance values similar to or higher than those reported in the single case of wild fish mortalities reported to date. There was a recurrent pattern of seasonal change in infection with Z. seriolae in the populations of S. dumerili off Majorca, with substantially higher parasite loads during the warm season (April to June). Mean parasite abundance was significantly correlated with seawater temperature and associated with higher proportions of juvenile worms in the parasite populations, thus suggesting increased transmission rates at higher temperatures. There was a significant negative association between abundance of Z. seriolae and fish length. Comparisons with the samples of younger and older fish off Majorca indicated that whereas infection parameters gradually increased in the first year of juvenile fish life, larger/older fish (>43 cm; 1+) were much lightly infected than the smaller/younger (<30 cm; 0+) juvenile fish examined in the same season. The observed increases in abundance during the warm weather months were invariably associated with sharp increases in monogenean aggregation levels and this was in contrast with the markedly low levels for both parameters during the cold season months. These data, coupled with the strong negative correlation between the levels of aggregation of Z. seriolae and mean fish total length, indicate that heavily infected individuals are being rapidly removed (i.e. within 2-3 months) from the host population thus reducing the

  2. PHYTOPLANKTON AND ZOOPLANKTON SEASONAL DYNAMICS IN A SUBTROPICAL ESTUARY: IMPORTANCE OF CYANOBACTERIA

    EPA Science Inventory

    Murrell, Michael C. and Emile M. Lores. 2004. Phytoplankton and Zooplankton Seasonal Dynamics in a Subtropical Estuary: Importance of Cyanobacteria. J. Plankton Res. 26(3):371-382. (ERL,GB 1190).

    A seasonal study of phytoplankton and zooplankton was conducted from 1999-20...

  3. Seasonal frost effects on the dynamic behavior of a twenty-story office building

    USGS Publications Warehouse

    Yang, Z.; Dutta, U.; Xiong, F.; Biswas, N.; Benz, H.

    2008-01-01

    Studies have shown that seasonal frost can significantly affect the seismic behavior of a bridge foundation system in cold regions. However, little information could be found regarding seasonal frost effects on the dynamic behavior of buildings. Based on the analysis of building vibration data recorded by a permanent strong-motion instrumentation system, the objective of this paper is to show that seasonal frost can impact the building dynamic behavior and the magnitude of impact may be different for different structures. Ambient noise and seismic data recorded on a twenty-story steel-frame building have been analyzed to examine the building dynamic characteristics in relationship to the seasonal frost and other variables including ground shaking intensity. Subsequently, Finite Element modeling of the foundation-soil system and the building superstructure was conducted to verify the seasonal frost effects. The Finite Element modeling was later extended to a reinforced-concrete (RC) type building assumed to exist at a similar site as the steel-frame building. Results show that the seasonal frost has great impact on the foundation stiffness in the horizontal direction and a clear influence on the building dynamic behavior. If other conditions remain the same, the effects of seasonal frost on structural dynamic behavior may be much more prominent for RC-type buildings than for steel-frame buildings. ?? 2007 Elsevier B.V. All rights reserved.

  4. Dynamically downscaled multi-model ensemble seasonal forecasts over Ethiopia

    NASA Astrophysics Data System (ADS)

    Asharaf, Shakeel; Fröhlich, Kristina; Fernandez, Jesus; Cardoso, Rita; Nikulin, Grigory; Früh, Barbara

    2016-04-01

    Truthful and reliable seasonal rainfall predictions have an important social and economic value for the east African countries as their economy is highly dependent on rain-fed agriculture and pastoral systems. Only June to September (JJAS) seasonal rainfall accounts to more than 80% crop production in Ethiopia. Hence, seasonal foresting is a crucial concern for the region. The European Provision of Regional Impact Assessment on a seasonal to decadal timescale (EUPORIAS) project offers a common framework to understand hindcast uncertainties through the use of multi-model and multi-member simulations over east Africa. Under this program, the participating regional climate models (RCMs) were driven by the atmospheric-only version of the ECEARTH global climate model, which provides hindcasts of a five-months period (May to September) from 1991-2012. In this study the RCMs downscaled rainfall is evaluated with respect to the observed JJAS rainfall over Ethiopia. Both deterministic and probabilistic based forecast skills are assessed. Our preliminary results show the potential usefulness of multi-model ensemble simulations in forecasting the seasonal rainfall over the region.

  5. Influence of Seasonal Food Availability on the Dynamics of Seabird Feeding Flocks at a Coastal Upwelling Area.

    PubMed

    Anguita, Cristóbal; Simeone, Alejandro

    2015-01-01

    The formation of multi-species feeding flocks (MSFFs) through visual recruitment is considered an important strategy for obtaining food in seabirds and its functionality has been ascribed to enhanced foraging efficiency. Its use has been demonstrated in much of the world's oceans and includes numerous species. However, there is scant information on the temporal stability of the composition and abundance of MSFFs as well as the effect of seasonal food availability on their dynamics. Between July 2006 and September 2014, we conducted monthly at-sea seabird counts at Valparaiso Bay (32°56' to 33°01'S, 71°36' to 71°46'W) within the area of influence of the Humboldt Current in central Chile. This area is characterized by a marked seasonality in primary and secondary production associated with upwelling, mainly during austral spring-summer. Based on studies that provide evidence that flocking is most frequent when food is both scarce and patchy, we hypothesized that seabird MSFF attributes (i.e. frequency of occurrence, abundance and composition) will be modified according to the seasonal availability of food. Using generalized linear models (GLMs), our results show that the contrasting seasonality in food availability of the study area (using chlorophyll-a concentration as a proxy) had no significant influence on MSFF attributes, sparsely explaining their variations (P>0.05). Rather than seasonal food availability, the observed pattern for MSFF attributes at Valparaiso Bay suggests a substantial influence of reproductive and migratory (boreal and austral migrants) habits of birds that modulates MSFF dynamics consistently throughout the whole year in this highly variable and patchy environment. We highlight the importance of visual recruitment as a mechanism by which migratory and resident birds interact. This would allow them to reduce resource unpredictability, which in turn has a major impact on structuring seabird's MSFF dynamics. PMID:26125630

  6. Influence of Seasonal Food Availability on the Dynamics of Seabird Feeding Flocks at a Coastal Upwelling Area

    PubMed Central

    Anguita, Cristóbal; Simeone, Alejandro

    2015-01-01

    The formation of multi-species feeding flocks (MSFFs) through visual recruitment is considered an important strategy for obtaining food in seabirds and its functionality has been ascribed to enhanced foraging efficiency. Its use has been demonstrated in much of the world's oceans and includes numerous species. However, there is scant information on the temporal stability of the composition and abundance of MSFFs as well as the effect of seasonal food availability on their dynamics. Between July 2006 and September 2014, we conducted monthly at-sea seabird counts at Valparaiso Bay (32°56′ to 33°01′S, 71°36′ to 71°46′W) within the area of influence of the Humboldt Current in central Chile. This area is characterized by a marked seasonality in primary and secondary production associated with upwelling, mainly during austral spring-summer. Based on studies that provide evidence that flocking is most frequent when food is both scarce and patchy, we hypothesized that seabird MSFF attributes (i.e. frequency of occurrence, abundance and composition) will be modified according to the seasonal availability of food. Using generalized linear models (GLMs), our results show that the contrasting seasonality in food availability of the study area (using chlorophyll-a concentration as a proxy) had no significant influence on MSFF attributes, sparsely explaining their variations (P>0.05). Rather than seasonal food availability, the observed pattern for MSFF attributes at Valparaiso Bay suggests a substantial influence of reproductive and migratory (boreal and austral migrants) habits of birds that modulates MSFF dynamics consistently throughout the whole year in this highly variable and patchy environment. We highlight the importance of visual recruitment as a mechanism by which migratory and resident birds interact. This would allow them to reduce resource unpredictability, which in turn has a major impact on structuring seabird’s MSFF dynamics. PMID:26125630

  7. Belowground Water Dynamics Under Contrasting Annual and Perennial Plant Communities in an Agriculturally-Dominated Landscape

    NASA Astrophysics Data System (ADS)

    Mora, G.; Asbjornsen, H.; Helmers, M. J.; Shepherd, G. W.

    2005-12-01

    The conversion from grasslands and forests to row-crops in the Midwest has affected soil water cycling because plant characteristics are one of the main parameters determining soil storage capacity, infiltration rates, and surface runoff. Little is known, however, about the extent of modification of soil water dynamics under different plant communities. To address this important issue, we are documenting soil water dynamics under contrasting perennial and annual plant communities in an agriculturally-dominated landscape. Measurements of soil moisture and depths of uptake of source water were obtained for six vegetative cover types (corn and soybean field, brome pasture, degraded savanna, restored savanna, and restored prairie) at the Neal Smith National Wildlife Refuge in Prairie City, Iowa. The depths of uptake of soil water were determined on the basis of oxygen isotope composition of soil water and stem water. Measurements were performed once a month during an entire growing season. Preliminary results indicate that soil water present under the different vegetation types show similar profiles with depth during the dry months. Soil water in the upper 5 cm is enriched in oxygen-18 by about 5 per mil relative to soil water at 100 cm. Our preliminary results also indicate that the isotopic composition of stem water from annual plants is typically higher by about 2 per mil relative to that of stem water from perennial plants during the dry period. Whereas the oxygen isotopic composition for corn stem water is -5.49 per mil, that for elm and oak stem water is -7.62 and -7.51 per mil, respectively. The higher isotope values for corn suggest that annual crop plants are withdrawing water from shallower soil horizons relative to perennial plants. Moreover, our preliminary data suggest lower moisture content in soil under annual plant cover. We propose that the presence of deeper roots in the perennial vegetation allows these plants to tap into deeper water sources when

  8. Knowing your enemies: seasonal dynamics of host social parasite recognition

    NASA Astrophysics Data System (ADS)

    D'Ettorre, Patrizia; Brunner, Elisabeth; Wenseleers, Tom; Heinze, Jürgen

    2004-12-01

    Despite its evolutionary significance, behavioural flexibility of social response has rarely been investigated in insects. We studied a host social parasite system: the slave-making ant Polyergus rufescens and its host Formica rufibarbis. Free-living host workers from parasitized and from unparasitized areas were compared in their level of aggression against the parasite and alien conspecifics. We expected that a seasonal change would occur in the acceptance threshold of F. rufibarbis workers from a parasitized area towards the parasite, whereas F. rufibarbis workers from an unparasitized area would not show substantial changes connected with the parasite’s peak in activity (raiding and colony-founding season). The results showed a significant adaptive behavioural flexibility of host species workers and are consistent with the acceptance threshold model’s (Reeve 1989) prediction that recognition systems are not fixed but context-dependent. In particular, host workers from the unparasitized area were highly aggressive towards the parasite regardless of the season, whereas host workers from the parasitized area significantly increased their aggression towards the parasite during its raiding and colony-founding season. Being able to detect and possibly kill a Polyergus scout searching for host nests can be an effective strategy for a Formica colony to avoid being raided or usurped by a parasite queen.

  9. Development of a dynamic flow imaging phantom for dynamic contrast-enhanced CT

    SciTech Connect

    Driscoll, B.; Keller, H.; Coolens, C.

    2011-08-15

    Purpose: Dynamic contrast enhanced CT (DCE-CT) studies with modeling of blood flow and tissue perfusion are becoming more prevalent in the clinic, with advances in wide volume CT scanners allowing the imaging of an entire organ with sub-second image frequency and sub-millimeter accuracy. Wide-spread implementation of perfusion DCE-CT, however, is pending fundamental validation of the quantitative parameters that result from dynamic contrast imaging and perfusion modeling. Therefore, the goal of this work was to design and construct a novel dynamic flow imaging phantom capable of producing typical clinical time-attenuation curves (TACs) with the purpose of developing a framework for the quantification and validation of DCE-CT measurements and kinetic modeling under realistic flow conditions. Methods: The phantom is based on a simple two-compartment model and was printed using a 3D printer. Initial analysis of the phantom involved simple flow measurements and progressed to DCE-CT experiments in order to test the phantoms range and reproducibility. The phantom was then utilized to generate realistic input TACs. A phantom prediction model was developed to compute the input and output TACs based on a given set of five experimental (control) parameters: pump flow rate, injection pump flow rate, injection contrast concentration, and both control valve positions. The prediction model is then inversely applied to determine the control parameters necessary to generate a set of desired input and output TACs. A protocol was developed and performed using the phantom to investigate image noise, partial volume effects and CT number accuracy under realistic flow conditionsResults: This phantom and its surrounding flow system are capable of creating a wide range of physiologically relevant TACs, which are reproducible with minimal error between experiments ({sigma}/{mu} < 5% for all metrics investigated). The dynamic flow phantom was capable of producing input and output TACs using

  10. Seasonal leaf dynamics for tropical evergreen forests in a process-based global ecosystem model

    NASA Astrophysics Data System (ADS)

    De Weirdt, M.; Verbeeck, H.; Maignan, F.; Peylin, P.; Poulter, B.; Bonal, D.; Ciais, P.; Steppe, K.

    2012-09-01

    The influence of seasonal phenology on canopy photosynthesis in tropical evergreen forests remains poorly understood, and its representation in global ecosystem models is highly simplified, typically with no seasonal variation of canopy leaf properties taken into account. Including seasonal variation in leaf age and photosynthetic capacity could improve the correspondence of global vegetation model outputs with the wet-dry season CO2 patterns measured at flux tower sites in these forests. We introduced a leaf litterfall dynamics scheme in the global terrestrial ecosystem model ORCHIDEE based on seasonal variations in net primary production (NPP), resulting in higher leaf turnover in periods of high productivity. The modifications in the leaf litterfall scheme induce seasonal variation in leaf age distribution and photosynthetic capacity. We evaluated the results of the modification against seasonal patterns of three long-term in-situ leaf litterfall datasets of evergreen tropical forests in Panama, French Guiana and Brazil. In addition, we evaluated the impact of the model improvements on simulated latent heat (LE) and gross primary productivity (GPP) fluxes for the flux tower sites Guyaflux (French Guiana) and Tapajós (km 67, Brazil). The results show that the introduced seasonal leaf litterfall corresponds well with field inventory leaf litter data and times with its seasonality. Although the simulated litterfall improved substantially by the model modifications, the impact on the modelled fluxes remained limited. The seasonal pattern of GPP improved clearly for the Guyaflux site, but no significant improvement was obtained for the Tapajós site. The seasonal pattern of the modelled latent heat fluxes was hardly changed and remained consistent with the observed fluxes. We conclude that we introduced a realistic and generic litterfall dynamics scheme, but that other processes need to be improved in the model to achieve better simulations of GPP seasonal patterns

  11. High temporal resolution dynamic contrast MRI in a high risk group for placenta accreta.

    PubMed

    Tanaka, Y O; Sohda, S; Shigemitsu, S; Niitsu, M; Itai, Y

    2001-06-01

    Antenatal diagnosis of placenta accreta with MR is not easy even now because T2-weighted images (T2WI) cannot differentiate chorionic villi from decidua basalis. We performed dynamic contrast MRI to study whether trophoblastic villi could be separately demonstrated from the decidua basalis, and whether the contrast resolution between the placenta and myometrium could improve compared to T2WI. Six pregnant women with prior cesarean section were examined at 34-38 gestational weeks. Sagittal T2-weighted images with fast spin echo sequences and dynamic contrast studies with fast field echo sequence every 10-14 s after contrast injection were performed. We analyzed the enhancing pattern of the placenta and compared the contrast between placenta and myometrium. We reviewed medical records to identify complications during the placental delivery and the complications of their newborns. In the early phase after contrast enhancement, multiple foci of the strong lobular enhancement were observed in all cases. Other parts of placenta were slowly but strongly enhanced following them. We speculated that the former corresponded to intervillous space and the latter decidua basalis. The contrast between placenta and myometrium tended to be distinct near the inner cervical os on both T2WI and dynamic contrast study. On the other hand, it was indistinct in the upper part of the uterine body on T2WI despite it was clearly demonstrated on dynamic contrast study. The placentae were delivered without any complication in all cases. Although two neonates showed fetal distress, none of the infant remained any sequelae at the time of the discharge. The other four were well although one of them complicated with meconium staining. As dynamic contrast MRI can differentiate chorionic villi and decidua basalis, and can provide excellent contrast between placenta and myometrium at anywhere within the uterus, it may be a promising technique for antepartum diagnosis of the placenta accreta. PMID

  12. Structured and Unstructured Musical Contexts and Children's Ability to Demonstrate Tempo and Dynamic Contrasts.

    ERIC Educational Resources Information Center

    Flowers, Patricia J.; Wapnick, Joel; Ramsey, LaShell

    1997-01-01

    Tested 5- through 9-year-old children in structured and unstructured contexts to determine their ability to demonstrate contrasts in tempo and dynamics using a synthesizer keyboard. Shows that they were able to demonstrate contrasts in loudness and duration. Reports further results based on varied environmental situations. (DSK)

  13. Seasonal-Resolution δ18O in Speleothems by Ion Microprobe: Revealing Asian Monsoon Dynamics

    NASA Astrophysics Data System (ADS)

    Orland, I. J.; Edwards, R. L.; Cheng, H.; Kozdon, R.; Valley, J. W.

    2014-12-01

    Over the last decade, ion microprobe analysis of speleothems (cave carbonates) has increased the temporal resolution of their oxygen isotope (δ18O) paleoclimate proxy records. Recent improvements in methodology, standardization, and imaging at the WiscSIMS lab make it possible to examine sub-annual patterns of δ18O variability at 10-µm-scale, revealing new seasonal paleoenvironmental information. We applied this technique to an important suite of Chinese stalagmites with conventional drill-sampled δ18O records that reflect changes in Asian Monsoon dynamics across the last deglaciation. Seasonal-resolution δ18O analyses in the Chinese stalagmites reveal regular patterns of annual δ18O variability. Quantitative assessment of the patterns identifies two important components in the δ18O records. First, the source and rainout histories of water vapors that ultimately yield rainfall over China play a primary role in determining the δ18O value of speleothem calcite year-round. Second, intra-annual patterns of calcite δ18O variability indicate that the annual proportion of monsoon precipitation changes systematically during the last deglaciation; the annual proportion of monsoon rainfall is greater during the Holocene and Bølling-Allerød than during the Younger Dryas. This is the first time these components have been characterized in any speleothem δ18O record of monsoon dynamics because seasonal δ18O variability is lost by conventional drill-sampling. Ion microprobe analysis of speleothems can also produce year-by-year records of δ18O across abrupt climate change events. At the Younger Dryas-Holocene transition in a Kulishu Cave stalagmite, which spanned 16 years at 11.53 ky BP, there is a relatively smooth decrease in year-round δ18O(calcite). In contrast, the intra-annual δ18O patterns indicate that the increase in the annual proportion of monsoon rainfall across this transition is stochastic, implying that this record can distinguish the regional

  14. Contrast-enhanced dynamic magnetic resonance nephrography in healthy dogs.

    PubMed

    Fonseca-Matheus, J M; Pérez-García, C C; Ginja, M M D; Altónaga, J R; Orden, M A; Gonzalo-Orden, J M

    2011-09-01

    Twenty-three healthy mixed-breed male adult dogs were examined using serial magnetic resonance (MR) renograms. The images were obtained using a dynamic gradient-echo, fast SPGR, T1-weighted sequence and low doses of gadolinium chelates (0.025 mmol/kg). Time-intensity curves were obtained to assess typical urinary excretion parameters, namely, time to vascular peak (TVP), time to vascular drop (TVD), time to glomerular peak (TGP), parenchymal phase length (PPL), gradient of parenchymal phase (GPP) and pattern of excretory segment. The mean TVP, TVD, TGP and PPL were 31.6±11.8, 43.4±11.2, 154.0±36.2 and 115.2±37.7s, respectively. The GPP was 24.1±8.6% of signal intensity per min. The excretory segment was concave in all cases, and at the end of the examination, 87.1% of kidneys had shown a reduction in signal intensity of 50%. This MR nephrography protocol can provide adequate time-intensity curve parameters for the urinary system of dogs, offers excellent anatomical detail, and represents an alternative to radionuclide nephrography. PMID:20810295

  15. Nonrigid registration and classification of the kidneys in 3D dynamic contrast enhanced (DCE) MR images

    NASA Astrophysics Data System (ADS)

    Yang, Xiaofeng; Ghafourian, Pegah; Sharma, Puneet; Salman, Khalil; Martin, Diego; Fei, Baowei

    2012-02-01

    We have applied image analysis methods in the assessment of human kidney perfusion based on 3D dynamic contrast-enhanced (DCE) MRI data. This approach consists of 3D non-rigid image registration of the kidneys and fuzzy C-mean classification of kidney tissues. The proposed registration method reduced motion artifacts in the dynamic images and improved the analysis of kidney compartments (cortex, medulla, and cavities). The dynamic intensity curves show the successive transition of the contrast agent through kidney compartments. The proposed method for motion correction and kidney compartment classification may be used to improve the validity and usefulness of further model-based pharmacokinetic analysis of kidney function.

  16. Carbon dynamics and their link to dissolved organic matter quality across contrasting stream ecosystems.

    PubMed

    Bodmer, Pascal; Heinz, Marlen; Pusch, Martin; Singer, Gabriel; Premke, Katrin

    2016-05-15

    Streams represent active components of the carbon cycle as emitters of carbon dioxide (CO2) and methane to the atmosphere at a global scale. However, the mechanisms and governing factors of these emissions are still largely unknown, especially concerning the effect of land use. We compared dissolved and gaseous carbon dynamics in streams bordered by contrasting types of land use, specifically agriculture and forest. Carbon dioxide and methane partial pressures (pCO2 and pCH4, respectively) in the water body and carbon emissions via both gases were studied for 24h during four field expeditions. pCH4 did not differ between the two system types. pCO2 was constantly oversaturated in all streams and significantly higher in agricultural streams (annual mean 4282ppm) compared to forest streams (annual mean 2189ppm) during all seasons. However, emissions of CO2 were not significantly different between the stream types due to significantly higher gas transfer velocity in forest compared to agricultural streams. pCO2 was significantly positively correlated to the concentrations of dissolved organic carbon, dissolved nitrogen and soluble reactive phosphorus in the water. Furthermore, pCO2 was correlated to optical parameters of dissolved organic matter (DOM) quality, e.g., it increased with indicators of molecular size and an allochthonous fluorescent component identified by Parallel Factor Analysis (PARAFAC). This study demonstrates that different forms of land use may trigger a cascade of effects on the carbon production and emission of streams linked to changes in DOM quality. PMID:26938320

  17. Effects of drought - altered seasonality and low rainfall - in net ecosystem carbon exchange of three contrasting Mediterranean ecosystems

    NASA Astrophysics Data System (ADS)

    Pereira, J. S.; Mateus, J. A.; Aires, L. M.; Pita, G.; Pio, C.; Andrade, V.; Banza, J.; David, T. S.; Rodrigues, A.; David, J. S.

    2007-06-01

    Droughts cause reductions in gross primary production (GPP) and also in net ecosystem exchange (NEE), contributing to most of the inter-annual variability in terrestrial carbon sequestration. In seasonally dry climates (Mediterranean) droughts result from reductions in annual rainfall and from changes in rain seasonality. In western Iberia, the hydrological-year (i.e., from October to September) of 2004-2005 was extremely dry, with precipitation 50% below the long-term mean (691 mm in 1961-1990), but 2005-2006 was normal. We compared the carbon fluxes measured by the eddy covariance technique from three contrasting ecosystems in southern Portugal: an evergreen oak woodland (savannah-like) with ca. 21% tree cover; a Mediterranean C3/C4 grassland; and a coppiced eucalyptus plantation. During the dry hydrological-year of 2004-2005, NEE was lowest, the highest sink strength was in the eucalypt plantation (NEE = -399 g C m -2 year-1) as compared to the oak woodland (NEE = -88 g C m -2 year-1), and the grassland (NEE = +49 g C m -2 year -1). The latter was a source of carbon dioxide. The NEE values of the dry year were, however, much lower than those for wetter years, e.g. NEE = -861 g C m-2 year -1 in 2002-2003 in the eucalypt plantation. The NEE of the grassland and the oak savannah in the 2005-2006 hydrological-year, with annual precipitation above the long term mean, were -190 and -120 g C m -2 year-1, respectively. All ecosystems studied increased their rain-use efficiency (GPP per unit of rain volume) increased in dry years. In the case of annual vegetation - grassland and low tree density woodland, however &ndash, rain-use efficiency decreased with severe drought. However, this was more pronounced in the eucalypt plantation due to greater GPP and the use of deep soil water resources. Although both calendar years of 2004 and 2005 had equally low rainfall, the effect of drought on the eucalypt plantation was delayed until the second dry year. This suggests that the

  18. Food web dynamics in a seasonally varying wetland

    USGS Publications Warehouse

    DeAngelis, D.L.; Trexler, J.C.; Donalson, D.D.

    2008-01-01

    A spatially explicit model is developed to simulate the small fish community and its underlying food web, in the freshwater marshes of the Everglades. The community is simplified to a few small fish species feeding on periphyton and invertebrates. Other compartments are detritus, crayfish, and a piscivorous fish species. This unit food web model is applied to each of the 10,000 spatial cells on a 100 x 100 pixel landscape. Seasonal variation in water level is assumed and rules are assigned for fish movement in response to rising and falling water levels, which can cause many spatial cells to alternate between flooded and dry conditions. It is shown that temporal variations of water level on a spatially heterogeneous landscape can maintain at least three competing fish species. In addition, these environmental factors can strongly affect the temporal variation of the food web caused by top-down control from the piscivorous fish.

  19. Clustered breast microcalcifications: Evaluation by dynamic contrast-enhanced subtraction MRI

    SciTech Connect

    Gilles, R.; Tardivon, A.A.; Vanel, D.; Guinebretiere, J.M.; Arriagada, R.

    1996-01-01

    Our goal was to evaluate dynamic contrast-enhanced subtraction MRI in the diagnosis of isolated clustered calcifications of the breast. One hundred seventy-two patients underwent surgical biopsy for isolated clustered breast calcifications. Their mammograms showed round (n = 88) or linear/irregular (n = 84) microcalcifications. All patients had a preoperative Gd-DOTA-enhanced subtraction dynamic study. Any early contrast enhancement in the breast parenchyma concomitant with early enhancement of normal vessels was considered positive. Fifty-eight in situ carcinomas, 22 invasive carcinomas, and 92 benign lesions were found at histological analysis. Dynamic MR sequences showed early contrast enhancement in 76 of 80 malignant lesions (sensitivity 95%) and in 45 of 92 benign lesions (specificity 51%). Two invasive and two intraductal carcinomas did not show early contrast enhancement. Three independent observers agreed in rating early contrast enhancement in 143 of 172 lesions. Poor specificity limits the diagnostic accuracy of dynamic contrast-enhanced subtraction MRI in distinguishing benign from malignant microcalcifications on mammography. 8 refs., 2 figs., 2 tabs.

  20. Review of dynamic contrast-enhanced ultrasound guidance in ablation therapy for hepatocellular carcinoma

    PubMed Central

    Minami, Yasunori; Kudo, Masatoshi

    2011-01-01

    Local ablative techniques-percutaneous ethanol injection, microwave coagulation therapy and radiofrequency ablation (RFA)-have been developed to treat unresectable hepatocellular carcinoma (HCC). The success rate of percutaneous ablation therapy for HCC depends on correct targeting of the tumor via an imaging technique. However, probe insertion often is not completely accurate for small HCC nodules, which are poorly defined on conventional B-mode ultrasound (US) alone. Thus, multiple sessions of ablation therapy are frequently required in difficult cases. By means of two breakthroughs in US technology, harmonic imaging and the development of second-generation contrast agents, dynamic contrast-enhanced harmonic US imaging with an intravenous contrast agent can depict tumor vascularity sensitively and accurately, and is able to evaluate small hypervascular HCCs even when B-mode US cannot adequately characterize the tumors. Therefore, dynamic contrast-enhanced US can facilitate RFA electrode placement in hypervascular HCC, which is poorly depicted by B-mode US. The use of dynamic contrast-enhanced US guidance in ablation therapy for liver cancer is an efficient approach. Here, we present an overview of the current status of dynamic contrast-enhanced US-guided ablation therapy, and summarize the current indications and outcomes of reported clinical use in comparison with that of other modalities. PMID:22174544

  1. Characterizing the Seasonal Dynamics of Plant Community Photosynthesis Across a Range of Vegetation Types

    SciTech Connect

    Gu, Lianhong; Post, Wilfred M; Baldocchi, Dennis; Black, Andy; Suyker, A.E.,; Verma, Shashi; Vesala, Timo; Wofsy, Steve

    2009-01-01

    The seasonal cycle of plant community photosynthesis is one of the most important biotic oscillations to mankind. This study built upon previous efforts to develop a comprehensive framework to studying this cycle systematically with eddy covariance flux measurements. We proposed a new function to represent the cycle and generalized a set of phenological indices to quantify its dynamic characteristics. We suggest that the seasonal variation of plant community photosynthesis generally consists of five distinctive phases in sequence each of which results from the interaction between the inherent biological and ecological processes and the progression of climatic conditions and reflects the unique functioning of plant community at different stages of the growing season. We applied the improved methodology to seven vegetation sites ranging from evergreen and deciduous forests to crop to grasslands and covering both cool-season (vegetation active during cool months, e.g. Mediterranean climate grasslands) and warm-season (vegetation active during warm months, e.g. temperate and boreal forests) vegetation types. Our application revealed interesting phenomena that had not been reported before and pointed to new research directions. We found that for the warm-season vegetation type, the recovery of plant community photosynthesis at the beginning of the growing season was faster than the senescence at the end of the growing season while for the coolseason vegetation type, the opposite was true. Furthermore, for the warm-season vegetation type, the recovery was closely correlated with the senescence such that a faster photosynthetic recovery implied a speedier photosynthetic senescence and vice versa. There was evidence that a similar close correlation could also exist for the cool-season vegetation type, and furthermore, the recovery-senescence relationship may be invariant between the warm-season and cool-season vegetation types up to an offset in the intercept. We also

  2. Dynamic Contrast-Enhanced MRI of Cervical Cancers: Temporal Percentile Screening of Contrast Enhancement Identifies Parameters for Prediction of Chemoradioresistance

    SciTech Connect

    Andersen, Erlend K.F.; Hole, Knut Hakon; Lund, Kjersti V.; Sundfor, Kolbein; Kristensen, Gunnar B.; Lyng, Heidi; Malinen, Eirik

    2012-03-01

    Purpose: To systematically screen the tumor contrast enhancement of locally advanced cervical cancers to assess the prognostic value of two descriptive parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Methods and Materials: This study included a prospectively collected cohort of 81 patients who underwent DCE-MRI with gadopentetate dimeglumine before chemoradiotherapy. The following descriptive DCE-MRI parameters were extracted voxel by voxel and presented as histograms for each time point in the dynamic series: normalized relative signal increase (nRSI) and normalized area under the curve (nAUC). The first to 100th percentiles of the histograms were included in a log-rank survival test, resulting in p value and relative risk maps of all percentile-time intervals for each DCE-MRI parameter. The maps were used to evaluate the robustness of the individual percentile-time pairs and to construct prognostic parameters. Clinical endpoints were locoregional control and progression-free survival. The study was approved by the institutional ethics committee. Results: The p value maps of nRSI and nAUC showed a large continuous region of percentile-time pairs that were significantly associated with locoregional control (p < 0.05). These parameters had prognostic impact independent of tumor stage, volume, and lymph node status on multivariate analysis. Only a small percentile-time interval of nRSI was associated with progression-free survival. Conclusions: The percentile-time screening identified DCE-MRI parameters that predict long-term locoregional control after chemoradiotherapy of cervical cancer.

  3. Seasonal differences in aerosol abundance and radiative forcing in months of contrasting emissions and rainfall over northern South Asia

    NASA Astrophysics Data System (ADS)

    Sadavarte, P.; Venkataraman, C.; Cherian, R.; Patil, N.; Madhavan, B. L.; Gupta, T.; Kulkarni, S.; Carmichael, G. R.; Adhikary, B.

    2016-01-01

    A modeling framework was used to examine gaps in understanding of seasonal and spatial heterogeneity in aerosol abundance and radiative forcing over northern South Asia, whose glimpses are revealed in observational studies. Regionally representative emissions were used in chemical transport model simulations at a spatial resolution of 60 × 60 km2, in April, July and September, chosen as months of contrasting emissions and rainfall. Modeled aerosol abundance in northern South Asia was predominantly found to be dust and carbonaceous in April, dust and sulfate in July and sulfate and carbonaceous in September. Anthropogenic aerosols arose from energy-use emissions (from industrial sources, residential biofuel cooking, brick kilns) in all months, additionally from field burning in April, and incursion from East Asia in September. In April, carbonaceous aerosols were abundant from open burning of agricultural fields even at high altitude locations (Godavari), and of forests in the eastern Gangetic Plain (Kolkata). Direct radiative forcing and heating rate, calculated from OPAC-SBDART, using modeled aerosol fields, and corrected by MODIS AOD observations, showed regionally uniform atmospheric forcing in April, compared to that in other months, influenced by both dust and black carbon abundance. A strong spatial heterogeneity of radiative forcing and heating rate was found, with factor of 2.5-3.5 lower atmospheric forcing over the Tibet plateau than that over the Ganga Plain and Northwest in July and September. However, even over the remote Tibet plateau, there was significant anthropogenic contribution to atmospheric forcing and heating rate (45% in Apr, 75% in Sep). Wind fields showed black carbon transport from south Asia in April and east Asia in September. Further evaluation of the transport of dust and anthropogenic emissions from various source regions and their deposition in the Himalaya and Tibet, is important in understanding regional air quality and climate

  4. Seasonal Variations of the James Webb Space Telescope Orbital Dynamics

    NASA Technical Reports Server (NTRS)

    Brown, Jonathan; Petersen, Jeremy; Villac, Benjamin; Yu, Wayne

    2015-01-01

    While spacecraft orbital variations due to the Earth's tilt and orbital eccentricity are well-known phenomena, the implications for the James Webb Space Telescope present unique features. We investigate the variability of the observatory trajectory characteristics, and present an explanation of some of these effects using invariant manifold theory and local approximation of the dynamics in terms of the restricted three-body problem.

  5. Optimized dynamic contrast-enhanced cone-beam CT for target visualization during liver SBRT

    NASA Astrophysics Data System (ADS)

    Jones, Bernard L.; Altunbas, Cem; Kavanagh, Brian; Schefter, Tracey; Miften, Moyed

    2014-03-01

    The pharmacokinetic behavior of iodine contrast agents makes it difficult to achieve significant enhancement during contrast-enhanced cone-beam CT (CE-CBCT). This study modeled this dynamic behavior to optimize CE-CBCT and improve the localization of liver lesions for SBRT. We developed a model that allows for controlled study of changing iodine concentrations using static phantoms. A projection database consisting of multiple phantom images of differing iodine/scan conditions was built. To reconstruct images of dynamic hepatic concentrations, hepatic contrast enhancement data from conventional CT scans were used to re-assemble the projections to match the expected amount of contrast. In this way the effect of various parameters on image quality was isolated, and using our dynamic model we found parameters for iodine injection, CBCT scanning, and injection/scanning timing which optimize contrast enhancement. Increasing the iodine dose, iodine injection rate, and imaging dose led to significant increases in signal-to-noise ratio (SNR). Reducing the CBCT imaging time also increased SNR, as the image can be completed before the iodine exits the liver. Proper timing of image acquisition played a significant role, as a 30 second error in start time resulted in a 40% SNR decrease. The effect of IV contrast is severely degraded in CBCT, but there is promise that, with optimization of the injection and scan parameters to account for iodine pharmacokinetics, CE-CBCT which models venous-phase blood flow kinetics will be feasible for accurate localization of liver lesions.

  6. Monthly to seasonal low flow prediction: statistical versus dynamical models

    NASA Astrophysics Data System (ADS)

    Ionita-Scholz, Monica; Klein, Bastian; Meissner, Dennis; Rademacher, Silke

    2016-04-01

    While the societal and economical impacts of floods are well documented and assessable, the impacts of lows flows are less studied and sometimes overlooked. For example, over the western part of Europe, due to intense inland waterway transportation, the economical loses due to low flows are often similar compared to the ones due to floods. In general, the low flow aspect has the tendency to be underestimated by the scientific community. One of the best examples in this respect is the facts that at European level most of the countries have an (early) flood alert system, but in many cases no real information regarding the development, evolution and impacts of droughts. Low flows, occurring during dry periods, may result in several types of problems to society and economy: e.g. lack of water for drinking, irrigation, industrial use and power production, deterioration of water quality, inland waterway transport, agriculture, tourism, issuing and renewing waste disposal permits, and for assessing the impact of prolonged drought on aquatic ecosystems. As such, the ever-increasing demand on water resources calls for better a management, understanding and prediction of the water deficit situation and for more reliable and extended studies regarding the evolution of the low flow situations. In order to find an optimized monthly to seasonal forecast procedure for the German waterways, the Federal Institute of Hydrology (BfG) is exploring multiple approaches at the moment. On the one hand, based on the operational short- to medium-range forecasting chain, existing hydrological models are forced with two different hydro-meteorological inputs: (i) resampled historical meteorology generated by the Ensemble Streamflow Prediction approach and (ii) ensemble (re-) forecasts of ECMWF's global coupled ocean-atmosphere general circulation model, which have to be downscaled and bias corrected before feeding the hydrological models. As a second approach BfG evaluates in cooperation with

  7. Seasonality and Dynamic Spatial Contagion of Air Pollution in 42 Chinese Cities

    PubMed Central

    He, Zhanqiong; Sriboonchita, Songsak; He, Min

    2013-01-01

    To monitor and improve the urban air quality, the Chinese government has begun to make many efforts, and the interregional cooperation to cut and improve air quality has been required. In this paper, we focus on the seasonality of the first and second moments of the daily air pollution indexes (APIs) of 42 Chinese sample cities over 10 years, from June 5, 2000 to March 4, 2010, and investigate the dynamic correlation of air pollution indexes (APIs) between 42 Chinese cities and their corresponding regional and national levels; comparison with the model without seasonal consideration is made. By adopting a DCC-GARCH model that accounts for the seasonality, we found that (i) the transformed DCC-GARCH model including seasonality dummies improves the estimation result in this study; (ii) the seasonality feature of the second moment follows that of the first moment, with the condition mean and variance of the second and autumn significantly lower than spring, whereas that of winter is higher than spring; (iii) the correlation between local APIs and their corresponding regional and national levels is dynamic; (iv) comparing with the DCC-GARCH model estimation, the transformed model does not change the feature of the dynamic correlations very much. PMID:23533348

  8. Diversity in plant hydraulic traits explains seasonal and inter-annual variations of vegetation dynamics in seasonally dry tropical forests.

    PubMed

    Xu, Xiangtao; Medvigy, David; Powers, Jennifer S; Becknell, Justin M; Guan, Kaiyu

    2016-10-01

    We assessed whether diversity in plant hydraulic traits can explain the observed diversity in plant responses to water stress in seasonally dry tropical forests (SDTFs). The Ecosystem Demography model 2 (ED2) was updated with a trait-driven mechanistic plant hydraulic module, as well as novel drought-phenology and plant water stress schemes. Four plant functional types were parameterized on the basis of meta-analysis of plant hydraulic traits. Simulations from both the original and the updated ED2 were evaluated against 5 yr of field data from a Costa Rican SDTF site and remote-sensing data over Central America. The updated model generated realistic plant hydraulic dynamics, such as leaf water potential and stem sap flow. Compared with the original ED2, predictions from our novel trait-driven model matched better with observed growth, phenology and their variations among functional groups. Most notably, the original ED2 produced unrealistically small leaf area index (LAI) and underestimated cumulative leaf litter. Both of these biases were corrected by the updated model. The updated model was also better able to simulate spatial patterns of LAI dynamics in Central America. Plant hydraulic traits are intercorrelated in SDTFs. Mechanistic incorporation of plant hydraulic traits is necessary for the simulation of spatiotemporal patterns of vegetation dynamics in SDTFs in vegetation models. PMID:27189787

  9. Coccolithophore Dynamics In Alfonso Basin: Seasonal Variation And Species Composition

    NASA Astrophysics Data System (ADS)

    Cortés, M. Y.; Urcádiz-Cázares, F. J.; Silverberg, N.; Aguirre-Bahena, F.; Bollmann, J.

    2007-05-01

    The production of organic and inorganic carbon by coccolithophores is considered to play a significant role in the global carbon cycle. Therefore, detailed knowledge of their vertical flux is needed. Here we present a time-series record of coccolithophore standing stock and vertical coccolith flux from Alfonso Basin, southwest coast of the Gulf of California. This location is of particular interest as it is very sensitive to changes in environmental conditions and these may be preserved in laminated underlying sediments. Coccolithophore standing stock and assemblage composition were obtained from plankton samples taken at 3- month intervals during 2002-2003. Furthermore, coccolith flux and species composition were determined in samples from a time-series sediment trap (sampling intervals 7-14 days) deployed at 350 m depth from January 2002 to October 2003. The coccolithophore standing stock and coccolith flux varied considerably between sampling periods but, in general, a seasonal pattern was apparent, with low fluxes in spring-summer and maximal values in autumn- winter. During 2002, fluxes ranged from 0.02x108 coccoliths m-2 d-1 in summer to 64.7x108 coccoliths m-2 d-1 in autumn. Values increased considerably during 2003: registering 52.4 x108 coccoliths m-2 d-1 in spring to the highest (128.8x108 coccoliths m-2 d-1) in late summer/autumn. The latter are related to hurricanes that occurred during the sampling period. In total 47 taxa were identified but only three species, Gephyrocapsa oceanica (43.6%), Emiliania huxleyi (28%) and Florisphera profunda (15.7%), constituted 88 percent of the total coccolith flux. This corresponds to the species composition observed in the water column. G. oceanica was always present and its flux pattern followed that of the total flux. The flux of E. huxleyi remained almost constant during the observed time period whereas F. profunda showed peak fluxes in autumn. Although the cosmopolitan species E. huxleyi has been considered the

  10. Measurement of nano-particle diffusion in the simulated dynamic light scattering by contrast of dynamic images

    NASA Astrophysics Data System (ADS)

    Wu, Xiaobin; Qiu, Jian; Luo, Kaiqing; Han, Peng

    2015-08-01

    Dynamic Light Scattering is used for measuring particle size distribution of nano-particle under Brownian motion. Signal is detected through a photomultiplier and processed by correlation analysis, and results are inverted at last. Method by using CCD camera can record the procedure of motion. However, there are several weaknesses such as low refresh speed and noise from CCD camera, and this method depends on particle size and detecting angle. A simulation of nano-particle under Brownian motion is proposed to record dynamic images, studies contrast of dynamic images which can represent speed of diffusion, and its characteristic under different conditions. The results show that through contrast of dynamic images diffusion coefficient can be obtained, which is independent on density of scattering volume.

  11. Seasonal Population Dynamics and Kernel Damage of the Brown Stink Bug (Heteroptera: Pentatomidae) in Corn

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seasonal population dynamics of the brown stink bug, Euschistus servus (Say) (Heteroptera: Pentatomidae) in corn was monitored weekly using pheromone traps between May and September in 2005 and 2006. Ten traps were used per field (ca. one acre), and three fields were used each year. The number of ...

  12. Age distribution and seasonal dynamics of abomasal helminths in wild red deer from central Spain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study on age distribution and seasonal dynamics of abomasal helminths in wild red deer was conducted in Central Spain, by monthly samplings of fawns ( 2 yr) animals. Both intensity and prevalence of abomasal parasitism was higher in older animals, particularl...

  13. Optical tracking of contrast medium bolus to optimize bolus shape and timing in dynamic computed tomography

    NASA Astrophysics Data System (ADS)

    Eisa, Fabian; Brauweiler, Robert; Peetz, Alexander; Hupfer, Martin; Nowak, Tristan; Kalender, Willi A.

    2012-05-01

    One of the biggest challenges in dynamic contrast-enhanced CT is the optimal synchronization of scan start and duration with contrast medium administration in order to optimize image contrast and to reduce the amount of contrast medium. We present a new optically based approach, which was developed to investigate and optimize bolus timing and shape. The time-concentration curve of an intravenously injected test bolus of a dye is measured in peripheral vessels with an optical sensor prior to the diagnostic CT scan. The curves can be used to assess bolus shapes as a function of injection protocols and to determine contrast medium arrival times. Preliminary results for phantom and animal experiments showed the expected linear behavior between dye concentration and absorption. The kinetics of the dye was compared to iodinated contrast medium and was found to be in good agreement. The contrast enhancement curves were reliably detected in three mice with individual bolus shapes and delay times of 2.1, 3.5 and 6.1 s, respectively. The optical sensor appears to be a promising approach to optimize injection protocols and contrast enhancement timing and is applicable to all modalities without implying any additional radiation dose. Clinical tests are still necessary.

  14. A quantitative evaluation of the dynamic cathodoluminescence contrast of gliding dislocations in semiconductor crystals

    NASA Astrophysics Data System (ADS)

    Vasnyov, S.; Schreiber, J.; Hoering, L.

    2004-01-01

    Dark cathodoluminescence (CL) defect contrasts observed in CL video movies taken on GaAs and ZnO samples disclose the intrinsic recombination properties of glide dislocations during their slip motion. This way, the kinematical SEM CL microscopy provides, for the first time, direct information on the possible relationship between the dynamics and electronic activity of glide dislocations as expected from structural alterations or kink processes related to defect movement. The dark CL defect contrasts observed for various dislocation types in both materials indicate defect-bound non-radiative excess carrier recombination. Quantitative CL contrast analysis is performed to discover differences in the recombination strength of distinct dislocation structures resulting from the type and dynamic state of the glide dislocations studied.

  15. In vivo optical imaging and dynamic contrast methods for biomedical research

    PubMed Central

    Hillman, Elizabeth M. C.; Amoozegar, Cyrus B.; Wang, Tracy; McCaslin, Addason F. H.; Bouchard, Matthew B.; Mansfield, James; Levenson, Richard M.

    2011-01-01

    This paper provides an overview of optical imaging methods commonly applied to basic research applications. Optical imaging is well suited for non-clinical use, since it can exploit an enormous range of endogenous and exogenous forms of contrast that provide information about the structure and function of tissues ranging from single cells to entire organisms. An additional benefit of optical imaging that is often under-exploited is its ability to acquire data at high speeds; a feature that enables it to not only observe static distributions of contrast, but to probe and characterize dynamic events related to physiology, disease progression and acute interventions in real time. The benefits and limitations of in vivo optical imaging for biomedical research applications are described, followed by a perspective on future applications of optical imaging for basic research centred on a recently introduced real-time imaging technique called dynamic contrast-enhanced small animal molecular imaging (DyCE). PMID:22006910

  16. In vivo optical imaging and dynamic contrast methods for biomedical research.

    PubMed

    Hillman, Elizabeth M C; Amoozegar, Cyrus B; Wang, Tracy; McCaslin, Addason F H; Bouchard, Matthew B; Mansfield, James; Levenson, Richard M

    2011-11-28

    This paper provides an overview of optical imaging methods commonly applied to basic research applications. Optical imaging is well suited for non-clinical use, since it can exploit an enormous range of endogenous and exogenous forms of contrast that provide information about the structure and function of tissues ranging from single cells to entire organisms. An additional benefit of optical imaging that is often under-exploited is its ability to acquire data at high speeds; a feature that enables it to not only observe static distributions of contrast, but to probe and characterize dynamic events related to physiology, disease progression and acute interventions in real time. The benefits and limitations of in vivo optical imaging for biomedical research applications are described, followed by a perspective on future applications of optical imaging for basic research centred on a recently introduced real-time imaging technique called dynamic contrast-enhanced small animal molecular imaging (DyCE). PMID:22006910

  17. Dynamical analysis of seasonal migrating population; the effect of regular hunting to the coexistence

    NASA Astrophysics Data System (ADS)

    Sambas, T. J. M.; Khaliq, B. F.; Waluyo, D. S. Y. S.; Putra, P. S.; Soewono, E.

    2016-04-01

    Seasonal migration among wild populations is commonly seen especially in the wild life region. The migration takes place during a certain season where logistical condition and the existing territory can no longer support the life of the whole population. In this case portion of the population migrate to the better place as part of their survival, and returning back to the home place when the logistical condition is improved. Here we model the dynamic of North-South annual migration of Impala population in Zimbabwe, where portion of population in the Southern part move to the North in the beginning of the dry season and portion of them return back to the South in the wet season. Here the North area has a better environmental carrying capacity than the South. Different processes take place during the year, partial migration to the south (during the month of December and January), partial migration to the north (during the month of June and July), and birth process (during the month of November and December). We construct a discrete dynamical model for simulating the annual migrating process. It is found that a stable co-existence always occurs when no hunting takes place in all season. When hunting is allowed, the co-existence could be severely affected. We obtain here a threshold condition for co-existence and show numerical simulations for different hunting scenarios.

  18. Human birth seasonality: latitudinal gradient and interplay with childhood disease dynamics.

    PubMed

    Martinez-Bakker, Micaela; Bakker, Kevin M; King, Aaron A; Rohani, Pejman

    2014-05-22

    More than a century of ecological studies have demonstrated the importance of demography in shaping spatial and temporal variation in population dynamics. Surprisingly, the impact of seasonal recruitment on infectious disease systems has received much less attention. Here, we present data encompassing 78 years of monthly natality in the USA, and reveal pronounced seasonality in birth rates, with geographical and temporal variation in both the peak birth timing and amplitude. The timing of annual birth pulses followed a latitudinal gradient, with northern states exhibiting spring/summer peaks and southern states exhibiting autumn peaks, a pattern we also observed throughout the Northern Hemisphere. Additionally, the amplitude of United States birth seasonality was more than twofold greater in southern states versus those in the north. Next, we examined the dynamical impact of birth seasonality on childhood disease incidence, using a mechanistic model of measles. Birth seasonality was found to have the potential to alter the magnitude and periodicity of epidemics, with the effect dependent on both birth peak timing and amplitude. In a simulation study, we fitted an susceptible-exposed-infected-recovered model to simulated data, and demonstrated that ignoring birth seasonality can bias the estimation of critical epidemiological parameters. Finally, we carried out statistical inference using historical measles incidence data from New York City. Our analyses did not identify the predicted systematic biases in parameter estimates. This may be owing to the well-known frequency-locking between measles epidemics and seasonal transmission rates, or may arise from substantial uncertainty in multiple model parameters and estimation stochasticity. PMID:24695423

  19. Predicting the evolutionary dynamics of seasonal adaptation to novel climates in Arabidopsis thaliana.

    PubMed

    Fournier-Level, Alexandre; Perry, Emily O; Wang, Jonathan A; Braun, Peter T; Migneault, Andrew; Cooper, Martha D; Metcalf, C Jessica E; Schmitt, Johanna

    2016-05-17

    Predicting whether and how populations will adapt to rapid climate change is a critical goal for evolutionary biology. To examine the genetic basis of fitness and predict adaptive evolution in novel climates with seasonal variation, we grew a diverse panel of the annual plant Arabidopsis thaliana (multiparent advanced generation intercross lines) in controlled conditions simulating four climates: a present-day reference climate, an increased-temperature climate, a winter-warming only climate, and a poleward-migration climate with increased photoperiod amplitude. In each climate, four successive seasonal cohorts experienced dynamic daily temperature and photoperiod variation over a year. We measured 12 traits and developed a genomic prediction model for fitness evolution in each seasonal environment. This model was used to simulate evolutionary trajectories of the base population over 50 y in each climate, as well as 100-y scenarios of gradual climate change following adaptation to a reference climate. Patterns of plastic and evolutionary fitness response varied across seasons and climates. The increased-temperature climate promoted genetic divergence of subpopulations across seasons, whereas in the winter-warming and poleward-migration climates, seasonal genetic differentiation was reduced. In silico "resurrection experiments" showed limited evolutionary rescue compared with the plastic response of fitness to seasonal climate change. The genetic basis of adaptation and, consequently, the dynamics of evolutionary change differed qualitatively among scenarios. Populations with fewer founding genotypes and populations with genetic diversity reduced by prior selection adapted less well to novel conditions, demonstrating that adaptation to rapid climate change requires the maintenance of sufficient standing variation. PMID:27140640

  20. Dynamic illusory size contrast: A relative-size illusion modulated by stimulus motion and eye movements

    PubMed Central

    Mruczek, Ryan E. B.; Blair, Christopher D.; Caplovitz, Gideon P.

    2014-01-01

    We present a novel size-contrast illusion that depends on the dynamic nature of the stimulus. In the dynamic illusory size-contrast (DISC) effect, the viewer perceives the size of a target bar to be shrinking when it is surrounded by an expanding box and when there are additional dynamic cues such as eye movements, changes in retinal eccentricity of the bar, or changes in the spatial position of the bar. Importantly, the expanding box was necessary but not sufficient to obtain an illusory percept, distinguishing the DISC effect from other size-contrast illusions. We propose that the visual system is weighting the different sources of information that contribute to size perception based on the level of uncertainty in the retinal image size of the object. Whereas the growing box normally has a weak influence on the perceived size of the target bar, this influence is enhanced when other dynamic changes in the environment (e.g., eye movements, changes in retinal eccentricity, and target motion) lead to uncertainty in the retinal size of the target bar. Given the compelling nature of the DISC effect and the inherently dynamic nature of our environment, these factors are likely to play an important role in everyday size judgments. PMID:24591567

  1. The Seasonal Dynamics of Artificial Nest Predation Rates along Edges in a Mosaic Managed Reedbed

    PubMed Central

    Malzer, Iain; Helm, Barbara

    2015-01-01

    Boundaries between different habitats can be responsible for changes in species interactions, including modified rates of encounter between predators and prey. Such ‘edge effects’ have been reported in nesting birds, where nest predation rates can be increased at habitat edges. The literature concerning edge effects on nest predation rates reveals a wide variation in results, even within single habitats, suggesting edge effects are not fixed, but dynamic throughout space and time. This study demonstrates the importance of considering dynamic mechanisms underlying edge effects and their relevance when undertaking habitat management. In reedbed habitats, management in the form of mosaic winter reed cutting can create extensive edges which change rapidly with reed regrowth during spring. We investigate the seasonal dynamics of reedbed edges using an artificial nest experiment based on the breeding biology of a reedbed specialist. We first demonstrate that nest predation decreases with increasing distance from the edge of cut reed blocks, suggesting edge effects have a pivotal role in this system. Using repeats throughout the breeding season we then confirm that nest predation rates are temporally dynamic and decline with the regrowth of reed. However, effects of edges on nest predation were consistent throughout the season. These results are of practical importance when considering appropriate habitat management, suggesting that reed cutting may heighten nest predation, especially before new growth matures. They also contribute directly to an overall understanding of the dynamic processes underlying edge effects and their potential role as drivers of time-dependent habitat use. PMID:26448338

  2. The Seasonal Dynamics of Artificial Nest Predation Rates along Edges in a Mosaic Managed Reedbed.

    PubMed

    Malzer, Iain; Helm, Barbara

    2015-01-01

    Boundaries between different habitats can be responsible for changes in species interactions, including modified rates of encounter between predators and prey. Such 'edge effects' have been reported in nesting birds, where nest predation rates can be increased at habitat edges. The literature concerning edge effects on nest predation rates reveals a wide variation in results, even within single habitats, suggesting edge effects are not fixed, but dynamic throughout space and time. This study demonstrates the importance of considering dynamic mechanisms underlying edge effects and their relevance when undertaking habitat management. In reedbed habitats, management in the form of mosaic winter reed cutting can create extensive edges which change rapidly with reed regrowth during spring. We investigate the seasonal dynamics of reedbed edges using an artificial nest experiment based on the breeding biology of a reedbed specialist. We first demonstrate that nest predation decreases with increasing distance from the edge of cut reed blocks, suggesting edge effects have a pivotal role in this system. Using repeats throughout the breeding season we then confirm that nest predation rates are temporally dynamic and decline with the regrowth of reed. However, effects of edges on nest predation were consistent throughout the season. These results are of practical importance when considering appropriate habitat management, suggesting that reed cutting may heighten nest predation, especially before new growth matures. They also contribute directly to an overall understanding of the dynamic processes underlying edge effects and their potential role as drivers of time-dependent habitat use. PMID:26448338

  3. Organic and inorganic carbon fluxes in a tropical river system (Tana River, Kenya) during contrasting wet seasons

    NASA Astrophysics Data System (ADS)

    Geeraert, Naomi; Omengo, Fred O.; Bouillon, Steven; Borges, Alberto V.; Govers, Gerard

    2015-04-01

    Tropical river systems are often subjected to strong seasonality; in the Tana River (Kenya), for example, ~60% of the annual discharge takes place during a 4-month period. As different carbon pools are transported by the river, seasonal differences in carbon fluxes will also occur. This can furthermore be enhanced or attenuated due to changes in the intensity of carbon transformation processes, such as microbial respiration and primary production, during the wet season. Besides that, seasonal flooding of flood plains or flooded forest is known to be a major driver of the biogeochemical and ecological functioning of tropical rivers ("flood pulse concept") and has been shown to be one of the major drivers of the CO2 emissions from the Amazon River. We monitored the fluxes of different carbon pools at two sites spaced 385 km apart along the lower Tana River (Kenya), which is characterized by a highly seasonal flow regime. Water samples were taken at daily resolution during three wet seasons. During one of those seasons (May-June 2013), considerable flooding took place between both stations, while the other two wet seasons (Oct-Nov 2012 and April-May 2014) were characterised by several distinct discharge peaks, without leading to substantial overbank flooding. The flux of particulate organic carbon (POC) was observed to decrease in the downstream direction by 8 to 33% during all measurement periods. Fluxes of dissolved organic carbon (DOC) also decreased in the downstream direction during the wet seasons without flooding (by 10-38%) but increased drastically (increase of 231%) during the wet season with flooding. The dissolved inorganic carbon (DIC) flux increased downstream (by 6% to 62%) during all measurement periods. The total carbon flux (POC+DOC+DIC) increased by 33% in the wet season with flooding (2013), but decreased by 23% and 3%, respectively, during the 2012 and 2014 wet seasons. Flooding thus affected the relative contribution of different C pools to the

  4. Batrachochytrium dendrobatidis infection dynamics vary seasonally in upstate New York, USA.

    PubMed

    Lenker, Melissa A; Savage, Anna E; Becker, C Guilherme; Rodriguez, David; Zamudio, Kelly R

    2014-08-21

    The amphibian disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a major cause of worldwide amphibian declines and extinctions. Although several studies indicate that Bd prevalence and infection intensity vary seasonally, temporal variation of Bd at high-latitude sites, such as the northeastern USA, is still poorly characterized. We screened amphibians for Bd monthly at 2 study sites in New York State from April to October 2011 and used quantitative polymerase chain reaction (qPCR) to detect and quantify temporal variability in Bd infection prevalence and intensity. We found pronounced seasonal variation in both Bd infection prevalence and intensity at the community level, and our data indicate that this pattern is due to a few species (Lithobates catesbeianus, L. clamitans, and Notophthalmus viridescens) that drive temporal variability in disease dynamics. Amphibian body mass and sex were significant predictors of infection intensity but not infection prevalence. Understanding the temporal dynamics of Bd host-pathogen interactions provides important insight into regional, seasonal, and host-specific determinants of disease outbreaks. Further, our study elucidates the most relevant and informative timing for Bd surveys in temperate amphibian assemblages. Seasonal variation of infection dynamics suggests that Bd surveys from different sampling time points are not comparable, and summer surveys to evaluate chytridiomycosis may significantly underestimate Bd prevalence and intensity, leading to false conclusions about the severity of chytridiomycosis-induced amphibian mortality and population decline. PMID:25144117

  5. Seasonal diversity and dynamics of haptophytes in the Skagerrak, Norway, explored by high-throughput sequencing.

    PubMed

    Egge, Elianne Sirnaes; Johannessen, Torill Vik; Andersen, Tom; Eikrem, Wenche; Bittner, Lucie; Larsen, Aud; Sandaa, Ruth-Anne; Edvardsen, Bente

    2015-06-01

    Microalgae in the division Haptophyta play key roles in the marine ecosystem and in global biogeochemical processes. Despite their ecological importance, knowledge on seasonal dynamics, community composition and abundance at the species level is limited due to their small cell size and few morphological features visible under the light microscope. Here, we present unique data on haptophyte seasonal diversity and dynamics from two annual cycles, with the taxonomic resolution and sampling depth obtained with high-throughput sequencing. From outer Oslofjorden, S Norway, nano- and picoplanktonic samples were collected monthly for 2 years, and the haptophytes targeted by amplification of RNA/cDNA with Haptophyta-specific 18S rDNA V4 primers. We obtained 156 operational taxonomic units (OTUs), from c. 400.000 454 pyrosequencing reads, after rigorous bioinformatic filtering and clustering at 99.5%. Most OTUs represented uncultured and/or not yet 18S rDNA-sequenced species. Haptophyte OTU richness and community composition exhibited high temporal variation and significant yearly periodicity. Richness was highest in September-October (autumn) and lowest in April-May (spring). Some taxa were detected all year, such as Chrysochromulina simplex, Emiliania huxleyi and Phaeocystis cordata, whereas most calcifying coccolithophores only appeared from summer to early winter. We also revealed the seasonal dynamics of OTUs representing putative novel classes (clades HAP-3-5) or orders (clades D, E, F). Season, light and temperature accounted for 29% of the variation in OTU composition. Residual variation may be related to biotic factors, such as competition and viral infection. This study provides new, in-depth knowledge on seasonal diversity and dynamics of haptophytes in North Atlantic coastal waters. PMID:25893259

  6. Seasonal diversity and dynamics of haptophytes in the Skagerrak, Norway, explored by high-throughput sequencing

    PubMed Central

    Egge, Elianne Sirnæs; Johannessen, Torill Vik; Andersen, Tom; Eikrem, Wenche; Bittner, Lucie; Larsen, Aud; Sandaa, Ruth-Anne; Edvardsen, Bente

    2015-01-01

    Microalgae in the division Haptophyta play key roles in the marine ecosystem and in global biogeochemical processes. Despite their ecological importance, knowledge on seasonal dynamics, community composition and abundance at the species level is limited due to their small cell size and few morphological features visible under the light microscope. Here, we present unique data on haptophyte seasonal diversity and dynamics from two annual cycles, with the taxonomic resolution and sampling depth obtained with high-throughput sequencing. From outer Oslofjorden, S Norway, nano- and picoplanktonic samples were collected monthly for 2 years, and the haptophytes targeted by amplification of RNA/cDNA with Haptophyta-specific 18S rDNA V4 primers. We obtained 156 operational taxonomic units (OTUs), from c. 400.000 454 pyrosequencing reads, after rigorous bioinformatic filtering and clustering at 99.5%. Most OTUs represented uncultured and/or not yet 18S rDNA-sequenced species. Haptophyte OTU richness and community composition exhibited high temporal variation and significant yearly periodicity. Richness was highest in September–October (autumn) and lowest in April–May (spring). Some taxa were detected all year, such as Chrysochromulina simplex, Emiliania huxleyi and Phaeocystis cordata, whereas most calcifying coccolithophores only appeared from summer to early winter. We also revealed the seasonal dynamics of OTUs representing putative novel classes (clades HAP-3–5) or orders (clades D, E, F). Season, light and temperature accounted for 29% of the variation in OTU composition. Residual variation may be related to biotic factors, such as competition and viral infection. This study provides new, in-depth knowledge on seasonal diversity and dynamics of haptophytes in North Atlantic coastal waters. PMID:25893259

  7. Numerical Modeling of 3-D Dynamics of Ultrasound Contrast Agent Microbubbles Using the Boundary Integral Method

    NASA Astrophysics Data System (ADS)

    Calvisi, Michael; Manmi, Kawa; Wang, Qianxi

    2014-11-01

    Ultrasound contrast agents (UCAs) are microbubbles stabilized with a shell typically of lipid, polymer, or protein and are emerging as a unique tool for noninvasive therapies ranging from gene delivery to tumor ablation. The nonspherical dynamics of contrast agents are thought to play an important role in both diagnostic and therapeutic applications, for example, causing the emission of subharmonic frequency components and enhancing the uptake of therapeutic agents across cell membranes and tissue interfaces. A three-dimensional model for nonspherical contrast agent dynamics based on the boundary integral method is presented. The effects of the encapsulating shell are approximated by adapting Hoff's model for thin-shell, spherical contrast agents to the nonspherical case. A high-quality mesh of the bubble surface is maintained by implementing a hybrid approach of the Lagrangian method and elastic mesh technique. Numerical analyses for the dynamics of UCAs in an infinite liquid and near a rigid wall are performed in parameter regimes of clinical relevance. The results show that the presence of a coating significantly reduces the oscillation amplitude and period, increases the ultrasound pressure amplitude required to incite jetting, and reduces the jet width and velocity.

  8. DyCoH: an innovative tool to dynamic contrast enhancement analysis.

    PubMed

    Russo, Valentina; Setola, Roberto; Del Vescovo, Riccardo; Grasso, Rosario Francesco; Zobel, Bruno Beomonte

    2007-01-01

    Contrast-Enhancement (CE) is an innovative approach, used in radiological framework, to evaluate the vascularization of the diseases. This non-invasive method determines the nature of a diseases, analysing the perfusion' dynamic of contrast media in the tissues. In this paper we present an innovative tool named DyCoH (Dynamic Contrast Enhancement). This software, being specifically designed for this type of analysis, provides to medical doctor, in a very user-friendly framework, all the information needed to perform the CE analysis. DyCoH produces four inspectionable colour-maps that radiologists can use to identify the most relevant areas over which dynamically evaluates the contrast enhancement curve. However, the most interesting feature of DyCoH is its capability to manage, into a single framework, DICOM images produced by US, CT and MR of different vendors, allowing to support many types of clinical tests and to compare results provided by different diagnostic devices. Clinical tests have shown the effectiveness of the software and its capability to concretely support CE diagnoses. PMID:18001889

  9. A spatial analysis of seasonal variation in dissolved nutrients and greenhouse gasses along two river networks draining watersheds of contrasting land use

    NASA Astrophysics Data System (ADS)

    Dee, Martha; Tank, Jennifer; Marzadri, Alessandra; Tonina, Daniele; Bellin, Alberto

    2016-04-01

    Widespread human activity such as agriculture and urban land use has increased the availability of dissolved reactive nutrients in river networks. As such, the biogeochemical processing of these nutrients in streams and rivers may make them significant sources of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) gasses which are responsible for the majority of heat trapping capacity in the modern atmosphere. We replicated a synoptic sampling regime across seasons to measure dissolved inorganic nutrients and gasses at 80 stream/river sites in two contrasting U.S. watersheds, the Manistee River Basin (MI) which is ~83% forested and the Tippecanoe River Basin (IN) is 82% agricultural land use. We used Spatial Stream Network (SSN) geostatistical modeling to differentiate the spatial heterogeneity of dissolved nutrients and greenhouse gasses among seasons and between watersheds of contrasting land use. We modeled the spatial distribution of dissolved nutrients in each basin to separate the effects of catchment and in-stream processes compounded with fine-scale versus broad-scale gradients of stream water chemistry. Preliminary results suggest that dissolved nutrient and gas concentrations in both river networks during winter and spring were strongly influenced by land use type, exhibiting an "accumulating" broad-scale gradient. In contrast, during the primary growing season of summer and early autumn we found that networks displayed an array of "hotspots" or small-scale spatial dependence. As the world's land area undergoes continued development, high-resolution datasets will be critical in understanding the seasonal heterogeneity of spatial patterns along river networks and will allow us to predict the future impact of land use in a changing climate.

  10. Dynamical seasonal prediction of summer sea surface temperatures in the Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Spillman, C. M.; Alves, O.

    2009-03-01

    Coral bleaching is a serious problem threatening the world coral reef systems, triggered by high sea surface temperatures (SST) which are becoming more prevalent as a result of global warming. Seasonal forecasts from coupled ocean-atmosphere models can be used to predict anomalous SST months in advance. In this study, we assess the ability of the Australian Bureau of Meteorology seasonal forecast model (POAMA) to forecast SST anomalies in the Great Barrier Reef, Australia, with particular focus on the major 1998 and 2002 bleaching events. Advance warning of potential bleaching events allows for the implementation of management strategies to minimise reef damage. This study represents the first attempt to apply a dynamical seasonal model to the problem of coral bleaching and predict SST over a reef system for up to 6 months lead-time, a potentially invaluable tool for reef managers.

  11. Bulk volumetric liquid water content in a seasonal snowpack: modeling its dynamics in different climatic conditions

    NASA Astrophysics Data System (ADS)

    Avanzi, Francesco; Yamaguchi, Satoru; Hirashima, Hiroyuki; De Michele, Carlo

    2015-12-01

    We focus on the dynamics of volumetric liquid water content in seasonal snow covers. This is a key variable describing the fate of snowpacks during the melting season. However, its measurement and/or prediction by means of models at high spatial and temporal resolutions is still difficult due to both practical and theoretical reasons. To overcome these limitations in operational applications, we test the capability of a one-dimensional model to predict the dynamics of bulk volumetric liquid water content during a snow season. Multi-year data collected in three experimental sites in Japan are used as an evaluation. These sites are subjected to different climatic conditions. The model requires the calibration of one or two parameters, according to the degree of detail used. Either a simple temperature-index or a coupled melt-freeze temperature-index approach are considered to predict melting and/or melt-freeze dynamics of liquid water. Results show that, if melt-freeze dynamics are modeled, median absolute differences between data and predictions are consistently lower than 1 vol% at the sites where data of liquid water content are available. In addition, we find also that the model predicts correctly a dry condition in 80% of the observed cases at a site where calibration data are scarce. At the same site, observed isothermal conditions of the snow cover at 0 °C correspond to predictions of bulk volumetric liquid water content that are greater than 0.

  12. Vibrational dynamics of zero-field-splitting hamiltonian in gadolinium-based MRI contrast agents from ab initio molecular dynamics.

    PubMed

    Lasoroski, Aurélie; Vuilleumier, Rodolphe; Pollet, Rodolphe

    2014-07-01

    The electronic relaxation of gadolinium complexes used as MRI contrast agents was studied theoretically by following the short time evolution of zero-field-splitting parameters. The statistical analysis of ab initio molecular dynamics trajectories provided a clear separation between static and transient contributions to the zero-field-splitting. For the latter, the correlation time was estimated at approximately 0.1 ps. The influence of the ligand was also probed by replacing one pendant arm of our reference macrocyclic complex by a bulkier phosphonate arm. In contrast to the transient contribution, the static zero-field-splitting was significantly influenced by this substitution. PMID:25005282

  13. Vibrational dynamics of zero-field-splitting hamiltonian in gadolinium-based MRI contrast agents from ab initio molecular dynamics

    SciTech Connect

    Lasoroski, Aurélie; Vuilleumier, Rodolphe; Pollet, Rodolphe

    2014-07-07

    The electronic relaxation of gadolinium complexes used as MRI contrast agents was studied theoretically by following the short time evolution of zero-field-splitting parameters. The statistical analysis of ab initio molecular dynamics trajectories provided a clear separation between static and transient contributions to the zero-field-splitting. For the latter, the correlation time was estimated at approximately 0.1 ps. The influence of the ligand was also probed by replacing one pendant arm of our reference macrocyclic complex by a bulkier phosphonate arm. In contrast to the transient contribution, the static zero-field-splitting was significantly influenced by this substitution.

  14. Predictive Understanding of Seasonal Hydrological Dynamics under Climate and Land Use-Land Cover Change

    NASA Astrophysics Data System (ADS)

    Batra, N.; Yang, Y. E.; Choi, H. I.; Kumar, P.; Cai, X.; Fraiture, C. D.

    2008-12-01

    Water has always been and will continue to be an important factor in agricultural production and any alteration in the seasonal distribution of water availability due to climate and land use-land cover change (LULCC) will significantly impact the future production. To achieve the ecologic, economic and social objectives of sustainability, physical understanding of the linkages between climatic changes, LULCC and hydrological response is required. Aided by satellite data, modeling and understanding of the interactions between physical processes of the climate system and society, more reliable regional LULCC and climate change projections are now available. However, resulting quantitative projection of changes on the regional scale hydrological components at the seasonal time scale are sparse. This study attempts to quantify the seasonal hydrological response due to projected LULCC and climate change scenario of Intergovernmental Panel on Climate Change (IPCC) in different hydro-climatic regions of the world. The Common Land Model (CLM) is used for global assessment of future hydrologic response with the development of a consistent global GIS based database for the surface boundary conditions and meteorological forcing of the model. Future climate change projections are derived from the IPCC Fourth Assessment Report: Working Group I - The Physical Science Basis. The study is performed over nine river basins selected from Asia, Africa and North America to present the broad climatic and landscape controls on the seasonal hydrological dynamics. Future changes in water availability are quite evident from our results based upon changes in the volume and seasonality of precipitation, runoff and evapotranspiration. Severe water scarcity is projected to occur in certain seasons which may not be known through annual estimates. Knowledge of the projected seasonal hydrological response can be effectively used for developing adaptive management strategies for the sustainability

  15. Host and pathogen ecology drive the seasonal dynamics of a fungal disease, white-nose syndrome

    PubMed Central

    Langwig, Kate E.; Frick, Winifred F.; Reynolds, Rick; Parise, Katy L.; Drees, Kevin P.; Hoyt, Joseph R.; Cheng, Tina L.; Kunz, Thomas H.; Foster, Jeffrey T.; Kilpatrick, A. Marm

    2015-01-01

    Seasonal patterns in pathogen transmission can influence the impact of disease on populations and the speed of spatial spread. Increases in host contact rates or births drive seasonal epidemics in some systems, but other factors may occasionally override these influences. White-nose syndrome, caused by the emerging fungal pathogen Pseudogymnoascus destructans, is spreading across North America and threatens several bat species with extinction. We examined patterns and drivers of seasonal transmission of P. destructans by measuring infection prevalence and pathogen loads in six bat species at 30 sites across the eastern United States. Bats became transiently infected in autumn, and transmission spiked in early winter when bats began hibernating. Nearly all bats in six species became infected by late winter when infection intensity peaked. In summer, despite high contact rates and a birth pulse, most bats cleared infections and prevalence dropped to zero. These data suggest the dominant driver of seasonal transmission dynamics was a change in host physiology, specifically hibernation. Our study is the first, to the best of our knowledge, to describe the seasonality of transmission in this emerging wildlife disease. The timing of infection and fungal growth resulted in maximal population impacts, but only moderate rates of spatial spread. PMID:25473016

  16. Host and pathogen ecology drive the seasonal dynamics of a fungal disease, white-nose syndrome.

    PubMed

    Langwig, Kate E; Frick, Winifred F; Reynolds, Rick; Parise, Katy L; Drees, Kevin P; Hoyt, Joseph R; Cheng, Tina L; Kunz, Thomas H; Foster, Jeffrey T; Kilpatrick, A Marm

    2015-01-22

    Seasonal patterns in pathogen transmission can influence the impact of disease on populations and the speed of spatial spread. Increases in host contact rates or births drive seasonal epidemics in some systems, but other factors may occasionally override these influences. White-nose syndrome, caused by the emerging fungal pathogen Pseudogymnoascus destructans, is spreading across North America and threatens several bat species with extinction. We examined patterns and drivers of seasonal transmission of P. destructans by measuring infection prevalence and pathogen loads in six bat species at 30 sites across the eastern United States. Bats became transiently infected in autumn, and transmission spiked in early winter when bats began hibernating. Nearly all bats in six species became infected by late winter when infection intensity peaked. In summer, despite high contact rates and a birth pulse, most bats cleared infections and prevalence dropped to zero. These data suggest the dominant driver of seasonal transmission dynamics was a change in host physiology, specifically hibernation. Our study is the first, to the best of our knowledge, to describe the seasonality of transmission in this emerging wildlife disease. The timing of infection and fungal growth resulted in maximal population impacts, but only moderate rates of spatial spread. PMID:25473016

  17. Bacterial dynamics within the mucus, tissue and skeleton of the coral Porites lutea during different seasons

    NASA Astrophysics Data System (ADS)

    Li, Jie; Chen, Qi; Long, Li-Juan; Dong, Jun-De; Yang, Jian; Zhang, Si

    2014-12-01

    Investigation of the response of coral microbial communities to seasonal ecological environment at the microscale will advance our understanding of the relationship between coral-associated bacteria community and coral health. In this study, we examined bacteria community composition from mucus, tissue and skeleton of Porites lutea and surrounding seawater every three months for 1 year on Luhuitou fringing reef. The bacterial communities were analyzed using pyrosequencing of the V1-V2 region of the 16S rRNA gene, which demonstrated diverse bacterial consortium profiles in corals. The bacterial communities in all three coral compartments studied were significantly different from the surrounding seawater. Moreover, they had a much more dynamic seasonal response compared to the seawater communities. The bacterial communities in all three coral compartments collected in each seasonal sample tended to cluster together. Analysis of the relationship between bacterial assemblages and the environmental parameters showed that the bacterial community correlated to dissolved oxygen and rainfall significantly at our study site. This study highlights a dynamic relationship between the high complexity of coral associated bacterial community and seasonally varying ecosystem parameters.

  18. Seasonal forecast skill of Arctic sea ice area in a dynamical forecast system

    NASA Astrophysics Data System (ADS)

    Sigmond, M.; Fyfe, J. C.; Flato, G. M.; Kharin, V. V.; Merryfield, W. J.

    2013-02-01

    AbstractWe assess the <span class="hlt">seasonal</span> forecast skill of pan-Arctic sea ice area in a <span class="hlt">dynamical</span> forecast system that includes interactive atmosphere, ocean, and sea ice components. Forecast skill is quantified by the correlation skill score computed from 12 month ensemble forecasts initialized in each month between January 1979 to December 2009. We find that forecast skill is substantial for all lead times and predicted <span class="hlt">seasons</span> except spring but is mainly due to the strong downward trend in observations for lead times of about 4 months and longer. Skill is higher when evaluated against an observation-based dataset with larger trends. The forecast skill when linear trends are removed from the forecasts and verifying observations is small and generally not statistically significant at lead times greater than 2 to 3 months, except for January/February when forecast skill is moderately high up to an 11 month lead time. For short lead times, high trend-independent forecast skill is found for October, while low skill is found for November/December. This is consistent with the <span class="hlt">seasonal</span> variation of observed lag correlations. For most predicted months and lead times, trend-independent forecast skill exceeds that of an anomaly persistence forecast, highlighting the potential for <span class="hlt">dynamical</span> forecast systems to provide valuable <span class="hlt">seasonal</span> predictions of Arctic sea ice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ClDy...43.2131M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ClDy...43.2131M"><span id="translatedtitle"><span class="hlt">Seasonal</span> prediction of global sea level anomalies using an ocean-atmosphere <span class="hlt">dynamical</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miles, Elaine R.; Spillman, Claire M.; Church, John A.; McIntosh, Peter C.</p> <p>2014-10-01</p> <p>Advanced warning of extreme sea level events is an invaluable tool for coastal communities, allowing the implementation of management policies and strategies to minimise loss of life and infrastructure damage. This study is an initial attempt to apply a <span class="hlt">dynamical</span> coupled ocean-atmosphere model to the prediction of <span class="hlt">seasonal</span> sea level anomalies (SLA) globally for up to 7 months in advance. We assess the ability of the Australian Bureau of Meteorology's operational <span class="hlt">seasonal</span> <span class="hlt">dynamical</span> forecast system, the Predictive Ocean Atmosphere Model for Australia (POAMA), to predict <span class="hlt">seasonal</span> SLA, using gridded satellite altimeter observation-based analyses over the period 1993-2010 and model reanalysis over 1981-2010. Hindcasts from POAMA are based on a 33-member ensemble of <span class="hlt">seasonal</span> forecasts that are initialised once per month for the period 1981-2010. Our results show POAMA demonstrates high skill in the equatorial Pacific basin and consistently exhibits more skill globally than a forecast based on persistence. Model predictability estimates indicate there is scope for improvement in the higher latitudes and in the Atlantic and Southern Oceans. Most characteristics of the asymmetric SLA fields generated by El-Nino/La Nina events are well represented by POAMA, although the forecast amplitude weakens with increasing lead-time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25475855','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25475855"><span id="translatedtitle">Bacterial <span class="hlt">dynamics</span> within the mucus, tissue and skeleton of the coral Porites lutea during different <span class="hlt">seasons</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Jie; Chen, Qi; Long, Li-Juan; Dong, Jun-De; Yang, Jian; Zhang, Si</p> <p>2014-01-01</p> <p>Investigation of the response of coral microbial communities to <span class="hlt">seasonal</span> ecological environment at the microscale will advance our understanding of the relationship between coral-associated bacteria community and coral health. In this study, we examined bacteria community composition from mucus, tissue and skeleton of Porites lutea and surrounding seawater every three months for 1 year on Luhuitou fringing reef. The bacterial communities were analyzed using pyrosequencing of the V1-V2 region of the 16S rRNA gene, which demonstrated diverse bacterial consortium profiles in corals. The bacterial communities in all three coral compartments studied were significantly different from the surrounding seawater. Moreover, they had a much more <span class="hlt">dynamic</span> <span class="hlt">seasonal</span> response compared to the seawater communities. The bacterial communities in all three coral compartments collected in each <span class="hlt">seasonal</span> sample tended to cluster together. Analysis of the relationship between bacterial assemblages and the environmental parameters showed that the bacterial community correlated to dissolved oxygen and rainfall significantly at our study site. This study highlights a <span class="hlt">dynamic</span> relationship between the high complexity of coral associated bacterial community and <span class="hlt">seasonally</span> varying ecosystem parameters. PMID:25475855</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4256709','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4256709"><span id="translatedtitle">Bacterial <span class="hlt">dynamics</span> within the mucus, tissue and skeleton of the coral Porites lutea during different <span class="hlt">seasons</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Jie; Chen, Qi; Long, Li-Juan; Dong, Jun-De; Yang, Jian; Zhang, Si</p> <p>2014-01-01</p> <p>Investigation of the response of coral microbial communities to <span class="hlt">seasonal</span> ecological environment at the microscale will advance our understanding of the relationship between coral-associated bacteria community and coral health. In this study, we examined bacteria community composition from mucus, tissue and skeleton of Porites lutea and surrounding seawater every three months for 1 year on Luhuitou fringing reef. The bacterial communities were analyzed using pyrosequencing of the V1-V2 region of the 16S rRNA gene, which demonstrated diverse bacterial consortium profiles in corals. The bacterial communities in all three coral compartments studied were significantly different from the surrounding seawater. Moreover, they had a much more <span class="hlt">dynamic</span> <span class="hlt">seasonal</span> response compared to the seawater communities. The bacterial communities in all three coral compartments collected in each <span class="hlt">seasonal</span> sample tended to cluster together. Analysis of the relationship between bacterial assemblages and the environmental parameters showed that the bacterial community correlated to dissolved oxygen and rainfall significantly at our study site. This study highlights a <span class="hlt">dynamic</span> relationship between the high complexity of coral associated bacterial community and <span class="hlt">seasonally</span> varying ecosystem parameters. PMID:25475855</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OcMod.100...20V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OcMod.100...20V"><span id="translatedtitle">Downscaling and extrapolating <span class="hlt">dynamic</span> <span class="hlt">seasonal</span> marine forecasts for coastal ocean users</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vanhatalo, Jarno; Hobday, Alistair J.; Little, L. Richard; Spillman, Claire M.</p> <p>2016-04-01</p> <p>Marine weather and climate forecasts are essential in planning strategies and activities on a range of temporal and spatial scales. However, <span class="hlt">seasonal</span> <span class="hlt">dynamical</span> forecast models, that provide forecasts in monthly scale, often have low offshore resolution and limited information for inshore coastal areas. Hence, there is increasing demand for methods capable of fine scale <span class="hlt">seasonal</span> forecasts covering coastal waters. Here, we have developed a method to combine observational data with <span class="hlt">dynamical</span> forecasts from POAMA (Predictive Ocean Atmosphere Model for Australia; Australian Bureau of Meteorology) in order to produce <span class="hlt">seasonal</span> downscaled, corrected forecasts, extrapolated to include inshore regions that POAMA does not cover. We demonstrate the method in forecasting the monthly sea surface temperature anomalies in the Great Australian Bight (GAB) region. The resolution of POAMA in the GAB is approximately 2° × 1° (lon. × lat.) and the resolution of our downscaled forecast is approximately 1° × 0.25°. We use data and model hindcasts for the period 1994-2010 for forecast validation. The predictive performance of our statistical downscaling model improves on the original POAMA forecast. Additionally, this statistical downscaling model extrapolates forecasts to coastal regions not covered by POAMA and its forecasts are probabilistic which allows straightforward assessment of uncertainty in downscaling and prediction. A range of marine users will benefit from access to downscaled and nearshore forecasts at <span class="hlt">seasonal</span> timescales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23996577','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23996577"><span id="translatedtitle">What drives the <span class="hlt">dynamics</span> of a soil mite population under <span class="hlt">seasonal</span> flooding? A null model analysis.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pequeno, Pedro Aurélio Costa Lima; Franklin, Elizabeth</p> <p>2014-02-01</p> <p>Floods can inflict high mortality on terrestrial organisms, but may also promote adaptive evolution. In <span class="hlt">seasonal</span> floodplains, several taxa show flood-related traits that may be important for their long-term persistence, but the available evidence is conflicting. Here, we used a simulation approach to investigate the interplay between <span class="hlt">seasonal</span> floods and submersion resistance in driving the population <span class="hlt">dynamics</span> of the parthenogenetic soil mite Rostrozetes ovulum in an Amazonian blackwater floodplain. First, we gathered data from two flood cycles to estimate field survival rate. Next, we used further data from a submersion survival laboratory experiment and a historical flood record to build a null model for R. ovulum's survival rate under <span class="hlt">seasonal</span> flooding, and then tested it against field survival estimates. Floods caused marked density declines, but the two estimates of field survival rate were statistically equivalent, suggesting relatively constant survival across years. Submersion survival time varied tenfold among individuals, but its variability was within the range known for life history traits of other asexual invertebrates. Both field survival rates were consistent with the null model, supporting <span class="hlt">seasonal</span> flooding as the main mortality factor. Surprisingly, though, average flood duration was actually larger than the average mite could survive, suggesting that population persistence relies on relatively rare, super-resistant phenotypes. Overall, the studied R. ovulum population appears to have a mainly density-independent <span class="hlt">dynamics</span> across years, with its viability depending on mechanisms that buffer flood survival rate against temporal oscillations. PMID:23996577</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3946831','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3946831"><span id="translatedtitle">Iodinated <span class="hlt">Contrast</span> Does Not Alter Clotting <span class="hlt">Dynamics</span> in Acute Ischemic Stroke as Measured by Thromboelastography</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>McDonald, Mark M; Archeval-Lao, Joancy M; Cai, Chunyan; Peng, Hui; Sangha, Navdeep; Parker, Stephanie A; Wetzel, Jeremy; Riney, Stephen A; Cherches, Matt F; Guthrie, Greer J; Roper, Tiffany C; Kawano-Castillo, Jorge F; Pandurengan, Renga; Rahbar, Mohammad H; Grotta, James C</p> <p>2014-01-01</p> <p>Background and Purpose Iodinated <span class="hlt">contrast</span> agents used for computed tomography angiography (CTA) may alter fibrin fiber characteristics and decrease fibrinolysis by tissue plasminogen activator (tPA). Thromboelastography (TEG™) measures the <span class="hlt">dynamics</span> of coagulation and correlates with thrombolysis in acute ischemic stroke (AIS) patients. We hypothesized that receiving CTA prior to tPA will not impair thrombolysis as measured by TEG™. Methods AIS patients receiving 0.9 mg/kg tPA within 4.5 hours of symptom onset were prospectively enrolled. For CTA, 350 mg/dL of iohexol or 320 mg/dL of iodixanol at a dose of 2.2 ml/kg was administered. TEG™ was measured prior to tPA and 10-minutes after tPA bolus. CTA timing was left to the discretion of the treating physician. Results Of 136 AIS patients who received tPA, 47 had CTA prior to tPA bolus, and 42 had either CTA following tPA and post-tPA TEG™ draw or no CTA (non-<span class="hlt">contrast</span> group). The median change in clot lysis (LY30) following tPA was 95.3% in the <span class="hlt">contrast</span> group vs. 95.0% in the non-<span class="hlt">contrast</span> group (p = 0.74). Thus, tPA-induced thrombolysis did not differ between <span class="hlt">contrast</span> and non-<span class="hlt">contrast</span> groups. Additionally, there was no effect of <span class="hlt">contrast</span> on any pre-tPA TEG™ value. Conclusions Our data do not support an effect of iodinated <span class="hlt">contrast</span> agents on clot formation or tPA activity. PMID:24370757</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PMB....50.5031L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PMB....50.5031L"><span id="translatedtitle"><span class="hlt">Dynamic</span> imaging of the lungs using x-ray phase <span class="hlt">contrast</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lewis, R. A.; Yagi, N.; Kitchen, M. J.; Morgan, M. J.; Paganin, D.; Siu, K. K. W.; Pavlov, K.; Williams, I.; Uesugi, K.; Wallace, M. J.; Hall, C. J.; Whitley, J.; Hooper, S. B.</p> <p>2005-11-01</p> <p>High quality real-time imaging of lungs in vivo presents considerable challenges. We demonstrate here that phase <span class="hlt">contrast</span> x-ray imaging is capable of <span class="hlt">dynamically</span> imaging the lungs. It retains many of the advantages of simple x-ray imaging, whilst also being able to map weakly absorbing soft tissues based on refractive index differences. Preliminary results reported herein show that this novel imaging technique can identify and locate airway liquid and allows lung aeration in newborn rabbit pups to be <span class="hlt">dynamically</span> visualized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18051148','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/18051148"><span id="translatedtitle">De-enhancing the <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced breast MRI for robust registration.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zheng, Yuanjie; Yu, Jingyi; Kambhamettu, Chandra; Englander, Sarah; Schnall, Mitchell D; Shen, Dinggang</p> <p>2007-01-01</p> <p><span class="hlt">Dynamic</span> enhancement causes serious problems for registration of <span class="hlt">contrast</span> enhanced breast MRI, due to variable uptakes of agent on different tissues or even same tissues in the breast. We present an iterative optimization algorithm to de-enhance the <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced breast MRI and then register them for avoiding the effects of enhancement on image registration. In particular, the spatially varying enhancements are modeled by a Markov Random Field, and estimated by a locally smooth function with boundaries using a graph cut algorithm. The de-enhanced images are then registered by conventional B-spline based registration algorithm. These two steps benefit from each other and are repeated until the results converge. Experimental results show that our two-step registration algorithm performs much better than conventional mutual information based registration algorithm. Also, the effects of tumor shrinking in the conventional registration algorithms can be effectively avoided by our registration algorithm. PMID:18051148</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27430260','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27430260"><span id="translatedtitle"><span class="hlt">Dynamic</span> <span class="hlt">contrast</span> enhanced CT in nodule characterization: How we review and report.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Qureshi, Nagmi R; Shah, Andrew; Eaton, Rosemary J; Miles, Ken; Gilbert, Fiona J</p> <p>2016-01-01</p> <p>Incidental indeterminate solitary pulmonary nodules (SPN) that measure less than 3 cm in size are an increasingly common finding on computed tomography (CT) worldwide. Once identified there are a number of imaging strategies that can be performed to help with nodule characterization. These include interval CT, <span class="hlt">dynamic</span> <span class="hlt">contrast</span> enhanced computed tomography (DCE-CT), (18)F-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG-PET-CT). To date the most cost effective and efficient non-invasive test or combination of tests for optimal nodule characterization has yet to be determined.DCE-CT is a functional test that involves the acquisition of a <span class="hlt">dynamic</span> series of images of a nodule before and following the administration of intravenous iodinated <span class="hlt">contrast</span> medium. This article provides an overview of the current indications and limitations of DCE- CT in nodule characterization and a systematic approach to how to perform, analyse and interpret a DCE-CT scan. PMID:27430260</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...46.1001L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...46.1001L"><span id="translatedtitle">Potential negative effects of groundwater <span class="hlt">dynamics</span> on dry <span class="hlt">season</span> convection in the Amazon River basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Yen-Heng; Lo, Min-Hui; Chou, Chia</p> <p>2016-02-01</p> <p>Adding a groundwater component to land surface models affects modeled precipitation. The additional water supply from the subsurface contributes to increased water vapor in the atmosphere, resulting in modifications of atmospheric convection. This study focuses on how groundwater <span class="hlt">dynamics</span> affect atmospheric convection in the Amazon River basin (ARB) during July, typically the driest month. Coupled groundwater-land-atmosphere model simulations show that groundwater storage increases evapotranspiration rates (latent heat fluxes) and lowers surface temperatures, which increases the surface pressure gradient and thus, anomalous surface divergence. Therefore, the convection over the Southern Hemispheric ARB during the dry <span class="hlt">season</span> becomes weaker when groundwater <span class="hlt">dynamics</span> are included in the model. Additionally, the changes in atmospheric vertical water vapor advection are associated with decreases in precipitation that results from downwelling transport anomalies. The results of this study highlight the importance of subsurface hydrological processes in the Amazon climate system, with implications for precipitation changes during the dry <span class="hlt">season</span>, observed in most current climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005TellA..57..409D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005TellA..57..409D"><span id="translatedtitle">Statistical and <span class="hlt">dynamical</span> downscaling of precipitation over Spain from DEMETER <span class="hlt">seasonal</span> forecasts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Díez, E.; Primo, C.; García-Moya, J. A.; Gutiérrez, J. M.; Orfila, B.</p> <p>2005-05-01</p> <p>Statistical and <span class="hlt">dynamical</span> downscaling methods are tested and compared for downscaling <span class="hlt">seasonal</span> precipitation forecasts over Spain from two DEMETER models: the European Centre for Medium-Range Weather Forecasts (ECMWF) and the UK Meteorological Office (UKMO). The statistical method considered is a particular implementation of the standard analogue technique, based on close neighbours of the predicted atmospheric geopotential and humidity fields. <span class="hlt">Dynamical</span> downscaling is performed using the Rossby Centre Climate Atmospheric model, which has been nested to the ECMWF model output, and run in climate mode for six months. We first check the performance of the direct output models in the period 1986 1997 and compare it with the results obtained applying the analogue method. We have found that the direct outputs underestimate the precipitation amount and that the statistical downscaling method improves the results as the skill of the direct forecast increases. The highest skills relative operating characteristic skill areas (RSAs) above 0.6 are associated with early and late spring, summer and autumn <span class="hlt">seasons</span> at zero- and one-month lead times. On the other hand, models have poor skill during winter with the exception of the El Niño period (1986 1988), especially in the south of Spain. In this case, high RSAs and economic values have been found. We also compare statistical and <span class="hlt">dynamical</span> downscaling during four <span class="hlt">seasons</span>, obtaining no concluding result. Both methods outperform direct output from DEMETER models, but depending on the <span class="hlt">season</span> and on the region of Spain one method is better than the other. Moreover, we have seen that <span class="hlt">dynamical</span> and statistical methods can be used in combination, yielding the best skill scores in some cases of the study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PMB....58.6111P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PMB....58.6111P"><span id="translatedtitle">Computational fluid <span class="hlt">dynamics</span> modelling of perfusion measurements in <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced computed tomography: development, validation and clinical applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peladeau-Pigeon, M.; Coolens, C.</p> <p>2013-09-01</p> <p><span class="hlt">Dynamic</span> <span class="hlt">contrast</span>-enhanced computed tomography (DCE-CT) is an imaging tool that aids in evaluating functional characteristics of tissue at different stages of disease management: diagnostic, radiation treatment planning, treatment effectiveness, and monitoring. Clinical validation of DCE-derived perfusion parameters remains an outstanding problem to address prior to perfusion imaging becoming a widespread standard as a non-invasive quantitative measurement tool. One approach to this validation process has been the development of quality assurance phantoms in order to facilitate controlled perfusion ex vivo. However, most of these systems fail to establish and accurately replicate physiologically relevant capillary permeability and exchange performance. The current work presents the first step in the development of a prospective suite of physics-based perfusion simulations based on coupled fluid flow and particle transport phenomena with the goal of enhancing the understanding of clinical <span class="hlt">contrast</span> agent kinetics. Existing knowledge about a controllable, two-compartmental fluid exchange phantom was used to validate the computational fluid <span class="hlt">dynamics</span> (CFD) simulation model presented herein. The sensitivity of CFD-derived <span class="hlt">contrast</span> uptake curves to <span class="hlt">contrast</span> injection parameters, including injection duration and flow rate, were quantified and found to be within 10% accuracy. The CFD model was employed to evaluate two commonly used clinical kinetic algorithms used to derive perfusion parameters: Fick's principle and the modified Tofts model. Neither kinetic model was able to capture the true transport phenomena it aimed to represent but if the overall <span class="hlt">contrast</span> concentration after injection remained identical, then successive DCE-CT evaluations could be compared and could indeed reflect differences in regional tissue flow. This study sets the groundwork for future explorations in phantom development and pharmaco-kinetic modelling, as well as the development of novel <span class="hlt">contrast</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SPIE.8580E..07H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SPIE.8580E..07H"><span id="translatedtitle">Measurement of <span class="hlt">dynamic</span> scattering beneath stationary layers using multiple-exposure laser speckle <span class="hlt">contrast</span> analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirst, Evan; Thompson, Oliver; Andrews, Mike</p> <p>2013-02-01</p> <p>The retina/choroid structure is an example of a complex biological target featuring highly perfused tissues and vessel flows both near the surface and at some depth. Laser speckle imaging can be used to image blood flows but static scattering paths present a problem for extracting quantifiable data. The speckle <span class="hlt">contrast</span> is artificially increased by any residual specular reflection and light paths where no moving scatterers are encountered. Here we present results from phantom experiments demonstrating that the static and <span class="hlt">dynamic</span> contributions to laser speckle <span class="hlt">contrast</span> can be separated when camera exposures of varying duration are used. The stationary <span class="hlt">contrast</span> parameter follows the thickness and strength of the overlying scatterer while the <span class="hlt">dynamic</span> proportion of the scatter resulting from vessel flows and Brownian motion is unchanged. The importance of separating the two scatter components is illustrated by in vivo measurements from a scarred human retina, where the effect of the un-perfused scar tissue can be decoupled from the <span class="hlt">dynamic</span> speckle from the intact tissue beneath it.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25023101','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25023101"><span id="translatedtitle"><span class="hlt">Dynamic</span> <span class="hlt">contrast</span>-enhanced ultrasound of slaughterhouse porcine livers in machine perfusion.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Izamis, Maria-Louisa; Efstathiades, Andreas; Keravnou, Christina; Leen, Edward L; Averkiou, Michalakis A</p> <p>2014-09-01</p> <p>The aim of this study was to enable investigations into novel imaging and surgical techniques by developing a readily accessible, versatile liver machine perfusion system. Slaughterhouse pig livers were used, and <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced ultrasound was introduced to optimize the procurement process and provide real-time perfusion monitoring. The system comprised a single pump, oxygenator, bubble trap and two flowmeters for pressure-controlled perfusion of the vessels using an off-the-shelf perfusate at room temperature. Successful livers exhibited homogeneous perfusion in both the portal vein and hepatic artery with <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced ultrasound, which correlated with stable oxygen uptake, bile production and hepatic resistance and normal histology at the end of 3 h of perfusion. <span class="hlt">Dynamic</span> <span class="hlt">contrast</span>-enhanced ultrasound revealed perfusion abnormalities invisible to the naked eye, thereby providing context to the otherwise systemic biochemical/hemodynamic measurements and focal biopsy findings. The model developed here is a simple, cost-effective approach for stable ex vivo whole-organ machine perfusion. PMID:25023101</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19890026972&hterms=Year&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D20%26Ntt%3DYear','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19890026972&hterms=Year&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D20%26Ntt%3DYear"><span id="translatedtitle"><span class="hlt">Dynamical</span> component of <span class="hlt">seasonal</span> and year-to-year changes in Antarctic and global ozone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tung, Ka Kit; Yang, HU</p> <p>1988-01-01</p> <p>The <span class="hlt">dynamics</span> of the ozone concetration components of the Antarctic ozone hole as related to <span class="hlt">seasonal</span> and year-to-year temperature changes in August, September, October, and November during the 1979-1985 period is studied using a zonally averaged model in which all transport fields are fixed by input temperature data. The results suggest that, prior to 1984, both the <span class="hlt">seasonal</span> and year-to year variability of the zonal-mean Antarctic ozone minimum and the surrounding maximum can be accounted for by temperature <span class="hlt">dynamics</span> without invoking changes in chemical composition (e.g., chlorine content) or special chemistry. The same <span class="hlt">dynamical</span> mechanism also accounts for the good simulation of the observed <span class="hlt">seasonal</span> and latitudinal structure of column ozone in other parts of the world. However, chemical depletion of ozone may have become more important after 1984. The model also appears to underpredict the September ozone decline in years, leading to an underprediction of the recent minimum values in the Antarctic ozone hole.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/1001084','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/1001084"><span id="translatedtitle">Changes in <span class="hlt">seasonal</span> energy <span class="hlt">dynamics</span> of alewife (Alosa pseudoharengus) in Lake Michigan after invasion of dreissenid mussels</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Madenjian, Charles P.; Pothoven, Steven A.; Dettmers, John M.; Holuszko, Jeffrey D.</p> <p>2006-01-01</p> <p>The dreissenid mussel invasion of Lake Michigan during the 1990s has been linked to a concomitant decrease in the abundance of the amphipod Diporeia. We tracked the <span class="hlt">seasonal</span> energy <span class="hlt">dynamics</span> of alewife (Alosa pseudoharengus) in Lake Michigan during 2002–2004 and compared our findings with previously published results for years 1979–1981. Adult alewife energy density exhibited a pronounced <span class="hlt">seasonal</span> cycle during both the pre-invasion and post-invasion periods, with energy density in October or November nearly twice as high as that in early summer. However, on average, adult alewife energy density was 23% lower during the post-invasion period compared with the pre-invasion period. This significant decline in energy density was attributable to decreased importance of Diporeia in adult alewife diet. In <span class="hlt">contrast</span>, energy density of juvenile alewives did not significantly differ between the pre-invasion and post-invasion periods. To attain a weight of 8 kg by age 4, bioenergetics modeling indicated that a Chinook salmon (Oncorhynchus tshawytscha) in Lake Michigan would have to consume 22.1% more alewives during the post-invasion period compared with the pre-invasion period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24200007','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24200007"><span id="translatedtitle"><span class="hlt">Seasonal</span> bacterial community <span class="hlt">dynamics</span> in a full-scale enhanced biological phosphorus removal plant.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Flowers, Jason J; Cadkin, Tracey A; McMahon, Katherine D</p> <p>2013-12-01</p> <p>Activated sludge is one of the most abundant and effective wastewater treatment process used to treat wastewater, and has been used in developed countries for nearly a century. In all that time, several hundreds of studies have explored the bacterial communities responsible for treatment, but most studies were based on a handful of samples and did not consider temporal <span class="hlt">dynamics</span>. In this study, we used the DNA fingerprinting technique called automated ribosomal intergenic spacer region analysis (ARISA) to study bacterial community <span class="hlt">dynamics</span> over a two-year period in two different treatment trains. We also used quantitative PCR to measure the variation of five phylogenetically-defined clades within the Accumulibacter lineage, which is a model polyphosphate accumulating organism. The total bacterial community exhibited <span class="hlt">seasonal</span> patterns of change reminiscent of those observed in lakes and oceans. Surprisingly, all five Accumulibacter clades were present throughout the study, and the total Accumulibacter community was relatively stable. However, the abundance of each clade did fluctuate through time. Clade IIA <span class="hlt">dynamics</span> correlated positively with temperature (ρ = 0.65, p < 0.05) while Clade IA <span class="hlt">dynamics</span> correlated negatively with temperature (ρ = -0.35, p < 0.05). This relationship with temperature hints at the mechanisms that may be driving the <span class="hlt">seasonal</span> patterns in overall bacterial community <span class="hlt">dynamics</span> and provides further evidence for ecological differentiation among clades within the Accumulibacter lineage. This work provides a valuable baseline for activated sludge bacterial community variation. PMID:24200007</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4520395','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4520395"><span id="translatedtitle"><span class="hlt">Seasonal</span> bacterial community <span class="hlt">dynamics</span> in a full-scale enhanced biological phosphorus removal plant</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Flowers, Jason J.; Cadkin, Tracey A.; McMahon, Katherine D.</p> <p>2014-01-01</p> <p>Activated sludge is one of the most abundant and effective wastewater treatment process used to treat wastewater, and has been used in developed countries for nearly a century. In all that time, several hundreds of studies have explored the bacterial communities responsible for treatment, but most studies were based on a handful of samples and did not consider temporal <span class="hlt">dynamics</span>. In this study, we used the DNA fingerprinting technique called automated ribosomal intergenic spacer region analysis (ARISA) to study bacterial community <span class="hlt">dynamics</span> over a two-year period in two different treatment trains. We also used quantitative PCR to measure the variation of five phylogenetically-defined clades within the Accumulibacter lineage, which is a model polyphosphate accumulating organism. The total bacterial community exhibited <span class="hlt">seasonal</span> patterns of change reminiscent of those observed in lakes and oceans. Surprisingly, all five Accumulibacter clades were present throughout the study, and the total Accumulibacter community was relatively stable. However, the abundance of each clade did fluctuate through time. Clade IIA <span class="hlt">dynamics</span> correlated positively with temperature (ρ = 0.65, p < 0.05) while Clade IA <span class="hlt">dynamics</span> correlated negatively with temperature (ρ = –0.35, p < 0.05). This relationship with temperature hints at the mechanisms that may be driving the <span class="hlt">seasonal</span> patterns in overall bacterial community <span class="hlt">dynamics</span> and provides further evidence for ecological differentiation among clades within the Accumulibacter lineage. This work provides a valuable baseline for activated sludge bacterial community variation. PMID:24200007</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23213908','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23213908"><span id="translatedtitle">[<span class="hlt">Seasonal</span> <span class="hlt">dynamics</span> of soil active carbon pool in a purple paddy soil in southwest China].</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wu, Yan; Jiang, Chang-sheng; Hao, Qing-ju</p> <p>2012-08-01</p> <p>The <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of soil organic carbon (SOC), readily oxidized carbon (ROC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC) in a purple paddy soil were studied in a long-term field experimental station in Chongqing, China. The results showed that the <span class="hlt">seasonal</span> variations of the contents of SOC, ROC and MBC had similar trends in the rape growing <span class="hlt">season</span>. The contents were much higher in the early and late stages than in the middle stage of the rape growth. SOC, ROC and MBC all achieved the highest values of 16.20 g x kg(-1), 3.58 g x kg(-1) and 309.70 mg x kg(-1) at the end of the growing period, respectively. The <span class="hlt">seasonal</span> change of DOC content presented as a single peak and reached to the highest value of 37.64 mg x kg(-1) at the middle stage of the rape growth. The temporal <span class="hlt">dynamics</span> of the allocation ratios of ROC, MBC and DOC were similar to that of their contents. The allocation ratios of ROC, MBC and DOC were 15.49%-23.93%, 1.44%-2.06% and 0.11%-0.32% during the rape growing <span class="hlt">season</span>, respectively. The influencing factors of SOC and ROC contents were the soil temperature at 5 cm soil depth, soil total nitrogen content and pH. MBC content was jointly impacted by the soil temperature at 5 cm soil depth, root biomass and its C and N contents. DOC content was mainly affected by soil moisture. PMID:23213908</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23510081','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23510081"><span id="translatedtitle">Migration phenology and <span class="hlt">seasonal</span> fidelity of an Arctic marine predator in relation to sea ice <span class="hlt">dynamics</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cherry, Seth G; Derocher, Andrew E; Thiemann, Gregory W; Lunn, Nicholas J</p> <p>2013-07-01</p> <p>Understanding how <span class="hlt">seasonal</span> environmental conditions affect the timing and distribution of synchronized animal movement patterns is a central issue in animal ecology. Migration, a behavioural adaptation to <span class="hlt">seasonal</span> environmental fluctuations, is a fundamental part of the life history of numerous species. However, global climate change can alter the spatiotemporal distribution of resources and thus affect the <span class="hlt">seasonal</span> movement patterns of migratory animals. We examined sea ice <span class="hlt">dynamics</span> relative to migration patterns and <span class="hlt">seasonal</span> geographical fidelity of an Arctic marine predator, the polar bear (Ursus maritimus). Polar bear movement patterns were quantified using satellite-linked telemetry data collected from collars deployed between 1991-1997 and 2004-2009. We showed that specific sea ice characteristics can predict the timing of <span class="hlt">seasonal</span> polar bear migration on and off terrestrial refugia. In addition, fidelity to specific onshore regions during the ice-free period was predicted by the spatial pattern of sea ice break-up but not by the timing of break-up. The timing of migration showed a trend towards earlier arrival of polar bears on shore and later departure from land, which has been driven by climate-induced declines in the availability of sea ice. Changes to the timing of migration have resulted in polar bears spending progressively longer periods of time on land without access to sea ice and their marine mammal prey. The links between increased atmospheric temperatures, sea ice <span class="hlt">dynamics</span>, and the migratory behaviour of an ice-dependent species emphasizes the importance of quantifying and monitoring relationships between migratory wildlife and environmental cues that may be altered by climate change. PMID:23510081</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1215..182J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1215..182J"><span id="translatedtitle">The <span class="hlt">dynamic</span> of FUS-induced BBB Opening in Mouse Brain assessed by <span class="hlt">contrast</span> enhanced MRI</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jenne, Jürgen W.; Krafft, Axel J.; Maier, Florian; Krause, Marie N.; Kleber, Susanne; Huber, Peter E.; Martin-Villalba, Ana; Bock, Michael</p> <p>2010-03-01</p> <p>Focused ultrasound (FUS) in combination with the administration of gas-filled microbubbles, can induce a localized and reversible opening of the blood brain barrier (BBB). <span class="hlt">Contrast</span> enhanced magnetic resonance imaging (MRI) has been demonstrated as a precise tool to monitor such a local BBB disruption. However, the opening/closing mechanisms of the BBB with FUS are still largely unknown. In this ongoing project, we study the BBB opening <span class="hlt">dynamics</span> in mouse brain comparing an interstitial and an intravascular MR <span class="hlt">contrast</span> agent (CA). FUS in mouse brain was performed with an MRI compatible treatment setup (1.7 MHz fix-focus US transducer, f' = 68 mm, NA = 0.44; focus: 8.1 mm length; O/ = 1.1 mm) in a 1.5 T whole body MRI system. For BBB opening, forty 10 ms-long FUS-pulses were applied at a repetition rate of 1 Hz at 1 MPa. The i.v. administration of the micro bubbles (50 μl SonoVue®) was started simultaneously with FUS exposure. To analyze the BBB opening process, short-term and long-term MRI signal <span class="hlt">dynamics</span> of the interstitial MR <span class="hlt">contrast</span> agent Magnevist® and the intravascular CA Vasovist® (Bayer-Schering) were studied. To assess short-term signal <span class="hlt">dynamics</span>, T1-weighted inversion recovery turbo FLASH images (1s) were repeatedly acquired. Repeated 3D FLASH acquisitions (90 s) were used to assess long-term MRI signal <span class="hlt">dynamics</span>. The short-term MRI signal enhancements showed comparable time constants for both types of MR <span class="hlt">contrast</span> agents: 1.1 s (interstitial) vs. 0.8 s (intravascular). This time constant may serve as a time constant of the BBB opening process with the given FUS exposure parameters. For the long-term signal <span class="hlt">dynamics</span> the intravascular CA (62±10 min) showed a fife times greater time constant as the interstitial <span class="hlt">contrast</span> agent (12±10 min). This might be explained by the high molecular weight (˜60 kDa) of the intravascular Vasovist due to its reversible binding to blood serum albumin resulting in a prolonged half-life in the blood stream compared to the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JGRC..11210016R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JGRC..11210016R"><span id="translatedtitle"><span class="hlt">Seasonal</span> circulation around Tasmania: An interface between eastern and western boundary <span class="hlt">dynamics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ridgway, K. R.</p> <p>2007-10-01</p> <p>The <span class="hlt">seasonal</span> circulation connecting the Pacific and Indian oceans around Tasmania is documented using <span class="hlt">seasonal</span> maps from satellite altimetry and sea surface temperature (SST) and in situ mean fields from a high-resolution climatology of the region (Commonwealth Scientific and Industrial Research Organisation (CSIRO) Atlas of Regional Seas (CARS)). In general, the surface variability displays a very different character off the east and west coasts. Off the east coast the variability is generated externally, being dominated by the western boundary <span class="hlt">dynamics</span> of the East Australian Current (EAC). In the west it is weaker and arises from the <span class="hlt">seasonal</span> rise and fall of the coastal sea level, which is due to the <span class="hlt">seasonal</span> reversing wind patterns. A high-variability tongue associated with the EAC stretches poleward off the east coast, tracing out a waveguide between the major topographic structures. It has a broad peak in power between 180 and 365 days (>0.08 m), which is a surface height expression of the energetic mesoscale eddy activity associated with the EAC. Distinctive summer and winter patterns of the surface circulation are described which are influenced by the EAC and the Zeehan Current (ZC), respectively. On the east coast in summer (January-March), there is a poleward advection of warm, saline water forced by an episodic coastal boundary flow. The cross-shelf pressure gradient driving this flow is formed from the difference between the <span class="hlt">seasonal</span> changes in coastal sea level and the offshore eddies. There is a <span class="hlt">seasonal</span> reversal of this flow in winter with cool, fresh, modified subantarctic surface waters drawn up from the south. Off the west coast the Zeehan Current operates 180° out of phase with the EAC. It is strongest in winter when it projects warm, relatively saline waters down the western Tasmania coast and around the southern tip of Tasmania. There is a sharp division between the EAC and ZC influence adjacent to the Tasman Peninsula off southeast Tasmania.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21908435','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21908435"><span id="translatedtitle"><span class="hlt">Contrasting</span> physiological responses of two co-occurring eucalypts to <span class="hlt">seasonal</span> drought at restored bauxite mine sites.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Szota, Christopher; Farrell, Claire; Koch, John M; Lambers, Hans; Veneklaas, Erik J</p> <p>2011-10-01</p> <p>This study describes the physiological response of two co-occurring tree species (Eucalyptus marginata and Corymbia calophylla) to <span class="hlt">seasonal</span> drought at low- and high-quality restored bauxite mine sites in south-western Australia. <span class="hlt">Seasonal</span> changes in photosynthesis (A), stomatal conductance (g(s)), leaf water potential (ψ), leaf osmotic potential (ψ), leaf relative water content (RWC) and pressure-volume analysis were captured over an 18-month field study to (i) determine the nature and severity of physiological stress in relation to site quality and (ii) identify any physiological differences between the two species. Root system restriction at the low-quality site reduced maximum rates of gas exchange (g(s) and A) and increased water stress (midday ψ and daily RWC) in both species during drought. Both species showed high stomatal sensitivity during drought; however, E. marginata demonstrated a higher dehydration tolerance where ψ and RWC fell to -3.2 MPa and 73% compared with -2.4 MPa and 80% for C. calophylla. Corymbia calophylla showed lower g(s) and higher ψ and RWC during drought, indicating higher drought tolerance. Pressure-volume curves showed that cell-wall elasticity of E. marginata leaves increased in response to drought, while C. calophylla leaves showed lower osmotic potential at zero turgor in summer than in winter, indicating osmotic adjustment. Both species are clearly able to tolerate <span class="hlt">seasonal</span> drought at hostile sites; however, by C. calophylla closing stomata earlier in the drought cycle, maintaining a higher water status during drought and having the additional mechanism of osmotic adjustment, it may have a greater capacity to survive extended periods of drought. PMID:21908435</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4102451','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4102451"><span id="translatedtitle">Long-Term and <span class="hlt">Seasonal</span> <span class="hlt">Dynamics</span> of Dengue in Iquitos, Peru</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Stoddard, Steven T.; Wearing, Helen J.; Reiner, Robert C.; Morrison, Amy C.; Astete, Helvio; Vilcarromero, Stalin; Alvarez, Carlos; Ramal-Asayag, Cesar; Sihuincha, Moises; Rocha, Claudio; Halsey, Eric S.; Scott, Thomas W.; Kochel, Tadeusz J.; Forshey, Brett M.</p> <p>2014-01-01</p> <p>Introduction Long-term disease surveillance data provide a basis for studying drivers of pathogen transmission <span class="hlt">dynamics</span>. Dengue is a mosquito-borne disease caused by four distinct, but related, viruses (DENV-1-4) that potentially affect over half the world's population. Dengue incidence varies <span class="hlt">seasonally</span> and on longer time scales, presumably driven by the interaction of climate and host susceptibility. Precise understanding of dengue <span class="hlt">dynamics</span> is constrained, however, by the relative paucity of laboratory-confirmed longitudinal data. Methods We studied 10 years (2000–2010) of laboratory-confirmed, clinic-based surveillance data collected in Iquitos, Peru. We characterized inter and intra-annual patterns of dengue <span class="hlt">dynamics</span> on a weekly time scale using wavelet analysis. We explored the relationships of case counts to climatic variables with cross-correlation maps on annual and trimester bases. Findings Transmission was dominated by single serotypes, first DENV-3 (2001–2007) then DENV-4 (2008–2010). After 2003, incidence fluctuated inter-annually with outbreaks usually occurring between October and April. We detected a strong positive autocorrelation in case counts at a lag of ∼70 weeks, indicating a shift in the timing of peak incidence year-to-year. All climatic variables showed modest <span class="hlt">seasonality</span> and correlated weakly with the number of reported dengue cases across a range of time lags. Cases were reduced after citywide insecticide fumigation if conducted early in the transmission <span class="hlt">season</span>. Conclusions Dengue case counts peaked <span class="hlt">seasonally</span> despite limited intra-annual variation in climate conditions. Contrary to expectations for this mosquito-borne disease, no climatic variable considered exhibited a strong relationship with transmission. Vector control operations did, however, appear to have a significant impact on transmission some years. Our results indicate that a complicated interplay of factors underlie DENV transmission in contexts such as Iquitos. PMID</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JGRG..113.3029A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JGRG..113.3029A"><span id="translatedtitle">Spatial and <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of riverine carbon fluxes of the Brantas catchment in East Java</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aldrian, Edvin; Chen, Chen-Tung Arthur; Adi, Seno; Prihartanto, null; Sudiana, Nana; Nugroho, Sutopo Purwo</p> <p>2008-09-01</p> <p>Dissolved and particulate organic and inorganic carbon concentrations and flux were measured from July 2005 to June 2006 in the Brantas River basin, a midsized tropical mountainous river and the second largest in Java. There were large <span class="hlt">seasonal</span> differences in carbon fluxes. Dissolved inorganic carbon (DIC) fluxes were 9.3 times greater and dissolved organic carbon (DOC) fluxes were 532 times greater in the wet <span class="hlt">season</span> (October to April) than in the dry <span class="hlt">season</span>. These large <span class="hlt">contrasts</span> in concentration lead to large differences in load between dry and wet months. In the wet <span class="hlt">season</span> between January and April, DIC and DOC fluxes are 66% and 87%, respectively, of the total annual fluxes. Most of the annual fluxes of total suspended solids (2.7 × 106 t a-1), total dissolved solids (2.3 × 106 t a-1), DIC (0.26 × 106 t a-1), and DOC (0.2 × 106 t a-1) are transported into the Madura Strait. Accordingly, the Brantas River ranks number 17 among the top 20 rivers that originate at elevations above 3000 m. The concentration of DIC is consistently high all yearlong due to carbonate weathering in the river basin, except in the middle part of the basin, whereas the concentration of DOC is highly <span class="hlt">seasonal</span> because of variations in biological activities. The total inorganic carbon concentration substantially exceeded the total organic carbon concentration, but the differences decreased from January to April when DOC increased sharply. The carbon budget indicates that the upstream river is a carbon source, and the middle sections of the river are a carbon sink. No carbon trapping was observed by the several impoundments over the basin while sediment trapping was obvious.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4564196','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4564196"><span id="translatedtitle">Nutrient <span class="hlt">Dynamics</span> of Estuarine Invertebrates Are Shaped by Feeding Guild Rather than <span class="hlt">Seasonal</span> River Flow</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ortega-Cisneros, Kelly; Scharler, Ursula M.</p> <p>2015-01-01</p> <p>This study aimed to determine the variability of carbon and nitrogen elemental content, stoichiometry and diet proportions of invertebrates in two sub-tropical estuaries in South Africa experiencing <span class="hlt">seasonal</span> changes in rainfall and river inflow. The elemental ratios and stable isotopes of abiotic sources, zooplankton and macrozoobenthos taxa were analyzed over a dry/wet <span class="hlt">seasonal</span> cycle. Nutrient content (C, N) and stoichiometry of suspended particulate matter exhibited significant spatio-temporal variations in both estuaries, which were explained by the variability in river inflow. Sediment particulate matter (%C, %N and C:N) was also influenced by the variability in river flow but to a lesser extent. The nutrient content and ratios of the analyzed invertebrates did not significantly vary among <span class="hlt">seasons</span> with the exception of the copepod Pseudodiaptomus spp. (C:N) and the tanaid Apseudes digitalis (%N, C:N). These changes did not track the <span class="hlt">seasonal</span> variations of the suspended or sediment particulate matter. Our results suggest that invertebrates managed to maintain their stoichiometry independent of the <span class="hlt">seasonality</span> in river flow. A significant variability in nitrogen content among estuarine invertebrates was recorded, with highest % N recorded from predators and lowest %N from detritivores. Due to the otherwise general lack of <span class="hlt">seasonal</span> differences in elemental content and stoichiometry, feeding guild was a major factor shaping the nutrient <span class="hlt">dynamics</span> of the estuarine invertebrates. The nutrient richer suspended particulate matter was the preferred food source over sediment particulate matter for most invertebrate consumers in many, but not all <span class="hlt">seasons</span>. The most distinct preference for suspended POM as a food source was apparent from the temporarily open/closed system after the estuary had breached, highlighting the importance of river flow as a driver of invertebrate nutrient <span class="hlt">dynamics</span> under extreme events conditions. Moreover, our data showed that estuarine</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26352433','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26352433"><span id="translatedtitle">Nutrient <span class="hlt">Dynamics</span> of Estuarine Invertebrates Are Shaped by Feeding Guild Rather than <span class="hlt">Seasonal</span> River Flow.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ortega-Cisneros, Kelly; Scharler, Ursula M</p> <p>2015-01-01</p> <p>This study aimed to determine the variability of carbon and nitrogen elemental content, stoichiometry and diet proportions of invertebrates in two sub-tropical estuaries in South Africa experiencing <span class="hlt">seasonal</span> changes in rainfall and river inflow. The elemental ratios and stable isotopes of abiotic sources, zooplankton and macrozoobenthos taxa were analyzed over a dry/wet <span class="hlt">seasonal</span> cycle. Nutrient content (C, N) and stoichiometry of suspended particulate matter exhibited significant spatio-temporal variations in both estuaries, which were explained by the variability in river inflow. Sediment particulate matter (%C, %N and C:N) was also influenced by the variability in river flow but to a lesser extent. The nutrient content and ratios of the analyzed invertebrates did not significantly vary among <span class="hlt">seasons</span> with the exception of the copepod Pseudodiaptomus spp. (C:N) and the tanaid Apseudes digitalis (%N, C:N). These changes did not track the <span class="hlt">seasonal</span> variations of the suspended or sediment particulate matter. Our results suggest that invertebrates managed to maintain their stoichiometry independent of the <span class="hlt">seasonality</span> in river flow. A significant variability in nitrogen content among estuarine invertebrates was recorded, with highest % N recorded from predators and lowest %N from detritivores. Due to the otherwise general lack of <span class="hlt">seasonal</span> differences in elemental content and stoichiometry, feeding guild was a major factor shaping the nutrient <span class="hlt">dynamics</span> of the estuarine invertebrates. The nutrient richer suspended particulate matter was the preferred food source over sediment particulate matter for most invertebrate consumers in many, but not all <span class="hlt">seasons</span>. The most distinct preference for suspended POM as a food source was apparent from the temporarily open/closed system after the estuary had breached, highlighting the importance of river flow as a driver of invertebrate nutrient <span class="hlt">dynamics</span> under extreme events conditions. Moreover, our data showed that estuarine</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4803741','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4803741"><span id="translatedtitle">Living on the Edge: <span class="hlt">Contrasted</span> Wood-Formation <span class="hlt">Dynamics</span> in Fagus sylvatica and Pinus sylvestris under Mediterranean Conditions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Martinez del Castillo, Edurne; Longares, Luis A.; Gričar, Jožica; Prislan, Peter; Gil-Pelegrín, Eustaquio; Čufar, Katarina; de Luis, Martin</p> <p>2016-01-01</p> <p>Wood formation in European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.) was intra-annually monitored to examine plastic responses of the xylem phenology according to altitude in one of the southernmost areas of their distribution range, i.e., in the Moncayo Natural Park, Spain. The monitoring was done from 2011 to 2013 at 1180 and 1580 m a.s.l., corresponding to the lower and upper limits of European beech forest in this region. Microcores containing phloem, cambium and xylem were collected biweekly from twenty-four trees from the beginning of March to the end of November to assess the different phases of wood formation. The samples were prepared for light microscopy to observe the following phenological phases: onset and end of cell production, onset and end of secondary wall formation in xylem cells and onset of cell maturation. The temporal <span class="hlt">dynamics</span> of wood formation widely differed among years, altitudes and tree species. For Fagus sylvatica, the onset of cambial activity varied between the first week of May and the third week of June. Cambial activity then slowed down and stopped in summer, resulting in a length of growing <span class="hlt">season</span> of 48–75 days. In <span class="hlt">contrast</span>, the growing <span class="hlt">season</span> for P. sylvestris started earlier and cambium remained active in autumn, leading to a period of activity varying from 139-170 days. The intra-annual wood-formation pattern is site and species-specific. Comparison with other studies shows a clear latitudinal trend in the duration of wood formation, positive for Fagus sylvatica and negative for P. sylvestris. PMID:27047534</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26283349','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26283349"><span id="translatedtitle">Quantifying <span class="hlt">seasonal</span> population fluxes driving rubella transmission <span class="hlt">dynamics</span> using mobile phone data.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wesolowski, Amy; Metcalf, C J E; Eagle, Nathan; Kombich, Janeth; Grenfell, Bryan T; Bjørnstad, Ottar N; Lessler, Justin; Tatem, Andrew J; Buckee, Caroline O</p> <p>2015-09-01</p> <p>Changing patterns of human aggregation are thought to drive annual and multiannual outbreaks of infectious diseases, but the paucity of data about travel behavior and population flux over time has made this idea difficult to test quantitatively. Current measures of human mobility, especially in low-income settings, are often static, relying on approximate travel times, road networks, or cross-sectional surveys. Mobile phone data provide a unique source of information about human travel, but the power of these data to describe epidemiologically relevant changes in population density remains unclear. Here we quantify <span class="hlt">seasonal</span> travel patterns using mobile phone data from nearly 15 million anonymous subscribers in Kenya. Using a rich data source of rubella incidence, we show that patterns of population travel (fluxes) inferred from mobile phone data are predictive of disease transmission and improve significantly on standard school term time and weather covariates. Further, combining <span class="hlt">seasonal</span> and spatial data on travel from mobile phone data allows us to characterize <span class="hlt">seasonal</span> fluctuations in risk across Kenya and produce <span class="hlt">dynamic</span> importation risk maps for rubella. Mobile phone data therefore offer a valuable previously unidentified source of data for measuring key drivers of <span class="hlt">seasonal</span> epidemics. PMID:26283349</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70032414','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70032414"><span id="translatedtitle"><span class="hlt">Seasonal</span> timing of first rain storms affects rare plant population <span class="hlt">dynamics</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Levine, J.M.; McEachern, A.K.; Cowan, C.</p> <p>2011-01-01</p> <p>A major challenge in forecasting the ecological consequences of climate change is understanding the relative importance of changes to mean conditions vs. changes to discrete climatic events, such as storms, frosts, or droughts. Here we show that the first major storm of the growing <span class="hlt">season</span> strongly influences the population <span class="hlt">dynamics</span> of three rare and endangered annual plant species in a coastal California (USA) ecosystem. In a field experiment we used moisture barriers and water addition to manipulate the timing and temperature associated with first major rains of the <span class="hlt">season</span>. The three focal species showed two- to fivefold variation in per capita population growth rates between the different storm treatments, comparable to variation found in a prior experiment imposing eightfold differences in <span class="hlt">season</span>-long precipitation. Variation in germination was a major demographic driver of how two of three species responded to the first rains. For one of these species, the timing of the storm was the most critical determinant of its germination, while the other showed enhanced germination with colder storm temperatures. The role of temperature was further supported by laboratory trials showing enhanced germination in cooler treatments. Our work suggests that, because of species-specific cues for demographic transitions such as germination, changes to discrete climate events may be as, if not more, important than changes to <span class="hlt">season</span>-long variables.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20180911','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20180911"><span id="translatedtitle"><span class="hlt">Seasonally</span> <span class="hlt">dynamic</span> fungal communities in the Quercus macrocarpa phyllosphere differ between urban and nonurban environments.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jumpponen, A; Jones, K L</p> <p>2010-04-01</p> <p>*The fungal richness, diversity and community composition in the Quercus macrocarpa phyllosphere were compared across a growing <span class="hlt">season</span> in trees located in six stands within and outside a small urban center using 454-sequencing and DNA tagging. The approaches did not differentiate between endophytic and epiphytic fungal communities. *Fungi accumulated in the phyllosphere rapidly and communities were temporally <span class="hlt">dynamic</span>, with more than a third of the analyzed operational taxonomic units (OTUs) and half of the BLAST-inferred genera showing distinct <span class="hlt">seasonal</span> patterns. The <span class="hlt">seasonal</span> patterns could be explained by fungal life cycles or environmental tolerances. *The communities were hyperdiverse and differed between the urban and nonurban stands, albeit not consistently across the growing <span class="hlt">season</span>. Foliar macronutrients (nitrogen (N), potassium (K) and sulfur (S)), micronutrients (boron (B), manganese (Mn) and selenium (Se)) and trace elements (cadmium (Cd), lead (Pb) and zinc (Zn)) were enriched in the urban trees, probably as a result of anthropogenic activities. Because of correlations with the experimental layout, these chemical elements should not be considered as community drivers without further empirical studies. *We suggest that a combination of mechanisms leads to differences between urban and nonurban communities. Among those are stand isolation and size, nutrient and pollutant accumulation plus stand management, including fertilization and litter removal. PMID:20180911</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4568255','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4568255"><span id="translatedtitle">Quantifying <span class="hlt">seasonal</span> population fluxes driving rubella transmission <span class="hlt">dynamics</span> using mobile phone data</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wesolowski, Amy; Metcalf, C. J. E.; Eagle, Nathan; Kombich, Janeth; Grenfell, Bryan T.; Bjørnstad, Ottar N.; Lessler, Justin; Tatem, Andrew J.; Buckee, Caroline O.</p> <p>2015-01-01</p> <p>Changing patterns of human aggregation are thought to drive annual and multiannual outbreaks of infectious diseases, but the paucity of data about travel behavior and population flux over time has made this idea difficult to test quantitatively. Current measures of human mobility, especially in low-income settings, are often static, relying on approximate travel times, road networks, or cross-sectional surveys. Mobile phone data provide a unique source of information about human travel, but the power of these data to describe epidemiologically relevant changes in population density remains unclear. Here we quantify <span class="hlt">seasonal</span> travel patterns using mobile phone data from nearly 15 million anonymous subscribers in Kenya. Using a rich data source of rubella incidence, we show that patterns of population travel (fluxes) inferred from mobile phone data are predictive of disease transmission and improve significantly on standard school term time and weather covariates. Further, combining <span class="hlt">seasonal</span> and spatial data on travel from mobile phone data allows us to characterize <span class="hlt">seasonal</span> fluctuations in risk across Kenya and produce <span class="hlt">dynamic</span> importation risk maps for rubella. Mobile phone data therefore offer a valuable previously unidentified source of data for measuring key drivers of <span class="hlt">seasonal</span> epidemics. PMID:26283349</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=281892','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=281892"><span id="translatedtitle">Relative influence of plant quality and natural enemies on the <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of bemisia tabaci (Hemiptera: Aleyrodidae) in cotton</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>The abundance and distribution of insect herbivores is determined by, among other things, plant quality and natural enemies. These two factors vary temporally and spatially, subsequently affecting <span class="hlt">seasonal</span> population <span class="hlt">dynamics</span>. The relative influence of plant quality and natural enemies on the <span class="hlt">season</span>...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23190200','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23190200"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">dynamics</span> and age of stemwood nonstructural carbohydrates in temperate forest trees.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Richardson, Andrew D; Carbone, Mariah S; Keenan, Trevor F; Czimczik, Claudia I; Hollinger, David Y; Murakami, Paula; Schaberg, Paul G; Xu, Xiaomei</p> <p>2013-02-01</p> <p>Nonstructural carbohydrate reserves support tree metabolism and growth when current photosynthates are insufficient, offering resilience in times of stress. We monitored stemwood nonstructural carbohydrate (starch and sugars) concentrations of the dominant tree species at three sites in the northeastern United States. We estimated the mean age of the starch and sugars in a subset of trees using the radiocarbon ((14) C) bomb spike. With these data, we then tested different carbon (C) allocation schemes in a process-based model of forest C cycling. We found that the nonstructural carbohydrates are both highly <span class="hlt">dynamic</span> and about a decade old. <span class="hlt">Seasonal</span> <span class="hlt">dynamics</span> in starch (two to four times higher in the growing <span class="hlt">season</span>, lower in the dormant <span class="hlt">season</span>) mirrored those of sugars. Radiocarbon-based estimates indicated that the mean age of the starch and sugars in red maple (Acer rubrum) was 7-14 yr. A two-pool (fast and slow cycling reserves) model structure gave reasonable estimates of the size and mean residence time of the total NSC pool, and greatly improved model predictions of interannual variability in woody biomass increment, compared with zero- or one-pool structures used in the majority of existing models. This highlights the importance of nonstructural carbohydrates in the context of forest ecosystem carbon cycling. PMID:23190200</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015OcDyn..65..951F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015OcDyn..65..951F"><span id="translatedtitle">Impact of wind and tides on the Lena River freshwater plume <span class="hlt">dynamics</span> in the summer <span class="hlt">season</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fofonova, Vera; Danilov, Sergey; Androsov, Alexey; Janout, Markus; Bauer, Martin; Overduin, Paul; Itkin, Polona; Wiltshire, Karen Helen</p> <p>2015-07-01</p> <p>The Lena plume <span class="hlt">dynamics</span> in the Lena Delta region of the Laptev Sea are explored in simulations performed with the Finite Volume Coastal Ocean Model (FVCOM) on a mesh with the horizontal resolution 0.4-5 km. The impact of wind and tides on the Lena plume propagation is analysed based on simulations for the summer <span class="hlt">season</span> of 2008 and also on idealised experiments. All main Lena River freshwater channels (Trofimovskaya, Bykovskaya, Tumatskaya and Olenekskaya) produce buoyant outflows in the summer <span class="hlt">season</span>. The surface plume buoyancy signature proves to be highly variable in time, especially in case of upwelling favourable wind events. Winds stronger than 6 m s-1 can already turn the <span class="hlt">dynamics</span> of flows from all main freshwater channels to the wind-driven state. During the summer <span class="hlt">season</span>, the bulk of freshwater from the Lena River stays in the eastern Laptev Sea because of location of the main Lena River freshwater channels, their large Kelvin numbers and light summer winds. Westward and northward plume excursions are wind-driven, and the model skill in simulating them depends on the available wind forcing. The main mechanism of tidal influence in the freshwater plume zone is through tidally induced mixing, except for the northern vicinity of the delta, where residual circulation may contribute to the plume eastward transport significantly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3195376','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3195376"><span id="translatedtitle">Development and characterization of a <span class="hlt">dynamic</span> lesion phantom for the quantitative evaluation of <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced MRI</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Freed, Melanie; de Zwart, Jacco A.; Hariharan, Prasanna; R. Myers, Matthew; Badano, Aldo</p> <p>2011-01-01</p> <p>Purpose: To develop a <span class="hlt">dynamic</span> lesion phantom that is capable of producing physiological kinetic curves representative of those seen in human <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced MRI (DCE-MRI) data. The objective of this phantom is to provide a platform for the quantitative comparison of DCE-MRI protocols to aid in the standardization and optimization of breast DCE-MRI. Methods: The <span class="hlt">dynamic</span> lesion consists of a hollow, plastic mold with inlet and outlet tubes to allow flow of a <span class="hlt">contrast</span> agent solution through the lesion over time. Border shape of the lesion can be controlled using the lesion mold production method. The configuration of the inlet and outlet tubes was determined using fluid transfer simulations. The total fluid flow rate was determined using x-ray images of the lesion for four different flow rates (0.25, 0.5, 1.0, and 1.5 ml∕s) to evaluate the resultant kinetic curve shape and homogeneity of the <span class="hlt">contrast</span> agent distribution in the <span class="hlt">dynamic</span> lesion. High spatial and temporal resolution x-ray measurements were used to estimate the true kinetic curve behavior in the <span class="hlt">dynamic</span> lesion for benign and malignant example curves. DCE-MRI example data were acquired of the <span class="hlt">dynamic</span> phantom using a clinical protocol. Results: The optimal inlet and outlet tube configuration for the lesion molds was two inlet molds separated by 30° and a single outlet tube directly between the two inlet tubes. X-ray measurements indicated that 1.0 ml∕s was an appropriate total fluid flow rate and provided truth for comparison with MRI data of kinetic curves representative of benign and malignant lesions. DCE-MRI data demonstrated the ability of the phantom to produce realistic kinetic curves. Conclusions: The authors have constructed a <span class="hlt">dynamic</span> lesion phantom, demonstrated its ability to produce physiological kinetic curves, and provided estimations of its true kinetic curve behavior. This lesion phantom provides a tool for the quantitative evaluation of DCE-MRI protocols, which may lead to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H54A..06T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H54A..06T"><span id="translatedtitle"><span class="hlt">Contrasting</span> Li and Mg isotope behaviour in small Alpine rivers: tracing <span class="hlt">seasonal</span> changes in weathering processes (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tipper, E.; Hindshaw, R. S.; Bourdon, B.; Lemarchand, E.</p> <p>2013-12-01</p> <p><span class="hlt">Seasonal</span> changes in river chemistry offer the potential to assess how weathering processes respond to changing meteorological parameters and ultimately how chemical weathering might respond to climatic parameters. A key observation with time-series data on river waters is that variations in elemental concentrations (typically less than an order of magnitude) are damped compared to variations in discharge (up to several orders of magnitude). This behavior is referred to as chemostatic. However, both radiogenic and stable isotope ratios of the solutes show significant, systematic temporal variations than indicate that there is not a chemostasis in the elemental release of solutes during dissolution. Here we discuss systematic <span class="hlt">seasonal</span> variations in lithium and magnesium isotope ratios (the 7Li/6Li 26Mg/24Mg ratio expressed as delta7Li and delta26Mg in per mil units) in stream waters from a mono-lithological granitic, weathering-limited, first order catchment from the Swiss Alps (Damma glacier). Rain, ground, and pore-waters, in addition to plants, rocks, mineral separates and soil are also reported. Whilst the concentration response of Li and Mg in the river waters is attenuated compared to the large changes in discharge that occur over an annual cycle the systematic trends in both the Mg and Li isotope data imply that either the source of the Li and Mg changes in a systematic manner, or that the process by which Mg and Li are released into solution changes as a function of discharge. In the first order the Mg and Li isotope data appear to show similar trends. However, when examined in more detail, it is difficult to reconcile the data by one pair of fractionation factors for Li and Mg. This provides an additional constraint on how weathering processes vary over a <span class="hlt">seasonal</span> cycle, and perhaps indications an incomplete equilibrium or kinetic limitation to weathering. The reasons behind these trends will be discussed in the context of the apparent chemostatic behavior</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9697E..26A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9697E..26A&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Dynamic</span> full field OCT: metabolic <span class="hlt">contrast</span> at subcellular level (Conference Presentation)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Apelian, Clement; Harms, Fabrice; Thouvenin, Olivier; Boccara, Claude A.</p> <p>2016-03-01</p> <p>Cells shape or density is an important marker of tissues pathology. However, individual cells are difficult to observe in thick tissues frequently presenting highly scattering structures such as collagen fibers. Endogenous techniques struggle to image cells in these conditions. Moreover, exogenous <span class="hlt">contrast</span> agents like dyes, fluorophores or nanoparticles cannot always be used, especially if non-invasive imaging is required. Scatterers motion happening down to the millisecond scale, much faster than the still and highly scattering structures (global motion of the tissue), allowed us to develop a new approach based on the time dependence of the FF-OCT signals. This method reveals hidden cells after a spatiotemporal analysis based on singular value decomposition and wavelet analysis concepts. It does also give us access to local <span class="hlt">dynamics</span> of imaged scatterers. This <span class="hlt">dynamic</span> information is linked with the local metabolic activity that drives these scatterers. Our technique can explore subcellular scales with micrometric resolution and <span class="hlt">dynamics</span> ranging from the millisecond to seconds. By this mean we studied a wide range of tissues, animal and human in both normal and pathological conditions (cancer, ischemia, osmotic shock…) in different organs such as liver, kidney, and brain among others. Different cells, undetectable with FF-OCT, were identified (erythrocytes, hepatocytes…). Different scatterers clusters express different characteristic times and thus can be related to different mechanisms that we identify with metabolic functions. We are confident that the D-FFOCT, by accessing to a new spatiotemporal metabolic <span class="hlt">contrast</span>, will be a leading technique on tissue imaging and for better medical diagnosis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23681894','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23681894"><span id="translatedtitle"><span class="hlt">Dynamic</span> Vascular Pattern (DVP), a quantification tool for <span class="hlt">contrast</span> enhanced ultrasound.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cui, X W; Ignee, A; Jedrzejczyk, M; Dietrich, C F</p> <p>2013-05-01</p> <p><span class="hlt">Contrast</span>-enhanced ultrasound (CEUS) is widely applied in tumour diagnosis, especially for focal liver lesions (FLL), due to its high sensitivity and specificity. According to the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) CEUS guidelines (2012) and non-liver guidelines (2011), the majority of tumours, regardless of location, show specific CEUS enhancement patterns that can distinguish benign from malignant lesions. However, even experienced clinicians evaluating FLL may find occasional irregularities in these patterns, due to particular FLL pathologies, that make a definitive diagnosis difficult. Hence, there is a need to train physicians to utilize <span class="hlt">contrast</span> enhancement kinetics to aid in the correct interpretation of data from CEUS examinations in patients with divergent liver tumour pathologies. Here we report on a CEUS quantitation software, SonoLiver®, to verify and improve diagnostic accuracy in the characterization of suspicious liver lesions through the analysis of <span class="hlt">dynamic</span> vascular patterns (DVP). PMID:23681894</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26296122','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26296122"><span id="translatedtitle">Intramolecular Force <span class="hlt">Contrast</span> and <span class="hlt">Dynamic</span> Current-Distance Measurements at Room Temperature.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huber, F; Matencio, S; Weymouth, A J; Ocal, C; Barrena, E; Giessibl, F J</p> <p>2015-08-01</p> <p>Scanning probe microscopy can be used to probe the internal atomic structure of flat organic molecules. This technique requires an unreactive tip and has, until now, been demonstrated only at liquid helium and liquid nitrogen temperatures. We demonstrate intramolecular and intermolecular force <span class="hlt">contrast</span> at room temperature on PTCDA molecules adsorbed on a Ag/Si(111)-(√[3]×√[3]) surface. The oscillating force sensor allows us to <span class="hlt">dynamically</span> measure the vertical decay constant of the tunneling current. The precision of this method is increased by quantifying the transimpedance of the current to voltage converter and accounting for the tip oscillation. This measurement yields a clear <span class="hlt">contrast</span> between neighboring molecules, which we attribute to the different charge states. PMID:26296122</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvL.115f6101H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvL.115f6101H"><span id="translatedtitle">Intramolecular Force <span class="hlt">Contrast</span> and <span class="hlt">Dynamic</span> Current-Distance Measurements at Room Temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huber, F.; Matencio, S.; Weymouth, A. J.; Ocal, C.; Barrena, E.; Giessibl, F. J.</p> <p>2015-08-01</p> <p>Scanning probe microscopy can be used to probe the internal atomic structure of flat organic molecules. This technique requires an unreactive tip and has, until now, been demonstrated only at liquid helium and liquid nitrogen temperatures. We demonstrate intramolecular and intermolecular force <span class="hlt">contrast</span> at room temperature on PTCDA molecules adsorbed on a Ag /Si (111 )-(√{3 }×√{3 }) surface. The oscillating force sensor allows us to <span class="hlt">dynamically</span> measure the vertical decay constant of the tunneling current. The precision of this method is increased by quantifying the transimpedance of the current to voltage converter and accounting for the tip oscillation. This measurement yields a clear <span class="hlt">contrast</span> between neighboring molecules, which we attribute to the different charge states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4672962','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4672962"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">dynamics</span> of threshold friction velocity and dust emission in Central Asia</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xi, Xin; Sokolik, Irina N</p> <p>2015-01-01</p> <p>An improved model representation of mineral dust cycle is critical to reducing the uncertainty of dust-induced environmental and climatic impact. Here we present a mesoscale model study of the <span class="hlt">seasonal</span> dust activity in the semiarid drylands of Central Asia, focusing on the effects of wind speed, soil moisture, surface roughness heterogeneity, and vegetation phenology on the threshold friction velocity (u*t) and dust emission during the dust <span class="hlt">season</span> of 1 March to 31 October 2001. The dust model WRF-Chem-DuMo allows us to examine the uncertainties in <span class="hlt">seasonal</span> dust emissions due to the selection of dust emission scheme and soil grain size distribution data. To account for the vegetation effects on the u*t, we use the Moderate Resolution Imaging Spectroradiometer monthly normalized difference vegetation index to derive the <span class="hlt">dynamic</span> surface roughness parameters required by the physically based dust schemes of Marticorena and Bergametti (1995, hereinafter MB) and Shao et al. (1996, hereinafter Shao). We find the springtime u*t is strongly enhanced by the roughness effects of temperate steppe and desert ephemeral plants and, to less extent, the binding effects of increased soil moisture. The u*t decreases as the aboveground biomass dies back and soil moisture depletes during summer. The u*t <span class="hlt">dynamics</span> determines the dust <span class="hlt">seasonality</span> by causing more summer dust emission, despite a higher frequency of strong winds during spring. Due to the presence of more erodible materials in the saltation diameter range of 60–200 µm, the dry-sieved soil size distribution data lead to eight times more <span class="hlt">season</span>-total dust emission than the soil texture data, but with minor differences in the temporal distribution. On the other hand, the Shao scheme produces almost the same amount of <span class="hlt">season</span>-total dust emission as the MB scheme, but with a strong shift toward summer due to the strong sensitivity of the u*t to vegetation. By simply averaging the MB and Shao model experiments, we obtain a mean</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3358025','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3358025"><span id="translatedtitle">Linking activity, composition and <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of atmospheric methane oxidizers in a meadow soil</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Shrestha, Pravin Malla; Kammann, Claudia; Lenhart, Katharina; Dam, Bomba; Liesack, Werner</p> <p>2012-01-01</p> <p>Microbial oxidation is the only biological sink for atmospheric methane. We assessed <span class="hlt">seasonal</span> changes in atmospheric methane oxidation and the underlying methanotrophic communities in grassland near Giessen (Germany), along a soil moisture gradient. Soil samples were taken from the surface layer (0–10 cm) of three sites in August 2007, November 2007, February 2008 and May 2008. The sites showed <span class="hlt">seasonal</span> differences in hydrological parameters. Net uptake rates varied <span class="hlt">seasonally</span> between 0 and 70 μg CH4 m−2 h−1. Greatest uptake rates coincided with lowest soil moisture in spring and summer. Over all sites and <span class="hlt">seasons</span>, the methanotrophic communities were dominated by uncultivated methanotrophs. These formed a monophyletic cluster defined by the RA14, MHP and JR1 clades, referred to as upland soil cluster alphaproteobacteria (USCα)-like group. The copy numbers of pmoA genes ranged between 3.8 × 105–1.9 × 106 copies g−1 of soil. Temperature was positively correlated with CH4 uptake rates (P<0.001), but had no effect on methanotrophic population <span class="hlt">dynamics</span>. The soil moisture was negatively correlated with CH4 uptake rates (P<0.001), but showed a positive correlation with changes in USCα-like diversity (P<0.001) and pmoA gene abundance (P<0.05). These were greatest at low net CH4 uptake rates during winter times and coincided with an overall increase in bacterial 16S rRNA gene abundances (P<0.05). Taken together, soil moisture had a significant but opposed effect on CH4 uptake rates and methanotrophic population <span class="hlt">dynamics</span>, the latter being increasingly stimulated by soil moisture contents >50 vol% and primarily related to members of the MHP clade. PMID:22189499</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012CorRe..31..683F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012CorRe..31..683F"><span id="translatedtitle">Interaction of herbivory and <span class="hlt">seasonality</span> on the <span class="hlt">dynamics</span> of Caribbean macroalgae</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferrari, Renata; Gonzalez-Rivero, Manuel; Ortiz, Juan Carlos; Mumby, Peter J.</p> <p>2012-09-01</p> <p>Many Caribbean coral reefs are undergoing a phase shift from coral to macroalgal dominance. Understanding the processes driving changes in algal abundance and community structure requires clarification of the relative effects of top-down (e.g., herbivory) and bottom-up processes (e.g., light, temperature, and nutrients). To date, a number of studies have examined the relative effects of grazing versus nutrification but interactions between herbivory and natural, <span class="hlt">seasonal</span> fluctuations in temperature and light have not been investigated. This study considered the <span class="hlt">dynamics</span> of three Caribbean macroalgal species [ Lobophora variegata (Lamouroux), Dictyota pulchella (Hörnig and Schnetter), and Halimeda opuntia (Linnaeus)] and algal turf. A field experiment was established to measure species-specific algal <span class="hlt">dynamics</span> (changes in abundance) over 13 months in the presence and absence of herbivory. Both herbivory and <span class="hlt">seasonal</span> changes were important processes controlling macroalgal and turf abundance. Water temperature and light had a key role on D. pulchella; this species' abundance significantly increased in the summer, when water temperature and light were the highest, and decreased during winter. Surprisingly, herbivory did not seem to control D. pulchella directly. However, herbivory was the most important process controlling the abundance of L. variegata, H. opuntia, and turf . The abundance of both algal species was correlated with <span class="hlt">seasonal</span> changes in the environment, but was depleted outside cages throughout the year. The abundance of H. opuntia was positively correlated with temperature and light, but there was no statistical interaction between drivers. The statistical interaction between temperature and light was significant for the abundance of L. variegata and turf, but algal abundance declined as both factors increased. Overall, macroalgal and turf cover were mainly controlled by herbivory, while community structure (which species contributed to the overall cover</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26629993','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26629993"><span id="translatedtitle"><span class="hlt">Dynamics</span> of Chytridiomycosis during the Breeding <span class="hlt">Season</span> in an Australian Alpine Amphibian.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brannelly, Laura A; Hunter, David A; Lenger, Daniel; Scheele, Ben C; Skerratt, Lee F; Berger, Lee</p> <p>2015-01-01</p> <p>Understanding disease <span class="hlt">dynamics</span> during the breeding <span class="hlt">season</span> of declining amphibian species will improve our understanding of how remnant populations persist with endemic infection, and will assist the development of management techniques to protect disease-threatened species from extinction. We monitored the endangered Litoria verreauxii alpina (alpine treefrog) during the breeding <span class="hlt">season</span> through capture-mark-recapture (CMR) studies in which we investigated the <span class="hlt">dynamics</span> of chytridiomycosis in relation to population size in two populations. We found that infection prevalence and intensity increased throughout the breeding <span class="hlt">season</span> in both populations, but infection prevalence and intensity was higher (3.49 and 2.02 times higher prevalence and intensity, respectively) at the site that had a 90-fold higher population density. This suggests that Bd transmission is density-dependent. Weekly survival probability was related to disease state, with heavily infected animals having the lowest survival. There was low recovery from infection, especially when animals were heavily infected with Bd. Sympatric amphibian species are likely to be reservoir hosts for the disease and can play an important role in the disease ecology of Bd. Although we found 0% prevalence in crayfish (Cherax destructor), we found that a sympatric amphibian (Crinia signifera) maintained 100% infection prevalence at a high intensity throughout the <span class="hlt">season</span>. Our results demonstrate the importance of including infection intensity into CMR disease analysis in order to fully understand the implications of disease on the amphibian community. We recommend a combined management approach to promote lower population densities and ensure consistent progeny survival. The most effective management strategy to safeguard the persistence of this susceptible species might be to increase habitat area while maintaining a similar sized suitable breeding zone and to increase water flow and area to reduce drought. PMID:26629993</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4668081','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4668081"><span id="translatedtitle"><span class="hlt">Dynamics</span> of Chytridiomycosis during the Breeding <span class="hlt">Season</span> in an Australian Alpine Amphibian</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Brannelly, Laura A.; Hunter, David A.; Lenger, Daniel; Scheele, Ben C.; Skerratt, Lee F.; Berger, Lee</p> <p>2015-01-01</p> <p>Understanding disease <span class="hlt">dynamics</span> during the breeding <span class="hlt">season</span> of declining amphibian species will improve our understanding of how remnant populations persist with endemic infection, and will assist the development of management techniques to protect disease-threatened species from extinction. We monitored the endangered Litoria verreauxii alpina (alpine treefrog) during the breeding <span class="hlt">season</span> through capture-mark-recapture (CMR) studies in which we investigated the <span class="hlt">dynamics</span> of chytridiomycosis in relation to population size in two populations. We found that infection prevalence and intensity increased throughout the breeding <span class="hlt">season</span> in both populations, but infection prevalence and intensity was higher (3.49 and 2.02 times higher prevalence and intensity, respectively) at the site that had a 90-fold higher population density. This suggests that Bd transmission is density-dependent. Weekly survival probability was related to disease state, with heavily infected animals having the lowest survival. There was low recovery from infection, especially when animals were heavily infected with Bd. Sympatric amphibian species are likely to be reservoir hosts for the disease and can play an important role in the disease ecology of Bd. Although we found 0% prevalence in crayfish (Cherax destructor), we found that a sympatric amphibian (Crinia signifera) maintained 100% infection prevalence at a high intensity throughout the <span class="hlt">season</span>. Our results demonstrate the importance of including infection intensity into CMR disease analysis in order to fully understand the implications of disease on the amphibian community. We recommend a combined management approach to promote lower population densities and ensure consistent progeny survival. The most effective management strategy to safeguard the persistence of this susceptible species might be to increase habitat area while maintaining a similar sized suitable breeding zone and to increase water flow and area to reduce drought. PMID:26629993</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.B51G0383S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.B51G0383S&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Seasonally-Dynamic</span> SPARROW Modeling of Nitrogen Flux Using Earth Observation Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smith, R. A.; Schwarz, G. E.; Brakebill, J. W.; Hoos, A. B.; Moore, R. B.; Shih, J.; Nolin, A. W.; Macauley, M.; Alexander, R. B.</p> <p>2013-12-01</p> <p>SPARROW models are widely used to identify and quantify the sources of contaminants in watersheds and to predict their flux and concentration at specified locations downstream. Conventional SPARROW models describe the average relationship between sources and stream conditions based on long-term water quality monitoring data and spatially-referenced explanatory information. But many watershed management issues stem from intra- and inter-annual changes in contaminant sources, hydrologic forcing, or other environmental conditions which cause a temporary imbalance between inputs and stream water quality. <span class="hlt">Dynamic</span> behavior of the system relating to changes in watershed storage and processing then becomes important. In this study, we describe <span class="hlt">dynamically</span> calibrated SPARROW models of total nitrogen flux in three sub-regional watersheds: the Potomac River Basin, Long Island Sound drainage, and coastal South Carolina drainage. The models are based on <span class="hlt">seasonal</span> water quality and watershed input data for a total 170 monitoring stations for the period 2001 to 2008. Frequently-reported, spatially-detailed input data on the phenology of agricultural production, terrestrial vegetation growth, and snow melt are often challenging requirements of <span class="hlt">seasonal</span> modeling of reactive nitrogen. In this NASA-funded research, we use Enhanced Vegetation Index (EVI), gross primary production and snow/ice cover data from MODIS to parameterize <span class="hlt">seasonal</span> uptake and release of nitrogen from vegetation and snowpack. The spatial reference frames of the models are 1:100,000-scale stream networks, and the computational time steps are 0.25-year <span class="hlt">seasons</span>. Precipitation and temperature data are from PRISM. The model formulation accounts for storage of nitrogen from nonpoint sources including fertilized cropland, pasture, urban land, and atmospheric deposition. Model calibration is by non-linear regression. Once calibrated, model source terms based on previous <span class="hlt">season</span> export allow for recursive <span class="hlt">dynamic</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27031994','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27031994"><span id="translatedtitle">Tumor Heterogeneity in Lung Cancer: Assessment with <span class="hlt">Dynamic</span> <span class="hlt">Contrast</span>-enhanced MR Imaging.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yoon, Soon Ho; Park, Chang Min; Park, Sang Joon; Yoon, Jeong-Hwa; Hahn, Seokyung; Goo, Jin Mo</p> <p>2016-09-01</p> <p>Purpose To evaluate histogram and texture parameters on pretreatment <span class="hlt">dynamic</span> <span class="hlt">contrast</span> material-enhanced (DCE) magnetic resonance (MR) images in lung cancer in terms of temporal change, optimal time for analysis, and prognostic potential. Materials and Methods This retrospective study was approved by the institutional review board, and the requirement to obtain informed consent was waived. Thirty-eight patients with pathologically proved lung cancer undergoing standard pretreatment DCE MR imaging were included. A fat-suppressed, T1-weighted, volume-interpolated breath-hold MR sequence was performed every 30 seconds for 300 and 480 seconds after <span class="hlt">contrast</span> material administration. A region of interest was manually drawn in the largest cross-sectional area of the tumor on DCE MR images to extract semiquantitative perfusion, histogram, and texture parameters. Predictability of 2-year progression-free survival (PFS) was analyzed by using the Kaplan-Meier method and Cox regression analysis. Results MR histogram and texture parameters increased rapidly 30-60 seconds after <span class="hlt">contrast</span> material administration. Standard deviation and entropy then plateaued, whereas skewness and kurtosis rapidly decreased. Univariate Cox regression analysis revealed that standard deviation and entropy were significant predictors of survival; their statistical significance was preserved from 60 to 300 seconds, with the smallest P values (P ≤ .001) occurring from 120 to 180 seconds. At multivariate Cox regression analysis, entropy was the sole significant predictor of 2-year PFS (hazard ratio at 180 seconds, 10.098 [95% confidence interval: 1.579, 64.577], P = .015; hazard ratio at 120 seconds: 11.202 [95% confidence interval: 1.761, 71.260], P = .010). Conclusion Histogram and texture parameter changes varied after <span class="hlt">contrast</span> material injection. The 120-180-second window after <span class="hlt">contrast</span> material injection was optimal for MR imaging-derived texture parameter and entropy at DCE MR imaging. (©) RSNA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ThApC.tmp..145L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016ThApC.tmp..145L&link_type=ABSTRACT"><span id="translatedtitle">Carbon dioxide <span class="hlt">seasonality</span> in <span class="hlt">dynamically</span> ventilated caves: the role of advective fluxes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lang, Marek; Faimon, Jiří; Godissart, Jean; Ek, Camille</p> <p>2016-07-01</p> <p>The <span class="hlt">seasonality</span> in cave CO2 levels was studied based on (1) a new data set from the <span class="hlt">dynamically</span> ventilated Comblain-au-Pont Cave (Dinant Karst Basin, Belgium), (2) archive data from Moravian Karst caves, and (3) published data from caves worldwide. A simplified <span class="hlt">dynamic</span> model was proposed for testing the effect of all conceivable CO2 fluxes on cave CO2 levels. Considering generally accepted fluxes, i.e., the direct diffusive flux from soils/epikarst, the indirect flux derived from dripwater degassing, and the input/output fluxes linked to cave ventilation, gives the cave CO2 level maxima of 1.9 × 10-2 mol m-3 (i.e., ˜ 440 ppmv), which only slightly exceed external values. This indicates that an additional input CO2 flux is necessary for reaching usual cave CO2 level maxima. The modeling indicates that the additional flux could be a convective advective CO2 flux from soil/epikarst driven by airflow (cave ventilation) and enhanced soil/epikarstic CO2 concentrations. Such flux reaching up to 170 mol s-1 is capable of providing the cave CO2 level maxima up to 3 × 10-2 mol m-3 (70,000 ppmv). This value corresponds to the maxima known from caves worldwide. Based on cave geometry, three types of <span class="hlt">dynamic</span> caves were distinguished: (1) the caves with the advective CO2 flux from soil/epikarst at downward airflow ventilation mode, (2) the caves with the advective soil/epikarstic flux at upward airflow ventilation mode, and (3) the caves without any soil/epikarstic advective flux. In addition to CO2 <span class="hlt">seasonality</span>, the model explains both the short-term and <span class="hlt">seasonal</span> variations in δ13C in cave air CO2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JGRD..10916S05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JGRD..10916S05S"><span id="translatedtitle">Aerosol chemical composition in New York state from integrated filter samples: Urban/rural and <span class="hlt">seasonal</span> <span class="hlt">contrasts</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schwab, James J.; Felton, H. D.; Demerjian, Kenneth L.</p> <p>2004-08-01</p> <p>Filter samples have been collected and analyzed for chemical composition at a number of sites in New York state for more than 2 years. Because of the broad focus of the New York Environmental Protection Agency Supersite program, these sites include remote, rural, and urban sites in midsized and large cities. Calculated blanks and laboratory reported minimum detection limits (MDLs) for all measured species are presented. Data are averaged by location and <span class="hlt">season</span> and presented for six sites throughout New York state. Data are presented for PM2.5 mass, sulfate, nitrate, ammonium and carbon, and selected metals and groups of trace elements. An approximate ion balance of the major inorganic ionic species is also calculated, which shows a predominately negative ion balance with the rural and remote sites being the most negative. In addition to chemical composition values in mass per unit volume (reported to ambient conditions), we also calculate ratios of the mass concentration values for five sites referenced to our site that is closest to background, Whiteface Mountain in the Adirondacks. By computing base ratios for the various chemical components and ratios of ratios referenced to mass concentrations, we can provide some insight into the sources of these chemical components relative to the sources of PM2.5 mass. The ratio of ratios analysis indicated that sulfate and potassium are the most regional species considered and that EC and some metal species have the strongest urban (especially New York City) sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3837O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3837O"><span id="translatedtitle"><span class="hlt">Seasonal</span> and long-term rainfall and cloud <span class="hlt">dynamics</span> in the Mt. Kilimanjaro region as observed from local and remote sensing time series</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Otte, Insa; Detsch, Florian; Mwangomo, Ephraim; Nauss, Thomas; Appelhans, Tim</p> <p>2015-04-01</p> <p>The melting glaciers of Mt. Kilimanjaro have become a synonym for global change. In <span class="hlt">contrast</span>, the non-glaciated areas receive much less public attention. Aside from a brief examination of air-temperature, in-situ rainfall and remotely sensed cloud <span class="hlt">dynamics</span> are analyzed to determine <span class="hlt">seasonal</span> and long-term climate trends in the Mt. Kilimanjaro region in this study. The in-situ air-temperature is based on NOAA'S GSOD datasets, the in-situ rainfall data is obtained from the Tanzania Meteorological Agency. Both datasets span from 1973 to 2013. Rainfall data was obtained from two in-situ stations at Moshi and Kilimanjaro Airport, both situated in the Kilimanjaro area, which were considered to be representative at least for the greater region after correlation analysis with in-situ station data from the southern slopes of Mt. Kilimanjaro. While a temperature increase of about 0.29 K per decade can be identified, no long-term rainfall trends are observable. However, humid and dry decades are evident with so called "short" (with a peak around December) and "long" (March to May) rains. <span class="hlt">Seasonality</span> has changed especially during the long rains between March and May. As rainfall and cloud cover were analyzed with respect of the status of El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) some <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> could be linked to these large-scale drivers. Characteristic <span class="hlt">seasonal</span> patterns related to ENSO and IOD teleconnections show enhanced rainfall in the onset year and in the post-ENSO year for most El Niño events. During La Niña years, rainfall increases in the following year, while for the onset year scenarios must be regarded differentiated. Positive IOD events lead to enhanced rainfall amounts, highlighting the importance of IOD events in modifying ENSO related rainfall <span class="hlt">dynamics</span> in the Kilimanjaro area Additionally, cloud <span class="hlt">dynamics</span> have been analyzed using daily Aqua-MODIS cloud products between 2002 and 2013. In <span class="hlt">contrast</span> to the rainfall <span class="hlt">dynamics</span>, cloud</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19272996','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19272996"><span id="translatedtitle">Quantitative analysis of <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced MR images based on Bayesian P-splines.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schmid, Volker J; Whitcher, Brandon; Padhani, Anwar R; Yang, Guang-Zhong</p> <p>2009-06-01</p> <p><span class="hlt">Dynamic</span> <span class="hlt">contrast</span>-enhanced magnetic resonance imaging (DCE-MRI) is an important tool for detecting subtle kinetic changes in cancerous tissue. Quantitative analysis of DCE-MRI typically involves the convolution of an arterial input function (AIF) with a nonlinear pharmacokinetic model of the <span class="hlt">contrast</span> agent concentration. Parameters of the kinetic model are biologically meaningful, but the optimization of the nonlinear model has significant computational issues. In practice, convergence of the optimization algorithm is not guaranteed and the accuracy of the model fitting may be compromised. To overcome these problems, this paper proposes a semi-parametric penalized spline smoothing approach, where the AIF is convolved with a set of B-splines to produce a design matrix using locally adaptive smoothing parameters based on Bayesian penalized spline models (P-splines). It has been shown that kinetic parameter estimation can be obtained from the resulting deconvolved response function, which also includes the onset of <span class="hlt">contrast</span> enhancement. Detailed validation of the method, both with simulated and in vivo data, is provided. PMID:19272996</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3147123','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3147123"><span id="translatedtitle">Optimal Analysis Method for <span class="hlt">Dynamic</span> <span class="hlt">Contrast</span>-Enhanced Diffuse Optical Tomography</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ghijsen, Michael; Lin, Yuting; Hsing, Mitchell; Nalcioglu, Orhan; Gulsen, Gultekin</p> <p>2011-01-01</p> <p>Diffuse Optical Tomography (DOT) is an optical imaging modality that has various clinical applications. However, the spatial resolution and quantitative accuracy of DOT is poor due to strong photon scatting in biological tissue. Structural a priori information from another high spatial resolution imaging modality such as Magnetic Resonance Imaging (MRI) has been demonstrated to significantly improve DOT accuracy. In addition, a <span class="hlt">contrast</span> agent can be used to obtain differential absorption images of the lesion by using <span class="hlt">dynamic</span> <span class="hlt">contrast</span> enhanced DOT (DCE-DOT). This produces a relative absorption map that consists of subtracting a reconstructed baseline image from reconstructed images in which optical <span class="hlt">contrast</span> is included. In this study, we investigated and compared different reconstruction methods and analysis approaches for regular endogenous DOT and DCE-DOT with and without MR anatomical a priori information for arbitrarily-shaped objects. Our phantom and animal studies have shown that superior image quality and higher accuracy can be achieved using DCE-DOT together with MR structural a priori information. Hence, implementation of a combined MRI-DOT system to image ICG enhancement can potentially be a promising tool for breast cancer imaging. PMID:21811492</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PMB....60.5225S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PMB....60.5225S"><span id="translatedtitle">Automatic indicator dilution curve extraction in <span class="hlt">dynamic-contrast</span> enhanced imaging using spectral clustering</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saporito, Salvatore; Herold, Ingeborg HF; Houthuizen, Patrick; van den Bosch, Harrie CM; Korsten, Hendrikus HM; van Assen, Hans C.; Mischi, Massimo</p> <p>2015-07-01</p> <p>Indicator dilution theory provides a framework for the measurement of several cardiovascular parameters. Recently, <span class="hlt">dynamic</span> imaging and <span class="hlt">contrast</span> agents have been proposed to apply the method in a minimally invasive way. However, the use of <span class="hlt">contrast</span>-enhanced sequences requires the definition of regions of interest (ROIs) in the <span class="hlt">dynamic</span> image series; a time-consuming and operator dependent task, commonly performed manually. In this work, we propose a method for the automatic extraction of indicator dilution curves, exploiting the time domain correlation between pixels belonging to the same region. Individual time intensity curves were projected into a low dimensional subspace using principal component analysis; subsequently, clustering was performed to identify the different ROIs. The method was assessed on clinically available DCE-MRI and DCE-US recordings, comparing the derived IDCs with those obtained manually. The robustness to noise of the proposed approach was shown on simulated data. The tracer kinetic parameters derived on real images were in agreement with those obtained from manual annotation. The presented method is a clinically useful preprocessing step prior to further ROI-based cardiac quantifications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013OptEn..52j2002R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013OptEn..52j2002R"><span id="translatedtitle"><span class="hlt">Dynamic</span> range reduction and <span class="hlt">contrast</span> adjustment of infrared images in surveillance scenarios</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rossi, Alessandro; Acito, Nicola; Diani, Marco; Corsini, Giovanni</p> <p>2013-10-01</p> <p>The high thermal sensitivity of modern infrared (IR) cameras allows us to distinguish objects with small temperature variations. In comparison with the <span class="hlt">dynamics</span> of standard displays, the sensed IR images have a high <span class="hlt">dynamic</span> range (HDR). In this context, suitable techniques to display HDR images are required in order to improve the visibility of the details without introducing distortions. In the recent literature of IR image processing, a common framework to perform HDR image visualization relies on DR reduction (DRR) with a cascaded processing for local <span class="hlt">contrast</span> adjustment (CA). In this work, a novel method, named cluster-based DRR and <span class="hlt">contrast</span> adjustment (CDCA) is introduced for the visualization of IR images. The CDCA method is composed of two cascaded steps: (1) DRR clustering-based approach and (2) a CA module specifically designed to account for IR image features. The effectiveness of the introduced technique is analyzed using IR images of surveillance scenarios collected in different operating conditions. The results are compared with those given by other IR-HDR visualization methods and show the benefits of the proposed CDCA in terms of details enhancement, robustness against the horizon effect and presence of hot objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4222794','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4222794"><span id="translatedtitle">Validation of <span class="hlt">Dynamic</span> <span class="hlt">Contrast</span>-Enhanced Ultrasound in Predicting Outcomes of Antiangiogenic Therapy for Solid Tumors</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lassau, Nathalie; Bonastre, Julia; Kind, Michèle; Vilgrain, Valérie; Lacroix, Joëlle; Cuinet, Marie; Taieb, Sophie; Aziza, Richard; Sarran, Antony; Labbe-Devilliers, Catherine; Gallix, Benoit; Lucidarme, Olivier; Ptak, Yvette; Rocher, Laurence; Caquot, Louis-Michel; Chagnon, Sophie; Marion, Denis; Luciani, Alain; Feutray, Sylvaine; Uzan-Augui, Joëlle; Coiffier, Benedicte; Benastou, Baya; Koscielny, Serge</p> <p>2014-01-01</p> <p>Objectives <span class="hlt">Dynamic</span> <span class="hlt">contrast</span>-enhanced ultrasound (DCE-US) has been used in single-center studies to evaluate tumor response to antiangiogenic treatments: the change of area under the perfusion curve (AUC), a criterion linked to blood volume, was consistently correlated with the Response Evaluation Criteria in Solid Tumors response. The main objective here was to do a multicentric validation of the use of DCE-US to evaluate tumor response in different solid tumor types treated by several antiangiogenic agents. A secondary objective was to evaluate the costs of the procedure. Materials and Methods This prospective study included patients from 2007 to 2010 in 19 centers (8 teaching hospitals and 11 comprehensive cancer centers). All patients treated with antiangiogenic therapy were eligible. <span class="hlt">Dynamic</span> <span class="hlt">contrast</span>-enhanced ultrasound examinations were performed at baseline as well as on days 7, 15, 30, and 60. For each examination, a perfusion curve was recorded during 3 minutes after injection of a <span class="hlt">contrast</span> agent. Change from baseline at each time point was estimated for each of 7 fitted criteria. The main end point was freedom from progression (FFP). Criterion/time-point combinations with the strongest correlation with FFP were analyzed further to estimate an optimal cutoff point. Results A total of 1968 DCE-US examinations in 539 patients were analyzed. The median follow-up was 1.65 years. Variations from baseline were significant at day 30 for several criteria, with AUC having the most significant association with FFP (P = 0.00002). Patients with a greater than 40% decrease in AUC at day 30 had better FFP (P = 0.005) and overall survival (P = 0.05). The mean cost of each DCE-US was 180€, which corresponds to $250 using the current exchange rate. Conclusions <span class="hlt">Dynamic</span> <span class="hlt">contrast</span>-enhanced ultrasound is a new functional imaging technique that provides a validated criterion, namely, the change of AUC from baseline to day 30, which is predictive of tumor progression in a large</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3164269','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3164269"><span id="translatedtitle">Porcine Ex Vivo Liver Phantom for <span class="hlt">Dynamic</span> <span class="hlt">Contrast</span>-Enhanced Computed Tomography: Development and Initial Results</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Thompson, Scott M.; Giraldo, Juan C. Ramirez; Knudsen, Bruce; Grande, Joseph P.; Christner, Jodie A.; Xu, Man; Woodrum, David A.; McCollough, Cynthia H.; Callstrom, Matthew R.</p> <p>2011-01-01</p> <p>Objectives To demonstrate the feasibility of developing a fixed, dual-input, biological liver phantom for <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced computed tomography (CT) imaging and to report initial results of use of the phantom for quantitative CT perfusion imaging. Materials and Methods Porcine livers were obtained from completed surgical studies and perfused with saline and fixative. The phantom was placed in a body-shaped, CT-compatible acrylic container and connected to a perfusion circuit fitted with a <span class="hlt">contrast</span> injection port. Flow-controlled <span class="hlt">contrast</span>-enhanced imaging experiments were performed using a 128-slice and 64 slice, dual-source multidetector CT scanners. CT angiography protocols were employed to obtain portal venous and hepatic arterial vascular enhancement, reproduced over a period of four to six months. CT perfusion protocols were employed at different input flow rates to correlate input flow with calculated tissue perfusion, to test reproducibility and demonstrate the feasibility of simultaneous dual input liver perfusion. Histologic analysis of the liver phantom was also performed. Results CT angiogram 3D reconstructions demonstrated homogenous tertiary and quaternary branching of the portal venous system out to the periphery of all lobes of the liver as well as enhancement of the hepatic arterial system to all lobes of the liver and gallbladder throughout the study period. For perfusion CT, the correlation between the calculated mean tissue perfusion in a volume of interest and input pump flow rate was excellent (R2 = 0.996) and color blood flow maps demonstrated variations in regional perfusion in a narrow range. Repeat perfusion CT experiments demonstrated reproducible time-attenuation curves and dual-input perfusion CT experiments demonstrated that simultaneous dual input liver perfusion is feasible. Histologic analysis demonstrated that the hepatic microvasculature and architecture appeared intact and well preserved at the completion of four to six</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1811362L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1811362L&link_type=ABSTRACT"><span id="translatedtitle">The <span class="hlt">Dynamics</span> of Halite Precipitation in the Dead Sea: <span class="hlt">Seasonal</span> and Spatial Variations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lensky, Nadav G.; Sirota, Ido; Arnon, Ali</p> <p>2016-04-01</p> <p>The Dead Sea is a deep hypersaline terminal lake that actively precipitates halite as a response to the negative water balance of the lake (evaporation > inflows). From mass balance consideration, a uniform ~3 m thick halite sequence is expected to cover the lake floor following the ~30 m level drop; however such a massive layer does not exist in the shallow water. In this talk we present new insights on the <span class="hlt">dynamics</span> of halite precipitation and dissolution in a <span class="hlt">seasonally</span> stratified lake, based on field observations. In situ monthly observations include the depth profile of the following: (i) halite precipitation rate, (ii) temperature, (iii) salinity, (iv) halite saturation, and (v) underwater photography of the sea floor and the water column - documentation of active halite precipitation/dissolution. We found a clear relation between the thermohaline stratification of the water column and halite precipitation/dissolution. The epilimnion experiences <span class="hlt">seasonal</span> dissolution/precipitation cycle, while the hypolimnion continuously precipitates halite. We discuss the <span class="hlt">seasonal</span> variations of the atmospheric forcing - the heat and water fluxes, and the response of the lake - thermohaline stratification and the precipitation/dissolution of halite along the water column and lake floor. We also discuss the role of diapycnal flux on the precipitation of halite and the salt fluxes. Geological implications on the lateral extent and thickness variations of evaporitic layers in evaporitic environments are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRC..116.2018C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRC..116.2018C"><span id="translatedtitle"><span class="hlt">Dynamics</span> of the <span class="hlt">seasonal</span> variation of the North Equatorial Current bifurcation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Zhaohui; Wu, Lixin</p> <p>2011-02-01</p> <p>The <span class="hlt">dynamics</span> of the <span class="hlt">seasonal</span> variation of the North Equatorial Current (NEC) bifurcation is studied using a 1.5-layer nonlinear reduced-gravity Pacific basin model and a linear, first-mode baroclinic Rossby wave model. The model-simulated bifurcation latitude exhibits a distinct <span class="hlt">seasonal</span> cycle with the southernmost latitude in June and the northernmost latitude in November, consistent with observational analysis. It is found that the <span class="hlt">seasonal</span> migration of the NEC bifurcation latitude (NBL) not only is determined by wind locally in the tropics, as suggested in previous studies, but is also significantly intensified by the extratropical wind through coastal Kelvin waves. The model further demonstrates that the amplitude of the NEC bifurcation is also associated with stratification. A strong (weak) stratification leads to a fast (slow) phase speed of first-mode baroclinic Rossby waves, and thus large (small) annual range of the bifurcation latitude. Therefore, it is expected that in a warm climate the NBL should have a large range of annual migration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26942410','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26942410"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">Dynamics</span> of the Airborne Bacterial Community and Selected Viruses in a Children's Daycare Center.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Prussin, Aaron J; Vikram, Amit; Bibby, Kyle J; Marr, Linsey C</p> <p>2016-01-01</p> <p>Children's daycare centers appear to be hubs of respiratory infectious disease transmission, yet there is only limited information about the airborne microbial communities that are present in daycare centers. We have investigated the microbial community of the air in a daycare center, including <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> in the bacterial community and the presence of specific viral pathogens. We collected filters from the heating, ventilation, and air conditioning (HVAC) system of a daycare center every two weeks over the course of a year. Amplifying and sequencing the 16S rRNA gene revealed that the air was dominated by Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes that are commonly associated with the human skin flora. Clear <span class="hlt">seasonal</span> differences in the microbial community were not evident; however, the community structure differed when the daycare center was closed and unoccupied for a 13-day period. These results suggest that human occupancy, rather than the environment, is the major driver in shaping the microbial community structure in the air of the daycare center. Using PCR for targeted viruses, we detected a <span class="hlt">seasonal</span> pattern in the presence of respiratory syncytial virus that included the period of typical occurrence of the disease related to the virus; however, we did not detect the presence of adenovirus or rotavirus at any time. PMID:26942410</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OcDyn..64.1137G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OcDyn..64.1137G"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">dynamics</span> of physical and biological processes in the central California Current System: A modeling study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guo, Lin; Chai, Fei; Xiu, Peng; Xue, Huijie; Rao, Shivanesh; Liu, Yuguang; Chavez, Francisco P.</p> <p>2014-08-01</p> <p>A 3-D physical and biological model is used to study the <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of physical and biological processes in the central California Current System. Comparisons of model results with remote sensing and in situ observations along CalCOFI Line 67 indicate our model can capture the spatial variations of key variables (temperature, nutrients, chlorophyll, and so on) on annual mean and <span class="hlt">seasonal</span> cycle. In the coastal upwelling system, it is the alongshore wind stress that upwells high nutrients to surface from 60 m and stimulates enhanced plankton biomass and productivity in the upwelling <span class="hlt">season</span>. As a result, coastal species peak in the late upwelling period (May-July), and oceanic species reach the annual maxima in the oceanic period (August-October). The annual maximum occurs in the late upwelling period for new production and in the oceanic period for regenerated production. From the late upwelling period to the oceanic period, stratification is intensified while coastal upwelling becomes weaker. Correspondingly, the coastal ecosystem retreats from ˜300 to ˜100 km offshore with significant decline in chlorophyll and primary production, and the oceanic ecosystem moves onshore. During this transition, the decline in phytoplankton biomass is due to the grazing pressure by mesozooplankton in the 0-150 km domain, but is regulated by low growth rates in the 150-500 km offshore domain. Meanwhile, the growth rates of phytoplankton increase in the coastal waters due to deeper light penetration, while the decrease in offshore growth rates is caused by lower nitrate concentrations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRC..121.1424J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRC..121.1424J"><span id="translatedtitle"><span class="hlt">Dynamics</span> of the Chesapeake Bay outflow plume: Realistic plume simulation and its <span class="hlt">seasonal</span> and interannual variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Long; Xia, Meng</p> <p>2016-02-01</p> <p>The three-dimensional unstructured-grid Finite Volume Coastal Ocean Model (FVCOM) was implemented for Chesapeake Bay and its adjacent coastal ocean to delineate the realistic Chesapeake Bay outflow plume (CBOP) as well as its <span class="hlt">seasonal</span> and interannual variability. Applying the appropriate horizontal and vertical resolution, the model exhibited relatively high skill in matching the observational water level, temperature, and salinity from 2003 to 2012. The simulated surface plume structure was verified by comparing output to the HF radar current measurements, earlier field observations, and the MODIS and AVHRR satellite imagery. According to the orientation, shape, and size of the CBOP from both model snapshots and satellite images, five types of real-time plume behavior were detected, which implied strong regulation by wind and river discharge. In addition to the episodic plume modulation, horizontal and vertical structure of the CBOP exhibited variations on <span class="hlt">seasonal</span> and interannual temporal scales. <span class="hlt">Seasonally</span>, river discharge with a 1 month lag was primarily responsible for the surface plume area variation, while the plume thickness was mainly correlated to wind magnitude. On the interannual scale, river discharge was the predominant source of variability in both surface plume area and depth; however, the southerly winds also influenced the offshore plume depth. In addition, large-scale climate variability, such as the North Atlantic Oscillation, could potentially affect the plume signature in the long term by altering wind and upwelling <span class="hlt">dynamics</span>, underlining the need to understand the impacts of climate change on buoyant plumes, such as the CBOP.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....5538S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....5538S"><span id="translatedtitle">Holocene record of <span class="hlt">seasonal</span> stratification <span class="hlt">dynamics</span> in the NW European shelf seas: modelling and empirical evidence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scourse, J. D.; Austin, W. E. N.; Long, B. T.; Marret, F.; Scott, G. A.; Kennedy, H.</p> <p>2003-04-01</p> <p><span class="hlt">Seasonal</span> thermal stratification is the dominant hydrodynamic phenomena of tide-dominated shelf seas in the middle and high latitudes. Stratification occurs when summer heating of the sea surface exceeds tidal stirring and the resultant fronts,separating mixed from stratified water, are zones of enhanced primary production and support a coupled pelagic-benthic ecosystem which influences organic sedimentation and the production/preservation of microfossils. The potential of shelf sequences for preserving a long-term record of stratification <span class="hlt">dynamics</span> was first provided by M2 palaeotidal models of the NW European shelf seas. These model data, which indicated changes in frontal position and the areal extent of summer stratification for selected Holocene timeslices, have been successfully tested using stable isotopic records from a long well-dated Holocene record from a stratified location in the Celtic Sea. Coeval positive and negative trends, in benthic foraminiferal delta 18O and delta 13C respectively, indicate early Holocene cooling of bottom water and organic matter remineralisation, both of which are consistent with a transition from <span class="hlt">seasonally</span> tidally mixed to stratified water at this core location. Isotopic offsets between species imply a <span class="hlt">seasonal</span> contribution to the vital effect and a diagenetic effect related to epifaunal/infaunal habitat. Multivariate statistical analyses of dead and live benthic foraminiferal distributions from across the Celtic Sea front define distinct assemblages related to mixed, frontal and stratified watermasses. These same assemblages occur downcore and are stratigraphically consistent with the mixed to frontal gradient indicated by the stable isotopic data. Isotopic evidence from living Celtic Sea foraminifera supports the concept of a "<span class="hlt">seasonal</span> effect" in which different species calcify their tests at different times of the year and therefore in water of different temperature. Sea surface reconstructions have been based on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.1536X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.1536X"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">dynamics</span> of threshold friction velocity and dust emission in Central Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xi, Xin; Sokolik, Irina N.</p> <p>2015-02-01</p> <p>An improved model representation of mineral dust cycle is critical to reducing the uncertainty of dust-induced environmental and climatic impact. Here we present a mesoscale model study of the <span class="hlt">seasonal</span> dust activity in the semiarid drylands of Central Asia, focusing on the effects of wind speed, soil moisture, surface roughness heterogeneity, and vegetation phenology on the threshold friction velocity (u*t) and dust emission during the dust <span class="hlt">season</span> of 1 March to 31 October 2001. The dust model WRF-Chem-DuMo allows us to examine the uncertainties in <span class="hlt">seasonal</span> dust emissions due to the selection of dust emission scheme and soil grain size distribution data. To account for the vegetation effects on the u*t, we use the Moderate Resolution Imaging Spectroradiometer monthly normalized difference vegetation index to derive the <span class="hlt">dynamic</span> surface roughness parameters required by the physically based dust schemes of Marticorena and Bergametti (1995, hereinafter MB) and Shao et al. (1996, hereinafter Shao). We find the springtime u*t is strongly enhanced by the roughness effects of temperate steppe and desert ephemeral plants and, to less extent, the binding effects of increased soil moisture. The u*t decreases as the aboveground biomass dies back and soil moisture depletes during summer. The u*t <span class="hlt">dynamics</span> determines the dust <span class="hlt">seasonality</span> by causing more summer dust emission, despite a higher frequency of strong winds during spring. Due to the presence of more erodible materials in the saltation diameter range of 60-200 µm, the dry-sieved soil size distribution data lead to eight times more <span class="hlt">season</span>-total dust emission than the soil texture data, but with minor differences in the temporal distribution. On the other hand, the Shao scheme produces almost the same amount of <span class="hlt">season</span>-total dust emission as the MB scheme, but with a strong shift toward summer due to the strong sensitivity of the u*t to vegetation. By simply averaging the MB and Shao model experiments, we obtain a mean</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.B44B..02N&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.B44B..02N&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Seasonal</span> Oxygen <span class="hlt">Dynamics</span> in a Thermokarst Bog in Interior Alaska: Implications for Rates of Methane Oxidation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neumann, R. B.; Moorberg, C.; Wong, A.; Waldrop, M. P.; Turetsky, M. R.</p> <p>2015-12-01</p> <p>Methane is a potent greenhouse gas, and wetlands represent the largest natural source of methane to the atmosphere. However, much of the methane generated in anoxic wetlands never gets emitted to the atmosphere; up to >90% of generated methane can get oxidized to carbon dioxide. Thus, oxidation is an important methane sink and changes in the rate of methane oxidation can affect wetland methane emissions. Most methane is aerobically oxidized at oxic-anoxic interfaces where rates of oxidation strongly depend on methane and oxygen concentrations. In wetlands, oxygen is often the limiting substrate. To improve understanding of belowground oxygen <span class="hlt">dynamics</span> and its impact on methane oxidation, we deployed two planar optical oxygen sensors in a thermokarst bog in interior Alaska. Previous work at this site indicated that, similar to other sites, rates of methane oxidation decrease over the growing <span class="hlt">season</span>. We used the sensors to track spatial and temporal patterns of oxygen concentrations over the growing <span class="hlt">season</span>. We coupled these in-situ oxygen measurements with periodic oxygen injection experiments performed against the sensor to quantify belowground rates of oxygen consumption. We found that over the <span class="hlt">season</span>, the thickness of the oxygenated water layer at the peatland surface decreased. Previous research has indicated that in sphagnum-dominated peatlands, like the one studied here, rates of methane oxidation are highest at or slightly below the water table. It is in these saturated but oxygenated locations that both methane and oxygen are available. Thus, a <span class="hlt">seasonal</span> reduction in the thickness of the oxygenated water layer could restrict methane oxidation. The decrease in thickness of the oxygenated layer coincided with an increase in the rate of oxygen consumption during our oxygen injection experiments. The increase in oxygen consumption was not explained by temperature; we infer it was due to an increase in substrate availability for oxygen consuming reactions and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.H21H..04L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.H21H..04L"><span id="translatedtitle"><span class="hlt">Seasonal</span> to Interannual Hydroclimatic Prediction: From Identification of <span class="hlt">Dynamics</span> to Multi-Attribute Forecasts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lall, U.</p> <p>2004-12-01</p> <p><span class="hlt">Dynamical</span> and Statistical Models for <span class="hlt">seasonal</span> to interannual forecasts of key hydroclimatic state variables have been explored in recent years. Many authors report success based on typical performance metrics. Thus, a casual external observer may feel that we are at the verge of a breakthrough in hydrologic prediction, and hence in water resource management. This talk explores this notion, with particular regard to the multi-scale (time and space) nature of hydrologic fluxes, and of the management variables and styles that the water resources community has become accustomed to. A conceptual framework for the nascent predictive science of hydroclimatology is developed and exemplified. Aspects of the <span class="hlt">dynamics</span> that need to be understood, and a unifying estimation/inference framework are proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUSM.H23F..06L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUSM.H23F..06L"><span id="translatedtitle"><span class="hlt">Seasonal</span> to Interannual Hydroclimatic Prediction: From Identification of <span class="hlt">Dynamics</span> to Multi-Attribute Forecasts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lall, U.</p> <p>2004-05-01</p> <p><span class="hlt">Dynamical</span> and Statistical Models for <span class="hlt">seasonal</span> to interannual forecasts of key hydroclimatic state variables have been explored in recent years. Many authors report success based on typical performance metrics. Thus, a casual external observer may feel that we are at the verge of a breakthrough in hydrologic prediction, and hence in water resource management. This talk explores this notion, with particular regard to the multi-scale (time and space) nature of hydrologic fluxes, and of the management variables and styles that the water resources community has become accustomed to. A conceptual framework for the nascent predictive science of hydroclimatology is developed and exemplified. Aspects of the <span class="hlt">dynamics</span> that need to be understood, and a unifying estimation/inference framework are proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27410682','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27410682"><span id="translatedtitle"><span class="hlt">Dynamics</span> of the Water Circulations in the Southern South China Sea and Its <span class="hlt">Seasonal</span> Transports.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Daryabor, Farshid; Ooi, See Hai; Samah, Azizan Abu; Akbari, Abolghasem</p> <p>2016-01-01</p> <p>A three-dimensional Regional Ocean Modeling System is used to study the <span class="hlt">seasonal</span> water circulations and transports of the Southern South China Sea. The simulated <span class="hlt">seasonal</span> water circulations and estimated transports show consistency with observations, e.g., satellite altimeter data set and re-analysis data of the Simple Ocean Data Assimilation. It is found that the <span class="hlt">seasonal</span> water circulations are mainly driven by the monsoonal wind stress and influenced by the water outflow/inflow and associated currents of the entire South China Sea. The intrusion of the strong current along the East Coast of Peninsular Malaysia and the eddies at different depths in all <span class="hlt">seasons</span> are due to the conservation of the potential vorticity as the depth increases. Results show that the water circulation patterns in the northern part of the East Coast of Peninsular Malaysia are generally dominated by the geostrophic currents while those in the southern areas are due solely to the wind stress because of negligible Coriolis force there. This study clearly shows that individual surface freshwater flux (evaporation minus precipitation) controls the sea salinity balance in the Southern South China Sea thermohaline circulations. Analysis of climatological data from a high resolution Regional Ocean Modeling System reveals that the complex bathymetry is important not only for water exchange through the Southern South China Sea but also in regulating various transports across the main passages in the Southern South China Sea, namely the Sunda Shelf and the Strait of Malacca. Apart from the above, in comparision with the <span class="hlt">dynamics</span> of the Sunda Shelf, the Strait of Malacca reflects an equally significant role in the annual transports into the Andaman Sea. PMID:27410682</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4943643','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4943643"><span id="translatedtitle"><span class="hlt">Dynamics</span> of the Water Circulations in the Southern South China Sea and Its <span class="hlt">Seasonal</span> Transports</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ooi, See Hai; Samah, Azizan Abu; Akbari, Abolghasem</p> <p>2016-01-01</p> <p>A three-dimensional Regional Ocean Modeling System is used to study the <span class="hlt">seasonal</span> water circulations and transports of the Southern South China Sea. The simulated <span class="hlt">seasonal</span> water circulations and estimated transports show consistency with observations, e.g., satellite altimeter data set and re-analysis data of the Simple Ocean Data Assimilation. It is found that the <span class="hlt">seasonal</span> water circulations are mainly driven by the monsoonal wind stress and influenced by the water outflow/inflow and associated currents of the entire South China Sea. The intrusion of the strong current along the East Coast of Peninsular Malaysia and the eddies at different depths in all <span class="hlt">seasons</span> are due to the conservation of the potential vorticity as the depth increases. Results show that the water circulation patterns in the northern part of the East Coast of Peninsular Malaysia are generally dominated by the geostrophic currents while those in the southern areas are due solely to the wind stress because of negligible Coriolis force there. This study clearly shows that individual surface freshwater flux (evaporation minus precipitation) controls the sea salinity balance in the Southern South China Sea thermohaline circulations. Analysis of climatological data from a high resolution Regional Ocean Modeling System reveals that the complex bathymetry is important not only for water exchange through the Southern South China Sea but also in regulating various transports across the main passages in the Southern South China Sea, namely the Sunda Shelf and the Strait of Malacca. Apart from the above, in comparision with the <span class="hlt">dynamics</span> of the Sunda Shelf, the Strait of Malacca reflects an equally significant role in the annual transports into the Andaman Sea. PMID:27410682</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18247062','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/18247062"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">dynamics</span> of ectomycorrhizal fungus assemblages on oak seedlings in the southeastern Appalachian Mountains.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Walker, John F; Miller, Orson K; Horton, Jonathan L</p> <p>2008-03-01</p> <p>The potential for <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> in ectomycorrhizal (EM) fungal assemblages has important implications for the ecology of both the host trees and the fungal associates. We compared EM fungus distributions on root systems of out-planted oak seedlings at two sites in mixed southeastern Appalachian Mountain forests at the Coweeta Hydrologic Laboratory in North Carolina, from samples taken in mid-July and early September. Species level EM fungus type specificity, and identification in some cases, was enabled by direct sequencing of the mycobionts from the seedling roots. Seventy-four EM fungal ITS types were documented, most of which occurred only in the midsummer or early-fall samples, respectively. Cenococcum geophilum (morphotyped) was ubiquitously present and accounted for the majority of root tips sampled. Abundance and relative frequency of types other than C. geophilum were significantly higher in the July samples, while C. geophilum was significantly more frequent and abundant in September. Several generalistic dominants were found fairly equally at both sites and on both sample dates. Other taxa with relatively high frequency were recovered from both sites and tree seedling species, but were reliable indicators occurring primarily in the July sample (e.g., Laccaria cf laccata). Notable shifts in mycobiont dominance were apparent in relation to sample date, including increases in Cortinarius spp. richness, decreases in Thelephoraceae richness, and the disappearance of Amanita spp. types in the early fall compared to midsummer samples. However, diversity and rarity were high and differences in overall community composition (other than C. geophilum) by <span class="hlt">season</span> were not significant based on multi-response permutation procedures. Although these results based on a single growing <span class="hlt">season</span> are preliminary, changes in abundance and frequency, detection of significant indicator species, and the apparent systematic affinities of shifting EM types support the potential</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy..tmp..109K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy..tmp..109K"><span id="translatedtitle"><span class="hlt">Dynamical</span>-statistical <span class="hlt">seasonal</span> prediction for western North Pacific typhoons based on APCC multi-models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Ok-Yeon; Kim, Hye-Mi; Lee, Myong-In; Min, Young-Mi</p> <p>2016-03-01</p> <p>This study aims at predicting the <span class="hlt">seasonal</span> number of typhoons (TY) over the western North Pacific with an Asia-Pacific Climate Center (APCC) multi-model ensemble (MME)-based <span class="hlt">dynamical</span>-statistical hybrid model. The hybrid model uses the statistical relationship between the number of TY during the typhoon <span class="hlt">season</span> (July-October) and the large-scale key predictors forecasted by APCC MME for the same <span class="hlt">season</span>. The cross validation result from the MME hybrid model demonstrates high prediction skill, with a correlation of 0.67 between the hindcasts and observation for 1982-2008. The cross validation from the hybrid model with individual models participating in MME indicates that there is no single model which consistently outperforms the other models in predicting typhoon number. Although the forecast skill of MME is not always the highest compared to that of each individual model, the skill of MME presents rather higher averaged correlations and small variance of correlations. Given large set of ensemble members from multi-models, a relative operating characteristic score reveals an 82 % (above-) and 78 % (below-normal) improvement for the probabilistic prediction of the number of TY. It implies that there is 82 % (78 %) probability that the forecasts can successfully discriminate between above normal (below-normal) from other years. The forecast skill of the hybrid model for the past 7 years (2002-2008) is more skillful than the forecast from the Tropical Storm Risk consortium. Using large set of ensemble members from multi-models, the APCC MME could provide useful deterministic and probabilistic <span class="hlt">seasonal</span> typhoon forecasts to the end-users in particular, the residents of tropical cyclone-prone areas in the Asia-Pacific region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3596938','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3596938"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">Dynamics</span> of Ant Community Structure in the Moroccan Argan Forest</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Keroumi, Abderrahim El; Naamani, Khalid; Soummane, Hassna; Dahbi, Abdallah</p> <p>2012-01-01</p> <p>In this study we describe the structure and composition of ant communities in the endemic Moroccan Argan forest, using pitfall traps sampling technique throughout the four <span class="hlt">seasons</span> between May 2006 and February 2007. The study focused on two distinct climatic habitats within the Essaouira Argan forest, a semi-continental site at Lahssinate, and a coastal site at Boutazarte. Thirteen different ant species were identified, belonging to seven genera. Monomorium subopacum Smith and Tapinoma simrothi Krausse-Heldrungen (Hymenoptera: Formicidae) were the most abundant and behaviorally dominant ant species in the arganeraie. In addition, more specimens were captured in the semi-continental site than in the coastal area. However, no significant difference was observed in species richness, evenness, or diversity between both sites. Composition and community structure showed clear <span class="hlt">seasonal</span> <span class="hlt">dynamics</span>. The number of species, their abundance, their diversity, and their evenness per Argan tree were significantly dissimilar among <span class="hlt">seasons</span>. The richness (except between summer and autumn), and the abundance and the evenness of ant species among communities, showed a significant difference between the dry period (summer and spring) and the rainy period (winter and autumn). Higher abundance and richness values occurred in the dry period of the year. Ant species dominance and <span class="hlt">seasonal</span> climatic variations in the arganeraie might be among the main factors affecting the composition, structure, and foraging activity of ant communities. This study, together with recent findings on ant predation behavior below Argan trees, highlights the promising use of dominant ant species as potential agents of Mediterranean fruit fly bio-control in the Argan forest and surrounding ecosystems. PMID:23421815</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C33A0805J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C33A0805J"><span id="translatedtitle"><span class="hlt">Seasonal</span> Snow Cold Content <span class="hlt">Dynamics</span> in the Alpine and Sub-Alpine, Niwot Ridge, Colorado, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jennings, K. S.; Molotch, N. P.</p> <p>2015-12-01</p> <p>Cold content represents the energy required to warm a sub-freezing snowpack to an isothermal 0°C. Across daily and <span class="hlt">seasonal</span> time scales it is a <span class="hlt">dynamic</span> interplay between the forces of snowpack accumulation/cooling and warming. Cold content determines snowmelt timing and is an important component of the annual energy budget of mountain sites with <span class="hlt">seasonal</span> snowpacks. However, little is understood about <span class="hlt">seasonal</span> snowpack cold content <span class="hlt">dynamics</span> as calculating cold content requires depth-weighted snowpack temperature and snow water equivalent (SWE) measurements, which are scarce. A spatially distributed network of snow pits has been sampled since 1993 at the Niwot Ridge Long Term Ecological Research site on the eastern slope of the Continental Divide in Colorado's Front Range mountains. This study uses data from 3 pit sites that have at least 8 years of observations and represent alpine and sub-alpine environments. For these pits, cold content is strongly related to SWE during the cold content accumulation phase, here defined as December, January, and February. Average peak cold content ranges between -2.5 MJ m-2 and -9.2 MJ m-2 for the three sites and is strongly related to peak SWE. On average, cold content reaches its maximum on February 26, which is 61 days before the average date of peak SWE (i.e., the snowpack's cold content is satisfied over an average of 61 days). At the alpine site, later peak cold content and SWE was observed relative to the lower elevation sub-alpine sites. Interestingly, the alpine site had a smaller gap between peak cold content and SWE (55 days versus 67 days for the alpine and sub-alpine sites, respectively). The gap between peak cold content and peak SWE is primarily a function of the increase in SWE between the two dates. Hence, persistent snowfall after the date of peak cold content can delay the onset of snowmelt even if peak cold content was relatively low. Improving our understanding of <span class="hlt">seasonal</span> cold content <span class="hlt">dynamics</span> in mountain</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9707E..0TA&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9707E..0TA&link_type=ABSTRACT"><span id="translatedtitle">Subcellular metabolic <span class="hlt">contrast</span> in living tissue using <span class="hlt">dynamic</span> full field OCT (D-FFOCT) (Conference Presentation)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Apelian, Clement; Harms, Fabrice; Thouvenin, Olivier; Boccara, Claude A.</p> <p>2016-03-01</p> <p>Cells shape or density is an important marker of tissues pathology. However, individual cells are difficult to observe in thick tissues frequently presenting highly scattering structures such as collagen fibers. Endogenous techniques struggle to image cells in these conditions. Moreover, exogenous <span class="hlt">contrast</span> agents like dyes, fluorophores or nanoparticles cannot always be used, especially if non-invasive imaging is required. Scatterers motion happening down to the millisecond scale, much faster than the fix and highly scattering structures (global motion of the tissue), allowed us to develop a new approach based on the time dependence of the FF-OCT signals. This method reveals hidden cells after a spatiotemporal analysis based on singular value decomposition and wavelet analysis concepts. It does also give us access to local <span class="hlt">dynamics</span> of imaged scatterers. This <span class="hlt">dynamic</span> information is linked with the local metabolic activity that drives these scatterers. Our technique can explore subcellular scales with micrometric resolution and <span class="hlt">dynamics</span> ranging from the millisecond to seconds. By this mean we studied a wide range of tissues, animal and human in both normal and pathological conditions (cancer, ischemia, osmotic shock…) in different organs such as liver, kidney, and brain among others. Different cells, undetectable with FF-OCT, were identified (erythrocytes, hepatocytes…). Different scatterer clusters express different characteristic times and thus can be related to different mechanisms that we identify with metabolic functions. We are confident that the D-FFOCT, by accessing to a new spatiotemporal metabolic <span class="hlt">contrast</span>, will be a leading technique on tissue imaging and could lead to better medical diagnosis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSM42A..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSM42A..01S"><span id="translatedtitle"><span class="hlt">Seasonal</span> variation and <span class="hlt">dynamics</span> of Saturn's magnetospheric plasma, after 8 years of Cassini in orbit.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sergis, N.</p> <p>2012-12-01</p> <p>Saturn orbits the Sun with a period of nearly 29.5 years and has an obliquity of 26.73°. As a result, Saturn presents <span class="hlt">seasonal</span> variations similar to Earth's, but with much longer <span class="hlt">seasons</span>, as the tilt between the planet's spin axis and the solar wind vary (approximately sinusoidally) with time between solstices. Saturn was close to its equinox (tilt below 8.1°) during the Pioneer 11 and Voyager 1 and 2 flybys that took place between September 1979 and August 1981, so any <span class="hlt">seasonal</span> effects would have been relatively hard to see in the limited data from these missions. More than 2 decades later, on July 4, 2004, Cassini began orbiting Saturn, returning a variety of in situ and remote measurements. During the last 8 years, Cassini covered a large part of the Saturnian system and offered the opportunity of sampling the planetary magnetosphere not just at different <span class="hlt">seasons</span>, but also at <span class="hlt">seasonal</span> phases that are symmetric to the Saturnian equinox (August 2009). In this talk, we focus on the <span class="hlt">seasonal</span> effects seen in the magnetosphere of Saturn as the angle between the solar wind flow and the Saturn-Sun direction changes from +23.7° (northern hemisphere winter) at the arrival of Cassini, to -14.9° (northern hemisphere summer) on July 2012. Particle and magnetic field data taken from a extensive set of equatorial and high latitude orbits of Cassini, at various distances and local times, show that: (a) the plasma sheet of Saturn has the form of a magnetodisk, with an energy-dependent vertical structure, being thicker by a factor of ~2 in the energetic particle range than in the electron plasma, and (b) it exhibits intense <span class="hlt">dynamical</span> behavior, evident in in-situ particle measurements but also in energetic neutral atom (ENA) emissions. The study of the pre-equinox high latitude orbits revealed that the night side plasma sheet was tilted northward beyond a radial distance of ~15 Rs (1Rs=60,258 km). As equinox approached, Cassini observed a clear decrease in the tilt of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4436227','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4436227"><span id="translatedtitle"><span class="hlt">Seasonal</span> Differences in Extinction and Colonization Drive Occupancy <span class="hlt">Dynamics</span> of an Imperilled Amphibian</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Randall, Lea A.; Smith, Des H. V.; Jones, Breana L.; Prescott, David R. C.; Moehrenschlager, Axel</p> <p>2015-01-01</p> <p>A detailed understanding of the population <span class="hlt">dynamics</span> of many amphibian species is lacking despite concerns about declining amphibian biodiversity and abundance. This paper explores temporal patterns of occupancy and underlying extinction and colonization <span class="hlt">dynamics</span> in a regionally imperiled amphibian species, the Northern leopard frog (Lithobates pipiens) in Alberta. Our study contributes to elucidating regional occupancy <span class="hlt">dynamics</span> at northern latitudes, where climate extremes likely have a profound effect on <span class="hlt">seasonal</span> occupancy. The primary advantage of our study is its wide geographic scale (60,000 km2) and the use of repeat visual surveys each spring and summer from 2009–2013. We find that occupancy varied more dramatically between <span class="hlt">seasons</span> than years, with low spring and higher summer occupancy. Between spring and summer, colonization was high and extinction low; inversely, colonization was low and extinction high over the winter. The <span class="hlt">dynamics</span> of extinction and colonization are complex, making conservation management challenging. Our results reveal that Northern leopard frog occupancy was constant over the last five years and thus there is no evidence of decline or recovery within our study area. Changes to equilibrium occupancy are most sensitive to increasing colonization in the spring or declining extinction in the summer. Therefore, conservation and management efforts should target actions that are likely to increase spring colonization; this could be achieved through translocations or improving the quality or access to breeding habitat. Because summer occupancy is already high, it may be difficult to improve further. Nevertheless, summer extinction could be reduced by predator control, increasing water quality or hydroperiod of wetlands, or increasing the quality or quantity of summer habitat. PMID:25993256</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4559774','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4559774"><span id="translatedtitle"><span class="hlt">Dynamic</span> <span class="hlt">Contrast</span>-Enhanced MRI Using a Macromolecular MR <span class="hlt">Contrast</span> Agent (P792): Evaluation of Antivascular Drug Effect in a Rabbit VX2 Liver Tumor Model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Park, Hee Sun; Lee, Jeong Min; Kim, Young Il; Woo, Sungmin; Yoon, Jung Hwan; Choi, Jin-Young; Choi, Byung Ihn</p> <p>2015-01-01</p> <p>Objective To evaluate the utility of <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced magnetic resonance imaging (DCE-MRI) using macromolecular <span class="hlt">contrast</span> agent (P792) for assessment of vascular disrupting drug effect in rabbit VX2 liver tumor models. Materials and Methods This study was approved by our Institutional Animal Care and Use Committee. DCE-MRI was performed with 3-T scanner in 13 VX2 liver tumor-bearing rabbits, before, 4 hours after, and 24 hours after administration of vascular disrupting agent (VDA), using gadomelitol (P792, n = 7) or low molecular weight <span class="hlt">contrast</span> agent (gadoterate meglumine [Gd-DOTA], n = 6). P792 was injected at a of dose 0.05 mmol/kg, while that of Gd-DOTA was 0.2 mmol/kg. DCE-MRI parameters including volume transfer coefficient (Ktrans) and initial area under the gadolinium concentration-time curve until 60 seconds (iAUC) of tumors were compared between the 2 groups at each time point. DCE-MRI parameters were correlated with tumor histopathology. Reproducibility in measurement of DCE-MRI parameters and image quality of source MR were compared between groups. Results P792 group showed a more prominent decrease in Ktrans and iAUC at 4 hours and 24 hours, as compared to the Gd-DOTA group. Changes in DCE-MRI parameters showed a weak correlation with histologic parameters (necrotic fraction and microvessel density) in both groups. Reproducibility of DCE-MRI parameters and overall image quality was not significantly better in the P792 group, as compared to the Gd-DOTA group. Conclusion <span class="hlt">Dynamic</span> <span class="hlt">contrast</span>-enhanced magnetic resonance imaging using a macromolecular <span class="hlt">contrast</span> agent shows changes of hepatic perfusion more clearly after administration of the VDA. Gadolinium was required at smaller doses than a low molecular <span class="hlt">contrast</span> agent. PMID:26357497</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B34B..06M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B34B..06M"><span id="translatedtitle">Estuarine Nitrogen <span class="hlt">Dynamics</span> Along the Alaskan Beaufort Sea Coast: <span class="hlt">Seasonal</span> Patterns and Potential Climate Change Effects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McClelland, J. W.; Connelly, T. L.; Crump, B. C.; Kellogg, C.; Dunton, K. H.</p> <p>2014-12-01</p> <p><span class="hlt">Seasonal</span> runoff and sea-ice cover create highly <span class="hlt">dynamic</span> estuarine conditions in the Arctic. Studies focusing on major systems such as the Mackenzie have demonstrated how these variables interact to influence nutrient supply and uptake <span class="hlt">dynamics</span>. Far less is known about the <span class="hlt">seasonality</span> of smaller estuarine systems in the Arctic. Data collected from lagoons along the eastern Alaska Beaufort Sea coast show that salinities range from near zero in the spring to as high as 50 in the winter. Runoff and sea-ice thaw in the spring create highly stratified conditions, with hyper-saline bottom waters persisting through the summer in some locations. These variations in physical conditions are accompanied by variations in nitrogen availability within the lagoons. High concentrations of ammonium, and to a lesser extent nitrate, build up under the ice during the winter months. These nutrients are rapidly depleted during the ice break-up period and remain low throughout the summer. Concentrations of organic nitrogen, on the other hand, peak during the ice break-up period. While river inputs contribute directly to this nitrogen peak through the supply of land-derived organic matter, fatty acid markers also show that locally produced organic matter (primarily diatoms) peaks during the ice break-up period. <span class="hlt">Seasonal</span> changes in nitrogen are accompanied by distinct shifts in microbial community composition as well as changes in stable isotope values of metazoan consumers. Changes in climate that are altering both runoff and sea-ice have the potential to influence the quantity and timing of nutrient availability and associated biological production in arctic coastal waters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23747926','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23747926"><span id="translatedtitle">Understanding myxozoan infection <span class="hlt">dynamics</span> in the sea: <span class="hlt">seasonality</span> and transmission of Ceratomyxa puntazzi.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alama-Bermejo, Gema; Šíma, Radek; Raga, Juan A; Holzer, Astrid S</p> <p>2013-08-01</p> <p>Ceratomyxa puntazzi affects the sharpsnout seabream, Diplodus puntazzo, a recently explored aquaculture species in the Mediterranean. Little is known about the transmission and <span class="hlt">seasonality</span> of marine myxozoans, although this knowledge is of considerable importance for the design of management strategies for aquaculture. In the present study on C. puntazzi we investigated the potential pathways of transmission as well as the parasite abundance in fish and its density in environmental water samples, throughout a full year. We performed monthly sentinel fish exposures in a C. puntazzi enzootic environment and quantified waterborne stages in seawater. Two novel C. puntazzi-specific PCR and quantitative PCR assays were developed to determine infection levels in fish and water samples. Ceratomyxa puntazzi presents marked <span class="hlt">seasonal</span> changes in parasite density, with a double-peaked prevalence of infection in sentinel fish in spring and late summer/autumn, at 16-24°C, and a covert infection during the winter months. Invasive blood stages were detected all year round by PCR. The combination of sentinel fish exposure with the quantification of waterborne stages allowed us to attribute this pattern in C. puntazzi density to higher numbers of actinospores in the water, while myxospores are predominant in summer and winter. We demonstrated that temperature increase triggered actinospore production in the invertebrate host in a benthic habitat and we suggest that the life cycle <span class="hlt">dynamics</span> of the invertebrate host explain the double-peaked infection prevalence in fish. Experimental transmission of different C. puntazzi developmental stages in seawater or by oral and intracoelomic injection was unsuccessful which indicates fish-to-fish transmission is unlikely to occur in aquaculture systems. This is the first model studying <span class="hlt">seasonality</span> and infection <span class="hlt">dynamics</span> of a marine myxozoan. PMID:23747926</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.springerlink.com/content/y6g282578tv5360t/abstract/','USGSPUBS'); return false;" href="http://www.springerlink.com/content/y6g282578tv5360t/abstract/"><span id="translatedtitle">Modeling <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of the small fish cohorts in fluctuating freshwater marsh landscapes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jopp, Fred; DeAngelis, Donald L.; Trexler, Joel C.</p> <p>2010-01-01</p> <p>Small-bodied fishes constitute an important assemblage in many wetlands. In wetlands that dry periodically except for small permanent waterbodies, these fishes are quick to respond to change and can undergo large fluctuations in numbers and biomasses. An important aspect of landscapes that are mixtures of marsh and permanent waterbodies is that high rates of biomass production occur in the marshes during flooding phases, while the permanent waterbodies serve as refuges for many biotic components during the dry phases. The temporal and spatial <span class="hlt">dynamics</span> of the small fishes are ecologically important, as these fishes provide a crucial food base for higher trophic levels, such as wading birds. We develop a simple model that is analytically tractable, describing the main processes of the spatio-temporal <span class="hlt">dynamics</span> of a population of small-bodied fish in a <span class="hlt">seasonal</span> wetland environment, consisting of marsh and permanent waterbodies. The population expands into newly flooded areas during the wet <span class="hlt">season</span> and contracts during declining water levels in the dry <span class="hlt">season</span>. If the marsh dries completely during these times (a drydown), the fish need refuge in permanent waterbodies. At least three new and general conclusions arise from the model: (1) there is an optimal rate at which fish should expand into a newly flooding area to maximize population production; (2) there is also a fluctuation amplitude of water level that maximizes fish production, and (3) there is an upper limit on the number of fish that can reach a permanent waterbody during a drydown, no matter how large the marsh surface area is that drains into the waterbody. Because water levels can be manipulated in many wetlands, it is useful to have an understanding of the role of these fluctuations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3625260','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3625260"><span id="translatedtitle">Structure of the rare archaeal biosphere and <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of active ecotypes in surface coastal waters</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hugoni, Mylène; Taib, Najwa; Debroas, Didier; Domaizon, Isabelle; Jouan Dufournel, Isabelle; Bronner, Gisèle; Salter, Ian; Agogué, Hélène; Mary, Isabelle; Galand, Pierre E.</p> <p>2013-01-01</p> <p>Marine Archaea are important players among microbial plankton and significantly contribute to biogeochemical cycles, but details regarding their community structure and long-term <span class="hlt">seasonal</span> activity and <span class="hlt">dynamics</span> remain largely unexplored. In this study, we monitored the interannual archaeal community composition of abundant and rare biospheres in northwestern Mediterranean Sea surface waters by pyrosequencing 16S rDNA and rRNA. A detailed analysis of the rare biosphere structure showed that the rare archaeal community was composed of three distinct fractions. One contained the rare Archaea that became abundant at different times within the same ecosystem; these cells were typically not dormant, and we hypothesize that they represent a local seed bank that is specific and essential for ecosystem functioning through cycling <span class="hlt">seasonal</span> environmental conditions. The second fraction contained cells that were uncommon in public databases and not active, consisting of aliens to the studied ecosystem and representing a nonlocal seed bank of potential colonizers. The third fraction contained Archaea that were always rare but actively growing; their affiliation and <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> were similar to the abundant microbes and could not be considered a seed bank. We also showed that the major archaeal groups, Thaumarchaeota marine group I and Euryarchaeota group II.B in winter and Euryarchaeota group II.A in summer, contained different ecotypes with varying activities. Our findings suggest that archaeal diversity could be associated with distinct metabolisms or life strategies, and that the rare archaeal biosphere is composed of a complex assortment of organisms with distinct histories that affect their potential for growth. PMID:23536290</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24924438','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24924438"><span id="translatedtitle">Daily and <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of remotely sensed photosynthetic efficiency in tree canopies.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pieruschka, Roland; Albrecht, Hendrik; Muller, Onno; Berry, Joseph A; Klimov, Denis; Kolber, Zbigniew S; Malenovský, Zbyněk; Rascher, Uwe</p> <p>2014-07-01</p> <p>The photosynthesis of various species or even a single plant varies dramatically in time and space, creating great spatial heterogeneity within a plant canopy. Continuous and spatially explicit monitoring is, therefore, required to assess the <span class="hlt">dynamic</span> response of plant photosynthesis to the changing environment. This is a very challenging task when using the existing portable field instrumentation. This paper reports on the application of a technique, laser-induced fluorescence transient (LIFT), developed for ground remote measurement of photosynthetic efficiency at a distance of up to 50 m. The LIFT technique was used to monitor the <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of selected leaf groups within inaccessible canopies of deciduous and evergreen tree species. Electron transport rates computed from LIFT measurements varied over the growth period between the different species studied. The LIFT canopy data and light-use efficiency measured under field conditions correlated reasonably well with the single-leaf pulse amplitude-modulated measurements of broadleaf species, but differed significantly in the case of conifer tree species. The LIFT method has proven to be applicable for a remote sensing assessment of photosynthetic parameters on a diurnal and <span class="hlt">seasonal</span> scale; further investigation is, however, needed to evaluate the influence of complex heterogeneous canopy structures on LIFT-measured chlorophyll fluorescence parameters. PMID:24924438</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26812008','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26812008"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">dynamics</span> and microgeographical spatial heterogeneity of malaria along the China-Myanmar border.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hu, Yue; Zhou, Guofa; Ruan, Yonghua; Lee, Ming-chieh; Xu, Xin; Deng, Shuang; Bai, Yao; Zhang, Jie; Morris, James; Liu, Huaie; Wang, Ying; Fan, Qi; Li, Peipei; Wu, Yanrui; Yang, Zhaoqing; Yan, Guiyun; Cui, Liwang</p> <p>2016-05-01</p> <p>Malaria transmission is heterogeneous in the Greater Mekong Subregion with most of the cases occurring along international borders. Knowledge of transmission hotspots is essential for targeted malaria control and elimination in this region. This study aimed to determine the <span class="hlt">dynamics</span> of malaria transmission and possible existence of transmission hotspots on a microgeographical scale along the China-Myanmar border. Microscopically confirmed clinical malaria cases were recorded in five border villages through a recently established surveillance system between January 2011 and December 2014. A total of 424 clinical cases with confirmed spatial and temporal information were analyzed, of which 330 (77.8%) were Plasmodium vivax and 88 (20.8%) were Plasmodium falciparum, respectively. The P. vivax and P. falciparum case ratio increased dramatically from 2.2 in 2011 to 4.7 in 2014, demonstrating that P. vivax malaria has become the predominant parasite species. Clinical infections showed a strong bimodal <span class="hlt">seasonality</span>. There were significant differences in monthly average incidence rates among the study villages with rates in a village in China being 3-8 folds lower than those in nearby villages in Myanmar. Spatial analysis revealed the presence of clinical malaria hotspots in four villages. This information on malaria <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> and transmission hotspots should be harnessed for planning targeted control. PMID:26812008</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRG..117.1007C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRG..117.1007C"><span id="translatedtitle">Stability and resilience of seagrass meadows to <span class="hlt">seasonal</span> and interannual <span class="hlt">dynamics</span> and environmental stress</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carr, Joel A.; D'Odorico, Paolo; McGlathery, Karen J.; Wiberg, Patricia L.</p> <p>2012-03-01</p> <p>Shallow coastal bays provide habitat for diverse fish and invertebrate populations and are an important source of sediment for surrounding marshes. The sediment <span class="hlt">dynamics</span> of these bays are strongly affected by seagrass meadows, which limit sediment resuspension, thereby providing a more favorable light environment for their own survival and growth. Due to this positive feedback between seagrass and light conditions, it has been suggested that bare sediment and seagrass meadows are potential alternate stable states of the benthos in shallow coastal bays. To investigate the stability and resilience of seagrass meadows subjected to variation in environmental conditions (e.g., light, temperature), a coupled model of vegetation-sediment-water flow interactions and vegetation growth was developed. The model was used to examine the effect of <span class="hlt">dynamically</span> varying <span class="hlt">seasonal</span> and interannual seagrass density on sediment resuspension, water column turbidity, and the subsequent light environment on hourly time steps and then run over decadal time scales. A daily growth model was designed to capture both belowground biomass and the growth and senescence of aboveground biomass structural components (e.g., leaves and stems). This allowed us to investigate how the annual and <span class="hlt">seasonal</span> variability in shoot and leaf density within a meadow affects the strength of positive feedbacks between seagrass and their light environment. The model demonstrates both the emergence of bistable behavior from 1.6 to 1.8 m mean sea level due to the strength of the positive feedback, as well as the limited resilience of seagrass meadows within this bistable range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23879839','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23879839"><span id="translatedtitle">Biophysical controls on cluster <span class="hlt">dynamics</span> and architectural differentiation of microbial biofilms in <span class="hlt">contrasting</span> flow environments.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hödl, Iris; Mari, Lorenzo; Bertuzzo, Enrico; Suweis, Samir; Besemer, Katharina; Rinaldo, Andrea; Battin, Tom J</p> <p>2014-03-01</p> <p>Ecology, with a traditional focus on plants and animals, seeks to understand the mechanisms underlying structure and <span class="hlt">dynamics</span> of communities. In microbial ecology, the focus is changing from planktonic communities to attached biofilms that dominate microbial life in numerous systems. Therefore, interest in the structure and function of biofilms is on the rise. Biofilms can form reproducible physical structures (i.e. architecture) at the millimetre-scale, which are central to their functioning. However, the spatial <span class="hlt">dynamics</span> of the clusters conferring physical structure to biofilms remains often elusive. By experimenting with complex microbial communities forming biofilms in <span class="hlt">contrasting</span> hydrodynamic microenvironments in stream mesocosms, we show that morphogenesis results in 'ripple-like' and 'star-like' architectures--as they have also been reported from monospecies bacterial biofilms, for instance. To explore the potential contribution of demographic processes to these architectures, we propose a size-structured population model to simulate the <span class="hlt">dynamics</span> of biofilm growth and cluster size distribution. Our findings establish that basic physical and demographic processes are key forces that shape apparently universal biofilm architectures as they occur in diverse microbial but also in single-species bacterial biofilms. PMID:23879839</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PMB....55..473J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PMB....55..473J"><span id="translatedtitle">NOTE: Characterizing early <span class="hlt">contrast</span> uptake of ductal carcinoma in situ with high temporal resolution <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced MRI of the breast: a pilot study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jansen, S. A.; Fan, X.; Medved, M.; Abe, H.; Shimauchi, A.; Yang, C.; Zamora, M.; Foxley, S.; Olopade, O. I.; Karczmar, G. S.; Newstead, G. M.</p> <p>2010-10-01</p> <p>Improvements in the reliable diagnosis of preinvasive ductal carcinoma in situ (DCIS) by <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced magnetic resonance imaging (DCE-MRI) are needed. In this study, we present a new characterization of early <span class="hlt">contrast</span> kinetics of DCIS using high temporal resolution (HiT) DCE-MRI and compare it with other breast lesions and normal parenchyma. Forty patients with mammographic calcifications suspicious for DCIS were selected for HiT imaging using T1-weighted DCE-MRI with ~7 s temporal resolution for 90 s post-<span class="hlt">contrast</span> injection. Pixel-based and whole-lesion kinetic curves were fit to an empirical mathematical model (EMM) and several secondary kinetic parameters derived. Using the EMM parameterized and fitted concentration time curve for subsequent analysis allowed for calculation of kinetic parameters that were less susceptible to fluctuations due to noise. The parameters' initial area under the curve (iAUC) and <span class="hlt">contrast</span> concentration at 1 min (C1 min) provided the highest diagnostic accuracy in the task of distinguishing pathologically proven DCIS from normal tissue. There was a trend for DCIS lesions with solid architectural pattern to exhibit a negative slope at 1 min (i.e. increased washout rate) compared to those with a cribriform pattern (p < 0.04). This pilot study demonstrates the feasibility of quantitative analysis of early <span class="hlt">contrast</span> kinetics at high temporal resolution and points to the potential for such an analysis to improve the characterization of DCIS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4824432','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4824432"><span id="translatedtitle">Kinetic Curve Type Assessment for Classification of Breast Lesions Using <span class="hlt">Dynamic</span> <span class="hlt">Contrast</span>-Enhanced MR Imaging</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chen, Jun-Ming; Zhang, Geoffrey; Liao, Yen-Hsiu; Huang, Tzung-Chi</p> <p>2016-01-01</p> <p>Objective The aim of this study was to employ a kinetic model with <span class="hlt">dynamic</span> <span class="hlt">contrast</span> enhancement-magnetic resonance imaging to develop an approach that can efficiently distinguish malignant from benign lesions. Materials and Methods A total of 43 patients with 46 lesions who underwent breast <span class="hlt">dynamic</span> <span class="hlt">contrast</span> enhancement-magnetic resonance imaging were included in this retrospective study. The distribution of malignant to benign lesions was 31/15 based on histological results. This study integrated a single-compartment kinetic model and <span class="hlt">dynamic</span> <span class="hlt">contrast</span> enhancement-magnetic resonance imaging to generate a kinetic modeling curve for improving the accuracy of diagnosis of breast lesions. Kinetic modeling curves of all different lesions were analyzed by three experienced radiologists and classified into one of three given types. Receiver operating characteristic and Kappa statistics were used for the qualitative method. The findings of the three radiologists based on the time-signal intensity curve and the kinetic curve were compared. Results An average sensitivity of 82%, a specificity of 65%, an area under the receiver operating characteristic curve of 0.76, and a positive predictive value of 82% and negative predictive value of 63% was shown with the kinetic model (p = 0.017, 0.052, 0.068), as compared to an average sensitivity of 80%, a specificity of 55%, an area under the receiver operating characteristic of 0.69, and a positive predictive value of 79% and negative predictive value of 57% with the time-signal intensity curve method (p = 0.003, 0.004, 0.008). The diagnostic consistency of the three radiologists was shown by the κ-value, 0.857 (p<0.001) with the method based on the time-signal intensity curve and 0.826 (p<0.001) with the method of the kinetic model. Conclusions According to the statistic results based on the 46 lesions, the kinetic modeling curve method showed higher sensitivity, specificity, positive and negative predictive values as compared with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B44C..02W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B44C..02W"><span id="translatedtitle">Quantifying <span class="hlt">Seasonal</span> <span class="hlt">Dynamics</span> of Surface Inundation on the Barrow Peninsula, AK</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilson, C. J.; Chen, M.; Rowland, J. C.; Altmann, G. L.</p> <p>2013-12-01</p> <p>Wetlands are commonly distributed across the Arctic Coastal Plain of Northern Alaska, a low-gradient region underlain by continuous permafrost. They are important components of the global biogeochemical cycle because of the large carbon stores and potential release of this carbon as CO2 and CH4 due to climate change. These wetlands are recharged <span class="hlt">seasonally</span> by water from snowmelt and summer rainfall, but their area shrinks significantly during the snow free <span class="hlt">season</span> every year. While <span class="hlt">seasonal</span> and long-term thaw lake area change is well documented, the <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of smaller wetland features including polygon ponds is poorly quantified. Understanding and quantifying the factors driving and controlling the spatial redistribution of surface water will help in the parameterization of models and evaluation of predictions of water, energy and carbon budgets for lowland Arctic regions. In this study, we used high spatial resolution images (WorldView 2 and QuickBird) on 9 dates from 2006-2012 to investigate the <span class="hlt">seasonal</span> change and spatial pattern of surface water area for a 4700 ha wetland near Barrow, AK. We found that the surface water area decreased dramatically throughout the summer each year. For example, it decreased by 782 ha (74%) from June 24 to July 21 and continued to decrease by 153 ha (54%) from July 21 to August 4 in 2010. The correlation between the <span class="hlt">seasonal</span> change in surface water area and local precipitation minus evapotranspiration was low, indicating that the local water balance had little direct control on the change in surface water area through the Summer. Instead, the post snowmelt change in the area of surface inundation as a function of time was well fit by the equation for hydrograph recession, indicating that drainage of ponded water in July and August may be primarily controlled by shallow subsurface flow rather than through evapotranspiration, even in this very low gradient environment. The rate of drainage of surface water was significantly</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC23C1087K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC23C1087K"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">dynamics</span> of particulate organic carbon and nitrogen in Alaskan Arctic streams and rivers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khosh, M. S.; McClelland, J. W.; Jacobson, A. D.; Douglas, T. A.; Lehn, G. O.; Barker, A. J.</p> <p>2012-12-01</p> <p>The impacts of Arctic climate warming include an accelerated hydrological cycle, longer snow and ice free <span class="hlt">seasons</span>, and wide-scale permafrost degradation. Such changes will alter the quantity, <span class="hlt">seasonality</span>, and flow paths of water in Arctic river catchments. Biogeochemical processes will be impacted, with responses becoming apparent during an earlier spring melt transition from winter to summer, and in the later summer to early fall when the extent of the <span class="hlt">seasonally</span> thawed active layer reaches its maximum depth. While knowledge of the <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of water-borne constituents in Arctic rivers is improving, the shoulder <span class="hlt">seasons</span> of spring and fall to early winter, have historically been times of the year that Arctic rivers have been under sampled. This presentation will focus on characterizing the <span class="hlt">seasonality</span> of particulate organic carbon (POC) and particulate organic nitrogen (PON) concentrations and composition, using bulk measurements and stable isotope ratios (δ13C and δ15N), with a major emphasis placed on high resolution sampling during the periods of spring snowmelt and late summer until fall freeze-up. Between May and October of 2009 we collected surface water samples from 6 different rivers underlain by continuous permafrost in the vicinity of Toolik Field Station on the North Slope of Alaska's Brooks Range, with catchment sizes ranging from 1.6 km2 to 610 km2. Three rivers drain low-gradient tussock tundra landscape, while the other three rivers are within high-gradient mountainous terrain, draining predominantly exposed bedrock. At both tundra and mountain sites, POC and PON concentrations show markedly similar patterns qualitatively and quantitatively. Concentrations are highest during the spring snowmelt and decline throughout the summer with the lowest values observed during the fall. At both tundra and mountain sites, POC stable isotope ratios are highest during the spring, reach minima during the summer, and then increase slightly in the fall. PON</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AdAtS..21..456L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AdAtS..21..456L"><span id="translatedtitle">Recent advances in <span class="hlt">dynamical</span> extra-<span class="hlt">seasonal</span> to annual climate prediction at IAP/CAS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Zhaohui; Wang, Huijun; Zhou, Guangqing; Chen, Hong; Lang, Xianmei; Zhao, Yan; Zeng, Qingcun</p> <p>2004-06-01</p> <p>Recent advances in <span class="hlt">dynamical</span> climate prediction at the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS) during the last five years have been briefly described in this paper. Firstly, the second generation of the IAP <span class="hlt">dynamical</span> climate prediction system (IAP DCP-II) has been described, and two sets of hindcast experiments of the summer rainfall anomalies over China for the periods of 1980 1994 with different versions of the IAP AGCM have been conducted. The comparison results show that the predictive skill of summer rainfall anomalies over China is improved with the improved IAP AGCM in which the surface albedo parameterization is modified. Furthermore, IAP DCP-II has been applied to the real-time prediction of summer rainfall anomalies over China since 1998, and the verification results show that IAP DCP-II can quite well capture the large scale patterns of the summer flood/drought situations over China during the last five years (1998 2002). Meanwhile, an investigation has demonstrated the importance of the atmospheric initial conditions on the <span class="hlt">seasonal</span> climate prediction, along with studies on the influences from surface boundary conditions (e.g., land surface characteristics, sea surface temperature). Certain conclusions have been reached, such as, the initial atmospheric anomalies in spring may play an important role in the summer climate anomalies, and soil moisture anomalies in spring can also have a significant impact on the summer climate anomalies over East Asia. Finally, several practical techniques (e.g., ensemble technique, correction method, etc.), which lead to the increase of the prediction skill for summer rainfall anomalies over China, have also been illustrated. The paper concludes with a list of critical requirements needed for the further improvement of <span class="hlt">dynamical</span> <span class="hlt">seasonal</span> climate prediction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26372033','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26372033"><span id="translatedtitle">Latency as a region <span class="hlt">contrast</span>: Measuring ERP latency differences with <span class="hlt">Dynamic</span> Time Warping.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zoumpoulaki, A; Alsufyani, A; Filetti, M; Brammer, M; Bowman, H</p> <p>2015-12-01</p> <p>Methods for measuring onset latency <span class="hlt">contrasts</span> are evaluated against a new method utilizing the <span class="hlt">dynamic</span> time warping (DTW) algorithm. This new method allows latency to be measured across a region instead of single point. We use computer simulations to compare the methods' power and Type I error rates under different scenarios. We perform per-participant analysis for different signal-to-noise ratios and two sizes of window (broad vs. narrow). In addition, the methods are tested in combination with single-participant and jackknife average waveforms for different effect sizes, at the group level. DTW performs better than the other methods, being less sensitive to noise as well as to placement and width of the window selected. PMID:26372033</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015SPIE.9414E..1XL&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015SPIE.9414E..1XL&link_type=ABSTRACT"><span id="translatedtitle">Automated lesion detection in <span class="hlt">dynamic</span> <span class="hlt">contrast</span> enhanced magnetic resonance imaging of breast</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, Xi; Kotagiri, Romamohanarao; Frazer, Helen; Yang, Qing</p> <p>2015-03-01</p> <p>We propose an automated method in detecting lesions to assist radiologists in interpreting <span class="hlt">dynamic</span> <span class="hlt">contrast</span> enhanced magnetic resonance imaging (DCE-MRI) of breast. The aim is to highlight the suspicious regions of interest to reduce the searching time of the lesions and the possibility of radiologists overlooking small regions. In our method, we locate the suspicious regions by applying a threshold on essential features. The features are normalized to reduce the variation between patients. Support vector machine classifier is then applied to exclude normal tissues from these regions, using both kinetic and morphological features extracted in the lesions. In the evaluation of the system on 21 patients with 50 lesions, all lesions were successfully detected with 5.02 false positive regions per breast.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014SPIE.9035E..11H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014SPIE.9035E..11H&link_type=ABSTRACT"><span id="translatedtitle">Improved parameter extraction and classification for <span class="hlt">dynamic</span> <span class="hlt">contrast</span> enhanced MRI of prostate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haq, Nandinee Fariah; Kozlowski, Piotr; Jones, Edward C.; Chang, Silvia D.; Goldenberg, S. Larry; Moradi, Mehdi</p> <p>2014-03-01</p> <p>Magnetic resonance imaging (MRI), particularly <span class="hlt">dynamic</span> <span class="hlt">contrast</span> enhanced (DCE) imaging, has shown great potential in prostate cancer diagnosis and prognosis. The time course of the DCE images provides measures of the <span class="hlt">contrast</span> agent uptake kinetics. Also, using pharmacokinetic modelling, one can extract parameters from the DCE-MR images that characterize the tumor vascularization and can be used to detect cancer. A requirement for calculating the pharmacokinetic DCE parameters is estimating the Arterial Input Function (AIF). One needs an accurate segmentation of the cross section of the external femoral artery to obtain the AIF. In this work we report a semi-automatic method for segmentation of the cross section of the femoral artery, using circular Hough transform, in the sequence of DCE images. We also report a machine-learning framework to combine pharmacokinetic parameters with the model-free <span class="hlt">contrast</span> agent uptake kinetic parameters extracted from the DCE time course into a nine-dimensional feature vector. This combination of features is used with random forest and with support vector machine classi cation for cancer detection. The MR data is obtained from patients prior to radical prostatectomy. After the surgery, wholemount histopathology analysis is performed and registered to the DCE-MR images as the diagnostic reference. We show that the use of a combination of pharmacokinetic parameters and the model-free empirical parameters extracted from the time course of DCE results in improved cancer detection compared to the use of each group of features separately. We also validate the proposed method for calculation of AIF based on comparison with the manual method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21372286','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21372286"><span id="translatedtitle">Comparison Between Perfusion Computed Tomography and <span class="hlt">Dynamic</span> <span class="hlt">Contrast</span>-Enhanced Magnetic Resonance Imaging in Rectal Cancer</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kierkels, Roel G.J.; Backes, Walter H.; Janssen, Marco H.M.; Buijsen, Jeroen; Beets-Tan, Regina G.H.; Lambin, Philippe; Lammering, Guido; Oellers, Michel C.; Aerts, Hugo J.W.L.</p> <p>2010-06-01</p> <p>Purpose: To compare pretreatment scans with perfusion computed tomography (pCT) vs. <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced magnetic resonance imaging (DCE-MRI) in rectal tumors. Methods and Materials: Nineteen patients diagnosed with rectal cancer were included in this prospective study. All patients underwent both pCT and DCE-MRI. Imaging was performed on a dedicated 40-slice CT-positron emission tomography system and a 3-T MRI system. <span class="hlt">Dynamic</span> <span class="hlt">contrast</span> enhancement was measured in tumor tissue and the external iliac artery. Tumor perfusion was quantified in terms of pharmacokinetic parameters: transfer constant K{sup trans}, fractional extravascular-extracellular space v{sub e}, and fractional plasma volume v{sub p}. Pharmacokinetic parameter values and their heterogeneity (by 80% quantile value) were compared between pCT and DCE-MRI. Results: Tumor K{sup trans} values correlated significantly for the voxel-by-voxel-derived median (Kendall's tau correlation, tau = 0.81, p < 0.001) and 80% quantile (tau = 0.54, p = 0.04), as well as for the averaged uptake (tau = 0.58, p = 0.03). However, no significant correlations were found for v{sub e} and v{sub p} derived from the voxel-by-voxel-derived median and 80% quantile and derived from the averaged uptake curves. Conclusions: This study demonstrated for the first time that pCT provides K{sup trans} values comparable to those of DCE-MRI. However, no correlation was found for the v{sub e} and v{sub p} parameters between CT and MRI. Computed tomography can serve as an alternative modality to MRI for the in vivo evaluation of tumor angiogenesis in terms of the transfer constant K{sup trans}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25753990','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25753990"><span id="translatedtitle">Bacterial community <span class="hlt">dynamics</span> during polysaccharide degradation at <span class="hlt">contrasting</span> sites in the Southern and Atlantic Oceans.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wietz, Matthias; Wemheuer, Bernd; Simon, Heike; Giebel, Helge-Ansgar; Seibt, Maren A; Daniel, Rolf; Brinkhoff, Thorsten; Simon, Meinhard</p> <p>2015-10-01</p> <p>The bacterial degradation of polysaccharides is central to marine carbon cycling, but little is known about the bacterial taxa that degrade specific marine polysaccharides. Here, bacterial growth and community <span class="hlt">dynamics</span> were studied during the degradation of the polysaccharides chitin, alginate and agarose in microcosm experiments at four <span class="hlt">contrasting</span> locations in the Southern and Atlantic Oceans. At the Southern polar front, chitin-supplemented microcosms were characterized by higher fractions of actively growing cells and a community shift from Alphaproteobacteria to Gammaproteobacteria and Bacteroidetes. At the Antarctic ice shelf, chitin degradation was associated with growth of Bacteroidetes, with 24% higher cell numbers compared with the control. At the Patagonian continental shelf, alginate and agarose degradation covaried with growth of different Alteromonadaceae populations, each with specific temporal growth patterns. At the Mauritanian upwelling, only the alginate hydrolysis product guluronate was consumed, coincident with increasing abundances of Alteromonadaceae and possibly cross-feeding SAR11. 16S rRNA gene amplicon libraries indicated that growth of the Bacteroidetes-affiliated genus Reichenbachiella was stimulated by chitin at all cold and temperate water stations, suggesting comparable ecological roles over wide geographical scales. Overall, the predominance of location-specific patterns showed that bacterial communities from <span class="hlt">contrasting</span> oceanic biomes have members with different potentials to hydrolyse polysaccharides. PMID:25753990</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4228420','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4228420"><span id="translatedtitle">DCE@urLAB: a <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced MRI pharmacokinetic analysis tool for preclinical data</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2013-01-01</p> <p>Background DCE@urLAB is a software application for analysis of <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced magnetic resonance imaging data (DCE-MRI). The tool incorporates a friendly graphical user interface (GUI) to interactively select and analyze a region of interest (ROI) within the image set, taking into account the tissue concentration of the <span class="hlt">contrast</span> agent (CA) and its effect on pixel intensity. Results Pixel-wise model-based quantitative parameters are estimated by fitting DCE-MRI data to several pharmacokinetic models using the Levenberg-Marquardt algorithm (LMA). DCE@urLAB also includes the semi-quantitative parametric and heuristic analysis approaches commonly used in practice. This software application has been programmed in the Interactive Data Language (IDL) and tested both with publicly available simulated data and preclinical studies from tumor-bearing mouse brains. Conclusions A user-friendly solution for applying pharmacokinetic and non-quantitative analysis DCE-MRI in preclinical studies has been implemented and tested. The proposed tool has been specially designed for easy selection of multi-pixel ROIs. A public release of DCE@urLAB, together with the open source code and sample datasets, is available at http://www.die.upm.es/im/archives/DCEurLAB/. PMID:24180558</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18044593','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/18044593"><span id="translatedtitle">Segmentation and classification of breast tumor using <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced MR images.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zheng, Yuanjie; Baloch, Sajjad; Englander, Sarah; Schnall, Mitchell D; Shen, Dinggang</p> <p>2007-01-01</p> <p>Accuracy of automatic cancer diagnosis is largely determined by two factors, namely, the precision of tumor segmentation, and the suitability of extracted features for discrimination between malignancy and benignancy. In this paper, we propose a new framework for accurate characterization of tumors in <span class="hlt">contrast</span> enhanced MR images. First, a new graph cut based segmentation algorithm is developed for refining coarse manual segmentation, which allows precise identification of tumor regions. Second, by considering serial <span class="hlt">contrast</span>-enhanced images as a single spatio-temporal image, a spatio-temporal model of segmented tumor is constructed to extract Spatio-Temporal Enhancement Patterns (STEPs). STEPs are designed to capture not only <span class="hlt">dynamic</span> enhancement and architectural features, but also spatial variations of pixel-wise temporal enhancement of the tumor. While temporal enhancement features are extracted through Fourier transform, the resulting STEP framework captures spatial patterns of temporal enhancement features via moment invariants and rotation invariant Gabor textures. High accuracy of the proposed framework is a direct consequence of this two pronged approach, which is validated through experiments yielding, for instance, an area of 0.97 under the ROC curve. PMID:18044593</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4487918','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4487918"><span id="translatedtitle">Using <span class="hlt">Dynamic</span> <span class="hlt">Contrast</span> Enhanced MRI to Quantitatively Characterize Maternal Vascular Organization in the Primate Placenta</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Frias, A.E.; Schabel, M.C.; Roberts, V.H.J.; Tudorica, A.; Grigsby, P.L.; Oh, K.Y.; Kroenke, C. D.</p> <p>2015-01-01</p> <p>Purpose The maternal microvasculature of the primate placenta is organized into 10-20 perfusion domains that are functionally optimized to facilitate nutrient exchange to support fetal growth. This study describes a <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced magnetic resonance imaging (DCE-MRI) method for identifying vascular domains, and quantifying maternal blood flow in them. Methods A rhesus macaque on the 133rd day of pregnancy (G133, term=165 days) underwent Doppler ultrasound (US) procedures, DCE-MRI, and Cesarean-section delivery. Serial T1-weighted images acquired throughout intravenous injection of a <span class="hlt">contrast</span> reagent (CR) bolus were analyzed to obtain CR arrival time maps of the placenta. Results Watershed segmentation of the arrival time map identified 16 perfusion domains. The number and location of these domains corresponded to anatomical cotyledonary units observed following delivery. Analysis of the CR wave front through each perfusion domain enabled determination of volumetric flow, which ranged from 9.03 to 44.9 mL/sec (25.2 ± 10.3 mL/sec). These estimates are supported by Doppler US results. Conclusions The DCE-MRI analysis described here provides quantitative estimates of the number of maternal perfusion domains in a primate placenta, and estimates flow within each domain. Anticipated extensions of this technique are to the study placental function in nonhuman primate models of obstetric complications. PMID:24753177</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SPIE.8670E..33F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SPIE.8670E..33F"><span id="translatedtitle">Semi-quantitative assessment of pulmonary perfusion in children using <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced MRI</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fetita, Catalin; Thong, William E.; Ou, Phalla</p> <p>2013-03-01</p> <p>This paper addresses the study of semi-quantitative assessment of pulmonary perfusion acquired from <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced magnetic resonance imaging (DCE-MRI) in a study population mainly composed of children with pulmonary malformations. The automatic analysis approach proposed is based on the indicator-dilution theory introduced in 1954. First, a robust method is developed to segment the pulmonary artery and the lungs from anatomical MRI data, exploiting 2D and 3D mathematical morphology operators. Second, the time-dependent <span class="hlt">contrast</span> signal of the lung regions is deconvolved by the arterial input function for the assessment of the local hemodynamic system parameters, ie. mean transit time, pulmonary blood volume and pulmonary blood flow. The discrete deconvolution method implements here a truncated singular value decomposition (tSVD) method. Parametric images for the entire lungs are generated as additional elements for diagnosis and quantitative follow-up. The preliminary results attest the feasibility of perfusion quantification in pulmonary DCE-MRI and open an interesting alternative to scintigraphy for this type of evaluation, to be considered at least as a preliminary decision in the diagnostic due to the large availability of the technique and to the non-invasive aspects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=116599','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=116599"><span id="translatedtitle"><span class="hlt">Dynamic</span> <span class="hlt">contrast</span>-enhanced magnetic resonance imaging of the sarcopenic muscle</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Nicolato, Elena; Farace, Paolo; Asperio, Roberto M; Marzola, Pasquina; Lunati, Ernesto; Sbarbati, Andrea; Osculati, Francesco</p> <p>2002-01-01</p> <p>Background Studies about capillarity of the aged muscle provided conflicting results and no data are currently available about the magnetic resonance imaging (MRI) in vivo characteristics of the microvascular bed in aged rats. We have studied age-related modifications of the skeletal muscle by in vivo T2-relaxometry and <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced magnetic resonance imaging (CE-MRI) at high field intensity (4.7 T). The aim of the work was to test the hypothesis that the ageing process involves microvessels in skeletal muscle. Methods The study was performed in 4-month-old (n = 6) and 20-month-old (n = 6) rats. Results At MRI examination, the relaxation time T2 of the gastrocnemius muscle showed no significant difference between these two groups. The kinetic of <span class="hlt">contrast</span> penetration in the tissue showed that in 4-month-old rats the enhancement values of the signal intensity at different time-points were significantly higher than those found in senescent rats. Conclusion The reported finding suggests that there is a modification of the microcirculatory function in skeletal muscle of aged rats. This work also demonstrates that CE-MRI allows for an in vivo quantification of the multiple biological processes involving the skeletal muscle during aging. Therefore, CE-MRI could represent a further tool for the follow up of tissue modification and therapeutic intervention both in patients with sarcopenia and in experimental models of this pathology. PMID:12049675</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3577870','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3577870"><span id="translatedtitle">The Role of Stream Water Carbon <span class="hlt">Dynamics</span> and Export in the Carbon Balance of a Tropical <span class="hlt">Seasonal</span> Rainforest, Southwest China</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhou, Wen-Jun; Zhang, Yi-Ping; Schaefer, Douglas A.; Sha, Li-Qing; Deng, Yun; Deng, Xiao-Bao; Dai, Kai-Jie</p> <p>2013-01-01</p> <p>A two-year study (2009 ∼ 2010) was carried out to investigate the <span class="hlt">dynamics</span> of different carbon (C) forms, and the role of stream export in the C balance of a 23.4-ha headwater catchment in a tropical <span class="hlt">seasonal</span> rainforest at Xishuangbanna (XSBN), southwest China. The <span class="hlt">seasonal</span> volumetric weighted mean (VWM) concentrations of total inorganic C (TIC) and dissolved inorganic C (DIC) were higher, and particulate inorganic C (PIC) and organic C (POC) were lower, in the dry <span class="hlt">season</span> than the rainy <span class="hlt">season</span>, while the VWM concentrations of total organic C (TOC) and dissolved organic C (DOC) were similar between <span class="hlt">seasons</span>. With increased monthly stream discharge and stream water temperature (SWT), only TIC and DIC concentrations decreased significantly. The most important C form in stream export was DIC, accounting for 51.8% of the total C (TC) export; DOC, POC, and PIC accounted for 21.8%, 14.9%, and 11.5% of the TC export, respectively. <span class="hlt">Dynamics</span> of C flux were closely related to stream discharge, with the greatest export during the rainy <span class="hlt">season</span>. C export in the headwater stream was 47.1 kg C ha−1 yr−1, about 2.85% of the annual net ecosystem exchange. This finding indicates that stream export represented a minor contribution to the C balance in this tropical <span class="hlt">seasonal</span> rainforest. PMID:23437195</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4762948','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4762948"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">Dynamics</span> of Phlebotomine Sand Fly Species Proven Vectors of Mediterranean Leishmaniasis Caused by Leishmania infantum</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Alten, Bulent; Maia, Carla; Afonso, Maria Odete; Campino, Lenea; Jiménez, Maribel; González, Estela; Molina, Ricardo; Bañuls, Anne Laure; Prudhomme, Jorian; Vergnes, Baptiste; Toty, Celine; Cassan, Cécile; Rahola, Nil; Thierry, Magali; Sereno, Denis; Bongiorno, Gioia; Bianchi, Riccardo; Khoury, Cristina; Tsirigotakis, Nikolaos; Dokianakis, Emmanouil; Antoniou, Maria; Christodoulou, Vasiliki; Mazeris, Apostolos; Karakus, Mehmet; Ozbel, Yusuf; Arserim, Suha K.; Erisoz Kasap, Ozge; Gunay, Filiz; Oguz, Gizem; Kaynas, Sinan; Tsertsvadze, Nikoloz; Tskhvaradze, Lamzira; Gramiccia, Marina; Volf, Petr; Gradoni, Luigi</p> <p>2016-01-01</p> <p>Background The recent geographical expansion of phlebotomine vectors of Leishmania infantum in the Mediterranean subregion has been attributed to ongoing climate changes. At these latitudes, the activity of sand flies is typically <span class="hlt">seasonal</span>; because <span class="hlt">seasonal</span> phenomena are also sensitive to general variations in climate, current phenological data sets can provide a baseline for continuing investigations on sand fly population <span class="hlt">dynamics</span> that may impact on future scenarios of leishmaniasis transmission. With this aim, in 2011–2013 a consortium of partners from eight Mediterranean countries carried out entomological investigations in sites where L. infantum transmission was recently reported. Methods/Principal Findings A common protocol for sand fly collection included monthly captures by CDC light traps, complemented by sticky traps in most of the sites. Collections were replicated for more than one <span class="hlt">season</span> in order to reduce the effects of local weather events. In each site, the trapping effort was left unchanged throughout the survey to legitimate inter-<span class="hlt">seasonal</span> comparisons. Data from 99,000 collected specimens were analyzed, resulting in the description of <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of 56,000 sand flies belonging to L. infantum vector species throughout a wide geographical area, namely P. perniciosus (Portugal, Spain and Italy), P. ariasi (France), P. neglectus (Greece), P. tobbi (Cyprus and Turkey), P. balcanicus and P. kandelakii (Georgia). Time of sand fly appearance/disappearance in collections differed between sites, and <span class="hlt">seasonal</span> densities showed variations in each site. Significant correlations were found between latitude/mean annual temperature of sites and i) the first month of sand fly appearance, that ranged from early April to the first half of June; ii) the type of density trend, varying from a single peak in July/August to multiple peaks increasing in magnitude from May through September. A 3-modal trend, recorded for P. tobbi in Cyprus, represents a novel</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4032566','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4032566"><span id="translatedtitle">Evaluation of liver parenchyma and perfusion using <span class="hlt">dynamic</span> <span class="hlt">contrast</span>-enhanced computed tomography and <span class="hlt">contrast</span>-enhanced ultrasonography in captive green iguanas (Iguana iguana) under general anesthesia</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2014-01-01</p> <p>Background <span class="hlt">Contrast</span>-enhanced diagnostic imaging techniques are considered useful in veterinary and human medicine to evaluate liver perfusion and focal hepatic lesions. Although hepatic diseases are a common occurrence in reptile medicine, there is no reference to the use of <span class="hlt">contrast</span>-enhanced ultrasound (CEUS) and <span class="hlt">contrast</span>-enhanced computed tomography (CECT) to evaluate the liver in lizards. Therefore, the aim of this study was to evaluate the pattern of change in echogenicity and attenuation of the liver in green iguanas (Iguana iguana) after administration of specific <span class="hlt">contrast</span> media. Results An increase in liver echogenicity and density was evident during CEUS and CECT, respectively. In CEUS, the mean ± SD (median; range) peak enhancement was 19.9% ± 7.5 (18.3; 11.7-34.6). Time to peak enhancement was 134.0 ± 125.1 (68.4; 59.6-364.5) seconds. During CECT, first visualization of the <span class="hlt">contrast</span> medium was at 3.6 ± 0.5 (4; 3-4) seconds in the aorta, 10.7 ± 2.2 (10.5; 7-14) seconds in the hepatic arteries, and 15 ± 4.5 (14.5; 10-24) seconds in the liver parenchyma. Time to peak was 14.1 ± 3.4 (13; 11-21) and 31 ± 9.6 (29; 23-45) seconds in the aorta and the liver parenchyma, respectively. Conclusion CEUS and <span class="hlt">dynamic</span> CECT are practical means to determine liver hemodynamics in green iguanas. Distribution of <span class="hlt">contrast</span> medium in iguana differed from mammals. Specific reference ranges of hepatic perfusion for diagnostic evaluation of the liver in iguanas are necessary since the use of mammalian references may lead the clinician to formulate incorrect diagnostic suspicions. PMID:24885935</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26708030','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26708030"><span id="translatedtitle">DUSTER: <span class="hlt">dynamic</span> <span class="hlt">contrast</span> enhance up-sampled temporal resolution analysis method.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liberman, Gilad; Louzoun, Yoram; Artzi, Moran; Nadav, Guy; Ewing, James R; Ben Bashat, Dafna</p> <p>2016-05-01</p> <p><span class="hlt">Dynamic</span> <span class="hlt">contrast</span> enhanced (DCE) MRI using Tofts' model for estimating vascular permeability is widely accepted, yet inter-tissue differences in bolus arrival time (BAT) are generally ignored. In this work we propose a method, incorporating the BAT in the analysis, demonstrating its applicability and advantages in healthy subjects and patients. A method for DCE Up Sampled TEmporal Resolution (DUSTER) analysis is proposed which includes: baseline T1 map using DESPOT1 analyzed with flip angle (FA) correction; preprocessing; raw-signal-to-T1-to-concentration time curves (CTC) conversion; automatic arterial input function (AIF) extraction at temporal super-resolution; model fitting with model selection while incorporating BAT in the pharmacokinetic (PK) model, and fits <span class="hlt">contrast</span> agent CTC while using exhaustive search in the BAT dimension in super-resolution. The method was applied to simulated data and to human data from 17 healthy subjects, six patients with glioblastoma, and two patients following stroke. BAT values were compared to time-to-peak (TTP) values extracted from <span class="hlt">dynamic</span> susceptibility <span class="hlt">contrast</span> imaging. Results show that the method improved the AIF estimation and allowed extraction of the BAT with a resolution of 0.8 s. In simulations, lower mean relative errors were detected for all PK parameters extracted using DUSTER compared to analysis without BAT correction (vp:5% vs. 20%, Ktrans: 9% vs. 24% and Kep: 8% vs. 17%, respectively), and BAT estimates demonstrated high correlations (r = 0.94, p < 1e− 10) with true values. In real data, high correlations between BAT values were detected when extracted from data acquired with high temporal resolution (2 s) and sub-sampled standard resolution data (6 s) (mean r = 0.85,p < 1e− 10). BAT and TTP values were significantly correlated in the different brain regions in healthy subjects (mean r = 0.72,p = < 1e− 3), as were voxel-wise comparisons in patients (mean r = 0.89, p < 1e− 10). In conclusion</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26551588','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26551588"><span id="translatedtitle">Soil radon <span class="hlt">dynamics</span> in the Amer fault zone: An example of very high <span class="hlt">seasonal</span> variations.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moreno, V; Bach, J; Font, Ll; Baixeras, C; Zarroca, M; Linares, R; Roqué, C</p> <p>2016-01-01</p> <p>Soil radon levels of the Amer fault zone have been measured for a 4 year-period with the aim of checking <span class="hlt">seasonal</span> fluctuations obtained in previous studies and to understand radon origin and <span class="hlt">dynamics</span>. In this manuscript additional results are presented: updated continuous and integrated soil radon measurements, radionuclide content of soil materials and a detailed analysis of an urban profile by means of the electrical resistivity imaging technique and punctual soil radon, thoron and CO2 measurements. Integrated and continuous measurements present a wide range of values, [0.2-151.6] kBq m(-3) for radon, [4.5-39.6] kBq m(-3) for thoron and [4.0-71.2] g m(-2) day(-1) for CO2. The highest soil radon levels in the vicinity of the Amer fault (>40 kBq m(-3)) are found close to the fractured areas and present very important fluctuations repeated every year, with values in summer much higher than in winter, confirming previous studies. The highest radon values, up to 150 kBq m(-3), do not have a local origin because the mean value of radium concentration in this soil (19 ± 5 Bq kg(-1)) could not explain these values. Then soil radon migration through the fractures, influenced by atmospheric parameters, is assumed to account for such a high <span class="hlt">seasonal</span> fluctuation. As main conclusion, in fractured areas, <span class="hlt">seasonal</span> variations of soil radon concentration can be very important even in places where average soil radon concentration and radium content are not especially high. In these cases the migration capability of the soil is given not by intrinsic permeability but by the fracture structure. Potential risk estimation based on soil radon concentration and intrinsic permeability must be complemented with geological information in fractured systems. PMID:26551588</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4887004','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4887004"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">Dynamics</span> of Water Use Strategy of Two Salix Shrubs in Alpine Sandy Land, Tibetan Plateau</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhu, Yajuan; Wang, Guojie; Li, Renqiang</p> <p>2016-01-01</p> <p>Water is a limiting factor for plant growth and vegetation <span class="hlt">dynamics</span> in alpine sandy land of the Tibetan Plateau, especially with the increasing frequency of extreme precipitation events and drought caused by climate change. Therefore, a relatively stable water source from either deeper soil profiles or ground water is necessary for plant growth. Understanding the water use strategy of dominant species in the alpine sandy land ecosystem is important for vegetative rehabilitation and ecological restoration. The stable isotope methodology of δD, δ18O, and δ13C was used to determine main water source and long-term water use efficiency of Salix psammophila and S. cheilophila, two dominant shrubs on interdune of alpine sandy land in northeastern Tibetan Plateau. The root systems of two Salix shrubs were investigated to determine their distribution pattern. The results showed that S. psammophila and S. cheilophila absorbed soil water at different soil depths or ground water in different <span class="hlt">seasons</span>, depending on water availability and water use strategy. Salix psammophila used ground water during the growing <span class="hlt">season</span> and relied on shallow soil water recharged by rain in summer. Salix cheilophila used ground water in spring and summer, but relied on shallow soil water recharged by rain in spring and deep soil water recharged by ground water in fall. The two shrubs had dimorphic root systems, which is coincident with their water use strategy. Higher biomass of fine roots in S. psammophila and longer fine roots in S. cheilophila facilitated to absorb water in deeper soil layers. The long-term water use efficiency of two Salix shrubs increased during the dry <span class="hlt">season</span> in spring. The long-term water use efficiency was higher in S. psammophila than in S. cheilophila, as the former species is better adapted to semiarid climate of alpine sandy land. PMID:27243772</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007ECSS...74..119S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007ECSS...74..119S"><span id="translatedtitle"><span class="hlt">Dynamics</span> of summer flounder, Paralichthys dentatus, <span class="hlt">seasonal</span> migrations based on ultrasonic telemetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sackett, Dana K.; Able, Kenneth W.; Grothues, Thomas M.</p> <p>2007-08-01</p> <p>Migrations of summer flounder, Paralichthys dentatus, to and from estuaries to the continental shelf in the Mid-Atlantic Bight (MAB) occur <span class="hlt">seasonally</span> but their <span class="hlt">dynamics</span> are poorly understood. Ultrasonic telemetry, both passive and active, was used during 2003-2005 to determine timing and rate of juvenile and adult summer flounder (268-535 mm TL) migrating to and from the Mullica River-Great Bay estuary in southern New Jersey. Additionally, 7 years of inner continental shelf surveys off New Jersey were used to assess complementary <span class="hlt">seasonal</span> movements. Most tagged fish emigrated from the estuary between July and September, though emigration lasted into December and appeared to be influenced by a number of factors. In July 2004, more tagged fish emigrated, at increased rates of movement, at low barometric pressure during a storm event. Trawl collections on the inner shelf demonstrated the same approximate immigration times as seen with telemetry. Later in the fall, increased numbers of tagged summer flounder emigrated from the estuary when dissolved oxygen was decreasing. Fall trawl surveys showed increased numbers of fish on the inner shelf when dissolved oxygen was decreasing in the Mullica River-Great Bay estuary, supporting the telemetry results. Fish emigrated from the estuary during the day and night but nighttime movements were in deeper water at slightly slower rates of movement. Exit and re-entry also occurred during the fall emigration. Ultrasonically tagged individuals demonstrated homing by returning to the same estuary, in March through June, in the second and third year of the study (39-6%, respectively). In summary, immigration may result from homing for a large proportion of summer flounder. Emigration may be associated with storms on an episodic scale, and dissolved oxygen and temperature on a <span class="hlt">seasonal</span> scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017205','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017205"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">dynamics</span> of groundwater-lake interactions at Doñana National Park, Spain</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Sacks, Laura A.; Herman, Janet S.; Konikow, Leonard F.; Vela, Antonio L.</p> <p>1992-01-01</p> <p>The hydrologic and solute budgets of a lake can be strongly influenced by transient groundwater flow. Several shallow interdunal lakes in southwest Spain are in close hydraulic connection with the shallow ground water. Two permanent lakes and one intermittent lake have chloride concentrations that differ by almost an order of magnitude. A two-dimensional solute-transport model, modified to simulate transient groundwater-lake interaction, suggests that the rising water table during the wet <span class="hlt">season</span> leads to local flow reversals toward the lakes. Response of the individual lakes, however, varies depending on the lake's position in the regional flow system. The most dilute lake is a flow-through lake during the entire year; the through flow is driven by regional groundwater flow. The other permanent lake, which has a higher solute concentration, undergoes <span class="hlt">seasonal</span> groundwater flow reversals at its downgradient end, resulting in complex seepage patterns and higher solute concentrations in the ground water near the lake. The solute concentration of the intermittent lake is influenced more strongly by the <span class="hlt">seasonal</span> wetting and drying cycle than by the regional flow system. Although evaporation is the major process affecting the concentration of conservative solutes in the lakes, geochemical and biochemical reactions influence the concentration of nonconservative solutes. Probable reactions in the lakes include biological uptake of solutes and calcite precipitation; probable reactions as lake water seeps into the aquifer are sulfate reduction and calcite dissolution. Seepage reversals can result in water composition that appears inconsistent with predictions based on head measurements because, under transient flow conditions, the flow direction at any instant may not satisfactorily depict the source of the water. Understanding the <span class="hlt">dynamic</span> nature of groundwater-lake interaction aids in the interpretation of hydrologic and chemical relations between the lakes and the ground</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B21A0001Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B21A0001Z"><span id="translatedtitle">Multiclass relevance vector machine classification to explore annual and <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of an Invasive reed</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zaman, B.; Torres, A.; McKee, M.</p> <p>2014-12-01</p> <p>Phragmites Australis forms dense stands which shade native vegetation and alter the ecosystem. Information on annual and <span class="hlt">seasonal</span> <span class="hlt">dynamics</span> of this plant contributes to the decision support system of wetland management. The study area is the Bear River Migratory bird refuge (BRMBR) which encompasses the Bear river and its delta where it flows into the northern part of theGreat Salt Lake, Utah. <span class="hlt">Seasonal</span> change detection was carried out between the months of June 2010 and September 2010. The imagery from June 2011 and July 2011 were used for annual change detection. The remote sensing data was acquired by AggieAir, an unmanned aerial vehicle (UAV) platform, flown autonomously via pre-programmed flight plans at low altitudes to limit atmospheric effects. This UAV acquires high resolution multispectral images in the visible, near-infrared and thermal bands and has a flight interval of about 30 minutes. The reflectance values of the classes in wavebands 550, 650 and 850 nm were used to train the Multiclass relevance vector machine (MCRVM) model developed to classify the imagery of study area. There were a total of 5 classes: water, phragmites australis, marshy land, mixed vegetation and salt flats and three attributes. The multiclass classification accuracy achieved for June 2010, September 2010 and July 2011 were 95.2%, 95% and 98.7% respectively. The <span class="hlt">seasonal</span> change detection indicated an average increase of 17% in area of phragmites and annual change detection results indicated an average increase of 110% from June 2010 to July 2011. It's astonishing rate of increase in distribution and abundance was alarming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27243772','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27243772"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">Dynamics</span> of Water Use Strategy of Two Salix Shrubs in Alpine Sandy Land, Tibetan Plateau.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhu, Yajuan; Wang, Guojie; Li, Renqiang</p> <p>2016-01-01</p> <p>Water is a limiting factor for plant growth and vegetation <span class="hlt">dynamics</span> in alpine sandy land of the Tibetan Plateau, especially with the increasing frequency of extreme precipitation events and drought caused by climate change. Therefore, a relatively stable water source from either deeper soil profiles or ground water is necessary for plant growth. Understanding the water use strategy of dominant species in the alpine sandy land ecosystem is important for vegetative rehabilitation and ecological restoration. The stable isotope methodology of δD, δ18O, and δ13C was used to determine main water source and long-term water use efficiency of Salix psammophila and S. cheilophila, two dominant shrubs on interdune of alpine sandy land in northeastern Tibetan Plateau. The root systems of two Salix shrubs were investigated to determine their distribution pattern. The results showed that S. psammophila and S. cheilophila absorbed soil water at different soil depths or ground water in different <span class="hlt">seasons</span>, depending on water availability and water use strategy. Salix psammophila used ground water during the growing <span class="hlt">season</span> and relied on shallow soil water recharged by rain in summer. Salix cheilophila used ground water in spring and summer, but relied on shallow soil water recharged by rain in spring and deep soil water recharged by ground water in fall. The two shrubs had dimorphic root systems, which is coincident with their water use strategy. Higher biomass of fine roots in S. psammophila and longer fine roots in S. cheilophila facilitated to absorb water in deeper soil layers. The long-term water use efficiency of two Salix shrubs increased during the dry <span class="hlt">season</span> in spring. The long-term water use efficiency was higher in S. psammophila than in S. cheilophila, as the former species is better adapted to semiarid climate of alpine sandy land. PMID:27243772</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20692868','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20692868"><span id="translatedtitle">Highly diverse and <span class="hlt">seasonally</span> <span class="hlt">dynamic</span> protist community in a pristine peat bog.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lara, Enrique; Mitchell, Edward A D; Moreira, David; López García, Purificación</p> <p>2011-01-01</p> <p>Culture-independent molecular methods based on the amplification, cloning and sequencing of small-subunit ribosomal RNA genes (SSU rDNAs) are powerful tools to study the diversity of microorganisms. Despite so, the eukaryotic microbial diversity of many ecosystems, including peatlands has not yet received much attention. We analysed the eukaryotic diversity by molecular surveys in water from the centre of a pristineSphagnum-dominated peatland in the Jura Mountains of Switzerland during a complete <span class="hlt">seasonal</span> cycle. The clone libraries constructed from five different temporal samplings revealed a high diversity of protists with representatives of all major eukaryotic phyla. In addition, four sequence types could not be assigned to any known high-level eukaryotic taxon but branched together with a rather good statistic support, raising the possibility of a novel, deep branching eukaryotic clade. The analysis of <span class="hlt">seasonal</span> patterns of phylotypes showed a clear change in the eukaryotic communities between the warm period (late spring and summer) and the cold period (autumn and winter). Chrysophytes dominated the samples in the cold period while testate amoebae (Arcellinida and Euglyphida) and a few other groups peaked in summer. A few phylotypes (such as a cryptomonad and a perkinsid) were abundant at given sampling times and then almost disappeared, suggesting bloom-like <span class="hlt">dynamics</span>. PMID:20692868</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2042099','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2042099"><span id="translatedtitle"><span class="hlt">Seasonal</span> <span class="hlt">Dynamics</span> of Arbuscular Mycorrhizal Fungal Communities in Roots in a Seminatural Grassland▿ †</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Santos-González, Juan C.; Finlay, Roger D.; Tehler, Anders</p> <p>2007-01-01</p> <p>Symbiotic arbuscular mycorrhizal fungi (AMF) have been shown to influence both the diversity and productivity of grassland plant communities. These effects have been postulated to depend on the differential effects of individual mycorrhizal taxa on different plant species; however, so far there are few detailed studies of the <span class="hlt">dynamics</span> of AMF colonization of different plant species. In this study, we characterized the communities of AMF colonizing the roots of two plant species, Prunella vulgaris and Antennaria dioica, in a Swedish seminatural grassland at different times of the year. The AMF small subunit rRNA genes were subjected to PCR, cloning, sequencing, and phylogenetic analysis. Nineteen discrete sequence types belonging to Glomus groups A and B and to the genus Acaulospora were distinguished. No significant <span class="hlt">seasonal</span> changes in the species compositions of the AMF communities as a whole were observed. However, the two plant species hosted significantly different AMF communities. P. vulgaris hosted a rich AMF community throughout the entire growing <span class="hlt">season</span>. The presence of AMF in A. dioica decreased dramatically in autumn, while an increased presence of Ascomycetes species was detected. PMID:17630308</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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