Sample records for accumulation rates measured

  1. Using transplants to measure accumulation rates of epiphytic bryophytes in forests of western Oregon

    USGS Publications Warehouse

    Rosso, A.L.; Muir, Patricia S.; Rambo, T.

    2001-01-01

    We sought a simple and effective transplant method that could be used to measure biomass accumulation rates of epiphytic bryophytes. Trials were carried out in the Pseudotsuga menziesii-dominated forests of western Oregon. We tested multiple transplant methods over a 13-month period while comparing accumulation rates of Antitrichia curtipendula (Hedw.) Brid. and Isothecium myosuroides Brid. among an old-growth stand, a young stand, and a recent clearcut. In our study area, Antitrichia is considered to be an old-growth associate while Isothecium is a more ubiquitous species. Methods tested included containment in net bags, containment in hairnets, and directly tying mats to substrates. Three sizes of transplants were tested with both natural and inert artificial substrates. Transplants of approximately five g enclosed in plastic net bags and tied to either natural or artificial substrates worked well for our purposes. Only minor differences were found in mean accumulation rates between the old growth and young stand, though variation in accumulation rates was higher in the old growth. Neither species appeared capable of surviving in the clearcut. Antitrichia accumulated biomass 60% faster in the canopy than in the understory on average. Antitrichia also accumulated at a faster rate than Isothecium, with mean 13-month biomass increases of 11.8 and 3.7% respectively for 5 g transplants in the understory. Our results suggest that Antitrichia's association with old growth may be due more to dispersal or establishment limitations than to a decreased ability to grow in young stands.

  2. Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.

    2002-01-01

    An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the areally Integrated snow accumulation and the net ice discharge of the ice sheet. Uncertainties in this calculation Include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken from isolated spots across the ice sheet. The sparse data associated with ice cores juxtaposed against the high spatial and temporal resolution provided by remote sensing , has motivated scientists to investigate relationships between accumulation rate and microwave observations as an option for obtaining spatially contiguous estimates. The objective of this PARCA continuation proposal was to complete an estimate of surface accumulation rate on the Greenland Ice Sheet derived from C-band radar backscatter data compiled in the ERS-1 SAR mosaic of data acquired during, September-November, 1992. An empirical equation, based on elevation and latitude, is used to determine the mean annual temperature. We examine the influence of accumulation rate, and mean annual temperature on C-band radar backscatter using a forward model, which incorporates snow metamorphosis and radar backscatter components. Our model is run over a range of accumulation and temperature conditions. Based on the model results, we generate a look-up table, which uniquely maps the measured radar backscatter, and mean annual temperature to accumulation rate. Our results compare favorably with in situ accumulation rate measurements falling within our study area.

  3. Understanding Ozark Forest Litter Variability Through a Synthesis of Accumulation Rates and Fire Events

    Treesearch

    Michael C. Stambaugh; Richard P. Guyette; Keith W. Grabner; Jeremy Kolaks

    2006-01-01

    Measuring success of fuels management is improved by understanding rates of litter accumulation and decay in relation to disturbance events. Despite the broad ecological importance of litter, little is known about the parameters of accumulation and decay rates in Ozark forests. Previously published estimates were used to derive accumulation rates and combined litter...

  4. Radon exhalation rates from building materials using electret ion chamber radon monitors in accumulators.

    PubMed

    Kotrappa, Payasada; Stieff, Frederick

    2009-08-01

    An electret ion chamber (EIC) radon monitor in a sealed accumulator measures the integrated average radon concentration at the end of the accumulation duration. Theoretical equations have been derived to relate such radon concentrations (Bq m(-3) ) to the radon emanation rate (Bq d(-1)) from building materials enclosed in the accumulator. As an illustration, a 4-L sealable glass jar has been used as an accumulator to calculate the radon emanation rate from different granite samples. The radon emanation rate was converted into radon flux (Bq mm(-2) d(-1)) by dividing the emanation rate by surface area of the sample. Fluxes measured on typical, commercially available granites ranged from 20-30 Bq m(-2) d(-1). These results are similar to the results reported in the literature. The lower limit of detection for a 2-d measurement works out to be 7 Bq m(-2) d(-1). Equations derived can also be used for other sealable accumulators and other integrating detectors, such as alpha track detectors.

  5. Constant strain accumulation rate between major earthquakes on the North Anatolian Fault.

    PubMed

    Hussain, Ekbal; Wright, Tim J; Walters, Richard J; Bekaert, David P S; Lloyd, Ryan; Hooper, Andrew

    2018-04-11

    Earthquakes are caused by the release of tectonic strain accumulated between events. Recent advances in satellite geodesy mean we can now measure this interseismic strain accumulation with a high degree of accuracy. But it remains unclear how to interpret short-term geodetic observations, measured over decades, when estimating the seismic hazard of faults accumulating strain over centuries. Here, we show that strain accumulation rates calculated from geodetic measurements around a major transform fault are constant for its entire 250-year interseismic period, except in the ~10 years following an earthquake. The shear strain rate history requires a weak fault zone embedded within a strong lower crust with viscosity greater than ~10 20  Pa s. The results support the notion that short-term geodetic observations can directly contribute to long-term seismic hazard assessment and suggest that lower-crustal viscosities derived from postseismic studies are not representative of the lower crust at all spatial and temporal scales.

  6. Accumulation rates of airborne heavy metals in wetlands

    USGS Publications Warehouse

    Souch, C.J.; Filippelli, G.M.; Dollar, N.; Perkins, S.; Mastalerz, Maria

    2002-01-01

    Accumulation rates of heavy metals (Cd, Cr, Cu, Mn, Pb, and Zn) retained in wetland sediments in northwest Indiana-downwind of the Chicago-Gary-Hammond industrial area-are quantified to assess anthropogenic influences on atmospheric fluxes. Metal concentrations for 22 sediment cores are determined by ICP-AES after ashing and strong acid extraction. Relations between organic content and metal concentrations at depth are used to separate natural and anthropogenic sources. Accumulation rates over the lifetime of the wetlands (???4500 years) have averaged 0.2 (Cd), 1.4 (Cu), 1.7 (Cr), 13.4 (Mn), 4.8 (Pb), and 18.7 (Zn) mg m-2 y-1. Rates for the last 100 years have increased on average by factors of 6 (Cd), 8 (Cu), 10 (Mn), 15 (Pb), and 30 (Zn), remaining effectively constant for Cr. Where the wetlands have been drained, metals have been lost from the sediments, owing to changes in organic content and local hydrochemistry (exposure to acidic rainfall). Sediment-based accumulation rates at the undrained sites are higher, though generally consistent, with measured and modeled atmospheric fluxes documented by short-term studies conducted over the last three decades. The fraction of the total metals in the wetlands estimated to be of anthropogenic origin ranges from approximately 3% for Cr, up to approximately 35% for Pb, and 70% for Zn. This historic legacy of contamination must be considered in land management decisions, particularly when wetlands are drained.

  7. Temperature-dependence of biomass accumulation rates during secondary succession.

    PubMed

    Anderson, Kristina J; Allen, Andrew P; Gillooly, James F; Brown, James H

    2006-06-01

    Rates of ecosystem recovery following disturbance affect many ecological processes, including carbon cycling in the biosphere. Here, we present a model that predicts the temperature dependence of the biomass accumulation rate following disturbances in forests. Model predictions are derived based on allometric and biochemical principles that govern plant energetics and are tested using a global database of 91 studies of secondary succession compiled from the literature. The rate of biomass accumulation during secondary succession increases with average growing season temperature as predicted based on the biochemical kinetics of photosynthesis in chloroplasts. In addition, the rate of biomass accumulation is greater in angiosperm-dominated communities than in gymnosperm-dominated ones and greater in plantations than in naturally regenerating stands. By linking the temperature-dependence of photosynthesis to the rate of whole-ecosystem biomass accumulation during secondary succession, our model and results provide one example of how emergent, ecosystem-level rate processes can be predicted based on the kinetics of individual metabolic rate.

  8. Annual Greenland Accumulation Rates (2009-2012) from Airborne Snow Radar

    NASA Technical Reports Server (NTRS)

    Koenig, Lora S.; Ivanoff, Alvaro; Alexander, Patrick M.; MacGregor, Joseph A.; Fettweis, Xavier; Panzer, Ben; Paden, John D.; Forster, Richard R.; Das, Indrani; McConnell, Joseph R.; hide

    2016-01-01

    Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2-6.5 gigahertz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semi-automated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009-2012. The uncertainty in these radar-derived accumulation rates is on average 14 percent. A comparison of the radarderived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and longterm mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR - Modele Atmospherique Regional for Greenland and vicinity) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models.

  9. Atmospheric Pb and Ti accumulation rates from Sphagnum moss: dependence upon plant productivity.

    PubMed

    Kempter, H; Krachler, M; Shotyk, W

    2010-07-15

    The accumulation rates of atmospheric Pb and Ti were obtained using the production rates of Sphagnum mosses collected in four ombrotrophic bogs from two regions of southern Germany: Upper Bavaria (Oberbayern, OB) and the Northern Black Forest (Nordschwarzwald, NBF). Surfaces of Sphagnum carpets were marked with plastic mesh and one year later the production of plant matter was harvested. Metal concentrations were determined in acid digests using sector field ICP-MS employing well established analytical procedures. Up to 12 samples (40 x 40 cm) were collected per site, and 6-10 sites were investigated per bog. Variations within a given sampling site were in the range 2.3-4x for Pb concentrations, 1.8-2.5x for Ti concentrations, 3-8.3x for Pb/Ti, 5.6-7.8x for Pb accumulation rates, and 2.3-6.4x for Ti accumulation rates. However, the median values of these parameters for the sites (6-10 per bog) were quite consistent. The mosses from the bogs in NBF exhibited significantly greater productivity (187-202 g m(-2) a(-1)) compared to the OB peat bogs (71-91 g m(-2) a(-1)), and these differences had a pronounced effect on the Pb and Ti accumulation rates. Highly productive mosses showed no indication of a "dilution effect" of Pb or Ti concentrations, suggesting that more productive plants were simply able to accumulate more particles from the air. The median rates of net Pb accumulation by the mosses are in excellent agreement with the fluxes obtained by direct atmospheric measurements at nearby monitoring stations in both regions (EMEP and MAPESI data).

  10. A Probabilistic Method of Assessing Carbon Accumulation Rate at Imnavait Creek Peatland, Arctic Long Term Ecological Research Station, Alaska

    NASA Technical Reports Server (NTRS)

    Nichols, Jonathan E.; Peteet, Dorothy M.; Frolking, Steve; Karavias, John

    2017-01-01

    Arctic peatlands are an important part of the global carbon cycle, accumulating atmospheric carbon as organic matter since the Late glacial. Current methods for understanding the changing efficiency of the peatland carbon sink rely on peatlands with an undisturbed stratigraphy. Here we present a method of estimating primary carbon accumulation rate from a site where permafrost processes have either vertically or horizontally translocated nearby carbon-rich sediment out of stratigraphic order. Briefly, our new algorithm estimates the probability of the age of deposition of a random increment of sediment in the core. The method assumes that if sediment age is measured at even depth increments, dates are more likely to occur during intervals of higher accumulation rate and vice versa. Multiplying estimated sedimentation rate by measured carbon density yields carbon accumulation rate. We perform this analysis at the Imnavait Creek Peatland, near the Arctic Long Term Ecological Research network site at Toolik Lake, Alaska. Using classical radiocarbon age modeling, we find unreasonably high rates of carbon accumulation at various Holocene intervals. With our new method, we find accumulation rate changes that are in improved agreement within the context of other sites throughout Alaska and the rest of the Circum-Arctic region.

  11. A comparative study of accumulation rates derived by He and Th isotope analysis of marine sediments

    NASA Astrophysics Data System (ADS)

    Marcantonio, Franco; Kumar, Niraj; Stute, Martin; Anderson, Robert F.; Seidl, Michele A.; Schlosser, Peter; Mix, Alan

    1995-07-01

    We present a detailed down-core analysis of helium isotope ratios and concentrations for bulk sediments from the central Equatorial Pacific that span the last two glacial-interglacial cycles. Measured 3He/4He ratios range from 1.0 × 10 -5 to 2.1 × 10 -4, or 7.4 to 149 times the atmospheric ratio. The 3He from interplanetary dust particles (IDPs) constitutes virtually all of the 3He measured within the sediment. Because carbonate accumulation rates are high in the Equatorial Pacific, the measured 3He concentrations are lower than have been measured elsewhere, and range from 4.7 × 10 -13 to 3.0 × 10 -12 cm 3STP · g -1. If the cosmic dust 3He-flux is constant with time, sediment mass accumulation rates can be determined from the 3He concentration in sediments. The excess 230Th technique is an entirely independent method for calculating sediment mass accumulation rates because its source is in-situ decay of 234U in seawater. To first order, initial excess 230Th activities correlate with 3He concentrations within this core. Based on the 230Th results, we estimate the 3He-flux to the Earth's surface as (9.6 ± 2.0) × 10 -16 cm 3STP · cm -2 · a -1. If this flux has remained constant over extended periods of time, it can be used to determine sediment accumulation rates beyond the 230Th range (300,000 yr).

  12. Determining rates of sediment accumulation on the Mekong shelf: Timescales, steady-state assumptions, and radiochemical tracers

    NASA Astrophysics Data System (ADS)

    DeMaster, D. J.; Liu, J. P.; Eidam, E.; Nittrouer, C. A.; Nguyen, T. T.

    2017-09-01

    Thirty-two kasten cores, collected from the proximal Mekong continental shelf, have been analyzed for their excess 210Pb distributions in an effort to establish rates of sediment accumulation over the past 100 years. The length of the cores varied from 0.5 to 3 m, and stations sampled topset, foreset, and bottomset beds (water depths 7-21 m). Apparent excess 210Pb sediment accumulation rates ranged from > 10 cm/y (no down-core decrease of excess activity over 300 cm core length) near the Song Hau river mouth, to 1-3 cm/y in topset and foreset beds within 20-50 km of the river mouth, to rates as low as 0.4 cm/y in cores from bottomset beds. The 210Pb sediment accumulation rates yield an overall sediment burial rate of 6.1 × 1013 g/y for the proximal deltaic deposits, which corresponds to 43% of the total modern Mekong sediment burial on the southern Vietnam shelf (1.4 × 1014 g/y; based on our 210Pb and seismic data and 210Pb data from the literature). This shelf burial rate is in reasonable agreement with current long-term estimates of Mekong River sediment discharge (1.3-1.6 × 1014 g/y) from the literature. The inventory of excess 210Pb in the proximal Mekong deltaic deposits indicates that the shoreward flow of offshore water (entrained during river/ocean mixing) is approximately twice the flow of the Mekong freshwater discharge. Organic-carbon 14C ages were measured on 10 cores from the proximal Mekong delta and compared to 210Pb sediment accumulation rates in the same core. The 210Pb accumulation rates in all 10 cores were considered to be more robust and accurate than the 14C geochronologies, primarily because of down-core variations in the source of organic carbon deposited on the seafloor (old terrestrial carbon versus younger marine carbon). Variations in the source of organic carbon accumulating in the seabed were resolved by measuring the δ13C value of the seabed organic carbon.

  13. Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.

    2001-01-01

    An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the snow accumulation and the ice discharge of the ice sheet. Uncertainties in this calculation include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken throughout the ice sheet. The sparse data associated with ice cores, coupled with the high spatial and temporal resolution provided by remote sensing, have motivated scientists to investigate relationships between accumulation rate and microwave observations.

  14. Rate of production, dissolution and accumulation of biogenic solids in the ocean

    NASA Technical Reports Server (NTRS)

    Arrhenius, G.

    1988-01-01

    The equatorial current system, by its response to global circulation changes, provides a unique recording mechanism for long range climatic oscillations. A permanent record of the changes in rate of upwelling and organic production is generated in the equatorial deep sea sediments, particularly by such biogenic components which are unaffected by secondary dissolution. In order to determine the rates of accumulation of various sedimentary components, a reliable differential measurement of age of the strata must be obtained. Various approaches to this problem are reviewed, and sources of error discussed. Secondary dissolution of calcium carbonate introduces a substantial and variable difference between the dissolution-modified, and hence a priori unknown, rate of deposition on one hand and the rate of accumulation, derivable from the observed concentration, on the other. The cause and magnitude of these variations are of importance, particularly since some current dating schemes are based on assumed constancy in the rate of accumulation of this and, in some cases, also all other sedimentary components. The concepts used in rate evaluation are discussed with emphasis on the difference between the state of dissolution, an observable property of the sediment, and the rate of dissolution, a parameter that requires deduction of the carbonate fraction dissolved, and of the time differential. As a most likely cause of the enhanced state of dissolution of the interglacial carbonate sediments is proposed the lowered rates of biogenic production and deposition, which cause longer exposure of the carbonate microfossils to corrosion in the bioturbated surface layer of the sediment. Historical perspective is included in the discussion in view of the dedication of the Symposium to Hans Pettersson, the leader of the Swedish Deep Sea Expedition 1947-1948, an undertaking that opened a new era in deep sea research and planetary dynamics.

  15. A True Eddy Accumulation - Eddy Covariance hybrid for measurements of turbulent trace gas fluxes

    NASA Astrophysics Data System (ADS)

    Siebicke, Lukas

    2016-04-01

    Eddy covariance (EC) is state-of-the-art in directly and continuously measuring turbulent fluxes of carbon dioxide and water vapor. However, low signal-to-noise ratios, high flow rates and missing or complex gas analyzers limit it's application to few scalars. True eddy accumulation, based on conditional sampling ideas by Desjardins in 1972, requires no fast response analyzers and is therefore potentially applicable to a wider range of scalars. Recently we showed possibly the first successful implementation of True Eddy Accumulation (TEA) measuring net ecosystem exchange of carbon dioxide of a grassland. However, most accumulation systems share the complexity of having to store discrete air samples in physical containers representing entire flux averaging intervals. The current study investigates merging principles of eddy accumulation and eddy covariance, which we here refer to as "true eddy accumulation in transient mode" (TEA-TM). This direct flux method TEA-TM combines true eddy accumulation with continuous sampling. The TEA-TM setup is simpler than discrete accumulation methods while avoiding the need for fast response gas analyzers and high flow rates required for EC. We implemented the proposed TEA-TM method and measured fluxes of carbon dioxide (CO2), methane (CH4) and water vapor (H2O) above a mixed beech forest at the Hainich Fluxnet and ICOS site, Germany, using a G2301 laser spectrometer (Picarro Inc., USA). We further simulated a TEA-TM sampling system using measured high frequency CO2 time series from an open-path gas analyzer. We operated TEA-TM side-by-side with open-, enclosed- and closed-path EC flux systems for CO2, H2O and CH4 (LI-7500, LI-7200, LI-6262, LI-7700, Licor, USA, and FGGA LGR, USA). First results show that TEA-TM CO2 fluxes were similar to EC fluxes. Remaining differences were similar to those between the three eddy covariance setups (open-, enclosed- and closed-path gas analyzers). Measured TEA-TM CO2 fluxes from our physical

  16. Greenland annual accumulation along the EGIG line, 1959-2004, from ASIRAS airborne radar and neutron-probe density measurements

    NASA Astrophysics Data System (ADS)

    Overly, Thomas B.; Hawley, Robert L.; Helm, Veit; Morris, Elizabeth M.; Chaudhary, Rohan N.

    2016-08-01

    We report annual snow accumulation rates from 1959 to 2004 along a 250 km segment of the Expéditions Glaciologiques Internationales au Groenland (EGIG) line across central Greenland using Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) radar layers and high resolution neutron-probe (NP) density profiles. ASIRAS-NP-derived accumulation rates are not statistically different (95 % confidence interval) from in situ EGIG accumulation measurements from 1985 to 2004. ASIRAS-NP-derived accumulation increases by 20 % below 3000 m elevation, and increases by 13 % above 3000 m elevation for the period 1995 to 2004 compared to 1985 to 1994. Three Regional Climate Models (PolarMM5, RACMO2.3, MAR) underestimate snow accumulation below 3000 m by 16-20 % compared to ASIRAS-NP from 1985 to 2004. We test radar-derived accumulation rates sensitivity to density using modeled density profiles in place of NP densities. ASIRAS radar layers combined with Herron and Langway (1980) model density profiles (ASIRAS-HL) produce accumulation rates within 3.5 % of ASIRAS-NP estimates in the dry snow region. We suggest using Herron and Langway (1980) density profiles to calibrate radar layers detected in dry snow regions of ice sheets lacking detailed in situ density measurements, such as those observed by the Operation IceBridge campaign.

  17. Radiocarbon dating, chronologic framework, and changes in accumulation rates of holocene estuarine sediments from Chesapeake Bay

    USGS Publications Warehouse

    Colman, Steven M.; Baucom, P.C.; Bratton, J.F.; Cronin, T. M.; McGeehin, J.P.; Willard, D.; Zimmerman, A.R.; Vogt, P.R.

    2002-01-01

    Rapidly accumulating Holocene sediments in estuaries commonly are difficult to sample and date. In Chesapeake Bay, we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelarator mass spectrometry methods to provide the first detailed chronologies of Holocene sediment accumulation in the bay. Carbon in these sediments is a complex mixture of materials from a variety of sources. Analyses of different components of the sediments show that total organic carbon ages are largely unreliable, because much of the carbon (including coal) has been transported to the bay from upstream sources and is older than sediments in which it was deposited. Mollusk shells (clams, oysters) and foraminifera appear to give reliable results, although reworking and burrowing are potential problems. Analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower Chesapeake Bay. The biogenic carbonate radiocarbon ages are compatible with 210 Pb and 137 Cs data and pollen stratigraphy from the same sites. Post-settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries, including the Chesapeake. Our data show that large variations in sediment mass accumulation rates occur among sites. At shallow water sites, local factors seem to control changes in accumulation rates with time. Our two relatively deep-water sites in the axial channel of the bay have different long-term average accumulation rates, but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay. Mass accumulation rates at the two deep-water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the Chesapeake watershed.

  18. Determination of mass accumulation rates and sediment radionuclide inventories in the deep Black Sea

    NASA Astrophysics Data System (ADS)

    Buesseler, Ken O.; Benitez, Claudia R.

    1994-11-01

    Accumulation rates were determined from a detailed profile of 210Pb excess in the top 3 cm of a box core from the deep waters of the western Black Sea. The data suggest a mass accumulation rate (MAR) of 69 ± 3g m -2y -1, less than half the MAR determined by varve counting. It is concluded that recognizable laminae couplets are not formed annually in these sediments. Further support for this conclusion is provided by the well documented fallout peaks of 239,240Pu and 137Cs from atmospheric nuclear weapons testing in the 1960s and the 1986 Chernobyl reactor accident. The 210Pb derived MAR from the top 3 cm is significantly higher than the long-term MAR determined from 14C data, suggesting an increase in accumulation rates within the past 1000-2000 years. The sedimen inventories of 210Pb excess and 239,240Pu match their expected supply, whereas most of the fallout 137Cs remains in the water column. The measured increase in 226Ra inventory in the top cm of this core matches the previously observed decrease in water column 226Ra during the past 30 years.

  19. Relationships between salinity and short-term soil carbon accumulation rates form marsh types across a landscape in the Mississippi River Delta

    USGS Publications Warehouse

    Baustian, Melissa M.; Stagg, Camille L.; Perry, Carey L.; Moss, Leland C; Carruthers, Tim J.B.; Allison, Mead

    2017-01-01

    Salinity alterations will likely change the plant and environmental characteristics in coastal marshes thereby influencing soil carbon accumulation rates. Coastal Louisiana marshes have been historically classified as fresh, intermediate, brackish, or saline based on resident plant community and position along a salinity gradient. Short-term total carbon accumulation rates were assessed by collecting 10-cm deep soil cores at 24 sites located in marshes spanning the salinity gradient. Bulk density, total carbon content, and the short-term accretion rates obtained with feldspar horizon markers were measured to determine total carbon accumulation rates. Despite some significant differences in soil properties among marsh types, the mean total carbon accumulation rates among marsh types were not significantly different (mean ± std. err. of 190 ± 27 g TC m−2 year−1). However, regression analysis indicated that mean annual surface salinity had a significant negative relationship with total carbon accumulation rates. Based on both analyses, the coastal Louisiana total marsh area (1,433,700 ha) accumulates about 2.7 to 3.3 Tg C year−1. Changing salinities due to increasing relative sea level or resulting from restoration activities may alter carbon accumulation rates in the short term and significantly influence the global carbon cycle.

  20. Accumulation effects in modulation spectroscopy with high-repetition-rate pulses: Recursive solution of optical Bloch equations

    NASA Astrophysics Data System (ADS)

    Osipov, Vladimir Al.; Pullerits, Tõnu

    2017-10-01

    Application of the phase-modulated pulsed light for advance spectroscopic measurements is the area of growing interest. The phase modulation of the light causes modulation of the signal. Separation of the spectral components of the modulations allows to distinguish the contributions of various interaction pathways. The lasers with high repetition rate used in such experiments can lead to appearance of the accumulation effects, which become especially pronounced in systems with long-living excited states. Recently it was shown that such accumulation effects can be used to evaluate parameters of the dynamical processes in the material. In this work we demonstrate that the accumulation effects are also important in the quantum characteristics measurements provided by modulation spectroscopy. In particular, we consider a model of quantum two-level system driven by a train of phase-modulated light pulses, organized in analogy with the two-dimensional spectroscopy experiments. We evaluate the harmonics' amplitudes in the fluorescent signal and calculate corrections appearing from the accumulation effects. We show that the corrections can be significant and have to be taken into account at analysis of experimental data.

  1. Death rates reflect accumulating brain damage in arthropods.

    PubMed

    Fonseca, Duane B; Brancato, Carolina L; Prior, Andrew E; Shelton, Peter M J; Sheehy, Matt R J

    2005-09-22

    We present the results of the first quantitative, whole-lifespan study of the relationship between age-specific neurolipofuscin concentration and natural mortality rate in any organism. In a convenient laboratory animal, the African migratory locust, Locusta migratoria, we find an unusual delayed-onset neurolipofuscin accumulation pattern that is highly correlated with exponentially accelerating age-specific Gompertz-Makeham death rates in both males (r=0.93, p=0.0064) and females (r=0.97, p=0.0052). We then test the conservation of this association by aggregating the locust results with available population-specific data for a range of other terrestrial, freshwater, marine, tropical and temperate arthropods whose longevities span three orders of magnitude. This synthesis shows that the strong association between neurolipofuscin deposition and natural mortality is a phylogenetically and environmentally widespread phenomenon (r=0.96, p < 0.0001). These results highlight neurolipofuscin as a unique and outstanding integral biomarker of ageing. They also offer compelling evidence for the proposal that, in vital organs like the brain, either the accumulation of toxic garbage in the form of lipofuscin itself, or the particular molecular reactions underlying lipofuscinogenesis, including free-radical damage, are the primary events in senescence.

  2. Elevated rates of organic carbon, nitrogen, and phosphorus accumulation in a highly impacted mangrove wetland

    NASA Astrophysics Data System (ADS)

    Sanders, Christian J.; Eyre, Bradley D.; Santos, Isaac R.; Machado, Wilson; Luiz-Silva, Wanilson; Smoak, Joseph M.; Breithaupt, Joshua L.; Ketterer, Michael E.; Sanders, Luciana; Marotta, Humberto; Silva-Filho, Emmanoel

    2014-04-01

    The effect of nutrient enrichment on mangrove sediment accretion and carbon accumulation rates is poorly understood. Here we quantify sediment accretion through radionuclide tracers to determine organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) accumulation rates during the previous 60 years in both a nutrient-enriched and a pristine mangrove forest within the same geomorphological region of southeastern Brazil. The forest receiving high nutrient loads has accumulated OC, TN, and TP at rates that are fourfold, twofold, and eightfold respectively, higher than those from the undisturbed mangrove. Organic carbon and TN stable isotopes (δ13C and δ15N) reflect an increased presence of organic matter (OM) originating with either phytoplankton, benthic algae, or another allochthonous source within the more rapidly accumulated sediments of the impacted mangrove. This suggests that the accumulation rate of OM in eutrophic mangrove systems may be enhanced through the addition of autochthonous and allochthonous nonmangrove material.

  3. Accumulate-Repeat-Accumulate-Accumulate-Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Sam; Thorpe, Jeremy

    2004-01-01

    Inspired by recently proposed Accumulate-Repeat-Accumulate (ARA) codes [15], in this paper we propose a channel coding scheme called Accumulate-Repeat-Accumulate-Accumulate (ARAA) codes. These codes can be seen as serial turbo-like codes or as a subclass of Low Density Parity Check (LDPC) codes, and they have a projected graph or protograph representation; this allows for a high-speed iterative decoder implementation using belief propagation. An ARAA code can be viewed as a precoded Repeat-and-Accumulate (RA) code with puncturing in concatenation with another accumulator, where simply an accumulator is chosen as the precoder; thus ARAA codes have a very fast encoder structure. Using density evolution on their associated protographs, we find examples of rate-lJ2 ARAA codes with maximum variable node degree 4 for which a minimum bit-SNR as low as 0.21 dB from the channel capacity limit can be achieved as the block size goes to infinity. Such a low threshold cannot be achieved by RA or Irregular RA (IRA) or unstructured irregular LDPC codes with the same constraint on the maximum variable node degree. Furthermore by puncturing the accumulators we can construct families of higher rate ARAA codes with thresholds that stay close to their respective channel capacity thresholds uniformly. Iterative decoding simulation results show comparable performance with the best-known LDPC codes but with very low error floor even at moderate block sizes.

  4. Carbon isotope evidence for recent climate-related enhancement of CO 2 assimilation and peat accumulation rates in Antarctica.

    PubMed

    Royles, Jessica; Ogée, Jérôme; Wingate, Lisa; Hodgson, Dominic A; Convey, Peter; Griffiths, Howard

    2012-10-01

    Signy Island, maritime Antarctic, lies within the region of the Southern Hemisphere that is currently experiencing the most rapid rates of environmental change. In this study, peat cores up to 2 m in depth from four moss banks on Signy Island were used to reconstruct changes in moss growth and climatic characteristics over the late Holocene. Measurements included radiocarbon dating (to determine peat accumulation rates) and stable carbon isotope composition of moss cellulose (to estimate photosynthetic limitation by CO 2 supply and model CO 2 assimilation rate). For at least one intensively 14 C-dated Chorisodontium aciphyllum moss peat bank, the vertical accumulation rate of peat was 3.9 mm yr -1 over the last 30 years. Before the industrial revolution, rates of peat accumulation in all cores were much lower, at around 0.6-1 mm yr -1 . Carbon-13 discrimination (Δ), corrected for background and anthropogenic source inputs, was used to develop a predictive model for CO 2 assimilation. Between 1680 and 1900, there had been a gradual increase in Δ, and hence assimilation rate. Since 1800, assimilation has also been stimulated by the changes in atmospheric CO 2 concentration, but a recent decline in Δ (over the past 50-100 years) can perhaps be attributed to documented changes in temperature and/or precipitation. The overall increase in CO 2 assimilation rate ( 13 C proxy) and enhanced C accumulation ( 14 C proxy) are consistent with warmer and wetter conditions currently generating higher growth rates than at any time in the past three millennia, with the decline in Δ perhaps compensated by a longer growing season. © 2012 Blackwell Publishing Ltd.

  5. Laboratory Determination of Molybdenum Accumulation Rates as a Measure of Hypoxic Conditions

    EPA Science Inventory

    Redox sensitive metals, such as molybdenum (Mo), are enriched in reducing sediments due to authigenic fixation in anoxic interstitial waters of sediments. This study tested whether the process of fixation and accumulation of Mo in sediments could provide a geochemical indicator o...

  6. Preservation efficiencies and accumulation rates for biogenic silica and organic C, N, and P in high-latitude sediments: The Ross Sea

    NASA Astrophysics Data System (ADS)

    Demaster, David J.; Ragueneau, Olivier; Nittrouer, Charles A.

    1996-08-01

    Rates of biogenic sediment accumulation (biogenic silica and organic C, N, and P) and pore water flux have been established for a variety of depositional environments in the Ross Sea. On the basis of 14C measurements in kasten cores, sediment accumulation rates ranged from 250 cm kyr-1 in the coastal basin of Granite Harbor to 1-2 cm kyr-1 in the shelf and slope environments of the northern and eastern Ross Sea. Burial of biogenic material was most rapid in the southwestern Ross Sea, where biogenic silica accumulation rates ranged from 2 to 31 g cm-2 kyr-1 and organic carbon accumulation rates ranged from 0.05 to 1.4 g cm-2 kyr-1. In the northern and eastern Ross Sea, biogenic silica and organic carbon accumulation rates typically equaled 0.02-0.03 g SiO2 cm-2 kyr-1 and 0.002-0.004 g C cm-2 kyr-1. Flux core measurements were used to estimate seabed regeneration rates for biogenic silica, organic carbon, and phosphorus. Pore water fluxes, in general, showed much less variability across the Ross Sea than did the biogenic accumulation rates. Pore water silicate fluxes in the study area ranged from 0.6 to 5.3 g SiO2 cm-2 kyr-1, whereas carbon fluxes ranged from 0.1 to 1.2 g C cm-2 kyr-1 and phosphate fluxes varied from -0.006 to 0.012 g P cm-2 kyr-1. Seabed preservation efficiencies were calculated for biogenic silica, organic carbon, and phosphorus by combining the solid-phase and pore water data. The seabed preservation efficiencies for biogenic silica (1-86%) were greater than for organic carbon (1-71%) at all nine stations examined. The preferential preservation of biogenic silica relative to organic carbon also was apparent in Ross Sea sediments because the biogenic silica/organic carbon ratio in the material buried in the seabed generally was 2 times greater than the ratio in sediment particles arriving at the sediment-water interface. Sediment accumulation rate correlated strongly with both the biogenic silica and the organic carbon preservation efficiency data

  7. Constant Flux Proxies and Pleistocene Sediment Accumulation Rates on the Juan de Fuca Ridge in the Northeast Pacific

    NASA Astrophysics Data System (ADS)

    Middleton, J. L.; Mukhopadhyay, S.; Langmuir, C. H.; Costa, K.; McManus, J. F.; d'Almeida, M.; Huybers, P. J.; Winckler, G.

    2016-12-01

    Mass accumulation rates of marine sediments are often employed to constrain deposition rates of important proxies such as terrigenous dust, carbonate, and biogenic opal to quantitatively examine variations in continental aridity, atmospheric transport, and biologic productivity across changing climatic conditions. However, deposition rates that are estimated using traditional mass accumulation rates calculated from sediment core age models can be subject to bias from lateral sediment transport and limited age model resolution. Constant flux proxies, such as extraterrestrial helium-3 (3HeET) and excess thorium-230 (230ThXS), can be used to calculate vertical sediment accumulation rates that are independent of age model uncertainties and the effects of lateral sediment transport. While a short half-life limits analyses of 230ThXS to the past 500 ka, 3HeET is stable and could be used to constrain sedimentary fluxes during much of the Cenozoic. Despite the vast paleoceanographic potential of constant flux proxies, few studies have directly compared the behavior of 230ThXS and 3HeET using measurements from the same samples. Sediment grain size fractionation and local scavenging effects may differentially bias one or both proxy systems and complicate the interpretation of 230ThXS or 3HeET data. We will present a new record of vertical sediment accumulation rates spanning the past 600 ka in the Northeast Pacific constrained using analyses of both 3HeET and 230ThXS in two sediment cores from cruise AT26-19 on the Juan de Fuca Ridge. Such a record allows for intercomparison of both constant flux proxies in the mid-ocean ridge environment and examination of sedimentary behavior across multiple glacial cycles. The 230ThXS-derived accumulation rates typically range from 0.5 to 2 g cm-2 ka-1 over the past 450 ka, with periods of maximum deposition coinciding with glacial maxima. Preliminary results of samples analyzed with both 3HeET and 230ThXS indicate relative consistency

  8. Winter Insulation By Snow Accumulation in a Subarctic Treeline Ecosystem Increases Summer Carbon Cycling Rates

    NASA Astrophysics Data System (ADS)

    Parker, T.; Subke, J. A.; Wookey, P. A.

    2014-12-01

    The effect of snow accumulation on soil carbon and nutrient cycling is attracting substantial attention from researchers. We know that deeper snow accumulation caused by high stature vegetation increases winter microbial activity and therefore carbon and nitrogen flux rates. However, until now the effect of snow accumulation, by buffering winter soil temperature, on subsequent summer soil processes, has scarcely been considered. We carried out an experiment at an alpine treeline in subarctic Sweden in which soil monoliths, contained within PVC collars, were transplanted between forest (deep winter snow) and tundra heath (shallow winter snow). We measured soil CO2efflux over two growing seasons and quantified soil microbial biomass after the second winter. We showed that respiration rates of transplanted forest soil were significantly reduced compared with control collars (remaining in the forest) as a consequence of colder, but more variable, winter temperatures. We hypothesised that microbial biomass would be reduced in transplanted forests soils but found there was no difference compared to control. We therefore further hypothesised that the similarly sized microbial pool in the control is assembled differently to the transplant. We believe that the warmer winters in forests foster more active consortia of decomposer microbes as a result of different abiotic selection pressures. Using an ecosystem scale experimental approach, we have identified a mechanism that influences summer carbon cycling rates based solely on the amount of snow that accumulates the previous winter. We conclude that modification of snow depth as a consequence of changes in vegetation structure is an important mechanism influencing soil C stocks in ecosystems where snow persists for a major fraction of the year.

  9. Project Hotspot: Linear accumulation rates of late Cenozoic basalt at Kimama, Idaho, and implications for crustal strain and subsidence rates of the central Snake River Plain

    NASA Astrophysics Data System (ADS)

    Rodgers, D. W.; Potter, K. E.; Shervais, J. W.; Champion, D. E.; Duncan, R. A.

    2013-12-01

    Project Hotspot's Kimama drill hole on the Snake River Plain, Idaho recovered a 1912 m thick section of basalt core that ranges in age from ~700 ka to at least 6.14 Ma, based on five 40Ar/39Ar analyses and twenty paleomagnetic age assignments. Fifty-four flow groups comprising 510 individual flows were defined, yielding an average recurrence interval of ~11,400 years between flows. Age-depth analysis indicate that, over thicknesses >150 m and age spans >500 k.y., accumulation rates were constant at 30 m/100 k.y. The existence and persistence of this linear accumulation rate for greater than 5 m.y. documents an external tectonic control on eruption dynamics. One conceptual model relates accumulation rates to horizontal crustal strain, such that far-field extension rate controls the periodicity of dikes that feed basalt flows. In this model, each of the 54 flow groups would have a deep-seated, relatively wide (1-10m) dike that branches upward into a network of narrow (10-100 cm) dikes feeding individual lava flows. Assuming an east-west lateral lava flow extent of up to 50 km, the Kimama data record a steady-state crustal strain rate of 10-9 to 10-10 y-1. This rate is comparable to modern, decadal strain rates measured with GPS in the adjacent Basin & Range province, but exceeds decadal strain rates of zero measured in the eastern Snake River Plain. Linear accumulation rates also provide insight into basalt subsidence history. In this model, the middle-upper crust subsides due to the added weight of lava flows, the added weight of mid-crustal sills/dikes, and thermal contraction in the wake of the Yellowstone hot spot. Isostatic compensation would occur in the (nearly) molten lower crust. Assuming constant surface elevation and a basalt density of 2.6 g/cm3, the lava flow weight would account for 87% of the burial through time, yielding a steady-state "tectonic" subsidence rate of 4 m/100 k.y. attributed to the driving forces of mid-crustal injection and/or thermal

  10. Ice shelf snow accumulation rates from the Amundsen-Bellingshausen Sea sector of West Antarctica derived from airborne radar

    NASA Astrophysics Data System (ADS)

    Medley, B.; Kurtz, N. T.; Brunt, K. M.

    2015-12-01

    The large ice shelves surrounding the Antarctic continent buttress inland ice, limiting the grounded ice-sheet flow. Many, but not all, of the thick ice shelves located along the Amundsen-Bellingshausen Seas are experiencing rapid thinning due to enhanced basal melting driven by the intrusion of warm circumpolar deep water. Determination of their mass balance provides an indicator as to the future of the shelves buttressing capability; however, measurements of surface accumulation are few, limiting the precision of the mass balance estimates. Here, we present new radar-derived measurements of snow accumulation primarily over the Getz and Abbott Ice Shelves, as well as the Dotson and Crosson, which have been the focus of several of NASA's Operation IceBridge airborne surveys between 2009 and 2014. Specifically, we use the Center for Remote Sensing of Ice Sheets (CReSIS) snow radar to map the near-surface (< 30 m) internal stratigraphy to measure snow accumulation. Due to the complexities of the local topography (e.g., ice rises and rumples) and their relative proximity to the ocean, the spatial pattern of accumulation can be equally varied. Therefore, atmospheric models might not be able to reproduce these small-scale features because of their limited spatial resolution. To evaluate whether this is the case over these narrow shelves, we will compare the radar-derived accumulation rates with those from atmospheric models.

  11. Verification of International Space Station Component Leak Rates by Helium Accumulation Method

    NASA Technical Reports Server (NTRS)

    Underwood, Steve D.; Smith, Sherry L.

    2003-01-01

    Discovery of leakage on several International Space Station U.S. Laboratory Module ammonia system quick disconnects (QDs) led to the need for a process to quantify total leakage without removing the QDs from the system. An innovative solution was proposed allowing quantitative leak rate measurement at ambient external pressure without QD removal. The method utilizes a helium mass spectrometer configured in the detector probe mode to determine helium leak rates inside a containment hood installed on the test component. The method was validated through extensive developmental testing. Test results showed the method was viable, accurate and repeatable for a wide range of leak rates. The accumulation method has been accepted by NASA and is currently being used by Boeing Huntsville, Boeing Kennedy Space Center and Boeing Johnson Space Center to test welds and valves and will be used by Alenia to test the Cupola. The method has been used in place of more expensive vacuum chamber testing which requires removing the test component from the system.

  12. Comparison of elemental accumulation rates between ferromanganese deposits and sediments in the South Pacific Ocean

    USGS Publications Warehouse

    Kraemer, T.; Schornick, J.C.

    1974-01-01

    Rates of accumulation of Fe and Mn, as well as Cu, Ni, Co, Pb, Zn, Hg, U and Th have been determined for five ferromanganese deposits from four localities in the South Pacific Ocean. Manganese is accumulating in nodules and crusts at a rate roughly equivalent to that found to be accumulating in sediments in the same area. Iron shows a deficiency in accumulation in nodules and crusts with respect to sediments, especially near the continents, but also in the central and south-central Pacific. Copper is accumulating in nodules and crusts at a rate one order of magnitude less than the surrounding sediments. This is interpreted as meaning that most of the Mn is supplied as an authigenic phase to both sediments and nodules while Fe is supplied mostly by ferromanganese micro-nodules and by detrital and adsorbed components of sediments; and Cu is enriched in sediments relative to nodules and crusts most probably through biological activity. ?? 1974.

  13. Accumulate repeat accumulate codes

    NASA Technical Reports Server (NTRS)

    Abbasfar, A.; Divsalar, D.; Yao, K.

    2004-01-01

    In this paper we propose an innovative channel coding scheme called Accumulate Repeat Accumulate codes. This class of codes can be viewed as trubo-like codes, namely a double serial concatenation of a rate-1 accumulator as an outer code, a regular or irregular repetition as a middle code, and a punctured accumulator as an inner code.

  14. Complementary system for long term measurements of radon exhalation rate from soil

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

    Mazur, J.; Kozak, K., E-mail: Krzysztof.Kozak@ifj.edu.pl

    A special set-up for continuous measurements of radon exhalation rate from soil is presented. It was constructed at Laboratory of Radiometric Expertise, Institute of Nuclear Physics Polish Academy of Sciences (IFJ PAN), Krakow, Poland. Radon exhalation rate was determined using the AlphaGUARD PQ2000 PRO (Genitron) radon monitor together with a special accumulation container which was put on the soil surface during the measurement. A special automatic device was built and used to raise and lower back onto the ground the accumulation container. The time of raising and putting down the container was controlled by an electronic timer. This set-up mademore » it possible to perform 4–6 automatic measurements a day. Besides, some additional soil and meteorological parameters were continuously monitored. In this way, the diurnal and seasonal variability of radon exhalation rate from soil can be studied as well as its dependence on soil properties and meteorological conditions.« less

  15. IMPACT OF PARTICLE AGGLOMERATION ON ACCUMULATION RATES IN THE GLASS DISCHARGE RISER OF HLW MELTER

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

    Matyas, Josef; Jansik, Danielle P.; Owen, Antionette T.

    2013-08-05

    The major factor limiting waste loading in continuous high-level radioactive waste (HLW) melters is an accumulation of particles in the glass discharge riser during a frequent and periodic idling of more than 20 days. An excessive accumulation can produce robust layers a few centimeters thick, which may clog the riser, preventing molten glass from being poured into canisters. Since the accumulation rate is driven by the size of particles we investigated with X-ray microtomography, scanning electron microscopy, and image analysis the impact of spinel forming components, noble metals, and alumina on the size, concentration, and spatial distribution of particles, andmore » on the accumulation rate. Increased concentrations of Fe and Ni in the baseline glass resulted in the formation of large agglomerates that grew over the time to an average size of ~185±155 µm, and produced >3 mm thick layer after 120 h at 850 °C. The noble metals decreased the particle size, and therefore significantly slowed down the accumulation rate. Addition of alumina resulted in the formation of a network of spinel dendrites which prevented accumulation of particles into compact layers.« less

  16. Impact Of Particle Agglomeration On Accumulation Rates In The Glass Discharge Riser Of HLW Melter

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

    Kruger, A. A.; Rodriguez, C. A.; Matyas, J.

    2012-11-12

    The major factor limiting waste loading in continuous high-level radioactive waste (HLW) melters is an accumulation of particles in the glass discharge riser during a frequent and periodic idling of more than 20 days. An excessive accumulation can produce robust layers a few centimeters thick, which may clog the riser, preventing molten glass from being poured into canisters. Since the accumulation rate is driven by the size of particles we investigated with x-ray microtomography, scanning electron microscopy, and image analysis the impact of spinel forming components, noble metals, and alumina on the size, concentration, and spatial distribution of particles, andmore » on the accumulation rate. Increased concentrations of Fe and Ni in the baseline glass resulted in the formation of large agglomerates that grew over the time to an average size of ~185+-155 {mu}m, and produced >3 mm thick layer after 120 h at 850 deg C. The noble metals decreased the particle size, and therefore significantly slowed down the accumulation rate. Addition of alumina resulted in the formation of a network of spinel dendrites which prevented accumulation of particles into compact layers.« less

  17. Soil carbon stocks and their rates of accumulation and loss in a boreal forest landscape

    USGS Publications Warehouse

    Rapalee, G.; Trumbore, S.E.; Davidson, E.A.; Harden, J.W.; Veldhuis, H.

    1998-01-01

    Boreal forests and wetlands are thought to be significant carbon sinks, and they could become net C sources as the Earth warms. Most of the C of boreal forest ecosystems is stored in the moss layer and in the soil. The objective of this study was to estimate soil C stocks (including moss layers) and rates of accumulation and loss for a 733 km2 area of the BOReal Ecosystem-Atmosphere Study site in northern Manitoba, using data from smaller-scale intensive field studies. A simple process-based model developed from measurements of soil C inventories and radiocarbon was used to relate soil C storage and dynamics to soil drainage and forest stand age. Soil C stocks covary with soil drainage class, with the largest C stocks occurring in poorly drained sites. Estimated rates of soil C accumulation or loss are sensitive to the estimated decomposition constants for the large pool of deep soil C, and improved understanding of deep soil C decomposition is needed. While the upper moss layers regrow and accumulate C after fires, the deep C dynamics vary across the landscape, from a small net sink to a significant source. Estimated net soil C accumulation, averaged for the entire 733 km2 area, was 20 g C m-2 yr-1 (28 g C m-2 yr-1 accumulation in surface mosses offset by 8 g C m-2 yr-1 lost from deep C pools) in a year with no fire. Most of the C accumulated in poorly and very poorly drained soils (peatlands and wetlands). Burning of the moss layer in only 1% of uplands would offset the C stored in the remaining 99% of the area. Significant interannual variability in C storage is expected because of the irregular occurrence of fire in space and time. The effects of climate change and management on fire frequency and on decomposition of immense deep soil C stocks are key to understanding future C budgets in boreal forests.

  18. Trawling-induced alterations of deep-sea sediment accumulation rates during the Anthropocene

    NASA Astrophysics Data System (ADS)

    Puig, P.; Paradis, S.; Masque, P.; Martin, J.; Juan, X.; Palanques, A.

    2015-12-01

    Commercial bottom trawling causes direct physical disturbance of the marine sedimentary environments by scraping and ploughing the seabed, generating periodic resuspension of surface sediments. However, the quantification of the sediment that is removed by trawling and exported across the continental margin remains largely unaddressed, and the preservation of the signal of such impacts in the geological record have been mostly overlooked. The analysis of sediment cores collected along the Catalan margin (NW Mediterranean) has allowed evaluating the contribution of this anthropogenic activity to the present-day sediment dynamics. Sediment cores at intensively trawled sites are characterized by over-consolidated sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sedimentary deposits. In turn, combined 210Pb and 137Cs chronologies indicate a significant increase of sediment accumulation rates within submarine canyon environments since the 1970s, coincidently with a strong impulse in the industrialization of the trawling fleets of this region. Two sampling sites that exhibited high sediment accumulation rates (0.6-0.7 cm/y) were reoccupied 1-2 decades after the first studies and revealed a second and even larger increase of sediment accumulation rates (>2 cm/y) occurring at the beginning of the XXI century. This recent change has been attributed to a preferential displacement of the trawling fleet towards fishing grounds surrounding submarine canyons and, also, to technical improvements in trawling vessels, presumably related to financial subsidies provided to the fishing sector. The alteration of sediment accumulation rates described in this continental margin may occur in many regions of the World's oceans given the wide geographical distribution of this human activity, and therefore, it could represent a potential marker of the Anthropocene in deep-sea environments.

  19. Patterns of sediment accumulation in the tidal marshes of Maine

    USGS Publications Warehouse

    Wood, M.E.; Kelley, J.T.; Belknap, D.F.

    1989-01-01

    One year's measurements of surficial sedimentation rates (1986-1987) for 26 Maine marsh sites were made over marker horizons of brick dust. Observed sediment accumulation rates, from 0 to 13 mm yr-1, were compared with marsh morphology, local relative sea-level rise rate, mean tidal range, and ice rafting activity. Marshes with four different morphologies (back-barrier, fluvial, bluff-toe, and transitional) showed distinctly different sediment accumulation rates. In general, back-barrier marshes had the highest accumulation rates and blufftoe marshes had the lowest rates, with intermediate values for transitional and fluvial marshes. No causal relationship between modern marsh sediment accumulation rate and relative sea-level rise rate (from tide gauge records) was observed. Marsh accretionary balance (sediment accumulation rate minus relative sea-level rise rate) did not correlate with mean tidal range for this meso- to macro-tidal area. Estimates of ice-rafted debris on marsh sites ranged from 0% to >100% of measured surficial sedimentation rates, indicating that ice transport of sediment may make a significant contribution to surficial sedimentation on Maine salt marshes. ?? 1989 Estuarine Research Federation.

  20. Measurement of radon/thoron exhalation rates and gamma-ray dose rate in granite areas in Japan.

    PubMed

    Prasad, G; Ishikawa, T; Hosoda, M; Sahoo, S K; Kavasi, N; Sorimachi, A; Tokonami, S; Uchida, S

    2012-11-01

    Radon and thoron exhalation rates and gamma-ray dose rate in different places in Hiroshima Prefecture were measured. Exhalation rates were measured using an accumulation chamber method. The radon exhalation rate was found to vary from 3 to 37 mBq m(-2) s(-1), while the thoron exhalation rate ranged from 40 to 3330 mBq m(-2) s(-1). The highest radon exhalation rate (37 mBq m(-2) s(-1)) and gamma-ray dose rate (92 nGy h(-1)) were found in the same city (Kure City). In Kure City, indoor radon and thoron concentrations were previously measured at nine selected houses using a radon-thoron discriminative detector (Raduet). The indoor radon concentrations varied from 16 to 78 Bq m(-3), which was higher than the average value in Japan (15.5 Bq m(-3)). The indoor thoron concentration ranged from ND (not detected: below a detection limit of approximately 10 Bq m(-3)) to 314 Bq m(-3). The results suggest that radon exhalation rate from the ground is an influential factor for indoor radon concentration.

  1. Accumulation rates of Th-230, Pa-231, and some transition metals on the Bermuda Rise

    USGS Publications Warehouse

    Bacon, M.P.; Rosholt, J.N.

    1982-01-01

    Measurements of 238U, 234U, 230Th, 232Th, 231Pa, Mn, Fe, Co, Ni, Cu, and Zn were made on 23 samples from core GPC-5, a 29-m giant piston core from a water depth of 4583 m on the northeastern Bermuda Rise (33??41.2???N, 57??36.9???W). This area is characterized by rapid deposition of sediment transported by abyssal currents. Unsupported 230Th and 231Pa are present throughout the core but, because of large variations in the sedimentation rate, show marked departures from exponential decay with depth. The trend with depth of the 231Paex 230Thex ratio is consistent with the average accumulation rate of 36 cm/1000 y reported earlier on the basis of radiocarbon dating and CaCO3 stratigraphy. When expressed on a carbonate-free basis, concentrations of Mn, Co, Ni, Cu, Zn, 230Thex, and 231Paex all show cyclic variations positively correlated with those of CaCO3. The correlations can be explained by a model in which all of these constituents, including CaCO3, are supplied to the sediments from the water column at a constant rate. Concentration variations are controlled mainly by varying inputs of terrigenous detritus, with low inputs occurring during interglacials and high inputs during glacials. Relationships between the metal and 230Thex concentrations permit estimates of the rates at which the metals are removed to the sediment by scavenging from the water column. The results, in ??g/cm2-1000 y, are: 4300 ?? 1100 for Mn, 46 ?? 16 for Ni and 76 ?? 26 for Cu. These rates are somewhat larger than ocean-wide averages estimated by other methods, and the absolute rate of 230Th accumulation in GPC-5 averages about nine times higher than production in the overlying water column. This part of the Bermuda Rise and similar bottom-current deposits may act as important accumulators of elements scavenged from seawater. ?? 1982.

  2. Detailed scour measurements around a debris accumulation

    USGS Publications Warehouse

    Mueller, David S.; Parola, Arthur C.

    1998-01-01

    Detailed scour measurements were made at Farm-Market 2004 over the Brazos River near Lake Jackson, Tex. during flooding in October 1994. Woody debris accumulations on bents 6, 7, and 8 obstructed flow through the bridge, causing scour of the streambed. Measurements at the site included three-dimensional velocities, channel bathymetry, water-surface elevations, water-surface slope, and discharge. Channel geometry upstream from the bridge caused approach conditions to be nonuniform.

  3. Recent accumulation rates of an alpine glacier derived from firn cores and repeated helicopter-borne GPR

    NASA Astrophysics Data System (ADS)

    Sold, L.; Huss, M.; Eichler, A.; Schwikowski, M.; Hoelzle, M.

    2014-08-01

    The spatial representation of accumulation measurements is a major limitation for current glacier mass balance monitoring approaches. Here, we present a new method for estimating annual accumulation rates on a temperate alpine glacier based on the interpretation of internal reflection horizons (IRH) in helicopter-borne ground-penetrating radar (GPR) data. For each individual GPR measurement, the signal traveltime is combined with a simple model for firn densification and refreezing of meltwater. The model is calibrated at locations where GPR profiles intersect in two subsequent years and the densification can be tracked over time. Two 10.5 m long firn cores provide a reference for the density and chronology of firn layers. Thereby, IRH correspond to density maxima, but not exclusively to former summer glacier surfaces. From GPR profiles across the accumulation area, we obtain spatial distributions of water equivalent for at least four annual firn layers, reaching a mean density of 0.74 g cm-3. Refreezing accounts for 9% of the density increase over time and depth. The strongest limitation to our method is the dependence on layer chronology assumptions. The uncertainties inherent to the modelling approach itself are in the same order of conventional point measurements in snow pits. We show that GPR can be used to complement existing mass balance monitoring programs on temperate alpine glaciers, but also to retrospectively extend newly initiated time series.

  4. Carbon and Nitrogen Accumulation Rates in Salt Marshes in Oregon, USA

    EPA Science Inventory

    Two important ecosystem services of wetlands are carbon sequestration and filtration of nutrients and particulates. We quantified the carbon and nitrogen accumulation rates in salt marshes at 135 plots distributed across eight estuaries located in Oregon, USA. Net carbon and ...

  5. USE OF RELAXED EDDY ACCUMULATION TO MEASURE BIOSPHERE-ATMOSPHERE EXCHANGE OF ISOPRENE AND OTHER BIOLOGICAL TRACE GASES

    EPA Science Inventory

    The micrometeorological flux measurement technique known as relaxed eddy accumulation (REA) holds promise as a powerful new tool for ecologists. The more popular eddy covariance (eddy correlation) technique requires the use of sensors that can respond at fast rates (10 Hz), and t...

  6. Accumulate repeat accumulate codes

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative channel coding scheme called 'Accumulate Repeat Accumulate codes' (ARA). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes, thus belief propagation can be used for iterative decoding of ARA codes on a graph. The structure of encoder for this class can be viewed as precoded Repeat Accumulate (RA) code or as precoded Irregular Repeat Accumulate (IRA) code, where simply an accumulator is chosen as a precoder. Thus ARA codes have simple, and very fast encoder structure when they representing LDPC codes. Based on density evolution for LDPC codes through some examples for ARA codes, we show that for maximum variable node degree 5 a minimum bit SNR as low as 0.08 dB from channel capacity for rate 1/2 can be achieved as the block size goes to infinity. Thus based on fixed low maximum variable node degree, its threshold outperforms not only the RA and IRA codes but also the best known LDPC codes with the dame maximum node degree. Furthermore by puncturing the accumulators any desired high rate codes close to code rate 1 can be obtained with thresholds that stay close to the channel capacity thresholds uniformly. Iterative decoding simulation results are provided. The ARA codes also have projected graph or protograph representation that allows for high speed decoder implementation.

  7. Measurements of undoped accumulation-mode SiGe quantum dot devices

    NASA Astrophysics Data System (ADS)

    Eng, Kevin; Borselli, Mathew; Holabird, Kevin; Milosavljevic, Ivan; Schmitz, Adele; Deelman, Peter; Huang, Biqin; Sokolich, Marko; Warren, Leslie; Hazard, Thomas; Kiselev, Andrey; Ross, Richard; Gyure, Mark; Hunter, Andrew

    2012-02-01

    We report transport measurements of undoped single-well accumulation-mode SiGe quantum dot devices with an integrated dot charge sensor. The device is designed so that individual forward-biased circular gates have dominant control of dot charge occupancy, and separate intervening gates have dominant control of tunnel rates and exchange coupling. We have demonstrated controlled loading of the first electron in single and double quantum dots. We used magneto-spectroscopy to measure singlet-triplet splittings in our quantum dots: values are typically ˜0.1 meV. Tunnel rates of single electrons to the baths can be controlled from less than 1 Hz to greater than 10 MHz. We are able to control the (0,2) to (1,1) coupling in a double quantum dot from under-coupled (tc < kT˜ 5μeV) to over-coupled (tc ˜ 0.1 meV) with a bias control of one exchange gate. Sponsored by the United States Department of Defense. Approved for Public Release, Distribution Unlimited. The views expressed are those of the author and do not reflect the official policy or position of the Department of Defense or the U.S. Government.

  8. Topographic control and accumulation rate of some Holocene coral reefs: south Florida and Dry Tortugas

    USGS Publications Warehouse

    Shinn, E.A.; Hudson, J.H.; Halley, R.B.; Lidz, B.H.; Taylor, D.L.

    1977-01-01

    Core drilling and examination of underwater excavation on 6 reef sites in south Florida and Dry Tortugas revealed that underlying topography is the major factor controlling reef morphology. Carbon-14 dating on coral recovered from cores enables calculation of accumulation rates. Accumulation rates were found to range from 0.38 m/1000 years in thin Holocene reefs to as much as 4.85 m/1000 years in thicker buildups. Cementation and alteration of corals were found to be more pronounced in areas of low buildup rates than in areas of rapid accumulation rates. Acropora palmata, generally considered the major reef builder in Florida, was found to be absent in most reefs drilled. At Dry Tortugas, the more than 13-meter thick Holocene reef did not contain A. palmata. The principal reef builders in this outer reef are the same as those which built the Pleistocene Key Largo formation, long considered to be fossilized patch reef complex.

  9. Evidence Accumulation and Change Rate Inference in Dynamic Environments.

    PubMed

    Radillo, Adrian E; Veliz-Cuba, Alan; Josić, Krešimir; Kilpatrick, Zachary P

    2017-06-01

    In a constantly changing world, animals must account for environmental volatility when making decisions. To appropriately discount older, irrelevant information, they need to learn the rate at which the environment changes. We develop an ideal observer model capable of inferring the present state of the environment along with its rate of change. Key to this computation is an update of the posterior probability of all possible change point counts. This computation can be challenging, as the number of possibilities grows rapidly with time. However, we show how the computations can be simplified in the continuum limit by a moment closure approximation. The resulting low-dimensional system can be used to infer the environmental state and change rate with accuracy comparable to the ideal observer. The approximate computations can be performed by a neural network model via a rate-correlation-based plasticity rule. We thus show how optimal observers accumulate evidence in changing environments and map this computation to reduced models that perform inference using plausible neural mechanisms.

  10. Daily accumulation rates of marine debris on sub-Antarctic island beaches.

    PubMed

    Eriksson, Cecilia; Burton, Harry; Fitch, Stuart; Schulz, Martin; van den Hoff, John

    2013-01-15

    The worlds' oceans contain a large but unknown amount of plastic debris. We made daily collections of marine debris stranded at two sub-Antarctic islands to establish (a) physical causes of strandings, and (b) a sampling protocol to better estimate the oceans' plastic loading. Accumulation rates at some beaches were dependent on tide and onshore winds. Most of the 6389 items collected were plastic (Macquarie 95%, Heard 94%) and discarded or lost fishing gear comprised 22% of those plastic items. Stalked barnacles (Lepas spp.) were a regular attachment on Macquarie debris but not at Heard Island. The daily accumulation rate of plastic debris on Macquarie Island was an order of magnitude higher than that estimated from monthly surveys during the same 4 months in the previous 5 years. This finding suggests that estimates of the oceans' plastic loading are an order of magnitude too low. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. Improving age-depth models using sedimentary proxies for accumulation rates in fluvio-lacustrine deposits

    NASA Astrophysics Data System (ADS)

    Minderhoud, Philip S. J.; Cohen, Kim M.; Toonen, Willem. H. J.; Erkens, Gilles; Hoek, Wim Z.

    2017-04-01

    Lacustrine fills, including those of oxbow lakes in river floodplains, often hold valuable sedimentary and biological proxy records of palaeo-environmental change. Precise dating of accumulated sediments at levels throughout these records is crucial for interpretation and correlation of (proxy) data existing within the fills. Typically, dates are gathered from multiple sampled levels and their results are combined in age-depth models to estimate the ages of events identified between the datings. In this paper, a method of age-depth modelling is presented that varies the vertical accumulation rate of the lake fill based on continuous sedimentary data. In between Bayesian calibrated radiocarbon dates, this produces a modified non-linear age-depth relation based on sedimentology rather than linear or spline interpolation. The method is showcased on a core of an infilled palaeomeander at the floodplain edge of the river Rhine near Rheinberg (Germany). The sequence spans from 4.7 to 2.9 ka cal BP and consists of 5.5 meters of laminated lacustrine, organo-clastic mud, covered by 1 meter of peaty clay. Four radiocarbon dates provide direct dating control, mapping and dating in the wider surroundings provide additional control. The laminated, organo-clastic facies of the oxbow fill contains a record of nearby fluvial-geomorphological activity, including meander reconfiguration events and passage of rare large floods, recognized as fluctuations in coarseness and amount of allochthonous clastic sediment input. Continuous along-core sampling and measurement of loss-on-ignition (LOI) provided a fast way of expressing the variation in clastic sedimentation influx from the nearby river versus autochthonous organic deposition derived from biogenic production in the lake itself. This low-cost sedimentary proxy data feeds into the age-depth modelling. The sedimentology-modelled age-depth relation (re)produces the distinct lithological boundaries in the fill as marked changes in

  12. Accumulation rates and predominant atmospheric sources of natural and anthropogenic Hg and Pb on the Faroe Islands

    NASA Astrophysics Data System (ADS)

    Shotyk, W.; Goodsite, M. E.; Roos-Barraclough, F.; Givelet, N.; Le Roux, G.; Weiss, D.; Cheburkin, A. K.; Knudsen, K.; Heinemeier, J.; van Der Knaap, W. O.; Norton, S. A.; Lohse, C.

    2005-01-01

    A monolith representing 5420 14C yr of peat accumulation was collected from a blanket bog at Myrarnar, Faroe Islands. The maximum Hg concentration (498 ng/g at a depth of 4.5 cm) coincides with the maximum concentration of anthropogenic Pb (111 μg/g). Age dating of recent peat accumulation using 210Pb (CRS model) shows that the maxima in Hg and Pb concentrations occur at AD 1954 ± 2. These results, combined with the isotopic composition of Pb in that sample ( 206Pb/ 207Pb = 1.1720 ± 0.0017), suggest that coal burning was the dominant source of both elements. From the onset of peat accumulation (ca. 4286 BC) until AD 1385, the ratios Hg/Br and Hg/Se were constant (2.2 ± 0.5 × 10 -4 and 8.5 ± 1.8 × 10 -3, respectively). Since then, Hg/Br and Hg/Se values have increased, also reaching their maxima in AD 1954. The age date of the maximum concentrations of anthropogenic Hg and Pb in the Faroe Islands is consistent with a previous study of peat cores from Greenland and Denmark (dated using the atmospheric bomb pulse curve of 14C), which showed maximum concentrations in AD 1953. The average rate of atmospheric Hg accumulation from 1520 BC to AD 1385 was 1.27 ± 0.38 μg/m 2/yr. The Br and Se concentrations and the background Hg/Br and Hg/Se ratios were used to calculate the average rate of natural Hg accumulation for the same period, 1.32 ± 0.36 μg/m 2/yr and 1.34 ± 0.29 μg/m 2/yr, respectively. These fluxes are similar to the preanthropogenic rates obtained using peat cores from Switzerland, southern Greenland, southern Ontario, Canada, and the northeastern United States. Episodic volcanic emissions and the continual supply of marine aerosols to the Faroe Islands, therefore, have not contributed significantly to the Hg inventory or the Hg accumulation rates, relative to these other areas. The maximum rate of Hg accumulation was 34 μg/m 2/yr. The greatest fluxes of anthropogenic Hg accumulation calculated using Br and Se, respectively, were 26 and 31 μg/m 2

  13. Carbon stocks and accumulation rates in Pacific Northwest forests: role of stand age, plant community, and productivity

    Treesearch

    Andrew N. Gray; Thomas R. Whittier; Mark E. Harmon

    2016-01-01

    Forest ecosystems are removing significant amounts of carbon from the atmosphere. Both abiotic resource availability and biotic interactions during forest succession affect C accumulation rates and maximum C stocks. However, the timing and controls on the peak and decline in C accumulation rates as stands age, trees increase in size, and canopy gaps become prevalent...

  14. Rates of species accumulation and taxonomic diversification during phototrophic biofilm development are controlled by both nutrient supply and current velocity.

    PubMed

    Larson, Chad A; Passy, Sophia I

    2013-03-01

    The accumulation of new and taxonomically diverse species is a marked feature of community development, but the role of the environment in this process is not well understood. To address this problem, we subjected periphyton in laboratory streams to low (10-cm · s(-1)), high (30-cm · s(-1)), and variable (9- to 32-cm · s(-1)) current velocity and low- versus high-nutrient inputs. We examined how current velocity and resource supply constrained (i) the rates of species accumulation, a measure of temporal beta-diversity, and (ii) the rates of diversification of higher taxonomic categories, defined here as the rate of higher taxon richness increase with the increase of species richness. Temporal biofilm dynamics were controlled by a strong nutrient-current interaction. Nutrients accelerated the rates of accumulation of new species, when flow velocity was not too stressful. Species were more taxonomically diverse under variable than under low-flow conditions, indicating that flow heterogeneity increased the niche diversity in the high-nutrient treatments. Conversely, the lower diversification rates under high- than under low-nutrient conditions at low velocity are explained with finer resource partitioning among species, belonging to a limited number of related genera. The overall low rates of diversification in high-current treatments suggest that the ability to withstand current stress was conserved within closely related species. Temporal heterogeneity of disturbance has been shown to promote species richness, but here we further demonstrate that it also affects two other components of biodiversity, i.e., temporal beta-diversity and diversification rate. Therefore, management efforts for preserving the inherent temporal heterogeneity of natural ecosystems will have detectable positive effects on biodiversity.

  15. Rates of Species Accumulation and Taxonomic Diversification during Phototrophic Biofilm Development Are Controlled by both Nutrient Supply and Current Velocity

    PubMed Central

    2013-01-01

    The accumulation of new and taxonomically diverse species is a marked feature of community development, but the role of the environment in this process is not well understood. To address this problem, we subjected periphyton in laboratory streams to low (10-cm · s−1), high (30-cm · s−1), and variable (9- to 32-cm · s−1) current velocity and low- versus high-nutrient inputs. We examined how current velocity and resource supply constrained (i) the rates of species accumulation, a measure of temporal beta-diversity, and (ii) the rates of diversification of higher taxonomic categories, defined here as the rate of higher taxon richness increase with the increase of species richness. Temporal biofilm dynamics were controlled by a strong nutrient-current interaction. Nutrients accelerated the rates of accumulation of new species, when flow velocity was not too stressful. Species were more taxonomically diverse under variable than under low-flow conditions, indicating that flow heterogeneity increased the niche diversity in the high-nutrient treatments. Conversely, the lower diversification rates under high- than under low-nutrient conditions at low velocity are explained with finer resource partitioning among species, belonging to a limited number of related genera. The overall low rates of diversification in high-current treatments suggest that the ability to withstand current stress was conserved within closely related species. Temporal heterogeneity of disturbance has been shown to promote species richness, but here we further demonstrate that it also affects two other components of biodiversity, i.e., temporal beta-diversity and diversification rate. Therefore, management efforts for preserving the inherent temporal heterogeneity of natural ecosystems will have detectable positive effects on biodiversity. PMID:23335757

  16. Recent increases in sediment and nutrient accumulation in Bear Lake, Utah/Idaho, USA

    USGS Publications Warehouse

    Smoak, J.M.; Swarzenski, P.W.

    2004-01-01

    This study examines historical changes in sediment and nutrient accumulation rates in Bear Lake along the northeastern Utah/Idaho border, USA. Two sediment cores were dated by measuring excess 210Pb activities and applying the constant rate of supply (CRS) dating model. Historical rates of bulk sediment accumulation were calculated based on the ages within the sediment cores. Bulk sediment accumulation rates increased throughout the last 100 years. According to the CRS model, bulk sediment accumulation rates were <25mg cm-2 year-1 prior to 1935. Between 1935 and 1980, bulk sediment accumulation rates increased to approximately 40mg cm -2 year-1. This increase in sediment accumulation probably resulted from the re-connection of Bear River to Bear Lake. Bulk sediment accumulation rates accelerated again after 1980. Accumulation rates of total phosphorus (TP), total nitrogen (TN), total inorganic carbon (TIC), and total organic carbon (TOC) were calculated by multiplying bulk sediment accumulation rates times the concentrations of these nutrients in the sediment. Accumulation rates of TP, TN, TIC, and TOC increased as a consequence of increased bulk sediment accumulation rates after the re-connection of Bear River with Bear Lake.

  17. Accumulation rate and mixing of shelf sediments in the Monterey Bay National Marine Sanctuary

    USGS Publications Warehouse

    Lewis, R.C.; Coale, K.H.; Edwards, B.D.; Marot, M.; Douglas, J.N.; Burton, E.J.

    2002-01-01

    The distribution of excess 210Pb in 31 sediment cores was used to determine modern (last 100 yr) mass accumulation rates and the depth of sediment mixing on the continental shelf between Pacifica and Monterey, California, USA. Apparent mass accumulation rates average 0.27 g cm-2 yr-1 and range from 0.42 g cm-2 yr-1 to 0.12 g cm-2 yr-1. Accumulation rates were highest at mid-shelf water depths (60-100 m) adjacent to major rivers and near the head of the Ascension submarine canyon. Cores from water depths of less than 65 m had low, uniform 210Pb activity profiles and sandy textures. The uppermost 5-13 cm of 15 cores had uniform 210Pb activity profiles above a region of steadily decreasing 210Pb activity. This phenomenon was attributed to sediment mixing. The thickness of this upper layer of uniform 210Pb activity decreased southward from 13 cm, west of Pacifica, to less than 5 cm, near Monterey Canyon. This southward decrease may be attributed to shallower bioturbation in the southern study area. Integrated excess 210Pb activities were generally higher where sedimentation rates were high. They were also higher with increasing distance from major rivers. Thus, sedimentation rate alone does not explain the distribution of integrated excess 210Pb in this study area. Excess 210Pb in the seafloor is controlled by other factors such as sediment texture, the atmospheric deposition rate of 210Pb, and the residence time of sediment particles in the water column. ?? 2002 Elsevier Science B.V. All rights reserved.

  18. Recent rates of carbon accumulation in montane fens ofYosemite National Park, California, U.S.A.

    USGS Publications Warehouse

    Drexler, Judith; Fuller, Christopher C.; Orlando, James L.; Moore, Peggy E.

    2016-01-01

    Little is known about recent rates of carbon storage in montane peatlands, particularly in the western United States. Here we report on recent rates of carbon accumulation (past 50 to 100 years) in montane groundwater-fed peatlands (fens) of Yosemite National Park in central California, U.S.A. Peat cores were collected at three sites ranging in elevation from 2070 to 2500 m. Core sections were analyzed for bulk density, % organic carbon, and 210Pb activities for dating purposes. Organic carbon densities ranged from 0.026 to 0.065 g C cm-3. Mean vertical accretion rates estimated using210Pb over the 50-year period from ∼1960 to 2011 and the 100-year period from ∼1910 to 2011 were 0.28 (standard deviation = ±0.09) and 0.18 (±-0.04) cm yr-1, respectively. Mean carbon accumulation rates over the 50- and 100-year periods were 95.4 (±25.4) and 74.7 (±17.2) g C m-2 yr-1, respectively. Such rates are similar to recent rates of carbon accumulation in rich fens in western Canada, but more studies are needed to definitively establish both the similarities and differences in peat formation between boreal and temperate montane fens.

  19. Regional Greenland accumulation variability from Operation IceBridge airborne accumulation radar

    NASA Astrophysics Data System (ADS)

    Lewis, Gabriel; Osterberg, Erich; Hawley, Robert; Whitmore, Brian; Marshall, Hans Peter; Box, Jason

    2017-03-01

    The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. An improved understanding of temporal and spatial variability of snow accumulation will reduce uncertainties in GrIS mass balance models and improve projections of Greenland's contribution to sea-level rise, currently estimated at 0.089 ± 0.03 m by 2100. Here we analyze 25 NASA Operation IceBridge accumulation radar flights totaling > 17 700 km from 2013 to 2014 to determine snow accumulation in the GrIS dry snow and percolation zones over the past 100-300 years. IceBridge accumulation rates are calculated and used to validate accumulation rates from three regional climate models. Averaged over all 25 flights, the RMS difference between the models and IceBridge accumulation is between 0.023 ± 0.019 and 0.043 ± 0.029 m w.e. a-1, although each model shows significantly larger differences from IceBridge accumulation on a regional basis. In the southeast region, for example, the Modèle Atmosphérique Régional (MARv3.5.2) overestimates by an average of 20.89 ± 6.75 % across the drainage basin. Our results indicate that these regional differences between model and IceBridge accumulation are large enough to significantly alter GrIS surface mass balance estimates. Empirical orthogonal function analysis suggests that the first two principal components account for 33 and 19 % of the variance, and correlate with the Atlantic Multidecadal Oscillation (AMO) and wintertime North Atlantic Oscillation (NAO), respectively. Regions that disagree strongest with climate models are those in which we have the fewest IceBridge data points, requiring additional in situ measurements to verify model uncertainties.

  20. Natural and Anthropogenic Causes of Accelerated Sediment Accumulation Rates in Nehalem Bay Salt Marshes, Oregon

    NASA Astrophysics Data System (ADS)

    Molino, G. D.; Wheatcroft, R. A.; Peck, E. K.; Brophy, L.

    2016-12-01

    Vertical sediment accretion in estuarine salt marshes occurs as sediments settle out of the water column and onto marsh soils during periods of tidal inundation - thus accretion is influenced by both relative sea level rise (RSLR) and sediment flux to the estuary. Oregon estuaries are understudied compared to their East and Gulf Coast counterparts, but provide a unique opportunity to disentangle these effects. A broader study in three Oregon estuaries (Peck et al., this session) indicates RSLR as the dominant factor controlling sedimentation rates. Working in Nehalem Bay (northern Oregon coast), replicate sediment cores were taken along several transects across an elevation gradient for analysis of sediment and carbon accumulation using CT scans, gamma detection of Pb-210, X-Ray Fluorescence (XRF) and Loss-on-Ignition (LOI). Preliminary results indicate sediment accumulation rates over the past century are higher than rates seen in other comparable Oregon salt marshes; this is consistent with past studies and preliminary analysis of remote sensing data that show significant horizontal expansion of Nehalem marshes. A number of possible causes for the high sediment accumulation rates - hydroclimate of Nehalem River, extensive timber harvesting, forest fires such as the so-called Tillamook Burns, and diking of adjacent marshes - are being explored.

  1. Transverse beam stability measurement and analysis for the SNS accumulator ring

    DOE PAGES

    Xie, Zaipeng; Deibele, Craig; Schulte, Michael J.; ...

    2015-07-01

    In a Field-programmable gate array (FPGA) based transverse feedback damper system we implemented in the Spallation Neutron Source (SNS) accumulator ring with the intention to stabilize the electron-proton (e-p) instability in a frequency range from 1 MHz to 300 MHz. The transverse damper could also be used as a diagnostic tool by measuring the beam transfer function (BTF). An analysis of the BTF measurement provides the stability diagram for the production beam at SNS. Our paper describes the feedback damper system and its set-up as the BTF diagnostic tool. Experimental BTF results are presented and beam stability analysis is performedmore » based on the BTF measurements for the SNS accumulator ring.« less

  2. GPS measurements of strain accumulation across the Imperial Valley, California: 1986-1989

    NASA Technical Reports Server (NTRS)

    Larsen, Shawn; Reilinger, Robert

    1989-01-01

    The Global Positioning System (GPS) data collected in southern California from 1986 to 1989 indicate considerable strain accumulation across the Imperial Valley. Displacements are computed at 29 stations in and near the valley from 1986 to 1988, and at 11 sites from 1988 to 1989. The earlier measurements indicate 5.9 +/- 1.0 cm/yr right-lateral differential velocity across the valley, although the data are heavily influenced by the 1987 Superstition Hills earthquake sequence. Some measurements, especially the east-trending displacements, are suspects for large errors. The 1988 to 1989 GPS displacements are best modeled by 5.2 +/- 0.9 cm/yr of valley crossing deformation, but rates calculated from conventional geodetic measurements (3.4 to 4.3 cm/yr) fit the data nearly as well. There is evidence from GPS and Very Long Base Interferometry (VLBI) observations that the present slip rate along the southern San Andreas fault is smaller than the long-term geologic estimate, suggesting a lower earthquake potential than is currently assumed. Correspondingly, a higher earthquake potential is indicated for the San Jacinto fault. The Imperial Valley GPS sites form part of a 183 station network in southern California and northern Baja California, which spans a cross-section of the North American-Pacific plate boundary.

  3. Recent accumulation rates of an Alpine glacier derived from repeated airborne GPR and firn cores

    NASA Astrophysics Data System (ADS)

    Sold, Leo; Huss, Matthias; Eichler, Anja; Schwikowski, Margit; Hoelzle, Martin

    2014-05-01

    The topmost areas of glaciers contain a valuable record of their past accumulation rates. The water equivalent of annual firn layers can be used to initiate or extend existing time series of local mass balance and, ultimately, to consolidate the knowledge on the response of glaciers to changing climatic conditions. Measurements of the thickness and density of firn layers typically involve drilling in remote areas and core analysis and are thus expensive in terms of time and effort. Here, we discuss measurements from 2012 on Findelengletscher, Switzerland, a large Alpine valley glacier, using two in-situ firn cores and airborne Ground-Penetrating Radar (GPR). The firn cores were analysed regarding their density, major ions and deuterium concentration. The ammonium (NH4+) concentration is known to show seasonality due to a higher source activity and pronounced vertical transportation in the atmosphere in summer. The deuterium concentration serves as a proxy for air temperature during precipitation formation. Together, they provide depth and dating of annual summer surfaces. GPR has previously been used for a non-destructive assessment of internal layers in snow, firn and ice. Signal reflections indicate changes in the dielectric properties of the material, e.g. density changes at former summer surfaces. Airborne surveys allow measurements to be taken in remote and inaccessible areas. However, to transfer information from the GPR pulse travel time to the depth domain, the dielectric permittivity of the material is required, that changes with density of the firn. We observed a good agreement of the GPR signal with pronounced changes in the density profile, ice layers and peak contents of major ions. This underlines the high potential of GPR for detecting firn layers. However, not all peak-densities and thick ice layers represent a former glacier summer surface but can also be due to melting and refreezing during winter. We show that up to four years of annual

  4. Peat Accumulation in the Everglades (USA) during the Past 4000 Years: Rates, Drivers, and Sources of Error

    NASA Astrophysics Data System (ADS)

    Glaser, P. H.; Volin, J. C.; Givnish, T. J.; Hansen, B. C.; Stricker, C. A.

    2012-12-01

    Tropical and sub-tropical wetlands are considered to be globally important sources for greenhouse gases but their capacity to store carbon is presumably limited by warm soil temperatures and high rates of decomposition. Unfortunately, these assumptions can be difficult to test across long timescales because the chronology, cumulative mass, and completeness of a sedimentary profile are often difficult to establish. We therefore made a detailed analysis of a core from the principal drainage outlet of the Everglades of South Florida, to assess these problems and determine the factors that could govern carbon accumulation in this large sub-tropical wetland. AMS-14C dating provided direct evidence for both hard-water and open-system sources of dating errors, whereas cumulative mass varied depending upon the type of method used. Radiocarbon dates of gastropod shells, nevertheless, seemed to provide a reliable chronology for this core once the hard-water error was quantified and subtracted. Long-term accumulation rates were then calculated to be 12.1 g m-2 yr-1 for carbon, which is less than half the average rate reported for northern and tropical peatlands. Moreover, accumulation rates remained slow and relatively steady for both organic and inorganic strata, and the slow rate of sediment accretion ( 0.2 mm yr-1) tracked the correspondingly slow rise in sea level (0.35 mm yr-1 ) reported for South Florida over the past 4000 years. These results suggest that sea level and the local geologic setting may impose long-term constraints on rates of sediment and carbon accumulation in the Everglades and other wetlands

  5. Vocal Dose Measures: Quantifying Accumulated Vibration Exposure in Vocal Fold Tissues

    PubMed Central

    Titze, Ingo R.; Švec, Jan G.; Popolo, Peter S.

    2011-01-01

    To measure the exposure to self-induced tissue vibration in speech, three vocal doses were defined and described: distance dose, which accumulates the distance that tissue particles of the vocal folds travel in an oscillatory trajectory; energy dissipation dose, which accumulates the total amount of heat dissipated over a unit volume of vocal fold tissues; and time dose, which accumulates the total phonation time. These doses were compared to a previously used vocal dose measure, the vocal loading index, which accumulates the number of vibration cycles of the vocal folds. Empirical rules for viscosity and vocal fold deformation were used to calculate all the doses from the fundamental frequency (F0) and sound pressure level (SPL) values of speech. Six participants were asked to read in normal, monotone, and exaggerated speech and the doses associated with these vocalizations were calculated. The results showed that large F0 and SPL variations in speech affected the dose measures, suggesting that accumulation of phonation time alone is insufficient. The vibration exposure of the vocal folds in normal speech was related to the industrial limits for hand-transmitted vibration, in which the safe distance dose was derived to be about 500 m. This limit was found rather low for vocalization; it was related to a comparable time dose of about 17 min of continuous vocalization, or about 35 min of continuous reading with normal breathing and unvoiced segments. The voicing pauses in normal speech and dialogue effectively prolong the safe time dose. The derived safety limits for vocalization will likely require refinement based on a more detailed knowledge of the differences in hand and vocal fold tissue morphology and their response to vibrational stress, and on the effect of recovery of the vocal fold tissue during voicing pauses. PMID:12959470

  6. Vocal dose measures: quantifying accumulated vibration exposure in vocal fold tissues.

    PubMed

    Titze, Ingo R; Svec, Jan G; Popolo, Peter S

    2003-08-01

    To measure the exposure to self-induced tissue vibration in speech, three vocal doses were defined and described: distance dose, which accumulates the distance that tissue particles of the vocal folds travel in an oscillatory trajectory; energy dissipation dose, which accumulates the total amount of heat dissipated over a unit volume of vocal fold tissues; and time dose, which accumulates the total phonation time. These doses were compared to a previously used vocal dose measure, the vocal loading index, which accumulates the number of vibration cycles of the vocal folds. Empirical rules for viscosity and vocal fold deformation were used to calculate all the doses from the fundamental frequency (F0) and sound pressure level (SPL) values of speech. Six participants were asked to read in normal, monotone, and exaggerated speech and the doses associated with these vocalizations were calculated. The results showed that large F0 and SPL variations in speech affected the dose measures, suggesting that accumulation of phonation time alone is insufficient. The vibration exposure of the vocal folds in normal speech was related to the industrial limits for hand-transmitted vibration, in which the safe distance dose was derived to be about 500 m. This limit was found rather low for vocalization; it was related to a comparable time dose of about 17 min of continuous vocalization, or about 35 min of continuous reading with normal breathing and unvoiced segments. The voicing pauses in normal speech and dialogue effectively prolong the safe time dose. The derived safety limits for vocalization will likely require refinement based on a more detailed knowledge of the differences in hand and vocal fold tissue morphology and their response to vibrational stress, and on the effect of recovery of the vocal fold tissue during voicing pauses.

  7. Accumulation rate in a tropical Andean glacier as a proxy for northern Amazon precipitation

    NASA Astrophysics Data System (ADS)

    da Rocha Ribeiro, Rafael; Simões, Jefferson Cardia; Ramirez, Edson; Taupin, Jean-Denis; Assayag, Elias; Dani, Norberto

    2018-04-01

    Andean tropical glaciers have shown a clear shrinkage throughout the last few decades. However, it is unclear how this general retreat is associated with variations in rainfall patterns in the Amazon basin. To investigate this question, we compared the annual net accumulation variations in the Bolivian Cordillera Real (Andes), which is derived from an ice core from the Nevado Illimani (16° 37' S, 67° 46' W), covering the period 1960-1999 using the Amazonian Rainfall Index, Northern Atlantic Index (TNA), Multivariate ENSO Index (MEI), and Pacific Decadal Oscillation (PDO). The accumulation rate at the Nevado Illimani ice core decreased by almost 25% after 1980, from 1.02 w.eq. a-1 (water equivalent per year) in the 1961-1981 period to 0.76 w.eq. a-1 in the 1981-1999 period. The Northern Amazonian Rainfall (NAR) index best reflects changes in accumulation rates in the Bolivian ice core. Our proposal is based on two observations: (1) This area shows reduced rainfall associated with a more frequent and intense El Niño (during the positive phase of the MEI). The opposite (more rain) is true during La Niña phases. (2) Comparisons of the ice core record and NAR, PDO, and MEI indexes showed similar trends for the early 1980s, represented by a decrease in the accumulation rates and its standard deviations, probably indicating the same causality. The general changes observed by early 1980s coincided with the beginning of a PDO warm phase. This was followed by an increase in the Amazonian and tropical Andean precipitation from 1999, coinciding with a new PDO phase. However, this increase did not result in an expansion of the Zongo Glacier area.

  8. Surface Creep Rate and Moment Accumulation Rate Along the Aceh Segment of the Sumatran Fault From L-band ALOS-1/PALSAR-1 Observations

    NASA Astrophysics Data System (ADS)

    Tong, X.; Sandwell, D. T.; Schmidt, D. A.

    2018-04-01

    We analyzed the interferometric synthetic aperture radar data from the ALOS-1/PALSAR-1 satellite to image the interseismic deformation along the Sumatran fault. The interferometric synthetic aperture radar time series analysis reveals up to 20 mm/year of aseismic creep on the Aceh segment along the Northern Sumatran fault. This is a large fraction of the total slip rate across this fault. The spatial extent of the aseismic creep extends for 100 km. The along-strike variation of the aseismic creep has an inverse "U" shape. An analysis of the moment accumulation rate shows that the central part of the creeping section accumulates moment at approximately 50% of the rate of the surrounding locked segments. An initial analysis of temporal variations suggests that the creep rate may be decelerating with time, suggesting that the creep rate is adjusting to a stress perturbation from nearby seismic activity. Our study has implications to the earthquake hazard along the northern Sumatran fault.

  9. The accumulation rate of meteorite falls at the earth's surface - The view from Roosevelt County, New Mexico

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Wells, Gordon L.; Rendell, Helen M.

    1990-01-01

    The discovery of 154 meteorite fragments within an 11-sq km area of wind-excavated basins in Roosevelt County, New Mexico, permits a new calculation of the accumulation rate of meteorite falls at the earth's surface. Thermoluminescence dating of the coversand unit comprising the prime recovery surface suggests the maximum terrestrial age of the meteorites to be about 16.0 ka. The 68 meteorite fragments subjected to petrological analyses represent a minimum of 49 individual falls. Collection bias has largely excluded carbonaceous chondrites and achondrites, requiring the accumulation rate derived from the recovered samples to be increased by a factor of 1.25. Terrestrial weathering destroying ordinary chondrites can be modeled as a first-order decay process with an estimated half-life of 3.5 + or - 1.9 ka on the semiarid American High Plains. Having accounted for the age of the recovery surface, area of field searches, pairing of finds, collection bias and weathering half-life, an accumulation rate of 940 falls/a per 10 to the 6th sq km is calculated for falls greater than 10 g total mass. This figure exceeds the best-constrained previous estimate by more than an order of magnitude. One possible reason for this disparity may be the extraordinary length of the fall record preserved in the surficial geology of Roosevelt County. The high accumulation rate determined for the past 16 ka may point to the existence of periods when the meteorite fall rate was significantly greater than at present.

  10. Tracing nitrogen accumulation in decaying wood and examining its impact on wood decomposition rate

    NASA Astrophysics Data System (ADS)

    Rinne, Katja T.; Rajala, Tiina; Peltoniemi, Krista; Chen, Janet; Smolander, Aino; Mäkipää, Raisa

    2016-04-01

    Decomposition of dead wood, which is controlled primarily by fungi is important for ecosystem carbon cycle and has potentially a significant role in nitrogen fixation via diazotrophs. Nitrogen content has been found to increase with advancing wood decay in several studies; however, the importance of this increase to decay rate and the sources of external nitrogen remain unclear. Improved knowledge of the temporal dynamics of wood decomposition rate and nitrogen accumulation in wood as well as the drivers of the two processes would be important for carbon and nitrogen models dealing with ecosystem responses to climate change. To tackle these questions we applied several analytical methods on Norway spruce logs from Lapinjärvi, Finland. We incubated wood samples (density classes from I to V, n=49) in different temperatures (from 8.5oC to 41oC, n=7). After a common seven day pre-incubation period at 14.5oC, the bottles were incubated six days in their designated temperature prior to CO2 flux measurements with GC to determine the decomposition rate. N2 fixation was measured with acetylene reduction assay after further 48 hour incubation. In addition, fungal DNA, (MiSeq Illumina) δ15N and N% composition of wood for samples incubated at 14.5oC were determined. Radiocarbon method was applied to obtain age distribution for the density classes. The asymbiotic N2 fixation rate was clearly dependent on the stage of wood decay and increased from stage I to stage IV but was substantially reduced in stage V. CO2 production was highest in the intermediate decay stage (classes II-IV). Both N2 fixation and CO2 production were highly temperature sensitive having optima in temperature 25oC and 31oC, respectively. We calculated the variation of annual levels of respiration and N2 fixation per hectare for the study site, and used the latter data together with the 14C results to determine the amount of N2 accumulated in wood in time. The proportion of total nitrogen in wood

  11. Holocene carbon stocks and carbon accumulation rates altered in soils undergoing permafrost thaw

    Treesearch

    Caitlin E. Hicks Pries; Edward A.G. Schuur; K. Grace Crummer

    2012-01-01

    Permafrost soils are a significant global store of carbon (C) with the potential to become a large C source to the atmosphere. Climate change is causing permafrost to thaw, which can affect primary production and decomposition, therefore affecting ecosystem C balance. We modeled decadal and millennial soil C inputs, decomposition constants, and C accumulation rates by...

  12. Temporal variability in sediment PAHs accumulation in the northern Gulf of Mexico Shelf

    NASA Astrophysics Data System (ADS)

    Bam, W.; Maiti, K.; Adhikari, P. L.

    2017-12-01

    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous group of organic pollutants, some of which are known to be toxic, and/or carcinogenic to humans. The major source of these PAHs into the northern Gulf of Mexico (NGOM) are Mississippi River discharge, coastal erosion, atmospheric deposition, and numerous natural oil seeps and spills. In addition to these background source of PAHs, the Deepwater Horizon (DWH) oil spill in 2010 added 21,000 tons of PAHs into the NGOM water. In this study, we measured PAHs distribution and accumulation rates in coastal sediments near the Mississippi River mouth in 2011 and 2015 to understand the effect of DWH oil spill in PAHs accumulation in coastal sediments. Sediment cores were collected and sliced at 1 cm interval to measure PAHs concentration, and to estimate 210Pb-based sedimentation and the PAHs' accumulation rates. The results showed that the sediment deposition rates in this region varied between 0.5 to 0.9 cm/yr. The results also showed that the concentration of total PAHs (ΣPAH43) and their accumulation rates vary between 68 - 100 ng g-1 and 7 - 160 ng cm-2 yr-1, respectively. While the PAHs accumulation rate in coastal sediment varied over the years, there is no significant variation in PAHs accumulation rate before and after the DWH oil spill.

  13. RELATING ACCUMULATOR MODEL PARAMETERS AND NEURAL DYNAMICS

    PubMed Central

    Purcell, Braden A.; Palmeri, Thomas J.

    2016-01-01

    Accumulator models explain decision-making as an accumulation of evidence to a response threshold. Specific model parameters are associated with specific model mechanisms, such as the time when accumulation begins, the average rate of evidence accumulation, and the threshold. These mechanisms determine both the within-trial dynamics of evidence accumulation and the predicted behavior. Cognitive modelers usually infer what mechanisms vary during decision-making by seeing what parameters vary when a model is fitted to observed behavior. The recent identification of neural activity with evidence accumulation suggests that it may be possible to directly infer what mechanisms vary from an analysis of how neural dynamics vary. However, evidence accumulation is often noisy, and noise complicates the relationship between accumulator dynamics and the underlying mechanisms leading to those dynamics. To understand what kinds of inferences can be made about decision-making mechanisms based on measures of neural dynamics, we measured simulated accumulator model dynamics while systematically varying model parameters. In some cases, decision- making mechanisms can be directly inferred from dynamics, allowing us to distinguish between models that make identical behavioral predictions. In other cases, however, different parameterized mechanisms produce surprisingly similar dynamics, limiting the inferences that can be made based on measuring dynamics alone. Analyzing neural dynamics can provide a powerful tool to resolve model mimicry at the behavioral level, but we caution against drawing inferences based solely on neural analyses. Instead, simultaneous modeling of behavior and neural dynamics provides the most powerful approach to understand decision-making and likely other aspects of cognition and perception. PMID:28392584

  14. Character, paleoenvironment, rate of accumulation, and evidence for seismic triggering of Holocene turbidites, Canada Abyssal Plain, Arctic Ocean

    USGS Publications Warehouse

    Grantz, A.; Phillips, R.L.; Mullen, M.W.; Starratt, S.W.; Jones, Glenn A.; Naidu, A.S.; Finney, B.P.

    1996-01-01

    Four box cores and one piston core show that Holocene sedimentation on the southern Canada Abyssal Plain for the last 8010??120 yr has consisted of a continuing rain of pelagic organic and ice-rafted elastic sediment with a net accumulation rate during the late Holocene of ???10 mm/1000 yr, and episodically emplaced turbidites 1-5 m thick deposited at intervals of 830 to 3450 yr (average 2000 yr). The average net accumulation rate of the mixed sequence of turbidites and thin pelagite interbeds in the cores is about 1.2 m/1000 yr. Physiography suggests that the turbidites originated on the Mackenzie Delta or its clinoform, and ??13C values of -27 to - 25??? in the turbidites are compatible with a provenance on a delta. Extant displaced neritic and lower slope to basin plain calcareous benthic foraminifers coexist in the turbidite units. Their joint occurence indicates that the turbidites originated on the modern continental shelf and entrained sediment from the slope and rise enroute to their final resting place on the Canada Abyssal Plain. The presence of Middle Pleistocene diatoms in the turbidites suggests, in addition, that the turbidites may have originated in shallow submarine slides beneath the upper slope or outer shelf. Small but consistent differences in organic carbon content and ??13C values between the turbidite units suggest that they did not share an identical provenance, which is at least compatible with an origin in slope failures. The primary provenance of the ice-rafted component of the pelagic beds was the glaciated terrane of northwestern Canada; and the provenance of the turbidite units was Pleistocene and Holocene sedimentary deposits on the outer continental shelf and upper slope of the Mackenzie Delta. Largely local derivation of the sediment of the Canada Abyssal Plain indicates that sediment accumulation rates in the Arctic Ocean are valid only for regions with similar depositional sources and processes, and that these rates cannot be

  15. Rates of post-fire vegetation recovery and fuel accumulation as a function of burn severity and time-since-burn in four western U.S. ecosystems

    USDA-ARS?s Scientific Manuscript database

    Vegetation recovery and fuel accumulation rates following wildfire are useful measures of ecosystem resilience, yet few studies have quantified these variables over 10 years post-fire. Conventional wisdom is that recovery time to pre-fire condition will be slower as a function of burn severity, as i...

  16. Mauna Loa lava accumulation rates at the Hilo drill site: Formation of lava deltas during a period of declining overall volcanic growth

    USGS Publications Warehouse

    Lipman, P.W.; Moore, J.G.

    1996-01-01

    Accumulation rates for lava flows erupted from Mauna Loa, as sampled in the uppermost 280 m of the Hilo drill hole, vary widely for short time intervals (several thousand years), but overall are broadly similar to those documented elsewhere on this volcano since 100 ka. Thickness variations and accumulation rates for Mauna Loa lavas at the Hilo drill site have been strongly affected by local paleotopography, including funneling and ponding between Mauna Kea and Kilauea. In addition, gentle submerged slopes of Mauna Kea in Hilo Bay have permitted large shoreline displacements by Mauna Loa flows. Ages of eruptive intervals have been determined from published isotopic data and from eustatic sea level curves modified to include the isostatic subsidence of the island of Hawaii at 2.2-2.6 mm/yr. Prior to 10 ka, rates of Mauna Loa lava accumulation at the drill site varied from 0.6 to 4.3 mm/yr for dateable intervals, with an overall rate of 1.8 mm/yr. Major eruptive pulses at about 1.3 and 10 ka, each probably representing a single long-lived eruption based on lack of weathering between flow units, increase the overall accumulation rate to 2.4 mm/yr. The higher rate since 10 ka reflects construction of thick near-shoreline lava deltas as postglacial sea levels rose rapidly. Large lava deltas form only along coastal segments where initially subaerial slopes have been submerged by the combined effects of eustatic sea level rise, isostatic subsidence, or spreading of volcano flanks. Overall accumulation of 239 m of lava at the drill site since 100-120 ka closely balances submergence of the Hilo area, suggesting that processes of coastal lava deposition have been modulated by rise in sea level. The Hilo accumulation rate is slightly higher than average rates of 1-2 mm/yr determined elsewhere along the Mauna Loa coast, based on rates of shoreline coverage and dated sea cliff and fault scarp exposures. Low rates of coastal lava accumulation since 100 ka, near or below the rate

  17. Accumulation Rates in the Dry Snow Zone of the Greenland Ice Sheet Inferred from L-band InSAR Data

    NASA Astrophysics Data System (ADS)

    Chen, A. C.; Zebker, H. A.

    2012-12-01

    The Greenland ice sheet contains about 2.9 million km3 of ice and would raise global sea levels by about 7.1 m if it melted completely. Two unusually large iceberg calving events at Petermann Glacier in the past several years, along with the unusually large extent of ice sheet melt this summer point to the relevance of understanding the mass balance of the Greenland ice sheet. In this study, we use data from the PALSAR instrument aboard the ALOS satellite to form L-band (23-centimeter carrier wavelength) InSAR images of the dry snow zone of the Greenland ice sheet. We form geocoded differential interferograms, using the ice sheet elevation model produced by Howat et.al. [1]. By applying phase and radiometric calibration, we can examine interferograms formed between any pair of transmit and receive polarization channels. In co-polarized interferograms, the InSAR correlation ranges from about 0.35 at the summit (38.7 deg W, 73.0 deg N) where accumulation is about 20 cm w.e./yr to about 0.70 at the north-eastern part of the dry snow zone (35.1 deg W, 77.1 deg N), where accumulation is about 11.7 cm w.e./yr. Cross-polarized interferograms show similar geographic variation with overall lower correlation. We compare our InSAR data with in-situ measurements published by Bales et.al. [2]. We examine the applicability of dense-medium radiative transfer electromagnetic scattering models for estimating accumulation rates from L-band InSAR data. The large number and broad coverage of ALOS scenes acquired between 2007 and 2009 with good InSAR coherence at 46-day repeat times and 21.5 degree incidence angles gives us the opportunity to examine the empirical relationship between in-situ accumulation rate observations and the polarimetric InSAR correlation and radar brightness at this particular imaging geometry. This helps us quantify the accuracy of accumulation rates estimated from InSAR data. In some regions, 46-day interferograms acquired in the winters of several consecutive

  18. Carbon and sediment accumulation in the Everglades (USA) during the past 4000 years: rates, drivers, and sources of error

    USGS Publications Warehouse

    Glaser, Paul H.; Volin, John C.; Givnish, Thomas J.; Hansen, Barbara C. S.; Stricker, Craig A.

    2012-01-01

    Tropical and sub-tropical wetlands are considered to be globally important sources for greenhouse gases but their capacity to store carbon is presumably limited by warm soil temperatures and high rates of decomposition. Unfortunately, these assumptions can be difficult to test across long timescales because the chronology, cumulative mass, and completeness of a sedimentary profile are often difficult to establish. We therefore made a detailed analysis of a core from the principal drainage outlet of the Everglades of South Florida, to assess these problems and determine the factors that could govern carbon accumulation in this large sub-tropical wetland. Accelerator mass spectroscopy dating provided direct evidence for both hard-water and open-system sources of dating errors, whereas cumulative mass varied depending upon the type of method used. Radiocarbon dates of gastropod shells, nevertheless, seemed to provide a reliable chronology for this core once the hard-water error was quantified and subtracted. Long-term accumulation rates were then calculated to be 12.1 g m-2 yr-1 for carbon, which is less than half the average rate reported for northern and tropical peatlands. Moreover, accumulation rates remained slow and relatively steady for both organic and inorganic strata, and the slow rate of sediment accretion ( 0.2 mm yr-1) tracked the correspondingly slow rise in sea level (0.35 mm yr-1 ) reported for South Florida over the past 4000 years. These results suggest that sea level and the local geologic setting may impose long-term constraints on rates of sediment and carbon accumulation in the Everglades and other wetlands.

  19. Predicting Regional Pattern of Longitudinal β-Amyloid Accumulation by Baseline PET.

    PubMed

    Guo, Tengfei; Brendel, Matthias; Grimmer, Timo; Rominger, Axel; Yakushev, Igor

    2017-04-01

    Knowledge about spatial and temporal patterns of β-amyloid (Aβ) accumulation is essential for understanding Alzheimer disease (AD) and for design of antiamyloid drug trials. Here, we tested whether the regional pattern of longitudinal Aβ accumulation can be predicted by baseline amyloid PET. Methods: Baseline and 2-y follow-up 18 F-florbetapir PET data from 58 patients with incipient and manifest dementia due to AD were analyzed. With the determination of how fast amyloid deposits in a given region relative to the whole-brain gray matter, a pseudotemporal accumulation rate for each region was calculated. The actual accumulation rate of 18 F-florbetapir was calculated from follow-up data. Results: Pseudotemporal measurements from baseline PET data explained 87% ( P < 0.001) of the variance in longitudinal accumulation rate across 62 regions. The method accurately predicted the top 10 fast and slow accumulating regions. Conclusion: Pseudotemporal analysis of baseline PET images is capable of predicting the regional pattern of longitudinal Aβ accumulation in AD at a group level. This approach may be useful in exploring spatial patterns of Aβ accumulation in other amyloid-associated disorders such as Lewy body disease and atypical forms of AD. In addition, the method allows identification of brain regions with a high accumulation rate of Aβ, which are of particular interest for antiamyloid clinical trials. © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

  20. Including Deposition Rate in Models of Cosmogenic Nuclide Accumulation in Fluvial Sediments to Improve Terrace Abandonment Ages

    NASA Astrophysics Data System (ADS)

    Norton, K. P.; Wang, N.; Van Dissen, R. J.; Little, T.

    2017-12-01

    Fluvial sediments are archives of the erosional, transport, and depositional processes occurring in the catchment. Terraces become robust markers for geomorphic analysis if their time of abandonment can be determined. Methods such as OSL can determine burial ages for fine grained sediments within the terrace fill but may not be directly related to the terrace abandonment age. Cosmogenic nuclides can be used to determine exposure ages for geologically young terraces but the surface being dated may have been subsequently eroded and the material itself may have been deposited with an inherited nuclide concentration. To deal with this problem, many researchers collect multiple samples with depth to model the depth-dependent nuclide concentration to help constrain inheritance and post-depositional erosion. It is often, however, assumed that the entire sediment pile accumulated instantaneously. In this submission, we present the results of a depth profile model that incorporates sediment accumulation rate to improve terrace age estimates. We test this model on fault-offset river terraces near Kaikoura, New Zealand. We measured depth profiles of OSL ages and cosmogenic nuclide concentrations of two late Quaternary terraces that are offset by up to 800 m across the Kekerengu Fault. OSL ages and dated tephras in the overlying loess provide minimum age constraints for both terraces while OSL ages of fine-grained sediments within the fill provide depositional ages. The predicted sedimentation rates for the terraces are as high as 0.5m/yr, consistent with geologically instantaneous deposition. Modelled abandonment ages from cosmogenic nuclides for the terraces are consistent with OSL and tephra constraints at 9.7 +/- 3.8 ka and 30.4 +/- 2.1 ka, respectively. These terrace abandonment ages yield dextral slip rates of 18.5-20.5 mm/yr and 25-28 mm/yr, respectively, consistent with the rapid slip rate on the adjacent Hope Fault.

  1. Highly anomalous accumulation rates of C and N recorded by a relic, free-floating peatland in Central Italy

    PubMed Central

    Zaccone, Claudio; Lobianco, Daniela; Shotyk, William; Ciavatta, Claudio; Appleby, Peter G.; Brugiapaglia, Elisabetta; Casella, Laura; Miano, Teodoro M.; D’Orazio, Valeria

    2017-01-01

    Floating islands mysteriously moving around on lakes were described by several Latin authors almost two millennia ago. These fascinating ecosystems, known as free-floating mires, have been extensively investigated from ecological, hydrological and management points of view, but there have been no detailed studies of their rates of accumulation of organic matter (OM), organic carbon (OC) and total nitrogen (TN). We have collected a peat core 4 m long from the free-floating island of Posta Fibreno, a relic mire in Central Italy. This is the thickest accumulation of peat ever found in a free-floating mire, yet it has formed during the past seven centuries and represents the greatest accumulation rates, at both decadal and centennial timescale, of OM (0.63 vs. 0.37 kg/m2/yr), OC (0.28 vs. 0.18 kg/m2/yr) and TN (3.7 vs. 6.1 g/m2/yr) ever reported for coeval peatlands. The anomalously high accretion rates, obtained using 14C age dating, were confirmed using 210Pb and 137Cs: these show that the top 2 m of Sphagnum-peat has accumulated in only ~100 years. As an environmental archive, Posta Fibreno offers a temporal resolution which is 10x greater than any terrestrial peat bog, and promises to provide new insight into environmental changes occurring during the Anthropocene. PMID:28230066

  2. Response of salt-marsh carbon accumulation to climate change.

    PubMed

    Kirwan, Matthew L; Mudd, Simon M

    2012-09-27

    About half of annual marine carbon burial takes place in shallow water ecosystems where geomorphic and ecological stability is driven by interactions between the flow of water, vegetation growth and sediment transport. Although the sensitivity of terrestrial and deep marine carbon pools to climate change has been studied for decades, there is little understanding of how coastal carbon accumulation rates will change and potentially feed back on climate. Here we develop a numerical model of salt marsh evolution, informed by recent measurements of productivity and decomposition, and demonstrate that competition between mineral sediment deposition and organic-matter accumulation determines the net impact of climate change on carbon accumulation in intertidal wetlands. We find that the direct impact of warming on soil carbon accumulation rates is more subtle than the impact of warming-driven sea level rise, although the impact of warming increases with increasing rates of sea level rise. Our simulations suggest that the net impact of climate change will be to increase carbon burial rates in the first half of the twenty-first century, but that carbon-climate feedbacks are likely to diminish over time.

  3. Temperature-fluctuation-sensitive accumulative effect of the phase measurement errors in low-coherence interferometry in characterizing arrayed waveguide gratings.

    PubMed

    Zhao, Changyun; Wei, Bing; Yang, Longzhi; Wang, Gencheng; Wang, Yuehai; Jiang, Xiaoqing; Li, Yubo; Yang, Jianyi

    2015-09-20

    We investigate the accumulative effect of the phase measurement errors in characterizing optical multipath components by low-coherence interferometry. The accumulative effect is caused by the fluctuation of the environment temperature, which leads to the variation of the refractive index of the device under test. The resulting phase measurement errors accumulate with the increasing of the phase difference between the two interferometer arms. Our experiments were carried out to demonstrate that the accumulative effect is still obvious even though the thermo-optical coefficient of the device under test is quite small. Shortening the measurement time to reduce the fluctuation of the environment temperature can effectively restrain the accumulative effect. The experiments show that when the scanning speed increases to 4.8 mm/s, the slope of the phase measurement errors decreases to 5.52×10(-8), which means the accumulative effect can be ignored.

  4. Field Validation of Molybdenum Accumulation as an Indicator of Hypoxic Water Conditions

    EPA Science Inventory

    Laboratory experiments have shown that the accumulation rate of authigenic molybdenum (Mo) in marine sediments may serve as a quantitative surrogate for direct measurement of hypoxic conditions in overlying waters: Mo accumulation in the top 1 cm of sediment is linearly related t...

  5. Atmospheric mercury accumulation and washoff processes on impervious urban surfaces

    USGS Publications Warehouse

    Eckley, C.S.; Branfireun, B.; Diamond, M.; Van Metre, P.C.; Heitmuller, F.

    2008-01-01

    The deposition and transport of mercury (Hg) has been studied extensively in rural environments but is less understood in urbanized catchments, where elevated atmospheric Hg concentrations and impervious surfaces may efficiently deliver Hg to waterways in stormwater runoff. We determined the rate at which atmospheric Hg accumulates on windows, identified the importance of washoff in removing accumulated Hg, and measured atmospheric Hg concentrations to help understand the relationship between deposition and surface accumulation. The main study location was Toronto, Ontario. Similar samples were also collected from Austin, Texas for comparison of Hg accumulation between cities. Windows provided a good sampling surface because they are ubiquitous in urban environments and are easy to clean/blank allowing the assessment of contemporary Hg accumulation. Hg Accumulation rates were spatially variable ranging from 0.82 to 2.7 ng m-2 d-1 in Toronto and showed similar variability in Austin. The highest accumulation rate in Toronto was at the city center and was 5?? higher than the rural comparison site (0.58 ng m-2 d-1). The atmospheric total gaseous mercury (TGM) concentrations were less than 2?? higher between the rural and urban locations (1.7 ?? 0.3 and 2.7 ?? 1.1 ng m-3, respectively). The atmospheric particulate bound fraction (HgP), however, was more than 3?? higher between the rural and urban sites, which may have contributed to the higher urban Hg accumulation rates. Windows exposed to precipitation had 73 ?? 9% lower accumulation rates than windows sheltered from precipitation. Runoff collected from simulated rain events confirmed that most Hg accumulated on windows was easily removed and that most of the Hg in washoff was HgP. Our results indicate that the Hg flux from urban catchments will respond rapidly to changes in atmospheric concentrations due to the mobilization of the majority of the surface accumulated Hg during precipitation events. ?? 2008 Elsevier

  6. Tyrosine content, influx and accumulation rate, and catecholamine biosynthesis measured in vivo, in the central nervous system and in peripheral organs of the young rat. Influence of neonatal hypo- and hyperthyroidism.

    PubMed

    Diarra, A; Lefauconnier, J M; Valens, M; Georges, P; Gripois, D

    1989-10-01

    The influence of neonatal hypo- and hyperthyroidism on different aspects of tyrosine metabolism in the hypothalamus, striatum, brainstem, adrenal glands, heart and brown adipose tissue (BAT) were studied in 14-day old rats. The synthesis rate of catecholamines (CA) was also determined in vivo after the injection of labelled tyrosine. Hypothyroidism increases tyrosinaemia and endogenous tyrosine concentration in the hypothalamus and BAT. Hyperthyroidism decreases tyrosinaemia and endogenous tyrosine levels in the striatum, adrenals and heart. The accumulation rate of tyrosine determined 30 min after an intravenous injection of the labelled amino acid has been determined in the organs, together with the influx of the amino acid, determined within 20s. Hypothyroidism increases tyrosine accumulation rate in all the organs studied, and tyrosine clearance is decreased in the striatum and brainstem; together with an increased tyrosinaemia, this leads to a normal influx. The influx of tyrosine is increased in the hypothalamus. Hyperthyroidism decreases tyrosine accumulation rate in all the organs except the adrenals. These results indicate that the thyroid status of the young rat can influence tyrosine uptake mechanisms, without modifying an organ's tyrosine content. The fact that hypothyroidism increases tyrosine influx in the hypothalamus without modifying it in the brainstem and striatum reflects an heterogeneous reactivity to the lack of thyroid hormones in different brain structures. Neonatal hypothyroidism decreases the CA synthesis rate in the striatum, the heart and the interscapular brown adipose tissue, while synthesis was enhanced in the brainstem and the adrenals. It is likely that these variations in CA synthesis are due to thyroid hormone modulation of tyrosine hydroxylase activity, the enzyme which catalyses the rate limiting step in CA biosynthesis.

  7. Age-related accumulation of the advanced glycation endproduct pentosidine in human articular cartilage aggrecan: the use of pentosidine levels as a quantitative measure of protein turnover.

    PubMed

    Verzijl, N; DeGroot, J; Bank, R A; Bayliss, M T; Bijlsma, J W; Lafeber, F P; Maroudas, A; TeKoppele, J M

    2001-11-01

    During aging, non-enzymatic glycation results in the formation and accumulation of the advanced glycation endproduct pentosidine in long-lived proteins, such as articular cartilage collagen. In the present study, we investigated whether pentosidine accumulation also occurs in cartilage aggrecan. Furthermore, pentosidine levels in aggrecan subfractions of different residence time were used to explore pentosidine levels as a quantitative measure of aggrecan turnover. In order to compare protein turnover rates, protein residence time was measured as racemization of aspartic acid. As has previously been shown for collagen, pentosidine levels increase with age in cartilage aggrecan. Consistent with the faster turnover of aggrecan compared to collagen, the rate of pentosidine accumulation was threefold lower in aggrecan than in collagen. In the subfractions of aggrecan, pentosidine levels increased with protein residence time. These pentosidine levels were used to estimate the half-life of the globular hyaluronan-binding domain of aggrecan to be 19.5 years. This value is in good agreement with the half-life of 23.5 years that was estimated based on aspartic acid racemization. In aggrecan from osteoarthritic (OA) cartilage, decreased pentosidine levels were found compared with normal cartilage, which reflects increased aggrecan turnover during the OA disease process. In conclusion, we showed that pentosidine accumulates with age in aggrecan and that pentosidine levels can be used as a measure of turnover of long-lived proteins, both during normal aging and during disease.

  8. Water filtration rate and infiltration/accumulation of low density lipoproteins in 3 different modes of endothelial/smooth muscle cell co-cultures.

    PubMed

    Ding, ZuFeng; Fan, YuBo; Deng, XiaoYan

    2009-11-01

    Using different endothelial/smooth muscle cell co-culture modes to simulate the intimal structure of blood vessels, the water filtration rate and the infiltration/accumulation of LDL of the cultured cell layers were studied. The three cell culture modes of the study were: (i) The endothelial cell monolayer (EC/Phi); (ii) endothelial cells directly co-cultured on the smooth muscle cell monolayer (EC-SMC); (iii) endothelial cells and smooth muscle cells cultured on different sides of a Millicell-CM membrane (EC/SMC). It was found that under the same condition, the water filtration rate was the lowest for the EC/SMC mode and the highest for the EC/Phi mode, while the infiltration/accumulation of DiI-LDLs was the lowest in the EC/Phi mode and the highest in the EC-SMC mode. It was also found that DiI-LDL infiltration/accumulation in the cultured cell layers increased with the increasing water filtration rate. The results from the in vitro model study therefore suggest that the infiltration/accumulation of the lipids within the arterial wall is positively correlated with concentration polarization of atherogenic lipids, and the integrity of the endothelium plays an important role in the penetration and accumulation of atherogenic lipids in blood vessel walls.

  9. Constant-Differential-Pressure Two-Fluid Accumulator

    NASA Technical Reports Server (NTRS)

    Piecuch, Benjamin; Dalton, Luke T.

    2010-01-01

    A two-fluid accumulator has been designed, built, and demonstrated to provide an acceptably close approximation to constant differential static pressure between two fluids over the full ranges of (1) accumulator stroke, (2) rates of flow of the fluids, and (3) common static pressure applied to the fluids. Prior differential- pressure two-fluid accumulators are generally not capable of maintaining acceptably close approximations to constant differential pressures. The inadequacies of a typical prior differential-pressure two-fluid accumulator can be summarized as follows: The static differential pressure is governed by the intrinsic spring rate (essentially, the stiffness) of an accumulator tank. The spring rate can be tailored through selection of the tank-wall thickness, selection of the number and/or shape of accumulator convolutions, and/or selection of accumulator material(s). Reliance on the intrinsic spring rate of the tank results in three severe limitations: (1) The spring rate and the expulsion efficiency tend to be inversely proportional to each other: that is to say, as the stiffness (and thus the differential pressure) is increased, the range of motion of the accumulator is reduced. (2) As the applied common static pressure increases, the differential pressure tends to decrease. An additional disadvantage, which may or may not be considered limiting, depending on the specific application, is that an increase in stiffness entails an increase in weight. (3) The additional weight required by a low expulsion efficiency accumulator eliminates the advantage given to such gas storage systems. The high expulsion efficiency provided by this two-fluid accumulator allows for a lightweight, tightly packaged system, which can be used in conjunction with a fuel cell-based system.

  10. Measurement of the accumulation of water ice on optical components in cryogenic vacuum environments

    NASA Astrophysics Data System (ADS)

    Moeller, Trevor M.; Montgomery Smith, L.; Collins, Frank G.; Labello, Jesse M.; Rogers, James P.; Lowry, Heard S.; Crider, Dustin H.

    2012-11-01

    Standard vacuum practices mitigate the presence of water vapor and contamination inside cryogenic vacuum chambers. However, anomalies can occur in the facility that can cause the accumulation of amorphous water ice on optics and test articles. Under certain conditions, the amorphous ice on optical components shatters, which leads to a reduction in signal or failure of the component. An experiment was performed to study and measure the deposition of water (H2O) ice on optical surfaces under high-vacuum cryogenic conditions. Water was introduced into a cryogenic vacuum chamber, via a hydrated molecular sieve zeolite, through an effusion cell and impinged upon a quartz-crystal microbalance (QCM) and first-surface gold-plated mirror. A laser and photodiode setup, external to the vacuum chamber, monitored the multiple-beam interference reflectance of the ice-mirror configuration while the QCM measured the mass deposition. Data indicates that water ice, under these conditions, accumulates as a thin film on optical surfaces to thicknesses over 45 microns and can be detected and measured by nonintrusive optical methods which are based upon multiple-beam interference phenomena. The QCM validated the interference measurements. This experiment established proof-of-concept for a miniature system for monitoring ice accumulation within the chamber.

  11. Carbon storage and long-term rate of accumulation in high-altitude Andean peatlands of Bolivia

    Treesearch

    J.A. Hribljan; D.J. Cooper; J. Sueltenfuss; E.C. Wolf; K.A. Heckman; Erik Lilleskov; R.A. Chimner

    2015-01-01

    The high-altitude (4,500+ m) Andean mountain range of north-western Bolivia contains many peatlands. Despite heavy grazing pressure and potential damage from climate change, little is known about these peatlands. Our objective was to quantify carbon pools, basal ages and long-term peat accumulation rates in peatlands in two areas of the arid puna ecoregion of Bolivia:...

  12. Measurement of snow interception and canopy effects on snow accumulation and melt in a mountainous maritime climate, Oregon, United States

    NASA Astrophysics Data System (ADS)

    Storck, Pascal; Lettenmaier, Dennis P.; Bolton, Susan M.

    2002-11-01

    The results of a 3 year field study to observe the processes controlling snow interception by forest canopies and under canopy snow accumulation and ablation in mountain maritime climates are reported. The field study was further intended to provide data to develop and test models of forest canopy effects on beneath-canopy snowpack accumulation and melt and the plot and stand scales. Weighing lysimeters, cut-tree experiments, and manual snow surveys were deployed at a site in the Umpqua National Forest, Oregon (elevation 1200 m). A unique design for a weighing lysimeter was employed that allowed continuous measurements of snowpack evolution beneath a forest canopy to be taken at a scale unaffected by variability in canopy throughfall. Continuous observations of snowpack evolution in large clearings were made coincidentally with the canopy measurements. Large differences in snow accumulation and ablation were observed at sites beneath the forest canopy and in large clearings. These differences were not well described by simple relationships between the sites. Over the study period, approximately 60% of snowfall was intercepted by the canopy (up to a maximum of about 40 mm water equivalent). Instantaneous sublimation rates exceeded 0.5 mm per hour for short periods. However, apparent average sublimation from the intercepted snow was less than 1 mm per day and totaled approximately 100 mm per winter season. Approximately 72 and 28% of the remaining intercepted snow was removed as meltwater drip and large snow masses, respectively. Observed differences in snow interception rate and maximum snow interception capacity between Douglas fir (Pseudotsuga menziesii), white fir (Abies concolor), ponderosa pine (Pinus ponderosa), and lodgepole pine (Pinus contorta) were minimal.

  13. Systems Level Regulation of Rhythmic Growth Rate and Biomass Accumulation in Grasses

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

    Kay, Steve A.

    Objectives: Several breakthroughs have been recently made in our understanding of plant growth and biomass accumulation. It was found that plant growth is rhythmically controlled throughout the day by the circadian clock through a complex interplay of light and phytohormone signaling pathways. While plants such as the C4 energy crop sorghum (Sorghum bicolor (L.) Moench) and possibly the C3 grass Brachypodium distachyon also exhibit daily rhythms in growth rate, the molecular details of its regulation remain to be explored. A better understanding of diurnally regulated growth behavior in grasses may lead to species-specific mechanisms highly relevant to future strategies tomore » optimize energy crop biomass yield. Here we propose to devise a systems approach to identify, in parallel, regulatory hubs associated with rhythmic growth in C3 and C4 plants. We propose to use rhythmicity in daily growth patterns to drive the discovery of regulatory network modules controlling biomass accumulation. Description: The project is divided in three main parts: 1) Performing time-lapse imaging and growth measurement in B. distachyon and S. bicolor to determine growth rate dynamic during the day/night cycle. Identifying growth-associated genes whose expression patterns follow the observed growth dynamics using deep sequencing technology, 2) identifying regulators of these genes by screening for DNA-binding proteins interacting with the growth-associated gene promoters identified in Aim 1. Screens will be performed using a validated yeast-one hybrid strategy paired with a specifically designed B. distachyon and S. bicolor transcription factor libraries (1000 clones each), and 3) Selecting 50 potential growth regulators from the screen for downstream characterization. The selection will be made by using a sytems biology approach by calculating the connectivity between growth rate, rhythmic gene expression profiles and TF expression profile and determine which TF is likely part of

  14. Different efflux rates may determine the cellular accumulation of various bis(guanylhydrazones).

    PubMed Central

    Alhonen-Hongisto, L; Fagerström, R; Laine, R; Elo, H; Jänne, J

    1984-01-01

    Three bis(guanylhydrazones) (those of methylglyoxal, glyoxal and ethylglyoxal) were compared for their affinity for the putative polyamine carrier and for their cellular retention in L1210 mouse leukaemia cells. All the bis(guanylhydrazones) inhibited equally effectively the uptake of spermidine by the tumour cells, indicating that the compounds had roughly equal affinity for the polyamine carrier. The fact that methylglyoxal bis(guanylhydrazone) and glyoxal bis(guanylhydrazone) were much more effectively concentrated in the animal cells than was ethylglyoxal bis(guanylhydrazone) was obviously attributable to the finding that the efflux rate of ethylglyoxal bis(guanylhydrazone) greatly exceeded that of the other bis(guanylhydrazones). The rate of efflux of the drugs was slowed down if the tumour cells were treated with 2-difluoromethylornithine before exposure to the bis(guanylhydrazones). These results suggest that intracellular binding of the bis(guanylhydrazones) determines their cellular accumulation. PMID:6431972

  15. Deformational injection rate measuring method

    NASA Astrophysics Data System (ADS)

    Marčič, Milan

    2002-09-01

    After completing the diesel engine endurance testing, we detected various traces of thermal load on the walls of combustion chambers located in the engine pistons. The engines were fitted with ω combustion chambers. The thermal load of different intensity levels occurred where the spray of fuel, fuel vapor, and air interacted with the combustion chamber wall. The uneven thermal load distribution of the combustion chamber wall results from varying injection rates in each injection nozzle hole. The most widely applied controlling methods so far for injection rate measurement, such as the Zeuch and Bosch concepts, allow measurement of only the total injection rate in multihole nozzles, without providing any indication whatsoever of the injection rate differences in individual injection nozzle holes. The new deformational measuring method described in the article allows the injection rate to be measured in each hole of the multihole nozzle. The results of the measurements using this method showed that the differences occurred in injection rates of individual injection nozzle holes. These differences may be the cause of various thermal loads on the combustion chamber walls. The criterion for injection rate is the deformation of the membrane due to an increase in the fuel quantity in the measuring space and due to the pressure waves resulting from the fuel being injected into the measuring space. The membrane deformation is measured using strain gauges, glued to the membrane and forming the Wheatstone's bridge. We devoted special attention to the temperature compensation of the Wheatstone's bridge and the membrane, heated up during the measurements.

  16. Environmental dynamics and carbon accumulation rate of a tropical peatland in Central Sumatra, Indonesia

    NASA Astrophysics Data System (ADS)

    Hapsari, Kartika Anggi; Biagioni, Siria; Jennerjahn, Tim C.; Reimer, Peter Meyer; Saad, Asmadi; Achnopha, Yudhi; Sabiham, Supiandi; Behling, Hermann

    2017-08-01

    Tropical peatlands are important for the global carbon cycle as they store 18% of the total global peat carbon. As they are vulnerable to changes in temperature and precipitation, a rapidly changing environment endangers peatlands and their carbon storage potential. Understanding the mechanisms of peatland carbon accumulation from studying past developments may, therefore, help to assess the future role of tropical peatlands. Using a multi-proxy palaeoecological approach, a peat core taken from the Sungai Buluh peatland in Central Sumatra has been analyzed for its pollen and spore, macro charcoal and biogeochemical composition. The result suggests that peat and C accumulation rates were driven mainly by sea level change, river water level, climatic variability and anthropogenic activities. It is also suggested that peat C accumulation in Sungai Buluh is correlated to the abundance of Freycinetia, Myrtaceae, Calophyllum, Stemonuraceae, Ficus and Euphorbiaceae. Sungai Buluh has reasonable potential for being a future global tropical peat C sinks. However, considering the impact of rapid global climate change in addition to land-use change following rapid economic growth in Indonesia, such potential may be lost. Taking advantage of available palaeoecological records and advances made in Quaternary studies, some considerations for management practice such as identification of priority taxa and conservation sites are suggested.

  17. Belowground carbon balance and carbon accumulation rate in the successional series of monsoon evergreen broad-leaved forest

    USGS Publications Warehouse

    Zhou, G.; Liu, S.; Tang, X.; Ouyang, X.; Zhang, Dongxiao; Liu, J.; Yan, J.; Zhou, C.; Luo, Y.; Guan, L.; Liu, Yajing

    2006-01-01

    The balance, accumulation rate and temporal dynamics of belowground carbon in the successional series of monsoon evergreen broadleaved forest are obtained in this paper, based on long-term observations to the soil organic matter, input and standing biomass of litter and coarse woody debris, and dissolved organic carbon carried in the hydrological process of subtropical climax forest ecosystem—monsoon evergreen broad-leaved forest, and its two successional forests of natural restoration—coniferous and broad-leaved mixed forest and Pinus massoniana forest, as well as data of root biomass obtained once every five years and respiration measurement of soil, litter and coarse woody debris respiration for 1 year. The major results include: the belowground carbon pools of monsoon evergreen broad-leaved forest, coniferous and broad-leaved mixed forest, and Pinus massoniana forest are 23191 ± 2538 g · m−2, 16889 ± 1936 g · m−2 and 12680 ± 1854 g · m−2, respectively, in 2002. Mean annual carbon accumulation rates of the three forest types during the 24a from 1978 to 2002 are 383 ± 97 g · m−2 · a−1, 193 ± 85 g · m−2 · a−1 and 213 ± 86 g · m−2 · a−1, respectively. The belowground carbon pools in the three forest types keep increasing during the observation period, suggesting that belowground carbon pools are carbon sinks to the atmosphere. There are seasonal variations, namely, they are strong carbon sources from April to June, weak carbon sources from July to September; while they are strong carbon sinks from October to November, weak carbon sinks from December to March.

  18. Open charcoal chamber method for mass measurements of radon exhalation rate from soil surface.

    PubMed

    Tsapalov, Andrey; Kovler, Konstantin; Miklyaev, Peter

    2016-08-01

    Radon exhalation rate from the soil surface can serve as an important criterion in the evaluation of radon hazard of the land. Recently published international standard ISO 11665-7 (2012) is based on the accumulation of radon gas in a closed container. At the same time since 1998 in Russia, as a part of engineering and environmental studies for the construction, radon flux measurements are made using an open charcoal chamber for a sampling duration of 3-5 h. This method has a well-defined metrological justification and was tested in both favorable and unfavorable conditions. The article describes the characteristics of the method, as well as the means of sampling and measurement of the activity of radon absorbed. The results of the metrological study suggest that regardless of the sampling conditions (weather, the mechanism and rate of radon transport in the soil, soil properties and conditions), uncertainty of method does not exceed 20%, while the combined standard uncertainty of radon exhalation rate measured from the soil surface does not exceed 30%. The results of the daily measurements of radon exhalation rate from the soil surface at the experimental site during one year are reported. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Carbon, nitrogen, and phosphorus accumulation in floodplains of Atlantic Coastal Plain rivers, USA

    USGS Publications Warehouse

    Noe, G.B.; Hupp, C.R.

    2005-01-01

    Net nutrient accumulation rates were measured in riverine floodplains of the Atlantic Coastal Plain in Virginia, Maryland, and Delaware, USA. The floodplains were located in watersheds with different land use and included two sites on the Chickahominy River (urban), one site on the Mattaponi River (forested), and five sites on the Pocomoke River (agricultural). The Pocomoke River floodplains lie along reaches with natural hydrogeomorphology and on reaches with restricted flooding due to channelization and levees. A network of feldspar clay marker horizons was placed on the sediment surface of each floodplain site 3-6 years prior to sampling. Sediment cores were collected from the material deposited over the feldspar clay pads. This overlying sediment was separated from the clay layer and then dried, weighed, and analyzed for its total carbon (C), nitrogen (N), and phosphorus (P) content. Mean C accumulation rates ranged from 61 to 212 g??m-2??yr-1, N accumulation rates ranged from 3.5 to 13.4 g??m -2??yr-1, and P accumulation rates ranged from 0.2 to 4.1 g??m-2??yr-1 among the eight floodplains. Patterns of intersite variation in mineral sediment and P accumulation rates were similar to each other, as was variation in organic sediment and C and N accumulation rates. The greatest sediment and C, N, and P accumulation rates were observed on Chickahominy River floodplains downstream from the growing metropolitan area of Richmond, Virginia. Nutrient accumulation rates were lowest on Pocomoke River floodplains that have been hydraulically disconnected from the main channel by channelization and levees. Sediment P concentrations and P accumulation rates were much greater on the hydraulically connected floodplain immediately downstream of the limit of channelization and dense chicken agriculture of the upper Pocomoke River watershed. These findings indicate that (1) watershed land use has a large effect on sediment and nutrient retention in floodplains, and (2) limiting

  20. Measuring zebrafish turning rate.

    PubMed

    Mwaffo, Violet; Butail, Sachit; di Bernardo, Mario; Porfiri, Maurizio

    2015-06-01

    Zebrafish is becoming a popular animal model in preclinical research, and zebrafish turning rate has been proposed for the analysis of activity in several domains. The turning rate is often estimated from the trajectory of the fish centroid that is output by commercial or custom-made target tracking software run on overhead videos of fish swimming. However, the accuracy of such indirect methods with respect to the turning rate associated with changes in heading during zebrafish locomotion is largely untested. Here, we compare two indirect methods for the turning rate estimation using the centroid velocity or position data, with full shape tracking for three different video sampling rates. We use tracking data from the overhead video recorded at 60, 30, and 15 frames per second of zebrafish swimming in a shallow water tank. Statistical comparisons of absolute turning rate across methods and sampling rates indicate that, while indirect methods are indistinguishable from full shape tracking, the video sampling rate significantly influences the turning rate measurement. The results of this study can aid in the selection of the video capture frame rate, an experimental design parameter in zebrafish behavioral experiments where activity is an important measure.

  1. Net ecosystem production: A comprehensive measure of net carbon accumulation by ecosystems

    USGS Publications Warehouse

    Randerson, J.T.; Chapin, F. S.; Harden, J.W.; Neff, J.C.; Harmon, M.E.

    2002-01-01

    The conceptual framework used by ecologists and biogeochemists must allow for accurate and clearly defined comparisons of carbon fluxes made with disparate techniques across a spectrum of temporal and spatial scales. Consistent with usage over the past four decades, we define "net ecosystem production" (NEP) as the net carbon accumulation by ecosystems. Past use of this term has been ambiguous, because it has been used conceptually as a measure of carbon accumulation by ecosystems, but it has often been calculated considering only the balance between gross primary production (GPP) and ecosystem respiration. This calculation ignores other carbon fluxes from ecosystems (e.g., leaching of dissolved carbon and losses associated with disturbance). To avoid conceptual ambiguities, we argue that NEP be defined, as in the past, as the net carbon accumulation by ecosystems and that it explicitly incorporate all the carbon fluxes from an ecosystem, including autotrophic respiration, heterotrophic respiration, losses associated with disturbance, dissolved and particulate carbon losses, volatile organic compound emissions, and lateral transfers among ecosystems. Net biome productivity (NBP), which has been proposed to account for carbon loss during episodic disturbance, is equivalent to NEP at regional or global scales. The multi-scale conceptual framework we describe provides continuity between flux measurements made at the scale of soil profiles and chambers, forest inventories, eddy covariance towers, aircraft, and inversions of remote atmospheric flask samples, allowing a direct comparison of NEP estimates made at all temporal and spatial scales.

  2. Sexual difference in polychlorinated biphenyl accumulation rates of walleye (Stizostedion vitreum)

    USGS Publications Warehouse

    Madenjian, Charles P.; Noguchi, George E.; Haas, Robert C.; Schrouder, Kathrin S.

    1998-01-01

    Adult male walleye (Stizostedion vitreum) exhibited significantly higher polychlorinated biphenyl (PCB) concentrations than similarly aged female walleye from Saginaw Bay (Lake Huron). To explain this difference, we tested the following three hypotheses: (i) females showed a considerably greater reduction in PCB concentration immediately following spawning than males, (ii) females grew at a faster rate and therefore exhibited lower PCB concentrations than males, and (iii) males spent more time in the Saginaw River system than females, and therefore received a greater exposure to PCBs. The first hypothesis was tested by comparing PCB concentration in gonadal tissue with whole-body concentration, the second hypothesis was tested via bioenergetics modeling, and we used mark-recapture data from the Saginaw Bay walleye fishery to address the third hypothesis. The only plausible explanation for the observed difference in PCB accumulation rate was that males spent substantially more time in the highly contaminated Saginaw River system than females, and therefore were exposed to greater environmental concentrations of PCBs. Based on the results of our study, we strongly recommend a stratified random sampling design for monitoring PCB concentration in Saginaw Bay walleye, with fixed numbers of females and males sampled each year.

  3. Measuring a critical stress for continuous prevention of marine biofouling accumulation with aeration.

    PubMed

    Menesses, Mark; Belden, Jesse; Dickenson, Natasha; Bird, James

    2017-10-01

    When cleaning the hull of a ship, significant shear stresses are needed to remove established biofouling organisms. Given that there exists a link between the amount of time that fouling accumulates and the stress required to remove it, it is not surprising that more frequent grooming requires less shear stress. Yet, it is unclear if there is a minimum stress needed to prevent the growth of macrofouling in the limit of continuous grooming. This manuscript shows that single bubble stream aeration provides continuous grooming and prevents biofouling accumulation in regions where the average wall stress exceeds ~0.01 Pa. This value was found by comparing observations of biofouling growth from field studies with complementary laboratory measurements that probe the associated flow fields. These results suggest that aeration and other continuous grooming systems must exceed a wall stress of 0.01 Pa to prevent macrofouling accumulation.

  4. Sensor for Injection Rate Measurements

    PubMed Central

    Marcic, Milan

    2006-01-01

    A vast majority of the medium and high speed Diesel engines are equipped with multi-hole injection nozzles nowadays. Inaccuracies in workmanship and changing hydraulic conditions in the nozzles result in differences in injection rates between individual injection nozzle holes. The new deformational measuring method described in the paper allows injection rate measurement in each injection nozzle hole. The differences in injection rates lead to uneven thermal loads of Diesel engine combustion chambers. All today known measuring method, such as Bosch and Zeuch give accurate results of the injection rate in diesel single-hole nozzles. With multihole nozzles they tell us nothing about possible differences in injection rates between individual holes of the nozzle. At deformational measuring method, the criterion of the injected fuel is expressed by the deformation of membrane occurring due to the collision of the pressure wave against the membrane. The pressure wave is generated by the injection of the fuel into the measuring space. For each hole of the nozzle the measuring device must have a measuring space of its own into which fuel is injected as well as its measuring membrane and its own fuel outlet. During measurements procedure the measuring space must be filled with fuel to maintain an overpressure of 5 kPa. Fuel escaping from the measuring device is conducted into the graduated cylinders for measuring the volumetric flow through each hole of the nozzle.The membrane deformation is assessed by strain gauges. They are glued to the membrane and forming the full Wheatstone's bridge. We devoted special attention to the membrane shape and temperature compensation of the strain gauges.

  5. Accumulated financial strain and women's health over three decades.

    PubMed

    Shippee, Tetyana Pylypiv; Wilkinson, Lindsay R; Ferraro, Kenneth F

    2012-09-01

    Drawing from cumulative inequality theory, this research examines how accumulated financial strain affects women's self-rated health in middle and later life. Using data from the National Longitudinal Survey of Mature Women (1967-2003), we employ random-coefficient growth curve models to examine whether recurring financial strain influences women's health, above and beyond several measures of objective social status. Predicted probabilities of poor health were estimated by the frequency of financial strain. Financial strain is associated with rapid declines in women's health during middle and later life, especially for those women who reported recurrent strain. Changes in household income and household wealth were also associated with women's health but did not eliminate the effects due to accumulated financial strain. Accumulated financial strain has long-term effects on women's health during middle and later life. The findings demonstrate the importance of measuring life course exposure to stressors in studies of health trajectories.

  6. Net accumulation rates derived from ice core stable isotope records of Pío XI glacier, Southern Patagonia Icefield

    NASA Astrophysics Data System (ADS)

    Schwikowski, M.; Schläppi, M.; Santibañez, P.; Rivera, A.; Casassa, G.

    2012-12-01

    Pío XI, the largest glacier of the Southern Patagonia Icefield, reached its neoglacial maximum extent in 1994 and is one of the few glaciers in that area which is not retreating. In view of the recent warming it is important to understand glacier responses to climate changes. Due to its remoteness and the harsh conditions in Patagonia, no systematic mass balance studies have been performed. In this study we derived net accumulation rates for the period 2000 to 2006 from a 50 m (33.2 4 m weq) ice core collected in the accumulation area of Pío XI (2600 m a.s.l., 49°16´40´´ S, 73°21´14´´ W). Borehole temperatures indicate near temperate ice, but the average melt percent is only 16% ± 14%. Records of stable isotopes are well preserved and were used for identification of annual layers. Net accumulation rates range from 3.4 to 7.1 water equivalent (m weq) with an average of 5.8 m weq, comparable to precipitation amounts at the Chilean coast, but not as high as expected for the Icefield. Ice core stable isotope data correlate well with upper air temperatures and may be used as temperature proxy.

  7. Unprecedented last-glacial mass accumulation rates determined by luminescence dating of loess from western Nebraska

    USGS Publications Warehouse

    Roberts, H.M.; Muhs, D.R.; Wintle, A.G.; Duller, G.A.T.; Bettis, E. Arthur

    2003-01-01

    A high-resolution chronology for Peoria (last glacial period) Loess from three sites in Nebraska, midcontinental North America, is determined by applying optically stimulated luminescence (OSL) dating to 35-50 ??m quartz. At Bignell Hill, Nebraska, an OSL age of 25,000 yr near the contact of Peoria Loess with the underlying Gilman Canyon Formation shows that dust accumulation occurred early during the last glacial maximum (LGM), whereas at Devil's Den and Eustis, Nebraska, basal OSL ages are significantly younger (18,000 and 21,000 yr, respectively). At all three localities, dust accumulation ended at some time after 14,000 yr ago. Mass accumulation rates (MARs) for western Nebraska, calculated using the OSL ages, are extremely high from 18,000 to 14,000 yr-much higher than those calculated for any other pre-Holocene location worldwide. These unprecedented MARs coincide with the timing of a mismatch between paleoenvironmental evidence from central North America, and the paleoclimate simulations from atmospheric global circulation models (AGCMs). We infer that the high atmospheric dust loading implied by these MARs may have played an important role, through radiative forcing, in maintaining a colder-than-present climate over central North America for several thousand years after summer insolation exceeded present-day values. ?? 2003 Elsevier Science (USA). All rights reserved.

  8. Estimation of net accumulation rate at a Patagonian glacier by ice core analyses using snow algae

    NASA Astrophysics Data System (ADS)

    Kohshima, Shiro; Takeuchi, Nozomu; Uetake, Jun; Shiraiwa, Takayuki; Uemura, Ryu; Yoshida, Naohiro; Matoba, Sumito; Godoi, Maria Angelica

    2007-10-01

    Snow algae in a 45.97-m-long ice core from the Tyndall Glacier (50°59'05″S, 73°31'12″W, 1756 m a.s.l.) in the Southern Patagonian Icefield were examined for potential use in ice core dating and estimation of the net accumulation rate. The core was subjected to visual stratigraphic observation and bulk density measurements in the field, and later to analyses of snow algal biomass, water isotopes ( 18O, D), and major dissolved ions. The ice core contained many algal cells that belonged to two species of snow algae growing in the snow near the surface: Chloromonas sp. and an unknown green algal species. Algal biomass and major dissolved ions (Na +, K +, Mg 2+, Ca 2+, Cl -, SO 42-) exhibited rapid decreases in the upper 3 m, probably owing to melt water elution and/or decomposition of algal cells. However, seasonal cycles were still found for the snow algal biomass, 18O, D-excess, and major ions, although the amplitudes of the cycles decreased with depth. Supposing that the layers with almost no snow algae were the winter layers without the melt water essential to algal growth, we estimated that the net accumulation rate at this location was 12.9 m a - 1 from winter 1998 to winter 1999, and 5.1 m from the beginning of winter to December 1999. These estimates are similar to the values estimated from the peaks of 18O (17.8 m a - 1 from summer 1998 to summer 1999 and 11.0 m from summer to December 1999) and those of D-excess (14.7 m a - 1 from fall 1998 to fall 1999 and 8.6 m a - 1 from fall to December 1999). These values are much higher than those obtained by past ice core studies in Patagonia, but are of the same order of magnitude as those predicted from various observations at ablation areas of Patagonian glaciers.

  9. Accumulate-Repeat-Accumulate-Accumulate Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Samuel; Thorpe, Jeremy

    2007-01-01

    Accumulate-repeat-accumulate-accumulate (ARAA) codes have been proposed, inspired by the recently proposed accumulate-repeat-accumulate (ARA) codes. These are error-correcting codes suitable for use in a variety of wireless data-communication systems that include noisy channels. ARAA codes can be regarded as serial turbolike codes or as a subclass of low-density parity-check (LDPC) codes, and, like ARA codes they have projected graph or protograph representations; these characteristics make it possible to design high-speed iterative decoders that utilize belief-propagation algorithms. The objective in proposing ARAA codes as a subclass of ARA codes was to enhance the error-floor performance of ARA codes while maintaining simple encoding structures and low maximum variable node degree.

  10. Coulomb Stress Accumulation along the San Andreas Fault System

    NASA Technical Reports Server (NTRS)

    Smith, Bridget; Sandwell, David

    2003-01-01

    Stress accumulation rates along the primary segments of the San Andreas Fault system are computed using a three-dimensional (3-D) elastic half-space model with realistic fault geometry. The model is developed in the Fourier domain by solving for the response of an elastic half-space due to a point vector body force and analytically integrating the force from a locking depth to infinite depth. This approach is then applied to the San Andreas Fault system using published slip rates along 18 major fault strands of the fault zone. GPS-derived horizontal velocity measurements spanning the entire 1700 x 200 km region are then used to solve for apparent locking depth along each primary fault segment. This simple model fits remarkably well (2.43 mm/yr RMS misfit), although some discrepancies occur in the Eastern California Shear Zone. The model also predicts vertical uplift and subsidence rates that are in agreement with independent geologic and geodetic estimates. In addition, shear and normal stresses along the major fault strands are used to compute Coulomb stress accumulation rate. As a result, we find earthquake recurrence intervals along the San Andreas Fault system to be inversely proportional to Coulomb stress accumulation rate, in agreement with typical coseismic stress drops of 1 - 10 MPa. This 3-D deformation model can ultimately be extended to include both time-dependent forcing and viscoelastic response.

  11. An oscillating microbalance for meteorological measurements of ice and volcanic ash accumulation from a weather balloon platform

    NASA Astrophysics Data System (ADS)

    Airey, Martin; Harrison, Giles; Nicoll, Keri; Williams, Paul; Marlton, Graeme

    2017-04-01

    A new, low cost, instrument has been developed for meteorological measurements of the accumulation of ice and volcanic ash that can be readily deployed using commercial radiosondes and weather balloons. It is based on principles used by [1], an instrument originally developed to measure supercooled liquid water profiles in clouds. This new instrument introduces numerous improvements in terms of reduced complexity and cost. It uses the oscillating microbalance principle, whereby a wire vibrating at its natural frequency is subjected to increased loading of the property to be measured. The increase in mass modifies the wire properties such that its natural frequency of oscillation changes. By measuring this frequency, the increase in mass can be inferred and transmitted to a ground base station through the radiosonde's UHF antenna via the PANDORA interface [2], which has been previously developed to provide power and connection to the radiosonde telemetry. The device consists of a simple circuit board controlled by an ATMEGA microcontroller. For calibration, the controller is capable of driving the wire at specified frequencies via excitation by a piezo sounder upon which the wire is mounted. The same piezo sounder is also used during active operation to measure the frequency of the wire in its non-driven state in order to infer the mass change on the wire. A phase-locked loop implemented on the board identifies when resonance occurs and the measured frequency is stable, prompting the microcontroller to send the measurement through the data interface. The device may be used for any application that requires the measurement of incremental mass variation e.g. ice accumulation, frosting, or particle accumulation such as dust and volcanic ash. For the solid particle accumulation, a low temperature, high-tack, adhesive may be applied to the wire prior to deployment to collect the material. In addition, the same instrument may be used for ground-based applications, such as

  12. GPS measurement of relative motion of the Cocos and Caribbean Plates and strain accumulation across the Middle America Trench

    NASA Astrophysics Data System (ADS)

    Dixon, Timothy H.

    1993-10-01

    Global Positioning System (GPS) measurements in 1988 and 1991 on Cocos Island (Cocos plate), San Andres Island (Caribbean plate), and Liberia (Caribbean plate, mainland Costa Rica) provide an estimate of relative motion between the Cocos and Caribbean plates. The data for Cocos and San Andres Islands, both located more than 400 km from the Middle America Trench, define a velocity that is equivalent within two standard errors (7 mm/yr rate, 5 degrees azimuth) to the NUVEL-1 plate motion model. The data for Liberia, 120 km from the trench, define a velocity that is similar in azimuth but substantially different in rate from NUVEL-1. The discrepancy can be explained with a simple model of elastic strain accumulation with a subduction zone that is locked to a relatively shallow (20±5 km) depth.

  13. An approach to bioassessment of water quality using diversity measures based on species accumulative curves.

    PubMed

    Xu, Guangjian; Zhang, Wei; Xu, Henglong

    2015-02-15

    Traditional community-based bioassessment is time-consuming because they rely on full species-abundance data of a community. To improve bioassessment efficiency, the feasibility of the diversity measures based on species accumulative curves for bioassessment of water quality status was studied based on a dataset of microperiphyton fauna. The results showed that: (1) the species accumulative curves well fitted the Michaelis-Menten equation; (2) the β- and γ-diversity, as well as the number of samples to 50% of the maximum species number (Michaelis-Menten constant K), can be statistically estimated based on the formulation; (3) the rarefied α-diversity represented a significant negative correlation with the changes in the nutrient NH4-N; and (4) the estimated β-diversity and the K constant were significantly positively related to the concentration of NH4-N. The results suggest that the diversity measures based on species accumulative curves might be used as a potential bioindicator of water quality in marine ecosystems. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Sub-annual North Pacific hydroclimate variability since 1450AD from updated St. Elias ice core isotope and accumulation rate records

    NASA Astrophysics Data System (ADS)

    Kreutz, K. J.; Campbell, S. W.; Winski, D.; Osterberg, E. C.; Kochtitzky, W. H.; Copland, L.; Dixon, D.; Introne, D.; Medrzycka, D.; Main, B.; Bernsen, S.; Wake, C. P.

    2017-12-01

    A growing array of high-resolution paleoclimate records from the terrestrial region bordering the Gulf of Alaska (GoA) continues to reveal details about ocean-atmosphere variability in the region during the Common Era. Ice core records from high-elevation ranges in proximity to the GoA provide key information on extratropical hydroclimate, and potential teleconnections to low latitude regions. In particular, stable water isotope and snow accumulation reconstructions from ice cores collected in high precipitation locations are uniquely tied to regional water cycle changes. Here we present new data collected in 2016 and 2017 from the St. Elias Mountains (Eclipse Icefield, Yukon Territories, Canada), including a range of ice core and geophysical measurements. Low- and high-frequency ice penetrating radar data enable detailed mapping of icefield bedrock topography and internal reflector stratigraphy. The 1911 Katmai eruption layer can be clearly traced across the icefield, and tied definitively to the coeval ash layer found in the 345 meter ice core drilled at Eclipse Icefield in 2002. High-resolution radar data are used to map spatial variability in 2015/16 and 2016/17 snow accumulation. Ice velocity data from repeat GPS stake measurements and remote sensing feature tracking reveal a clear divide flow regime on the icefield. Shallow firn/ice cores (20 meters in 2017 and 65 meters in 2016) are used to update the 345 meter ice core drilled at Eclipse Icefield in 2002. We use new algorithm-based layer counting software to improve and provide error estimates on the new ice core chronology, which extends from 2017 to 1450AD. 3D finite element modeling, incorporating all available geophysical data, is used to refine the reconstructed accumulation rate record and account for vertical and horizontal ice flow. Together with high-resolution stable water isotope data, the updated Eclipse record provides detailed, sub-annual resolution data on several aspects of the regional

  15. Microscopic Measurements of Axial Accumulation of Red Blood Cells in Capillary Flows Effects of Deformability

    NASA Astrophysics Data System (ADS)

    Sasaki, Takahiro; Seki, Junji; Itano, Tomoaki; Sugihara-Seki, Masako

    2017-11-01

    In the microcirculation, red blood cells (RBCs) are known to accumulate in the region near the central axis of microvessels, which is called the ``axial accumulation''. Although this behavior of RBCs is considered to originate from high deformability of RBCs, there have been few experimental studies on the mechanism. In order to elucidate the effect of RBC deformability on the axial accumulation, we measured the cross-sectional distributions of RBCs flowing through capillary tubes with a high spatial resolution by a newly devised observation system for intact and softened RBCs as well as hardened RBCs to various degrees. It was found that the intact and softened RBCs are concentrated in the small area centered on the tube axis, whereas the hardened RBCs are dispersed widely over the tube cross section dependent on the degree of hardness. These results demonstrate clearly the essential role of the deformability of RBCs in the ``axial accumulation'' of RBCs. JSPS KAKENHI Grant Number 17H03176, Kansai University ORDIST group funds.

  16. Experimental measurement and modeling of snow accumulation and snowmelt in a mountain microcatchment

    NASA Astrophysics Data System (ADS)

    Danko, Michal; Krajčí, Pavel; Hlavčo, Jozef; Kostka, Zdeněk; Holko, Ladislav

    2016-04-01

    Fieldwork is a very useful source of data in all geosciences. This naturally applies also to the snow hydrology. Snow accumulation and snowmelt are spatially very heterogeneous especially in non-forested, mountain environments. Direct field measurements provide the most accurate information about it. Quantification and understanding of processes, that cause these spatial differences are crucial in prediction and modelling of runoff volumes in spring snowmelt period. This study presents possibilities of detailed measurement and modeling of snow cover characteristics in a mountain experimental microcatchment located in northern part of Slovakia in Western Tatra mountains. Catchment area is 0.059 km2 and mean altitude is 1500 m a.s.l. Measurement network consists of 27 snow poles, 3 small snow lysimeters, discharge measurement device and standard automatic weather station. Snow depth and snow water equivalent (SWE) were measured twice a month near the snow poles. These measurements were used to estimate spatial differences in accumulation of SWE. Snowmelt outflow was measured by small snow lysimeters. Measurements were performed in winter 2014/2015. Snow water equivalent variability was very high in such a small area. Differences between particular measuring points reached 600 mm in time of maximum SWE. The results indicated good performance of a snow lysimeter in case of snowmelt timing identification. Increase of snowmelt measured by the snow lysimeter had the same timing as increase in discharge at catchment's outlet and the same timing as the increase in air temperature above the freezing point. Measured data were afterwards used in distributed rainfall-runoff model MIKE-SHE. Several methods were used for spatial distribution of precipitation and snow water equivalent. The model was able to simulate snow water equivalent and snowmelt timing in daily step reasonably well. Simulated discharges were slightly overestimated in later spring.

  17. Dose accumulation of multiple high dose rate prostate brachytherapy treatments in two commercially available image registration systems.

    PubMed

    Poder, Joel; Yuen, Johnson; Howie, Andrew; Bece, Andrej; Bucci, Joseph

    2017-11-01

    The purpose of this study was to assess whether deformable image registration (DIR) is required for dose accumulation of multiple high dose rate prostate brachytherapy (HDRPBT) plans treated with the same catheter pattern on two different CT datasets. DIR was applied to 20 HDRPBT patients' planning CT images who received two treatment fractions on sequential days, on two different CT datasets, with the same implant. Quality of DIR in Velocity and MIM image registration systems was assessed by calculating the Dice Similarity Coefficient (DSC) and mean distance to agreement (MDA) for the prostate, urethra and rectum contours. Accumulated doses from each system were then calculated using the same DIR technique and dose volume histogram (DVH) parameters compared to manual addition with no DIR. The average DSC was found to be 0.83 (Velocity) and 0.84 (MIM), 0.80 (Velocity) and 0.80 (MIM), 0.80 (Velocity) and 0.81 (MIM), for the prostate, rectum and urethra contours, respectively. The average difference in calculated DVH parameters between the two systems using dose accumulation was less than 1%, and there was no statistically significant difference found between deformably accumulated doses in the two systems versus manual DVH addition with no DIR. Contour propagation using DIR in velocity and MIM was shown to be at least equivalent to inter-observer contouring variability on CT. The results also indicate that dose accumulation through manual addition of DVH parameters may be sufficient for HDRPBT treatments treated with the same catheter pattern on two different CT datasets. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

  18. Strain accumulation in the Shumagin Islands: Results of initial GPS measurements

    USGS Publications Warehouse

    Larson, Kristine M.; Lisowski, Michael

    1994-01-01

    Deformation in the Shumagin seismic gap has been monitored with repeated trilateration (EDM) in the 1980–1987 interval and with the Global Positioning System (GPS) in the 1987–1991 interval. The geodetic network extends for 100-km across the Shumagin Islands to the Alaska Peninsula. Results from the GPS surveys are consistent with those previously reported for the EDM surveys: we failed to detect significant strain accumulation in the N30°W direction of plate convergence. Using the method of simultaneous reduction for position and strain rates, we found the average rate of extension in the direction of plate convergence to be −25±25 nanostrain/yr (nstrain/yr) during the 1987–1991 interval of GPS surveys compared with −20±15 nstrain/yr during the 1981–1987 interval of complete EDM surveys. We found a marginally significant −26±12 nstrain/yr extension rate in the 1981–1991 interval covered by the combined EDM and GPS surveys. Strain rates are higher, but not significantly so, in the part of the network closest to the trench. Spatial variation in the deformation is observed in the 1980–1991 average station velocities, where three of the four stations closest to the trench have an arcward velocity of a few mm/yr. The observed strain rates are an order of magnitude lower than the −200 nstrain/yr rate predicted by dislocation models.

  19. Enhanced land subsidence in Galveston Bay, Texas: Interaction between sediment accumulation rates and relative sea level rise

    NASA Astrophysics Data System (ADS)

    Al Mukaimi, Mohammad E.; Dellapenna, Timothy M.; Williams, Joshua R.

    2018-07-01

    Galveston Bay is the second largest estuary along the northern Gulf of Mexico coast, with a watershed containing one of largest concentrations of petroleum and chemical industries globally, as well as Houston, the fifth largest metropolitan area in the USA. Throughout the last century, extensive groundwater extraction to support these industries and an expanding population has resulted in significantly enhanced land subsidence (0.6-3.0 cm yr-1). The highest subsidence rates observed in the bay are within the lower 15 km of the San Jacinto River/Houston Ship Channel region (SJR/HSC), with distal areas in East and West Galveston Bays having subsidence rates on the order of 0.2 cm yr-1. In order to investigate the impacts of subsidence on sedimentation, a series of 22 vibracores were collected throughout the bay, and 210Pb and 137Cs radioisotope geochronologies and grain size distributions were determined. Sediment accumulation rates are highest (1.9 ± 0.5 cm yr-1) in the SJR/HSC, and decrease (<0.6 cm yr-1) both seaward and towards low subsidence regions. These results indicate sedimentation rates are significantly (p < 0.01) higher in areas with elevated Relative Sea Level Rise (RSLR). However, throughout most of Galveston Bay sedimentation rates are lower (as much as 50%) than estimated RSLR, indicating a sediment accretionary deficit. In areas (e.g., Scott Bay) within the SJR/HSC, the bay has deepened by more than 1.5 m, suggesting that sediment accumulation cannot keep pace with RSLR. Ultimately, this has resulted in a loss of coastal wetlands and a conversion of marine habitats from relatively shallow to deeper water settings.

  20. Total carbon accumulation in a tropical forest landscape.

    PubMed

    Sierra, Carlos A; Del Valle, Jorge I; Restrepo, Hector I

    2012-12-19

    Regrowing tropical forests worldwide sequester important amounts of carbon and restore part of the C emissions emitted by deforestation. However, there are large uncertainties concerning the rates of carbon accumulation after the abandonment of agricultural and pasture land. We report here accumulation of total carbon stocks (TCS) in a chronosequence of secondary forests at a mid-elevation landscape (900-1200 m asl) in the Andean mountains of Colombia. We found positive accumulation rates for all ecosystem pools except soil carbon, which showed no significant trend of recovery after 36 years of secondary succession. We used these data to develop a simple model to predict accumulation of TCS over time. This model performed remarkably well predicting TCS at other chronosequences in the Americas (Root Mean Square Error < 40 Mg C ha-1), which provided an opportunity to explore different assumptions in the calculation of large-scale carbon budgets. Simulations of TCS with our empirical model were used to test three assumptions often made in carbon budgets: 1) the use of carbon accumulation in tree aboveground biomass as a surrogate for accumulation of TCS, 2) the implicit consideration of carbon legacies from previous land-use, and 3) the omission of landscape age in calculating accumulation rates of TCS. Our simulations showed that in many situations carbon can be released from regrowing secondary forests depending on the amount of carbon legacies and the average age of the landscape. In most cases, the rates used to predict carbon accumulation in the Americas were above the rates predicted in our simulations. These biome level rates seemed to be realistic only in landscapes not affected by carbon legacies from previous land-use and mean ages of around 10 years.

  1. Total carbon accumulation in a tropical forest landscape

    PubMed Central

    2012-01-01

    Background Regrowing tropical forests worldwide sequester important amounts of carbon and restore part of the C emissions emitted by deforestation. However, there are large uncertainties concerning the rates of carbon accumulation after the abandonment of agricultural and pasture land. We report here accumulation of total carbon stocks (TCS) in a chronosequence of secondary forests at a mid-elevation landscape (900-1200 m asl) in the Andean mountains of Colombia. Results We found positive accumulation rates for all ecosystem pools except soil carbon, which showed no significant trend of recovery after 36 years of secondary succession. We used these data to develop a simple model to predict accumulation of TCS over time. This model performed remarkably well predicting TCS at other chronosequences in the Americas (Root Mean Square Error < 40 Mg C ha-1), which provided an opportunity to explore different assumptions in the calculation of large-scale carbon budgets. Simulations of TCS with our empirical model were used to test three assumptions often made in carbon budgets: 1) the use of carbon accumulation in tree aboveground biomass as a surrogate for accumulation of TCS, 2) the implicit consideration of carbon legacies from previous land-use, and 3) the omission of landscape age in calculating accumulation rates of TCS. Conclusions Our simulations showed that in many situations carbon can be released from regrowing secondary forests depending on the amount of carbon legacies and the average age of the landscape. In most cases, the rates used to predict carbon accumulation in the Americas were above the rates predicted in our simulations. These biome level rates seemed to be realistic only in landscapes not affected by carbon legacies from previous land-use and mean ages of around 10 years. PMID:23249727

  2. Current algebras, measures quasi-invariant under diffeomorphism groups, and infinite quantum systems with accumulation points

    NASA Astrophysics Data System (ADS)

    Sakuraba, Takao

    The approach to quantum physics via current algebra and unitary representations of the diffeomorphism group is established. This thesis studies possible infinite Bose gas systems using this approach. Systems of locally finite configurations and systems of configurations with accumulation points are considered, with the main emphasis on the latter. In Chapter 2, canonical quantization, quantization via current algebra and unitary representations of the diffeomorphism group are reviewed. In Chapter 3, a new definition of the space of configurations is proposed and an axiom for general configuration spaces is abstracted. Various subsets of the configuration space, including those specifying the number of points in a Borel set and those specifying the number of accumulation points in a Borel set are proved to be measurable using this axiom. In Chapter 4, known results on the space of locally finite configurations and Poisson measure are reviewed in the light of the approach developed in Chapter 3, including the approach to current algebra in the Poisson space by Albeverio, Kondratiev, and Rockner. Goldin and Moschella considered unitary representations of the group of diffeomorphisms of the line based on self-similar random processes, which may describe infinite quantum gas systems with clusters. In Chapter 5, the Goldin-Moschella theory is developed further. Their construction of measures quasi-invariant under diffeomorphisms is reviewed, and a rigorous proof of their conjectures is given. It is proved that their measures with distinct correlation parameters are mutually singular. A quasi-invariant measure constructed by Ismagilov on the space of configurations with accumulation points on the circle is proved to be singular with respect to the Goldin-Moschella measures. Finally a generalization of the Goldin-Moschella measures to the higher-dimensional case is studied, where the notion of covariance matrix and the notion of condition number play important roles. A

  3. Sediment accumulation rates and high-resolution stratigraphy of recent fluvial suspension deposits in various fluvial settings, Morava River catchment area, Czech Republic

    NASA Astrophysics Data System (ADS)

    Sedláček, Jan; Bábek, Ondřej; Kielar, Ondřej

    2016-02-01

    We present a comprehensive study concerning sedimentary processes in fluvial sediment traps within the Morava River catchment area (Czech Republic) involving three dammed reservoirs, four meanders and oxbow lakes, and several natural floodplain sites. The objective of the study was to determine sediment accumulation rates (SAR), estimate erosion rates, calculating these using a combination of the 137Cs method and historical data. Another purpose of this study was to provide insight into changing erosion and accumulation rates over the last century. Extensive water course modifications were carried out in the Morava River catchment area during the twentieth century, which likely affected sedimentation rates along the river course. Other multiproxy stratigraphic methods (X-ray densitometry, magnetic susceptibility, and visible-light reflectance spectrometry) were applied to obtain additional information about sediment infill. Sediment stratigraphy revealed distinct distal-to-proximal patterns, especially in reservoirs. Granulometrically, silts and sandy silts prevailed in sediments. Oxbow lakes and meanders contained larger amounts of clay and organic matter, which is the main difference between them and reservoirs. Pronounced 137Cs peaks were recorded in all studied cores (maximum 377 Bq·kg- 1), thus indicating Chernobyl fallout from 1986 or older events. Calculated sediment accumulation rates were lowest in distal parts of reservoirs (0.13-0.58 cm/y) and floodplains (0.45-0.88 cm/y), moderately high rates were found in proximal parts of reservoirs and oxbow lakes (2.27-4.4 cm/y), and the highest rates in some oxbow lakes located near the river (6-8 cm/y). The frequency of the inundation still can be high in some natural areas as in the Litovelské Pomoraví protected area, whereas the decreasing frequency of the inundation in other modified parts can contribute to a lower sedimentation rate. The local effects such as difference between SARs in oxbow lakes and

  4. Elucidating effects of atmospheric deposition and peat decomposition processes on mercury accumulation rates in a northern Minnesota peatland over last 10,000 cal years

    NASA Astrophysics Data System (ADS)

    Nater, E. A.; Furman, O.; Toner, B. M.; Sebestyen, S. D.; Tfaily, M. M.; Chanton, J.; Fissore, C.; McFarlane, K. J.; Hanson, P. J.; Iversen, C. M.; Kolka, R. K.

    2014-12-01

    Climate change has the potential to affect mercury (Hg), sulfur (S) and carbon (C) stores and cycling in northern peatland ecosystems (NPEs). SPRUCE (Spruce and Peatland Responses Under Climate and Environmental change) is an interdisciplinary study of the effects of elevated temperature and CO2 enrichment on NPEs. Peat cores (0-3.0 m) were collected from 16 large plots located on the S1 peatland (an ombrotrophic bog treed with Picea mariana and Larix laricina) in August, 2012 for baseline characterization before the experiment begins. Peat samples were analyzed at depth increments for total Hg, bulk density, humification indices, and elemental composition. Net Hg accumulation rates over the last 10,000 years were derived from Hg concentrations and peat accumulation rates based on peat depth chronology established using 14C and 13C dating of peat cores. Historic Hg deposition rates are being modeled from pre-industrial deposition rates in S1 scaled by regional lake sediment records. Effects of peatland processes and factors (hydrology, decomposition, redox chemistry, vegetative changes, microtopography) on the biogeochemistry of Hg, S, and other elements are being assessed by comparing observed elemental depth profiles with accumulation profiles predicted solely from atmospheric deposition. We are using principal component analyses and cluster analyses to elucidate relationships between humification indices, peat physical properties, and inorganic and organic geochemistry data to interpret the main processes controlling net Hg accumulation and elemental concentrations in surface and subsurface peat layers. These findings are critical to predicting how climate change will affect future accumulation of Hg as well as existing Hg stores in NPE, and for providing reference baselines for SPRUCE future investigations.

  5. Measurement of the surface charge accumulation using anodic aluminum oxide(AAO) structure in an inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Park, Ji-Hwan; Oh, Seung-Ju; Lee, Hyo-Chang; Kim, Yu-Sin; Kim, Young-Cheol; Kim, June Young; Ha, Chang-Seoung; Kwon, Soon-Ho; Lee, Jung-Joong; Chung, Chin-Wook

    2014-10-01

    As the critical dimension of the nano-device shrinks, an undesired etch profile occurs during plasma etch process. One of the reasons is the local electric field due to the surface charge accumulation. To demonstrate the surface charge accumulation, an anodic aluminum oxide (AAO) membrane which has high aspect ratio is used. The potential difference between top electrode and bottom electrode in an anodic aluminum oxide contact structure is measured during inductively coupled plasma exposure. The voltage difference is changed with external discharge conditions, such as gas pressure, input power, and gas species and the result is analyzed with the measured plasma parameters.

  6. Geomorphic Evolution and Slip rate Measurements of the Noushki Segment , Chaman Fault Zone, Pakistan

    NASA Astrophysics Data System (ADS)

    Abubakar, Y.; Khan, S. D.; Owen, L. A.; Khan, A.

    2012-12-01

    The Nushki segment of the Chaman fault system is unique in its nature as it records both the imprints of oblique convergence along the western Indian Plate boundary as well as the deformation along the Makran subduction zone. The left-lateral Chaman transform zone has evolved from a subduction zone along the Arabian-Eurasian collision complex to a strike-slip fault system since the collision of the Indian Plate with the Eurasia. The geodetically and geologically constrained displacement rates along the Chaman fault varies from about 18 mm/yr to about 35 mm/yr respectively throughout its total length of ~ 860 km. Two major hypothesis has been proposed by workers for these variations; i) Variations in rates of elastic strain accumulation along the plate boundary and, ii) strain partitioning along the plate boundary. Morphotectonic analysis is a very useful tool in investigations of spatial variations in tectonic activities both regionally and locally. This work uses morphotectonic analysis to investigate the degree of variations in active tectonic deformation, which can be directly related to elastic strain accumulation and other kinematics in the western boundary of the plate margin. Geomorphic mapping was carried out using remotely sensed data. ASTER and RADAR data were used in establishing Quaternary stratigraphy and measurement of geomorphic indices such as stream length gradient index, valley floor width to height ratio and, river/stream longitudinal profile within the study area. High resolution satellite images (e.g., IKONOS imagery) and 30m ASTER DEMs were employed to measure displacement recorded by landforms along individual strands of the fault. Results from geomorphic analysis shows three distinct levels of tectonic deformation. Areas showing high levels of tectonic deformation are characterized by displaced fan surfaces, deflected streams and beheaded streams. Terrestrial Cosmogenic nuclide surface exposure dating of the displaced landforms is being

  7. Digital accumulators in phase and frequency tracking loops

    NASA Technical Reports Server (NTRS)

    Hinedi, Sami; Statman, Joseph I.

    1990-01-01

    Results on the effects of digital accumulators in phase and frequency tracking loops are presented. Digital accumulators or summers are used extensively in digital signal processing to perform averaging or to reduce processing rates to acceptable levels. For tracking the Doppler of high-dynamic targets at low carrier-to-noise ratios, it is shown through simulation and experiment that digital accumulators can contribute an additional loss in operating threshold. This loss was not considered in any previous study and needs to be accounted for in performance prediction analysis. Simulation and measurement results are used to characterize the loss due to the digital summers for three different tracking loops: a digital phase-locked loop, a cross-product automatic frequency tracking loop, and an extended Kalman filter. The tracking algorithms are compared with respect to their frequency error performance and their ability to maintain lock during severe maneuvers at various carrier-to-noise ratios. It is shown that failure to account for the effect of accumulators can result in an inaccurate performance prediction, the extent of which depends highly on the algorithm used.

  8. Late 20th Century increase in South Pole snow accumulation

    USGS Publications Warehouse

    Mosley-Thompson, E.; Paskievitch, J.F.; Gow, A.J.; Thompson, L.G.

    1999-01-01

    A compilation of the 37-year history of net accumulation at the South Pole [Mosley-Thompson et al., 1995] suggests an increase in net annual accumulation since 1965. This record is sporadic and its quality is compromised by spatially restricted observations and nonsystematic measurement procedures. Results from a new, spatially extensive network of 236 accumulation poles document that the current 5-year (1992-1997) average annual net accumulation at the South Pole is 84.5??8.9 mm water equivalent (w.e.). This accumulation rate reflects a 30% increase since the 1960s when the best, although not optimal, records indicate that it was 65 mm w.e. Identification of two prominent beta radioactivity horizons (1954/1955 and 1964/1965) in six firn cores confirms an increase in accumulation since 1965. Viewed from a longer perspective of accumulation provided by ice cores and a snow mine study, the net accumulation of the 30-year period, 1965-1994, is the highest 30-year average of this millennium. Limited data suggest this recent accumulation increase extends beyond the South Pole region and may be characteristic of the high East Antarctic Plateau. Enhanced accumulation over the polar ice sheets has been identified as a potential early indicator of warmer sea surface temperatures and may offset a portion of the current rise in global sea level. Copyright 1999 by the American Geophysical Union.

  9. Under-canopy snow accumulation and ablation measured with airborne scanning LiDAR altimetry and in-situ instrumental measurements, southern Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Kirchner, P. B.; Bales, R. C.; Musselman, K. N.; Molotch, N. P.

    2012-12-01

    We investigated the influence of canopy on snow accumulation and melt in a mountain forest using paired snow on and snow off scanning LiDAR altimetry, synoptic measurement campaigns and in-situ time series data of snow depth, SWE, and radiation collected from the Kaweah River watershed, Sierra Nevada, California. Our analysis of forest cover classified by dominant species and 1 m2 grided mean under canopy snow accumulation calculated from airborne scanning LiDAR, demonstrate distinct relationships between forest class and under-canopy snow depth. The five forest types were selected from carefully prepared 1 m vegetation classifications and named for their dominant tree species, Giant Sequoia, Jeffrey Pine, White Fir, Red Fir, Sierra Lodgepole, Western White Pine, and Foxtail Pine. Sufficient LiDAR returns for calculating mean snow depth per m2 were available for 31 - 44% of the canopy covered area and demonstrate a reduction in snow depth of 12 - 24% from adjacent open areas. The coefficient of variation in snow depth under canopies ranged from 0.2 - 0.42 and generally decreased as elevation increased. Our analysis of snow density snows no statistical significance between snow under canopies and in the open at higher elevations with a weak significance for snow under canopies at lower elevations. Incident radiation measurements made at 15 minute intervals under forest canopies show an input of up to 150 w/m2 of thermal radiation from vegetation to the snow surface on forest plots. Snow accumulated on the mid to high elevation forested slopes of the Sierra Nevada represents the majority of winter snow storage. However snow estimates in forested environments demonstrate a high level of uncertainty due to the limited number of in-situ observations and the inability of most remote sensing platforms to retrieve reflectance under dense vegetation. Snow under forest canopies is strongly mediated by forest cover and decoupled from the processes that dictate accumulation

  10. Organic carbon accumulation in Brazilian mangal sediments

    NASA Astrophysics Data System (ADS)

    Sanders, Christian J.; Smoak, Joseph M.; Sanders, Luciana M.; Sathy Naidu, A.; Patchineelam, Sambasiva R.

    2010-12-01

    This study reviews the organic carbon (OC) accumulation rates in mangrove forests, margins and intertidal mudflats in geographically distinct areas along the Brazilian coastline (Northeastern to Southern). Our initial results indicate that the mangrove forests in the Northeastern region of Brazil are accumulating more OC (353 g/m 2/y) than in the Southeastern areas (192 g/m 2/y) being that the sediment accumulation rates, 2.8 and 2.5 mm/y, and OC content ˜7.1% and ˜5.8% (dry sediment weight) were contributing factors to the discrepancies between the forests. The intertidal mudflats on the other hand showed substantially greater OC accumulation rates, sedimentation rates and content 1129 g/m 2/y and 234 g/m 2/y; 7.3 and 3.4 mm/y; 10.3% and ˜2.7% (OC of dry sediment weight content), respectively, in the Northeastern compared to the Southeastern region. Mangrove forests in the South-Southeastern regions of Brazil may be more susceptible to the rising sea level, as they are geographically constricted by the vast mountain ranges along the coastline.

  11. The impact of EDTA on the rate of accumulation and root/shoot partitioning of cadmium in mature dwarf sunflowers.

    PubMed

    Meighan, Michelle M; Fenus, Taressa; Karey, Emma; MacNeil, Joseph

    2011-06-01

    In addition to increasing the mobility of metal ions in the soil solution, chelating agents such as EDTA have been reported to alter both the total metal accumulated by plants and its distribution within the plant structures. Here, mature Mini-Sun Hybrid dwarf sunflowers exposed to 300 μM Cd(2+) in hydroponic solution had initial translocation rates of at least 0.12 mmol kg(-1)h(-1) and reached leaf saturation levels within a day when a 3-fold molar excess of EDTA was used. EDTA also promoted cadmium transfer from roots to the shoots. A threefold excess of EDTA increased the translocation factor (TF) 100-fold, resulting in cadmium levels in the leaves of 580 μg g(-1) and extracting 1400 μg plant(-1). When plants were exposed to dissolved cadmium without EDTA, the vast majority of the metal remained bound to the exterior of the root. The initial accumulation could be successfully modeled with a standard biosorption pseudo second-order kinetic equation. Initial accumulation rates ranged from 0.0359 to 0.262 mg g(-1)min(-1). The cadmium binding could be cycled, and did not show evidence of saturation under the experimental conditions employed, suggesting it might be a viable biosorbant for aqueous cadmium. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. Inconsistencies between 14C and short-lived radionuclides-based sediment accumulation rates: Effects of long-term remineralization.

    PubMed

    Baskaran, M; Bianchi, T S; Filley, T R

    2017-08-01

    14 C is the most widely utilized geochronometer to investigate geological, geochemical and geophysical problems over the past 5 decades. Establishment of precise sedimentation rates is crucial for the reconstruction of paleo-climate, -ecological and - environmental studies when extrapolation of sedimentation rates is utilized for time scales beyond the dating range. However, agreement between short-term and long-term sedimentation rates in anthropogenically unperturbed sediment cores has not been shown. Here we show that the AMS 14 C-based long-term mass accumulation rate (MAR) of an organic-rich (>70%) sediment core from Mud Lake, Florida to be ∼5 times lower than the short-term MAR obtained using 239,240 Pu, 137 Cs and excess 210 Pb ( 210 Pb xs ). The measured sediment inventories of 210 Pb xs , 137 Cs and 239,240 Pu are comparable to the atmospheric fallout for the sampling site, indicating very little accelerated sediment erosion over the past several decades. Presence of sharp fallout peaks of 239,240 Pu indicates very little sediment mixing. The penetration depths of 137 Cs and 239,240 Pu were found to be much deeper than expected and this is attributed to their post-depositional mobility. MAR calculated using 14 C-ages in successive layers also indicated decreasing MARs with depth, and was reflective of progressive remineralization. Using first-order kinetics, the sediment remineralization rate was found to be 4.4 × 10 -4 y -1 and propose that over the long-term, remineralization of organic-rich sediment affected the long-term MAR, but not the ratio of 14 C/ 12 C. Thus, the MAR and linear sedimentation rate obtained using 14 C (and other isotope-based methods) could be erroneous, although 14 C ages may not be affected by such remineralization. Long-term remineralization rates of organic matter has a direct bearing on the biogeochemical cycling of elements in aqueous systems and mass balance of elements needs to be taken into consideration. Copyright

  13. Field assessment of innovative sensor for monitoring of sediment accumulation at inshore coral reefs.

    PubMed

    Thomas, Séverine; Ridd, Peter

    2005-01-01

    Sediment accumulation rate is a frequently required parameter in environmental and management studies, in particular near coral reefs where sediment accumulation can potentially cause severe impact. However, opportunities to obtain accurate sediment accumulation measurements are often limited by a lack of adequate instrumentation, in particular for high temporal resolution monitoring. For instance the traditional use of sediment traps, as the most widespread technique, offers poor temporal resolution (commonly of weeks) besides having significant hydrodynamic shortcomings. Therefore, a new optical backscatter sediment accumulation sensor (SAS) was developed to continuously measure in situ short-term sediment accumulation in sensitive riverine and coastal environments, enabling high temporal and vertical resolution (order of 1 h and with a deposited thickness resolution in the order of 20 microm respectively). This allows investigations of various parameters that influence accumulation: tides, current, waves, rain, or anthropogenic activity such as sediment dumping. This paper briefly describes the SAS and presents three field applications on nearshore coral reefs at Ishigaki Island (Japan), Lihir Island (Papua New Guinea), and Magnetic Island (Australia).

  14. Measurement of Outgassing Rates of Steels.

    PubMed

    Park, Chongdo; Kim, Se-Hyun; Ki, Sanghoon; Ha, Taekyun; Cho, Boklae

    2016-12-13

    Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of steels meet the criterion of low outgassing required for high or ultrahigh vacuum applications. However, a given material can present different outgassing rates depending on its manufacturing process or the various pretreatment processes involved during the fabrication. Thus, the measurement of outgassing rates is highly desirable for a specific vacuum application. For this reason, the rate-of-pressure rise (RoR) method is often used to measure the outgassing of hydrogen after bakeout. In this article, a detailed description of the design and execution of the experimental protocol involved in the RoR method is provided. The RoR method uses a spinning rotor gauge to minimize errors that stem from outgassing or the pumping action of a vacuum gauge. The outgassing rates of two ordinary steels (stainless steel and mild steel) were measured. The measurements were made before and after the heat pretreatment of the steels. The heat pretreatment of steels was performed to reduce the outgassing. Extremely low rates of outgassing (on the order of 10 - 11 Pa m 3 sec - 1 m - 2 ) can be routinely measured using relatively small samples.

  15. Rate of tree carbon accumulation increases continuously with tree size.

    PubMed

    Stephenson, N L; Das, A J; Condit, R; Russo, S E; Baker, P J; Beckman, N G; Coomes, D A; Lines, E R; Morris, W K; Rüger, N; Alvarez, E; Blundo, C; Bunyavejchewin, S; Chuyong, G; Davies, S J; Duque, A; Ewango, C N; Flores, O; Franklin, J F; Grau, H R; Hao, Z; Harmon, M E; Hubbell, S P; Kenfack, D; Lin, Y; Makana, J-R; Malizia, A; Malizia, L R; Pabst, R J; Pongpattananurak, N; Su, S-H; Sun, I-F; Tan, S; Thomas, D; van Mantgem, P J; Wang, X; Wiser, S K; Zavala, M A

    2014-03-06

    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.

  16. Rate of tree carbon accumulation increases continuously with tree size

    USGS Publications Warehouse

    Stephenson, N.L.; Das, A.J.; Condit, R.; Russo, S.E.; Baker, P.J.; Beckman, N.G.; Coomes, D.A.; Lines, E.R.; Morris, W.K.; Rüger, N.; Álvarez, E.; Blundo, C.; Bunyavejchewin, S.; Chuyong, G.; Davies, S.J.; Duque, Á.; Ewango, C.N.; Flores, O.; Franklin, J.F.; Grau, H.R.; Hao, Z.; Harmon, M.E.; Hubbell, S.P.; Kenfack, D.; Lin, Y.; Makana, J.-R.; Malizia, A.; Malizia, L.R.; Pabst, R.J.; Pongpattananurak, N.; Su, S.-H.; Sun, I-F.; Tan, S.; Thomas, D.; van Mantgem, P.J.; Wang, X.; Wiser, S.K.; Zavala, M.A.

    2014-01-01

    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle—particularly net primary productivity and carbon storage - increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to understand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.

  17. Variation of Accumulation Rates Over the Last Eight Centuries on the East Antarctic Plateau Derived from Volcanic Signals in Ice Cores

    NASA Technical Reports Server (NTRS)

    Anschuetz, H.; Sinisalo, A.; Isaksson, E.; McConnell, J. R.; Hamran, S.-E.; Bisiaux, M. M.; Pasteris, D.; Neumann, T. A.; Winther, J.-G.

    2011-01-01

    Volcanic signatures in ice-core records provide an excellent means to date the cores and obtain information about accumulation rates. From several ice cores it is thus possible to extract a spatio-temporal accumulation pattern. We show records of electrical conductivity and sulfur from firn cores from the Norwegian-USA scientific traverse during the International Polar Year 2007-2009 (IPY) through East Antarctica. Major volcanic eruptions are identified and used to assess century-scale accumulation changes. The largest changes seem to occur in the most recent decades with accumulation over the period 1963- 2007/08 being up to 25 % different from the long-term record. There is no clear overall trend, some sites show an increase in accumulation over the period 1963 to present while others show a decrease. Almost all of the sites above 3200 m above sea level (asl) suggest a decrease. These sites also show a significantly lower accumulation value than large-scale assessments both for the period 1963 to present and for the long-term mean at the respective drill sites. The spatial accumulation distribution is influenced mainly by elevation and distance to the ocean (continentality), as expected. Ground-penetrating radar data around the drill sites show a spatial variability within 10-20 % over several tens of kilometers, indicating that our drill sites are well representative for the area around them. Our results are important for large-scale assessments of Antarctic mass balance and model validation.

  18. Sediment accumulation in prairie wetlands under a changing climate: The relative roles of landscape and precipitation

    USGS Publications Warehouse

    Skagen, Susan K.; Burris, Lucy E.; Granfors, Diane A.

    2016-01-01

    Sediment accumulation threatens the viability and hydrologic functioning of many naturally formed depressional wetlands across the interior regions of North America. These wetlands provide many ecosystem services and vital habitats for diverse plant and animal communities. Climate change may further impact sediment accumulation rates in the context of current land use patterns. We estimated sediment accretion in wetlands within a region renowned for its large populations of breeding waterfowl and migrant shorebirds and examined the relative roles of precipitation and land use context in the sedimentation process. We modeled rates of sediment accumulation from 1971 through 2100 using the Revised Universal Soil Loss Equation (RUSLE) with a sediment delivery ratio and the Unit Stream Power Erosion Deposition model (USPED). These models predicted that by 2100, 21–33 % of wetlands filled completely with sediment and 27–46 % filled by half with sediments; estimates are consistent with measured sediment accumulation rates in the region reported by empirical studies. Sediment accumulation rates were strongly influenced by size of the catchment, greater coverage of tilled landscape within the catchment, and steeper slopes. Conservation efforts that incorporate the relative risk of infilling of wetlands with sediments, thus emphasizing areas of high topographic relief and large watersheds, may benefit wetland-dependent biota.

  19. Declining growth of Mauna Loa during the last 100,000 years: Rates of lava accumulation vs. gravitational subsidence

    NASA Astrophysics Data System (ADS)

    Lipman, Peter W.

    Long-term growth rates of Hawaiian volcanoes are difficult to determine because of the short historical record, problems in dating tholeiitic basalt by K-Ar methods, and concealment of lower volcanic flanks by 5 km of seawater. Combined geologic mapping, petrologic and geochemical studies, geochronologic determinations, marine studies, and scientific drilling have shown that, despite frequent large historical eruptions (avg. 1 per 7 years since mid 19th century), the lower subaerial flanks of Mauna Loa have grown little during the last hundred thousand years. Coastal lava-accumulation rates have averaged less than 2 mm/year since 10 to 100 ka along the Mauna Loa shoreline, slightly less than recent isostatic subsidence rates of 2.4-2.6 mm/yr. Since 30 ka, lava accumulation has been greatest on upper flanks of the volcano at times of summit caldera overflows; rift eruptions have been largely confined to vents at elevations above +2,500 m, and activity has diminished lower along both rift zones. Additional indicators of limited volcanic construction at lower levels and declining eruptive activity include: (1) extensive near-surface preservation of Pahala Ash along the southeast coast, dated as older than about 30 ka; (2) preservation in the Ninole Hills of block-slumped ancestral Mauna Loa lavas erupted at 100-200 ka; (3) preservation low in the subaerial Kealakekua landslide fault scarp of lavas newly dated by K-Ar as 166±53 ka; (4) preservation of submerged coral reefs (150 m depth) dated at 14 ka and fossil shoreline features (as much as 350-400 m depth), with estimated ages of 130-150 ka, that have survived without burial by younger Mauna Loa lavas and related ocean-entry debris; (5) incomplete filling of old landslide breakaway scars; (6) limited deposition of post-landslide lava on lower submarine slopes (accumulation mostly <1,000 m depth); and (7) decreased deformation and gravitational instability of the volcanic edifice. In addition, the estimated recent

  20. Economic stress in childhood and adulthood, and self-rated health: a population based study concerning risk accumulation, critical period and social mobility.

    PubMed

    Lindström, Martin; Hansen, Kristina; Rosvall, Maria

    2012-09-11

    Research in recent decades increasingly indicates the importance of conditions in early life for health in adulthood. Only few studies have investigated socioeconomic conditions in both childhood and adulthood in relation to health testing the risk accumulation, critical period, and social mobility hypotheses within the same setting. This study investigates the associations between economic stress in childhood and adulthood, and self-rated health with reference to the accumulation, critical period and social mobility hypotheses in life course epidemiology, taking demographic, social support, trust and lifestyle factors into account. The public health survey in Skåne (southern Sweden) in 2008 is a cross-sectional postal questionnaire study based on a random sample, in which 28,198 persons aged 18-80 years participated (55% participation). Logistic regression models were used to investigate associations between economic stress in childhood and adulthood, and self-rated health. Three life-course socioeconomic models concerning the association between economic stress and self-rated health (SRH) were investigated. The results showed a graded association between the combined effect of childhood and adulthood economic stress and poor SRH in accordance with the accumulation hypothesis. Furthermore, upward social mobility showed a protecting effect and downward mobility increased odds ratios of poor SRH in accordance with the social mobility hypothesis. High/severe economic stress exposures in both stages of life were independently associated with poor SRH in adulthood. Furthermore, stratifying the study population into six age groups showed similar odds ratios of poor SRH regarding economic stress exposure in childhood and adulthood in all age groups among both men and women. The accumulation and social mobility hypotheses were confirmed. The critical period model was confirmed in the sense that both economic stress in childhood and adulthood had independent effects on

  1. A mesocosm study using four native Hawaiian plants to assess nitrogen accumulation under varying surface water nitrogen concentrations.

    PubMed

    Unser, C U; Bruland, G L; Hood, A; Duin, K

    2010-01-01

    Accumulation of nitrogen (N) by native Hawaiian riparian plants from surface water was measured under a controlled experimental mesocosm setting. Four species, Cladium jamaicense, Cyperus javanicus, Cyperus laevigatus, and Cyperus polystachyos were tested for their ability to survive in coconut fiber coir log media with exposure to differing N concentrations. It was hypothesized that the selected species would have significantly different tissue total nitrogen (TN) concentrations, aboveground biomass, and TN accumulation rates because of habitat preference and physiological growth differences. A general linear model (GLM) analysis of variance (ANOVA) determined that species differences accounted for the greatest proportion of variance in tissue TN concentration, aboveground biomass growth, and accumulation rates, when compared with the other main effects (i.e. N concentration, time) and their interactions. A post hoc test of means demonstrated that C. jamaicense had significantly higher tissue TN concentration, aboveground biomass growth, and accumulation rates than the other species under all N concentrations. It was also hypothesized that tissue TN concentrations and biomass growth would increase in plants exposed to elevated N concentrations, however data did not support this hypothesis. Nitrogen accumulation rates by species were controlled by differences in plant biomass growth.

  2. Marine debris accumulation in the Northwestern Hawaiian Islands: an examination of rates and processes.

    PubMed

    Dameron, Oliver J; Parke, Michael; Albins, Mark A; Brainard, Russell

    2007-04-01

    Large amounts of derelict fishing gear accumulate and cause damage to shallow coral reefs of the Northwestern Hawaiian Islands (NWHI). To facilitate maintenance of reefs cleaned during 1996-2005 removal efforts, we identify likely high-density debris areas by assessing reef characteristics (depth, benthic habitat type, and energy regime) that influence sub-regional debris accumulation. Previously cleaned backreef and lagoonal reefs at two NWHI locations were resurveyed for accumulated debris using two survey methods. Accumulated debris densities and weights were found to be greater in lagoonal reef areas. Sample weight-based debris densities are extrapolated to similar habitats throughout the NWHI using a spatial 'net habitat' dataset created by generalizing IKONOS satellite derivatives for depth and habitat classification. Prediction accuracy for this dataset is tested using historical debris point data. Annual NWHI debris accumulation is estimated to be 52.0 metric tonnes. For planning purposes, individual NWHI atolls/reefs are allotted a proportion of this total.

  3. Variations in the accumulation, localization and rate of metabolization of selenium in mature Zea mays plants supplied with selenite or selenate.

    PubMed

    Longchamp, Mélanie; Castrec-Rouelle, Maryse; Biron, Philippe; Bariac, Thierry

    2015-09-01

    Quantification of selenium bioavailability from foods is a key challenge following the discovery of the antioxidant role of this micronutrient in human health. This study presents the uptake, accumulation and rate of metabolization in mature Zea mays plants grown in hydroponic solution supplemented with selenate or selenite. Selenium content was lower in plants supplemented with selenate and accumulated mainly in the leaves compared with selenite-treated plants where the selenium was retained in the roots. Selenite-treated grains accumulated more selenium. Selenate was metabolized less than selenite in whole plants, but in grains selenium was present exclusively as organic selenium compounds. For humans, the bioavailability of organic selenium was evaluated at 90% compared with only 50% for inorganic forms. Our results show that the potential for selenium bioavailability is increased with selenite treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Angular-Rate Estimation Using Quaternion Measurements

    NASA Technical Reports Server (NTRS)

    Azor, Ruth; Bar-Itzhack, Y.; Deutschmann, Julie K.; Harman, Richard R.

    1998-01-01

    In most spacecraft (SC) there is a need to know the SC angular rate. Precise angular rate is required for attitude determination, and a coarse rate is needed for attitude control damping. Classically, angular rate information is obtained from gyro measurements. These days, there is a tendency to build smaller, lighter and cheaper SC, therefore the inclination now is to do away with gyros and use other means and methods to determine the angular rate. The latter is also needed even in gyro equipped satellites when performing high rate maneuvers whose angular-rate is out of range of the on board gyros or in case of gyro failure. There are several ways to obtain the angular rate in a gyro-less SC. When the attitude is known, one can differentiate the attitude in whatever parameters it is given and use the kinematics equation that connects the derivative of the attitude with the satellite angular-rate and compute the latter. Since SC usually utilize vector measurements for attitude determination, the differentiation of the attitude introduces a considerable noise component in the computed angular-rate vector.

  5. Measurement of the magnetotail reconnection rate

    NASA Astrophysics Data System (ADS)

    Blanchard, G. T.; Lyons, L. R.; de la Beaujardière, O.; Doe, R. A.; Mendillo, M.

    1996-07-01

    A technique to measure the magnetotail reconnection rate from the ground is described and applied to 71 hours of measurements from 20 nights. The reconnection rate is obtained from the ionospheric flow across the polar cap boundary in the frame of reference of the boundary, measured by the Sondrestrom incoherent scatter radar. For our measurements, the polar cap boundary is located using 6300 Å auroral emissions and E region electron density. The average experimental uncertainty of the reconnection rate measurement is 11.6 mVm-1 in the ionospheric electric field. By using a large data set, we obtain the dependence of the reconnection rate on magnetic local time, the interplanetary magnetic field, and substorm activity, with much higher accuracy. We find that two thirds of the average polar cap potential drop occurs over the 4-hour segment of the separatrix centered on 2330 MLT, that the linear correlation between the reconnection electric field and the half-wave rectified dawn-dusk solar wind electric field VBs peaks between 1.0 and 1.5 hours, with a maximum linear correlation coefficient of 0.46 at 70 min; and that following substorm expansion phase onset, the reconnection electric field becomes larger than the experimental uncertainty, with an average delay of 23 min. The 70-min delay of the reconnection rate with respect to VBs is a typical convection time for a flux tube across the polar cap. This result indicates that reconnection in the magnetotail is influenced by the solar wind electric field VBs on the field line being reconnected.

  6. Accumulation of cadmium in tissue and its effect on live performance

    NASA Astrophysics Data System (ADS)

    Akyolcu, M. C.; Ozcelik, D.; Dursun, S.; Toplan, S.; Kahraman, R.

    2003-05-01

    Heavy metal pollution has gained more importance for environment as a result of increased industrialization rate all over the world. In present study investigation of effects of cadmium on live-weight due to accumulation in different tissues that taken in food were aimed. For such a purpose after their birth for four weeks chickens were fed by Cd added fodder (25 mg Cd/kg as cadmium sulfate). At the end offour weeks feeding period the chickens were scaled and sacrificed. For tissue cadmium level measurements, liver, kidney, muscle and bone dissections were performed on both experimental and same age contrai group animals. The measurements were performed in atomic absorption spectrophotometer. At the end of evaluation of data it was observed that live mean weight of experimental group was significantly lower than that of control group animals (p < 0.001). On the other hand tissue cadmium concentrations of experimental group were found to be significantly higher than that of control group values. So accumulation of cadmium in tissue as a heavy metal may lead decreased rate of growth.

  7. DISTRIBUTED AND ACCUMULATED REINFORCEMENT ARRANGEMENTS: EVALUATIONS OF EFFICACY AND PREFERENCE

    PubMed Central

    DELEON, ISER G.; CHASE, JULIE A.; FRANK-CRAWFORD, MICHELLE A.; CARREAU-WEBSTER, ABBEY B.; TRIGGS, MANDY M.; BULLOCK, CHRISTOPHER E.; JENNETT, HEATHER K.

    2015-01-01

    We assessed the efficacy of, and preference for, accumulated access to reinforcers, which allows uninterrupted engagement with the reinforcers but imposes an inherent delay required to first complete the task. Experiment 1 compared rates of task completion in 4 individuals who had been diagnosed with intellectual disabilities when reinforcement was distributed (i.e., 30-s access to the reinforcer delivered immediately after each response) and accumulated (i.e., 5-min access to the reinforcer after completion of multiple consecutive responses). Accumulated reinforcement produced response rates that equaled or exceeded rates during distributed reinforcement for 3 participants. Experiment 2 used a concurrent-chains schedule to examine preferences for each arrangement. All participants preferred delayed, accumulated access when the reinforcer was an activity. Three participants also preferred accumulated access to edible reinforcers. The collective results suggest that, despite the inherent delay, accumulated reinforcement is just as effective and is often preferred by learners over distributed reinforcement. PMID:24782203

  8. Distributed and accumulated reinforcement arrangements: evaluations of efficacy and preference.

    PubMed

    DeLeon, Iser G; Chase, Julie A; Frank-Crawford, Michelle A; Carreau-Webster, Abbey B; Triggs, Mandy M; Bullock, Christopher E; Jennett, Heather K

    2014-01-01

    We assessed the efficacy of, and preference for, accumulated access to reinforcers, which allows uninterrupted engagement with the reinforcers but imposes an inherent delay required to first complete the task. Experiment 1 compared rates of task completion in 4 individuals who had been diagnosed with intellectual disabilities when reinforcement was distributed (i.e., 30-s access to the reinforcer delivered immediately after each response) and accumulated (i.e., 5-min access to the reinforcer after completion of multiple consecutive responses). Accumulated reinforcement produced response rates that equaled or exceeded rates during distributed reinforcement for 3 participants. Experiment 2 used a concurrent-chains schedule to examine preferences for each arrangement. All participants preferred delayed, accumulated access when the reinforcer was an activity. Three participants also preferred accumulated access to edible reinforcers. The collective results suggest that, despite the inherent delay, accumulated reinforcement is just as effective and is often preferred by learners over distributed reinforcement. © Society for the Experimental Analysis of Behavior.

  9. Snow Densification and Recent Accumulation Along the iSTAR Traverse, Pine Island Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Morris, E. M.; Mulvaney, R.; Arthern, R. J.; Davies, D.; Gurney, R. J.; Lambert, P.; De Rydt, J.; Smith, A. M.; Tuckwell, R. J.; Winstrup, M.

    2017-12-01

    Neutron probe measurements of snow density from 22 sites in the Pine Island Glacier basin have been used to determine mean annual accumulation using an automatic annual layer identification routine. A mean density profile which can be used to convert radar two-way travel times to depth has been derived, and the effect of annual fluctuations in density on estimates of the depth of radar reflectors is shown to be insignificant, except very near the surface. Vertical densification rates have been derived from the neutron probe density profiles and from deeper firn core density profiles available at 9 of the sites. These rates are consistent with the rates predicted by the Herron and Langway model for stage 1 densification (by grain-boundary sliding, grain growth and intracrystalline deformation) and stage 2 densification (predominantly by sintering), except in a transition zone extending from ≈8 to ≈13 m from the surface in which 10-14% of the compaction occurs. Profiles of volumetric strain rate at each site show that in this transition zone the rates are consistent with the Arthern densification model. Comparison of the vertical densification rates and volumetric strain rates indicates that the expected relation to mean annual accumulation breaks down at high accumulation rates even when corrections are made for horizontal ice velocity divergence.

  10. Strain Partitioning and Accumulation across Overlapping Spreading Centers: Geodetic GPS Measurements in South Iceland

    NASA Astrophysics Data System (ADS)

    La Femina, P. C.; Dixon, T. H.; Malservisi, R.; Árnadóttir, T.; Sigmundsson, F.; Sturkell, E.

    2004-12-01

    Overlapping spreading centers (OSCs) and propagating ridges are important classes of mid-ocean ridges. Kinematic models of OSCs predict along strike variability in spreading rate associated with the propagation of one center and deactivation of the other. Iceland offers a unique opportunity to investigate strain accumulation and partitioning across slow, overlapping spreading centers, and the influence of a ridge centered hotspot on ridge kinematics and morphology. We present results of detailed GPS observations across the Eastern and Western Volcanic Zones, south Iceland, spanning a seven to nine year inter-rifting period, and compare our observations with two-dimensional elastic half-space models that simulate the long-term spreading process. We then compare the elastic half-space models with simple viscoelastic coupling models. We model three velocity profiles across the EVZ-WVZ system, solving for the spreading rate, locking depth and horizontal location of each spreading center. Our spreading rate estimates indicate along strike variations as expected in an OSC system and total spreading rates consistent with geodetic and geologic plate motion models. Spreading rates in the WVZ increase from northeast (3 ±1 mm/yr) to southwest (7 ±1 mm/yr). Spreading rates in the southwest propagating EVZ decrease from northeast (17 ±1 mm/yr) to southwest (12 ±1 mm/yr). These results are consistent with a model whereby the WVZ is deactivating in the direction of EVZ propagation. The morphology of the two spreading centers reflects the spreading rate differences and their location relative to the Iceland hotspot. The predicted locations of the spreading axis for each zone are consistent with mapped Holocene fissure swarms. The neovolcanic zone of the slower WVZ consists of a narrow (10-20 km wide) axial graben and has had few Holocene eruptions. The faster EVZ consists of two parallel neovolcanic zones separated by a 20 km gap of inactivity, little normal faulting, higher

  11. A closer look at the Neogene erosion and accumulation rate increase

    NASA Astrophysics Data System (ADS)

    Willenbring, J.; von Blanckenburg, F.

    2008-12-01

    Glacial erosion and Quaternary cold-stage warm-stage climate cycling have been cited as mechanisms to explain observations of increased Neogene marine sedimentation rates. Quantification of long-term glacial erosion rates from cosmogenic radionuclides from large areas mostly covered by cold-based ice during the Quaternary show very low erosion rates over several glacial cycles. In addition, isotope ratio proxies of dissolved metals in seawater, measured in chemical ocean sediments, lack clear evidence for an increase in terrigenous denudation. In particular, the stable isotope 9Be, derived from continental erosion, shows no change in its ratio to meteoric cosmogenic nuclide 10Be, derived from rain over the past 10 My. Radiogenic Pb and Nd isotopes, mainly show a change in the style of denudation from more chemical to more physical processes in the Quaternary. These data are at odds with a suggested increase in marine sedimentation rates during the late Cenozoic. In order to resolve this contradiction we have scrutinized these sedimentation rate calculations from ocean cores to identify whether they might show only apparent increases in the Neogene sections. Potential explanations are that in some cases, measured sediment thicknesses for different time intervals lack corrections for sediment compaction. Compaction of the lower portions of the cores drastically increases the apparent thickness of the more recent (Quaternary) sediment. In addition, sedimentation rates often only appear higher for recent sections in cores due to an artifact of an averaging timescale that decreases up-core. Such an averaging time scale decrease arises from better chronological resolution in recent times (Sadler et al., 1999). Cannibalization of older sediment might add to this effect. Together, these data question a clear, global-scale Quaternary climate-erosion connection that would be unique in Earth's history.

  12. Using strain rates to forecast seismic hazards

    USGS Publications Warehouse

    Evans, Eileen

    2017-01-01

    One essential component in forecasting seismic hazards is observing the gradual accumulation of tectonic strain accumulation along faults before this strain is suddenly released as earthquakes. Typically, seismic hazard models are based on geologic estimates of slip rates along faults and historical records of seismic activity, neither of which records actively accumulating strain. But this strain can be estimated by geodesy: the precise measurement of tiny position changes of Earth’s surface, obtained from GPS, interferometric synthetic aperture radar (InSAR), or a variety of other instruments.

  13. Processes and rates of sediment and wood accumulation in the headwater streams of the Oregon Coast Range, U.S.A.

    Treesearch

    C. L. May; R. E. Gresswell

    2003-01-01

    Abstract - Channels that have been scoured to bedrock by debris flows provide unique opportunities to calculate the rate of sediment and wood accumulation in low-order streams, to understand the temporal succession of channel morphology following disturbance, and to make inferences about processes associated with input and transport of sediment. Dendrochronology was...

  14. Accumulating Data to Optimally Predict Obesity Treatment (ADOPT) Core Measures: Psychosocial Domain.

    PubMed

    Sutin, Angelina R; Boutelle, Kerri; Czajkowski, Susan M; Epel, Elissa S; Green, Paige A; Hunter, Christine M; Rice, Elise L; Williams, David M; Young-Hyman, Deborah; Rothman, Alexander J

    2018-04-01

    Within the Accumulating Data to Optimally Predict obesity Treatment (ADOPT) Core Measures Project, the psychosocial domain addresses how psychosocial processes underlie the influence of obesity treatment strategies on weight loss and weight maintenance. The subgroup for the psychosocial domain identified an initial list of high-priority constructs and measures that ranged from relatively stable characteristics about the person (cognitive function, personality) to dynamic characteristics that may change over time (motivation, affect). This paper describes (a) how the psychosocial domain fits into the broader model of weight loss and weight maintenance as conceptualized by ADOPT; (b) the guiding principles used to select constructs and measures for recommendation; (c) the high-priority constructs recommended for inclusion; (d) domain-specific issues for advancing the science; and (e) recommendations for future research. The inclusion of similar measures across trials will help to better identify how psychosocial factors mediate and moderate the weight loss and weight maintenance process, facilitate research into dynamic interactions with factors in the other ADOPT domains, and ultimately improve the design and delivery of effective interventions. © 2018 The Obesity Society.

  15. Toward relaxed eddy accumulation measurements of sediment-water exchange in aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Lemaire, Bruno J.; Noss, Christian; Lorke, Andreas

    2017-09-01

    Solute transport across the sediment-water interface has major implications for water quality and biogeochemical cycling in aquatic ecosystems. Existing measurement techniques, however, are not capable of resolving sediment-water fluxes of most constituents under in situ flow conditions. We investigated whether relaxed eddy accumulation (REA), a micrometeorological technique with conditional sampling of turbulent updrafts and downdrafts, can be adapted to the aquatic environment. We simulated REA fluxes by reanalyzing eddy covariance measurements from a riverine lake. We found that the empirical coefficient that relates mass fluxes to the concentration difference between both REA samples is invariant with scalar and flow and responds as predicted by a joint Gaussian distribution of linearly correlated variables. Simulated REA fluxes differed on average by around 30% from eddy covariance fluxes (mean absolute error). Assessment of the lower quantification limit suggests that REA can potentially be applied for measuring benthic fluxes of a new range of constituents that cannot be assessed by standard eddy covariance methods.

  16. Soil and biomass carbon re-accumulation after landslide disturbances

    NASA Astrophysics Data System (ADS)

    Schomakers, Jasmin; Jien, Shih-Hao; Lee, Tsung-Yu; Huang-Chuan, Jr.; Hseu, Zeng-Yei; Lin, Zan Liang; Lee, Li-Chin; Hein, Thomas; Mentler, Axel; Zehetner, Franz

    2017-07-01

    In high-standing islands of the Western Pacific, typhoon-triggered landslides occasionally strip parts of the landscape of its vegetative cover and soil layer and export large amounts of biomass and soil organic carbon (OC) from land to the ocean. After such disturbances, new vegetation colonizes the landslide scars and OC starts to re-accumulate. In the subtropical mountains of Taiwan and in other parts of the world, bamboo (Bambusoideae) species may invade at a certain point in the succession of recovering landslide scars. Bamboo has a high potential for carbon sequestration because of its fast growth and dense rooting system. However, it is still largely unknown how these properties translate into soil OC re-accumulation rates after landslide disturbance. In this study, a chronosequence was established on four former landslide scars in the Central Mountain Range of Taiwan, ranging in age from 6 to 41 years post disturbance as determined by landslide mapping from remote sensing. The younger landslide scars were colonized by Miscanthus floridulus, while after approx. 15 to 20 years of succession, bamboo species (Phyllostachys) were dominating. Biomass and soil OC stocks were measured on the recovering landslide scars and compared to an undisturbed Cryptomeria japonica forest stand in the area. After initially slow re-vegetation, biomass carbon accumulated in Miscanthus stands with mean annual accretion rates of 2 ± 0.5 Mg C ha- 1 yr- 1. Biomass carbon continued to increase after bamboo invasion and reached 40% of that in the reference forest site after 41 years of landslide recovery. Soil OC accumulation rates were 2.0 Mg C ha- 1 yr- 1, 6 to 41 years post disturbance reaching 64% of the level in the reference forest. Our results from this in-situ study suggest that recovering landslide scars are strong carbon sinks once an initial lag period of vegetation re-establishment is overcome.

  17. Dual physiological rate measurement instrument

    NASA Technical Reports Server (NTRS)

    Cooper, Tommy G. (Inventor)

    1990-01-01

    The object of the invention is to provide an instrument for converting a physiological pulse rate into a corresponding linear output voltage. The instrument which accurately measures the rate of an unknown rectangular pulse wave over an extended range of values comprises a phase-locked loop including a phase comparator, a filtering network, and a voltage-controlled oscillator, arranged in cascade. The phase comparator has a first input responsive to the pulse wave and a second input responsive to the output signal of the voltage-controlled oscillator. The comparator provides a signal dependent on the difference in phase and frequency between the signals appearing on the first and second inputs. A high-input impedance amplifier accepts an output from the filtering network and provides an amplified output DC signal to a utilization device for providing a measurement of the rate of the pulse wave.

  18. Accuracy of smartphone apps for heart rate measurement.

    PubMed

    Coppetti, Thomas; Brauchlin, Andreas; Müggler, Simon; Attinger-Toller, Adrian; Templin, Christian; Schönrath, Felix; Hellermann, Jens; Lüscher, Thomas F; Biaggi, Patric; Wyss, Christophe A

    2017-08-01

    Background Smartphone manufacturers offer mobile health monitoring technology to their customers, including apps using the built-in camera for heart rate assessment. This study aimed to test the diagnostic accuracy of such heart rate measuring apps in clinical practice. Methods The feasibility and accuracy of measuring heart rate was tested on four commercially available apps using both iPhone 4 and iPhone 5. 'Instant Heart Rate' (IHR) and 'Heart Fitness' (HF) work with contact photoplethysmography (contact of fingertip to built-in camera), while 'Whats My Heart Rate' (WMH) and 'Cardiio Version' (CAR) work with non-contact photoplethysmography. The measurements were compared to electrocardiogram and pulse oximetry-derived heart rate. Results Heart rate measurement using app-based photoplethysmography was performed on 108 randomly selected patients. The electrocardiogram-derived heart rate correlated well with pulse oximetry ( r = 0.92), IHR ( r = 0.83) and HF ( r = 0.96), but somewhat less with WMH ( r = 0.62) and CAR ( r = 0.60). The accuracy of app-measured heart rate as compared to electrocardiogram, reported as mean absolute error (in bpm ± standard error) was 2 ± 0.35 (pulse oximetry), 4.5 ± 1.1 (IHR), 2 ± 0.5 (HF), 7.1 ± 1.4 (WMH) and 8.1 ± 1.4 (CAR). Conclusions We found substantial performance differences between the four studied heart rate measuring apps. The two contact photoplethysmography-based apps had higher feasibility and better accuracy for heart rate measurement than the two non-contact photoplethysmography-based apps.

  19. Metal accumulation in marine bivalves under various tributyltin burdens.

    PubMed

    Tang, Chuan-Ho; Lin, Chan-Shing; Wang, Wei-Hsien

    2009-11-01

    In the present study, a field survey was conducted to measure the accumulation of butyltin, Cu, Zn, and Cd in green mussels (Perna viridis) and Pacific oysters (Crassostrea gigas) at the regions along a tributyltin pollution gradient. A negative correlation was found between the tributyltin/total butyltin ratio (0.87-0.31) and tributyltin content (114-5,817 ng/g as tin dry wt) in oysters, while the Cu content (44.2-381 mg/kg dry wt) was positively correlated with the logarithm of tributyltin content during the summer and winter. This suggests that as the tributyltin burden increases, the rates of tributyltin metabolism may be elevated, leading to enhanced Cu accumulation. A similar accumulation pattern for Zn was also found in oysters. In mussels, however, the tributyltin/total butyltin ratio and the Cu and Zn contents remained relatively constant (~ 0.7, 12, and 100 mg/kg dry wt, respectively) regardless of the tributyltin burden. Clearly, the butyltin and Cu/Zn accumulation processes in oysters differ from those in mussels under tributyltin pollution. These observations provide valuable information for those who evaluate or compare tributyltin and/or Cu/Zn pollution using oysters and mussels as bioindicators.

  20. The Accumulating Data to Optimally Predict Obesity Treatment (ADOPT) Core Measures Project: Rationale and Approach.

    PubMed

    MacLean, Paul S; Rothman, Alexander J; Nicastro, Holly L; Czajkowski, Susan M; Agurs-Collins, Tanya; Rice, Elise L; Courcoulas, Anita P; Ryan, Donna H; Bessesen, Daniel H; Loria, Catherine M

    2018-04-01

    Individual variability in response to multiple modalities of obesity treatment is well documented, yet our understanding of why some individuals respond while others do not is limited. The etiology of this variability is multifactorial; however, at present, we lack a comprehensive evidence base to identify which factors or combination of factors influence treatment response. This paper provides an overview and rationale of the Accumulating Data to Optimally Predict obesity Treatment (ADOPT) Core Measures Project, which aims to advance the understanding of individual variability in response to adult obesity treatment. This project provides an integrated model for how factors in the behavioral, biological, environmental, and psychosocial domains may influence obesity treatment responses and identify a core set of measures to be used consistently across adult weight-loss trials. This paper provides the foundation for four companion papers that describe the core measures in detail. The accumulation of data on factors across the four ADOPT domains can inform the design and delivery of effective, tailored obesity treatments. ADOPT provides a framework for how obesity researchers can collectively generate this evidence base and is a first step in an ongoing process that can be refined as the science advances. © 2018 The Obesity Society.

  1. Hospital performance measures and 30-day readmission rates.

    PubMed

    Stefan, Mihaela S; Pekow, Penelope S; Nsa, Wato; Priya, Aruna; Miller, Lauren E; Bratzler, Dale W; Rothberg, Michael B; Goldberg, Robert J; Baus, Kristie; Lindenauer, Peter K

    2013-03-01

    Lowering hospital readmission rates has become a primary target for the Centers for Medicare & Medicaid Services, but studies of the relationship between adherence to the recommended hospital care processes and readmission rates have provided inconsistent and inconclusive results. To examine the association between hospital performance on Medicare's Hospital Compare process quality measures and 30-day readmission rates for patients with acute myocardial infarction (AMI), heart failure and pneumonia, and for those undergoing major surgery. We assessed hospital performance on process measures using the 2007 Hospital Inpatient Quality Reporting Program. The process measures for each condition were aggregated in two separate measures: Overall Measure (OM) and Appropriate Care Measure (ACM) scores. Readmission rates were calculated using Medicare claims. Risk-standardized 30-day all-cause readmission rate was calculated as the ratio of predicted to expected rate standardized by the overall mean readmission rate. We calculated predicted readmission rate using hierarchical generalized linear models and adjusting for patient-level factors. Among patients aged ≥ 66 years, the median OM score ranged from 79.4 % for abdominal surgery to 95.7 % for AMI, and the median ACM scores ranged from 45.8 % for abdominal surgery to 87.9 % for AMI. We observed a statistically significant, but weak, correlation between performance scores and readmission rates for pneumonia (correlation coefficient R = 0.07), AMI (R = 0.10), and orthopedic surgery (R = 0.06). The difference in the mean readmission rate between hospitals in the 1st and 4th quartiles of process measure performance was statistically significant only for AMI (0.25 percentage points) and pneumonia (0.31 percentage points). Performance on process measures explained less than 1 % of hospital-level variation in readmission rates. Hospitals with greater adherence to recommended care processes did not achieve

  2. Uridine prevents tamoxifen-induced liver lipid droplet accumulation

    PubMed Central

    2014-01-01

    Background Tamoxifen, an agonist of estrogen receptor, is widely prescribed for the prevention and long-term treatment of breast cancer. A side effect of tamoxifen is fatty liver, which increases the risk for non-alcoholic fatty liver disease. Prevention of tamoxifen-induced fatty liver has the potential to improve the safety of long-term tamoxifen usage. Methods Uridine, a pyrimidine nucleoside with reported protective effects against drug-induced fatty liver, was co-administered with tamoxifen in C57BL/6J mice. Liver lipid levels were evaluated with lipid visualization using coherent anti-Stokes Raman scatting (CARS) microscopy, biochemical assay measurement of triacylglyceride (TAG), and liquid chromatography coupled with mass spectrometry (LC-MS) measurement of membrane phospholipid. Blood TAG and cholesterol levels were measured. Mitochondrial respiration of primary hepatocytes in the presence of tamoxifen and/or uridine was evaluated by measuring oxygen consumption rate with an extracellular flux analyzer. Liver protein lysine acetylation profiles were evaluated with 1D and 2D Western blots. In addition, the relationship between endogenous uridine levels, fatty liver, and tamoxifen administration was evaluated in transgenic mice UPase1−/−and UPase1-TG. Results Uridine co-administration prevented tamoxifen-induced liver lipid droplet accumulation in mice. The most prominent effect of uridine co-administration with tamoxifen was the stimulation of liver membrane phospholipid biosynthesis. Uridine had no protective effect against tamoxifen-induced impairment to mitochondrial respiration of primary hepatocytes or liver TAG and cholesterol export. Uridine had no effect on tamoxifen-induced changes to liver protein acetylation profile. Transgenic mice UPase1−/−with increased pyrimidine salvage activity were protected against tamoxifen-induced liver lipid droplet accumulation. In contrast, UPase1-TG mice with increased pyrimidine catabolism activity had

  3. Uridine prevents tamoxifen-induced liver lipid droplet accumulation.

    PubMed

    Le, Thuc T; Urasaki, Yasuyo; Pizzorno, Giuseppe

    2014-05-23

    Tamoxifen, an agonist of estrogen receptor, is widely prescribed for the prevention and long-term treatment of breast cancer. A side effect of tamoxifen is fatty liver, which increases the risk for non-alcoholic fatty liver disease. Prevention of tamoxifen-induced fatty liver has the potential to improve the safety of long-term tamoxifen usage. Uridine, a pyrimidine nucleoside with reported protective effects against drug-induced fatty liver, was co-administered with tamoxifen in C57BL/6J mice. Liver lipid levels were evaluated with lipid visualization using coherent anti-Stokes Raman scatting (CARS) microscopy, biochemical assay measurement of triacylglyceride (TAG), and liquid chromatography coupled with mass spectrometry (LC-MS) measurement of membrane phospholipid. Blood TAG and cholesterol levels were measured. Mitochondrial respiration of primary hepatocytes in the presence of tamoxifen and/or uridine was evaluated by measuring oxygen consumption rate with an extracellular flux analyzer. Liver protein lysine acetylation profiles were evaluated with 1D and 2D Western blots. In addition, the relationship between endogenous uridine levels, fatty liver, and tamoxifen administration was evaluated in transgenic mice UPase1-/-and UPase1-TG. Uridine co-administration prevented tamoxifen-induced liver lipid droplet accumulation in mice. The most prominent effect of uridine co-administration with tamoxifen was the stimulation of liver membrane phospholipid biosynthesis. Uridine had no protective effect against tamoxifen-induced impairment to mitochondrial respiration of primary hepatocytes or liver TAG and cholesterol export. Uridine had no effect on tamoxifen-induced changes to liver protein acetylation profile. Transgenic mice UPase1-/-with increased pyrimidine salvage activity were protected against tamoxifen-induced liver lipid droplet accumulation. In contrast, UPase1-TG mice with increased pyrimidine catabolism activity had intrinsic liver lipid droplet

  4. Simultaneous measurement at multiple depths of in situ rates of denitrification in the bed of a groundwater-fed river

    NASA Astrophysics Data System (ADS)

    Lansdown, Katrina; Trimmer, Mark; Heppell, Kate

    2010-05-01

    Typically characterised by steep chemical gradients and variable redox conditions, the hyporheic zone is considered a 'hotpot' or site of enhanced biogeochemical activity in the aquatic environment. As such the importance of the hyporheic zone for the attenuation of nutrients such as nitrate in a fluvial network has long been recognised. Controls on nitrogen transformations, however, especially at depths greater than 10cm below the sediment-water interface, remain comparatively less understood. Most work aimed at quantifying denitrification in the hyporheic zone has involved laboratory incubation of recovered sediments which is likely to affect the estimate of the true in situ rate. Results of such studies are usually cited as 'potential' rates of denitrification and have undoubtedly improved the understanding of nitrogen cycling in the aquatic environment. There is, however, a need for in situ measurement to improve our knowledge of nitrogen cycling in the river bed. Here, rates of denitrification in the hyporheic zone have been measured at multiple depths, simultaneously using 'push-pull' methodology (e.g. Snodgrass and Kitanidis 1998). The 'push-pull' technique involves injection of a solution containing reactant(s) (e.g. nitrate) and a conservative tracer (e.g. chloride) into the sediment and extraction of pore water samples over time. Recovered samples are screened for the removal of reactant(s) and/or the accumulation of products(s). Temporal changes in the conservative tracer are used to correct the concentration of the reactant(s) and product(s) for dispersion and advection. The disadvantage of the 'traditional' 'push-pull' methodology is that rates of nitrate removal are measured rather than rates of denitrification. In this research, comparison of measured and 'corrected' nitrate concentrations allowed the rate of nitrate removal (or production) to be quantified. In order to determine in situ rates of denitrification we used 15N-enriched nitrate as the

  5. Can Observation Skills of Citizen Scientists Be Estimated Using Species Accumulation Curves?

    PubMed

    Kelling, Steve; Johnston, Alison; Hochachka, Wesley M; Iliff, Marshall; Fink, Daniel; Gerbracht, Jeff; Lagoze, Carl; La Sorte, Frank A; Moore, Travis; Wiggins, Andrea; Wong, Weng-Keen; Wood, Chris; Yu, Jun

    2015-01-01

    Volunteers are increasingly being recruited into citizen science projects to collect observations for scientific studies. An additional goal of these projects is to engage and educate these volunteers. Thus, there are few barriers to participation resulting in volunteer observers with varying ability to complete the project's tasks. To improve the quality of a citizen science project's outcomes it would be useful to account for inter-observer variation, and to assess the rarely tested presumption that participating in a citizen science projects results in volunteers becoming better observers. Here we present a method for indexing observer variability based on the data routinely submitted by observers participating in the citizen science project eBird, a broad-scale monitoring project in which observers collect and submit lists of the bird species observed while birding. Our method for indexing observer variability uses species accumulation curves, lines that describe how the total number of species reported increase with increasing time spent in collecting observations. We find that differences in species accumulation curves among observers equates to higher rates of species accumulation, particularly for harder-to-identify species, and reveals increased species accumulation rates with continued participation. We suggest that these properties of our analysis provide a measure of observer skill, and that the potential to derive post-hoc data-derived measurements of participant ability should be more widely explored by analysts of data from citizen science projects. We see the potential for inferential results from analyses of citizen science data to be improved by accounting for observer skill.

  6. Can Observation Skills of Citizen Scientists Be Estimated Using Species Accumulation Curves?

    PubMed Central

    Kelling, Steve; Johnston, Alison; Hochachka, Wesley M.; Iliff, Marshall; Fink, Daniel; Gerbracht, Jeff; Lagoze, Carl; La Sorte, Frank A.; Moore, Travis; Wiggins, Andrea; Wong, Weng-Keen; Wood, Chris; Yu, Jun

    2015-01-01

    Volunteers are increasingly being recruited into citizen science projects to collect observations for scientific studies. An additional goal of these projects is to engage and educate these volunteers. Thus, there are few barriers to participation resulting in volunteer observers with varying ability to complete the project’s tasks. To improve the quality of a citizen science project’s outcomes it would be useful to account for inter-observer variation, and to assess the rarely tested presumption that participating in a citizen science projects results in volunteers becoming better observers. Here we present a method for indexing observer variability based on the data routinely submitted by observers participating in the citizen science project eBird, a broad-scale monitoring project in which observers collect and submit lists of the bird species observed while birding. Our method for indexing observer variability uses species accumulation curves, lines that describe how the total number of species reported increase with increasing time spent in collecting observations. We find that differences in species accumulation curves among observers equates to higher rates of species accumulation, particularly for harder-to-identify species, and reveals increased species accumulation rates with continued participation. We suggest that these properties of our analysis provide a measure of observer skill, and that the potential to derive post-hoc data-derived measurements of participant ability should be more widely explored by analysts of data from citizen science projects. We see the potential for inferential results from analyses of citizen science data to be improved by accounting for observer skill. PMID:26451728

  7. Growth, nitrogen accumulation and nitrogen transfer by legume species established on mine spoils

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

    Jefferies, R.A.; Bradshaw, A.D.; Putwain, P.D.

    1981-12-01

    Nitrogen deficiency is an important factor limiting plant growth on many types of mine and mineral spoils. One method of overcoming this problem is to use legume species which are able to accumulate nitrogen in such spoils. The growth, nitrogen accumulation and nitrogen transfer to a companion species was compared in contrasting legume species established on colliery spoil and on sand waste from the extraction of china clay. Legumes can be effective means of accumulating nitrogen in such spoils with rates as high as 295 kg N ha/sup -1/ yr/sup -1/ being measured for Lupinus perennis sown on sand waste.more » Nitrogen transfer from legumes to a companion grass was also apparent. Trifolium repens sown on colliery spoil increased the nitrogen content of the companion grass by 76 kg ha/sup -1/ within 2 yr of sowing. It is concluded that a wider range of legume species than conventionally used is available, offering greater tolerance of the extreme conditions of mine spoils combined with high rates of nitrogen accumulation. It is necessary to develop reclamation strategies which incorporate such species.« less

  8. Low acetate concentrations favor polyphosphate-accumulating organisms over glycogen-accumulating organisms in enhanced biological phosphorus removal from wastewater.

    PubMed

    Tu, Yunjie; Schuler, Andrew J

    2013-04-16

    Glycogen-accumulating organisms (GAOs) are thought to compete with polyphosphate-accumulating organisms (PAOs) in enhanced biological phosphorus removal (EBPR) wastewater treatment systems. A laboratory sequencing batch reactor (SBR) was operated for one year to test the hypothesis that PAOs have a competitive advantage at low acetate concentrations, with a focus on low pH conditions previously shown to favor GAOs. PAOs dominated the system under conventional SBR operation with rapid acetate addition (producing high in-reactor concentrations) and pH values of 7.4-8.4. GAOs dominated when the pH was decreased (6.4-7.0). Decreasing the acetate addition rate led to very low reactor acetate concentrations, and PAOs recovered, supporting the study hypothesis. When the acetate feed rate was increased, EBPR failed again. Dominant PAOs and GAOs were Candidatus Accumulibacter phosphatis and Defluviicoccus Cluster 2, respectively, according to fluorescent in situ hybridization and 454 pyrosequencing. Surprisingly, GAOs were not the immediate causes of PAO failures, based on functional and population measurements. Pyrosequencing results suggested Dechloromonas and Tetrasphaera spp. may have also been PAOs, and additional potential GAOs were also identified. Full-scale systems typically have lower in-reactor acetate concentrations than laboratory SBRs, and so, previous laboratory studies may have overestimated the practical importance of GAOs as causes of EBPR failure.

  9. Heritability of Performance Deficit Accumulation During Acute Sleep Deprivation in Twins

    PubMed Central

    Kuna, Samuel T.; Maislin, Greg; Pack, Frances M.; Staley, Bethany; Hachadoorian, Robert; Coccaro, Emil F.; Pack, Allan I.

    2012-01-01

    Study Objectives: To determine if the large and highly reproducible interindividual differences in rates of performance deficit accumulation during sleep deprivation, as determined by the number of lapses on a sustained reaction time test, the Psychomotor Vigilance Task (PVT), arise from a heritable trait. Design: Prospective, observational cohort study. Setting: Academic medical center. Participants: There were 59 monozygotic (mean age 29.2 ± 6.8 [SD] yr; 15 male and 44 female pairs) and 41 dizygotic (mean age 26.6 ± 7.6 yr; 15 male and 26 female pairs) same-sex twin pairs with a normal polysomnogram. Interventions: Thirty-eight hr of monitored, continuous sleep deprivation. Measurements and Results: Patients performed the 10-min PVT every 2 hr during the sleep deprivation protocol. The primary outcome was change from baseline in square root transformed total lapses (response time ≥ 500 ms) per trial. Patient-specific linear rates of performance deficit accumulation were separated from circadian effects using multiple linear regression. Using the classic approach to assess heritability, the intraclass correlation coefficients for accumulating deficits resulted in a broad sense heritability (h2) estimate of 0.834. The mean within-pair and among-pair heritability estimates determined by analysis of variance-based methods was 0.715. When variance components of mixed-effect multilevel models were estimated by maximum likelihood estimation and used to determine the proportions of phenotypic variance explained by genetic and nongenetic factors, 51.1% (standard error = 8.4%, P < 0.0001) of twin variance was attributed to combined additive and dominance genetic effects. Conclusion: Genetic factors explain a large fraction of interindividual variance among rates of performance deficit accumulations on PVT during sleep deprivation. Citation: Kuna ST; Maislin G; Pack FM; Staley B; Hachadoorian R; Coccaro EF; Pack AI. Heritability of performance deficit accumulation

  10. CONCEPTUAL MODEL FOR ORIGIN OF ABNORMALLY PRESSURED GAS ACCUMULATIONS IN LOW-PERMEABILITY RESERVOIRS.

    USGS Publications Warehouse

    Law, B.E.; Dickinson, W.W.

    1985-01-01

    The paper suggests that overpressured and underpressured gas accumulations of this type have a common origin. In basins containing overpressured gas accumulations, rates of thermogenic gas accumulation exceed gas loss, causing fluid (gas) pressure to rise above the regional hydrostatic pressure. Free water in the larger pores is forced out of the gas generation zone into overlying and updip, normally pressured, water-bearing rocks. While other diagenetic processes continue, a pore network with very low permeability develops. As a result, gas accumulates in these low-permeability reservoirs at rates higher than it is lost. In basins containing underpressured gas accumulations, rates of gas generation and accumulation are less than gas loss. The basin-center gas accumulation persists, but because of changes in the basin dynamics, the overpressured accumulation evolves into an underpressured system.

  11. Accumulating Data to Optimally Predict Obesity Treatment (ADOPT) Core Measures: Behavioral Domain.

    PubMed

    Lytle, Leslie A; Nicastro, Holly L; Roberts, Susan B; Evans, Mary; Jakicic, John M; Laposky, Aaron D; Loria, Catherine M

    2018-04-01

    The ability to identify and measure behaviors that are related to weight loss and the prevention of weight regain is crucial to understanding the variability in response to obesity treatment and the development of tailored treatments. The overarching goal of the Accumulating Data to Optimally Predict obesity Treatment (ADOPT) Core Measures Project is to provide obesity researchers with guidance on a set of constructs and measures that are related to weight control and that span and integrate obesity-related behavioral, biological, environmental, and psychosocial domains. This article describes how the behavioral domain subgroup identified the initial list of high-priority constructs and measures to be included, and it describes practical considerations for assessing the following four behavioral areas: eating, activity, sleep, and self-monitoring of weight. Challenges and considerations for advancing the science related to weight loss and maintenance behaviors are also discussed. Assessing a set of core behavioral measures in combination with those from other ADOPT domains is critical to improve our understanding of individual variability in response to adult obesity treatment. The selection of behavioral measures is based on the current science, although there continues to be much work needed in this field. © 2018 The Obesity Society.

  12. Patterns and controls of mercury accumulation in sediments from three thermokarst lakes on the Arctic Coastal Plain of Alaska

    USGS Publications Warehouse

    Burke, Samantha M.; Zimmerman, Christian E.; Branfireun, Brian A.; Koch, Joshua C.; Swanson, Heidi K.

    2018-01-01

    The biogeochemical cycle of mercury will be influenced by climate change, particularly at higher latitudes. Investigations of historical mercury accumulation in lake sediments inform future predictions as to how climate change might affect mercury biogeochemistry; however, in regions with a paucity of data, such as the thermokarst-rich Arctic Coastal Plain of Alaska (ACP), the trajectory of mercury accumulation in lake sediments is particularly uncertain. Sediment cores from three thermokarst lakes on the ACP were analyzed to understand changes in, and drivers of, Hg accumulation over the past ~ 100 years. Mercury accumulation in two of the three lakes was variable and high over the past century (91.96 and 78.6 µg/m2/year), and largely controlled by sedimentation rate. Mercury accumulation in the third lake was lower (14.2 µg/m2/year), more temporally uniform, and was more strongly related to sediment Hg concentration than sedimentation rate. Sediment mercury concentrations were quantitatively related to measures of sediment composition and VRS-inferred chlorophyll a, and sedimentation rates were related to various catchment characteristics. These results were compared to data from 37 previously studied Arctic and Alaskan lakes. Results from the meta-analysis indicate that thermokarst lakes have significantly higher and more variable Hg accumulation rates than non-thermokarst lakes, suggesting that certain properties (e.g., thermal erosion, thaw slumping, low hydraulic conductivity) likely make lakes prone to high and variable Hg accumulation rates. Differences and high variability in Hg accumulation among high latitude lakes highlight the complexity of predicting future climate-related change impacts on mercury cycling in these environments.

  13. Arctic Circle Traverse 2010 (ACT-10): South East Greenland snow accumulation variability from firn coring and ice sounding radar

    NASA Astrophysics Data System (ADS)

    Forster, R. R.; Miege, C.; Box, J. E.; McConnell, J.; Spikes, V. B.; Burgess, E. W.

    2010-12-01

    The Greenland Ice Sheet plays an important role in Earth’s climate system evolution. The snow accumulation rate is the largest single mass budget term. With only 14% of the ice sheet area, Southeast Greenland contains the highest accumulation rates, accounting for one third of the total snow accumulation and annual variability. The high accumulation rates have made the region less desirable for long climate record ice cores and therefore, contain relatively very few in situ measurements to constrain the ice sheet mass budget. We present annual snow accumulation rates from the Arctic Circle Traverse 2010 (ACT-10). During April and May 2010 we acquired three 50 m firn cores connected by surface-based 400 MHz ground penetrating radar (GPR) in Southeast Greenland. The traverse repeated and extended the original Arctic Circle Traverse in 2004 (Spikes et al., 2004). Dating is achieved using geochemical analysis of the cores to identify isochronal layers detected by the GPR yielding annual accumulation estimates along the traverse between the core sites. The 300 km ACT-10 GPR snowmobile traverse extended the ACT-04 path 80 km to the lowest elevation core site at 1776 m. Meanwhile, airborne radars, operating as part of NASA’s Operation IceBridge also acquired data over the full length of the ACT-10 path, simultaneously with a portion of the traverse and within days for the remaining segments. The IceBridge and ACT-10 data are to be combined in a calibration effort such that snow accumulation rates may be mapped elsewhere in Greenland and even in Antarctica.

  14. ACCUMULATION RATE OF MICROBIAL BIOMASS AT TWO PERMEABLE REACTIVE BARRIER SITES

    EPA Science Inventory

    Accumulation of mineral precipitates and microbial biomass are key factors that impact the long-term performance of in-situ Permeable Reactive Barriers for treating contaminated groundwater. Both processes can impact remedial performance by decreasing zero-valent iron reactivity...

  15. Impact of slope inclination on salt accumulation

    NASA Astrophysics Data System (ADS)

    Nachshon, Uri

    2017-04-01

    Field measurements indicated on high variability in salt accumulation along natural and cultivated slopes, even for relatively homogeneous soil conditions. It was hypothesised that slope inclination has an impact on the location of salt accumulation along the slope. A set of laboratory experiments and numerical models were used to explore the impact of slope inclination on salt accumulation. It was shown, experimentally, that for conditions of saline water source at the lower boundary of the slope - salt accumulates in low concentrations and homogeneously along the entire slope, for moderate slopes. However, as inclination increases high salt concentrations were observed at the upper parts of the slope, leaving the lower parts of the slope relatively free of salt. The traditional flow and transport models did not predict the experimental observations as they indicated also for the moderate slopes on salt accumulation in the elevated parts of the slope, away of the saline water source. Consequently - a conceptual model was raised to explain the laboratory observations. It was suggested that the interactions between slope angle, evaporation rates, hydraulic conductivity of the medium and distribution of wetness along the slope affect the saline water flow path through the medium. This lead to preferential flow path close to the soil-atmosphere interface for the steep slopes, which leads to constant wash of the salts from the evaporation front upward towards the slope upper parts, whereas for the moderate slopes, flow path is below the soil-atmosphere interface, therefore salt that accumulates at the evaporation front is not being transported upward. Understanding of salt dynamics along slopes is important for agricultural and natural environments, as well as for civil engineering purposes. Better understanding of the salt transport processes along slopes will improve our ability to minimize and to cope with soil salinization processes. The laboratory experiments and

  16. True cadence and step accumulation are not equivalent: the effect of intermittent claudication on free-living cadence.

    PubMed

    Stansfield, B; Clarke, C; Dall, P; Godwin, J; Holdsworth, R; Granat, M

    2015-02-01

    'True cadence' is the rate of stepping during the period of stepping. 'Step accumulation' is the steps within an epoch of time (e.g. 1min). These terms have been used interchangeably in the literature. These outcomes are compared within a population with intermittent claudication (IC). Multiday, 24h stepping activity of those with IC (30) and controls (30) was measured objectively using the activPAL physical activity monitor. 'True cadence' and 'step accumulation' outcomes were calculated. Those with IC took fewer steps/d 6531±2712 than controls 8692±2945 (P=0.003). However, these steps were taken within approximately the same number of minute epochs (IC 301±100min/d; controls 300±70min/d, P=0.894) with only slightly lower true cadence (IC 69 (IQ 66,72) steps/min; controls 72 (IQ 68,76) steps/min, P=0.026), giving substantially lower step accumulation (IC 22 (IQ 19,24) steps/min; controls 30 (IQ 23,34) steps/min) (P<0.001). However, the true cadence of stepping within the blocks of the 1, 5, 20, 30 and 60min with the maximum number of steps accumulated was lower for those with IC than controls (P<0.05). Those with IC took 1300 steps fewer per day above a true cadence of 90 steps/min. True cadence and step accumulation outcomes were radically different for the outcomes examined. 'True cadence' and 'step accumulation' were not equivalent in those with IC or controls. The measurement of true cadence in the population of people with IC provides information about their stepping rate during the time they are stepping. True cadence should be used to correctly describe the rate of stepping as performed. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Accumulating Data to Optimally Predict Obesity Treatment (ADOPT) Core Measures: Environmental Domain.

    PubMed

    Saelens, Brian E; Arteaga, S Sonia; Berrigan, David; Ballard, Rachel M; Gorin, Amy A; Powell-Wiley, Tiffany M; Pratt, Charlotte; Reedy, Jill; Zenk, Shannon N

    2018-04-01

    There is growing interest in how environment is related to adults' weight and activity and eating behaviors. However, little is known about whether environmental factors are related to the individual variability seen in adults' intentional weight loss or maintenance outcomes. The environmental domain subgroup of the Accumulating Data to Optimally Predict obesity Treatment (ADOPT) Core Measures Project sought to identify a parsimonious set of objective and perceived neighborhood and social environment constructs and corresponding measures to include in the assessment of response to adult weight-loss treatment. Starting with the home address, the environmental domain subgroup recommended for inclusion in future weight-loss or maintenance studies constructs and measures related to walkability, perceived land use mix, food outlet accessibility (perceived and objective), perceived food availability, socioeconomics, and crime-related safety (perceived and objective) to characterize the home neighborhood environment. The subgroup also recommended constructs and measures related to social norms (perceived and objective) and perceived support to characterize an individual's social environment. The 12 neighborhood and social environment constructs and corresponding measures provide a succinct and comprehensive set to allow for more systematic examination of the impact of environment on adults' weight loss and maintenance. © 2018 The Obesity Society.

  18. 19 CFR 10.534 - Accumulation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Singapore Free Trade Agreement Rules of Origin § 10.534 Accumulation. (a) Originating materials of Singapore or the United States that...

  19. Measuring Your Peak Flow Rate

    MedlinePlus

    ... Living with Asthma > Managing Asthma Measuring Your Peak Flow Rate Download Instructions A peak flow meter is ... to use. Who Benefits from Using a Peak Flow Meter? Many healthcare providers believe that people who ...

  20. 19 CFR 10.458 - Accumulation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Chile Free Trade Agreement Rules of Origin § 10.458 Accumulation. (a) Originating goods or materials of Chile or the United States...

  1. Angular-Rate Estimation Using Star Tracker Measurements

    NASA Technical Reports Server (NTRS)

    Azor, R.; Bar-Itzhack, I.; Deutschmann, Julie K.; Harman, Richard R.

    1999-01-01

    This paper presents algorithms for estimating the angular-rate vector of satellites using quaternion measurements. Two approaches are compared, one that uses differentiated quatemion measurements to yield coarse rate measurements which are then fed into two different estimators. In the other approach the raw quatemion measurements themselves are fed directly into the two estimators. The two estimators rely on the ability to decompose the non-linear rate dependent part of the rotational dynamics equation of a rigid body into a product of an angular-rate dependent matrix and the angular-rate vector itself This decomposition, which is not unique, enables the treatment of the nonlinear spacecraft dynamics model as a linear one and, consequently, the application of a Pseudo-Linear Kalman Filter (PSELIKA). It also enables the application of a special Kalman filter which is based on the use of the solution of the State Dependent Algebraic Riccati Equation (SDARE) in order to compute the Kalman gain matrix and thus eliminates the need to propagate and update the filter covariance matrix. The replacement of the elaborate rotational dynamics by a simple first order Markov model is also examined. In this paper a special consideration is given to the problem of delayed quatemion measurements. Two solutions to this problem are suggested and tested. Real Rossi X-Ray Timing Explorer (RXTE) data is used to test these algorithms, and results of these tests are presented.

  2. Angular-Rate Estimation using Star Tracker Measurements

    NASA Technical Reports Server (NTRS)

    Azor, R.; Bar-Itzhack, Itzhack Y.; Deutschmann, Julie K.; Harman, Richard R.

    1999-01-01

    This paper presents algorithms for estimating the angular-rate vector of satellites using quaternion measurements. Two approaches are compared, one that uses differentiated quaternion measurements to yield coarse rate measurements which are then fed into two different estimators. In the other approach the raw quaternion measurements themselves are fed directly into the two estimators. The two estimators rely on the ability to decompose the non-linear rate dependent part of the rotational dynamics equation of a rigid body into a product of an angular-rate dependent matrix and the angular-rate vector itself. This decomposition, which is not unique, enables the treatment of the nonlinear spacecraft dynamics model as a linear one and, consequently, the application of a Pseudo-Linear Kalman Filter (PSELIKA). It also enables the application of a special Kalman filter which is based on the use of the solution of the State Dependent Algebraic Riccati Equation (SDARE) in order to compute the Kalman gain matrix and thus eliminates the need to propagate and update the filter covariance matrix. The replacement of the elaborate rotational dynamics by a simple first order Markov model is also examined. In this paper a special consideration is given to the problem of delayed quaternion measurements. Two solutions to this problem are suggested and tested. Real Rossi X-Ray Timing Explorer (RXTE) data is used to test these algorithms, and results of these tests are presented.

  3. Carbon accumulation and sequestration of lakes in China during the Holocene.

    PubMed

    Wang, Mei; Chen, Huai; Yu, Zicheng; Wu, Jianghua; Zhu, Qiu'an; Peng, Changhui; Wang, Yanfen; Qin, Boqiang

    2015-12-01

    Understanding the responses of lake systems to past climate change and human activity is critical for assessing and predicting the fate of lake carbon (C) in the future. In this study, we synthesized records of the sediment accumulation from 82 lakes and of C sequestration from 58 lakes with direct organic C measurements throughout China. We also identified the controlling factors of the long-term sediment and C accumulation dynamics in these lakes during the past 12 ka (1 ka = 1000 cal yr BP). Our results indicated an overall increasing trend of sediment and C accumulation since 12 ka, with an accumulation peak in the last couple of millennia for lakes in China, corresponding to terrestrial organic matter input due to land-use change. The Holocene lake sediment accumulation rate (SAR) and C accumulation rate (CAR) averaged (mean ± SE) 0.47 ± 0.05 mm yr(-1) and 7.7 ± 1.4 g C m(-2)  yr(-1) in China, respectively, comparable to the previous estimates for boreal and temperate regions. The SAR for lakes in the East Plain of subtropical China (1.05 ± 0.28 mm yr(-1) ) was higher than those in other regions (P < 0.05). However, CAR did not vary significantly among regions. Overall, the variability and history of climate and anthropogenic interference regulated the temporal and spatial dynamics of sediment and C sequestration for lakes in China. We estimated the total amount of C burial in lakes of China as 8.0 ± 1.0 Pg C. This first estimation of total C storage and dynamics in lakes of China confirms the importance of lakes in land C budget in monsoon-influenced regions. © 2015 John Wiley & Sons Ltd.

  4. Progressive addition lenses--measurements and ratings.

    PubMed

    Sheedy, Jim; Hardy, Raymond F; Hayes, John R

    2006-01-01

    This study is a followup to a previous study in which the optics of several progressive addition lens (PALs) designs were measured and analyzed. The objective was to provide information about various PAL designs to enable eye care practitioners to select designs based on the particular viewing requirements of the patient. The optical properties of 12 lenses of the same power for each of 23 different PAL designs were measured with a Rotlex Class Plus lens analyzer. Lenses were ordered through optical laboratories and specified to be plano with a +2.00 diopters add. Measurements were normalized to plano at the manufacturer-assigned location for the distance power to eliminate laboratory tolerance errors. The magnitude of unwanted astigmatism and the widths and areas of the distance, intermediate, and near viewing zones were calculated from the measured data according to the same criteria used in a previous study. The optical characteristics of the different PAL designs were significantly different from one another. The differences were significant in terms of the sizes and widths of the viewing zones, the amount of unwanted astigmatism, and the minimum fitting height. Ratings of the distance, intermediate, and near viewing areas were calculated for each PAL design based on the widths and sizes of those zones. Ratings for unwanted astigmatism and recommended minimum fitting heights were also determined. Ratings based on combinations of viewing zone ratings are also reported. The ratings are intended to be used to select a PAL design that matches the particular visual needs of the patient and to evaluate the success and performance of currently worn PALs. Reasoning and task analyses suggest that these differences can be used to select a PAL design to meet the individual visual needs of the patient; clinical trials studies are required to test this hypothesis.

  5. Aluminum X-ray mass-ablation rate measurements

    DOE PAGES

    Kline, John L.; Hager, Jonathan D.

    2016-10-15

    Measurements of the mass ablation rate of aluminum (Al) have been completed at the Omega Laser Facility. Measurements of the mass-ablation rate show Al is higher than plastic (CH), comparable to high density carbon (HDC), and lower than beryllium. The mass-ablation rate is consistent with predictions using a 1D Lagrangian code, Helios. Lastly, the results suggest Al capsules have a reasonable ablation pressure even with a higher albedo than beryllium or carbon ablators warranting further investigation into the viability of Al capsules for ignition should be pursued.

  6. Discharge rate measurements in a canal using radiotracer methods.

    PubMed

    Pant, H J; Goswami, Sunil; Biswal, Jayashree; Samantray, J S; Sharma, V K

    2016-06-01

    Discharge rates of water were measured in a canal using radiotracer methods with an objective to validate the efficacy of Concrete Volute Pumps (CVPs) installed at various pumping stations along the canal. Pulse velocity and dilution methods were applied to measure the discharge rates using Iodine-131 as a radiotracer. The discharge rate measured in one of the sections of the canal using the pulse velocity method was found to be 22.5m(3)/s, whereas the discharge rates measured using the dilution method in four different sections of the canal varied from 20.27 to 20.62m(3)/s with single CVP in operation. The standard error in discharge rate measurements using dilution method ranged from ±1.1 to ±1.8%. The experimentally measured values of the discharge rate were in good agreement with the design value of the discharge rate (20m(3)/s) thus validating the performance of the CVPs used in the canal. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Strain accumulation and rotation in the Eastern California Shear Zone

    USGS Publications Warehouse

    Savage, J.C.; Gan, Weijun; Svarc, J.L.

    2001-01-01

    Although the Eastern California Shear Zone (ECSZ) (strike ???N25??W) does not quite coincide with a small circle drawn about the Pacific-North America pole of rotation, trilateration and GPS measurements demonstrate that the motion within the zone corresponds to right-lateral simple shear across a vertical plane (strike N33??W??5??) roughly parallel to the tangent to that local small circle (strike ???N40??W). If the simple shear is released by slip on faults subparallel to the shear zone, the accumulated rotation is also released, leaving no secular rotation. South of the Garlock fault the principal faults (e.g., Calico-Blackwater fault) strike ???N40??W, close enough to the strike of the vertical plane across which maximum right-lateral shear accumulates to almost wholly accommodate that accumulation of both strain and rotation by right-lateral slip. North of the Garlock fault dip slip as well as strike slip on the principal faults (strike ???N20??W) is required to accommodate the simple shear accumulation. In both cases the accumulated rotation is released with the shear strain. The Garlock fault, which transects the ECSZ, is not offset by north-northwest striking faults nor, despite geological evidence for long-term left-lateral slip, does it appear at the present time to be accumulating left-lateral simple shear strain across the fault due to slip at depth. Rather the motion is explained by right-lateral simple shear across the orthogonal ECSZ. Left-lateral slip on the Garlock fault will release the shear strain accumulating there but would augment the accumulating rotation, resulting in a secular clockwise rotation rate ???80 nrad yr-1 (4.6?? Myr-1).

  8. Accuracy of real time radiography burning rate measurement

    NASA Astrophysics Data System (ADS)

    Olaniyi, Bisola

    The design of a solid propellant rocket motor requires the determination of a propellant's burning-rate and its dependency upon environmental parameters. The requirement that the burning-rate be physically measured, establishes the need for methods and equipment to obtain such data. A literature review reveals that no measurement has provided the desired burning rate accuracy. In the current study, flash x-ray modeling and digitized film-density data were employed to predict motor-port area to length ratio. The pre-fired port-areas and base burning rate were within 2.5% and 1.2% of their known values, respectively. To verify the accuracy of the method, a continuous x-ray and a solid propellant rocket motor model (Plexiglas cylinder) were used. The solid propellant motor model was translated laterally through a real-time radiography system at different speeds simulating different burning rates. X-ray images were captured and the burning-rate was then determined. The measured burning rate was within 1.65% of the known values.

  9. 29 CFR 530.202 - Piece rates-work measurement.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... different types of items produced using stop watch time studies or other work measurement methods... Hour Division. (b) The fact that an employer bases piece rates on work measurements which indicate that... 29 Labor 3 2010-07-01 2010-07-01 false Piece rates-work measurement. 530.202 Section 530.202 Labor...

  10. The effects of moderately high temperature on zeaxanthin accumulation and decay.

    PubMed

    Zhang, Ru; Kramer, David M; Cruz, Jeffrey A; Struck, Kimberly R; Sharkey, Thomas D

    2011-09-01

    Moderately high temperature reduces photosynthetic capacities of leaves with large effects on thylakoid reactions of photosynthesis, including xanthophyll conversion in the lipid phase of the thylakoid membrane. In previous studies, we have found that leaf temperature of 40°C increased zeaxanthin accumulation in dark-adapted, intact tobacco leaves following a brief illumination, but did not change the amount of zeaxanthin in light-adatped leaves. To investigate heat effects on zeaxanthin accumulation and decay, zeaxanthin level was monitored optically in dark-adapted, intact tobacco and Arabidopsis thaliana leaves at either 23 or 40°C under 45-min illumination. Heated leaves had more zeaxanthin following 3-min light but had less or comparable amounts of zeaxanthin by the end of 45 min of illumination. Zeaxanthin accumulated faster at light initiation and decayed faster upon darkening in leaves at 40°C than leaves at 23°C, indicating that heat increased the activities of both violaxanthin de-epoxidase (VDE) and zeaxanthin epoxidase (ZE). In addition, our optical measurement demonstrated in vivo that weak light enhances zeaxanthin decay relative to darkness in intact leaves of tobacco and Arabidopsis, confirming previous observations in isolated spinach chloroplasts. However, the maximum rate of decay is similar for weak light and darkness, and we used the maximum rate of decay following darkness as a measure of the rate of ZE during steady-state light. A simulation indicated that high temperature should cause a large shift in the pH dependence of the amount of zeaxanthin in leaves because of differential effects on VDE and ZE. This allows for the reduction in ΔpH caused by heat to be offset by increased VDE activity relative to ZE.

  11. Dynamic Modeling of the Main Blow in Basic Oxygen Steelmaking Using Measured Step Responses

    NASA Astrophysics Data System (ADS)

    Kattenbelt, Carolien; Roffel, B.

    2008-10-01

    In the control and optimization of basic oxygen steelmaking, it is important to have an understanding of the influence of control variables on the process. However, important process variables such as the composition of the steel and slag cannot be measured continuously. The decarburization rate and the accumulation rate of oxygen, which can be derived from the generally measured waste gas flow and composition, are an indication of changes in steel and slag composition. The influence of the control variables on the decarburization rate and the accumulation rate of oxygen can best be determined in the main blow period. In this article, the measured step responses of the decarburization rate and the accumulation rate of oxygen to step changes in the oxygen blowing rate, lance height, and the addition rate of iron ore during the main blow are presented. These measured step responses are subsequently used to develop a dynamic model for the main blow. The model consists of an iron oxide and a carbon balance and an additional equation describing the influence of the lance height and the oxygen blowing rate on the decarburization rate. With this simple dynamic model, the measured step responses can be explained satisfactorily.

  12. Precision of NO2 photolysis rate measurements

    NASA Technical Reports Server (NTRS)

    Dickerson, R. R.; Stedman, D. H.

    1980-01-01

    Gas-phase kinetic calculations indicate that actinometric measurements of the rate of solar photolysis of NO2 in nitrogen can be in error by +5 to -15% or more, unless odd oxygen N2O5 chemistry, and trace oxygen content are considered. A field experiment confirms that the effect of the quartz tube on the measured photolysis rate is less than 1.7%.

  13. Measuring and modelling the impact of the bark beetle forest disturbance on snow accumulation and ablation at a plot scale

    NASA Astrophysics Data System (ADS)

    Jenicek, Michal; Matejka, Ondrej; Hotovy, Ondrej

    2017-04-01

    The knowledge of water volume stored in the snowpack and its spatial distribution is important to predict the snowmelt runoff. The objective of this study was to quantify the role of different forest structures on the snowpack distribution at a plot scale during snow accumulation and snow ablation periods. Special interest was put in the role of the forest affected by the bark beetle (Ips typographus). We performed repeated detailed manual field survey at selected mountain plots with different canopy structure located at the same elevation and without influence of topography and wind on the snow distribution. The forest canopy structure was described using parameters calculated from hemispherical photographs, such as canopy closure, leaf area index (LAI) and potential irradiance. Additionally, we used shortwave radiation measured using CNR4 Net radiometers placed in plots with different canopy structure. Two snow accumulation and ablation models were set-up to simulate the snow water equivalent (SWE) in plots with different vegetation cover. First model was physically-based using the energy balance approach, second model was conceptual and it was based on the degree-day approach. Both models accounted for snow interception in different forest types using LAI as a parameter. The measured SWE in the plot with healthy forest was on average by 41% lower than in open area during snow accumulation period. The disturbed forest caused the SWE reduction by 22% compared to open area indicating increasing snow storage after forest defoliation. The snow ablation in healthy forest was by 32% slower compared to open area. On the contrary, the snow ablation in disturbed forest (due to the bark beetle) was on average only by 7% slower than in open area. The relative decrease in incoming solar radiation in the forest compared to open area was much bigger compared to the relative decrease in snowmelt rates. This indicated that the decrease in snowmelt rates cannot be explained only

  14. Angular-Rate Estimation Using Delayed Quaternion Measurements

    NASA Technical Reports Server (NTRS)

    Azor, R.; Bar-Itzhack, I. Y.; Harman, R. R.

    1999-01-01

    This paper presents algorithms for estimating the angular-rate vector of satellites using quaternion measurements. Two approaches are compared one that uses differentiated quaternion measurements to yield coarse rate measurements, which are then fed into two different estimators. In the other approach the raw quaternion measurements themselves are fed directly into the two estimators. The two estimators rely on the ability to decompose the non-linear part of the rotas rotational dynamics equation of a body into a product of an angular-rate dependent matrix and the angular-rate vector itself. This non unique decomposition, enables the treatment of the nonlinear spacecraft (SC) dynamics model as a linear one and, thus, the application of a PseudoLinear Kalman Filter (PSELIKA). It also enables the application of a special Kalman filter which is based on the use of the solution of the State Dependent Algebraic Riccati Equation (SDARE) in order to compute the gain matrix and thus eliminates the need to compute recursively the filter covariance matrix. The replacement of the rotational dynamics by a simple Markov model is also examined. In this paper special consideration is given to the problem of delayed quaternion measurements. Two solutions to this problem are suggested and tested. Real Rossi X-Ray Timing Explorer (RXTE) data is used to test these algorithms, and results are presented.

  15. Instability of bottom-water redox conditions during accumulation of Quaternary sediment in the Japan Sea

    USGS Publications Warehouse

    Piper, D.Z.; Isaacs, C.M.

    1996-01-01

    The concentrations of Cd, Cr, Cu, Mo, Ni, Sb, U, V, and Zn were measured in early Quaternary sediment (1.32 to 1.08 Ma) from the Oki Ridge in the Japan Sea. The elements were partitioned between a detrital fraction, composed of terrigenous and volcaniclastic aluminosilicate debris, and a marine fraction, composed of biogenic and hydrogenous debris derived from seawater. The most important factors controlling minor-element accumulation rates in the marine fraction were (1) primary productivity in the photic zone, which largely controlled the flux of particulate organic-matter-bound minor elements settling through the water column and onto the seafloor, and (2) bottom-water redox, which determined the suite of elements that accumulated directly from seawater. This marine fraction of minor elements on Oki Ridge recorded six periods of high minor-element abundance. Assuming a constant bulk sediment accumulation rate, each period lasted roughly 5,000 to 10,000 years with a 41,000-year cycle. Accumulation rates of individual elements such as Cd, Mo, and U suggest sulfate-reducing conditions were established in the bottom water during the 10,000-year periods; accumulation rates of Cr and V during the intervening periods are indicative of less reducing, denitrifying conditions. Interelement ratios, for example, Cu:Mo, V:Cr, and Sb:Mo, further reflect bottom-water instability, such that bottom-water redox actually varied from sulfate reducing to denitrifying during the periods of highest minor-element accumulation rates; it varied from denitrifying to oxidizing during the intervening periods. Sediment lithology supports these interpretations of the minor-element distributions; the sediment is finely laminated for several of the periods represented by Cd, Mo, and U maxima and weakly laminated to bioturbated for the intervening periods. The geochemistry of this sediment demonstrates the unambiguous signal of Mo, principally, but of several other minor elements as well in

  16. Hamming and Accumulator Codes Concatenated with MPSK or QAM

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Samuel

    2009-01-01

    In a proposed coding-and-modulation scheme, a high-rate binary data stream would be processed as follows: 1. The input bit stream would be demultiplexed into multiple bit streams. 2. The multiple bit streams would be processed simultaneously into a high-rate outer Hamming code that would comprise multiple short constituent Hamming codes a distinct constituent Hamming code for each stream. 3. The streams would be interleaved. The interleaver would have a block structure that would facilitate parallelization for high-speed decoding. 4. The interleaved streams would be further processed simultaneously into an inner two-state, rate-1 accumulator code that would comprise multiple constituent accumulator codes - a distinct accumulator code for each stream. 5. The resulting bit streams would be mapped into symbols to be transmitted by use of a higher-order modulation - for example, M-ary phase-shift keying (MPSK) or quadrature amplitude modulation (QAM). The novelty of the scheme lies in the concatenation of the multiple-constituent Hamming and accumulator codes and the corresponding parallel architectures of the encoder and decoder circuitry (see figure) needed to process the multiple bit streams simultaneously. As in the cases of other parallel-processing schemes, one advantage of this scheme is that the overall data rate could be much greater than the data rate of each encoder and decoder stream and, hence, the encoder and decoder could handle data at an overall rate beyond the capability of the individual encoder and decoder circuits.

  17. Estimation of uptake rate constants for PCB congeners accumulated by semipermeable membrane devices and brown treat (Salmo trutta)

    USGS Publications Warehouse

    Meadows, J.C.; Echols, K.R.; Huckins, J.N.; Borsuk, F.A.; Carline, R.F.; Tillitt, D.E.

    1998-01-01

    The triolein-filled semipermeable membrane device (SPMD) is a simple and effective method of assessing the presence of waterborne hydrophobic chemicals. Uptake rate constants for individual chemicals are needed to accurately relate the amounts of chemicals accumulated by the SPMD to dissolved water concentrations. Brown trout and SPMDs were exposed to PCB- contaminated groundwater in a spring for 28 days to calculate and compare uptake rates of specific PCB congeners by the two matrixes. Total PCB congener concentrations in water samples from the spring were assessed and corrected for estimated total organic carbon (TOC) sorption to estimate total dissolved concentrations. Whole and dissolved concentrations averaged 4.9 and 3.7 ??g/L, respectively, during the exposure. Total concentrations of PCBs in fish rose from 0.06 to 118.3 ??g/g during the 28-day exposure, while concentrations in the SPMD rose from 0.03 to 203.4 ??g/ g. Uptake rate constants (k1) estimated for SPMDs and brown trout were very similar, with k1 values for SPMDs ranging from one to two times those of the fish. The pattern of congener uptake by the fish and SPMDs was also similar. The rates of uptake generally increased or decreased with increasing K(ow), depending on the assumption of presence or absence of TOC.The triolein-filled semipermeable membrane device (SPMD) is a simple and effective method of assessing the presence of waterborne hydrophobic chemicals. Uptake rate constants for individual chemicals are needed to accurately relate the amounts of chemicals accumulated by the SPMB to dissolved water concentrations. Brown trout and SPMDs were exposed to PCB-contaminated groundwater in a spring for 28 days to calculate and compare uptake rates of specific PCB congeners by the two matrixes. Total PCB congener concentrations in water samples from the spring were assessed and corrected for estimated total organic carbon (TOC) sorption to estimate total dissolved concentrations. Whole and

  18. Measuring radiative capture rates at DRAGON

    NASA Astrophysics Data System (ADS)

    Hager, U.; Davids, B.; Fallis, J.; Greife, U.; Hutcheon, D. A.; Rojas, A.; Ruiz, C.

    2013-04-01

    The DRAGON recoil separator facility is located at the ISAC facility at TRIUMF, Vancouver. It is designed to measure radiative alpha and proton capture reactions of astrophysical importance in inverse kinematics. The Supernanogan ion source at ISAC provides stable beams of high intensities. The DRAGON collaboration has taken advantage of this over the last years by measuring several reactions requiring high-intensity stable oxygen beams. In particular,the ^17O(p,γ) and ^16O(α,γ) reaction rates were recently measured. The former reaction is part of the hot CNO cycle, and strongly influences the abundance of ^18F in classical novae. Because of its relatively long lifetime, ^18F is a possible target for satellite-based gamma-ray spectroscopy. The ^16O(α,γ) reaction plays a role in steady-state helium burning in massive stars, where it follows the ^12C(α,γ) reaction. At astrophysically relevant energies, the reaction proceeds exclusively via direct capture, resulting in a low rate. In both cases, the unique capabilities of DRAGON enabled determination not only of the total reaction rates, but also of decay branching ratios. Results from both experiments will be presented.

  19. Rhizosphere Bacteria Enhance Selenium Accumulation and Volatilization by Indian Mustard1

    PubMed Central

    de Souza, Mark P.; Chu, Dara; Zhao, May; Zayed, Adel M.; Ruzin, Steven E.; Schichnes, Denise; Terry, Norman

    1999-01-01

    Indian mustard (Brassica juncea L.) accumulates high tissue Se concentrations and volatilizes Se in relatively nontoxic forms, such as dimethylselenide. This study showed that the presence of bacteria in the rhizosphere of Indian mustard was necessary to achieve the best rates of plant Se accumulation and volatilization of selenate. Experiments with the antibiotic ampicillin showed that bacteria facilitated 35% of plant Se volatilization and 70% of plant tissue accumulation. These results were confirmed by inoculating axenic plants with rhizosphere bacteria. Compared with axenic controls, plants inoculated with rhizosphere bacteria had 5-fold higher Se concentrations in roots (the site of volatilization) and 4-fold higher rates of Se volatilization. Plants with bacteria contained a heat-labile compound in their root exudate; when this compound was added to the rhizosphere of axenic plants, Se accumulation in plant tissues increased. Plants with bacteria had an increased root surface area compared with axenic plants; the increased area was unlikely to have caused their increased tissue Se accumulation because they did not accumulate more Se when supplied with selenite or selenomethionine. Rhizosphere bacteria also possibly increased plant Se volatilization because they enabled plants to overcome a rate-limiting step in the Se volatilization pathway, i.e. Se accumulation in plant tissues. PMID:9952452

  20. Antarctic Firn Compaction Rates from Repeat-Track Airborne Radar Data: I. Methods

    NASA Technical Reports Server (NTRS)

    Medley, B.; Ligtenberg, S. R. M.; Joughin, I.; Van Den Broeke, M. R.; Gogineni, S.; Nowicki, S.

    2015-01-01

    While measurements of ice-sheet surface elevation change are increasingly used to assess mass change, the processes that control the elevation fluctuations not related to ice-flow dynamics (e.g. firn compaction and accumulation) remain difficult to measure. Here we use radar data from the Thwaites Glacier (West Antarctica) catchment to measure the rate of thickness change between horizons of constant age over different time intervals: 2009-10, 2010-11 and 2009-11. The average compaction rate to approximately 25m depth is 0.33ma(exp -1), with largest compaction rates near the surface. Our measurements indicate that the accumulation rate controls much of the spatio-temporal variations in the compaction rate while the role of temperature is unclear due to a lack of measurements. Based on a semi-empirical, steady-state densification model, we find that surveying older firn horizons minimizes the potential bias resulting from the variable depth of the constant age horizon. Our results suggest that the spatiotemporal variations in the firn compaction rate are an important consideration when converting surface elevation change to ice mass change. Compaction rates varied by up to 0.12ma(exp -1) over distances less than 6km and were on average greater than 20% larger during the 2010-11 interval than during 2009-10.

  1. Lava effusion rate definition and measurement: a review

    USGS Publications Warehouse

    Calvari, Sonia; Dehn, Jonathan; Harris, A.

    2007-01-01

    Measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics, as well as for monitoring efforts during on-going eruptions. However, its exact definition remains a source of confusion, and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales, or measured using different approaches. Thus our aims are to: (1) define effusion rate terminology; and (2) assess the various measurement methods and their results. We first distinguish between instantaneous effusion rate, and time-averaged discharge rate. Eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began. The ultimate extension of this is mean output rate, this being the final volume of erupted lava divided by total eruption duration. Whether these values are total values, i.e. the flux feeding all flow units across the entire flow field, or local, i.e. the flux feeding a single active unit within a flow field across which many units are active, also needs to be specified. No approach is without its problems, and all can have large error (up to ∼50%). However, good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here. There are three important factors to consider and state when measuring, giving or using an effusion rate. First, the time-period over which the value was averaged; second, whether the measurement applies to the entire active flow field, or a single lava flow within that field; and third, the measurement technique and its accompanying assumptions.

  2. High Resolution Measurement of the Glycolytic Rate

    PubMed Central

    Bittner, Carla X.; Loaiza, Anitsi; Ruminot, Iván; Larenas, Valeria; Sotelo-Hitschfeld, Tamara; Gutiérrez, Robin; Córdova, Alex; Valdebenito, Rocío; Frommer, Wolf B.; Barros, L. Felipe

    2010-01-01

    The glycolytic rate is sensitive to physiological activity, hormones, stress, aging, and malignant transformation. Standard techniques to measure the glycolytic rate are based on radioactive isotopes, are not able to resolve single cells and have poor temporal resolution, limitations that hamper the study of energy metabolism in the brain and other organs. A new method is described in this article, which makes use of a recently developed FRET glucose nanosensor to measure the rate of glycolysis in single cells with high temporal resolution. Used in cultured astrocytes, the method showed for the first time that glycolysis can be activated within seconds by a combination of glutamate and K+, supporting a role for astrocytes in neurometabolic and neurovascular coupling in the brain. It was also possible to make a direct comparison of metabolism in neurons and astrocytes lying in close proximity, paving the way to a high-resolution characterization of brain energy metabolism. Single-cell glycolytic rates were also measured in fibroblasts, adipocytes, myoblasts, and tumor cells, showing higher rates for undifferentiated cells and significant metabolic heterogeneity within cell types. This method should facilitate the investigation of tissue metabolism at the single-cell level and is readily adaptable for high-throughput analysis. PMID:20890447

  3. Effects of Accumulating Work Shifts on Performance-Based Fatigue Using Multiple Strength Measurements in Day and Night Shift Nurses and Aides.

    PubMed

    Thompson, Brennan J; Stock, Matt S; Banuelas, Victoria K

    2017-05-01

    Objective This study aimed to examine the effects of accumulating nursing work on maximal and rapid strength characteristics in female nurses and compare these effects in day versus night shift workers. Background Nurses exhibit among the highest nonfatal injury rates of all occupations, which may be a consequence of long, cumulative work shift schedules. Fatigue may accumulate across multiple shifts and lead to performance impairments, which in turn may be linked to injury risks. Method Thirty-seven nurses and aides performed isometric strength-based performance testing of three muscle groups, including the knee extensors, knee flexors, and wrist flexors (hand grip), as well as countermovement jumps, at baseline and following exposure to three 12-hour work shifts in a four-day period. Variables included peak torque (PT) and rate of torque development (RTD) from isometric strength testing and jump height and power output. Results The rigorous work period resulted in significant decreases (-7.2% to -19.2%) in a large majority (8/9) of the isometric strength-based measurements. No differences were noted for the day versus night shift workers except for the RTD at 200 millisecond variable, for which the night shift had greater work-induced decreases than the day shift workers. No changes were observed for jump height or power output. Conclusions A compressed nursing work schedule resulted in decreases in strength-based performance abilities, being indicative of performance fatigue. Application Compressed work schedules involving long shifts lead to functional declines in nurse performance capacities that may pose risks for both the nurse and patient quality of care. Fatigue management plans are needed to monitor and regulate increased levels of fatigue.

  4. Utilizing a Water-Soluble Cryptophane with Fast Xenon Exchange Rates for Picomolar Sensitivity NMR Measurements

    PubMed Central

    Bai, Yubin; Hill, P. Aru; Dmochowski, Ivan J.

    2012-01-01

    Hyperpolarized 129Xe chemical exchange saturation transfer (129Xe Hyper-CEST) NMR is a powerful technique for the ultrasensitive, indirect detection of Xe host molecules (e.g., cryptophane-A). Irradiation at the appropriate Xe-cryptophane resonant radio frequency results in relaxation of the bound hyperpolarized 129Xe and rapid accumulation of depolarized 129Xe in bulk solution. The cryptophane effectively ‘catalyzes’ this process by providing a unique molecular environment for spin depolarization to occur, while allowing xenon exchange with the bulk solution during the hyperpolarized lifetime (T1 ≈ 1 min). Following this scheme, a triacetic acid cryptophane-A derivative (TAAC) was indirectly detected at 1.4 picomolar concentration at 320 K in aqueous solution, which is the record for a single-unit xenon host. To investigate this sensitivity enhancement, the xenon binding kinetics of TAAC in water was studied by NMR exchange lifetime measurement. At 297 K, kon ≈ 1.5 × 106 M−1s−1 and koff = 45 s−1, which represent the fastest Xe association and dissociation rates measured for a high-affinity, water-soluble xenon host molecule near rt. NMR linewidth measurements provided similar exchange rates at rt, which we assign to solvent-Xe exchange in TAAC. At 320 K, koff was estimated to be 1.1 × 103 s−1. In Hyper-CEST NMR experiments, the rate of 129Xe depolarization achieved by 14 pM TAAC in the presence of RF pulses was calculated to be 0.17 µM·s−1. On a per cryptophane basis, this equates to 1.2 × 104 129Xe atoms s−1 (or 4.6 × 104 Xe atoms s−1, all Xe isotopes), which is more than an order of magnitude faster than koff, the directly measurable Xe-TAAC exchange rate. This compels us to consider multiple Xe exchange processes for cryptophane-mediated bulk 129Xe depolarization, which provide at least 107-fold sensitivity enhancements over directly detected hyperpolarized 129Xe NMR signals. PMID:23106513

  5. Timescale bias in measuring river migration rate

    NASA Astrophysics Data System (ADS)

    Donovan, M.; Belmont, P.; Notebaert, B.

    2016-12-01

    River channel migration plays an important role in sediment routing, water quality, riverine ecology, and infrastructure risk assessment. Migration rates may change in time and space due to systematic changes in hydrology, sediment supply, vegetation, and/or human land and water management actions. The ability to make detailed measurements of lateral migration over a wide range of temporal and spatial scales has been enhanced from increased availability of historical landscape-scale aerial photography and high-resolution topography (HRT). Despite a surge in the use of historical and contemporary aerial photograph sequences in conjunction with evolving methods to analyze such data for channel change, we found no research considering the biases that may be introduced as a function of the temporal scales of measurement. Unsteady processes (e.g.; sedimentation, channel migration, width changes) exhibit extreme discontinuities over time and space, resulting in distortion when measurements are averaged over longer temporal scales, referred to as `Sadler effects' (Sadler, 1981; Gardner et al., 1987). Using 12 sets of aerial photographs for the Root River (Minnesota), we measure lateral migration over space (110 km) and time (1937-2013) assess whether bias arises from different measurement scales and whether rates shift systematically with increased discharge over time. Results indicate that measurement-scale biases indeed arise from the time elapsed between measurements. We parsed the study reach into three distinct reaches and examine if/how recent increases in river discharge translate into changes in migration rate.

  6. Capturing Functional Independence Measure (FIM®) Ratings.

    PubMed

    Torres, Audrey

    The aim of the study was to identify interventions to capture admission functional independence measure (FIM®) ratings on the day of admission to an inpatient rehabilitation facility. A quantitative evidence-based practice quality improvement study utilizing descriptive statistics. Admission FIM® ratings from patients discharged in June 2012 (retrospective review) were compared to admission FIM® ratings from patients discharged in June 2014 (prospective review). The logic model was utilized to determine the project inputs, outputs, and outcomes. Interventions to capture admission FIM® ratings on the day of admission are essential to accurately predict the patient's burden of care, length of stay, and reimbursement. Waiting until Day 2 or Day 3 after admission to capture the admission FIM® assessment resulted in inflated admission FIM® ratings and suboptimal quality outcomes. Interventions to capture admission FIM® ratings on the day of admission were successful at improving the quality of care, length of stay efficiency, and accurately recording admission FIM® ratings to determine the patient's burden of care.

  7. Heart rate measurement based on a time-lapse image.

    PubMed

    Takano, Chihiro; Ohta, Yuji

    2007-10-01

    Using a time-lapse image acquired from a CCD camera, we developed a non-contact and non-invasive device, which could measure both the respiratory and pulse rate simultaneously. The time-lapse image of a part of the subject's skin was consecutively captured, and the changes in the average image brightness of the region of interest (ROI) were measured for 30s. The brightness data were processed by a series of operations of interpolation as follows a first-order derivative, a low pass filter of 2 Hz, and a sixth-order auto-regressive (AR) spectral analysis. Fourteen sound and healthy female subjects (22-27 years of age) participated in the experiments. Each subject was told to keep a relaxed seating posture with no physical restriction. At the same time, heart rate was measured by a pulse oximeter and respiratory rate was measured by a thermistor placed at the external naris. Using AR spectral analysis, two clear peaks could be detected at approximately 0.3 and 1.2 Hz. The peaks were thought to correspond to the respiratory rate and the heart rate. Correlation coefficients of 0.90 and 0.93 were obtained for the measurement of heart rate and respiratory rate, respectively.

  8. Renyi entropy measures of heart rate Gaussianity.

    PubMed

    Lake, Douglas E

    2006-01-01

    Sample entropy and approximate entropy are measures that have been successfully utilized to study the deterministic dynamics of heart rate (HR). A complementary stochastic point of view and a heuristic argument using the Central Limit Theorem suggests that the Gaussianity of HR is a complementary measure of the physiological complexity of the underlying signal transduction processes. Renyi entropy (or q-entropy) is a widely used measure of Gaussianity in many applications. Particularly important members of this family are differential (or Shannon) entropy (q = 1) and quadratic entropy (q = 2). We introduce the concepts of differential and conditional Renyi entropy rate and, in conjunction with Burg's theorem, develop a measure of the Gaussianity of a linear random process. Robust algorithms for estimating these quantities are presented along with estimates of their standard errors.

  9. Drinking water boosts food intake rate, body mass increase and fat accumulation in migratory blackcaps (Sylvia atricapilla).

    PubMed

    Tsurim, Ido; Sapir, Nir; Belmaker, Jonathan; Shanni, Itai; Izhaki, Ido; Wojciechowski, Michał S; Karasov, William H; Pinshow, Berry

    2008-05-01

    Fat accumulation by blackcaps (Sylvia atricapilla) is a prerequisite for successful migratory flight in the autumn and has recently been determined to be constrained by availability of drinking water. Birds staging in a fruit-rich Pistacia atlantica plantation that had access to water increased their body mass and fat reserves both faster and to a greater extent than birds deprived of water. We conducted a series of laboratory experiments on birds captured during the autumn migration period in which we tested the hypotheses that drinking water increases food use by easing limitations on the birds' dietary choices and, consequently, feeding and food processing rates, and that the availability of drinking water leads to improved digestion and, therefore, to higher apparent metabolizable energy. Blackcaps were trapped in autumn in the Northern Negev Desert, Israel and transferred to individual cages in the laboratory. Birds were provided with P. atlantica fruit and mealworms, and had either free access to water (controls) or were water-deprived. In experiment 1, in which mealworm availability was restricted, water-deprived birds had a fourfold lower fruit and energy intake rates and, consequently, gained less fat and total mass than control birds. Water availability did not affect food metabolizability. In experiment 2, in which mealworms were provided ad libitum, water availability influenced the birds' diet: water-restricted birds ate more mealworms, while control birds consumed mainly P. atlantica fruit. Further, in experiment 2, fat and mass gain did not differ between the two treatment groups. We conclude that water availability may have important consequences for fat accumulation in migrating birds while they fatten at stopover sites, especially when water-rich food is scarce. Restricted water availability may also impede the blackcap's dietary shift from insectivory to frugivory, a shift probably necessary for successful pre-migratory fattening.

  10. Dose-rate-dependent damage of cerium dioxide in the scanning transmission electron microscope

    PubMed Central

    Johnston-Peck, Aaron C.; DuChene, Joseph S.; Roberts, Alan D.; Wei, Wei David; Herzing, Andrew A.

    2016-01-01

    Beam damage caused by energetic electrons in the transmission electron microscope is a fundamental constraint limiting the collection of artifact-free information. Through understanding the influence of the electron beam, experimental routines may be adjusted to improve the data collection process. Investigations of CeO2 indicate that there is not a critical dose required for the accumulation of electron beam damage. Instead, measurements using annular dark field scanning transmission electron microscopy and electron energy loss spectroscopy demonstrate that the onset of measurable damage occurs when a critical dose rate is exceeded. The mechanism behind this phenomenon is that oxygen vacancies created by exposure to a 300 keV electron beam are actively annihilated as the sample re-oxidizes in the microscope environment. As a result, only when the rate of vacancy creation exceeds the recovery rate will beam damage begin to accumulate. This observation suggests that dose-intensive experiments can be accomplished without disrupting the native structure of the sample when executed using dose rates below the appropriate threshold. Furthermore, the presence of an encapsulating carbonaceous layer inhibits processes that cause beam damage, markedly increasing the dose rate threshold for the accumulation of damage. PMID:27469265

  11. Age-related accumulation of pentosidine in aggrecan and collagen from normal and degenerate human intervertebral discs

    PubMed Central

    Sivan, Sarit Sara; Tsitron, Eve; Wachtel, Ellen; Roughley, Peter; Sakkee, Nico; van der Ham, Frits; Degroot, Jeroen; Maroudas, Alice

    2006-01-01

    During aging and degeneration, many changes occur in the structure and composition of human cartilaginous tissues, which include the accumulation of the AGE (advanced glycation end-product), pentosidine, in long-lived proteins. In the present study, we investigated the accumulation of pentosidine in constituents of the human IVD (intervertebral disc), i.e. collagen, aggrecan-derived PG (proteoglycan) (A1) and its fractions (A1D1–A1D6) in health and pathology. We found that, after maturity, pentosidine accumulates with age. Over the age range studied, a linear 6-fold increase was observed in pentosidine accumulation for A1 and collagen with respective rates of 0.12 and 0.66 nmol·(g of protein)−1·year−1. Using previously reported protein turnover rate constants (kT) obtained from measurements of the D-isomer of aspartic residue in collagen and aggrecan of human IVD, we could calculate the pentosidine formation rate constants (kF) for these constituents [Sivan, Tsitron, Wachtel, Roughley, Sakkee, van der Ham, DeGroot, Roberts and Maroudas (2006) J. Biol. Chem. 281, 13009–13014; Tsitron (2006) MSc Thesis, Technion-Israel Institute of Technology, Haifa, Israel]. In spite of the comparable formation rate constants obtained for A1D1 and collagen [1.81±0.25 compared with 3.71±0.26 μmol of pentosidine·(mol of lysine)−1·year−1 respectively], the higher pentosidine accumulation in collagen is consistent with its slower turnover (0.005 year−1 compared with 0.134 year−1 for A1D1). Pentosidine accumulation increased with decreasing buoyant density and decreasing turnover of the proteins from the most glycosaminoglycan-rich PG components (A1D1) to the least (A1D6), with respective kF values of 1.81±0.25 and 3.18±0.37 μmol of pentosidine·(mol of lysine)−1·year−1. We concluded that protein turnover is an important determinant of pentosidine accumulation in aggrecan and collagen of human IVD, as was found for articular cartilage. Correlation of

  12. 19 CFR 10.597 - Accumulation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. Dominican Republic-Central America-United States Free Trade Agreement Rules of Origin § 10.597 Accumulation. (a) Originating materials from the...

  13. Optimization of free ammonia concentration for nitrite accumulation in shortcut biological nitrogen removal process.

    PubMed

    Chung, Jinwook; Shim, Hojae; Park, Seong-Jun; Kim, Seung-Jin; Bae, Wookeun

    2006-03-01

    A shortcut biological nitrogen removal (SBNR) utilizes the concept of a direct conversion of ammonium to nitrite and then to nitrogen gas. A successful SBNR requires accumulation of nitrite in the system and inhibition of the activity of nitrite oxidizers. A high concentration of free ammonia (FA) inhibits nitrite oxidizers, but unfortunately decreases the ammonium removal rate as well. Therefore, the optimal range of FA concentration is necessary not only to stabilize nitrite accumulation but also to achieve maximum ammonium removal. In order to derive such optimal FA concentrations, the specific substrate utilization rates of ammonium and nitrite oxidizers were measured. The optimal FA concentration range appeared to be 5-10 mg/L for the adapted sludge. The simulated results from the modified inhibition model expressed by FA and ammonium/nitrite concentrations were shown very similar to the experimental results.

  14. Using SO2 camera imagery and seismicity to examine degassing and gas accumulation at Kīlauea Volcano, May 2010

    USGS Publications Warehouse

    Nadeau, Patricia A; Werner, Cynthia A.; Waite, Gregory P.; Carn, Simon A; Brewer, Ian D; Elias, Tamar; Sutton, Andrew; Kern, Christoph

    2015-01-01

    SO2 camera measurements at Kīlauea Volcano, Hawaii, in May of 2010 captured two occurrences of lava lake rise and fall within the Halema'um'au Crater summit vent. During high lava stands we observed diminished SO2 emission rates and decreased seismic tremor. Similar events at Kīlauea have been described as the result of sporadic degassing following gas accumulation beneath a mostly impermeable lava lake surface. Incorporation of SO2 camera data into a multi-parameter dataset gives credence to the likelihood of shallow gas accumulation as the cause of these high stand events, with accumulated gas release upon lake-level drop compensating for the gas deficit reached during accumulation.

  15. Estimation of hydrocarbon biodegradation rates in gasoline-contaminated sediment from measured respiration rates

    USGS Publications Warehouse

    Baker, R.J.; Baehr, A.L.; Lahvis, M.A.

    2000-01-01

    An open microcosm method for quantifying microbial respiration and estimating biodegradation rates of hydrocarbons in gasoline-contaminated sediment samples has been developed and validated. Stainless-steel bioreactors are filled with soil or sediment samples, and the vapor-phase composition (concentrations of oxygen (O2), nitrogen (N2), carbon dioxide (CO2), and selected hydrocarbons) is monitored over time. Replacement gas is added as the vapor sample is taken, and selection of the replacement gas composition facilitates real-time decision-making regarding environmental conditions within the bioreactor. This capability allows for maintenance of field conditions over time, which is not possible in closed microcosms. Reaction rates of CO2 and O2 are calculated from the vapor-phase composition time series. Rates of hydrocarbon biodegradation are either measured directly from the hydrocarbon mass balance, or estimated from CO2 and O2 reaction rates and assumed reaction stoichiometries. Open microcosm experiments using sediments spiked with toluene and p-xylene were conducted to validate the stoichiometric assumptions. Respiration rates calculated from O2 consumption and from CO2 production provide estimates of toluene and p- xylene degradation rates within about ??50% of measured values when complete mineralization stoichiometry is assumed. Measured values ranged from 851.1 to 965.1 g m-3 year-1 for toluene, and 407.2-942.3 g m-3 year-1 for p- xylene. Contaminated sediment samples from a gasoline-spill site were used in a second set of microcosm experiments. Here, reaction rates of O2 and CO2 were measured and used to estimate hydrocarbon respiration rates. Total hydrocarbon reaction rates ranged from 49.0 g m-3 year-1 in uncontaminated (background) to 1040.4 g m-3 year-1 for highly contaminated sediment, based on CO2 production data. These rate estimates were similar to those obtained independently from in situ CO2 vertical gradient and flux determinations at the

  16. Neuronal Susceptibility to GRIM in Drosophila melanogaster Measures the Rate of Genetic Changes that Scale to Lifespan

    PubMed Central

    Bedoukian, Matthew A.; Rodriguez, Sarah M.; Cohen, Matthew B.; Duncan Smith, Stuart V.; Park, Jennifer

    2009-01-01

    Gene expression in Drosophila melanogaster changes significantly throughout life and some of these changes can be delayed by lowering ambient temperature and also by dietary restriction. These two interventions are known to slow the rate of aging as well as the accumulation of damage. It is unknown, however, whether gene expression changes that occur during development and early adult life make an animal more vulnerable to death. Here we develop a method capable of measuring the rate of programmed genetic changes during young adult life in Drosophila melanogaster and show that these changes can be delayed or accelerated in a manner that is predictive of longevity. We show that temperature shifts and dietary restriction, which slow the rate of aging in Drosophila melanogaster, extend the window of neuronal susceptibility to GRIM over-expression in a way that scales to lifespan. We propose that this susceptibility can be used to test compounds and genetic manipulations that alter the onset of senescence by changing the programmed timing of gene expression that correlates and may be causal to aging. PMID:19428445

  17. Measuring task-related changes in heart rate variability.

    PubMed

    Moses, Ziev B; Luecken, Linda J; Eason, James C

    2007-01-01

    Small beat-to-beat differences in heart rate are the result of dynamic control of the cardiovascular system by the sympathetic and parasympathetic nervous systems. Heart rate variability (HRV) has been positively correlated with both mental and physical health. While many studies measure HRV under rest conditions, few have measured HRV during stressful situations. We describe an experimental protocol designed to measure baseline, task, and recovery values of HRV as a function of three different types of stressors. These stressors involve an attention task, a cold pressor test, and a videotaped speech presentation. We found a measurable change in heart rate in participants (n=10) during each task (all p's < 0.05). The relative increase or decrease from pre-task heart rate was predicted by task (one-way ANOVA, p= 0.0001). Spectral analysis of HRV during the attention task revealed consistently decreased measures of both high (68+/-7%, mean+/-S.E.) and low (62+/-13%) frequency HRV components as compared to baseline. HRV spectra for the cold pressor and speech tasks revealed no consistent patterns of increase or decrease from baseline measurements. We also found no correlation in reactivity measures between any of our tasks. These findings suggest that each of the tasks in our experimental design elicits a different type of stress response in an individual. Our experimental approach may prove useful to biobehavioral researchers searching for factors that determine individual differences in responses to stress in daily life.

  18. Uncertainty in Estimates of Net Seasonal Snow Accumulation on Glaciers from In Situ Measurements

    NASA Astrophysics Data System (ADS)

    Pulwicki, A.; Flowers, G. E.; Radic, V.

    2017-12-01

    Accurately estimating the net seasonal snow accumulation (or "winter balance") on glaciers is central to assessing glacier health and predicting glacier runoff. However, measuring and modeling snow distribution is inherently difficult in mountainous terrain, resulting in high uncertainties in estimates of winter balance. Our work focuses on uncertainty attribution within the process of converting direct measurements of snow depth and density to estimates of winter balance. We collected more than 9000 direct measurements of snow depth across three glaciers in the St. Elias Mountains, Yukon, Canada in May 2016. Linear regression (LR) and simple kriging (SK), combined with cross correlation and Bayesian model averaging, are used to interpolate estimates of snow water equivalent (SWE) from snow depth and density measurements. Snow distribution patterns are found to differ considerably between glaciers, highlighting strong inter- and intra-basin variability. Elevation is found to be the dominant control of the spatial distribution of SWE, but the relationship varies considerably between glaciers. A simple parameterization of wind redistribution is also a small but statistically significant predictor of SWE. The SWE estimated for one study glacier has a short range parameter (90 m) and both LR and SK estimate a winter balance of 0.6 m w.e. but are poor predictors of SWE at measurement locations. The other two glaciers have longer SWE range parameters ( 450 m) and due to differences in extrapolation, SK estimates are more than 0.1 m w.e. (up to 40%) lower than LR estimates. By using a Monte Carlo method to quantify the effects of various sources of uncertainty, we find that the interpolation of estimated values of SWE is a larger source of uncertainty than the assignment of snow density or than the representation of the SWE value within a terrain model grid cell. For our study glaciers, the total winter balance uncertainty ranges from 0.03 (8%) to 0.15 (54%) m w

  19. Compact Instruments Measure Helium-Leak Rates

    NASA Technical Reports Server (NTRS)

    Stout, Stephen; Immer, Christopher

    2003-01-01

    Compact, lightweight instruments have been developed for measuring small flows of helium and/or detecting helium leaks in solenoid valves when the valves are nominally closed. These instruments do not impede the flows when the valves are nominally open. They can be integrated into newly fabricated valves or retrofitted to previously fabricated valves. Each instrument includes an upstream and a downstream thermistor separated by a heater, plus associated analog and digital heater-control, signal- conditioning, and data-processing circuits. The thermistors and heater are off-the-shelf surface mount components mounted on a circuit board in the flow path. The operation of the instrument is based on a well-established thermal mass-flow-measurement technique: Convection by the flow that one seeks to measure gives rise to transfer of heat from the heater to the downstream thermistor. The temperature difference measured by the thermistors is directly related to the rate of flow. The calibration curve from temperature gradient to helium flow is closely approximated via fifth-order polynomial. A microprocessor that is part of the electronic circuitry implements the calibration curve to compute the flow rate from the thermistor readings.

  20. Effect of famine-phase reduced aeration on polyhydroxyalkanoate accumulation in aerobic granules.

    PubMed

    Vjayan, T; Vadivelu, V M

    2017-12-01

    The effects of variable aeration in the famine period on polyhydroxyalkanoate (PHA) accumulation in aerobic granules were investigated. Results showed that regardless of the aeration rates used during famine period, all aerobic granules achieved a similar chemical oxygen demand removal and PHA content. The decrease in famine-period aeration rates accelerated the maximum PHA accumulation together with increase in granular size and settling ability. The PHA-accumulating microorganisms were found to have shifted closer to the surface of the granules when the aeration rate was reduced. Moreover, PHA compositional changes occurred, where the hydroxyvalerate content had increased with the reduction in aeration rate. Ultimately, the results indicate that the requirement of aeration for PHA accumulation in aerobic granules is highly insignificant in the famine phase. PHA production in aerobic granules under zero aeration in the famine period may result in an energy input reduction of up to 74%. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Heart rate measurement based on face video sequence

    NASA Astrophysics Data System (ADS)

    Xu, Fang; Zhou, Qin-Wu; Wu, Peng; Chen, Xing; Yang, Xiaofeng; Yan, Hong-jian

    2015-03-01

    This paper proposes a new non-contact heart rate measurement method based on photoplethysmography (PPG) theory. With this method we can measure heart rate remotely with a camera and ambient light. We collected video sequences of subjects, and detected remote PPG signals through video sequences. Remote PPG signals were analyzed with two methods, Blind Source Separation Technology (BSST) and Cross Spectral Power Technology (CSPT). BSST is a commonly used method, and CSPT is used for the first time in the study of remote PPG signals in this paper. Both of the methods can acquire heart rate, but compared with BSST, CSPT has clearer physical meaning, and the computational complexity of CSPT is lower than that of BSST. Our work shows that heart rates detected by CSPT method have good consistency with the heart rates measured by a finger clip oximeter. With good accuracy and low computational complexity, the CSPT method has a good prospect for the application in the field of home medical devices and mobile health devices.

  2. cyclostratigraphy, sequence stratigraphy and organic matter accumulation mechanism

    NASA Astrophysics Data System (ADS)

    Cong, F.; Li, J.

    2016-12-01

    The first member of Maokou Formation of Sichuan basin is composed of well preserved carbonate ramp couplets of limestone and marlstone/shale. It acts as one of the potential shale gas source rock, and is suitable for time-series analysis. We conducted time-series analysis to identify high-frequency sequences, reconstruct high-resolution sedimentation rate, estimate detailed primary productivity for the first time in the study intervals and discuss organic matter accumulation mechanism of source rock under sequence stratigraphic framework.Using the theory of cyclostratigraphy and sequence stratigraphy, the high-frequency sequences of one outcrop profile and one drilling well are identified. Two third-order sequences and eight fourth-order sequences are distinguished on outcrop profile based on the cycle stacking patterns. For drilling well, sequence boundary and four system tracts is distinguished by "integrated prediction error filter analysis" (INPEFA) of Gamma-ray logging data, and eight fourth-order sequences is identified by 405ka long eccentricity curve in depth domain which is quantified and filtered by integrated analysis of MTM spectral analysis, evolutive harmonic analysis (EHA), evolutive average spectral misfit (eASM) and band-pass filtering. It suggests that high-frequency sequences correlate well with Milankovitch orbital signals recorded in sediments, and it is applicable to use cyclostratigraphy theory in dividing high-frequency(4-6 orders) sequence stratigraphy.High-resolution sedimentation rate is reconstructed through the study interval by tracking the highly statistically significant short eccentricity component (123ka) revealed by EHA. Based on sedimentation rate, measured TOC and density data, the burial flux, delivery flux and primary productivity of organic carbon was estimated. By integrating redox proxies, we can discuss the controls on organic matter accumulation by primary production and preservation under the high-resolution sequence

  3. 19 CFR 10.597 - Accumulation.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Accumulation. 10.597 Section 10.597 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. Dominican Republic-Central America-United...

  4. 19 CFR 10.597 - Accumulation.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Accumulation. 10.597 Section 10.597 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. Dominican Republic-Central America-United...

  5. 19 CFR 10.597 - Accumulation.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Accumulation. 10.597 Section 10.597 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. Dominican Republic-Central America-United...

  6. 19 CFR 10.597 - Accumulation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Accumulation. 10.597 Section 10.597 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. Dominican Republic-Central America-United...

  7. [Accelerated senescence of fresh-cut Chinese water chestnut tissues in relation to hydrogen peroxide accumulation].

    PubMed

    Peng, Li-Tao; Jiang, Yue-Ming; Yang, Shu-Zhen; Pan, Si-Yi

    2005-10-01

    Accelerated senescence of fresh-cut Chinese water chestnut (CWC) tissues in relation to active oxygen species (AOS) metabolism was investigated. Fresh-cut CWC (2 mm thick) and intact CWC were stored at 4 degrees C in trays wrapped with plastic films. Changes in superoxide anion production rate, activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) were monitored, while contents of hydrogen peroxide, ascorbic acid, MDA as well as electrolyte leakage were measured. Fresh-cutting of CWC induced activities of SOD, CAT and APX to a certain extent (Fig. 2B and Fig. 3), but simultaneously stimulated superoxide anion production markedly (Fig. 2A), enhanced hydrogen peroxide accumulation and accelerated loss in ascorbic acid (Figs. 4 and 5), which resulted in increased lipid peroxidation indicated by malondialdehyde (MDA) content and electrolyte leakage (Fig. 1). Statistics analysis indicated that there was a significantly positive correlation among hydrogen peroxide accumulation, MDA content and electrolyte leakage (Table 1). Histochemical detection with 3, 3'-diaminobenzidine further demonstrated that hydrogen peroxide accumulation increased in fresh-cut CWC during storage (Fig. 5). AOS production rate and activities of SOD, CAT and APX changed little while no obvious hydrogen peroxide accumulation was observed, in intact CWC during storage.

  8. Evidence Accumulator or Decision Threshold – Which Cortical Mechanism are We Observing?

    PubMed Central

    Simen, Patrick

    2012-01-01

    Most psychological models of perceptual decision making are of the accumulation-to-threshold variety. The neural basis of accumulation in parietal and prefrontal cortex is therefore a topic of great interest in neuroscience. In contrast, threshold mechanisms have received less attention, and their neural basis has usually been sought in subcortical structures. Here I analyze a model of a decision threshold that can be implemented in the same cortical areas as evidence accumulators, and whose behavior bears on two open questions in decision neuroscience: (1) When ramping activity is observed in a brain region during decision making, does it reflect evidence accumulation? (2) Are changes in speed-accuracy tradeoffs and response biases more likely to be achieved by changes in thresholds, or in accumulation rates and starting points? The analysis suggests that task-modulated ramping activity, by itself, is weak evidence that a brain area mediates evidence accumulation as opposed to threshold readout; and that signs of modulated accumulation are as likely to indicate threshold adaptation as adaptation of starting points and accumulation rates. These conclusions imply that how thresholds are modeled can dramatically impact accumulator-based interpretations of this data. PMID:22737136

  9. Mineral transformation and biomass accumulation associated with uranium bioremediation at Rifle, Colorado

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

    Li, L.; Steefel, C.I.; Williams, K.H.

    2009-04-20

    Injection of organic carbon into the subsurface as an electron donor for bioremediation of redox-sensitive contaminants like uranium often leads to mineral transformation and biomass accumulation, both of which can alter the flow field and potentially bioremediation efficacy. This work combines reactive transport modeling with a column experiment and field measurements to understand the biogeochemical processes and to quantify the biomass and mineral transformation/accumulation during a bioremediation experiment at a uranium contaminated site near Rifle, Colorado. We use the reactive transport model CrunchFlow to explicitly simulate microbial community dynamics of iron and sulfate reducers, and their impacts on reaction rates.more » The column experiment shows clear evidence of mineral precipitation, primarily in the form of calcite and iron monosulfide. At the field scale, reactive transport simulations suggest that the biogeochemical reactions occur mostly close to the injection wells where acetate concentrations are highest, with mineral precipitate and biomass accumulation reaching as high as 1.5% of the pore space. This work shows that reactive transport modeling coupled with field data can be an effective tool for quantitative estimation of mineral transformation and biomass accumulation, thus improving the design of bioremediation strategies.« less

  10. Mineral transformation and biomass accumulation associated with uranium bioremediation at Rifle, Colorado.

    PubMed

    Li, Li; Steefel, Carl I; Williams, Kenneth H; Wilkins, Michael J; Hubbard, Susan S

    2009-07-15

    Injection of organic carbon into the subsurface as an electron donor for bioremediation of redox-sensitive contaminants like uranium often leads to mineral transformation and biomass accumulation, both of which can alter the flow field and potentially bioremediation efficacy. This work combines reactive transport modeling with a column experiment and field measurements to understand the biogeochemical processes and to quantify the biomass and mineral transformation/accumulation during a bioremediation experiment at a uranium contaminated site near Rifle, Colorado. We use the reactive transport model CrunchFlow to explicitly simulate microbial community dynamics of iron and sulfate reducers, and their impacts on reaction rates. The column experiment shows clear evidence of mineral precipitation, primarily in the form of calcite and iron monosulfide. At the field scale, reactive transport simulations suggest that the biogeochemical reactions occur mostly close to the injection wells where acetate concentrations are highest, with mineral precipitate and biomass accumulation reaching as high as 1.5% of the pore space. This work shows that reactive transport modeling coupled with field data can bean effective tool for quantitative estimation of mineral transformation and biomass accumulation, thus improving the design of bioremediation strategies.

  11. [Status of lead exposure and its impact on health of workers in an accumulator factory].

    PubMed

    Liang, Jiabin; Zhang, Jian; Guo, Xiaojing; Mai, Jianping; Wang, Zhi; Liu, Yimin

    2014-02-01

    To identify the occupational hazard factors in an accumulator factory, to analyze the status of internal and external lead exposure and evaluate the impact of lead exposure on the health of workers in the accumulator industry, and to provide a theoretical basis for improved lead exposure criteria and technical support for the control of lead contamination in the accumulator industry. An on-site investigation was carried out to monitor and evaluate the lead fume and dust in the workplaces of an accumulator factory, and occupational health examination was performed in all workers. The occupational hazard safeguards in the accumulator factory were unadvanced. The contamination of lead fume and dust was serious. The abnormal rate of blood lead was up to 79.80%, and many workers developed anemia and mild peripheral nerve disease. Lead contamination is serious in the accumulator factory, leading to poor health of workers. It is essential to take effective control measures, improve the working environment, provide occupational health education, increase workers' self-protection awareness, and periodically conduct occupational hazard monitoring and health surveillance. The government must reinforce occupational health supervision of such enterprises.

  12. 19 CFR 10.772 - Accumulation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Accumulation. 10.772 Section 10.772 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Morocco Free Trade Agreement...

  13. 19 CFR 10.875 - Accumulation.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Accumulation. 10.875 Section 10.875 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Oman Free Trade Agreement Rules...

  14. 19 CFR 10.875 - Accumulation.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Accumulation. 10.875 Section 10.875 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Oman Free Trade Agreement Rules...

  15. 19 CFR 10.875 - Accumulation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Accumulation. 10.875 Section 10.875 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Oman Free Trade Agreement Rules...

  16. 19 CFR 10.875 - Accumulation.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Accumulation. 10.875 Section 10.875 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Oman Free Trade Agreement Rules...

  17. Spatial Variability of accumulation across the Western Greenland Ice Sheet Percolation Zone from ground-penetrating-radar and shallow firn cores

    NASA Astrophysics Data System (ADS)

    Lewis, G.; Osterberg, E. C.; Hawley, R. L.; Marshall, H. P.; Birkel, S. D.; Meehan, T. G.; Graeter, K.; Overly, T. B.; McCarthy, F.

    2017-12-01

    The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. Increased melting in the GrIS percolation zone over the past several decades has led to increased mass loss at lower elevations due to recent warming. Uncertainties in mass balance are especially large in regions with sparse and/or outdated in situ measurements. This study is the first to calculate in situ accumulation over a large region of western Greenland since the Program for Arctic Regional Climate Assessment campaign during the 1990s. Here we analyze 5000 km of 400 MHz ground penetrating radar data and sixteen 25-33 m-long firn cores in the western GrIS percolation zone to determine snow accumulation over the past 50 years. The cores and radar data were collected as part of the 2016-2017 Greenland Traverse for Accumulation and Climate Studies (GreenTrACS). With the cores and radar profiles we capture spatial accumulation gradients between 1850-2500 m a.s.l and up to Summit Station. We calculate accumulation rates and use them to validate five widely used regional climate models and to compare with IceBridge snow and accumulation radars. Our results indicate that while the models capture most regional spatial climate patterns, they lack the small-scale spatial variability captured by in situ measurements. Additionally, we evaluate temporal trends in accumulation at ice core locations and throughout the traverse. Finally, we use empirical orthogonal function and correlation analyses to investigate the principal drivers of radar-derived accumulation rates across the western GrIS percolation zone, including major North Atlantic climate modes such as the North Atlantic Oscillation, Atlantic Multidecadal Oscillation, and Greenland Blocking Index.

  18. A High Frequency Response Relaxed Eddy Accumulation Flux Measurement System for Sampling Short-Lived Biogenic Volatile Organic Compounds

    EPA Science Inventory

    A second-generation relaxed eddy accumulation system was built and tested with the capability to measure vertical biogenic volatile organic compound (VOC) fluxes at levels as low as 10 µg C m−2 hr−1. The system features a continuous, integrated gas-phase ozo...

  19. Sedimentation and belowground carbon accumulation rates in mangrove forests that differ in diversity and land use: a tale of two mangroves

    Treesearch

    Richard A. MacKenzie; Patra B. Foulk; J. Val Klump; Kimberly Weckerly; Joko Purbospito; Daniel Murdiyarso; Daniel C. Donato; Vien Ngoc Nam

    2016-01-01

    Increased sea level is the climate change effect expected to have the greatest impact on mangrove forest survival. Mangroves have survived extreme fluctuations in sea level in the past through sedimentation and belowground carbon (C) accumulation, yet it is unclear what factors may influence these two parameters. We measured sedimentation, vertical accretion, and...

  20. Geomorphic influences on the contribution of vegetation to soil C accumulation and accretion in Spartina alterniflora marshes

    NASA Astrophysics Data System (ADS)

    Elsey-Quirk, Tracy; Unger, Viktoria

    2018-01-01

    Salt marshes are important hotspots of long-term belowground carbon (C) storage, where plant biomass and allochthonous C can be preserved in the soil for thousands of years. However, C accumulation rates, as well as the sources of C, may differ depending on environmental conditions influencing plant productivity, allochthonous C deposition, and C preservation. For this study, we examined the relationship between belowground root growth, turnover, decay, above- and belowground biomass, and previously reported longer-term rates of total, labile, and refractory organic C accumulation and accretion in Spartina alterniflora-dominated marshes across two mid-Atlantic, US estuaries. Tidal range, long-term rates of mineral sedimentation, C accumulation, and accretion were higher and salinities were lower in marshes of the coastal plain estuary (Delaware Bay) than in the coastal lagoon (Barnegat Bay). We expected that the conditions promoting high rates of C accumulation would also promote high plant productivity and greater biomass. We further tested the influence of environmental conditions on belowground growth (roots + rhizomes), decomposition, and biomass of S. alterniflora. The relationship between plant biomass and C accumulation rate differed between estuaries. In the sediment-limited coastal lagoon, rates of total, labile, and refractory organic C accumulation were directly and positively related to above- and belowground biomass. Here, less flooding and a higher mineral sedimentation rate promoted greater above- and belowground biomass and, in turn, higher soil C accumulation and accretion rates. In the coastal plain estuary, the C accumulation rate was related only to aboveground biomass, which was positively related to the rate of labile C accumulation. Soil profiles indicated that live root and rhizome biomass was positively associated with labile C density for most marshes, yet high labile C densities below the live root zone and in marshes with high mineral

  1. Measurement of CPAS Main Parachute Rate of Descent

    NASA Technical Reports Server (NTRS)

    Ray, Eric S.

    2011-01-01

    The Crew Exploration Vehicle Parachute Assembly System (CPAS) is being designed to land the Orion Crew Module (CM) at a safe rate of descent at splashdown. Flight test performance must be measured to a high degree of accuracy to ensure this requirement is met with the most efficient design possible. Although the design includes three CPAS Main parachutes, the requirement is that the system must not exceed 33 ft/s under two Main parachutes, should one of the Main parachutes fail. Therefore, several tests were conducted with clusters of two Mains. All of the steady-state rate of descent data are normalized to standard sea level conditions and checked against the limit. As the Orion design gains weight, the system is approaching this limit to within measurement precision. Parachute "breathing," cluster interactions, and atmospheric anomalies can cause the rate of descent to vary widely and lead to challenges in characterizing parachute terminal performance. An early test had contradictory rate of descent results from optical trajectory and Differential Global Positioning Systems (DGPS). A thorough analysis of the data sources and error propagation was conducted to determine the uncertainty in the trajectory. It was discovered that the Time Space Position Information (TSPI) from the optical tracking provided accurate position data. However, the velocity from TPSI must be computed via numerical differentiation, which is prone to large error. DGPS obtains position through pseudo-range calculations from multiple satellites and velocity through Doppler shift of the carrier frequency. Because the velocity from DGPS is a direct measurement, it is more accurate than TSPI velocity. To remedy the situation, a commercial off-the-shelf product that combines GPS and an Inertial Measurement Unit (IMU) was purchased to significantly improve rate of descent measurements. This had the added benefit of solving GPS dropouts during aircraft extraction. Statistical probability

  2. Resistive Wall Growth Rate Measurements in the Fermilab Recycler

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

    Ainsworth, R.; Adamson, P.; Burov, A.

    2016-10-05

    Impedance could represent a limitation of running high intensity beams in the Fermilab recycler. With high intensity upgrades foreseen, it is important to quantify the impedance. To do this,studies have been performed measuring the growth rate of presumably the resistive wall instability. The growth rates at varying intensities and chromaticities are shown. The measured growth rates are compared to ones calculated with the resistive wall impedance.

  3. Current strain accumulation in the hinterland of the northwest Himalaya constrained by landscape analyses, basin-wide denudation rates, and low temperature thermochronology

    NASA Astrophysics Data System (ADS)

    Morell, Kristin D.; Sandiford, Mike; Kohn, Barry; Codilean, Alexandru; Fülöp, Réka-H.; Ahmad, Talat

    2017-11-01

    Rupture associated with the 25 April 2015 Mw 7.8 Gorkha (Nepal) earthquake highlighted our incomplete understanding of the structural architecture and seismic cycle processes that lead to Himalayan mountain building in Central Nepal. In this paper we investigate the style and kinematics of active mountain building in the Himalayan hinterland of Northwest India, approximately 400 km to the west of the hypocenter of the Nepal earthquake, via a combination of landscape metrics and long- (Ma) and short-term (ka) erosion rate estimates (from low temperature thermochronometry and basin-wide denudation rate estimates from 10Be concentrations). We focus our analysis on the area straddling the PT2, the physiographic transition between the Lesser and High Himalaya that has yielded important insights into the nature of hinterland deformation across much of the Himalaya. Our results from Northwest India reveal a distinctive PT2 that separates a Lesser Himalaya region with moderate relief (∼1000 m) and relatively slow erosion (<1 mm/yr) from a High Himalaya with extreme relief (∼2500 m), steep channels, and erosion rates that approach or exceed 1 mm/yr. The close spatial similarity in relative rates of long- and short-term erosion suggests that the gradient in rock uplift rates inferred from the landscape metrics across the PT2 has persisted in the same relative position since at least the past 1.5 Ma. We interpret these observations to suggest that strain accumulation in this hinterland region throughout at least the past 1.5 Ma has been accomplished both by crustal thickening via duplexing and overthrusting along transient emergent faults. Despite the >400 km distance between them, similar spatiotemporal patterns of erosion and deformation observed in Northwest India and Central Nepal suggest both regions experience similar styles of active strain accumulation and both are susceptible to large seismic events.

  4. Long-term carbon accumulation in Andes peatlands

    NASA Astrophysics Data System (ADS)

    Huaman, Yizet; Moreira-turq, Patricia; Willems, Bram; Espinoza, Raul; Turq, Bruno; Apaéstegui, James; Llanos, Romina

    2017-04-01

    High-altitude peatlands of the Andes still remain relatively unexplored since most of the studies on carbon capture in tropical soils have focused on peatlands in low altitude areas, leaving aside the importance of the study of high mountain wetlands, currently called "bofedales" located between 3000 and 5000 masl, covering most of the Andes mountains in South America. These peatlands in turn may also represent important paleoclimatic records. In this study, we investigated three peatland cores (APA-01, APA2-01, and APA2-02) at different altitudes (4210 m, 4420 m and 4432 m, respectively) in high Andean Peatlands of southern Peru. The peatland studied is located at the headwater basin Cachi River, in the town of Ayacucho, Peru. The aim of this study was to evaluate the role played by past climatic changes on the peatlands carbon accumulation. Each core was sectioned centimeter by centimeter and sub samples (n = 31) were collected for radiocarbon dating by AMS (acceleration mass spectrometer) and were used to create a sedimentological model based on the program Clam2.2R. The concentrations of carbon and nitrogen were determined from a C / H / N elemental analyzer and the stable carbon and nitrogen isotopes (δ13C and δ15N) were also analyzed. The bulk density was determined based on the volume occupied by the sediment (g /cm3). Finally, the carbon accumulation rate (gC m-2año-1) was determined. The three cores were characterized by two sedimentary units, the results present in the first sedimentary unit of APA01 an average long-term carbon accumulation rate of 59 gC m-2año-1, APA2-01 with 32 gC m-2año-1 and finally APA2-02 with 24 gC m-2año-1; for the second sedimentary unit we have: APA01 on average 17 gC m-2año-1, APA2-01 with 33 gC m-2año-1 and finally APA2-02 with 49 gC m-2año-1. In conclusion, we can say that the carbon accumulation rate for the first sedimentary unit of the three cores decreases as the altitude increases; on the other hand, we have the

  5. VOC flux measurements using a novel Relaxed Eddy Accumulation GC-FID system in urban Houston, Texas

    NASA Astrophysics Data System (ADS)

    Park, C.; Schade, G.; Boedeker, I.

    2008-12-01

    Houston experiences higher ozone production rates than most other major cities in the US, which is related to high anthropogenic VOC emissions from both area/mobile sources (car traffic) and a large number of petrochemical facilities. The EPA forecasts that Houston is likely to still violate the new 8-h NAAQS in 2020. To monitor neighborhood scale pollutant fluxes, we established a tall flux tower installation a few kilometers north of downtown Houston. We measure energy and trace gas fluxes, including VOCs from both anthropogenic and biogenic emission sources in the urban surface layer using eddy covariance and related techniques. Here, we describe a Relaxed Eddy Accumulation (REA) system combined with a dual-channel GC-FID used for VOC flux measurements, including first results. Ambient air is sampled at approximately 15 L min-1 through a 9.5 mm OD PFA line from 60 m above ground next to a sonic anemometer. Subsamples of this air stream are extracted through an ozone scrubber and pushed into two Teflon bag reservoirs, from which they are transferred to the GC pre-concentration units consisting of carbon-based adsorption traps encapsulated in heater blocks for thermal desorption. We discuss the performance of our system and selected measurement results from the 2008 spring and summer seasons in Houston. We present diurnal variations of the fluxes of the traffic tracers benzene, toluene, ethylbenzene, and xylenes (BTEX) during different study periods. Typical BTEX fluxes ranged from -0.36 to 3.10 mg m-2 h-1 for benzene, and -0.47 to 5.04 mg m-2 h-1 for toluene, and exhibited diurnal cycles with two dominant peaks related to rush-hour traffic. A footprint analysis overlaid onto a geographic information system (GIS) will be presented to reveal the dominant emission sources and patterns in the study area.

  6. Accelerated Mutation Accumulation in Asexual Lineages of a Freshwater Snail

    PubMed Central

    Neiman, Maurine; Hehman, Gery; Miller, Joseph T.; Logsdon, John M.; Taylor, Douglas R.

    2010-01-01

    Sexual reproduction is both extremely costly and widespread relative to asexual reproduction, meaning that it must also confer profound advantages in order to persist. One theorized benefit of sex is that it facilitates the clearance of harmful mutations, which would accumulate more rapidly in the absence of recombination. The extent to which ineffective purifying selection and mutation accumulation are direct consequences of asexuality and whether the accelerated buildup of harmful mutations in asexuals can occur rapidly enough to maintain sex within natural populations, however, remain as open questions. We addressed key components of these questions by estimating the rate of mutation accumulation in the mitochondrial genomes of multiple sexual and asexual representatives of Potamopyrgus antipodarum, a New Zealand snail characterized by mixed sexual/asexual populations. We found that increased mutation accumulation is associated with asexuality and occurs rapidly enough to be detected in recently derived asexual lineages of P. antipodarum. Our results demonstrate that increased mutation accumulation in asexuals can differentially affect coexisting and ecologically similar sexual and asexual lineages. The accelerated rate of mutation accumulation observed in asexual P. antipodarum provides some of the most direct evidence to date for a link between asexuality and mutation accumulation and implies that mutational buildup could be rapid enough to contribute to the short-term evolutionary mechanisms that favor sexual reproduction. PMID:19995828

  7. Magnitude and variability of Holocene sediment accumulation in Santa Monica Bay, California

    USGS Publications Warehouse

    Sommerfield, C.K.; Lee, H.J.

    2003-01-01

    The spatial variability of Holocene (past 10,000 years) sediment accumulation in Santa Monica Bay (California) was examined to identify controls sediment trapping in a bathymetrically complex coastal embayment and to provide geologic context for the post-industrial sedimentary record and associated pollution gradients. Sediment chronologies based on downcore AMS 14C dates were used to quantify long-term (millennia) accumulation rates in an effort to elucidate particle-transport pathways and sinks. Sediment accumulation rates for the full range of bayfloor environments (50-630 m water depths) range from 22 to 102 mg/cm2/year (15-88 mm/100 year), have an overall mean of 51??21 mg/cm2/year (1??, n=11), and are comparable to rates reported for adjacent borderland basins. Maximal accumulation rates on the Malibu shelf and within a reentrant to Redondo canyon are interpreted to reflect (1) proximity to sediment sources and (2) localized oceanographic and topographic conditions conducive to sediment trapping and deposition. The 14C-derived accumulation rates are 2-10 times lower than rates determined through 210Pb geochronology for the same sites in a related study, revealing that Holocene sediment accumulation has been non-steady-state. Santa Monica Bay is an important sink for suspended matter; averaged over the past several millennia a mass of sediment equivalent to 10-80% of the modern annual river supply is sequestered yearly. Net influx of suspended matter derived from the adjacent Palos Verdes shelf is evinced by a concentration gradient of p,p???-DDE in bayfloor sediments, whereas the distribution of anthropogenic silver suggests transport from Santa Monica shelf to the southeastern boundary of the bay. The results of this study provide new insight to the long-term fates of particulate matter in Los Angeles coastal waters. ?? 2003 Elsevier Science Ltd. All rights reserved.

  8. Dose-rate-dependent damage of cerium dioxide in the scanning transmission electron microscope.

    PubMed

    Johnston-Peck, Aaron C; DuChene, Joseph S; Roberts, Alan D; Wei, Wei David; Herzing, Andrew A

    2016-11-01

    Beam damage caused by energetic electrons in the transmission electron microscope is a fundamental constraint limiting the collection of artifact-free information. Through understanding the influence of the electron beam, experimental routines may be adjusted to improve the data collection process. Investigations of CeO 2 indicate that there is not a critical dose required for the accumulation of electron beam damage. Instead, measurements using annular dark field scanning transmission electron microscopy and electron energy loss spectroscopy demonstrate that the onset of measurable damage occurs when a critical dose rate is exceeded. The mechanism behind this phenomenon is that oxygen vacancies created by exposure to a 300keV electron beam are actively annihilated as the sample re-oxidizes in the microscope environment. As a result, only when the rate of vacancy creation exceeds the recovery rate will beam damage begin to accumulate. This observation suggests that dose-intensive experiments can be accomplished without disrupting the native structure of the sample when executed using dose rates below the appropriate threshold. Furthermore, the presence of an encapsulating carbonaceous layer inhibits processes that cause beam damage, markedly increasing the dose rate threshold for the accumulation of damage. Published by Elsevier B.V.

  9. Biomass accumulation rates of Amazonian secondary forest and biomass of old-growth forests from Landsat time series and the Geoscience Laser Altimeter System

    Treesearch

    E. H. Helmer; M. A. Lefsky; D. A. Roberts

    2009-01-01

    We estimate the age of humid lowland tropical forests in Rondônia, Brazil, from a somewhat densely spaced time series of Landsat images (1975–2003) with an automated procedure, the Threshold Age Mapping Algorithm (TAMA), first described here. We then estimate a landscape-level rate of aboveground woody biomass accumulation of secondary forest by combining forest age...

  10. Validating a new device for measuring tear evaporation rates.

    PubMed

    Rohit, Athira; Ehrmann, Klaus; Naduvilath, Thomas; Willcox, Mark; Stapleton, Fiona

    2014-01-01

    To calibrate and validate a commercially available dermatology instrument to measure tear evaporation rate of contact lens wearers. A dermatology instrument was modified by attaching a swim goggle cup such that the cup sealed around the eye socket. Results for the unmodified instrument are dependent on probe area and enclosed volume. Calibration curves were established using a model eye, to account for individual variations in chamber volume and exposed area. Fifteen participants were recruited and the study included a contact lens wear and a no contact lens wear stage. Day and diurnal variation of the measurements were assessed by taking the measurement three times a day over 2 days. The coefficient of repeatability of the measurement was calculated and a linear mixed model assessed the influence of humidity, temperature, contact lens wear, day and diurnal variations on tear evaporation rate. The associations between variables were assessed using Pearson correlation coefficient. Absolute evaporation rates with and without contact lens wear were calculated based on the new calibration. The measurements were most repeatable during the evening with no lens wear (COR = 49 g m⁻² h) and least repeatable during the evening with contact lens wear (COR = 93 g m⁻² h). Humidity (p = 0.007), and contact lens wear (p < 0.01), significantly affected the tear evaporation rate. However, temperature (p = 0.54) diurnal variation (p = 0.85) and different days (p = 0.65) had no significant effect after controlling for humidity. Tear evaporation rates can be measured using a modified dermatology instrument. Measurements were higher and more variable with lens wear consistent with previous literature. Control of environmental conditions is important as a higher humidity results in a reduced evaporation rate. © 2013 The Authors Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

  11. Measurement of Carbon Dioxide Accumulation and Physiological Function in the Launch and Entry and Advanced Crew Escape Suits

    NASA Technical Reports Server (NTRS)

    Bishop, Phillip; Greenisen, M. C.

    1997-01-01

    The Launch and Entry Suit (LES) and Advanced Crew Escape Suit (ACES) are worn by astronauts for launch and entry. Previous work by Waligora, et al., 1992, Waligora and Gilbert, 1992, and Dalrymple 1996, have found that carbon dioxide (CO2) accumulation in the LES/ACES helmet may be problematic. CO2 accumulation is important because high inspired levels of CO2 reduce physical function and pose a safety hazard (e.g. levels of CO2 accumulation of 3.6% in the Extravehicular Mobility Unit are sufficient to terminate Extra Vehicular Activities). My task was to design a suitable test protocol for determining the important physiological aspects of LES/ACES use. Three basic issues arose. First was the determination of the astronaut's CO2 inspiration during visor-down use at rest and during walking at 3.5 mph. A sub-issue was the impact of a pneumotach on CO2 since it has been previously observed that when the Aerosport pneumotach was used, performance seemed improved, which might be attributable to a lowered respiration rate when using the pneumotach. The second issue was the energy costs of waLking in the LES/ACES with various G-suit inflation levels, since G-suit inflation increases metabolic costs and metabolic costs influence the C02 production in the LES/ACES helmet. Since G-suit inflation improves orthostatic tolerance after space flight, but likely increases the energy costs of walking, the balance between G-suit inflation and C02 accumulation is an important safety consideration. The third issue which arose from pilot work was the substantial reduction in physical function after a 10 min visor-down period prior to walk.

  12. Seasonal arsenic accumulation in stream sediments at a groundwater discharge zone.

    PubMed

    MacKay, Allison A; Gan, Ping; Yu, Ran; Smets, Barth F

    2014-01-21

    Seasonal changes in arsenic and iron accumulation rates were examined in the sediments of a brook that receives groundwater discharges of arsenic and reduced iron. Clean glass bead columns were deployed in sediments for known periods over the annual hydrologic cycle to monitor changes in arsenic and iron concentrations in bead coatings. The highest accumulation rates occurred during the dry summer period (July-October) when groundwater discharges were likely greatest at the sample locations. The intermediate flow period (October-March), with higher surface water levels, was associated with losses of arsenic and iron from bead column coatings at depths below 2-6 cm. Batch incubations indicated iron releases from solids to be induced by biological reduction of iron (oxy)hydroxide solids. Congruent arsenic releases during incubation were limited by the high arsenic sorption capacity (0.536 mg(As)/mg(Fe)) of unreacted iron oxide solids. The flooded spring (March-June) with high surface water flows showed the lowest arsenic and iron accumulation rates in the sediments. Comparisons of accumulation rates across a shoreline transect were consistent with greater rates at regions exposed above surface water levels for longer times and greater losses at locations submerged below surface water. Iron (oxy)hydroxide solids in the shallowest sediments likely serve as a passive barrier to sorb arsenic released to pore water at depth by biological iron reduction.

  13. Effects of frame rate and image resolution on pulse rate measured using multiple camera imaging photoplethysmography

    NASA Astrophysics Data System (ADS)

    Blackford, Ethan B.; Estepp, Justin R.

    2015-03-01

    Non-contact, imaging photoplethysmography uses cameras to facilitate measurements including pulse rate, pulse rate variability, respiration rate, and blood perfusion by measuring characteristic changes in light absorption at the skin's surface resulting from changes in blood volume in the superficial microvasculature. Several factors may affect the accuracy of the physiological measurement including imager frame rate, resolution, compression, lighting conditions, image background, participant skin tone, and participant motion. Before this method can gain wider use outside basic research settings, its constraints and capabilities must be well understood. Recently, we presented a novel approach utilizing a synchronized, nine-camera, semicircular array backed by measurement of an electrocardiogram and fingertip reflectance photoplethysmogram. Twenty-five individuals participated in six, five-minute, controlled head motion artifact trials in front of a black and dynamic color backdrop. Increasing the input channel space for blind source separation using the camera array was effective in mitigating error from head motion artifact. Herein we present the effects of lower frame rates at 60 and 30 (reduced from 120) frames per second and reduced image resolution at 329x246 pixels (one-quarter of the original 658x492 pixel resolution) using bilinear and zero-order downsampling. This is the first time these factors have been examined for a multiple imager array and align well with previous findings utilizing a single imager. Examining windowed pulse rates, there is little observable difference in mean absolute error or error distributions resulting from reduced frame rates or image resolution, thus lowering requirements for systems measuring pulse rate over sufficient length time windows.

  14. Strain accumulation across the Coast Ranges at the latitude of San Francisco, 1994-2000

    USGS Publications Warehouse

    Savage, J.C.; Gan, Weijun; Prescott, W.H.; Svarc, J.L.

    2004-01-01

    A 66-monument geodetic array spanning the Coast Ranges near San Francisco has been surveyed more than eight times by GIPS between late 1993 and early 2001. The measured horizontal velocities of the monuments are well represented by uniform, right-lateral, simple shear parallel to N29??W. (The local strike of the San Andreas Fault is ???N34??W. The observed areal dilatation rate of 6.9 ?? 10.0 nstrain yr-1 (quoted uncertainty is one standard deviation and extension is reckoned positive) is not significantly different from zero, which implies that the observed strain accumulation could be released by strike-slip faulting alone. Our results are consistent with the slip rates assigned by the Working Group on California Earthquake Probabilities [2003] to the principal faults (San Gregorio, San Andreas, Hayward-Rodgers Creek, Calaveras-Concord-Green Valley, and Greenville Faults) cutting across the GPS array. The vector sum of those slip rates is 39.8 ?? 2.6 mm yr-1 N29.8??W ?? 2.8??, whereas the motion across the GPS array (breadth 120 km) inferred from the uniform strain rate approximation is 38.7 ?? 1.2 mm yr-1 N29.0?? ?? 0.9?? right-lateral shear and 0.4 ?? 0.9 mm yr-1 N61??E ?? 0.9?? extension. We interpret the near coincidence of these rates and the absence of significant accumulation of areal dilatation to imply that right-lateral slip on the principal faults can release the accumulating strain; major strain release on reverse faults subparallel to the San Andreas Fault within the Coast Ranges is not required. Copyright 2004 by the American Geophysical union.

  15. DGT estimates cadmium accumulation in wheat and potato from phosphate fertilizer applications

    PubMed Central

    Pérez, Angela L.; Anderson, Kim A.

    2014-01-01

    Cadmium is a common impurity in phosphatic fertilizers and may contribute to soil Cd accumulation. Changes in total and bioavailable Cd burdens to agricultural soils and the potential for plant Cd accumulation resulting from fertilizer input was investigated. Three year field studies were conducted using three dose levels of cadmium-rich, commercial, phosphate fertilizers applied at four agricultural sites. Labile Cd concentrations, measured using the passive sampling device Diffusive Gradients in Thin Films (CdDGT), increased with increasing fertilizer application rates. Cd also accumulated in the edible portion of wheat and potato crops grown at the sites, and showed strong positive dose response with fertilizer treatment. Regression models were calculated for each site, year, and for individual crops. Model comparisons indicated that soil physical and chemical parameters in addition to soil Cd fractions, were important determinants of CdDGT. Significant factors contributing to CdDGT concentrations were Cd from fertilizer input (Cdfertilizer), pH, cation exchange capacity (CEC), and total recoverable Cd (Cdtotal). Important factors used to determine Cd concentrations in wheat grain (Cdwheat) and in potato (Cdpotato) were as follows: Cdwheat:Cdfertilizer, and CdDGT; and Cdpotato:Cdfertilizer, CdDGT, % O.M. The effective concentration, CE, calculated from DGT did not correlate well with Cdwheat or with Cdpotato. Direct measurements of CdDGT correlated better with Cd found in edible plant tissue. The modeling approach presented in this study helps to estimate Cd accumulation in plant tissue over multiple years and in distinct agricultural soil systems. PMID:19552942

  16. Dual Mode NOx Sensor: Measuring Both the Accumulated Amount and Instantaneous Level at Low Concentrations

    PubMed Central

    Groß, Andrea; Beulertz, Gregor; Marr, Isabella; Kubinski, David J.; Visser, Jaco H.; Moos, Ralf

    2012-01-01

    The accumulating-type (or integrating-type) NOx sensor principle offers two operation modes to measure low levels of NOx: The direct signal gives the total amount dosed over a time interval and its derivative the instantaneous concentration. With a linear sensor response, no baseline drift, and both response times and recovery times in the range of the gas exchange time of the test bench (5 to 7 s), the integrating sensor is well suited to reliably detect low levels of NOx. Experimental results are presented demonstrating the sensor’s integrating properties for the total amount detection and its sensitivity to both NO and to NO2. We also show the correlation between the derivative of the sensor signal and the known gas concentration. The long-term detection of NOx in the sub-ppm range (e.g., for air quality measurements) is discussed. Additionally, a self-adaption of the measurement range taking advantage of the temperature dependency of the sensitivity is addressed. PMID:22736980

  17. High-rate measurement-device-independent quantum cryptography

    NASA Astrophysics Data System (ADS)

    Pirandola, Stefano; Ottaviani, Carlo; Spedalieri, Gaetana; Weedbrook, Christian; Braunstein, Samuel L.; Lloyd, Seth; Gehring, Tobias; Jacobsen, Christian S.; Andersen, Ulrik L.

    2015-06-01

    Quantum cryptography achieves a formidable task—the remote distribution of secret keys by exploiting the fundamental laws of physics. Quantum cryptography is now headed towards solving the practical problem of constructing scalable and secure quantum networks. A significant step in this direction has been the introduction of measurement-device independence, where the secret key between two parties is established by the measurement of an untrusted relay. Unfortunately, although qubit-implemented protocols can reach long distances, their key rates are typically very low, unsuitable for the demands of a metropolitan network. Here we show, theoretically and experimentally, that a solution can come from the use of continuous-variable systems. We design a coherent-state network protocol able to achieve remarkably high key rates at metropolitan distances, in fact three orders of magnitude higher than those currently achieved. Our protocol could be employed to build high-rate quantum networks where devices securely connect to nearby access points or proxy servers.

  18. On Utilization of NEXRAD Scan Strategy Information to Infer Discrepancies Associated With Radar and Rain Gauge Surface Volumetric Rainfall Accumulations

    NASA Technical Reports Server (NTRS)

    Roy, Biswadev; Datta, Saswati; Jones, W. Linwood; Kasparis, Takis; Einaudi, Franco (Technical Monitor)

    2000-01-01

    To evaluate the Tropical Rainfall Measuring Mission (TRMM) monthly Ground Validation (GV) rain map, 42 quality controlled tipping bucket rain gauge data (1 minute interpolated rain rates) were utilized. We have compared the gauge data to the surface volumetric rainfall accumulation of NEXRAD reflectivity field, (converting to rain rates using a 0.5 dB resolution smooth Z-R table). The comparison was carried out from data collected at Melbourne, Florida during the month of July 98. GV operational level 3 (L3 monthly) accumulation algorithm was used to obtain surface volumetric accumulations for the radar. The gauge records were accumulated using the 1 minute interpolated rain rates while the radar Volume Scan (VOS) intervals remain less than or equal to 75 minutes. The correlation coefficient for the radar and gauge totals for the monthly time-scale remain at 0.93, however, a large difference was noted between the gauge and radar derived rain accumulation when the radar data interval is either 9 minute, or 10 minute. This difference in radar and gauge accumulation is being explained in terms of the radar scan strategy information. The discrepancy in terms of the Volume Coverage Pattern (VCP) of the NEXRAD is being reported where VCP mode is ascertained using the radar tilt angle information. Hourly radar and gauge accumulations have been computed using the present operational L3 method supplemented with a threshold period of +/- 5 minutes (based on a sensitivity analysis). These radar and gauge accumulations are subsequently improved using a radar hourly scan weighting factor (taking ratio of the radar scan frequency within a time bin to the 7436 total radar scans for the month). This GV procedure is further being improved by introducing a spatial smoothing method to yield reasonable bulk radar to gauge ratio for the hourly and daily scales.

  19. Measuring star formation rates in blue galaxies

    NASA Technical Reports Server (NTRS)

    Gallagher, John S., III; Hunter, Deidre A.

    1987-01-01

    The problems associated with measurements of star formation rates in galaxies are briefly reviewed, and specific models are presented for determinations of current star formation rates from H alpha and Far Infrared (FIR) luminosities. The models are applied to a sample of optically blue irregular galaxies, and the results are discussed in terms of star forming histories. It appears likely that typical irregular galaxies are forming stars at nearly constant rates, although a few examples of systems with enhanced star forming activity are found among HII regions and luminous irregular galaxies.

  20. Local Spatial Heterogeneity of Holocene Carbon Accumulation throughout the Peat Profile of an Ombrotrophic Northern Minnesota Bog

    DOE PAGES

    McFarlane, Karis J.; Hanson, Paul J.; Iversen, Colleen M.; ...

    2018-05-30

    Here, we evaluated the spatial heterogeneity of historical carbon accumulation rates in a forested, ombrotrophic bog in Minnesota to aid understanding of responses to an ongoing decade-long warming manipulation. Eighteen peat cores indicated that the bog has been accumulating carbon for over 11,000 years, to yield 176±40 kg C m –2 to 225±58 cm of peat depth. Estimated peat basal ages ranged from 5100 to 11,100 cal BP. The long-term apparent rate of carbon accumulation over the entire peat profile was 22±2 kg C m –2yr –1. Plot location within the study area did not affect carbon accumulation rates, butmore » estimated basal ages were younger in profiles from plots closer to the bog lagg and farther from the bog outlet. In addition, carbon accumulation varied considerably over time. Early Holocene net carbon accumulation rates were 30±6 g C m –2yr –1. Around 3300 calendar BP, net carbon accumulation rates dropped to 15±8 g C m –2yr –1until the last century when net accumulation rates increased again to 74±57 g C m –2yr –1. During this period of low accumulation, regional droughts may have lowered the water table, allowing for enhanced aerobic decomposition and making the bog more susceptible to fire. These results suggest that experimental warming treatments, as well as a future warmer climate may reduce net carbon accumulation in peat in this and other southern boreal peatlands. Furthermore, our we caution against historical interpretations extrapolated from one or a few peat cores.« less

  1. Local Spatial Heterogeneity of Holocene Carbon Accumulation throughout the Peat Profile of an Ombrotrophic Northern Minnesota Bog

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

    McFarlane, Karis J.; Hanson, Paul J.; Iversen, Colleen M.

    Here, we evaluated the spatial heterogeneity of historical carbon accumulation rates in a forested, ombrotrophic bog in Minnesota to aid understanding of responses to an ongoing decade-long warming manipulation. Eighteen peat cores indicated that the bog has been accumulating carbon for over 11,000 years, to yield 176±40 kg C m –2 to 225±58 cm of peat depth. Estimated peat basal ages ranged from 5100 to 11,100 cal BP. The long-term apparent rate of carbon accumulation over the entire peat profile was 22±2 kg C m –2yr –1. Plot location within the study area did not affect carbon accumulation rates, butmore » estimated basal ages were younger in profiles from plots closer to the bog lagg and farther from the bog outlet. In addition, carbon accumulation varied considerably over time. Early Holocene net carbon accumulation rates were 30±6 g C m –2yr –1. Around 3300 calendar BP, net carbon accumulation rates dropped to 15±8 g C m –2yr –1until the last century when net accumulation rates increased again to 74±57 g C m –2yr –1. During this period of low accumulation, regional droughts may have lowered the water table, allowing for enhanced aerobic decomposition and making the bog more susceptible to fire. These results suggest that experimental warming treatments, as well as a future warmer climate may reduce net carbon accumulation in peat in this and other southern boreal peatlands. Furthermore, our we caution against historical interpretations extrapolated from one or a few peat cores.« less

  2. Element accumulation in tall fescue and alfalfa

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

    Stucky, D.J.; Newman, T.S.

    This study was initiated to examine the effect of three application rates of dried anaerobically digested sludge on two different soil media on the establishment, yield, duration, and element accumulation in tall fescue and alfalfa. In a greenhouse study, acid strip-mine spoil and agricultural soil were used to compare plant growth in sewage-amended and untreated media. Sludge was applied at 0, 314, and 627 metric tons/hectare to the agricultural soil control and the strip mine spoil. Plant yields were significantly higher for strip-mine spoil amended with 627 metric tons/ha and for agricultural soil amended with 314 and 627 metric tons/ha.more » Concentrations of Mn, Ni, Cd, Zn, and Cu were measured in plants and soils. Concentrations of Mn, Zn, Ni, and Cd in tall fescue and alfalfa grown in strip-mine spoils were higher at higher sludge application rates. Sludge application rate did not affect Cu uptake. Concentrations of Mn, Zn, Ni, and Cd in tall fescue were highest during the 180 toese is the fluctuation in nutrient salt concentrations:agreement of experimental and calculated data is obtton beam.« less

  3. Glycolysis-induced discordance between glucose metabolic rates measured with radiolabeled fluorodeoxyglucose and glucose

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

    Ackermann, R.F.; Lear, J.L.

    We have developed an autoradiographic method for estimating the oxidative and glycolytic components of local CMRglc (LCMRglc), using sequentially administered ({sup 18}F)fluorodeoxyglucose (FDG) and ({sup 14}C)-6-glucose (GLC). FDG-6-phosphate accumulation is proportional to the rate of glucose phosphorylation, which occurs before the divergence of glycolytic (GMg) and oxidative (GMo) glucose metabolism and is therefore related to total cerebral glucose metabolism GMt: GMg + GMo = GMt. With oxidative metabolism, the {sup 14}C label of GLC is temporarily retained in Krebs cycle-related substrate pools. We hypothesize that with glycolytic metabolism, however, a significant fraction of the {sup 14}C label is lost frommore » the brain via lactate production and efflux from the brain. Thus, cerebral GLC metabolite concentration may be more closely related to GMo than to GMt. If true, the glycolytic metabolic rate will be related to the difference between FDG- and GLC-derived LCMRglc. Thus far, we have studied normal awake rats, rats with limbic activation induced by kainic acid (KA), and rats visually stimulated with 16-Hz flashes. In KA-treated rats, significant discordance between FDG and GLC accumulation, which we attribute to glycolysis, occurred only in activated limbic structures. In visually stimulated rats, significant discordance occurred only in the optic tectum.« less

  4. Gas flow meter and method for measuring gas flow rate

    DOEpatents

    Robertson, Eric P.

    2006-08-01

    A gas flow rate meter includes an upstream line and two chambers having substantially equal, fixed volumes. An adjustable valve may direct the gas flow through the upstream line to either of the two chambers. A pressure monitoring device may be configured to prompt valve adjustments, directing the gas flow to an alternate chamber each time a pre-set pressure in the upstream line is reached. A method of measuring the gas flow rate measures the time required for the pressure in the upstream line to reach the pre-set pressure. The volume of the chamber and upstream line are known and fixed, thus the time required for the increase in pressure may be used to determine the flow rate of the gas. Another method of measuring the gas flow rate uses two pressure measurements of a fixed volume, taken at different times, to determine the flow rate of the gas.

  5. Optical measurement of high-temperature melt flow rate.

    PubMed

    Bizjan, Benjamin; Širok, Brane; Chen, Jinpeng

    2018-05-20

    This paper presents an optical method and system for contactless measurement of the mass flow rate of melts by digital cameras. The proposed method is based on reconstruction of melt stream geometry and flow velocity calculation by cross correlation, and is very cost-effective due its modest hardware requirements. Using a laboratory test rig with a small inductive melting pot and reference mass flow rate measurement by weighing, the proposed method was demonstrated to have an excellent dynamic response (0.1 s order of magnitude) while producing deviations from the reference of about 5% in the steady-state flow regime. Similar results were obtained in an industrial stone wool production line for two repeated measurements. Our method was tested in a wide range of melt flow rates (0.05-1.2 kg/s) and did not require very fast cameras (120 frames per second would be sufficient for most industrial applications).

  6. Development of a portable photosynthesis rate measurement device

    NASA Astrophysics Data System (ADS)

    Wang, Junsheng; Xing, Da; Xu, Wenhai

    2006-09-01

    Photosynthesis is a very important chemical reaction in the plant, and its measurement plays critical role in the agriculture production and science research of plant. Delayed fluorescence (DF) in plants is an intrinsic label of efficiency of charge separation at P680 in photosystem II (PS II). In this paper, a portable photosynthesis rate measurement device by means of DF is proposed. It can achieve DF of plant with high sensitivity and signal-to-noise ratio basing on ultra-weak luminescence detection technique, and get photosynthesis rate by the corresponding relation between DF and photosynthesis rate. The device has its illumination power and can obtain all-weather measurement with less interference of the environment. Locale live survey can be realized by hermetic darkroom design and battery power supply. The system carries out data acquisition and processing by single-chip microcomputer control. The results show that this instrument has a lot of values such as low cost, high accuracy and good reliability and convenience.

  7. Content-specific evidence accumulation in inferior temporal cortex during perceptual decision-making

    PubMed Central

    Tremel, Joshua J.; Wheeler, Mark E.

    2015-01-01

    During a perceptual decision, neuronal activity can change as a function of time-integrated evidence. Such neurons may serve as decision variables, signaling a choice when activity reaches a boundary. Because the signals occur on a millisecond timescale, translating to human decision-making using functional neuroimaging has been challenging. Previous neuroimaging work in humans has identified patterns of neural activity consistent with an accumulation account. However, the degree to which the accumulating neuroimaging signals reflect specific sources of perceptual evidence is unknown. Using an extended face/house discrimination task in conjunction with cognitive modeling, we tested whether accumulation signals, as measured using functional magnetic resonance imaging (fMRI), are stimulus-specific. Accumulation signals were defined as a change in the slope of the rising edge of activation corresponding with response time (RT), with higher slopes associated with faster RTs. Consistent with an accumulation account, fMRI activity in face- and house-selective regions in the inferior temporal cortex increased at a rate proportional to decision time in favor of the preferred stimulus. This finding indicates that stimulus-specific regions perform an evidence integrative function during goal-directed behavior and that different sources of evidence accumulate separately. We also assessed the decision-related function of other regions throughout the brain and found that several regions were consistent with classifications from prior work, suggesting a degree of domain generality in decision processing. Taken together, these results provide support for an integration-to-boundary decision mechanism and highlight possible roles of both domain-specific and domain-general regions in decision evidence evaluation. PMID:25562821

  8. Strontium-90 Accumulation on Plant Foliage During Rainfall.

    PubMed

    Menzel, R G; Roberts, H; Stewart, E H; Mackenzie, A J

    1963-11-01

    Accumulation of strontium-90 in field-grown crops was measured during the spring of 1962. Each rainfall markedly increased the strontium-90 content of the crops, except when the plants were very small. Accumulation between rains was comparatively small, about equal to the expected uptake from the soil.

  9. Effect of collagen turnover on the accumulation of advanced glycation end products.

    PubMed

    Verzijl, N; DeGroot, J; Thorpe, S R; Bank, R A; Shaw, J N; Lyons, T J; Bijlsma, J W; Lafeber, F P; Baynes, J W; TeKoppele, J M

    2000-12-15

    Collagen molecules in articular cartilage have an exceptionally long lifetime, which makes them susceptible to the accumulation of advanced glycation end products (AGEs). In fact, in comparison to other collagen-rich tissues, articular cartilage contains relatively high amounts of the AGE pentosidine. To test the hypothesis that this higher AGE accumulation is primarily the result of the slow turnover of cartilage collagen, AGE levels in cartilage and skin collagen were compared with the degree of racemization of aspartic acid (% d-Asp, a measure of the residence time of a protein). AGE (N(epsilon)-(carboxymethyl)lysine, N(epsilon)-(carboxyethyl)lysine, and pentosidine) and % d-Asp concentrations increased linearly with age in both cartilage and skin collagen (p < 0.0001). The rate of increase in AGEs was greater in cartilage collagen than in skin collagen (p < 0.0001). % d-Asp was also higher in cartilage collagen than in skin collagen (p < 0.0001), indicating that cartilage collagen has a longer residence time in the tissue, and thus a slower turnover, than skin collagen. In both types of collagen, AGE concentrations increased linearly with % d-Asp (p < 0.0005). Interestingly, the slopes of the curves of AGEs versus % d-Asp, i.e. the rates of accumulation of AGEs corrected for turnover, were identical for cartilage and skin collagen. The present study thus provides the first experimental evidence that protein turnover is a major determinant in AGE accumulation in different collagen types. From the age-related increases in % d-Asp the half-life of cartilage collagen was calculated to be 117 years and that of skin collagen 15 years, thereby providing the first reasonable estimates of the half-lives of these collagens.

  10. Endogenously Generated Plasmin at the Vascular Wall Injury Site Amplifies Lysine Binding Site-Dependent Plasminogen Accumulation in Microthrombi

    PubMed Central

    Brzoska, Tomasz; Tanaka-Murakami, Aki; Suzuki, Yuko; Sano, Hideto; Kanayama, Naohiro; Urano, Tetsumei

    2015-01-01

    The fibrinolytic system plays a pivotal role in the regulation of hemostasis; however, it remains unclear how and when the system is triggered to induce thrombolysis. Using intra-vital confocal fluorescence microscopy, we investigated the process of plasminogen binding to laser-induced platelet-rich microthrombi generated in the mesenteric vein of transgenic mice expressing green fluorescent protein (GFP). The accumulation of GFP-expressing platelets as well as exogenously infused Alexa Fluor 568-labeled Glu-plasminogen (Glu-plg) on the injured vessel wall was assessed by measuring the increase in the corresponding fluorescence intensities. Glu-plg accumulated in a time-dependent manner in the center of the microthrombus, where phosphatidylserine is exposed on platelet surfaces and fibrin formation takes place. The rates of binding of Glu-plg in the presence of ε-aminocaproic acid and carboxypeptidase B, as well as the rates of binding of mini-plasminogen lacking kringle domains 1-4 and lysine binding sites, were significantly lower than that of Glu-plg alone, suggesting that the binding was dependent on lysine binding sites. Furthermore, aprotinin significantly suppressed the accumulation of Glu-plg, suggesting that endogenously generated plasmin activity is a prerequisite for the accumulation. In spite of the endogenous generation of plasmin and accumulation of Glu-plg in the center of microthrombi, the microthrombi did not change in size during the 2-hour observation period. When human tissue plasminogen activator was administered intravenously, Glu-plg further accumulated and the microthrombi were lysed. Glu-plg appeared to accumulate in the center of microthrombi in the early phase of microthrombus formation, and plasmin activity and lysine binding sites were required for this accumulation. PMID:25806939

  11. Seasonality of snow accumulation at Mount Wrangell, Alaska, USA

    NASA Astrophysics Data System (ADS)

    Kanamori, Syosaku; Benson, Carl S.; Truffer, Martin; Matoba, Sumito; Solie, Daniel J.; Shiraiwa, Takayuki

    We recorded the burial times of temperature sensors mounted on a specially constructed tower to determine snow accumulation during individual storms in the summit caldera of Mount Wrangell, Alaska, USA, (62°N, 144°W; 4100 m a.s.l.) during the accumulation year June 2005 to June 2006. The experiment showed most of the accumulation occurred in episodic large storms, and half of the total accumulation was delivered in late summer. The timing of individual events correlated well with storms recorded upwind, at Cordova, the closest Pacific coastal weather station (200 km south-southeast), although the magnitude of events showed only poor correlation. Hence, snow accumulation at Mount Wrangell appears to be a reflection of synoptic-scale regional weather systems. The accumulation at Mount Wrangell's summit (>2.5 m w.e.) exceeded the precipitation at Cordova. Although the direct relationship between accumulation of individual storms at the summit of Mount Wrangell and precipitation events at Cordova may be unique in the region, it is useful for interpreting ice cores obtained on Mount Wrangell. This is especially the case here because the high rate of accumulation allows high time resolution within the core.

  12. Spatiotemporal patterns of mercury accumulation in lake sediments of western North America

    USGS Publications Warehouse

    Drevnick, Paul; Cooke, Colin A.; Barraza, Daniella; Blais, Jules M.; Coale, Kenneth; Cumming, Brian F.; Curtis, Chris; Das, Biplob; Donahue, William F.; Eagles-Smith, Collin A.; Engstrom, Daniel R.; Fitzgerald, William F.; Furl, Chad V.; Gray, John R.; Hall, Roland I.; Jackson, Togwell A.; Laird, Kathleen R.; Lockhart, W. Lyle; Macdonald, Robie W.; Mast, M. Alisa; Mathieu, Callie; Muir, Derek C.G.; Outridge, Peter; Reinemann, Scott; Rothenberg, Sarah E.; Ruiz-Fernandex, Ana Carolina; St. Louis, V.L.; Sanders, Rhea; Sanei, Hamed; Skierszkan, Elliott; Van Metre, Peter C.; Veverica, Timothy; Wiklund, Johan A.; Wolfe, Brent B.

    2016-01-01

    For the Western North America Mercury Synthesis, we compiled mercury records from 165 dated sediment cores from 138 natural lakes across western North America. Lake sediments are accepted as faithful recorders of historical mercury accumulation rates, and regional and sub-regional temporal and spatial trends were analyzed with descriptive and inferential statistics. Mercury accumulation rates in sediments have increased, on average, four times (4×) from 1850 to 2000 and continue to increase by approximately 0.2 μg/m2 per year. Lakes with the greatest increases were influenced by the Flin Flon smelter, followed by lakes directly affected by mining and wastewater discharges. Of lakes not directly affected by point sources, there is a clear separation in mercury accumulation rates between lakes with no/little watershed development and lakes with extensive watershed development for agricultural and/or residential purposes. Lakes in the latter group exhibited a sharp increase in mercury accumulation rates with human settlement, stabilizing after 1950 at five times (5×) 1850 rates. Mercury accumulation rates in lakes with no/little watershed development were controlled primarily by relative watershed size prior to 1850, and since have exhibited modest increases (in absolute terms and compared to that described above) associated with (regional and global) industrialization. A sub-regional analysis highlighted that in the ecoregion Northwestern Forest Mountains, <1% of mercury deposited to watersheds is delivered to lakes. Research is warranted to understand whether mountainous watersheds act as permanent sinks for mercury or if export of “legacy” mercury (deposited in years past) will delay recovery when/if emissions reductions are achieved.

  13. Low Velocity Difference Thermal Shear Layer Mixing Rate Measurements

    NASA Technical Reports Server (NTRS)

    Bush, Robert H.; Culver, Harry C. M.; Weissbein, Dave; Georgiadis, Nicholas J.

    2013-01-01

    Current CFD modeling techniques are known to do a poor job of predicting the mixing rate and persistence of slot film flow in co-annular flowing ducts with relatively small velocity differences but large thermal gradients. A co-annular test was devised to empirically determine the mixing rate of slot film flow in a constant area circular duct (D approx. 1ft, L approx. 10ft). The axial rate of wall heat-up is a sensitive measure of the mixing rate of the two flows. The inflow conditions were varied to simulate a variety of conditions characteristic of moderate by-pass ratio engines. A series of air temperature measurements near the duct wall provided a straightforward means to measure the axial temperature distribution and thus infer the mixing rate. This data provides a characterization of the slot film mixing rates encountered in typical jet engine environments. The experimental geometry and entrance conditions, along with the sensitivity of the results as the entrance conditions vary, make this a good test for turbulence models in a regime important to modern air-breathing propulsion research and development.

  14. Acute toxicity and accumulation of the piscicide 3-trifluoromethyl-4- nitrophenol (TFM) in freshwater mussels (Bivalvia: Unionidae)

    USGS Publications Warehouse

    Waller, D.L.; Rach, J.J.; Luoma, J.A.

    1998-01-01

    We compared the acute toxicity and initial accumulation of the piscicide TFM (3-trifluoromethyl-4-nitrophenol) in the freshwater unionacean mussels, Obliquaria reflexa and Fusconaia flava. Acute 48 h toxicity tests were conducted to determine the LC50 values for each species. The initial uptake clearances of TFM were measured by exposing the mussels to [14C]-TFM and counting the radioactivity in four organ tissues (foot, gill, mantle and viscera) over 48 h. TFM was about 2-fold more toxic to O. reflexa (LC50 1.80 mg I-1) than to F. flava (LC50 3.81 mg L-1) and the difference was not explained by accumulation patterns. The initial uptake clearance rates (0-6 h) for the whole body were similar between the species (11.2 ml g-1 h-2 in O. reflexa and 9.5 ml g-1 h-1 in F. flava). The accumulation of TFM residues among the organ tissues was also similar between species. The uptake clearance rates (ml g-1 h-1) of TFM equivalents were generally highest in the gill, but not significantly different than other organ tissues. The normalized concentration of TFM residues (??g per g whole body) was highest in the viscera. The toxicity data suggest that the mortality of both species would be minimal from sea lamprey control treatments with TFM. However, the behavioural effects and accumulation rates also indicate that mussels do not effectively avoid TFM exposure by valve closure.

  15. Acute toxicity and accumulation of the piscicide 3-trifluoromethyl-4-nitrophenol (TFM) in freshwater mussels (Bivalvia: Unionidae)

    USGS Publications Warehouse

    Waller, Diane L.; Rach, Jeffrey J.; Luoma, James A.

    1998-01-01

    We compared the acute toxicity and initial accumulation of the piscicide TFM (3-trifluoromethyl-4-nitrophenol) in the freshwater unionacean mussels, Obliquaria reflexa and Fusconaia flava. Acute 48 h toxicity tests were conducted to determine the LC50 values for each species. The initial uptake clearances of TFM were measured by exposing the mussels to [14C]-TFM and counting the radioactivity in four organ tissues (foot, gill, mantle and viscera) over 48 h. TFM was about 2-fold more toxic to O. reflexa (LC50 1.80 mg l-1) than to F. flava (LC50 3.81 mg L-1) and the difference was not explained by accumulation patterns. The initial uptake clearance rates (0–6 h) for the whole body were similar between the species (11.2 ml g-1 h-2 in O. reflexa and 9.5 ml g-1 h-1 in F. flava). The accumulation of TFM residues among the organ tissues was also similar between species. The uptake clearance rates (ml g-1 h-1) of TFM equivalents were generally highest in the gill, but not significantly different than other organ tissues. The normalized concentration of TFM residues (μg per g whole body) was highest in the viscera. The toxicity data suggest that the mortality of both species would be minimal from sea lamprey control treatments with TFM. However, the behavioural effects and accumulation rates also indicate that mussels do not effectively avoid TFM exposure by valve closure.

  16. Measurements of file transfer rates over dedicated long-haul connections

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

    Rao, Nageswara S; Settlemyer, Bradley W; Imam, Neena

    2016-01-01

    Wide-area file transfers are an integral part of several High-Performance Computing (HPC) scenarios. Dedicated network connections with high capacity, low loss rate and low competing traffic, are increasingly being provisioned over current HPC infrastructures to support such transfers. To gain insights into these file transfers, we collected transfer rate measurements for Lustre and xfs file systems between dedicated multi-core servers over emulated 10 Gbps connections with round trip times (rtt) in 0-366 ms range. Memory transfer throughput over these connections is measured using iperf, and file IO throughput on host systems is measured using xddprof. We consider two file systemmore » configurations: Lustre over IB network and xfs over SSD connected to PCI bus. Files are transferred using xdd across these connections, and the transfer rates are measured, which indicate the need to jointly optimize the connection and host file IO parameters to achieve peak transfer rates. In particular, these measurements indicate that (i) peak file transfer rate is lower than peak connection and host IO throughput, in some cases by as much as 50% or lower, (ii) xdd request sizes that achieve peak throughput for host file IO do not necessarily lead to peak file transfer rates, and (iii) parallelism in host IO and TCP transport does not always improve the file transfer rates.« less

  17. Crystal accumulation in the Hanford Waste Treatment Plant high level waste melter: Summary of FY2016 experiements

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

    Fox, K.; Fowley, M.; Miller, D.

    2016-12-01

    Five experiments were completed with the full-scale, room temperature Hanford Waste Treatment and Immobilization Plant (WTP) high-level waste (HLW) melter riser test system to observe particle flow and settling in support of a crystal tolerant approach to melter operation. A prototypic pour rate was maintained based on the volumetric flow rate. Accumulation of particles was observed at the bottom of the riser and along the bottom of the throat after each experiment. Measurements of the accumulated layer thicknesses showed that the settled particles at the bottom of the riser did not vary in thickness during pouring cycles or idle periods.more » Some of the settled particles at the bottom of the throat were re-suspended during subsequent pouring cycles, and settled back to approximately the same thickness after each idle period. The cause of the consistency of the accumulated layer thicknesses is not year clear, but was hypothesized to be related to particle flow back to the feed tank. Additional experiments reinforced the observation of particle flow along a considerable portion of the throat during idle periods. Limitations of the system are noted in this report and may be addressed via future modifications. Follow-on experiments will be designed to evaluate the impact of pouring rate on particle re-suspension, the influence of feed tank agitation on particle accumulation, and the effect of changes in air lance positioning on the accumulation and re-suspension of particles at the bottom of the riser. A method for sampling the accumulated particles will be developed to support particle size distribution analyses. Thicker accumulated layers will be intentionally formed via direct addition of particles to select areas of the system to better understand the ability to continue pouring and re-suspend particles. Results from the room temperature system will be correlated with observations and data from the Research Scale Melter (RSM) at Pacific Northwest National

  18. Contemporary deposition and long-term accumulation of sediment and nutrients by tidal freshwater forested wetlands impacted by sea level rise

    USGS Publications Warehouse

    Noe, Gregory; Hupp, Cliff R.; Bernhardt, Christopher E.; Krauss, Ken W.

    2016-01-01

    Contemporary deposition (artificial marker horizon, 3.5 years) and long-term accumulation rates (210Pb profiles, ~150 years) of sediment and associated carbon (C), nitrogen (N), and phosphorus (P) were measured in wetlands along the tidal Savannah and Waccamaw rivers in the southeastern USA. Four sites along each river spanned an upstream-to-downstream salinification gradient, from upriver tidal freshwater forested wetland (TFFW), through moderately and highly salt-impacted forested wetlands, to oligohaline marsh downriver. Contemporary deposition rates (sediment, C, N, and P) were greatest in oligohaline marsh and lowest in TFFW along both rivers. Greater rates of deposition in oligohaline and salt-stressed forested wetlands were associated with a shift to greater clay and metal content that is likely associated with a change from low availability of watershed-derived sediment to TFFW and to greater availability of a coastal sediment source to oligohaline wetlands. Long-term accumulation rates along the Waccamaw River had the opposite spatial pattern compared to contemporary deposition, with greater rates in TFFW that declined to oligohaline marsh. Long-term sediment and elemental mass accumulation rates also were 3–9× lower than contemporary deposition rates. In comparison to other studies, sediment and associated nutrient accumulation in TFFW are lower than downriver/estuarine freshwater, oligohaline, and salt marshes, suggesting a reduced capacity for surface sedimentation (short-term) as well as shallow soil processes (long-term sedimentation) to offset sea level rise in TFFW. Nonetheless, their potentially large spatial extent suggests that TFFW have a large impact on the transport and fate of sediment and nutrients in tidal rivers and estuaries.

  19. Estimation of uncertainty in tracer gas measurement of air change rates.

    PubMed

    Iizuka, Atsushi; Okuizumi, Yumiko; Yanagisawa, Yukio

    2010-12-01

    Simple and economical measurement of air change rates can be achieved with a passive-type tracer gas doser and sampler. However, this is made more complex by the fact many buildings are not a single fully mixed zone. This means many measurements are required to obtain information on ventilation conditions. In this study, we evaluated the uncertainty of tracer gas measurement of air change rate in n completely mixed zones. A single measurement with one tracer gas could be used to simply estimate the air change rate when n = 2. Accurate air change rates could not be obtained for n ≥ 2 due to a lack of information. However, the proposed method can be used to estimate an air change rate with an accuracy of <33%. Using this method, overestimation of air change rate can be avoided. The proposed estimation method will be useful in practical ventilation measurements.

  20. Mutation rates among RNA viruses

    PubMed Central

    Drake, John W.; Holland, John J.

    1999-01-01

    The rate of spontaneous mutation is a key parameter in modeling the genetic structure and evolution of populations. The impact of the accumulated load of mutations and the consequences of increasing the mutation rate are important in assessing the genetic health of populations. Mutation frequencies are among the more directly measurable population parameters, although the information needed to convert them into mutation rates is often lacking. A previous analysis of mutation rates in RNA viruses (specifically in riboviruses rather than retroviruses) was constrained by the quality and quantity of available measurements and by the lack of a specific theoretical framework for converting mutation frequencies into mutation rates in this group of organisms. Here, we describe a simple relation between ribovirus mutation frequencies and mutation rates, apply it to the best (albeit far from satisfactory) available data, and observe a central value for the mutation rate per genome per replication of μg ≈ 0.76. (The rate per round of cell infection is twice this value or about 1.5.) This value is so large, and ribovirus genomes are so informationally dense, that even a modest increase extinguishes the population. PMID:10570172

  1. Effects of hydrologic connectivity and land use on floodplain sediment accumulation at the Savannah River Site, South Carolina.

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

    Eddy, Jeremy Edward

    Floodplains, and the sediment accumulating naturally on them,are important to maintain stream water quality and serve as sinks for organic and inorganic carbon. Newer theories contend that land use and hydrologic connectivity (water-mediated transport of matter, energy, and/or organisms within or between elements of the hydrologic cycle) play important roles in determining sediment accumulation on floodplains. This study hypothesizes that changes in hydrologic connectivity have a greater impact on floodplain sediment accumulation than changes in land use. Nine sediment cores from seven sub-basins were collected from the Savannah River Site (SRS), South Carolina, and processed for grain-size, radionuclide dating (7Be,more » 137Cs, 210Pb), particulate organic carbon (POC), and microscopy. Historical records, including aerial and satellite imagery,were used to identify anthropogenic disturbances in the sub-basins, as well as to calculate the percentages of natural vegetation land cover at the SRS in 1951, and 2014. LiDAR and field survey data identified 251 flow impediments, measured elevation, and recorded standard stream characteristics (e.g., bank height) that canaffect hydrologic connectivity. Radionuclide dating was used to calculate sediment mass accumulation rates (MARs) and linear accumulation rates (LARs) for each core. Results indicate that sedimentation rates have increased across all SRS sub-basins over the past 40-50 years, shortly after site restoration and recovery efforts began.Findings show that hydrologic connectivity proxies (i.e., stream characteristics and impediments) have stronger relationships to MARs and LARs than the land use proxy (i.e., vegetation cover), confirming the hypothesis. Asstream channel depth and the number of impediments increase,floodplain sedimentation rates also increase. This knowledge can help future stream restoration efforts by focusing resources to more efficiently attain stated goals, particularly in terms of

  2. Using Structure-from-Motion to Quantify Sediment Accumulation and Bedrock Erosion in a Debris-Flow Dominated Channel

    NASA Astrophysics Data System (ADS)

    Reitman, N. G.; Rengers, F.; Kean, J. W.

    2016-12-01

    One of the highest frequencies of observed debris flows in the US is located at the Chalk Cliffs in central Colorado. This high rate of debris-flow activity ( 3 per year) is supported by a similarly high rate of sediment supply from rock fall and ravel due to frost weathering of the highly-erodible, hydrothermally-altered quartz monzonite cliffs during the winter months. A first step toward understanding debris-flow initiation, and channel and hillslope evolution, is to quantify the magnitude and spatial distribution of sediment that accumulates by the end of the winter period. Here we test the ability of structure-from-motion photogrammetric surveys to produce high-resolution point clouds in order to quantify sediment deposition, and possibly bedrock erosion. We use point clouds obtained from surveys conducted in late September 2015 and early June 2016 to measure sediment deposition in a 42-m-long channel over one winter. All surveys are co-registered with control points (screws drilled into bedrock) measured in a local coordinate system with a total station. Point clouds derived from these surveys have average point densities >200,000 pts/m2, and accuracies within 2 cm. Initial analysis shows accumulation of 10-50 cm ( 10 m3) of unconsolidated loose sediment over eight months, providing ample material for debris-flow initiation during the following summer season. Sediment accumulated in a spatially-variable pattern dependent on existing channel-bottom bedrock topography. Future surveys are planned in order to measure bedrock erosion by debris flows and variation in sediment deposition rate through time. Our analysis indicates that photogrammetric surveys provide a high level of detail at low cost, and thus are a useful geomorphic monitoring tool that will ultimately lead to better understanding of the processes that contribute to debris-flow activity and landscape evolution.

  3. Sedimentation rates measurements in former channels of the upper Rhône river using Chernobyl 137Cs and 134Cs as tracers.

    PubMed

    Rostan, J C; Juget, J; Brun, A M

    1997-01-30

    Former river channels are aquatic ecosystems with a different geomorphology generated by fluvial dynamics more or less linked to the main channel. They present different ecological successions to become terrestrial ecosystems and are thus supposed to have different sedimentation rates. The aim of this paper is to assess this sedimentation rate using radioactive tracer methodology commonly used in lake studies. Chernobyl impacts, expressed in 137Cs concentration and 137Cs/134Cs ratio, were determined in sediment cores. Sites (21) were sampled in the alluvial plain of the Upper Rhône River from 1989 to 1994. The contamination presented a high spatial heterogeneity. The maximum values encountered by site ranged between 34 and 541 Bq/kg of dry matter. The method generally gave good core profiles. Sedimentation rate ranged between 0.14 and 0.70 cm/year for the former meanders and between 0.14 and 2.86 cm/year for the braided channels. The sediment accumulation rates ranged from 0.03 to 0.25 g/cm2 per year and 0.03 to 2.26 g/cm2 per year, respectively. These values are similar to those found for Lake Geneva. The importance of the former channels in relation to the main channel is enhanced by the higher contamination and radionuclides retention. The sediment accumulation rate is related to the organic carbon content in the sediment. A comparison between two former channels with different productivity showed that the the allogenous driven system presents a high organic sediment accumulation rate with a low organic content in the sediment and inversely, a low organic sediment accumulation rate with a high organic carbon content was found for the autogenous drive system.

  4. An assessment of the efficacy and peak catch rates of emergence tents for measuring bee nesting.

    PubMed

    Pane, Alexander M; Harmon-Threatt, Alexandra N

    2017-06-01

    Emergence tents are a new tool used to understand nesting ecology of ground nesting bee species. However, many questions remain about how to use tents effectively. We assessed (a) variance in tent capture rates over time, (b) the effects of site characteristics on proportion of tents capturing bees, and (c) the effect of soil characteristics on nest site choice. Emergence tents were placed out for one week in May, June, and August and checked daily. Soil, bee, and floral characteristics were recorded. Across all sites and months the average number of tents capturing bees was less than 20% during one week of sampling, but this varied between sites. Tent captures decreased after 48 h deployment, but accumulation differed seasonally, with slower accumulation of total bees caught in May than in June or August. Although capture rates were not affected by bee or floral abundance, soil moisture beneath a tent influenced where bees were captured. Effective use of emergence tents may require adjusting the length of deployment depending on season and will require a minimum of 48 h installation to help maximize efficacy. The overall low capture rates demonstrate the need to optimize emergence tent use.

  5. 29 CFR 530.202 - Piece rates-work measurement.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 3 2011-07-01 2011-07-01 false Piece rates-work measurement. 530.202 Section 530.202 Labor... Piece rates—work measurement. (a) No certificate will be issued pursuant to § 530.101 of subpart B to an... different types of items produced using stop watch time studies or other work measurement methods...

  6. Surface-atmosphere decoupling limits accumulation at Summit, Greenland

    PubMed Central

    Berkelhammer, Max; Noone, David C.; Steen-Larsen, Hans Christian; Bailey, Adriana; Cox, Christopher J.; O’Neill, Michael S.; Schneider, David; Steffen, Konrad; White, James W. C.

    2016-01-01

    Despite rapid melting in the coastal regions of the Greenland Ice Sheet, a significant area (~40%) of the ice sheet rarely experiences surface melting. In these regions, the controls on annual accumulation are poorly constrained owing to surface conditions (for example, surface clouds, blowing snow, and surface inversions), which render moisture flux estimates from myriad approaches (that is, eddy covariance, remote sensing, and direct observations) highly uncertain. Accumulation is partially determined by the temperature dependence of saturation vapor pressure, which influences the maximum humidity of air parcels reaching the ice sheet interior. However, independent proxies for surface temperature and accumulation from ice cores show that the response of accumulation to temperature is variable and not generally consistent with a purely thermodynamic control. Using three years of stable water vapor isotope profiles from a high altitude site on the Greenland Ice Sheet, we show that as the boundary layer becomes increasingly stable, a decoupling between the ice sheet and atmosphere occurs. The limited interaction between the ice sheet surface and free tropospheric air reduces the capacity for surface condensation to achieve the rate set by the humidity of the air parcels reaching interior Greenland. The isolation of the surface also acts to recycle sublimated moisture by recondensing it onto fog particles, which returns the moisture back to the surface through gravitational settling. The observations highlight a unique mechanism by which ice sheet mass is conserved, which has implications for understanding both past and future changes in accumulation rate and the isotopic signal in ice cores from Greenland. PMID:27386509

  7. Surface-atmosphere decoupling limits accumulation at Summit, Greenland.

    PubMed

    Berkelhammer, Max; Noone, David C; Steen-Larsen, Hans Christian; Bailey, Adriana; Cox, Christopher J; O'Neill, Michael S; Schneider, David; Steffen, Konrad; White, James W C

    2016-04-01

    Despite rapid melting in the coastal regions of the Greenland Ice Sheet, a significant area (~40%) of the ice sheet rarely experiences surface melting. In these regions, the controls on annual accumulation are poorly constrained owing to surface conditions (for example, surface clouds, blowing snow, and surface inversions), which render moisture flux estimates from myriad approaches (that is, eddy covariance, remote sensing, and direct observations) highly uncertain. Accumulation is partially determined by the temperature dependence of saturation vapor pressure, which influences the maximum humidity of air parcels reaching the ice sheet interior. However, independent proxies for surface temperature and accumulation from ice cores show that the response of accumulation to temperature is variable and not generally consistent with a purely thermodynamic control. Using three years of stable water vapor isotope profiles from a high altitude site on the Greenland Ice Sheet, we show that as the boundary layer becomes increasingly stable, a decoupling between the ice sheet and atmosphere occurs. The limited interaction between the ice sheet surface and free tropospheric air reduces the capacity for surface condensation to achieve the rate set by the humidity of the air parcels reaching interior Greenland. The isolation of the surface also acts to recycle sublimated moisture by recondensing it onto fog particles, which returns the moisture back to the surface through gravitational settling. The observations highlight a unique mechanism by which ice sheet mass is conserved, which has implications for understanding both past and future changes in accumulation rate and the isotopic signal in ice cores from Greenland.

  8. Measurement and Modeling of Respiration Rate of Tomato (Cultivar Roma) for Modified Atmosphere Storage.

    PubMed

    Kandasamy, Palani; Moitra, Ranabir; Mukherjee, Souti

    2015-01-01

    Experiments were conducted to determine the respiration rate of tomato at 10, 20 and 30 °C using closed respiration system. Oxygen depletion and carbon dioxide accumulation in the system containing tomato was monitored. Respiration rate was found to decrease with increasing CO2 and decreasing O2 concentration. Michaelis-Menten type model based on enzyme kinetics was evaluated using experimental data generated for predicting the respiration rate. The model parameters that obtained from the respiration rate at different O2 and CO2 concentration levels were used to fit the model against the storage temperatures. The fitting was fair (R2 = 0.923 to 0.970) when the respiration rate was expressed as O2 concentation. Since inhibition constant for CO2 concentration tended towards negetive, the model was modified as a function of O2 concentration only. The modified model was fitted to the experimental data and showed good agreement (R2 = 0.998) with experimentally estimated respiration rate.

  9. Particle sorting during sediment redistribution processes and the effect on 230Th-normalized mass accumulation rates

    NASA Astrophysics Data System (ADS)

    Marcantonio, Franco; Lyle, Mitchell; Ibrahim, Rami

    2014-08-01

    The 230Th method of determining mass accumulation rates (MARs) assumes that little to no fractionation occurs during sediment redistribution processes at the seafloor. We examine 230Th inventories in radiocarbon-dated multicore sediments from paired winnowed and focused sites at Cocos and Carnegie Ridges, Panama Basin. Radiocarbon-derived sand MARs, which likely represent the vertical rain of particles poorly transported by bottom currents, are similar at each of the paired sites but are different using 230Th normalization. 230Th-normalized MARs are about 60% lower at focused sites and likely underestimate vertical MARs, while the reverse is true for winnowed sites. We hypothesize that size fractionation occurs most frequently at lower current velocities, resulting in the coarse fraction being left behind and primarily the fine 230Th-rich grains being transported downslope. 230Th-normalization works well for recording fine-grained (detrital and opal), but not coarse-grained (carbonate), fluxes in regions that have undergone sediment redistribution.

  10. Long-term phenological trends, species accumulation rates, aphid traits and climate: five decades of change in migrating aphids.

    PubMed

    Bell, James R; Alderson, Lynda; Izera, Daniela; Kruger, Tracey; Parker, Sue; Pickup, Jon; Shortall, Chris R; Taylor, Mark S; Verrier, Paul; Harrington, Richard

    2015-01-01

    Aphids represent a significant challenge to food production. The Rothamsted Insect Survey (RIS) runs a network of 12·2-m suction-traps throughout the year to collect migrating aphids. In 2014, the RIS celebrated its 50th anniversary. This paper marks that achievement with an extensive spatiotemporal analysis and the provision of the first British annotated checklist of aphids since 1964. Our main aim was to elucidate mechanisms that advance aphid phenology under climate change and explain these using life-history traits. We then highlight emerging pests using accumulation patterns. Linear and nonlinear mixed-effect models estimated the average rate of change per annum and effects of climate on annual counts, first and last flights and length of flight season since 1965. Two climate drivers were used: the accumulated day degrees above 16 °C (ADD16) indicated the potential for migration during the aphid season; the North Atlantic Oscillation (NAO) signalled the severity of the winter before migration took place. All 55 species studied had earlier first flight trends at rate of β = -0·611 ± SE 0·015 days year(-1). Of these species, 49% had earlier last flights, but the average species effect appeared relatively stationary (β = -0·010 ± SE 0·022 days year(-1)). Most species (85%) showed increasing duration of their flight season (β = 0·336 ± SE 0·026 days year(-1)), even though only 54% increased their log annual count (β = 0·002 ± SE <0·001 year(-1)). The ADD16 and NAO were shown to drive patterns in aphid phenology in a spatiotemporal context. Early in the year when the first aphids were migrating, the effect of the winter NAO was highly significant. Further into the year, ADD16 was a strong predictor. Latitude had a near linear effect on first flights, whereas longitude produced a generally less-clear effect on all responses. Aphids that are anholocyclic (permanently parthenogenetic) or are monoecious (non

  11. Confidence bands for measured economically optimal nitrogen rates

    USDA-ARS?s Scientific Manuscript database

    While numerous researchers have computed economically optimal N rate (EONR) values from measured yield – N rate data, nearly all have neglected to compute or estimate the statistical reliability of these EONR values. In this study, a simple method for computing EONR and its confidence bands is descr...

  12. High Pressure Burn Rate Measurements on an Ammonium Perchlorate Propellant

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

    Glascoe, E A; Tan, N

    2010-04-21

    High pressure deflagration rate measurements of a unique ammonium perchlorate (AP) based propellant are required to design the base burn motor for a Raytheon weapon system. The results of these deflagration rate measurements will be key in assessing safety and performance of the system. In particular, the system may experience transient pressures on the order of 100's of MPa (10's kPSI). Previous studies on similar AP based materials demonstrate that low pressure (e.g. P < 10 MPa or 1500 PSI) burn rates can be quite different than the elevated pressure deflagration rate measurements (see References and HPP results discussed herein),more » hence elevated pressure measurements are necessary in order understand the deflagration behavior under relevant conditions. Previous work on explosives have shown that at 100's of MPa some explosives will transition from a laminar burn mechanism to a convective burn mechanism in a process termed deconsolidative burning. The resulting burn rates that are orders-of-magnitude faster than the laminar burn rates. Materials that transition to the deconsolidative-convective burn mechanism at elevated pressures have been shown to be considerably more violent in confined heating experiments (i.e. cook-off scenarios). The mechanisms of propellant and explosive deflagration are extremely complex and include both chemical, and mechanical processes, hence predicting the behavior and rate of a novel material or formulation is difficult if not impossible. In this work, the AP/HTPB based material, TAL-1503 (B-2049), was burned in a constant volume apparatus in argon up to 300 MPa (ca. 44 kPSI). The burn rate and pressure were measured in-situ and used to calculate a pressure dependent burn rate. In general, the material appears to burn in a laminar fashion at these elevated pressures. The experiment was reproduced multiple times and the burn rate law using the best data is B = (0.6 {+-} 0.1) x P{sup (1.05{+-}0.02)} where B is the burn rate in

  13. [Nitrate accumulating capability of some market garden vegetables].

    PubMed

    Blanc, D

    1976-01-01

    Nitrate accumulation in plant is essentially function of the amount of nitrate nitrogen present in the substrate. That can be provided by mineral fertilizers or by organic manure. Due to the amount of nitrogen fertilizers needed in order to obtain sufficient yields the presence of nitrate is a general phenomenon in vegetable. Nevertheless the distribution of nitrate ions in the different parts of the plant influences the importance of the accumulation in the different kinds of vegetable. The experiments reported showed that leaves contain more nitrate ions than roots and roots more than fruit. The results obtained in soilless culture on lettuces, tomatoes and egg-plant demonstrated that the amount of accumulated nitrate is also dependent on the equilibrium between the different ions in the nutrient solution. Ammonium, potassium, sulfate and molybdenum have been shown to influence the rate of nitrate accumulation in the different species. It appears that it is not possible to obtain vegetable without nitrate, but it is possible, by an equilibrated fertilization, to reduce the amount accumulated in the tissue.

  14. Essentiality Is a Strong Determinant of Protein Rates of Evolution during Mutation Accumulation Experiments in Escherichia coli

    PubMed Central

    Alvarez-Ponce, David; Sabater-Muñoz, Beatriz; Toft, Christina; Ruiz-González, Mario X.; Fares, Mario A.

    2016-01-01

    Abstract The Neutral Theory of Molecular Evolution is considered the most powerful theory to understand the evolutionary behavior of proteins. One of the main predictions of this theory is that essential proteins should evolve slower than dispensable ones owing to increased selective constraints. Comparison of genomes of different species, however, has revealed only small differences between the rates of evolution of essential and nonessential proteins. In some analyses, these differences vanish once confounding factors are controlled for, whereas in other cases essentiality seems to have an independent, albeit small, effect. It has been argued that comparing relatively distant genomes may entail a number of limitations. For instance, many of the genes that are dispensable in controlled lab conditions may be essential in some of the conditions faced in nature. Moreover, essentiality can change during evolution, and rates of protein evolution are simultaneously shaped by a variety of factors, whose individual effects are difficult to isolate. Here, we conducted two parallel mutation accumulation experiments in Escherichia coli, during 5,500–5,750 generations, and compared the genomes at different points of the experiments. Our approach (a short-term experiment, under highly controlled conditions) enabled us to overcome many of the limitations of previous studies. We observed that essential proteins evolved substantially slower than nonessential ones during our experiments. Strikingly, rates of protein evolution were only moderately affected by expression level and protein length. PMID:27566759

  15. Understanding the rates of nonpolar organic chemical accumulation into passive samplers deployed in the environment: Guidance for passive sampler deployments.

    PubMed

    Apell, Jennifer N; Tcaciuc, A Patricia; Gschwend, Philip M

    2016-07-01

    Polymeric passive samplers have become a common method for estimating freely dissolved concentrations in environmental media. However, this approach has not yet been adopted by investigators conducting remedial investigations of contaminated environmental sites. Successful adoption of this sampling methodology relies on an understanding of how passive samplers accumulate chemical mass as well as developing guidance for the design and deployment of passive samplers. Herein, we outline the development of a simple mathematical relationship of the environmental, polymer, and chemical properties that control the uptake rate. This relationship, called a timescale, is then used to illustrate how each property controls the rate of equilibration in samplers deployed in the water or in the sediment. Guidance is also given on how to use the timescales to select an appropriate polymer, deployment time, and suite of performance reference compounds. Integr Environ Assess Manag 2016;12:486-492. © 2015 SETAC. © 2015 SETAC.

  16. ION EFFECTS IN THE APS PARTICLE ACCUMULATOR RING

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

    Calvey, J.; Harkay, K.; Yao, CY.

    2017-06-25

    Trapped ions in the APS Particle Accumulator Ring (PAR) lead to a positive coherent tune shift in both planes, which increases along the PAR cycle as more ions accumulate. This effect has been studied using an ion simulation code developed at SLAC. After modifying the code to include a realistic vacuum profile, multiple ionization, and the effect of shaking the beam to measure the tune, the simulation agrees well with our measurements. This code has also been used to evaluate the possibility of ion instabilities at the high bunch charge needed for the APS-Upgrade.

  17. Accumulate Repeat Accumulate Coded Modulation

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative coded modulation scheme called 'Accumulate Repeat Accumulate Coded Modulation' (ARA coded modulation). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes that are combined with high level modulation. Thus at the decoder belief propagation can be used for iterative decoding of ARA coded modulation on a graph, provided a demapper transforms the received in-phase and quadrature samples to reliability of the bits.

  18. Continuous Flow Hygroscopicity-Resolved Relaxed Eddy Accumulation (Hy-Res REA) Method of Measuring Size-Resolved Sea-Salt Particle Fluxes

    NASA Astrophysics Data System (ADS)

    Meskhidze, N.; Royalty, T. M.; Phillips, B.; Dawson, K. W.; Petters, M. D.; Reed, R.; Weinstein, J.; Hook, D.; Wiener, R.

    2017-12-01

    The accurate representation of aerosols in climate models requires direct ambient measurement of the size- and composition-dependent particle production fluxes. Here we present the design, testing, and analysis of data collected through the first instrument capable of measuring hygroscopicity-based, size-resolved particle fluxes using a continuous-flow Hygroscopicity-Resolved Relaxed Eddy Accumulation (Hy-Res REA) technique. The different components of the instrument were extensively tested inside the US Environmental Protection Agency's Aerosol Test Facility for sea-salt and ammoniums sulfate particle fluxes. The new REA system design does not require particle accumulation, therefore avoids the diffusional wall losses associated with long residence times of particles inside the air collectors of the traditional REA devices. The Hy-Res REA system used in this study includes a 3-D sonic anemometer, two fast-response solenoid valves, two Condensation Particle Counters (CPCs), a Scanning Mobility Particle Sizer (SMPS), and a Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA). A linear relationship was found between the sea-salt particle fluxes measured by eddy covariance and REA techniques, with comparable theoretical (0.34) and measured (0.39) proportionality constants. The sea-salt particle detection limit of the Hy-Res REA flux system is estimated to be 6x105 m-2s-1. For the conditions of ammonium sulfate and sea-salt particles of comparable source strength and location, the continuous-flow Hy-Res REA instrument was able to achieve better than 90% accuracy of measuring the sea-salt particle fluxes. In principle, the instrument can be applied to measure fluxes of particles of variable size and distinct hygroscopic properties (i.e., mineral dust, black carbon, etc.).

  19. Parametric study of injection rates with solenoid injectors in an injection quantity and rate measuring device

    DOE PAGES

    Busch, Stephen; Miles, Paul C.

    2015-03-31

    A Moehwald HDA (HDA is a German acronym: Hydraulischer Druckanstieg: hydraulic pressure increase) injection quantity and rate measuring unit is used to investigate injection rates obtained with a fast-acting, preproduction diesel solenoid injector. Experimental parametric variations are performed to determine their impact on measured injection rate traces. A pilot–main injection strategy is investigated for various dwell times; these preproduction injectors can operate with very short dwell times with distinct pilot and main injection events. Dwell influences the main injection rate shape. Furthermore, a comparison between a diesel-like fuel and a gasoline-like fuel shows that injection rates are comparable for amore » single injection but dramatically different for multiple injections with short dwells.« less

  20. Enhanced decomposition offsets enhanced productivity and soil carbon accumulation in coastal wetlands responding to climate change

    USGS Publications Warehouse

    Kirwan, M.L.; Blum, L.K.

    2011-01-01

    Coastal wetlands are responsible for about half of all carbon burial in oceans, and their persistence as a valuable ecosystem depends largely on the ability to accumulate organic material at rates equivalent to relative sea level rise. Recent work suggests that elevated CO2 and temperature warming will increase organic matter productivity and the ability of marshes to survive sea level rise. However, we find that organic decomposition rates increase by about 12% per degree of warming. Our measured temperature sensitivity is similar to studies from terrestrial systems, twice as high as the response of salt marsh productivity to temperature warming, and roughly equivalent to the productivity response associated with elevated CO2 in C3 marsh plants. Therefore, enhanced CO2 and warmer temperatures may actually make marshes less resilient to sea level rise, and tend to promote a release of soil carbon. Simple projections indicate that elevated temperatures will increase rates of sea level rise more than any acceleration in organic matter accumulation, suggesting the possibility of a positive feedback between climate, sea level rise, and carbon emissions in coastal environments.

  1. Patient-rated versus proxy-rated cognitive and functional measures in older adults

    PubMed Central

    Howland, Molly; Allan, Kevin C; Carlton, Caitlin E; Tatsuoka, Curtis; Smyth, Kathleen A; Sajatovic, Martha

    2017-01-01

    Objectives Patients with cognitive impairment may have difficulty reporting their functional and cognitive abilities, which are important clinical outcomes. Health care proxies may be able to corroborate patient self-reports. Several studies reported discrepancy between patient and proxy ratings, though the literature is sparse on changes over time of these ratings. Our goals in this 12-month study were to compare patient and proxy reports on functioning, cognition, and everyday executive function, and to further elucidate correlates of patient–proxy discrepancy. Methods This was a prospective cohort study of individuals older than 70 years who ranged from having no cognitive impairment to having moderate dementia who had a proxy available to complete instruments at baseline (N=76). Measurements included Alzheimer’s Disease Cooperative Study–Activities of Daily Living Inventory (ADCS-ADLI), Neuro-QOL Executive Function, PROMIS Applied Cognition (PROMIS-Cog), Mini-Mental State Examination (MMSE), and Geriatric Depression Scale. Results Patient- and proxy-rated ADCS-ADLI were correlated at baseline and at 1-year follow-up. Patient and proxy ratings were discrepant on Neuro-QOL Executive Function and PROMIS-Cog. Greater patient–proxy discrepancy on PROMIS-Cog was associated with younger age and less depression, and greater patient–proxy discrepancy on Neuro-QOL Executive Function was associated with less depression and worse cognitive impairment. Patient–proxy discrepancy increased over time for everyday executive function. Changes in proxy-rated but not patient-rated ADCS-ADLI correlated with MMSE changes. Conclusion Patients and proxies generally agree in reporting on activities of daily living. Patient and proxy reports differ in their respective evaluation of cognitive functioning and everyday executive function. Ratings from both sources may be preferred for these two domains, though studies using gold standard measures are necessary. It is important

  2. Strain accumulation in southern California, 1973-1980.

    USGS Publications Warehouse

    Savage, J.C.; Prescott, W.H.; Lisowski, M.; King, N.E.

    1981-01-01

    Frequent surveys of seven trilateration networks in southern California over the interval 1973-1980 suggest that a regional increment in strain may have occurred in 1978-1979. Prior to 1978 and after late 1979 the strain accumulation has been predominantly a uniaxial north-south compression. This secular trend was interrupted sometime in 1978-1979 by an increment in both north-south and east-west extension in five of the seven networks. The onset of this change appears to have occurred first in the networks farthest south. The changes occurred without any unusual seismicity within the networks, but the overall seismicity in southern California was unusually low prior to and has been unusually high since the occurrence. The average principal strain rates for the seven networks in the 1973-1980 interval are 0.17 mu strain/yr north- south contraction and 0.08 mu strain/yr east-west extension. Although the observed increment in strain could be related to unidentified systematic error in the measuring system, a careful review of the measurements and comparisons with three other measuring systems reveal no appreciable cumulative systematic error. -Authors

  3. Methane fluxes above the Hainich forest by True Eddy Accumulation and Eddy Covariance

    NASA Astrophysics Data System (ADS)

    Siebicke, Lukas; Gentsch, Lydia; Knohl, Alexander

    2016-04-01

    Understanding the role of forests for the global methane cycle requires quantifying vegetation-atmosphere exchange of methane, however observations of turbulent methane fluxes remain scarce. Here we measured turbulent fluxes of methane (CH4) above a beech-dominated old-growth forest in the Hainich National Park, Germany, and validated three different measurement approaches: True Eddy Accumulation (TEA, closed-path laser spectroscopy), and eddy covariance (EC, open-path and closed-path laser spectroscopy, respectively). The Hainich flux tower is a long-term Fluxnet and ICOS site with turbulent fluxes and ecosystem observations spanning more than 15 years. The current study is likely the first application of True Eddy Accumulation (TEA) for the measurement of turbulent exchange of methane and one of the very few studies comparing open-path and closed-path eddy covariance (EC) setups side-by-side. We observed uptake of methane by the forest during the day (a methane sink with a maximum rate of 0.03 μmol m-2 s-1 at noon) and no or small fluxes of methane from the forest to the atmosphere at night (a methane source of typically less than 0.01 μmol m-2 s-1) based on continuous True Eddy Accumulation measurements in September 2015. First results comparing TEA to EC CO2 fluxes suggest that True Eddy Accumulation is a valid option for turbulent flux quantifications using slow response gas analysers (here CRDS laser spectroscopy, other potential techniques include mass spectroscopy). The TEA system was one order of magnitude more energy efficient compared to closed-path eddy covariance. The open-path eddy covariance setup required the least amount of user interaction but is often constrained by low signal-to-noise ratios obtained when measuring methane fluxes over forests. Closed-path eddy covariance showed good signal-to-noise ratios in the lab, however in the field it required significant amounts of user intervention in addition to a high power consumption. We conclude

  4. Measurement of Solid Rocket Propellant Burning Rate Using X-ray Imaging

    NASA Astrophysics Data System (ADS)

    Denny, Matthew D.

    The burning rate of solid propellants can be difficult to measure for unusual burning surface geometries, but X-ray imaging can be used to measure burning rate. The objectives of this work were to measure the baseline burning rate of an electrically-controlled solid propellant (ESP) formulation with real-time X-ray radiography and to determine the uncertainty of the measurements. Two edge detection algorithms were written to track the burning surface in X-ray videos. The edge detection algorithms were informed by intensity profiles of simulated 2-D X-ray images. With a 95% confidence level, the burning rates measured by the Projected-Slope Intersection algorithm in the two combustion experiments conducted were 0.0839 in/s +/-2.86% at an average pressure of 407 psi +/-3.6% and 0.0882 in/s +/-3.04% at 410 psi +/-3.9%. The uncertainty percentages were based on the statistics of a Monte Carlo analysis on burning rate.

  5. An improved method of measuring heart rate using a webcam

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Ouyang, Jianfei; Yan, Yonggang

    2014-09-01

    Measuring heart rate traditionally requires special equipment and physical contact with the subject. Reliable non-contact and low-cost measurements are highly desirable for convenient and comfortable physiological self-assessment. Previous work has shown that consumer-grade cameras can provide useful signals for remote heart rate measurements. In this paper a simple and robust method of measuring the heart rate using low-cost webcam is proposed. Blood volume pulse is extracted by proper Region of Interest (ROI) and color channel selection from image sequences of human faces without complex computation. Heart rate is subsequently quantified by spectrum analysis. The method is successfully applied under natural lighting conditions. Results of experiments show that it takes less time, is much simpler, and has similar accuracy to the previously published and widely used method of Independent Component Analysis (ICA). Benefitting from non-contact, convenience, and low-costs, it provides great promise for popularization of home healthcare and can further be applied to biomedical research.

  6. Robust sensor fusion of unobtrusively measured heart rate.

    PubMed

    Wartzek, Tobias; Brüser, Christoph; Walter, Marian; Leonhardt, Steffen

    2014-03-01

    Contactless vital sign measurement technologies often have the drawback of severe motion artifacts and periods in which no signal is available. However, using several identical or physically different sensors, redundancy can be used to decrease the error in noncontact heart rate estimation, while increasing the time period during which reliable data are available. In this paper, we show for the first time two major results in case of contactless heart rate measurements deduced from a capacitive ECG and optical pulse signals. First, an artifact detection is an essential preprocessing step to allow a reliable fusion. Second, the robust but computationally efficient median already provides good results; however, using a Bayesian approach, and a short time estimation of the variance, best results in terms of difference to reference heart rate and temporal coverage can be achieved. In this paper, six sensor signals were used and coverage increased from 0-90% to 80-94%, while the difference between the estimated heart rate and the gold standard was less than ±2 BPM.

  7. Simultaneous measurement of breathing rate and heart rate using a microbend multimode fiber optic sensor

    NASA Astrophysics Data System (ADS)

    Chen, Zhihao; Lau, Doreen; Teo, Ju Teng; Ng, Soon Huat; Yang, Xiufeng; Kei, Pin Lin

    2014-05-01

    We propose and demonstrate the feasibility of using a highly sensitive microbend multimode fiber optic sensor for simultaneous measurement of breathing rate (BR) and heart rate (HR). The sensing system consists of a transceiver, microbend multimode fiber, and a computer. The transceiver is comprised of an optical transmitter, an optical receiver, and circuits for data communication with the computer via Bluetooth. Comparative experiments conducted between the sensor and predicate commercial physiologic devices showed an accuracy of ±2 bpm for both BR and HR measurement. Our preliminary study of simultaneous measurement of BR and HR in a clinical trial conducted on 11 healthy subjects during magnetic resonance imaging (MRI) also showed very good agreement with measurements obtained from conventional MR-compatible devices.

  8. Historical Accumulation of Nonindigenous Forest Pests in the Continental United States

    Treesearch

    J.E. Aukema; D.G. McCullough; B.V. Holle; A.M. Liebhold; S.J. Frankel

    2010-01-01

    Nonindigenous forest insects and pathogens affect a range of ecosystems, industries, and property owners in the United States. Evaluating temporal patterns in the accumulation of these nonindigenous forest pests can inform regulatory and policy decisions. We compiled a comprehensive species list to assess the accumulation rates of nonindigenous forest insects and...

  9. Historical accumulation of nonindigenous forest pests in the Continental United States

    Treesearch

    J.E. Aukema; D.G. McCullough; B. Von Holle; Andrew Liebhold; Kerry Britton; S.J. Frankel

    2010-01-01

    Nonindigenous forest insects and pathogens affect a range of ecosystems, industries, and property owners in the United States. Evaluating temporal patterns in the accumulation of these nonindigenous forest pests can inform regulatory and policy decisions. We compiled a comprehensive species list to assess the accumulation rates of nonindigenous forest insects and...

  10. Simple non-invasive assessment of advanced glycation endproduct accumulation.

    PubMed

    Meerwaldt, R; Graaff, R; Oomen, P H N; Links, T P; Jager, J J; Alderson, N L; Thorpe, S R; Baynes, J W; Gans, R O B; Smit, A J

    2004-07-01

    The accumulation of AGE is thought to play a role in the pathogenesis of chronic complications of diabetes mellitus and renal failure. All current measurements of AGE accumulation require invasive sampling. We exploited the fact that several AGE exhibit autofluorescence to develop a non-invasive tool for measuring skin AGE accumulation, the Autofluorescence Reader (AFR). We validated its use by comparing the values obtained using the AFR with the AGE content measured in extracts from skin biopsies of diabetic and control subjects. Using the AFR with an excitation light source of 300-420 nm, fluorescence of the skin was measured at the arm and lower leg in 46 patients with diabetes (Type 1 and 2) and in 46 age- and sex-matched control subjects, the majority of whom were Caucasian. Autofluorescence was defined as the average fluorescence per nm over the entire emission spectrum (420-600 nm) as ratio of the average fluorescence per nm over the 300-420-nm range. Skin biopsies were obtained from the same site of the arm, and analysed for collagen-linked fluorescence (CLF) and specific AGE: pentosidine, N(epsilon)-(carboxymethyl)lysine (CML) and N(epsilon)-(carboxyethyl)lysine (CEL). Autofluorescence correlated with CLF, pentosidine, CML, and CEL ( r=0.47-0.62, pmeasurement of AGE accumulation and, to date, has been validated in non-pigmented skin. The AFR may prove to be a useful clinical tool for rapid risk assessment of AGE-related long-term complications in diabetes mellitus and in other conditions associated with AGE accumulation.

  11. Holocene Accumulation and Ice Flow near the West Antarctic Ice Sheet Divide Ice Core Site

    NASA Technical Reports Server (NTRS)

    Koutnik, Michelle R.; Fudge, T.J.; Conway, Howard; Waddington, Edwin D.; Neumann, Thomas A.; Cuffey, Kurt M.; Buizert, Christo; Taylor, Kendrick C.

    2016-01-01

    The West Antarctic Ice Sheet Divide Core (WDC) provided a high-resolution climate record from near the Ross-Amundsen Divide in Central West Antarctica. In addition, radar-detected internal layers in the vicinity of the WDC site have been dated directly from the ice core to provide spatial variations in the age structure of the region. Using these two data sets together, we first infer a high-resolution Holocene accumulation-rate history from 9.2 thousand years of the ice-core timescale and then confirm that this climate history is consistent with internal layers upstream of the core site. Even though the WDC was drilled only 24 kilometers from the modern ice divide, advection of ice from upstream must be taken into account. We evaluate histories of accumulation rate by using a flowband model to generate internal layers that we compare to observed layers. Results show that the centennially averaged accumulation rate was over 20 percent lower than modern at 9.2 thousand years before present (B.P.), increased by 40 percent from 9.2 to 2.3 thousand years B.P., and decreased by at least 10 percent over the past 2 thousand years B.P. to the modern values; these Holocene accumulation-rate changes in Central West Antarctica are larger than changes inferred from East Antarctic ice-core records. Despite significant changes in accumulation rate, throughout the Holocene the regional accumulation pattern has likely remained similar to today, and the ice-divide position has likely remained on average within 5 kilometers of its modern position. Continent-scale ice-sheet models used for reconstructions of West Antarctic ice volume should incorporate this accumulation history.

  12. Plastic Accumulation in the Mediterranean Sea

    PubMed Central

    Cózar, Andrés; Sanz-Martín, Marina; Martí, Elisa; González-Gordillo, J. Ignacio; Ubeda, Bárbara; Gálvez, José Á.; Irigoien, Xabier; Duarte, Carlos M.

    2015-01-01

    Concentrations of floating plastic were measured throughout the Mediterranean Sea to assess whether this basin can be regarded as a great accumulation region of plastic debris. We found that the average density of plastic (1 item per 4 m2), as well as its frequency of occurrence (100% of the sites sampled), are comparable to the accumulation zones described for the five subtropical ocean gyres. Plastic debris in the Mediterranean surface waters was dominated by millimeter-sized fragments, but showed a higher proportion of large plastic objects than that present in oceanic gyres, reflecting the closer connection with pollution sources. The accumulation of floating plastic in the Mediterranean Sea (between 1,000 and 3,000 tons) is likely related to the high human pressure together with the hydrodynamics of this semi-enclosed basin, with outflow mainly occurring through a deep water layer. Given the biological richness and concentration of economic activities in the Mediterranean Sea, the affects of plastic pollution on marine and human life are expected to be particularly frequent in this plastic accumulation region. PMID:25831129

  13. Plastic accumulation in the Mediterranean sea.

    PubMed

    Cózar, Andrés; Sanz-Martín, Marina; Martí, Elisa; González-Gordillo, J Ignacio; Ubeda, Bárbara; Gálvez, José Á; Irigoien, Xabier; Duarte, Carlos M

    2015-01-01

    Concentrations of floating plastic were measured throughout the Mediterranean Sea to assess whether this basin can be regarded as a great accumulation region of plastic debris. We found that the average density of plastic (1 item per 4 m2), as well as its frequency of occurrence (100% of the sites sampled), are comparable to the accumulation zones described for the five subtropical ocean gyres. Plastic debris in the Mediterranean surface waters was dominated by millimeter-sized fragments, but showed a higher proportion of large plastic objects than that present in oceanic gyres, reflecting the closer connection with pollution sources. The accumulation of floating plastic in the Mediterranean Sea (between 1,000 and 3,000 tons) is likely related to the high human pressure together with the hydrodynamics of this semi-enclosed basin, with outflow mainly occurring through a deep water layer. Given the biological richness and concentration of economic activities in the Mediterranean Sea, the affects of plastic pollution on marine and human life are expected to be particularly frequent in this plastic accumulation region.

  14. 40 CFR 86.000-26 - Mileage and service accumulation; emission measurements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... conducted under the Standard Self-Approval Durability Program of § 86.094-13(f). The manufacturer determines... describes it in the application for certification. Service accumulation under the Standard Self-Approval... method is subject to advance approval by the Administrator and to verification by an in-use verification...

  15. Determinants of reinforcer accumulation during an operant task.

    PubMed

    McFarland, J M; Lattal, K A

    2001-11-01

    Responses by rats on an earn lever made available food pellets that were delivered to a food cup by responses on a second, collect, lever. The rats could either collect and immediately consume or accumulate (defined as the percentage of multiple earn responses and as the number of pellets earned before a collect response) earned pellets. In Experiment 1, accumulation varied as a function of variations in the earn or collect response requirements and whether the earn and collect levers were proximal (31 cm) or distal (248 cm) to one another. Some accumulation occurred under all but one of the conditions, but generally was higher when the earn and collect levers were distal to one another, particularly when the earn response requirement was fixed-ratio (FR) 1. In Experiment 2, the contributions of responses and time to accumulation were assessed by comparing an FR 20 earn response requirement to a condition in which only a single earn response was required at the end of a time interval nominally yoked to the FR interval. When 248 cm separated the earn and collect levers, accumulation was always greater in the FR condition, and it was not systematically related to reinforcement rate. In Experiment 3, increasing the earn response requirement with a progressive-ratio schedule that reset only with a collect response increased the likelihood of accumulation when the collect and earn levers were 248 cm apart, even though such accumulation increased the next earn response requirement. Reinforcer accumulation is an understudied dimension of operant behavior that relates to the analysis of such phenomena as hoarding and self-control, in that they too involve accumulating versus immediately collecting or consuming reinforcers.

  16. Device accurately measures and records low gas-flow rates

    NASA Technical Reports Server (NTRS)

    Branum, L. W.

    1966-01-01

    Free-floating piston in a vertical column accurately measures and records low gas-flow rates. The system may be calibrated, using an adjustable flow-rate gas supply, a low pressure gage, and a sequence recorder. From the calibration rates, a nomograph may be made for easy reduction. Temperature correction may be added for further accuracy.

  17. Determining the ventilation and aerosol deposition rates from routine indoor-air measurements.

    PubMed

    Halios, Christos H; Helmis, Costas G; Deligianni, Katerina; Vratolis, Sterios; Eleftheriadis, Konstantinos

    2014-01-01

    Measurement of air exchange rate provides critical information in energy and indoor-air quality studies. Continuous measurement of ventilation rates is a rather costly exercise and requires specific instrumentation. In this work, an alternative methodology is proposed and tested, where the air exchange rate is calculated by utilizing indoor and outdoor routine measurements of a common pollutant such as SO2, whereas the uncertainties induced in the calculations are analytically determined. The application of this methodology is demonstrated, for three residential microenvironments in Athens, Greece, and the results are also compared against ventilation rates calculated from differential pressure measurements. The calculated time resolved ventilation rates were applied to the mass balance equation to estimate the particle loss rate which was found to agree with literature values at an average of 0.50 h(-1). The proposed method was further evaluated by applying a mass balance numerical model for the calculation of the indoor aerosol number concentrations, using the previously calculated ventilation rate, the outdoor measured number concentrations and the particle loss rates as input values. The model results for the indoors' concentrations were found to be compared well with the experimentally measured values.

  18. Snow interception, accumulation, accumulation, and melt in lodgepole pine forests in the Blue Mountains of eastern Oregon.

    Treesearch

    Norman H. Miner; James M. Trappe

    1957-01-01

    Lodgepole pine (Pinus contorta) forests in the Blue Mountains of eastern Oregon occupy important water-producing lands. These forests generally occur at middle to high elevations on north slopes, where a substantial portion of the precipitation is snow. To learn more about the influence of lodgepole pine forests on accumulation of mow and rate of...

  19. The impact of shrubbification on soil organic matter accumulation

    NASA Astrophysics Data System (ADS)

    Street, L.; Wookey, P. A.; Subke, J. A.; Baxter, R.; Garnett, M.

    2017-12-01

    The degree to which increasing vegetation productivity in the Arctic can offset permafrost carbon emissions under a warming climate is highly uncertain. Most ecosystem or earth system models predict that plant C inputs to permafrost soils will balance or exceed losses with warming, at least until about mid-century. Observations on the ground however, question whether vegetation change in Arctic ecosystems will result in even a transient net C sink. In the European Arctic, for example, rhizosphere processes associated with ectomycorrhizal (ECM) fungi have been implicated in driving rapid cycling - and thus lower storage - of soil organic C (SOC) under deciduous shrubs. Short-term incubation studies also show that decomposition of SOC can be stimulated or "primed" by new inputs of labile plant C. The implication is that as Arctic vegetation shifts towards a greater abundance of productive, and mostly ECM, deciduous trees and shrubs, net C losses from soils may result. Over decadal timescales however, the impact of changing vegetation and associated rhizosphere processes on C stock trajectories is complex - shifts in productivity and mycorrhizal status will be accompanied by other biological and physical changes that can impact decomposition. Encroachment of shrubs will likely influence both litter quality and quantity, as well as soil temperature and moisture regimes due to altered transpiration rates, shading and snow accumulation. Short-term studies, and those based on instantaneous flux measurements, can provide only limited information as to what the impact of shrubbification on SOC stocks will be. Here we use radiocarbon data, in combination with a vertically-resolved isotopic model, to examine how and why SOC accumulation in tundra soils differs between vegetation types over decades to centuries. We compare soil profiles under ECM birch, N-fixing alder, and ericaceous/lichen heath tundra in the Canadian Arctic. Early model results suggest that under alder

  20. Using perceptual cues for brake response to a lead vehicle: Comparing threshold and accumulator models of visual looming.

    PubMed

    Xue, Qingwan; Markkula, Gustav; Yan, Xuedong; Merat, Natasha

    2018-06-18

    Previous studies have shown the effect of a lead vehicle's speed, deceleration rate and headway distance on drivers' brake response times. However, how drivers perceive this information and use it to determine when to apply braking is still not quite clear. To better understand the underlying mechanisms, a driving simulator experiment was performed where each participant experienced nine deceleration scenarios. Previously reported effects of the lead vehicle's speed, deceleration rate and headway distance on brake response time were firstly verified in this paper, using a multilevel model. Then, as an alternative to measures of speed, deceleration rate and distance, two visual looming-based metrics (angular expansion rate θ˙ of the lead vehicle on the driver's retina, and inverse tau τ -1 , the ratio between θ˙ and the optical size θ), considered to be more in line with typical human psycho-perceptual responses, were adopted to quantify situation urgency. These metrics were used in two previously proposed mechanistic models predicting brake onset: either when looming surpasses a threshold, or when the accumulated evidence (looming and other cues) reaches a threshold. Results showed that the looming threshold model did not capture the distribution of brake response time. However, regardless of looming metric, the accumulator models fitted the distribution of brake response times better than the pure threshold models. Accumulator models, including brake lights, provided a better model fit than looming-only versions. For all versions of the mechanistic models, models using τ -1 as the measure of looming fitted better than those using θ˙, indicating that the visual cues drivers used during rear-end collision avoidance may be more close to τ -1 . Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Absolute Density Calibration Cell for Laser Induced Fluorescence Erosion Rate Measurements

    NASA Technical Reports Server (NTRS)

    Domonkos, Matthew T.; Stevens, Richard E.

    2001-01-01

    Flight qualification of ion thrusters typically requires testing on the order of 10,000 hours. Extensive knowledge of wear mechanisms and rates is necessary to establish design confidence prior to long duration tests. Consequently, real-time erosion rate measurements offer the potential both to reduce development costs and to enhance knowledge of the dependency of component wear on operating conditions. Several previous studies have used laser-induced fluorescence (LIF) to measure real-time, in situ erosion rates of ion thruster accelerator grids. Those studies provided only relative measurements of the erosion rate. In the present investigation, a molybdenum tube was resistively heated such that the evaporation rate yielded densities within the tube on the order of those expected from accelerator grid erosion. This work examines the suitability of the density cell as an absolute calibration source for LIF measurements, and the intrinsic error was evaluated.

  2. Essentiality Is a Strong Determinant of Protein Rates of Evolution during Mutation Accumulation Experiments in Escherichia coli.

    PubMed

    Alvarez-Ponce, David; Sabater-Muñoz, Beatriz; Toft, Christina; Ruiz-González, Mario X; Fares, Mario A

    2016-09-26

    The Neutral Theory of Molecular Evolution is considered the most powerful theory to understand the evolutionary behavior of proteins. One of the main predictions of this theory is that essential proteins should evolve slower than dispensable ones owing to increased selective constraints. Comparison of genomes of different species, however, has revealed only small differences between the rates of evolution of essential and nonessential proteins. In some analyses, these differences vanish once confounding factors are controlled for, whereas in other cases essentiality seems to have an independent, albeit small, effect. It has been argued that comparing relatively distant genomes may entail a number of limitations. For instance, many of the genes that are dispensable in controlled lab conditions may be essential in some of the conditions faced in nature. Moreover, essentiality can change during evolution, and rates of protein evolution are simultaneously shaped by a variety of factors, whose individual effects are difficult to isolate. Here, we conducted two parallel mutation accumulation experiments in Escherichia coli, during 5,500-5,750 generations, and compared the genomes at different points of the experiments. Our approach (a short-term experiment, under highly controlled conditions) enabled us to overcome many of the limitations of previous studies. We observed that essential proteins evolved substantially slower than nonessential ones during our experiments. Strikingly, rates of protein evolution were only moderately affected by expression level and protein length. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  3. Mitochondrial Mutation Rate, Spectrum and Heteroplasmy in Caenorhabditis elegans Spontaneous Mutation Accumulation Lines of Differing Population Size.

    PubMed

    Konrad, Anke; Thompson, Owen; Waterston, Robert H; Moerman, Donald G; Keightley, Peter D; Bergthorsson, Ulfar; Katju, Vaishali

    2017-06-01

    Mitochondrial genomes of metazoans, given their elevated rates of evolution, have served as pivotal markers for phylogeographic studies and recent phylogenetic events. In order to determine the dynamics of spontaneous mitochondrial mutations in small populations in the absence and presence of selection, we evolved mutation accumulation (MA) lines of Caenorhabditis elegans in parallel over 409 consecutive generations at three varying population sizes of N = 1, 10, and 100 hermaphrodites. The N =1 populations should have a minimal influence of natural selection to provide the spontaneous mutation rate and the expected rate of neutral evolution, whereas larger population sizes should experience increasing intensity of selection. New mutations were identified by Illumina paired-end sequencing of 86 mtDNA genomes across 35 experimental lines and compared with published genomes of natural isolates. The spontaneous mitochondrial mutation rate was estimated at 1.05 × 10-7/site/generation. A strong G/C→A/T mutational bias was observed in both the MA lines and the natural isolates. This suggests that the low G + C content at synonymous sites is the product of mutation bias rather than selection as previously proposed. The mitochondrial effective population size per worm generation was estimated to be 62. Although it was previously concluded that heteroplasmy was rare in C. elegans, the vast majority of mutations in this study were heteroplasmic despite an experimental regime exceeding 400 generations. The frequencies of frameshift and nonsynonymous mutations were negatively correlated with population size, which suggests their deleterious effects on fitness and a potent role for selection in their eradication. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  4. Growth rate measurement in free jet experiments

    NASA Astrophysics Data System (ADS)

    Charpentier, Jean-Baptiste; Renoult, Marie-Charlotte; Crumeyrolle, Olivier; Mutabazi, Innocent

    2017-07-01

    An experimental method was developed to measure the growth rate of the capillary instability for free liquid jets. The method uses a standard shadow-graph imaging technique to visualize a jet, produced by extruding a liquid through a circular orifice, and a statistical analysis of the entire jet. The analysis relies on the computation of the standard deviation of a set of jet profiles, obtained in the same experimental conditions. The principle and robustness of the method are illustrated with a set of emulated jet profiles. The method is also applied to free falling jet experiments conducted for various Weber numbers and two low-viscosity solutions: a Newtonian and a viscoelastic one. Growth rate measurements are found in good agreement with linear stability theory in the Rayleigh's regime, as expected from previous studies. In addition, the standard deviation curve is used to obtain an indirect measurement of the initial perturbation amplitude and to identify beads on a string structure on the jet. This last result serves to demonstrate the capability of the present technique to explore in the future the dynamics of viscoelastic liquid jets.

  5. Examination of sludge accumulation rates and sludge characteristics for a decentralized community wastewater treatment systems with individual primary clarifier tanks located in Wardsville (Ontario, Canada).

    PubMed

    Lossing, Heather; Champagne, Pascale; McLellan, P James

    2010-01-01

    In conventional septic systems, settling and partial treatment via anaerobic digestion occurs in the septic tank. One of the byproducts of solids separation in the septic tank is a semi-liquid material known as septage, which must be periodically pumped out. Septage includes the liquid portion within the tank, as well as the sludge that settles at the bottom of the tank and the scum that floats to the surface of the liquid layer. A number of factors can influence septage characteristics, as well as the sludge and scum accumulation rates within the tank. This paper presents the results of a 2007 field sampling study conducted in Wardsville (Ontario, Canada). The field study examined 29 individual residential two-chamber septic tanks in a community serviced by a decentralized wastewater treatment system in operation for approximately 7 years without septage removal. The field investigation provided a comprehensive data set that allowed for statistical analysis of the data to assess the more critical factors influencing solids accumulation rates within each of the clarifier chambers. With this data, a number of predictive models were developed using water usage data for each residence as an explanatory variable.

  6. Classroom Use of a Verbal Measure of Information Rate: An Exploratory Study.

    ERIC Educational Resources Information Center

    Finkler, Deana; Thompson, Patricia

    The Verbal Measure of Information Rate (VMIR) is a measure of information rate which reflects the elements, features, and changes in a complex environment. Subjects rated 14 bipolar adjective pairs to indicate an appropriate description of the learning situation or information load (simple-complex, novel-familiar). The measure was administered to…

  7. 150,000 years of loess accumulation in central Alaska

    NASA Astrophysics Data System (ADS)

    Jensen, Britta J. L.; Evans, Michael E.; Froese, Duane G.; Kravchinsky, Vadim A.

    2016-03-01

    The Halfway House site in interior Alaska is arguably the most studied loess deposit in northwestern North America. The site contains a complex paleomagnetic and paleoenvironmental record, but has lacked the robust chronologic control that would allow its full potential to be exploited. Detailed reexamination of stratigraphy, paleomagnetics and tephrostratigraphy reveals a relatively complete marine isotope stage (MIS) 6 to Holocene record constrained by the Old Crow (124 ± 10 ka), VT (106 ± 10 ka), Sheep Creek-Klondike (ca. 80 ka), Dominion Creek (77 ± 8 ka) and Dawson (ca. 30.2 cal ka BP) tephras. We show two well-developed paleosols formed during Marine Isotope Stages (MIS) 5e and 5a, while MIS 5c and 5b are either poorly represented or absent. The new tephrostratigraphy presented here is the most complete one to date for the late Pleistocene and indicates MIS 5 sediments are more common than previously recognized. A magnetic excursion within the sediments is identified as the post-Blake excursion (94.1 ± 7.8 ka), providing independent age control and adding to the increasing body of evidence that Alaskan loess is a detailed recorder of variations of the Earth's magnetic field over time. A high-resolution magnetic susceptibility profile placed into this new chronostratigraphic framework supports the hypothesis that wind-intensity is the main variable controlling fluctuations in susceptibility. Correlation of the susceptibility record to global marine δ18O records is complicated by highly variable accumulation rates. We find the lowest rates of accumulation during peak warm and cold stages, while abrupt increases are associated with periods of transition between marine isotope (sub)stages. Building on previous accumulation models for Alaska, surface roughness is likely a leading variable controlling loess accumulation rates during transitions and peak cold periods, but the negligible accumulation during MIS 5e and 5a suggests that loess production was

  8. Chlorophyll, Carotenoid and Anthocyanin Accumulation in Mung Bean Seedling Under Clinorotation

    NASA Astrophysics Data System (ADS)

    Nakajima, Shusaku; Shiraga, Keiichiro; Suzuki, Tetsuhito; Kondo, Naoshi; Ogawa, Yuichi

    2017-12-01

    The accumulation of plant pigments in mung bean ( Vigna radiata L.) seedlings was measured after clinorotation (2 rpm for 2-4 days), and compared to a stationary control. The pigments measured included chlorophyll and carotenoid in primary leaves, and the anthocyanin in seedlings. While significant changes in chlorophyll and carotenoid accumulation were not observed during the initial 2 to 4 days of cultivation, by day 4 the seedlings grown on the clinostat had lower levels of anthocyanin, compared to those in the control seedlings. To further detail the cause for the observed reduction in anthocyanin accumulation under altered gravity conditions, seedlings were grown in the presence of silver nitrate, a known ethylene inhibitor, for 4 days, since it is known ethylene has a negative impact on anthocyanin accumulation. Silver nitrate promoted anthocyanin accumulation in the clinostat seedlings, and as a result there was no significant difference between the control and clinostat seedlings in anthocyanin accumulation. The results suggest that slow clinorotation negatively impacts anthocyanin pigmentation in mung bean seedlings, with endogenous ethylene suspected to be involved in this.

  9. Accumulation of carboxymethyl-lysine (CML) in human cortical bone.

    PubMed

    Thomas, Corinne J; Cleland, Timothy P; Sroga, Grazyna E; Vashishth, Deepak

    2018-05-01

    Advanced glycation end-products (AGEs) are a category of post translational modification associated with the degradation of the structural properties of multiple different types of tissues. Typically, AGEs are the result of a series of post-translational modification reactions between sugars and proteins through a process known as non-enzymatic glycation (NEG). Increases in the rate of NEG of bone tissue are associated with type 2 diabetes and skeletal fragility. Current methods of assessing NEG and its impact on bone fracture risk involve measurement of pentosidine or total fluorescent AGEs (fAGEs). However, pentosidine represents only a small fraction of possible fAGEs present in bone, and neither pentosidine nor total fAGE measurement accounts for non-fluorescent AGEs, which are known to form in significant amounts in skin and other collagenous tissues. Carboxymethyl-lysine (CML) is a non-fluorescent AGE that is often measured and has been shown to accumulate in tissues such as skin, heart, arteries, and intervertebral disks, but is currently not assessed in bone. Here we show the localization of CML to collagen I using mass spectrometry for the first time in human bone. We then present a new method using demineralization followed by heating and trypsin digestion to measure CML content in human bone and demonstrate that CML in bone is 40-100 times greater than pentosidine (the current most commonly used marker of AGEs in bone). We then establish the viability of CML as a measurable AGE in bone by showing that levels of CML, obtained from bone using this technique, increase with age (p<0.05) and are correlated with previously reported measures of bone toughness. Thus, CML is a viable non-fluorescent AGE target to assess AGE accumulation and fragility in bone. The method developed here to extract and measure CML from human bone could facilitate the development of a new diagnostic assay to evaluate fracture risk and potentially lead to new therapeutic approaches to

  10. Short and long-term soil carbon accumulation in marsh salinity types of the Mississippi River Deltaic Plain: implications for future global climate change and coastal restoration

    NASA Astrophysics Data System (ADS)

    Baustian, M. M.; Stagg, C. L.; Perry, C. L.; Moss, L.; Carruthers, T.; Allison, M. A.

    2017-12-01

    The vegetation community and environmental characteristics of marsh habitats influence how carbon is produced, decomposed, and accumulated. In coastal Louisiana, marsh habitats have historically been classified as fresh, intermediate, brackish, and saline based on their position along the salinity gradient. Changing environmental conditions, such as sea-level rise and coastal restoration activities, may change the relative extent of the four marsh habitats and how soil carbon is accumulated in the short and long term. Soil cores (100 cm) were collected at each of 24 sites within the four marsh habitats in two coastal Louisiana basins, Terrebonne and Barataria. Each core was sectioned into 2-cm depth intervals and analyzed for bulk density, organic matter, and radionuclide geochronology (137Cs and 210Pb). Feldspar marker horizon data was utilized to estimate short-term accretion rates. Short-term total carbon accumulation rates (using the top 10 cm soil properties and feldspar horizon markers) among marsh type categories were not significantly different (mean ± std. err of 190 ± 27 g TC m-2 yr-1, n = 15). However, regression analysis, on measured salinity at individual sites, indicated that mean annual salinity had a significant negative relationship suggesting that more saline marshes may be accumulating less carbon in the short term. Coastal Louisiana marsh area (1,433,700 ha) soils store in the short term about 2.7 to 3.3 Tg C yr-1. Long-term carbon accumulation rates of classified marsh type categories also did not differ (mean ± std. err of 80.0 ±8.9 g TC m-2 yr-1, n = 16) and were over two times lower than short-term accumulation rates. Coast-wide, in Louisiana, these soils bury approximately 1.2 Tg TC yr-1 in the long term and contribute about 1-5% of the global marsh/mangrove carbon sink budget. Carbon accumulation and storage rates tend to decrease over long time periods and estimating these rates from varying soil core depths (10 vs. 100 cm) has

  11. High dose rate brachytherapy source measurement intercomparison.

    PubMed

    Poder, Joel; Smith, Ryan L; Shelton, Nikki; Whitaker, May; Butler, Duncan; Haworth, Annette

    2017-06-01

    This work presents a comparison of air kerma rate (AKR) measurements performed by multiple radiotherapy centres for a single HDR 192 Ir source. Two separate groups (consisting of 15 centres) performed AKR measurements at one of two host centres in Australia. Each group travelled to one of the host centres and measured the AKR of a single 192 Ir source using their own equipment and local protocols. Results were compared to the 192 Ir source calibration certificate provided by the manufacturer by means of a ratio of measured to certified AKR. The comparisons showed remarkably consistent results with the maximum deviation in measurement from the decay-corrected source certificate value being 1.1%. The maximum percentage difference between any two measurements was less than 2%. The comparisons demonstrated the consistency of well-chambers used for 192 Ir AKR measurements in Australia, despite the lack of a local calibration service, and served as a valuable focal point for the exchange of ideas and dosimetry methods.

  12. Estimating Rain Rates from Tipping-Bucket Rain Gauge Measurements

    NASA Technical Reports Server (NTRS)

    Wang, Jianxin; Fisher, Brad L.; Wolff, David B.

    2007-01-01

    This paper describes the cubic spline based operational system for the generation of the TRMM one-minute rain rate product 2A-56 from Tipping Bucket (TB) gauge measurements. Methodological issues associated with applying the cubic spline to the TB gauge rain rate estimation are closely examined. A simulated TB gauge from a Joss-Waldvogel (JW) disdrometer is employed to evaluate effects of time scales and rain event definitions on errors of the rain rate estimation. The comparison between rain rates measured from the JW disdrometer and those estimated from the simulated TB gauge shows good overall agreement; however, the TB gauge suffers sampling problems, resulting in errors in the rain rate estimation. These errors are very sensitive to the time scale of rain rates. One-minute rain rates suffer substantial errors, especially at low rain rates. When one minute rain rates are averaged to 4-7 minute or longer time scales, the errors dramatically reduce. The rain event duration is very sensitive to the event definition but the event rain total is rather insensitive, provided that the events with less than 1 millimeter rain totals are excluded. Estimated lower rain rates are sensitive to the event definition whereas the higher rates are not. The median relative absolute errors are about 22% and 32% for 1-minute TB rain rates higher and lower than 3 mm per hour, respectively. These errors decrease to 5% and 14% when TB rain rates are used at 7-minute scale. The radar reflectivity-rainrate (Ze-R) distributions drawn from large amount of 7-minute TB rain rates and radar reflectivity data are mostly insensitive to the event definition.

  13. Accumulation patterns around Dome C, East Antarctica, in the last 73 kyr

    NASA Astrophysics Data System (ADS)

    Cavitte, Marie G. P.; Parrenin, Frédéric; Ritz, Catherine; Young, Duncan A.; Van Liefferinge, Brice; Blankenship, Donald D.; Frezzotti, Massimo; Roberts, Jason L.

    2018-04-01

    We reconstruct the pattern of surface accumulation in the region around Dome C, East Antarctica, since the last glacial. We use a set of 18 isochrones spanning all observable depths of the ice column, interpreted from various ice-penetrating radar surveys and a 1-D ice flow model to invert for accumulation rates in the region. The shallowest four isochrones are then used to calculate paleoaccumulation rates between isochrone pairs using a 1-D assumption where horizontal advection is negligible in the time interval of each layer. We observe that the large-scale (100s km) surface accumulation gradient is spatially stable through the last 73 kyr, which reflects current modeled and observed precipitation gradients in the region. We also observe small-scale (10 s km) accumulation variations linked to snow redistribution at the surface, due to changes in its slope and curvature in the prevailing wind direction that remain spatially stationary since the last glacial.

  14. Determinants of reinforcer accumulation during an operant task.

    PubMed Central

    McFarland, J M; Lattal, K A

    2001-01-01

    Responses by rats on an earn lever made available food pellets that were delivered to a food cup by responses on a second, collect, lever. The rats could either collect and immediately consume or accumulate (defined as the percentage of multiple earn responses and as the number of pellets earned before a collect response) earned pellets. In Experiment 1, accumulation varied as a function of variations in the earn or collect response requirements and whether the earn and collect levers were proximal (31 cm) or distal (248 cm) to one another. Some accumulation occurred under all but one of the conditions, but generally was higher when the earn and collect levers were distal to one another, particularly when the earn response requirement was fixed-ratio (FR) 1. In Experiment 2, the contributions of responses and time to accumulation were assessed by comparing an FR 20 earn response requirement to a condition in which only a single earn response was required at the end of a time interval nominally yoked to the FR interval. When 248 cm separated the earn and collect levers, accumulation was always greater in the FR condition, and it was not systematically related to reinforcement rate. In Experiment 3, increasing the earn response requirement with a progressive-ratio schedule that reset only with a collect response increased the likelihood of accumulation when the collect and earn levers were 248 cm apart, even though such accumulation increased the next earn response requirement. Reinforcer accumulation is an understudied dimension of operant behavior that relates to the analysis of such phenomena as hoarding and self-control, in that they too involve accumulating versus immediately collecting or consuming reinforcers. PMID:11768714

  15. Measurement of the Spin Relaxation Lifetime (T 1) in a One-Electron Strained-Si Accumulation-Mode Quantum Dot

    NASA Astrophysics Data System (ADS)

    Croke, Edward; Borselli, Matthew; Kiselev, Andrey; Deelman, Peter; Milosavljevic, Ivan; Alvarado-Rodriguez, Ivan; Ross, Richard; Schmitz, Adele; Gyure, Mark; Hunter, Andrew

    2011-03-01

    We report measurements of the spin-relaxation lifetime (T1) as a function of magnetic field in a strained-Si, accumulation-mode quantum dot. An integrated quantum-point contact (QPC) charge sensor was used to detect changes in dot occupancy as a function of bias applied to a single gate electrode. The addition spectra we obtained are consistent with theoretical predictions starting at N=0. The conductance of the charge sensor was measured by applying an AC voltage across the QPC and a 3 k Ω resistor. Lifetime measurements were conducted using a three-pulse technique consisting of a load, read, and flush sequence. T1 was measured by observing the decay of the spin bump amplitude as a function of the load pulse length. We measured decay times ranging from approximately 75 msec at 2T to 12 msec at 3T, consistent with previous reports and theoretical predictions. Sponsored by United States Department of Defense. Approved for Public Release, Distribution Unlimited.

  16. Continuous and Episodic Modern Sediment Accumulation on Monterey Fan: Evidence from Ddt, 137Cs and Excess 210Pb

    NASA Astrophysics Data System (ADS)

    Gwiazda, R.; Paull, C. K.; Alexander, C. R.; Ussler, W.

    2012-12-01

    The mode and magnitude of fine-grained sediment accumulation on the Monterey Fan off the California central coast was investigated using pesticide concentrations and radioactive tracer profiles in sediment cores. DDT is a man-made pesticide that was used extensively in central California between 1945 and 1970. As such, its presence in marine sediments is a telltale sign of a modern sedimentation age. DDT and its metabolites, DDE and DDD, (collectively referred to as DDTr) were measured in fifty-five ~20cm-long sediment cores collected from the surface of the Monterey Fan up to 250 km to the south and 210 km to the west of the Monterey Canyon head, and in four transects across the Monterey Canyon channel at maximum water depths of 3160, 3380, 3580, and 3880 meters. Profiles of excess 210Pb (210Pbxs) and 137Cs were measured in 5 cores from the Fan to estimate recent sedimentation rates. Detectable levels of DDTr were observed in all but one of these cores, with DDTr concentrations characteristically highest at the surface and decreasing with depth. The area-normalized and depth-integrated DDTr content measured in all the cores in the Fan and in the deepest two channel transects was geographically fairly homogenous, with no statistical relationship between DDTr inventory and distance from the main channel crossing the Fan. The total sediment mass deposited on the Fan over the last 60 years, inferred from the total inventory of DDTr present in the area surveyed, is consistent with the amount of sediment delivered by the Salinas River over the same time period. 210Pbxs activities are fairly homogeneous within an uppermost layer of variable thickness (4.6-8cm) and decrease exponentially below it, but these exponential decreases are often interrupted by horizons with constant or increased 210Pbxs activity. Moreover, the coexistence of variable DDTr concentrations with homogeneous 210Pbxs activities in the top sediment indicates that the uniformity of 210Pbxs is not due

  17. Hydraulic conductance as well as nitrogen accumulation plays a role in the higher rate of leaf photosynthesis of the most productive variety of rice in Japan

    PubMed Central

    Taylaran, Renante D.; Adachi, Shunsuke; Ookawa, Taiichiro; Usuda, Hideaki; Hirasawa, Tadashi

    2011-01-01

    An indica variety Takanari is known as one of the most productive rice varieties in Japan and consistently produces 20–30% heavier dry matter during ripening than Japanese commercial varieties in the field. The higher rate of photosynthesis of individual leaves during ripening has been recognized in Takanari. By using pot-grown plants under conditions of minimal mutual shading, it was confirmed that the higher rate of leaf photosynthesis is responsible for the higher dry matter production after heading in Takanari as compared with a japonica variety, Koshihikari. The rate of leaf photosynthesis and shoot dry weight became larger in Takanari after the panicle formation and heading stages, respectively, than in Koshihikari. Roots grew rapidly in the panicle formation stage until heading in Takanari compared with Koshihikari. The higher rate of leaf photosynthesis in Takanari resulted not only from the higher content of leaf nitrogen, which was caused by its elevated capacity for nitrogen accumulation, but also from higher stomatal conductance. When measured under light-saturated conditions, stomatal conductance was already decreased due to the reduction in leaf water potential in Koshihikari even under conditions of a relatively small difference in leaf–air vapour pressure difference. In contrast, the higher stomatal conductance was supported by the maintenance of higher leaf water potential through the higher hydraulic conductance in Takanari with the larger area of root surface. However, no increase in root hydraulic conductivity was expected in Takanari. The larger root surface area of Takanari might be a target trait in future rice breeding for increasing dry matter production. PMID:21527630

  18. Hydraulic conductance as well as nitrogen accumulation plays a role in the higher rate of leaf photosynthesis of the most productive variety of rice in Japan.

    PubMed

    Taylaran, Renante D; Adachi, Shunsuke; Ookawa, Taiichiro; Usuda, Hideaki; Hirasawa, Tadashi

    2011-07-01

    An indica variety Takanari is known as one of the most productive rice varieties in Japan and consistently produces 20-30% heavier dry matter during ripening than Japanese commercial varieties in the field. The higher rate of photosynthesis of individual leaves during ripening has been recognized in Takanari. By using pot-grown plants under conditions of minimal mutual shading, it was confirmed that the higher rate of leaf photosynthesis is responsible for the higher dry matter production after heading in Takanari as compared with a japonica variety, Koshihikari. The rate of leaf photosynthesis and shoot dry weight became larger in Takanari after the panicle formation and heading stages, respectively, than in Koshihikari. Roots grew rapidly in the panicle formation stage until heading in Takanari compared with Koshihikari. The higher rate of leaf photosynthesis in Takanari resulted not only from the higher content of leaf nitrogen, which was caused by its elevated capacity for nitrogen accumulation, but also from higher stomatal conductance. When measured under light-saturated conditions, stomatal conductance was already decreased due to the reduction in leaf water potential in Koshihikari even under conditions of a relatively small difference in leaf-air vapour pressure difference. In contrast, the higher stomatal conductance was supported by the maintenance of higher leaf water potential through the higher hydraulic conductance in Takanari with the larger area of root surface. However, no increase in root hydraulic conductivity was expected in Takanari. The larger root surface area of Takanari might be a target trait in future rice breeding for increasing dry matter production.

  19. Direct Measurements of the Ozone Production Rate: Methods, Measurements, and Implications for Air Quality Monitoring

    NASA Astrophysics Data System (ADS)

    Brune, W. H.; Baier, B.; Miller, D. O.; Apel, E. C.; Wisthaler, A.; Fried, A.; Cantrell, C. A.; Blake, D. R.; Brown, S. S.; McDuffie, E. E.; Kaser, L.; Long, R.; Weinheimer, A. J.

    2017-12-01

    Ground level ozone pollution remains a health hazard in the United States despite dramatic reductions due to regulatory actions over the past three decades. The key to understanding the link between the ozone precursor gases, nitrogen oxides (NOx) and volatile organic compounds (VOCs), and ozone pollution is the ozone production rate. However, in air quality models, uncertainties in emissions and meteorology hide the true sensitivity of modeled ozone to the chemistry of the ozone production rate. A better way to understand the ozone production rate is to measure it directly. We devised a method for measuring the ozone production rate directly and have deployed it in a few field studies. In this presentation, we will discuss some fairly recent observations, the strengths and weaknesses of the current method, and a path toward routine monitoring of the ozone production rate.

  20. Spectro-Temporal Electrocardiogram Analysis for Noise-Robust Heart Rate and Heart Rate Variability Measurement

    PubMed Central

    Tobón, Diana P.; Jayaraman, Srinivasan

    2017-01-01

    The last few years has seen a proliferation of wearable electrocardiogram (ECG) devices in the market with applications in fitness tracking, patient monitoring, athletic performance assessment, stress and fatigue detection, and biometrics, to name a few. The majority of these applications rely on the computation of the heart rate (HR) and the so-called heart rate variability (HRV) index via time-, frequency-, or non-linear-domain approaches. Wearable/portable devices, however, are highly susceptible to artifacts, particularly those resultant from movement. These artifacts can hamper HR/HRV measurement, thus pose a serious threat to cardiac monitoring applications. While current solutions rely on ECG enhancement as a pre-processing step prior to HR/HRV calculation, existing artifact removal algorithms still perform poorly under extremely noisy scenarios. To overcome this limitation, we take an alternate approach and propose the use of a spectro-temporal ECG signal representation that we show separates cardiac components from artifacts. More specifically, by quantifying the rate-of-change of ECG spectral components over time, we show that heart rate estimates can be reliably obtained even in extremely noisy signals, thus bypassing the need for ECG enhancement. With such HR measurements in hands, we then propose a new noise-robust HRV index termed MD-HRV (modulation-domain HRV) computed as the standard deviation of the obtained HR values. Experiments with synthetic ECG signals corrupted at various different signal-to-noise levels, as well as recorded noisy signals show the proposed measure outperforming several HRV benchmark parameters computed post wavelet-based enhancement. These findings suggest that the proposed HR measures and derived MD-HRV metric are well-suited for ambulant cardiac monitoring applications, particularly those involving intense movement (e.g., elite athletic training). PMID:29255653

  1. Implications of Bishop Tuff zircon U-Pb ages for rates of zircon growth and magma accumulation

    NASA Astrophysics Data System (ADS)

    Reid, M. R.; Schmitt, A. K.

    2012-12-01

    Rates of geologic processes obtained from natural studies rely on accurate geochronologic information. An important benchmark in geochronology as well as a valuable source of insights into the evolution of voluminous explosive eruptions is the >600 km3 Bishop Tuff (BT). A recently determined weighted mean 206Pb/238U date of 767.1±0.9 ka for a BT zircon population [1] is indistinguishable from the recalibrated 40Ar/39Ar sanidine date of 767.4±2.2 ka [2], potentially providing a key intercalibration point between astronomical and radio-isotopic dating approaches. Consequences of these results are linear zircon growth rates of >1×10-14 cm/sec and magma accumulation rates of >200 km3/ka. In contrast, spatially selective SIMS U-Pb dating of BT zircons yielded mean pre-eruption ages of 850 ka [3], a difference that raises questions about the validity of intercalibration between U-Pb and K-Ar dating methods and the history of magma accumulation. We obtained new SIMS analyses of the BT zircons using more spatially and analytically sensitive methods and verifying our accuracy against the TIMS dated Quaternary zircon 61.308A (2.488±0.002 Ma). Analyses were performed on zircon rims and on oriented cross-sections exposed during optical interferometry-calibrated serial sectioning removing the outermost ~31 μm. Sputtering by a 100 nA ion beam versus the normally employed 10-12 nA beam resulted in enhanced radiogenic Pb yields and analytical uncertainties for Quaternary zircon approaching the U-Pb age reproducibility of the primary zircon standard (~1-2 % for AS3). Ages obtained at ~31 μm depth (representing <5% of crystal growth in most cases) average 892±26ka (MSWD=0.29), corroborating previous evidence for residence times of several tens of ka. Rim ages average 781±22 ka (MSWD=0.61), overlapping Ar/Ar determinations of eruption age and corroborating the importance of near-eruption aged zircon growth. Our results confirm the presence of BT zircon domains that predate

  2. Flow rate measurement in a volume

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

    Galvez, Cristhian

    A system for measuring flow rate within a volume includes one or more transmission devices that transmit one or more signals through fluid contained within the volume. The volume may be bounded, at least in part, by an outer structure and by an object at least partially contained within the outer structure. A transmission device located at a first location of the outer structure transmits a first signal to a second location of the outer structure. A second signal is transmitted through the fluid from the second location to a third location of the outer structure. The flow rate ofmore » the fluid within the volume may be determined based, at least in part, on the time of flight of both the first signal and the second signal.« less

  3. Early diagenesis and trace element accumulation in North American Arctic margin sediments

    NASA Astrophysics Data System (ADS)

    Kuzyk, Zou Zou A.; Gobeil, Charles; Goñi, Miguel A.; Macdonald, Robie W.

    2017-04-01

    Concentrations of redox-sensitive elements (S, Mn, Mo, U, Cd, Re) were analyzed in a set of 27 sediment cores collected along the North American Arctic margin (NAAM) from the North Bering Sea to Davis Strait via the Canadian Archipelago. Sedimentary distributions and accumulation rates of the elements were used to evaluate early diagenesis in sediments along this section and to estimate the importance of this margin as a sink for key elements in the polar and global oceans. Distributions of Mn, total S and reduced inorganic S demonstrated that diagenetic conditions and thus sedimentary carbon turnover in the NAAM is organized regionally: undetectable or very thin layers (<0.5 cm) of surface Mn enrichment occurred in the Bering-Chukchi shelves; thin layers (1-5 cm) of surface Mn enrichment occurred in Barrow Canyon and Lancaster Sound; and thick layers (5-20 cm) of surface Mn enrichment occurred in the Beaufort Shelf, Canadian Archipelago, and Davis Strait. Inventories of authigenic S below the Mn-rich layer decreased about fivefold from Bering-Chukchi shelf and Barrow Canyon to Lancaster Sound and more than ten-fold from Bering-Chukchi shelf to Beaufort Shelf, Canadian Archipelago and Davis Strait. The Mn, total S and reduced inorganic S distributions imply strong organic carbon (OC) flux and metabolism in the Bering-Chukchi shelves, lower aerobic OC metabolism in Barrow Canyon and Lancaster Sound, and deep O2 penetration and much lower OC metabolism in the Beaufort Shelf, Canadian Archipelago, and Davis Strait. Accumulation rates of authigenic S, Mo, Cd, Re, and U displayed marked spatial variability along the NAAM reflecting the range in sedimentary redox conditions. Strong relationships between the accumulation rates and vertical carbon flux, estimated from regional primary production values and water depth at the coring sites, indicate that the primary driver in the regional patterns is the supply of labile carbon to the seabed. Thus, high primary production

  4. Wireless Measurement of Rotation and Displacement Rate

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E.; Taylor, Bryant D.

    2007-01-01

    A magnetic field response sensor is designed to measure displacement or rotation rate without a physical connection to a power source, microprocessor, data acquisition equipment, or electrical circuitry. The sensor works with the magnetic field response recorder, which was described in Magnetic-Field-Response Measurement-Acquisition System, NASA Tech Briefs, Vol. 30, No. 6 (June 2006), page 28. These sensors are wirelessly powered and interrogated, and the measurement acquisition system and sensors are extremely lightweight.The response recorder uses oscillating magnetic fields to power the sensors. Once powered, the sensors respond with their own magnetic field. For displacement/ rotation measurements, the response recorder uses the sensor s response amplitude, which is dependent on the distance from the antenna. The recorder s antenna orientation and position are kept fixed, and the sampling period is constant.

  5. The Effects of the Capital Accumulation Ratio on Wealth

    ERIC Educational Resources Information Center

    Harness, Nathaniel J.; Finke, Michael S.; Chatterjee, Swarn

    2009-01-01

    The capital accumulation ratio (CAR) is commonly used in academic research as a measure of household portfolio quality. This study tested whether a higher initial CAR impacts change in wealth over a decade among households in the accumulation life cycle stage. Meeting the 25% CAR guideline resulted in a 28.1% increase in net worth between 1994 and…

  6. Diverging temperature responses of CO2 assimilation and plant development explain the overall effect of temperature on biomass accumulation in wheat leaves and grains.

    PubMed

    Collins, Nicholas C; Parent, Boris

    2017-01-09

    There is a growing consensus in the literature that rising temperatures influence the rate of biomass accumulation by shortening the development of plant organs and the whole plant and by altering rates of respiration and photosynthesis. A model describing the net effects of these processes on biomass would be useful, but would need to reconcile reported differences in the effects of night and day temperature on plant productivity. In this study, the working hypothesis was that the temperature responses of CO 2 assimilation and plant development rates were divergent, and that their net effects could explain observed differences in biomass accumulation. In wheat (Triticum aestivum) plants, we followed the temperature responses of photosynthesis, respiration and leaf elongation, and confirmed that their responses diverged. We measured the amount of carbon assimilated per "unit of plant development" in each scenario and compared it to the biomass that accumulated in growing leaves and grains. Our results suggested that, up to a temperature optimum, the rate of any developmental process increased with temperature more rapidly than that of CO 2 assimilation and that this discrepancy, summarised by the CO 2 assimilation rate per unit of plant development, could explain the observed reductions in biomass accumulation in plant organs under high temperatures. The model described the effects of night and day temperature equally well, and offers a simple framework for describing the effects of temperature on plant growth. Published by Oxford University Press on behalf of the Annals of Botany Company.

  7. Diverging temperature responses of CO2 assimilation and plant development explain the overall effect of temperature on biomass accumulation in wheat leaves and grains

    PubMed Central

    Lohraseb, Iman; Collins, Nicholas C.

    2017-01-01

    Abstract There is a growing consensus in the literature that rising temperatures influence the rates of biomass accumulation by shortening the development of plant organs and the whole plant and by altering the rates of respiration and photosynthesis. A model describing the net effects of these processes on biomass would be useful, but would need to reconcile reported differences in the effects of night and day temperature on plant productivity. In this study, the working hypothesis was that the temperature responses of CO2 assimilation and plant development rates were divergent, and that their net effects could explain observed differences in biomass accumulation. In wheat (Triticum aestivum) plants, we followed the temperature responses of photosynthesis, respiration and leaf elongation, and confirmed that their responses diverged. We measured the amount of carbon assimilated per ‘unit of plant development’ in each scenario and compared it to the biomass that accumulated in growing leaves and grains. Our results suggested that, up to a temperature optimum, the rate of any developmental process increased with temperature more rapidly than that of CO2 assimilation and that this discrepancy, summarised by the CO2 assimilation rate per unit of plant development, could explain the observed reductions in biomass accumulation in plant organs under high temperatures. The model described the effects of night and day temperature equally well, and offers a simple framework for describing the effects of temperature on plant growth. PMID:28069595

  8. Selenium accumulation by plants

    PubMed Central

    White, Philip J.

    2016-01-01

    Background Selenium (Se) is an essential mineral element for animals and humans, which they acquire largely from plants. The Se concentration in edible plants is determined by the Se phytoavailability in soils. Selenium is not an essential element for plants, but excessive Se can be toxic. Thus, soil Se phytoavailability determines the ecology of plants. Most plants cannot grow on seleniferous soils. Most plants that grow on seleniferous soils accumulate <100 mg Se kg–1 dry matter and cannot tolerate greater tissue Se concentrations. However, some plant species have evolved tolerance to Se, and commonly accumulate tissue Se concentrations >100 mg Se kg–1 dry matter. These plants are considered to be Se accumulators. Some species can even accumulate Se concentrations of 1000–15 000 mg Se kg–1 dry matter and are called Se hyperaccumulators. Scope This article provides an overview of Se uptake, translocation and metabolism in plants and highlights the possible genetic basis of differences in these between and within plant species. The review focuses initially on adaptations allowing plants to tolerate large Se concentrations in their tissues and the evolutionary origin of species that hyperaccumulate Se. It then describes the variation in tissue Se concentrations between and within angiosperm species and identifies genes encoding enzymes limiting the rates of incorporation of Se into organic compounds and chromosomal loci that might enable the development of crops with greater Se concentrations in their edible portions. Finally, it discusses transgenic approaches enabling plants to tolerate greater Se concentrations in the rhizosphere and in their tissues. Conclusions The trait of Se hyperaccumulation has evolved several times in separate angiosperm clades. The ability to tolerate large tissue Se concentrations is primarily related to the ability to divert Se away from the accumulation of selenocysteine and selenomethionine, which might be incorporated

  9. Selenium accumulation by plants.

    PubMed

    White, Philip J

    2016-02-01

    Selenium (Se) is an essential mineral element for animals and humans, which they acquire largely from plants. The Se concentration in edible plants is determined by the Se phytoavailability in soils. Selenium is not an essential element for plants, but excessive Se can be toxic. Thus, soil Se phytoavailability determines the ecology of plants. Most plants cannot grow on seleniferous soils. Most plants that grow on seleniferous soils accumulate <100 mg Se kg(-1) dry matter and cannot tolerate greater tissue Se concentrations. However, some plant species have evolved tolerance to Se, and commonly accumulate tissue Se concentrations >100 mg Se kg(-1) dry matter. These plants are considered to be Se accumulators. Some species can even accumulate Se concentrations of 1000-15 000 mg Se kg(-1 )dry matter and are called Se hyperaccumulators. This article provides an overview of Se uptake, translocation and metabolism in plants and highlights the possible genetic basis of differences in these between and within plant species. The review focuses initially on adaptations allowing plants to tolerate large Se concentrations in their tissues and the evolutionary origin of species that hyperaccumulate Se. It then describes the variation in tissue Se concentrations between and within angiosperm species and identifies genes encoding enzymes limiting the rates of incorporation of Se into organic compounds and chromosomal loci that might enable the development of crops with greater Se concentrations in their edible portions. Finally, it discusses transgenic approaches enabling plants to tolerate greater Se concentrations in the rhizosphere and in their tissues. The trait of Se hyperaccumulation has evolved several times in separate angiosperm clades. The ability to tolerate large tissue Se concentrations is primarily related to the ability to divert Se away from the accumulation of selenocysteine and selenomethionine, which might be incorporated into non-functional proteins

  10. Sludge accumulation pattern inside oxidation ditch case study.

    PubMed

    Fouad, Moharram; El-Morsy, Ahmed

    2014-01-01

    The sludge accumulation pattern of an oxidation ditch (OD) plant treating municipal wastewater was observed under dry and wet weather conditions, during 3 years of operation. The accumulation patterns along the ditches and their rates were revealed. In addition, the composition of the accumulation was investigated. Finally, the ratio of sand and volatile particles, mixed liquor suspended solids (MLSS), and mixed liquor volatile suspended solids, as well as the removal efficiency were also observed against the accumulated sludge. Further, a laboratory-scale channel was used to investigate the settleability of grit after mixing with variable values of MLSS. The observed results indicated that the economical design and operation of ODs using a velocity value between 0.3-0.35 m/s is not recommended, to avoid the settling of all solids. High values of MLSS and sludge age need high horizontal velocity (more than 0.35 m/s) and more power to avoid settling problems and system failure. The influence of flow velocity on the sludge settleability was studied, enabling better planning of future ditch design and operation.

  11. Outstanding accumulation of Sphagnum palustre in central-southern Italy

    NASA Astrophysics Data System (ADS)

    Casella, Laura; Zaccone, Claudio

    2017-04-01

    Lake Fibreno is a site where some outstanding anomalies for the flora and vegetation of the wetlands of peninsular Italy are concentrated. Here one the southernmost European population of Sphagnum palustre occurs, and is restricted on the surface of a free-floating island, i.e., a round-shaped portion of fen (with a core of Sphagnum), erratically floating on the surface of a submerged sinkhole. Geological evidences point out the existence in the area of a large lacustrine basin since Late Pleistocene. The progressive filling of the lake, caused by changing in climatic conditions and neotectonic events, resulted in the formation of peat deposits in the area, following different depositional cycles in a swampy environment. So that, the studied free-floating island, probably originated around lake margins in the waterlogged area, was somehow isolated from the bank and started to float. Once the separation occurred, sedge peat stopped to accumulate, thus enhancing the role of S. palustre as the main peat-forming plant. The vegetation occurring at the moment of the isolation of the island was a coverage of Salix cinerea/Populus tremula stands below which cushions of moss and, in a lower extent, Thelypteris palustris/Equisetum palustre accumulated resulting in the formation of 2-3 meters of peat dominated by reeds and sedges. This vegetation has been partially degraded by grazing until 1970s, while in 1980s the lake became a nature reserve. Since then, the succession could resume in a spontaneous and natural way and it was possible for the vegetation to recover to natural dynamics and growing rate. The Sphagnum tussocks were measured in an empirical way at a distance of about 60 years after the last signaling and the result was a measurement of an accretion open to about 70 cm thick. Moreover, in a recent study, a 4-m deep peat core was collected from the centre of the island and results were surprising. In fact, 14C age dating, confirmed using 210Pb and 137Cs, showed

  12. Correcting reaction rates measured by saturation-transfer magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Gabr, Refaat E.; Weiss, Robert G.; Bottomley, Paul A.

    2008-04-01

    Off-resonance or spillover irradiation and incomplete saturation can introduce significant errors in the estimates of chemical rate constants measured by saturation-transfer magnetic resonance spectroscopy (MRS). Existing methods of correction are effective only over a limited parameter range. Here, a general approach of numerically solving the Bloch-McConnell equations to calculate exchange rates, relaxation times and concentrations for the saturation-transfer experiment is investigated, but found to require more measurements and higher signal-to-noise ratios than in vivo studies can practically afford. As an alternative, correction formulae for the reaction rate are provided which account for the expected parameter ranges and limited measurements available in vivo. The correction term is a quadratic function of experimental measurements. In computer simulations, the new formulae showed negligible bias and reduced the maximum error in the rate constants by about 3-fold compared to traditional formulae, and the error scatter by about 4-fold, over a wide range of parameters for conventional saturation transfer employing progressive saturation, and for the four-angle saturation-transfer method applied to the creatine kinase (CK) reaction in the human heart at 1.5 T. In normal in vivo spectra affected by spillover, the correction increases the mean calculated forward CK reaction rate by 6-16% over traditional and prior correction formulae.

  13. Kinetic model of cadmium accumulation and elimination and metallothionein response in Ruditapes decussatus.

    PubMed

    Serafim, Angela; Bebianno, Maria João

    2007-05-01

    The aim of the present study was to determine the response of metallothionein (MT) during Cd accumulation and elimination in different tissues of the estuarine bivalve Ruditapes decussatus exposed to two nominal Cd concentrations (4 and 40 microg/L) for 40 d, followed by a depuration period of 50 d. Cadmium was accumulated in all tissues of R. decussatus at both exposure concentrations, and the accumulation was tissue dependent. Use of the kinetic model showed that in the gills and remaining tissues, Cd was assimilated faster at the beginning of the exposure and decreased with time, possibly limited by the diffusion rate of this metal within the cell. In the digestive gland, however, the Cd was continuously accumulated. This could reflect that the Cd uptake rate is considerably higher than the loss rate and, therefore, that this tissue has a higher capacity to accumulate Cd compared to the other two tissues. Moreover, the application of this kinetic model in the different subcellular fractions showed that the bioconcentration factor was significantly higher in the low-molecular-weight fraction (where MT is found), suggesting that this fraction binds Cd faster, with a high uptake rate (K(u) = 32/d), and eliminates this metal more slowly (K(1) = 0.005/d). During the depuration phase, MT decreased simultaneously with Cd elimination in all tissues, although with a shorter half-life. In conclusion, the MT response prevented Cd in the tissues of R. decussatus from interfering in the normal clam metabolism; therefore, MT acts as a detoxification mechanism of Cd.

  14. Modelling past, present and future peatland carbon accumulation across the pan-Arctic region

    NASA Astrophysics Data System (ADS)

    Chaudhary, Nitin; Miller, Paul A.; Smith, Benjamin

    2017-09-01

    Most northern peatlands developed during the Holocene, sequestering large amounts of carbon in terrestrial ecosystems. However, recent syntheses have highlighted the gaps in our understanding of peatland carbon accumulation. Assessments of the long-term carbon accumulation rate and possible warming-driven changes in these accumulation rates can therefore benefit from process-based modelling studies. We employed an individual-based dynamic global ecosystem model with dynamic peatland and permafrost functionalities and patch-based vegetation dynamics to quantify long-term carbon accumulation rates and to assess the effects of historical and projected climate change on peatland carbon balances across the pan-Arctic region. Our results are broadly consistent with published regional and global carbon accumulation estimates. A majority of modelled peatland sites in Scandinavia, Europe, Russia and central and eastern Canada change from carbon sinks through the Holocene to potential carbon sources in the coming century. In contrast, the carbon sink capacity of modelled sites in Siberia, far eastern Russia, Alaska and western and northern Canada was predicted to increase in the coming century. The greatest changes were evident in eastern Siberia, north-western Canada and in Alaska, where peat production hampered by permafrost and low productivity due the cold climate in these regions in the past was simulated to increase greatly due to warming, a wetter climate and higher CO2 levels by the year 2100. In contrast, our model predicts that sites that are expected to experience reduced precipitation rates and are currently permafrost free will lose more carbon in the future.

  15. Low-cost photonic sensors for carbon dioxide exchange rate measurement

    NASA Astrophysics Data System (ADS)

    Bieda, Marcin S.; Sobotka, Piotr; Lesiak, Piotr; Woliński, Tomasz R.

    2017-10-01

    Carbon dioxide (CO2) measurement has an important role in atmosphere monitoring. Usually, two types of measurements are carried out. The first one is based on gas concentration measurement while the second involves gas exchange rate measurement between earth surface and atmosphere [1]. There are several methods which allow gas concentration measurement. However, most of them require expensive instrumentation or large devices (i.e. gas chambers). In order to precisely measure either CO2 concentration or CO2 exchange rate, preferably a sensors network should be used. These sensors must have small dimensions, low power consumption, and they should be cost-effective. Therefore, this creates a great demand for a robust low-power and low-cost CO2 sensor [2,3]. As a solution, we propose a photonic sensor that can measure CO2 concentration and also can be used to measure gas exchange by using the Eddy covariance method [1].

  16. A new method to measure heart rate with EMFi and PVDF materials.

    PubMed

    Kärki, S; Lekkala, J

    2009-01-01

    In this paper we propose a new simple method to measure the heart rate of a person sitting on a chair or lying in a bed. The heart rate is measured with a thin sensor pad consisting of separate electromechanical film (EMFi) and polyvinylidenefluoride (PVDF) transducers located beneath the leg of chair or bed. This study aims to evaluate the operation of the sensor system with measurements, and also to compare the results provided by the two transducer materials. Based on the results obtained here, the heart rates measured with the transducers mainly corresponded to the values of reference ECG signal. Some minor differences between the heart rate values of PVDF and EMFi appeared, especially in supine position, possible due to the material sensitivities to different force directions. However, to conclude, both materials seem to be convenient for this kind of measurement of heart rate.

  17. Enhanced decomposition offsets enhanced productivity and soil carbon accumulation in coastal wetlands responding to climate change

    USGS Publications Warehouse

    Kirwan, M.L.; Blum, L.K.

    2011-01-01

    Coastal wetlands are responsible for about half of all carbon burial in oceans, and their persistence as a valuable ecosystem depends largely on the ability to accumulate organic material at rates equivalent to relative sea level rise. Recent work suggests that elevated CO2 and temperature warming will increase organic matter productivity and the ability of marshes to survive sea level rise. However, we find that organic decomposition rates increase by about 12% per degree of warming. Our measured temperature sensitivity is similar to studies from terrestrial systems, twice as high as the response of salt marsh productivity to temperature warming, and roughly equivalent to the productivity response associated with elevated CO2 in C3 marsh plants. Therefore, enhanced CO2 and warmer temperatures may actually make marshes less resilient to sea level rise, and tend to promote a release of soil carbon. Simple projections indicate that elevated temperatures will increase rates of sea level rise more than any acceleration in organic matter accumulation, suggesting the possibility of a positive feedback between climate, sea level rise, and carbon emissions in coastal environments. ?? 2011 Author(s).

  18. Measurement of glomerular filtration rate using inulin prepared from Vernonia herbacea, a Brazilian native species.

    PubMed

    Dias-Tagliacozzo, G M; Dietrich, S M; Mello-Aires, M

    1996-10-01

    Vernonia herbacea (Vell.) Rusby (Asteraceae) is a perennial herb native to the cerrado vegetation of tropical areas in Brazil, which accumulates inulin in the underground reserve organs. The aim of this paper was to determine whether the inulin extracted from V. herbacea could replace commercial inulin for the measurement of glomerular filtration rate (GFR). Underground organs of vegetative plants were collected from a preserved area of the Brazilian cerrado. The inulin fraction utilized was obtained by ethanol precipitation after discarding the high molecular mass fructans in the freeze-thawing precipitate. GFR was determined in male Wistar rats anesthetized with inactin (100 mg/kg), which received intravenously commercial inulin obtained from Dahlia sp (Sigma) or Vernonia herbacea inulin (30 mg/100 g) as a priming dose and 0.05 mg min-1 100 g-1 as a sustaining dose in isotonic saline at the rate of 0/055 ml/min. Clearance was determined during 3 periods, with urine collected from the bladder and blood from the carotid artery. There was no significant difference in the GFR measured by clearance in inulin from both sources even when the plasma concentration of inulin from V. herbacea was doubled. The mean arterial pressure did not vary after the application of both inulins, indicating that they do not produce systemic side effects. The filtered load and the excreted amount of inulin from V. herbacea were equal, showing that the substance is not influenced by tubular function. These results demonstrate that the inulin from V. herbacea can substitute for imported inulin for the determination of GFR and in experiments of kidney microperfusion as a marker of tubular water reabsorption.

  19. Contact-free heart rate measurement using multiple video data

    NASA Astrophysics Data System (ADS)

    Hung, Pang-Chan; Lee, Kual-Zheng; Tsai, Luo-Wei

    2013-10-01

    In this paper, we propose a contact-free heart rate measurement method by analyzing sequential images of multiple video data. In the proposed method, skin-like pixels are firstly detected from multiple video data for extracting the color features. These color features are synchronized and analyzed by independent component analysis. A representative component is finally selected among these independent component candidates to measure the HR, which achieves under 2% deviation on average compared with a pulse oximeter in the controllable environment. The advantages of the proposed method include: 1) it uses low cost and high accessibility camera device; 2) it eases users' discomfort by utilizing contact-free measurement; and 3) it achieves the low error rate and the high stability by integrating multiple video data.

  20. Organochlorines accumulate in heron and egret chicks sampled in the Houston Ship Channel

    USGS Publications Warehouse

    Custer, T.W.; Shipley, Frank S.; Kiesling, Russell W.

    1991-01-01

    The National Contaminant Monitoring Program (NCBP) is an effort of the U.S. Fish and Wildlife Service to measure concentrations of DDT and other persistent chemicals in the environment and to quantify changes in these levels. The NCBP has established a network of sampling stations in segments of the environment for which Federal agencies have authority. The wildlife component of this program, administered by the Patuxent Wildlife Research Center, includes the periodic sampling of European starlings (Sturnus vulgaris), mallards (Anas platyrhynchos), and American black ducks (Anas rubripes). In order to include an estuarine component into the NCBP, herons and egrets are being evaluated. Eggs and chicks (five, ten, and 15 days of age) of snowy egrets (Egretta thula), and black-crowned night-herons (Nycticorax nycticorax) were collected in Naragansett Bay, RI; the Houston Ship Channel (HSC), TX; and San Francisco Bay, CA. Great egret (Casmerodius albus) eggs and chicks also were collected at the Texas colony. Eggs and chicks were analyzed for organochlorines; trace element and petroleum hydrocarbon analyses are pending. DDE and polychlorinated biphenyls (PCBs) were detected in all eggs and chicks, and they accumulated as the chicks grew. At each location, black-crowned nightheron chicks accumulated both DDE and PCBs more rapidly than snowy egrets or great egrets. PCBs accumulated more rapidly in night-heron chicks in Rhode Island than California; however, PCB accumulation for snowy egret chicks did not differ among locations. Contaminant accumulation rates in heron and egret chicks could be used as a new wetland component of the NCBP.

  1. Historical trace metal accumulation in the sediments of an urbanized region of the Lake Champlain watershed, Burlington, Vermont

    USGS Publications Warehouse

    Mecray, E.L.; King, J.W.; Appleby, P.G.; Hunt, A.S.

    2001-01-01

    This study documents the history of pollution inputs in the Burlington region of Lake Champlain, Vermont using measurements of anthropogenic metals (Cu, Zn, Cr, Pb, Cd, and Ag) in four age-dated sediment cores. Sediments record a history of contamination in a region and can be used to assess the changing threat to biota over time and to evaluate the effectiveness of discharge regulations on anthropogenic inputs. Grain size, magnetic susceptibility, radiometric dating and pollen stratigraphy were combined with trace metal data to provide an assessment of the history of contamination over the last 350 yr in the Burlington region of Lake Champlain. Magnetic susceptibility was initially used to identify land-use history for each site because it is a proxy indicator of soil erosion. Historical trends in metal inputs in the Burlington region from the seventeenth through the twentieth centuries are reflected in downcore variations in metal concentrations and accumulation rates. Metal concentrations increase above background values in the early to mid nineteenth century. The metal input rate to the sediments increases around 1920 and maximum concentrations and accumulation rates are observed in the late 1960s. Decreases in concentration and accumulation rate between 1970 and the present are observed, for most metals. The observed trends are primarily a function of variations in anthropogenic inputs and not variations in sediment grain size. Grain size data were used to remove texture variations from the metal profiles and results show trends in the anthropogenic metal signals remain. Radiometric dating and pollen stratigraphy provide well-constrained dates for the sediments thereby allowing the metal profiles to be interpreted in terms of land-use history.This study documents the history of pollution inputs in the Burlington region of Lake Champlain, Vermont using measurements of anthropogenic metals (Cu, Zn, Cr, Pb, Cd, and Ag) in four age-dated sediment cores. Sediments

  2. From the clouds to the ground - snow precipitation patterns vs. snow accumulation patterns

    NASA Astrophysics Data System (ADS)

    Gerber, Franziska; Besic, Nikola; Mott, Rebecca; Gabella, Marco; Germann, Urs; Bühler, Yves; Marty, Mauro; Berne, Alexis; Lehning, Michael

    2017-04-01

    Knowledge about snow distribution and snow accumulation patterns is important and valuable for different applications such as the prediction of seasonal water resources or avalanche forecasting. Furthermore, accumulated snow on the ground is an important ground truth for validating meteorological and climatological model predictions of precipitation in high mountains and polar regions. Snow accumulation patterns are determined by many different processes from ice crystal nucleation in clouds to snow redistribution by wind and avalanches. In between, snow precipitation undergoes different dynamical and microphysical processes, such as ice crystal growth, aggregation and riming, which determine the growth of individual particles and thereby influence the intensity and structure of the snowfall event. In alpine terrain the interaction of different processes and the topography (e.g. lifting condensation and low level cloud formation, which may result in a seeder-feeder effect) may lead to orographic enhancement of precipitation. Furthermore, the redistribution of snow particles in the air by wind results in preferential deposition of precipitation. Even though orographic enhancement is addressed in numerous studies, the relative importance of micro-physical and dynamically induced mechanisms on local snowfall amounts and especially snow accumulation patterns is hardly known. To better understand the relative importance of different processes on snow precipitation and accumulation we analyze snowfall and snow accumulation between January and March 2016 in Davos (Switzerland). We compare MeteoSwiss operational weather radar measurements on Weissfluhgipfel to a spatially continuous snow accumulation map derived from airborne digital sensing (ADS) snow height for the area of Dischma valley in the vicinity of the weather radar. Additionally, we include snow height measurements from automatic snow stations close to the weather radar. Large-scale radar snow accumulation

  3. Analyzing the importance of wind-blown snow accumulations on Mount

    NASA Astrophysics Data System (ADS)

    Nestler, Alexander; Huss, Matthias; Ambartsumian, Rouben; Hambarian, Artak; Mohr, Sandra; Santi, Flavio

    2013-04-01

    Armenia's climate has a predominantly continental character with high amounts of precipitation and low temperatures during wintertime and a lack of precipitation together with high temperatures during summer. On the volcano Mount Aragatz, snow is relocated by strong winds into massive accumulations between 2500 and 4100 m a.s.l. during the winter season. These snow accumulations appear every winter in regular patterns as cornices on the lee side of sharp edges, such as those of ridges and canyons, which are arranged in a radial manner around the central crater. The biggest cornices almost outlast the hot period and provide considerable amounts of melt water until they disappear completely by the end of August. Snow melt water is known to have a high economic importance for agriculture on the slopes of Mount Aragatz and in the surroundings of Armenia's captial Yerewan. The aim of this study is to estimate the quantity of water naturally stored as snow on Mount Aragatz, and to what degree the use of geotextiles can prolong the lives of these snow accumulations. The characteristics and the spatial distribution of snow cornices on Mount Aragatz were determined using classical glaciological methods in June/July 2011 and 2012, involving snow depth soundings, water equivalent measurements and snow melt monitoring using ablation stakes, together with GPS mappings and classifications obtained from satellite images of the snow cornices. The combination of these data with ASTER DEMs and local weather data allows the modelling of the formation of wind-driven snow accumulations. Statistical relationships between the measured extent and volume of the snow cornices and surface parameters such as slope, aspect and curvature are established. In order to analyze the meltdown of the snow accumulations and the consequent impacts on runoff generation and the hydrological regime, a glacio-hydrological model integrating topographic parameters and meteorological data is applied. The

  4. Accumulation of BSA in Packed-bed Microfluidics

    NASA Astrophysics Data System (ADS)

    Summers, Samantha; Hu, Chuntian; Hartman, Ryan

    2012-11-01

    Alzheimers and Parkinsons are two diseases that are associated with protein deposition in the brain, causing loss of either cognitive or muscle functioning. Protein deposition diseases are considered progressive diseases since the continual aggregation of protein causes the patient's symptoms to slowly worsen over time. There are currently no known means of treatment for protein deposition diseases. Our goal is to understand the potential for packed-bed microfluidics to study protein accumulation. Measurement of the resistance to flow through micro-scale packed-beds is critical to understanding the process of protein accumulation. Aggregation in bulk is fundamentally different from accumulation on surfaces. Our study attempts to distinguish between either mechanism. The results from our experiments involving protein injection through a microfluidic system will be presented and discussed. Funding received by NSF REU Grant 1062611.

  5. Consistency of Self-Ratings Across Measurement Conditions and Test Administrations.

    ERIC Educational Resources Information Center

    Froberg, Debra G.

    1984-01-01

    Using participants in a continuing education conference, an experiment was conducted to examine: (1) the consistency of self-ratings of ability across four different measurement conditions; and, (2) the relative leniency of retrospective pretest self-ratings compared to pretest self-ratings. Implications for evaluators are discussed. (Author/BS)

  6. Factors influencing the accumulation of ciprofloxacin in Pseudomonas aeruginosa.

    PubMed Central

    Celesk, R A; Robillard, N J

    1989-01-01

    Ciprofloxacin accumulation in Pseudomonas aeruginosa was measured by a bioassay. Drug accumulation in strain PAO2 was compared with that of three spontaneous ciprofloxacin-resistant mutants selected with 0.5 micrograms of ciprofloxacin per ml. PAO4701 cfxA2 contains a mutation in the gyrA gene, PAO4742 cfxB5 may represent a permeability mutant based on pleiotropic drug resistance, and PAO4700 cfxA1 cfxB1 contains both types of mutations. In all strains, drug accumulation was similar, reaching steady state during the first minute of exposure. Drug accumulation was unsaturable over a range of 5 to 80 micrograms/ml, suggesting that ciprofloxacin accumulates by diffusion in P. aeruginosa. Although all four strains accumulated two- to sevenfold more ciprofloxacin in the presence of the inhibitor carbonyl cyanide m-chlorophenylhydrazone, the cfxB mutants accumulated two- to fourfold less drug than either PAO2 or the cfxA2 mutant. Polyacrylamide gel analysis revealed a protein common to cfxB mutants only, while all strains had similar lipopolysaccharide profiles. The results suggest that ciprofloxacin accumulation in P. aeruginosa is a complex phenomenon that may be affected by both an energy-dependent drug efflux process and outer envelope composition. Images PMID:2514623

  7. Using Brillouin microspectroscopy to characterize adipocytes' response to lipid droplet accumulation

    NASA Astrophysics Data System (ADS)

    Troyanova-Wood, Maria; Coker, Zachary; Traverso, Andrew; Yakovlev, Vladislav V.

    2017-02-01

    Obesity and overweight are accompanied by an enlargement of adipocytes, which is commonly related to the increasing number or size of lipid droplets within the cells. Some studies have shown that the accumulation of lipid droplets within adipocytes results in their increased stiffness. Recently, Brillouin microspectroscopy has been introduced as a nondestructive method of imaging the elasticity of cells. Unlike other imaging modalities, it is capable of assessing the elastic properties on both tissue- and cell levels. In this study, Brillouin spectroscopy was used to measure the elasticity changes in response to accumulation of lipid droplets within adipocyte during adipogenesis. The cell line used in the study is 3T3-L1, with chemically-induced differentiation from pre-adipocytes to mature adipocytes. The Brillouin shift measurements of the cells before and after differentiation indicate that the stiffness of adipocytes increases due to accumulation of lipid droplets. The results are in agreement with previous atomic force microscopy (AFM) nanoindentation studies. Brillouin microspectroscopy is a technique suitable for measuring the changes of elasticity of adipocytes in response to lipid droplet accumulation.

  8. MODELING LONG-TERM DYNAMICS OF LITTER ACCUMULATION IN RESPONSE TO STATIC AND VARIABLE HYDROPERIODS

    EPA Science Inventory

    Accumulated litter from emergent species like the cattail hybrid (Typha glauca Godr.) can influence local abiotic conditions, other biota, and ecosystem processes. Litter accumulation results from high production coupled with slow breakdown rates. Wetland managers regularly mani...

  9. Direct measurements of intramolecular electron transfer rates between cytochrome c and cytochrome c peroxidase: effects of exothermicity and primary sequence on rate

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

    Cheung, E.; Taylor, K.; Kornblatt, J.A.

    1986-03-01

    Rapid mixing of ferrocytochrome c peroxidase (cyt c peroxidase(II)) and ferricytochrome c (cyt c(III)) results in the reduction of cyt c(III) by cyt c peroxidase(II). In 10 mM phosphate, pH 7.0, the rate of decay of cyt c peroxidase(II) and the rate of accumulation of cyt c(II) give equal first-order rate constants. Equivalent results are obtained by pulse radiolysis using isopropanol radical as the reducing agent. This rate is independent of the initial cyt c(III):cyt c peroxidase(II) ratios. These results are consistent with unimolecular electron transfer occurring within a cyt c(III)-cyt c peroxidase(II) complex. When cyt c is replaced bymore » porphyrin cyt c (iron-free cyt c), a complex still forms with cyt c peroxidase. On radiolysis intracomplex electron transfer occurs from the porphyrin cyt c anion radical to cyt c peroxidase(III). This large rate increase suggest that the barrier for intracomplex electron transfer is large. Finally, the authors have briefly investigated how the cyt c peroxidase(II) ..-->.. cyt c(III) rate depends on the primary structure of cyt c(III). They find the reactivity order to be as follows: yeast > horse > tuna.« less

  10. Calibration of Safecast dose rate measurements.

    PubMed

    Cervone, Guido; Hultquist, Carolynne

    2018-10-01

    A methodology is presented to calibrate contributed Safecast dose rate measurements acquired between 2011 and 2016 in the Fukushima prefecture of Japan. The Safecast data are calibrated using observations acquired by the U.S. Department of Energy at the time of the 2011 Fukushima Daiichi power plant nuclear accident. The methodology performs a series of interpolations between the U.S. government and contributed datasets at specific temporal windows and at corresponding spatial locations. The coefficients found for all the different temporal windows are aggregated and interpolated using quadratic regressions to generate a time dependent calibration function. Normal background radiation, decay rates, and missing values are taken into account during the analysis. Results show that the standard Safecast static transformation function overestimates the official measurements because it fails to capture the presence of two different Cesium isotopes and their changing magnitudes with time. A model is created to predict the ratio of the isotopes from the time of the accident through 2020. The proposed time dependent calibration takes into account this Cesium isotopes ratio, and it is shown to reduce the error between U.S. government and contributed data. The proposed calibration is needed through 2020, after which date the errors introduced by ignoring the presence of different isotopes will become negligible. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. Peat accumulation in drained thermokarst lake basins in continuous, ice-rich permafrost, northern Seward Peninsula, Alaska

    USGS Publications Warehouse

    Jones, Miriam C.; Grosse, Guido; Jones, Benjamin M.; Anthony, Katey Walter

    2012-01-01

    Thermokarst lakes and peat-accumulating drained lake basins cover a substantial portion of Arctic lowland landscapes, yet the role of thermokarst lake drainage and ensuing peat formation in landscape-scale carbon (C) budgets remains understudied. Here we use measurements of terrestrial peat thickness, bulk density, organic matter content, and basal radiocarbon age from permafrost cores, soil pits, and exposures in vegetated, drained lake basins to characterize regional lake drainage chronology, C accumulation rates, and the role of thermokarst-lake cycling in carbon dynamics throughout the Holocene on the northern Seward Peninsula, Alaska. Most detectable lake drainage events occurred within the last 4,000 years with the highest drainage frequency during the medieval climate anomaly. Peat accumulation rates were highest in young (50–500 years) drained lake basins (35.2 g C m−2 yr−1) and decreased exponentially with time since drainage to 9 g C m−2 yr−1 in the oldest basins. Spatial analyses of terrestrial peat depth, basal peat radiocarbon ages, basin geomorphology, and satellite-derived land surface properties (Normalized Difference Vegetation Index (NDVI); Minimum Noise Fraction (MNF)) from Landsat satellite data revealed significant relationships between peat thickness and mean basin NDVI or MNF. By upscaling observed relationships, we infer that drained thermokarst lake basins, covering 391 km2 (76%) of the 515 km2 study region, store 6.4–6.6 Tg organic C in drained lake basin terrestrial peat. Peat accumulation in drained lake basins likely serves to offset greenhouse gas release from thermokarst-impacted landscapes and should be incorporated in landscape-scale C budgets.

  12. Measurement of thoron exhalation rates from building materials.

    PubMed

    de With, G; de Jong, P; Röttger, A

    2014-09-01

    Thoron (220Rn) exhalation from building materials has become increasingly recognized as a potential source for radiation exposure in dwellings. However, contrary to radon (220Rn), limited information on thoron exposure is available. The purpose of this study is to develop a test method for the determination of the thoron exhalation rate from building materials. The method is validated, and subsequently the thoron exhalation rates from 10 widely-applied concretes, gypsums, brick, limestone, and mortar are determined. The measured thoron exhalation rates of these materials range from 0.01 Bq m-2 s-1 to 0.43 Bq m-2 s-1, with relative standard uncertainties between 6% to 14%.

  13. A Holocene Sediment Record of Phosphorus Accumulation in Shallow Lake Harris, Florida (USA) Offers New Perspectives on Recent Cultural Eutrophication

    PubMed Central

    Kenney, William F.; Brenner, Mark; Curtis, Jason H.; Arnold, T. Elliott; Schelske, Claire L.

    2016-01-01

    We studied a complete Holocene sediment record from shallow (zmax = 9.7 m) Lake Harris, Florida (USA) to infer the historical development of the lake and its current eutrophic status. We used 210Pb and 14C to date the 5.9-m sediment sequence (core LH-6-13) and determined accumulation rates for bulk sediment, organic matter, calcium carbonate, phosphorus fractions and biogenic silica fractions. The chronology of changes in sediment characteristics for LH-6-13 is consistent with the general paleoenvironmental framework established by core studies from other Florida lakes. Lake Harris began to fill with water in the early Holocene, ca. 10,680 cal a BP. A shift from carbonate-dominated to organic-rich sediments ca. 5,540 cal a BP corresponds to a transition to wetter climate in the middle Holocene. A rapid increase in diatom biogenic silica concentrations and accumulation rates ca. 2,600 cal a BP signals that the lake had deepened to its modern limnetic state. In LH-6-13, an up-core decrease in rates of accumulation for several sediment variables indicates time-course oligotrophication of the lake through the Holocene. In near-surface sediments, abrupt increases in the accumulation rates of these same variables indicate progressive cultural eutrophication after ca. AD 1900. Comparison of the modern state of Lake Harris to its condition 50–100 years ago provides a measure of the impact of recent cultural eutrophication. Because the pre-disturbance trajectory of this lake was one of oligotrophication, the true impact of cultural eutrophication is even greater than what is inferred from the changes over the past century. PMID:26789518

  14. Observations of strain accumulation across the San Andreas fault near Palmdale, California, with a two-color geodimeter

    USGS Publications Warehouse

    Langbein, J.O.; Linker, M.F.; McGarr, A.; Slater, L.E.

    1982-01-01

    Two-color laser ranging measurements during a 15-month period over a geodetic network spanning the San Andreas fault near Palmdale, California, indicate that the crust expands and contracts aseismically in episodes as short as 2 weeks. Shear strain parallel to the fault has accumulated monotonically since November 1980, but at a variable rate. Improvements in measurement precision and temporal resolution over those of previous geodetic studies near Palmdale have resulted in the definition of a time history of crustal deformation that is much more complex than formerly realized. Copyright ?? 1982 AAAS.

  15. Visual cortical activity reflects faster accumulation of information from cortically blind fields

    PubMed Central

    Martin, Tim; Das, Anasuya; Huxlin, Krystel R.

    2012-01-01

    Brain responses (from functional magnetic resonance imaging) and components of information processing were investigated in nine cortically blind observers performing a global direction discrimination task. Three of these subjects had responses in perilesional cortex in response to blind field stimulation, whereas the others did not. We used the EZ-diffusion model of decision making to understand how cortically blind subjects make a perceptual decision on stimuli presented within their blind field. We found that these subjects had slower accumulation of information in their blind fields as compared with their good fields and to intact controls. Within cortically blind subjects, activity in perilesional tissue, V3A and hMT+ was associated with a faster accumulation of information for deciding direction of motion of stimuli presented in the blind field. This result suggests that the rate of information accumulation is a critical factor in the degree of impairment in cortical blindness and varies greatly among affected individuals. Retraining paradigms that seek to restore visual functions might benefit from focusing on increasing the rate of information accumulation. PMID:23169923

  16. Accumulation by fish of contaminants released from dredged sediments

    USGS Publications Warehouse

    Seelye, James G.; Hesselberg, Robert J.; Mac, Michael J.

    1982-01-01

    Inasmuch as the process of dredging and disposing of dredged materials causes a resuspension of these materials and an increase in bioavailability of associated contaminants, we conducted a series of experiments to examine the potential accumulation by fish of contaminants from suspended sediments. In the first experiment we compared accumulation of contaminants by yellow perch of hatchery and lake origin and found that after 10 days of exposure to nonaerated sediments, fish of hatchery origin accumulated PCBs and Fe, while fish of lake origin accumulated As, Cr, Fe, and Na. Two additional exposures were conducted to evaluate the effects of aerating the sediments prior to measuring bioavailability of associated contaminants. Fish of hatchery origin exposed to nonaerated sediments for 10 days accumulated PCBs and Hg, while fish of hatchery origin exposed to aerated sediments for 10 days accumulated PCBs, DDE, Zn, Fe, Cs, and Se. These results demonstrated not only the potential for uptake of contaminants by fish as a result of dredging but also the potential utility of fish bioassays in evaluating proposed dredging operations.

  17. Modeling sediment accumulation in North American playa wetlands in response to climate change, 1940-2100

    USGS Publications Warehouse

    Burris, Lucy; Skagen, Susan K.

    2013-01-01

    Playa wetlands on the west-central Great Plains of North America are vulnerable to sediment infilling from upland agriculture, putting at risk several important ecosystem services as well as essential habitats and food resources of diverse wetland-dependent biota. Climate predictions for this semi-arid area indicate reduced precipitation which may alter rates of erosion, runoff, and sedimentation of playas. We forecasted erosion rates, sediment depths, and resultant playa wetland depths across the west-central Great Plains and examined the relative roles of land use context and projected changes in precipitation in the sedimentation process. We estimated erosion with the Revised Universal Soil Loss Equation (RUSLE) using historic values and downscaled precipitation predictions from three general circulation models and three emissions scenarios. We calibrated RUSLE results using field sediment measurements. RUSLE is appealing for regional scale modeling because it uses climate forecasts with monthly resolution and other widely available values including soil texture, slope and land use. Sediment accumulation rates will continue near historic levels through 2070 and will be sufficient to cause most playas (if not already filled) to fill with sediment within the next 100 years in the absence of mitigation. Land use surrounding the playa, whether grassland or tilled cropland, is more influential in sediment accumulation than climate-driven precipitation change.

  18. Antimicrobial proteins in human unstimulated whole saliva in relation to each other, and to measures of health status, dental plaque accumulation and composition.

    PubMed

    Rudney, J D; Krig, M A; Neuvar, E K; Soberay, A H; Iverson, L

    1991-01-01

    Saliva antimicrobial proteins may interact in a common system to influence the oral ecology. Clinical studies of antimicrobial protein action thus may require a multiple-protein approach. Multivariate statistical methods have been used to describe possible patterns of interaction for lysozyme, lactoferrin, salivary peroxidase and secretory IgA in stimulated parotid saliva. However, oral microbes are most likely to encounter antimicrobial proteins in mixed resting saliva. Relationships among levels of lysozyme, lactoferrin, salivary peroxidase, and secretory IgA therefore were investigated in whole saliva from 216 subjects, and an attempt made to relate interperson variation in those proteins to differences in health and status, and dental plaque accumulation and composition. All proteins were significantly (alpha = 0.05) correlated with each other (r = 0.38-0.52, p less than 0.001). There was only one axis of common variation among proteins, and that axis was significantly correlated (p less than 0.001) with total protein (r = 0.84) and flow rate (r = -0.56). That pattern deviated from the previous finding that proteins of acinar origin tended to vary independently from proteins of ductal origin in stimulated parotid saliva. The difference between parotid and whole saliva may reflect constitutive secretion of all proteins at low levels of stimulation. Common variation of unstimulated saliva proteins suggests that antimicrobial actions can be compared in subjects at population extremes. There were no significant associations between antimicrobial proteins in whole saliva and measures of health status or plaque accumulation. However, the proportions of Streptococcus sanguis were significantly correlated with lysozyme (r = -0.26), lactoferrin (r = -0.34), peroxidase (r = -0.30), total protein (r = -0.37), flow rate (r = 0.24) and principal-components scores (r = -0.33) in a subset of subjects (n = 85) where commercial biochemical tests were used to supplement species

  19. Looking for Off-Fault Deformation and Measuring Strain Accumulation During the Past 70 years on a Portion of the Locked San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Vadman, M.; Bemis, S. P.

    2017-12-01

    Even at high tectonic rates, detection of possible off-fault plastic/aseismic deformation and variability in far-field strain accumulation requires high spatial resolution data and likely decades of measurements. Due to the influence that variability in interseismic deformation could have on the timing, size, and location of future earthquakes and the calculation of modern geodetic estimates of strain, we attempt to use historical aerial photographs to constrain deformation through time across a locked fault. Modern photo-based 3D reconstruction techniques facilitate the creation of dense point clouds from historical aerial photograph collections. We use these tools to generate a time series of high-resolution point clouds that span 10-20 km across the Carrizo Plain segment of the San Andreas fault. We chose this location due to the high tectonic rates along the San Andreas fault and lack of vegetation, which may obscure tectonic signals. We use ground control points collected with differential GPS to establish scale and georeference the aerial photograph-derived point clouds. With a locked fault assumption, point clouds can be co-registered (to one another and/or the 1.7 km wide B4 airborne lidar dataset) along the fault trace to calculate relative displacements away from the fault. We use CloudCompare to compute 3D surface displacements, which reflect the interseismic strain accumulation that occurred in the time interval between photo collections. As expected, we do not observe clear surface displacements along the primary fault trace in our comparisons of the B4 lidar data against the aerial photograph-derived point clouds. However, there may be small scale variations within the lidar swath area that represent near-fault plastic deformation. With large-scale historical photographs available for the Carrizo Plain extending back to at least the 1940s, we can potentially sample nearly half the interseismic period since the last major earthquake on this portion of

  20. Accumulation of Spontaneous Mutations in the Ciliate Tetrahymena thermophila

    PubMed Central

    Long, Hong-An; Paixão, Tiago; Azevedo, Ricardo B. R.; Zufall, Rebecca A.

    2013-01-01

    Knowledge of the rate and fitness effects of mutations is essential for understanding the process of evolution. Mutations are inherently difficult to study because they are rare and are frequently eliminated by natural selection. In the ciliate Tetrahymena thermophila, mutations can accumulate in the germline genome without being exposed to selection. We have conducted a mutation accumulation (MA) experiment in this species. Assuming that all mutations are deleterious and have the same effect, we estimate that the deleterious mutation rate per haploid germline genome per generation is U = 0.0047 (95% credible interval: 0.0015, 0.0125), and that germline mutations decrease fitness by s = 11% when expressed in a homozygous state (95% CI: 4.4%, 27%). We also estimate that deleterious mutations are partially recessive on average (h = 0.26; 95% CI: –0.022, 0.62) and that the rate of lethal mutations is <10% of the deleterious mutation rate. Comparisons between the observed evolutionary responses in the germline and somatic genomes and the results from individual-based simulations of MA suggest that the two genomes have similar mutational parameters. These are the first estimates of the deleterious mutation rate and fitness effects from the eukaryotic supergroup Chromalveolata and are within the range of those of other eukaryotes. PMID:23934880

  1. Millimeter wave attenuation prediction using a piecewise uniform rain rate model

    NASA Technical Reports Server (NTRS)

    Persinger, R. R.; Stutzman, W. L.; Bostian, C. W.; Castle, R. E., Jr.

    1980-01-01

    A piecewise uniform rain rate distribution model is introduced as a quasi-physical model of real rain along earth-space millimeter wave propagation paths. It permits calculation of the total attenuation from specific attenuation in a simple fashion. The model predications are verified by comparison with direct attenuation measurements for several frequencies, elevation angles, and locations. Also, coupled with the Rice-Holmberg rain rate model, attenuation statistics are predicated from rainfall accumulation data.

  2. Practical remarks on the heart rate and saturation measurement methodology

    NASA Astrophysics Data System (ADS)

    Kowal, M.; Kubal, S.; Piotrowski, P.; Staniec, K.

    2017-05-01

    A surface reflection-based method for measuring heart rate and saturation has been introduced as one having a significant advantage over legacy methods in that it lends itself for use in special applications such as those where a person’s mobility is of prime importance (e.g. during a miner’s work) and excluding the use of traditional clips. Then, a complete ATmega1281-based microcontroller platform has been described for performing computational tasks of signal processing and wireless transmission. In the next section remarks have been provided regarding the basic signal processing rules beginning with raw voltage samples of converted optical signals, their acquisition, storage and smoothing. This chapter ends with practical remarks demonstrating an exponential dependence between the minimum measurable heart rate and the readout resolution at different sampling frequencies for different cases of averaging depth (in bits). The following section is devoted strictly to the heart rate and hemoglobin oxygenation (saturation) measurement with the use of the presented platform, referenced to measurements obtained with a stationary certified pulsoxymeter.

  3. Skeletal accumulation of fluorescently tagged zoledronate is higher in animals with early stage chronic kidney disease.

    PubMed

    Swallow, E A; Aref, M W; Chen, N; Byiringiro, I; Hammond, M A; McCarthy, B P; Territo, P R; Kamocka, M M; Winfree, S; Dunn, K W; Moe, S M; Allen, M R

    2018-06-11

    This work examines the skeletal accumulation of fluorescently tagged zoledronate in an animal model of chronic kidney disease. The results show higher accumulation in 24-h post-dose animals with lower kidney function due to greater amounts of binding at individual surfaces. Chronic kidney disease (CKD) patients suffer from increased rates of skeletal-related mortality from changes driven by biochemical abnormalities. Bisphosphonates are commonly used in reducing fracture risk in a variety of diseases, yet their use is not recommended in advanced stages of CKD. This study aimed to characterize the accumulation of a single dose of fluorescently tagged zoledronate (FAM-ZOL) in the setting of reduced kidney function. At 25 weeks of age, FAM-ZOL was administered to normal and CKD rats. Twenty-four hours later, multiple bones were collected and assessed using bulk fluorescence imaging, two-photon imaging, and dynamic histomorphometry. CKD animals had significantly higher levels of FAM-ZOL accumulation in the proximal tibia, radius, and ulna, but not in lumbar vertebral body or mandible, based on multiple measurement modalities. Although a majority of trabecular bone surfaces were covered with FAM-ZOL in both normal and CKD animals, the latter had significantly higher levels of fluorescence per unit bone surface in the proximal tibia. These results provide new data regarding how reduced kidney function affects drug accumulation in rat bone.

  4. Processes and rates of sediment and wood accumulation in headwater streams of the Oregon Coast Range, USA

    USGS Publications Warehouse

    May, Christine L.; Gresswell, Robert E.

    2003-01-01

    Channels that have been scoured to bedrock by debris flows provide unique opportunities to calculate the rate of sediment and wood accumulation in low-order streams, to understand the temporal succession of channel morphology following disturbance, and to make inferences about processes associated with input and transport of sediment. Dendrochronology was used to estimate the time since the previous debris flow and the time since the last stand-replacement fire in unlogged basins in the central Coast Range of Oregon. Debris flow activity increased 42 per cent above the background rate in the decades immediately following the last wildfire. Changes in wood and sediment storage were quantified for 13 streams that ranged from 4 to 144 years since the previous debris flow. The volume of wood and sediment in the channel, and the length of channel with exposed bedrock, were strongly correlated with the time since the previous debris flow. Wood increased the storage capacity of the channel and trapped the majority of the sediment in these steep headwater streams. In the absence of wood, channels that have been scoured to bedrock by a debris flow may lack the capacity to store sediment and could persist in a bedrock state for an extended period of time. With an adequate supply of wood, low-order channels have the potential of storing large volumes of sediment in the interval between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain.

  5. HIV populations are large and accumulate high genetic diversity in a nonlinear fashion.

    PubMed

    Maldarelli, Frank; Kearney, Mary; Palmer, Sarah; Stephens, Robert; Mican, JoAnn; Polis, Michael A; Davey, Richard T; Kovacs, Joseph; Shao, Wei; Rock-Kress, Diane; Metcalf, Julia A; Rehm, Catherine; Greer, Sarah E; Lucey, Daniel L; Danley, Kristen; Alter, Harvey; Mellors, John W; Coffin, John M

    2013-09-01

    HIV infection is characterized by rapid and error-prone viral replication resulting in genetically diverse virus populations. The rate of accumulation of diversity and the mechanisms involved are under intense study to provide useful information to understand immune evasion and the development of drug resistance. To characterize the development of viral diversity after infection, we carried out an in-depth analysis of single genome sequences of HIV pro-pol to assess diversity and divergence and to estimate replicating population sizes in a group of treatment-naive HIV-infected individuals sampled at single (n = 22) or multiple, longitudinal (n = 11) time points. Analysis of single genome sequences revealed nonlinear accumulation of sequence diversity during the course of infection. Diversity accumulated in recently infected individuals at rates 30-fold higher than in patients with chronic infection. Accumulation of synonymous changes accounted for most of the diversity during chronic infection. Accumulation of diversity resulted in population shifts, but the rates of change were low relative to estimated replication cycle times, consistent with relatively large population sizes. Analysis of changes in allele frequencies revealed effective population sizes that are substantially higher than previous estimates of approximately 1,000 infectious particles/infected individual. Taken together, these observations indicate that HIV populations are large, diverse, and slow to change in chronic infection and that the emergence of new mutations, including drug resistance mutations, is governed by both selection forces and drift.

  6. Does raking basal duff affect tree growth rates or mortality?

    Treesearch

    Erin Noonan-Wright; Sharon M. Hood; Danny R. Cluck

    2010-01-01

    Mortality and reduced growth rates due to raking accumulated basal duff were evaluated for old, large-diameter ponderosa and Jeffrey pine trees on the Lassen National Forest, California. No fire treatments were included to isolate the effect of raking from fire. Trees were monitored annually for 5 years after the raking treatment for mortality and then cored to measure...

  7. Measurement of diffusion coefficients from solution rates of bubbles

    NASA Technical Reports Server (NTRS)

    Krieger, I. M.

    1979-01-01

    The rate of solution of a stationary bubble is limited by the diffusion of dissolved gas molecules away from the bubble surface. Diffusion coefficients computed from measured rates of solution give mean values higher than accepted literature values, with standard errors as high as 10% for a single observation. Better accuracy is achieved with sparingly soluble gases, small bubbles, and highly viscous liquids. Accuracy correlates with the Grashof number, indicating that free convection is the major source of error. Accuracy should, therefore, be greatly increased in a gravity-free environment. The fact that the bubble will need no support is an additional important advantage of Spacelab for this measurement.

  8. Anthropogenic Mercury Accumulation in Watersheds of the Northern Appalachian Mountains

    NASA Astrophysics Data System (ADS)

    Boyer, E. W.; Drohan, P. J.; Lawler, D.; Grimm, J.; Grant, C.; Eklof, K. J.; Bennett, J.; Naber, M. D.

    2014-12-01

    Atmospheric deposition of mercury (Hg) is a critical environmental stress that affects ecosystems and human health. Mercury emissions to the atmosphere from coal-fired power plants and other sources such as waste incineration can be deposited over large geographic areas to downwind landscapes in precipitation and in dry fallout. The northern Appalachian Mountains are downwind of major atmospheric mercury emissions sources. Some mercury reaches watersheds and streams, where it can accumulate in sediments and biota. Human exposure to mercury occurs primarily through fish consumption, and currently mercury fish eating advisories are in place for many of the streams and lakes in the region. Here, we explored mercury accumulation in forested landscapes - in air, soils, water, and biota. To quantify atmospheric mercury deposition, we measured both wet and dry mercury deposition at 10 forested locations, from which we present variation in mercury deposition and initial assessments of factors affecting the patterns. To quantify mercury accumulation in terrestrial environments, we measured soil mercury concentrations within and surrounding 12 vernal pools spanning various physiographic settings in the region. Given that vernal pools have large inputs of water via precipitation yet do not have any stream discharge outflow, they are likely spots within the forested landscape to accumulate pollutants that enter via wet atmospheric deposition. To quantify mercury accumulation in aquatic environments, we sampled mercury concentrations in streams draining 35 forested watersheds, spanning gradients of atmospheric deposition, climate and geology. Mercury concentrations were measured in stream water under base-flow conditions, in streambed sediments, aquatic mosses, and in fish tissues from brook trout. Results indicate that wet and dry atmospheric deposition is a primary source of mercury that is accumulating in watersheds of the Northern Appalachian Mountains.

  9. Variations of radon concentration in the atmosphere. Gamma dose rate

    NASA Astrophysics Data System (ADS)

    Tchorz-Trzeciakiewicz, D. E.; Solecki, A. T.

    2018-02-01

    The purposes of research were following: observation and interpretation of variations of radon concentration in the atmosphere - vertical, seasonal, spatial and analysis of relation between average annual radon concentration and ground natural radiation and gamma dose rate. Moreover we wanted to check the occurrence of radon density currents and the possibility of radon accumulation at the foot of the spoil tip. The surveys were carried out in Okrzeszyn (SW Poland) in the area of the spoil tip formed during uranium mining that took place in 60's of 20th century. The measurements were carried out in 20 measurements points at three heights: 0.2 m, 1 m and 2 m a.g.l. using SSNTD LR-115. The survey lasted one year and detectors were exchanged at the beginning of every season. Uranium eU (ppm), thorium eTh (ppm) and potassium K (%) contents were measured using gamma ray spectrometer Exploranium RS-230, ambient gamma dose rate using radiometer RK-100. The average radon concentration on this area was 52.8 Bq m-3. The highest radon concentrations were noted during autumn and the lowest during winter. We observed vertical variations of radon concentration. Radon concentrations decreased with increase of height above ground level. The decrease of radon with increase of height a.g.l. had logarithmic character. Spatial variations of radon concentrations did not indicate the occurrence of radon density currents and accumulation of radon at the foot of the spoil tip. The analysis of relation between average radon concentrations and ground natural radiation (uranium and thorium content) or gamma dose rate revealed positive relation between those parameters. On the base of results mentioned above we suggested that gamma spectrometry measurements or even cheaper and simpler ambient gamma dose rate measurements can be a useful tool in determining radon prone areas. This should be confirmed by additional research.

  10. Optimized inorganic carbon regime for enhanced growth and lipid accumulation in Chlorella vulgaris.

    PubMed

    Lohman, Egan J; Gardner, Robert D; Pedersen, Todd; Peyton, Brent M; Cooksey, Keith E; Gerlach, Robin

    2015-01-01

    Large-scale algal biofuel production has been limited, among other factors, by the availability of inorganic carbon in the culture medium at concentrations higher than achievable with atmospheric CO2. Life cycle analyses have concluded that costs associated with supplying CO2 to algal cultures are significant contributors to the overall energy consumption. A two-phase optimal growth and lipid accumulation scenario is presented, which (1) enhances the growth rate and (2) the triacylglyceride (TAG) accumulation rate in the oleaginous Chlorophyte Chlorella vulgaris strain UTEX 395, by growing the organism in the presence of low concentrations of NaHCO3 (5 mM) and controlling the pH of the system with a periodic gas sparge of 5 % CO2 (v/v). Once cultures reached the desired cell densities, which can be "fine-tuned" based on initial nutrient concentrations, cultures were switched to a lipid accumulation metabolism through the addition of 50 mM NaHCO3. This two-phase approach increased the specific growth rate of C. vulgaris by 69 % compared to cultures sparged continuously with 5 % CO2 (v/v); further, biomass productivity (g L(-1) day(-1)) was increased by 27 %. Total biodiesel potential [assessed as total fatty acid methyl ester (FAME) produced] was increased from 53.3 to 61 % (FAME biomass(-1)) under the optimized conditions; biodiesel productivity (g FAME L(-1) day(-1)) was increased by 7.7 %. A bicarbonate salt screen revealed that American Chemical Society (ACS) and industrial grade NaHCO3 induced the highest TAG accumulation (% w/w), whereas Na2CO3 did not induce significant TAG accumulation. NH4HCO3 had a negative effect on cell health presumably due to ammonia toxicity. The raw, unrefined form of trona, NaHCO3∙Na2CO3 (sodium sesquicarbonate) induced TAG accumulation, albeit to a slightly lower extent than the more refined forms of sodium bicarbonate. The strategic addition of sodium bicarbonate was found to enhance growth and lipid accumulation rates in

  11. Comparing methods for measuring the rate of spread of invading populations

    Treesearch

    Marius Gilbert; Andrew Liebhold

    2010-01-01

    Measuring rates of spread during biological invasions is important for predicting where and when invading organisms will spread in the future as well as for quantifying the influence of environmental conditions on invasion speed. While several methods have been proposed in the literature to measure spread rates, a comprehensive comparison of their accuracy when applied...

  12. Maximum likelihood decoding analysis of Accumulate-Repeat-Accumulate Codes

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    Repeat-Accumulate (RA) codes are the simplest turbo-like codes that achieve good performance. However, they cannot compete with Turbo codes or low-density parity check codes (LDPC) as far as performance is concerned. The Accumulate Repeat Accumulate (ARA) codes, as a subclass of LDPC codes, are obtained by adding a pre-coder in front of RA codes with puncturing where an accumulator is chosen as a precoder. These codes not only are very simple, but also achieve excellent performance with iterative decoding. In this paper, the performance of these codes with (ML) decoding are analyzed and compared to random codes by very tight bounds. The weight distribution of some simple ARA codes is obtained, and through existing tightest bounds we have shown the ML SNR threshold of ARA codes approaches very closely to the performance of random codes. We have shown that the use of precoder improves the SNR threshold but interleaving gain remains unchanged with respect to RA code with puncturing.

  13. Field Validation of Molybdenum Accumulation in Sediments as an Indication of Hypoxic Water Conditions

    EPA Science Inventory

    Accumulation of authigenic molybdenum (Mo) in marine sediments has often been used as qualitative indicator of periods of hypoxic bottom water, but rarely, if ever, used quantitatively. Laboratory experiments have shown that the accumulation rate of Mo may serve as a quantitative...

  14. Measuring pretest-posttest change with a Rasch Rating Scale Model.

    PubMed

    Wolfe, E W; Chiu, C W

    1999-01-01

    When measures are taken on the same individual over time, it is difficult to determine whether observed differences are the result of changes in the person or changes in other facets of the measurement situation (e.g., interpretation of items or use of rating scale). This paper describes a method for disentangling changes in persons from changes in the interpretation of Likert-type questionnaire items and the use of rating scales (Wright, 1996a). The procedure relies on anchoring strategies to create a common frame of reference for interpreting measures that are taken at different times and provides a detailed illustration of how to implement these procedures using FACETS.

  15. Enhancing phytoextraction: the effect of chemical soil manipulation on mobility, plant accumulation, and leaching of heavy metals.

    PubMed

    Schmidt, Ulrich

    2003-01-01

    For heavy metal-contaminated agricultural land, low-cost, plant-based phytoextraction measures can be a key element for a new land management strategy. When agents are applied into the soil, the solubility of heavy metals and their subsequent accumulation by plants can be increased, and, therefore, phytoextraction enhanced. An overview is given of the state of the art of enhancing heavy metal solubility in soils, increasing the heavy metal accumulation of several high-biomass-yielding and metal-tolerant plants, and the effect of these measures on the risk of heavy metal leaching. Several organic as well as inorganic agents can effectively and specifically increase solubility and, therefore, accumulation of heavy metals by several plant species. Crops like willow (Salix viminalis L.), Indian mustard [Brassica juncea (L.) Czern.], corn (Zea mays L.), and sunflower (Helianthus annuus L.) show high tolerance to heavy metals and are, therefore, to a certain extent able to use the surpluses that originate from soil manipulation. More than 100-fold increases of lead concentrations in the biomass of crops were reported, when ethylenediaminetetraacetic acid (EDTA) was applied to contaminated soils. Uranium concentrations could be strongly increased when citric acid was applied. Cadmium and zinc concentrations could be enhanced by inorganic agents like elemental sulfur or ammonium sulfate. However, leaching of heavy metals due to increased mobility in soils cannot be excluded. Thus, implementation on the field scale must consider measures to minimize leaching. So, the application of more than 1 g EDTA kg(-1) becomes inefficient as lead concentration in crops is not enhanced and leaching rate increases. Moreover, for large-scale applications, agricultural measures as placement of agents, dosage splitting, the kind and amount of agents applied, and the soil properties are important factors governing plant growth, heavy metal concentrations, and leaching rates. Effective

  16. Outcome Rating Scale and Session Rating Scale in Psychological Practice: Clinical Utility of Ultra-Brief Measures

    ERIC Educational Resources Information Center

    Campbell, Alistair; Hemsley, Samantha

    2009-01-01

    The validity and reliability of the Outcome Rating Scale (ORS) and the Session Rating Scale (SRS) were evaluated against existing longer measures, including the Outcome Questionnaire-45, Working Alliance Inventory, Depression Anxiety Stress Scale-21, Quality of Life Scale, Rosenberg Self-Esteem Scale and General Self-efficacy Scale. The measures…

  17. In vivo measurements for high dose rate brachytherapy with optically stimulated luminescent dosimeters

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

    Sharma, Renu; Jursinic, Paul A.

    2013-07-15

    Purpose: To show the feasibility of clinical implementation of OSLDs for high dose-rate (HDR) in vivo dosimetry for gynecological and breast patients. To discuss how the OSLDs were characterized for an Ir-192 source, taking into account low gamma energy and high dose gradients. To describe differences caused by the dose calculation formalism of treatment planning systems.Methods: OSLD irradiations were made using the GammaMedplus iX Ir-192 HDR, Varian Medical Systems, Milpitas, CA. BrachyVision versions 8.9 and 10.0, Varian Medical Systems, Milpitas, CA, were used for calculations. Version 8.9 used the TG-43 algorithm and version 10.0 used the Acuros algorithm. The OSLDsmore » (InLight Nanodots) were characterized for Ir-192. Various phantoms were created to assess calculated and measured doses and the angular dependence and self-absorption of the Nanodots. Following successful phantom measurements, patient measurements for gynecological patients and breast cancer patients were made and compared to calculated doses.Results: The OSLD sensitivity to Ir-192 compared to 6 MV is between 1.10 and 1.25, is unique to each detector, and changes with accumulated dose. The measured doses were compared to those predicted by the treatment planning system and found to be in agreement for the gynecological patients to within measurement uncertainty. The range of differences between the measured and Acuros calculated doses was -10%-14%. For the breast patients, there was a discrepancy of -4.4% to +6.5% between the measured and calculated doses at the skin surface when the Acuros algorithm was used. These differences were within experimental uncertainty due to (random) error in the location of the detector with respect to the treatment catheter.Conclusions: OSLDs can be successfully used for HDR in vivo dosimetry. However, for the measurements to be meaningful one must account for the angular dependence, volume-averaging, and the greater sensitivity to Ir-192 gamma rays than to 6

  18. A Simple Device to Measure Root Growth Rates

    ERIC Educational Resources Information Center

    Rauser, Wilfried E.; Horton, Roger F.

    1975-01-01

    Describes construction and use of a simple auxanometer which students can use to accurately measure root growth rates of intact seedlings. Typical time course data are presented for the effect of ethylene and indole acetic acid on pea root growth. (Author/BR)

  19. Growth of the eye lens: I. Weight accumulation in multiple species

    PubMed Central

    2014-01-01

    Purpose To examine the accumulation of wet and/or dry weight in the ocular lens as a function of age in different species. Methods Wet weights and/or fixed dry weights were obtained from measurements in the author’s laboratory and from the literature for over 14,000 lenses of known-ages, representing 130 different species. Various algorithms were tested to determine the most suitable for describing the relationship between lens weight and age. Results For 126 of the species examined, lens growth is continuous throughout life but asymptotic and can be reasonably described with a single logistic equation, W=Wm e-(k/A), where W is lens wet or dry weight; Wm is the maximum asymptotic weight, k is the logistic growth constant and A is the time from conception. For humans, elephants, hippopotami, minks, wild goats and woodchucks, lens growth appears to be biphasic. No gender differences could be detected in the lens weights for 70 species but male lenses are reportedly 10% larger than those of females in northern fur seals and pheasants. Dry weight accumulation is faster than that for wet weight in all species except birds and reptiles where the rates are the same. Low lens growth rates are associated with small animals with short gestation periods and short life spans. Conclusions Lens growth is continuous throughout life and, for most species, is independent of gender. For most, growth takes place through a monophasic asymptotic mode and is unaffected by events such as hibernation. This makes lens weight measurement a reliable tool for age determination of species culled in the wild. Compaction of the growing lens generates different properties, appropriate to an animal's lifestyle. How these events are controlled remains to be established. PMID:24715758

  20. Dynamics of polyhydroxyalkanoate accumulation in aerobic granules during the growth-disintegration cycle.

    PubMed

    Gobi, K; Vadivelu, V M

    2015-11-01

    The polyhydroxyalkanoate (PHA) accumulation dynamics in aerobic granules that undergo the growth-disintegration cycle were investigated. Four sequencing batch reactors (SBR) were inoculated with aerobic granules at different stages of development (different sizes). Different sizes of aerobic granules showed varying PHA contents. Thus, further study was conducted to investigate the diffusion of substrate and oxygen on PHA accumulation using various organic loading rates (OLR) and aeration rates (AR). An increase in OLR from 0.91 to 3.64kg COD/m(3)day increased the PHA content from 0.66 to 0.87g PHA/g CDW. Meanwhile, an AR increase from 1 to 4L/min only accelerated the maximum PHA accumulation without affecting the PHA content. However, the PHA composition only changes with AR, while the hydroxyvalerate (HV) content increased at a higher AR. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Photosynthesis down-regulation precedes carbohydrate accumulation under sink limitation in Citrus.

    PubMed

    Nebauer, Sergio G; Renau-Morata, Begoña; Guardiola, José Luis; Molina, Rosa-Victoria

    2011-02-01

    Photosynthesis down-regulation due to an imbalance between sources and sinks in Citrus leaves could be mediated by excessive accumulation of carbohydrates. However, there is limited understanding of the physiological role of soluble and insoluble carbohydrates in photosynthesis regulation and the elements triggering the down-regulation process. In this work, the role of non-structural carbohydrates in the regulation of photosynthesis under a broad spectrum of source-sink relationships has been investigated in the Salustiana sweet orange. Soluble sugar and starch accumulation in leaves, induced by girdling experiments, did not induce down-regulation of the photosynthetic rate in the presence of sinks (fruits). The leaf-to-fruit ratio did not modulate photosynthesis but allocation of photoassimilates to the fruits. The lack of strong sink activity led to a decrease in the photosynthetic rate and starch accumulation in leaves. However, photosynthesis down-regulation due to an excess of total soluble sugars or starch was discarded because photosynthesis and stomatal conductance reduction occurred prior to any significant accumulation of these carbohydrates. Gas exchange and fluorescence parameters suggested biochemical limitations to photosynthesis. In addition, the expression of carbon metabolism-related genes was altered within 24 h when strong sinks were removed. Sucrose synthesis and export genes were inhibited, whereas the expression of ADP-glucose pyrophosphorylase was increased to cope with the excess of assimilates. In conclusion, changes in starch and soluble sugar turnover, but not sugar content per se, could provide the signal for photosynthesis regulation. In these conditions, non-stomatal limitations strongly inhibited the photosynthetic rate prior to any significant increase in carbohydrate levels.

  2. Heart rate measurement as a tool to quantify sedentary behavior.

    PubMed

    Åkerberg, Anna; Koshmak, Gregory; Johansson, Anders; Lindén, Maria

    2015-01-01

    Sedentary work is very common today. The aim of this pilot study was to attempt to differentiate between typical work situations and to investigate the possibility to break sedentary behavior, based on physiological measurement among office workers. Ten test persons used one heart rate based activity monitor (Linkura), one pulse oximeter device (Wrist) and one movement based activity wristband (Fitbit Flex), in different working situations. The results showed that both heart rate devices, Linkura and Wrist, were able to detect differences in heart rate between the different working situations (resting, sitting, standing, slow walk and medium fast walk). The movement based device, Fitbit Flex, was only able to separate differences in steps between slow walk and medium fast walk. It can be concluded that heart rate measurement is a promising tool for quantifying and separating different working situations, such as sitting, standing and walking.

  3. Stability of the accumulation pattern around Dome C over the last glacial cycle

    NASA Astrophysics Data System (ADS)

    Cavitte, Marie; Parrenin, Frédéric; Ritz, Catherine; Blankenship, Donald; Young, Duncan; Frezzotti, Massimo; Roberts, Jason; van Ommen, Tas

    2017-04-01

    The "Candidate A" region, just to the south of Dome C, is one of the climate community's targets for retrieving "old ice", aiming for an ice core bottom age of 1.5 million-years. The region lies along the divide that separates the Byrd and Totten glacier catchments, and thus its position could be sensitive to differential behavior of those two systems. In the winter of 15/16, the University of Texas at Austin Institute for Geophysics (UTIG) collected a detailed airborne radar survey known as OIA (Old Ice A) (Young et al., in review). Seventeen internal radar reflections are mapped through this survey, encompassing both sides of the divide, spanning the last three glacial cycles, from 38 ka and 366 kyrs. Dates are obtained where the internal reflections intersect the EPICA Dome C ice core and the AICC20112 age-depth chronology can be transferred to each individual reflection. These internal reflections are easily traced in the OIA survey for several reasons: (1) Candidate A is a region of relatively stable ice, close to the ice divide, so very little horizontal flow has occurred and the radar reflections exhibit near-horizontal stratigraphy, (2) the gridded geometry of the survey design implies a high number of crossovers which allow regular checks on the accuracy of the reflection mapping, and supports the isochronal character of the reflections. Older airborne UTIG radar surveys in the region augment the dataset to provide constraints further away from the divide, and the same set of isochrones are traced throughout (previously published in Cavitte et al., 2016). We use a 1D inverse model (Parrenin et al., in prep) to reconstruct the patterns of paleo-accumulation through time all the way back to the penultimate interglacial (127 kyr). To do this, we first fit the isochrones' geometries and ages to invert for the steady-state accumulation rate, the basal melting rate and the p exponent in the Lliboutry flow formulation. We then reconstruct paleo-accumulation rates

  4. Calculations vs. measurements of remnant dose rates for SNS spent structures

    NASA Astrophysics Data System (ADS)

    Popova, I. I.; Gallmeier, F. X.; Trotter, S.; Dayton, M.

    2018-06-01

    Residual dose rate measurements were conducted on target vessel #13 and proton beam window #5 after extraction from their service locations. These measurements were used to verify calculation methods of radionuclide inventory assessment that are typically performed for nuclear waste characterization and transportation of these structures. Neutronics analyses for predicting residual dose rates were carried out using the transport code MCNPX and the transmutation code CINDER90. For transport analyses complex and rigorous geometry model of the structures and their surrounding are applied. The neutronics analyses were carried out using Bertini and CEM high energy physics models for simulating particles interaction. Obtained preliminary calculational results were analysed and compared to the measured dose rates and overall are showing good agreement with in 40% in average.

  5. FACTORS ASSOCIATED WITH PENTOSIDINE ACCUMULATION IN THE HUMAN VITREOUS.

    PubMed

    van Deemter, Marielle; Bank, Ruud A; Vehof, Jelle; Hooymans, Johanna M M; Los, Leonoor I

    2017-04-01

    To explore factors associated with pentosidine accumulation in the human vitreous. Vitreous samples were obtained during trans pars plana vitrectomy for macular hole or rhegmatogenous retinal detachment. Patient characteristics included age, gender, and diabetes mellitus. Ocular characteristics included pseudophakia, posterior vitreous detachment, and presence of intraocular fibrosis (epiretinal membrane, proliferative vitreoretinopathy, or both). Pentosidine concentration as a measure of accumulation of advanced glycation end products was determined by high performance liquid chromatography. Pentosidine concentrations were measured in 222 vitrectomy samples (118 female and 104 male patients [median age 66 years], treated for macular hole [n = 105] or rhegmatogenous retinal detachment [n = 117]). Pentosidine was found to accumulate significantly with age (P < 0.001). After correction for age, a multivariable linear regression model revealed significantly higher pentosidine values in eyes with intraocular fibrosis (P = 0.001), in phakic as compared with pseudophakic eyes (P = 0.02), and in the absence of a complete posterior vitreous detachment (P = 0.018). The authors found no association with diabetes mellitus or gender. This study confirmed an age-related pentosidine accumulation in the vitreous and found new factors relating to pentosidine levels. Findings support the hypothesis of enzyme-induced vitreous liquefaction and the hypothesis of pentosidine as a pro-fibrotic factor.

  6. Systems Level Regulation of Rhythmic Growth Rate and Biomass Accumulation in Grasses

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

    Kay, Steve A.; Hazen, Samuel; Mullet, John

    Critical to the development of renewable energy sources from biofuels is the improvement of biomass from energy feedstocks, such as sorghum and maize. The specific goals of this project include 1) characterize the growth and gene expression patterns under diurnal and circadian conditions, 2) select transcription factors associated with growth and build a cis-regulatory network in yeast, and 3) perturb these transcription factors in planta using transgenic Brachypodium and sorghum, and characterize the phenotypic outcomes as they relate to biomass accumulation. A better understanding of diurnally regulated growth behavior in grasses may lead to species-specific mechanisms highly relevant to futuremore » strategies to optimize energy crop biomass yield.« less

  7. Growth and Lead Accumulation Capacity of Lemna minor and Spirodela polyrhiza (Lemnaceae): Interactions with Nutrient Enrichment

    PubMed Central

    Aksoy, Ahmet

    2010-01-01

    A study to understand the biological effects of samples prepared with lead and the effects of lead were conducted on Lemna minor L. and Spirodela polyrhiza (L.) Schleid. This study was intended to test the hypothesis that nutrient enrichment (P, NO3−–N and SO42−) enhances the metal tolerance of floating macrophytes. The plants were exposed to Pb concentrations 0, 1, 5, 10, 25, and 50 mg l−1 for a period of 1, 3, 5, and 7 days. L. minor accumulated 561 mg g−1 dry weight (dw) Pb, and S. polyrhiza accumulated 330 mg g−1 dw Pb after 7 days, whereas in the groups enriched with nutrients, L. minor accumulated 128.7 mg g−1 Pb and S. polyrhiza accumulated 68.7 mg g−1 dw Pb after 7 days. Relative growth rates and photosynthetic pigments (chlorophyll a, b, and carotenoid) were measured in L. minor and S. polyrhiza exposed to different Pb concentrations under laboratory conditions. Relative growth rates were negatively correlated with metal exposure, but nutrient addition was found to suppress this effect. Photosynthetic pigment levels were found negatively correlated with metal exposure, and nutrient addition attenuated chlorophyll decrease in response to metal exposure. Metal and nutrient concentration in water decreased throughout the experiments. The study concluded that nutrient enrichment increases the tolerance of L. minor and S. polyrhiza to metals, that L. minor and S. polyrhiza are suitable candidates for the phytoremediation of low-level lead pollution, and that L. minor was more effective in extracting lead than was S. polyrhiza. PMID:21258435

  8. Automatable Measurement of Gas Exchange Rate in Streams: Oxygen-Carbon Method

    NASA Astrophysics Data System (ADS)

    Pennington, R.; Haggerty, R.; Argerich, A.; Wondzell, S. M.

    2015-12-01

    Gas exchange rates between streams and the atmosphere are critically important to measurement of in-stream ecologic processes, as well as fate and transport of hazardous pollutants such as mercury and PCBs. Methods to estimate gas exchange rates include empirical relations to hydraulics, and direct injection of a tracer gas such as propane or SF6. Empirical relations are inconsistent and inaccurate, particularly for lower order, high-roughness streams. Gas injections are labor-intensive, and measured gas exchange rates are difficult to extrapolate in time since they change with discharge and stream geometry. We propose a novel method for calculation of gas exchange rates utilizing O2, pCO2, pH, and temperature data. Measurements, which can be automated using data loggers and probes, are made on the upstream and downstream end of the study reach. Gas exchange rates are then calculated from a solution to the transport equations for oxygen and dissolved inorganic carbon. Field tests in steep, low order, high roughness streams of the HJ Andrews Experimental Forest indicate the method to be viable along stream reaches with high downstream gas concentration gradients and high rates of gas transfer velocity. Automated and continuous collection of oxygen and carbonate chemistry data is increasingly common, thus the method may be used to estimate gas exchange rates through time, and is well suited for interactivity with databases.

  9. Calcite dissolution rate spectra measured by in situ digital holographic microscopy.

    PubMed

    Brand, Alexander S; Feng, Pan; Bullard, Jeffrey W

    2017-09-01

    Digital holographic microscopy in reflection mode is used to track in situ , real-time nanoscale topography evolution of cleaved (104) calcite surfaces exposed to flowing or static deionized water. The method captures full-field holograms of the surface at frame rates of up to 12.5 s -1 . Numerical reconstruction provides 3D surface topography with vertical resolution of a few nanometers and enables measurement of time-dependent local dissolution fluxes. A statistical distribution, or spectrum, of dissolution rates is generated by sampling multiple area domains on multiple crystals. The data show, as has been demonstrated by Fischer et al. (2012), that dissolution is most fully described by a rate spectrum, although the modal dissolution rate agrees well with published mean dissolution rates ( e.g. , 0.1 µmol m -2 s -1 to 0.3 µmol m -2 s -1 ). Rhombohedral etch pits and other morphological features resulting from rapid local dissolution appear at different times and are heterogeneously distributed across the surface and through the depth. This makes the distribution in rates measured on a single crystal dependent both on the sample observation field size and on time, even at nominally constant undersaturation. Statistical analysis of the inherent noise in the DHM measurements indicates that the technique is robust and that it likely can be applied to quantify and interpret rate spectra for the dissolution or growth of other minerals.

  10. Cadmium accumulation in the rootless macrophyte Wolffia globosa and its potential for phytoremediation.

    PubMed

    Xie, Wan-Ying; Huang, Qing; Li, Gang; Rensing, Christopher; Zhu, Yong-Guan

    2013-01-01

    Cadmium (Cd) pollution around the world is a serious issue demanding acceptable solutions, one of which is phytoremediation that is both cost-effective and eco-friendly. Removal of Cd from contaminated water using plants with high growth rates and sufficient Cd accumulation abilities could be an appropriate choice. Here, we investigated a potential Cd accumulator, Wolffia, a rootless duckweed with high growth rate. Cd uptake, accumulation, tolerance, and phytofiltration ability by Wolffia globosa were examined. Furthermore, the effects of arsenic (As) on Cd uptake and phytofiltration by W. globosa were also studied. Cd uptake kinetics showed a linear pattern and a hyperbolic pattern without a plateau in lower (0-2 microM) and higher (0-200 microM) Cd concentration ranges, respectively, suggesting rapid Cd uptake by W. globosa Cd accumulation ability by W. globosa was higher at Cd concentrations < 10 microM than at >10 microM. All the five species of Wolffia exposed to I microM Cd for 5 days accumulated > 500 mg Cd kg(-1) DW. Ten gram fresh W. globosa could diminish almost all the Cd (2 microM) in a 200 mL solution. This enormous accumulation ability was mostly due to passive adsorption of Cd by the apoplast. Arsenic had no significant effect on Cd uptake and phytofiltration. The fresh fronds also showed a great As extracting ability. The results indicated that Wolffia is a strong Cd accumulator and has great Cd phytoremediation potential. Therefore, this plant can be used in fresh aquatic environments co-contaminated by low-levels of Cd and As.

  11. Carbon Monoxide Accumulation in the Extravehicular Mobility Unit

    NASA Technical Reports Server (NTRS)

    Conkin, J.; Norcrosss, J. R.; Alexander, D. J.; Sanders, R. W.; Makowski, M. S.

    2016-01-01

    Introduction: Life support technology in large closed systems like submarines and space stations catalyzes carbon monoxide (CO) to carbon dioxide, which is easily removed. However, in a small system like the Extravehicular Mobility Unit (EMU), spacesuit, CO from exogenous (contaminated oxygen (O (sub 2) supply) and endogenous (human metabolism) sources will accumulate in the free suit volume. The free volume becomes a sink for CO that is rebreathed by the astronaut. The accumulation through time depends on many variables: the amount absorbed by the astronaut, the amount produced by the astronaut (between 0.28 and 0.34 ?moles per hour per kilogram)[1], the amount that enters the suit from contaminated O (sub 2), the amount removed through suit leak, the free volume of the suit, and the O (sub 2) partial pressure[2], just to list a few. Contamination of the EMU O (sub 2) supply with no greater than 1 part per million CO was the motivation for empirical measurements from CO pulse oximetry (SpCO) as well as mathematical modeling of the EMU as a rebreather for CO. Methods: We developed a first-order differential mixing equation as well as an iterative method to compute CO accumulation in the EMU. Pre-post measurements of SpCO (Rad-57, Masimo Corporation) from EMU ground training and on-orbit extravehicular activities (EVAs) were collected. Results: Initial modeling without consideration of the astronaut as a sink but only the source of CO showed that after 8 hours breathing 100 percent O (sub 2) with a 10 milliliter per minute (760 millimeters Hg at 21 degrees Centigrade standard) suit leak, an endogenous production rate of 0.23 moles per hour per kilogram for a 70 kilogram person with 42 liters (1.5 cubic feet) free suit volume resulted in a peak CO partial pressure (pCO) of 0.047 millimeters Hg at 4.3 pounds per square inch absolute (222 millimeters Hg). Preliminary results based on a 2008 model[3] with consideration of the astronaut as a sink and source of CO

  12. Axonal transport rate decreased at the onset of optic neuritis in EAE mice

    PubMed Central

    Lin, Tsen-Hsuan; Kim, Joong Hee; Perez-Torres, Carlos; Chiang, Chia-Wen; Trinkaus, Kathryn; Cross, Anne H.; Song, Sheng-Kwei

    2014-01-01

    Optic neuritis is frequently the first symptom of multiple sclerosis (MS), an inflammatory demyelinating neurodegenerative disease. Impaired axonal transport has been considered as an early event of neurodegenerative diseases. However, few studies have assessed the integrity of axonal transport in MS or its animal models. We hypothesize that axonal transport impairment occurs at the onset of optic neuritis in experimental autoimmune encephalomyelitis (EAE) mice. In this study, we employed manganese-enhanced MRI (MEMRI) to assess axonal transport in optic nerves in EAE mice at the onset of optic neuritis. Axonal transport was assessed as (a) optic nerve Mn2+ accumulation rate (in % signal change/hour) by measuring the rate of increased total optic nerve signal enhancement, and (b) Mn2+ transport rate (in mm/hour) by measuring the rate of change in optic nerve length enhanced by Mn2+. Compared to sham-treated healthy mice, Mn2+ accumulation rate was significantly decreased by 19% and 38% for EAE mice with moderate and severe optic neuritis, respectively. The axonal transport rate of Mn2+ was significantly decreased by 43% and 65% for EAE mice with moderate and severe optic neuritis, respectively. The degree of axonal transport deficit correlated with the extent of impaired visual function and diminished microtubule-associated tubulins, as well as the severity of inflammation, demyelination, and axonal injury at the onset of optic neuritis. PMID:24936685

  13. The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

    USGS Publications Warehouse

    Kirwanm, M.L.; Langley, J.A.; Guntenspergen, Gleen R.; Megonigal, J.P.

    2013-01-01

    The balance between organic matter production and decay determines how fast coastal wetlands accumulate soil organic matter. Despite the importance of soil organic matter accumulation rates in influencing marsh elevation and resistance to sea-level rise, relatively little is known about how decomposition rates will respond to sea-level rise. Here, we estimate the sensitivity of decomposition to flooding by measuring rates of decay in 87 bags filled with milled sedge peat, including soil organic matter, roots and rhizomes. Experiments were located in field-based mesocosms along 3 mesohaline tributaries of the Chesapeake Bay. Mesocosm elevations were manipulated to influence the duration of tidal inundation. Although we found no significant influence of inundation on decay rate when bags from all study sites were analyzed together, decay rates at two of the sites increased with greater flooding. These findings suggest that flooding may enhance organic matter decay rates even in water-logged soils, but that the overall influence of flooding is minor. Our experiments suggest that sea-level rise will not accelerate rates of peat accumulation by slowing the rate of soil organic matter decay. Consequently, marshes will require enhanced organic matter productivity or mineral sediment deposition to survive accelerating sea-level rise.

  14. The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

    NASA Astrophysics Data System (ADS)

    Kirwan, M. L.; Langley, J. A.; Guntenspergen, G. R.; Megonigal, J. P.

    2013-03-01

    The balance between organic matter production and decay determines how fast coastal wetlands accumulate soil organic matter. Despite the importance of soil organic matter accumulation rates in influencing marsh elevation and resistance to sea-level rise, relatively little is known about how decomposition rates will respond to sea-level rise. Here, we estimate the sensitivity of decomposition to flooding by measuring rates of decay in 87 bags filled with milled sedge peat, including soil organic matter, roots and rhizomes. Experiments were located in field-based mesocosms along 3 mesohaline tributaries of the Chesapeake Bay. Mesocosm elevations were manipulated to influence the duration of tidal inundation. Although we found no significant influence of inundation on decay rate when bags from all study sites were analyzed together, decay rates at two of the sites increased with greater flooding. These findings suggest that flooding may enhance organic matter decay rates even in water-logged soils, but that the overall influence of flooding is minor. Our experiments suggest that sea-level rise will not accelerate rates of peat accumulation by slowing the rate of soil organic matter decay. Consequently, marshes will require enhanced organic matter productivity or mineral sediment deposition to survive accelerating sea-level rise.

  15. The impact of sea-level rise on organic matter decay rates in Chesapeake Bay brackish tidal marshes

    NASA Astrophysics Data System (ADS)

    Kirwan, M. L.; Langley, J. A.; Guntenspergen, G. R.; Megonigal, J. P.

    2012-10-01

    The balance between organic matter production and decay determines how fast coastal wetlands accumulate soil organic matter. Despite the importance of soil organic matter accumulation rates in influencing marsh elevation and resistance to sea-level rise, relatively little is known about how decomposition rates will respond to sea-level rise. Here, we estimate the sensitivity of decomposition to flooding by measuring rates of decay in 87 bags filled with milled sedge peat, including soil organic matter, roots and rhizomes. Experiments were located in field-based mesocosms along 3 mesohaline tributaries of the Chesapeake Bay. Mesocosm elevations were manipulated to influence the duration of tidal inundation. Although we found no significant influence of inundation on decay rate when bags from all study sites were analyzed together, decay rates at two of the sites increased with greater flooding. These findings suggest that flooding may enhance organic matter decay rates even in water-logged soils, but that the overall influence of flooding is minor. Our experiments suggest that sea-level rise will not accelerate rates of peat accumulation by slowing the rate of soil organic matter decay. Consequently, marshes will require enhanced organic matter productivity or mineral sediment deposition to survive accelerating sea-level rise.

  16. Optical extinction efficiency measurements on fine and accumulation mode aerosol using single particle cavity ring-down spectroscopy.

    PubMed

    Cotterell, Michael I; Mason, Bernard J; Preston, Thomas C; Orr-Ewing, Andrew J; Reid, Jonathan P

    2015-06-28

    A new experiment is presented for the measurement of single aerosol particle extinction efficiencies, Qext, combining cavity ring-down spectroscopy (CRDS, λ = 405 nm) with a Bessel beam trap (λ = 532 nm) in tandem with phase function (PF) measurements. This approach allows direct measurements of the changing optical cross sections of individual aerosol particles over indefinite time-frames facilitating some of the most comprehensive measurements of the optical properties of aerosol particles so far made. Using volatile 1,2,6-hexanetriol droplets, Qext is measured over a continuous radius range with the measured Qext envelope well described by fitted cavity standing wave (CSW) Mie simulations. These fits allow the refractive index at 405 nm to be determined. Measurements are also presented of Qext variation with RH for two hygroscopic aqueous inorganic systems ((NH4)2SO4 and NaNO3). For the PF and the CSW Mie simulations, the refractive index, nλ, is parameterised in terms of the particle radius. The radius and refractive index at 532 nm are determined from PFs, while the refractive index at 405 nm is determined by comparison of the measured Qext to CSW Mie simulations. The refractive indices determined at the shorter wavelength are larger than at the longer wavelength consistent with the expected dispersion behaviour. The measured values at 405 nm are compared to estimates from volume mixing and molar refraction mixing rules, with the latter giving superior agreement. In addition, the first single-particle Qext measurements for accumulation mode aerosol are presented for droplets with radii as small as ∼300 nm.

  17. Glacial-interglacial dynamics of Antarctic firn columns: comparison between simulations and ice core air-δ15N measurements

    NASA Astrophysics Data System (ADS)

    Capron, E.; Landais, A.; Buiron, D.; Cauquoin, A.; Chappellaz, J.; Debret, M.; Jouzel, J.; Leuenberger, M.; Martinerie, P.; Masson-Delmotte, V.; Mulvaney, R.; Parrenin, F.; Prié, F.

    2012-12-01

    Correct estimate of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice cores studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation: output of a firn densification model and measurements of δ15N of N2 in air trapped in ice core. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI) and semi coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic regions. Combined with available δ15N measurements performed from the EPICA Dome C (EDC) site, the studied regions encompass a large range of surface accumulation rate and temperature conditions. While firn densification simulations are able to correctly represent most of the δ15N trends over the last deglaciation measured in the EDC, BI, TALDICE and EDML ice cores, they systematically fail to capture BI and EDML δ15N glacial levels, a mismatch previously seen for Central East Antarctic ice cores. Using empirical constraints of the EDML gas-ice depth offset during the Laschamp event (~ 41 ka), we can rule out the existence of a large convective zone as the explanation of the glacial firn model-δ15N data mismatch for this site. The good match between modelled and measured δ15N at TALDICE as well as the lack of any clear correlation between insoluble dust concentration in snow and δ15N records in the different ice cores suggest that past changes in loads of impurities are not the only main driver of glacial-interglacial changes in firn lock-in depth. We conclude that firn densification dynamics may instead be driven mostly by accumulation rate changes. The mismatch between modelled and measured δ15N may be due to inaccurate reconstruction of past accumulation rate or underestimated influence of accumulation rate in firnification models.

  18. Collector design for measuring high intensity time variant sprinkler application rates

    USDA-ARS?s Scientific Manuscript database

    Peak water application rate in relation to soil water infiltration rate and soil surface storage capacity is important in the design of center pivot sprinkler irrigation systems for efficient irrigation and soil erosion control. Measurement of application rates of center pivot irrigation systems ha...

  19. Spatially resolved heat release rate measurements in turbulent premixed flames

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

    Ayoola, B.O.; Kaminski, C.F.; Balachandran, R.

    Heat release rate is a fundamental property of great importance for the theoretical and experimental elucidation of unsteady flame behaviors such as combustion noise, combustion instabilities, and pulsed combustion. Investigations of such thermoacoustic interactions require a reliable indicator of heat release rate capable of resolving spatial structures in turbulent flames. Traditionally, heat release rate has been estimated via OH or CH radical chemiluminescence; however, chemiluminescence suffers from being a line-of-sight technique with limited capability for resolving small-scale structures. In this paper, we report spatially resolved two-dimensional measurements of a quantity closely related to heat release rate. The diagnostic technique usesmore » simultaneous OH and CH{sub 2}O planar laser-induced fluorescence (PLIF), and the pixel-by-pixel product of the OH and CH{sub 2}O PLIF signals has previously been shown to correlate well with local heat release rates. Results from this diagnostic technique, which we refer to as heat release rate imaging (HR imaging), are compared with traditional OH chemiluminescence measurements in several flames. Studies were performed in lean premixed ethylene flames stabilized between opposed jets and with a bluff body. Correlations between bulk strain rates and local heat release rates were obtained and the effects of curvature on heat release rate were investigated. The results show that the heat release rate tends to increase with increasing negative curvature for the flames investigated for which Lewis numbers are greater than unity. This correlation becomes more pronounced as the flame gets closer to global extinction.« less

  20. Carbon accumulation in peatlands of West Siberia over the last 2000 years

    NASA Astrophysics Data System (ADS)

    Beilman, David W.; MacDonald, Glen M.; Smith, Laurence C.; Reimer, Paula J.

    2009-03-01

    We use a network of cores from 77 peatland sites to determine controls on peat C content and peat C accumulation over the last 2000 years (since 2 ka) across Russia's West Siberian Lowland (WSL), the world's largest wetland region. Our results show a significant influence of fossil plant composition on peat C content, with peats dominated by Sphagnum having a lower C content. Radiocarbon-derived C accumulation since 2 ka at 23 sites is highly variable from site to site, but displays a significant N-S trend of decreasing accumulation at higher latitudes. Northern WSL peatlands show relatively small C accumulation of 7 to 35 kg C m-2 since 2 ka. In contrast, peatlands south of 60°N show larger accumulation of 42 to 88 kg C m-2. Carbon accumulation since 2 ka varies significantly with modern mean annual air temperature, with maximum C accumulation found between -1 and 0°C. Rates of apparent C accumulation since 2 ka show no significant relationship to long-term Holocene averages based on total C accumulation. A GIS-based extrapolation of our site data suggests that a substantial amount (˜40%) of total WSL peat C has accumulated since 2 ka, with much of this accumulation south of 60°N. The large peatlands in the southern WSL may be an important component of the Eurasian terrestrial C sink, and future warming could result in a shift northward in long-term WSL C sequestration.

  1. Comparison of axillary bud growth and patatin accumulation in potato leaf cuttings as assays for tuber induction

    NASA Technical Reports Server (NTRS)

    Wheeler, R. M.; Hannapel, D. J.; Tibbitts, T. W.

    1988-01-01

    Single-node leaf cuttings from potatoes (Solanum tuberosum L.) cvs. Norland, Superior, Norchip, and Kennebec, were used to assess tuber induction in plants grown under 12, 16, and 20 h daily irradiation (400 micromol s-1 m-2 PPF). Leaf cuttings were taken from plants at four, six and 15 weeks after planting and cultured for 14 d in sand trays in humid environments. Tuber induction was determined by visually rating the type of growth at the attached axillary bud, and by measuring the accumulation of the major tuber protein, patatin, in the base of the petioles. Axillary buds from leaf cuttings of plants grown under the 12 h photoperiod consistently formed round, sessile tubers at the axils for all four cultivars at all harvests. Buds from cuttings of plants grown under the 16 and 20 h photoperiods exhibited mixed tuber, stolon, and leafy shoot growth. Patatin accumulation was highest in petioles of cuttings taken from 12 h plants for all cultivars at all harvests, with levels in 16 and 20 h cuttings approx. one-half that of the 12 h cuttings. Trends, both in visual ratings of axillary buds and in petiole patatin accumulation, followed the harvest index (ratio of tuber to total plant dry matter), suggesting that either method is an acceptable assay for tuber induction in the potato.

  2. Accumulation of peptidyl tRNA is lethal to Escherichia coli.

    PubMed Central

    Menninger, J R

    1979-01-01

    A mutant strain of Escherichia coli with temperature-sensitive peptidyl-tRNA hydrolase grows at 30 degrees C but, when shifted to 40 degrees C, dies at rates affected by physiological, pharmacological, and genetical perturbations. The rate of killing correlates with the relative accumulation of peptidyl-tRNA, suggesting that it is responsible for the death of the cells. PMID:368041

  3. Himalayan Strain Accumulation 100 ka Timescales

    NASA Astrophysics Data System (ADS)

    Cannon, J. M.; Murphy, M. A.; Liu, Y.

    2015-12-01

    Crustal scale fault systems and tectonostratigraphic units in the Himalaya can be traced for 2500 km along strike. However regional studies have shown that there is variability in the location and rate of strain accumulation which appears to be driven by Main Himalayan Thrust (MHT) geometry and convergence obliquity. GPS illuminates the modern interseismic strain rate and the historical record of great earthquakes elucidates variations in strain accumulation over 103 years. To connect these patterns with the 106 year structural and thermochronometric geologic record we examine normalized river channel steepness (ksn), a proxy for rock uplift rate, which develops over 104 - 105 years. Here we present a ksn map of the Himalaya and compare it with bedrock geology, precipitation, the historic earthquake record, GPS, seismicity, and seismotectonic models. Our map shows significant along strike changes in the magnitude of channel steepness, the areal extent of swaths of high ksn channels, and their location with respect to the range front. Differences include the juxtaposition of two narrow (30 - 40 km) range parallel belts of high ksn in west Nepal and Bhutan coincident with MHT duplexes and belts of microseismcity, with a single broad (70 km) swath of high ksn and microseismicity in central and eastern Nepal. Separating west and central Nepal a band of low ksn crosses the range coincident with the West Nepal Fault (WNF) and the lowest rate of microseismicity in Nepal. To the west the orogen is obliquely convergent and has less high ksn channels, while the orthogonally convergent region to the east contains the highest concentration of oversteepened channels in the Himalaya supporting the idea that the WNF is a strain partitioning boundary. The syntaxes are characterized by locally high channel steepness surrounded by low to moderate ksn channels consistent with the hypothesis that rapid exhumation within the syntaxes is sustained by an influx of lower crust.

  4. Modern sediment characteristics and accumulation rates from the delta front to prodelta of the Yellow River (Huanghe)

    NASA Astrophysics Data System (ADS)

    Zhou, Liangyong; Liu, Jian; Saito, Yoshiki; Gao, Maosheng; Diao, Shaobo; Qiu, Jiandong; Pei, Shaofeng

    2016-08-01

    Since 1976, the main channel of the Yellow River (Huanghe) has been on the east side of the delta complex, and the river has prograded a broad new delta lobe in Laizhou Bay of the Bohai Sea. In 2012, extensive bathymetric and high-resolution seismic profiles were conducted and sediment cores were collected off the new delta lobe. This study examined delta sedimentation and morphology along a profile across the modern subaqueous Yellow River delta and into Laizhou Bay, by analyzing sediment radionuclides (137Cs, 210Pb and 7Be), sedimentary structure, grain-size composition, organic carbon content, and morphological changes between 1976 and 2012. The change in the bathymetric profile, longitudinal to the river's course, reveals subaqueous delta progradation during this period. The subbottom boundary between the new delta lobe sediment and the older seafloor sediment (before the 1976 course shift) was identified in terms of lithology and radionuclide distributions, and recognized as a downlap surface in the seismic record. The accumulation rate of the new delta lobe sediment is estimated to be 5-18.6 cm year-1 on the delta front slope, 2 cm year-1 at the toe of the slope, and 1-2 cm year-1 in the shelf areas of Laizhou Bay. Sediment facies also change offshore, from alternations of gray and brown sediment in the proximal area to gray bioturbated fine sediment in the distal area. Based on 7Be distribution, the shorter-term deposition rate was at least 20 cm year-1 in the delta front.

  5. Leaf Photosynthetic Parameters Related to Biomass Accumulation in a Global Rice Diversity Survey1[OPEN

    PubMed Central

    Zheng, Guangyong; Hamdani, Saber; Essemine, Jemaa; Song, Qingfeng; Wang, Hongru

    2017-01-01

    Mining natural variations is a major approach to identify new options to improve crop light use efficiency. So far, successes in identifying photosynthetic parameters positively related to crop biomass accumulation through this approach are scarce, possibly due to the earlier emphasis on properties related to leaf instead of canopy photosynthetic efficiency. This study aims to uncover rice (Oryza sativa) natural variations to identify leaf physiological parameters that are highly correlated with biomass accumulation, a surrogate of canopy photosynthesis. To do this, we systematically investigated 14 photosynthetic parameters and four morphological traits in a rice population, which consists of 204 U.S. Department of Agriculture-curated minicore accessions collected globally and 11 elite Chinese rice cultivars in both Beijing and Shanghai. To identify key components responsible for the variance of biomass accumulation, we applied a stepwise feature-selection approach based on linear regression models. Although there are large variations in photosynthetic parameters measured in different environments, we observed that photosynthetic rate under low light (Alow) was highly related to biomass accumulation and also exhibited high genomic inheritability in both environments, suggesting its great potential to be used as a target for future rice breeding programs. Large variations in Alow among modern rice cultivars further suggest the great potential of using this parameter in contemporary rice breeding for the improvement of biomass and, hence, yield potential. PMID:28739819

  6. Calculations vs. measurements of remnant dose rates for SNS spent structures

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

    Popova, Irina I.; Gallmeier, Franz X.; Trotter, Steven M.

    Residual dose rate measurements were conducted on target vessel #13 and proton beam window #5 after extraction from their service locations. These measurements were used to verify calculation methods of radionuclide inventory assessment that are typically performed for nuclear waste characterization and transportation of these structures. Neutronics analyses for predicting residual dose rates were carried out using the transport code MCNPX and the transmutation code CINDER90. For transport analyses complex and rigorous geometry model of the structures and their surrounding are applied. The neutronics analyses were carried out using Bertini and CEM high energy physics models for simulating particles interaction.more » Obtained preliminary calculational results were analysed and compared to the measured dose rates and overall are showing good agreement with in 40% in average.« less

  7. Coupled Gravity and Elevation Measurements of Ice Sheet Mass Change

    NASA Technical Reports Server (NTRS)

    Jezek, K. C.

    2005-01-01

    We measured surface gravity and position at ten locations about two glaciological measurement networks located on the South-central Greenland Ice during June 2004. Six of the individual sites of the first network were occupied the previous year. At the repeat sites we were able to measure annual accumulation rate and surface displacement by referencing measurements to aluminum poles left in the firn the previous year. We occupied 4 additional sites at a second measurement network for the first time since initial observations were last made at the network in 1981. At each individual site, we operated a GPS unit for 90 minutes - the unit was operated simultaneously with a base station unit in Sondrestrom Fjord so as to enable differential, post-processing of the data. We installed an aluminum, accumulation-rate-pole at each site. The base section of the pole also served as the mount for the GPS antenna. A new, Scintrex gravimeter was used at each site and relative gravity measurements were tied to the network of absolute gravity stations in Sondrestrom. We measured snow physical properties in two shallow pits. This report summarizes our observations and data analysis.

  8. Hydrologic Connectivity and Land Use Effects on Sediment Accumulation on Stream Floodplains of the Savannah River Site, South Carolina.

    NASA Astrophysics Data System (ADS)

    Eddy, J.; Yeager, K. M.; Barton, C.; Phillips, J. D.

    2016-12-01

    Natural sediment accumulation on floodplains is important to maintain water quality of streams, to support regional biodiversity as an ecotone between aquatic and terrestrial environments, and to serve as a sink for organic and inorganic carbon. Recent research suggests that land use and hydrologic connectivity play important roles in determining rates of sediment accumulation. This study hypothesizes that changes in hydrologic connectivity have a greater impact on sediment accumulation rates than changes in land use. Nine sediment cores from seven sub-basins were taken from the Savannah River Site, South Carolina, and processed for grain-size, radioisotope dating, particulate organic carbon (POC), and microscopy. Stratigraphic columns were created for all nine cores. Extensive historical records, aerial, and satellite imagery are used to identify anthropogenic disturbances which may have influenced rates of sediment accumulation, as well as to calculate the percentage of natural vegetation in 1951 and 2014. Grain-size analysis and microscopy indicate that the majority of sediment studied is sand-sized quartz; changes in grain-size classification is used to indicate potential differences in sediment sources. LiDAR and field survey data were used to identify 251 stream flow impediments that potentially affect hydrologic connectivity. Results from radioisotope dating and POC have been used to calculate sediment mass accumulation rates (SMAR; g cm-2 y-1) and linear accumulation rates (LAR; cm y-1) for each of the cores. Preliminary findings show that plots of SMAR versus the number of flow impediments have steeper slopes than plots of SMAR versus the percent difference in vegetation (from 1951 to 2014). This signifies that flow impediments, as a proxy for hydrologic connectivity, have a stronger effect on sediment accumulation rates than changes in land use. This knowledge can help future stream restoration efforts by focusing resources to more efficiently attain

  9. Predicting the extent of metabolism using in vitro permeability rate measurements and in silico permeability rate predictions

    PubMed Central

    Hosey, Chelsea M; Benet, Leslie Z

    2015-01-01

    The Biopharmaceutics Drug Disposition Classification System (BDDCS) can be utilized to predict drug disposition, including interactions with other drugs and transporter or metabolizing enzyme effects based on the extent of metabolism and solubility of a drug. However, defining the extent of metabolism relies upon clinical data. Drugs exhibiting high passive intestinal permeability rates are extensively metabolized. Therefore, we aimed to determine if in vitro measures of permeability rate or in silico permeability rate predictions could predict the extent of metabolism, to determine a reference compound representing the permeability rate above which compounds would be expected to be extensively metabolized, and to predict the major route of elimination of compounds in a two-tier approach utilizing permeability rate and a previously published model predicting the major route of elimination of parent drug. Twenty-two in vitro permeability rate measurement data sets in Caco-2 and MDCK cell lines and PAMPA were collected from the literature, while in silico permeability rate predictions were calculated using ADMET Predictor™ or VolSurf+. The potential for permeability rate to differentiate between extensively and poorly metabolized compounds was analyzed with receiver operating characteristic curves. Compounds that yielded the highest sensitivity-specificity average were selected as permeability rate reference standards. The major route of elimination of poorly permeable drugs was predicted by our previously published model and the accuracies and predictive values were calculated. The areas under the receiver operating curves were >0.90 for in vitro measures of permeability rate and >0.80 for the VolSurf+ model of permeability rate, indicating they were able to predict the extent of metabolism of compounds. Labetalol and zidovudine predicted greater than 80% of extensively metabolized drugs correctly and greater than 80% of poorly metabolized drugs correctly in Caco

  10. Calcite dissolution rate spectra measured by in situ digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Brand, Alexander S.; Feng, Pan; Bullard, Jeffrey W.

    2017-09-01

    Digital holographic microscopy in reflection mode is used to track in situ, real-time nanoscale topography evolution of cleaved (104) calcite surfaces exposed to flowing or static deionized water. The method captures full-field holograms of the surface at frame rates of up to 12.5 s-1. Numerical reconstruction provides 3D surface topography with vertical resolution of a few nanometers and enables measurement of time-dependent local dissolution fluxes. A statistical distribution, or spectrum, of dissolution rates is generated by sampling multiple area domains on multiple crystals. The data show, as has been demonstrated by Fischer et al. (2012), that dissolution is most fully described by a rate spectrum, although the modal dissolution rate agrees well with published mean dissolution rates (e.g., 0.1 μmol m-2 s-1 to 0.3 μmol m-2 s-1). Rhombohedral etch pits and other morphological features resulting from rapid local dissolution appear at different times and are heterogeneously distributed across the surface and through the depth. This makes the distribution in rates measured on a single crystal dependent both on the sample observation field size and on time, even at nominally constant undersaturation. Statistical analysis of the inherent noise in the DHM measurements indicates that the technique is robust and that it likely can be applied to quantify and interpret rate spectra for the dissolution or growth of other minerals.

  11. Measurement of tectonic surface uplift rate in a young collisional mountain belt

    USGS Publications Warehouse

    Abbott, L.D.; Silver, E.A.; Anderson, R. Scott; Smith, R.; Ingle, J.C.; Kling, S.A.; Haig, D.; Small, E.; Galewsky, J.; Sliter, W.

    1997-01-01

    Measurement of the rate of tectonically driven surface uplift is crucial to a complete understanding of mountain building dynamics. The lack of a suitable rock record typically prevents determination of this quantity, but the unusual geology of Papua New Guinea's Finisterre mountains makes measurement of this rate possible. The tectonic surface uplift rate at the Finisterre range is 0.8-2.1 mm yr-1, approximately that expected to arise from crustal thickening.

  12. Image quality assessment metric for frame accumulated image

    NASA Astrophysics Data System (ADS)

    Yu, Jianping; Li, Gang; Wang, Shaohui; Lin, Ling

    2018-01-01

    The medical image quality determines the accuracy of diagnosis, and the gray-scale resolution is an important parameter to measure image quality. But current objective metrics are not very suitable for assessing medical images obtained by frame accumulation technology. Little attention was paid to the gray-scale resolution, basically based on spatial resolution and limited to the 256 level gray scale of the existing display device. Thus, this paper proposes a metric, "mean signal-to-noise ratio" (MSNR) based on signal-to-noise in order to be more reasonable to evaluate frame accumulated medical image quality. We demonstrate its potential application through a series of images under a constant illumination signal. Here, the mean image of enough images was regarded as the reference image. Several groups of images by different frame accumulation and their MSNR were calculated. The results of the experiment show that, compared with other quality assessment methods, the metric is simpler, more effective, and more suitable for assessing frame accumulated images that surpass the gray scale and precision of the original image.

  13. Measuring respiration rates in marine fish larvae: challenges and advances.

    PubMed

    Peck, M A; Moyano, M

    2016-01-01

    Metabolic costs can be extremely high in marine fish larvae and gaining reliable estimates of the effects of intrinsic and extrinsic factors on those costs is important to understand environmental constraints on early growth and survival. This review provides an historical perspective of measurements of larval marine fish respiration (O2 consumption) including the methods (Winkler, manometric, polarographic, paramagnetic and optodes) and systems (closed system to intermittent-flow) used. This study compares and systematically reviews the results (metabolic rates, ontogenetic changes and taxonomic differences) obtained from 59 studies examining 53 species from 30 families. Standard (anaesthetized or darkness), routine and active respiration rates were reported in 14, 94 and 8% of the studies and much more work has been performed on larvae of temperate (88%) compared with tropical (9%) and polar (3%) species. More than 35% of the studies have been published since 2000 owing to both advances in oxygen sensors and the growing emphasis on understanding physiological effects of environmental change. Common protocols are needed to facilitate cross-taxa comparisons such as the effect of temperature (Q10 : 1·47-3·47), body mass (slope of allometric changes in O2 consumption rate from 0·5 to 1·3) and activity level on metabolic costs as measured via respiration rate. A set of recommendations is provided that will make it easier for researchers to design measurement systems, to judge the reliability of measurements and to make inter-comparisons among studies and species. © 2016 The Fisheries Society of the British Isles.

  14. Measuring methylphenidate response in attention-deficit/hyperactvity disorder: how are laboratory classroom-based measures related to parent ratings?

    PubMed

    Sonuga-Barke, Edmund J S; Coghill, David; DeBacker, Marc; Swanson, James

    2009-12-01

    Methylphenidate (MPH) is an efficacious and normally well-tolerated treatment for attention-deficit/hyperactivity disorder (ADHD). Although treatment effects are usually assessed using parent-rating scales, these can be supplemented by more objective methods. Here we examine the associations between ratings and one such method, assessments made across the day in the laboratory classroom. Comparison of Methylphenidates in the Analog Classroom Setting (COMACS) was made in a large (n = 184) placebo-controlled trial comparing Equasym XL/Metadate CD, Concerta, and placebo (PLA) using a Laboratory School protocol. Therapeutic effects were measured using direct observation, scores on a simple math productivity task and parent ratings. Treatment effects were observed on all measures. Laboratory measures were correlated with each other, most strongly between Swanson, Kotkin, Agler, M-Flynn and Pelham Scale (SKAMP) inattention and Permanent Product Measure of Performance (PERMP). Parental ratings were correlated with classroom measures during the main morning period (1.5-4.5 hours after dosing) and to a lesser extent in the afternoon (6.0-7.5 hours after dosing), but not, by and large, immediately after dosing or in the evening. The morning correlations seemed stronger for female than for male participants. The results suggest that parental ratings and direct observations tap different aspects of MPH response and that both may be required for comprehensive assessment.

  15. The Rim Inertial Measuring System (RIMS). [to measure angular rate and linear acceleration of a moving vehicle

    NASA Technical Reports Server (NTRS)

    Groom, N. J.

    1979-01-01

    The rim inertial measuring system (RIMS) is introduced and an approach for extracting angular rate and linear acceleration information from a RIMS unit is presented and discussed. The RIMS consists of one or more small annular momentum control devices (AMCDs), mounted in a strapped down configuration, which are used to measure angular rates and linear accelerations of a moving vehicle. An AMCD consists of a spinning rim, a set of noncontacting magnetic bearings for supporting the rim, and a noncontacting electromagnetic spin motor. The approach for extracting angular rate and linear acceleration information is for a single spacecraft mounted RIMS unit.

  16. 26 CFR 1.263A-11 - Accumulated production expenditures.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... extent they would otherwise be taken into account under the taxpayer's method of accounting (e.g., after.... For purposes of determining accumulated production expenditures on any measurement date during a... capitalized on the day immediately following the end of the computation period. For any subsequent measurement...

  17. A quantum inspired model of radar range and range-rate measurements with applications to weak value measurements

    NASA Astrophysics Data System (ADS)

    Escalante, George

    2017-05-01

    Weak Value Measurements (WVMs) with pre- and post-selected quantum mechanical ensembles were proposed by Aharonov, Albert, and Vaidman in 1988 and have found numerous applications in both theoretical and applied physics. In the field of precision metrology, WVM techniques have been demonstrated and proven valuable as a means to shift, amplify, and detect signals and to make precise measurements of small effects in both quantum and classical systems, including: particle spin, the Spin-Hall effect of light, optical beam deflections, frequency shifts, field gradients, and many others. In principal, WVM amplification techniques are also possible in radar and could be a valuable tool for precision measurements. However, relatively limited research has been done in this area. This article presents a quantum-inspired model of radar range and range-rate measurements of arbitrary strength, including standard and pre- and post-selected measurements. The model is used to extend WVM amplification theory to radar, with the receive filter performing the post-selection role. It is shown that the description of range and range-rate measurements based on the quantum-mechanical measurement model and formalism produces the same results as the conventional approach used in radar based on signal processing and filtering of the reflected signal at the radar receiver. Numerical simulation results using simple point scatterrer configurations are presented, applying the quantum-inspired model of radar range and range-rate measurements that occur in the weak measurement regime. Potential applications and benefits of the quantum inspired approach to radar measurements are presented, including improved range and Doppler measurement resolution.

  18. Normative evidence accumulation in unpredictable environments

    PubMed Central

    Glaze, Christopher M; Kable, Joseph W; Gold, Joshua I

    2015-01-01

    In our dynamic world, decisions about noisy stimuli can require temporal accumulation of evidence to identify steady signals, differentiation to detect unpredictable changes in those signals, or both. Normative models can account for learning in these environments but have not yet been applied to faster decision processes. We present a novel, normative formulation of adaptive learning models that forms decisions by acting as a leaky accumulator with non-absorbing bounds. These dynamics, derived for both discrete and continuous cases, depend on the expected rate of change of the statistics of the evidence and balance signal identification and change detection. We found that, for two different tasks, human subjects learned these expectations, albeit imperfectly, then used them to make decisions in accordance with the normative model. The results represent a unified, empirically supported account of decision-making in unpredictable environments that provides new insights into the expectation-driven dynamics of the underlying neural signals. DOI: http://dx.doi.org/10.7554/eLife.08825.001 PMID:26322383

  19. RaD-X: Complementary measurements of dose rates at aviation altitudes

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M.; Matthiä, Daniel; Forkert, Tomas; Wirtz, Michael; Scheibinger, Markus; Hübel, Robert; Mertens, Christopher J.

    2016-09-01

    The RaD-X stratospheric balloon flight organized by the National Aeronautics and Space Administration was launched from Fort Sumner on 25 September 2015 and carried several instruments to measure the radiation field in the upper atmosphere at the average vertical cutoff rigidity Rc of 4.1 GV. The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt) in cooperation with Lufthansa German Airlines supported this campaign with an independent measuring flight at the altitudes of civil aviation on a round trip from Germany to Japan. The goal was to measure dose rates under similar space weather conditions over an area on the Northern Hemisphere opposite to the RaD-X flight. Dose rates were measured in the target areas, i.e., around vertical cutoff rigidity Rc of 4.1 GV, at two flight altitudes for about 1 h at each position with acceptable counting statistics. The analysis of the space weather situation during the flights shows that measuring data were acquired under stable and moderate space weather conditions with a virtually undisturbed magnetosphere. The measured rates of absorbed dose in silicon and ambient dose equivalent complement the data recorded during the balloon flight. The combined measurements provide a set of experimental data suitable for validating and improving numerical models for the calculation of radiation exposure at aviation altitudes.

  20. Ultra-High Rate Measurements of Spent Fuel Gamma-Ray Emissions

    NASA Astrophysics Data System (ADS)

    Rodriguez, Douglas; Vandevender, Brent; Wood, Lynn; Glasgow, Brian; Taubman, Matthew; Wright, Michael; Dion, Michael; Pitts, Karl; Runkle, Robert; Campbell, Luke; Fast, James

    2014-03-01

    Presently there are over 200,000 irradiated spent nuclear fuel (SNF) assemblies in the world, each containing a concerning amount of weapons-usable material. Both facility operators and safeguards inspectors want to improve composition determination. Current measurements are expensive and difficult so new methods are developed through models. Passive measurements are limited since a few specific decay products and the associated down-scatter overwhelm the gamma rays of interest. Active interrogation methods produce gamma rays beyond 3 MeV, minimizing the impact of the passive emissions that drop off sharply above this energy. New devices like the Ultra-High Rate Germanium (UHRGe) detector are being developed to advance these novel measurement methods. Designed for reasonable resolution at 106 s-1 output rates (compared to ~ 1 - 10 e 3 s-1 standards), SNF samples were directly measured using UHRGe and compared to models. Model verification further enables using Los Alamos National Laboratory SNF assembly models, developed under the Next Generation Safeguards Initiative, to determine emission and signal expectations. Measurement results and future application requirements for UHRGe will be discussed.

  1. Modeling physical and biogeochemical controls over carbon accumulation in a boreal forest soil

    USGS Publications Warehouse

    Carrasco, J.J.; Neff, J.C.; Harden, J.W.

    2006-01-01

    Boreal soils are important to the global C cycle owing to large C stocks, repeated disturbance from fire, and the potential for permafrost thaw to expose previously stable, buried C. To evaluate the primary mechanisms responsible for both short- and long-term C accumulation in boreal soils, we developed a multi-isotope (12,14C) Soil C model with dynamic soil layers that develop through time as soil organic matter burns and reaccumulates. We then evaluated the mechanisms that control organic matter turnover in boreal regions including carbon input rates, substrate recalcitrance, soil moisture and temperature, and the presence of historical permafrost to assess the importance of these factors in boreal C accumulation. Results indicate that total C accumulation is controlled by the rate of carbon input, decomposition rates, and the presence of historical permafrost. However, unlike more temperate ecosystems, one of the key mechanisms involved in C preservation in boreal soils examined here is the cooling of subsurface soil layers as soil depth increases rather than increasing recalcitrance in subsurface soils. The propagation of the 14C bomb spike into soils also illustrates the importance of historical permafrost and twentieth century warming in contemporary boreal soil respiration fluxes. Both 14C and total C simulation data also strongly suggest that boreal SOM need not be recalcitrant to accumulate; the strong role of soil temperature controls on boreal C accumulation at our modeling test site in Manitoba, Canada, indicates that carbon in the deep organic soil horizons is probably relatively labile and thus subject to perturbations that result from changing climatic conditions in the future. Copyright 2006 by the American Geophysical Union.

  2. Grazing suppression of dimethylsulphoniopropionate (DMSP) accumulation in iron-fertilised, sub-Antarctic waters

    NASA Astrophysics Data System (ADS)

    Archer, S. D.; Safi, K.; Hall, A.; Cummings, D. G.; Harvey, M.

    2011-03-01

    The impact of in situ iron fertilisation on the production of particulate dimethylsulphoniopropionate (DMSPp) and its breakdown product dimethyl sulphide (DMS) was monitored during the SOLAS air-sea gas exchange experiment (SAGE). The experiment was conducted in the high nitrate, low chlorophyll (HNLC) waters of the sub-Antarctic Southern Ocean (46.7°S 172.5°E) to the south-east of New Zealand, during March-April, 2004. In addition to monitoring net changes in the standing stocks of DMSPp and DMS, a series of dilution experiments were used to determine the DMSPp production and consumption rates in relation to increased iron availability. In contrast to previous experiments in the Southern Ocean, DMS concentrations decreased over the course of the 15-d iron-fertilisation experiment, from an integrated volume-specific concentration in the mixed layer on day 0 of 0.78 nM (measured values 0.65-0.91 nM) to 0.46 nM (measured values 0.42-0.47 nM) by day 15, in parallel with the surrounding waters. DMSPp, chlorophyll a and the abundance of photosynthetic picoeukaryotes exhibited indiscernible or only moderate increases in response to the raised iron availability, despite an obvious physiological response by the phytoplankton. High specific growth rates of DMSPp, equivalent to 0.8-1.2 doublings d -1, occurred at the simulated 60% light level of the dilution experiments. Despite the high production rates, DMSPp accumulation was suppressed in part by microzooplankton grazers who consumed between 61% d -1 and 126% d -1 of the DMSPp production. Temporal trends in the rates of production and consumption illustrated a close coupling between the DMSP-producing phytoplankton and their microzooplankton grazers. Similar grazing and production rates were observed for the eukaryotic picophytoplankton that dominated the phytoplankton biomass, partial evidence that picoeukaryotes contributed a substantial proportion of the DMSP synthesis. These rates for DMSPp and picoeukaryotes were

  3. Fecal coliform accumulation within a river subject to seasonally-disinfected wastewater discharges.

    PubMed

    Mitch, Azalea A; Gasner, Katherine C; Mitch, William A

    2010-09-01

    As pathogen contamination is a leading cause of surface water impairment, there has been increasing interest in the implications of seasonal disinfection practices of wastewater effluents for meeting water quality goals. For receiving waters designated for recreational use, disinfection during the winter months is often considered unnecessary due to reduced recreational usage, and assumptions that lower temperatures may reduce pathogen accumulation. For a river subject to seasonal disinfection, we sought to evaluate whether fecal coliforms accumulate during the winter to concentrations that would impair river water quality. Samples were collected from municipal wastewater outfalls along the river, as well as upstream and downstream of each outfall during the winter, when disinfection is not practiced, and during the summer, when disinfection is practiced. During both seasons, fecal coliform concentrations reached 2000-5000 CFU/100 mL, nearly an order of magnitude higher than levels targeted for the river to achieve primary contact recreational uses. During the summer, wastewater effluents were not significant contributors to fecal coliform loadings to the river. During the winter, fecal coliform accumulated along the river predominantly due to loadings from successive wastewater outfalls. In addition to the exceedance of fecal coliform criteria within the river, the accumulation of wastewater-derived fecal coliform along the river during the winter season suggests that wastewater outfalls may contribute elevated loads of pathogens to the commercial shellfish operations occurring at the mouth of the river. Reductions in fecal coliform concentrations between wastewater outfalls were attributed to dilution or overall removal. Combining discharge measurements from gauging stations, tributaries and wastewater outfalls to estimate seepage, dilution between wastewater outfalls was estimated, along with the percentage of the river deriving from wastewater outfalls. After

  4. One-day rate measurements for estimating net nitrification potential in humid forest soils

    USGS Publications Warehouse

    Ross, D.S.; Fredriksen, G.; Jamison, A.E.; Wemple, B.C.; Bailey, S.W.; Shanley, J.B.; Lawrence, G.B.

    2006-01-01

    Measurements of net nitrification rates in forest soils have usually been performed by extended sample incubation (2-8 weeks), either in the field or in the lab. Because of disturbance effects, these measurements are only estimates of nitrification potential and shorter incubations may suffice. In three separate studies of northeastern USA forest soil surface horizons, we found that laboratory nitrification rates measured over 1 day related well to those measured over 4 weeks. Soil samples of Oa or A horizons were mixed by hand and the initial extraction of subsamples, using 2 mol L-1 KCl, occurred in the field as soon as feasible after sampling. Soils were kept near field temperature and subsampled again the following day in the laboratory. Rates measured by this method were about three times higher than the 4-week rates. Variability in measured rates was similar over either incubation period. Because NO3- concentrations were usually quite low in the field, average rates from 10 research watersheds could be estimated with only a single, 1-day extraction. Methodological studies showed that the concentration of NH4+ increased slowly during contact time with the KCl extractant and, thus, this contact time should be kept similar during the procedure. This method allows a large number of samples to be rapidly assessed. ?? 2006 Elsevier B.V. All rights reserved.

  5. Acoustic measurement of the Deepwater Horizon Macondo well flow rate

    PubMed Central

    Camilli, Richard; Di Iorio, Daniela; Bowen, Andrew; Reddy, Christopher M.; Techet, Alexandra H.; Yoerger, Dana R.; Whitcomb, Louis L.; Seewald, Jeffrey S.; Sylva, Sean P.; Fenwick, Judith

    2012-01-01

    On May 31, 2010, a direct acoustic measurement method was used to quantify fluid leakage rate from the Deepwater Horizon Macondo well prior to removal of its broken riser. This method utilized an acoustic imaging sonar and acoustic Doppler sonar operating onboard a remotely operated vehicle for noncontact measurement of flow cross-section and velocity from the well’s two leak sites. Over 2,500 sonar cross-sections and over 85,000 Doppler velocity measurements were recorded during the acquisition process. These data were then applied to turbulent jet and plume flow models to account for entrained water and calculate a combined hydrocarbon flow rate from the two leak sites at seafloor conditions. Based on the chemical composition of end-member samples collected from within the well, this bulk volumetric rate was then normalized to account for contributions from gases and condensates at initial leak source conditions. Results from this investigation indicate that on May 31, 2010, the well’s oil flow rate was approximately 0.10 ± 0.017 m3 s-1 at seafloor conditions, or approximately 85 ± 15 kg s-1 (7.4 ± 1.3 Gg d-1), equivalent to approximately 57,000 ± 9,800 barrels of oil per day at surface conditions. End-member chemical composition indicates that this oil release rate was accompanied by approximately an additional 24 ± 4.2 kg s-1 (2.1 ± 0.37 Gg d-1) of natural gas (methane through pentanes), yielding a total hydrocarbon release rate of 110 ± 19 kg s-1 (9.5 ± 1.6 Gg d-1). PMID:21903931

  6. Late Quaternary carbonate accumulation along eastern South Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Crabill, K.; Slowey, N. C.; Foreman, A. D.; Charles, C.

    2016-12-01

    Water masses originating from both the North Atlantic Ocean and the Southern Ocean intersect the Walvis Ridge and Namibian margin of southwest Africa. Changes in the distribution and properties of these water masses through time are reflected by variations in the nature of the sediments accumulating along this margin. A suite of piston and gravity cores that possess sediment records corresponding to the most recent glacial-interglacial cycles were collected from the water depth range of 550 to 3700 meters. Sediment dry bulk density, XRF analyses and the concentration of CaCO3 were precisely determined at regular depth intervals in these cores. Foraminiferal δ18O along with XRF Fe/Ca data provide an age-depth model for key cores. The age-depth model and dry bulk density will be used with the calcium carbonate contents to calculate the accumulation rates of CaCO3 during each MIS 1-5e. The spatial and temporal variability in both the CaCO3 content and the CaCO3 mass accumulation rates along the Namibian continental slope will be described. Based on comparisons of these two parameters, inferences will be made about how variations of CaCO3 production, dilution of by non-CaCO3 sediment components, and dissolution of CaCO3 due to changes in ocean circulation/climate have occurred during intervals of the last glacial-interglacial cycle.

  7. A straw chambers' tracker for the high rate experiment 835 at the Fermilab accumulator

    NASA Astrophysics Data System (ADS)

    Bagnasco, S.; Dughera, G.; Giraudo, G.; Govi, G.; Marchetto, F.; Menichetti, E.; Pastrone, N.; Rumerio, P.; Trapani, P. P.

    1998-02-01

    Two layers of proportional drift tubes (aluminum mylar straws) are staggered in two cylindrical light chambers to measure charged particles' azimuthal angle. To stand the high rates (˜10 kHz/ cm2) and minimize the pile-up of the high luminosity experiment 835 at FNAL, a fast ASIC Amplifier-Shaper-Discriminator (ASD-8B) was chosen. The front-end electronics, designed exclusively with SMD components, was mounted on the downstream end plug of each chamber to avoid oscillations and noise. Design, construction and operational performances of these detectors are presented.

  8. WTP Waste Feed Qualification: Hydrogen Generation Rate Measurement Apparatus Testing Report

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

    Stone, M. E.; Newell, J. D.; Smith, T. E.

    The generation rate of hydrogen gas in the Hanford tank waste will be measured during the qualification of the staged tank waste for processing in the Hanford Tank Waste Treatment and Immobilization Plant. Based on a review of past practices in measurement of the hydrogen generation, an apparatus to perform this measurement has been designed and tested for use during waste feed qualification. The hydrogen generation rate measurement apparatus (HGRMA) described in this document utilized a 100 milliliter sample in a continuously-purged, continuously-stirred vessel, with measurement of hydrogen concentration in the vent gas. The vessel and lid had a combinedmore » 220 milliliters of headspace. The vent gas system included a small condenser to prevent excessive evaporative losses from the sample during the test, as well as a demister and filter to prevent particle migration from the sample to the gas chromatography system. The gas chromatograph was an on line automated instrument with a large-volume sample-injection system to allow measurement of very low hydrogen concentrations. This instrument automatically sampled the vent gas from the hydrogen generation rate measurement apparatus every five minutes and performed data regression in real time. The fabrication of the hydrogen generation rate measurement apparatus was in accordance with twenty three (23) design requirements documented in the conceptual design package, as well as seven (7) required developmental activities documented in the task plan associated with this work scope. The HGRMA was initially tested for proof of concept with physical simulants, and a remote demonstration of the system was performed in the Savannah River National Laboratory Shielded Cells Mockup Facility. Final verification testing was performed using non-radioactive simulants of the Hanford tank waste. Three different simulants were tested to bound the expected rheological properties expected during waste feed qualification testing

  9. Characterization of distinct Arctic aerosol accumulation modes and their sources

    NASA Astrophysics Data System (ADS)

    Lange, R.; Dall'Osto, M.; Skov, H.; Nøjgaard, J. K.; Nielsen, I. E.; Beddows, D. C. S.; Simo, R.; Harrison, R. M.; Massling, A.

    2018-06-01

    In this work we use cluster analysis of long term particle size distribution data to expand an array of different shorter term atmospheric measurements, thereby gaining insights into longer term patterns and properties of Arctic aerosol. Measurements of aerosol number size distributions (9-915 nm) were conducted at Villum Research Station (VRS), Station Nord in North Greenland during a 5 year record (2012-2016). Alongside this, measurements of aerosol composition, meteorological parameters, gaseous compounds and cloud condensation nuclei (CCN) activity were performed during different shorter occasions. K-means clustering analysis of particle number size distributions on daily basis identified several clusters. Clusters of accumulation mode aerosols (main size modes > 100 nm) accounted for 56% of the total aerosol during the sampling period (89-91% during February-April, 1-3% during June-August). By association to chemical composition, cloud condensation nuclei properties, and meteorological variables, three typical accumulation mode aerosol clusters were identified: Haze (32% of the time), Bimodal (14%) and Aged (6%). In brief: (1) Haze accumulation mode aerosol shows a single mode at 150 nm, peaking in February-April, with highest loadings of sulfate and black carbon concentrations. (2) Accumulation mode Bimodal aerosol shows two modes, at 38 nm and 150 nm, peaking in June-August, with the highest ratio of organics to sulfate concentrations. (3) Aged accumulation mode aerosol shows a single mode at 213 nm, peaking in September-October and is associated with cloudy and humid weather conditions during autumn. The three aerosol clusters were considered alongside CCN concentrations. We suggest that organic compounds, that are likely marine biogenic in nature, greatly influence the Bimodal cluster and contribute significantly to its CCN activity. This stresses the importance of better characterizing the marine ecosystem and the aerosol-mediated climate effects in the

  10. Accumulation and phytotoxicity of technical hexabromocyclododecane in maize.

    PubMed

    Wu, Tong; Huang, Honglin; Zhang, Shuzhen

    2016-04-01

    To investigate the accumulation and phytotoxicity of technical hexabromocyclododecane (HBCD) in maize, young seedlings were exposed to solutions of technical HBCD at different concentrations. The uptake kinetics showed that the HBCD concentration reached an apparent equilibrium within 96hr, and the accumulation was much higher in roots than in shoots. HBCD accumulation in maize had a positive linear correlation with the exposure concentration. The accumulation of different diastereoisomers followed the order γ-HBCD>β-HBCD>α-HBCD. Compared with their proportions in the technical HBCD exposure solution, the diastereoisomer contribution increased for β-HBCD and decreased for γ-HBCD in both maize roots and shoots with exposure time, whereas the contribution of α-HBCD increased in roots and decreased in shoots throughout the experimental period. These results suggest the diastereomer-specific accumulation and translocation of HBCD in maize. Inhibitory effects of HBCD on the early development of maize followed the order of germination rate>root biomass≥root elongation>shoot biomass≥shoot elongation. Hydroxyl radical (OH) and histone H2AX phosphorylation (γ-H2AX) were induced in maize by HBCD exposure, indicative of the generation of oxidative stress and DNA double-strand breaks in maize. An OH scavenger inhibited the expression of γ-H2AX foci in both maize roots and shoots, which suggests the involvement of OH generation in the HBCD-induced DNA damage. The results of this study will offer useful information for a more comprehensive assessment of the environmental behavior and toxicity of technical HBCD. Copyright © 2015. Published by Elsevier B.V.

  11. High mutation rates limit evolutionary adaptation in Escherichia coli

    PubMed Central

    Wagner, Andreas

    2018-01-01

    Mutation is fundamental to evolution, because it generates the genetic variation on which selection can act. In nature, genetic changes often increase the mutation rate in systems that range from viruses and bacteria to human tumors. Such an increase promotes the accumulation of frequent deleterious or neutral alleles, but it can also increase the chances that a population acquires rare beneficial alleles. Here, we study how up to 100-fold increases in Escherichia coli’s genomic mutation rate affect adaptive evolution. To do so, we evolved multiple replicate populations of asexual E. coli strains engineered to have four different mutation rates for 3000 generations in the laboratory. We measured the ability of evolved populations to grow in their original environment and in more than 90 novel chemical environments. In addition, we subjected the populations to whole genome population sequencing. Although populations with higher mutation rates accumulated greater genetic diversity, this diversity conveyed benefits only for modestly increased mutation rates, where populations adapted faster and also thrived better than their ancestors in some novel environments. In contrast, some populations at the highest mutation rates showed reduced adaptation during evolution, and failed to thrive in all of the 90 alternative environments. In addition, they experienced a dramatic decrease in mutation rate. Our work demonstrates that the mutation rate changes the global balance between deleterious and beneficial mutational effects on fitness. In contrast to most theoretical models, our experiments suggest that this tipping point already occurs at the modest mutation rates that are found in the wild. PMID:29702649

  12. Forest canopy effects on snow accumulation and ablation: an integrative review of empirical results

    Treesearch

    Andres Varhola; Nicholas C. Coops; Markus Weiler; R. Dan Moore

    2010-01-01

    The past century has seen significant research comparing snow accumulation and ablation in forested and open sites. In this review we compile and standardize the results of previous empirical studies to generate statistical relations between changes in forest cover and the associated changes in snow accumulation and ablation rate. The analysis drew upon 33 articles...

  13. Fermentation, degradation and microbial nitrogen partitioning for three forage colour phenotypes within anthocyanidin-accumulating Lc-alfalfa progeny.

    PubMed

    Jonker, Arjan; Gruber, Margaret Y; Wang, Yuxi; Narvaez, Nelmy; Coulman, Bruce; McKinnon, John J; Christensen, David A; Azarfar, Arash; Yu, Peiqiang

    2012-08-30

    Alfalfa has the disadvantage of having a rapid initial rate of protein degradation, which results in pasture bloat, low efficiency of protein utilisation and excessive nitrogen (N) pollution into the environment for cattle. Introducing a gene that stimulates the accumulation of monomeric/polymeric anthocyanidins might reduce the ruminal protein degradation rate (by fixing protein and/or direct interaction with microbes) and additionally reduce methane emission. The objectives of this study were to evaluate in vitro fermentation, degradation and microbial N partitioning of three forage colour phenotypes (green, light purple-green (LPG) and purple-green (PG)) within newly developed Lc-progeny and to compare them with those of parental green non-transgenic (NT) alfalfa. PG-Lc accumulated more anthocyanidin compared with Green-Lc (P < 0.05), with LPG-Lc intermediate. Volatile fatty acids and potentially degradable dry matter (DM) and N were similar among the four phenotypes. Gas, methane and ammonia accumulation rates were slower for the two purple-Lc phenotypes compared with NT-alfalfa (P < 0.05), while Green-Lc was intermediate. Effective degradable DM and N were lower in the three Lc-phenotypes (P < 0.05) compared with NT-alfalfa. Anthocyanidin concentration was negatively correlated (P < 0.05) with gas and methane production rates and effective degradability of DM and N. The Lc-alfalfa phenotypes accumulated anthocyanidin. Fermentation and degradation parameters indicated a reduced rate of fermentation and effective degradability for both purple anthocyanidin-accumulating Lc-alfalfa phenotypes compared with NT-alfalfa. Copyright © 2012 Society of Chemical Industry.

  14. Measurement of Fluorine Atom Concentrations and Reaction Rates in Chemical Laser Systems.

    DTIC Science & Technology

    1981-09-01

    AD-A1RA 070 AERODYNEERESEARCHUINC BEDFORDM MA F/6_20/5 MEASURE MENT OF FLUORINE ATOM CONCENTRATIONS AND REACTION RATFS -ETC(U) SEP_ A A C STANT ON...0772 LEVELIg 00 ~ARI-RR-272 cO0 MEASUREMENT OF FLUORINE ATOM CONCENTRATIONS AND REACTION RATES IN CHEMICAL LASER SYSTEMS ANNUAL TECHNICAL REPORT by...MEASUREMENT OF FLUORINE ATOM CONCENTRATIONS AND Annual Report REACTION RATES IN CHEMICAL LASER SYSTEMS 23 July 1980 - 23 July 1981 S. PERFORMING ORG. REPORT

  15. Method and apparatus for measuring the mass flow rate of a fluid

    DOEpatents

    Evans, Robert P.; Wilkins, S. Curtis; Goodrich, Lorenzo D.; Blotter, Jonathan D.

    2002-01-01

    A non invasive method and apparatus is provided to measure the mass flow rate of a multi-phase fluid. An accelerometer is attached to a pipe carrying a multi-phase fluid. Flow related measurements in pipes are sensitive to random velocity fluctuations whose magnitude is proportional to the mean mass flow rate. An analysis of the signal produced by the accelerometer shows a relationship between the mass flow of a fluid and the noise component of the signal of an accelerometer. The noise signal, as defined by the standard deviation of the accelerometer signal allows the method and apparatus of the present invention to non-intrusively measure the mass flow rate of a multi-phase fluid.

  16. Fast repetition rate (FRR) fluorometer and method for measuring fluorescence and photosynthetic parameters

    DOEpatents

    Kolber, Zbigniew; Falkowski, Paul

    1995-06-20

    A fast repetition rate fluorometer device and method for measuring in vivo fluorescence of phytoplankton or higher plants chlorophyll and photosynthetic parameters of phytoplankton or higher plants by illuminating the phytoplankton or higher plants with a series of fast repetition rate excitation flashes effective to bring about and measure resultant changes in fluorescence yield of their Photosystem II. The series of fast repetition rate excitation flashes has a predetermined energy per flash and a rate greater than 10,000 Hz. Also, disclosed is a flasher circuit for producing the series of fast repetition rate flashes.

  17. Evolution of Tethyan phosphogenesis along the northern edges of the Arabian--African shield during the Cretaceous--Eocene as deduced from temporal variations of Ca and Nd isotopes and rates of P accumulation

    NASA Astrophysics Data System (ADS)

    Soudry, D.; Glenn, C. R.; Nathan, Y.; Segal, I.; VonderHaar, D.

    2006-09-01

    The evolution of Tethyan phosphogenesis during the Cretaceous-Eocene is examined to try to explain fluctuations of phosphogenesis through time, and whether or not they reflect long-term changes in ocean circulation or in continental weathering. Twenty-seven time-stratigraphic phosphate levels in various Tethyan sites, covering a time span of about 90 Myr from the Hauterivian to the Eocene, were analyzed for 44Ca/ 42Ca and 143Nd/ 144Nd in their carbonate fluorapatite (CFA) fraction. P and Ca accumulation rates and bulk sedimentation rates were quantified throughout the Cretaceous-Eocene Negev sequence to examine how changes in 44Ca/ 42Ca and 143Nd/ 144Nd are reflected in the intensity of phosphogenesis. A clear-cut change occurs in ɛNd( T) and δ44Ca and in the rates of P and Ca accumulation and bulk sedimentation through the time analyzed. ɛNd( T) is much lower in the Hauterivian-Lower Cenomanian (- 12.8 to - 10.9) than in the Upper Cenomanian-Eocene (- 7.8 to - 5.9). Much lower δ44Ca values occur in the Hauterivian-Turonian (- 0.22 to + 0.02) than in the Coniacian-Eocene (+ 0.23 to + 0.40). P accumulation rates in the Negev steeply increase from < 200 μmol cm - 2 k yr - 1 in the Albian-Coniacian to ˜ 1500 μmol cm - 2 k yr - 1 in the Campanian, whereas a strong decrease is concomitantly recorded in the rates of Ca accumulation and bulk sedimentation. In addition, distinct ɛNd( T) values are shown by the phosphorites of the Negev (- 6.7 to - 6.4) and Egypt (- 9.1 to - 7.6) during the Campanian, and by those of the Negev (- 7.8 to - 6.3) and North Africa (- 10.1 to - 8.9) during the Maastrichtian-Eocene. The culmination of P accumulation rates in the Negev during the Campanian, occurring with a high in ɛNd( T) and δ44Ca and a low in sedimentation rates, indicates that paleoceanographic and paleogeographical factors mostly governed phosphorite accumulation in this area. The abrupt ɛNd( T) rise after the Cenomanian is attributed to increased incursion of

  18. Errors of car wheels rotation rate measurement using roller follower on test benches

    NASA Astrophysics Data System (ADS)

    Potapov, A. S.; Svirbutovich, O. A.; Krivtsov, S. N.

    2018-03-01

    The article deals with rotation rate measurement errors, which depend on the motor vehicle rate, on the roller, test benches. Monitoring of the vehicle performance under operating conditions is performed on roller test benches. Roller test benches are not flawless. They have some drawbacks affecting the accuracy of vehicle performance monitoring. Increase in basic velocity of the vehicle requires increase in accuracy of wheel rotation rate monitoring. It determines the degree of accuracy of mode identification for a wheel of the tested vehicle. To ensure measurement accuracy for rotation velocity of rollers is not an issue. The problem arises when measuring rotation velocity of a car wheel. The higher the rotation velocity of the wheel is, the lower the accuracy of measurement is. At present, wheel rotation frequency monitoring on roller test benches is carried out by following-up systems. Their sensors are rollers following wheel rotation. The rollers of the system are not kinematically linked to supporting rollers of the test bench. The roller follower is forced against the wheels of the tested vehicle by means of a spring-lever mechanism. Experience of the test bench equipment operation has shown that measurement accuracy is satisfactory at small rates of vehicles diagnosed on roller test benches. With a rising diagnostics rate, rotation velocity measurement errors occur in both braking and pulling modes because a roller spins about a tire tread. The paper shows oscillograms of changes in wheel rotation velocity and rotation velocity measurement system’s signals when testing a vehicle on roller test benches at specified rates.

  19. Impact of Pitot tube calibration on the uncertainty of water flow rate measurement

    NASA Astrophysics Data System (ADS)

    de Oliveira Buscarini, Icaro; Costa Barsaglini, Andre; Saiz Jabardo, Paulo Jose; Massami Taira, Nilson; Nader, Gilder

    2015-10-01

    Water utility companies often use Cole type Pitot tubes to map velocity profiles and thus measure flow rate. Frequent monitoring and measurement of flow rate is an important step in identifying leaks and other types of losses. In Brazil losses as high as 42% are common and in some places even higher values are found. When using Cole type Pitot tubes to measure the flow rate, the uncertainty of the calibration coefficient (Cd) is a major component of the overall flow rate measurement uncertainty. A common practice is to employ the usual value Cd = 0.869, in use since Cole proposed his Pitot tube in 1896. Analysis of 414 calibrations of Cole type Pitot tubes show that Cd varies considerably and values as high 0.020 for the expanded uncertainty are common. Combined with other uncertainty sources, the overall velocity measurement uncertainty is 0.02, increasing flowrate measurement uncertainty by 1.5% which, for the Sao Paulo metropolitan area (Brazil) corresponds to 3.5 × 107 m3/year.

  20. Evaluating standard airborne sound insulation measures in terms of annoyance, loudness, and audibility ratings.

    PubMed

    Park, H K; Bradley, J S

    2009-07-01

    This paper reports the results of an evaluation of the merits of standard airborne sound insulation measures with respect to subjective ratings of the annoyance and loudness of transmitted sounds. Subjects listened to speech and music sounds modified to represent transmission through 20 different walls with sound transmission class (STC) ratings from 34 to 58. A number of variations in the standard measures were also considered. These included variations in the 8-dB rule for the maximum allowed deficiency in the STC measure as well as variations in the standard 32-dB total allowed deficiency. Several spectrum adaptation terms were considered in combination with weighted sound reduction index (R(w)) values as well as modifications to the range of included frequencies in the standard rating contour. A STC measure without an 8-dB rule and an R(w) rating with a new spectrum adaptation term were better predictors of annoyance and loudness ratings of speech sounds. R(w) ratings with one of two modified C(tr) spectrum adaptation terms were better predictors of annoyance and loudness ratings of transmitted music sounds. Although some measures were much better predictors of responses to one type of sound than were the standard STC and R(w) values, no measure was remarkably improved for predicting annoyance and loudness ratings of both music and speech sounds.

  1. Measurement of filtration rates by infaunal bivalves in a recirculating flume

    USGS Publications Warehouse

    Cole, B.E.; Thompson, J.K.; Cloern, J.E.

    1992-01-01

    A flume system and protocol for measuring the filtration rate of infaunal bivalves is described. Assemblages of multi-sized clams, at natural densities and in normal filter-feeding positions, removed phytoplankton suspended in a unidirectional flow of water. The free-stream velocity and friction velocity of the flow, and bottom roughness height were similar to those in natural estuarine waters. Continuous variations in phytoplankton (Chroomonas salinay) cell density were used to measure the filtration rate of the suspension-feeding clam Potamocorbula amurensis for periods of 2 to 28 h. Filtration rates of P. amurensis varied from 100 to 580 liters (gd)-1 over a free-stream velocity range of 9 to 25 cm s-1. Phytoplankton loss rates were usually constant throughout the experiments. Our results suggest that suspension-feeding by infaunal bivalves is sensitive to flow velocity. ?? 1992 Springer-Verlag.

  2. [Effects of nitrogen application rate on light interception and dry matter distribution at diffe-rent layers in wheat canopy under supplemental irrigation based on measuring soil moisture.

    PubMed

    Zheng, Xue Jiao; Yu, Zhen Wen; Zhang, Yong Li; Shi, Yu

    2018-02-01

    With the large-spike wheat cultivar Shannong 23 as test material,a field experiment was conducted by increasing the relative soil moisture content to 70% and 65% at jointing and anthesis stages. Four nitrogen levels,0 (N 0 ), 180 (N 1 ), 240 (N 2 ) and 300 kg·hm -2 (N 3 ), were designed to examine the effects of nitrogen application rates on the interception of photosynthetic active radiation (PAR) and dry matter distribution of wheat at different canopy layers. The results showed that the total stem number of wheat population at anthesis stage, the leaf area index at 10, 20 and 30 days after anthesis, PAR capture ratio at upper and middle layers and total PAR capture ratio in wheat canopy on day 20 after anthesis of treatment N 2 were significantly higher than those in the treatments of both N 0 and N 1 . Those indexes showed no significant increase when the application rate increased to 300 kg·hm -2 (N 3 ). The vegetative organ dry matter accumulation of all layers at maturity stage of treatment N 2 were significantly higher than N 0 and N 1 . Compared with treatment N 0 and N 1 , N 2 increased the grain and total dry matter accumulation by 36.7% and 35.4%, 9.5% and 10.2%, respectively, but had no significant difference with treatment N 3 . The vegetative organ dry matter accumulation at all layers, grain and total dry matter accumulation were significantly and positively correlated with PAR capture ratio at upper and middle layers, and had no significant correlation with that at lower layer. The vegetative organ dry matter accumulation at all layers was significantly and positively correlated with grain dry matter accumulation. The application rate at 240 kg·hm -2 (N 2 ) would be the optimum treatment under the present experimental condition.

  3. Metabolic rate measurements comparing supine with upright upper-body exercises

    NASA Technical Reports Server (NTRS)

    Fortney, Suzanne M.; Greenisen, Michael C.; Loftin, Karin C.; Beene, Donya; Freeman-Perez, Sondra; Hnatt, Linda

    1993-01-01

    The ground-based study that tested the hypothesis that metabolic rates during supine and upright upper-body exercises are similar (mean value of 200 kcal/h) is presented. Six subjects each performed supine or upright exercise at three exercise stations, a hand-cycle ergometer, a rope-pull device, and a torque wrench. After a baseline measurement of the metabolic rate at rest, the metabolic rate was measured twice at each exercise station. The mean metabolic rates (kcal/h) during supine (n = 6) and upright control (n = 4) exercise stations were not significantly different except for the rope-pull station, 153.5 +/- 16.6 (supine) as compared to 247.0 +/- 21.7 (upright), p is less than 0.05. This difference may be due in part to an increased mechanical efficiency of supine exercises (15.0 +/- 0.7 percent) as compared to that of upright exercises (11.0 +/- 1.08 percent), p is less than 0.05. The net energy input was significantly smaller for the supine rope-pull exercise (64 +/- 18) as compared to upright (176 +/- 20). The relationship between best-rest exercises, metabolic rates, and the incidence of decompression sickness (DCS) should be examined to determine the true risk of DCS in spaceflight extravehicular activities.

  4. Modeling dynamic accumulation of gas hydrates in Shenhu area, northern South China Sea

    NASA Astrophysics Data System (ADS)

    Su, Z.; Cao, Y.; Wu, N.

    2013-12-01

    The accumulation of the hydrates in Shenhu area on northern continental slope of the South China Sea (SCS) could not be well quantified by the numerical models. The formation mechanism of the hydrate deposits remains an open question. Here, a conceptual model was applied for illustrating the formation pattern of hydrate accumulation in Shenhu area based on the studies of sedimentary and tectonic geologies. Our results indicated that the present hydrate deposits were a development of 'ancient hydrates' in the faulted sediment. The dynamic accumulation of the hydrates was further quantified by using a numerical model with two controlling parameters of seafloor sedimentation rate and water flow rate. The model results were testified with the hydrate saturations derived from the chloride abnormalities at site SH2 in Shenhu area. It suggested that the hydrate accumulation in Shenhu area had experienced two typical stages. In the first stage, the gas hydrates grew in the fractured sediment ~1.5 Ma. High permeability of the fractured sediment permitted rapid water flow that carrying methane gas toward the seafloor. Massive gas transformed to gas hydrate in the gas hydrate stability zone (GHSZ) at water flow rate of 50m/kyr within 40kyrs. The 'ancient hydrate' filled 20% volume of the sediment pores in the stage. The second stage was initiated after ending of the last faulting activity. The water flow rate dropped to 0.7m/kyr due to quick burial of fine-grained sediments. Inadequate gas supply could merely sustain hydrate growth slowly at the base of GHSZ, and ultimately yielded the current hydrate deposits in Shenhu area after a subsequent evolution of 1.5 Myrs.

  5. Patterns of nitrogen accumulation and cycling in riparian floodplain ecosystems along the Green and Yampa rivers

    USGS Publications Warehouse

    Carol E., Adair; Binkley, Dan; Andersen, Douglas C.

    2004-01-01

    Patterns of nitrogen (N) accumulation and turnover in riparian systems in semi-arid regions are poorly understood, particularly in those ecosystems that lack substantial inputs from nitrogen fixing vegetation. We investigated sources and fluxes of N in chronosequences of riparian forests along the regulated Green River and the free-flowing Yampa River in semi-arid northwestern Colorado. Both rivers lack significant inputs from N-fixing vegetation. Total soil nitrogen increased through time along both rivers, at a rate of about 7.8 g N m−2 year−1 for years 10–70, and 2.7 g N m−2year−1 from years 70–170. We found that the concentration of N in freshly deposited sediments could account for most of the soil N that accumulated in these floodplain soils. Available N (measured by ion exchange resin bags) increased with age along both rivers, more than doubling in 150 years. In contrast to the similar levels of total soil N along these rivers, N turnover rates, annual N mineralization, net nitrification rates, resin-N, and foliar N were all 2–4 times higher along the Green River than the Yampa River. N mineralization and net nitrification rates generally increased through time to steady or slightly declining rates along the Yampa River. Along the Green River, rates of mineralization and nitrification were highest in the youngest age class. The high levels of available N and N turnover in young sites are not characteristic of riparian chronosequences and could be related to changes in hydrology or plant community composition associated with the regulation of the Green River.

  6. Positive effects of duckweed polycultures on starch and protein accumulation.

    PubMed

    Li, Yang; Zhang, Fantao; Daroch, Maurycy; Tang, Jie

    2016-10-01

    The effect of duckweed species composition (Lemna aequinoctialis 5505, Landoltia punctata 5506 and Spirodela polyrhiza 5507) in polyculture and monoculture on biomass and starch/protein content were investigated at different levels of temperature, light intensity, nitrogen and phosphorus concentrations. The three growth parameters significantly affect duckweed biomass accumulation. Different combinations of duckweed species greatly varied in starch/protein content. Although all the polycultures showed a median relative growth rate and the majority of the polycultures showed a median and starch/protein content as compared with their respective monocultures, some of the polycultures were found to promote the accumulation of starch/protein at different growth conditions. These findings indicated that proper combination of duckweed species could facilitate desirable biomass accumulation and improve biomass quality. The present study provides useful references for future large-scale duckweed cultivation. © 2016 The Author(s).

  7. Positive effects of duckweed polycultures on starch and protein accumulation

    PubMed Central

    Li, Yang; Zhang, Fantao; Daroch, Maurycy; Tang, Jie

    2016-01-01

    The effect of duckweed species composition (Lemna aequinoctialis 5505, Landoltia punctata 5506 and Spirodela polyrhiza 5507) in polyculture and monoculture on biomass and starch/protein content were investigated at different levels of temperature, light intensity, nitrogen and phosphorus concentrations. The three growth parameters significantly affect duckweed biomass accumulation. Different combinations of duckweed species greatly varied in starch/protein content. Although all the polycultures showed a median relative growth rate and the majority of the polycultures showed a median and starch/protein content as compared with their respective monocultures, some of the polycultures were found to promote the accumulation of starch/protein at different growth conditions. These findings indicated that proper combination of duckweed species could facilitate desirable biomass accumulation and improve biomass quality. The present study provides useful references for future large-scale duckweed cultivation. PMID:27515418

  8. Automated measurements for individualized heart rate correction of the QT interval.

    PubMed

    Mason, Jay W; Moon, Thomas E

    2015-04-01

    Subject-specific electrocardiographic QT interval correction for heart rate is often used in clinical trials with frequent electrocardiographic recordings. However, in these studies relatively few 10-s, 12-lead electrocardiograms may be available for calculating the individual correction. Highly automated QT and RR measurement tools have made it practical to measure electrocardiographic intervals on large volumes of continuous electrocardiogram data. The purpose of this study was to determine whether an automated method can be used in lieu of a manual method. In 49 subjects who completed all treatments in a four-armed crossover study we compared two methods for derivation of individualized rate-correction coefficients: manual measurement on 10-s electrocardiograms and automated measurement of QT and RR during continuous 24-h electrocardiogram recordings. The four treatments, received by each subject in a latin-square randomization sequence were placebo, moxifloxacin, and two doses of an investigational drug. Analysis of continuous electrocardiogram data yielded a lower standard deviation of QT:RR regression values than the manual method, though the differences were not statistically significant. The within-subject and within-treatment coefficients of variation between the manual and automated methods were not significantly different. Corrected QT values from the two methods had similar rates of true and false positive identification of moxifloxacin's QT prolonging effect. An automated method for individualized rate correction applied to continuous electrocardiogram data could be advantageous in clinical trials, as the automated method is simpler, is based upon a much larger volume of data, yields similar results, and requires no human over-reading of the measurements. © The Author(s) 2015.

  9. Dense Accumulation of Lipiodol Emulsion in Hepatocellular Carcinoma Nodule during Selective Balloon-occluded Transarterial Chemoembolization: Measurement of Balloon-occluded Arterial Stump Pressure

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

    Irie, Toshiyuki, E-mail: toshiyuki.irie.rq@hitachi.com; Kuramochi, Masashi, E-mail: masashi.kuramochi.sh@hitachi.com; Takahashi, Nobuyuki, E-mail: nbyktakahashiodn@yahoo.co.jp

    2013-06-15

    Purpose. To reveal the mechanism of dense accumulation of lipiodol emulsion (LE) in hepatocellular carcinoma (HCC) during selective balloon-occluded transarterial chemoembolization (B-TACE). Methods. Balloon-occluded arterial stump pressure (BOASP) at the embolization portion was measured during selective B-TACE for 43 nodules in 42 patients. Fluoroscopy and digital subtraction angiography were prospectively observed during selective B-TACE to note whether dense LE accumulation in HCC occurred. The LE concentration ratio of HCC to embolized liver parenchyma (LECHL ratio) was also calculated for each treatment on the basis of the computed tomographic scan obtained immediately after selective B-TACE. The relationships between degree of LEmore » accumulation and the BOASP, as well as the LECHL ratio, were analyzed. Results. Arterial flow beyond the catheter tip was maintained even after balloon inflation. In 39 of 43 treatments, LE inflow into the nontumorous liver parenchyma ceased immediately after LE droplets were filled in arteries of the nontumorous liver parenchyma while LE inflow into the HCC nodule continued (group 1). More dense LE accumulation in HCC nodule was obtained in these 39 treatments. In four treatments, LE inflow both into the nontumorous liver parenchyma and into the HCC nodule continued, and no dense LE accumulation in HCC nodule was observed (group 2). In these four treatments, thick anastomotic vessels with collateral artery were noted. The BOASP in group 1 was (mean {+-} SD) 33.8 {+-} 12.8 mmHg (range 13-64 mmHg) and that in group 2 was 92.3 {+-} 7.4 mmHg (range 83-100 mmHg). There was a statistically significant difference in BOASP between groups (p = 0.00004, Welch's t test). The LECHL ratio in group 1 was 18.3 {+-} 13.9 (range 2.9-54.2) and that in group 2 was 2.6 {+-} 1.1 (range 1.7-4.2). There was a statistically significant difference in the LECHL ratio between the groups (p = 0.000034, Welch's t test). Conclusion. Selective B

  10. Snow as an accumulator of air pollutants

    Treesearch

    Robert T. Brown

    1976-01-01

    Using simple analytical techniques, the amounts of air pollutants accumulated in winter snow were determined and the results correlated with lichen survival on trees. Pollutants measured were particulate matter, sulfate, and chloride. An inverse relationship was found between amounts of each of these pollutants and the abundance of various lichens.

  11. Blood orange juice inhibits fat accumulation in mice.

    PubMed

    Titta, L; Trinei, M; Stendardo, M; Berniakovich, I; Petroni, K; Tonelli, C; Riso, P; Porrini, M; Minucci, S; Pelicci, P G; Rapisarda, P; Reforgiato Recupero, G; Giorgio, M

    2010-03-01

    To analyze the effect of the juice obtained from two varieties of sweet orange (Citrus sinensis L. Osbeck), Moro (a blood orange) and Navelina (a blond orange), on fat accumulation in mice fed a standard or a high-fat diet (HFD). Obesity was induced in male C57/Bl6 mice by feeding a HFD. Moro and Navelina juices were provided instead of water. The effect of an anthocyanin-enriched extract from Moro oranges or purified cyanidin-3-glucoside (C3G) was also analyzed. Body weight and food intake were measured regularly over a 12-week period. The adipose pads were weighted and analyzed histologically; total RNA was also isolated for microarray analysis. Dietary supplementation of Moro juice, but not Navelina juice significantly reduced body weight gain and fat accumulation regardless of the increased energy intake because of sugar content. Furthermore, mice drinking Moro juice were resistant to HFD-induced obesity with no alterations in food intake. Only the anthocyanin extract, but not the purified C3G, slightly affected fat accumulation. High-throughput gene expression analysis of fat tissues confirmed that Moro juice could entirely rescue the high fat-induced transcriptional reprogramming. Moro juice anti-obesity effect on fat accumulation cannot be explained only by its anthocyanin content. Our findings suggest that multiple components present in the Moro orange juice might act synergistically to inhibit fat accumulation.

  12. Information accumulation system by inheritance and diffusion

    NASA Astrophysics Data System (ADS)

    Shin, J. K.

    2009-09-01

    This paper suggests a new model, called as the IAS (Information Accumulation System), for the description of the dynamic process that people use to accumulate their information (knowledge or opinion) for specific issues. Using the concept of information, both the internal and the external mechanism of the opinion dynamics are treated on a unified frame. The information is quantified as a real number with fixed bounds. New concepts, such as inheritance and differential absorption, are incorporated in IAS in addition to the conventional diffusive interaction between people. Thus, the dynamics of the IAS are governed by following three factors: inheritance rate, diffusivity and absorption rate. The original set of equations was solved with an agent based modeling technique. In addition, the individual equations for each of the agents were assembled and transformed into a set of equations for the ensemble averages, which are greatly reduced in number and can be solved analytically. The example simulations showed interesting results such as the critical behavior with respect to diffusivity, the information polarization out of zero-sum news and the dependence of the solutions on the initial conditions alone. The results were speculated in relation to today’s modern society where the diffusivity of information has been greatly increased through the internet and mobile phones.

  13. Impact of measurement uncertainty from experimental load distribution factors on bridge load rating

    NASA Astrophysics Data System (ADS)

    Gangone, Michael V.; Whelan, Matthew J.

    2018-03-01

    Load rating and testing of highway bridges is important in determining the capacity of the structure. Experimental load rating utilizes strain transducers placed at critical locations of the superstructure to measure normal strains. These strains are then used in computing diagnostic performance measures (neutral axis of bending, load distribution factor) and ultimately a load rating. However, it has been shown that experimentally obtained strain measurements contain uncertainties associated with the accuracy and precision of the sensor and sensing system. These uncertainties propagate through to the diagnostic indicators that in turn transmit into the load rating calculation. This paper will analyze the effect that measurement uncertainties have on the experimental load rating results of a 3 span multi-girder/stringer steel and concrete bridge. The focus of this paper will be limited to the uncertainty associated with the experimental distribution factor estimate. For the testing discussed, strain readings were gathered at the midspan of each span of both exterior girders and the center girder. Test vehicles of known weight were positioned at specified locations on each span to generate maximum strain response for each of the five girders. The strain uncertainties were used in conjunction with a propagation formula developed by the authors to determine the standard uncertainty in the distribution factor estimates. This distribution factor uncertainty is then introduced into the load rating computation to determine the possible range of the load rating. The results show the importance of understanding measurement uncertainty in experimental load testing.

  14. Accumulation and turnover of carbon in organic and mineral soils of the BOREAS northern study area

    USGS Publications Warehouse

    Trumbore, S.E.; Harden, J.W.

    1997-01-01

    Rates of input, accumulation, and turnover of C differ markedly within soil profiles and in soils with different drainage in the BOREAS northern study area. Soil C storage increases from ???3 kg C m-2 in well-drained, sandy soils to greater than 100 kg C m-2 in wetlands. Two modes of C accumulation were observed in upland soil profiles. Large annual C inputs (0.06-0.1 kg C m-2 yr-1) and slow decomposition (turnover times of 6-250 years) lead to rapid C accumulation in regrowing surface moss and detrital layers following fire. Deep organic layers that have accumulated over the millennia since the initiation of soil development, and are located below the most recent charred horizon, show slower rates of input (0.015-0.03 kg C m-2 yr-1) and turnover (100-1600 years) and accumulate C about 10 times slower than surface detrital layers. Rates of C input to soils derived from C and 14C data were in accord with net primary production estimates, with highest rates of input (0.14-0.6 kg C m-2 yr-1) in wetlands. Turnover times for C in surface detrital layers were 6-15 years for well-drained sand soils that showed highest soil temperatures in summer, 30-40 years for wetlands, and 36-250 years for uplands with thick moss cover and black spruce trees. Long (>100 years) turnover times in upland black spruce/clay soils most likely reflect the influence of woody debris incorporated into detrital layers. Turnover times for deep organic and mineral layer C were controlled by drainage, with fastest turnover (80-130 years) in well-drained sand soils and slowest turnover (>3000 years) in wetlands. Total C accumulation rates, which account for C losses from both deep organic and surface detrital layers, are close to zero for sand/jack pine soils, 0.003-0.01 kg C m-2 yr-1 for moderately to poorly drained sites in mature forest stands, and 0.03 kg C m-2 yr-1 for a productive fen. Decomposition of organic matter more than several decades old accounts for 9-22% of total heterotrophic

  15. Accumulation, biotransformation, histopathology and paralysis in the Pacific calico scallop Argopecten ventricosus by the paralyzing toxins of the dinoflagellate Gymnodinium catenatum.

    PubMed

    Escobedo-Lozano, Amada Y; Estrada, Norma; Ascencio, Felipe; Contreras, Gerardo; Alonso-Rodriguez, Rosalba

    2012-05-01

    The dinoflagellate Gymnodinium catenatum produces paralyzing shellfish poisons that are consumed and accumulated by bivalves. We performed short-term feeding experiments to examine ingestion, accumulation, biotransformation, histopathology, and paralysis in the juvenile Pacific calico scallop Argopecten ventricosus that consume this dinoflagellate. Depletion of algal cells was measured in closed systems. Histopathological preparations were microscopically analyzed. Paralysis was observed and the time of recovery recorded. Accumulation and possible biotransformation of toxins were measured by HPLC analysis. Feeding activity in treated scallops showed that scallops produced pseudofeces, ingestion rates decreased at 8 h; approximately 60% of the scallops were paralyzed and melanin production and hemocyte aggregation were observed in several tissues at 15 h. HPLC analysis showed that the only toxins present in the dinoflagellates and scallops were the N-sulfo-carbamoyl toxins (C1, C2); after hydrolysis, the carbamate toxins (epimers GTX2/3) were present. C1 and C2 toxins were most common in the mantle, followed by the digestive gland and stomach-complex, adductor muscle, kidney and rectum group, and finally, gills. Toxin profiles in scallop tissue were similar to the dinoflagellate; biotransformations were not present in the scallops in this short-term feeding experiment.

  16. Interseismic strain accumulation across the Ashkabad fault (NE Iran) from MERIS-corrected ASAR data

    NASA Astrophysics Data System (ADS)

    Walters, R. J.; Elliott, J. R.; Li, Z.; Parsons, B. E.

    2011-12-01

    The right-lateral Ashkabad Fault separates deforming NE Iran from the stable Turkmenistan platform to the north, and also facilitates the north-westwards extrusion of the South Caspian block (along with the left-lateral Shahrud fault zone). The fault represents the northernmost boundary of significant deformation of the Arabia-Eurasia collision in NE Iran. The 1948 M 7.3 Ashkabad earthquake, which killed around 110,000 people and was the deadliest earthquake to hit Europe or the Middle East in the 20th Century, also possibly occurred on this fault. However, the slip rate and therefore the seismic hazard that the Ashkabad fault represents are not well known. GPS data in NE Iran are sparse, and there are no direct geological or quaternary rates for the main strand of the fault. We use Envisat ASAR data acquired between 2003 and 2010 to measure interseismic strain accumulation across the fault, and hence estimate the slip rate across it. Due to the proximity of this region to the Caspian Sea and the presence of highly variable weather systems, we use data from Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument, as well as modelled weather data from the European Centre for Medium-Range Weather Forecasting (ECMWF), to correct interferograms for differences in water vapour and atmospheric pressure. We mitigate the effects of remaining noise by summing the 13 corrected interferograms that cover the fault, effectively creating a 30 year interferogram with improved signal-to-noise ratio, and we empirically correct for orbital errors. Our measurements of rates of displacement are consistent with an interseismic model for the Ashkabad fault where deformation occurs at depth on a narrow shear zone below a layer in which the fault is locked. We invert the data to solve for best fitting model parameters, estimating both the slip rate and the depth to which the fault is locked. Our measurements show that the Ashkabad fault is accumulating strain at a rate of 9 mm

  17. Activity and heart rate-based measures for outpatient cardiac rehabilitation.

    PubMed

    Bidargaddi, N P; Sarela, A

    2008-01-01

    Derive activity and heart rate (HR) monitor-based clinically relevant measures for outpatient cardiac rehabilitation (CR). We are currently collecting activity/ECG data from patients undergoing cardiac rehabilitation over duration of six weeks. From these data sets, we a) derive various measures which can be used in assessing home-based CR patients remotely and b) investigate the usefulness of continuous ambulatory HR and heart rate variability (HRV) for various core components of CR. The information provided by these measures is interpreted according to the CR guidelines framework by American Association of Cardiovascular and Pulmonary Rehabilitation (AACVPR), thus showing how these tools can be used in assessing the progress of patients' condition. The usefulness and significance of these measures from a health care professional perspective is also presented by evaluating them against the existing hospital-based measures through examples. Hospital-based CR programs, despite their clinical benefits are severely under-utilized and resource-demanding. Ambulatory monitoring technologies, which provide a means for continuous physiological monitoring of patients at home compared to hospital-based tools, can enable home-based CR. The clinically relevant measures derived from these tools not only reflect patients' condition in a similar way as conventional tools but also show the continuous status of functional capacity (FC).

  18. Measurements of Aperture Averaging on Bit-Error-Rate

    NASA Technical Reports Server (NTRS)

    Bastin, Gary L.; Andrews, Larry C.; Phillips, Ronald L.; Nelson, Richard A.; Ferrell, Bobby A.; Borbath, Michael R.; Galus, Darren J.; Chin, Peter G.; Harris, William G.; Marin, Jose A.; hide

    2005-01-01

    We report on measurements made at the Shuttle Landing Facility (SLF) runway at Kennedy Space Center of receiver aperture averaging effects on a propagating optical Gaussian beam wave over a propagation path of 1,000 in. A commercially available instrument with both transmit and receive apertures was used to transmit a modulated laser beam operating at 1550 nm through a transmit aperture of 2.54 cm. An identical model of the same instrument was used as a receiver with a single aperture that was varied in size up to 20 cm to measure the effect of receiver aperture averaging on Bit Error Rate. Simultaneous measurements were also made with a scintillometer instrument and local weather station instruments to characterize atmospheric conditions along the propagation path during the experiments.

  19. Measurements of aperture averaging on bit-error-rate

    NASA Astrophysics Data System (ADS)

    Bastin, Gary L.; Andrews, Larry C.; Phillips, Ronald L.; Nelson, Richard A.; Ferrell, Bobby A.; Borbath, Michael R.; Galus, Darren J.; Chin, Peter G.; Harris, William G.; Marin, Jose A.; Burdge, Geoffrey L.; Wayne, David; Pescatore, Robert

    2005-08-01

    We report on measurements made at the Shuttle Landing Facility (SLF) runway at Kennedy Space Center of receiver aperture averaging effects on a propagating optical Gaussian beam wave over a propagation path of 1,000 m. A commercially available instrument with both transmit and receive apertures was used to transmit a modulated laser beam operating at 1550 nm through a transmit aperture of 2.54 cm. An identical model of the same instrument was used as a receiver with a single aperture that was varied in size up to 20 cm to measure the effect of receiver aperture averaging on Bit Error Rate. Simultaneous measurements were also made with a scintillometer instrument and local weather station instruments to characterize atmospheric conditions along the propagation path during the experiments.

  20. Radio Frequency Sensing of Particulate Matter Accumulation on a Gasoline Particulate Filter

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

    Parks, James; Prikhodko, Vitaly Y.; Sappok, Alex

    Filter Sensing Technology’s radio frequency (RF) sensor for particulate filter on-board diagnostics (OBD) was studied on a lean gasoline engine at the National Transportation Research Center (NTRC) at Oak Ridge National Laboratory (ORNL). The response of the RF sensor to particulate matter (PM) or “soot” accumulation on the gasoline particulate filter (GPF) installed in the engine exhaust was evaluated. In addition, end plugs of the GPF were purposely removed, and subsequent changes to the RF sensor measured soot loading on the GPF were characterized. Results from the study showed that the RF sensor can accurately measure soot accumulation on amore » GPF; furthermore, the predicted decreased soot accumulation due to plug removal was detected by the RF sensor. Overall, the studies were short and preliminary in nature; however, clearly, the RF sensor demonstrated the capability of measuring GPF soot loading at a level suitable for use in lean gasoline engine emission control OBD and control.« less

  1. Propylene glycol accumulation in critically ill patients receiving continuous intravenous lorazepam infusions.

    PubMed

    Horinek, Erica L; Kiser, Tyree H; Fish, Douglas N; MacLaren, Robert

    2009-12-01

    Lorazepam is recommended by the Society of Critical Care Medicine as the preferred agent for sedation of critically ill patients. Intravenous lorazepam contains propylene glycol, which has been associated with toxicity when high doses of lorazepam are administered. To evaluate the accumulation of propylene glycol in critically ill patients receiving lorazepam by continuous infusion and determine factors associated with propylene glycol concentration. A 6-month, retrospective, safety assessment was conducted of adults admitted to the medical intensive care unit who were receiving lorazepam by continuous infusion for 12 hours or more. Propylene glycol serum concentrations were obtained 24-48 hours after continuous-infusion lorazepam was initiated and every 3-5 days thereafter. Propylene glycol accumulation was defined as concentrations of 25 mg/dL or more. Groups with and without propylene glycol accumulation were compared and factors associated with propylene glycol concentration were determined using multivariate correlation regression analyses. Forty-eight propylene glycol serum samples were obtained from 33 patients. Fourteen (42%) patients had propylene glycol accumulation, representing 23 (48%) serum samples. Univariate analyses showed the following factors were related to propylene glycol accumulation: baseline renal dysfunction, presence of alcohol withdrawal, sex, age, Acute Physiology and Chronic Health Evaluation (APACHE II) score, rate of lorazepam continuous infusion, and 24-hour lorazepam dose. Multivariate linear regression modeling demonstrated that propylene glycol concentration was strongly associated with the continuous infusion rate and 24-hour dose (adjusted r(2) > or = 0.77; p < 0.001). Independent correlation analyses showed that these 2 variables were so strongly associated with propylene glycol concentration (r(2) > or = 0.71; p < 0.001) that they alone predicted propylene glycol concentration. Seven (21%) patients developed renal dysfunction

  2. Carbon allocation and accumulation in conifers

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

    Gower, S.T.; Isebrands, J.G.; Sheriff, D.W.

    1995-07-01

    Forests cover approximately 33% of the land surface of the earth, yet they are responsible for 65% of the annual carbon (C) accumulated by all terrestrial biomes. In general, total C content and net primary production rates are greater for forests than for other biomes, but C budgets differ greatly among forests. Despite several decades of research on forest C budgets, there is still an incomplete understanding of the factors controlling C allocation. Yet, if we are to understand how changing global events such as land use, climate change, atmospheric N deposition, ozone, and elevated atmospheric CO{sub 2} affect themore » global C budget, a mechanistic understanding of C assimilation, partitioning, and allocation is necessary. The objective of this chapter is to review the major factors that influence C allocation and accumulation in conifer trees and forests. In keeping with the theme of this book, we will focus primarily on evergreen conifers. However, even among evergreen conifers, leaf, canopy, and stand-level C and nutrient allocation patterns differ, often as a function of leaf development and longevity. The terminology related to C allocation literature is often inconsistent, confusing and inadequate for understanding and integrating past and current research. For example, terms often used synonymously to describe C flow or movement include translocation, transport, distribution, allocation, partitioning, apportionment, and biomass allocation. A common terminology is needed because different terms have different meanings to readers. In this paper we use C allocation, partitioning, and accumulation according to the definitions of Dickson and Isebrands (1993). Partitioning is the process of C flow into and among different chemical, storage, and transport pools. Allocation is the distribution of C to different plant parts within the plant (i.e., source to sink). Accumulation is the end product of the process of C allocation.« less

  3. A comparison of methods to estimate anaerobic capacity: Accumulated oxygen deficit and W' during constant and all-out work-rate profiles.

    PubMed

    Muniz-Pumares, Daniel; Pedlar, Charles; Godfrey, Richard; Glaister, Mark

    2017-12-01

    This study investigated (i) whether the accumulated oxygen deficit (AOD) and curvature constant of the power-duration relationship (W') are different during constant work-rate to exhaustion (CWR) and 3-min all-out (3MT) tests and (ii) the relationship between AOD and W' during CWR and 3MT. Twenty-one male cyclists (age: 40 ± 6 years; maximal oxygen uptake [V̇O 2max ]: 58 ± 7 ml · kg -1 · min -1 ) completed preliminary tests to determine the V̇O 2 -power output relationship and V̇O 2max . Subsequently, AOD and W' were determined as the difference between oxygen demand and oxygen uptake and work completed above critical power, respectively, in CWR and 3MT. There were no differences between tests for duration, work, or average power output (P ≥ 0.05). AOD was greater in the CWR test (4.18 ± 0.95 vs. 3.68 ± 0.98 L; P = 0.004), whereas W' was greater in 3MT (9.55 ± 4.00 vs. 11.37 ± 3.84 kJ; P = 0.010). AOD and W' were significantly correlated in both CWR (P < 0.001, r = 0.654) and 3MT (P < 0.001, r = 0.654). In conclusion, despite positive correlations between AOD and W' in CWR and 3MT, between-test differences in the magnitude of AOD and W', suggest that both measures have different underpinning mechanisms.

  4. Measuring Flow Rate in Crystalline Bedrock Wells Using the Dissolved Oxygen Alteration Method.

    PubMed

    Vitale, Sarah A; Robbins, Gary A

    2017-07-01

    Determination of vertical flow rates in a fractured bedrock well can aid in planning and implementing hydraulic tests, water quality sampling, and improving interpretations of water quality data. Although flowmeters are highly accurate in flow rate measurement, the high cost and logistics may be limiting. In this study the dissolved oxygen alteration method (DOAM) is expanded upon as a low-cost alternative to determine vertical flow rates in crystalline bedrock wells. The method entails altering the dissolved oxygen content in the wellbore through bubbler aeration, and monitoring the vertical advective movement of the dissolved oxygen over time. Measurements were taken for upward and downward flows, and under ambient and pumping conditions. Vertical flow rates from 0.06 to 2.30 Lpm were measured. To validate the method, flow rates determined with the DOAM were compared to pump discharge rates and found to be in agreement within 2.5%. © 2017, National Ground Water Association.

  5. Measurement of flying and diving metabolic rate in wild animals: Review and recommendations.

    PubMed

    Elliott, Kyle H

    2016-12-01

    Animals' abilities to fly long distances and dive to profound depths fascinate earthbound researchers. Due to the difficulty of making direct measurements during flying and diving, many researchers resort to modeling so as to estimate metabolic rate during each of those activities in the wild, but those models can be inaccurate. Fortunately, the miniaturization, customization and commercialization of biologgers has allowed researchers to increasingly follow animals on their journeys, unravel some of their mysteries and test the accuracy of biomechanical models. I provide a review of the measurement of flying and diving metabolic rate in the wild, paying particular attention to mass loss, doubly-labelled water, heart rate and accelerometry. Biologgers can impact animal behavior and influence the very measurements they are designed to make, and I provide seven guidelines for the ethical use of biologgers. If biologgers are properly applied, quantification of metabolic rate across a range of species could produce robust allometric relationships that could then be generally applied. As measuring flying and diving metabolic rate in captivity is difficult, and often not directly translatable to field conditions, I suggest that applying multiple techniques in the field to reinforce one another may be a viable alternative. The coupling of multi-sensor biologgers with biomechanical modeling promises to improve precision in the measurement of flying and diving metabolic rate in wild animals. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Influence of hydrophobicity on ice accumulation process under sleet and wind conditions

    NASA Astrophysics Data System (ADS)

    Xu, Ke; Hu, Jianlin; Shu, Lichun; Jiang, Xingliang; Huang, Zhengyong

    2018-03-01

    Glaze, the most dangerous ice type in natural environment, forms during sleet weather, which is usually accompanied with wind. The icing performance of hydrophobic coatings under the impact of wind needs further research. This paper studies the influence of hydrophobicity on ice accumulation process under sleet and wind conditions by computer simulations and icing tests. The results indicate that the heat dissipation process of droplets on samples with various hydrophobicity will be accelerated by wind significantly and that a higher hydrophobicity cannot reduce the cooling rate effectively. However, on different hydrophobic surfaces, the ice accumulation process has different characteristics. On a hydrophilic surface, the falling droplets form continuously water film, which will be cooled fast. On superhydrophobic surface, the frozen droplets form ice bulges, which can shield from wind and slow down the heat dissipation process. These ice accumulation characteristics lead to the difference in ice morphology and make a higher hydrophobic surface to have a lower ice mass growth rate in long period icing tests. As a conclusion, superhydrophobic coating remain icephobic under wind and sleet conditions.

  7. Fast repetition rate (FRR) fluorometer and method for measuring fluorescence and photosynthetic parameters

    DOEpatents

    Kolber, Z.; Falkowski, P.

    1995-06-20

    A fast repetition rate fluorometer device and method for measuring in vivo fluorescence of phytoplankton or higher plants chlorophyll and photosynthetic parameters of phytoplankton or higher plants is revealed. The phytoplankton or higher plants are illuminated with a series of fast repetition rate excitation flashes effective to bring about and measure resultant changes in fluorescence yield of their Photosystem II. The series of fast repetition rate excitation flashes has a predetermined energy per flash and a rate greater than 10,000 Hz. Also, disclosed is a flasher circuit for producing the series of fast repetition rate flashes. 14 figs.

  8. Dust Accumulation on Mars

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Since landing on Mars a year ago, NASA's pair of six-wheeled geologists have been constantly exposed to martian winds and dust. As a result, the Spirit rover has gradually experienced a slight decline in power as a thin layer of dust has accumulated on the solar panels, blocking some of the sunlight that is converted to electricity. In this enlarged image of a postage-stamp-size (3-centimeter-square, 1.2-inch-square) portion of one of Spirit's solar panels, a fine layer of martian dust coats electrical connections and metal surfaces. Individual silt grains or clumps of dust are visible where sediment has accumulated in crevices between solar cells and circuits. The upper right half of the image shows the edge of one of the rover's solar cells. The lower left half shows electrical wires bonded with silicon adhesive to the underlying composite surface; the circular abrasions are the result of sanding by hand on Earth. The braided wire is connected to a thermocouple used to measure temperature based on electrical resistance. Spirit took this image with its microscopic imager on martian day, or sol, 350 (Dec. 26, 2004).

  9. 30 CFR 75.1709 - Accumulations of methane and coal dust on surface coal-handling facilities.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Accumulations of methane and coal dust on... Miscellaneous § 75.1709 Accumulations of methane and coal dust on surface coal-handling facilities. [Statutory Provisions] Adequate measures shall be taken to prevent methane and coal dust from accumulating in excessive...

  10. Mental workload measurement: Event-related potentials and ratings of workload and fatigue

    NASA Technical Reports Server (NTRS)

    Biferno, M. A.

    1985-01-01

    Event-related potentials were elicited when a digitized word representing a pilot's call-sign was presented. This auditory probe was presented during 27 workload conditions in a 3x3x3 design where the following variables were manipulated: short-term load, tracking task difficulty, and time-on-task. Ratings of workload and fatigue were obtained between each trial of a 2.5-hour test. The data of each subject were analyzed individually to determine whether significant correlations existed between subjective ratings and ERP component measures. Results indicated that a significant number of subjects had positive correlations between: (1) ratings of workload and P300 amplitude, (2) ratings of workload and N400 amplitude, and (3) ratings of fatigue and P300 amplitude. These data are the first to show correlations between ratings of workload or fatigue and ERP components thereby reinforcing their validity as measures of mental workload and fatigue.

  11. Nibbled to Death by Ducks: The Accumulation of Disadvantage

    NASA Astrophysics Data System (ADS)

    Simpson, Caroline E.

    2010-05-01

    One of the consequences of unconscious bias is the accumulation of advantage/disadvantage. Research has shown that over time, minor imbalances will accrue and eventually have major impacts regarding promotion, salary, prestige, and advancement to leadership positions. For example, an unconscious bias during an evaluation leading to an underestimate of performance will result in a lower success rate, which then feeds back into the next evaluation and the cycle repeats. How can we address this? We'll be discussing how to become informed and conscious of the problem, and we'll look at recommendations for developing and implementing departmental and institutional policies and practices aimed at increasing awareness and countering these accumulations of imbalances that impact us all.

  12. HUBBLE SPACE TELESCOPE ON TRACK FOR MEASURING THE EXPANSION RATE OF THE UNIVERSE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    rate with an estimate of how much matter is in space. The younger age values from each team assume the Universe is at a critical density where it contains just enough matter to expand indefinitely. The higher age estimates are calculated based on a low density of matter in space. (See 'Science Background' for more information on the expanding Universe.) 'A point of great interest is whether the age of the Universe arrived at this way is really older than the independently derived ages of the oldest stars,' said Saha, an investigator on both Hubble teams. 'The numbers lean on the side that the stellar ages are a little lower, or that the hypothesis that we live in a critical density universe needs to be questioned,' said Saha. 'As further results accumulate over the next few years, we hope to tighten the constraints on these issues.' THE OBSERVATIONS The Key Project team is midway along in their three-year program to derive the expansion rate of the Universe based on precise distance measurements to galaxies. They have now measured Cepheid distances to a dozen galaxies, and are about halfway through their overall program. The Key Project team also presented a preliminary estimate of the distance to the Fornax cluster of galaxies. The estimate was obtained through the detection and measurement with the Hubble Space Telescope of pulsating stars known as Cepheid variables found in the Fornax cluster. The Fornax cluster is measured to be approximately as far away as the Virgo cluster of galaxies -- about 60 million light-years. The Key Project team member who led this effort, Caltech astronomer Barry Madore said, 'This cluster allows us to make independent estimates of the expansion rate of the Universe using a number of different techniques. All of these methods are now in excellent agreement. With Fornax we are now at turning point in this field.' The team is measuring Cepheid distances to the Virgo and Fornax clusters of galaxies as a complementary test. Their strategy

  13. Test Plan - Solids Accumulation Scouting Studies

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

    Duignan, M. R.; Steeper, T. J.; Steimke, J. L.

    This plan documents the highlights of the Solids Accumulations Scouting Studies test; a project, from Washington River Protection Solutions (WRPS), that began on February 1, 2012. During the last 12 weeks considerable progress has been made to design and plan methods that will be used to estimate the concentration and distribution of heavy fissile solids in accumulated solids in the Hanford double-shell tank (DST) 241-AW-105 (AW-105), which is the primary goal of this task. This DST will be one of the several waste feed delivery staging tanks designated to feed the Pretreatment Facility (PTF) of the Waste Treatment and Immobilizationmore » Plant (WTP). Note that over the length of the waste feed delivery mission AW-105 is currently identified as having the most fill empty cycles of any DST feed tanks, which is the reason for modeling this particular tank. At SRNL an existing test facility, the Mixing Demonstration Tank, which will be modified for the present work, will use stainless steel particles in a simulant that represents Hanford waste to perform mock staging tanks transfers that will allow solids to accumulate in the tank heel. The concentration and location of the mock fissile particles will be measured in these scoping studies to produce information that will be used to better plan larger scaled tests. Included in these studies is a secondary goal of developing measurement methods to accomplish the primary goal. These methods will be evaluated for use in the larger scale experiments. Included in this plan are the several pretest activities that will validate the measurement techniques that are currently in various phases of construction. Aspects of each technique, e.g., particle separations, volume determinations, topographical mapping, and core sampling, have been tested in bench-top trials, as discussed herein, but the actual equipment to be employed during the full test will need evaluation after fabrication and integration into the test facility.« less

  14. Electrodes as social glue: measuring heart rate promotes giving in the trust game.

    PubMed

    Van Lange, Paul A M; Finkenauer, Catrin; Popma, Arne; van Vugt, Mark

    2011-06-01

    While physiological measures are increasingly used to help us understand the workings of interpersonal trust (and related behaviors), we know very little about the effects of such measures on trust. We examined the effects of a classic measure, the measurement of heart rate using a standard protocol, on behavioral trust in dyads of women who did not know each other. Behavioral trust was assessed in the trust game, in which the trustor decides how much money from their subject payment to give to a trustee, while knowing that the experimenter triples that amount before giving it to the trustee, after which the trustee decides how much money to return to the trustor. As predicted, we found greater levels of behavioral trust in the trust game, as well as greater returns by the trustees (which were accounted for by trustor's giving), in the heart rate (HR) than in no heart rate (NHR) measurement condition. Parallel findings were observed for self-reported trust. Findings are discussed in terms of the idea that the elusive effects of a protocol for measuring heart rate can cause pronounced effects on subsequent social interactions via enhanced interpersonal trust. 2011 Elsevier B.V. All rights reserved.

  15. A novel setup for wafer curvature measurement at very high heating rates.

    PubMed

    Islam, T; Zechner, J; Bernardoni, M; Nelhiebel, M; Pippan, R

    2017-02-01

    The curvature evolution of a thin film layer stack containing a top Al layer is measured during temperature cycles with very high heating rates. The temperature cycles are generated by means of programmable electrical power pulses applied to miniaturized polysilicon heater systems embedded inside a semiconductor chip and the curvature is measured by a fast wafer curvature measurement setup. Fast temperature cycles with heating duration of 100 ms are created to heat the specimen up to 270 °C providing an average heating rate of 2500 K/s. As a second approach, curvature measurement utilizing laser scanning Doppler vibrometry is also demonstrated which verifies the results obtained from the fast wafer curvature measurement setup. Film stresses calculated from the measured curvature values compare well to literature results, indicating that the new method can be used to measure curvature during fast temperature cycling.

  16. Predictive modeling of crystal accumulation in high-level waste glass melters processing radioactive waste

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

    Matyáš, Josef; Gervasio, Vivianaluxa; Sannoh, Sulaiman E.

    The effectiveness of HLW vitrification is limited by precipitation/accumulation of spinel crystals [(Fe, Ni, Mn, Zn)(Fe, Cr)2O4] in the glass discharge riser of Joule-heated ceramic melters during idling. These crystals do not affect glass durability; however, if accumulated in thick layer, they can clog the melter and prevent discharge of molten glass into canisters. To address this problem, an empirical model was developed that can predict thicknesses of accumulated layers as a function of glass composition. This model predicts well the accumulation of single crystals and/or small-scale agglomerates, but, excessive agglomeration observed in high-Ni-Fe glass resulted in an under-prediction ofmore » accumulated layers, which gradually worsen over time as an increased number of agglomerates formed. Accumulation rate of ~53.8 ± 3.7 µm/h determined for this glass will result in ~26 mm thick layer in 20 days of melter idling.« less

  17. Predictive modeling of crystal accumulation in high-level waste glass melters processing radioactive waste

    NASA Astrophysics Data System (ADS)

    Matyáš, Josef; Gervasio, Vivianaluxa; Sannoh, Sulaiman E.; Kruger, Albert A.

    2017-11-01

    The effectiveness of high-level waste vitrification at Hanford's Waste Treatment and Immobilization Plant may be limited by precipitation/accumulation of spinel crystals [(Fe, Ni, Mn, Zn)(Fe, Cr)2O4] in the glass discharge riser of Joule-heated ceramic melters during idling. These crystals do not affect glass durability; however, if accumulated in thick layers, they can clog the melter and prevent discharge of molten glass into canisters. To address this problem, an empirical model was developed that can predict thicknesses of accumulated layers as a function of glass composition. This model predicts well the accumulation of single crystals and/or small-scale agglomerates, but excessive agglomeration observed in high-Ni-Fe glass resulted in an underprediction of accumulated layers, which gradually worsened over time as an increased number of agglomerates formed. The accumulation rate of ∼53.8 ± 3.7 μm/h determined for this glass will result in a ∼26 mm-thick layer after 20 days of melter idling.

  18. Standard magnetic resonance-based measurements of the Pi→ATP rate do not index the rate of oxidative phosphorylation in cardiac and skeletal muscles

    PubMed Central

    Ugurbil, Kamil

    2011-01-01

    Magnetic resonance spectroscopy-based magnetization transfer techniques (MT) are commonly used to assess the rate of oxidative (i.e., mitochondrial) ATP synthesis in intact tissues. Physiologically appropriate interpretation of MT rate data depends on accurate appraisal of the biochemical events that contribute to a specific MT rate measurement. The relative contributions of the specific enzymatic reactions that can contribute to a MT Pi→ATP rate measurement are tissue dependent; nonrecognition of this fact can bias the interpretation of MT Pi→ATP rate data. The complexities of MT-based measurements of mitochondrial ATP synthesis rates made in striated muscle and other tissues are reviewed, following which, the adverse impacts of erroneous Pi→ATP rate data analyses on the physiological inferences presented in selected published studies of cardiac and skeletal muscle are considered. PMID:21368294

  19. Irradiation-induced defect formation and damage accumulation in single crystal CeO2

    NASA Astrophysics Data System (ADS)

    Graham, Joseph T.; Zhang, Yanwen; Weber, William J.

    2018-01-01

    The accumulation of irradiation-induced disorder in single crystal CeO2 has been investigated over a wide range of ion fluences. Room temperature irradiations of epitaxial CeO2 thin films using 2 MeV Au2+ ions were carried out up to a total fluence of 1.3 ×1016 cm-2 Post-irradiation disorder was characterized using ion channeling Rutherford backscattering spectrometry (RBS/C) and confocal Raman spectroscopy. The Raman measurements were interpreted by means of a phonon confinement model, which employed rigid ion calculations to determine the phonon correlation length in the irradiated material. Comparison between the dose dependent changes in correlation length of the Raman measurements and the Ce disorder fraction from RBS/C provides complementary quantitative details on the rate of point and extended defect formation on the Ce and O sub-lattices over a broad range of ion fluences. Raman measurements, which are significantly more sensitive than RBS/C at low doses, reveal that the nucleation rate of defects is highest below 0.1 displacements per atom (dpa). Comparison between Raman and RBS/C measurements suggests that between 0.1 and 10 dpa the damage evolution is characterized by modest growth of point defects and/or small clusters, while above 10 dpa the preexisting defects rapidly grow into extended clusters and/or loops.

  20. Irradiation-induced defect formation and damage accumulation in single crystal CeO 2

    DOE PAGES

    Graham, Joseph T.; Zhang, Yanwen; Weber, William J.

    2017-11-15

    Here, the accumulation of irradiation-induced disorder in single crystal CeO 2 has been investigated over a wide range of ion fluences. Room temperature irradiations of epitaxial CeO 2 thin films using 2 MeV Au 2+ ions were carried out up to a total fluence of 1.3 x 10 16 cm –2 Post-irradiation disorder was characterized using ion channeling Rutherford backscattering spectrometry (RBS/C) and confocal Raman spectroscopy. The Raman measurements were interpreted by means of a phonon confinement model, which employed rigid ion calculations to determine the phonon correlation length in the irradiated material. Comparison between the dose dependent changes inmore » correlation length of the Raman measurements and the Ce disorder fraction from RBS/C provides complementary quantitative details on the rate of point and extended defect formation on the Ce and O sub-lattices over a broad range of ion fluences. Raman measurements, which are significantly more sensitive than RBS/C at low doses, reveal that the nucleation rate of defects is highest below 0.1 displacements per atom (dpa). Comparison between Raman and RBS/C measurements suggests that between 0.1 and 10 dpa the damage evolution is characterized by modest growth of point defects and/or small clusters, while above 10 dpa the preexisting defects rapidly grow into extended clusters and/or loops.« less