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Sample records for 222-radon concentrations variability

  1. Relevance of air conditioning for 222Radon concentration in shops of the Savona Province, Italy.

    PubMed

    Panatto, Donatella; Ferrari, Paola; Lai, Piero; Gallelli, Giovanni

    2006-02-15

    Radon (222Rn) concentration was evaluated in shops of the Savona Province, Italy, between summer 2002 and winter 2002-2003. The main characteristics of each shops were recorded through a questionnaire investigating the ventilation rate and factors related to 222Rn precursors in the soil and the construction materials. The main variables that were related to radon concentration were the following: age of the building, level of the shop above ground, season of the year, wind exposure, active windows, and type of heating system. Shops equipped with individual air heating/conditioning systems exhibited radon concentrations that were three times higher than those of shops heated by centralized furnaces. Our data indicate that the level of pollution in the shops was of medium level, with an expected low impact on the salespersons' health. Only in wintertime, the action level of 200 Bq m(-3) for the confined environment was reached in 10 shops equipped with individual air heating/conditioning systems.

  2. Occurrence of Uranium and 222Radon in Glacial and Bedrock Aquifers in the Northern United States, 1993-2003

    USGS Publications Warehouse

    Ayotte, Joseph D.; Flanagan, Sarah M.; Morrow, William S.

    2007-01-01

    Water-quality data collected from 1,426 wells during 1993-2003 as part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) program were evaluated to characterize the water quality in glacial and bedrock aquifers of the northern United States. One of the goals of the NAWQA program is to synthesize data from individual studies across the United States to gain regional- and national-scale information about the behavior of contaminants. This study focused on the regional occurrence and distribution of uranium and 222radon in ground water in the glacial aquifer system of the United States as well as in the Cambrian-Ordovician and the New York and New England crystalline aquifer systems that underlie the glacial aquifer system. The occurrence of uranium and 222radon in ground water has long been a concern throughout the United States. In the glacial aquifers, as well as the Cambrian-Ordovician and the New York and New England crystalline aquifer systems of the United States, concentrations of uranium and 222radon were highly variable. High concentrations of uranium and 222radon affect ground water used for drinking water and for agriculture. A combination of information or data on (1) national-scale ground-water regions, (2) regional-scale glacial depositional models, (3) regional-scale geology, and (4) national-scale terrestrial gamma-ray emissions were used to confirm and(or) refine the regions used in the analysis of the water-chemistry data. Significant differences in the occurrence of uranium and 222radon, based primarily on geologic information were observed and used in this report. In general, uranium was highest in the Columbia Plateau glacial, West-Central glacial, and the New York and New England crystalline aquifer groups (75th percentile concentrations of 22.3, 7.7, and 2.9 micrograms per liter (ug/L), respectively). In the Columbia Plateau glacial and the West-Central glacial aquifer groups, more than 10 percent of wells sampled had

  3. The potential risk from 222radon posed to archaeologists and earth scientists: reconnaissance study of radon concentrations, excavations, and archaeological shelters in the Great Cave of Niah, Sarawak, Malaysia.

    PubMed

    Gillmore, Gavin; Gilbertson, David; Grattan, John; Hunt, Chris; McLaren, Sue; Pyatt, Brian; Mani Banda, Richard; Barker, Graeme; Denman, Antony; Phillips, Paul; Reynolds, Tim

    2005-02-01

    This reconnaissance study of radon concentrations in the Great Cave of Niah in Sarawak shows that in relatively deep pits and trenches in surficial deposits largely covered by protective shelters with poor ventilation, excavators are working in a micro-environment in which radon concentrations at the ground surface can exceed those of the surrounding area by a factor of > x 2. Although radon concentrations in this famous cave are low by world standards (alpha track-etch results ranging from 100 to 3075 Bq m(-3)), they still may pose a health risk to both excavators (personal dosemeter readings varied from 0.368 to 0.857 mSv for 60 days of work) and cave occupants (1 yr exposure at 15 h per day with an average radon level of 608 Bq m(-3) giving a dose of 26.42 mSv). The data here presented also demonstrate that there is considerable local variation in radon levels in such environments as these.

  4. A process-based 222radon flux map for Europe and its comparison to long-term observations

    NASA Astrophysics Data System (ADS)

    Karstens, U.; Schwingshackl, C.; Schmithüsen, D.; Levin, I.

    2015-11-01

    Detailed 222radon (222Rn) flux maps are an essential pre-requisite for the use of radon in atmospheric transport studies. Here we present a high-resolution 222Rn flux map for Europe, based on a parameterization of 222Rn production and transport in the soil. The 222Rn exhalation rate is parameterized based on soil properties, uranium content, and modelled soil moisture from two different land-surface reanalysis data sets. Spatial variations in exhalation rates are primarily determined by the uranium content of the soil, but also influenced by soil texture and local water-table depth. Temporal variations are related to soil moisture variations as the molecular diffusion in the unsaturated soil zone depends on available air-filled pore space. The implemented diffusion parameterization was tested against campaign-based 222Rn soil profile measurements. Monthly 222Rn exhalation rates from European soils were calculated with a nominal spatial resolution of 0.083° × 0.083° and compared to long-term direct measurements of 222Rn exhalation rates in different areas of Europe. The two realizations of the 222Rn flux map, based on the different soil moisture data sets, both realistically reproduce the observed seasonality in the fluxes but yield considerable differences for absolute flux values. The mean 222Rn flux from soils in Europe is estimated to be 10 mBq m-2 s-1 (ERA-Interim/Land soil moisture) or 15 mBq m-2 s-1 (GLDAS (Global Land Data Assimilation System) Noah soil moisture) for the period 2006-2010. The corresponding seasonal variations with low fluxes in winter and high fluxes in summer range in the two realizations from ca. 7 to ca. 14 mBq m-2 s-1 and from ca. 11 to ca. 20 mBq m-2 s-1, respectively. These systematic differences highlight the importance of realistic soil moisture data for a reliable estimation of 222Rn exhalation rates. Comparison with observations suggests that the flux estimates based on the GLDAS Noah soil moisture model on average better

  5. City scale pollen concentration variability

    NASA Astrophysics Data System (ADS)

    van der Molen, Michiel; van Vliet, Arnold; Krol, Maarten

    2016-04-01

    Pollen are emitted in the atmosphere both in the country-side and in cities. Yet the majority of the population is exposed to pollen in cities. Allergic reactions may be induced by short-term exposure to pollen. This raises the question how variable pollen concentration in cities are in temporally and spatially, and how much of the pollen in cities are actually produced in the urban region itself. We built a high resolution (1 × 1 km) pollen dispersion model based on WRF-Chem to study a city's pollen budget and the spatial and temporal variability in concentration. It shows that the concentrations are highly variable, as a result of source distribution, wind direction and boundary layer mixing, as well as the release rate as a function of temperature, turbulence intensity and humidity. Hay Fever Forecasts based on such high resolution emission and physical dispersion modelling surpass traditional hay fever warning methods based on temperature sum methods. The model gives new insights in concentration variability, personal and community level exposure and prevention. The model will be developped into a new forecast tool to serve allergic people to minimize their exposure and reduce nuisance, coast of medication and sick leave. This is an innovative approach in hay fever warning systems.

  6. Inferring coastal processes from regional-scale mapping of 222Radon and salinity: examples from the Great Barrier Reef, Australia.

    PubMed

    Stieglitz, Thomas C; Cook, Peter G; Burnett, William C

    2010-07-01

    The radon isotope 222Rn and salinity in coastal surface water were mapped on regional scales, to improve the understanding of coastal processes and their spatial variability. Radon was measured with a surface-towed, continuously recording multi-detector setup on a moving vessel. Numerous processes and locations of land-ocean interaction along the Central Great Barrier Reef coastline were identified and interpreted based on the data collected. These included riverine fluxes, terrestrially-derived fresh submarine groundwater discharge (SGD) and the tidal pumping of seawater through mangrove forests. Based on variations in the relationship of the tracers radon and salinity, some aspects of regional freshwater inputs to the coastal zone and to estuaries could be assessed. Concurrent mapping of radon and salinity allowed an efficient qualitative assessment of land-ocean interaction on various spatial and temporal scales, indicating that such surveys on coastal scales can be a useful tool to obtain an overview of SGD locations and processes.

  7. Temporal variability in airborne pollen concentrations.

    PubMed

    Raynor, G S; Hayes, J V; Ogden, E C

    1976-06-01

    Tests were conducted to determine the relationship between concentrations of airborne pollens and sampling time, using sequential rotoslide samplers at urban and rural locations. Short-period data showed an increase in variability with time between samples. Two-hour data showed a stronger trend for the first 12 hours but better agreement as the time between samples approached one day.

  8. Spatial variability in airborne pollen concentrations.

    PubMed

    Raynor, G S; Ogden, E C; Hayes, J V

    1975-03-01

    Tests were conducted to determine the relationship between airborne pollen concentrations and distance. Simultaneous samples were taken in 171 tests with sets of eight rotoslide samplers spaced from one to 486 M. apart in straight lines. Use of all possible pairs gave 28 separation distances. Tests were conducted over a 2-year period in urban and rural locations distant from major pollen sources during both tree and ragweed pollen seasons. Samples were taken at a height of 1.5 M. during 5-to 20-minute periods. Tests were grouped by pollen type, location, year, and direction of the wind relative to the line. Data were analyzed to evaluate variability without regard to sampler spacing and variability as a function of separation distance. The mean, standard deviation, coefficient of variation, ratio of maximum to the mean, and ratio of minimum to the mean were calculated for each test, each group of tests, and all cases. The average coefficient of variation is 0.21, the maximum over the mean, 1.39 and the minimum over the mean, 0.69. No relationship was found with experimental conditions. Samples taken at the minimum separation distance had a mean difference of 18 per cent. Differences between pairs of samples increased with distance in 10 of 13 groups. These results suggest that airborne pollens are not always well mixed in the lower atmosphere and that a sample becomes less representative with increasing distance from the sampling location.

  9. A detailed examination of the chemical, hydrological, and geological properties influencing the mobility of {sup 222}radon and parent radionuclides in groundwater

    SciTech Connect

    Sexsmith, K.S.

    1996-12-31

    This study examines hydrological, geological and geochemical controls on {sup 222}Rn variability in groundwater in the Front Range of Colorado. Specific objectives of the study are: (1) to determine if there are any correlations or spatial relationships between {sup 222}Rn and the geological, geochemical and hydrogeological data; and (2) to determine whether it is geochemically reasonable for observed {sup 222}Rn levels to be the result of U and {sup 226}Ra accumulation by fracture filling minerals. Domestic-water wells were sampled and tested to determine the local aquifer characteristics and aqueous geochemistry. A multivariate and staged approach was used in the data analyses. Analysis of variance tests were used to test for relationships between {sup 222}Rn and the lithology of the study wells. The effects of rock-type were then removed from the chemical and hydrological variables by subtracting the mean value for each rock-type from each of the measured values within that rock-type (a residual transformation). Linear and linear multiple regression techniques were used to test for expected relationships between residual {sup 222}Rn levels and these variables, and stepwise linear regressions were used to test for any unforeseen multivariate relationships in the data. Correlograms, distance-weighted average and inverse-distance-weighted average predictions were used to look for spatial relationships in the data.

  10. Variability and Predictors of Urinary Bisphenol A Concentrations during Pregnancy

    PubMed Central

    Braun, Joe M.; Kalkbrenner, Amy E.; Calafat, Antonia M.; Bernert, John T.; Ye, Xiaoyun; Silva, Manori J.; Barr, Dana Boyd; Sathyanarayana, Sheela; Lanphear, Bruce P.

    2011-01-01

    Background Prenatal bisphenol A (BPA) exposure may be associated with developmental toxicity, but few studies have examined the variability and predictors of urinary BPA concentrations during pregnancy. Objective Our goal was to estimate the variability and predictors of serial urinary BPA concentrations taken during pregnancy. Methods We measured BPA concentrations during pregnancy and at birth in three spot urine samples from 389 women. We calculated the intraclass correlation coefficient (ICC) to assess BPA variability and estimated associations between log10-transformed urinary BPA concentrations and demographic, occupational, dietary, and environmental factors, using mixed models. Results Geometric mean (GM) creatinine-standardized concentrations (micrograms per gram) were 1.7 (16 weeks), 2.0 (26 weeks), and 2.0 (birth). Creatinine-standardized BPA concentrations exhibited low reproducibility (ICC = 0.11). By occupation, cashiers had the highest BPA concentrations (GM: 2.8 μg/g). Consuming canned vegetables at least once a day was associated with higher BPA concentrations (GM = 2.3 μg/g) compared with those consuming no canned vegetables (GM = 1.6 μg/g). BPA concentrations did not vary by consumption of fresh fruits and vegetables, canned fruit, or store-bought fresh and frozen fish. Urinary high-molecular-weight phthalate and serum tobacco smoke metabolite concentrations were positively associated with BPA concentrations. Conclusions These results suggest numerous sources of BPA exposure during pregnancy. Etiological studies may need to measure urinary BPA concentrations more than once during pregnancy and adjust for phthalates and tobacco smoke exposures. PMID:21205581

  11. Modeling variability and trends in pesticide concentrations in streams

    USGS Publications Warehouse

    Vecchia, A.V.; Martin, J.D.; Gilliom, R.J.

    2008-01-01

    A parametric regression model was developed for assessing the variability and long-term trends in pesticide concentrations in streams. The dependent variable is the logarithm of pesticide concentration and the explanatory variables are a seasonal wave, which represents the seasonal variability of concentration in response to seasonal application rates; a streamflow anomaly, which is the deviation of concurrent daily streamflow from average conditions for the previous 30 days; and a trend, which represents long-term (inter-annual) changes in concentration. Application of the model to selected herbicides and insecticides in four diverse streams indicated the model is robust with respect to pesticide type, stream location, and the degree of censoring (proportion of nondetections). An automatic model fitting and selection procedure for the seasonal wave and trend components was found to perform well for the datasets analyzed. Artificial censoring scenarios were used in a Monte Carlo simulation analysis to show that the fitted trends were unbiased and the approximate p-values were accurate for as few as 10 uncensored concentrations during a three-year period, assuming a sampling frequency of 15 samples per year. Trend estimates for the full model were compared with a model without the streamflow anomaly and a model in which the seasonality was modeled using standard trigonometric functions, rather than seasonal application rates. Exclusion of the streamflow anomaly resulted in substantial increases in the mean-squared error and decreases in power for detecting trends. Incorrectly modeling the seasonal structure of the concentration data resulted in substantial estimation bias and moderate increases in mean-squared error and decreases in power. ?? 2008 American Water Resources Association.

  12. Immunoglobulin G concentration in canine colostrum: Evaluation and variability.

    PubMed

    Mila, Hanna; Feugier, Alexandre; Grellet, Aurélien; Anne, Jennifer; Gonnier, Milène; Martin, Maelys; Rossig, Lisa; Chastant-Maillard, Sylvie

    2015-11-01

    Canine neonates are born hypogammaglobulinemic, and colostrum is their main source of immunoglobulins. The purpose of this study was to evaluate the immune quality of canine colostrum and its variability both among bitches and among mammary glands. The immune quality was estimated from immunoglobulin G (IgG) concentration (ELISA test). The correlation of IgG concentration with refractometry was evaluated. From a total of 44 bitches from 13 different breeds from a single breeding kennel, samples of colostrum and blood were collected one day after the parturition onset. Colostrum was collected separately from each pair of mammary glands (180 pairs). The mean colostrum IgG concentration in our population was 20.8 ± 8.1g/L (ranging from 8.0 to 41.7 g/L) with no influence of breed size, litter size, age of dam or serum IgG concentration. Colostrum IgG concentration varied widely among pairs of mammary glands within one bitch (variation coefficient: 42 ± 32.1%). Nevertheless, no single pair of mammary glands was found to produce regularly a secretion of higher quality. No difference in IgG concentration was recorded between anterior and posterior pairs either. The BRIX index and the refractive index were significantly, but moderately correlated with colostrum IgG concentration (r=0.53 and 0.42, respectively). This study demonstrates a great variability in immune quality of colostrum among bitches and among mammary glands within one bitch. Further studies on the suckling behavior of puppies and on determination of the minimal immune quality of colostrum are required to evaluate their impact of this high variability on neonatal mortality in dogs.

  13. Natural variability in the surface ocean carbonate ion concentration

    NASA Astrophysics Data System (ADS)

    Lovenduski, N. S.; Long, M. C.; Lindsay, K.

    2015-11-01

    We investigate variability in the surface ocean carbonate ion concentration ([CO32-]) on the basis of a~long control simulation with an Earth System Model. The simulation is run with a prescribed, pre-industrial atmospheric CO2 concentration for 1000 years, permitting investigation of natural [CO32-] variability on interannual to multi-decadal timescales. We find high interannual variability in surface [CO32-] in the tropical Pacific and at the boundaries between the subtropical and subpolar gyres in the Northern Hemisphere, and relatively low interannual variability in the centers of the subtropical gyres and in the Southern Ocean. Statistical analysis of modeled [CO32-] variance and autocorrelation suggests that significant anthropogenic trends in the saturation state of aragonite (Ωaragonite) are already or nearly detectable at the sustained, open-ocean time series sites, whereas several decades of observations are required to detect anthropogenic trends in Ωaragonite in the tropical Pacific, North Pacific, and North Atlantic. The detection timescale for anthropogenic trends in pH is shorter than that for Ωaragonite, due to smaller noise-to-signal ratios and lower autocorrelation in pH. In the tropical Pacific, the leading mode of surface [CO32-] variability is primarily driven by variations in the vertical advection of dissolved inorganic carbon (DIC) in association with El Niño-Southern Oscillation. In the North Pacific, surface [CO32-] variability is caused by circulation-driven variations in surface DIC and strongly correlated with the Pacific Decadal Oscillation, with peak spectral power at 20-30-year periods. North Atlantic [CO32-] variability is also driven by variations in surface DIC, and exhibits weak correlations with both the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation. As the scientific community seeks to detect the anthropogenic influence on ocean carbonate chemistry, these results will aid the interpretation of trends

  14. Natural variability in the surface ocean carbonate ion concentration

    NASA Astrophysics Data System (ADS)

    Lovenduski, N. S.; Long, M. C.; Lindsay, K.

    2015-08-01

    We investigate variability in the surface ocean carbonate ion concentration ([CO32-]) on the basis of a long control simulation with a fully-coupled Earth System Model. The simulation is run with a prescribed, pre-industrial atmospheric CO2 concentration for 1000 years, permitting investigation of natural [CO32-] variability on interannual to multi-decadal timescales. We find high interannual variability in surface [CO32-] in the tropical Pacific and at the boundaries between the subtropical and subpolar gyres in the Northern Hemisphere, and relatively low interannual variability in the centers of the subtropical gyres and in the Southern Ocean. Statistical analysis of modeled [CO32-] variance and autocorrelation suggests that significant anthropogenic trends in the saturation state of aragonite (Ωaragonite) are already or nearly detectable at the sustained, open-ocean timeseries sites, whereas several decades of observations are required to detect anthropogenic trends in Ωaragonite in the tropical Pacific, North Pacific, and North Atlantic. The detection timescale for anthropogenic trends in pH is shorter than that for Ωaragonite, due to smaller noise-to-signal ratios and lower autocorrelation in pH. In the tropical Pacific, the leading mode of surface [CO32-] variability is primarily driven by variations in the vertical advection of dissolved inorganic carbon (DIC) in association with El Niño-Southern Oscillation. In the North Pacific, surface [CO32-] variability is caused by circulation-driven variations in surface DIC and strongly correlated with the Pacific Decadal Oscillation, with peak spectral power at 20-30 year periods. North Atlantic [CO32-] variability is also driven by variations in surface DIC, and exhibits weak correlations with both the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation. As the scientific community seeks to detect the anthropogenic influence on ocean carbonate chemistry, these results will aid the

  15. Intraspecific genotypic variability determines concentrations of key truffle volatiles.

    PubMed

    Splivallo, Richard; Valdez, Nayuf; Kirchhoff, Nina; Ona, Marta Castiella; Schmidt, Jean-Pierre; Feussner, Ivo; Karlovsky, Petr

    2012-05-01

    • Aroma variability in truffles has been attributed to maturation (Tuber borchii), linked to environmental factors (Tuber magnatum), but the involvement of genetic factors has been ignored. We investigated aroma variability in Tuber uncinatum, a species with wide distribution. Our aim was to assess aroma variability at different spatial scales (i.e. trees, countries) and to quantify how aroma was affected by genotype, fruiting body maturity, and geographical origin. • A volatile fingerprinting method was used to analyze the aroma of 223 T. uncinatum fruiting bodies from seven European countries. Maturity was estimated from spore melanization. Genotypic fingerprinting was performed by amplified fragment length polymorphism (AFLP). • Discriminant analysis revealed that, regardless of the geographical origin of the truffles, most of the aroma variability was caused by eight-carbon-containing volatiles (C8-VOCs). In an orchard of T. uncinatum, truffles producing different concentrations of C8-VOCs clustered around distinct host trees. This clustering was not associated with maturity, but was associated with fungal genotype. • These results indicate that the variation in C8-VOCs in truffles is most likely under genetic control. They exemplify that understanding the factors behind aroma variability requires a holistic approach. Furthermore, they also raise new questions regarding the ecological role of 1-octen-3-ol in truffles.

  16. Precipitation driving of droplet concentration variability in marine low clouds

    NASA Astrophysics Data System (ADS)

    Wood, Robert; Leon, David; Lebsock, Matthew; Snider, Jefferson; Clarke, Antony D.

    2012-10-01

    The concentration Nd of cloud droplets in marine low clouds is a primary determinant of their ability to reflect sunlight and modulates their ability to precipitate. Previous studies have focused upon aerosol source variability as the key driver of variability in Nd. Here, we use a highly simplified aerosol budget model to examine the impact of precipitation on Nd. This model considers: precipitation (coalescence) scavenging, constrained using new satellite measurements of light precipitation; entrainment of aerosol from above cloud combined with constant aerosol concentration based on recent field observations of aerosol particles in the free troposphere; and sea-surface aerosol production estimated using a wind speed dependent source function. Despite the highly simplified nature of this model, it skillfully predicts the geographical variability ofNd in regions of extensive marine low clouds. Inclusion of precipitation results in reduction in Nd by factors of 2-3 over the remote oceans. Within 500 km of coastlines the reduction in Nd due to precipitation is weak but in these regions the model is not able to accurately predict Ndbecause of strong pollution sources. In general, neither free-tropospheric nor surface CCN sources alone are sufficient to maintainNd against precipitation losses. The results demonstrate that even the light precipitation rates typical of marine stratocumulus profoundly impact the radiative properties of marine low clouds.

  17. Variability of surface pigment concentrations in the South Atlantic Bight

    NASA Technical Reports Server (NTRS)

    Mcclain, Charles R.; Yoder, James A.; Blanton, J. O.; Atkinson, L. P.; Lee, T. N.

    1988-01-01

    A time sequence of surface pigment images of the South Atlantic Bight (SAB), derived from the Nimbus 7 CZCS for the period between November 1978 and October 1979, was correlated with in situ observations of hydrographic parameters, fresh-water discharge, sea level, coastal winds, and currents in order to couple physical processes and the spatial and temporal variability of the surface pigment fields. A definite seasonal modulation of the surface pigment fields was found, with the concentrations in the Georgia Bight being highest in summer, and those north of Cape Romain highest in winter. This phase difference was found to be the result of variations in wind fields, Gulf Stream-shelf interactions, and fresh-water discharge patterns. At some locations (e.g., near Charleston) the alongshore band of high pigment concentrations increased in width throughout the year; at other locations (near Jacksonville), the alongsore band exhibited a minimum width in the summer and a maximum width in the fall of 1979.

  18. Variability of piperacillin concentrations in relation to tazobactam concentrations in critically ill patients.

    PubMed

    Zander, Johannes; Döbbeler, Gundula; Nagel, Dorothea; Scharf, Christina; Huseyn-Zada, Mikayil; Jung, Jette; Frey, Lorenz; Vogeser, Michael; Zoller, Michael

    2016-10-01

    Therapeutic drug monitoring for critically ill patients receiving piperacillin/tazobactam is described as a useful tool. However, the minimum inhibitory concentration of piperacillin depends on a sufficiently high concentration of tazobactam in case of β-lactamase-producing strains. Therefore, the relationship between piperacillin and tazobactam concentrations was assessed in a heterogeneous group of critically ill patients. Sixty patients with severe infections receiving 4.5 g of piperacillin/tazobactam 2-3 times daily by intermittent infusion were included in this prospective observational study (NCT01793012). Over 4 days, multiple serum samples were obtained to determine the total piperacillin and tazobactam concentrations. The target ranges were defined as trough levels >16 mg/L (>22.5 mg/L) and >4 mg/L (>5.7 mg/L) for the calculated unbound concentrations (measured total concentrations) of piperacillin and tazobactam, respectively. Despite a high correlation coefficient (r = 0.93) comparing piperacillin and tazobactam trough levels, the piperacillin/tazobactam quotients varied between ca. 1 and 10. From linear regression analysis of piperacillin versus tazobactam values, it follows that a piperacillin trough level of 22.5 mg/L might be associated with tazobactam trough levels ranging from 1.5 mg/L to 10.1 mg/L. A 70 mg/L threshold for total piperacillin trough levels would be necessary to ensure that tazobactam concentrations are >5.7 mg/L. Because of the observed variability of piperacillin/tazobactam quotients, defining the total piperacillin target range ≥70 mg/L might be useful to ensure that tazobactam concentrations do not fall below 5.7 mg/L. Further studies are necessary to confirm that the used therapeutic ranges are associated with optimal outcomes in critically ill patients.

  19. Uniform Concentration-Compactness for Sobolev Spaces on Variable Domains

    NASA Astrophysics Data System (ADS)

    Bucur, Dorin

    2000-04-01

    We present a new method for proving existence results in shape optimization problems involving the eigenvalues of the Dirichlet-Laplace operator. This method brings together the γ-convergence theory and the concentration-compactness principle. Given a sequence of open sets (An)n∈N in RN, not necessarily bounded, but of uniformly bounded measure, we prove a concentration-compactness result in L(L2(RN)) for the sequence of resolvent operators (RAn)n∈N, where RAn: L2(RN)→H10(An), RAn=(-Δ)-1.

  20. Variability of air ion concentrations in urban Paris

    NASA Astrophysics Data System (ADS)

    Dos Santos, V. N.; Herrmann, E.; Manninen, H. E.; Hussein, T.; Hakala, J.; Nieminen, T.; Aalto, P. P.; Merkel, M.; Wiedensohler, A.; Kulmala, M.; Petäjä, T.; Hämeri, K.

    2015-12-01

    Air ion concentrations influence new particle formation and consequently the global aerosol as potential cloud condensation nuclei. We aimed to evaluate air ion concentrations and characteristics of new particle formation events (NPF) in the megacity of Paris, France, within the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric Pollution and climate effects, and Integrated tools for assessment and mitigation) project. We measured air ion number size distributions (0.8-42 nm) with an air ion spectrometer and fine particle number concentrations (> 6 nm) with a twin differential mobility particle sizer in an urban site of Paris between 26 June 2009 and 4 October 2010. Air ions were size classified as small (0.8-2 nm), intermediate (2-7 nm), and large (7-20 nm). The median concentrations of small and large ions were 670 and 680 cm-3, respectively, (sum of positive and negative polarities), whereas the median concentration of intermediate ions was only 20 cm-3, as these ions were mostly present during new particle formation bursts, i.e. when gas-to-particle conversion produced fresh aerosol particles from gas phase precursors. During peaks in traffic-related particle number, the concentrations of small and intermediate ions decreased, whereas the concentrations of large ions increased. Seasonal variations affected the ion population differently, with respect to their size and polarity. NPF was observed in 13 % of the days, being most frequent in spring and late summer (April, May, July, and August). The results also suggest that NPF was favoured on the weekends in comparison to workdays, likely due to the lower levels of condensation sinks in the mornings of weekends (CS weekdays 09:00: 18 × 10-3 s-1; CS weekend 09:00: 8 × 10-3 s-1). The median growth rates (GR) of ions during the NPF events varied between 3 and 7 nm h-1, increasing with the ion size and being higher on workdays than on weekends for intermediate and large ions. The median GR of

  1. Spatial variability of fine particle concentrations in three European areas

    NASA Astrophysics Data System (ADS)

    Hoek, Gerard; Meliefste, Kees; Cyrys, Josef; Lewné, Marie; Bellander, Tom; Brauer, Mike; Fischer, Paul; Gehring, Ulrike; Heinrich, Joachim; van Vliet, Patricia; Brunekreef, Bert

    Epidemiological studies of long-term air pollution effects have been hampered by difficulties in characterizing the spatial variation in air pollution. We conducted a study to assess the risk of long-term exposure to traffic-related air pollution for the development of inhalant allergy and asthma in children in Stockholm county, Munich and the Netherlands. Exposure to traffic-related air pollution was assessed through a 1-year monitoring program and regression modeling using exposure indicators. This paper documents the performance of the exposure monitoring strategy and the spatial variation of ambient particle concentrations. We measured the ambient concentration of PM2.5 and the reflectance of PM2.5 filters ('soot') at 40-42 sites representative of different exposure conditions of the three study populations. Each site was measured during four 14-day average sampling periods spread over one year (spring 1999 to summer 2000). In each study area, a continuous measurement site was operated to remove potential bias due to temporal variation. The selected approach was an efficient method to characterize spatial differences in annual average concentration between a large number of sites in each study area. Adjustment with data from the continuous measurement site improved the precision of the calculated annual averages, especially for PM2.5. Annual average PM2.5 concentrations ranged from 11 to 20 μg/m 3 in Munich, from 8 to 16 μg/m 3 in Stockholm and from 14 to 26 μg/m 3 in the Netherlands. Larger spatial contrasts were found for the absorption coefficient of PM2.5. PM2.5 concentrations were on average 17-18% higher at traffic sites than at urban background sites, but PM2.5 absorption coefficients at traffic sites were between 31% and 55% increased above background. This suggests that spatial variation of traffic-related air pollution may be underestimated if PM2.5 only is measured.

  2. Correlations between cadmium concentration in urine and exposure variables

    NASA Astrophysics Data System (ADS)

    Schwarz, Elmar; Chutsch, Martina; Krause, Christian M.; Schulz, Christine; Thefeld, Wolfgang

    1993-03-01

    As part of the study 'UMWELT und GESUNDHEIT 1985/86', a representative samples of the population of the Federal Republic of Germany was examined for urinary Cd. A log-linear prediction model based on 2109 cases led to an explained variance portion of R2 equals .32. Strong associations were revealed between urinary cadmium and the smoking history and age of the subjects. This is evidence of the function urinary cadmium has as an indicator of the Cd body burden. However, there are also clear connections with physiological parameters (urinary creatinine and serum urea), which are taken to be a modification of Cd excretion by renal function. The association between urinary Cd and serum urea can also be interpreted as a cadmium-induced renal dysfunction. Urinary Cd concentrations tend to be lower in regions with low industrial nitrogen oxide emissions and high economic dynamics, as well as in non- urban residential structures.

  3. Interannual variability of ammonia concentrations over the United States: sources and implications

    NASA Astrophysics Data System (ADS)

    Schiferl, Luke D.; Heald, Colette L.; Van Damme, Martin; Clarisse, Lieven; Clerbaux, Cathy; Coheur, Pierre-François; Nowak, John B.; Neuman, J. Andrew; Herndon, Scott C.; Roscioli, Joseph R.; Eilerman, Scott J.

    2016-09-01

    The variability of atmospheric ammonia (NH3), emitted largely from agricultural sources, is an important factor when considering how inorganic fine particulate matter (PM2.5) concentrations and nitrogen cycling are changing over the United States. This study combines new observations of ammonia concentration from the surface, aboard aircraft, and retrieved by satellite to both evaluate the simulation of ammonia in a chemical transport model (GEOS-Chem) and identify which processes control the variability of these concentrations over a 5-year period (2008-2012). We find that the model generally underrepresents the ammonia concentration near large source regions (by 26 % at surface sites) and fails to reproduce the extent of interannual variability observed at the surface during the summer (JJA). Variability in the base simulation surface ammonia concentration is dominated by meteorology (64 %) as compared to reductions in SO2 and NOx emissions imposed by regulation (32 %) over this period. Introduction of year-to-year varying ammonia emissions based on animal population, fertilizer application, and meteorologically driven volatilization does not substantially improve the model comparison with observed ammonia concentrations, and these ammonia emissions changes have little effect on the simulated ammonia concentration variability compared to those caused by the variability of meteorology and acid-precursor emissions. There is also little effect on the PM2.5 concentration due to ammonia emissions variability in the summer when gas-phase changes are favored, but variability in wintertime emissions, as well as in early spring and late fall, will have a larger impact on PM2.5 formation. This work highlights the need for continued improvement in both satellite-based and in situ ammonia measurements to better constrain the magnitude and impacts of spatial and temporal variability in ammonia concentrations.

  4. Determination of water quality variables, endotoxin concentration, and enterobacteriaceae concentration and identification in Southern High Plains dairy lagoons

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objectives of this study were to determine the concentration of endotoxin, determine 20 water quality variables, and identify and enumerate fungal and bacterial pathogens from United States southern High Plains dairy lagoons and control lakes during summer and winter. Water samples were collecte...

  5. The influence of environmental variables on platelet concentration in horse platelet-rich plasma.

    PubMed

    Rinnovati, Riccardo; Romagnoli, Noemi; Gentilini, Fabio; Lambertini, Carlotta; Spadari, Alessandro

    2016-07-04

    Platelet-rich plasma (PRP) commonly refers to blood products which contain a higher platelet (PLT) concentration as compared to normal plasma. Autologous PRP has been shown to be safe and effective in promoting the natural processes of soft tissue healing or reconstruction in humans and horses. Variability in PLT concentration has been observed in practice between PRP preparations from different patients or from the same individual under different conditions. A change in PLT concentration could modify PRP efficacy in routine applications. The aim of this study was to test the influence of environmental, individual and agonistic variables on the PLT concentration of PRP in horses. Six healthy Standardbred mares were exposed to six different variables with a one-week washout period between variables, and PRP was subsequently obtained from each horse. The variables were time of withdrawal during the day (morning/evening), hydration status (overhydration/dehydration) treatment with anti-inflammatory drugs and training periods on a treadmill. The platelet concentration was significantly higher in horses treated with a non-steroidal anti-inflammatory drug (P = 0.03). The leukocyte concentration increased 2-9 fold with respect to whole blood in the PRP which was obtained after exposure to all the variable considered. Environmental variation in platelet concentration should be taken into consideration during PRP preparation.

  6. Hormone Concentrations and Variability: Associations with Self-Reported Moods and Energy in Early Adolescent Girls.

    ERIC Educational Resources Information Center

    Buchanan, Christy Miller

    Examined were relations between concentrations and variability of hormones (testosterone, estradiol, follicle stimulating hormone, and leutenizing hormone) and mood intensity, mood variability (within and across days), energy, and restlessness in early adolescent girls. The study also considered the issue of whether hormones have effects on mood…

  7. Predictors and Variability of Urinary Paraben Concentrations in Men and Women, Including before and during Pregnancy

    PubMed Central

    Smith, Kristen W.; Braun, Joe M.; Williams, Paige L.; Ehrlich, Shelley; Correia, Katharine F.; Calafat, Antonia M.; Ye, Xiaoyun; Ford, Jennifer; Keller, Myra; Meeker, John D.

    2012-01-01

    Background: Parabens are suspected endocrine disruptors and ubiquitous preservatives used in personal care products, pharmaceuticals, and foods. No studies have assessed the variability of parabens in women, including during pregnancy. Objective: We evaluated predictors and variability of urinary paraben concentrations. Methods: We measured urinary concentrations of methyl (MP), propyl (PP), and butyl paraben (BP) among couples from a fertility center. Mixed-effects regression models were fit to examine demographic predictors of paraben concentrations and to calculate intraclass correlation coefficients (ICCs). Results: Between 2005 and 2010, we collected 2,721 spot urine samples from 245 men and 408 women. The median concentrations were 112 µg/L (MP), 24.2 µg/L (PP), and 0.70 µg/L (BP). Urinary MP and PP concentrations were 4.6 and 7.8 times higher in women than men, respectively, and concentrations of both MP and PP were 3.8 times higher in African Americans than Caucasians. MP and PP concentrations we CI re slightly more variable in women (ICC = 0.42, 0.43) than men (ICC = 0.54, 0.51), and were weakly correlated between partners (r = 0.27–0.32). Among 129 pregnant women, urinary paraben concentrations were 25–45% lower during pregnancy than before pregnancy, and MP and PP concentrations were more variable (ICCs of 0.38 and 0.36 compared with 0.46 and 0.44, respectively). Conclusions: Urinary paraben concentrations were more variable in women compared with men, and during pregnancy compared with before pregnancy. However, results for this study population suggest that a single urine sample may reasonably represent an individual’s exposure over several months, and that a single sample collected during pregnancy may reasonably classify gestational exposure. PMID:22721761

  8. Robustness of the large-scale modes of variability of winter Arctic sea ice concentration

    NASA Astrophysics Data System (ADS)

    Close, Sally; Houssais, Marie-Noëlle; Herbaut, Christophe

    2016-04-01

    The dominant mode of variability of Arctic winter sea ice concentration has previously been suggested to be represented by a double-dipole structure, with the loading pattern of the first empirical orthogonal mode having phase of one sign in the Sea of Okhotsk and Barents Sea and opposing sign in the Labrador and Bering Seas. In this study, we build on this previous work, examining the robustness of the primary modes of large-scale variability of the winter sea ice concentration in the Arctic based on the satellite data record. We find that the double-dipole structure does not emerge as a robust mode of variability: rather, the primary mode can be considered as a tripole, explaining significant variability only in the Sea of Okhotsk, Barents and Bering Seas. In contrast, the Labrador Sea emerges in isolation in the second empirical orthogonal mode. The relative magnitude of the poles of variability in the empirical orthogonal function loading patterns are sensitive to the detrending of the data; however, the isolation of the variability of the Labrador Sea ice remains a robust feature. We find that there is no significant interannual-scale co-variability amongst the sea ice areas of the four seas comprising the double-dipole after low-frequency variability has been removed.

  9. Seasonal and interannual variability of pigment concentrations across a California Current frontal zone

    NASA Technical Reports Server (NTRS)

    Thomas, A. C.; Strub, P. T.

    1990-01-01

    The seasonal and interannual variability of the latitudinal position of the California Current frontal zone was investigated by examining satellite images of phytoplankton pigment from the coastal-zone color scanner for the periods 1979-1983 and 1986. The pigment concentrations associated with the zonal front were also determined. A general seasonal cycle of pigment concentrations is was established. It was found that variations in the frontal structure are controlled primarily by changes in pigment concentration north of the front. Seasonal variations were found to be minimal south of the front, where pigment concentrations remain low throughout the spring, summer, and fall.

  10. South Asian summer monsoon variability in a model with doubled atmospheric carbon dioxide concentration

    SciTech Connect

    Meehl, G.A.; Washington, W.M. )

    1993-05-21

    Doubled atmospheric carbon dioxide concentration in a global coupled ocean-atmosphere climate model produced increased surface temperatures and evaporation and greater mean precipitation in the south Asian summer monsoon region. As a partial consequence, interannual variability of area-averaged monsoon rainfall was enhanced. Consistent with the climate sensitivity results from the model, observations showed a trend of increased interannual variability of Indian monsoon precipitation associated with warmer land and ocean temperatures in the monsoon region. 26 refs., 3 figs., 1 tab.

  11. Nitrogen and phosphorus concentrations from agricultural catchments—influence of spatial and temporal variables

    NASA Astrophysics Data System (ADS)

    Arheimer, B.; Lidén, R.

    2000-01-01

    The eutrophication problem has drawn attention to nutrient leaching from arable land in southern Sweden, and further understanding of spatial and temporal variability is needed in order to develop decision-making tools. Thus, the influence of spatial and temporal variables was analysed statistically using empirical time series of different nutrient species from 35 well-documented catchments (2-35 km 2), which have been monitored for an average of 5 years. In the spatial analysis several significant correlations between winter median concentrations and catchment characteristics were found. The strongest correlation was found between inorganic nitrogen and land use, while concentrations of different phosphorus species were highly correlated to soil texture. Multiple linear regression models gave satisfactory results for prediction of median winter concentrations in unmeasured catchments, especially for inorganic nitrogen and phosphate. In the analysis of temporal variability within catchments, internal variables from a dynamic hydrological model (HBV) were linked to concentration fluxes. It was found that phosphorus and inorganic nitrogen concentrations were elevated during flow increase at low-flow conditions, while they were diluted as the wetness in the catchment increased. During unmonitored periods regression models were successful in predicting temporal variability of total phosphorus, phosphate and inorganic nitrogen, while organic nitrogen and particulate phosphorus could not be predicted with this approach. Dividing the data into different flow categories did not improve the prediction of nutrient concentration dynamics. The results and literature review presented, confirm parts of the present HBV-N model approach and will be useful for further development of nutrient routines linked to dynamic hydrological models.

  12. High variability of indoor radon concentrations in uraniferous bedrock areas in the Balkan region.

    PubMed

    Zunić, Z S; Ujić, P; Nađđerđ, L; Yarmoshenko, I V; Radanović, S B; Komatina Petrović, S; Celiković, I; Komatina, M; Bossew, P

    2014-12-01

    In this work the strong influence of geological factors on the variability of indoor radon is found in two of three geologically very different regions of South-Eastern Europe. A method to estimate the annual mean concentration when one seasonal measurement is missing is proposed. Large differences of radon concentrations in different rooms of the same house and significant difference in radon concentrations in one season comparing it to the others are noted in certain cases. Geological factors that can lead to such behavior are discussed.

  13. 9-fold Fresnel-Köhler concentrator with Fresnel lens of variable focal point.

    PubMed

    Mendes-Lopes, João; Benítez, Pablo; Zamora, Pablo; Miñano, Juan C

    2014-06-30

    Non-uniform irradiance patterns over Multi-Junction Cells gives rise to power losses, especially when considering spectral irradiance distributions over different junctions. Thermal effects on Silicone-on-Glass lenses affect spectral irradiance distributions. A new Photovoltaic Concentrator (CPV), formed by nine optical channels, each one with a Köhler configuration, has been designed to overcome these effects at high concentrations for a large acceptance angle. A Fresnel Lens with a Variable Focal Point is proposed to prevent optical crosstalk in multichannel systems. When integrated into the concentrator, improves the acceptance angle. These designs are designed to fulfill the expected requirements of four junction CPV systems.

  14. High Variability of Plasma Drug Concentrations in Dual Protease Inhibitor Regimens

    PubMed Central

    Guiard-Schmid, Jean-Baptiste; Poirier, Jean-Marie; Meynard, Jean-Luc; Bonnard, Philippe; Gbadoe, Ayi Hola; Amiel, Corinne; Calligaris, Frédérique; Abraham, Bruno; Pialoux, Gilles; Girard, Pierre-Marie; Jaillon, Patrice; Rozenbaum, Willy

    2003-01-01

    Ritonavir (RTV) strongly increases the concentrations of protease inhibitors (PIs) in plasma in patients given a combination of RTV and another PI. This pharmacological interaction is complex and poorly characterized and shows marked inter- and intraindividual variations. In addition, RTV interacts differently with saquinavir (SQV), indinavir (IDV), amprenavir (APV), and lopinavir (LPV). In this retrospective study on 542 human immunodeficiency virus-infected patients, we compared inter- and intraindividual variability of plasma PI concentrations and correlations between the Cmin (minimum concentration of drug in plasma) values for RTV and the coadministered PI Cmin values. Mean RTV Cmins are significantly lower in patients receiving combinations containing APV or LPV than in combinations with SQV or IDV. With the most common PI dose regimens (600 mg of IDV twice a day [BID], 800 mg of SQV BID, and 400 mg of LPV BID), the interindividual Cmin variability of patients treated with a PI and RTV seemed to be lower with APV and LPV than with IDV and SQV. As regards intraindividual variability, APV also differed from the other PIs, exhibiting lower Cmin variability than with the other combinations. Significant positive correlations between RTV Cmin and boosted PI Cmin were observed with IDV, SQV, and LPV, but not with APV. Individual dose adjustments must take into account the specificity the pharmacological interaction of each RTV/PI combination and the large inter- and intraindividual variability of plasma PI levels to avoid suboptimal plasma drug concentrations which may lead to treatment failure and too high concentrations which may induce toxicity and therefore reduce patient compliance. PMID:12604531

  15. The Thermocline Layer and Chlorophyll-a Concentration Variability during Southeast Monsoon in the Banda Sea

    NASA Astrophysics Data System (ADS)

    Pusparini, Nikita; Prasetyo, Budi; Ambariyanto; Widowati, Ita

    2017-02-01

    Thermocline layer and chlorophyll-a concentration can be used to investigate the upwelling region. This investigation is focused in the Banda Sea because the upwelling event in this area is quite large and has a longer upwelling duration than other waters in Indonesia. In addition, Banda Sea is also influenced by climatic factors such as monsoon. The aim of this research is to determine the validation of secondary data (from satellite imagery data and model) and in situ observation data (from research cruise) and to determine the variability of thermocline layer and chlorophyll-a concentration during Southeast Monsoon in the Banda Sea. The data used in this study were chlorophyll-a concentration, seawater vertical temperature at depths 0-400 meters, and sea surface temperature from remote sensing and in situ data. Spatial and temporal analysis of all parameters was conducted by quantitative descriptive method. The results showed that the variability of thermocline layer and the chlorophyll-a distribution were strongly related to seasonal pattern. In most cases, the estimates of thermocline layer and chlorophyll-a concentration using remote sensing algorithm were higher than in situ measured values. The greatest variability occurred in the eastern Banda Sea during the Southeast Monsoon with shallower thermocline layer, more abundance of chlorophyll-a concentration, and lower sea surface temperature.

  16. Phosphorus concentration and solubility in dairy feces: variability and affecting factors.

    PubMed

    Chapuis-Lardy, L; Fiorini, J; Toth, J; Dou, Z

    2004-12-01

    Recent data from phosphorus (P) feeding trials have demonstrated that P concentration in dairy feces is directly affected by P levels in diets and that farm P surpluses as well as potential environmental losses can be reduced through dietary manipulation. The current study was conducted to examine the variability of fecal P under farm conditions and to elucidate factors affecting the concentration and solubility of fecal P. Feed and fecal samples from >30 commercial dairies in the Northeast and Mid-Atlantic regions were analyzed. Dietary P concentrations ranged from 3.45 to 5.78 g/kg of feed DM (DM), and P determined in acid digests (TP) of feces from 5.84 to 12.84 g/kg of fecal DM. On average, 50% of fecal TP was water soluble; of the latter, 83% was inorganic (Pi). Across-farm variability (n=33) had CV averaging 18.9% for fecal TP and >20% for Pi and total P (Pt) in water extracts. Within-farm variability based on multiple samples per herd had the same magnitude as across-farm and was independent of sample numbers from individual farms (n=7 to 30). Of all fecal parameters determined, pH and DM had the lowest variability (CV <10%), water-soluble Pi, Pt, and Ca the highest (CV of 20 to 30%), and total P, Ca, and Mg determined by acid digests were intermediate (CV 10 to 20%). Water-soluble Pi concentrations determined in dried-ground fecal samples were lower than in wet samples. The drying-grinding process changes Pi solubility and the change is not linear. This study confirms that dietary P concentration is the dominating factor affecting fecal P excretion; however, Ca concentration, DIM, and fecal pH also made small, but statistically significant contributions, although some of the mechanisms remain to be thoroughly investigated.

  17. Variability of Urinary Phthalate Metabolite and Bisphenol A Concentrations before and during Pregnancy

    PubMed Central

    Braun, Joe M.; Smith, Kristen W.; Williams, Paige L.; Calafat, Antonia M.; Berry, Katharine; Ehrlich, Shelley

    2012-01-01

    Background: Gestational phthalate and bisphenol A (BPA) exposure may increase the risk of adverse maternal/child health outcomes, but there are few data on the variability of urinary biomarkers before and during pregnancy. Objective: We characterized the variability of urinary phthalate metabolite and BPA concentrations before and during pregnancy and the ability of a single spot urine sample to classify average gestational exposure. Methods: We collected 1,001 urine samples before and during pregnancy from 137 women who were partners in couples attending a Boston fertility clinic and who had a live birth. Women provided spot urine samples before (n ≥ 2) and during (n ≥ 2) pregnancy. We measured urinary concentrations of monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), mono-iso-butyl phthalate, monobenzyl phthalate (MBzP), four metabolites of di-(2-ethylhexyl) phthalate (DEHP), and BPA. After adjusting for specific gravity, we characterized biomarker variability using intraclass correlation coefficients (ICCs) and conducted several surrogate category analyses to determine whether a single spot urine sample could adequately classify average gestational exposure. Results: Absolute concentrations of phthalate metabolites and BPA were similar before and during pregnancy. Variability was higher during pregnancy than before pregnancy for BPA and MBzP, but similar during and before pregnancy for MBP, MEP, and ΣDEHP. During pregnancy, MEP (ICC = 0.50) and MBP (ICC = 0.45) were less variable than BPA (ICC = 0.12), MBzP (ICC = 0.25), and ΣDEHP metabolites (ICC = 0.08). Surrogate analyses suggested that a single spot urine sample may reasonably classify MEP and MBP concentrations during pregnancy, but more than one sample may be necessary for MBzP, DEHP, and BPA. Conclusions: Urinary phthalate metabolites and BPA concentrations were variable before and during pregnancy, but the magnitude of variability was biomarker specific. A single spot urine sample

  18. Sequential Measurement of Intermodal Variability in Public Transportation PM2.5 and CO Exposure Concentrations.

    PubMed

    Che, W W; Frey, H Christopher; Lau, Alexis K H

    2016-08-16

    A sequential measurement method is demonstrated for quantifying the variability in exposure concentration during public transportation. This method was applied in Hong Kong by measuring PM2.5 and CO concentrations along a route connecting 13 transportation-related microenvironments within 3-4 h. The study design takes into account ventilation, proximity to local sources, area-wide air quality, and meteorological conditions. Portable instruments were compacted into a backpack to facilitate measurement under crowded transportation conditions and to quantify personal exposure by sampling at nose level. The route included stops next to three roadside monitors to enable comparison of fixed site and exposure concentrations. PM2.5 exposure concentrations were correlated with the roadside monitors, despite differences in averaging time, detection method, and sampling location. Although highly correlated in temporal trend, PM2.5 concentrations varied significantly among microenvironments, with mean concentration ratios versus roadside monitor ranging from 0.5 for MTR train to 1.3 for bus terminal. Measured inter-run variability provides insight regarding the sample size needed to discriminate between microenvironments with increased statistical significance. The study results illustrate the utility of sequential measurement of microenvironments and policy-relevant insights for exposure mitigation and management.

  19. Causes of variability in concentrations and diastereomer patterns of hexabromocyclododecanes in indoor dust.

    PubMed

    Harrad, Stuart; Abdallah, Mohamed Abou-Elwafa; Covaci, Adrian

    2009-04-01

    The temporal evolution of concentrations of alpha-, beta-, and gamma-hexabromocyclododecanes (HBCDs), and pentabromocyclododecenes (PBCDs--degradation products of HBCDs) was studied in separate aliquots of a well-homogenized indoor dust sample. These were: (a) exposed to natural light, and (b) kept in the dark. Results revealed a rapid photolytically-mediated shift from gamma-HBCD to alpha-HBCD that was complete after 1 week of exposure, and a slower degradative loss of HBCDs via elimination of HBr. Under the specific conditions studied in this experiment, calculated half-lives (t(1/2)) showed the decay in SigmaHBCDs concentration was faster in light-exposed samples (t(1/2)=12 weeks), than in light-shielded dust (t(1/2)=26 weeks). Within-room spatial and temporal variability in concentrations and diastereomer patterns were studied in six and three rooms respectively. While in some rooms, little variability was detected, in others it was substantial. In one room, concentrations of SigmaHBCDs and the relative abundance of gamma-HBCD declined dramatically with increasing distance from a TV. The same TV appears to have influenced strongly the temporal variation in that room; with higher concentrations observed in its presence and when the TV was moved closer to the area sampled. Significant negative correlation was observed in one room between concentrations of SigmaHBCDs and dust loading (g dust m(-2) floor), implying "dilution" occurs at higher dust loadings.

  20. Winter monsoon variability and its impact on aerosol concentrations in East Asia.

    PubMed

    Jeong, Jaein I; Park, Rokjin J

    2017-02-01

    We investigate the relationship between winter aerosol concentrations over East Asia and variability in the East Asian winter monsoon (EAWM) using GEOS-Chem 3-D global chemical transport model simulations and ground-based aerosol concentration data. We find that both observed and modeled surface aerosol concentrations have strong relationships with the intensity of the EAWM over northern (30-50°N, 100-140°E) and southern (20-30°N, 100-140°E) East Asia. In strong winter monsoon years, compared to weak winter monsoon years, lower and higher surface PM2.5 concentrations by up to 25% are shown over northern and southern East Asia, respectively. Analysis of the simulated results indicates that the southward transport of aerosols is a key process controlling changes in aerosol concentrations over East Asia associated with the EAWM. Variability in the EAWM is found to play a major role in interannual variations in aerosol concentrations; consequently, changes in the EAWM will be important for understanding future changes in wintertime air quality over East Asia.

  1. Determination of water quality variables, endotoxin concentration, and Enterobacteriaceae concentration and identification in southern High Plains dairy lagoons.

    PubMed

    Purdy, C W; Clark, R N; Straus, D C

    2010-04-01

    The objectives of this study were to determine the concentration of endotoxin, determine 20 water quality variables, and identify and enumerate fungal and bacterial pathogens from United States southern High Plains dairy lagoons and control lakes during summer and winter. Water samples were collected in triplicate from the north, south, east, and west quadrants of each body of water. The mean (+/- SEM) winter dairy lagoon endotoxin concentration was significantly higher (9,678+/-1,834 ng/mL) than the summer concentration (3,220+/-810 ng/mL). The mean endotoxin concentration of the 2 control lakes (summer: 58.1+/-8.8 ng/mL; winter: 38.6+/-4.2 ng/mL) was significantly less than that of the dairy lagoons. Two hundred-one Salmonella enterica spp. isolates were identified, 7 serovars were recovered from the dairy lagoons, and 259 Salmonella ssp. were identified from 5 other dairy locations (milk barn, ditch effluent, settling basin, feed alley pad flush, and center pivots). Twenty-eight Salmonella spp. were identified from center pivot water. Escherichia coli O157:H7 pathogens were isolated from other dairy locations but not from lagoons. Neither Salmonella spp. nor E. coli O157:H7 were identified from control lakes. Enterobacteriaceae opportunistic pathogens were isolated from both dairies and control lakes. Important mesophilic and thermophilic catabolic (to manure biosolids) fungal isolates were identified from dairy effluent locations, but no thermophilic fungal isolates were cultured from the control lakes. Adequate curing of green forage following center pivot irrigation is important to kill lagoon water enteric pathogens, even though the lagoon water is mixed with fresh water. Recirculating lagoon water to flush the feed alley pad, where cows stand while eating, to remove manure and using lagoon water to abate dairy dust in loafing pens and unimproved dairy roads is inconsistent with good environmental practice management.

  2. Effect of variable viscosity and thermal conductivity on high-speed slip flow between concentric cylinders

    NASA Technical Reports Server (NTRS)

    Lin, T C; Street, R E

    1954-01-01

    Schamberg was the first to solve the differential equations of slip flow, including the Burnett terms, for concentric circular cylinders assuming constant coefficients of viscosity and thermal conductivity. The problem is solved for variable coefficients of viscosity and thermal conductivity in this paper by applying a transformation which leads to an iteration method. Starting with the solution for constant coefficients, this method enables one to approximate the solution for variable coefficients very closely after one or two steps. Satisfactory results are shown to follow from Schamberg's solution by using his values of constant coefficients multiplied by a constant factor, leading to what are denoted as the effective coefficients of viscosity and thermal conductivity.

  3. Variability of serum indomethacin concentrations after oral and intravenous administration to preterm infants.

    PubMed

    Mrongovius, R; Imbeck, H; Wille, L; Müller, H; Seyberth, H W

    1982-03-01

    Fifteen preterm infants with patent ductus arteriosus and respiratory distress syndrome were given indomethacin (0.2 mg/kg) at 12 h intervals up to three times, either orally or intravenously, in an uncontrolled, non-randomized study. Serum indomethacin concentrations were determined in blood samples taken 12 h after dosing. There was considerable variability in the serum indomethacin concentrations, especially after oral administration, although the mean concentrations after each of the three doses were similar after both oral and intravenous administration. The frequency of closures and transient closures of the ductus arteriosus was also similar for both routes of administration. There was, however, no relation between concentration and effect in individual patients. The sustained exposure to indomethacin which appears to be necessary for ductal closure can sometimes be attained by oral administration.

  4. Why are the PCB concentrations of salmonine individuals from the same lake so highly variable?

    USGS Publications Warehouse

    Madenjian, Charles P.; Carpenter, Stephen R.; Rand, Peter S.

    1994-01-01

    An individual-based model (IBM) was applied to the Lake Michigan rainbow trout (Oncorhynchus mykiss) population, with the objectives of explaining the observed variation in growth and in polychlorinated biphenyl (PCB) concentration within the population. When variation in prey PCB concentration was incorporated into the model, variability in PCB concentration among individual rainbow trout was fully explained by the IBM. Although number of spawnings and number of years spent in a stream prior to first entering the lake were factors in determining growth, these life history characteristics appeared to have only a minor impact on PCB accumulation rate in rainbow trout. The IBM application to the rainbow trout population was compared with an application to the Lake Michigan lake trout (Salvelinus namaycush) population. Modeling results indicated that the lower observed PCB concentrations in rainbow trout compared with lake trout were chiefly due to greater longevity in lake trout. The IBM simulations identified gross growth efficiency, assimilation efficiency of PCBs from food, and diet as other important sources of variability in salmonine PCB concentrations.

  5. Energy efficient fluid powered linear actuator with variable area and concentric chambers

    DOEpatents

    Lind, Randall F.; Love, Lonnie J.

    2016-11-15

    Hydraulic actuation systems having concentric chambers, variable displacements and energy recovery capabilities include cylinders with pistons disposed inside of barrels. When operating in energy consuming modes, high speed valves pressurize extension chambers or retraction chambers to provide enough force to meet or counteract an opposite load force. When operating in energy recovery modes, high speed valves return a working fluid from extension chambers or retraction chambers, which are pressurized by a load, to an accumulator for later use.

  6. Adaptation by macrophytes to inorganic carbon down a river with naturally variable concentrations of CO2.

    PubMed

    Maberly, S C; Berthelot, S A; Stott, A W; Gontero, B

    2015-01-01

    The productivity and ecological distribution of freshwater plants can be controlled by the availability of inorganic carbon in water despite the existence of different mechanisms to ameliorate this, such as the ability to use bicarbonate. Here we took advantage of a short, natural gradient of CO2 concentration, against a background of very high and relatively constant concentration of bicarbonate, in a spring-fed river, to study the effect of variable concentration of CO2 on the ability of freshwater plants to use bicarbonate. Plants close to the source, where the concentration of CO2 was up to 24 times air equilibrium, were dominated by Berula erecta. pH-drift results and discrimination against (13)C were consistent with this and the other species being restricted to CO2 and unable to use the high concentration of bicarbonate. There was some indication from stable (13)C data that B. erecta may have had access to atmospheric CO2 at low water levels. In contrast, species downstream, where concentrations of CO2 were only about 5 times air-equilibrium were almost exclusively able to use bicarbonate, based on pH-drift results. Discrimination against (13)C was also consistent with bicarbonate being the main source of inorganic carbon for photosynthesis in these species. There was, therefore, a transect downstream from the source of increasing ability to use bicarbonate that closely matched the decreasing concentration of CO2. This was produced largely by altered species composition, but partly by phenotypic changes in individual species.

  7. Spatial variability of soil gas concentration and methane oxidation capacity in landfill covers.

    PubMed

    Röwer, Inga Ute; Geck, Christoph; Gebert, Julia; Pfeiffer, Eva-Maria

    2011-05-01

    In order to devise design criteria for biocovers intended to enhance the microbial oxidation of landfill methane it is critical to understand the factors influencing gas migration and methane oxidation in landfill cover soils. On an old municipal solid waste landfill in north-western Germany soil gas concentrations (10, 40, 90 cm depth), topsoil methane oxidation capacity and soil properties were surveyed at 40 locations along a 16 m grid. As soil properties determine gas flow patterns it was hypothesized that the variability in soil gas composition and the subsequent methanotrophic activity would correspond to the variability of soil properties. Methanotrophic activity was found to be subject to high spatial variability, with values ranging between 0.17 and 9.80 g CH(4)m(-2)h(-1)(.) Considering the current gas production rate of 0.03 g CH(4)m(-2)h(-1), the oxidation capacity at all sampled locations clearly exceeded the flux to the cover, and can be regarded as an effective instrument for mitigating methane fluxes. The methane concentration in the cover showed a high spatial heterogeneity with values between 0.01 and 0.32 vol.% (10 cm depth), 22.52 vol.% (40 cm), and 36.85 vol.% (90 cm). The exposure to methane raised the oxidation capacity, suggested by a statistical correlation to an increase in methane concentration at 90 cm depth. Methane oxidation capacity was further affected by the methanotroph bacteria pH optimum and nutrient availability, and increased with decreasing pH towards neutrality, and increased with soluble ion concentration). Soil methane and carbon dioxide concentration increased with lower flow resistance of the cover, as represented by the soil properties of a reduced bulk density, increase in air capacity and in relative ground level.

  8. Extreme infrared variables from UKIDSS - I. A concentration in star-forming regions

    NASA Astrophysics Data System (ADS)

    Contreras Peña, C.; Lucas, P. W.; Froebrich, D.; Kumar, M. S. N.; Goldstein, J.; Drew, J. E.; Adamson, A.; Davis, C. J.; Barentsen, G.; Wright, N. J.

    2014-04-01

    We present initial results of the first panoramic search for high-amplitude near-infrared variability in the Galactic plane. We analyse the widely separated two-epoch K-band photometry in the fifth and seventh data releases of the UKIDSS Galactic plane survey. We find 45 stars with ΔK > 1 mag, including two previously known OH/IR stars and a Nova. Even though the mid-plane is not yet included in the data set, we find the majority (66 per cent) of our sample to be within known star-forming regions (SFRs), with two large concentrations in the Serpens OB2 association (11 stars) and the Cygnus-X complex (12 stars). Sources in SFRs show spectral energy distributions that support classification as young stellar objects (YSOs). This indicates that YSOs dominate the Galactic population of high-amplitude infrared variable stars at low luminosities and therefore likely dominate the total high-amplitude population. Spectroscopic follow up of the DR5 sample shows at least four stars with clear characteristics of eruptive pre-main-sequence variables, two of which are deeply embedded. Our results support the recent concept of eruptive variability comprising a continuum of outburst events with different time-scales and luminosities, but triggered by a similar physical mechanism involving unsteady accretion. Also, we find what appears to be one of the most variable classical Be stars.

  9. Spatio-Temporal Variability in Fecal Indicator Bacteria Concentrations at Huntington Beach: Connections to Physical Forcing

    NASA Astrophysics Data System (ADS)

    Rippy, M. A.; Feddersen, F.; Leichter, J.; Omand, M.; Moore, D. F.; McGee, C.; Franks, P. J.

    2007-05-01

    Two major factors determine the spatial and temporal distributions of fecal indicator bacteria (FIB) at a given beach: local circulation & mixing patterns, and bacterial inactivation rates. High frequency and spatial resolution bacterial sampling combined with measurements of physical processes can be used to infer inactivation rates, enabling differentiation between dilution & mortality as factors driving variability in nearshore FIB abundance. A FIB sampling experiment (HB06) took place on 16 October 2006, at Huntington State Beach, a site selected due to its persistent problems with FIB pollution. Water samples were taken at 20-minute intervals (from 6:50am to 11:50am) at ten locations; four in an alongshore transect spanning 1 km at the shoreline, and the remainder in a 300-m long cross-shore transect. All samples were analyzed for FIB concentration (Total Coliforms, E. coli & Enterococci) and, for a subset, species level Enterococcus composition was determined. As part of the HB06 experiment, currents, temperature, waves, and chlorophyll fluorescence were measured simultaneously in the cross-shore direction with rapid CTD casts 300 m offshore. Results indicate that E. coli and Enterococcus concentrations exhibit exponential decreases with time, with smaller decay rates associated with depth and with sites in the Talbert Marsh and Santa Ana River. FIB concentrations are also noticeably lower farther offshore (300 m). Spatio-temporal patterns in FIB concentration will be presented in conjunction with the nearshore physical data allowing the relationship between physical dynamics and biological variability to be addressed.

  10. Quantitative Imaging and In Situ Concentration Measurements of Quantum Dot Nanomaterials in Variably Saturated Porous Media

    DOE PAGES

    Uyuşur, Burcu; Snee, Preston T.; Li, Chunyan; ...

    2016-01-01

    Knowledge of the fate and transport of nanoparticles in the subsurface environment is limited, as techniques to monitor and visualize the transport and distribution of nanoparticles in porous media and measure their in situ concentrations are lacking. To address these issues, we have developed a light transmission and fluorescence method to visualize and measure in situ concentrations of quantum dot (QD) nanoparticles in variably saturated environments. Calibration cells filled with sand as porous medium and various known water saturation levels and QD concentrations were prepared. By measuring the intensity of the light transmitted through porous media exposed to fluorescent lightmore » and by measuring the hue of the light emitted by the QDs under UV light exposure, we obtained simultaneously in situ measurements of water saturation and QD nanoparticle concentrations with high spatial and temporal resolutions. Water saturation was directly proportional to the light intensity. A linear relationship was observed between hue-intensity ratio values and QD concentrations for constant water saturation levels. The advantages and limitations of the light transmission and fluorescence method as well as its implications for visualizing and measuring in situ concentrations of QDs nanoparticles in the subsurface environment are discussed.« less

  11. Variability of mercury concentrations in domestic well water, New Jersey Coastal Plain

    USGS Publications Warehouse

    Szabo, Zoltan; Barringer, Julia L.; Jacobsen, Eric; Smith, Nicholas P; Gallagher, Robert A; Sites, Andrew

    2010-01-01

    Concentrations of total (unfiltered) mercury (Hg) exceed the Maximum Contaminant Level (2 µg/L) in the acidic water withdrawn by more than 700 domestic wells from the areally extensive unconfined Kirkwood-Cohansey aquifer system. Background concentrations of Hg generally are <0.01 µg/L. The source of the Hg contamination has been hypothesized to arise from Hg of pesticide-application, atmospheric, and geologic origin being mobilized by some component(s) of septic-system effluent or urban leachates in unsewered residential areas. Initial results at many affected wells were not reproducible upon later resampling despite rigorous quality assurance, prompting concerns that duration of well flushing could affect the Hg concentrations. A cooperative study by the U.S. Geological Survey and the New Jersey Department of Environmental Protection examined variability in Hg results during the flushing of domestic wells. Samples were collected at regular intervals (about 10 minutes) during flushing for eight domestic wells, until stabilization criteria was met for field-measured parameters; the Hg concentrations in the final samples ranged from about 0.0005 to 11 µg/L. Unfiltered Hg concentrations in samples collected during purging varied slightly, but particulate Hg concentration (unfiltered – filtered (0.45 micron capsule) concentration) typically was highly variable for each well, with no consistent pattern of increase or decrease in concentration. Surges of particulates probably were associated with pump cycling. Pre-pumping samples from the holding tanks generally had the lowest Hg concentrations among the samples collected at the well that day. Comparing the newly obtained results at each well to results from previous sampling indicated that Hg concentrations in water from the Hg-contaminated areas were generally greater among samples collected on different dates (long-term variations, months to years) than among samples collected on the same day (short

  12. Variability of chlorophyll-a concentration in the Gulf of Guinea and its relation to physical oceanographic variables

    NASA Astrophysics Data System (ADS)

    Nieto, Karen; Mélin, Frédéric

    2017-02-01

    The Gulf of Guinea represents a wide tract of the African coast with complex and rich coastal ecosystems undergoing various pressures. The seasonal variations of chlorophyll-a concentration (Chla) along the Gulf of Guinea (GoG) and their relations with physical oceanographic variables were analyzed using satellite observations covering the period 2002-2012. The effects of sea surface temperature (SST), sea level anomalies (SLA), winds, geostrophic currents, eddy kinetic energy (EKE), mesoscale eddies and fronts were considered on a monthly time scale. The analysis for each unit area was carried out on a chlorophyll index (IChla) computed as the product of the mean distance from the coast to the eutrophic threshold (1 mg m-3 isoline) and the average Chla in the eutrophic area. The study, based on satellite-derived Chla, was allowed by the unprecedented coverage given by the products distributed by the ESA Ocean Colour Climate Change Initiative (OC_CCI) resulting from the merging of data from several satellite missions. The physical variables served as potential predictors in a statistical Boosted Regression Tree (BRT) model. To account for the heterogeneous nature of the GoG, the analysis was conducted on eight systems that made up a partition of the whole region defined on the basis of the BRT model results and climatological properties. The western-most domain, from Guinea-Bissau to Sierra Leone, was associated with upwelling properties in boreal winter and appeared to share some characteristics with the overall Northwest African upwelling system. The region of Ivory Coast and Ghana also had upwelling properties but the main upwelling season was in boreal summer. In general upwelling conditions with cold SST, negative SLA, fairly strong frontal activity, and moderate winds, appeared as the environmental window most favorable to high IChla values. For these systems, the BRT model fitted the IChla data well with a percentage of explained total deviance D2 between 70

  13. Intra-seasonal variability of atmospheric CO2 concentrations over India during summer monsoons

    NASA Astrophysics Data System (ADS)

    Ravi Kumar, K.; Valsala, Vinu; Tiwari, Yogesh K.; Revadekar, J. V.; Pillai, Prasanth; Chakraborty, Supriyo; Murtugudde, Raghu

    2016-10-01

    In a study based on a data assimilation product of the terrestrial biospheric fluxes of CO2 over India, the subcontinent was hypothesized to be an anomalous source (sink) of CO2 during the active (break) spells of rain in the summer monsoon from June to September (Valsala et al., 2013). We test this hypothesis here by investigating intraseasonal variability in the atmospheric CO2 concentrations over India by utilizing a combination of ground-based and satellite observations and model outputs. The results show that the atmospheric CO2 concentration also varies in synchrony with the active and break spells of rainfall with amplitude of ±2 ppm which is above the instrumental uncertainty of the present day techniques of atmospheric CO2 measurements. The result is also consistent with the signs of the Net Ecosystem Exchange (NEE) flux anomalies estimated in our earlier work. The study thus offers the first observational affirmation of the above hypothesis although the data gap in the satellite measurements during monsoon season and the limited ground-based stations over India still leaves some uncertainty in the robust assertion of the hypothesis. The study highlights the need to capture these subtle variabilities and their responses to climate variability and change since it has implications for inverse estimates of terrestrial CO2 fluxes.

  14. Variability of CO2 concentrations and fluxes in and above an urban street canyon

    NASA Astrophysics Data System (ADS)

    Lietzke, Björn; Vogt, Roland

    2013-08-01

    The variability of CO2 concentrations and fluxes in dense urban environments is high due to the inherent heterogeneity of these complex areas and their spatio-temporally variable anthropogenic sources. With a focus on micro- to local-scale CO2-exchange processes, measurements were conducted in a street canyon in the city of Basel, Switzerland in 2010. CO2 fluxes were sampled at the top of the canyon (19 m) and at 39 m while vertical CO2 concentration profiles were measured in the center and at a wall of the canyon. CO2 concentration distributions in the street canyon and exchange processes with the layers above show, apart from expected general diurnal patterns due mixing layer heights, a strong dependence on wind direction relative to the canyon. As a consequence of the resulting corkscrew-like canyon vortex, accumulation of CO2 inside the canyon is modulated with distinct distribution patterns. The evaluation of diurnal traffic data provides good explanations for the vertical and horizontal differences in CO2-distribution inside the canyon. Diurnal flux characteristics at the top of the canyon can almost solely be explained with traffic density expressed by the strong linear dependence. Even the diurnal course of the flux at 39 m shows a remarkable relationship to traffic density for east wind conditions while, for west wind situations, a change toward source areas with lower emissions leads to a reduced flux.

  15. Multi-scale variability and long-range memory in indoor Radon concentrations from Coimbra, Portugal

    NASA Astrophysics Data System (ADS)

    Donner, Reik V.; Potirakis, Stelios; Barbosa, Susana

    2014-05-01

    The presence or absence of long-range correlations in the variations of indoor Radon concentrations has recently attracted considerable interest. As a radioactive gas naturally emitted from the ground in certain geological settings, understanding environmental factors controlling Radon concentrations and their dynamics is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we re-analyze two high-resolution records of indoor Radon concentrations from Coimbra, Portugal, each of which spans several months of continuous measurements. In order to evaluate the presence of long-range correlations and fractal scaling, we utilize a multiplicity of complementary methods, including power spectral analysis, ARFIMA modeling, classical and multi-fractal detrended fluctuation analysis, and two different estimators of the signals' fractal dimensions. Power spectra and fluctuation functions reveal some complex behavior with qualitatively different properties on different time-scales: white noise in the high-frequency part, indications of some long-range correlated process dominating time scales of several hours to days, and pronounced low-frequency variability associated with tidal and/or meteorological forcing. In order to further decompose these different scales of variability, we apply two different approaches. On the one hand, applying multi-resolution analysis based on the discrete wavelet transform allows separately studying contributions on different time scales and characterize their specific correlation and scaling properties. On the other hand, singular system analysis (SSA) provides a reconstruction of the essential modes of variability. Specifically, by considering only the first leading SSA modes, we achieve an efficient de-noising of our environmental signals, highlighting the low-frequency variations together with some distinct scaling on sub-daily time-scales resembling

  16. Occurrence and variability of iodinated trihalomethanes concentrations within two drinking-water distribution networks.

    PubMed

    Ioannou, Panagiotis; Charisiadis, Pantelis; Andra, Syam S; Makris, Konstantinos C

    2016-02-01

    Non-iodo-containing trihalomethanes (TTHM) are frequently detected in chlorinated tap water and currently regulated against their carcinogenic potential. Iodinated THM (ITHM) may also form in disinfected with chlorine waters that are high in iodine content, but little is known about their magnitude and variability within the drinking-water pipe distribution network of urban areas. The main objective of this study was to determine the magnitude and variability of ITHM and TTHM levels and their corresponding daily intake estimates within the drinking water distribution systems of Limassol and Nicosia cities of Cyprus, using tap samples collected from individual households (n=37). In Limassol, mean household tap water ITHM and TTHM levels was 0.58 and 38 μg L(-1), respectively. Dichloroiodomethane (DCIM) was the dominant species of the two measured ITHM compounds accounting for 77% of total ITHM and in the range of 0.032 and 1.65 μg L(-1). The range of DCIM concentrations in Nicosia tap water samples was narrower (0.032 - 0.848 μg L(-1)). Mean total iodine concentration in tap water samples from the seaside city of Limassol was 15 μg L(-1) and approximately twice to those observed in samples from the mainland Nicosia city. However, iodine concentrations did not correlate with the ITHM levels. The calculated chronic daily intake rates of ITHM were low when compared with those of TTHM, but because of their widespread occurrence in tap water and their enhanced mammalian cell toxicity, additional research is warranted to assess the magnitude and variability of human ITHM exposures.

  17. Ocular tissue concentrations of mitomycin C with variable dose and duration of application time in rabbits.

    PubMed

    Hara, T; Shirato, S; Suzuki, Y

    1998-01-01

    We measured mitomycin C (MMC) concentrations in ocular tissues in rabbits with variable dose (0.1, 0.2, or 0.4 mg) and duration of application time (1, 3, or 5 minutes) of MMC using high-performance liquid chromatography. Mitomycin C concentrations at the administered site after single subconjunctival application of MMC and after irrigation showed significant correlation with dose and duration of time of application. By multiple regression analysis, MMC concentrations (microg/g) at the conjunctiva were described as -6.73 + 67.4 x Dose (mg) + 1.66 x Time (minutes) (R2 0.65); at the sclera, -1.85 + 38.2 x Dose + 0.927 x Time (R2 0.63); at the cornea, -0.727 + 8.44 x Dose (R2 0.46). With a 0.2-mg MMC dose, in all three application times (1, 3, or 5 minutes), MMC concentrations in the conjunctiva at the administered quadrant were three times higher than in the neighboring quadrants and 6 to 7 times higher than in the opposite quadrant. In the sclera, MMC concentrations were 3.5 times higher than in the neighboring sites and over 8 to 9 times higher than in the opposite site. In the cornea, MMC concentrations were 2 to 3 times higher than in the neighboring sites and opposite site. In the iris-ciliary body, MMC concentrations were 0.61 microg/g at the administered site with 0.2 mg for 3-minute application, 2 times higher than in neighboring sites, and 2 times higher than in opposite sites.

  18. Seasonal and nonseasonal variability of satellite-derived surface pigment concentration in the California Current

    NASA Technical Reports Server (NTRS)

    Strub, P. Ted; James, Corinne; Thomas, Andrew C.; Abbott, Mark R.

    1990-01-01

    The large-scale patterns of satellite-derived surface pigment concentration off the west coast of North America are presented and are averaged into monthly mean surface wind fields over the California Current system (CCS) for the July 1979 to June 1986 period. The patterns are discussed in terms of both seasonal and nonseasonal variability for the indicated time period. The large-scale seasonal characteristics of the California Current are summarized. The data and methods used are described, and the problems known to affect the satellite-derived pigment concentrations and the wind data used in the study are discussed. The statistical analysis results are then presented and discussed in light of past observations and theory. Details of the CZCS data processing are described, and details of the principal estimator pattern methodology used here are given.

  19. Analysis of the influence of rainfall variables on urban effluents concentrations and fluxes in wet weather

    NASA Astrophysics Data System (ADS)

    Gooré Bi, Eustache; Monette, Frédéric; Gasperi, Johnny

    2015-04-01

    Urban rainfall runoff has been a topic of increasing importance over the past years, a result of both the increase in impervious land area arising from constant urban growth and the effects of climate change on urban drainage. The main goal of the present study is to assess and analyze the correlations between rainfall variables and common indicators of urban water quality, namely event mean concentrations (EMCs) and event fluxes (EFs), in order to identify and explain the impacts of each of the main rainfall variables on the generation process of urban pollutants during wet periods. To perform this analysis, runoff from eight summer rainfall events that resulted in combined sewer overflow (CSO) was sampled simultaneously from two distinct catchment areas in order to quantify discharges at the respective outfalls. Pearson statistical analysis of total suspended solids (TSS), chemical oxygen demand (COD), carbonaceous biochemical oxygen demand at 5 days (CBOD5), total phosphorus (Ptot) and total kedjal nitrogen (N-TKN) showed significant correlations (ρ = 0.05) between dry antecedent time (DAT) and EMCs on one hand, and between total rainfall (TR) and the volume discharged (VD) during EFs, on the other. These results show that individual rainfall variables strongly affect either EMCs or EFs and are good predictors to consider when selecting variables for statistical modeling of urban runoff quality. The results also show that in a combined sewer network, there is a linear relationship between TSS event fluxes and COD, CBOD5, Ptot, and N-TKN event fluxes; this explains 97% of the variability of these pollutants which adsorb onto TSS during wet weather, which therefore act as tracers. Consequently, the technological solution selected for TSS removal will also lead to a reduction of these pollutants. Given the huge volumes involved, urban runoffs contribute substantially to pollutant levels in receiving water bodies, a situation which, in a climate change context, may

  20. Spatial Variability of Arsenic Concentrations in two Villages in Araihazar Upazila, Narayanganj District of Bangladesh

    NASA Astrophysics Data System (ADS)

    Dhar, R.; Zheng, Y.; Zheng, Y.; Stute, M.; Stute, M.; van Geen, A.; Gavrieli, I.; Gavrieli, I.; Versteeg, R.; Versteeg, R.; Steckler, M.; Goodbred, S.; Horneman, A.; Simpson, H. J.; Ahmed, K. M.

    2001-05-01

    In the Ganges-Brahmaputra Delta, concentrations of arsenic in tube wells have been known to vary spatially on both the basin (tens of km) and the local (tens of meter) scale. Based on arsenic concentration measured in 5000 contiguous tube wells from Araihazar Upazila, 20 km east of Dhaka, we began to investigate the geological, hydrological and geochemical controls on the arsenic spatial heterogeneity in two villages on spatial scales of order 100 m in January, 2001. In Dari Satyabhadi village (23.785° N, 90.603° E), arsenic concentrations in 157 wells range from <5 ug/L to 800 ug/L (123 +/- 154 ug/L), with 51% of wells containing >50 ug/L. Arsenic concentrations in 124 wells from Baylakandi village (23.780° N, 90.640° E) range from 10 ug/L to 520 ug/L (266 +/- 95 ug/L), with 98% of wells above 50 ug/L. Sediment coring in both villages to 92 m depth recovered a fine-grained clay zone separating an upper, perhaps less confined aquifer and a lower, confined aquifer. In Dari Satyabhadi village, The clay is located between 13 m and 30 m, with a thin silty sand layer at 20.1-20.7 m and a peat layer at 20.7-21.4 m. Below the clay, all existing tube wells, as well as monitoring wells, are found to have arsenic concentrations <50 ug/L. In Baylakandi village, a clay layer was found at greater depth between 30 and 50 m, with a silty sand layer between 36 and 43 m. None of the existing tube wells are deeper than the clay in Baylakandi, but monitoring wells installed at 53 m and 92 m yield water containing <50 ug/L arsenic. Results from both villages suggest that a lower aquifer isolated by a clay layer from shallow, high-arsenic aquifer contains little arsenic. In contrast, there is, however, considerable spatial variability in arsenic concentrations in both villages within the upper aquifer. In Dari Satyabhadi, arsenic concentrations in 120 shallow wells (< 30 m) from the upper aquifer ranges from <5 ug/L to 800 ug/L (158 +/- 160 ug/L), with 66% of wells above 50 ug

  1. Factors controlling spatial variability of DOC concentrations in soil solution at European level

    NASA Astrophysics Data System (ADS)

    Camino Serrano, Marta; Janssens, Ivan; Luyssaert, Sebastiaan; Gielen, Bert; Guenet, Bertrand; De Vos, Bruno; Ciais, Philippe

    2013-04-01

    The lateral transport of dissolved organic carbon (DOC) is an important and not well-understood process linking terrestrial and aquatic ecosystems. Up to day very few Earth System Models (ESMs) represent explicitly this process despite its crucial role in the global carbon cycle. However, to be able to integrate DOC leaching in ESMs, more accurate information is needed in order to better understand and predict DOC dynamics. DOC concentrations mainly vary by geographical location, soil and vegetation types, topography, season and climate. Within this framework, a database was designed to compile data on DOC in soil solution at different depths in different ecosystems around the world, with special focus on European sites. The database contains information on 349 sites, with 304 being forest, gathered from published literature and datasets accessible on the internet. A substantial dataset was provided by International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests). The database also includes other meta-data related to the sites, such as land cover, soil properties, climate, annual water balance and other soil solution parameters. The analysis of the database has been focused on: 1) the study of the environmental and physical factors that are acting as drivers of DOC concentrations changes in soil solution across sites at European level , and 2) the DOC distribution through the soil profile and how this varies with different vegetation types and soil properties. The preliminary results show that variables related to biological processes (Dry weight of the organic layer, for example) are the most important in explaining the spatial distribution of the DOC concentration in soil solution at the European scale. However, the interactions between variables are complex and we will need further analysis in order to draw more robust conclusions. With regards to the vertical profile of DOC, we found that there is a

  2. Temporal Variability of Stemflow Dissolved Organic Carbon (DOC) Concentrations and Quality from Morphologically Contrasting Deciduous Canopies

    NASA Astrophysics Data System (ADS)

    van Stan, J. T.; Levia, D. F.; Inamdar, S. P.; Mitchell, M. J.; Mage, S. M.

    2010-12-01

    Dissolved organic carbon (DOC) inputs from canopy-derived hydrologic fluxes play a significant role in the terrestrial carbon budgets of forested ecosystems. However, no studies known to the authors have examined the variability of both DOC concentrations and quality for stemflow across time scales, nor has any study to date evaluated the effects of canopy structure on stemflow DOC characteristics. This investigation seeks to rectify this knowledge gap by examining the variability of stemflow DOC concentrations and quality across contrasting canopy morphologies and time scales (seasonal, storm and intrastorm). Bulk and intrastorm stemflow samples from a less dense, rough-barked, more plagiophile (Liriodendron tulipifera L. (tulip poplar)) and a denser, thin-barked, more erectophile (Fagus grandifolia Ehrh. (American beech)) canopy were collected and analyzed for DOC quality using metrics derived from UV-vis spectroscopy (E2:E3 ratio, SUVA254, select spectral slope (S), and spectral slope ratios (SR)). Our results suggest that stemflow DOC concentrations and quality change as crown architectural traits enhance or diminish hydrologic retention time within the canopy. The architecture of L. tulipifera canopies likely retards the flow of intercepted water, increasing chemical exchange with bark and foliar surfaces. UV-vis metrics indicated that this increased chemical exchange, particularly with bark surfaces, generally enhanced aromatic hydrocarbon content and increased molecular weight. Because leaf presence influenced DOC quality, stemflow DOC characteristics also varied seasonally in response to canopy condition. At the inter- and intrastorm scale, stemflow DOC concentration and quality varied with meteorological and antecedent canopy conditions. Since recent studies have linked stemflow production to preferential subsurface transport of dissolved chemistries, trends in DOC speciation and fluxes described in this study may impact soil environments within wooded

  3. Improving the Accuracy of Laplacian Estimation with Novel Variable Inter-Ring Distances Concentric Ring Electrodes

    PubMed Central

    Makeyev, Oleksandr; Besio, Walter G.

    2016-01-01

    Noninvasive concentric ring electrodes are a promising alternative to conventional disc electrodes. Currently, the superiority of tripolar concentric ring electrodes over disc electrodes, in particular, in accuracy of Laplacian estimation, has been demonstrated in a range of applications. In our recent work, we have shown that accuracy of Laplacian estimation can be improved with multipolar concentric ring electrodes using a general approach to estimation of the Laplacian for an (n + 1)-polar electrode with n rings using the (4n + 1)-point method for n ≥ 2. This paper takes the next step toward further improving the Laplacian estimate by proposing novel variable inter-ring distances concentric ring electrodes. Derived using a modified (4n + 1)-point method, linearly increasing and decreasing inter-ring distances tripolar (n = 2) and quadripolar (n = 3) electrode configurations are compared to their constant inter-ring distances counterparts. Finite element method modeling and analytic results are consistent and suggest that increasing inter-ring distances electrode configurations may decrease the truncation error resulting in more accurate Laplacian estimates compared to respective constant inter-ring distances configurations. For currently used tripolar electrode configuration, the truncation error may be decreased more than two-fold, while for the quadripolar configuration more than a six-fold decrease is expected. PMID:27294933

  4. Determinants and Within-Person Variability of Urinary Cadmium Concentrations among Women in Northern California

    PubMed Central

    Gunier, Robert B.; Horn-Ross, Pamela L.; Canchola, Alison J.; Duffy, Christine N.; Reynolds, Peggy; Hertz, Andrew; Garcia, Erika

    2013-01-01

    Background: Cadmium (Cd) is a toxic metal associated with increased morbidity and mortality. Urinary Cd (U-Cd) concentration is considered a biomarker of long-term exposure. Objectives: Our objectives were to evaluate the within-person correlation among repeat samples and to identify predictors of U-Cd concentrations. Methods: U-Cd concentrations (micrograms per liter) were measured in 24-hr urine samples collected from 296 women enrolled in the California Teachers Study in 2000 and a second 24-hr sample collected 3–9 months later from 141 of the participants. Lifestyle and sociodemographic characteristics were obtained via questionnaires. The Total Diet Study database was used to quantify dietary cadmium intake based on a food frequency questionnaire. We estimated environmental cadmium emissions near participants’ residences using a geographic information system. Results: The geometric mean U-Cd concentration was 0.27 µg/L and the range was 0.1–3.6 µg/L. The intraclass correlation among repeat samples from an individual was 0.50. The use of a single 24-hr urine specimen to characterize Cd exposure in a case–control study would result in an observed odds ratio of 1.4 for a true odds ratio of 2.0. U-Cd concentration increased with creatinine, age, and lifetime pack-years of smoking among ever smokers or lifetime intensity-years of passive smoking among nonsmokers, whereas it decreased with greater alcohol consumption and number of previous pregnancies. These factors explained 42–44% of the variability in U-Cd concentrations. Conclusion: U-Cd levels varied with several individual characteristics, and a single measurement of U-Cd in a 24-hr sample did not accurately reflect medium- to long-term body burden. PMID:23552363

  5. Variability of residue concentrations of ciprofloxacin in honey from treated hives.

    PubMed

    Chan, Danny; Macarthur, Roy; Fussell, Richard J; Wilford, Jack; Budge, Giles

    2017-04-01

    Honey bees (Apis mellifera L.) were treated with a model veterinary drug compound (ciprofloxacin) in a 3-year study (2012-14) to investigate the variability of residue concentration in honey. Sucrose solution containing ciprofloxacin was administered to 45 hives (1 g of ciprofloxacin per hive) at the beginning of the honey flow in late May/mid-June 2012, 2013 and 2014. Buckfast honey bees (A. mellifera - hybrid) were used in years 2012 and 2013. Carniolan honey bees (A. mellifera carnica) were used instead of the Buckfast honey bees as a replacement due to unforeseen circumstances in the final year of the study (2014). Honey was collected over nine scheduled time points from May/June till late October each year. Up to five hives were removed and their honey analysed per time point. Honey samples were analysed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine ciprofloxacin concentration. Statistical assessment of the data shows that the inter-hive variation of ciprofloxacin concentrations in 2012/13 is very different compared with that of 2014 with relative standard deviations (RSDs) of 138% and 61%, respectively. The average ciprofloxacin concentration for 2014 at the last time point was more than 10 times the concentration compared with samples from 2012/13 at the same time point. The difference between the 2012/13 data compared with the 2014 data is likely due to the different type of honey bees used in this study (2012/13 Buckfast versus 2014 Carniolan). Uncertainty estimates for honey with high ciprofloxacin concentration (upper 95th percentile) across all hives for 55-day withdrawal samples gave residual standard errors (RSEs) of 22%, 20% and 11% for 2012, 2013 and 2014, respectively. If the number of hives were to be reduced for future studies, RSEs were estimated to be 52% (2012), 54% (2013) and 26% (2014) for one hive per time point (nine total hives).

  6. Equilibrium and dynamic osmotic behaviour of aqueous solutions with varied concentration at constant and variable volume.

    PubMed

    Minkov, Ivan L; Manev, Emil D; Sazdanova, Svetla V; Kolikov, Kiril H

    2013-01-01

    Osmosis is essential for the living organisms. In biological systems the process usually occurs in confined volumes and may express specific features. The osmotic pressure in aqueous solutions was studied here experimentally as a function of solute concentration (0.05-0.5 M) in two different regimes: of constant and variable solution volume. Sucrose, a biologically active substance, was chosen as a reference solute for the complex tests. A custom made osmotic cell was used. A novel operative experimental approach, employing limited variation of the solution volume, was developed and applied for the purpose. The established equilibrium values of the osmotic pressure are in agreement with the theoretical expectations and do not exhibit any evident differences for both regimes. In contrast, the obtained kinetic dependences reveal striking divergence in the rates of the process at constant and varied solution volume for the respective solute concentrations. The rise of pressure is much faster at constant solution volume, while the solvent influx is many times greater in the regime of variable volume. The results obtained suggest a feasible mechanism for the way in which the living cells rapidly achieve osmotic equilibrium upon changes in the environment.

  7. Cadmium concentrations in new zealand pastures: relationships to soil and climate variables.

    PubMed

    Reiser, René; Simmler, Michael; Portmann, Denise; Clucas, Lynne; Schulin, Rainer; Robinson, Brett

    2014-05-01

    Cadmium (Cd) is a nonessential element that occurs at above-background concentrations in many New Zealand (NZ) soils. Most of this Cd is due to the historical application of single superphosphate that was made from Nauru phosphate rock containing between 400 and 600 mg Cd kg P. Pasture Cd uptake exacerbates the entry of Cd into animal products. We sought to determine the critical environmental factors affecting Cd uptake in NZ pastures and to calculate the likely Cd intake of sheep and cattle. We tested 69 pastures throughout NZ for a range of variables, including Cd. Soil Cd and pasture Cd were positively correlated with soil P and soil concentrations of other elements found in phosphate fertilizers. We found that no single environmental variable adequately predicted pasture Cd uptake. Nevertheless, pseudo-total soil Cd and Cd extracted using a 0.05 mol L Ca(NO) solution were positively correlated with pasture Cd. Although soil pH, soil Fe, and soil Cd provided an excellent predictor of the Ca(NO)-extractable soil Cd fraction, regression models explained just 38% of the variation of the Cd concentration in pasture grasses. Incorporating the effect of pasture species composition is a crucial next step in improving these models. A calculation of the likely exposure to Cd of sheep and cattle revealed that no pastures tested resulted in sheep and cattle ingesting Cd at a rate that would result in breaching muscle-tissue food standards. For offal products, which the NZ meat industry does not sell for human consumption, food safety standards exceedence was calculated in a few cases.

  8. Dust deposition and ambient PM10 concentration in northwest China: spatial and temporal variability

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao-Xiao; Sharratt, Brenton; Chen, Xi; Wang, Zi-Fa; Liu, Lian-You; Guo, Yu-Hong; Li, Jie; Chen, Huan-Sheng; Yang, Wen-Yi

    2017-02-01

    Eolian dust transport and deposition are important geophysical processes which influence global bio-geochemical cycles. Currently, reliable deposition data are scarce in central and east Asia. Located at the boundary of central and east Asia, Xinjiang Province of northwestern China has long played a strategic role in cultural and economic trade between Asia and Europe. In this paper, we investigated the spatial distribution and temporal variation in dust deposition and ambient PM10 (particulate matter in aerodynamic diameter ≤ 10 µm) concentration from 2000 to 2013 in Xinjiang Province. This variation was assessed using environmental monitoring records from 14 stations in the province. Over the 14 years, annual average dust deposition across stations in the province ranged from 255.7 to 421.4 t km-2. Annual dust deposition was greater in southern Xinjiang (663.6 t km-2) than northern (147.8 t km-2) and eastern Xinjiang (194.9 t km-2). Annual average PM10 concentration across stations in the province varied from 100 to 196 µg m-3 and was 70, 115 and 239 µg m-3 in northern, eastern and southern Xinjiang, respectively. The highest annual dust deposition (1394.1 t km-2) and ambient PM10 concentration (352 µg m-3) were observed in Hotan, which is located in southern Xinjiang and at the southern boundary of the Taklamakan Desert. Dust deposition was more intense during the spring and summer than other seasons. PM10 was the main air pollutant that significantly influenced regional air quality. Annual average dust deposition increased logarithmically with ambient PM10 concentration (R2 ≥ 0.81). While the annual average dust storm frequency remained unchanged from 2000 to 2013, there was a positive relationship between dust storm days and dust deposition and PM10 concentration across stations. This study suggests that sand storms are a major factor affecting the temporal variability and spatial distribution of dust deposition in northwest China.

  9. Point source pollution and variability of nitrate concentrations in water from shallow aquifers

    NASA Astrophysics Data System (ADS)

    Nemčić-Jurec, Jasna; Jazbec, Anamarija

    2016-01-01

    Agriculture is one of the several major sources of nitrate pollution, and therefore the EU Nitrate Directive, designed to decrease pollution, has been implemented. Point sources like septic systems and broken sewage systems also contribute to water pollution. Pollution of groundwater by nitrate from 19 shallow wells was studied in a typical agricultural region, middle Podravina, in northwest Croatia. The concentration of nitrate ranged from <0.1 to 367 mg/l in water from wells, and 29.8 % of 253 total samples were above maximum acceptable value of 50 mg/l (MAV). Among regions R1-R6, there was no statistically significant difference in nitrate concentrations (F = 1.98; p = 0.15) during the years 2002-2007. Average concentrations of nitrate in all 19 wells for all the analyzed years were between recommended limit value of 25 mg/l (RLV) and MAV except in 2002 (concentration was under RLV). The results of the repeated measures ANOVA showed statistically significant differences between the wells at the point source distance (proximity) of <10 m, compared to the wells at the point source distance of >20 m (F = 10.6; p < 0.001). Average annual concentrations of nitrate during the years studied are not statistically different, but interaction between proximity and years is statistically significant (F = 2.07; p = 0.04). Results of k-means clustering confirmed division into four clusters according to the pollution. Principal component analysis showed that there is only one significant factor, proximity, which explains 91.6 % of the total variability of nitrate. Differences in water quality were found as a result of different environmental factors. These results will contribute to the implementation of the Nitrate Directive in Croatia and the EU.

  10. Spatial and temporal variability of trace element concentrations in an urban subtropical watershed, Honolulu, Hawaii

    USGS Publications Warehouse

    Heinen, De Carlo E.; Anthony, S.S.

    2002-01-01

    Trace metal concentrations in soils and in stream and estuarine sediments from a subtropical urban watershed in Hawaii are presented. The results are placed in the context of historical studies of environmental quality (water, soils, and sediment) in Hawaii to elucidate sources of trace elements and the processes responsible for their distribution. This work builds on earlier studies on sediments of Ala Wai Canal of urban Honolulu by examining spatial and temporal variations in the trace elements throughout the watershed. Natural processes and anthropogenic activity in urban Honolulu contribute to spatial and temporal variations of trace element concentrations throughout the watershed. Enrichment of trace elements in watershed soils result, in some cases, from contributions attributed to the weathering of volcanic rocks, as well as to a more variable anthropogenic input that reflects changes in land use in Honolulu. Varying concentrations of As, Cd, Cu, Pb and Zn in sediments reflect about 60 a of anthropogenic activity in Honolulu. Land use has a strong impact on the spatial distribution and abundance of selected trace elements in soils and stream sediments. As noted in continental US settings, the phasing out of Pb-alkyl fuel additives has decreased Pb inputs to recently deposited estuarine sediments. Yet, a substantial historical anthropogenic Pb inventory remains in soils of the watershed and erosion of surface soils continues to contribute to its enrichment in estuarine sediments. Concentrations of other elements (e.g., Cu, Zn, Cd), however, have not decreased with time, suggesting continued active inputs. Concentrations of Ba, Co, Cr, Ni, V and U, although elevated in some cases, typically reflect greater proportions attributed to natural sources rather than anthropogenic input. ?? 2002 Elsevier Science Ltd. All rights reserved.

  11. Variability in Saponin Content, Cancer Antiproliferative Activity and Physicochemical Properties of Concentrated Agave Sap.

    PubMed

    Santos-Zea, Liliana; Rosas-Pérez, Aratza Mireya; Leal-Díaz, Ana María; Gutiérrez-Uribe, Janet A

    2016-08-01

    Concentrated agave sap (CAS) has gained popularity as an unrefined sweetener. It is obtained by boiling "aguamiel" that contains phytochemicals with diverse bioactivities. Saponins have been the most widely studied agave phytochemicals due to their cancer antiproliferative effect but their concentration may vary due to maturity of the agave plant and collection site. In this study, 18 CAS samples produced in different states of Mexico were analyzed using multivariate methods to determine which physicochemical or phytochemical parameters were responsible for variation. Additionally, extracts with different saponin profiles were tested to determine possible correlations with antiproliferative activity. Total soluble solids, pH, and water activity were similar to those reported for other agave sweeteners. Antioxidant capacity of samples was correlated to browning index. Eleven steroidal saponins were found in CAS samples and they were the main source of variability. Magueyoside B, a kammogenin tetraglycoside, was the most abundant saponin in all samples. With respect to bioactivity, multivariate analysis indicated that magueyoside B and a gentrogenin tetraglycoside were compounds strongly related with bioactivity. CAS from Hidalgo, Puebla, and Veracruz had higher concentration of magueyoside B than from the other kamogenin tetraglycoside found in the samples from other Mexican states. These results could be used as a first approach to characterize and standardize CAS to validate the potential health benefits derived from its consumption.

  12. Long-term variability of surface nutrient concentrations in the North Pacific

    NASA Astrophysics Data System (ADS)

    Yasunaka, S.; Ono, T.; Nojiri, Y.; Whitney, F. A.; Wada, C.; Murata, A.; Nakaoka, S.; Hosoda, S.

    2016-04-01

    We present the spatial distributions and temporal changes of the long-term variability of surface nutrient concentrations in the North Pacific by using nutrient samples collected by volunteer ships and research vessels from 1961 to 2012. Nutrient samples are optimally interpolated onto 1° × 1° monthly grid boxes. When the Pacific Decadal Oscillation is in its positive phase, nutrient concentrations in the western North Pacific are significantly higher than the climatological means, and those in the eastern North Pacific are significantly lower. When the North Pacific Gyre Oscillation is in its positive phase, nutrient concentrations in the subarctic are significantly higher than the climatological means. The trends of phosphate and silicate averaged over the North Pacific are -0.012 ± 0.005 µmol l-1 decade-1 and -0.38 ± 0.13 µmol l-1 decade-1, whereas the nitrate trend is not significant (0.01 ± 0.13 µmol l-1 decade-1).

  13. Food safety objectives should integrate the variability of the concentration of pathogen.

    PubMed

    Rieu, Emilie; Duhem, Koenraad; Vindel, Elisabeth; Sanaa, Moez

    2007-04-01

    The World Trade Organization introduced the concept of appropriate level of protection (ALOP) as a public health target. For this public health objective to be interpretable by the actors in the food chain, the concept of food safety objective (FSO) was proposed by the International Commission on Microbiological Specifications for Foods and adopted later by the Codex Alimentarius Food Hygiene Committee. The way to translate an ALOP into a FSO is still in debate. The purpose of this article is to develop a methodological tool to derive a FSO from an ALOP being expressed as a maximal annual marginal risk. We explore the different models relating the annual marginal risk to the parameters of the FSO depending on whether the variability in the survival probability and in the concentration of the pathogen are considered or not. If they are not, determination of the FSO is straightforward. If they are, we propose to use stochastic Monte Carlo simulation models and logistic discriminant analysis in order to determine which sets of parameters are compatible with the ALOP. The logistic discriminant function was chosen such that the kappa coefficient is maximized. We illustrate this method by the example of the risks of listeriosis and salmonellosis in one type of soft cheese. We conclude that the definition of the FSO should integrate three dimensions: the prevalence of contamination, the average concentration per contaminated typical serving, and the dispersion of the concentration among those servings.

  14. Variability of concentration and composition of hydrocarbons in frontal zones of the Kara Sea

    NASA Astrophysics Data System (ADS)

    Nemirovskaya, I. A.

    2015-07-01

    The distribution and composition of aliphatic and polycyclic aromatic hydrocarbons (HC) in dissolved and particulate forms, as well as in bottom sediments, was studied along the route of a vessel and at stations. It was found that the widest variability of HC concentrations in surface waters was characteristic for the frontal zones of the Yenisei River mouth (4.8-69 µg/L) and for the western branch of the St. Anna Trough (5.5-80.4 µg/L). The increased concentrations of aliphatic HC coincide with those of chlorophyll and particulate matter, as well as with the growth of the intensity of fluorescence, and are caused by natural processes. This is confirmed by HC composition. Bottom sediments are characterized by low HC concentrations, both in terms of dry mass (14 µg/g on average, with the maximum of 36.8 µg/g at station 5018 in the layer of 3-17 cm) and within Corg compositions (0.88%). Natural terrigenous homologues are prevailing in alkane composition of the sediments. The marginal filters of the Ob and Yenisei rivers were compared. It is shown that oil HC transferred by the rivers are deposited in the zone of marginal filters without reaching the open waters of the Kara Sea.

  15. Tetrodotoxin concentrations in Pleurobranchaea maculata: temporal, spatial and individual variability from New Zealand populations.

    PubMed

    Wood, Susanna A; Taylor, David I; McNabb, Paul; Walker, Jarrod; Adamson, Janet; Cary, Stephen Craig

    2012-01-01

    Tetrodotoxin (TTX) is a potent neurotoxin that has been identified in a range of phylogenetically unrelated marine and terrestrial organisms. Tetrodotoxin was recently detected in New Zealand in Pleurobranchaea maculata (the grey side-gilled sea slug). From June 2010 to June 2011 wild specimens were collected from 10 locations around New Zealand. At one site (Narrow Neck Beach, Auckland) up to 10 individuals were collected monthly for 6 months. Attempts were also made to rear P. maculata in captivity. Tetrodotoxin was detected in samples from eight of the ten sites. The highest average (368.7 mg kg⁻¹) and maximum (1414.0 mg kg⁻¹) concentrations were measured in samples from Illiomama Rock (Auckland). Of the toxic populations tested there was significant variability in TTX concentrations among individuals, with the highest difference (62 fold) measured at Illiomama Rock. Tetrodotoxin concentrations in samples from Narrow Neck Beach varied temporally, ranging from an average of 184 mg kg⁻¹ in June 2010 to 17.5 mg kg⁻¹ by December 2010. There was no correlation between TTX levels and mass. The highest levels correspond with the egg laying season (June-August) and this, in concert with the detection of high levels of TTX in eggs and early larval stages, suggests that TTX may have a defensive function in P. maculata. Only one larva was successfully reared to full maturation and no TTX was detected.

  16. Spatial variability of aerosol and black carbon concentrations in the troposphere of the Russian Arctic

    NASA Astrophysics Data System (ADS)

    Kozlov, Valerii S.; Panchenko, Mikhail V.; Paris, Jean D.; Nédéléc, Philippe; Chernov, Dmitry G.; Shmargunov, Vladimir P.

    2015-11-01

    A cycle of flights of the Optik TU-134 Flying Laboratory of IAO SB RAS over regions of Western Siberia and the Russian Arctic (55.0-74.8°N, 61.3-82.9°E) was carried out on October 15-17 of 2014 within the framework of the YAK-AEROSIB Russian—French Project. The mass concentrations of submicron aerosol and Black Carbon (BC) in the troposphere up to a height of 8.5 km were measured in the flights. The ranges of variability were 0.3-20 μg/m3 for the aerosol concentration and 0.02-1 μg/m3 for the BC concentration. In the subpolar latitudes of 71-74.8°N, the lower levels of aerosol (0.8-6 μg/m3) and BC (0.02-0.3 μg/m3) were observed. The comparison of the results of airborne sensing in 2008 and 2014 has shown that in the Western Subartic the aerosol and BC concentrations in the vertical profiles up to six times exceeded those observed in the Eastern Subarctic (0.3-1 μg/m3 and 10-50 ng/m3). The excess of the mean integral BC concentrations and the aerosol optical depth was, on average, 2-2.5 times (0.16 mg/m2; 0.02). In the region of the Kara Sea at heights of 0.5-2 and 4-6 km, the excess of the aerosol content in the western sector in comparison with the eastern one was, on average, 2 times, while for the black carbon the excess achieved 7 times at heights of 1-2 km (0.25- 0.035 μg/m3). The mean integral concentrations of aerosol and black carbon ˜ 1.3 times exceeded those in the clearer eastern region of the sea (0.31 mg/m2; 0.049). The obtained estimates indicate the decrease of the aerosol and BC concentrations in the subpolar latitudes of the Russian Federation from the west to the east.

  17. Variable Time Normalization Analysis: General Graphical Elucidation of Reaction Orders from Concentration Profiles.

    PubMed

    Burés, Jordi

    2016-12-23

    The recent technological evolution of reaction monitoring techniques has not been paralleled by the development of modern kinetic analyses. The analyses currently used disregard part of the data acquired, thus requiring an increased number of experiments to obtain sufficient kinetic information for a given chemical reaction. Herein, we present a simple graphical analysis method that takes advantage of the data-rich results provided by modern reaction monitoring tools. This analysis uses a variable normalization of the time scale to enable the visual comparison of entire concentration reaction profiles. As a result, the order in each component of the reaction, as well as kobs  , is determined with just a few experiments using a simple and quick mathematical data treatment. This analysis facilitates the rapid extraction of relevant kinetic information and will be a valuable tool for the study of reaction mechanisms.

  18. Methane and Nitrous Oxide Temporal and Spatial Variability in Midwestern Streams Containing High Nitrate Concentrations

    NASA Astrophysics Data System (ADS)

    Smith, R. L.; Bohlke, J. K.

    2015-12-01

    Interest in greenhouse gases in fluvial environments, e.g. CH4 and N2O, is increasing in relation to atmospheric gas budgets and the relative contribution of streams to drivers of global climate change. Typically these gases are examined individually in environments in which each is expected to be dominant; however their co-occurrence and potential interactions may be important. Spatial and temporal variability of CH4 and N2O concentrations were measured in 2 nitrate-rich (40-1200 μM) streams draining >90% agricultural land use in the Midwestern USA and that differed ~12-fold in flow. Long-term (biweekly), short-term (hourly), and transport-oriented (Lagrangian) sampling approaches were compared. Dissolved gas concentrations exceeded atmospheric equilibrium values up to 700x and 16x, for CH4 and N2O, respectively. Mean concentrations were higher in the larger stream than in the smaller stream. In both streams, CH4 was negatively correlated with flow and nitrate while N2O was positively correlated. N2O was generally constant with transport (21 km) in the small stream, with variation in localized reaches, and increased somewhat in May/June in the larger stream (38 km), but not during September base flow. Base flow transport trends for CH4 were similar to N2O in both streams. In the small stream, substantial diel fluctuations were evident in CH4 concentrations and N2O δ18O values, with more subtle fluctuations in CH4 isotopes (δ2H & δ13C), N2O concentrations, and N2O δ15N values. Seasonal mean total (CH4 + N2O) areal emission rates, expressed as CO2 warming potential equivalents, were similar for the two streams, but the total reach-scale emission rate for the larger stream was about 2x that of the smaller stream (15.4 vs 8.3 kg CO2 km-1 day-1, respectively). The CH4 contribution to this flux was 12-30%, despite the relatively high nitrate and oxygen concentrations in the streams, indicating contributions from groundwater or subsurface sediment reactions.

  19. The Influence of Atmospheric CO2 Concentration and Climate Variability on Amazon Tropical Forest

    NASA Astrophysics Data System (ADS)

    Castanho, A. D. D. A.; Galbraith, D.; Zhang, K.; Coe, M. T.; Costa, M. H.; Moorcroft, P. R.

    2014-12-01

    Tropical forests are important regulators of atmospheric CO2 concentration and any change in tropical forest C balance will directly affect global climate. Long term studies from undisturbed old-growth forest monitoring sites distributed across Amazonia have presented an overall increase in aboveground biomass in the last decades, and the increase in atmospheric CO2 concentrations is considered the main driver for this observed carbon sink. The main goal of this work was to use simulations from dynamic global vegetation models (DGVM) to explore how much of the observed historical (1970-2008) increase in biomass in undisturbed tropical forest in Amazonia could be attributed to the CO2 fertilization effect or associated to climate change. We compared simulated biomass and productivity from three DGVMs (IBIS, ED2 and JULES) with observations from forest plots (RAINFOR). The analyses helped clarify the variability of historical and potential future simulations.The analyses showed that models shared similar results and deficiencies. The three models represented the two major model types: conventional dynamic global vegetation models that simulate community dynamics and competition between plant functional types (PFTs) using an aggregated 'big-leaf' representation (IBIS and Jules), and a size-and-age structured terrestrial ecosystem model that captures individual scale dynamics and competition (ED2). In general, the ED2 model results were more sensitive to climate, but all models greatly underestimate the impact of extreme climatic events (e.g. drought) compared to field data.All the DGVM's studied tend to simulate the average biomass well and to overestimate productivity of vegetation under current conditions. All the models presented very low spatial variability compared to field observation. The lack of spatial variability of biomass and productivity is attributed to the lack of nutrient and residence time spatial heterogeneity. All of the DGVMs results suggest that

  20. Temporal Variability of Polybrominated Diphenyl Ether (PBDE) Serum Concentrations over One Year

    PubMed Central

    2015-01-01

    Polybrominated diphenyl ethers (PBDEs) are flame retardant chemicals used in consumer products. They are common contaminants in human serum and associated with adverse health effects. Our objectives were to characterize PBDE serum concentrations in a New England cohort and assess temporal variability of this exposure biomarker over a one-year period. We collected three repeated measurements at six-month intervals from 52 office workers from the greater Boston (MA, United States) area from 2010 to 2011. The intraclass correlation coefficient for BDEs 28, 47, 99, 100, and 153 ranged from 0.87 to 0.99, indicating that a single serum measurement can reliably estimate exposure over a one-year period. This was true for both lipid adjusted and nonlipid adjusted concentrations. The kappa statistics, quantifying the level of agreement of categorical exposure classification, based on medians, tertiles, or quartiles ranged from 0.67 to 0.90. Some congeners showed nonsignificant increases from sampling round 1 (winter) to round 2 (summer) and significant decreases from round 2 to round 3 (winter). This study highlights the high reliability of a single serum PBDE measurement for use in human epidemiologic studies. PMID:25383963

  1. Seasonal variability of soil-gas radon concentration in central California

    USGS Publications Warehouse

    King, C.-Y.; Minissale, A.

    1994-01-01

    Radon concentrations in soil gas were measured by the track-etch method in 60 shallow holes, each 70 cm deep and supported by a capped plastic tube, along several major faults in central California during 1975-1985. This set of data was analyzed to investigate the seasonal variability of soil-gas radon concentration in an area which has various geological conditions but similar climate. The results show several different patterns of seasonal variations, but all of which can be largely attributed to the water-saturation and moisture-retention characteristics of the shallow part of the soil. During the rainy winter and spring seasons, radon tended to be confined underground by the water-saturated surface soil which had much reduced gas permeability, while during the sunny summer and autumn seasons, it exhaled more readily as the soil became drier and more permeable. At several sites located on creeping faults, the radon-variation patterns changed with time, possibly because of disturbance of site condition by fault movement. ?? 1994.

  2. Effect of anionic surfactant concentration on the variable range hopping conduction in polypyrrole nanoparticles

    SciTech Connect

    Rawal, Ishpal; Kaur, Amarjeet

    2014-01-28

    The mechanism of charge transport in polypyrrole (PPy) nanoparticles prepared with different concentrations (5 to 30 mM) of anionic surfactant (sodium dodecyl sulfate) is reported. Transmission electron microscopy technique confirms the formation of PPy nanoparticles of sizes ∼52 to 28 nm under surfactant directed approach. The room temperature electrical conductivity of the prepared nanoparticles found to increase from 3 to 22 S/cm with surfactant concentration. The temperature dependent activation energy rules out the possibility of band conduction mechanism in the prepared PPy nanoparticles and thus the synthesized nanoparticles are analyzed under variable range hopping (VRH) model for conduction mechanism. The PPy nanoparticles, reduced with liquid ammonia, hold 3D VRH conduction mechanism for the charge transport. However, in the doped samples, some deviation from 3D VRH conduction behavior at higher temperatures (>150 K) has been observed. This may be attributed to the presence of anionic surfactant in these samples. The doping of anionic surfactant causes rise in conducting islands, which may lead to the change in the shape/distribution of density of states governed by Gaussian or exponential type near Fermi level.

  3. Urinary phthalate metabolite concentrations among pregnant women in Northern Puerto Rico: Distribution, temporal variability, and predictors

    PubMed Central

    Cantonwine, David E.; Cordero, José F.; Rivera-González, Luis O.; Del Toro, Liza V. Anzalota; Ferguson, Kelly K.; Mukherjee, Bhramar; Calafat, Antonia M.; Crespo, Noe; Jiménez-Vélez, Braulio; Padilla, Ingrid Y.; Alshawabkeh, Akram N.; Meeker, John D.

    2013-01-01

    Background Phthalate contamination exists in the North coast karst aquifer system in Puerto Rico. In light of potential health impacts associated with phthalate exposure, targeted action for elimination of exposure sources may be warranted, especially for sensitive populations such as pregnant women. However, information on exposure to phthalates from a variety of sources in Puerto Rico is lacking. The objective of this study was to determine concentrations and predictors of urinary phthalate biomarkers measured at multiple times during pregnancy among women living in the Northern karst area of Puerto Rico. Methods We recruited 139 pregnant women in Northern Puerto Rico and collected urine samples and questionnaire data at three separate visits (18±2 weeks, 22±2 weeks, and 26±2 weeks of gestation). Urine samples were analyzed for eleven phthalate metabolites: mono-2-ethylhexyl phthalate (MEHP), mono-2-ethyl-5-hydroxyhexyl phthalate, mono-2-ethyl-5-oxohexyl phthalate, mono-2-ethyl-5-carboxypentyl phthalate, mono-ethyl phthalate (MEP), mono-n-butyl phthalate, mono-benzyl phthalate, mono-isobutyl phthalate, mono-3-carboxypropyl phthalate (MCPP), mono carboxyisononyl phthalate (MCNP), and mono carboxyisooctyl phthalate (MCOP). Results Detectable concentrations of phthalate metabolites among pregnant women living in Puerto Rico was prevalent, and metabolite concentrations tended to be higher than or similar to those measured in women of reproductive age from the general US population. Intraclass correlation coefficients ranged from very weak (MCNP; 0.05) to moderate (MEP; 0.44) reproducibility among all phthalate metabolites. We observed significant or suggestive positive associations between urinary phthalate metabolites concentrations and water usage/storage habits (MEP, MCNP, MCOP), use of personal care products (MEP), and consumption of certain food items (MCPP, MCNP, and MCOP). Conclusions To our knowledge this is the first study to report concentrations

  4. Temporal Variability of Pesticide Concentrations in Homes and Implications for Attenuation Bias in Epidemiologic Studies

    PubMed Central

    Ward, Mary H.; Bell, Erin M.; Whitehead, Todd P.; Gunier, Robert B.; Friesen, Melissa C.; Nuckols, John R.

    2013-01-01

    Background: Residential pesticide exposure has been linked to adverse health outcomes in adults and children. High-quality exposure estimates are critical for confirming these associations. Past epidemiologic studies have used one measurement of pesticide concentrations in carpet dust to characterize an individual’s average long-term exposure. If concentrations vary over time, this approach could substantially misclassify exposure and attenuate risk estimates. Objectives: We assessed the repeatability of pesticide concentrations in carpet dust samples and the potential attenuation bias in epidemiologic studies relying on one sample. Methods: We collected repeated carpet dust samples (median = 3; range, 1–7) from 21 homes in Fresno County, California, during 2003–2005. Dust was analyzed for 13 pesticides using gas chromatography–mass spectrometry. We used mixed-effects models to estimate between- and within-home variance. For each pesticide, we computed intraclass correlation coefficients (ICCs) and the estimated attenuation of regression coefficients in a hypothetical case–control study collecting a single dust sample. Results: The median ICC was 0.73 (range, 0.37–0.95), demonstrating higher between-home than within-home variability for most pesticides. The expected magnitude of attenuation bias associated with using a single dust sample was estimated to be ≤ 30% for 7 of the 13 compounds evaluated. Conclusions: For several pesticides studied, use of one dust sample to represent an exposure period of approximately 2 years would not be expected to substantially attenuate odds ratios. Further study is needed to determine if our findings hold for longer exposure periods and for other pesticides. PMID:23462689

  5. What has driven the interannual variability of atmospheric methane concentrations over the last three decades?

    NASA Astrophysics Data System (ADS)

    Coulon, A.; Stenke, A.; Peter, T.

    2015-12-01

    Atmospheric methane (CH4) is the second most anthropogenic greenhouse gas (IPCC, 2013). Observations of methane concentrations at the surface from the last three decades show puzzling fluctuations; from the early 1980s they indicate a nearly constant increase of 8.7 ppbv/year until 2000, including a slowdown after 1990. After a period of about eight years with near zero growh rates, methane concentrations have again been rising since 2007 (Sussmann et al., 2012). Simulations forced with prescribed meteorological fields have been performed for the 1980-2010 period using the chemistry-climate model (CCM) SOCOL. 48 methane tracers have been included in SOCOL and used together with flux boundary conditions for CH4 to allow the tracking of methane emissions from different source categories, such as wetlands, rice paddies, ruminants, industry…, as well as geographical regions. These new simulations provide an innovative way to better understand methane variability, both in terms of emission changes and changes in tropospheric OH, which is investigated with a tracer based on methyl chloroform emissions. An analysis of the tracers elucidates the impact of different emission source categories for different time periods. For 1980-1990, positive gobal methane growth rates result from increasing anthropogenic emissions over Europe, India, and China. A decrease of anthropogenic emissions over Europe after 1990 is consistent with the slow down in the global methane growth rate for 1990-2000. During this period short-lived events such as the eruption of Mount Pinatubo and the strong 1997-1998 El-Niño also affect global methane concentrations, largely by a decrease in wetlands emissions during 1992 and high levels of biomass burning in tropical Asia, respectively. The near-zero trend is maintained after 2000 because of reduced natural emissions, again from wetlands. After 2005, our simulations show a positive global methane growth rate, in agreement with the observations, due

  6. Airborne black carbon concentrations over an urban region in western India-temporal variability, effects of meteorology, and source regions.

    PubMed

    Bapna, Mukund; Sunder Raman, Ramya; Ramachandran, S; Rajesh, T A

    2013-03-01

    This study characterizes over 5 years of high time resolution (5 min), airborne black carbon (BC) concentrations (July 2003 to December 2008) measured over Ahmedabad, an urban region in western India. The data were used to obtain different time averages of BC concentrations, and these averages were then used to assess the diurnal, seasonal, and annual variability of BC over the study region. Assessment of diurnal variations revealed a strong association between BC concentrations and vehicular traffic. Peaks in BC concentration were co-incident with the morning (0730 to 0830, LST) and late evening (1930 to 2030, LST) rush hour traffic. Additionally, diurnal variability in BC concentrations during major festivals (Diwali and Dushera during the months of October/November) revealed an increase in BC concentrations due to fireworks displays. Maximum half hourly BC concentrations during the festival days were as high as 79.8 μg m(-3). However, the high concentrations rapidly decayed suggesting that local meteorology during the festive season was favorable for aerosol dispersion. A multiple linear regression (MLR) model with BC as the dependent variable and meteorological parameters as independent variables was fitted. The variability in temperature, humidity, wind speed, and wind direction accounted for about 49% of the variability in measured BC concentrations. Conditional probability function (CPF) analysis was used to identify the geographical location of local source regions contributing to the effective BC measured (at 880 nm) at the receptor site. The east north-east (ENE) direction to the receptor was identified as a major source region. National highway (NH8) and two coal-fired thermal power stations (at Gandhinagar and Sabarmati) were located in the identified direction, suggesting that local traffic and power plant emissions were likely contributors to the measured BC.

  7. Variability of trace gas concentrations over Asian region: satellite observations vs model

    NASA Astrophysics Data System (ADS)

    Sheel, Varun; Richter, Andreas; Srivastava, Shuchita; Lal, Shyam

    2012-07-01

    Nitrogen dioxide (NO_2) and Carbon Monoxide (CO) play a key role in the chemistry of the tropospheric ozone and are emitted mainly by anthropogenic processes. These emissions have been increasing over Asia over the past few years due to rapid economic growth and yet there are very few systematic ground based observations of these species over this region. We have analysed ten years of data from space borne instruments: Global Ozone Monitoring Experiment (GOME), SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) and Measurements of Pollution in the Troposphere (MOPITT), which have been measuring the tropospheric abundance of these trace gases. We have examined trends over the period 1996-2008 in NO_2 and CO over a few Indian regions where high economic growth in the present decade is likely to see increased emissions for these species. However, even the highest growth rate of these species seen in the present study, is less when compared with similar polluted regions of China, where a much more rapid increase has been observed. In order to understand the trends and variability in atmospheric trace gas concentrations, one must take into account changes in emissions and transport. Only by assessing the relevance of each of these factors will it be possible to predict future changes with reasonable confidence. To this effect we have used a global chemical transport model, MOZART, to simulate concentrations of NO_2 and CO using the POET (European) and REAS (Asian) emission inventories. These are compared with satellite measurements to study seasonal variations and the discrepancies are discussed. The combined uncertainties of the emission inventory and retrieval of the satellite data could be contributing factors to the discrepancies. It may be thus worthwhile to develop emission inventories for India at a higher resolution to include local level activity data.

  8. Spatial and Temporal Variability of the Concentration Field from Localized Releases in a Regular Building Array

    NASA Astrophysics Data System (ADS)

    Goulart, E. V.; Coceal, O.; Branford, S.; Thomas, T. G.; Belcher, S. E.

    2016-05-01

    Spatial and temporal fluctuations in the concentration field from an ensemble of continuous point-source releases in a regular building array are analyzed from data generated by direct numerical simulations. The release is of a passive scalar under conditions of neutral stability. Results are related to the underlying flow structure by contrasting data for an imposed wind direction of 0° and 45° relative to the buildings. Furthermore, the effects of distance from the source and vicinity to the plume centreline on the spatial and temporal variability are documented. The general picture that emerges is that this particular geometry splits the flow domain into segments (e.g., "streets" and "intersections") in each of which the air is, to a first approximation, well mixed. Notable exceptions to this general rule include regions close to the source, near the plume edge, and in unobstructed channels to which the flow is aligned. In the oblique (45°) case the strongly three-dimensional nature of the flow enhances mixing of a scalar within the canopy leading to reduced temporal and spatial concentration fluctuations within the plume core. These fluctuations are in general larger for the parallel flow (0°) case, especially so in the long unobstructed channels. Due to the more complex flow structure in the canyon-type streets behind buildings, fluctuations are lower than in the open channels, though still substantially larger than for oblique flow. These results are relevant to the formulation of simple models for dispersion in urban areas and to the quantification of the uncertainties in their predictions.

  9. Abiotic variables affect STX concentration in a meso-oligotrophic subtropical coastal lake dominated by Cylindrospermopsis raciborskii (Cyanophyceae).

    PubMed

    Brentano, Débora Monteiro; Giehl, Eduardo L Hettwer; Petrucio, Maurício Mello

    2016-06-01

    The cyanobacterium Cylindrospermopsis raciborskii is capable of producing toxins including saxitoxin (STX). Few studies have verified the influence of environmental variables on the production of STX and most have only been studied in the laboratory. The goal of this work was to identify the abiotic variables related to STX concentration in situ. The relationship among STX concentration and the physical variables, nutrients and chlorophyll-a (chl-a) concentration was examined in a meso-oligotrophic subtropical coastal lake dominated by C. raciborskii. A generalized linear model was developed, incorporating all variables measured monthly over a 45-month monitoring period. Conductivity and dissolved inorganic nitrogen (DIN) concentration provided the greatest explanatory power for STX concentration in situ. Previous studies suggested that C. raciborskii cells exposed to stress associated with higher ionic concentrations appear to activate the biosynthesis of STX suggesting that STX can elicit changes cell permeability and may contribute to the homeostasis of this organism. An increase of DIN concentration results in a higher concentration of STX which may be related to a reduced metabolic demand, since the uptake of inorganic nitrogen requires less energy than N2-fixation. Thus, increased DIN can favor the growth of C. raciborskii population or improve cellular homeostasis, both potentially increasing STX concentration in the aquatic system, which was observed through a delayed response pattern. The developed model, while providing only a moderate predictive power, can assist in the understanding of the environmental variables associated with increases in STX concentration, and in monitoring and minimizing the risks of toxic blooms.

  10. Effects of variable dietary sitostanol concentrations on plasma lipid profile and phytosterol metabolism in hamsters.

    PubMed

    Ntanios, F Y; Jones, P J

    1998-02-23

    To examine how variable sitostanol (SI) levels in phytosterol-supplemented diets influence plasma and hepatic lipid concentrations, fifty hamsters were divided into five groups and fed semipurified diets containing 0.25% (w/w) cholesterol for 45 days ad libitum. Four groups were fed this diet with 1% (w/w) phytosterol mixtures which contained 0.01% (w/w) SI derived from soybean, 0.2% (w/w) SI derived from tall oil, 0.2% (w/w) synthetic SI mixture (SIM) and 1% (w/w) pure SI, respectively. A control group did not receive phytosterols. Dietary SI supplementation at 1% (w/w) decreased total and non-apolipoprotein-A cholesterol levels in plasma by 34% (P=0.001) and 55% (P=0.04), respectively, whereas mean plasma total cholesterol level in the 0.2% (w/w) SI group was 23% (P=0.001) lower than that of the control group. Conversely, plasma lipid profile in hamsters fed 1 or 0.2% (w/w) SI did not differ from the 0.01% (w/w) SI group. Liver weights were 15 and 20% (P=0.012) higher in the control group compared with those fed 0.01% and 1% (w/w) SI, respectively, while the hepatic cholesterol content in the control group was greater (P<0.0001) than that of all other groups. Plasma campesterol levels were higher (P=0.04) in the 0.01% and 0.2% (w/w) SI fed groups than in the control, 0.2% (w/w) SIM and 1% (w/w) SI groups. Hepatic sitosterol content was elevated (P=0.002) in the SIM fed group compared to other groups. We conclude that dietary SI effect is proportional to its concentration in phytosterol mixtures and in the diet. Dietary SI lowered plasma cholesterol levels at concentrations higher than 0.2% (w/w) in hamsters. (c) 1998 Elsevier Science B.V.

  11. What drove Dissolved Organic Carbon (DOC) concentration variability in the River Thames (UK) between 1884 and 2014?

    NASA Astrophysics Data System (ADS)

    Noacco, Valentina; Wagener, Thorsten; Howden, Nicholas; Duffy, Christopher

    2016-04-01

    Climate and atmospheric circulation patterns influence the variability of basin hydrochemistry, therefore understanding their influence is essential to put short-term water quality trends into the right context and to predict future hydrochemistry responses in the face of climate change. We investigate the drivers of DOC concentration variability in the Thames basin over 130 years. Our previous work has shown that increased urbanization since the 1880s in the Thames basin was the major driver for the increase in riverine DOC, but it does not explain DOC variability. Our current work investigates the links between hydro-climatic variability (temperature, precipitation and runoff) and teleconnections (ENSO and NAO), and the variability in DOC concentration. Moreover we compare the impact of hydro-climatic variability on riverine DOC, to the impact of land-use change and population increase. We use singular spectrum analysis to identify and then compare the dominant oscillatory components of hydro-climatic and hydro-biogeochemical variables. We use phase-plane trajectories of the noise-free, intra-annual to inter-annual reconstructed components to elucidate the biogeochemical and hydro-climatic dynamics of the system. This allows us to elucidate the links between the variability of hydro-climatic variables and DOC. Moreover they enable the identification of points in time where the dynamics of the system have changed, e.g. due to anthropogenic influences. Further, lag-correlations between teleconnections, DOC and flow are explored, to consider the hydrological memory of the catchment due to the permeable geology present. We show that the high seasonal to inter-annual variability in DOC concentration is linked to the variability of precipitation and runoff, rather than temperature. The dominant inter-annual modes of variability in DOC are connected to the ENSO oscillatory components. During strong El Niño and La Niña years there is statistically significant positive

  12. The expression of a carbon concentrating mechanism in Chlamydomonas acidophila under variable phosphorus, iron, and CO2 concentrations.

    PubMed

    Spijkerman, Elly

    2011-09-01

    The CO(2) acquisition was analyzed in Chlamydomonas acidophila at pH 2.4 in a range of medium P and Fe concentrations and at high and low CO(2) condition. The inorganic carbon concentrating factor (CCF) was related to cellular P quota (Q(p)), maximum CO(2)-uptake rate by photosynthesis (V(max,O2)), half saturation constant for CO(2) uptake (K(0.5)), and medium Fe concentration. There was no effect of the medium Fe concentration on the CCF. The CCF increased with increasing Q(p) in both high and low CO(2) grown algae, but maximum Q(p) was 6-fold higher in the low CO(2) cells. In high CO(2) conditions, the CCF was low, ranging between 0.8 and 3.5. High CCF values up to 9.1 were only observed in CO(2)-limited cells, but P- and CO(2)-colimited cells had a low CCF. High CCF did not relate with a low K(0.5) as all CO(2)-limited cells had a low K(0.5) (<4 μM CO(2)). High C(i)-pools in cells with high Q(p) suggested the presence of an active CO(2)-uptake mechanism. The CCF also increased with increasing V(max,O2) which reflect an adaptation to the nutrient in highest demand (CO(2)) under balanced growth conditions. It is proposed that the size of the CCF in C. acidophila is more strongly related to porter density for CO(2) uptake (reflected in V(max,O2)) and less- to high-affinity CO(2) uptake (low K(0.5)) at balanced growth. In addition, high CCF can only be realized with high Q(p).

  13. Plasma variables, meat quality, and glycolytic potential in broilers stunned with different carbon dioxide concentrations.

    PubMed

    Xu, L; Ji, F; Yue, H Y; Wu, S G; Zhang, H J; Zhang, L; Qi, G H

    2011-08-01

    This study aimed to investigate the effects of different CO(2) concentrations on blood variables, glycolytic potential (GP), and meat quality of hot-boned muscles in broilers. Thirty broilers were exposed to one of the following 5 gas mixtures for 90 s: 40% CO(2) + 30% O(2) + N(2) (control), 30% CO(2) + 21% O(2) + N(2) (G30%), 40% CO(2) + 21% O(2) + N(2) (G40%), 50% CO(2) + 21% O(2) + N(2) (G50%), and 60% CO(2) + 21% O(2) + N(2) (G60%). Samples were taken from the pectoralis major (PM), musculus iliofibularis (MI), and tibialis anterior muscles 45 min postmortem. The ultimate pH in both the PM (vs. G30% and G40%) and MI (vs. G40%) was decreased with G60% (P < 0.05), whereas drip loss in the PM (vs. G30%, P = 0.01) was increased with G60%. Drip loss in the MI (vs. control and G30%, P < 0.01) was increased with G50%. Lightness after 24 h in PM (vs. G30% and G40%, P < 0.01) was increased with G50%. In MI, lightness after 24 h was slightly decreased with G40% compared with the control (P < 0.10). The GP value in the PM was lower in the G30% and G40% than in G60% (P < 0.05), and the GP value in the tibialis anterior was the lowest in G30% (P < 0.01). Plasma corticosterone, plasma glucose, and meat quality (pH, lightness, redness, yellowness) 45 min postmortem were not affected by CO(2) levels (P > 0.05). In conclusion, stunning broilers with low CO(2) levels (30 and 40%) improved meat quality but had no advantage in animal welfare compared with high CO(2) levels (50 and 60%).

  14. Concentration variability of halocarbons over an electronics industrial park and its implication in compliance with the Montreal protocol.

    PubMed

    Chang, C C; Lo, G G; Tsai, C H; Wang, J L

    2001-08-15

    This work investigated fugitive emissions of anthropogenic halocarbons in a semiconductor and electronics industrial park in Taiwan using both flask and in-situ measurement methods. Large concentration variabilities in methylchloroform, trichloroethene, and tetrachloroethene suggested substantial usage and emissions in the industrial park. While the variability of CFC-113, CCl4, and CFC-11 was rather small using the flask sampling technique, the in-situ method with its higher frequency, however, showed significantly larger variability arising from observing periodic emission episodes, which were highly correlated with wind direction and topography of the park.

  15. Relation of pH and other soil variables to concentrations of Pb, Cu, Zn, Cd, and Se in earthworms

    USGS Publications Warehouse

    Beyer, W.N.; Hensler, G.L.; Moore, J.

    1987-01-01

    Various soil treatments (clay, composted peat, superphosphate, sulfur, calcium carbonate, calcium chloride, zinc chloride, selenous acid) were added to experimental field plots to test the effect of different soil variables on the concentrations of 5 elements in earthworms (Pb, Cu, Zn, Cd, Se). Concentrations of the 5 elements were related to 9 soil variables (soil Pb, soil Cu, soil Zn, pH, organic matter, P, K, Mg, and Ca) with linear multiple regression. Lead concentrations in earthworms were positively correlated with soil Pb and soil organic matter, and negatively correlated with soil pH and soil Mg, with an R2 of 64%. Se concentrations were higher in earthworms from plots amended with Se, and Zn concentrations were higher in earthworms from plots amended with Zn. However, none of the other soil variables had important effects on the concentrations of Cu, Zn, Cd and Se in earthworms. Although some significant statistical relations were demonstrated, the values of r2 of all relations (> 20%) were so low that they had little predictive value.

  16. Intra- and Inter-Individual Variability of Urinary Phthalate Metabolite Concentrations in Hmong Women of Reproductive Age

    PubMed Central

    Peck, Jennifer David; Sweeney, Anne M; Symanski, Elaine; Gardiner, Joseph; Silva, Manori J.; Calafat, Antonia M.; Schantz, Susan L

    2010-01-01

    The reproducibility of urinary phthalate metabolite concentrations has not been well characterized in nonpregnant women of reproductive age. Our primary study objectives were to describe the distribution of urinary phthalate metabolites concentrations among a population of Hmong women of reproductive age, and to evaluate intra- and inter-individual variability of phthalate metabolite concentrations. Ten phthalate metabolites were measured in first morning urine samples collected from 45 women and 20 of their spouses who were members of the Fox River Environment and Diet Study cohort in Green Bay, Wisconsin. Repeated first morning urine samples were collected and analyzed from 25 women who provided up to three samples over approximately one month. Measurement variability was assessed using intraclass correlations (ICCs) and surrogate category analysis. Linear mixed models were used to evaluate the associations between participant characteristics and phthalate metabolite concentrations. Nine of the 10 phthalate metabolites were detected in > 80% of all samples analyzed, of which seven were detected in all samples. As a measure of reliability, ICCs were strongest for monobenzyl phthalate (0.64) and weakest for the metabolites of di(2-ethylhexyl)phthalate (DEHP) (ranging from 0.13 to 0.22). Similarly, surrogate category analysis suggested that a single urine sample characterized average one-month exposure with reasonable accuracy across low, medium and high tertiles for all metabolites except the DEHP metabolites. Geometric mean concentrations of monoethyl phthalate increased with age, but patterns by education, income, body mass index, environmental tobacco smoke or season were not observed when measures were adjusted for urinary dilution. Our results suggest that the participant characteristics assessed in this study have limited influence on inter-individual variability of phthalate metabolite concentrations. With regard to intra-individual variability, our results

  17. DETERMINANTS OF TEMPORAL VARIABILITY IN NHEXAS-MARYLAND ENVIRONMENTAL CONCENTRATIONS, EXPOSURES, AND BIOMARKERS

    EPA Science Inventory

    The longitudinal NHEXAS-Maryland study measured metals, PAHs, and pesticides in several media to capture temporal variability. Questionnaires were concurrently administered to identify factors that influenced changes in contaminant levels over time. We constructed mixed-effects...

  18. Application of geostatistics with Indicator Kriging for analyzing spatial variability of groundwater arsenic concentrations in Southwest Bangladesh.

    PubMed

    Hassan, M Manzurul; Atkins, Peter J

    2011-01-01

    This article seeks to explore the spatial variability of groundwater arsenic (As) concentrations in Southwestern Bangladesh. Facts about spatial pattern of As are important to understand the complex processes of As concentrations and its spatial predictions in the unsampled areas of the study site. The relevant As data for this study were collected from Southwest Bangladesh and were analyzed with Flow Injection Hydride Generation Atomic Absorption Spectrometry (FI-HG-AAS). A geostatistical analysis with Indicator Kriging (IK) was employed to investigate the regionalized variation of As concentration. The IK prediction map shows a highly uneven spatial pattern of arsenic concentrations. The safe zones are mainly concentrated in the north, central and south part of the study area in a scattered manner, while the contamination zones are found to be concentrated in the west and northeast parts of the study area. The southwest part of the study area is contaminated with a highly irregular pattern. A Generalized Linear Model (GLM) was also used to investigate the relationship between As concentrations and aquifer depths. A negligible negative correlation between aquifer depth and arsenic concentrations was found in the study area. The fitted value with 95 % confidence interval shows a decreasing tendency of arsenic concentrations with the increase of aquifer depth. The adjusted mean smoothed lowess curve with a bandwidth of 0.8 shows an increasing trend of arsenic concentration up to a depth of 75 m, with some erratic fluctuations and regional variations at the depth between 30 m and 60 m. The borehole lithology was considered to analyze and map the pattern of As variability with aquifer depths. The study has performed an investigation of spatial pattern and variation of As concentrations.

  19. Spatial and temporal variability in nutrient concentrations in surface waters of the Chattahoochee River basin near Atlanta, Georgia, USA

    USGS Publications Warehouse

    Peters, N.E.; Buell, G.R.; Frick, E.A.

    1997-01-01

    Nutrient concentrations from the early 1970s through 1995 were evaluated at several sites along the Chattahoochee River and its tributaries near Atlanta, to determine general patterns and processes controlling nutrient concentrations in the river. A spatial analysis was conducted on data collected in 1994 and 1995 from an intensive nutrient study of the Chattahoochee River and its tributaries by the Georgia Department of Natural Resources, Environmental Protection Division. The 1994-1995 data show step increases in ammonium (NH4-N), nitrite plus nitrate (NO2 + NO3-N), and total-phosphorus (Tot-P) concentrations in the river. The step increases occur downstream of two wastewater treatment facilities (WWTFs) and Peachtree Creek, a small tributary inflow with degraded water quality draining a predominantly urban and industrial area. Median NO2 + NO3-N and Tot-P concentrations in the mainstem increase downstream of these inputs from 0.5 to 1 mg 1-1 and from 0.04 to 0.13 mg 1-1, respectively. NH4-N concentrations were typically low with 95% of the 2575 observations less than 0.2 mg 1-1 throughout the river system, except some high values (>1 mg 1-1) in some tributaries, particularly near the central part of Atlanta. High NH4-N concentrations are attributed to sewage discharge as they also are associated with high biological oxygen demand and faecal coliform bacteria concentrations. Nutrient concentrations vary temporally. An assessment of four sites, two mainstem and two tributaries, from 1970 to 1995 indicates a progressive increase and variability in NO2 + NO3-N concentrations during the period. The progressive increase in NO2 + NO3-N concentrations and their variability is similar to that reported for surface waters throughout the world and for which increased fertilizer usage has been attributed. Tot-P concentrations increase at mainstem sites through the middle to late 1980s and decrease markedly thereafter, due to improvements to WWTFs and a 1990 phosphate

  20. Detecting the spatial and temporal variability of chlorophylla concentration and total suspended solids in Apalachicola Bay, Florida using MODIS imagery

    USGS Publications Warehouse

    Wang, Hongfang; Hladik, C.M.; Huang, W.; Milla, K.; Edmiston, L.; Harwell, M.A.; Schalles, J.F.

    2010-01-01

    Apalachicola Bay, Florida, accounts for 90% of Florida's and 10% of the nation's eastern oyster (Crassostrea virginica) harvesting. Chlorophyll-a concentration and total suspended solids (TSS) are two important water quality variables, among other environmental factors such as salinity, for eastern oyster production in Apalachicola Bay. In this research, we developed regression models of the relationships between the reflectance of the Moderate-Resolution Imaging Spectroradiometer (MODIS) Terra 250 m data and the two water quality variables based on the Bay-wide field data collected during 14-17 October 2002, a relatively dry period, and 3-5 April 2006, a relatively wet period, respectively. Then we selected the best regression models (highest coefficient of determination, R2) to derive Bay-wide maps of chlorophylla concentration and TSS for the two periods. The MODIS-derived maps revealed large spatial and temporal variations in chlorophylla concentration and TSS across the entire Apalachicola Bay. ?? 2010 Taylor & Francis.

  1. Spatial variability of carbonaceous aerosol concentrations in East and West Jerusalem.

    PubMed

    von Schneidemesser, Erika; Zhou, Iiabin; Stone, Elizabeth A; Schauer, James I; Shpund, Jacob; Brenner, Shmuel; Qasrawi, Radwan; Abdeen, Ziad; Sarnat, Jeremy A

    2010-03-15

    Carbonaceous aerosol concentrations and sources were compared during a year long study at two sites in East and West Jerusalem that were separated by a distance of approximately 4 km. One in six day 24-h PM(2.5) elemental and organic carbon concentrations were measured, along with monthly average concentrations of particle-phase organic compound tracers for primary and secondary organic aerosol sources.Tracer compounds were used in a chemical mass balance ICMB) model to determine primary and secondary source contributions to organic carbon. The East Jerusalem sampling site at Al Quds University experienced higher concentrations of organic carbon (OC) and elemental carbon (EC) compared to the West Jerusalem site at Hebrew University. The annual average concentrations of OC and EC at the East Jerusalem site were 5.20 and 2.19 μg m(-3), respectively, and at the West Jerusalem site were 4.03 and 1.14 μg m(-3), respectively. Concentrations and trends of secondary organic aerosol and vegetative detritus were similar at both sites, but large differences were observed in the concentrations of organic aerosol from fossil fuel combustion and biomass burning, which was the cause of the large differences in OC and EC concentrations observed at the two sites.

  2. Spatial Variability of Nitrate Concentrations under Diverse Conditions in Tributaries to a Lake Watershed

    EPA Science Inventory

    Nitrate-nitrogen (NO3-N) concentrations in stream water often respond uniquely to changes in inter-annual (e.g., biological N uptake, precipitation) conditions in individual catchments. In this paper, we assess (1) how the spatial distribution of NO3-N concentrations varies acro...

  3. Concentrated flow erodibility for physically-based erosion models: temporal variability in disturbed and undisturbed rangelands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Current physically based overland flow erosion models for rangeland application do not separate disturbed and undisturbed conditions in modeling concentrated flow erosion. In this study, concentrated flow simulations on disturbed and undisturbed rangelands were used to estimate the erodibility and t...

  4. Variable aggregation rates in colloidal gold: Kernel homogeneity dependence on aggregant concentration

    NASA Astrophysics Data System (ADS)

    Olivier, B. J.; Sorensen, C. M.

    1990-02-01

    Dynamic light scattering is used to study the dependence of the aggregation kernel homogeneity λ on the aggregant concentration [HCl] for aqueous gold sols. We find the cluster growth kinetics are well described by a powerlaw, Rapp~tz/D, where Rapp is the measured apparent radius, D the cluster fractal dimension, and z=1/(1-λ) for all aggregant concentrations. The values for the dynamic exponent z, and hence the homogeneity λ, are functions of HCl concentration. We find the larger HCl concentrations yield a fast-aggregation regime characterized by λ~=-0.6. Smaller HCl concentrations yield a continuum of aggregation regimes characterized by homogeneities evolving from λ~=-0.6 towards 1.0. Our results do not support the view that aggregation in gold colloids is based on two limiting regimes, diffusion-limited and reaction-limited aggregation.

  5. Effect of variable viscosity and thermal conductivity on high-speed slip flow between concentric cylinders

    NASA Technical Reports Server (NTRS)

    Lin, T C; Street, R E

    1953-01-01

    The differential equations of slip flow, including the Burnett terms, were first solved by Schamberg assuming that the coefficients of viscosity and heat conduction of the gas were constants. The problem is solved herein for variable coefficients of viscosity and thermal conductivity by applying a transformation leading to an iteration method. The method, starting with the solution for constant coefficients, enables one to approximate the solution for variable coefficients very closely after one or two steps. Satisfactory results are shown to follow from Schamberg's solution by using his values of the constant coefficients multiplied by a constant factor 'N', leading to what are denoted as the effective coefficients of viscosity and thermal conductivity.

  6. Atmospheric trace elements at Enewetak Atoll. I Concentrations, sources, and temporal variability

    NASA Astrophysics Data System (ADS)

    Duce, R. A.; Arimoto, R.; Ray, B. J.; Unni, C. K.; Harder, P. J.

    1983-06-01

    The concentrations of 29 elements in aerosol particles collected in 1979 during Searex (Sea/Air Exchange) experiments at Enewetak Atoll (11 deg N, 162 deg E), in the tropical North Pacific, are measured. The concentrations of Na, Mg, Cl, K, Ca, and Br are dominated by marine sources; the elements have similar mass-size distributions, and their atmospheric concentration ratios (normalized to Na) are similar to the corresponding ratios in bulk seawater. Atmospheric inputs of aluminosilicate particles from crustal weathering are found to control the aerosol particle concentration of Al, Sc, Mn, Fe, Co, Cs, Ba, Ce, Eu, Hf, Ta, and Th. The mean concentrations of these crustally derived elements decrease by an average of 91 percent (+ or - 4.1 percent) from the local dry season (April to May) to the wet season (July to August); this general decrease is attributed to the abatement of dust storms in Asia. At times, the influx of dust from Asia dominates the concentrations of V, Cr, Rb, and Cu in aerosol particles, but when dust concentrations decrease, noncrustal sources for these elements manifest themselves.

  7. Impact of atmospheric boundary layer depth variability and wind reversal on the diurnal variability of aerosol concentration at a valley site.

    PubMed

    Pal, S; Lee, T R; Phelps, S; De Wekker, S F J

    2014-10-15

    The development of the atmospheric boundary layer (ABL) plays a key role in affecting the variability of atmospheric constituents such as aerosols, greenhouse gases, water vapor, and ozone. In general, the concentration of any tracers within the ABL varies due to the changes in the mixing volume (i.e. ABL depth). In this study, we investigate the impact on the near-surface aerosol concentration in a valley site of 1) the boundary layer dilution due to vertical mixing and 2) changes in the wind patterns. We use a data set obtained during a 10-day field campaign in which a number of remote sensing and in-situ instruments were deployed, including a ground-based aerosol lidar system for monitoring of the ABL top height (zi), a particle counter to determine the number concentration of aerosol particles at eight different size ranges, and tower-based standard meteorological instruments. Results show a clearly visible decreasing trend of the mean daytime zi from 2900 m AGL (above ground level) to 2200 m AGL during a three-day period which resulted in increased near-surface pollutant concentrations. An inverse relationship exists between the zi and the fine fraction (0.3-0.7 μm) accumulation mode particles (AMP) on some days due to the dilution effect in a well-mixed ABL. These days are characterized by the absence of daytime upvalley winds and the presence of northwesterly synoptic-driven winds. In contrast, on the days with an onset of an upvalley wind circulation after the morning transition, the wind-driven local transport mechanism outweighs the ABL-dilution effect in determining the variability of AMP concentration. The interplay between the ABL depth evolution and the onset of the upvalley wind during the morning transition period significantly governs the air quality in a valley and could be an important component in the studies of mountain meteorology and air quality.

  8. EXPOSURE TO CONCENTRATED AMBIENT PARTICLES IN DETROIT ALTERS HEART RATE VARIABILITY IN SPONTANEOUSLY HYPERTENSIVE RATS

    EPA Science Inventory

    Elevations in airborne particulate matter (PM) are linked to increased mortality and morbidity in humans with cardiopulmonary disease. Clinical studies show that PM is associated with altered heart rate variability (HRV) and suggests that loss of autonomic control may underlie ca...

  9. Modeling Geographic and Demographic Variability in Residential Concentrations of Environmental Tobacco Smoke Using National Data Sets

    EPA Science Inventory

    Despite substantial attention toward environmental tobacco smoke (ETS) exposure, previous studies have not provided adequate information to apply broadly within community-scale risk assessments. We aim to estimate residential concentrations of particulate matter (PM) from ETS in ...

  10. Spatial variability of dissolved phosphorous concentrations and alkaline phosphatase activity in the East China Sea

    NASA Astrophysics Data System (ADS)

    Liu, H.; Chang, J.; Ho, T.; Gong, G.

    2010-12-01

    The concentrations of dissolved inorganic phosphorus (DIP) and alkaline phosphatase activity (APA) have been determined at about 25 sampling stations in the East China Sea since 2003. The stations are mainly distributed from the Changjiang river mouth to northern Taiwan and east to the shelf break. In addition to the Changjiang discharge, we have found a specific nutrient source around a coastal site (122° 2’30’’ E, 28° 40’ N). Elevated DIP and nitrate concentrations have been constantly observed around the sampling station for 8 years, where the surface DIP concentrations are generally around 0.3 µM. The nutrient source may either originate from ground water discharge or coastal upwelling, where lower temperature has been observed in the water column around the station. In general, APA has been negatively correlated with DIP concentrations in the studies sites, with lowest APA around the high DIP station and the Changjiang river mouth.

  11. Variability of atmospheric krypton-85 activity concentrations observed close to the ITCZ in the southern hemisphere.

    PubMed

    Bollhöfer, A; Schlosser, C; Ross, J O; Sartorius, H; Schmid, S

    2014-01-01

    Krypton-85 activity concentrations in surface air have been measured at Darwin, which is located in northern Australia and is influenced by seasonal monsoonal activity. Measurements between August 2007 and May 2010 covered three wet seasons. The mean activity concentration of krypton-85 measured during this period was 1.31±0.02Bqm(-3). A linear model fitted to the average monthly data, using month and monsoon as predictors, shows that krypton-85 activity concentration measured during the sampling period has declined by 0.01Bqm(-3) per year. Although there is no statistically significant difference in mean activity concentration of krypton-85 between wet and dry season, the model implies that activity concentration is higher by about 0.015Bqm(-3) during months influenced by the monsoon when a north westerly flow prevails. Backward dispersion runs using the Lagrangian particle dispersion model Hysplit4 highlight possible source regions during an active monsoon located deep in the northern hemisphere, and include reprocessing facilities in Japan and India. However, the contribution of these facilities to krypton-85 activity concentrations in Darwin would be less than 0.003Bqm(-3).

  12. Statistical evaluation of biogeochemical variables affecting spatiotemporal distributions of multiple free metal ion concentrations in an urban estuary.

    PubMed

    Dong, Zhao; Lewis, Christopher G; Burgess, Robert M; Coull, Brent; Shine, James P

    2016-05-01

    Free metal ion concentrations have been recognized as a better indicator of metal bioavailability in aquatic environments than total dissolved metal concentrations. However, our understanding of the determinants of free ion concentrations, especially in a metal mixture, is limited, due to underexplored techniques for measuring multiple free metal ions simultaneously. In this work, we performed statistical analyses on a large dataset containing repeated measurements of free ion concentrations of Cu, Zn, Pb, Ni, and Cd, the most commonly measured metals in seawater, at five inshore locations in Boston Harbor, previously collected using an in-situ equilibrium-based multi-metal free ion sampler, the 'Gellyfish'. We examined correlations among these five metals by season, and evaluated effects of 10 biogeochemical variables on free ion concentrations over time and location through multivariate regressions. We also explored potential clustering among the five metals through a principal component analysis. We found significant correlations among metals, with varying patterns over season. Our regression results suggest that instead of dissolved metals, pH, salinity, temperature and rainfall were the most significant determinants of free metal ion concentrations. For example, a one-unit decrease in pH was associated with a 2.2 (Cd) to 99 (Cu) times increase in free ion concentrations. This work is among the first to reveal key contributors to spatiotemporal variations in free ion concentrations, and demonstrated the usefulness of the Gellyfish sampler in routine sampling of free ions within metal mixtures and in generating data for statistical analyses.

  13. Genetic variability associated with photosynthetic pigment concentration, and photochemical and nonphotochemical quenching, in strains of the cyanobacterium Microcystis aeruginosa.

    PubMed

    Bañares-España, Elena; López-Rodas, Victoria; Costas, Eduardo; Salgado, Concepción; Flores-Moya, Antonio

    2007-06-01

    Although populations of cyanobacteria are usually considered to be clonal, their capacity to survive environmental changes suggests intrapopulation genetic variation. We therefore estimated the genetic variability on the basis of two processes important for any photoautotroph - photochemical and nonphotochemical quenching - as well as photosynthetic pigment concentrations. For this purpose, two parameters related to photochemical and nonphotochemical quenching were measured using specific experimental and statistical procedures, in 25 strains of the cyanobacterium Microcystis aeruginosa, along with their contents of chlorophyll a, total carotenoids and phycocyanin. The experimental procedure allowed discrimination between genetic and nongenetic (or residual) variability among strains. The high genetic variability found in photosynthetic pigments and both photosynthetic parameters denotes large differences even among strains isolated from the same community. The high genetic diversity within a population could be important for the evolutionary success of cyanobacteria.

  14. Temperature and precipitation drive temporal variability in aquatic carbon and GHG concentrations and fluxes in a peatland catchment.

    PubMed

    Dinsmore, K J; Billett, M F; Dyson, K E

    2013-07-01

    The aquatic pathway is increasingly being recognized as an important component of catchment carbon and greenhouse gas (GHG) budgets, particularly in peatland systems due to their large carbon store and strong hydrological connectivity. In this study, we present a complete 5-year data set of all aquatic carbon and GHG species from an ombrotrophic Scottish peatland. Measured species include particulate and dissolved forms of organic carbon (POC, DOC), dissolved inorganic carbon (DIC), CO2 , CH4 and N2 O. We show that short-term variability in concentrations exists across all species and this is strongly linked to discharge. Seasonal cyclicity was only evident in DOC, CO2 and CH4 concentration; however, temperature correlated with monthly means in all species except DIC. Although the temperature correlation with monthly DOC and POC concentrations appeared to be related to biological productivity in the terrestrial system, we suggest the temperature correlation with CO2 and CH4 was primarily due to in-stream temperature-dependent solubility. Interannual variability in total aquatic carbon concentration was strongly correlated with catchment gross primary productivity (GPP) indicating a strong potential terrestrial aquatic linkage. DOC represented the largest aquatic carbon flux term (19.3 ± 4.59 g C m(-2)  yr(-1) ), followed by CO2 evasion (10.0 g C m(-2)  yr(-1) ). Despite an estimated contribution to the total aquatic carbon flux of between 8 and 48%, evasion estimates had the greatest uncertainty. Interannual variability in total aquatic carbon export was low in comparison with variability in terrestrial biosphere-atmosphere exchange, and could be explained primarily by temperature and precipitation. Our results therefore suggest that climatic change is likely to have a significant impact on annual carbon losses through the aquatic pathway, and as such, aquatic exports are fundamental to the understanding of whole catchment responses to climate change.

  15. Diurnal variability of polycyclic aromatic compound (PAC) concentrations: Relationship with meteorological conditions and inferred sources

    NASA Astrophysics Data System (ADS)

    Alam, Mohammed S.; Keyte, Ian J.; Yin, Jianxin; Stark, Christopher; Jones, Alan M.; Harrison, Roy M.

    2015-12-01

    Polycyclic aromatic hydrocarbons (PAH) and their nitro and oxy derivatives have been sampled every three hours over one week in winter at two sites in Birmingham UK. One site is heavily influenced by road traffic and is close to residential dwellings, while the other site is a background urban location at some distance from both sources of emission. The time series of concentrations has been examined along with the ratio of concentrations between the two sampling sites. A comparison of averaged diurnal profiles has shown different patterns of behaviour which has been investigated through calculating ratios of concentration at 18:00-21:00 h relative to that at 06:00-09:00 h. This allows identification of those compounds with a strong contribution to a traffic-related maximum at 06:00-09:00 h which are predominantly the low molecular weight PAHs, together with a substantial group of quinones and nitro-PAHs. Changes in partitioning between vapour and particulate forms are unlikely to influence the ratio as the mean temperature at both times was almost identical. Most compounds show an appreciable increase in concentrations in the evening which is attributed to residential heating emissions. Compounds dominated by this source show high ratios of 18:00-21:00 concentrations relative to 06:00-09:00 concentrations and include higher molecular weight PAH and a substantial group of both quinones and nitro-PAH. The behaviour of retene, normally taken as an indicator of biomass burning, is suggestive of wood smoke only being one contributor to the evening peak in PAH and their derivatives, with coal combustion presumably being the other main contributor. Variations of PAH concentrations with wind speed show a dilution behaviour consistent with other primary pollutants, and high concentrations of a range of air pollutants were observed in an episode of low temperatures and low wind speeds towards the end of the overall sampling period consistent with poor local dispersion

  16. Intra-individual variability of mycophenolic acid concentration according to renal function in liver transplant recipients receiving mycophenolate monotherapy

    PubMed Central

    Song, Gi-Won; Jung, Dong-Hwan; Park, Gil-Chun; Ahn, Chul-Soo; Moon, Deok-Bog; Ha, Tae-Yong; Kim, Ki-Hun; Lee, Sung-Gyu

    2017-01-01

    Backgrounds/Aims Mycophenolate mofetil (MMF) has wide inter- and intra-individual variability of mycophenolic acid (MPA) after liver transplantation (LT). On this study, we aimed to analyse the intra-individual variability of MPA concentration in stable adult LT recipients receiving MMF monotherapy and develop a method to determine the target level in the situation of wide intra-individual variability. Methods This retrospective cross-sectional study included 30 LT recipients. All patients received MMF monotherapy at a dose of 500 mg twice daily for ≥2 years and were divided into two groups based on renal function. MPA concentration-associated values were presented as mean with standard deviation and coefficient of variation (CV). Results The normal renal function group (n=15) showed a mean 12-hour MPA concentration of 2.5±0.5 µg/ml (range, 1.8±0.5 to 3.6±0.7 µg/ml) and a mean CV of 20.4±7.7% (range, 8.7% to 39.4%). In the renal dysfunction group (n=15), the 12-hour MPA concentration fluctuated more widely with a mean value of 3.7±0.9 µg/ml (range, 2.8±0.8 to 5.1±1.2 µg/ml) and a mean CV of 24.5±4.9% (range, 17.1% to 37.5%). The 12-hour MPA concentration was significantly higher in the renal dysfunction group, as compared to the normal renal function group (p=0.001); whereas, the CV was not significantly different between the two groups (p=0.093). Conclusions We determined the inter- and intra-individual variability of 12-hour MPA concentration after LT. The results suggested that therapeutic drug monitoring of MPA is necessary due to the inter-individual and intra-individual variability of MMF pharmacokinetics, especially in LT recipients with renal dysfunction. PMID:28317040

  17. Effect of variable cerium concentration on photoluminescence behaviour in ZrO2 phosphor synthesized by combustion synthesis method

    NASA Astrophysics Data System (ADS)

    Dubey, Vikas; Kaur, Jagjeet

    2016-05-01

    Present paper reports synthesis and characterization of trivalent cerium (Ce3+) doped zirconium dioxide (ZrO2) phosphors. Effect of variable concentration of cerium on photoluminescence (PL) is studied. Samples were prepared by combustion synthesis technique which is suitable for less time taking techniques also for large scale production for phosphors. Starting material used for sample preparation are Zr(NO3)3 and Ce(NO3)3 and urea used as a fuel. All prepared phosphor with variable concentration of Ce3+ (0.1 to 2mol%) was studied by photoluminescence analysis it is found that the excitation spectra of prepared phosphor shows broad excitation centred at 390nm. The excitation spectra with variable concentration of Ce3+ show strong peaks at 447nm. Spectrophotometric determinations of peaks are evaluated by Commission Internationale de I'Eclairage technique. Using this phosphor, the desired CIE values including emissions throughout the violet (390 nm) and blue (427 nm) of the spectra were achieved. Efficient blue light emitting diodes were fabricated using Ce3+ doped phosphor based on near ultraviolet (NUV) excited LED lights.

  18. Constant-concentration boundary condition: Lessons from the HYDROCOIN variable-density groundwater benchmark problem

    USGS Publications Warehouse

    Konikow, L.F.; Sanford, W.E.; Campbell, P.J.

    1997-01-01

    In a solute-transport model, if a constant-concentration boundary condition is applied at a node in an active flow field, a solute flux can occur by both advective and dispersive processes. The potential for advective release is demonstrated by reexamining the Hydrologic Code Intercomparison (HYDROCOIN) project case 5 problem, which represents a salt dome overlain by a shallow groundwater system. The resulting flow field includes significant salinity and fluid density variations. Several independent teams simulated this problem using finite difference or finite element numerical models. We applied a method-of-characteristics model (MOCDENSE). The previous numerical implementations by HYDROCOIN teams of a constant-concentration boundary to represent salt release by lateral dispersion only (as stipulated in the original problem definition) was flawed because this boundary condition allows the release of salt into the flow field by both dispersion and advection. When the constant-concentration boundary is modified to allow salt release by dispersion only, significantly less salt is released into the flow field. The calculated brine distribution for case 5 depends very little on which numerical model is used, as long as the selected model is solving the proper equations. Instead, the accuracy of the solution depends strongly on the proper conceptualization of the problem, including the detailed design of the constant-concentration boundary condition. The importance and sensitivity to the manner of specification of this boundary does not appear to have been recognized previously in the analysis of this problem.

  19. Age-related Effects of Varying Ammonia Concentrations on Hematophysiological Variables in Broiler Chickens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study examined the response of different aged birds of the same genetic strain exposed to ammonia (NH3) at set concentrations on blood gases, electrolytes, and acid-base balance under environmentally controlled conditions. The experiment consisted of a 4 × 4 factorial with a randomized design. ...

  20. Coal pyrolysis to acetylene using dc hydrogen plasma torch: effects of system variables on acetylene concentration

    NASA Astrophysics Data System (ADS)

    Chen, Longwei; Meng, Yuedong; Shen, Jie; Shu, Xingsheng; Fang, Shidong; Xiong, Xinyang

    2009-03-01

    In order to unveil the inner mechanisms that determine acetylene concentration, experimental studies on the effect of several parameters such as plasma torch power, hydrogen flux and coal flux were carried out from coal pyrolysis in a dc plasma torch. Xinjiang long flame coals including volatile constituents at a level of about 42% were used in the experiment. Under the following experimental conditions, namely plasma torch power, hydrogen flow rate and pulverized coal feed speed of 2.12 MW, 32 kg h-1 and 900 kg h-1, respectively, acetylene volume concentration of about 9.4% was achieved. The experimental results indicate that parameters such as plasma torch power and coal flux play important roles in the formation of acetylene. Acetylene concentration increases inconspicuously with hydrogen flux. A chemical thermodynamic equilibrium model using the free energy method is introduced in this paper to numerically simulate each experimental condition. The numerical results are qualitatively consistent with the experimental results. Two parameters, i.e. the gas temperature and the ratio of hydrogen/carbon, are considered to be the dominant and independent factors that determine acetylene concentration.

  1. Variable rsponses of mesophyll conductance to substomatal carbon dioxide concentration in common bean and soybean

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Some reports indicate that mesophyll conductance to carbon dioxide varies greatly with the sub-stomatal carbon dioxide concentration during the measurement, while other reports indicate little or no change. I used the oxygen sensitivity of photosynthesis to determine the response of mesophyll condu...

  2. Spatio-temporal variability of groundwater nitrate concentration in Texas: 1960 to 2010.

    PubMed

    Chaudhuri, Sriroop; Ale, Srinivasulu; Delaune, Paul; Rajan, Nithya

    2012-01-01

    Nitrate (NO) is a major contaminant and threat to groundwater quality in Texas. High-NO groundwater used for irrigation and domestic purposes has serious environmental and health implications. The objective of this study was to evaluate spatio-temporal trends in groundwater NO concentrations in Texas on a county basis from 1960 to 2010 with special emphasis on the Texas Rolling Plains (TRP) using the Texas Water Development Board's groundwater quality database. Results indicated that groundwater NO concentrations have significantly increased in several counties since the 1960s. In 25 counties, >30% of the observations exceeded the maximum contamination level (MCL) for NO (44 mg L NO) in the 2000s as compared with eight counties in the 1960s. In Haskell and Knox Counties of the TRP, all observations exceeded the NO MCL in the 2000s. A distinct spatial clustering of high-NO counties has become increasingly apparent with time in the TRP, as indicated by different spatial indices. County median NO concentrations in the TRP region were positively correlated with county-based area estimates of crop lands, fertilized croplands, and irrigated croplands, suggesting a negative impact of agricultural practices on groundwater NO concentrations. The highly transmissive geologic and soil media in the TRP have likely facilitated NO movement and groundwater contamination in this region. A major hindrance in evaluating groundwater NO concentrations was the lack of adequate recent observations. Overall, the results indicated a substantial deterioration of groundwater quality by NO across the state due to agricultural activities, emphasizing the need for a more frequent and spatially intensive groundwater sampling.

  3. Observation of vertical variability of black carbon concentration in lower troposphere on campaigns in Poland

    NASA Astrophysics Data System (ADS)

    Chilinski, M. T.; Markowicz, K. M.; Markowicz, J.

    2016-07-01

    This study presents two methods for observation of black carbon (BC) vertical profiles in lower troposphere based on the micro-aethalometer AE-51. In the first method micro-aethalometer was carried by observer along trail on slope of mountain valley. Second method uses unmanned aerial vehicle as a platform for collecting data up to 1500 m above ground. Our study presents vertical profiles collected in and above Subcarphatian Wislok valley. Profiles measured on trial on slopes of Wislok valley, were collected during strong smog conditions during autumn/winter season, when BC concentration reached values above 60 μg/m3. The smog intensive layer is usually close to the surface (up to 100 m) as a results of surface inversion and the mountain breeze circulation, which during the night transports air pollution emitted from houses toward the valley's bottom. Usually the vertical profiles of BC concentration show significant reduction with the altitude, however, some multilayered structures are also observed during night time inversion conditions. It has found that smog condition can develop in clean air mass, and in those cases local pollution has significant impact on the columnar aerosol properties. During such conditions the aerosol optical depth shows diurnal cycle which is rather not observed in the long-term data. UAV flights in the lower troposphere were conducted during two sessions, one with clean polar air masses (BC concentration < 1 μg/m3) and second with moderate aerosol conditions (BC concentration 1-5 μg/m3). Profile of BC concentration shows stratification of absorbing aerosols in a shape of multi-layer structures similarly to the lidar/ceilometer signals.

  4. Genetic variability in melatonin concentrations in ewes originates in its synthesis, not in its catabolism.

    PubMed

    Zarazaga, L A; Malpaux, B; Guillaume, D; Bodin, L; Chemineau, P

    1998-06-01

    We investigated whether the genetic difference in plasma melatonin concentration in ewes was due to differences in the synthesis pathway from the pineal gland or in the catabolism of the hormone. Two groups of ewes [9 low (L) and 10 high (H)] were selected according to the breeding value of their mean nighttime plasma melatonin concentrations estimated at winter and summer solstices. In response to an identical dose of melatonin administered intravenously at 9:00 AM, no differences between groups were observed for any of the kinetic parameters: clearance rate, steady-state volume of distribution, terminal half-lives, and mean residence times. In the second experiment, two series of frequent blood samples were performed, one in the middle of the dark phase with samples taken every 5 min, and the other over 24 h with hourly samples. Highly significant differences between groups in nocturnal melatonin production rate were observed (L: 25.7 +/- 2.8 vs. H: 63.1 +/- 8.9 microg . kg-1 . h-1, P < 0.01). Thus the genetic differences in plasma melatonin concentrations in ewes originate in the synthesis pathway of the melatonin from the pineal gland rather than from differences in the catabolism of the hormone.

  5. Diurnal variability in concentrations and sources of Escherichia coli in three streams.

    PubMed

    Meays, Cindy L; Broersma, Klaas; Nordin, Rick; Mazumder, Asit; Samadpour, Mansour

    2006-11-01

    Microbial contamination is a major concern for drinking water worldwide. Many monitoring protocols that use one or very few samples are inadequate and introduce a very large margin of error. An intensive sampling program needs to be conducted to characterize the Escherichia coli concentrations of a source water stream prior to establishing a monitoring program so that the sample frequency can be determined statistically, based on an acceptable margin of error. Developing meaningful monitoring programs for managing bacterial water quality is dependant on scientific data that determine the bacterial sources. In this study, three streams from drinking water watersheds were sampled every 15 min over a 24 h period on three different days to determine the concentrations of E. coli and to identify their sources, using ribosomal RNA finger printing (ribotyping). The concentrations of E. coli varied throughout the day in each of the three streams. Ribotyping identified many different animal sources of E. coli in the samples. The sources of E. coli varied significantly with stream (P < 0.001, df = 16). The development of monitoring programs for watersheds needs to consider the watershed, and care needs to be taken in selecting appropriate sample sites, sampling regime, and number of samples taken during each sampling period. This note provides a prescription for the development of monitoring programs for watersheds.

  6. Effects of environmental and physiological variables on the accumulated concentrations of trace metals in the New Zealand cockle Austrovenus stutchburyi.

    PubMed

    Marsden, Islay D; Smith, Brian D; Rainbow, Phillip S

    2014-02-01

    We examined potential causes of variation in trace element accumulation in an estuarine bivalve Austrovenus stutchburyi from two estuarine systems in South Island, New Zealand which differed in their metal contamination and salinity regimes. Concentrations of Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V and Zn were measured (ICP-OES) in whole body tissues of bivalves collected from 10 sites, seston collected at high tide (a potential food resource) and in the sediment at the sites. All 13 elements showed a relationship between log bioaccumulated trace element concentration (mgkg(-1) dry weight tissue) and log shell length (mm), either in the whole data set or at least one site (ANCOVA). Growth rates of cockles varied significantly amongst sites. Accumulated soft tissue concentrations of Ag, As, Co and Cr increased with age of cockle, those of Pb and Zn decreased, with no clear age-related trend for the remaining metals (ANCOVA). Shell length was generally a good proxy for age when allowing for any size effect in metal accumulation by the cockle. There was no consistent pattern between the estuarine systems, probably reflecting unidentified contaminant inputs. Following depuration, tissue concentrations decreased significantly for some elements (Fe, Mn, Ti and V), indicating high concentrations of these metals in the gut contents. Trace element concentrations in the seston generally did not correlate with the bivalve tissue concentrations. There were few (Spearman's Rank) correlations between environmental variables at the time of sampling and cockle tissue trace element concentrations. The main sources of variation in bioaccumulated trace metal concentrations in the whole tissues of the cockle are location, shell length and age.

  7. Predictive models for Escherichia coli concentrations at inland lake beaches and relationship of model variables to pathogen detection

    USGS Publications Warehouse

    Francy, Donna S.; Stelzer, Erin A.; Duris, Joseph W.; Brady, Amie M.G.; Harrison, John H.; Johnson, Heather E.; Ware, Michael W.

    2013-01-01

    Predictive models, based on environmental and water quality variables, have been used to improve the timeliness and accuracy of recreational water quality assessments, but their effectiveness has not been studied in inland waters. Sampling at eight inland recreational lakes in Ohio was done in order to investigate using predictive models for Escherichia coli and to understand the links between E. coli concentrations, predictive variables, and pathogens. Based upon results from 21 beach sites, models were developed for 13 sites, and the most predictive variables were rainfall, wind direction and speed, turbidity, and water temperature. Models were not developed at sites where the E. coli standard was seldom exceeded. Models were validated at nine sites during an independent year. At three sites, the model resulted in increased correct responses, sensitivities, and specificities compared to use of the previous day's E. coli concentration (the current method). Drought conditions during the validation year precluded being able to adequately assess model performance at most of the other sites. Cryptosporidium, adenovirus, eaeA (E. coli), ipaH (Shigella), and spvC (Salmonella) were found in at least 20% of samples collected for pathogens at five sites. The presence or absence of the three bacterial genes was related to some of the model variables but was not consistently related to E. coli concentrations. Predictive models were not effective at all inland lake sites; however, their use at two lakes with high swimmer densities will provide better estimates of public health risk than current methods and will be a valuable resource for beach managers and the public.

  8. Predictive Models for Escherichia coli Concentrations at Inland Lake Beaches and Relationship of Model Variables to Pathogen Detection

    PubMed Central

    Stelzer, Erin A.; Duris, Joseph W.; Brady, Amie M. G.; Harrison, John H.; Johnson, Heather E.; Ware, Michael W.

    2013-01-01

    Predictive models, based on environmental and water quality variables, have been used to improve the timeliness and accuracy of recreational water quality assessments, but their effectiveness has not been studied in inland waters. Sampling at eight inland recreational lakes in Ohio was done in order to investigate using predictive models for Escherichia coli and to understand the links between E. coli concentrations, predictive variables, and pathogens. Based upon results from 21 beach sites, models were developed for 13 sites, and the most predictive variables were rainfall, wind direction and speed, turbidity, and water temperature. Models were not developed at sites where the E. coli standard was seldom exceeded. Models were validated at nine sites during an independent year. At three sites, the model resulted in increased correct responses, sensitivities, and specificities compared to use of the previous day's E. coli concentration (the current method). Drought conditions during the validation year precluded being able to adequately assess model performance at most of the other sites. Cryptosporidium, adenovirus, eaeA (E. coli), ipaH (Shigella), and spvC (Salmonella) were found in at least 20% of samples collected for pathogens at five sites. The presence or absence of the three bacterial genes was related to some of the model variables but was not consistently related to E. coli concentrations. Predictive models were not effective at all inland lake sites; however, their use at two lakes with high swimmer densities will provide better estimates of public health risk than current methods and will be a valuable resource for beach managers and the public. PMID:23291550

  9. Diurnal and seasonal variability of outdoor radon concentration in the area of the NRPI Prague.

    PubMed

    Jilek, K; Slezákova, M; Thomas, J

    2014-07-01

    In autumn 2010, an outdoor measuring station for measurement of atmospheric radon, gamma equivalent dose rate in the range of 100 nSv h(-1)-1 Sv h(-1) and proper meteorological parameters such as thermal air gradient, relative air humidity, wind speed and direction and solar radiation intensity was built in the area of the National Radiation Protection Institute vvi. The station was designed to be independent of an electrical network and enables on-line wireless transfer of all data. After introduction of the station, illustrations of its measurement properties and the results of measured diurnal and seasonal variability of atmospheric radon, based on annual continuous measurement using a high-volume scintillation cell at a height of 2.5 m above the ground, are presented.

  10. Standard dosing of amikacin and gentamicin in critically ill patients results in variable and subtherapeutic concentrations.

    PubMed

    Roger, Claire; Nucci, Bastian; Molinari, Nicolas; Bastide, Sophie; Saissi, Gilbert; Pradel, Gael; Barbar, Saber; Aubert, Clément; Lloret, Sophie; Elotmani, Loubna; Polge, Anne; Lefrant, Jean-Yves; Roberts, Jason A; Muller, Laurent

    2015-07-01

    Low peak plasma concentrations (Cmax) of amikacin and gentamicin are reported in intensive care unit (ICU) patients after administration of the first dose. The present study aimed to describe the proportion of ICU patients in whom an adequate Cmax was achieved throughout the course of therapy. Septic ICU patients with an indication for intravenous amikacin or gentamicin were eligible for inclusion in this single-centre observational study. The first and subsequent doses and the corresponding Cmax values were recorded. The target Cmax was ≥60mg/L for amikacin and ≥30mg/L for gentamicin. Amikacin and gentamicin plasma concentrations were available in 66 and 24 patients, respectively (59±17 years; 79±19kg; height 169±12cm; SAPS II score 46±19). Pulmonary, abdominal and urinary tract infections were diagnosed in 64 patients. Culture-positive infection was confirmed in 65 patients (72%). A target first Cmax was achieved in 17/90 patients (19%). For amikacin, the target Cmax was achieved in 16/66 patients (24%) after the initial dose. In the 50 remaining patients, a change in dosing was performed in 14 patients, leading adequate peak plasma level in 2 patients. For gentamicin, the targeted Cmax was achieved in only 1/24 patient (4%) after the initial dose and was never achieved after the third dose. In conclusion, standard dosing of amikacin or gentamicin led to adequate Cmax in only 19% of patients. Subtherapeutic Cmax were not significantly corrected after subsequent doses.

  11. Using Shoulder Straps Decreases Heart Rate Variability and Salivary Cortisol Concentration in Swedish Ambulance Personnel

    PubMed Central

    Karlsson, Kåre J.; Niemelä, Patrik H.; Jonsson, Anders R.; Törnhage, Carl-Johan A.

    2015-01-01

    Background Previous research has shown that paramedics are exposed to risks in the form of injuries to the musculoskeletal system. In addition, there are studies showing that they are also at increased risk of cardiovascular disease, cancer, and psychiatric diseases, which can partly be explained by their constant exposure to stress. The aim of this study is to evaluate whether the use of shoulder straps decreases physical effort in the form of decreased heart rate and cortisol concentration. Methods A stretcher with a dummy was carried by 20 participants for 400 m on two occasions, one with and one without the shoulder straps. Heart rate was monitored continuously and cortisol samples were taken at intervals of 0 minutes, 15 minutes, 30 minutes, 45 minutes, and 60 minutes. Each participant was her or his own control. Results A significant decrease in heart rate and cortisol concentration was seen when shoulder straps were used. The median values for men (with shoulder straps) at 0 minutes was 78 bpm/21.1 nmol/L (heart rate/cortisol concentration), at 15 minutes was 85 bpm/16.9 nmol/L, and at 60 minutes was 76 bpm/15.7 nmol/L; for men without shoulder straps, these values were 78 bpm/21.9 nmol/L, 93 bpm/21.9 nmol/L, and 73 bpm/20.5 nmol/L. For women, the values were 85 bpm/23.3 nmol/L, 92 bpm/20.8 nmol/L, and 70 bpm/18.4 nmol/L and 84 bpm/32.4 nmol/L, 100 bpm/32.5 nmol/L, and 75 bpm/25.2 nmol/L, respectively. Conclusion The use of shoulder straps decreases measurable physical stress and should therefore be implemented when heavy equipment or a stretcher needs to be carried. An easy way to ensure that staff use these or similar lifting aids is to provide them with personalized, well-adapted shoulder straps. Another better option would be to routinely sewn these straps into the staff's personal alarm jackets so they are always in place and ready to be used. PMID:27014488

  12. Landscape variability of the stable carbon isotope composition of soil CO2 concentrations and flux in complex terrain

    NASA Astrophysics Data System (ADS)

    Riveros-Iregui, Diego; Liang, Liyin; Risk, David

    2015-04-01

    Stable isotopes are commonly used to understand how physical and biological processes mediate the exchange of carbon between terrestrial ecosystems and the atmosphere. Numerous studies have described fundamental relationships between environmental variables, the carbon isotopic composition (δ13C) of recently assimilated sugars in plants, litter, soil carbon, or recently respired CO2. However, studies that examine the landscape scale variability of the 13C content of forest soils are lacking. We report on measurements of the carbon isotopic composition of soil CO2 concentrations (δ13CC) and flux (δ13CJ) across a subalpine forest of the northern Rocky Mountains of Montana, United States. Our analysis demonstrates that soil moisture and the lateral redistribution of soil water are strong predictors of the spatial variability of both δ13CC and δ13CJ at the watershed scale. Our analysis suggests that there are concomitant yet independent effects of soil water on physical (i.e., soil gas diffusivity) and biological (i.e., photosynthetic activity) processes that mediate the 13C composition of forest soils. We show systematic spatial variability in the δ13C of forest soils at the landscape scale that can be useful to accurately predict and model land-atmosphere CO2 exchange over complex terrain.

  13. Variability of suspended-sediment concentration at tidal to annual time scales in San Francisco Bay, USA

    USGS Publications Warehouse

    Schoellhamer, D.H.

    2002-01-01

    Singular spectrum analysis for time series with missing data (SSAM) was used to reconstruct components of a 6-yr time series of suspended-sediment concentration (SSC) from San Francisco Bay. Data were collected every 15 min and the time series contained missing values that primarily were due to sensor fouling. SSAM was applied in a sequential manner to calculate reconstructed components with time scales of variability that ranged from tidal to annual. Physical processes that controlled SSC and their contribution to the total variance of SSC were (1) diurnal, semidiurnal, and other higher frequency tidal constituents (24%), (2) semimonthly tidal cycles (21%), (3) monthly tidal cycles (19%), (4) semiannual tidal cycles (12%), and (5) annual pulses of sediment caused by freshwater inflow, deposition, and subsequent wind-wave resuspension (13%). Of the total variance 89% was explained and subtidal variability (65%) was greater than tidal variability (24%). Processes at subtidal time scales accounted for more variance of SSC than processes at tidal time scales because sediment accumulated in the water column and the supply of easily erodible bed sediment increased during periods of increased subtidal energy. This large range of time scales that each contained significant variability of SSC and associated contaminants can confound design of sampling programs and interpretation of resulting data.

  14. Concentration-discharge relationships for variably sized streams in Florida: Patterns and drivers in long-term catchment studies

    NASA Astrophysics Data System (ADS)

    Diamond, J.; Cohen, M.

    2012-12-01

    Catchment-scale analyses can provide important insight into the processes governing solute sources, transport and storage. Understanding solute dynamics is vital for water management both for accurate predictions of chemical fluxes as well as ecosystem responses to them. This project synthesized long-term (>15 years) hydrochemical data from 80 variably sized (101-105 m2) watersheds in Florida. Our goal was to evaluate scaling effects on flow-solute relationships, and determine the factors that control observed inter-catchment variation. We obtained long term records of a variety of chemical parameters include color, nutrients (N and P), and geogenic solutes (Ca, Si, Mg, Na, Cl) from stations where chemistry and flow data were matched. Catchment attributes (land use, terrain, surface geology) were obtained for each stream as potential covariates. Concentration-discharge relationships were modeled as power functions, the exponents (b) of which were categorized into three end-member scenarios: (1) b>0, or chemodynamic conditions, where increased discharge increases concentration, (2) b=0, or chemostatic conditions, where concentration is independent of discharge, and (3) b<0, or dilution conditions, where increased discharge decreases concentrations. Color was strongly chemodynamic, while geogenic solutes tended to be chemostatic;nutrient-flow relationships varied substantially (from dilution to chemodynamic) suggesting important ancillary controls. To assess between-site variability, power function exponents were compared against land use and catchment area. These results indicate that watersheds dominated by urban land use exhibit stronger dilution effects for most solutes while watersheds dominated by agricultural land use were generally chemostatic particularly for nutrients. This synthesis approach to understanding controls on observed concentration-discharge relationships is crucial to understanding the dynamics and early-warning indicators of anthropogenically

  15. Radon concentration in soil gas: a comparison of the variability resulting from different methods, spatial heterogeneity and seasonal fluctuations.

    PubMed

    Winkler, R; Ruckerbauer, F; Bunzl, K

    2001-05-14

    From the end of 1996 through March 1999, the spatial and temporal variability of the soil 222Rn concentration was investigated at a 20 m x 20 m test field with porous soil in 0.5 m and 1.0 m depth at nine positions each and at 1 m x 1 m plots at four positions each. For this, soil gas was collected weekly into evacuated scintillation cells and was analysed subsequently for radon activity. In the 20 m x 20 m field the spatial variability was characterized by coefficients of variation (C.V.) of 26% at 0.5 m, and 13% at 1.0 m depth. Within the 1 m x 1 m plots the C.V. values were 4% and 2%, i.e. within the uncertainty of the method. Time series analysis (TSA) of the soil radon data shows seasonal variations with maximum concentrations in the winter months. Radon concentrations ranged from 6 to 50 kBq m(-3) in 0.5 m depth, and from 8 to 34 kBq m(-3) in 1.0 m depth. Mostly, the concentrations were higher in 0.5 depth than in 1.0 m depth. However, seasonal variation of the 0.5 m to the 1.0 m concentration ratio has been verified by TSA. To test the variability resulting from different methods, additional procedures and instruments were investigated at the 20 m x 20 m field and at a second test field with a different soil type. Soil gas sampling into evacuated scintillation cells was selected as the reference procedure. Soil radon concentrations obtained with the different sampling procedures and detection methods at the 20 m x 20 m field essentially agreed within the limits of uncertainty of the methods tested. At the second test field, i.e. in a largely impermeable soil, deviations up to a factor of two related to the reference procedure were observed.

  16. Ergosterol concentration and variability in genotype-by-pathogen interaction for grain mold resistance in sorghum.

    PubMed

    Mpofu, Leo T; McLaren, Neal W

    2014-08-01

    A lack of understanding of host-by-pathogen relations can hinder the success of breeding for resistance to a major disease. Fungal strain pathogenicity has to be understood from the virulence it can cause on susceptible genotypes and host resistance indicates which genotypes have resistance genes. Where the two worlds meet lies the place where researchers match the prevalent pathogen in the area of production with resistant varieties. This paper uses ergosterol concentration analysis as a measure of fungal biomass accumulation to assess levels of resistance in host genotypes. 11 sorghum genotypes were inoculated with 5 strains of fungi that are known to be associated with grain mold disease of sorghum. The resulting interaction was analyzed using GGE Biplot analysis and Cluster analysis which showed that none of the genotypes were resistant to Phoma sorghina and Curvularia lunata. Three genotypes were resistant to Fusarium thapsinum. One fungal strain (Alternaria alternata) does not contribute any significant damage in the grain mold disease. Fusarium graminearum causes very little grain mold disease. There was no correlation between the fungal strains. Visual scoring did not correlate with ergosterol accumulation. Resistance to grain mold in sorghum is shown to be due to vertical or specific resistance genes. Sorghum breeders should, therefore, identify predominant fungal strains in their localities and then locate and tag these resistance genes in their germplasm and pyramid them in commercial varieties.

  17. Three years of concentric gravity wave variability in the mesopause as observed by IMAP/VISI

    NASA Astrophysics Data System (ADS)

    Perwitasari, S.; Sakanoi, T.; Nakamura, T.; Ejiri, M. K.; Tsutsumi, M.; Tomikawa, Y.; Otsuka, Y.; Yamazaki, A.; Saito, A.

    2016-11-01

    We report a statistical study on concentric gravity waves (CGWs) in the mesopause ( 95 km) using 3 years nightglow data obtained by Ionosphere, Mesosphere, upper Atmosphere and Plasmasphere/Visible and near-Infrared Spectral Imager. The 235 CGWs events were found with horizontal wavelength ranging from 40 to 250 km and maximum radius of 200 to 3000 km. The latitudinal distribution of the CGWs centers had peaks in mid latitude (40°N and 40°S) and minimum at low latitudes (10°S). More events were found in the summer hemisphere midlatitudes, with a rapid transition between northern and Southern Hemisphere around the equinoxes. The occurrence probability was significantly higher during nonsolstice months (February-May and August-November) than solstice months (June-July and December-January), suggesting that there was a little breaking or critical level absorption so the waves could reach the mesopause more often during these periods. The global distribution showed several preferable regions but very few events over tropical convective regions.

  18. Persistence of Hydrologic Variables and Reactive Stream Solute Concentrations in an East Tennessee Watershed

    SciTech Connect

    Koirala, Shesh R; Gentry, Randall W; Mulholland, Patrick J; Perfect, Edmund; Schwartz, John S; Sayler, Gary Steven

    2011-01-01

    Time and frequency domain analyses were conducted on weekly time series of water chemistry (nitrate, sulfate and calcium concentrations) collected from November 1995 to December 2005 at the West Fork of Walker Branch in Oak Ridge, Tennessee to evaluate the extent of their persistence and the relationship of this persistence to discharge and rainfall. In this study, spectral and wavelet analyses provided a theoretical basis for insights into long-term water chemistry behavior. All water chemistry parameters showed some level of persistence that was influenced by rainfall and/or discharge. Short-term persistence (less than a year) was related to the persistence of rainfall and discharge, whereas long-term persistence (more than a year) was related to the persistence of discharge. The Walker Branch conceptual hydrology model is augmented by these results that relate characteristic periodicities with flowpaths through different zones: the vadose zone (< 20 week period), saturated zone (20-50 week period) and bedrock zone (> 50 week period) with implications for reactive chemistries within the watershed. (C) 2011 Elsevier B.V. All rights reserved.

  19. Comparison of the seasonal and interannual variability of phytoplankton pigment concentrations in the Peru and California Current systems

    NASA Technical Reports Server (NTRS)

    Thomas, A. C.; Huang, F.; Strub, P. T.; James, C.

    1994-01-01

    Monthly composite images from the global coastal zone color scanner (CZCS) data set are used to provide an initial illustration and comparison of seasonal and interannual variability of phytoplankton pigment concentration along the western coasts of South and North America in the Peru Current system (PCS) and California Current system (CCS). The analysis utilizes the entire time series of available data (November 1978 to June 1986) to form a mean annual cycle and an index of interannual variability for a series of both latitudinal and cross-shelf regions within each current system. Within 100 km of the coast, the strongest seasonal cycles in the CCS are in two regions, one between 34 deg and 45 deg N and the second between 24 deg and 29 deg N, each with maximum concentrations (greater than 3.0 mg m(exp-3)) in May-June. Weaker seasonal variability is present north of 45 deg N and in the Southern California Bight region (32 deg N). Within the PCS, in the same 100-km-wide coastal region, highest (greater than 45 deg S) and lowest (less than 20 deg S) latitude regions have a similar seasonal cycle with maximum concentrations (greater than 1.5 mg m(exp -3)) during the austral spring, summer, and fall, matching that evident throughout the CCS. Between these regions, off northern and central Chile, the seasonal maximum occurs during July-August (austral winter), contrary to the influence of upwelling favorable winds. Within the CCS, the dominant feature of interannual variability in the 8-year time series is a strong negative concentration anomaly in 1983, an El Nino year. The relative value of this negative anomaly is strongest off central California and is followed by an even stronger negative anomaly is strongest off central California and is followed by an even stronger negative anomaly in 1984 off Baja, California. In the PCS, strong negative anomalies during the 1982-1983 El Nino period are evident only off the Peruvian coast and are evident there only in the

  20. The role of sample preparation in interpretation of trace element concentration variability in moss bioindication studies

    USGS Publications Warehouse

    Migaszewski, Z.M.; Lamothe, P.J.; Crock, J.G.; Galuszka, A.; Dolegowska, S.

    2011-01-01

    Trace element concentrations in plant bioindicators are often determined to assess the quality of the environment. Instrumental methods used for trace element determination require digestion of samples. There are different methods of sample preparation for trace element analysis, and the selection of the best method should be fitted for the purpose of a study. Our hypothesis is that the method of sample preparation is important for interpretation of the results. Here we compare the results of 36 element determinations performed by ICP-MS on ashed and on acid-digested (HNO3, H2O2) samples of two moss species (Hylocomium splendens and Pleurozium schreberi) collected in Alaska and in south-central Poland. We found that dry ashing of the moss samples prior to analysis resulted in considerably lower detection limits of all the elements examined. We also show that this sample preparation technique facilitated the determination of interregional and interspecies differences in the chemistry of trace elements. Compared to the Polish mosses, the Alaskan mosses displayed more positive correlations of the major rock-forming elements with ash content, reflecting those elements' geogenic origin. Of the two moss species, P. schreberi from both Alaska and Poland was also highlighted by a larger number of positive element pair correlations. The cluster analysis suggests that the more uniform element distribution pattern of the Polish mosses primarily reflects regional air pollution sources. Our study has shown that the method of sample preparation is an important factor in statistical interpretation of the results of trace element determinations. ?? 2010 Springer-Verlag.

  1. Modeling reactive geochemical transport of concentrated aqueous solutions in variably saturated media

    SciTech Connect

    Zhang, Guoxiang; Zheng, Zuoping; Wan, Jiamin

    2004-01-28

    Concentrated aqueous solutions (CAS) have unique thermodynamic and physical properties. Chemical components in CAS are incompletely dissociated, especially those containing divalent or polyvalent ions. The problem is further complicated by the interaction between CAS flow processes and the naturally heterogeneous sediments. As the CAS migrates through the porous media, the composition may be altered subject to fluid-rock interactions. To effectively model reactive transport of CAS, we must take into account ion-interaction. A combination of the Pitzer ion-interaction and the ion-association model would be an appropriate way to deal with multiple-component systems if the Pitzer' parameters and thermodynamic data of dissolved components and the related minerals are available. To quantify the complicated coupling of CAS flow and transport, as well as the involved chemical reactions in natural and engineered systems, we have substantially extended an existing reactive biogeochemical transport code, BIO-CORE{sup 2D}{copyright}, by incorporating a comprehensive Pitzer ion-interaction model. In the present paper, the model, and two test cases against measured data were briefly introduced. Finally we present an application to simulate a laboratory column experiment studying the leakage of the high alkaline waste fluid stored in Hanford (a site of the U.S. Department of Energy, located in Washington State, USA). With the Pitzer ion-interaction ionic activity model, our simulation captures measured pH evolution. The simulation indicates that all the reactions controlling the pH evolution, including cation exchanges, mineral precipitation and dissolution, are coupled.

  2. Linking particle number concentration (PNC), meteorology and traffic variables in a UK street canyon

    NASA Astrophysics Data System (ADS)

    Price, Heather D.; Arthur, Robert; BéruBé, Kelly A.; Jones, Tim P.

    2014-10-01

    Ambient particle number concentration (PNC) has been linked with adverse health outcomes such as asthma, reduced lung function and cardiovascular disease. To investigate the relationship between PNC, meteorology and traffic we measured size segregated respirable particles in a busy commuter street in Swansea, UK for ten months using a Dekati Electrical Low Pressure Impactor (ELPI). The ELPI segregates particles into 12 size fractions between 7 nm and 10 μm. The median PNC for the sampling period was 31,545 cm- 3. For the ultrafine particles (7-93 nm), the highest PNC was found in winter (46,615 cm- 3; 15 minute average) and the lowest for that size fraction in summer (29,696 cm- 3). For the particles below 93 nm there was a trimodal distribution to weekdays (particularly Monday to Wednesday), with PNC peaks at 09:00, 16:00 and 23:00. Wind direction had a significant influence on PNC and differed between particles in the fine range (below 2.5 μm) and more coarse particles (up to 10 μm). For fine particles, winds parallel to the canyon were associated with higher PNCs which were attributed to the replenishment of traffic particles. For coarse particles, PNCs were higher from winds perpendicular to the canyon and this was linked to source distribution around the sampling site and the recirculation of pollutants within the canyon. During times when vehicle volumes were high and vehicles were exhibiting stop-start behaviour, if this was combined with low wind speeds, ultrafine PNC was highest. This effect was generally observed during the morning rush hour. Current mass-based legislation does not take into account exposure to the number of particles or the change in population exposure diurnally.

  3. Variable Water Concentrations in the Asthenospheric and Lithospheric Mantle Underneath the Eastern United States

    NASA Astrophysics Data System (ADS)

    Soles, B.; Brennan, G. W.; Johnson, E. A.; Mazza, S. E.; Gazel, E.

    2014-12-01

    An Eocene (47-48 Ma) volcanic swarm in NW Virginia represents the youngest episode of volcanism in the Eastern US, possibly initiated by delamination of lithospheric mantle (Mazza 2014). The Eocene swarm is located along the MAGIC seismic array (Crampton 2013). The phenocrysts and mantle xenocrysts within these volcanic rocks are the most direct constraints on the water content of the mantle in this region and will aid interpretation of geophysical data. In this study, we measured structural hydroxyl concentrations, [OH], in clinopyroxene (cpx) and olivine (ol) xenocrysts and cpx phenocrysts from three basaltic intrusions: Mole Hill, a volcanic neck, Trimble Knob, a diatreme, and Rt.631, a dike. Polarized FTIR spectra were obtained at JMU and the Smithsonian Institution. Mineral compositions were obtained on the electron microprobe at the USGS, Reston. The cpx xenocrysts show hydration profiles, whereas cpx phenocrysts have flat or dehydration profiles. Cpx xenocryst cores contain [OH]=25-300 ppm H2O and ol xenocrysts have [OH]<2 ppm. Cpx xenocryst rims contain [OH]=160-1300 ppm, and cpx phenocrysts have [OH]=100-570 ppm, and a cpx from Trimble Knob conservatively contains 1500-3500 ppm. Magmatic water contents calculated using O'Leary (2010) range from 0.3-4.9 wt% for xenocryst rims and phenocrysts, and >6 wt% at Trimble Knob. P and T were calculated using equilibrium exchange reactions from Putirka (2008). Xenocryst rims from Mole Hill have P=13.7±1.7 kbar and T=1287±24°C, and cpx phenocrysts from the Rt.631 dike record similar conditions of P=16.1±2.8 kbar and T=1339±37°C. A cpx phenocryst from Trimble Knob has P=23.8±4.0 kbar and T=1143±124°C. We interpret our data to indicate a dry lithospheric mantle as represented by the cpx and ol xenocrysts, underplated by a wet layer at the lithosphere-asthenosphere boundary produced by fractional crystallization of magma generated deeper in the asthenosphere, as represented by the cpx phenocrysts.

  4. Finite element method modeling to assess Laplacian estimates via novel variable inter-ring distances concentric ring electrodes.

    PubMed

    Makeyev, Oleksandr; Besio, Walter G; Makeyev, Oleksandr; Besio, Walter G; Besio, Walter G; Makeyev, Oleksandr

    2016-08-01

    Noninvasive concentric ring electrodes are a promising alternative to conventional disc electrodes. Currently, superiority of tripolar concentric ring electrodes over disc electrodes, in particular, in accuracy of Laplacian estimation has been demonstrated in a range of applications. In our recent work we have shown that accuracy of Laplacian estimation can be improved with multipolar concentric ring electrodes using a general approach to estimation of the Laplacian for an (n + 1)-polar electrode with n rings using the (4n + 1)-point method for n ≥ 2. This paper takes the next step toward further improving the Laplacian estimate by proposing novel variable inter-ring distances concentric ring electrodes. Derived using a modified (4n + 1)-point method, linearly increasing and decreasing inter-ring distances tripolar (n = 2) and quadripolar (n = 3) electrode configurations are compared to their constant inter-ring distances counterparts using finite element method modeling. Obtained results suggest that increasing inter-ring distances electrode configurations may decrease the estimation error resulting in more accurate Laplacian estimates compared to respective constant inter-ring distances configurations. For currently used tripolar electrode configuration the estimation error may be decreased more than two-fold while for the quadripolar configuration more than six-fold decrease is expected.

  5. Estimation of time-variable fast flow path chemical concentrations for application in tracer-based hydrograph separation analyses

    NASA Astrophysics Data System (ADS)

    Kronholm, Scott C.; Capel, Paul D.

    2016-09-01

    Mixing models are a commonly used method for hydrograph separation, but can be hindered by the subjective choice of the end-member tracer concentrations. This work tests a new variant of mixing model that uses high-frequency measures of two tracers and streamflow to separate total streamflow into water from slowflow and fastflow sources. The ratio between the concentrations of the two tracers is used to create a time-variable estimate of the concentration of each tracer in the fastflow end-member. Multiple synthetic data sets, and data from two hydrologically diverse streams, are used to test the performance and limitations of the new model (two-tracer ratio-based mixing model: TRaMM). When applied to the synthetic streams under many different scenarios, the TRaMM produces results that were reasonable approximations of the actual values of fastflow discharge (±0.1% of maximum fastflow) and fastflow tracer concentrations (±9.5% and ±16% of maximum fastflow nitrate concentration and specific conductance, respectively). With real stream data, the TRaMM produces high-frequency estimates of slowflow and fastflow discharge that align with expectations for each stream based on their respective hydrologic settings. The use of two tracers with the TRaMM provides an innovative and objective approach for estimating high-frequency fastflow concentrations and contributions of fastflow water to the stream. This provides useful information for tracking chemical movement to streams and allows for better selection and implementation of water quality management strategies.

  6. Estimation of time-variable fast flow path chemical concentrations for application in tracer-based hydrograph separation analyses

    USGS Publications Warehouse

    Kronholm, Scott C.; Capel, Paul D.

    2016-01-01

    Mixing models are a commonly used method for hydrograph separation, but can be hindered by the subjective choice of the end-member tracer concentrations. This work tests a new variant of mixing model that uses high-frequency measures of two tracers and streamflow to separate total streamflow into water from slowflow and fastflow sources. The ratio between the concentrations of the two tracers is used to create a time-variable estimate of the concentration of each tracer in the fastflow end-member. Multiple synthetic data sets, and data from two hydrologically diverse streams, are used to test the performance and limitations of the new model (two-tracer ratio-based mixing model: TRaMM). When applied to the synthetic streams under many different scenarios, the TRaMM produces results that were reasonable approximations of the actual values of fastflow discharge (±0.1% of maximum fastflow) and fastflow tracer concentrations (±9.5% and ±16% of maximum fastflow nitrate concentration and specific conductance, respectively). With real stream data, the TRaMM produces high-frequency estimates of slowflow and fastflow discharge that align with expectations for each stream based on their respective hydrologic settings. The use of two tracers with the TRaMM provides an innovative and objective approach for estimating high-frequency fastflow concentrations and contributions of fastflow water to the stream. This provides useful information for tracking chemical movement to streams and allows for better selection and implementation of water quality management strategies.

  7. Understanding and modelling the variability in Dissolved Organic Carbon concentrations in catchment drainage

    NASA Astrophysics Data System (ADS)

    Coleman, Martin; Waldron, Susan; Scott, Marian; Drew, Simon

    2013-04-01

    Our knowledge of dynamic natural habitats could be improved through the deployment of automated sensor technology. Dissolved organic carbon concentrations, [DOC], are of interest to water companies as purification removes this pool and currently in environmental science, due in part to rising DOC levels and also as respiration of this C pool can lead to an increased CO2 efflux. Manual sampling of catchment drainage systems has revealed seasonal patterns in DOC (Williams, P.J.L., 1995) and that hydrological events export most DOC(Raymond, P.A. and J.E. Saiers, 2010). However, manual sampling precludes detailed characterisation of the dynamic fluctuation of DOC over shorter but important time periods e.g. immediately prior to an event; the transition from base flow to a surface run-off dominated system as surface flow pathways defrost. Such insight is only gained through deployment of continuous-monitoring equipment. Since autumn 2010 we have deployed an S::CAN Spectrolyser (which from absorbance gives a measurement of [DOC]) in a 7.5 kilometre squared peaty catchment draining Europe's largest windfarm, Whitelee. Since autumn 2011, we have an almost complete time series of [DOC] every 30. Here [DOC] has ranged from 12.2 to 58.4 mg/l C and during event flow DOC had a maximum variation of 23.5 mg/l within a single day. Simultaneously with the Spectrolyser, we have logged stage height, pH and conductivity using an In-Situ Inc MD Troll 9000. Generally there is an inverse relationship between [DOC] and both pH and conductivity, but a positive relationship (albeit with seasonal differences) with [DOC] and stage height, from which we can infer hydrological changes in the source of the DOC. Here, in addition to presenting the time series of the data, and a more accurate export budget estimate, I will explore statistical methods for the handling of large datasets. Trends in the data of such large and dynamic data sets are challenging to model. Simple relationships with stage

  8. Reconstruction of global atmospheric dust concentrations using dust flux measurements in paleoclimatic archives and dust model variables

    NASA Astrophysics Data System (ADS)

    Lambert, F.; Rojas, M.; Gallardo, L.; Mahowald, N. M.; Takemura, T.; KUG, J.; Winckler, G.; Park, R.; Abe-Ouchi, A.

    2013-12-01

    Aerosols are the second most potent agent affecting anthropogenic radiative forcing after greenhouse gases. However, despite some progress in the field, the uncertainty of aerosol impact on present and past climate remains much larger than for other species. The total atmospheric dust load is an important factor for the radiative budget of the atmosphere, and for the micronutrient supply to terrestrial and marine ecosystems. We have collected published dust flux (mass accumulation rate) measurements from marine sediment cores, ice cores, loess fields, and peat bogs. These measurements are interpolated to two global grids of average Holocene and Last Glacial Maximum (LGM) climatic conditions. The interpolation is performed using a kriging algorithm and its uncertainty shows regions where new measurements are most needed. We have developed a new method that combines observational dust flux measurements with dust depositional variables from climate models to reconstruct average Holocene and LGM atmospheric dust concentrations. Here we use dust simulations from two different coupled GCMs (CAM3-CCSM3 and SPRINTARS-MIROC) to give an idea of the uncertainties due to model variables. Our reconstructions give a different perspective on Holocene and LGM atmospheric dust loads from pure model simulations. The discrepancies between modeled and reconstructed dust concentrations and radiative forcing gives insights on regions and variables that may be improved in the models. In addition, this method allows to follow the temporal and spatial evolution of dust loads (and the resulting changes in radiative forcing and iron fertilization) through the glacial-interglacial transition. Top row: Interpolated Mass Accumulation Rates (MAR) for average Holocene (left column) and Last Glacial Maximum (right column) climatic conditions. The second and third row show simulated MAR from two different coupled climate models.

  9. Temporal variability and spatial dynamics of CO2 and CH4 concentrations and fluxes in the Zambezi River system

    NASA Astrophysics Data System (ADS)

    Teodoru, Cristian; Borges, Alberto; Bouillon, Steven; Nyoni, Frank; Nyambe, Imasiku

    2014-05-01

    Spanning over 2900 km in length and with a catchment of approximately 1.4 million km2, the Zambezi River is the fourth largest river in Africa and the largest flowing into the Indian Ocean from the African continent. Yet, there is surprisingly little or no information on carbon (C) cycling in this large river system. As part of a broader study on the riverine biogeochemistry in the Zambezi River basin, we present here mainstream dissolved CO2 and CH4 data collected during 2012 and 2013 over two climatic seasons (dry and wet) to constrain the interannual variability, seasonality and spatial heterogeneity of partial pressure of CO2 (pCO2) and CH4 concentrations and fluxes along the aquatic continuum, in relation to physico-chemical parameters (temperature, conductivity, oxygen, and pH) and various carbon pools (dissolved and particulate, organic and inorganic carbon, total alkalinity, primary production, respiration and net aquatic metabolism). Both pCO2 and CH4 variability was high, ranging from minimal values of 150 ppm and 7 nM, respectively, mainly in the two large reservoirs (the Kariba and the Cabora Bassa characterized by high pH and oxygen and low DOC), up to maximum values of 12,500 ppm and 12,130 nM, CO2 and CH4, respectively, mostly below floodplains/wetlands (low pH and oxygen levels, high DOC and POC concentrations). The interannual variability was relatively large for both CO2 and CH4 (mean pCO2: 2350 ppm in 2013 vs. 3180 ppm in 2013; mean CH4: 600 nM in 2012 vs. 1000 nM in 2013) and significantly higher (up to two fold) during wet season compared to dry season closely linked to distinct seasonal hydrological characteristics. Overall, no clear pattern was observed along the longitudinal gradient as river CO2 and CH4 concentrations are largely influenced by the presence of floodplains/wetlands, anthropogenic reservoirs or natural barriers (waterfalls/ rapids). Following closely the concentration patterns, river CO2 and CH4 mean fluxes of 3440 mg C-CO2 m

  10. Characterizing the influence of anthropogenic emissions and transport variability on sulfate aerosol concentrations at Mauna Loa Observatory

    NASA Astrophysics Data System (ADS)

    Potter, Lauren E.

    data were supplemented with observations of gaseous radon (Rn222) and carbon monoxide (CO), used as tracers of long distance continental influence. Our study applied trajectory analysis and multiple linear regression to interpret the relative roles of aerosol precursor emissions and large-scale transport characteristics on observed MLO sulfate aerosol variability. We conclude that observed sulfate aerosol at MLO likely originated from a combination of anthropogenic, volcanic, and biogenic sources that varied seasonally and from year to year. Analysis of chemical continental tracer concentrations and HYSPLIT back trajectories suggests that non-negligible long distance influence from either the Asian or North American continents can be detected at MLO during all seasons although large interannual variability was observed. Possible influence of circulation changes in the Pacific Basin related to the El Nino-Southern Oscillation were found to be both species and seasonally dependent. We further found an increasing trend in monthly mean sulfate aerosol concentrations at MLO of 4.8% (7.3 ng m-3) per year during 1995-2008, significant at the 95% confidence level. Multiple linear regression results suggest that the observed trend in sulfate concentrations at MLO cannot reasonably be explained by variations in meteorology and transport efficiency alone. An increasing sulfate trend of 5.8 ng m-3 per year, statistically significant at the 90% confidence level, was found to be associated with the variable representing East Asian SO2 emissions. The results of this study provide evidence that MLO sulfate aerosol observations during 1995-2008 reflect, in part, recent trends in anthropogenic SO2 emissions which are superimposed onto the natural meteorological variability affecting transport efficiency.

  11. Influence of wildfires on the variability and trend of ozone concentrations in the U.S. Intermountain West

    NASA Astrophysics Data System (ADS)

    Lu, Xiao; Zhang, Lin; Zhao, Yuanhong; Yue, Xu

    2016-04-01

    Wildfires are important sources of ozone by emitting large amounts of NOx and NMVOC, main ozone precursors at both global and regional scales. Their influences on ozone in the U.S. Intermountain West have recently received much interest because surface ozone concentrations over that region showed an increasing trend in the past two decades likely due to increasing wildfire emissions in a warming climate. Here we use the Lagrangian particle dispersion model (FLEXPART) as well as the GEOS-Chem chemical transport model to estimate wildfires' contribution on summer (June, July and August; JJA) ozone concentration variations, trends, and extremely high ozone events over the US Intermountain West for the past 22 years (1989-2010). We combine the resident time estimated from the FLEXPART 5-day backward trajectories and a high-resolution fire inventory to define a fire index representing the impact of wildfires on ozone concentration at a particular site for each day of summers 1989-2010. Over 26,000 FLEXPART back-trajectories are conducted for the whole time period and for 13 CASTNet surface monitoring sites. We build a stepwise multiple linear regression (SMLR) model of daily ozone concentrations using fire index and other meteorological variables for each site. The SMLR models explain 53% of the ozone variations (ranging from 12% to 68% for each site). We show that ozone produced from wildfires (calculated from SMLR model) are of high variability at daily scale (ranging from 0.1 ppbv to 20.7 ppbv), but are averaged to lower values of about 0.25-3.5 ppbv for summer mean. We estimate that wildfires magnify inter-annual variations of the regional mean summer ozone for about 32%, compared to the result with wildfires impact excluded from the SMLR model. Wildfire ozone enhancements increase at a rate of 0.04 ppbv per year, accouting for about 20% of the regional summer ozone trend during 1989-2010. Removing wildfires' impact would reduce 35% (46%) of the high-ozone days with

  12. Variability of suspended sand concentrations, transport and eddy diffusivity under non-breaking waves on the shoreface

    NASA Astrophysics Data System (ADS)

    Vincent, Christopher E.; Downing, Andrew

    1994-02-01

    Suspended sand concentration profiles and current speed measurements were made in 1.6 ± 0.4m water depth on the seaward side of a bar beyond the break point at Stanhope Lane beach, Prince Edward Island, Canada, during a 4 day period. Two mild storm events occurred and 7 min-long bursts of 4.4 Hz data were recorded approximately every hour. Concentration profiles, with a resolution of 5 mm and 7.5 mm, were obtained using a 3 MHz acoustic backscatter (ABS) instrument. Some data on bed form dimensions were obtained by divers between storm events. Multiple bed echoes from the ABS also provide further information on the ripple heights but no direct observations were available at times of higher waves. During the 4 day period the local position of the bed decreased by about 8 cm, erosion occurring in two short (⋟6 h) periods, one during each storm event. Mean currents at this location were weak (<0.1 m s -1). The resuspension coefficient γ 0, calculated from the concentration at 2 cm above the bed, decreased as the wave height increased (in the break-off range) supporting the observations of VINCENTet al. [(1991) Marine Geology, 96, 1-18]. Large inter-burst variability was observed in the concentration profiles and in the eddy diffusivity and suspended transport fluxes computed from these profiles. This variability was due to the short length of record (⋟7min) relative to wave groups and to the location of the ABS relative to bed forms; to obtain consistent concentration and transport fluxes it is necessary to average many bursts over a time scale that is long compared to both groupiness and bed form mobility. Except at the beginning and end of events when wave conditions were changing rapidly, averaging over groups of bursts with similar wave conditions produced eddy diffusivity profiles characterized by a linear ɛ s gradient of (20 ±2.5) cm s -1 from the sea bed to 20 ± 5cm, beyond which ɛ s slowly decreased, and a suspended sand transport which was all below

  13. Intraurban concentrations, spatial variability and correlation of ambient polycyclic aromatic hydrocarbons (PAH) and PM2.5

    NASA Astrophysics Data System (ADS)

    Anastasopoulos, Angelos T.; Wheeler, Amanda J.; Karman, Deniz; Kulka, Ryan H.

    2012-11-01

    To investigate the intraurban spatial variability of air toxics associated with respirable particulate matter (PM), ambient PM2.5 and 16 polycyclic aromatic hydrocarbons (PAH) species (vapour phase plus 2.5 μm particle phase) were sampled over a dense network of sites in Hamilton, Ontario, Canada in June/July 2009 and December 2009. PM2.5 levels ranged from 2.46 to 11.0 μg m-3 in the summer campaign and 6.52 to 13.4 μg m-3 in the winter campaign. Total sampled PAH (Σ16PAH) levels ranged from 10.2 to 83.7 ng m-3 in the summer campaign and 8.31 to 52.1 ng m-3 in the winter campaign. Ambient PM2.5 and PAH concentrations were greater below the city's escarpment with a below/above escarpment difference in concentration much greater for PAH than for PM2.5 in both summer and winter sampling campaigns. Elevated levels of both pollutants were observed to occur near or downwind of the central business district and industrialized harbourfront area, suggesting the contribution of local sources. Ambient PAH exhibited a substantially greater degree of intraurban variability than PM2.5 (coefficient of variation approximately three times greater in summer campaign, four times greater in winter campaign) both above and below the escarpment, particularly for heavy MW species found predominantly in the particle phase. Benzo(a)Pyrene-equivalent toxicity (BaP-TEQ) associated with ambient PAH showed a generally similar spatial distribution to Σ16PAH; however, several sites with relatively low Σ16PAH had high BaP-TEQ (enriched in more toxic heavy MW species), indicating potential hotspots for elevated PAH exposures and local source contributions. Co-located field sampling data showed that central site monitoring was a poor proxy for PM2.5 and particularly for PAH and associated toxicity (BaP-TEQ) across the urban centre, underestimating levels at many sites, likely due to the significant number of locally distributed sources and mixed land use. The much greater intraurban

  14. Variability of DOM concentration and quality in a peatland and forest headwater stream: seasonal and event characteristics

    NASA Astrophysics Data System (ADS)

    Broder, Tanja; Knorr, Klaus-Holger; Biester, Harald

    2016-04-01

    Export of terrestrial dissolved organic matter (DOM) from soils to aquatic systems plays a fundamental role in surface water chemistry. In many catchments, main sources are peatlands and peaty riparian zones. However, not only total DOM concentration is of great interest for e.g. the carbon cycle or drinking water generation. Also the quality of DOM strongly affects function and fate of DOM in aquatic systems. Moreover, changes in DOM quality can help to elucidate sources of DOM and underlying controls of mobilization. Therefore, this study focused on changes of DOM concentration and quality in a peatland and forest headwater stream considering seasonal patterns and hydrological dynamics. The study was conducted at the Odersprung bog, in a small headwater catchment characterized by an ombrotrophic peatland with adjacent, peaty forest soils in the Harz Mountains in northwestern Germany. During a one-year campaign, sampling of the headwater stream was conducted in biweekly intervals and in high resolution during selected high discharge events. DOM was characterized by spectrofluorometric indices, such as SUVA254nm, SR, HIX and FI, as well as by PARAFAC modelling of fluorescence spectra. Results showed major changes in DOM concentration, as well as in DOM quality during the sampling period. DOM concentrations ranged between 5 to 45 mg C L-1 and were mainly controlled by season with low concentrations during snowmelt and spring and higher concentrations in late summer and fall. Highest concentrations occurred at a fall high discharge event. Compared to the peatland, the forested site with a peaty riparian zone exhibited higher DOM concentrations and a stronger variability induced by hydrologic conditions. DOM quality changes as indicated by spectrofluorometric indices and modelled PARAFAC components were mainly induced by hydrology and showed no clear seasonal pattern. An increasing water level at the bog site caused hydrological connection of fresh DOM pools and a

  15. A new general dynamic model predicting radionuclide concentrations and fluxes in coastal areas from readily accessible driving variables.

    PubMed

    Håkanson, Lars

    2005-01-01

    This paper presents a general, process-based dynamic model for coastal areas for radionuclides (metals, organics and nutrients) from both single pulse fallout and continuous deposition. The model gives radionuclide concentrations in water (total, dissolved and particulate phases and concentrations in sediments and fish) for entire defined coastal areas. The model gives monthly variations. It accounts for inflow from tributaries, direct fallout to the coastal area, internal fluxes (sedimentation, resuspension, diffusion, burial, mixing and biouptake and retention in fish) and fluxes to and from the sea outside the defined coastal area and/or adjacent coastal areas. The fluxes of water and substances between the sea and the coastal area are differentiated into three categories of coast types: (i) areas where the water exchange is regulated by tidal effects; (ii) open coastal areas where the water exchange is regulated by coastal currents; and (iii) semi-enclosed archipelago coasts. The coastal model gives the fluxes to and from the following four abiotic compartments: surface water, deep water, ET areas (i.e., areas where fine sediment erosion and transport processes dominate the bottom dynamic conditions and resuspension appears) and A-areas (i.e., areas of continuous fine sediment accumulation). Criteria to define the boundaries for the given coastal area towards the sea, and to define whether a coastal area is open or closed are given in operational terms. The model is simple to apply since all driving variables may be readily accessed from maps and standard monitoring programs. The driving variables are: latitude, catchment area, mean annual precipitation, fallout and month of fallout and parameters expressing coastal size and form as determined from, e.g., digitized bathymetric maps using a GIS program. Selected results: the predictions of radionuclide concentrations in water and fish largely depend on two factors, the concentration in the sea outside the given

  16. Space and time variability of satellite-derived sea surface temperatures and phytoplankton pigment concentrations in the eastern North Atlantic

    SciTech Connect

    Oliveira, P.B.; Peliz, A.R.; Fiuza, A.F.G.

    1994-12-31

    An analysis of NOAA/AVHRR II sea surface temperatures (SST) and NIMBUS-7/CZCS phytoplankton pigment concentrations was conducted in order to characterize their mean distributions and their space-time variability in the eastern North Atlantic, particularly in the vicinity of the western Iberian Peninsula. A 9-year long (1982--1990) SST set relative to a large part of the North Atlantic was extensively processed and analyzed to obtain the highest space-time resolution possible using only measured values. A good compromise led to a 9-year sequence of weekly averages of SST at 90 km x 90 km resolution. The first applications of these data were the preparation of yearly, seasonal and monthly mean surface temperature distributions with unprecedented resolution, as well as the construction of sequences of weekly SST charts for the whole 9-year period. The latter were used to construct a color video-loop which clearly shows the seasonal and interannual evolution of SST in a large region of the North Atlantic, in particular the meridional migration of the isotherms, the variability of large-scale thermal features associated with the Gulf Stream, the Labrador Current, the Azores Current, and the coastal upwelling along the North Atlantic eastern boundary.

  17. Environmental variability and heavy metal concentrations from five lagoons in the Ionian Sea (Amvrakikos Gulf, W Greece)

    PubMed Central

    Pavloudi, Christina; Kalantzi, Ioanna; Apostolaki, Eugenia T.; Chatzigeorgiou, Giorgos; Chatzinikolaou, Eva; Pafilis, Evangelos; Papageorgiou, Nafsika; Fanini, Lucia; Konstas, Spyridon; Fragopoulou, Nina; Arvanitidis, Christos

    2016-01-01

    Abstract Background Coastal lagoons are ecosystems of major importance as they host a number of species tolerant to disturbances and they are highly productive. Therefore, these ecosystems should be protected to ensure stability and resilience. The lagoons of Amvrakikos Gulf form one of the most important lagoonal complexes in Greece. The optimal ecological status of these lagoons is crucial for the well-being of the biodiversity and the economic prosperity of the local communities. Thus, monitoring of the area is necessary to detect possible sources of disturbance and restore stability. New information The environmental variables and heavy metals concentrations, from five lagoons of Amvrakikos Gulf were measured from seasonal samplings and compared to the findings of previous studies in the area, in order to check for possible sources of disturbance. The analysis, showed that i) the values of the abiotic parameters vary with time (season), space (lagoon) and with space over time; ii) the variability of the environmental factors and enrichment in certain elements is naturally induced and no source of contamination is detected in the lagoons. PMID:27932906

  18. Changes in intracellular calcium concentration influence beat-to-beat variability of action potential duration in canine ventricular myocytes.

    PubMed

    Kistamas, K; Szentandrassy, N; Hegyi, B; Vaczi, K; Ruzsnavszky, F; Horvath, B; Banyasz, T; Nanasi, P P; Magyar, J

    2015-02-01

    The aim of the present work was to study the influence of changes in intracellular calcium concentration ([Ca(2+)]i) on beat-to-beat variability (short term variability, SV) of action potential duration (APD) in isolated canine ventricular cardiomyocytes. Series of action potentials were recorded from enzymatically isolated canine ventricular cells using conventional microelectrode technique. Drug effects on SV were evaluated as relative SV changes determined by plotting the drug-induced changes in SV against corresponding changes in APD and comparing these data to the exponential SV-APD function obtained with inward and outward current injections. Exposure of myocytes to the Ca(2+) chelator BAPTA-AM (5 μM) decreased, while Ca(2+) ionophore A23187 (1 μM) increased the magnitude of relative SV. Both effects were primarily due to the concomitant changes in APD. Relative SV was reduced by BAPTA-AM under various experimental conditions including pretreatment with veratridine, BAY K8644, dofetilide or E-4031. Contribution of transient changes of [Ca(2+)]i due to Ca(2+) released from the sarcoplasmic reticulum (SR) was studied using 10 μM ryanodine and 1 μM cyclopiazonic acid: relative SV was reduced by both agents. Inhibition of the Na(+)-Ca(2+) exchanger by 1 μM SEA0400 increased relative SV. It is concluded that elevation of [Ca(2+)]i increases relative SV significantly. More importantly, Ca(2+) released from the SR is an important component of this effect.

  19. Variability of pesticide detections and concentrations in field replicate water samples collected for the National Water-Quality Assessment Program, 1992-97

    USGS Publications Warehouse

    Martin, Jeffrey D.

    2002-01-01

    Correlation analysis indicates that for most pesticides and concentrations, pooled estimates of relative standard deviation rather than pooled estimates of standard deviation should be used to estimate variability because pooled estimates of relative standard deviation are less affected by heteroscedasticity. The 2 Variability of Pesticide Detections and Concentrations in Field Replicate Water Samples, 1992–97 median pooled relative standard deviation was calculated for all pesticides to summarize the typical variability for pesticide data collected for the NAWQA Program. The median pooled relative standard deviation was 15 percent at concentrations less than 0.01 micrograms per liter (µg/L), 13 percent at concentrations near 0.01 µg/L, 12 percent at concentrations near 0.1 µg/L, 7.9 percent at concentrations near 1 µg/L, and 2.7 percent at concentrations greater than 5 µg/L. Pooled estimates of standard deviation or relative standard deviation presented in this report are larger than estimates based on averages, medians, smooths, or regression of the individual measurements of standard deviation or relative standard deviation from field replicates. Pooled estimates, however, are the preferred method for characterizing variability because they provide unbiased estimates of the variability of the population. Assessments of variability based on standard deviation (rather than variance) underestimate the true variability of the population. Because pooled estimates of variability are larger than estimates based on other approaches, users of estimates of variability must be cognizant of the approach used to obtain the estimate and must use caution in the comparison of estimates based on different approaches.

  20. Variability in the Correlation between Asian Dust Storms and Chlorophyll a Concentration from the North to Equatorial Pacific

    PubMed Central

    Tan, Sai-Chun; Yao, Xiaohong; Gao, Hui-Wang; Shi, Guang-Yu; Yue, Xu

    2013-01-01

    A long-term record of Asian dust storms showed seven high-occurrence-frequency centers in China. The intrusion of Asian dust into the downwind seas, including the China seas, the Sea of Japan, the subarctic North Pacific, the North Pacific subtropical gyre, and the western and eastern Equatorial Pacific, has been shown to add nutrients to ocean ecosystems and enhance their biological activities. To explore the relationship between the transported dust from various sources to the six seas and oceanic biological activities with different nutrient conditions, the correlation between monthly chlorophyll a concentration in each sea and monthly dust storm occurrence frequencies reaching the sea during 1997–2007 was examined in this study. No correlations were observed between dust and chlorophyll a concentration in the <50 m China seas because atmospheric deposition is commonly believed to exert less impact on coastal seas. Significant correlations existed between dust sources and many sea areas, suggesting a link between dust and chlorophyll a concentration in those seas. However, the correlation coefficients were highly variable. In general, the correlation coefficients (0.54–0.63) for the Sea of Japan were highest, except for that between the subarctic Pacific and the Taklimakan Desert, where it was as high as 0.7. For the >50 m China seas and the North Pacific subtropical gyre, the correlation coefficients were in the range 0.32–0.57. The correlation coefficients for the western and eastern Equatorial Pacific were relatively low (<0.36). These correlation coefficients were further interpreted in terms of the geographical distributions of dust sources, the transport pathways, the dust deposition, the nutrient conditions of oceans, and the probability of dust storms reaching the seas. PMID:23460892

  1. Sea ice concentration temporal variability over the Weddell Sea and its relationship with tropical sea surface temperature

    USGS Publications Warehouse

    Barreira, S.; Compagnucci, R.

    2007-01-01

    Principal Components Analysis (PCA) in S-Mode (correlation between temporal series) was performed on sea ice monthly anomalies, in order to investigate which are the main temporal patterns, where are the homogenous areas located and how are they related to the sea surface temperature (SST). This analysis provides 9 patterns (4 in the Amundsen and Bellingshausen Seas and 5 in the Weddell Sea) that represent the most important temporal features that dominated sea ice concentration anomalies (SICA) variability in the Weddell, Amundsen and Bellingshausen Seas over the 1979-2000 period. Monthly Polar Gridded Sea Ice Concentrations data set derived from satellite information generated by NASA Team algorithm and acquired from the National Snow and Ice Data Center (NSIDC) were used. Monthly means SST are provided by the National Center for Environmental Prediction reanalysis. The first temporal pattern series obtained by PCA has its homogeneous area located at the external region of the Weddell and Bellingshausen Seas and Drake Passage, mostly north of 60°S. The second region is centered in 30°W and located at the southeast of the Weddell. The third area is localized east of 30°W and north of 60°S. South of the first area, the fourth PC series has its homogenous region, between 30° and 60°W. The last area is centered at 0° W and south of 60°S. Correlation charts between the five Principal Components series and SST were performed. Positive correlations over the Tropical Pacific Ocean were found for the five PCs when SST series preceded SICA PC series. The sign of the correlation could relate the occurrence of an El Niño/Southern Oscillation (ENSO) warm (cold) event with posterior positive (negative) anomalies of sea ice concentration over the Weddell Sea.

  2. Plasma coenzyme Q10 concentration, antioxidant status, and serum N-terminal pro-brain natriuretic peptide concentration in dogs with various cardiovascular diseases and the effect of cardiac treatment on measured variables.

    PubMed

    Svete, Alenka Nemec; Verk, Barbara; Seliškar, Alenka; Tomsič, Katerina; Križman, Petra Jazbec; Petrič, Aleksandra Domanjko

    2017-04-01

    OBJECTIVE To determine the plasma total antioxidant capacity, erythrocyte superoxide dismutase activity, whole blood glutathione peroxidase activity, and plasma coenzyme Q10 (CoQ10) concentration in dogs with various stages of cardiovascular diseases and in healthy dogs; assess the influence of cardiac treatment on the levels of antioxidant variables, plasma CoQ10 concentration, and serum N-terminal pro-brain natriuretic peptide (NT-proBNP) concentration, and determine any correlation between the disease severity (NT-proBNP concentration) and antioxidant variables or CoQ10 concentration. ANIMALS 43 dogs with various types and stages of cardiovascular diseases (congenital and acquired) and 29 healthy dogs. PROCEDURES Blood samples were collected from all dogs for spectrophotometric assessment of antioxidant variables. Plasma CoQ10 concentration was determined with a high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry method. Serum NT-proBNP concentration was measured with an ELISA. RESULTS Values for antioxidant variables did not differ among groups of dogs with cardiovascular diseases, regardless of disease stage or treatment. Plasma CoQ10 concentration was significantly increased in treated dogs with congestive heart failure (CHF), compared with untreated patients. However, plasma CoQ10 concentration did not differ among heart failure classes. A significant, negative correlation between serum NT-proBNP and plasma CoQ10 concentrations was identified in treated CHF-affected dogs, suggesting that low plasma CoQ10 concentration may be associated with increased severity of CHF. CONCLUSIONS AND CLINICAL RELEVANCE The antioxidant variables evaluated were not altered in dogs with CHF, regardless of cardiac disease stage or treatment. Further investigation into the possible effects of CoQ10 supplementation in dogs with advanced stages of CHF is warranted.

  3. Within-Person Variability in Urinary Phthalate Metabolite Concentrations: Measurements from Specimens after Long-Term Frozen Storage

    PubMed Central

    Baird, Donna Day; Saldana, Tina M.; Nepomnaschy, Pablo A.; Hoppin, Jane A.; Longnecker, Matthew P.; Weinberg, Clarice R.; Wilcox, Allen J.

    2017-01-01

    Laboratory studies show that exposure to phthalates during development can cause adverse effects, especially for males. Studies in humans would be facilitated by collection of urine during pregnancy, long-term storage, and measurement of phthalate metabolites at the time that offspring health is assessed. Our aims were to measure urinary phthalate metabolites after long-term freezer storage, to use those measurements to evaluate within-woman variability over two and four-week intervals, and to determine if the phases of the menstrual cycle affect metabolite levels. Samples were selected from daily first-morning urine specimens collected by 60 women and stored frozen since 1983-1985. Three specimens per woman were selected at approximately two-week intervals to include both follicular and luteal phase samples. Seven metabolites of five phthalates were measured by mass spectrometry. Statistical analyses were conducted with correlation, mixed model regression, and the Wilcoxon signed rank test. Creatinine-corrected urinary phthalate metabolite concentrations measured in samples after long-term storage tended to have a similar right-skewed distribution, though with somewhat higher concentrations than those reported for recently-collected U.S. samples. The concentrations of three metabolites of di(2-ethylhexyl)phthalate in the same specimen were very highly correlated (Pearson r = 0.85 – 0.97). Reproducibility over a 4-week interval was moderate for the metabolites of diethyl phthalate and benzylbutyl phthalate (intraclass correlation coefficients, ICCs, = 0.48 and 0.53, respectively), while five other metabolites had lower ICCs (0.21 – 0.37). Menstrual phase was not related to metabolite concentrations. Though the same samples have not been measured both before and after long-term storage, results suggest that measurement of phthalate metabolites after long-term sample storage yield generally similar distributions and temporal reliability as those reported for

  4. Sweating Rate and Sweat Sodium Concentration in Athletes: A Review of Methodology and Intra/Interindividual Variability.

    PubMed

    Baker, Lindsay B

    2017-03-01

    Athletes lose water and electrolytes as a consequence of thermoregulatory sweating during exercise and it is well known that the rate and composition of sweat loss can vary considerably within and among individuals. Many scientists and practitioners conduct sweat tests to determine sweat water and electrolyte losses of athletes during practice and competition. The information gleaned from sweat testing is often used to guide personalized fluid and electrolyte replacement recommendations for athletes; however, unstandardized methodological practices and challenging field conditions can produce inconsistent/inaccurate results. The primary objective of this paper is to provide a review of the literature regarding the effect of laboratory and field sweat-testing methodological variations on sweating rate (SR) and sweat composition (primarily sodium concentration [Na(+)]). The simplest and most accurate method to assess whole-body SR is via changes in body mass during exercise; however, potential confounding factors to consider are non-sweat sources of mass change and trapped sweat in clothing. In addition, variability in sweat [Na(+)] can result from differences in the type of collection system used (whole body or localized), the timing/duration of sweat collection, skin cleaning procedure, sample storage/handling, and analytical technique. Another aim of this paper is to briefly review factors that may impact intra/interindividual variability in SR and sweat [Na(+)] during exercise, including exercise intensity, environmental conditions, heat acclimation, aerobic capacity, body size/composition, wearing of protective equipment, sex, maturation, aging, diet, and/or hydration status. In summary, sweat testing can be a useful tool to estimate athletes' SR and sweat Na(+) loss to help guide fluid/electrolyte replacement strategies, provided that data are collected, analyzed, and interpreted appropriately.

  5. Temporal Variability of the Bioaerosol Background at a Subway Station: Concentration Level, Size Distribution, and Diversity of Airborne Bacteria

    PubMed Central

    Dybwad, Marius; Skogan, Gunnar

    2014-01-01

    Naturally occurring bioaerosol environments may present a challenge to biological detection-identification-monitoring (BIODIM) systems aiming at rapid and reliable warning of bioterrorism incidents. One way to improve the operational performance of BIODIM systems is to increase our understanding of relevant bioaerosol backgrounds. Subway stations are enclosed public environments which may be regarded as potential bioterrorism targets. This study provides novel information concerning the temporal variability of the concentration level, size distribution, and diversity of airborne bacteria in a Norwegian subway station. Three different air samplers were used during a 72-h sampling campaign in February 2011. The results suggested that the airborne bacterial environment was stable between days and seasons, while the intraday variability was found to be substantial, although often following a consistent diurnal pattern. The bacterial levels ranged from not detected to 103 CFU m−3 and generally showed increased levels during the daytime compared to the nighttime levels, as well as during rush hours compared to non-rush hours. The airborne bacterial levels showed rapid temporal variation (up to 270-fold) on some occasions, both consistent and inconsistent with the diurnal profile. Airborne bacterium-containing particles were distributed between different sizes for particles of >1.1 μm, although ∼50% were between 1.1 and 3.3 μm. Anthropogenic activities (mainly passengers) were demonstrated as major sources of airborne bacteria and predominantly contributed 1.1- to 3.3-μm bacterium-containing particles. Our findings contribute to the development of realistic testing and evaluation schemes for BIODIM equipment by providing information that may be used to simulate operational bioaerosol backgrounds during controlled aerosol chamber-based challenge tests with biological threat agents. PMID:24162566

  6. Variability of pesticides and nitrates concentrations along a river transect: chemical and isotopic evidence of groundwater - surface water interconnections

    NASA Astrophysics Data System (ADS)

    Baran, Nicole; Petelet-Giraud, Emmanuelle; Saplairoles, Maritxu

    2015-04-01

    concentration. Finally, downstream the quantified pesticides were different from those observed in the upper part of the Crieu but similar to those observed in groundwater. Sr isotopes together with major elements and Sr concentrations allow to identify 3 distinct end-members to explain the river quality evolution : 1) surface water, 2) groundwater and 3) sub-surface water. On this basis, we first demonstrate that the contribution of the different end-members to the river flow is highly variable from upstream to downstream. Secondly, we evidence water exchanges between the river and the groundwater compartment and vice-versa. The combination of the isotopic and geochemical approaches was essential to understand the complex relations and exchanges between surface and ground-waters occurring in few kilometers along the Crieu River. This understanding allows the comprehension of spatial variability of surface water quality. This is of primary importance when to help water managers to select relevant sampling points to be monitored in the framework of the WFD. Amalric L., et al. (2013). International Journal of Environmental Analytical Chemistry, 93: 1660-1675 Loos R. et al. (2010). Water Research, 44: 4115-4126 Stuart M. et al. (2012). Science of the Total Environment, 416: 1-21.

  7. Factors Affecting Spatial and Temporal Variability in Nutrient and Pesticide Concentrations in the Surficial Aquifer on the Delmarva Peninsula

    USGS Publications Warehouse

    Debrewer, Linda M.; Ator, Scott W.; Denver, Judith M.

    2007-01-01

    Water quality in the unconfined, unconsolidated surficial aquifer on the Delmarva Peninsula is influenced by the availability of soluble ions from natural and human sources, and by geochemical factors that affect the mobility and fate of these ions within the aquifer. Ground-water samples were collected from 60 wells completed in the surficial aquifer of the peninsula in 2001 and analyzed for major ions, nutrients, and selected pesticides and degradation products. Analytical results were compared to similar data from a subset of sampled wells in 1988, as well as to land use, soils, geology, depth, and other potential explanatory variables to demonstrate the effects of natural and human factors on water quality in the unconfined surficial aquifer. This study was conducted as part of the National Water-Quality Assessment Program of the U.S. Geological Survey, which is designed (in part) to describe the status and trends in ground-water quality and to provide an understanding of natural and human factors that affect ground-water chemistry in different parts of the United States. Results of this study may be useful for water-resources managers tasked with addressing water-quality issues of local and regional importance because the surficial aquifer on the Delmarva Peninsula is a major source of water for domestic and public supply and provides the majority of flow in local streams. Human impacts are apparent in ground-water quality throughout the surficial aquifer. The surficial aquifer on the Delmarva Peninsula is generally sandy and very permeable with well-oxygenated ground water. Dissolved constituents found throughout various depths of the unconfined aquifer are likely derived from the predominantly agricultural practices on the peninsula, although effects of road salt, mineral dissolution, and other natural and human influences are also apparent in some areas. Nitrate occurred at concentrations exceeding natural levels in many areas, and commonly exceeded 10

  8. Analysis on long-term variability of sea ice albedo and its relationship with sea ice concentration over Antarctica

    NASA Astrophysics Data System (ADS)

    Seo, Minji; Kim, Hyun-cheol; Seong, Noh-hun; Kwon, Chaeyoung; Kim, Honghee; Han, Kyung-Soo

    2016-10-01

    Sea ice is an important factor for understanding Antarctic climate change. Especially, annual change of sea ice shows different trend in Antarctica and Arctic. This different variation need to continuously observe the Polar Regions. Sea Ice Albedo (SIA) and Sea Ice Concentration (SIC) are an indicator of variation on sea ice. In addition, albedo is key parameter to understand the energy budget in Antarctica. This being so, it is important to analyze long-term variation of the two factors for observing of change of Antarctic environment. In this study, we analyzed long-term variability of SIC and SIA to understand the changes of sea ice over Antarctic and researched the relationship with two factors. We used the SIA data at The Satellite Application Facility on Climate Monitoring (CM SAF) and the SIC data provided by Ocean and Sea Ice Satellite Application Facility (OSI-SAF) from 1982 to 2009. The study period was selected to Antarctic summer season due to polar nights. We divided study periods into two terms, Nov-Dec(ND) and Jan-Feb(JF) in order to reflect the characteristics of sea ice area, which minimum extend occurred in September and maximum extend occurred in February. We analyzed the correlation between SIA and SIC. As a results, two variables have a strong positive correlation (each correlation coefficients are 0.91 in Nov-Dec and 0.90 in Jan-Feb). We performed time series analysis using linear regression to understand the spatial and temporal tendency of SIA and SIC. As a results, SIA and SIC have a same spatial trend such as Weddle sea and Ross sea sections show the positive trend and Bellingshausen Amundsen sea shows the negative trend of two factors. Moreover, annual SIA change rate is 0.26% 0.04% yr-1 over section where represent positive trend during two study periods. And annual SIA change rate is - 0.14 - 0.25 % yr-1 of in the other part where represent negative trend during two study periods.

  9. Defining an Abrasion Index for Lunar Surface Systems as a Function of Dust Interaction Modes and Variable Concentration Zones

    NASA Technical Reports Server (NTRS)

    Kobrick, Ryan L.; Klaus, David M.; Street, Kenneth W., Jr.

    2010-01-01

    Unexpected issues were encountered during the Apollo era of lunar exploration due to detrimental abrasion of materials upon exposure to the fine-grained, irregular shaped dust on the surface of the Moon. For critical design features involving contact with the lunar surface and for astronaut safety concerns, operational concepts and dust tolerance must be considered in the early phases of mission planning. To systematically define material selection criteria, dust interaction can be characterized by two-body or three-body abrasion testing, and subcategorically by physical interactions of compression, rolling, sliding and bending representing specific applications within the system. Two-body abrasion occurs when a single particle or asperity slides across a given surface removing or displacing material. Three-body abrasion occurs when multiple particles interact with a solid surface, or in between two surfaces, allowing the abrasives to freely rotate and interact with the material(s), leading to removal or displacement of mass. Different modes of interaction are described in this paper along with corresponding types of tests that can be utilized to evaluate each configuration. In addition to differential modes of abrasion, variable concentrations of dust in different zones can also be considered for a given system design and operational protocol. These zones include: (1) outside the habitat where extensive dust exposure occurs, (2) in a transitional zone such as an airlock or suitport, and (3) inside the habitat or spacesuit with a low particle count. These zones can be used to help define dust interaction frequencies, and corresponding risks to the systems and/or crew can be addressed by appropriate mitigation strategies. An abrasion index is introduced that includes the level of risk, R, the hardness of the mineralogy, H, the severity of the abrasion mode, S, and the frequency of particle interactions, F.

  10. Hydrologic and Climatic Variability in and Modeling of Streamwater Sulfate Concentrations at Panola Mountain Research Watershed, Georgia, U.S.A.

    NASA Astrophysics Data System (ADS)

    Aulenbach, B. T.; Huntington, T. G.

    2015-12-01

    Variability in streamwater sulfate concentrations at Panola Mountain Research Watershed (PMRW), a small 41-hectare forested watershed near Atlanta, Georgia, U.S.A., was assessed for the period 1996-2012. The source of sulfate at PMRW is predominantly atmospheric deposition of which about 85% is retained within the watershed. Sulfate concentrations increase with increasing streamflow due to an increasing contribution of soil water, which has higher concentrations than that of groundwater. Sulfate concentrations also increased when an intermittent stream in the upper part of the watershed with higher sulfate concentrations contributed larger portions to total streamflow. The highest streamwater sulfate concentrations were observed in hydrologic events that occurred during periods of wetting up after long periods of drought, which were most evident during July through December. These high sulfate concentrations presumably are the result of desorption of sulfate from the shallow soils that accumulated during droughts. Simple concentration-discharge models were fairly weak, with a model R2 of about 0.35, but improved to an R2 of about 0.4 when adding the ratio of streamflow between the upper part of the watershed and the outlet as an independent variable. Additional model improvements were attempted by separating the samples into various groups based on: (1) time of year that high sulfate values were observed; (2) current drought conditions, and; (3) drought conditions during the previous growing season. The largest improvements occurred when separate models were made based on the drought conditions during the previous growing season with model R2s ranging from 0.43 to 0.67 and improvement was observed across all prior drought conditions. The use of hydrologic and climatic variables and categorization led to an enhanced understanding of the factors that affect water-quality variability, and can strengthen predictions of concentrations and estimates of loads.

  11. Influence of seasonal and inter-annual hydro-meteorological variability on surface water fecal coliform concentration under varying land-use composition.

    PubMed

    St Laurent, Jacques; Mazumder, Asit

    2014-01-01

    Quantifying the influence of hydro-meteorological variability on surface source water fecal contamination is critical to the maintenance of safe drinking water. Historically, this has not been possible due to the scarcity of data on fecal indicator bacteria (FIB). We examined the relationship between hydro-meteorological variability and the most commonly measured FIB, fecal coliform (FC), concentration for 43 surface water sites within the hydro-climatologically complex region of British Columbia. The strength of relationship was highly variable among sites, but tended to be stronger in catchments with nival (snowmelt-dominated) hydro-meteorological regimes and greater land-use impacts. We observed positive relationships between inter-annual FC concentration and hydro-meteorological variability for around 50% of the 19 sites examined. These sites are likely to experience increased fecal contamination due to the projected intensification of the hydrological cycle. Seasonal FC concentration variability appeared to be driven by snowmelt and rainfall-induced runoff for around 30% of the 43 sites examined. Earlier snowmelt in nival catchments may advance the timing of peak contamination, and the projected decrease in annual snow-to-precipitation ratio is likely to increase fecal contamination levels during summer, fall, and winter among these sites. Safeguarding drinking water quality in the face of such impacts will require increased monitoring of FIB and waterborne pathogens, especially during periods of high hydro-meteorological variability. This data can then be used to develop predictive models, inform source water protection measures, and improve drinking water treatment.

  12. High nutrient pulses, tidal mixing and biological response in a small California estuary: Variability in nutrient concentrations from decadal to hourly time scales

    USGS Publications Warehouse

    Caffrey, J.M.; Chapin, T.P.; Jannasch, H.W.; Haskins, J.C.

    2007-01-01

    Elkhorn Slough is a small estuary in Central California, where nutrient inputs are dominated by runoff from agricultural row crops, a golf course, and residential development. We examined the variability in nutrient concentrations from decadal to hourly time scales in Elkhorn Slough to compare forcing by physical and biological factors. Hourly data were collected using in situ nitrate analyzers and water quality data sondes, and two decades of monthly monitoring data were analyzed. Nutrient concentrations increased from the mid 1970s to 1990s as pastures and woodlands were converted to row crops and population increased in the watershed. Climatic variability was also a significant factor controlling interannual nutrient variability, with higher nutrient concentrations during wet than drought years. Elkhorn Slough has a Mediterranean climate with dry and rainy seasons. Dissolved inorganic nitrogen (DIN) concentrations were relatively low (10-70 ??mol L-1) during the dry season and high (20-160 ??mol L-1) during the rainy season. Dissolved inorganic phosphorus (DIP) concentrations showed the inverse pattern, with higher concentrations during the dry season. Pulsed runoff events were a consistent feature controlling nitrate concentrations during the rainy season. Peak nitrate concentrations lagged runoff events by 1 to 6 days. Tidal exchange with Monterey Bay was also an important process controlling nutrient concentrations, particularly near the mouth of the Slough. Biological processes had the greatest effect on nitrate concentrations during the dry season and were less important during the rainy season. While primary production was enhanced by nutrient pulses, chlorophyll a concentrations were not. We believe that the generally weak biological response compared to the strong physical forcing in Elkhorn Slough occurred because the short residence time and tidal mixing rapidly diluted nutrient pulses. ?? 2006 Elsevier Ltd. All rights reserved.

  13. Variability over 1 Week in the Urinary Concentrations of Metabolites of Diethyl Phthalate and Di(2-Ethylhexyl) Phthalate among Eight Adults: An Observational Study

    PubMed Central

    Preau, James L.; Wong, Lee-Yang; Silva, Manori J.; Needham, Larry L.; Calafat, Antonia M.

    2010-01-01

    Background Phthalates are metabolized and eliminated in urine within hours after exposure. Several reports suggest that concentrations of phthalate metabolites in a spot urine sample can provide a reliable estimation of exposure to phthalates for up to several months. Objectives We examined inter- and intraperson and inter- and intraday variability in the concentrations of monoethyl phthalate (MEP), the major metabolite of diethyl phthalate, commonly used in personal care products, and mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), a metabolite of di(2-ethylhexyl) phthalate (DEHP), a polyvinyl chloride plasticizer of which diet is the principal exposure source, among eight adults who collected all urine voids (average, 7.6 samples/person/day) for 1 week. Methods We analyzed the urine samples using online solid-phase extraction coupled to isotope dilution–high-performance liquid chromatography–tandem mass spectrometry. Results Regardless of the type of void (spot, first morning, 24-hr collection), for MEP, interperson variability in concentrations accounted for > 75% of the total variance. By contrast, for MEHHP, within-person variability was the main contributor (69–83%) of the total variance. Furthermore, we observed considerable intraday variability in the concentrations of spot samples for MEHHP (51%) and MEP (21%). Conclusions MEP and MEHHP urinary concentrations varied considerably during 1 week, but the main contributors to the total variance differed (interday variability, MEHHP; interperson variability, MEP) regardless of the sampling strategy (spot, first morning, 24-hr collection). The nature of the exposure (diet vs. other lifestyle factors) and timing of urine sampling to evaluate exposure to phthalates should be considered. For DEHP and phthalates to which people are mostly exposed through diet, collecting 24-hr voids for only 1 day may not be advantageous compared with multiple spot collections. When collecting multiple spot urine samples

  14. Spatial and Temporal Variability in Nitrate Concentration below the Root Zone in an Almond Orchard and its Implications for Potential Groundwater Contamination

    NASA Astrophysics Data System (ADS)

    Baram, S.; Couvreur, V.

    2015-12-01

    Spatial and Temporal Variability in Nitrate Concentration below the Root Zone in an Almond Orchard and its Implications for Potential Groundwater Contamination S. Baram1, M. Read1, D. Smart2, T. Harter1, J Hopmans11Department of Land, Air & Water Resources University of California Davis 2Department of Viticulture and Enology University of California Davis Estimates of water and fertilizer losses below the root zone of nitrogen (N) intensive agricultural orchard crops are major concern in groundwater protection. However, microscopic and macroscopic heterogeneity in unsaturated soils make accurate loss estimates very challenging. In this study we aimed to examine field scale variability in nitrate (NO3-) losses below the root zone (>250cm) of a 15 years old almond orchard in Madera county California. Based on a soil variability survey, tensiometers and solution samplers were installed at 17 locations around the 40 acre orchard. The hydraulic potential and the NO3- concentrations were monitored over two growing seasons. Nitrate concentrations varied spatially and temporarily, and ranged from below to more than 30 times higher than the drinking water contamination standard of >10 mg NO3--N L-1. Principal component analysis of the relations between the NO3- concentration, presence of a hard pan in the subsurface, its depth and thickness, and the fertigation and irrigation events indicated that none of these factors explained the observed variability in pore-water NO3- concentrations, with hard pan being the most dominant factor. Throughout the irrigation season minimal leaching was observed, yet post-harvest and preseason flooding events led to deep drainage. Due to the high spatial and temporal variability in the NO3- concentration and the potential for deep drainage following a wet winter or flooding event we conclude that the most efficient way to protect ground water is by transitioning to high frequency low nitrogen fertigation which would retain NO3-in the active

  15. Seasonal variability of tritium and ion concentrations in rain at Kumamoto, Japan and back-trajectory analysis of air mass

    SciTech Connect

    Momoshima, N.; Sugihara, S.; Toyoshima, T.; Nagao, Y.; Takahashi, M.; Nakamura, Y.

    2008-07-15

    Tritium and major ion concentrations in rain were analyzed in Kumamoto (Japan)) between 2001 and 2006 to examine present tritium concentration and seasonal variation. The average tritium concentration was 0.36 {+-} 0.19 Bq/L (n=104) and higher tritium concentrations were observed in spring than the other seasons. Among the ions, non-sea-salt (nss) SO{sub 4}{sup 2}'- showed higher concentration in winter while other ions did not show marked increase in winter. Based on the back-trajectory analyses of air masses, the increase in tritium concentrations in spring arises from downward movement of naturally produced tritium from stratosphere to troposphere, while the increase of the nss-SO{sub 4}{sup 2-} concentrations in winter is due to long range transport of pollutants from China to Japan. (authors)

  16. Seed protein percentage and mineral concentration variability and correlation with other seed quality traits in the U.S. Peanut mini-core collection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Protein percentage and mineral concentrations were determined for 95 accessions of the U. S. peanut mini-core collection by nitrogen analysis and inductively coupled plasma – optical emission spectrometry, respectively, using material collected over two field seasons. Significant variability in the ...

  17. THE INFLUENCE OF VARIABLE ELIMINATION RATE AND BODY FAT MASS IN A PBPK MODEL FOR TCDD IN PREDICTING THE SERUM TCDD CONCENTRATIONS FROM VETERANS OF OPERATION RANCH HAND

    EPA Science Inventory

    The Influence of Variable Elimination Rate and Body Fat Mass in a PBPK Model for TCDD in Predicting the Serum TCDD Concentrations from Veterans of Operation Ranch Hand.
    C Emond1,2, LS Birnbaum2, JE Michalek3, MJ DeVito2
    1 National Research Council, National Academy of Scien...

  18. Longitudinal studies of cardiac troponin-I concentrations in serum from male Sprague Dawley rats: baseline reference ranges and effects of handling and placebo dosing on biological variability.

    PubMed

    Schultze, A Eric; Carpenter, Kent H; Wians, Frank H; Agee, Sara J; Minyard, Jennifer; Lu, Quynh Anh; Todd, John; Konrad, Robert J

    2009-10-01

    Serum cardiac troponin-I has been validated as a biomarker for cardiotoxicity in numerous animal models; however, baseline reference ranges for cTnI concentration in a healthy population of laboratory rats, as well as an investigation of biological cTnI variability in rats with respect to time, handling, and placebo dosing methods, have not been reported. In this study, we used an ultrasensitive cTnI immunoassay to quantify hourly concentrations of cTnI in live rats handled under standard laboratory conditions using 15 microL of serum per determination. The baseline reference range (mean 4.94 pg/mL, range 1-15 pg/mL, 99% confidence interval [CI]) of cTnI concentration in rats was consistent with previously reported reference ranges for cTnI in humans (1-12 pg/mL) and with preliminary studies in dogs (1-4 pg/mL) and monkeys (4-5 pg/mL) using the same cTnI assay method. In addition, cTnI concentrations in individual rat serum samples show minimal biological variability over a twenty-four-hour interval when compared to a meaningful reference change value of 193% to 206%. Furthermore, measurements of cTnI concentration were consistent within the reference limits in individual rats over long periods and under three different standard laboratory handling conditions. Thus, using this new method, rats can be followed longitudinally at hourly intervals, and a doubling of cTnI concentration would be significant above biological variability. This is a new paradigm for preclinical testing, which allows transient changes in cTnI concentration to be accurately quantified. This understanding of baseline and biological variability in rats will be fundamental for designing and analyzing future studies that assess potential cardiotoxicity in drug development.

  19. Concentrations of lead, cadmium and barium in urban garden-grown vegetables: the impact of soil variables

    PubMed Central

    McBride, Murray B.; Shayler, Hannah A.; Spliethoff, Henry M.; Mitchell, Rebecca G.; Marquez-Bravo, Lydia G.; Ferenz, Gretchen S.; Russell-Anelli, Jonathan M.; Casey, Linda; Bachman, Sharon

    2014-01-01

    Paired vegetable/soil samples from New York City and Buffalo, NY, gardens were analyzed for lead (Pb), cadmium (Cd) and barium (Ba). Vegetable aluminum (Al) was measured to assess soil adherence. Soil and vegetable metal concentrations did not correlate; vegetable concentrations varied by crop type. Pb was below health-based guidance values (EU standards) in virtually all fruits. 47% of root crops and 9% of leafy greens exceeded guidance values; over half the vegetables exceeded the 95th percentile of market-basket concentrations for Pb. Vegetable Pb correlated with Al; soil particle adherence/incorporation was more important than Pb uptake via roots. Cd was similar to market-basket concentrations and below guidance values in nearly all samples. Vegetable Ba was much higher than Pb or Cd, although soil Ba was lower than soil Pb. The poor relationship between vegetable and soil metal concentrations is attributable to particulate contamination of vegetables and soil characteristics that influence phytoavailability. PMID:25163429

  20. Concentrations of lead, cadmium and barium in urban garden-grown vegetables: the impact of soil variables.

    PubMed

    McBride, Murray B; Shayler, Hannah A; Spliethoff, Henry M; Mitchell, Rebecca G; Marquez-Bravo, Lydia G; Ferenz, Gretchen S; Russell-Anelli, Jonathan M; Casey, Linda; Bachman, Sharon

    2014-11-01

    Paired vegetable/soil samples from New York City and Buffalo, NY, gardens were analyzed for lead (Pb), cadmium (Cd) and barium (Ba). Vegetable aluminum (Al) was measured to assess soil adherence. Soil and vegetable metal concentrations did not correlate; vegetable concentrations varied by crop type. Pb was below health-based guidance values (EU standards) in virtually all fruits. 47% of root crops and 9% of leafy greens exceeded guidance values; over half the vegetables exceeded the 95th percentile of market-basket concentrations for Pb. Vegetable Pb correlated with Al; soil particle adherence/incorporation was more important than Pb uptake via roots. Cd was similar to market-basket concentrations and below guidance values in nearly all samples. Vegetable Ba was much higher than Pb or Cd, although soil Ba was lower than soil Pb. The poor relationship between vegetable and soil metal concentrations is attributable to particulate contamination of vegetables and soil characteristics that influence phytoavailability.

  1. Uranium concentrations from an aragonite speleothem as a proxy for Mesoamerican Monsoon Variability over the last 2,250 years

    NASA Astrophysics Data System (ADS)

    Crotty, C.; Lachniet, M. S.; Asmerom, Y.; Polyak, V. J.; Bernal, J. P.

    2015-12-01

    Trace element concentrations (Mg and U) were measured in an aragonite stalagmite (JX-6) from Juxtlahuaca Cave ("JX Cave"), in southwestern Mexico, using an inductively coupled plasma mass spectrometer (ICP-MS). These trace element concentrations were compared to previously analyzed δ18O and δ13C values from JX-6, and to the results of previous studies comparing U concentrations in speleothems to paleoclimate. U concentrations of JX-6 correlate well with δ13C and δ18O values, and we interpret them to be a proxy for soil moisture above Juxtlahuaca Cave. This study concludes that U concentrations in JX-6 may be controlled by changes in the pCO2 of overlying soils in relation to plant respiration possibly linked to the consistency of wet season (May - November) rainfall and temperature between 240 BCE to 1800 CE. Comparison to previous studies suggests that speleothem U concentrations are controlled by local cave conditions and are best used with the support of additional trace element and stable isotope data. Anomalous spikes in trace element concentrations were also observed in JX-6 at ~1862, 1871, 1904, and 1933 CE. These spikes were interpreted to be caused by increased U mobilization in overlying soils related to multiple deforestation events in association with the clearing of land above Juxtlahuaca Cave for agricultural use.

  2. Relationship among environmental quality variables, housing variables, and residential needs: a secondary analysis of the relationship among indoor, outdoor, and personal air (RIOPA) concentrations database

    NASA Astrophysics Data System (ADS)

    Garcia, Fausto; Shendell, Derek G.; Madrigano, Jaime

    2017-03-01

    Retrospective descriptive secondary analyses of data from relationships of indoor, outdoor, and personal air (RIOPA) study homes (in Houston, Texas; Los Angeles County, California; and, Elizabeth, New Jersey May 1999-February 2001) were conducted. Data included air exchange rates, associations between indoor and outdoor temperature and humidity, and calculated apparent temperature and humidex. Analyses examined if study homes provided optimum thermal comfort for residents during both heating and cooling seasons when compared to current American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) Standards 62/62.1 and 55. Results suggested outdoor temperature, humidex, and apparent temperature during the cooling season potentially served as indicators of indoor personal exposure to parameters of thermal comfort. Outdoor temperatures, humidex, and apparent temperature during the cooling season had statistically significant predictive abilities in predicting indoor temperature. During the heating season, only humidex in Texas and combined data across study states were statistically significant, but with weaker to moderate predicative ability. The high degree of correlation between outdoor and indoor environmental variables provided support for the validity of epidemiologic studies of weather relying on temporal comparisons. Results indicated most RIOPA study residents experienced thermal comfort; however, many values indicated how several residents may have experienced some discomfort depending on clothing and indoor activities. With climate change, increases in temperature are expected, with more days of extreme heat and humidity and, potentially harsher, longer winters. Homes being built or modernized should be created with the appropriate guidelines to provide comfort for residents daily and in extreme weather events.

  3. Relationship among environmental quality variables, housing variables, and residential needs: a secondary analysis of the relationship among indoor, outdoor, and personal air (RIOPA) concentrations database.

    PubMed

    Garcia, Fausto; Shendell, Derek G; Madrigano, Jaime

    2017-03-01

    Retrospective descriptive secondary analyses of data from relationships of indoor, outdoor, and personal air (RIOPA) study homes (in Houston, Texas; Los Angeles County, California; and, Elizabeth, New Jersey May 1999-February 2001) were conducted. Data included air exchange rates, associations between indoor and outdoor temperature and humidity, and calculated apparent temperature and humidex. Analyses examined if study homes provided optimum thermal comfort for residents during both heating and cooling seasons when compared to current American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) Standards 62/62.1 and 55. Results suggested outdoor temperature, humidex, and apparent temperature during the cooling season potentially served as indicators of indoor personal exposure to parameters of thermal comfort. Outdoor temperatures, humidex, and apparent temperature during the cooling season had statistically significant predictive abilities in predicting indoor temperature. During the heating season, only humidex in Texas and combined data across study states were statistically significant, but with weaker to moderate predicative ability. The high degree of correlation between outdoor and indoor environmental variables provided support for the validity of epidemiologic studies of weather relying on temporal comparisons. Results indicated most RIOPA study residents experienced thermal comfort; however, many values indicated how several residents may have experienced some discomfort depending on clothing and indoor activities. With climate change, increases in temperature are expected, with more days of extreme heat and humidity and, potentially harsher, longer winters. Homes being built or modernized should be created with the appropriate guidelines to provide comfort for residents daily and in extreme weather events.

  4. Relationship among environmental quality variables, housing variables, and residential needs: a secondary analysis of the relationship among indoor, outdoor, and personal air (RIOPA) concentrations database

    NASA Astrophysics Data System (ADS)

    Garcia, Fausto; Shendell, Derek G.; Madrigano, Jaime

    2016-08-01

    Retrospective descriptive secondary analyses of data from relationships of indoor, outdoor, and personal air (RIOPA) study homes (in Houston, Texas; Los Angeles County, California; and, Elizabeth, New Jersey May 1999-February 2001) were conducted. Data included air exchange rates, associations between indoor and outdoor temperature and humidity, and calculated apparent temperature and humidex. Analyses examined if study homes provided optimum thermal comfort for residents during both heating and cooling seasons when compared to current American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) Standards 62/62.1 and 55. Results suggested outdoor temperature, humidex, and apparent temperature during the cooling season potentially served as indicators of indoor personal exposure to parameters of thermal comfort. Outdoor temperatures, humidex, and apparent temperature during the cooling season had statistically significant predictive abilities in predicting indoor temperature. During the heating season, only humidex in Texas and combined data across study states were statistically significant, but with weaker to moderate predicative ability. The high degree of correlation between outdoor and indoor environmental variables provided support for the validity of epidemiologic studies of weather relying on temporal comparisons. Results indicated most RIOPA study residents experienced thermal comfort; however, many values indicated how several residents may have experienced some discomfort depending on clothing and indoor activities. With climate change, increases in temperature are expected, with more days of extreme heat and humidity and, potentially harsher, longer winters. Homes being built or modernized should be created with the appropriate guidelines to provide comfort for residents daily and in extreme weather events.

  5. Predictive models for Escherichia coli concentrations at inland lake beaches and relationship of model variables to pathogen detection

    EPA Science Inventory

    Methods are needed improve the timeliness and accuracy of recreational water‐quality assessments. Traditional culture methods require 18–24 h to obtain results and may not reflect current conditions. Predictive models, based on environmental and water quality variables, have been...

  6. Variability of suspended particulate matter concentrations and organic compounds in frontal zones of the Atlantic and Southern oceans

    NASA Astrophysics Data System (ADS)

    Nemirovskaya, I. A.; Kravchishina, M. D.

    2016-01-01

    The concentrations of suspended particulate matter (SPM) and particulate forms of the organic compounds (hydrocarbons, lipids, and chlorophyll a) were determined in the surface water layers of the Atlantic and Southern oceans during February to May of 2012 and 2014. It was found that the distribution of concentrations of the studied components is mainly affected by the location of frontal zones. When ice cover forms in the Southern Ocean, the changes in water temperature and phytoplankton development at the ice-water interface result in an increase of the concentrations of SPM, chlorophyll a, and, to a lesser extent, of lipids and hydrocarbons in the surface water layer. The occasional sharp increase of hydrocarbon concentrations caused by anthropogenic pollution was registered at local parts of water areas in the east of the Atlantic Ocean, as well as in the North and Baltic seas.

  7. Variability of the groundwater sulfate concentration in fractured rock slopes: a tool to identify active unstable areas

    NASA Astrophysics Data System (ADS)

    Binet, S.; Spadini, L.; Bertrand, C.; Guglielmi, Y.; Mudry, J.; Scavia, C.

    2009-12-01

    Water chemical analysis of 100 springs from the Orco and the Tinée valleys (Western Italy and Southern France) and a 7 year groundwater chemistry monitoring of the 5 main springs were performed. All these springs drain from crystalline rock slopes. Some of these drain from currently active gravitational slope deformations. All groundwaters flowing through presently unstable slopes show anomalies in the sulfate concentrations compared to stable aquifers. Particularly, an increase of sulfate concentrations was observed repeatedly after each of five consecutive landslides on the La Clapière slope, thus attesting to the mechanical deformations are at the origin of this concentration change. Significant changes in the water chemistry are produced even from slow (mm/year) and low magnitude deformations of the geological settings. Pyrite nuclei in open fractures were found to be coated by iron oxides. This suggests that the increase of dissolved sulfate relates to oxidative dissolution of Pyrite. Speciation calculations of Pyrite versus Gypsum confirmed that observed changes in the sulfate concentrations is predominantly provided from Pyrite. Calculated amounts of dissolved minerals in the springs water was obtained through inverse modelling of the major ion water analysis data. It is shown that the concentration ratio of calculated dissolved Pyrite versus calculated dissolved gneiss rock allows us to unambiguously distinguish water from stable and unstable areas. This result opens an interesting perspective for the follow-up of sliding or friction dynamic in landslides or in (a) seismic faults.

  8. Spatial variability of arsenic concentration in soils and plants, and its relationship with iron, manganese and phosphorus.

    PubMed

    Hossain, M B; Jahiruddin, M; Panaullah, G M; Loeppert, R H; Islam, M R; Duxbury, J M

    2008-12-01

    Spatial distribution of arsenic (As) concentrations of irrigation water, soil and plant (rice) in a shallow tube-well (STW) command area (8 ha), and their relationship with Fe, Mn and P were studied. Arsenic concentrations of water in the 110 m long irrigation channel clearly decreased with distance from the STW point, the range being 68-136 microg L(-1). Such decreasing trend was also noticed with Fe and P concentrations, but the trend for Mn concentrations was not remarkable. Concerning soil As, the concentration showed a decreasing tendency with distance from the pump. The NH(4)-oxalate extractable As contributed 36% of total As and this amount of As was associated with poorly crystalline Fe-oxides. Furthermore only 22% of total As was phosphate extractable so that most of the As was tightly retained by soil constituents and was not readily exchangeable by phosphate. Soil As (both total and extractable As) was significantly and positively correlated with rice grain As (0.296+/-0.063 microg g(-1), n=56). Next to drinking water, rice could be a potential source of As exposure of the people living in the As affected areas of Bangladesh.

  9. Seasonal variability of mercury concentration in soils, buds and leaves of Acer platanoides and Tilia platyphyllos in central Poland.

    PubMed

    Kowalski, Artur; Frankowski, Marcin

    2016-05-01

    In this paper, we present the results of mercury concentration in soils, buds and leaves of maple (Acer platanoides-Ap) and linden (Tilia platyphyllos-Tp) collected in four periods of the growing season of trees, i.e. in April (IV), June (VI), August (VIII) and November (IX) in 2013, from the area of Poznań city (Poland). The highest average concentration of mercury for 88 samples was determined in soils and it equaled 65.8 ± 41.7 ng g(-1) (range 14.5-238.9 ng g(-1)); lower average concentration was found in Ap samples (n = 66): 55.4 ± 18.1 ng g(-1) (range 26.5-106.9 ng g(-1)); in Tp samples 50.4 ± 15.8 ng g(-1) (range 23.1-88.7 ng g(-1)) and in 22 samples of Tp buds 40.8 ± 22.7 ng g(-1) (range 12.4-98.7 ng g(-1)) and Ap buds 28.2 ± 13.6 ng g(-1) (range 8.0-59.5 ng g(-1)). Based on the obtained results, it was observed that the highest concentration of mercury in soils occurred in the centre of Poznań city (95.5 ± 39.1 ng g(-1)), and it was two times higher than the concentration of mercury in other parts of the city. Similar dependencies were not observed for the leaf samples of Ap and Tp. It was found that mercury concentrations in the soil and leaves of maple and linden were different depending on the period of the growing season (April to November). Mercury content in the examined samples was higher in the first two research periods (April IV, June VI), and then, in the following periods, the accumulation of mercury decreased both in soil and leaf samples of the two tree species. There was no correlation found between mercury concentration in leaves and mercury concentration in soils during the four research periods (April-November). When considering the transfer coefficient, it was observed that the main source of mercury in leaves is the mercury coming from the atmosphere.

  10. Assessment of spatial variability of major-ion concentrations and del oxygen-18 values in surface snow, Upper Fremont Glacier, Wyoming, USA

    USGS Publications Warehouse

    Naftz, D.L.; Schuster, P.F.; Reddy, M.M.

    1994-01-01

    One hundred samples were collected from the surface of the Upper Fremont Glacier at equally spaced intervals defined by an 8100m2 snow grid to asesss the significance of lateral variability in major-ion concentrations and del oxygen-18 values. Comparison of the observed variability of each chemical constituent to the variability expected by measurement error indicated substantial lateral variability with the surface-snow layer. Results of the nested ANOVA indicate most of the variance for every constituent is in the values grouped at the two smaller geographic scales (between 506m2 and within 506m2 sections). The variance data from the snow grid were used to develop equations to evaluate the significance of both positive and negative concentration/value peaks of nitrate and del oxygen-18 with depth, in a 160m ice core. Values of del oxygen-18 in the section from 110-150m below the surface consistently vary outside the expected limits and possibly represents cooler temperatures during the Little Ice Age from about 1810 to 1725 A.D. -from Authors

  11. Dispersion for two classes of random variables: general theory and application to inference of an external ligand concentration by a cell.

    PubMed

    Barato, Andre C; Seifert, Udo

    2015-09-01

    We derive expressions for the dispersion for two classes of random variables in Markov processes. Random variables such as current and activity pertain to the first class, which is composed of random variables that change whenever a jump in the stochastic trajectory occurs. The second class corresponds to the time the trajectory spends in a state (or cluster of states). While the expression for the first class follows straightforwardly from known results in the literature, we show that a similar formalism can be used to derive an expression for the second class. As an application, we use this formalism to analyze a cellular two-component network estimating an external ligand concentration. The uncertainty related to this external concentration is calculated by monitoring different random variables related to an internal protein. We show that, inter alia, monitoring the time spent in the phosphorylated state of the protein leads to a finite uncertainty only if there is dissipation, whereas the uncertainty obtained from the activity of the transitions of the internal protein can reach the Berg-Purcell limit even in equilibrium.

  12. Variability in pigment concentration in warm-core rings as determined by coastal zone color scanner satellite imagery from the Mid-Atlantic Bight

    NASA Technical Reports Server (NTRS)

    Garcia-Moliner, Graciela; Yoder, James A.

    1994-01-01

    A time series of coastal zone color scanner (CZCS) derived chlorophyll (CZCS-chl) and sea surface temperature (SST) satellite imagery was developed for the Mid-Atlantic Bight (MAB). Warm-core rings (WCR) were identified by both the warmer SST signal as well as the low pigment concentrations of their cores. The variation in pigment concentrations and SST observed in satellite imagery over the geographic range and life span of four WCRs is investigated. The hypotheses are that pigment concentration increase during the lifetime of the WCR is a response to processes such as convective overturn, upwelling, edge enhancement due to increased vertical mixing, active convergence, or lateral exchange. Empirical orthogonal function analysis (EOF) is used to investigate the relationship between SST and pigment patterns observed in the presence of a WCR. The first two EOF modes explain more than 80% of the variability observed in all four WCRs and in both (SST and pigment) data sets. The results of this study show that, at the synoptic scales of staellite data, the variability observed in the WCRs is greater at the periphery of the rings. These results show that advective entrainment, rather than processes at ring center (e.g., shoaling of the pycnocline/nutricline in response to frictional decay) or at the periphery due to other processes such as vertical mixing, is the mechanism responsible for the observed variability.

  13. GROWTH PERFORMANCE AND PHYSIOLOGICAL VARIABLES FOR BROILER CHICKENS SUBJECTED TO SHORT-TERM ELEVATED CARBON DIOXIDE CONCENTRATIONS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Four trials were conducted to evaluate growth responses, blood chemistry and heart characteristics of broiler chicks subjected to progressive concentrations (0, 3,000, 6,000, 9,000 ppm) of carbon dioxide (CO2) gas from 1 to 14 days of age, which were then discontinued throughout the remainder of th...

  14. Water administration of medium-chain fatty acid caprylic acid produced variable efficacy against cecal Campylobacter jejuni concentrations in broilers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Campylobacter is one of the most common causes of foodborne illness, and poultry is considered a primary source of Campylobacter infections. Caprylic acid, an eight-carbon fatty acid, has been shown in previous studies to reduce enteric cecal Campylobacter concentrations in poultry when administere...

  15. Distribution, variability, and predictors of urinary concentrations of phenols and parabens among pregnant women in Puerto Rico.

    PubMed

    Meeker, John D; Cantonwine, David E; Rivera-González, Luis O; Ferguson, Kelly K; Mukherjee, Bhramar; Calafat, Antonia M; Ye, Xiaoyun; Anzalota Del Toro, Liza V; Crespo-Hernández, Noé; Jiménez-Vélez, Braulio; Alshawabkeh, Akram N; Cordero, José F

    2013-04-02

    Puerto Rico has higher rates of a range of endocrine-related diseases and disorders compared to the United States. However, little is known to date about human exposures to known or potential endocrine disrupting chemicals (EDCs) in Puerto Rico. We recruited 105 pregnant women in Northern Puerto Rico who provided urine samples and questionnaire data at three times (18 ± 2, 22 ± 2, and 26 ± 2 weeks) during gestation. We measured the urinary concentrations of five phenols and three parabens: 2,4-dichlorophenol (24-DCP), 2,5-dichlorophenol (25-DCP), benzophenone-3 (BP-3), bisphenol A (BPA), triclosan (TCS), butyl paraben (B-PB), methyl paraben (M-PB), and propyl paraben (P-PB). The frequent detection of these chemicals suggests that exposure is highly prevalent among these Puerto Rican pregnant women. Urinary concentrations of TCS, BP-3, and 25-DCP were higher than among women of reproductive age in the US general population, while concentrations of BPA, 24-DCP, and parabens were similar. Intraclass correlation coefficients (ICC) varied widely between biomarkers; BPA had the lowest ICC (0.24) and BP-3 had the highest (0.62), followed by 25-DCP (0.49) and TCS (0.47). We found positive associations between biomarker concentrations with self-reported use of liquid soap (TCS), sunscreen (BP-3), lotion (BP-3 and parabens), and cosmetics (parabens). Our results can inform future epidemiology studies and strategies to reduce exposure to these chemicals or their precursors.

  16. Spatial variability and temporal dynamics of greenhouse gas (CO2, CH4, N2O) concentrations and fluxes along the Zambezi River mainstem and major tributaries

    NASA Astrophysics Data System (ADS)

    Teodoru, C. R.; Nyoni, F. C.; Borges, A. V.; Darchambeau, F.; Nyambe, I.; Bouillon, S.

    2014-11-01

    Spanning over 3000 km in length and with a catchment of approximately 1.4 million km2, the Zambezi River is the fourth largest river in Africa and the largest flowing into the Indian Ocean from the African continent. As part of a~broader study on the riverine biogeochemistry in the Zambezi River basin, we present data on greenhouse gas (GHG, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)) concentrations and fluxes collected along the Zambezi River, reservoirs and several of its tributaries during 2012 and 2013 and over two climatic seasons (dry and wet) to constrain the interannual variability, seasonality and spatial heterogeneity along the aquatic continuum. All GHGs concentrations showed high spatial variability (coefficient of variation: 1.01 for CO2, 2.65 for CH4 and 0.21 for N2O). Overall, there was no unidirectional pattern along the river stretch (i.e. decrease or increase towards the ocean), as the spatial heterogeneity of GHGs appeared to be determined mainly by the connectivity with floodplains and wetlands, and the presence of man-made structures (reservoirs) and natural barriers (waterfalls, rapids). Highest CO2 and CH4 concentrations in the mainstream river were found downstream of extensive floodplains/wetlands. Undersaturated CO2 conditions, in contrast, were characteristic for the surface waters of the two large reservoirs along the Zambezi mainstem. N2O concentrations showed the opposite pattern, being lowest downstream of floodplains and highest in reservoirs. Among tributaries, highest concentrations of both CO2 and CH4 were measured in the Shire River whereas low values were characteristic for more turbid systems such as the Luangwa and Mazoe rivers. The interannual variability in the Zambezi River was relatively large for both CO2 and CH4, and significantly higher concentrations (up to two fold) were measured during wet seasons compared to the dry season. Interannual variability of N2O was less pronounced but generally higher

  17. Variability of Residence Time tracer Concentrations at the Southern Sierra Critical Zone Observatory during the California Drought

    NASA Astrophysics Data System (ADS)

    Visser, A.; Thaw, M.; Stacy, E.; Hunsaker, C. T.; Bibby, R. K.; Deinhart, A.; Schorzman, K.; Egnatuk, C. M.; Conklin, M. H.; Esser, B.

    2015-12-01

    California water supply from high elevation snow melt is vulnerable to climate change and prolonged drought conditions. Reduced snow pack and earlier snow melt will result in a greater reliance on man-made reservoirs and subsurface catchment storage. To gain insight into the subsurface storage volume of high elevation catchments, we studied the residence time distribution of surface water leaving the Southern Sierra Critical Zone Observatory. Since October 2014, we have collected monthly samples of two residence time tracers with contrasting half-lives: sulfur-35 (87.5 days) and tritium (12.32 years). Upstream catchment area at the three nested sampling locations is 1 km2 (P301 sub-catchment), 4 km2 (Providence Creek) and ~50 km2 (Big Creek). Samples were analyzed at LLNL by low level liquid scintillation counting and noble gas mass spectrometry after helium accumulation. Variations in tracer concentrations in precipitation, both for tritium (11-24 pCi/L) and sulfur-35 (24-100 mBq/L), complicate straightforward interpretation of residence times. Sulfur-35 concentrations show that last year precipitation contributes 1% - 10% of total stream flow, even during peak snowmelt. Tritium concentrations in stream flow vary between 40% and 60% of the initial concentration in precipitation (15.5 pCi/L), indicating that water leaving the catchment has a residence time on the order of years to decades. Additional analyses of sodium-22 (2.6 year half-life) will aid in deconvoluting the residence time distribution. These low tracer concentrations can be attributed to current severe drought conditions, resulting in low discharge rates and longer residence times. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675107

  18. Temporal variability of mineral dust in southern Tunisia: analysis of 2 years of PM10 concentration, aerosol optical depth, and meteorology monitoring

    NASA Astrophysics Data System (ADS)

    Bouet, Christel; Taieb Labiadh, Mohamed; Bergametti, Gilles; Rajot, Jean Louis; Marticorena, Béatrice; Sekrafi, Saâd; Ltifi, Mohsen; Féron, Anaïs; des Tureaux, Thierry Henry

    2016-04-01

    The south of Tunisia is a region very prone to wind erosion. During the last decades, changes in soil management have led to an increase in wind erosion. In February 2013, a ground-based station dedicated to the monitoring of mineral dust (that can be seen in this region as a proxy of the erosion of soils by wind) was installed at the Institut des Régions Arides (IRA) of Médenine (Tunisia) to document the temporal variability of mineral dust concentrations. This station allows continuous measurements of surface PM10 concentration (TEOM™), aerosol optical depth (CIMEL sunphotometer), and total atmospheric deposition of insoluble dust (CARAGA automatic sampler). The simultaneous monitoring of meteorological parameters (wind speed and direction, relative humidity, air temperature, atmospheric pressure, and precipitations) allows to analyse the factors controlling the variations of mineral dust concentration from the sub-daily to the annual scale. The results from the two first years of measurements of PM10 concentration are presented and discussed. In average on year 2014, PM10 concentration is 56 μg m-3. However, mineral dust concentration highly varies throughout the year: very high PM10 concentrations (up to 1,000 μg m-3 in daily mean) are frequently observed during wintertime and springtime, hardly ever in summer. These episodes of high PM10 concentration (when daily average PM10 concentration is higher than 240 μg m-3) sometimes last several days. By combining local meteorological data, air-masses trajectories, sunphotometer measurements, and satellite imagery, the part of the high PM10concentration due to local emissions and those linked to an advection of dusty air masses by medium and long range transport from the Sahara desert is quantified.

  19. Spatial and seasonal variabilities of the stable carbon isotope composition of soil CO2 concentration and flux in complex terrain

    NASA Astrophysics Data System (ADS)

    Liang, Liyin L.; Riveros-Iregui, Diego A.; Risk, David A.

    2016-09-01

    Biogeochemical processes driving the spatial variability of soil CO2 production and flux are well studied, but little is known about the variability in the spatial distribution of the stable carbon isotopes that make up soil CO2, particularly in complex terrain. Spatial differences in stable isotopes of soil CO2 could indicate fundamental differences in isotopic fractionation at the landscape level and may be useful to inform modeling of carbon cycling over large areas. We measured the spatial and seasonal variabilities of the δ13C of soil CO2 (δS) and the δ13C of soil CO2 flux (δP) in a subalpine forest ecosystem located in the Rocky Mountains of Montana. We found consistently more isotopically depleted values of δS and δP in low and wet areas of the landscape relative to steep and dry areas. Our results suggest that the spatial patterns of δS and δP are strongly mediated by soil water and soil respiration rate. More interestingly, our analysis revealed different temporal trends in δP across the landscape; in high landscape positions δP became more positive, whereas in low landscape positions δP became more negative with time. These trends might be the result of differential dynamics in the seasonality of soil moisture and its effects on soil CO2 production and flux. Our results suggest concomitant yet independent effects of water on physical (soil gas diffusivity) and biological (photosynthetic discrimination) processes that mediate δS and δP and are important when evaluating the δ13C of CO2 exchanged between soils and the atmosphere in complex terrain.

  20. Temporal variability in nutrient concentrations and loads in the River Tamar and its catchment (SW England) between 1974 and 2004.

    PubMed

    Tappin, Alan D; Mankasingh, Utra; McKelvie, Ian D; Worsfold, Paul J

    2013-06-01

    This study reports the results from the analyses of a 30-year (1974-2004) river water quality monitoring dataset for NO x -N (NO₃-N + NO2-N), NH₄-N, PO₄-P and SiO₂-Si at the tidal limit of the River Tamar (SW England), an agriculturally dominated and sparsely populated catchment. Annual mean concentrations of NH4-N, PO₄-P and SiO₂-Si were similar to other rural UK rivers, while annual mean concentrations of NO x -N were clearly lower. Estimated values for the 1940s were much lower than for those of post-1974, at least for NO₃-N and PO₄-P. Flow-weighted mean concentrations of PO₄-P decreased by approximately 60 % between 1974 and 2004, although this change cannot be unequivocally ascribed to either PO₄-P stripping from sewage treatment work effluents or reductions in phosphate fertiliser applications. Lower-resolution sampling (to once per month) in the late 1990s may also have led to the apparent decline; a similar trend was also seen for NH4-N. There were no temporal trends in the mean concentrations of NO x -N, emphasising the continuing difficulty in controlling diffuse pollution from agriculture. Concentrations of SiO₂-Si and NO x -N were significantly and positively correlated with river flows ≤15 m(3) s(-1), showing that diffuse inputs from the catchment were important, particularly during the wet winter periods. In contrast, concentrations of PO₄-P and NH4-N did not correlate across any flow window, despite the apparent importance of diffuse inputs for these constituents. This observation, coupled with the absence of a seasonal (monthly) cycle for these nutrients, indicates that, for PO₄-P and NH4-N, there were no dominant sources and/or both undergo extensive within-catchment processing. Analyses of nutrient fluxes reveal net losses for NO₃-N and SiO₂-Si during the non-winter months; for NO3-N, this may be due to denitrification. Areal fluxes of NO x -N from the catchment were towards the higher end of the range for the UK

  1. Ecological variables influencing trace element concentrations in bottlenose dolphins (Tursiops truncatus, Montagu 1821) stranded in continental Portugal.

    PubMed

    Monteiro, Sílvia S; Torres, Jordi; Ferreira, Marisa; Marçalo, Ana; Nicolau, Lídia; Vingada, José V; Eira, Catarina

    2016-02-15

    Both the conservation status of bottlenose dolphins (Tursiops truncatus) (Habitats Directive 92/43/CEE, Annex II) and the Marine Strategy Framework Directive demand for data on their ecology and anthropogenic threats. To evaluate the bottlenose dolphin's toxicological status in continental Portugal, several trace elements (As, Cd, Cu, Hg, Mn, Ni, Pb, Se, Zn) were determined in 25 stranded individuals. The potential effect of sex, body length and stranding location on trace element concentrations was analysed. In the present study, bottlenose dolphins presented high mercury levels, only exceeded by animals from the Mediterranean and Adriatic seas. Only essential elements were influenced by dolphin sex, whereas Cd, Hg and Pb bioaccumulated in larger dolphins, and hepatic Hg and Cd concentrations were higher in the northwest coast of continental Portugal. The location effect may relate to variations in bottlenose diet and trace element availability, according to the proximity to anthropogenic sources in the Atlantic Iberian coast.

  2. Development of Concentration-Dependent Diffusion Instability in Reactive Miscible Fluids Under Influence of Constant or Variable Inertia

    NASA Astrophysics Data System (ADS)

    Bratsun, Dmitry A.; Stepkina, Olga S.; Kostarev, Konstantin G.; Mizev, Alexey I.; Mosheva, Elena A.

    2016-12-01

    In this work, we focus on the processes which accompany a frontal neutralization reaction occurring between two miscible fluids filling a vertical Hele-Shaw cell. We have found that chemically-induced changes of reagent concentrations coupled with concentration- dependent diffusion (CDD) can produce spatially localized low density areas which are sensitive to the external inertial field. In the case of static gravity we have demonstrated both experimentally and theoretically that it can give rise to the development of perfectly periodic convective structure. This scenario is strikingly different from the irregular density fingering, which is typically observed in the miscible systems. When the system is under the influence of the periodic low-frequency vibrations perpendicular to the reaction front, we found numerically the excitation of a mixed-mode instability combining the double-diffusion instabilities and the Rayleigh-Taylor mechanism of the convection within the low density areas.

  3. Variability of tropospheric ozone concentrations: comparison of ground-level data with aircraft measurements during the "O 3 Reg" campaign (19-21 July 2000)

    NASA Astrophysics Data System (ADS)

    Pont, Véronique; Fontan, Jacques; Lopez, Alain

    The aim of the campaign presented here is to compare data networks' measurements of atmospheric pollutants (mainly tropospheric ozone) with airborne measurements in the atmospheric boundary layer. It is designed to determine whether ozone fields are homogeneous on a regional scale and to show the modulation, on a local scale, of ozone concentrations due to local emissions of anthropogenic and industrial primary pollutants, and/or meteorological thermal processes such as sea/land breeze. The study bears on ozone concentration variability within an anticyclonic air mass on a scale of about 500 km. The contribution of large-scale phenomena in the formation of ozone episodes is shown. Daily maximum ozone values are relatively well representative of tropospheric ozone aircraft measurements. Zooming in on southeastern France establishes that in this area, ozone concentrations arise from multiscale phenomena.

  4. Within-Vineyard, Within-Vine, and Within-Bunch Variability of the Rotundone Concentration in Berries of Vitis vinifera L. cv. Shiraz.

    PubMed

    Zhang, Pangzhen; Barlow, Snow; Krstic, Mark; Herderich, Markus; Fuentes, Sigfredo; Howell, Kate

    2015-05-06

    This study characterizes the environmental factors driving rotundone concentrations in grape berries by quantifying rotundone variability and correlating it with viticultural parameters. Dissection of the vineyard into distinct zones (on the basis of vigor, electrical soil conductivity, and slope), vine into orientations to sun (shaded/unshaded), and grape bunches into sectors (upper and lower and front and back) shows the influence of vine vigor, sunlight, and temperature. Occurrence of the highest rotundone concentration was observed in shaded bunch sectors and vines and from higher vigor vines in the southern-facing areas of the vineyard. The highest concentration of rotundone is consistently found at the top and in shaded sectors of bunches, and this correlates to lower grape surface temperatures. Modeling showed that berry temperature exceeding 25 °C negatively affects the rotundone concentration in Shiraz. Both natural and artificial shading modulated the grape surface and air temperature at the bunch zone and increased the rotundone concentration, without affecting other grape berry quality parameters. Thus, temperature and possibly sunlight interception are the main determinants of rotundone in grape berries. Vineyard topography, vine vigor, vine row, and grape bunch orientation influence the level of berry shading and can, therefore, adjust bunch surface and zone temperatures and influence the berry rotundone concentration.

  5. Spatial and temporal variability of fluoride concentrations in groundwater resources of Larestan and Gerash regions in Iran from 2003 to 2010.

    PubMed

    Amini, Hassan; Haghighat, Gholam Ali; Yunesian, Masud; Nabizadeh, Ramin; Mahvi, Amir Hossein; Dehghani, Mohammad Hadi; Davani, Rahim; Aminian, Abd-Rasool; Shamsipour, Mansour; Hassanzadeh, Naser; Faramarzi, Hossein; Mesdaghinia, Alireza

    2016-02-01

    There is discrepancy about intervals of fluoride monitoring in groundwater resources by Iranian authorities. Spatial and temporal variability of fluoride in groundwater resources of Larestan and Gerash regions in Iran were analyzed from 2003 to 2010 using a geospatial information system and the Mann-Kendall trend test. The mean concentrations of fluoride for the 8-year period in the eight cities and 31 villages were 1.6 and 2.0 mg/l, respectively; the maximum values were 2.4 and 3.8 mg/l, respectively. Spatial, temporal, and spatiotemporal variability of fluoride in overall groundwater resources were relatively constant over the years. However, results of the Mann-Kendall trend test revealed a monotonic trend in the time series of one city and 11 villages for the 8-year period. Specifically, one city and three villages showed positive significant Kendall's Tau values, suggesting an upward trend in fluoride concentrations over the 8-year period. In contrast, seven villages displayed negative significant Kendall's Tau values, arguing for a downward trend in fluoride concentrations over the years. From 2003 to 2010, approximately 52 % of the Larestan and Gerash areas have had fluoride concentrations above the maximum permissible Iranian drinking water standard fluoride level (1.4 mg/l), and about 116,000 people were exposed to such excess amounts. Therefore, our study supports for a close monitoring of fluoride concentrations from health authorities in monthly intervals, especially in villages and cities that showed positive trend in fluoride concentrations. Moreover, we recommend simultaneous implementation of cost-effective protective measures or interventions until a standard fluoride level is achieved.

  6. Temporal variability of urinary concentrations of phthalate metabolites, parabens and benzophenone-3 in a Belgian adult population.

    PubMed

    Dewalque, Lucas; Pirard, Catherine; Vandepaer, Sarah; Charlier, Corinne

    2015-10-01

    In the present study, we investigated the temporal within-person variability of the exposure biomarker for phthalates, parabens and benzophenone-3 (BP3) in 32 Belgian adults, each providing 11 urine spots during 4 months. We calculated the intraclass coefficient correlation (ICC), the sensitivity and the specificity to assess the temporal reproducibility and to investigate the predictive ability of the spot measurements for these classes of chemicals. Additionally, we explored the temporal variability of the estimation of the cumulative risk of exposure to phthalates (hazard index; HI). We observed fair ICC ranging from 0.55 to 0.68 for parabens, monoethyl phthalate (MEP), mono-iso-butyl phthalate (MiBP) and BP3, but lower ICC, from 0.20 to 0.49, for monobenzyl phthalate (MBzP), mono-n-butyl phthalate (MnBP), mono-2-ethylhexyl phthalate (MEHP), mono-2-ethyl-5-oxo-hexyl phthalate (5-oxo-MEHP) and mono-2-ethyl-5-hydroxy-hexyl phthalate (5-OH-MEHP). The ICC estimated for HI (0.49) reflected a moderate reproducibility. The measurements in spot samples were moderate to good predictor of the 4-month level of exposure for parabens, MEP, MnBP, MiBP, BP3 and HI (sensitivity ranging from 0.67 to 0.77), but lower predictor for MEHP, 5-oxo-MEHP, 5-OH-MEHP and MBzP (sensitivity ranging from 0.58 to 0.63). The sensitivity could be increased when several spot urinary levels were averaged to predict the long-term level of exposure. Globally, our results indicate that a single spot measurement seems to correctly represent the long-term exposure for parabens, BP3, MEP, MiBP and HI. Additional spot samples seemed to be needed for the proper exposure assessment of the other target compounds.

  7. Variability of Near-stream, Sub-surface Major-ion and Tracer Concentrations in an Acid Mine Drainage Environment

    NASA Astrophysics Data System (ADS)

    Bencala, K. E.; Kimball, B. A.; Runkel, R. L.

    2006-12-01

    In acid mine drainage environments, tracer-injection and synoptic sampling approaches provide tools for making operational estimates of solute loading within a stream segment. Identifying sub-surface contaminant sources remains a challenge both for characterization of in-stream metal loading and hydrological process research. There is a need to quantitatively define the character and source of contaminants entering streams from ground-water pathways, as well as the potential for changes in water chemistry and contaminant concentrations along these flow paths crossing the sediment-water interface. Complicating the identification of inflows is the mixing of solute sources which may occur in the `near-stream' subsurface areas and specifically along hyporheic exchange flows (HEFs). In Mineral Creek (Silverton, Colorado), major-ion (SO42-, Cl-, Na+, Ca2+, Mg2+) meter-scale sampling shows that subsurface inflows and likely HEFs occur in a hydro- geochemical setting of significant, one order-of-magnitude, spatial variation in the solute concentrations. Transient Storage Models (TSMs) are a tool for interpreting the in-stream responses of solute transport in streams influenced by hyporheic exchange flows. Simulations using the USGS TSM code OTIS are interpreted as suggesting that in Mineral Creek the strong concentration `tailing' of bromide following the tracer injection occurred, at least in part, from HEFs in a hydro - solute transport setting of likely multiple, dispersed and mixed sources of water along a 64 m sub-reach of the nominally gaining stream. In acid mine drainage environments, the ability to distinguish between local and deep solute sources is critical in modeling reactive transport along the stream, as well as in identifying the geochemical evolution of dispersed, subsurface inflows thorough the catchment.

  8. Modelling deposition and air concentration of reduced nitrogen in Poland and sensitivity to variability in annual meteorology.

    PubMed

    Kryza, Maciej; Dore, Anthony J; Błaś, Marek; Sobik, Mieczysław

    2011-04-01

    The relative contribution of reduced nitrogen to acid and eutrophic deposition in Europe has increased recently as a result of European policies which have been successful in reducing SO(2) and NO(x) emissions but have had smaller impacts on ammonia (NH(3)) emissions. In this paper the Fine Resolution Atmospheric Multi-pollutant Exchange (FRAME) model was used to calculate the spatial patterns of annual average ammonia and ammonium (NH(4)(+)) air concentrations and reduced nitrogen (NH(x)) dry and wet deposition with a 5 km × 5 km grid for years 2002-2005. The modelled air concentrations of NH(3) and dry deposition of NH(x) show similar spatial patterns for all years considered. The largest year to year changes were found for wet deposition, which vary considerably with precipitation amount. The FRAME modelled air concentrations and wet deposition are in reasonable agreement with available measurements (Pearson's correlation coefficients above 0.6 for years 2002-2005), and with spatial patterns of concentrations and deposition of NH(x) reported with the EMEP results, but show larger spatial gradients. The error statistics show that the FRAME model results are in better agreement with measurements if compared with EMEP estimates. The differences in deposition budgets calculated with FRAME and EMEP do not exceed 17% for wet and 6% for dry deposition, with FRAME estimates higher than for EMEP wet deposition for modelled period and lower or equal for dry deposition. The FRAME estimates of wet deposition budget are lower than the measurement-based values reported by the Chief Inspectorate of Environmental Protection of Poland, with the differences by approximately 3%. Up to 93% of dry and 53% of wet deposition of NH(x) in Poland originates from national sources. Over the western part of Poland and mountainous areas in the south, transboundary transport can contribute over 80% of total (dry + wet) NH(x) deposition. The spatial pattern of the relative contribution of

  9. Spatial and Temporal Variability of CO2 and CH4 Concentrations in the Atmospheric Surface Layer over West Siberia

    NASA Astrophysics Data System (ADS)

    Belan, Boris D.; Machida, Toshinobu; Sasakawa, Motoki; Davydov, Denis K.; Fofonov, Alexander V.; Krasnov, Oleg A.; Maksyutov, Shamil; Arshinov, Mikhail Yu.

    2015-04-01

    The investigation of greenhouse gas behavior in the atmosphere plays a key role in predicting the global changes of Earth's climate. In this connection, of particular importance is the study of the distribution of sources/sinks of trace gases in the atmospheric surface layer over the different regions of the globe. In order to fill a gap in the data on greenhouse gas concentrations in Russia, National Institute for Environmental Studies (NIES, Japan) and Institute of Atmospheric Optics (IAO SB RAS, Russia) established a network for GHG monitoring (JR-STATION, Japan-Russia Siberian Tall Tower Inland Observation Network). Gas analyzers and meteorological sensors were mounted at radio relay towers located in different regions of West Siberia. The checking equipment was placed in containers at the tower base. In the containers, the climatic parameters optimal for gas analyzer operation were maintained. The work on the network development started in 2001. Since at each of the sites the measurement duration could be different, in this paper we present the data of the greenhouse gas monitoring for eight sites which give the primary idea on the spatial distribution and temporal dynamics of CO2 and CH4 in the atmospheric surface layer over West Siberia. The analysis of the data showed that the average increase in concentration of carbon dioxide by results of our measurements in this territory increases within 1.95 - 2.53 ppm/year, depending on the area. The analysis of long-term data testifies about existence of growth of concentration of methane within 3.2 - 7.2 ppb / year. The presence of a distributed network of the sites operating in the monitoring regime makes it possible not only to investigate the temporal dynamics of CO2 and CH4 at each site and to determine the spatial differences between the concentrations by comparing the data, but also to plot the distribution charts for different moments of time. This work was supported by the Global Environment Research

  10. Spatial and temporal variability of nitrate and nitrous oxide concentrations in the unsaturated zone at a corn field in the US Midwest

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, G.; Negri, C.

    2011-12-01

    There has been a significant increase in reactive nitrogen in the environment as a result of human activity. Reactive nitrogen of anthropogenic origin now equals that derived from natural terrestrial nitrogen fixation and is expected to exceed it by the end of the decade. Nitrogen is applied to crops as fertilizer and impacts the environment through water quality impairments (mostly as nitrate) and as greenhouse gas emissions (as nitrous oxide). Research on environmental impacts resulting from nitrogen application in the form of fertilizers has focused disproportionately on the degradation of water quality from agricultural non-point sources. The impacts of this degradation are registered both locally, with runoff and percolation of agrochemicals into local surface water and groundwater, and on a larger scale, such as the increase in the anoxic zone in the Gulf of Mexico attributed to nitrate from the Mississippi River. Impacts to the global climate from increased production of nitrous oxide as a result of increased fertilization are equally significant. Nitrous oxide is a greenhouse gas with a warming potential that is approximately 300 times greater than carbon dioxide. Direct emissions of nitrous oxide from the soil have been expressed as 1% of the applied nitrogen. Indirect emissions due to runoff, leaching and volatilization of the nitrogen from the field have been expressed as 0.75% of the applied nitrogen. Many studies have focused on processes governing nitrogen fluxes in the soil, surface water and groundwater systems. However, research on the biogeochemical processes regulating nitrogen fluxes in the unsaturated zone and consequent impacts on nitrate and nitrous oxide concentrations in groundwater are lacking. Our study explores the spatial and temporal variability of nitrate and nitrous oxide concentrations in the vadose zone at a 15 acre corn field in the US Midwest and links it to the concentrations found in the groundwater at the field site. Results

  11. Variability of Urinary Concentrations of Polycyclic Aromatic Hydrocarbon Metabolite in General Population and Comparison of Spot, First-Morning, and 24-Hour Void Sampling

    PubMed Central

    Li, Zheng; Romanoff, Lovisa C.; Lewin, Michael D; Porter, Erin N; Trinidad, Debra A; Needham, Larry L; Patterson, Donald G; Sjödin, Andreas

    2015-01-01

    Urinary hydroxy polycyclic aromatic hydrocarbons (OH-PAHs) are commonly used in biomonitoring to assess exposure to polycyclic aromatic hydrocarbons (PAHs). Similar to other biologically non-persistent chemicals, OH-PAHs have relatively short biological half-lives (4.4–35 hours). Little information is available on their variability in urinary concentrations over time in non- occupationally exposed subjects. This study was designed to (i) study the variability of 9 urinary OH-PAH metabolite concentrations over time and (ii) calculate sample size requirements for future epidemiological studies based on spot urine, first morning void and 24-hour void sampling. Individual urine samples (n = 427) were collected during one week from 8 non-occupationally exposed adults. We recorded the time and volume of each urine excretion, dietary details, and the driving activities of the participants. Within subjects, the coefficients of variation (CV) for the wet-weight concentration of OH-PAHs in all samples ranged from 45% to 297%; creatinine adjustment reduced the CV to 19–288% (p < 0.001; paired t-test). The simulated 24-hour void concentrations were the least variable measure, with CVs ranging 13–182% for the 9 OH-PAHs. Within-day variability contributed on average 84%, and between-day variability accounted for 16% of the total variance of 1-hydroxypyrene (1-PYR). Intraclass correlation coefficients (ICC) of 1-PYR levels were 0.55 for spot urine samples, 0.60 for first-morning voids, and 0.76 for 24-hour voids, indicating a high degree of correlation between urine measurements collected from the same subject over time. Sample size calculations were performed to estimate the number of subjects needed for detecting differences in geometric mean at a statistical power of 80% for spot urine, first-morning, and 24-hour void sampling. These data will aid in the design of future studies of PAHs and possibly other biologically non-persistent chemicals and the interpretation of

  12. Effects of flunixin meglumine on selected clinicopathologic variables, and serum testosterone concentration in stallions after endotoxin administration.

    PubMed

    Danek, J

    2006-09-01

    Four clinically normal stallions were infused intravenously with endotoxin (LPS) from Escherichia coli 055:B5 at a dose of 0.3 microg/kg b.w. and four stallions were treated with flunixin meglumine (FM) as a single intravenous injection at a dose of 1.1 mg/kg b.w., 5 min after the infusion of LPS. In response to endotoxin infusion, stallions' reaction was fever (increased rectal and scrotal skin temperature), increased heart rate (HR) and leucopenia. Administration of endotoxin also influenced the level of testosterone (decrease at 3-24 h and increase at 48-72 h after LPS administration) in the blood serum. FM treatment prevented an endotoxin-induced increase in rectal and scrotal skin temperature, HR, with no influence on the decrease of leucocytes. Administration of FM only had a significant effect on the latter changes (at 24-72 h) of serum testosterone concentration after addition of endotoxin.

  13. Impact of the Atlantic meridional overturning circulation on the decadal variability of the Gulf Stream path and regional chlorophyll and nutrient concentrations

    NASA Astrophysics Data System (ADS)

    Sanchez-Franks, A.; Zhang, R.

    2015-11-01

    In this study, we show that the underlying physical driver for the decadal variability in the Gulf Stream (GS) path and the regional biogeochemical cycling is linked to the low frequency variability in the Atlantic meridional overturning circulation (AMOC). There is a significant anticorrelation between AMOC variations and the meridional shifts of the GS path at decadal time scale in both observations and two Earth system models (ESMs). The chlorophyll and nutrient concentrations in the GS region are found significantly correlated with the AMOC fingerprint and anticorrelated with the GS path at decadal time scale through coherent isopycnal changes in the GS front in the ESMs. Our results illustrate how changes in the large-scale ocean circulation, such as AMOC, are teleconnected with regional decadal physical and biogeochemical variations near the North American east coast. Such linkages are useful for predicting future physical and biogeochemical variations in this region.

  14. A flow system for generation of concentration perturbation in two-dimensional correlation near-infrared spectroscopy: application to variable selection in multivariate calibration.

    PubMed

    Pereira, Claudete Fernandes; Pasquini, Celio

    2010-05-01

    A flow system is proposed to produce a concentration perturbation in liquid samples, aiming at the generation of two-dimensional correlation near-infrared spectra. The system presents advantages in relation to batch systems employed for the same purpose: the experiments are accomplished in a closed system; application of perturbation is rapid and easy; and the experiments can be carried out with micro-scale volumes. The perturbation system has been evaluated in the investigation and selection of relevant variables for multivariate calibration models for the determination of quality parameters of gasoline, including ethanol content, MON (motor octane number), and RON (research octane number). The main advantage of this variable selection approach is the direct association between spectral features and chemical composition, allowing easy interpretation of the regression models.

  15. Spatial distribution and seasonal variability of chlorophyll-a concentration in the Azov Sea turbid waters by means of remote sensing and continuous fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Saprygin, V. V.

    2011-12-01

    The goal of this study was to apply continuous fluorometric and remote estimation of chlorophyll-a concentration (Cchl) techniques to complex turbid waters of Azov Sea and explore Cchl temporal variation and spatial pattern. Azov Sea is the shallowest sea in the world with maximum depth below 15 m. Its maximum salinity is about 14%; total suspended solids and chlorophyll-a concentrations reach 120 [tex]g m^{-3}[/tex] and 100 [tex]mg m^{-3}[/tex] respectively in Taganrog Bay, daily production varies up to 3.5 [tex]gC_{org} m^{-3}[/tex]. Chlorophyll-a concentrations were measured in 2008-2010 year-round spectrophotometrically, 446 water samples were taken to calibrate fluorometerical and remote sensing data. The highest recorded concentration was 149.3, the lowest - 0.3 [tex]mg m^{-3}[/tex]. Continuous-flow fluorometer was applied in the course of 3 expeditions to Taganrog Bay to measure chlorophyll-a fluorescence (Fchl) each 30 meters along the ship path. Two-cuvette fluorometer was used to discount the influence of dissolved organic matter. Fchl measurements were calibrated and Cchl profiles derieved to estimate Cchl spatial heterogeneity in close scale. Fchl measurements were also made during moorings each 6 seconds to estimate temporal Cchl variability. Recently published algorithm based on reflectance in the red and the near-infrared (NIR) spectral regions was applied to MERIS data for the remote estimation of Cchl. Taking in account fluorometric Cchl spatial heterogeneity estimation, the algorithm for culling the outliers in Cchl fields derived from satellite data was developed. 74 images were processed to Cchl maps and then averaged monthly. Consequently, Cchl spatial distribution and seasonal variability were studied. Spectrophotometric, flourumetric measurements and values obtained by NIR-red algorithm showed strong correlation in turbid Case II waters of Azov Sea. Fluorometric and remote measurements showed high Cchl variations in short and long terms

  16. Ozone and aerosol tropospheric concentrations variability analyzed using the ADRIMED measurements and the WRF and CHIMERE models

    NASA Astrophysics Data System (ADS)

    Menut, L.; Mailler, S.; Siour, G.; Bessagnet, B.; Turquety, S.; Rea, G.; Briant, R.; Mallet, M.; Sciare, J.; Formenti, P.; Meleux, F.

    2015-06-01

    During the months of June and July 2013, over the Euro-Mediterranean area, the ADRIMED (Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) project was dedicated to characterize the ozone and aerosol concentrations in the troposphere. It is first shown that this period was not highly polluted compared to previous summers in this region, with a moderate ozone production, no significant vegetation fire events and several precipitation periods scavenging the aerosol. The period is modeled with the WRF (Weather Research and Forecasting) and CHIMERE models, and their ability to quantify the observed pollution transport events is presented. The CHIMERE model simulating all kinds of sources (anthropogenic, biogenic, mineral dust, vegetation fires); the aerosol speciation, not available with the measurements, is presented: during the whole period, the aerosol was mainly constituted by mineral dust, sea salt and sulfates close to the surface and mainly by mineral dust in the troposphere. Compared to the AERONET (Aerosol Robotic Network) size distribution, it is shown that the model underestimates the coarse mode near mineral dust sources and overestimates the fine mode in the Mediterranean area, highlighting the need to improve the model representation of the aerosol size distribution both during emissions, long-range transport and deposition.

  17. Polycyclic aromatic hydrocarbons (PAHs) in plastic pellets: variability in the concentration and composition at different sediment depths in a sandy beach.

    PubMed

    Fisner, Mara; Taniguchi, Satie; Moreira, Fabiana; Bícego, Márcia C; Turra, Alexander

    2013-05-15

    Plastic pellets have the ability to adsorb organic pollutants such as PAHs. This study analyzed the variability in the concentration and composition of PAHs on plastic pellets sampled up to 1m deep in the sediment of a sandy beach. The toxic potential of PAHs was analyzed, and the possible sources of contamination are discussed. The total PAHs varied, with the highest concentrations in the surface layer; the priority PAHs showed a different pattern. PAHs at greater depths did not reach toxicity levels above the PEL. The composition of PAHs differed between pellets from the shallower and from deeper sediment layers, and was suggested a mixture of sources. These results provided the first information on the depth distribution of PAHs in sandy beaches, associated with plastic pellets; and evidenced the potential environmental risk. Similarly to the abundance of pellets, the toxic potential is underestimated in surface samples.

  18. Effect of the spatiotemporal variability of rainfall inputs in water quality integrated catchment modelling for dissolved oxygen concentrations

    NASA Astrophysics Data System (ADS)

    Moreno Ródenas, Antonio Manuel; Cecinati, Francesca; ten Veldhuis, Marie-Claire; Langeveld, Jeroen; Clemens, Francois

    2016-04-01

    Maintaining water quality standards in highly urbanised hydrological catchments is a worldwide challenge. Water management authorities struggle to cope with changing climate and an increase in pollution pressures. Water quality modelling has been used as a decision support tool for investment and regulatory developments. This approach led to the development of integrated catchment models (ICM), which account for the link between the urban/rural hydrology and the in-river pollutant dynamics. In the modelled system, rainfall triggers the drainage systems of urban areas scattered along a river. When flow exceeds the sewer infrastructure capacity, untreated wastewater enters the natural system by combined sewer overflows. This results in a degradation of the river water quality, depending on the magnitude of the emission and river conditions. Thus, being capable of representing these dynamics in the modelling process is key for a correct assessment of the water quality. In many urbanised hydrological systems the distances between draining sewer infrastructures go beyond the de-correlation length of rainfall processes, especially, for convective summer storms. Hence, spatial and temporal scales of selected rainfall inputs are expected to affect water quality dynamics. The objective of this work is to evaluate how the use of rainfall data from different sources and with different space-time characteristics affects modelled output concentrations of dissolved oxygen in a simplified ICM. The study area is located at the Dommel, a relatively small and sensitive river flowing through the city of Eindhoven (The Netherlands). This river stretch receives the discharge of the 750,000 p.e. WWTP of Eindhoven and from over 200 combined sewer overflows scattered along its length. A pseudo-distributed water quality model has been developed in WEST (mikedhi.com); this is a lumped-physically based model that accounts for urban drainage processes, WWTP and river dynamics for several

  19. Analysis of the variable factors influencing tacrolimus blood concentration during the switch from continuous intravenous infusion to oral administration after allogeneic hematopoietic stem cell transplantation.

    PubMed

    Suetsugu, Kimitaka; Ikesue, Hiroaki; Miyamoto, Toshihiro; Shiratsuchi, Motoaki; Yamamoto-Taguchi, Nanae; Tsuchiya, Yuichi; Matsukawa, Kumi; Uchida, Mayako; Watanabe, Hiroyuki; Akashi, Koichi; Masuda, Satohiro

    2017-03-01

    The aim of this retrospective study was to identify variable factors affecting tacrolimus blood concentration during the switch from continuous intravenous infusion to twice-daily oral administration in allogeneic hematopoietic stem cell transplant recipients (n = 73). The blood concentration/dose ratio of tacrolimus immediately before the change from continuous infusion (C/Div) was compared with that between 3 and 5 days after the change to oral administration (C/Dpo). Median (C/Dpo)/(C/Div) was 0.21 (range 0.04-0.58). Multiple regression analysis showed that concomitant use of oral itraconazole or voriconazole significantly increased the (C/Dpo)/(C/Div) of tacrolimus (p = 0.002), probably owing to the inhibition of enterohepatic cytochrome P450 3A4. In addition, 5 of 18 (28%) patients who had the lowest quartile (C/Dpo)/(C/Div) values developed acute graft-versus-host-disease (GVHD), which was significantly higher than in others [5 of 55 (9%) patients, p = 0.045]. Although the switch from intravenous to oral administration at a ratio of 1:5 appeared to be appropriate, a lower conversion ratio was suitable in patients taking oral itraconazole or voriconazole. In patients whose blood concentration decreases after the switch, the development of GVHD should be monitored and tacrolimus dosage should be readjusted to maintain an appropriate blood concentration.

  20. Assessing the Variability of Heavy Metal Concentrations in Liquid-Solid Two-Phase and Related Environmental Risks in the Weihe River of Shaanxi Province, China.

    PubMed

    Song, Jinxi; Yang, Xiaogang; Zhang, Junlong; Long, Yongqing; Zhang, Yan; Zhang, Taifan

    2015-07-17

    Accurate estimation of the variability of heavy metals in river water and the hyporheic zone is crucial for pollution control and environmental management. The biotoxicities and potential ecological risks of heavy metals (Cu, Zn, Pb, Cd) in a solid-liquid two-phase system were estimated using the Geo-accumulation Index, Potential Ecological Risk Assessment and Quality Standard Index methods in the Weihe River of Shaanxi Province, China. Water and sediment samples were collected from five study sites during spring, summer and winter, 2013. The dominant species in the streambed sediments were chironomids and flutter earthworm, whose bioturbation mainly ranged from 0 to 20 cm. The concentrations of heavy metals in surface water and pore water varied obviously in spring and summer. The degrees of concentration of Cu and Cd in spring and summer were higher than the U.S. water quality Criteria Maximum Concentrations. Furthermore, the biotoxicities of Pb and Zn demonstrated season-spatial variations. The concentrations of Cu, Zn, Pb and Cd in spring and winter were significantly higher than those in summer, and the pollution levels also varied obviously in different layers of the sediments. Moreover, the pollution level of Cd was the most serious, as estimated by all three assessment methods.

  1. Assessing the Variability of Heavy Metal Concentrations in Liquid-Solid Two-Phase and Related Environmental Risks in the Weihe River of Shaanxi Province, China

    PubMed Central

    Song, Jinxi; Yang, Xiaogang; Zhang, Junlong; Long, Yongqing; Zhang, Yan; Zhang, Taifan

    2015-01-01

    Accurate estimation of the variability of heavy metals in river water and the hyporheic zone is crucial for pollution control and environmental management. The biotoxicities and potential ecological risks of heavy metals (Cu, Zn, Pb, Cd) in a solid-liquid two-phase system were estimated using the Geo-accumulation Index, Potential Ecological Risk Assessment and Quality Standard Index methods in the Weihe River of Shaanxi Province, China. Water and sediment samples were collected from five study sites during spring, summer and winter, 2013. The dominant species in the streambed sediments were chironomids and flutter earthworm, whose bioturbation mainly ranged from 0 to 20 cm. The concentrations of heavy metals in surface water and pore water varied obviously in spring and summer. The degrees of concentration of Cu and Cd in spring and summer were higher than the U.S. water quality Criteria Maximum Concentrations. Furthermore, the biotoxicities of Pb and Zn demonstrated season-spatial variations. The concentrations of Cu, Zn, Pb and Cd in spring and winter were significantly higher than those in summer, and the pollution levels also varied obviously in different layers of the sediments. Moreover, the pollution level of Cd was the most serious, as estimated by all three assessment methods. PMID:26193293

  2. High concentration of vitamin E supplementation in sow diet during the last week of gestation and lactation affects the immunological variables and antioxidative parameters in piglets.

    PubMed

    Wang, Lin; Xu, Xiaodong; Su, Ge; Shi, Baoming; Shan, Anshan

    2017-02-01

    An experiment was conducted to investigate the effects of a high concentration of vitamin E supplementation in sow diet during the last week of gestation and lactation on the performance, milk composition, and vital immunological variables and antioxidative parameters in sows and piglets. The experiment started on day 107 of gestation and lasted until the piglets were weaned on day 21 of lactation. 48 sows were divided into two groups and fed either a basal diet with 44 IU/kg of vitamin E or a basal diet supplemented with additional vitamin E, total content of 250 IU/kg. Sow milk and blood samples were obtained on day 0 (farrowing) and on day 21 of lactation. One 21-day-old piglet per litter was selected to collect plasma. Results showed that supplementation of the maternal diet with 250 IU/kg vitamin E improved the average daily gain (ADG) and weaning weight of piglets (P < 0·05), and the concentrations of immunoglobulin G (IgG) and immunoglobulin A (IgA) in sow plasma, colostrum and milk. The concentrations of fat in the colostrum and milk were significantly increased by supplementation with 250 IU/kg of vitamin E (P < 0·05). The level of plasma IgG, IgA, total antioxidant capacity (T-AOC) and catalase (CAT) were all higher (P < 0·05) in piglets from sows that were fed 250 IU/kg of vitamin E than in those from the control group. The high concentration of vitamin E supplementation to the sows enhanced the concentrations of α-tocopherol in the sow milk and plasma as well as piglet plasma (P < 0·05). In conclusion, the addition to the maternal diet of vitamin E at high concentration improved the weight of piglets at weaning, and enhanced humoral immune function and antioxidant activity in sows and piglets.

  3. Coupled heat and mass transfer in mixed convection over a wedge with variable wall temperature and concentration in porous media: The entire regime

    SciTech Connect

    Yih, K.A.

    1998-11-01

    Convective heat transfer in a porous medium has a number of thermal engineering applications such as moisture transport in thermal insulations, ceramic processing, the extraction of geothermal energy, nuclear reactor cooling system, underground nuclear waste disposal, ground water pollution and filtration processes. Here, a boundary layer analysis is used to investigate both heat and mass transfer characteristics of mixed convection about a wedge in saturated porous media under the coupled effects of thermal and mass diffusion. The surface of the wedge is maintained at a variable wall temperature (VWT) and variable wall concentration (VWC). The nonsimilar governing equations are obtained by using a suitable transformation and solved by Keller box method. Numerical results are presented for the local Nusselt number and the local Sherwood number. Increasing the buoyancy ratio N, the exponent of wall temperature/concentration n and the wedge angle parameter {lambda} increases the local Nusselt number and the local Sherwood number. As mixed convection parameter {chi} varies from 0 to 1, the local Nusselt number and the local Sherwood number decrease initially, reach a minimum in the intermediate value of {chi} and then increase gradually. It is apparent that the Lewis number has a pronounced effect on the local Sherwood number than it does on the local Nusselt number. Furthermore, increasing the Lewis number decreases (increases) the local heat (mass) transfer rate.

  4. Extracting tidal variability of sea ice concentration from AMSR-E passive microwave single-swath data: a case study of the Ross Sea

    NASA Astrophysics Data System (ADS)

    Mack, Stefanie; Padman, Laurie; Klinck, John

    2013-02-01

    Abstract The periodic divergence of stress applied by ocean tidal currents to sea ice affects the time-averaged ice <span class="hlt">concentration</span> (Cice) and heat and freshwater fluxes at the ocean surface. We demonstrate that, at sufficiently high latitudes, tidal <span class="hlt">variability</span> in Cice can be extracted from single-swath data from the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) satellite passive microwave sensor, although time intervals between swaths are irregular. For the northwest Ross Sea where tidal currents are large, tidal divergence is the dominant cause of Cice <span class="hlt">variability</span> in winter, with a range of ±0.2 about a mean of ~0.8. Daily-averaged Cice values vary from >0.9 at neap tides to ~0.7 at spring tides. <span class="hlt">Variability</span> at the fundamental tidal periods is about half that expected from an inverse barotropic tide model for the Ross Sea, suggesting that the measured tidal signal in Cice may be used to diagnose sea ice mechanical properties and ice/ocean coupling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AtmRe.180..138T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AtmRe.180..138T"><span>Observations of ambient trace gas and PM10 <span class="hlt">concentrations</span> at Patna, Central Ganga Basin during 2013-2014: The influence of meteorological <span class="hlt">variables</span> on atmospheric pollutants</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tiwari, S.; Tunved, P.; Hopke, Philip K.; Srivastava, A. K.; Bisht, D. S.; Pandey, A. K.</p> <p>2016-11-01</p> <p>Atmospheric pollutants including ozone (O3), sulfur dioxide (SO2), oxides of nitrogen (NOx), carbon monoxide (CO), and inhalable particulate matter (PM10) were measured in the central Indo-Gangetic Basin (IGB) at Patna, India, from 1st March 2013 to 31st December 2014, and significant <span class="hlt">variability</span> was observed in the temporal patterns of these pollutant <span class="hlt">concentrations</span>. The mean O3, SO2, NO, NO2, CO (trace gases: TG), and PM10 (PM) <span class="hlt">concentrations</span> were 14.5 ± 4.8, 5.9 ± 4.8, 23.1 ± 22, 20.6 ± 14.6 ppb, 1.5 ± 0.7 ppm, and 192.0 ± 132.8 μg/m3, respectively, over the study period. The highest <span class="hlt">concentrations</span> of these species were during the post-monsoon and winter seasons except O3 and SO2 that showed the highest <span class="hlt">concentrations</span> during the pre-monsoon. The lowest <span class="hlt">concentrations</span> of TG and PM were observed during the monsoon season as a result of scavenging by rain. NO and NO2 along with PM <span class="hlt">concentrations</span> decreased by ~ 76, 19, and 63% when the wind speed (WS) was > 0.5 m/s. However, for O3, an opposite trend was observed with ~ 14% higher <span class="hlt">concentrations</span>. The WS was negatively correlated with PM during the winter (- 0.48) and post-monsoon (- 0.32) seasons. In order to investigate the source region of TG and PM, 5-day air mass back trajectories were computed. The dominance of the air masses (92, 53, and 49%) were from the IGB is highly polluted during the winter, pre-monsoon, and post-monsoon, respectively. The TG and PM were observed much higher during these periods. During the biomass burning period (post-monsoon), the trajectory analysis showed that the TG and PM <span class="hlt">concentrations</span> were around three-fold higher (flow from the IGB) than the other seasons. To improve air quality over IGB, the mitigation measures should be designed to reduce emissions from both local and regional sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21939215','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21939215"><span><span class="hlt">Variable</span> volume loading method: a convenient and rapid method for measuring the initial emittable <span class="hlt">concentration</span> and partition coefficient of formaldehyde and other aldehydes in building materials.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xiong, Jianyin; Yan, Wei; Zhang, Yinping</p> <p>2011-12-01</p> <p>The initial emittable formaldehyde and VOC <span class="hlt">concentration</span> in building materials (C(0)) is a key parameter for characterizing and classifying these materials. Various methods have been developed to measure this parameter, but these generally require a long test time. In this paper we develop a convenient and rapid method, the <span class="hlt">variable</span> volume loading (VVL) method, to simultaneously measure C(0) and the material/air partition coefficient (K). This method has the following features: (a) it requires a relatively short experimental time (less than 24 h for the cases studied); and (b) is convenient for routine measurement. Using this method, we determined C(0) and K of formaldehyde, propanal and hexanal in one kind of medium density fiberboard, and repeated experiments were performed to reduce measurement error. In addition, an extended-C-history method is proposed to determine the diffusion coefficient and the convective mass transfer coefficient. The VVL method is validated by comparing model predicted results based on the determined parameters with experimental data. The determined C(0) of formaldehyde obtained via this method is less than 10% of the total <span class="hlt">concentration</span> using the perforator method recommended by the Chinese National Standard, suggesting that the total <span class="hlt">concentration</span> may not be appropriate to predict emission characteristics, nor for material classification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.8221B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.8221B"><span>Spatial and Temporal <span class="hlt">Variability</span> in the <span class="hlt">Concentration</span> and Turnover of the Inorganic Phosphate and Adenosine-5'-triphosphate pools in the North Pacific Subtropical Gyre</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Björkman, Karin; Church, Matthew; Karl, David</p> <p>2015-04-01</p> <p>The microbial community's utilization of inorganic phosphate (Pi) and adenosine-5'-triphosphate (ATP) as a function of the Pi pool <span class="hlt">concentration</span> was studied over a multi-year period at Station ALOHA (22.75˚N, 158˚W) in the North Pacific Subtropical Gyre (NPSG). Additionally, the spatial <span class="hlt">variability</span> in these same properties was investigated along an east-west transect from California to Hawaii in the Fall of 2014. We used radiotracer techniques to determine the turnover times of the Pi or ATP pools respectively, and assessed the net production of dissolved organic phosphorus, and Pi hydrolysis rate from ATP. Pi <span class="hlt">concentrations</span> in the upper water column at Station ALOHA are temporally highly dynamic, with periods of <10 nM-P to near 200 nM-P recorded within the top 50 m over the past decades of observations. During the California to Hawaii transect Pi <span class="hlt">concentrations</span> showed a similarly large range (<10 to >200 nM-P), emphasizing the spatially and temporally mosaic nature of the upper ocean of this large biome. The Pi-pool turnover time ranged from a few hours to several weeks, and was strongly correlated with measured Pi pool <span class="hlt">concentrations</span> (r2=0.8; n=30 Station ALOHA; n=15 transect). The calculated Pi uptake rates at Station ALOHA averaged 3.7±1.3 nM-P d-1 (n=30), reflecting the typically low maximum Pi uptake rates of the Prochlorococcus dominated community and the predominantly non-limiting Pi conditions. The Pi uptake rates along the transect were more <span class="hlt">variable</span> than Station ALOHA (averaging 9.2±4.7 nM=P d-1, n=15), possibly due to a more diverse planktonic community structure, including stations with elevated <span class="hlt">concentrations</span> of chlorophyll and primary productivity. The turnover time of the dissolved ATP pool was typically substantially shorter than for the Pi-pool (2-5 days at Station ALOHA; 0.3-2.5 days along the transect), likely reflecting its low nanomolar to picomolar ambient pool <span class="hlt">concentrations</span>. However, at stations with the lowest SRP <span class="hlt">concentrations</span> the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16005970','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16005970"><span>Spatial <span class="hlt">variability</span> of shallow groundwater level, electrical conductivity and nitrate <span class="hlt">concentration</span>, and risk assessment of nitrate contamination in North China Plain.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hu, Kelin; Huang, Yuangfang; Li, Hong; Li, Baoguo; Chen, Deli; White, Robert Edlin</p> <p>2005-08-01</p> <p>In recent years, nitrate (NO3) contamination of groundwater has become a growing concern for people in rural areas in North China Plain (NCP) where groundwater is used as drinking water. The objective of this study was to evaluate groundwater resource level, to determine groundwater quality and to assess the risk of NO3 pollution in groundwater in Quzhou County in the NCP. Ordinary Kriging (OK) method was used to analyze the spatial <span class="hlt">variability</span> of shallow groundwater level, groundwater electrical conductivity (EC) and NO3-N <span class="hlt">concentrations</span>, and Indictor Kriging (IK) method was used to analyze the data with NO3-N <span class="hlt">concentrations</span> equal or greater than the groundwater NO3 pollution threshold (20 mg L(-1)). The results indicated that groundwater level averaged 9.81 m, a level 6 m lower than in 1990. The spatial correlation distances for groundwater level, EC and NO3-N <span class="hlt">concentration</span> were 21.93, 2.19 and 3.55 km, respectively. The contour map showed that shallow groundwater level areas extended from north to south across the County. Groundwater EC was above 3 dS m(-1) in the most part of the northern county. Groundwater NO3 pollution (NO3-N> or =20 mg L(-1)) mainly occurred in the County Seat areas due to wastewater irrigation and excessive fertilizer leaching from agricultural fields. At Henantuang town, besides suburban of the County Seat, groundwater was also contaminated by NO3 shown by the map generated using the IK method, which was not reflected in the map generated using the OK method. The map generated using the OK method could not reflect correctly the groundwater NO3 pollution status. The IK method is useful to assess the risk of NO3 pollution by giving the conditional probability of NO3 <span class="hlt">concentration</span> exceeding the threshold value. It is suggested that risk assessment of NO3 pollution is useful for better managing groundwater resource, preventing soil salinization and minimizing NO3 pollution in groundwater.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28017360','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28017360"><span>Estimation of daily PM10 <span class="hlt">concentrations</span> in Italy (2006-2012) using finely resolved satellite data, land use <span class="hlt">variables</span> and meteorology.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stafoggia, Massimo; Schwartz, Joel; Badaloni, Chiara; Bellander, Tom; Alessandrini, Ester; Cattani, Giorgio; De' Donato, Francesca; Gaeta, Alessandra; Leone, Gianluca; Lyapustin, Alexei; Sorek-Hamer, Meytar; de Hoogh, Kees; Di, Qian; Forastiere, Francesco; Kloog, Itai</p> <p>2017-02-01</p> <p>Health effects of air pollution, especially particulate matter (PM), have been widely investigated. However, most of the studies rely on few monitors located in urban areas for short-term assessments, or land use/dispersion modelling for long-term evaluations, again mostly in cities. Recently, the availability of finely resolved satellite data provides an opportunity to estimate daily <span class="hlt">concentrations</span> of air pollutants over wide spatio-temporal domains. Italy lacks a robust and validated high resolution spatio-temporally resolved model of particulate matter. The complex topography and the air mixture from both natural and anthropogenic sources are great challenges difficult to be addressed. We combined finely resolved data on Aerosol Optical Depth (AOD) from the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm, ground-level PM10 measurements, land-use <span class="hlt">variables</span> and meteorological parameters into a four-stage mixed model framework to derive estimates of daily PM10 <span class="hlt">concentrations</span> at 1-km2 grid over Italy, for the years 2006-2012. We checked performance of our models by applying 10-fold cross-validation (CV) for each year. Our models displayed good fitting, with mean CV-R2=0.65 and little bias (average slope of predicted VS observed PM10=0.99). Out-of-sample predictions were more accurate in Northern Italy (Po valley) and large conurbations (e.g. Rome), for background monitoring stations, and in the winter season. Resulting <span class="hlt">concentration</span> maps showed highest average PM10 levels in specific areas (Po river valley, main industrial and metropolitan areas) with decreasing trends over time. Our daily predictions of PM10 <span class="hlt">concentrations</span> across the whole Italy will allow, for the first time, estimation of long-term and short-term effects of air pollution nationwide, even in areas lacking monitoring data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ACP....1615777B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ACP....1615777B"><span>Trends and <span class="hlt">variability</span> of atmospheric PM2.5 and PM10-2.5 <span class="hlt">concentration</span> in the Po Valley, Italy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bigi, Alessandro; Ghermandi, Grazia</p> <p>2016-12-01</p> <p>The Po Valley is one of the largest European regions with a remarkably high <span class="hlt">concentration</span> level of atmospheric pollutants, both for particulate and gaseous compounds. In the last decade stringent regulations on air quality standards and on anthropogenic emissions have been set by the European Commission, including also for PM2.5 and its main components since 2008. These regulations have led to an overall improvement in air quality across Europe, including the Po Valley and specifically PM10, as shown in a previous study by Bigi and Ghermandi (2014). In order to assess the trend and <span class="hlt">variability</span> in PM2.5 in the Po Valley and its role in the decrease in PM10, we analysed daily gravimetric equivalent <span class="hlt">concentration</span> of PM2.5 and of PM10-2.5 at 44 and 15 sites respectively across the Po Valley. The duration of the times series investigated in this work ranges from 7 to 10 years. For both PM sizes, the trend in deseasonalized monthly means, annual quantiles and in monthly frequency distribution was estimated: this showed a significant decreasing trend at several sites for both size fractions and mostly occurring in winter. All series were tested for a significant weekly periodicity (a proxy to estimate the impact of primary anthropogenic emissions), yielding positive results for summer PM2.5 and for summer and winter PM10-2.5. Hierarchical cluster analysis showed moderate <span class="hlt">variability</span> in PM2.5 across the valley, with two to three main clusters, dividing the area in western, eastern and southern/Apennines foothill sectors. The trend in atmospheric <span class="hlt">concentration</span> was compared with the time series of local emissions, vehicular fleet details and fuel sales, suggesting that the decrease in PM2.5 and in PM10 originates from a drop both in primary and in precursors of secondary inorganic aerosol emissions, largely ascribed to vehicular traffic. Potentially, the increase in biomass burning emissions in winter and the modest decrease in NH3 weaken an otherwise even larger drop in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24070332','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24070332"><span>Fungal spore <span class="hlt">concentrations</span> in indoor and outdoor air in university libraries, and their variations in response to changes in meteorological <span class="hlt">variables</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Flores, María Elena Báez; Medina, Pável Gaxiola; Camacho, Sylvia Páz Díaz; de Jesús Uribe Beltrán, Magdalena; De la Cruz Otero, María del Carmen; Ramírez, Ignacio Osuna; Hernández, Martín Ernesto Tiznado</p> <p>2014-08-01</p> <p>The fungal spore <span class="hlt">concentration</span> (FSC) in the air poses a risk for human health. This work studied the FSC in university libraries and how it is affected by environmental factors. A total of 347 samples were obtained using a Microbio MB2(®) Aerosol Sampler. The wind speed (WS), cross wind (CW), temperature (T), relative humidity (HR), barometric pressure (BP) and dew point (DP) were recorded using a Kestrel(®) 4500 weather station. The median indoor/outdoor FSC was 360/1230 CFU m(-3). FSC correlated inversely with BP, HR and DP; and positively with WS and CW; whereas T showed negative or positive correlation with FSC, depending on the region or sampling time. Eleven fungal genera were found and the dominant isolates were identified as Aspergillus niger, Aspergillus tamarii and Aspergillus oryzae. All fungi identified are known to be allergenic. It was concluded that environmental <span class="hlt">variables</span> can influence the air FSC in different ways.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Ocgy...57..165P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Ocgy...57..165P"><span>Spatial <span class="hlt">variability</span> of <span class="hlt">concentrations</span> of chlorophyll a, dissolved organic matter and suspended particles in the surface layer of the Kara Sea in September 2011 from lidar data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pelevin, V. V.; Zavjalov, P. O.; Belyaev, N. A.; Konovalov, B. V.; Kravchishina, M. D.; Mosharov, S. A.</p> <p>2017-01-01</p> <p>The article presents results of underway remote laser sensing of the surface water layer in continuous automatic mode using the UFL-9 fluorescent lidar onboard the R/V Akademik Mstislav Keldysh during cruise 59 in the Kara Sea in 2011. The description of the lidar, the approach to interpreting seawater fluorescence data, and certain methodical aspects of instrument calibration and measurement are presented. Calibration of the lidar is based on laboratory analysis of water samples taken from the sea surface during the cruise. Spatial distribution of chlorophyll a, total organic carbon and suspended matter <span class="hlt">concentrations</span> in the upper quasi-homogeneous layer are mapped and the characteristic scales of the <span class="hlt">variability</span> are estimated. Some dependencies between the patchiness of the upper water layer and the atmospheric forcing and freshwater runoff are shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006ACPD....6.6801P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006ACPD....6.6801P"><span>Comparison of CO2 fluxes estimated using atmospheric and oceanic inversions, and role of fluxes and their interannual <span class="hlt">variability</span> in simulating atmospheric CO2 <span class="hlt">concentrations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Patra, P. K.; Mikaloff Fletcher, S. E.; Ishijima, K.; Maksyutov, S.; Nakazawa, T.</p> <p>2006-07-01</p> <p>We use a time-dependent inverse (TDI) model to estimate regional sources and sinks of atmospheric CO2 from 64 and then 22 regions based on atmospheric CO2 observations at 87 stations. The air-sea fluxes from the 64-region atmospheric-CO2 inversion are compared with fluxes from an analogous ocean inversion that uses ocean interior observations of dissolved inorganic carbon (DIC) and other tracers and an ocean general circulation model (OGCM). We find that, unlike previous atmospheric inversions, our flux estimates in the southern hemisphere are generally in good agreement with the results from the ocean inversion, which gives us added confidence in our flux estimates. In addition, a forward tracer transport model (TTM) is used to simulate the observed CO2 <span class="hlt">concentrations</span> using (1) estimates of fossil fuel emissions and a priori estimates of the terrestrial and oceanic fluxes of CO2, and (2) two sets of TDI model corrected fluxes. The TTM simulations of TDI model corrected fluxes show improvements in fitting the observed interannual <span class="hlt">variability</span> in growth rates and seasonal cycles in atmospheric CO2. Our analysis suggests that the use of interannually varying (IAV) meteorology and a larger observational network have helped to capture the regional representation and interannual <span class="hlt">variabilities</span> in CO2 fluxes realistically.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016CSR...126...15A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CSR...126...15A"><span>Spatio-temporal <span class="hlt">variability</span> of phytoplankton (Chlorophyll-a) in relation to salinity, suspended sediment <span class="hlt">concentration</span>, and light intensity in a macrotidal estuary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Azhikodan, Gubash; Yokoyama, Katsuhide</p> <p>2016-09-01</p> <p>The influences of environmental gradients on the spatio-temporal <span class="hlt">variability</span> of phytoplankton (Chlorophyll-a) in the macrotidal Chikugo River Estuary were studied during a two-week period of September 2010. Vertical profiles of salinity, turbidity, and light intensity were measured at 18 stations separated by a 1-km interval. Water samples for the determination of suspended sediment <span class="hlt">concentration</span> (SSC), <span class="hlt">concentration</span> of Chlorophyll-a (Chl-a) and Pheophytin-a (Pheo-a) were collected from the surface layer at all stations. The estuarine water column was vertically well mixed with high SSC (100-2000 mg L-1) during spring tide and the photic depth (zp) was less than 0.2 m. The mixing depth (zm) was more than 10 times the photic depth for the major part of the estuary. The estuary gradually changed to partially mixed with decrease in SSC (≤400 mg L-1) during the intermediate tide. The estuary became stratified with low SSC (20-50 mg L-1) during neap tide and the zp reached 4 m. The zm was less than 0.5 times the zp for the whole estuary. Light attenuation was dominated by SSC and the zp varied according to semidiurnal and semilunar tidal cycle. The zp: zm ratio did not show any relationship with Chl-a in the Chikugo river estuary. This is because the Chl-a <span class="hlt">concentration</span> reached maximum two to three days after the neap tide. The peak <span class="hlt">concentration</span> of Chl-a was located near the low salinity region and that of Pheo-a was located in the Estuarine Turbidity Maximum (ETM) zone. The Pheo-a <span class="hlt">concentration</span> reached maximum during the spring tide. A good relation between zp: zm ratio and Pheo-a indicates that the increase in Pheo-a was caused by the light limitation due to suspended sediment and the responses of the Pheo-a on the light condition was instantaneous. These phenomena were remarkably found in the interface between freshwater and saltwater. Light availability driven by mixing and ETM process during semidiurnal and semilunar tidal cycle is the controlling factor of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP23B1846K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP23B1846K"><span>Seasonal to centennial-scale <span class="hlt">variability</span> of microparticle <span class="hlt">concentration</span> and size distribution in the WAIS Divide ice core over the past 2.4 ka</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kreutz, K. J.; Koffman, B. G.; Breton, D. J.; Dunbar, N. W.; Kurbatov, A.</p> <p>2011-12-01</p> <p>We present results from continuous analysis of mineral dust in the upper 577 m (2.4 ka) of the WAIS Divide deep ice core, WDC06A. The core was melted using the UMaine WAIS Melt Monitor system, which allows accurate mm-scale depth co-registration of electrical conductivity and particle data, with subsequent collection of discrete samples for expanded particle, glaciochemical and geochemical analysis. The <span class="hlt">concentration</span> and size distribution of microparticles were measured using a flow-through Klotz Abakus laser particle detector, developed by Ruth et al (2002) and calibrated with Coulter-Counter measurements. We found that background dust <span class="hlt">concentrations</span> during the past two millennia have been low, comparable to other sites in interior Antarctica. Particle <span class="hlt">concentration</span> ranges seasonally from ~20-1000 particles/ml. Particle deposition generally shows an annual signal, although the phasing varies relative to seasonal chemical indicators such as nssSO42-. Dust deposition on decadal to centennial timescales appears to be linked to hemispheric-scale climate <span class="hlt">variability</span> during the late Holocene, and particularly to the Southern Annular Mode (SAM) climate oscillation. We compared the coarse particle percentage (5-10 μm diameter relative to 1-10 μm diameter) to a proxy record of the SAM developed using sea salt <span class="hlt">concentrations</span> in the Law Dome, East Antarctica, ice core (Goodwin et al, 2004). Spectral characteristics of the coarse particle percentage at WAIS Divide seem to match the Law Dome proxy for the SAM. This suggests a coherent signal for the SAM and the potential to develop a particle size distribution proxy for the strength of the circum-Antarctic atmospheric circulation. Within the past two centuries of dust deposition, there were several dusty decades in the early-to-mid 1900s followed by a dramatic increase around 1980. Given that the particle size distribution does not show significant coeval change, we infer that this increased dust deposition has been driven</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeCoA.190..332J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeCoA.190..332J"><span>Intra- and inter-annual uranium <span class="hlt">concentration</span> <span class="hlt">variability</span> in a Belizean stalagmite controlled by prior aragonite precipitation: A new tool for reconstructing hydro-climate using aragonitic speleothems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jamieson, Robert A.; Baldini, James U. L.; Brett, Marianne J.; Taylor, Jessica; Ridley, Harriet E.; Ottley, Chris J.; Prufer, Keith M.; Wassenburg, Jasper A.; Scholz, Denis; Breitenbach, Sebastian F. M.</p> <p>2016-10-01</p> <p>Aragonitic speleothems are increasingly utilised as palaeoclimate archives due to their amenability to high precision U-Th dating. Proxy records from fast-growing aragonitic stalagmites, precisely dated to annual timescales, can allow investigation of climatic events occurring on annual or even sub-annual timescales with minimal chronological uncertainty. However, the behaviour of many trace elements, such as uranium, in aragonitic speleothems has not thus far been as well constrained as in calcitic speleothems. Here, we use uranium <span class="hlt">concentration</span> shifts measured across primary calcite-to-aragonite mineralogical transitions in speleothems to calculate the distribution coefficient of uranium in aragonitic speleothems (derived DU = 3.74 ± 1.13). Because our calculated DU is considerably above 1 increased prior aragonite precipitation due to increased karst water residence time should strongly control stalagmite aragonite U/Ca values. Consequently, uranium <span class="hlt">concentrations</span> in aragonitic speleothems should act as excellent proxies for effective rainfall. We test this using a high-resolution ICP-MS derived trace element dataset from a Belizean stalagmite. YOK-G is an aragonitic stalagmite from Yok Balum cave in Belize with an extremely robust monthly-resolved chronology built using annual δ13C cycles. We interpret seasonal U/Ca variations in YOK-G as reflecting changes in the amount and seasonality of prior aragonite precipitation driven by <span class="hlt">variable</span> rainfall amounts. The U/Ca record strongly suggests that modern drying has occurred in Belize, and that this drying was primarily caused by a reduction in wet season rainfall. This is consistent with published stable isotope data from YOK-G also very strongly suggesting modern rainfall reductions, previously interpreted as the result of southward ITCZ displacement. Our results strongly suggest that U/Ca values in aragonitic speleothems are excellent proxies for rainfall <span class="hlt">variability</span>. This new tool, combined with the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/197554','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/197554"><span>PAH and PCB in the Baltic -- A budget approach including fluxes, occurrence and <span class="hlt">concentration</span> <span class="hlt">variability</span> in air, suspended and settling particulates in water, surface sediments and river water</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Broman, D.; Axelman, J.; Bandh, C.; Ishaq, R.; Naef, C.; Pettersen, H.; Zebuehr, Y.</p> <p>1995-12-31</p> <p>In order to study the fate and occurrence of two groups of hydrophobic compounds in the Baltic aquatic environment a large number of samples were collected from the southern Baltic proper to the northern Bothnian Bay for the analyses of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). The following sample matrices were collected; bottom surface sediments (0--1 cm, collected with gravity corer), settling particulate matter (collected with sediment traps), open water samples and over water samples (suspended particulates and dissolved fraction sampled by filtration) and air samples (aerosols and vapor phase sampled by filtration). All samples (except over water and air) were collected at open sea in the Baltic. The analyses results have been used to make a model approach on the whole Baltic and to elucidate different aspects of the behavior of PAHs and PCBs in the Baltic, such as the occurrence of the compounds in water and sediment, the total content as well as the <span class="hlt">concentration</span> <span class="hlt">variabilities</span> over such a large geographical area, Further, the data on settling particulate matter as well as the air <span class="hlt">concentration</span> data were used to estimate the total fluxes of PAHs and PCBs to the bottoms of the Baltic and t o the total water area of the Baltic, respectively. Further, data on the PAH and PCB content in river water from four major rivers provides rough estimates of the riverine input to the Baltic. The dynamics of PAHs and PCBs within the water mass have also been studied in terms of settling velocities and residence times in the water mass for these type of compounds in the open Baltic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.9618K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.9618K"><span>The spatial <span class="hlt">variability</span> of organic carbon <span class="hlt">concentrations</span>, C/N ratios and δ13C in surface sediments of two high Arctic fjords (Spitsbergen)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koziorowska, Katarzyna; Kuliński, Karol; Pempkowiak, Janusz</p> <p>2015-04-01</p> <p>The Arctic Ocean, and especially its shelf, is considered to be an important region for the global carbon cycle. This is due to the high, but <span class="hlt">concentrated</span> in a short time, primary production, specific thermohaline circulation and physicochemical conditions of sea water. It was estimated that the Arctic shelf seas are responsible for 7-11% of total carbon dioxide uptake by the oceans. Additionally, the Arctic Ocean is considered to be one of the youngest marine ecosystems in the world. This results in less trophic links in the food web and higher efficiency of organic matter burial in sediments than it is observed in the marine ecosystems of lower latitudes. The main aim of this study was to estimate the spatial <span class="hlt">variability</span> of organic carbon (OC) <span class="hlt">concentrations</span>, C/N ratios and δ13C in surface sediments from two high Arctic fiords: Hornsund and Adventfjorden. Hornsund is a southernmost fiord on the western coast of Spitsbergen. It is a medium size fiord with a complex coastline including numerous bays and fourteen tidewater glaciers entering directly the fjord. Adventfjorden belongs to the largest fjord system of the west Spitsbergen - Isfjorden. The innermost part of Adventfjorden is composed of a tidal flat formed at the mouth of two braided rivers (the Adventelva and the Longyearelva) feeded by meltwater from glaciers. Both fjords are under influence of different water masses. The whole Isfjorden is affected by warm and saline Atlantic water from the West Spitsbergen Current (WSC). In Hornsund the influence of WSC is less pronounced at the expense of strong pressure from cold and less saline waters of coastal Sørkapp Current coming from the northeastern Barents Sea. Surface sediments were sampled at four locations in each fiord along the fjords' axes starting from the tidal flat in Adventfjorden and the vicinity of Hornbree glacier in Hornsund. The OC <span class="hlt">concentrations</span> in Hornsund were much lower (from 1.6% to 1.8%) than those in Adventfjorden (from 2.4% to 5</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24175752','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24175752"><span>Modeling the uptake of neutral organic chemicals on XAD passive air samplers under <span class="hlt">variable</span> temperatures, external wind speeds and ambient air <span class="hlt">concentrations</span> (PAS-SIM).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Armitage, James M; Hayward, Stephen J; Wania, Frank</p> <p>2013-01-01</p> <p>The main objective of this study was to evaluate the performance and demonstrate the utility of a fugacity-based model of XAD passive air samplers (XAD-PAS) designed to simulate the uptake of neutral organic chemicals under <span class="hlt">variable</span> temperatures, external wind speeds and ambient air <span class="hlt">concentrations</span>. The model (PAS-SIM) simulates the transport of the chemical across the air-side boundary layer and within the sampler medium, which is segmented into a user-defined number of thin layers. Model performance was evaluated using data for polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from a field calibration study (i.e., active and XAD-PAS data) conducted in Egbert, Ontario, Canada. With some exceptions, modeled PAS uptake curves are in good agreement with the empirical PAS data. The results are highly encouraging, given the uncertainty in the active air sampler data used as input and other uncertainties related to model parametrization (e.g., sampler-air partition coefficients, the influence of wind speed on sampling rates). The study supports the further development and evaluation of the PAS-SIM model as a diagnostic (e.g., to aid interpretation of calibration studies and monitoring data) and prognostic (e.g., to inform design of future passive air sampling campaigns) tool.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24910986','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24910986"><span>Understanding the risks associated with the use of new psychoactive substances (NPS): high <span class="hlt">variability</span> of active ingredients <span class="hlt">concentration</span>, mislabelled preparations, multiple psychoactive substances in single products.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zamengo, Luca; Frison, Giampietro; Bettin, Chiara; Sciarrone, Rocco</p> <p>2014-08-17</p> <p>New psychoactive substances (NPS), are now a large group of substances of abuse not yet completely controlled by international drug conventions, which may pose a public health threat. Anxiety, paranoia, hallucinations, seizures, hyperthermia and cardiotoxicity are some of the common adverse effects associated with these compounds. In this paper, three case reports taken from the archive of processed cases of the authors' laboratory are presented and discussed to stress the risks of possible adverse consequences for NPS users: in particular, (i) the risk deriving from the difficulty of predicting the actual consumed dose, due to <span class="hlt">variability</span> of active ingredients <span class="hlt">concentration</span> in consumed products, (ii) the risk deriving from the difficulty of predicting the actual active ingredients present in consumed products, as opposed to those claimed by the manufacturer, and (iii) the risk deriving from the difficulty of predicting the actual pharmacological and toxicological effects related to the simultaneous consumption of different psychoactive ingredients contained in single products, whose interactions are mostly unknown. Each of them individually provide a source of concern for possible serious health related consequences. However, they should be considered in conjunction with each others, with the worldwide availability of NPS through the web and also with the incessantly growing business derived from the manipulation and synthesis of new substances. The resulting scenario is that of a cultural challenge which demands a global approach from different fields of knowledge.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012SPIE.8416E..2AZ','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012SPIE.8416E..2AZ"><span>Two-dimensional of uniform irradiation on target with the use of the <span class="hlt">concentricity</span> deviation lens arrays focus system of <span class="hlt">variable</span> focus length</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zheng, Jian-zhou; Yu, Qing-xu; Lu, Yong-jun; Guan, Shou-hua; Dong, Bin</p> <p>2012-10-01</p> <p>An optical system consisted of lens array with <span class="hlt">variable</span> focus width has been proposed for providing uniform irradiation on targets in inertial confinement fusion. This system was composed of two lenses arrays and the aspheric lens. Based on the adaxial matrix optics and the generalized diffraction integral theory, the principle of controllable focus profile was analyzed and the optimum design of the system parameters were presented, respectively. The simulated results showed that two-dimensional uniform focusing of laser beams with controllable width in the range of several hundred microns to several millimeters can be achieved by choosing appropriate system parameters. The system converted a circular laser beam into a flat-top square focused spot, presenting the transformation of beamshape and the uniform distribution of the spatial intensity at the same time. Appropriate <span class="hlt">concentricity</span> deviation of LA was made in the design of LA focus system, so that the diffraction patterns of different beamlets did not completely overlap and the large-scale intensity fluctuation reduced effectively, and a well-irradiated laser spot and great energy efficiency can be obtained in this scheme.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.6774T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.6774T"><span>Volatile <span class="hlt">concentrations</span> in <span class="hlt">variably</span> vesicular pyroclasts from the Rotongaio ash (181 AD Taupo eruption): did shallow magma degassing trigger exceptionally violent phreatomagmatic activity?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tuffen, Hugh; Houghton, Bruce F.; Dingwellp, Donald B.; Pinkerton, Harry</p> <p>2010-05-01</p> <p>Measurement of dissolved volatile <span class="hlt">concentrations</span> in pyroclasts has formed the basis of our understanding of the links between magma degassing and the explosivity of silicic eruptions[1]. To date these studies have focussed exclusively on the densest pyroclastic obsidians, which comprise on a tiny proportion of the erupted products, in order to bypass the difficulty of analysing vesicular material. As a consequence, crucial information is missing about how degassing in the densest clasts relates to the behaviour of the bulk of the magma volume. To overcome this shortcoming, the volatile content of <span class="hlt">variably</span> vesicular pyroclasts from the Rotongaio ash has been analysed using both micro-analytical (SIMS, synchrotron FTIR) and bulk techniques (TGA-MS). The Rotongaio ash was an exceptionally violent phase of phreatomagmatic activity during the 181 AD rhyolitic eruption of Taupo (New Zealand), the most powerful worldwide in the last 5000 years. The Rotongaio phase involved opening of new vents beneath Lake Taupo and the ash is characterised by a wide range of clast vesicularities (<10 to ~80 % by volume). Volatile measurement was challenging due to the high bubble number densities and small clast sizes. The mismatch between the water content of matrix glasses measured using bulk and micro-analytical techniques reflects pervasive post-eruption hydration of vesicle walls, which is most problematic at high vesicularities. Micron-scale maps of water <span class="hlt">concentration</span> variations around vesicles in 30-50 vol % vesicular samples were acquired using SIMS. They indicate strong hydration within ~5 microns of vesicle walls, with pockets of unhydrated glass remaining in the thickest septa. Analysis of these unhydrated domains allowed robust measurement of water contents in pyroclasts ranging from ~1 to >50 vol % vesicles. Matrix glasses had largely degassed (0.19-0.49 wt % H2O, compared with an initial <span class="hlt">concentration</span> in melt inclusions of ~3.6 wt %). The water contents measured using SIMS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10631623','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10631623"><span>CYP2D6 inhibition by fluoxetine, paroxetine, sertraline, and venlafaxine in a crossover study: intraindividual <span class="hlt">variability</span> and plasma <span class="hlt">concentration</span> correlations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alfaro, C L; Lam, Y W; Simpson, J; Ereshefsky, L</p> <p>2000-01-01</p> <p>The authors report the CYP2D6 inhibitory effects of fluoxetine, paroxetine, sertraline, and venlafaxine in an open-label, multiple-dose, crossover design. Twelve CYP2D6 extensive metabolizers were phenotyped, using the dextromethorphan/dextrorphan (DM/DX) urinary ratio, before and after administration of fluoxetine 60 mg (loading dose strategy), paroxetine 20 mg, sertraline 100 mg, and venlafaxine 150 mg. Paroxetine, sertraline, and venlafaxine sequences were randomized with 2-week washouts between treatments; fluoxetine was the last antidepressant (AD) administered. Comparing within groups, baseline DM/DX ratios (0.017) were significantly lower than DM/DX ratios after treatment (DM/DXAD) with fluoxetine (0.313, p < 0.0001) and paroxetine (0.601, p < 0.0001) but not for sertraline (0.026, p = 0.066) or venlafaxine (0.023, p = 0.485). Between groups, DM/DXAD ratios were significantly higher for fluoxetine and paroxetine compared to sertraline and venlafaxine. No differences between DM/DXAD ratios were found for fluoxetine and paroxetine although more subjects phenocopied to PM status after receiving the latter (42% vs. 83%; chi 2 = 4.44, p = 0.049, df = 1). Similarly, no differences between DM/DXAD ratios were found for sertraline and venlafaxine. Of note, the DM/DXAD for 1 subject was much lower after treatment with paroxetine (0.058) compared to fluoxetine (0.490), while another subject exhibited a much lower ratio after treatment with fluoxetine (0.095) compared to paroxetine (0.397). Significant correlations between AD plasma <span class="hlt">concentration</span> and DM/DXAD were found for paroxetine (r2 = 0.404, p = 0.026) and sertraline (r2 = 0.64, p = 0.002) but not fluoxetine or venlafaxine. In addition, DM/DXAD correlated with baseline isoenzyme activity for paroxetine, sertraline, and venlafaxine groups. These results demonstrate the potent, but <span class="hlt">variable</span>, CYP2D6 inhibition of fluoxetine and paroxetine compared to sertraline and venlafaxine. CYP2D6 inhibition may be related, in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23913910','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23913910"><span>Predicted no effect <span class="hlt">concentration</span> derivation as a significant source of <span class="hlt">variability</span> in environmental hazard assessments of chemicals in aquatic systems: an international analysis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hahn, Thorsten; Diamond, Jerry; Dobson, Stuart; Howe, Paul; Kielhorn, Janet; Koennecker, Gustav; Lee-Steere, Chris; Mangelsdorf, Inge; Schneider, Uwe; Sugaya, Yoshio; Taylor, Ken; Dam, Rick Van; Stauber, Jenny L</p> <p>2014-01-01</p> <p>Environmental hazard assessments for chemicals are carried out to define an environmentally "safe" level at which, theoretically, the chemical will not negatively affect any exposed biota. Despite this common goal, the methodologies in use are very diverse across different countries and jurisdictions. This becomes particularly obvious when international scientists work together on documents with global scope, e.g., in the World Health Organization (WHO) International Program on Chemical Safety. In this article, we present a study that describes the extent of such <span class="hlt">variability</span> and analyze the reasons that lead to different outcomes in deriving a "safe level" (termed the predicted no effect <span class="hlt">concentration</span> [PNEC] throughout this article). For this purpose, we chose 5 chemicals to represent well-known substances for which sufficient high-quality aquatic effects data were available: ethylene glycol, trichloroethylene, nonylphenol, hexachlorobenzene, and copper (Cu). From these data, 2 data sets for each chemical were compiled: the full data set, that contained all information from selected peer-review sources, and the base data set, a subsample of the full set simulating limited data. Scientists from the European Union (EU), United States, Canada, Japan, and Australia independently carried out hazard assessments for each of these chemicals using the same data sets. Their reasoning for key study selection, use of assessment factors, or use of probabilistic methods was comprehensively documented. The observed variation in the PNECs for all chemicals was up to 3 orders of magnitude, and this was not simply due to obvious factors such as the size of the data set or the methodology used. Rather, this was due to individual decisions of the assessors within the scope of the methodology used, especially key study selection, acute versus chronic definitions, and size of assessment factors. Awareness of these factors, together with transparency of the decision-making process, would</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2013/1255/pdf/ofr13-1255.pdf.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2013/1255/pdf/ofr13-1255.pdf.pdf"><span>seawaveQ: an R package providing a model and utilities for analyzing trends in chemical <span class="hlt">concentrations</span> in streams with a seasonal wave (seawave) and adjustment for streamflow (Q) and other ancillary <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ryberg, Karen R.; Vecchia, Aldo V.</p> <p>2013-01-01</p> <p>The seawaveQ R package fits a parametric regression model (seawaveQ) to pesticide <span class="hlt">concentration</span> data from streamwater samples to assess <span class="hlt">variability</span> and trends. The model incorporates the strong seasonality and high degree of censoring common in pesticide data and users can incorporate numerous ancillary <span class="hlt">variables</span>, such as streamflow anomalies. The model is fitted to pesticide data using maximum likelihood methods for censored data and is robust in terms of pesticide, stream location, and degree of censoring of the <span class="hlt">concentration</span> data. This R package standardizes this methodology for trend analysis, documents the code, and provides help and tutorial information, as well as providing additional utility functions for plotting pesticide and other chemical <span class="hlt">concentration</span> data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19200113','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19200113"><span>External <span class="hlt">concentration</span> of organic acid anions and pH: key independent <span class="hlt">variables</span> for studying how organic acids inhibit growth of bacteria in mildly acidic foods.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Carpenter, C E; Broadbent, J R</p> <p>2009-01-01</p> <p>Although the mechanisms by which organic acids inhibit growth of bacteria in mildly acidic foods are not fully understood, it is clear that intracellular accumulation of anions is a primary contributor to inhibition of bacterial growth. We hypothesize that intracellular accumulation of anions is driven by 2 factors, external anion <span class="hlt">concentration</span> and external acidity. This hypothesis follows from basic chemistry principles that heretofore have not been fully applied to studies in the field, and it has led us to develop a novel approach for predicting internal anion <span class="hlt">concentration</span> by controlling the external <span class="hlt">concentration</span> of anions and pH. This approach overcomes critical flaws in contemporary experimental design that invariably target <span class="hlt">concentration</span> of either protonated acid or total acid in the growth media thereby leaving anion <span class="hlt">concentration</span> to vary depending on the pK(a) of the acids involved. Failure to control external <span class="hlt">concentration</span> of anions has undoubtedly confounded results, and it has likely led to misleading conclusions regarding the antimicrobial action of organic acids. In summary, we advocate an approach for directing internal anion levels by controlling external <span class="hlt">concentration</span> of anions and pH because it presents an additional opportunity to study the mechanisms by which organic acids inhibit bacterial growth. Knowledge gained from such studies would have important application in the control of important foodborne pathogens such as Listeria monocytogenes, and may also facilitate efforts to promote the survival in foods or beverages of desirable probiotic bacteria.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70174334','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70174334"><span>Regional <span class="hlt">variability</span> in bed-sediment <span class="hlt">concentrations</span> of wastewater compounds, hormones and PAHs for portions of coastal New York and New Jersey impacted by hurricane Sandy</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Phillips, Patrick; Gibson, Cathy A; Fisher, Shawn C.; Fisher, Irene; Reilly, Timothy J.; Smalling, Kelly L.; Romanok, Kristin M.; Foreman, William T.; ReVello, Rhiannon C.; Focazio, Michael J.; Jones, Daniel K.</p> <p>2016-01-01</p> <p>Bed sediment samples from 79 coastal New York and New Jersey, USA sites were analyzed for 75 compounds including wastewater associated contaminants, PAHs, and other organic compounds to assess the post-Hurricane Sandy distribution of organic contaminants among six regions. These results provide the first assessment of wastewater compounds, hormones, and PAHs in bed sediment for this region. <span class="hlt">Concentrations</span> of most wastewater contaminants and PAHs were highest in the most developed region (Upper Harbor/Newark Bay, UHNB) and reflected the wastewater inputs to this area. Although the lack of pre-Hurricane Sandy data for most of these compounds make it impossible to assess the effect of the storm on wastewater contaminant <span class="hlt">concentrations</span>, PAH <span class="hlt">concentrations</span> in the UHNB region reflect pre-Hurricane Sandy conditions in this region. Lower hormone <span class="hlt">concentrations</span> than predicted by the total organic carbon relation occurred in UHNB samples, suggesting that hormones are being degraded in the UHNB region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24735095','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24735095"><span>Nutrient <span class="hlt">variability</span> in phloem: examining changes in K, Mg, Zn and Fe <span class="hlt">concentration</span> during grain loading in common wheat (Triticum aestivum).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Palmer, Lachlan J; Palmer, Lyndon T; Rutzke, Michael A; Graham, Robin D; Stangoulis, James C R</p> <p>2014-12-01</p> <p>In wheat, nutrients are transported to seeds via the phloem yet access to this vascular tissue for exudate collection and quantitative analysis of elemental composition is difficult. The purest phloem is collected through the use of aphid stylectomy with volumes of exudate collected normally in the range of 20-500 nl. In this work a new method using inductively coupled plasma mass spectroscopy (ICP-MS) was developed to measure the <span class="hlt">concentration</span> of K, Mg, Zn and Fe in volumes of wheat (Triticum aestivum, genotype Samnyt 16) phloem as small as 15.5 nl. This improved method was used to observe changes in phloem nutrient <span class="hlt">concentration</span> during the grain loading period. There were statistically significant increases in phloem Mg and Zn <span class="hlt">concentration</span> and a significant decrease in K over the period from 1-2 days after anthesis (DAA) to 9-12 DAA. During this period, there was no statistically significant change in phloem Fe <span class="hlt">concentration</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27177500','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27177500"><span>Regional <span class="hlt">variability</span> in bed-sediment <span class="hlt">concentrations</span> of wastewater compounds, hormones and PAHs for portions of coastal New York and New Jersey impacted by hurricane Sandy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Phillips, Patrick J; Gibson, Catherine A; Fisher, Shawn C; Fisher, Irene J; Reilly, Timothy J; Smalling, Kelly L; Romanok, Kristin M; Foreman, William T; ReVello, Rhiannon C; Focazio, Michael J; Jones, Daniel K</p> <p>2016-06-30</p> <p>Bed sediment samples from 79 coastal New York and New Jersey, USA sites were analyzed for 75 compounds including wastewater associated contaminants, PAHs, and other organic compounds to assess the post-Hurricane Sandy distribution of organic contaminants among six regions. These results provide the first assessment of wastewater compounds, hormones, and PAHs in bed sediment for this region. <span class="hlt">Concentrations</span> of most wastewater contaminants and PAHs were highest in the most developed region (Upper Harbor/Newark Bay, UHNB) and reflected the wastewater inputs to this area. Although the lack of pre-Hurricane Sandy data for most of these compounds make it impossible to assess the effect of the storm on wastewater contaminant <span class="hlt">concentrations</span>, PAH <span class="hlt">concentrations</span> in the UHNB region reflect pre-Hurricane Sandy conditions in this region. Lower hormone <span class="hlt">concentrations</span> than predicted by the total organic carbon relation occurred in UHNB samples, suggesting that hormones are being degraded in the UHNB region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19391677','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19391677"><span>Trout density and health in a stream with <span class="hlt">variable</span> water temperatures and trace element <span class="hlt">concentrations</span>: does a cold-water source attract trout to increased metal exposure?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Harper, David D; Farag, Aïda M; Hogstrand, Christer; Macconnell, Elizabeth</p> <p>2009-04-01</p> <p>A history of hard-rock mining has resulted in elevated <span class="hlt">concentrations</span> of heavy metals in Prickly Pear Creek (MT, USA). Remediation has improved water quality; however, dissolved zinc and cadmium <span class="hlt">concentrations</span> still exceed U.S. Environmental Protection Agency water-quality criteria. Physical habitat, salmonid density, fish health, and water quality were assessed, and metal <span class="hlt">concentrations</span> in fish tissues, biofilm, and macroinvertebrates were determined to evaluate the existing condition in the watershed. Cadmium, zinc, and lead <span class="hlt">concentrations</span> in fish tissues, biofilm, and invertebrates were significantly greater than those at the upstream reference site and an experimental site farther downstream of the confluence. Fish densities were greatest, and habitat quality for trout was better, downstream of the confluence, where water temperatures were relatively cool (16 degrees C). Measures of fish health (tissue metal residues, histology, metallothionein <span class="hlt">concentrations</span>, and necropsies), however, indicate that the health of trout at this site was negatively affected. Trout were in colder but more contaminated water and were subjected to increased trace element exposures and associated health effects. Maximum water temperatures in Prickly Pear Creek were significantly lower directly below Spring Creek (16 degrees C) compared to those at an experimental site 10 km downstream (26 degrees C). Trout will avoid dissolved metals at <span class="hlt">concentrations</span> below those measured in Prickly Pear Creek; however, our results suggest that the preference of trout to use cool water temperatures may supersede behaviors to avoid heavy metals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70034978','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70034978"><span>Trout density and health in a stream with <span class="hlt">variable</span> water temperatures and trace element <span class="hlt">concentrations</span>: does a cold-water source attract trout to increased metal exposure?</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Harper, D.D.; Farag, A.M.; Hogstr, C.; MacConnell, Elizabeth</p> <p>2009-01-01</p> <p>A history of hard-rock mining has resulted in elevated <span class="hlt">concentrations</span> of heavy metals in Prickly Pear Creek (MT. USA). Remediation has improved water quality; however, dissolved zinc and cadmium <span class="hlt">concentrations</span> still exceed U.S. Environmental Protection Agency water-quality criteria. Physical habitat, salmonid density, fish health, and water quality were assessed, and metal <span class="hlt">concentrations</span> in fish tissues, biofilm, and macroinvertebrates were determined to evaluate the existing condition in the watershed. Cadmium, zinc, and lead <span class="hlt">concentrations</span> in fish tissues, biofilm, and invertebrates were significantly greater than those at the upstream reference site and an experimental site farther downstream of the confluence. Fish densities were greatest, and habitat quality for trout was better, downstream of the confluence, where water temperatures were relatively cool (16??C). Measures of fish health (tissue metal residues, histology, metallothionein <span class="hlt">concentrations</span>, and necropsies), however, indicate that the health of trout at this site was negatively affected. Trout were in colder but more contaminated water and were subjected to increased trace element exposures and associated health effects. Maximum water temperatures in Prickly Pear Creek were significantly lower directly below Spring Creek (16??C) compared to those at an experimental site 10 km downstream (26??C). Trout will avoid dissolved metals at <span class="hlt">concentrations</span> below those measured in Prickly Pear Creek; however, our results suggest that the preference of trout to use cool water temperatures may supersede behaviors to avoid heavy metals. ?? 2009 SETAC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AtmEn..94..341H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AtmEn..94..341H"><span>Spatial <span class="hlt">variability</span> of particle number <span class="hlt">concentrations</span> and NOx in the Karlsruhe (Germany) area obtained with the mobile laboratory ‘AERO-TRAM'</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hagemann, Rowell; Corsmeier, Ulrich; Kottmeier, Christoph; Rinke, Rayk; Wieser, Andreas; Vogel, Bernhard</p> <p>2014-09-01</p> <p>For the first time in Germany, we obtained high-resolution spatial distributions of particle numbers and nitrogen oxides in an urban agglomeration using a tram system. In comparison to particle numbers the NOx <span class="hlt">concentration</span> decreased much faster with a significantly steeper gradient when going from the inner city to the surrounding area. In case of NOx the decrease was 70% while for particle number <span class="hlt">concentration</span> it was only 50%. We found an area in the rural surrounding with a second increase of particle numbers without simultaneous enhanced NOx levels. The source of the high particle numbers could be ascribed to industry emissions about 5-10 km away. The mean spatial distribution of particle number <span class="hlt">concentration</span> depended on wind direction, wind velocity and boundary layer stability. The dependency was particularly strong in the rural area affected by industrial emissions, where individual wind directions led to <span class="hlt">concentration</span> differences of up to 25%. The particulate <span class="hlt">concentration</span> was 40% higher during low wind velocities (1-5 m s-1) than during high wind velocities (>5 m s-1). We observed similar findings for the impact of boundary layer stability on particle numbers <span class="hlt">concentration</span>. Particle pollution was 40% higher for stable stratification compared to neutral or unstable cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19820016894','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19820016894"><span>Investigation of the winds and electron <span class="hlt">concentration</span> <span class="hlt">variability</span> in the D region of the ionosphere by the partial-reflection radar technique</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weiland, R. M.; Bowhill, S. A.</p> <p>1981-01-01</p> <p>The development and first observations of the partial-reflection drifts experiment at Urbana, Illinois (40 N) are described. The winds data from the drifts experiment are compared with electron <span class="hlt">concentration</span> data obtained by the differential-absorption technique to study the possible meteorological causes of the winter anomaly in the mesosphere at midlatitudes. winds data obtained by the meteor-radar experiment at Urbana are also compared with electron <span class="hlt">concentration</span> data measured at Urban. A significant correlation is shown is both cases between southward winds and increasing electron <span class="hlt">concentration</span> measured at the same location during winter. The possibility of stratospheric/mesospheric coupling is investigated by comparing satellite-measured 0.4 mbar geopotential data with mesospheric electron <span class="hlt">concentration</span> data. No significant coupling was observed. The winds measured at Saskatoon, Saskatchewan (52 N) are compared with the electron <span class="hlt">concentrations</span> measured at Urban, yielding constant fixed relationship, but significant correlations for short segments of the winter. A significant coherence is observed at discrete frequencies during segments of the winter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=203863&keyword=pearson+AND+correlation&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=85833934&CFTOKEN=29556762','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=203863&keyword=pearson+AND+correlation&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=85833934&CFTOKEN=29556762"><span>Spatial and Temporal <span class="hlt">Variability</span> of Outdoor Coarse Particulate Matter Mass <span class="hlt">Concentrations</span> Measured with a New Coarse Particulate Sampler during the Detroit Exposure and Aerosol Research Study</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The Detroit Exposure and Aerosol Research Study (DEARS) provided data to compare outdoor residential coarse particulate matter (PM<SUB>10-2.5</SUB>) <span class="hlt">concentrations</span> in six different areas of Detroit with data from a central monitoring site. Daily and seasonal influences on the spa...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=279061&keyword=Reproduction&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78764605&CFTOKEN=98803258','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=279061&keyword=Reproduction&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78764605&CFTOKEN=98803258"><span>An inter-laboratory study on the <span class="hlt">variability</span> in measured <span class="hlt">concentrations</span> of 17Beta-estradiol, testosterone and 11-ketotestosterone in white sucker: implications and recommendations</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Endocrine-disrupting chemicals (EDCs) are exogenous substances that can lead to impacts on the reproduction of fish sometimes by altering circulating <span class="hlt">concentrations</span> of 17â-estradiol (E2), testosterone (T) and 11-ketotestosterone (11-KT). Common methods to measure steroids in pla...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17484148','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17484148"><span>Protective effect of Carbopol on enzymatic degradation of a peptide-like substrate. I: Effect of various <span class="hlt">concentrations</span> and grades of Carbopol and other reaction <span class="hlt">variables</span> on trypsin activity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vaidya, A P; Wigent, R J; Moore, J C; Schwartz, J B</p> <p>2007-01-01</p> <p>The purpose of this study was to determine and compare the effect of various <span class="hlt">concentrations</span> and grades of Carbopol on trypsin-induced degradation of a prototype substrate, N(alpha)-benzoyl-L-arginine ethyl ester hydrochloride (BAEE). Effect of other reaction <span class="hlt">variables</span>, such as viscosity and ionic strength of the medium on the trypsin activity, was also analyzed simultaneously. Four <span class="hlt">concentrations</span> and three commercially available grades of Carbopol were used. The effect of Carbopol was expressed in terms of change in the velocity of degradation reaction. A modified trypsin assay was developed and used for analysis. Up to a <span class="hlt">concentration</span> of 0.35% w/v, Carbopol 934P showed a <span class="hlt">concentration</span>-dependent increase in its ability to reduce the rate of enzymatic hydrolysis of BAEE. Similar inhibitory effect was observed with all three grades of Carbopol. The activity of trypsin was unaffected by other reaction <span class="hlt">variables</span>, suggesting that interaction between the protein and the polymer could be the mechanism responsible for reduced trypsin activity. This study suggests that Carbopol can be a useful excipient for oral delivery of bioactive proteins and peptides, due to its ability to reduce the enzyme-induced degradation of these agents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1083066','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1083066"><span>Method of particle trajectory recognition in particle flows of high particle <span class="hlt">concentration</span> using a candidate trajectory tree process with <span class="hlt">variable</span> search areas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Shaffer, Franklin D.</p> <p>2013-03-12</p> <p>The application relates to particle trajectory recognition from a Centroid Population comprised of Centroids having an (x, y, t) or (x, y, f) coordinate. The method is applicable to visualization and measurement of particle flow fields of high particle. In one embodiment, the centroids are generated from particle images recorded on camera frames. The application encompasses digital computer systems and distribution mediums implementing the method disclosed and is particularly applicable to recognizing trajectories of particles in particle flows of high particle <span class="hlt">concentration</span>. The method accomplishes trajectory recognition by forming Candidate Trajectory Trees and repeated searches at varying Search Velocities, such that initial search areas are set to a minimum size in order to recognize only the slowest, least accelerating particles which produce higher local <span class="hlt">concentrations</span>. When a trajectory is recognized, the centroids in that trajectory are removed from consideration in future searches.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3068516','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3068516"><span>Genetic analysis of mouse strains with <span class="hlt">variable</span> serum sodium <span class="hlt">concentrations</span> identifies the Nalcn sodium channel as a novel player in osmoregulation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sinke, Anne P.; Caputo, Christina; Tsaih, Shirng-Wern; Yuan, Rong; Ren, Dejian; Deen, Peter M. T.</p> <p>2011-01-01</p> <p>In central osmoregulation, a 1–2% rise in plasma osmolality is detected by specialized osmoreceptors located in the circumventricular organs of the hypothalamus. A disturbance in this tightly regulated balance will result in either hyponatremia or hypernatremia, which are both common electrolyte disorders in hospitalized patients. Despite the high clinical importance of hypo- and hypernatremia and the fact that this vital process has been studied for many years, the genes and corresponding proteins involved in this process are just beginning to be identified. To identify novel genes involved in the (patho-)physiology of osmoregulation, we therefore employed haplotype association mapping on an aging group of 27 inbred mouse strains. Serum sodium <span class="hlt">concentrations</span> were determined in all strains at 6, 12, and 18 mo of age, and high-resolution mapping was performed for males and females separately. We identified a total of five loci associated with the serum sodium <span class="hlt">concentration</span> of which the locus on chromosome 14, containing only one known gene (Nalcn), showed the strongest correlation. Within this locus three different haplotypes could be distinguished, which associated with different average serum sodium levels. The association of Nalcn with sodium levels was confirmed by analysis of heterozygous Nalcn knockout mice, which displayed hypernatremia compared with wild-type littermates. Our study demonstrates that Nalcn associates with serum sodium <span class="hlt">concentrations</span> in mice and indicates that Nalcn is an important novel player in osmoregulation. PMID:21177381</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4997458','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4997458"><span>Spatiotemporal <span class="hlt">Variability</span> of Remotely Sensed PM2.5 <span class="hlt">Concentrations</span> in China from 1998 to 2014 Based on a Bayesian Hierarchy Model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Junming; Jin, Meijun; Xu, Zheng</p> <p>2016-01-01</p> <p>With the rapid industrial development and urbanization in China over the past three decades, PM2.5 pollution has become a severe environmental problem that threatens public health. Due to its unbalanced development and intrinsic topography features, the distribution of PM2.5 <span class="hlt">concentrations</span> over China is spatially heterogeneous. In this study, we explore the spatiotemporal variations of PM2.5 pollution in China and four great urban areas from 1998 to 2014. A space-time Bayesian hierarchy model is employed to analyse PM2.5 pollution. The results show that a stable “3-Clusters” spatial PM2.5 pollution pattern has formed. The mean and 90% quantile of the PM2.5 <span class="hlt">concentrations</span> in China have increased significantly, with annual increases of 0.279 μg/m3 (95% CI: 0.083−0.475) and 0.735 μg/m3 (95% CI: 0.261−1.210), respectively. The area with a PM2.5 pollution level of more than 70 μg/m3 has increased significantly, with an annual increase of 0.26 percentage points. Two regions in particular, the North China Plain and Sichuan Basin, are experiencing the largest amounts of PM2.5 pollution. The polluted areas, with a high local magnitude of more than 1.0 relative to the overall PM2.5 <span class="hlt">concentration</span>, affect an area with a human population of 949 million, which corresponded to 69.3% of the total population in 2010. North and south differentiation occurs in the urban areas of the Jingjinji and Yangtze Delta, and circular and radial gradient differentiation occur in the urban areas of the Cheng-Yu and Pearl Deltas. The spatial heterogeneity of the urban Jingjinji group is the strongest. Eighteen cities located in the Yangtze Delta urban group, including Shanghai and Nanjing, have experienced high PM2.5 <span class="hlt">concentrations</span> and faster local trends of increasing PM2.5. The percentage of exposure to PM2.5 <span class="hlt">concentrations</span> greater than 70 μg/m3 and 100 μg/m3 is increasing significantly. PMID:27490557</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4449767','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4449767"><span>High interindividual <span class="hlt">variability</span> in the CD4/CD8 T cell ratio and natalizumab <span class="hlt">concentration</span> levels in the cerebrospinal fluid of patients with multiple sclerosis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Harrer, A; Pilz, G; Wipfler, P; Oppermann, K; Sellner, J; Hitzl, W; Haschke-Becher, E; Afazel, S; Rispens, T; van der Kleij, D; Trinka, E; Kraus, J</p> <p>2015-01-01</p> <p>Strongly decreased leucocyte counts and a reduced CD4/CD8 T cell ratio in the cerebrospinal fluid (CSF) of natalizumab (NZB)-treated multiple sclerosis (MS) patients may have implications on central nervous (CNS) immune surveillance. With regard to NZB-associated progressive multi-focal leucoencephalopathy, we aimed at delineating a relationship between free NZB, cell-bound NZB, adhesion molecule (AM) expression and the treatment-associated shift in the CSF T cell ratio. Peripheral blood (PB) and CSF T cells from 15 NZB-treated MS patients, and CSF T cells from 10 patients with non-inflammatory neurological diseases and five newly diagnosed MS patients were studied. Intercellular adhesion molecule-1 (ICAM-1), leucocyte function antigen-1 (LFA-1), very late activation antigen-4 (VLA-4), NZB saturation levels, and T cell ratios were analysed by flow cytometry. NZB <span class="hlt">concentrations</span> were measured by enzyme-linked immunosorbent assay (ELISA). Lower NZB saturation levels (P < 0·02) and a higher surface expression of ICAM-1 and LFA-1 (P < 0·001) were observed on CSF CD8 T cells. CSF T cell ratios (0·3–2·1) and NZB <span class="hlt">concentrations</span> (0·01–0·42 µg/ml) showed a pronounced interindividual variance. A correlation between free NZB, cell-bound NZB or AM expression levels and the CSF T cell ratio was not found. Extremely low NZB <span class="hlt">concentrations</span> and a normalized CSF T cell ratio were observed in one case. The differential NZB saturation and AM expression of CSF CD8 T cells may contribute to their relative enrichment in the CSF. The reduced CSF T cell ratio appeared sensitive to steady-state NZB levels, as normalization occurred quickly. The latter may be important concerning a fast reconstitution of CNS immune surveillance. PMID:25603898</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25555556','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25555556"><span>Spatial and temporal <span class="hlt">variability</span> of organic C and N <span class="hlt">concentrations</span> and export from 30 boreal rivers induced by land use and climate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mattsson, Tuija; Kortelainen, Pirkko; Räike, Antti; Lepistö, Ahti; Thomas, David N</p> <p>2015-03-01</p> <p>Climate change scenarios for northern boreal regions indicate that there will be increasing temperature and precipitation, and the changes are expected to be larger in winter than in summer. These precipitation and discharge patterns, coupled with shorter ice cover/soil frost periods in the future would be expected to contribute significantly to changing flow paths of organic matter over a range of land use patterns. In order to study the impact of climate change on the seasonality of organic matter export we compared total organic carbon (TOC) and total organic nitrogen (TON) <span class="hlt">concentrations</span> and export, during different seasons and climatically different years, over 12 years for 30 Finnish rivers separated into forest, agriculture and peat dominated catchments. The mean monthly TOC <span class="hlt">concentrations</span> were highest during autumn and there was also a peak in May during the highest flow period. The mean monthly <span class="hlt">concentrations</span> of TON were lowest during winter, increased in spring and remaining high throughout summer and autumn. The TOC/TON ratios were lowest during summer and highest during winter, and in all seasons the ratios were lowest in catchments with a high proportion of agricultural land and highest in peat-dominated catchments. The seasonality of TOC and TON exports reflected geographical location, hydrology and land use patterns. Most of the TOC and TON were transported during the high flow following the spring snowmelt and during rainfall in autumn. In all catchments the relative importance of the spring snowmelt decreased in wet and warm years. However, in peat-dominated catchments the proportion of spring period was over 30% of the annual export even in these wet and warm years, while in other catchments the proportion was about 20%. This might be linked to the northern location of the peat-dominated catchments and the permanent snow cover and spring snowmelt, even in warm years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21788428','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21788428"><span>Effects of bacterial lipopolysaccharide injection on white blood cell counts, hematological <span class="hlt">variables</span>, and serum glucose, insulin, and cortisol <span class="hlt">concentrations</span> in ewes fed low- or high-protein diets.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yates, D T; Löest, C A; Ross, T T; Hallford, D M; Carter, B H; Limesand, S W</p> <p>2011-12-01</p> <p>Bacterial lipopolysaccharide endotoxins (LPS) elicit inflammatory responses reflective of acute bacterial infection. We determined if feeding ewes high-CP (15.5%) or low-CP (8.5%) diets for 10 d altered inflammatory responses to an intravenous bolus of 0 (control), 0.75 (L75), or 1.50 (L150) μg of LPS/kg of BW in a 2 × 3 factorial arrangement of treatments (n = 5/treatment). Rectal temperatures, heart and respiratory rates, blood leukocyte <span class="hlt">concentrations</span>, and serum cortisol, insulin, and glucose <span class="hlt">concentrations</span> were measured for 24 h after an LPS bolus (bolus = 0 h). In general, rectal temperatures were greater (P ≤ 0.05) in control ewes fed high CP, but LPS increased (P ≤ 0.05) rectal temperatures in a dose-dependent manner at most times between 2 and 24 h after the bolus. Peak rectal temperatures in L75 and L150 occurred 4 h after the bolus. A monophasic, dose-independent increase (P ≤ 0.023) in serum cortisol occurred from 0.5 to 24 h after the bolus, with peak cortisol at 4 h. Serum insulin was increased (P ≤ 0.016) by LPS in a dose-dependent manner from 4 to 24 h after the bolus. Insulin did not differ between control ewes fed high- and low-CP diets but was greater (P < 0.001) in L75 ewes fed low CP compared with high CP and in L150 ewes fed high CP compared with low CP. Increased insulin was not preceded by increased serum glucose. Total white blood cell <span class="hlt">concentrations</span> were not affected (P ≥ 0.135) by LPS, but the neutrophil and monocyte fractions of white blood cells were increased (P ≤ 0.047) by LPS at 12 and 24 h and at 24 h after the bolus, respectively, and the lymphocyte fraction was increased (P = 0.037) at 2 h and decreased (P ≤ 0.006) at 12 and 24 h after the bolus. Red blood cell and hemoglobin <span class="hlt">concentrations</span> and hematocrit (%) were increased (P ≤ 0.022) by LPS at 2 and 4 h after the bolus. Rectal temperatures and serum glucose were greater (P ≤ 0.033) in ewes fed a high-CP diet before LPS injection, but these effects were lost at</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4055214','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4055214"><span>Effects of Acute Bleeding Followed by Hydroxyethyl Starch 130/0.4 or a Crystalloid on Propofol <span class="hlt">Concentrations</span>, Cerebral Oxygenation, and Electroencephalographic and Haemodynamic <span class="hlt">Variables</span> in Pigs</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Venâncio, Carlos; Souza, Almir P.; Ferreira, Luísa Maria; Branco, Paula Sério; de Pinho, Paula Guedes; Amorim, Pedro; Ferreira, David A.</p> <p>2014-01-01</p> <p>Bleeding changes the haemodynamics, compromising organ perfusion. In this study, the effects of bleeding followed by replacement with hydroxyethyl starch 130/0.4 (HES) or lactated Ringer's (LR) on cerebral oxygenation and electroencephalogram-derived parameters were investigated. Twelve young pigs under propofol-remifentanil anaesthesia were bled 30 mL/kg and, after a 20-minute waiting period, volume replacement was performed with HES (GHES; N = 6) or LR (GRL; N = 6). Bleeding caused a decrease of more than 50% in mean arterial pressure (P < 0.01) and a decrease in cerebral oximetry (P = 0.039), bispectral index, and electroencephalogram total power (P = 0.04 and P < 0.01, resp.), while propofol plasma <span class="hlt">concentrations</span> increased (P < 0.01). Both solutions restored the haemodynamics and cerebral oxygenation similarly and were accompanied by an increase in electroencephalogram total power. No differences between groups were found. However, one hour after the end of the volume replacement, the cardiac output (P = 0.03) and the cerebral oxygenation (P = 0.008) decreased in the GLR and were significantly lower than in GHES (P = 0.02). Volume replacement with HES 130/0.4 was capable of maintaining the cardiac output and cerebral oxygenation during a longer period than LR and caused a decrease in the propofol plasma <span class="hlt">concentrations</span>. PMID:24971192</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AtmEn..35.5361C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AtmEn..35.5361C"><span><span class="hlt">Variability</span> of No x and No 2 <span class="hlt">concentrations</span> observed at pedestrian level in the city centre of a medium sized urban area</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coppalle, A.; Delmas, V.; Bobbia, M.</p> <p></p> <p>NO x and NO 2 <span class="hlt">concentrations</span> were measured at different locations in a city centre of an urban zone (Population 450 000) in order to study the variation of the outdoor exposure at pedestrian level. These measurements were carried out to understand the influence of traffic emissions at each measured site. The observations were done during four weeks in winter, including several days with high pollution levels. The results at different locations have been used to analyse criteria recommended for locating observation sites in a monitoring network. No large differences in background pollution averaged over several weeks have been found throughout the city centre, even during pollution peaks. Measurements were also carried out inside one street canyon. The contribution of the street traffic to the NO=NO x-NO 2 <span class="hlt">concentrations</span> observed at side-walk has been found important, i.e., several times the background level. On the other hand, the majority of observed NO 2 pollution is due to the contribution of background pollution within the street. The pollutant excess at pedestrian level is strongly correlated to the street traffic emission and to the atmospheric turbulence observed at roof level. Application of a box model to the street data demonstrates that such models can be useful to estimate the pollutant accumulation within the street.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70028571','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70028571"><span>Tracer test with As(V) under <span class="hlt">variable</span> redox conditions controlling arsenic transport in the presence of elevated ferrous iron <span class="hlt">concentrations</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hohn, R.; Isenbeck-Schroter, M.; Kent, D.B.; Davis, J.A.; Jakobsen, R.; Jann, S.; Niedan, V.; Scholz, C.; Stadler, S.; Tretner, A.</p> <p>2006-01-01</p> <p>To study transport and reactions of arsenic under field conditions, a small-scale tracer test was performed in an anoxic, iron-reducing zone of a sandy aquifer at the USGS research site on Cape Cod, Massachusetts, USA. For four weeks, a stream of groundwater with added As(V) (6.7????M) and bromide (1.6??mM), was injected in order to observe the reduction of As(V) to As(III). Breakthrough of bromide (Br-), As(V), and As(III) as well as additional parameters characterizing the geochemical conditions was observed at various locations downstream of the injection well over a period of 104??days. After a short lag period, nitrate and dissolved oxygen from the injectate oxidized ferrous iron and As(V) became bound to the freshly formed hydrous iron oxides. Approximately one week after terminating the injection, anoxic conditions had been reestablished and increases in As(III) <span class="hlt">concentrations</span> were observed within 1??m of the injection. During the observation period, As(III) and As(V) were transported to a distance of 4.5??m downgradient indicating significant retardation by sorption processes for both species. Sediment assays as well as elevated <span class="hlt">concentrations</span> of hydrogen reflected the presence of As(V) reducing microorganisms. Thus, microbial As(V) reduction was thought to be one major process driving the release of As(III) during the tracer test in the Cape Cod aquifer. ?? 2006 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/220642','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/220642"><span>Rapid-onset/offset, <span class="hlt">variably</span> scheduled 60 Hz electric and magnetic field exposure reduces nocturnal serum melatonin <span class="hlt">concentration</span> in nonhuman primates</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rogers, W.R.; Smith, H.D.; Reiter, R.J.; Barlow-Walden, L.</p> <p>1995-12-31</p> <p>Experiments with rodents indicate that power-frequency electric field (EF) or magnetic field (MF) exposure can suppress the normal nocturnal increase in melatonin <span class="hlt">concentration</span> in pineal gland and blood. In a separate set of three experiments conducted with nonhuman primates, the authors did not observe melatonin suppression as a result of 6 weeks of day-time exposure to combined 60 Hz electric and magnetic fields (E/MF) with regularly schedule ``slow`` E/MF onsets/offsets. The study described here used a different exposure paradigm in which two baboons were exposed to E/MF with ``rapid`` E/MF onsets/offsets accompanied by EF transients not found with slowly ramped E/MF onset/offset; profound reductions in nocturnal serum melatonin <span class="hlt">concentration</span> were observed in this experiment. If replicated in a more extensive experiment, the observation of melatonin suppression only in the presence of E/MF transients would suggest that very specific exposure parameters determine the effects of 60 Hz E/MF on melatonin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B13I..06A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B13I..06A"><span>Mercury <span class="hlt">Concentrations</span> in Fish and Sediment within Streams are Influenced by Watershed and Landscape <span class="hlt">Variables</span> including Historical Gold Mining in the Sierra Nevada, California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alpers, C. N.; Yee, J. L.; Ackerman, J. T.; Orlando, J. L.; Slotton, D. G.; Marvin-DiPasquale, M. C.</p> <p>2015-12-01</p> <p>We compiled available data on total mercury (THg) and methylmercury (MeHg) <span class="hlt">concentrations</span> in fish tissue and streambed sediment from stream sites in the Sierra Nevada, California, to assess whether spatial data, including information on historical mining, can be used to make robust predictions of fish fillet tissue THg <span class="hlt">concentrations</span>. A total of 1,271 fish from five species collected at 103 sites during 1980-2012 were used for the modeling effort: 210 brown trout, 710 rainbow trout, 79 Sacramento pikeminnow, 93 Sacramento sucker, and 179 smallmouth bass. Sediment data were used from 73 sites, including 106 analyses of THg and 77 analyses of MeHg. The dataset included 391 fish (mostly rainbow trout) and 28 sediment samples collected explicitly for this study during 2011-12. Spatial data on historical mining included the USGS Mineral Resources Data System and publicly available maps and satellite photos showing the areas of hydraulic mine pits and other placer mines. Modeling was done using multivariate linear regression and multi-model inference using Akaike Information Criteria. Results indicate that fish THg, accounting for species and length, can be predicted using geospatial data on mining history together with other landscape characteristics including land use/land cover. A model requiring only geospatial data, with an R2 value of 0.61, predicted fish THg correctly with respect to over-or-under 0.2 μg/g wet weight (a California regulatory threshold) for 108 of 121 (89 %) size-species combinations tested. Data for THg in streambed sediment did not improve the geospatial-only model. However, data for sediment MeHg, loss on ignition (organic content), and percent of sediment less than 0.063 mm resulted in a slightly improved model, with an R2 value of 0.63. It is anticipated that these models will be useful to the State of California and others to predict areas where mercury <span class="hlt">concentrations</span> in fish are likely to exceed regulatory criteria.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.V21D..07W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.V21D..07W"><span>Water-saturated phase-equilibrium experiments on rhyolite and dacite obsidians: the effect of <span class="hlt">variable</span> melt water <span class="hlt">concentration</span> on the composition of phenocrysts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waters, L.; Lange, R. A.; Andrews, B. J.</p> <p>2012-12-01</p> <p>Results of water-saturated phase equilibrium experiments on three obsidians ranging in composition from dacite to rhyolite (67-74 wt% SiO2) are presented and demonstrate the effect of changing melt water <span class="hlt">concentrations</span> on the composition of plagioclase and orthopyroxene phenocrysts. Experiments were conducted in a cold-seal Ni-rich pressure vessel (Waspaloy) with Ni filler rod, so that experiments were buffered at ΔNNO +1 (± 0.5) (Gershwind & Rutherford, 1992) and pressurized with H2O (where Ptotal= PH2O). Temperatures ranged from 750-900°C and pressures ranged from 100-300 MPa. Prior to the experiments, detailed petrologic studies were first conducted on the three obsidian samples, which are from Cascade and Mexican arcs. Overall phenocryst abundances in all three samples are low (<2.3%), with little to no microlite crystallization. Despite low phenocryst abundances, the obsidians are saturated in five to seven mineral phases: plagioclase + orthopyroxene + ilmenite + magnetite + apatite ± clinopyroxene ± biotite. Eruptive temperatures (±1σ), on the basis of Fe-Ti two oxide thermometry (Ghiorso & Evans, 2008), range from 760 ± 18°C to 943 ± 20°C; corresponding ΔNNO values (±1σ) range from -0.9 ± 0.1 and 0.7 ± 0.1. Plagioclase compositions span a wide range in each sample (e.g., 9-40 and 30-54 mol% An), despite low phenocryst abundances. Orthopyroxene compositions also span a wide range (≤ 15 mol% En), which correspond to Fe-MgKD(opx-liq) values that range from 0.18-0.46. Given the low crystallinity, absence of evidence for mixing of magmas, and no apparent change in oxygen fugacity recorded by iron oxides, the progressive loss of water from a melt, through degassing during rapid magma ascent, is a plausible hypothesis to explain the observed variation in phenocryst compositions. This hypothesis is evaluated with the run products from the water-saturated phase equilibrium experiments on the three obsidian samples. The experimental results indicate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4582T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4582T"><span>Investigating the relationship between Ambrosia pollen <span class="hlt">concentration</span> and meteorological <span class="hlt">variables</span> in a European domain based on CORDEX and CMIP5 simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Torma, Csaba Zsolt; Giorgi, Filippo</p> <p>2016-04-01</p> <p>As part of the European project, ATOPICA (atopic diseases in changing climate, land use & air quality) evaluation and scenario simulations were accomplished on 50-km grid spacing over a European domain which was defined in the framework of the international initiation called COordinated Regional Downscaling Experiment (CORDEX). Based on observational data collected from European pollen data bases, the pollen peak season of Ambrosia artemisiifolia L. (short or common ragweed) was found between the period: August-September (AS). One sub-region was selected (the most contaminated one: southern part of the Carpathian Basin) for further studies. Based on the ERA-Interim driven simulation of a regional climate model (RegCM) developed at the Abdus Salam International Centre of Theoretical Physics: temperature and precipitation indices are introduced related to the total common ragweed pollen <span class="hlt">concentration</span> amounts over the target region for the period 1984-2008. In each case (temperature, precipitation) the index was based on the August-September (AS, peak-season) and June-July (JJ, pre-season) means by subtracting the latter from the previous one. The results manifested in a relatively clear signal between total pollen amounts and the indices. The temperature index is negatively, while the precipitation index is positively correlated with the total pollen amounts. This means cooler and wetter pre-seasonal and relatively drier and warmer peak-season weather conditions are favorable for the common ragweed outburst with high pollen <span class="hlt">concentrations</span>. In total twenty global climate models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and five regional climate models from the CORDEX initiative were involved in the analyses in order to assess the link between the indices and the seasonal total pollen amounts. The temperature and precipitation indices presented in this study can be a useful tool for seasonal pollen forecasting in future studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23361442','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23361442"><span>Intra-urban spatial <span class="hlt">variability</span> in wintertime street-level <span class="hlt">concentrations</span> of multiple combustion-related air pollutants: the New York City Community Air Survey (NYCCAS).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Clougherty, Jane E; Kheirbek, Iyad; Eisl, Holger M; Ross, Zev; Pezeshki, Grant; Gorczynski, John E; Johnson, Sarah; Markowitz, Steven; Kass, Daniel; Matte, Thomas</p> <p>2013-01-01</p> <p>Although intra-urban air pollution differs by season, few monitoring networks provide adequate geographic density and year-round coverage to fully characterize seasonal patterns. Here, we report winter intra-urban monitoring and land-use regression (LUR) results from the New York City Community Air Survey (NYCCAS). Two-week integrated samples of fine particles (PM(2.5)), black carbon (BC), nitrogen oxides (NO(x)) and sulfur dioxide (SO(2)) were collected at 155 city-wide street-level locations during winter 2008-2009. Sites were selected using stratified random sampling, randomized across sampling sessions to minimize spatio-temporal confounding. LUR was used to identify GIS-based source indicators associated with higher <span class="hlt">concentrations</span>. Prediction surfaces were produced using kriging with external drift. Each pollutant varied twofold or more across sites, with higher <span class="hlt">concentrations</span> near midtown Manhattan. All pollutants were positively correlated, particularly PM(2.5) and BC (Spearman's r=0.84). Density of oil-burning boilers, total and truck traffic density, and temporality explained 84% of PM(2.5) variation. Densities of total traffic, truck traffic, oil-burning boilers and industrial space, with temporality, explained 65% of BC variation. Temporality, built space, bus route location, and traffic density described 67% of nitrogen dioxide variation. Residual oil-burning units, nighttime population and temporality explained 77% of SO(2) variation. Spatial variation in combustion-related pollutants in New York City was strongly associated with oil-burning and traffic density. Chronic exposure disparities and unique local sources can be identified through year-round saturation monitoring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70021081','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70021081"><span>Rate of strontium sorption and the effects of <span class="hlt">variable</span> aqueous <span class="hlt">concentrations</span> of sodium and potassium on strontium distribution coefficients of a surficial sediment at the Idaho National Engineering Laboratory, Idaho</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bunde, R.L.; Rosentreter, J.J.; Liszewski, M.J.</p> <p>1998-01-01</p> <p>The rate of strontium sorption and the effects of <span class="hlt">variable</span> aqueous <span class="hlt">concentrations</span> of sodium and potassium on strontium sorption were measured as part of an investigation to determine strontium chemical transport properties of a surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. Batch experimental techniques were used to determine the rate of strontium sorption and strontium distribution coefficients (K(d)s) between aqueous and solid phases. Rate experiments indicate that strontium in solution reached an apparent equilibrium with the sediment in 26 h. K(d)s were derived using the linear isotherm model at initial sodium <span class="hlt">concentrations</span> from 100 to 5,000 mg/l and initial potassium <span class="hlt">concentrations</span> from 2 to 150 mg/l. K(d)s ranged from 56 ?? 2 to 62 ?? 3 ml/g at initial aqueous <span class="hlt">concentrations</span> of sodium and potassium equal to or less than 300 and 150 mg/l, respectively. K(d)s hinged from 4.7 ?? 0.2 to 19 ?? 1 ml/g with initial aqueous <span class="hlt">concentrations</span> of sodium between 1,000 and 5,000 mg/l. These data indicate that sodium <span class="hlt">concentrations</span> greater than 300 mg/l in wastewater increase the availability of strontium for transport beneath waste disposal ponds at the INEL by decreasing strontium sorption on the surficial sediment. Wastewater <span class="hlt">concentrations</span> of sodium and potassium less than 300 and 150 mg/l, respectively, have little effect on the availability of strontium for transport.The rate of strontium sorption and the effects of <span class="hlt">variable</span> aqueous <span class="hlt">concentrations</span> of sodium and potassium on strontium sorption were measured as part of an investigation to determine strontium chemical transport properties of a surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. Batch experimental techniques were used to determine the rate of strontium sorption and strontium distribution coefficients (Kds) between aqueous and solid phases. Rate experiments indicate that strontium in solution reached an apparent equilibrium with the sediment in 26</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.1474Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.1474Y"><span>Spatial and temporal <span class="hlt">variabilities</span> of spring Asian dust events and their impacts on chlorophyll-a <span class="hlt">concentrations</span> in the western North Pacific Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yoon, Joo-Eun; Kim, Kitae; Macdonald, Alison M.; Park, Ki-Tae; Kim, Hyun-Cheol; Yoo, Kyu-Cheul; Yoon, Ho-Il; Yang, Eun Jin; Jung, Jinyoung; Lim, Jae-Hyun; Kim, Ju-Hyoung; Lee, Jiyoung; Choi, Tae-Jun; Song, Jae-Min; Kim, Il-Nam</p> <p>2017-02-01</p> <p>As the western North Pacific Ocean is located downwind of the source regions for spring Asian dust, it is an ideal location for determining the response of open waters to these events. Spatial analysis of spring Asian dust events from source regions to the western North Pacific, using long-term daily aerosol index data, revealed three different transport pathways supported by the westerly wind system: one passing across the northern East/Japan Sea (40°N-50°N), a second moving over the entire East/Japan Sea (35°N-55°N), and a third flowing predominantly over the Siberian continent (>50°N). Our results indicate that strong spring Asian dust events can increase ocean primary productivity by more than 70% (>2-fold increase in chlorophyll-a <span class="hlt">concentrations</span>) compared to weak/nondust conditions. Therefore, attention should be paid to the recent downturn in the number of spring Asian dust events and to the response of primary production in the western North Pacific to this change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815307G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815307G"><span>Allocation of recent photoassimilates in mature European beech and Norway spruce - seasonal <span class="hlt">variability</span> and responses to experimentally increased tropospheric O3 <span class="hlt">concentration</span> and long-term drought</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grams, Thorsten</p> <p>2016-04-01</p> <p> respiration is exclusively supplied by recently fixed C was rejected for both species. After long-term (7 years) exposure to elevated (i.e. twice-ambient) O3 <span class="hlt">concentrations</span>, allocation of recently fixed C to stems was distinctly affected when studied during later summer. In correspondence with significantly lowered woody biomass development in beech (- 40 %), C allocation to stems was reduced in response to O3 exposure. Conversely in spruce, photoassimilate allocation to stems and coarse root respiration was hardly affected, reflecting the overall lower sensitivity of spruce to elevated O3 <span class="hlt">concentrations</span>. Compartmental modeling characterized functional properties of substrate pools supplying respiratory C demands. Stem respiration of spruce appeared to be largely supplied by recent photoassimilates. Conversely in beech, stored C, putatively located in stem parenchyma cells, was a major source for respiration, reflecting the fundamental anatomical disparity between angiosperm beech and gymnosperm spruce. Overall, the observed differences in C allocation between the two study species reflect the high plasticity of beech trees in response to seasons and stressors such as drought and elevated O3, whereas spruce displayed much lower responsiveness to the applied stressors and along the seasonal course of the year.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26440193','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26440193"><span>Postweaning substitution of grazed forage with a high-energy <span class="hlt">concentrate</span> has <span class="hlt">variable</span> long-term effects on subcutaneous fat and marbling in Bos taurus genotypes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Greenwood, P L; Siddell, J P; Walmsley, B J; Geesink, G H; Pethick, D W; McPhee, M J</p> <p>2015-08-01</p> <p>The objective of this study was to quantify the effects and interactions of stage of growth and genotype on commercial carcass traits and intramuscular fat (IMF) content in 5 muscles of steers ( = 165) and to test the hypothesis that substituting pasture with a high-energy <span class="hlt">concentrate</span> during the immediate postweaning period increases IMF. Cattle of 3 genotypes (Angus, Hereford, and Wagyu × Angus; = 55/genotype) were selected at weaning from commercial herds, targeting genotypic differences in marbling and subcutaneous fatness. Following weaning, steers were fed for 168 d within 2 different improved, temperate pasture-based nutritional systems: a forage-only system (FS) and forage with high-energy supplemented system (SS), with 2 replicates per system. The supplement was fed at a level of 1% of average BW adjusted every 2 wk to provide an estimated 50% of energy requirements for 168 d from weaning. Pasture on offer in both systems was managed to match the BW of the FS and SS steers during the postweaning treatment period to avoid confounding due to differences in growth rate during this period. Steers were then regrouped into 2 replicates and backgrounded on improved, temperate pasture for 158 d and then grain fed within 1 group for 105 d (short fed) or 259 d (long fed). Groups were slaughtered at commencement (d 0) and end of postweaning nutritional treatments (d 168), end of backgrounding (d 326), and after short (d 431) or long feedlotting (d 585). Serial slaughter stage had an effect on all traits assessed ( < 0.01). The FS steers had more rib fat ( < 0.01) and higher Meat Standards Australia marbling score ( < 0.05) and a tendency ( < 0.10) to have greater eye muscle area than the SS steers throughout the study. Genotypic differences were evident ( < 0.05) for all traits assessed except HCW, dressing percentage, rib fat depth, ossification score, ultimate pH, and IMF in the semitendinosus muscle. The results for marbling and IMF do not support the use of a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18244942','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18244942"><span>Leaf-age effects on seasonal <span class="hlt">variability</span> in photosynthetic parameters and its relationships with leaf mass per area and leaf nitrogen <span class="hlt">concentration</span> within a Pinus densiflora crown.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Han, Qingmin; Kawasaki, Tatsuro; Nakano, Takashi; Chiba, Yukihiro</p> <p>2008-04-01</p> <p>In the temperate zone of Japan, Pinus densiflora Sieb. et Zucc. bears needles of up to three age classes in the upper crown and up to five age classes in the lower crown. To elucidate the effects of leaf age on photosynthetic parameters and its relationships with leaf mass per unit area (LMA) and leaf nitrogen (N(l)) <span class="hlt">concentration</span> on an area (N(a)) and mass (N(m)) basis, we measured seasonal variations in LMA, N(l), light-saturated photosynthetic rate (A(max)), stomatal conductance (g(s)), maximum rate of carboxylation (V(cmax)) and maximum rate of electron transport (J(max)) in leaves of all age classes in the upper and lower crown. Leaf mass per unit area increased by 27% with increasing leaf age in the lower crown, but LMA did not depend on age in the upper crown. Leaf age had a significant effect on N(m) but not on N(a) in both crown positions, indicating that decreases in N(m) resulted from dilution. Photosynthetic parameters decreased significantly with leaf age in the lower crown (39% for A(max) and 43% for V(cmax)), but the effect of leaf age was not as great in the upper crown, although these parameters exhibited seasonal variation in both crown positions. Regression analysis indicated a close relationship between LMA and N(a), regardless of age class or when each age class was pooled (r(2) = 0.57-0.86). Relationships between LMA and N(a) and among A(max), V(cmax) and J(max) were weak or not significant when all age classes were examined by regression analysis. However, compared with older leaves, relationships among LMA, N(a) and A(max) were stronger in younger leaves. These results indicate that changes in LMA and N(l) mainly reflect light acclimation during leaf development, but they are only slightly affected by irradiance in mature leaves. In conclusion, LMA and N(l) are useful parameters for estimating photosynthetic capacity, but age-related effects need to be taken into account, especially in evergreen conifers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21397999','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21397999"><span>Biotic, temporal and spatial <span class="hlt">variability</span> of tritium <span class="hlt">concentrations</span> in transpirate samples collected in the vicinity of a near-surface low-level nuclear waste disposal site and nearby research reactor.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Twining, J R; Hughes, C E; Harrison, J J; Hankin, S; Crawford, J; Johansen, M; Dyer, L</p> <p>2011-06-01</p> <p>The results of a 21 month sampling program measuring tritium in tree transpirate with respect to local sources are reported. The aim was to assess the potential of tree transpirate to indicate the presence of sub-surface seepage plumes. Transpirate gathered from trees near low-level nuclear waste disposal trenches contained activity <span class="hlt">concentrations</span> of (3)H that were significantly higher (up to ∼700 Bq L(-1)) than local background levels (0-10 Bq L(-1)). The effects of the waste source declined rapidly with distance to be at background levels within 10s of metres. A research reactor 1.6 km south of the site contributed significant (p < 0.01) local fallout (3)H but its influence did not reach as far as the disposal trenches. The elevated (3)H levels in transpirate were, however, substantially lower than groundwater <span class="hlt">concentrations</span> measured across the site (ranging from 0 to 91% with a median of 2%). Temporal patterns of tree transpirate (3)H, together with local meteorological observations, indicate that soil water within the active root zones comprised a mixture of seepage and rainfall infiltration. The degree of mixing was <span class="hlt">variable</span> given that the soil water activity <span class="hlt">concentrations</span> were heterogeneous at a scale equivalent to the effective rooting volume of the trees. In addition, water taken up by roots was not well mixed within the trees. Based on correlation modelling, net rainfall less evaporation (a surrogate for infiltration) over a period of from 2 to 3 weeks prior to sampling seems to be the optimum predictor of transpirate (3)H <span class="hlt">variability</span> for any sampled tree at this site. The results demonstrate successful use of (3)H in transpirate from trees to indicate the presence and general extent of sub-surface contamination at a low-level nuclear waste site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AtmEn..97..252E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AtmEn..97..252E"><span>Influence of local and regional sources on the observed spatial and temporal <span class="hlt">variability</span> of size resolved atmospheric aerosol mass <span class="hlt">concentrations</span> and water-soluble species in the Athens metropolitan area</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eleftheriadis, Konstantinos; Ochsenkuhn, Klaus M.; Lymperopoulou, Theopisti; Karanasiou, Angeliki; Razos, Panayiotis; Ochsenkuhn-Petropoulou, Maria</p> <p>2014-11-01</p> <p>The <span class="hlt">variability</span> of common aerosol species in large Metropolitan urban areas is a major air quality issue with strong health impacts of large populations. PM10 and PM2.5 particulate matter samples were obtained at three sites characteristic of industrial, urban traffic and sub-urban residential areas in the Athens basin. Samples were analysed for anions (Cl-, NO3-, SO42-) and cations (K+, Na+, Ca2+, Mg2+, NH4+) using ion chromatography. The spatial and temporal <span class="hlt">variability</span> for the particulate matter (PM) <span class="hlt">concentration</span> mass and water-soluble ionic species <span class="hlt">concentrations</span> for the investigated sites were studied. Mean PM fine <span class="hlt">concentration</span> levels were 20% higher at the industrial and the central urban areas compared to those in the suburban area (24.2 μg/m3). The mean values for the coarse fraction at those two sites were two to three times higher compared to those at the suburban site (12.4 μg/m3). Comparable <span class="hlt">concentration</span> levels of most species were observed in all areas, while SO42- and NO3- differ at a significant level. Furthermore, the average size distributions of the mass and individual ions at the suburban site (NCSR Demokritos) showed a bimodal size distribution. SO42- and NH4+ have their main peak in the fine fraction while NO3- showed equal distribution on the fine and coarse mode.. Good correlation was found for SO42- and NO3- with Ca2+ and Na+ with Cl- for the coarse fraction in the industrial area. NH4+ was closely correlated with SO42- in the fine particles and in all areas. For the urban site the best correlations in coarse particulates were reported between Na+/Mg2+-Cl-, Ca2+/Mg2+-SO42-, explained by neutralization of acidic aerosol by soil dust and sea salt in the coarse fraction. Moreover, time weighted <span class="hlt">concentrations</span> roses at the industrial and urban sites, showed no significant directional dependence, indicating either uniform generation of mainly the coarse species within the metropolitan area or major influence of the regional background for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16644593','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16644593"><span>Effects of light level, time of harvest and position within field on the <span class="hlt">variability</span> of tissue nitrate <span class="hlt">concentration</span> in commercial crops of lettuce (Lactuca sativa) and endive (Cichorium endiva).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Weightman, R M; Dyer, C; Buxton, J; Farrington, D S</p> <p>2006-05-01</p> <p>Seven commercial crops of lettuce and one crop of endive were sampled in order to study the <span class="hlt">variability</span> in plant tissue nitrate <span class="hlt">concentration</span> (TNC). Assuming that an appropriate sampling pattern was employed, ten plants were sufficient to give an acceptable estimate of the mean TNC. Short-term shading (24-48 h) had no significant effects on mean TNC, unlike the increase in TNC known to occur following dull periods 10-14 days before harvest. The effect on TNC of time of day harvested was significant, but there was no obvious pattern of diurnal variation. Averaged over all experiments, the coefficient of variation for TNC was in the order of 35%. Increasing the sample size from ten to 40 plants would only be expected to decrease the standard error of measurement of TNC from 16 to 12% of the mean because of the underlying analytical error, which would remain constant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AnGla..43..250L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AnGla..43..250L"><span>Seasonal <span class="hlt">variability</span> of ionic <span class="hlt">concentrations</span> in surface snow and elution processes in snow-firn packs at the PGPI site on Ürümqi glacier No. 1, eastern Tien Shan, China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Zhongqin; Edwards, Ross; Mosley-Thompson, E.; Wang, Feiteng; Dong, Zhibao; You, Xiaoni; Li, Huilin; Li, Chuanjin; Zhu, Yuman</p> <p></p> <p>To investigate the effects of both non-meltwater and meltwater-related post-depositional processes on chemical species within the snow-firn pack, a research program, the Program for Glacier Processes Investigation, was initiated in July 2002 by the Tien Shan Glaciological Station, Chinese Academy of Sciences. The seasonal <span class="hlt">variability</span> of the ionic <span class="hlt">concentrations</span> in surface snow samples and ion elution behavior in the snow-firn pack were assessed from surface samples collected year-round and 1011 samples collected from a snow pit at weekly intervals from September 2003 through September 2004. The results indicate that elevated ionic <span class="hlt">concentrations</span> in spring and summer result from Asian dust-storm-derived aerosol input and other aerosols entrained in precipitation. Potential sources of these chemical species are explored using correlation and factor analyses. The elution sequence through the snow-firn pack was determined to be SO42- > Ca2+ > Na+ > NO3- > Cl- > K+ > Mg2+ > NH4+. The elution of ions at the sampling site was found to be driven primarily by air temperature and became evident when a diurnal mean temperature of -3.6°C was attained. At 0.3°C all of the year-round new ionic input was leached from the snow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050223592','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050223592"><span><span class="hlt">Variability</span> of particulate organic carbon <span class="hlt">concentration</span> in the north polar Atlantic based on ocean color observations with Sea-viewing Wide Field-of-view Sensor (SeaWiFS)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stramska, Malgorzata; Stramski, Dariusz</p> <p>2005-01-01</p> <p>We use satellite data from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) to investigate distributions of particulate organic carbon (POC) <span class="hlt">concentration</span> in surface waters of the north polar Atlantic Ocean during the spring summer season (April through August) over a 6-year period from 1998 through 2003. By use of field data collected at sea, we developed regional relationships for the purpose of estimating POC from remote-sensing observations of ocean color. Analysis of several approaches used in the POC algorithm development and match-up analysis of coincident in situ derived and satellite-derived estimates of POC resulted in selection of an algorithm that is based on the blue-to-green ratio of remote-sensing reflectance R(sub rs) (or normalized water-leaving radiance L(sub wn)). The application of the selected algorithm to a 6-year record of SeaWiFS monthly composite data of L(sub wn) revealed patterns of seasonal and interannual <span class="hlt">variability</span> of POC in the study region. For example, the results show a clear increase of POC throughout the season. The lowest values, generally less than 200 mg per cubic meters, and at some locations often less than 50 mg per cubic meters, were observed in April. In May and June, POC can exceed 300 or even 400 mg per cubic meters in some parts of the study region. Patterns of interannual <span class="hlt">variability</span> are intricate, as they depend on the geographic location within the study region and particular time of year (month) considered. By comparing the results averaged over the entire study region and the entire season (April through August) for each year separately, we found that the lowest POC occurred in 2001 and the highest POC occurred in 2002 and 1999.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1980STIN...8024832B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1980STIN...8024832B"><span>Photovoltaic <span class="hlt">concentrators</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boes, E. C.</p> <p>1980-01-01</p> <p>A status report on photovoltaic (PV) <span class="hlt">concentrators</span> technology is presented. The major topics covered are as follows: (1) current PV <span class="hlt">concentrator</span> arrays; designs, performances, and costs; (2) current PV <span class="hlt">concentrator</span> array components; cells and cell assemblies, optical <span class="hlt">concentrators</span>, support structures, tracking, and drive; (3) design of PV <span class="hlt">concentrator</span> arrays; and (4) array manufacturing technology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21664665','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21664665"><span>Cryopreservation of turkey semen by the pellet method: effects of <span class="hlt">variables</span> such as the extender, cryoprotectant <span class="hlt">concentration</span>, cooling time and warming temperature on sperm quality determined through principal components analysis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Iaffaldano, Nicolaia; Romagnoli, Luca; Manchisi, Angelo; Rosato, Maria Pina</p> <p>2011-09-15</p> <p>This study was designed to identify the best pellet cryopreservation procedure for the cryosurvival of turkey semen among 192 different treatments established by variations and permutations of seven conditions used in the freezing/thawing process. These conditions were: diluent (IGGKPh, SPh or Tselutin); dilution rate (1:3 vs. 1:4); cooling time (45 vs. 60 min); dimethylacetamide (DMA) <span class="hlt">concentration</span> as cryoprotectant (6 vs. 8%); equilibration time in DMA (1 vs. 5 min); semen drop volume (50 vs. 80 μL) and thawing temperature (60 vs. 75 °C). Through principal components analysis (PCA), post-thaw sperm quality data (mobility, viability and membrane functional integrity) were reduced to a single output <span class="hlt">variable</span> (Sperm Quality) indicating overall post-thaw semen quality. All treatments induced a significant reduction in semen quality after warming (P < 0.01), though one set of seven conditions, or treatment, was identified by PCA to generate the highest Sperm Quality score and a further five treatments yielded a score not significantly different (P > 0.05) from this best score. Although still not fulfilling the requirements for commercial application, our findings serve to identify the critical steps in turkey sperm cryopreservation that need to be assessed in future studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814736S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814736S"><span>Seasonal and spatial <span class="hlt">variability</span> of aquatic N2O, CH4 and CO2 <span class="hlt">concentrations</span> and their contribution to the overall greenhouse gas budget of the river Tay catchment, NW Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Skiba, Ute; Harley, James; Carvalho, Laurence; Heal, Kate; Rees, Bob</p> <p>2016-04-01</p> <p>River networks act as a link between components of the terrestrial landscape with the atmosphere and oceans, and are believed to contribute significantly to global budgets of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). However, knowledge of flux magnitudes and drivers of seasonal and spatial <span class="hlt">variability</span> required to understand their contribution to the overall catchment greenhouse (GHG) flux is only available for relatively few river systems. For this reason we conducted a two year study of monthly GHG <span class="hlt">concentration</span> measurements from the river Tay. The river Tay is the largest river in Scotland, in terms of discharge and can be considered typical for many North European river systems. The Tay and its tributaries drain peat dominated uplands and agricultural lowlands before entering the North Sea via the large intertidal estuary. We collected water samples from 9 locations along the river monthly and analysed these sampes for dissolved <span class="hlt">concentrations</span> of N2O, CH4 and CO2, NH4+ , NO3-, O2, total organic carbon and nitrogen, pH and turbidity. Fluxes across the air water interface were calculated using published gas transfer equations. All GHGs showed considerable spatial and seasonal variation. Nitrous oxide emissions ranged from 176 to 1850 μg N m-2 d-1 over the almost two year period February 2009 to December 2010. Emissions were highest in the lowland tributaries related to higher nutrient <span class="hlt">concentrations</span> associated with more intensive agricultural activity. Methane emissions ranged from 1720 to 15500 μg C m-2 d-1, and in general decreased from upland to lowland sites. Variation in sediment quality was the predominant driving factor. Carbon dioxide emissions ranged from 517 to 2550 mg C m-2 d-1 and generally increased from upland to lowland sites. Emissions were highest in late summer and autumn and lowest in winter at most sites, highlighting the role of seasonal environmental controls such as temperature, light, and substrate availability</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SchpJ..1032900A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SchpJ..1032900A"><span>Ashtekar <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ashtekar, Abhay</p> <p>2015-05-01</p> <p>In the spirit of Scholarpedia, this invited article is addressed to students and younger researchers. It provides the motivation and background material, a summary of the main physical ideas, mathematical structures and results, and an outline of applications of the connection <span class="hlt">variables</span> for general relativity. These <span class="hlt">variables</span> underlie both the canonical/Hamiltonian and the spinfoam/path integral approaches in loop quantum gravity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5488879','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5488879"><span><span class="hlt">Concentrating</span> collectors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1981-06-01</p> <p>Selected specifications from sixteen <span class="hlt">concentrating</span> collector manufacturers are tabulated. Eleven are linear parabolic trough collectors, and the others include slats, cylindrical trough, linear Fresnel lens, parabolic cylindrical Fresnel lens, and two point focus parabolic dish collectors. Also included is a brief discussion of the operating temperatures and other design considerations for <span class="hlt">concentrating</span> collectors. (LEW)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Radioactivity&pg=4&id=EJ101536','ERIC'); return false;" href="http://eric.ed.gov/?q=Radioactivity&pg=4&id=EJ101536"><span><span class="hlt">Concentrating</span> Radioactivity</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Herrmann, Richard A.</p> <p>1974-01-01</p> <p>By <span class="hlt">concentrating</span> radioactivity contained on luminous dials, a teacher can make a high reading source for classroom experiments on radiation. The preparation of the source and its uses are described. (DT)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160005356','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160005356"><span>Data <span class="hlt">Concentrator</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Willett, Mike</p> <p>2015-01-01</p> <p>Orbital Research, Inc., developed, built, and tested three high-temperature components for use in the design of a data <span class="hlt">concentrator</span> module in distributed turbine engine control. The <span class="hlt">concentrator</span> receives analog and digital signals related to turbine engine control and communicates with a full authority digital engine control (FADEC) or high-level command processor. This data <span class="hlt">concentrator</span> follows the Distributed Engine Controls Working Group (DECWG) roadmap for turbine engine distributed controls communication development that operates at temperatures at least up to 225 C. In Phase I, Orbital Research developed detailed specifications for each component needed for the system and defined the total system specifications. This entailed a combination of system design, compiling existing component specifications, laboratory testing, and simulation. The results showed the feasibility of the data <span class="hlt">concentrator</span>. Phase II of this project focused on three key objectives. The first objective was to update the data <span class="hlt">concentrator</span> design modifications from DECWG and prime contractors. Secondly, the project defined requirements for the three new high-temperature, application-specific integrated circuits (ASICs): one-time programmable (OTP), transient voltage suppression (TVS), and 3.3V. Finally, the project validated each design by testing over temperature and under load.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27559198','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27559198"><span>Evolution of Welding-Fume Aerosols with Time and Distance from the Source: A study was conducted on the spatiotemporal <span class="hlt">variability</span> in welding-fume <span class="hlt">concentrations</span> for the characterization of first- and second-hand exposure to welding fumes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cena, L G; Chen, B T; Keane, M J</p> <p>2016-08-01</p> <p>Gas metal arc welding fumes were generated from mild-steel plates and measured near the arc (30 cm), representing first-hand exposure of the welder, and farther away from the source (200 cm), representing second-hand exposure of adjacent workers. Measurements were taken during 1-min welding runs and at subsequent 5-min intervals after the welding process was stopped. Number size distributions were measured in real time. Particle mass distributions were measured using a micro-orifice uniform deposition impactor, and total mass <span class="hlt">concentrations</span> were measured with polytetrafluorothylene filters. Membrane filters were used for collecting morphology samples for electron microscopy. Average mass <span class="hlt">concentrations</span> measured near the arc were 45 mg/m(3) and 9 mg/m(3) at the farther distance. The discrepancy in <span class="hlt">concentrations</span> at the two distances was attributed to the presence of spatter particles, which were observed only in the morphology samples near the source. As fumes aged over time, mass <span class="hlt">concentrations</span> at the farther distance decreased by 31% (6.2 mg/m(3)) after 5 min and an additional 13% (5.4 mg/m(3)) after 10 min. Particle number and mass distributions during active welding were similar at both distances, indicating similar exposure patterns for welders and adjacent workers. Exceptions were recorded for particles smaller than 50 nm and larger than 3 μm, where <span class="hlt">concentrations</span> were higher near the arc, indicating higher exposures of welders. These results were confirmed by microscopy analysis. As residence time increased, number <span class="hlt">concentrations</span> decreased dramatically. In terms of particle number <span class="hlt">concentrations</span>, second-hand exposures to welding fumes during active welding may be as high as first-hand exposures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/wri/wri03-4151/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/wri/wri03-4151/"><span>Seasonal <span class="hlt">Variability</span> and Effects of Stormflow on <span class="hlt">Concentrations</span> of Pesticides and their Degradates in Kisco River and Middle Branch Croton River Surface Water, Croton Reservoir System, New York, May 2000-February 2001</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Phillips, Patrick J.; Bode, Robert W.</p> <p>2004-01-01</p> <p>Seven herbicides (2,4-D, 2,4-D methyl ester, bromacil, dicamba, diuron, imazaquin, and sulfometuron), four insecticides (carbaryl, diazinon, imidacloprid, and malathion), two fungicides (metalaxyl and myclobutanil), and caffeine (an indicator of wastewater) were detected in at least one sample from the Kisco River at <span class="hlt">concentrations</span> above 0.1 ug/L (micrograms per liter). Four of these compounds - 2,4-D, 2,4-D methyl ester, dicamba, and metalaxyl - were detected in at least one sample from the Kisco River at a <span class="hlt">concentration</span> above 1 ug/L. Only three herbicides (2,4-D, imazethapyr, and prometon) and caffeine were detected at <span class="hlt">concentrations</span> above 0.1 ug/L in one or more of the Middle Branch Croton River samples, and no compounds were detected above 0.4 ug/L in Middle Branch Croton River samples. No samples contained <span class="hlt">concentrations</span> of pesticides that exceeded human health-based water-quality standards. However, samples from the Kisco River contained four insecticides (carbaryl, chlorpyrifos, diazinon, and malathion) and one herbicide (2,4-D) in <span class="hlt">concentrations</span> that exceeded water-quality criteria for the protection of aquatic life. Aquatic-life protection criteria were generally exceeded only in stormflow samples collected in June, September, and December 2000. No samples from the Middle Branch Croton River contained target compounds that exceeded water-quality criteria for the protection of aquatic life. Pesticide <span class="hlt">concentrations</span> were generally higher, and the numbers of compounds generally larger in samples from the Kisco River than in samples from the Middle Branch Croton River, probably because the Kisco River watershed has a greater population density and is more extensively developed. The highest <span class="hlt">concentrations</span> of most compounds in both streams were detected in stormflow samples collected in June, September, and December 2000. This indicates that stormflow sampling is essential in assessments of pesticide occurrence in streams that drain developed lands. The lowest</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4928225','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4928225"><span>Glucose <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Le Floch, Jean-Pierre; Kessler, Laurence</p> <p>2016-01-01</p> <p>Background: Glucose <span class="hlt">variability</span> has been suspected to be a major factor of diabetic complications. Several indices have been proposed for measuring glucose <span class="hlt">variability</span>, but their interest remains discussed. Our aim was to compare different indices. Methods: Glucose <span class="hlt">variability</span> was studied in 150 insulin-treated diabetic patients (46% men, 42% type 1 diabetes, age 52 ± 11 years) using a continuous glucose monitoring system (668 ± 564 glucose values; mean glucose value 173 ± 38 mg/dL). Results from the mean, the median, different indices (SD, MAGE, MAG, glucose fluctuation index (GFI), and percentages of low [<60 mg/dL] and high [>180 mg/dL] glucose values), and ratios (CV = SD/m, MAGE/m, MAG/m, and GCF = GFI/m) were compared using Pearson linear correlations and a multivariate principal component analysis (PCA). Results: CV, MAGE/m (ns), GCF and GFI (P < .05), MAG and MAG/m (P < .01) were not strongly correlated with the mean. The percentage of high glucose values was mainly correlated with indices. The percentage of low glucose values was mainly correlated with ratios. PCA showed 3 main axes; the first was associated with descriptive data (mean, SD, CV, MAGE, MAGE/m, and percentage of high glucose values); the second with ratios MAG/m and GCF and with the percentage of low glucose values; and the third with MAG, GFI, and the percentage of high glucose values. Conclusions: Indices and ratios provide complementary pieces of information associated with high and low glucose values, respectively. The pairs MAG+MAG/m and GFI+GCF appear to be the most reliable markers of glucose <span class="hlt">variability</span> in diabetic patients. PMID:26880391</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14716597','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14716597"><span>QT <span class="hlt">variability</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Berger, Ronald D</p> <p>2003-01-01</p> <p>We hypothesized that temporal lability in ventricular repolarization is a marker for, and is mechanistically related to, increased risk of malignant ventricular arrhythmias. To assess repolarization lability in the surface electrocardiogram, we developed an automated algorithm, based on template matching, to measure beat-to-beat changes in QT interval. We calculate a QT <span class="hlt">variability</span> index (QTVI) to quantify the relative magnitude of QT interval changes compared to heart rate <span class="hlt">variability</span>. We found that QTVI is a reproducible measure. It is elevated in patients with ischemic and nonischemic dilated cardiomyopathy compared with age-matched controls (P<.00001). We have also shown that QTVI is elevated in patients with malignant beta-myosin heavy-chain mutations associated with hypertrophic cardiomyopathy. In a study of patients undergoing electrophysiologic testing, QTVI identified patients with cardiac arrest better than electrophysiologic test result and better than other risk stratifiers included in the analysis. QT <span class="hlt">variability</span> is a marker of electrical disease in the ventricle and may be associated with enhanced risk of life-threatening arrhythmias.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1334893','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1334893"><span>Biological Sampling <span class="hlt">Variability</span> Study</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Amidan, Brett G.; Hutchison, Janine R.</p> <p>2016-11-08</p> <p>There are many sources of <span class="hlt">variability</span> that exist in the sample collection and analysis process. This paper addresses many, but not all, sources of <span class="hlt">variability</span>. The main focus of this paper was to better understand and estimate <span class="hlt">variability</span> due to differences between samplers. <span class="hlt">Variability</span> between days was also studied, as well as random <span class="hlt">variability</span> within each sampler. Experiments were performed using multiple surface materials (ceramic and stainless steel), multiple contaminant <span class="hlt">concentrations</span> (10 spores and 100 spores), and with and without the presence of interfering material. All testing was done with sponge sticks using 10-inch by 10-inch coupons. Bacillus atrophaeus was used as the BA surrogate. Spores were deposited using wet deposition. Grime was coated on the coupons which were planned to include the interfering material (Section 3.3). Samples were prepared and analyzed at PNNL using CDC protocol (Section 3.4) and then cultured and counted. Five samplers were trained so that samples were taken using the same protocol. Each sampler randomly sampled eight coupons each day, four coupons with 10 spores deposited and four coupons with 100 spores deposited. Each day consisted of one material being tested. The clean samples (no interfering materials) were run first, followed by the dirty samples (coated with interfering material). There was a significant difference in recovery efficiency between the coupons with 10 spores deposited (mean of 48.9%) and those with 100 spores deposited (mean of 59.8%). There was no general significant difference between the clean and dirty (containing interfering material) coupons or between the two surface materials; however, there was a significant interaction between <span class="hlt">concentration</span> amount and presence of interfering material. The recovery efficiency was close to the same for coupons with 10 spores deposited, but for the coupons with 100 spores deposited, the recovery efficiency for the dirty samples was significantly larger (65</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4407236','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4407236"><span>In Vivo Transmission of an IncA/C Plasmid in Escherichia coli Depends on Tetracycline <span class="hlt">Concentration</span>, and Acquisition of the Plasmid Results in a <span class="hlt">Variable</span> Cost of Fitness</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Singer, Randall S.; Isaacson, Richard E.; Danzeisen, Jessica L.; Lang, Kevin; Kobluk, Kristi; Rivet, Bernadette; Borewicz, Klaudyna; Frye, Jonathan G.; Englen, Mark; Anderson, Janet; Davies, Peter R.</p> <p>2015-01-01</p> <p>IncA/C plasmids are broad-host-range plasmids enabling multidrug resistance that have emerged worldwide among bacterial pathogens of humans and animals. Although antibiotic usage is suspected to be a driving force in the emergence of such strains, few studies have examined the impact of different types of antibiotic administration on the selection of plasmid-containing multidrug resistant isolates. In this study, chlortetracycline treatment at different <span class="hlt">concentrations</span> in pig feed was examined for its impact on selection and dissemination of an IncA/C plasmid introduced orally via a commensal Escherichia coli host. Continuous low-dose administration of chlortetracycline at 50 g per ton had no observable impact on the proportions of IncA/C plasmid-containing E. coli from pig feces over the course of 35 days. In contrast, high-dose administration of chlortetracycline at 350 g per ton significantly increased IncA/C plasmid-containing E. coli in pig feces (P < 0.001) and increased movement of the IncA/C plasmid to other indigenous E. coli hosts. There was no evidence of conjugal transfer of the IncA/C plasmid to bacterial species other than E. coli. In vitro competition assays demonstrated that bacterial host background substantially impacted the cost of IncA/C plasmid carriage in E. coli and Salmonella. In vitro transfer and selection experiments demonstrated that tetracycline at 32 μg/ml was necessary to enhance IncA/C plasmid conjugative transfer, while subinhibitory <span class="hlt">concentrations</span> of tetracycline in vitro strongly selected for IncA/C plasmid-containing E. coli. Together, these experiments improve our knowledge on the impact of differing <span class="hlt">concentrations</span> of tetracycline on the selection of IncA/C-type plasmids. PMID:25769824</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25769824','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25769824"><span>In Vivo Transmission of an IncA/C Plasmid in Escherichia coli Depends on Tetracycline <span class="hlt">Concentration</span>, and Acquisition of the Plasmid Results in a <span class="hlt">Variable</span> Cost of Fitness.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Johnson, Timothy J; Singer, Randall S; Isaacson, Richard E; Danzeisen, Jessica L; Lang, Kevin; Kobluk, Kristi; Rivet, Bernadette; Borewicz, Klaudyna; Frye, Jonathan G; Englen, Mark; Anderson, Janet; Davies, Peter R</p> <p>2015-05-15</p> <p>IncA/C plasmids are broad-host-range plasmids enabling multidrug resistance that have emerged worldwide among bacterial pathogens of humans and animals. Although antibiotic usage is suspected to be a driving force in the emergence of such strains, few studies have examined the impact of different types of antibiotic administration on the selection of plasmid-containing multidrug resistant isolates. In this study, chlortetracycline treatment at different <span class="hlt">concentrations</span> in pig feed was examined for its impact on selection and dissemination of an IncA/C plasmid introduced orally via a commensal Escherichia coli host. Continuous low-dose administration of chlortetracycline at 50 g per ton had no observable impact on the proportions of IncA/C plasmid-containing E. coli from pig feces over the course of 35 days. In contrast, high-dose administration of chlortetracycline at 350 g per ton significantly increased IncA/C plasmid-containing E. coli in pig feces (P < 0.001) and increased movement of the IncA/C plasmid to other indigenous E. coli hosts. There was no evidence of conjugal transfer of the IncA/C plasmid to bacterial species other than E. coli. In vitro competition assays demonstrated that bacterial host background substantially impacted the cost of IncA/C plasmid carriage in E. coli and Salmonella. In vitro transfer and selection experiments demonstrated that tetracycline at 32 μg/ml was necessary to enhance IncA/C plasmid conjugative transfer, while subinhibitory <span class="hlt">concentrations</span> of tetracycline in vitro strongly selected for IncA/C plasmid-containing E. coli. Together, these experiments improve our knowledge on the impact of differing <span class="hlt">concentrations</span> of tetracycline on the selection of IncA/C-type plasmids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27746899','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27746899"><span>Terrestrial Carbon Cycle <span class="hlt">Variability</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Baldocchi, Dennis; Ryu, Youngryel; Keenan, Trevor</p> <p>2016-01-01</p> <p>A growing literature is reporting on how the terrestrial carbon cycle is experiencing year-to-year <span class="hlt">variability</span> because of climate anomalies and trends caused by global change. As CO 2 <span class="hlt">concentration</span> records in the atmosphere exceed 50 years and as satellite records reach over 30 years in length, we are becoming better able to address carbon cycle <span class="hlt">variability</span> and trends. Here we review how <span class="hlt">variable</span> the carbon cycle is, how large the trends in its gross and net fluxes are, and how well the signal can be separated from noise. We explore mechanisms that explain year-to-year <span class="hlt">variability</span> and trends by deconstructing the global carbon budget. The CO 2 <span class="hlt">concentration</span> record is detecting a significant increase in the seasonal amplitude between 1958 and now. Inferential methods provide a variety of explanations for this result, but a conclusive attribution remains elusive. Scientists have reported that this trend is a consequence of the greening of the biosphere, stronger northern latitude photosynthesis, more photosynthesis by semi-arid ecosystems, agriculture and the green revolution, tropical temperature anomalies, or increased winter respiration. At the global scale, <span class="hlt">variability</span> in the terrestrial carbon cycle can be due to changes in constituent fluxes, gross primary productivity, plant respiration and heterotrophic (microbial) respiration, and losses due to fire, land use change, soil erosion, or harvesting. It remains controversial whether or not there is a significant trend in global primary productivity (due to rising CO 2, temperature, nitrogen deposition, changing land use, and preponderance of wet and dry regions). The degree to which year-to-year <span class="hlt">variability</span> in temperature and precipitation anomalies affect global primary productivity also remains uncertain. For perspective, interannual <span class="hlt">variability</span> in global gross primary productivity is relatively small (on the order of 2 Pg-C y (-1)) with respect to a large and uncertain background (123 +/- 4 Pg-C y (-1)), and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5040156','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5040156"><span>Terrestrial Carbon Cycle <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Baldocchi, Dennis; Ryu, Youngryel; Keenan, Trevor</p> <p>2016-01-01</p> <p>A growing literature is reporting on how the terrestrial carbon cycle is experiencing year-to-year <span class="hlt">variability</span> because of climate anomalies and trends caused by global change. As CO 2 <span class="hlt">concentration</span> records in the atmosphere exceed 50 years and as satellite records reach over 30 years in length, we are becoming better able to address carbon cycle <span class="hlt">variability</span> and trends. Here we review how <span class="hlt">variable</span> the carbon cycle is, how large the trends in its gross and net fluxes are, and how well the signal can be separated from noise. We explore mechanisms that explain year-to-year <span class="hlt">variability</span> and trends by deconstructing the global carbon budget. The CO 2 <span class="hlt">concentration</span> record is detecting a significant increase in the seasonal amplitude between 1958 and now. Inferential methods provide a variety of explanations for this result, but a conclusive attribution remains elusive. Scientists have reported that this trend is a consequence of the greening of the biosphere, stronger northern latitude photosynthesis, more photosynthesis by semi-arid ecosystems, agriculture and the green revolution, tropical temperature anomalies, or increased winter respiration. At the global scale, <span class="hlt">variability</span> in the terrestrial carbon cycle can be due to changes in constituent fluxes, gross primary productivity, plant respiration and heterotrophic (microbial) respiration, and losses due to fire, land use change, soil erosion, or harvesting. It remains controversial whether or not there is a significant trend in global primary productivity (due to rising CO 2, temperature, nitrogen deposition, changing land use, and preponderance of wet and dry regions). The degree to which year-to-year <span class="hlt">variability</span> in temperature and precipitation anomalies affect global primary productivity also remains uncertain. For perspective, interannual <span class="hlt">variability</span> in global gross primary productivity is relatively small (on the order of 2 Pg-C y -1) with respect to a large and uncertain background (123 +/- 4 Pg-C y -1), and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22130608','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22130608"><span>Seasonal <span class="hlt">variability</span> in cadmium, lead, copper, zinc and iron <span class="hlt">concentrations</span> in the three major fish species, Oreochromis niloticus, Lates niloticus and Rastrineobola argentea in Winam Gulf, Lake Victoria: impact of wash-off into the lake.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ongeri, David M K; Lalah, Joseph O; Wandiga, Shem O; Schramm, Karl-Werner; Michalke, Bernard</p> <p>2012-02-01</p> <p>Trace metals Cadmium (Cd), Lead (Pb), Copper (Cu), Zinc (Zn) and Iron (Fe) were analyzed in edible portions of three main finfish species namely Lates niloticus, Oreochromis niloticus and Rastrineobola argentea sampled from various beaches of Winam Gulf, Lake Victoria, Kenya, in order to determine any seasonal and site variations and the results showed significantly (p < 0.05) higher mean <span class="hlt">concentrations</span> of Cd, Cu, Zn and Fe during the wet season compared to the dry season for all the three species indicating the impact of wash-off into the lake during the rainy periods. The overall mean <span class="hlt">concentrations</span> of the heavy metals (in μg/g dry weight) in all combined samples ranged from 0.17-0.40 (Cd), 0.47-2.53 (Pb), 2.13-8.74 (Cu), 28.9-409.3 (Zn) and 31.4-208.1 (Fe), respectively. It was found that consumption of Rastrineobola argentea can be a significant source of heavy metals especially Zn, to humans, compared with Lates niloticus and Oreochromis niloticus, if only the muscle parts of the latter two are consumed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930093950','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930093950"><span>The solution of the laminar-boundary-layer equation for the flat plate for velocity and temperature fields for <span class="hlt">variable</span> physical properties and for the diffusion field at high <span class="hlt">concentration</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schuh, H</p> <p>1950-01-01</p> <p>In connection with Pohlhausen's solution for the temperature field on the flat plate, a series of formulas were indicated by means of which the velocity and temperature field for <span class="hlt">variable</span> physical characteristics can be computed by an integral equation and an iteration method based on it. With it, the following cases were solved: On the assumption that the viscosity simply varies with the temperature while the other fluid properties remain constant, the velocity and temperature field on the heated and cooled plate, respectively, was computed at the Prandtl numbers 12.5 and 100 (viscous fluids). A closer study of these two cases resulted in general relations: The calculations for a gas of Pr number 0.7 (air) were conducted on the assumption that all fluid properties vary with the temperature, and the velocities are low enough for the heat of friction to be discounted. The result was a thickening of the boundary layers, but no appreciable modification in shearing stress or heat-transfer coefficient.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16047774','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16047774"><span>Spatial and temporal <span class="hlt">variability</span> in air <span class="hlt">concentrations</span> of short-chain (C10-C13) and medium-chain (C14-C17) chlorinated n-alkanes measured in the U.K. atmosphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Barber, Jonathan L; Sweetman, Andy J; Thomas, Gareth O; Braekevelt, Eric; Stern, Gary A; Jones, Kevin C</p> <p>2005-06-15</p> <p>Two studies were carried out on short-chain (C10-C13) and medium-chain (C14-C17) polychlorinated n-alkanes (sPCAs and mPCAs) in U.K. air samples. The first study entailed taking 20 24-h air samples with a pair of Hi-Vol air samplers at the Hazelrigg field station, near Lancaster University. These samples were carefully selected to coincide with times when air masses were predicted to have a fairly constant back trajectory for 24 h and to give a broad spectrum of different origins. The second study was a spatial survey of PCAs in the air at 20 outdoor sites in northern England and four indoor locations in Lancaster, using polyurethane foam (PUF) disk passive air samplers. Levels of the sPCAs in the Hi-Vol samples ranged from <185 to 3430 pg m(-3) (average 1130 pg m(-3)) and were higher than those previously measured at this site in 1997. Levels of the mPCAs ranged from <811 to 14500 pg m(-3) (average 3040 pg m(-3)); that is, they were higher than sPCAs. Both sPCA and mPCA air <span class="hlt">concentrations</span> are of the same order of magnitude as PAH at this site. Back trajectory analysis showed that the history of the air mass in the 48 h prior to sampling had an important effect on the <span class="hlt">concentrations</span> observed, with overland samples having higher levels than oceanic, implying that the U.K. is probably responsible for most of the PCAs measured in the U.K. atmosphere. Amounts of both sPCAs and mPCAs in the passive air samples followed a rural-urban gradient. PCAs appear to be released from multiple sources around the country, as a result of the diffusive, open industrial and construction use of the technical mixtures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/862879','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/862879"><span>Vapor <span class="hlt">concentration</span> monitor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Bayly, John G.; Booth, Ronald J.</p> <p>1977-01-01</p> <p>An apparatus for monitoring the <span class="hlt">concentration</span> of a vapor, such as heavy water, having at least one narrow bandwidth in its absorption spectrum, in a sample gas such as air. The air is drawn into a chamber in which the vapor content is measured by means of its radiation absorption spectrum. High sensitivity is obtained by modulating the wavelength at a relatively high frequency without changing its optical path, while high stability against zero drift is obtained by the low frequency interchange of the sample gas to be monitored and of a reference sample. The <span class="hlt">variable</span> HDO background due to natural humidity is automatically corrected.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AtmEn..65..195P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AtmEn..65..195P"><span>Fluorescence spectra and elastic scattering characteristics of atmospheric aerosol in Las Cruces, New Mexico, USA: <span class="hlt">Variability</span> of <span class="hlt">concentrations</span> and possible constituents and sources of particles in various spectral clusters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pinnick, R. G.; Fernandez, E.; Rosen, J. M.; Hill, S. C.; Wang, Y.; Pan, Y. L.</p> <p>2013-02-01</p> <p>The UV-excited laser-induced-fluorescence (UV-LIF) spectra of single atmospheric particles and the three-band integrating-nephelometer elastic scattering of atmospheric aerosol were measured during four approximately 24-h periods on May 2007 in Las Cruces, New Mexico, USA. Aerosol scattering measurements in the nephelometer red channel (50-nm band centered at 700-nm) ranged from around 3-10 times the molecular (Rayleigh) scattering background. On average 22.8% of particles with size greater than about 1 μm diameter have fluorescence above a preset fluorescence threshold. A hierarchical cluster analysis indicates that most of the single-particle UV-LIF spectra fall into about 10 categories (spectral clusters) as found previously at other geographic sites (Pinnick et al., 2004; Pan et al., 2007). The clusters include spectra characteristic of various humic/fulvic acids, humic-like-substances (HULIS), chemically aged terpenes, fungal spores, polycyclic aromatic hydrocarbons, bacteria, cellulose/pollens, and mixtures of various organic carbon compounds. By far the most populated cluster category is similar to those of chemically aged terpenes/humic-materials; on average this population comprises about 62% of fluorescent particles. Clusters with spectra similar to that of some HULIS aerosol contain on average 10.0% of particles; those characteristic of some fungal spores (or perhaps mixtures of aromatic organic compounds) 8.4% of particles; bacteria-like spectra 1.6% of particles; and cellulose/pollen-like spectra 0.8% of particles. Measurements of fluorescent particles over relatively short (24 min) periods reveal that the <span class="hlt">concentrations</span> of particles in the most populated clusters are highly correlated, suggesting that the particles populating them derive from the same region; these particles might be composed of crustal material coated with secondary organic carbon. On the other hand, <span class="hlt">concentrations</span> of particles having cellulose-like spectra are generally</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA575163','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA575163"><span>Seasonal <span class="hlt">Variability</span> of the Black Sea Chlorophyll-a <span class="hlt">Concentration</span></span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2005-03-04</p> <p>the upper layer with nutrients but the phyto- plankton production remains low because of light limitation. The winter/spring bloom occurs in Febru- ary... gelatinous carnivore populations and subsequent decreases in herbivorous mesozooplankton stocks. The two maxima (winter/spring and fall) and one minimum...the primary production (Longhurst, 1995). In addition to this bbottom-upQ forcing, btop-downQ control by the gelatinous predators plays a remarkable</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=223987','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=223987"><span><span class="hlt">CONCENTRATIONS</span> AND <span class="hlt">VARIABILITY</span> OF ß-CRYPTOXANTHIN IN FRUITS</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>ß-cryptoxanthin is a carotenoid with an unusual capacity to increase bone formation. Furthermore, a number of experimental and rodent studies have shown that ß-cryptoxanthin appears to have an anabolic effect on bone, increasing osteoblasts and decreasing osteoclasts (Uchiyama et al 2005, Yamaguchi ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=215958&keyword=marketing&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78781868&CFTOKEN=35804142','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=215958&keyword=marketing&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=78781868&CFTOKEN=35804142"><span>Predicting <span class="hlt">variability</span> of aquatic <span class="hlt">concentrations</span> of human pharmaceuticals</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Potential exposure to active pharmaceutical ingredients (APIs) in the aquatic environment is a subject of ongoing concern. We recently estimated maximum likely potency-normalized exposure rates at the national level for several hundred commonly used human prescription pharmaceut...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/79305','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/79305"><span>Predicting indoor radon-222 <span class="hlt">concentration</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stowe, M.H.</p> <p>1994-12-31</p> <p>Radon, a cause of lung cancer among miners, is being investigated as a source of lung cancer in the general population due to long-term low-level exposures in residences. Assessment of cumulative residential radon exposure entails measurements in past residences, some of which no longer exist or are not accessible. Estimates of radon <span class="hlt">concentrations</span> in these missing homes are necessary for analysis of the radon-lung cancer association. Various approaches have been used by researchers attempting to predict the distribution of radon measurements in homes from specified geological and building characteristics. This study has modelled the set of basement radon measurements of 3788 Connecticut homes with several of these approaches, in addition to a descriptive tree method not previously utilized, and compared their validity on a random subset of homes not used in model construction. Each geographical and geological <span class="hlt">variable</span> was more predictive of radon <span class="hlt">concentration</span> than any of the housing characteristics. The single <span class="hlt">variable</span> which explained the largest fraction of the <span class="hlt">variability</span> in radon readings was the mean radon <span class="hlt">concentration</span> for the zipcode area in which the house was located (R{sup 2} = .157). Soil characteristics at individual housing sites were not available for these analyses. They would be expected to increase the predictive power of the models. Multiple regression models, both additive and multiplicative, were not able to explain more than 22% of the variation in radon readings. <span class="hlt">Variables</span> found to be significant in these models were zipcode mean, residential radon mean of bedrock unit, building age, type of foundation walls, type of water supply, aeroradioactivity reading, and lithology of the bedrock. A site potential index, based upon a classification of the bedrock underlying the house, was a better predictor of indoor radon level than other single geological <span class="hlt">variables</span>, yet only explained 8% of the radon <span class="hlt">variability</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=167886','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=167886"><span>Aflatoxin <span class="hlt">variability</span> in pistachios.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mahoney, N E; Rodriguez, S B</p> <p>1996-01-01</p> <p>Pistachio fruit components, including hulls (mesocarps and epicarps), seed coats (testas), and kernels (seeds), all contribute to <span class="hlt">variable</span> aflatoxin content in pistachios. Fresh pistachio kernels were individually inoculated with Aspergillus flavus and incubated 7 or 10 days. Hulled, shelled kernels were either left intact or wounded prior to inoculation. Wounded kernels, with or without the seed coat, were readily colonized by A. flavus and after 10 days of incubation contained 37 times more aflatoxin than similarly treated unwounded kernels. The aflatoxin levels in the individual wounded pistachios were highly <span class="hlt">variable</span>. Neither fungal colonization nor aflatoxin was detected in intact kernels without seed coats. Intact kernels with seed coats had limited fungal colonization and low aflatoxin <span class="hlt">concentrations</span> compared with their wounded counterparts. Despite substantial fungal colonization of wounded hulls, aflatoxin was not detected in hulls. Aflatoxin levels were significantly lower in wounded kernels with hulls than in kernels of hulled pistachios. Both the seed coat and a water-soluble extract of hulls suppressed aflatoxin production by A. flavus. PMID:8919781</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25770953','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25770953"><span><span class="hlt">Variable</span> contribution of functional prey groups in diets reveals inter- and intraspecific differences in faecal <span class="hlt">concentrations</span> of essential and non-essential elements in three sympatric avian aerial insectivores: a re-assessment of usefulness of bird faeces in metal biomonitoring.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Orłowski, Grzegorz; Kamiński, Piotr; Karg, Jerzy; Baszyński, Jędrzej; Szady-Grad, Małgorzata; Koim-Puchowska, Beata; Klawe, Jacek J</p> <p>2015-06-15</p> <p>Aerial insectivores through their insect diet can contribute to biotransfer of elements across habitats. We investigate the relationship between dietary composition as expressed by the contributions of six functional invertebrate prey groups (primarily of agriculturally subsidised invertebrates characteristic of agricultural areas in temperate regions of Europe) and <span class="hlt">concentrations</span> of essential (Na, K, Ca, Mg, Fe, Cu, Zn, Mn, Co) and non-essential (As, Cd, Pb) elements of environmental concern in the faeces of nestlings of three species of avian aerial insectivores - Common Swift Apus apus, Barn Swallow Hirundo rustica and House Martin Delichon urbicum - which breed sympatrically and use apparently similar resources of flying insect prey. There were significant differences between the species for 7 of the 12 elements (Ca, Zn, Cu, Co, As, Pb, Cd); these differences were attributable to the <span class="hlt">variable</span> dietary composition, even though the <span class="hlt">concentrations</span> of the elements varied enormously between the faecal samples from the individual species. Partial correlation analysis between the biomass (expressed in mg dry weight) of the six functional prey groups and faecal <span class="hlt">concentrations</span> of elements showed the highest number of significant relationships for toxic metals (As, Pb and Cd). The results of the General Regression Model explaining faecal element <span class="hlt">concentrations</span> revealed the different explanatory power of the effects of PCA (of six functional prey groups) dietary scores. A significant fit of GRM was obtained for 7 elements (Na, Mg, Fe, Mn, As, Pb, Cd) for Barn Swallows, 2 elements (Cu, As) for House Martins and 1 element (Mn) for Common Swifts. Overall, the results confirmed our predictions that the biomass of consumed coprophilous taxa and insects from crop habitats was positively correlated with the faecal <span class="hlt">concentrations</span> of toxic elements. Unexpectedly, however, the faecal samples (primarily those of Common Swifts) that contained many oil-seed rape insect pests had lower</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ERL.....9k4011B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ERL.....9k4011B"><span>Decomposing global crop yield <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ben-Ari, Tamara; Makowski, David</p> <p>2014-11-01</p> <p>Recent food crises have highlighted the need to better understand the between-year <span class="hlt">variability</span> of agricultural production. Although increasing future production seems necessary, the globalization of commodity markets suggests that the food system would also benefit from enhanced supplies stability through a reduction in the year-to-year <span class="hlt">variability</span>. Here, we develop an analytical expression decomposing global crop yield interannual <span class="hlt">variability</span> into three informative components that quantify how evenly are croplands distributed in the world, the proportion of cultivated areas allocated to regions of above or below average <span class="hlt">variability</span> and the covariation between yields in distinct world regions. This decomposition is used to identify drivers of interannual yield variations for four major crops (i.e., maize, rice, soybean and wheat) over the period 1961-2012. We show that maize production is fairly spread but marked by one prominent region with high levels of crop yield interannual <span class="hlt">variability</span> (which encompasses the North American corn belt in the USA, and Canada). In contrast, global rice yields have a small <span class="hlt">variability</span> because, although spatially <span class="hlt">concentrated</span>, much of the production is located in regions of below-average <span class="hlt">variability</span> (i.e., South, Eastern and South Eastern Asia). Because of these contrasted land use allocations, an even cultivated land distribution across regions would reduce global maize yield variance, but increase the variance of global yield rice. Intermediate results are obtained for soybean and wheat for which croplands are mainly located in regions with close-to-average <span class="hlt">variability</span>. At the scale of large world regions, we find that covariances of regional yields have a negligible contribution to global yield variance. The proposed decomposition could be applied at any spatial and time scales, including the yearly time step. By addressing global crop production stability (or lack thereof) our results contribute to the understanding of a key</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SPIE.8821E..0HL','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SPIE.8821E..0HL"><span>Thin solar <span class="hlt">concentrator</span> with high <span class="hlt">concentration</span> ratio</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Jhe-Syuan; Liang, Chao-Wen</p> <p>2013-09-01</p> <p>Solar <span class="hlt">concentrators</span> are often used in conjunction with III-V multi-junction solar cells for cost reduction and efficiency improvement purposes. High flux <span class="hlt">concentration</span> ratio, high optical efficiency and high manufacture tolerance are the key features required for a successful solar <span class="hlt">concentrator</span> design. This paper describes a novel solar <span class="hlt">concentrator</span> that combines the concepts, and thus the advantages, of both the refractive type ad reflective type. The proposed <span class="hlt">concentrator</span> design adopts the Etendue-cascading concept that allows the light beams from all the <span class="hlt">concentric</span> annular entrance pupils to be collected and transferred to the solar cell with minimal loss. This concept enables the system to perform near its Etendue-Limit and have a high <span class="hlt">concentration</span> ratio simultaneously. Thereby reducing the costs of solar cells and therefor achieves a better the per watts cost. The <span class="hlt">concentrator</span> demonstrated has a thing aspect ratio of 0.19 with a zero back focal distance. The numerical aperture at the solar cell immersed inside the dielectric <span class="hlt">concentrator</span> is as high as 1.33 achieving a unprecedented high optical <span class="hlt">concentration</span> ratio design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5707874','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5707874"><span>Theoretical maximum <span class="hlt">concentration</span> factors for solar <span class="hlt">concentrators</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nicolas, R.O.; Duran, J.C.</p> <p>1984-11-01</p> <p>The theoretical maximum <span class="hlt">concentration</span> factors are determined for different definitions of the factor for two-dimensional and three-dimensional solar <span class="hlt">concentrators</span> that are valid for any source with nonuniform intensity distribution. Results are obtained starting from those derived by Winston (1970) for Lambertian sources. In particular, maximum <span class="hlt">concentration</span> factors for three models of the solar-disk intensity distribution are calculated. 12 references.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.U11A..01P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.U11A..01P"><span>Solar <span class="hlt">Variability</span> and Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pap, J. M.</p> <p>2004-12-01</p> <p>One of the most exciting and important challenges in science today is to understand climate <span class="hlt">variability</span> and to make reliable predictions. The Earth's climate is a complex system driven by external and internal forces. Climate can vary over a large range of time scales as a consequence of natural <span class="hlt">variability</span> or anthropogenic influence, or both. Observations of steadily increasing <span class="hlt">concentrations</span> of greenhouse gases --primarily man-made-- in the Earth's atmosphere have led to an expectation of global warming during the coming decades. However, the greenhouse effect competes with other climate forcing mechanisms, such as solar <span class="hlt">variability</span>, cosmic ray flux changes, desertification, deforestation, and changes in natural and man-made atmospheric aerosols. Indeed, the climate is always changing, and has forever been so, including periods before the industrial era began. Since the dominant driving force of the climate system is the Sun, the accurate knowledge of the solar radiation received by Earth at various wavelengths and from energetic particles with varying intensities, as well as a better knowledge of the solar-terrestrial interactions and their temporal and spatial <span class="hlt">variability</span> are crucial to quantify the solar influence on climate and to distinguish between natural and anthropogenic influences. In this paper we give an overview on the recent results of solar irradiance measurements over the last three decades and the possible effects of solar <span class="hlt">variability</span> on climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/208259','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/208259"><span>Flat high <span class="hlt">concentration</span> devices</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Minano, J.C.; Gonzalez, J.C.; Zanesco, I.</p> <p>1994-12-31</p> <p>During the last five years new <span class="hlt">concentrators</span> achieving the theoretical maximum acceptance-angle-<span class="hlt">concentration</span> product have appeared. In addition, some of these <span class="hlt">concentrators</span> are very compact (<span class="hlt">concentrator</span> depth/aperture diameter smaller than 1/3). The feasibility of these <span class="hlt">concentrators</span> for photovoltaic applications is studied. It is concluded that these <span class="hlt">concentrators</span> may be useful for high <span class="hlt">concentration</span> cells (irradiance for maximum efficiency greater than 800 suns) if these cells have a small size (diameter smaller than 5 mm). The <span class="hlt">concentrators</span> may provide for this case an acceptance angle of {approx} {+-}2.7 degrees with <span class="hlt">concentration</span> factor around 1,000x and a <span class="hlt">concentrator</span> depth 10 times the cell diameter. Instantaneous direct insolation and ambient temperature measurements of Madrid and a thermal model of the heat sink is used to calculate the annual electric energy output with which different <span class="hlt">concentration</span> factors are compared. <span class="hlt">Concentration</span> of 1,000x is close to the one giving the maximum annual electrical output.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=pigeon&pg=6&id=EJ998525','ERIC'); return false;" href="http://eric.ed.gov/?q=pigeon&pg=6&id=EJ998525"><span><span class="hlt">Variability</span> as an Operant?</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Holth, Per</p> <p>2012-01-01</p> <p>A series of experiments on operant <span class="hlt">variability</span> by Neuringer and colleagues (e.g., Neuringer, 1986, 2002; Page & Neuringer, 1985) have been repeatedly cited as showing that behavioral <span class="hlt">variability</span> can be reinforced by making reinforcement contingent on it. They showed that the degree of <span class="hlt">variability</span> in pigeons' eight-peck sequences, as measured by U…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=325441','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=325441"><span><span class="hlt">Variable</span> rate irrigation (VRI)</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p><span class="hlt">Variable</span> rate irrigation (VRI) technology is now offered by all major manufacturers of moving irrigation systems, mostly on center pivot irrigation systems. <span class="hlt">Variable</span> irrigation depths may be controlled by sector only, in which case only the speed of the irrigation lateral is regulated. Or, <span class="hlt">variable</span> ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ACP....1612059H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ACP....1612059H"><span>Parameterizing cloud condensation nuclei <span class="hlt">concentrations</span> during HOPE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hande, Luke B.; Engler, Christa; Hoose, Corinna; Tegen, Ina</p> <p>2016-09-01</p> <p>An aerosol model was used to simulate the generation and transport of aerosols over Germany during the HD(CP)2 Observational Prototype Experiment (HOPE) field campaign of 2013. The aerosol number <span class="hlt">concentrations</span> and size distributions were evaluated against observations, which shows satisfactory agreement in the magnitude and temporal <span class="hlt">variability</span> of the main aerosol contributors to cloud condensation nuclei (CCN) <span class="hlt">concentrations</span>. From the modelled aerosol number <span class="hlt">concentrations</span>, number <span class="hlt">concentrations</span> of CCN were calculated as a function of vertical velocity using a comprehensive aerosol activation scheme which takes into account the influence of aerosol chemical and physical properties on CCN formation. There is a large amount of spatial <span class="hlt">variability</span> in aerosol <span class="hlt">concentrations</span>; however the resulting CCN <span class="hlt">concentrations</span> vary significantly less over the domain. Temporal <span class="hlt">variability</span> is large in both aerosols and CCN. A parameterization of the CCN number <span class="hlt">concentrations</span> is developed for use in models. The technique involves defining a number of best fit functions to capture the dependence of CCN on vertical velocity at different pressure levels. In this way, aerosol chemical and physical properties as well as thermodynamic conditions are taken into account in the new CCN parameterization. A comparison between the parameterization and the CCN estimates from the model data shows excellent agreement. This parameterization may be used in other regions and time periods with a similar aerosol load; furthermore, the technique demonstrated here may be employed in regions dominated by different aerosol species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.A41C0112J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.A41C0112J"><span>Observations of CCN <span class="hlt">Concentrations</span> and <span class="hlt">Concentration</span> Variations Related to Clouds and Cloud Scavenging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jha, V.; Noble, S.; Hudson, J. G.</p> <p>2008-12-01</p> <p>Maritime CCN <span class="hlt">concentrations</span> have traditionally been defined as number per cubic centimeter < 200. However, extensive aircraft measurements in the remote mid Pacific boundary layer during the PASE project (Aug.-Sep. 2007) consistently displayed CCN <span class="hlt">concentrations</span> in excess of 300 per cubic centimeter. By contrast measurements in the Caribbean during the RICO project (Dec.-Jan., 2004-05) showed <span class="hlt">concentrations</span> during 17 flights that were consistent with most previous maritime measurements, < 200 per cubic centimeter. The main difference between these projects was clouds, because RICO was a small cumulus cloud study whereas the location and season for PASE was chosen to minimize clouds. Boundary layer <span class="hlt">concentrations</span> were quite consistent throughout each of the 8-hour flights during both of these projects. In fact the measured <span class="hlt">concentration</span> consistency was comparable to the statistical <span class="hlt">variability</span> of the instruments. The <span class="hlt">concentration</span> <span class="hlt">variability</span> among the RICO flights was a factor of four (Hudson and Mishra 2007) whereas <span class="hlt">concentrations</span> varied by only a few percent among the PASE flights. Two summertime status cloud projects off the central California coast displayed stark contrasts in CCN <span class="hlt">concentrations</span> and <span class="hlt">variability</span>. Like PASE and RICO the 2005 MASE project showed consistent boundary layer <span class="hlt">concentrations</span> throughout most of each of 11 four hour flights. <span class="hlt">Concentration</span> <span class="hlt">variability</span> among the MASE flights was intermediate of the PASE and RICO projects, but the MASE <span class="hlt">concentrations</span> were always higher than PASE or RICO and thus not maritime; i.e., polluted. By contrast the 2008 POST stratus cloud project displayed much more day-to-day and within flight boundary layer CCN <span class="hlt">concentration</span> <span class="hlt">variability</span>. During POST <span class="hlt">concentrations</span> ranged up to those of MASE (polluted) but were often lower; i.e., down into the traditional maritime range, often < 100 per cubic centimeter. The polluted MASE cloud deck was widespread with little horizontal or vertical <span class="hlt">variability</span> during or among the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10176851','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10176851"><span>Photovoltaic <span class="hlt">concentrator</span> initiative: <span class="hlt">Concentrator</span> cell development</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wohlgemuth, J.H.; Narayanan, S.</p> <p>1993-05-01</p> <p>This project involves the development of a large-area, low-cost, high-efficiency <span class="hlt">concentrator</span> solar cell for use in the Entech 22-sun linear-focus Fresnel lens <span class="hlt">concentrator</span> system. The buried contact solar cell developed at the University of New South Wales was selected for this project. Both Entech and the University of New South Wales are subcontractors. This annual report presents the program efforts from November 1990 through December 1991, including the design of the cell, development of a baseline cell process, and presentation of the results of preliminary cell processing. Important results include a cell designed for operation in a real <span class="hlt">concentrator</span> system and substitution of mechanical grooving for the previously utilized laser scribing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1003207','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1003207"><span>Extended Storage of Pathogen Reduced Platelet <span class="hlt">Concentrates</span> (PRECON)</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2015-10-01</p> <p>platelet <span class="hlt">concentrates</span> . II. Storage <span class="hlt">variables</span> influencing platelet viability and function. Br J Haematol 1976;34(3):403-419. 2. Borgman MA...plt viability results from these two methods. As a control, a small aliquot of plts obtained from a standard 5-day stored plt <span class="hlt">concentrate</span> will be...Maryland 21702-5000. XX. LITERATURE REVIEW 1. Slichter SJ, Harker LA. Preparation and storage of platelet <span class="hlt">concentrates</span> . II. Storage <span class="hlt">variables</span> influencing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.epa.gov/outdoor-air-quality-data/air-data-concentration-map','PESTICIDES'); return false;" href="https://www.epa.gov/outdoor-air-quality-data/air-data-concentration-map"><span>Air Data - <span class="hlt">Concentration</span> Map</span></a></p> <p><a target="_blank" href="http://www.epa.gov/pesticides/search.htm">EPA Pesticide Factsheets</a></p> <p></p> <p></p> <p>Make a map of daily <span class="hlt">concentrations</span> over several days. The daily air quality can be displayed in terms of the Air Quality Index or in <span class="hlt">concentration</span> ranges for certain PM species like organic carbon, nitrates, and sulfates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1980IEEES..17...34B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1980IEEES..17...34B"><span>Photovoltaics. III - <span class="hlt">Concentrators</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Backus, C. E.</p> <p>1980-02-01</p> <p>Photovoltaic <span class="hlt">concentration</span> systems that redirect sunlight falling on a surface to a smaller solar-cell surface <span class="hlt">concentrating</span> the intensity of sunlight many times are examined. It is noted that solar cells for <span class="hlt">concentrating</span> systems must be designed for low internal resistance as well as for high sunlight intensities. Two designs of silicon cells are presented that perform well at high <span class="hlt">concentrations</span>; these are interdigitated back-contact cells and vertical multijunction cells. Attention is given to heat tapping of reemitted light.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130013891','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130013891"><span>Understanding Brown Dwarf <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Marley, Mark S.</p> <p>2013-01-01</p> <p>Surveys of brown dwarf <span class="hlt">variability</span> continue to find that roughly half of all brown dwarfs are <span class="hlt">variable</span>. While <span class="hlt">variability</span> is observed amongst all types of brown dwarfs, amplitudes are typically greatest for L-T transition objects. In my talk I will discuss the possible physical mechanisms that are responsible for the observed <span class="hlt">variability</span>. I will particularly focus on comparing and contrasting the effects of changes in atmospheric thermal profile and cloud opacity. The two different mechanisms will produce different <span class="hlt">variability</span> signatures and I will discuss the extent to which the current datasets constrain both mechanisms. By combining constraints from studies of <span class="hlt">variability</span> with existing spectral and photometric datasets we can begin to construct and test self-consistent models of brown dwarf atmospheres. These models not only aid in the interpretation of existing objects but also inform studies of directly imaged giant planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27797523','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27797523"><span>Factors Affecting Tocopherol <span class="hlt">Concentrations</span> in Soybean Seeds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Carrera, Constanza S; Seguin, Philippe</p> <p>2016-12-21</p> <p>Soybean seeds contain several health-beneficial compounds, including tocopherols, which are used by the nutraceutical and functional food industries. Soybean tocopherol <span class="hlt">concentrations</span> are, however, highly <span class="hlt">variable</span>. Large differences observed in tocopherol <span class="hlt">concentrations</span> among soybean genotypes together with the relatively simple biosynthetic pathway involving few genes support the feasibility of selecting for high-tocopherol soybean. Tocopherol <span class="hlt">concentrations</span> are also highly influenced by environmental factors and field management. Temperature during seed filling and soil moisture appear to be the main factors affecting tocopherol <span class="hlt">concentrations</span>; other factors such as soil fertility and solar radiation also affect <span class="hlt">concentrations</span> and composition. Field management decisions including seeding date, row spacing, irrigation, and fertilization also affect tocopherols. Knowledge of factors affecting soybean tocopherols is essential to develop management strategies that will lead to the production of seeds with consistent target <span class="hlt">concentrations</span> that will meet the needs of the nutraceutical and functional food industries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4196497','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4196497"><span><span class="hlt">VARIABLE</span> TIME DELAY MEANS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Clemensen, R.E.</p> <p>1959-11-01</p> <p>An electrically <span class="hlt">variable</span> time delay line is described which may be readily controlled simuitaneously with <span class="hlt">variable</span> impedance matching means coupied thereto such that reflections are prevented. Broadly, the delay line includes a signal winding about a magnetic core whose permeability is electrically <span class="hlt">variable</span>. Inasmuch as the inductance of the line varies directly with the permeability, the time delay and characteristic impedance of the line both vary as the square root of the permeability. Consequently, impedance matching means may be varied similariy and simultaneously w:th the electrically <span class="hlt">variable</span> permeability to match the line impedance over the entire range of time delay whereby reflections are prevented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990ApJ...364..259E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990ApJ...364..259E"><span>Chromospheric <span class="hlt">variability</span> of M giant semiregular <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eaton, Joel A.; Johnson, Hollis R.; Cadmus, Robert R., Jr.</p> <p>1990-11-01</p> <p>The results of monitoring the chromospheric emission from three M giant semiregular <span class="hlt">variables</span>, W Cyg, NU Pav, and Theta Aps at low dispersion with the IUE satellite are reported along with high-dispersion IUE spectra for R Lyr and Delta(2) Lyr. The chromospheric emission is <span class="hlt">variable</span> in all of the first three stars, and the Mg II strength generally follows changes in the continuum. However, the changes are not directly proportional, and there is a phase lag between the emission in the continuum and that in the Mg II lines, at least in W Cyg and probably in NU Pav. R Lyr showed changes in Mg II lines strengths and profiles uncorrelated with Al II 2669 A strength or with the strengths of fluorescent Fe I lines. The chromospheres of all these stars are clearly modified by stellar pulsation. The position and extent of the emitting layers of the chromospheres of the stars are estimated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPhEn...4.0995B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPhEn...4.0995B"><span>Recent trends in <span class="hlt">concentrated</span> photovoltaics <span class="hlt">concentrators</span>' architecture</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buljan, Marina; Mendes-Lopes, João; Benítez, Pablo; Miñano, Juan Carlos</p> <p>2014-01-01</p> <p>The field of <span class="hlt">concentrated</span> photovoltaics (CPV) has met some remarkable advances in recent years. The continuous increase in conversion efficiency of multijunction solar cells and new advancements in optics have led to new demands and opportunities for optical design in CPV. This paper is a mini-review on current requirements for CPV optical design, and it presents some of the main trends in recent years on CPV systems architecture.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Modeling+AND+Variable&pg=6&id=EJ646450','ERIC'); return false;" href="http://eric.ed.gov/?q=Modeling+AND+Variable&pg=6&id=EJ646450"><span>Latent <span class="hlt">Variable</span> Interaction Modeling.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Schumacker, Randall E.</p> <p>2002-01-01</p> <p>Used simulation to study two different approaches to latent <span class="hlt">variable</span> interaction modeling with continuous observed <span class="hlt">variables</span>: (1) a LISREL 8.30 program and (2) data analysis through PRELIS2 and SIMPLIS programs. Results show that parameter estimation was similar but standard errors were different. Discusses differences in ease of implementation.…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23790408','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23790408"><span>A variety of <span class="hlt">variables</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jupiter, Daniel C</p> <p>2014-01-01</p> <p>In designing studies and developing plans for analyses, we must consider which tests are appropriate for the types of <span class="hlt">variables</span> we are using. Here I describe the types of <span class="hlt">variables</span> available to us, and I briefly consider the appropriate tools to use in their analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=EL-2002-00543&hterms=Teen&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DTeen','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=EL-2002-00543&hterms=Teen&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DTeen"><span><span class="hlt">Variable</span> Density Tunnel</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1931-01-01</p> <p><span class="hlt">Variable</span> Density Tunnel in operation. Man at far right is probably Harold J. 'Cannonball' Tuner, longtime safety officer, who started with Curtiss in the teens. This view of the <span class="hlt">Variable</span> Density Tunnel clearly shows the layout of the Tunnel's surroundings, as well as the plumbing and power needs of the this innovative research tool.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1339632','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1339632"><span><span class="hlt">Variable</span> volume combustor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Ostebee, Heath Michael; Ziminsky, Willy Steve; Johnson, Thomas Edward; Keener, Christopher Paul</p> <p>2017-01-17</p> <p>The present application provides a <span class="hlt">variable</span> volume combustor for use with a gas turbine engine. The <span class="hlt">variable</span> volume combustor may include a liner, a number of micro-mixer fuel nozzles positioned within the liner, and a linear actuator so as to maneuver the micro-mixer fuel nozzles axially along the liner.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/EJ918254.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/EJ918254.pdf"><span>Reinforcing Saccadic Amplitude <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Paeye, Celine; Madelain, Laurent</p> <p>2011-01-01</p> <p>Saccadic endpoint <span class="hlt">variability</span> is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this <span class="hlt">variability</span> might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880002211','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880002211"><span>Basic properties and <span class="hlt">variability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Querci, Francois R.</p> <p>1987-01-01</p> <p>Giant and supergiant M, S, and C stars are discussed in this survey of research. Basic properties as determined by spectra, chemical composition, photometry, or <span class="hlt">variability</span> type are discussed. Space motions and space distributions of cool giants are described. Distribution of these stars in our galaxy and those nearby is discussed. Mira <span class="hlt">variables</span> in particular are surveyed with emphasis on the following topics: (1) phase lag phenomenon; (2) Mira light curves; (3) variations in color indices; (4) determination of multiple periods; (5) correlations between quantities such as period length, light-curve shape, infrared (IR) excess, and visible and IR color diagram; (6) semiregular (SR) <span class="hlt">variables</span> and different time scales in SR light variations; (7) irregular <span class="hlt">variable</span> Lb and Lc stars; (8) different time-scale light variations; (9) hydrogen-deficient carbon (HdC) stars, in particular RCB stars; and (10) irreversible changes and rapid evolution in red <span class="hlt">variable</span> stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ISPAr.XL1b...1A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ISPAr.XL1b...1A"><span>Aerosol <span class="hlt">Variability</span> Observed with Rpas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Altstädter, B.; Lampert, A.; Scholtz, A.; Bange, J.; Platis, A.; Hermann, M.; Wehner, B.</p> <p>2013-08-01</p> <p>To observe the origin, vertical and horizontal distribution and <span class="hlt">variability</span> of aerosol particles, and especially ultrafine particles recently formed, we plan to employ the remotely piloted aircraft system (RPAS) Carolo-P360 "ALADINA" of TU Braunschweig. The goal of the presented project is to investigate the vertical and horizontal distribution, transport and small-scale <span class="hlt">variability</span> of aerosol particles in the atmospheric boundary layer using RPAS. Two additional RPAS of type MASC of Tübingen University equipped with turbulence instrumentation add the opportunity to study the interaction of the aerosol <span class="hlt">concentration</span> with turbulent transport and exchange processes of the surface and the atmosphere. The combination of different flight patterns of the three RPAS allows new insights in atmospheric boundary layer processes. Currently, the different aerosol sensors are miniaturized at the Leibniz Institute for Tropospheric Research, Leipzig and together with the TU Braunschweig adapted to fit into the RPAS. Moreover, an additional meteorological payload for measuring temperature, humidity and turbulence properties is constructed by Tübingen University. Two condensation particle counters determine the total aerosol number with a different lower detection threshold in order to investigate the horizontal and vertical aerosol <span class="hlt">variability</span> and new particle formation (aerosol particles of some nm diameter). Further the aerosol size distribution in the range from about 0.300 to ~5 μm is given by an optical particle counter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982sert.rept..113D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982sert.rept..113D"><span><span class="hlt">Concentrating</span> photovoltaic systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dupas, A.</p> <p>1982-11-01</p> <p>Various configurations for <span class="hlt">concentrating</span> photovoltaic systems are described and their operating principles are explained. The effects of temperature and series resistance on system efficiency are discussed. As an example, the french family of photovoltaic <span class="hlt">concentrating</span> systems, SOPHOCLE, is described. The SOPHOCLE family of generators is characterized by the use of a heliostat with altazimuth mounting and by the choice of medium <span class="hlt">concentration</span> (C=45) by fresnel lenses on silicon cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940000363&hterms=transformer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtransformer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940000363&hterms=transformer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtransformer"><span>Magnetically Controlled <span class="hlt">Variable</span> Transformer</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kleiner, Charles T.</p> <p>1994-01-01</p> <p>Improved <span class="hlt">variable</span>-transformer circuit, output voltage and current of which controlled by use of relatively small current supplied at relatively low power to control windings on its magnetic cores. Transformer circuits of this type called "magnetic amplifiers" because ratio between controlled output power and power driving control current of such circuit large. This ratio - power gain - can be as large as 100 in present circuit. <span class="hlt">Variable</span>-transformer circuit offers advantages of efficiency, safety, and controllability over some prior <span class="hlt">variable</span>-transformer circuits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1238599','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1238599"><span><span class="hlt">Variability</span> study for saltstone</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harbour, J. R.; Edwards, T. B.; Hansen, E. K.; Williams, V. J.</p> <p>2005-10-01</p> <p>This report is a summary of the bench-scale experimental studies performed by the Savannah River National Laboratory (SRNL) for Waste Solidification Engineering (WSE) to establish the viability of a grout-based <span class="hlt">variability</span> study. In order for a <span class="hlt">variability</span> study to be useful, the property measurements of the fresh and cured Saltstone must be reproducible with an inherent variation that is small compared to the changes in the properties measured over the expected range of <span class="hlt">variability</span> for a Salt Batch. This scoping task addressed the issue of reproducibility for Saltstone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1290783','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1290783"><span><span class="hlt">Variability</span> in large-scale wind power generation: <span class="hlt">Variability</span> in large-scale wind power generation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kiviluoma, Juha; Holttinen, Hannele; Weir, David; Scharff, Richard; Söder, Lennart; Menemenlis, Nickie; Cutululis, Nicolaos A.; Danti Lopez, Irene; Lannoye, Eamonn; Estanqueiro, Ana; Gomez-Lazaro, Emilio; Bai, Jianhua; Wan, Yih-Huei; Milligan, Michael</p> <p>2015-10-25</p> <p>The paper demonstrates the characteristics of wind power <span class="hlt">variability</span> and net load <span class="hlt">variability</span> in multiple power systems based on real data from multiple years. Demonstrated characteristics include probability distribution for different ramp durations, seasonal and diurnal <span class="hlt">variability</span> and low net load events. The comparison shows regions with low <span class="hlt">variability</span> (Sweden, Spain and Germany), medium <span class="hlt">variability</span> (Portugal, Ireland, Finland and Denmark) and regions with higher <span class="hlt">variability</span> (Quebec, Bonneville Power Administration and Electric Reliability Council of Texas in North America; Gansu, Jilin and Liaoning in China; and Norway and offshore wind power in Denmark). For regions with low <span class="hlt">variability</span>, the maximum 1 h wind ramps are below 10% of nominal capacity, and for regions with high <span class="hlt">variability</span>, they may be close to 30%. Wind power <span class="hlt">variability</span> is mainly explained by the extent of geographical spread, but also higher capacity factor causes higher <span class="hlt">variability</span>. It was also shown how wind power ramps are autocorrelated and dependent on the operating output level. When wind power was <span class="hlt">concentrated</span> in smaller area, there were outliers with high changes in wind output, which were not present in large areas with well-dispersed wind power.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21507725','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21507725"><span>High <span class="hlt">concentration</span> plasma-reduced plateletapheresis <span class="hlt">concentrates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Perseghin, Paolo</p> <p>2011-06-01</p> <p>Single-donor hyperconcentrated plateletapheresis (dry-platelets) collection has been introduced in the 90's as a part of the newly developed multi-component collection strategy. This approach allowed to safely collect multiple components from a single apheresis donation, i.e. RBC, FFP and/or plateletpheresis units. Dry-platelets are usually resuspended in additive solution to maintain an adequate pH during the storage period until use. Some concern existed about possible higher degrees of platelet activation in dry-platelets units when compared to standard <span class="hlt">concentration</span> (1.0-1.6 × 10(6)/μL platelets) units and its possible correlation with lower in vivo efficiency and/or survival of the former units. Several authors investigated this specific issue, and dry-platelets units proved to be equally effective than standard <span class="hlt">concentration</span> plateletpheresis units in recipients. The use of dry-platelets units may reduce (i) the risk of passive infusion of naturally occurring ABO-related hemolytic antibodies when donor O platelets are given to group A, B, or AB recipient, (ii) the risk of TRALI when multiparous donors undergo plateletpheresis. Furthermore, dry-platelet collection may allow for an increased amount of FFP sent to industry. Finally, hyperconcentrated platelet units may be used for "niche" indications, such as intrauterine platelet transfusion or, in case of autologous dry-platelet collection, for further freezing for long term storage in selected patients within onco-hematological settings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5406874','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5406874"><span>Uranium <span class="hlt">concentrations</span> in asparagus</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tiller, B.L.; Poston, T.M.</p> <p>1992-05-01</p> <p><span class="hlt">Concentrations</span> of uranium were determined in asparagus collected from eight locations near and ten locations on the Hanford Site southcentral Washington State. Only one location (Sagemoor) had samples with elevated <span class="hlt">concentrations</span>. The presence of elevated uranium in asparagus at Sagemoor may be explained by the elevated levels in irrigation water. These levels of uranium are comparable to levels previously reported upstream and downstream of the 300-FF-1 Operable Unit on the Hanford Site (0.0008 {mu}g/g), but were below the 0.020-{mu}g/g level reported for brush collected at Sagemoor in a 1982 study. <span class="hlt">Concentrations</span> at all other onsite and offsite sample locations were considerably lower than <span class="hlt">concentrations</span> reported immediately upstream and downstream of the 300-FF-1 Operable Unit. Using an earlier analysis of the uranium <span class="hlt">concentrations</span> in asparagus collected from the Hanford Site constitutes a very small fraction of the US Department of Energy effective dose equivalent limit of 100 mrem.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1326208-solar-variability-datalogger','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1326208-solar-variability-datalogger"><span>Solar <span class="hlt">variability</span> datalogger</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Lave, Matthew; Stein, Joshua; Smith, Ryan</p> <p>2016-07-28</p> <p>To address the lack of knowledge of local solar <span class="hlt">variability</span>, we have developed and deployed a low-cost solar <span class="hlt">variability</span> datalogger (SVD). While most currently used solar irradiance sensors are expensive pyranometers with high accuracy (relevant for annual energy estimates), low-cost sensors display similar precision (relevant for solar <span class="hlt">variability</span>) as high-cost pyranometers, even if they are not as accurate. In this work, we present evaluation of various low-cost irradiance sensor types, describe the SVD, and present validation and comparison of the SVD collected data. In conclusion, the low cost and ease of use of the SVD will enable a greater understandingmore » of local solar <span class="hlt">variability</span>, which will reduce developer and utility uncertainty about the impact of solar photovoltaic (PV) installations and thus will encourage greater penetrations of solar energy.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1326208','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1326208"><span>Solar <span class="hlt">variability</span> datalogger</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lave, Matthew; Stein, Joshua; Smith, Ryan</p> <p>2016-07-28</p> <p>To address the lack of knowledge of local solar <span class="hlt">variability</span>, we have developed and deployed a low-cost solar <span class="hlt">variability</span> datalogger (SVD). While most currently used solar irradiance sensors are expensive pyranometers with high accuracy (relevant for annual energy estimates), low-cost sensors display similar precision (relevant for solar <span class="hlt">variability</span>) as high-cost pyranometers, even if they are not as accurate. In this work, we present evaluation of various low-cost irradiance sensor types, describe the SVD, and present validation and comparison of the SVD collected data. In conclusion, the low cost and ease of use of the SVD will enable a greater understanding of local solar <span class="hlt">variability</span>, which will reduce developer and utility uncertainty about the impact of solar photovoltaic (PV) installations and thus will encourage greater penetrations of solar energy.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1080016','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1080016"><span>Understanding Biomass Feedstock <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kevin L. Kenney; William A. Smith; Garold L. Gresham; Tyler L. Westover</p> <p>2013-01-01</p> <p>If the singular goal of biomass logistics and the design of biomass feedstock supply systems is to reduce the per ton supply cost of biomass, these systems may very well develop with ultimate unintended consequences of highly <span class="hlt">variable</span> and reduced quality biomass feedstocks. This paper demonstrates that due to inherent species <span class="hlt">variabilities</span>, production conditions, and differing harvest, collection, and storage practices, this is a very real scenario that biomass producers and suppliers as well as conversion developers should be aware of. Biomass feedstock attributes of ash, carbohydrates, moisture, and particle morphology will be discussed. We will also discuss specifications for these attributes, inherent <span class="hlt">variability</span> of these attributes in biomass feedstocks, and approaches and solutions for reducing <span class="hlt">variability</span> for improving feedstock quality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19730022052&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DVariable%2Bstars','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19730022052&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DVariable%2Bstars"><span>Discovery of <span class="hlt">variable</span> stars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kurochkin, N. Y.</p> <p>1973-01-01</p> <p>Instrumented methods of discovering <span class="hlt">variable</span> stars are reviewed, specifically the blink comparator, color contrast method, positive-negative method, and television method. Among the empirical methods discussed, the Van Gent method is the most important.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1121354','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1121354"><span>Understanding Biomass Feedstock <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kevin L. Kenney; Garold L. Gresham; William A. Smith; Tyler L. Westover</p> <p>2013-01-01</p> <p>If the singular goal of biomass logistics and the design of biomass feedstock supply systems is to reduce the per-ton supply cost of biomass, these systems may very well develop with ultimate unintended consequences of highly <span class="hlt">variable</span> and reduced quality biomass feedstocks. This paper demonstrates that, due to inherent species <span class="hlt">variabilities</span>, production conditions and differing harvest, collection and storage practices, this is a very real scenario that biomass producers and suppliers as well as conversion developers should be aware of. Biomass feedstock attributes of ash, carbohydrates, moisture and particle morphology will be discussed. We will also discuss specifications for these attributes, inherent <span class="hlt">variability</span> of these attributes in biomass feedstocks, and approaches and solutions for reducing <span class="hlt">variability</span> for improving feedstock quality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930084589','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930084589"><span><span class="hlt">Variable</span> pitch propeller</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pistolesi, Enrico</p> <p>1923-01-01</p> <p>The advantages of <span class="hlt">variable</span> pitch propellers over constant pitch propellers is presented along with different methods of varying the pitch. The technique of varying the shape of the propeller is presented as the most efficient one.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780019480','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780019480"><span><span class="hlt">Variable</span> contour securing system</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zebus, P. P.; Packer, P. N.; Haynie, C. C. (Inventor)</p> <p>1978-01-01</p> <p>A <span class="hlt">variable</span> contour securing system has a retaining structure for a member whose surface contains a <span class="hlt">variable</span> contour. The retaining mechanism includes a spaced array of adjustable spindles mounted on a housing. Each spindle has a base member support cup at one end. A vacuum source is applied to the cups for seating the member adjacent to the cups. A locking mechanism sets the spindles in a predetermined position once the member has been secured to the spindle support cups.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4675657','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4675657"><span><span class="hlt">VARIABLE</span>-THROW CAM</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Godsil, E.C.; Robinson, E.Y.</p> <p>1963-07-16</p> <p>A <span class="hlt">variable</span>-throw cam comprising inner and outer eccentric sleeves which are adjustably locked together is described. The cam throw is varied by unlocking the inner and outer sleeves, rotating the outer sleeve relative to the inner one until the desired throw is obtained, and locking the sleeves together again. The cam is useful in applications wherein a continuously-<span class="hlt">variable</span> throw is required, e.g., ram-and-die pressing operations, cyclic fatigue testing of materials, etc. (AEC)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070003579','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070003579"><span><span class="hlt">Concentration</span> of Hydrogen Peroxide</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parrish, Clyde F. (Inventor)</p> <p>2006-01-01</p> <p>Methods for <span class="hlt">concentrating</span> hydrogen peroxide solutions have been described. The methods utilize a polymeric membrane separating a hydrogen peroxide solution from a sweep gas or permeate. The membrane is selective to the permeability of water over the permeability of hydrogen peroxide, thereby facilitating the <span class="hlt">concentration</span> of the hydrogen peroxide solution through the transport of water through the membrane to the permeate. By utilizing methods in accordance with the invention, hydrogen peroxide solutions of up to 85% by volume or higher may be generated at a point of use without storing substantial quantities of the highly <span class="hlt">concentrated</span> solutions and without requiring temperatures that would produce explosive mixtures of hydrogen peroxide vapors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850000463&hterms=reflux&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dreflux','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850000463&hterms=reflux&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dreflux"><span>Nebulization Reflux <span class="hlt">Concentrator</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cofer, Wesley R., III; Collins, V. G.</p> <p>1986-01-01</p> <p>Nebulization reflux <span class="hlt">concentrator</span> extracts and <span class="hlt">concentrates</span> trace quantities of water-soluble gases for subsequent chemical analysis. Hydrophobic membrane and nebulizing nozzles form scrubber for removing trace quantities of soluble gases or other contaminants from atmosphere. Although hydrophobic membrane virtually blocks all transport of droplets, it offers little resistance to gas flow; hence, device permits relatively large volumes of gas scrubbed efficiently with very small volumes of liquid. This means analyzable quantities of contaminants <span class="hlt">concentrate</span> in extracting solutions in much shorter times than with conventional techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1129194','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1129194"><span><span class="hlt">Concentrating</span> photovoltaic solar panel</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Cashion, Steven A; Bowser, Michael R; Farrelly, Mark B; Hines, Braden E; Holmes, Howard C; Johnson, Jr., Richard L; Russell, Richard J; Turk, Michael F</p> <p>2014-04-15</p> <p>The present invention relates to photovoltaic power systems, photovoltaic <span class="hlt">concentrator</span> modules, and related methods. In particular, the present invention features <span class="hlt">concentrator</span> modules having interior points of attachment for an articulating mechanism and/or an articulating mechanism that has a unique arrangement of chassis members so as to isolate bending, etc. from being transferred among the chassis members. The present invention also features adjustable solar panel mounting features and/or mounting features with two or more degrees of freedom. The present invention also features a mechanical fastener for secondary optics in a <span class="hlt">concentrator</span> module.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21350940','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21350940"><span>Doxepin <span class="hlt">concentrations</span> in plasma and cerebrospinal fluid.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schomburg, Robert; Remane, Daniela; Fassbender, Klaus; Maurer, Hans H; Spiegel, Jörg</p> <p>2011-04-01</p> <p>Doxepin--like other antidepressant drugs (ADs)--shows a <span class="hlt">variable</span> antidepressant effect in clinical practice. The cause for this <span class="hlt">variability</span> is as yet unclear; however, pharmacokinetic factors such as the <span class="hlt">variable</span> permeability of doxepin into the cerebrospinal fluid (CSF), may contribute to the difference in therapeutic efficacy. We measured and correlated the <span class="hlt">concentration</span> of doxepin and its active metabolite nordoxepin in both the plasma and CSF. Plasma and CSF samples were taken simultaneously from 21 patients who were treated with doxepin due to different clinical indications. The plasma <span class="hlt">concentration</span> of both doxepin and nordoxepin correlated significantly with the oral dosage of doxepin (doxepin: r = +0.66, p < 0.001; nordoxepin: r = +0.78, p < 0.0001; Spearman's correlation). Furthermore, we found significant correlations between the plasma and CSF <span class="hlt">concentrations</span> of both doxepin (r = +0.71; p < 0.001; Pearson's correlation) and nordoxepin (r = +0.74; p < 0.001). These highly significant correlations between the plasma and CSF <span class="hlt">concentrations</span> indicate a constant CSF permeability of doxepin and its active metabolite nordoxepin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19690000591','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19690000591"><span>Cryogenic flux-<span class="hlt">concentrator</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bailey, B. M.; Brechna, H.; Hill, D. A.</p> <p>1969-01-01</p> <p>Flux <span class="hlt">concentrator</span> has high primary to secondary coupling efficiency enabling it to produce high magnetic fields. The device provides versatility in pulse duration, magnetic field strengths and power sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/987744','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/987744"><span>Water Sample <span class="hlt">Concentrator</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Idaho National Laboratory</p> <p>2009-07-21</p> <p>Automated portable device that <span class="hlt">concentrates</span> and packages a sample of suspected contaminated water for safe, efficient transport to a qualified analytical laboratory. This technology will help safeguard against pathogen contamination or chemical and biolog</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1981STIN...8224484L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1981STIN...8224484L"><span>High <span class="hlt">concentration</span> dust monitor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lilienfeld, P.</p> <p>1981-06-01</p> <p>The development, design, fabrication, and testing of a portable, self-contained prototype monitoring instrument capable of detecting and measuring airborne coal dust levels as <span class="hlt">concentrations</span> in the range of 20 to 500 g/cu m is described. The output of the high <span class="hlt">concentration</span> dust monitor is essentially independent of particle size and composition, with a response time of 10 seconds. Direct <span class="hlt">concentration</span> readout as well as internal memory or recording capabilities are incorporated in the device. The operation of the instrument is based on direct sensing of the mass <span class="hlt">concentration</span> of airborne dust by air-path beta radiation attenuation. The monitor is battery operated and incorporates a microprocessor that controls periodic automatic zero referencing, executes the mass computations, records the data for subsequent playback, and performs internal diagnostic checks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/sciencecinema/biblio/987744','SCIGOVIMAGE-SCICINEMA'); return false;" href="http://www.osti.gov/sciencecinema/biblio/987744"><span>Water Sample <span class="hlt">Concentrator</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/sciencecinema/">ScienceCinema</a></p> <p>Idaho National Laboratory</p> <p>2016-07-12</p> <p>Automated portable device that <span class="hlt">concentrates</span> and packages a sample of suspected contaminated water for safe, efficient transport to a qualified analytical laboratory. This technology will help safeguard against pathogen contamination or chemical and biolog</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AAS...22915604A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AAS...22915604A"><span>Classifying TDSS Stellar <span class="hlt">Variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amaro, Rachael Christina; Green, Paul J.; TDSS Collaboration</p> <p>2017-01-01</p> <p>The Time Domain Spectroscopic Survey (TDSS), a subprogram of SDSS-IV eBOSS, obtains classification/discovery spectra of point-source photometric <span class="hlt">variables</span> selected from PanSTARRS and SDSS multi-color light curves regardless of object color or lightcurve shape. Tens of thousands of TDSS spectra are already available and have been spectroscopically classified both via pipeline and by visual inspection. About half of these spectra are quasars, half are stars. Our goal is to classify the stars with their correct <span class="hlt">variability</span> types. We do this by acquiring public multi-epoch light curves for brighter stars (r<19.5mag) from the Catalina Sky Survey (CSS). We then run a number of light curve analyses from VARTOOLS, a program for analyzing astronomical time-series data, to constrain <span class="hlt">variable</span> type both for broad statistics relevant to future surveys like the Transiting Exoplanet Survey Satellite (TESS) and the Large Synoptic Survey Telescope (LSST), and to find the inevitable exotic oddballs that warrant further follow-up. Specifically, the Lomb-Scargle Periodogram and the Box-Least Squares Method are being implemented and tested against their known <span class="hlt">variable</span> classifications and parameters in the Catalina Surveys Periodic <span class="hlt">Variable</span> Star Catalog. <span class="hlt">Variable</span> star classifications include RR Lyr, close eclipsing binaries, CVs, pulsating white dwarfs, and other exotic systems. The key difference between our catalog and others is that along with the light curves, we will be using TDSS spectra to help in the classification of <span class="hlt">variable</span> type, as spectra are rich with information allowing estimation of physical parameters like temperature, metallicity, gravity, etc. This work was supported by the SDSS Research Experience for Undergraduates program, which is funded by a grant from Sloan Foundation to the Astrophysical Research Consortium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/wri/1988/4025/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/wri/1988/4025/report.pdf"><span>Distribution of gases in the unsaturated zone at a low-level radioactive-waste disposal site near Sheffield, Illinois</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Striegl, Robert G.</p> <p>1988-01-01</p> <p>The unsaturated zone is a medium that provides pneumatic communication for the movement of gases from wastes buried in landfills to the atmosphere, biota, and groundwater. Gases in unsaturated glacial and eolian deposits near a waste-disposal trench at the low-level radioactive-waste disposal site near Sheffield, Bureau County, Illinois, were identified, and the spatial and temporal distributions of the partial pressures of those gases were determined for the period January 1984 through January 1986. Methods for the collection and analyses of the gases are described, as are geologic and hydrologic characteristics of the unsaturated zone that affect gas transport. The identified gases, which are of natural and of waste origin, include nitrogen, oxygen, and argon, carbon dioxide, methane, propane, butane, tritiated water vapor, 14carbon dioxide, and <span class="hlt">222</span> <span class="hlt">radon</span>. <span class="hlt">Concentrations</span> of methane and 14carbon dioxide originated at the waste, as shown by partial-pressure gradients of the gases; 14carbon dioxide partial pressures exceeded natural background partial pressures by factors greater than 1 million at some locations. Variations in partial pressures of oxygen and carbon dioxide were seasonal among piezometers because of increased root and soil-microbe respiration during summer. Variations in methane and 14carbon dioxide partial pressures were apparently related to discrete releases from waste sources at unpredictable intervals of time. No greater than background partial pressures for tritiated water vapor or <span class="hlt">222</span> <span class="hlt">radon</span> were measured. (USGS)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1082936','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1082936"><span>Joined <span class="hlt">concentric</span> tubes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>DeJonghe, Lutgard; Jacobson, Craig; Tucker, Michael; Visco, Steven</p> <p>2013-01-01</p> <p>Tubular objects having two or more <span class="hlt">concentric</span> layers that have different properties are joined to one another during their manufacture primarily by compressive and friction forces generated by shrinkage during sintering and possibly mechanical interlocking. It is not necessary for the <span class="hlt">concentric</span> tubes to display adhesive-, chemical- or sinter-bonding to each other in order to achieve a strong bond. This facilitates joining of dissimilar materials, such as ceramics and metals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4166150','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4166150"><span>METHOD OF ISOTOPE <span class="hlt">CONCENTRATION</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Spevack, J.S.</p> <p>1957-04-01</p> <p>An isotope <span class="hlt">concentration</span> process is described which consists of exchanging, at two or more different temperature stages, two isotopes of an element between substances that are physically separate from each other and each of which is capable of containing either of the isotopes, and withdrawing from a point between at least two of the temperatare stages one of the substances containing an increased <span class="hlt">concentration</span> of the desired isotope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA109928','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA109928"><span>Atmospheric Infrared Radiance <span class="hlt">Variability</span>.</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1981-05-27</p> <p>CO <span class="hlt">concentrations</span> at high altitude. A change in homopause altitude from 110 to2 120 km approximately doubles <span class="hlt">concentrations</span> at higher altitudes, while...altitude model. The problem is in determining a reasonable temperature profile to bridge the gap between 90 and 150 km. In each case, several trials will</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.4351G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.4351G"><span>Seasonal <span class="hlt">Variability</span> in European Radon Measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Groves-Kirkby, C. J.; Denman, A. R.; Phillips, P. S.; Crockett, R. G. M.; Sinclair, J. M.</p> <p>2009-04-01</p> <p>In temperate climates, domestic radon <span class="hlt">concentration</span> levels are generally seasonally dependent, the level in the home reflecting the convolution of two time-dependent functions. These are the source soil-gas radon <span class="hlt">concentration</span> itself, and the principal force driving radon into the building from the soil, namely the pressure-difference between interior and exterior environment. While the meteorological influence can be regarded as relatively uniform on a European scale, its <span class="hlt">variability</span> being defined largely by the influence of North-Atlantic weather systems, soil-gas radon is generally more <span class="hlt">variable</span> as it is essentially geologically dependent. Seasonal <span class="hlt">variability</span> of domestic radon <span class="hlt">concentration</span> can therefore be expected to exhibit geographical <span class="hlt">variability</span>, as is indeed the case. To compensate for the <span class="hlt">variability</span> of domestic radon levels when assessing the long term radon health risks, the results of individual short-term measurements are generally converted to equivalent mean annual levels by application of a Seasonal Correction Factor (SCF). This is a multiplying factor, typically derived from measurements of a large number of homes, applied to the measured short-term radon <span class="hlt">concentration</span> to provide a meaningful annual mean <span class="hlt">concentration</span> for dose-estimation purposes. Following concern as to the universal applicability of a single SCF set, detailed studies in both the UK and France have reported location-specific SCF sets for different regions of each country. Further results indicate that SCFs applicable to the UK differ significantly from those applicable elsewhere in Europe and North America in both amplitude and phase, supporting the thesis that seasonal <span class="hlt">variability</span> in indoor radon <span class="hlt">concentration</span> cannot realistically be compensated for by a single national or international SCF scheme. Published data characterising the seasonal <span class="hlt">variability</span> of European national domestic radon <span class="hlt">concentrations</span>, has been collated and analysed, with the objective of identifying</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817712M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817712M"><span>Forecasting residual herbicide <span class="hlt">concentrations</span> in soil</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McGrath, Gavan; Scanlan, Craig; van Zwieten, Lukas; Rose, Mick; Rose, Terry</p> <p>2016-04-01</p> <p>High <span class="hlt">concentrations</span> of herbicides remaining in soil at the time of planting can adversely impact agricultural production and lead to off-site impacts in streams and groundwater. Being able to forecast the likelihood of residual <span class="hlt">concentrations</span> at specific times in the future offers the potential to improve environmental and economic outcomes. Here we develop a solution for the full transient probability density function for herbicide <span class="hlt">concentrations</span> in soil as a function of rainfall <span class="hlt">variability</span>. Quasi-analytical solutions that account for rainfall seasonality are also demonstrated. In addition, new rapid and relatively cost-effective bioassays to quantify herbicide <span class="hlt">concentrations</span> in near real-time, offers opportunities for data assimilation approaches to improve forecast risks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840014500','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840014500"><span><span class="hlt">Variable</span> stator radial turbine</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rogo, C.; Hajek, T.; Chen, A. G.</p> <p>1984-01-01</p> <p>A radial turbine stage with a <span class="hlt">variable</span> area nozzle was investigated. A high work capacity turbine design with a known high performance base was modified to accept a fixed vane stagger angle moveable sidewall nozzle. The nozzle area was varied by moving the forward and rearward sidewalls. Diffusing and accelerating rotor inlet ramps were evaluated in combinations with hub and shroud rotor exit rings. Performance of contoured sidewalls and the location of the sidewall split line with respect to the rotor inlet was compared to the baseline. Performance and rotor exit survey data are presented for 31 different geometries. Detail survey data at the nozzle exit are given in contour plot format for five configurations. A data base is provided for a <span class="hlt">variable</span> geometry concept that is a viable alternative to the more common pivoted vane <span class="hlt">variable</span> geometry radial turbine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4937352','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4937352"><span><span class="hlt">Variable</span> Lifting Index (VLI)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Waters, Thomas; Occhipinti, Enrico; Colombini, Daniela; Alvarez-Casado, Enrique; Fox, Robert</p> <p>2015-01-01</p> <p>Objective: We seek to develop a new approach for analyzing the physical demands of highly <span class="hlt">variable</span> lifting tasks through an adaptation of the Revised NIOSH (National Institute for Occupational Safety and Health) Lifting Equation (RNLE) into a <span class="hlt">Variable</span> Lifting Index (VLI). Background: There are many jobs that contain individual lifts that vary from lift to lift due to the task requirements. The NIOSH Lifting Equation is not suitable in its present form to analyze <span class="hlt">variable</span> lifting tasks. Method: In extending the prior work on the VLI, two procedures are presented to allow users to analyze <span class="hlt">variable</span> lifting tasks. One approach involves the sampling of lifting tasks performed by a worker over a shift and the calculation of the Frequency Independent Lift Index (FILI) for each sampled lift and the aggregation of the FILI values into six categories. The Composite Lift Index (CLI) equation is used with lifting index (LI) category frequency data to calculate the VLI. The second approach employs a detailed systematic collection of lifting task data from production and/or organizational sources. The data are organized into simplified task parameter categories and further aggregated into six FILI categories, which also use the CLI equation to calculate the VLI. Results: The two procedures will allow practitioners to systematically employ the VLI method to a variety of work situations where highly <span class="hlt">variable</span> lifting tasks are performed. Conclusions: The scientific basis for the VLI procedure is similar to that for the CLI originally presented by NIOSH; however, the VLI method remains to be validated. Application: The VLI method allows an analyst to assess highly <span class="hlt">variable</span> manual lifting jobs in which the task characteristics vary from lift to lift during a shift. PMID:26646300</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050214050&hterms=Radius&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DRadius','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050214050&hterms=Radius&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DRadius"><span><span class="hlt">Variable</span> Radius Nacelle Studies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McGowan, David M.</p> <p>2001-01-01</p> <p>An overview of the active shape control for a <span class="hlt">variable</span> radius nacelle leading edge program is presented. The current technical plan and schedule will be discussed. Results from the structural shape change of curved plates demonstration will be presented, as well as the NASA LaRC concept for a <span class="hlt">variable</span> radius nacelle leading edge. Results of a Boeing systems integration study of this concept will be discussed briefly. The status of the sensors, actuators, and computational design tools tasks will also be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1159845','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1159845"><span>Resonance-shifting luminescent solar <span class="hlt">concentrators</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Giebink, Noel Christopher; Wiederrecht, Gary P; Wasielewski, Michael R</p> <p>2014-09-23</p> <p>An optical system and method to overcome luminescent solar <span class="hlt">concentrator</span> inefficiencies by resonance-shifting, in which sharply directed emission from a bi-layer cavity into a glass substrate returns to interact with the cavity off-resonance at each subsequent reflection, significantly reducing reabsorption loss en route to the edges. In one embodiment, the system comprises a luminescent solar <span class="hlt">concentrator</span> comprising a transparent substrate, a luminescent film having a <span class="hlt">variable</span> thickness; and a low refractive index layer disposed between the transparent substrate and the luminescent film.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1174716','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1174716"><span>Airborne agent <span class="hlt">concentration</span> analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Gelbard, Fred</p> <p>2004-02-03</p> <p>A method and system for inferring airborne contaminant <span class="hlt">concentrations</span> in rooms without contaminant sensors, based on data collected by contaminant sensors in other rooms of a building, using known airflow interconnectivity data. The method solves a least squares problem that minimizes the difference between measured and predicted contaminant sensor <span class="hlt">concentrations</span> with respect to an unknown contaminant release time. Solutions are constrained to providing non-negative initial contaminant <span class="hlt">concentrations</span> in all rooms. The method can be used to identify a near-optimal distribution of sensors within the building, when then number of available sensors is less than the total number of rooms. This is achieved by having a system-sensor matrix that is non-singular, and by selecting that distribution which yields the lowest condition number of all the distributions considered. The method can predict one or more contaminant initial release points from the collected data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.109c1907S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.109c1907S"><span>Thermal cloak-<span class="hlt">concentrator</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shen, Xiangying; Li, Ying; Jiang, Chaoran; Ni, Yushan; Huang, Jiping</p> <p>2016-07-01</p> <p>For macroscopically manipulating heat flow at will, thermal metamaterials have opened a practical way, which possesses a single function, such as either cloaking or <span class="hlt">concentrating</span> the flow of heat even though environmental temperature varies. By developing a theory of transformation heat transfer for multiple functions, here we introduce the concept of intelligent thermal metamaterials with a dual function, which is in contrast to the existing thermal metamaterials with single functions. By assembling homogeneous isotropic materials and shape-memory alloys, we experimentally fabricate a kind of intelligent thermal metamaterials, which can automatically change from a cloak (or <span class="hlt">concentrator</span>) to a <span class="hlt">concentrator</span> (or cloak) when the environmental temperature changes. This work paves an efficient way for a controllable gradient of heat, and also provides guidance both for arbitrarily manipulating the flow of heat and for efficiently designing similar intelligent metamaterials in other fields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1243033','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1243033"><span>Photovoltaic solar <span class="hlt">concentrator</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Nielson, Gregory N.; Gupta, Vipin P.; Okandan, Murat; Watts, Michael R.</p> <p>2016-03-15</p> <p>A photovoltaic solar <span class="hlt">concentrator</span> is disclosed with one or more transverse-junction solar cells (also termed point contact solar cells) and a lens located above each solar cell to <span class="hlt">concentrate</span> sunlight onto the solar cell to generate electricity. Piezoelectric actuators tilt or translate each lens to track the sun using a feedback-control circuit which senses the electricity generated by one or more of the solar cells. The piezoelectric actuators can be coupled through a displacement-multiplier linkage to provide an increased range of movement of each lens. Each lens in the solar <span class="hlt">concentrator</span> can be supported on a frame (also termed a tilt plate) having three legs, with the movement of the legs being controlled by the piezoelectric actuators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1082448','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1082448"><span>Photovoltaic solar <span class="hlt">concentrator</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Nielson, Gregory N.; Okandan, Murat; Resnick, Paul J.; Cruz-Campa, Jose Luis</p> <p>2012-12-11</p> <p>A photovoltaic solar <span class="hlt">concentrator</span> is disclosed with one or more transverse-junction solar cells (also termed point contact solar cells) and a lens located above each solar cell to <span class="hlt">concentrate</span> sunlight onto the solar cell to generate electricity. Piezoelectric actuators tilt or translate each lens to track the sun using a feedback-control circuit which senses the electricity generated by one or more of the solar cells. The piezoelectric actuators can be coupled through a displacement-multiplier linkage to provide an increased range of movement of each lens. Each lens in the solar <span class="hlt">concentrator</span> can be supported on a frame (also termed a tilt plate) having three legs, with the movement of the legs being controlled by the piezoelectric actuators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6838561','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6838561"><span><span class="hlt">Concentrating</span> photovoltaic technology</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Edenburn, M.W.</p> <p>1984-01-01</p> <p>This paper will summarize the status and discuss likely future directions of photovoltaic <span class="hlt">concentrator</span> technology. A current commercial Si cell module has a peak efficiency of 15.5%, and 17% has been reached with an experimental module. Advanced cells and module design improvements offer still higher efficiencies. <span class="hlt">Concentrator</span> Fresnel lens array fields installed several years ago have all demonstrated very good electrical performance with little performance degradation. Fresnel lens arrays were commercially available and prices of $7/watt for installed one megawatt systems have been quoted. Cost projections predict that current technology <span class="hlt">concentrating</span> PV arrays can be installed for less than $2/watt if they are manufactured in large, steady quantities. More advanced designs may cost even less.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100011129','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100011129"><span>Hydrogen Peroxide <span class="hlt">Concentrator</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parrish, Clyde F.</p> <p>2007-01-01</p> <p>A relatively simple and economical process and apparatus for <span class="hlt">concentrating</span> hydrogen peroxide from aqueous solution at the point of use have been invented. The heart of the apparatus is a vessel comprising an outer shell containing tubular membranes made of a polymer that is significantly more permeable by water than by hydrogen peroxide. The aqueous solution of hydrogen peroxide to be <span class="hlt">concentrated</span> is fed through the interstitial spaces between the tubular membranes. An initially dry sweep gas is pumped through the interiors of the tubular membranes. Water diffuses through the membranes and is carried away as water vapor mixed into the sweep gas. Because of the removal of water, the hydrogen peroxide solution flowing from the vessel at the outlet end is more <span class="hlt">concentrated</span> than that fed into the vessel at the inlet end. The sweep gas can be air, nitrogen, or any other gas that can be conveniently supplied in dry form and does not react chemically with hydrogen peroxide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860019702','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860019702"><span>Nebulization reflux <span class="hlt">concentrator</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Collins, V. G.; Cofer, W. R., III</p> <p>1986-01-01</p> <p>A nebulization reflux <span class="hlt">concentrator</span> for removing trace gas contaminants from a sample gas is described. Sample gas from a gas supply is drawn by a suction source into a vessel. The gas enters the vessel through an atomizing nozzle, thereby atomizing and entraining a scrubbing liquid solvent drawn through a siphon tube from a scrubbing liquid reservoir. The gas and entrained liquid rise through a <span class="hlt">concentrator</span> and impinge upon a solvent phobic filter, whereby purified gas exits through the filter housing and contaminated liquid coalesces on the solvent phobic filter and falls into the reservoir.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=sociometry&id=EJ599105','ERIC'); return false;" href="http://eric.ed.gov/?q=sociometry&id=EJ599105"><span>Inner-City Schools: A Multiple-<span class="hlt">Variable</span> Discussion.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Van Horn, Royal</p> <p>1999-01-01</p> <p>Reviews <span class="hlt">variables</span> from several disciplines relevant to understanding and improving inner-city schools. Neighborhood and other sociological <span class="hlt">variables</span>, such as the <span class="hlt">concentration</span> effects of living in poverty areas, are significant. So are teacher competence, school climate, faculty sociometry, student background, and entry-level factors, including…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/7035681','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/7035681"><span>Continuously <span class="hlt">variable</span> transmission</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Itoh, H.; Okada, M.</p> <p>1986-11-25</p> <p>This patent describes a continuously <span class="hlt">variable</span> transmission for transmitting a torque from an engine to a final reduction gear, comprising: an input shaft connected with the engine at one end thereof; a continuously <span class="hlt">variable</span> transmission means having a driving pulley with a fixed member and a movable member, the movable member being actuated by an hydraulic cylinder to form a V-shaped opening between the fixed member and movable member, a driven pulley with another fixed member and another movable member. The other movable member is similarly actuated by another hydraulic cylinder to form another V-shaped opening between the other fixed member and the other movable member, and a belt member spanning the pulleys provides for a continuously <span class="hlt">variable</span> transmission ratio; a planetary gear unit including a sun gear, a plurality of pinion gears which mesh with the sun gear and are connected with the driven pulley and a ring gear which meshes with the plurality of pinion gears; and a rotation transmitting means for transmitting rotation of the input shaft to the planetary gear unit. The rotation transmitting means is provided between the input shaft and the planetary gear unit and includes a shaft connected with the sun gear of the planetary gear unit and a first gear connected with the input shaft. The first gear is located between the engine and the continuously <span class="hlt">variable</span> transmission means.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/873348','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/873348"><span><span class="hlt">Variable</span> thrust cartridge</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Taleyarkhan, Rusi P.</p> <p>2000-11-07</p> <p>The present invention is a <span class="hlt">variable</span> thrust cartridge comprising a water-molten aluminum reaction chamber from which a slug is propelled. The cartridge comprises a firing system that initiates a controlled explosion from the reaction chamber. The explosive force provides a thrust to a slug, preferably contained within the cartridge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19830011469','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19830011469"><span><span class="hlt">Variable</span> camber rotor study</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dadone, L.; Cowan, J.; Mchugh, F. J.</p> <p>1982-01-01</p> <p>Deployment of <span class="hlt">variable</span> camber concepts on helicopter rotors was analytically assessed. It was determined that <span class="hlt">variable</span> camber extended the operating range of helicopters provided that the correct compromise can be obtained between performance/loads gains and mechanical complexity. A number of <span class="hlt">variable</span> camber concepts were reviewed on a two dimensional basis to determine the usefulness of leading edge, trailing edge and overall camber variation schemes. The most powerful method to vary camber was through the trailing edge flaps undergoing relatively small motions (-5 deg to +15 deg). The aerodynamic characteristics of the NASA/Ames A-1 airfoil with 35% and 50% plain trailing edge flaps were determined by means of current subcritical and transonic airfoil design methods and used by rotor performance and loads analysis codes. The most promising <span class="hlt">variable</span> camber schedule reviewed was a configuration with a 35% plain flap deployment in an on/off mode near the tip of a blade. Preliminary results show approximately 11% reduction in power is possible at 192 knots and a rotor thrust coefficient of 0.09. The potential demonstrated indicates a significant potential for expanding the operating envelope of the helicopter. Further investigation into improving the power saving and defining the improvement in the operational envelope of the helicopter is recommended.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=229992','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=229992"><span><span class="hlt">Variable</span> Rate Irrigation</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Systems are available to producers with the ability to make <span class="hlt">variable</span>-rate applications of defoliants, fertilizer, lime, pesticides, plant growth regulators, and seed. These systems could potentially offer a producer great cost savings; however, the full potential of these benefits and savings cannot...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=271221','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=271221"><span><span class="hlt">Variable</span> rate irrigation</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Systems are available to producers to make <span class="hlt">variable</span>-rate applications of defoliants, fertilizer, lime, pesticides, plant growth regulators, and seed. These systems could potentially offer cost savings to a producer; however, the full potential of the benefits and savings cannot be realized if water ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890009953','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890009953"><span><span class="hlt">Variable</span> gravity research facility</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Allan, Sean; Ancheta, Stan; Beine, Donna; Cink, Brian; Eagon, Mark; Eckstein, Brett; Luhman, Dan; Mccowan, Daniel; Nations, James; Nordtvedt, Todd</p> <p>1988-01-01</p> <p>Spin and despin requirements; sequence of activities required to assemble the <span class="hlt">Variable</span> Gravity Research Facility (VGRF); power systems technology; life support; thermal control systems; emergencies; communication systems; space station applications; experimental activities; computer modeling and simulation of tether vibration; cost analysis; configuration of the crew compartments; and tether lengths and rotation speeds are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=218732&keyword=contour&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=77819095&CFTOKEN=36884355','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=218732&keyword=contour&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=77819095&CFTOKEN=36884355"><span>Lake Ontario: Nearshore <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>We conducted a high-resolution survey with towed electronic instrumentation along the Lake Ontario nearshore (720 km) at a 20 meter contour. The survey was conducted September 6-10, 2008 with a shorter 300 km survey conducted August 14-15 for comparing of temporal <span class="hlt">variability</span>. ...</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910013733','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910013733"><span><span class="hlt">Variable</span> polarity arc welding</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bayless, E. O., Jr.</p> <p>1991-01-01</p> <p>Technological advances generate within themselves dissatisfactions that lead to further advances in a process. A series of advances in welding technology which culminated in the <span class="hlt">Variable</span> Polarity Plasma Arc (VPPA) Welding Process and an advance instituted to overcome the latest dissatisfactions with the process: automated VPPA welding are described briefly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=231289','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=231289"><span>Genetic <span class="hlt">variability</span> in Macadamia</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>A genetic <span class="hlt">variability</span> analysis involving 45 accessions of Macadamia including four species, M. integrifolia, M. tetraphylla, M. ternifolia, and M. hildebrandii and a wild relative, Hicksbeachia pinnatifolia was performed usingeight enzyme systems encoded by 16 loci (Gpi-1 and 2, Idh-1 and 2, Lap, Md...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040016375&hterms=tide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtide','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040016375&hterms=tide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtide"><span>Tides and Decadal <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ray, Richard D.</p> <p>2003-01-01</p> <p>This paper reviews the mechanisms by which oceanic tides and decadal <span class="hlt">variability</span> in the oceans are connected. We distinguish between <span class="hlt">variability</span> caused by tides and <span class="hlt">variability</span> observed in the tides themselves. Both effects have been detected at some level. The most obvious connection with decadal timescales is through the 18.6-year precession of the moon's orbit plane. This precession gives rise to a small tide of the same period and to 18.6-year modulations in the phase and amplitudes of short-period tides. The 18.6-year "node tide" is very small, no more than 2 cm anywhere, and in sea level data it is dominated by the ocean's natural <span class="hlt">Variability</span>. Some authors have naively attributed climate variations with periods near 19 years directly to the node tide, but the amplitude of the tide is too small for this mechanism to be operative. The more likely explanation (Loder and Garrett, JGR, 83, 1967-70, 1978) is that the 18.6-y modulations in short-period tides, especially h e principal tide M2, cause variations in ocean mixing, which is then observed in temperature and other climatic indicators. Tidally forced <span class="hlt">variability</span> has also been proposed by some authors, either in response to occasional (and highly predictable) tidal extremes or as a nonlinear low-frequency oscillation caused by interactions between short-period tides. The former mechanism can produce only short-duration events hardly more significant than normal tidal ranges, but the latter mechanism can in principle induce low-frequency oscillations. The most recent proposal of this type is by Keeling and Whorf, who highlight the 1800-year spectral peak discovered by Bond et al. (1997). But the proposal appears contrived and should be considered, in the words of Munk et al. (2002), "as the most likely among unlikely candidates."</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19760000253&hterms=solar+dryer&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsolar%2Bdryer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19760000253&hterms=solar+dryer&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsolar%2Bdryer"><span>Solar <span class="hlt">concentrator</span>/absorber</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Von Tiesenhausen, G. F.</p> <p>1976-01-01</p> <p>Collector/energy converter, consisting of dual-slope optical <span class="hlt">concentrator</span> and counterflow thermal energy absorber, is attached to multiaxis support structure. Efficient over wide range of illumination levels, device may be used to generate high temperature steam, serve as solar powered dryer, or power absorption cycle cooler.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=flotation&id=EJ722387','ERIC'); return false;" href="http://eric.ed.gov/?q=flotation&id=EJ722387"><span>Dilution, <span class="hlt">Concentration</span>, and Flotation</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Liang, Ling; Schmuckler, Joseph S.</p> <p>2004-01-01</p> <p>As both classroom teaching practice and literature show, many students have difficulties learning science concepts such as density. Here are some investigations that identify the relationship between density and floating through experimenting with successive dilution of a liquid, or the systematic change of <span class="hlt">concentration</span> of a saltwater solution.…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1182608','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1182608"><span>Scattering Solar Thermal <span class="hlt">Concentrators</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Giebink, Noel C.</p> <p>2015-01-31</p> <p>This program set out to explore a scattering-based approach to <span class="hlt">concentrate</span> sunlight with the aim of improving collector field reliability and of eliminating wind loading and gross mechanical movement through the use of a stationary collection optic. The approach is based on scattering sunlight from the focal point of a fixed collection optic into the confined modes of a sliding planar waveguide, where it is transported to stationary tubular heat transfer elements located at the edges. Optical design for the first stage of solar <span class="hlt">concentration</span>, which entails focusing sunlight within a plane over a wide range of incidence angles (>120 degree full field of view) at fixed tilt, led to the development of a new, folded-path collection optic that dramatically out-performs the current state-of-the-art in scattering <span class="hlt">concentration</span>. Rigorous optical simulation and experimental testing of this collection optic have validated its performance. In the course of this work, we also identified an opportunity for <span class="hlt">concentrating</span> photovoltaics involving the use of high efficiency microcells made in collaboration with partners at the University of Illinois. This opportunity exploited the same collection optic design as used for the scattering solar thermal <span class="hlt">concentrator</span> and was therefore pursued in parallel. This system was experimentally demonstrated to achieve >200x optical <span class="hlt">concentration</span> with >70% optical efficiency over a full day by tracking with <1 cm of lateral movement at fixed latitude tilt. The entire scattering <span class="hlt">concentrator</span> waveguide optical system has been simulated, tested, and assembled at small scale to verify ray tracing models. These models were subsequently used to predict the full system optical performance at larger, deployment scale ranging up to >1 meter aperture width. Simulations at an aperture widths less than approximately 0.5 m with geometric gains ~100x predict an overall optical efficiency in the range 60-70% for angles up to 50 degrees from normal. However, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17162334','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17162334"><span>Mineral <span class="hlt">variability</span> among 177 commercial noni juices.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>West, Brett J; Tolson, Charles B; Vest, Randy G; Jensen, Summer; Lundell, Travis G</p> <p>2006-01-01</p> <p>The popularity of noni juice is increasing globally. As such, knowledge of its nutritional properties is needed to make informed decisions regarding its use. This industry-wide mineral profile was determined by analyses of 177 brands of commercial noni juice according to a modified Association of Official Analytical Chemists protocol. A large degree of <span class="hlt">variability</span> was found in the <span class="hlt">concentrations</span> of nine minerals. While potassium was found to be the most prominent mineral, its <span class="hlt">concentration</span> in most commercial brands is of minor nutritional significance. The wide <span class="hlt">variability</span> among the many brands of commercial noni juice precludes the assumption that all are the same. Many have a different nutrient profile to that published by the European Union for Tahitian Noni Juice. Such variances may thus require consumers, dieticians, and other healthcare professionals to obtain unlabelled nutrient information from manufacturers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014IAUS..298..265E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014IAUS..298..265E"><span>Gaia and <span class="hlt">variable</span> stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eyer, Laurent; Holl, Berry; Mowlavi, Nami</p> <p>2014-01-01</p> <p>The study of <span class="hlt">variable</span> phenomena (periodic, irregular or transient) provides a unique way to acquire knowledge about objects in our Universe. Currently, we are going through a rapid expansion of time-domain astrophysics. One reason for this expansion is the technological developments materialised in small to medium size observational projects such as HAT, OGLE, Catalina, PTF and upcoming very large projects such as Gaia or LSST. In this article, we are focusing on the ESA cornerstone mission Gaia. This spacecraft will provide astrometric, photometric and spectroscopic measurements for one billion stars. Among the existing and planned multi-epoch projects Gaia is unique because it will provide exquisite astrometric measurements for all objects it observes. We provide a brief overview of the literature concerning this mission and its expected contribution to <span class="hlt">variability</span> studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9292123','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9292123"><span>Medical examiner <span class="hlt">variability</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hinchcliffe, R</p> <p>1997-01-01</p> <p>There are undoubtedly many factors that contribute to inter-examiner <span class="hlt">variability</span> relevant to the use of medical practitioners in justiciable matters. One source of <span class="hlt">variability</span> with regard to claims relating to hearing disorders could well be the training and 'calibration' of medical examiners. A tentative analysis of the examination papers and of the declared roles of the specialties that provide these examiners lends support to such a thesis. One solution would be to train special specialists for medicolegal work, as envisaged by Boyarsky for forensic urology (Boyarsky, 1996). At the same time there is the need to change the role-perception of many examiners. There is also the need for medical examiners to express honest, unbiased opinions. There are also problems inherent in the litigation process which does not promote the interactive and adaptive processes between experts that characterise scientific discussions and enquiry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12336394','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12336394"><span>[Socioeconomic <span class="hlt">variables</span> and fertility].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Arguello, O</p> <p>1980-08-01</p> <p>While making comparative analyses of data collected by the World Fertility Survey regarding Latin America, a group of investigators of CELADE (Centro Latinoamericano de Demografia) realized that the selection of economic <span class="hlt">variables</span> for the study of fertility had serious limitations. Such limitations did not allow the elaboration of a theory which took into account the complicated process of fertility, in all its socioeconomic, cultural, and psychological manifestations. Thus, this paper intends to lay the theoretical basis for the selection of all relevant <span class="hlt">variables</span>, distinguishing, for example, the average fertility of women according to area of residence, place of early socialization, migrant status, social status, occupation of husband, level of instruction, occupation, and all changes in occupational activities of women in fertile age.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/907959','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/907959"><span><span class="hlt">Variable</span> Permanent Magnet Quadrupole</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mihara, T.; Iwashita, Y.; Kumada, M.; Spencer, C.M.; /SLAC</p> <p>2007-05-23</p> <p>A permanent magnet quadrupole (PMQ) is one of the candidates for the final focus lens in a linear collider. An over 120 T/m strong <span class="hlt">variable</span> permanent magnet quadrupole is achieved by the introduction of saturated iron and a 'double ring structure'. A fabricated PMQ achieved 24 T integrated gradient with 20 mm bore diameter, 100 mm magnet diameter and 20 cm pole length. The strength of the PMQ is adjustable in 1.4 T steps, due to its 'double ring structure': the PMQ is split into two nested rings; the outer ring is sliced along the beam line into four parts and is rotated to change the strength. This paper describes the <span class="hlt">variable</span> PMQ from fabrication to recent adjustments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880035410&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DVariable%2Bstars','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880035410&hterms=Variable+stars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DVariable%2Bstars"><span>Intrinsically <span class="hlt">variable</span> stars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bohm-Vitense, Erika; Querci, Monique</p> <p>1987-01-01</p> <p>The characteristics of intrinsically <span class="hlt">variable</span> stars are examined, reviewing the results of observations obtained with the IUE satellite since its launch in 1978. Selected data on both medium-spectral-class pulsating stars (Delta Cep stars, W Vir stars, and related groups) and late-type <span class="hlt">variables</span> (M, S, and C giants and supergiants) are presented in spectra, graphs, and tables and described in detail. Topics addressed include the calibration of the the period-luminosity relation, Cepheid distance determination, checking stellar evolution theory by the giant companions of Cepheids, Cepheid masses, the importance of the hydrogen convection zone in Cepheids, temperature and abundance estimates for Population II pulsating stars, mass loss in Population II Cepheids, SWP and LWP images of cold giants and supergiants, temporal variations in the UV lines of cold stars, C-rich cold stars, and cold stars with highly ionized emission lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27207811','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27207811"><span>Microbial <span class="hlt">variability</span> in growth and heat resistance of a pathogen and a spoiler: All <span class="hlt">variabilities</span> are equal but some are more equal than others.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>den Besten, Heidy M W; Aryani, Diah C; Metselaar, Karin I; Zwietering, Marcel H</p> <p>2017-01-02</p> <p>Quantitative microbiology is used in risk assessment studies, microbial shelf life studies, product development, and experimental design. Realistic prediction is, however, complicated by different sources of <span class="hlt">variability</span>. The final <span class="hlt">concentration</span> of microorganisms at the moment of consumption is affected by different sources of <span class="hlt">variability</span>: <span class="hlt">variability</span> in the storage times and temperatures, <span class="hlt">variability</span> in product characteristics, <span class="hlt">variability</span> in process characteristics, <span class="hlt">variability</span> in the initial contamination of the raw materials, and last but not least, microbiological <span class="hlt">variability</span>. This article compares different sources of microbiological <span class="hlt">variability</span> in growth and inactivation kinetics of a pathogen and a spoiler, namely experimental <span class="hlt">variability</span>, reproduction <span class="hlt">variability</span> (within strain <span class="hlt">variability</span>), strain <span class="hlt">variability</span> (between strain <span class="hlt">variability</span>) and <span class="hlt">variability</span> between individual cells within a population (population heterogeneity). Comparison of the different sources of microbiological <span class="hlt">variability</span> also allows to prioritize their importance. In addition, the microbiological <span class="hlt">variability</span> is compared to other <span class="hlt">variability</span> factors encountered in a model food chain to evaluate the impact of different <span class="hlt">variability</span> factors on the <span class="hlt">variability</span> in microbial levels encountered in the final product.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020048546','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020048546"><span>Climate <span class="hlt">Variability</span> Program</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Halpern, David (Editor)</p> <p>2002-01-01</p> <p>The Annual Report of the Climate <span class="hlt">Variability</span> Program briefly describes research activities of Principal Investigators who are funded by NASA's Earth Science Enterprise Research Division. The report is focused on the year 2001. Utilization of satellite observations is a singularity of research on climate science and technology at JPL (Jet Propulsion Laboratory). Research at JPL has two foci: generate new knowledge and develop new technology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/870298','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/870298"><span><span class="hlt">Variable</span> depth core sampler</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Bourgeois, Peter M.; Reger, Robert J.</p> <p>1996-01-01</p> <p>A <span class="hlt">variable</span> depth core sampler apparatus comprising a first circular hole saw member, having longitudinal sections that collapses to form a point and capture a sample, and a second circular hole saw member residing inside said first hole saw member to support the longitudinal sections of said first hole saw member and prevent them from collapsing to form a point. The second hole saw member may be raised and lowered inside said first hole saw member.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/131953','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/131953"><span><span class="hlt">Variable</span> reluctance drive system</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lipo, T.A.; Liang, F.</p> <p>1995-10-17</p> <p>A <span class="hlt">variable</span> reluctance drive system including a motor and corresponding converter for improved current commutation is described. The motor incorporates a salient pole rotor and a salient pole stator having one or more full pitch windings which operate by mutual inductance to transfer the current from the active short pitch winding following phase alignment. This increases output torque and/or speed and permits a number of simple and economical converter circuits. 17 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/866742','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/866742"><span><span class="hlt">Variable</span> laser attenuator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Foltyn, Stephen R.</p> <p>1988-01-01</p> <p>The disclosure relates to low loss, high power <span class="hlt">variable</span> attenuators comprng one or more transmissive and/or reflective multilayer dielectric filters. The attenuator is particularly suitable to use with unpolarized lasers such as excimer lasers. Beam attenuation is a function of beam polarization and the angle of incidence between the beam and the filter and is controlled by adjusting the angle of incidence the beam makes to the filter or filters. Filters are selected in accordance with beam wavelength.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6808499','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/6808499"><span><span class="hlt">Variable</span> laser attenuator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Foltyn, S.R.</p> <p>1987-05-29</p> <p>The disclosure relates to low loss, high power <span class="hlt">variable</span> attenuators comprising one or more transmissive and/or reflective multilayer dielectric filters. The attenuator is particularly suitable to use with unpolarized lasers such as excimer lasers. Beam attenuation is a function of beam polarization and the angle of incidence between the beam and the filter and is controlled by adjusting the angle of incidence the beam makes to the filter or filters. Filters are selected in accordance with beam wavelength. 9 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1009258','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1009258"><span><span class="hlt">Variable</span> Camber Morphing Wings</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2016-02-02</p> <p>exploring smart materials , aiming at achieving more efficient morphing capability in terms of control authority and energy consump- tion. Other specific...collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION. 1. REPORT...methodology of <span class="hlt">variable</span> camber morphing wings based on the use of active materials , namely piezoelectric materials and shape memory alloys. The research work</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/862467','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/862467"><span><span class="hlt">Variable</span> percentage sampler</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Miller, Jr., William H.</p> <p>1976-01-01</p> <p>A remotely operable sampler is provided for obtaining <span class="hlt">variable</span> percentage samples of nuclear fuel particles and the like for analyses. The sampler has a rotating cup for a sample collection chamber designed so that the effective size of the sample inlet opening to the cup varies with rotational speed. Samples of a desired size are withdrawn from a flowing stream of particles without a deterrent to the flow of remaining particles.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150022091','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150022091"><span><span class="hlt">Concentric</span> Split Flow Filter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stapleton, Thomas J. (Inventor)</p> <p>2015-01-01</p> <p>A <span class="hlt">concentric</span> split flow filter may be configured to remove odor and/or bacteria from pumped air used to collect urine and fecal waste products. For instance, filter may be designed to effectively fill the volume that was previously considered wasted surrounding the transport tube of a waste management system. The <span class="hlt">concentric</span> split flow filter may be configured to split the air flow, with substantially half of the air flow to be treated traveling through a first bed of filter media and substantially the other half of the air flow to be treated traveling through the second bed of filter media. This split flow design reduces the air velocity by 50%. In this way, the pressure drop of filter may be reduced by as much as a factor of 4 as compare to the conventional design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/351648','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/351648"><span><span class="hlt">Variable</span> displacement vane pump</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tschantz, J.S.; Bisson, B.J.</p> <p>1997-12-31</p> <p>What has been developed under this program is a pumping system which can vary the amount of fuel delivered according to engine needs, thereby reducing the temperature rise of the fuel to very low levels. This permits the elimination of the air/oil coolers and conserves the vital airflow through the fan. The <span class="hlt">variable</span> displacement vane pump (VDVP) also permits a substantial simplification of the control system with the elimination of complex metering valves, offering a significant reduction in fuel system cost. This program was initiated to develop a technology that embodied the ruggedness of the gear pump with the efficiency and metering versatility of the <span class="hlt">variable</span> displacement vane pump. Thick metal vanes emulate the teeth on pumping gears while the simple, elegant swing cam feature provides the <span class="hlt">variable</span> displacement capability without the unwieldy multiple cam segments found in other concepts. The result is a pumping architecture which is rugged, light in weight and extremely versatile, having demonstrated superb heat management and controllability in extensive bench and engine testing. This paper will report the results that the pumps have achieved to date both in terms of durability and efficiency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6628813','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6628813"><span>Cyclindrical <span class="hlt">concentrators</span> as a limit case of torodial <span class="hlt">concentrators</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Minano, J.C.</p> <p>1984-06-15</p> <p>Cylindrical <span class="hlt">concentrators</span> are viewed as a limit case of torodial <span class="hlt">concentrators</span> with the purpose of applying to them some results obtained for axisymmetrical optical systems. This enables us to obtain easily the directional intercept factor of a cyclindrical nonimaging <span class="hlt">concentrator</span> called the Ideal Tubular <span class="hlt">Concentrator</span>. A useful tool for designing new cylindrical <span class="hlt">concentrators</span> is also derived.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090039429','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090039429"><span>Electrolyte <span class="hlt">Concentrates</span> Treat Dehydration</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2009-01-01</p> <p>Wellness Brands Inc. of Boulder, Colorado, exclusively licensed a unique electrolyte <span class="hlt">concentrate</span> formula developed by Ames Research Center to treat and prevent dehydration in astronauts returning to Earth. Marketed as The Right Stuff, the company's NASA-derived formula is an ideal measure for athletes looking to combat dehydration and boost performance. Wellness Brands also plans to expand with products that make use of the formula's effective hydration properties to help treat conditions including heat stroke, altitude sickness, jet lag, and disease.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009344','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009344"><span>X-Ray <span class="hlt">Variability</span> and the Secondary Star</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Corcoran, M. F.; Ishibashi, K.</p> <p>2012-01-01</p> <p>We discuss the history of X-ray observations of the 11 Car system, <span class="hlt">concentrating</span> on the periodic <span class="hlt">variability</span> discovered in the 1990s. We discuss the interpretation of these variations, <span class="hlt">concentrating</span> on a model of the system as a "collidingwind" binary. This interpretation allows the physical and orbital parameters of eta Car and its companion star to be constrained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20002109','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20002109"><span>Isoprene reaction product <span class="hlt">concentrations</span> in central Texas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Friedfeld, S.J.; Fraser, M.P.</p> <p>1999-07-01</p> <p>Biogenic hydrocarbons play an important role in the formation of tropospheric ozone. Studies have shown that Texas contains significant amounts of vegetation types that emit isoprene. In this study the atmospheric <span class="hlt">concentrations</span> of methacrolein, formaldehyde, and other carbonyls were measured using the 2,4-dinitrophenyl hydrazine (DNPH) derivatization method on C18 cartridges and analyzed using high performance liquid chromatography (HPLC) with UV detection. Isoprene samples were collected concurrently by another group using stainless steel canisters and analyzed with GC-FID. The measurements were taken at one urban and three rural sites in Central Texas over a two-week period in August 1998. This paper reports the carbonyl <span class="hlt">concentrations</span> observed, compares the <span class="hlt">concentrations</span> with other studies, and discusses the temporal and spatial <span class="hlt">variability</span> of the results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AtmEn..45..174K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AtmEn..45..174K"><span>Tropospheric ozone <span class="hlt">variability</span> over the Iberian Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kulkarni, Pavan S.; Bortoli, D.; Salgado, R.; Antón, M.; Costa, M. J.; Silva, A. M.</p> <p>2011-01-01</p> <p>To study tropospheric ozone <span class="hlt">variability</span> over the Iberian Peninsula (IP), NASA Langley TOR data have been analyzed for the 1979-2005 period. The maximum tropospheric ozone <span class="hlt">concentration</span> over the entire IP was found in June (˜41 DU) and a minimum in December (˜29 DU). However the maximum tropospheric ozone <span class="hlt">concentration</span> was found over West Atlantic Coast (WAC) (˜44 DU), followed by Mediterranean Coast (MC) (˜42 DU), North Atlantic Coast (NAC) (˜41 DU), Central Iberian Peninsula (CIP) (˜40 DU) and Pyrenees Mountain Range (PMR) (˜39 DU) during June-July. The high <span class="hlt">concentration</span> of tropospheric ozone in July over the Atlantic Ocean near IP is due to the presence of Azores anticyclone and related photochemistry and dynamics, and affects the observed higher tropospheric ozone <span class="hlt">concentration</span> over WAC zone. Strong seasonal cycle in tropospheric ozone <span class="hlt">concentration</span> has been observed with large variation over NAC (˜49%), followed by WAC (˜48%) and MC (˜41%) compared to CIP and PMR (˜38%) zones. When the data are compared over the IP for the two periods (1979-1993 and 1997-2005), a systematic increase in the number of months with higher tropospheric ozone <span class="hlt">concentration</span> has been observed during the second period with respect to the first. These increases are almost 8% to 24% over NAC, 6% to 17% over WAC, 5% to 24% over CIP, 6% to 23% over MC and 13% to 18% over PMR, zones. It has been observed that topography, climatology and population density distribution plays a crucial role in the <span class="hlt">variability</span> of tropospheric ozone <span class="hlt">concentration</span> over the IP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1121068','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1121068"><span>Present and Future Modes of Low Frequency Climate <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cane, Mark A.</p> <p>2014-02-20</p> <p>This project addressed area (1) of the FOA, “Interaction of Climate Change and Low Frequency Modes of Natural Climate Variability”. Our overarching objective is to detect, describe and understand the changes in low frequency <span class="hlt">variability</span> between model simulations of the preindustrial climate and simulations of a doubled CO2 climate. The deliverables are a set of papers providing a dynamical characterization of interannual, decadal, and multidecadal <span class="hlt">variability</span> in coupled models with attention to the changes in this low frequency <span class="hlt">variability</span> between pre-industrial <span class="hlt">concentrations</span> of greenhouse gases and a doubling of atmospheric <span class="hlt">concentrations</span> of CO2. The principle mode of analysis, singular vector decomposition, is designed to advance our physical, mechanistic understanding. This study will include external natural <span class="hlt">variability</span> due to solar and volcanic aerosol variations as well as <span class="hlt">variability</span> internal to the climate system. An important byproduct is a set of analysis tools for estimating global singular vector structures from the archived output of model simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1191490','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1191490"><span><span class="hlt">Concentrated</span> Solar Thermoelectric Power</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chen, Gang; Ren, Zhifeng</p> <p>2015-07-09</p> <p>The goal of this project is to demonstrate in the lab that solar thermoelectric generators (STEGs) can exceed 10% solar-to-electricity efficiency, and STEGs can be integrated with phase-change materials (PCM) for thermal storage, providing operation beyond daylight hours. This project achieved significant progress in many tasks necessary to achieving the overall project goals. An accurate Themoelectric Generator (TEG) model was developed, which included realistic treatment of contact materials, contact resistances and radiative losses. In terms of fabricating physical TEGs, high performance contact materials for skutterudite TE segments were developed, along with brazing and soldering methods to assemble segmented TEGs. Accurate measurement systems for determining device performance (in addition to just TE material performance) were built for this project and used to characterize our TEGs. From the optical components’ side, a spectrally selective cermet surface was developed with high solar absorptance and low thermal emittance, with thermal stability at high temperature. A measurement technique was also developed to determine absorptance and total hemispherical emittance at high temperature, and was used to characterize the fabricated spectrally selective surfaces. In addition, a novel reflective cavity was designed to reduce radiative absorber losses and achieve high receiver efficiency at low <span class="hlt">concentration</span> ratios. A prototype cavity demonstrated that large reductions in radiative losses were possible through this technique. For the overall <span class="hlt">concentrating</span> STEG system, a number of devices were fabricated and tested in a custom built test platform to characterize their efficiency performance. Additionally, testing was performed with integration of PCM thermal storage, and the storage time of the lab scale system was evaluated. Our latest testing results showed a STEG efficiency of 9.6%, indicating promising potential for high performance <span class="hlt">concentrated</span> STEGs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4155547','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4155547"><span>METHOD OF ISOTOPE <span class="hlt">CONCENTRATION</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Taylor, T.I.; Spindel, W.</p> <p>1960-02-01</p> <p>A method of <span class="hlt">concentrating</span> N/sup 15/ in a liquid is described. Gaseous nitric oxide and at least one liquid selected from the group consisting of the aqueous oxyacids and oxides of nitrogen, wherein the atomic ratio of oxygen to nitrogen is greater than unity, are brought into intimate contact to cause an enrichment of the liquid and a depletion of the gas in N/sup 15/. The liquid is, thereafter, reacted with sulfur dioxide to produce a gas contuining nitric oxide. The gas contuining nitric oxide is then continuously passed in countercurrent contact with the liquid to cause further enrichment of the liquid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991JSP....62.1225V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991JSP....62.1225V"><span>Modeling of <span class="hlt">concentrated</span> suspensions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van den Brule, B. H. A. A.; Jongschaap, R. J. J.</p> <p>1991-03-01</p> <p>The constitutive equation of a <span class="hlt">concentrated</span> suspension of spherical particles in a Newtonian medium is derived. To this end the method of local volume averaging is employed. To calculate the contribution of the particles to the stress tensor it is assumed that the stress generated in the interstitial holes between the particles is negligible compared to the stress generated in !he narrow gaps separating the particles. The use of the resulting expression is demonstrated with two examples on a cubical arrangement of particles: pure shear and simple shear. Furthermore, the validity of the lubrication approximation employed in this work is checked against the results derived by Nunan and Keller for periodic suspensions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AIPC..630..134H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AIPC..630..134H"><span><span class="hlt">Concentric</span> Loop Surface Coil</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hernández-Flores, R.; Rodríguez-González, A. O.; Salgado-Lujambio, P.; Barrios-Alvarez, F. A.</p> <p>2002-08-01</p> <p>A surface coil for MRI consisted of two <span class="hlt">concentric</span> loops was developed for brain imaging. Prior to build the coil prototype, the magnetic field (B1) generated by the coil was numerically simulated. This field simulation is based on the Biot-Savart law for the circular- and square-shaped loops. From these theoretical results, we can appreciate an improvement on the B1 homogeneity. Brain images obtained at 1.5 Tesla show a good sensitivity in a particular region of interest. Also, these images compared well against images obtained with a circular-shaped coil. This receiver coil can generate high quality brain images.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6151697','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6151697"><span>Fixed solar energy <span class="hlt">concentrator</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Houghton, A.J.; Knasel, T.M.</p> <p>1981-01-20</p> <p>An apparatus for the <span class="hlt">concentration</span> of solar energy upon a fixed array of solar cells is disclosed. A transparent material is overlayed upon the cell array, and a diffuse reflective coating is applied to the surface area of the transparent medium in between cells. Radiant light, which reflects through the transparent layer and does not fall directly incident to a cell surface is reflected by the coating layer in an approximate cosine pattern. Thereafter, such light undergoes internal reflection and rediffusion until subsequently it either strikes a solar cell surface or is lost through the upper surface of the transparent material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5071395','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5071395"><span><span class="hlt">Concentric</span> layer ramjet fuel</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Burdette, G.W.; Francis, J.P.</p> <p>1988-03-08</p> <p>This patent describes a solid fuel ramjet grain comprising <span class="hlt">concentric</span> layers of solid ramjet fuel having a perforation therethrough along the center axis of the grain. The performation is connected to a combustion after-chamber. The solid ramjet fuel layers comprises a pure hydroxyl-terminated polybutadiene hydrocarbon fuel or a mixture of a hydroxyl-terminated polybutadiene hydrocarbon fuel and from about 5 to about 60 percent by weight of an additive to increase the fuel regression rate selected from the group consisting of magnesium, boron carbide, aluminum, and zirconium such that, when buried in the operation of the ramjet, each fuel layer produces a different level of thrust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080007455','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080007455"><span><span class="hlt">Variable</span> pressure washer</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smeltzer, III, Stanley S. (Inventor); Estrada, Hector (Inventor)</p> <p>2004-01-01</p> <p>A <span class="hlt">variable</span> pressure washer has two interlocking channel rings separated by a channel and retained by a captive set of fasteners. Within the channel between the rings are multiple rows of springs having at least two different spring moduli. The washer is particularly suited for use with a polar boss assembly secured to a bulkhead of a pressure vessel such as of propellent tank dome structure where the washer allows for the substantially uniform deflection of multiple O-rings as affected by the curved structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19120241','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19120241"><span>Zoonoses and climate <span class="hlt">variability</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cardenas, Rocio; Sandoval, Claudia M; Rodriguez-Morales, Alfonso J; Vivas, Paul</p> <p>2008-12-01</p> <p>Leishmaniasis in the Americas is transmitted by Lutzomyia spp., which have many animal reservoirs. Previous studies indicated potential changes in vectors of climate-related distribution, but impact outcomes need to be further studied. We report climatic and El Niño events during 1985-2002 that may have had an impact on leishmaniasis in 11 southern departments of Colombia: Amazonas, Caquetá, Cauca (Ca), Huila, Meta (Mt), Nariño, Putumayo (Py), Tolima, Valle (Va), Vaupes (Vp), and Vichada. Climatic data were obtained by satellite and epidemiologic data were obtained from the Health Ministry. NOAA climatic classification and SOI/ONI indexes were used as indicators of global climate <span class="hlt">variability</span>. Yearly variation comparisons and median trend deviations were made for disease incidence and climatic <span class="hlt">variability</span>. During this period there was considerable climatic <span class="hlt">variability</span>, with a strong El Niño for 6 years and a strong La Niña for 8. During this period, 19,212 cases of leishmaniasis were registered, for a mean of 4756.83 cases/year. Disease in the whole region increased (mean of 4.98%) during the El Niño years in comparison to the La Niña years, but there were differences between departments with increases during El Niño (Mt 6.95%, Vp 4.84%), but the rest showed an increase during La Niña (1.61%-64.41%). Differences were significant in Va (P= 0.0092), Py (P= 0.0001), Ca (P= 0.0313), and for the whole region (P= 0.0023), but not in the rest of the departments. The importance of climate change is shown by shifts in insect and animal distributions. These data reflect the importance of climate on transmission of leishmaniasis and open further investigations related to forecasting and monitoring systems, where understanding the relationship between zoonoses and climate <span class="hlt">variability</span> could help to improve the management of these emerging and reemerging diseases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5060766','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5060766"><span><span class="hlt">Variable</span> camshaft timing system</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Butterfield, R.P.; Smith, F.R.</p> <p>1989-09-05</p> <p>This patent describes an improvement in a <span class="hlt">variable</span> camshaft timing system for an internal combustion engine having intake and exhaust valves and a camshaft for each of the intake and exhaust valves, an intake sprocket and an exhaust sprocket keyed to their respective camshaft, only one of the camshafts being directly driven by an engine crankshaft, and a timing chain engaging both sprockets. The improvement comprising a single bracket carrying at least one idler sprocket engaging the timing chain, the bracket being mounted for movement to alter the timing relationship between the intake and exhaust sprockets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/862795','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/862795"><span><span class="hlt">Variable</span> leak gas source</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Henderson, Timothy M.; Wuttke, Gilbert H.</p> <p>1977-01-01</p> <p>A <span class="hlt">variable</span> leak gas source and a method for obtaining the same which includes filling a quantity of hollow glass micro-spheres with a gas, storing said quantity in a confined chamber having a controllable outlet, heating said chamber above room temperature, and controlling the temperature of said chamber to control the quantity of gas passing out of said controllable outlet. Individual gas filled spheres may be utilized for calibration purposes by breaking a sphere having a known quantity of a known gas to calibrate a gas detection apparatus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040171209&hterms=planetary+ionospheric+storm&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dplanetary%2Bionospheric%2Bstorm','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040171209&hterms=planetary+ionospheric+storm&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dplanetary%2Bionospheric%2Bstorm"><span>Ionospheric <span class="hlt">Variability</span> and Storms on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mendillo, Michael</p> <p>2004-01-01</p> <p>The goal of this grant was to conduct the first-ever study of ionospheric <span class="hlt">variability</span> on Mars. To do so, we used data from the Radio Science (RS) experiment onboard the Mars Global Surveyor (MGS) satellite. Dr. David Hinson of the RS team at Stanford University was a most helpful and valuable colleague throughout the studies we conducted. For the initial RS datasets available from the MGS mission, there were no severe storms caused by solar wind activity, so we <span class="hlt">concentrated</span> on day-to-day effects. This turned out to be a wise approach since understanding "normal <span class="hlt">variability</span>" had to be done before any claim could be made about "space weather" effects. Our approach was three-fold: (1) select a good dataset for characterization of ionosphere <span class="hlt">variability</span> at Mars, one for which excellent terrestrial data were also available. This turned out to be the period 9-27 March 1999; (2) once the <span class="hlt">variability</span> at Mars was described, develop and use a new photochemical model of the martian ionosphere to find the extent to which solar <span class="hlt">variability</span> on those days caused or contributed to the observed patterns; (3) use the results from the above, together with additional datasets from the MGS/RS experiment, to describe some practical consequences that the martian ionosphere would have upon NASA s proposed navigation and communications systems for Mars. The results of these studies showed that: (a) solar <span class="hlt">variability</span> is the dominant source of ionospheric <span class="hlt">variability</span> at Mars (during periods of quiet solar wind), (b) that current models do a good job in portraying such effects at the height of the ionospheric peak electron density, and (c) that ionospheric structure on Mars can affect attempts at precise position-fixing at Mars should relatively high (GPS-like) frequencies not be used in a Mars communications and navigation system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/516940','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/516940"><span>Optical oxygen <span class="hlt">concentration</span> monitor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Kebabian, P.</p> <p>1997-07-22</p> <p>A system for measuring and monitoring the <span class="hlt">concentration</span> of oxygen uses as a light source an argon discharge lamp, which inherently emits light with a spectral line that is close to one of oxygen`s A-band absorption lines. In a preferred embodiment, the argon line is split into sets of components of shorter and longer wavelengths by a magnetic field of approximately 2,000 Gauss that is parallel to the light propagation from the lamp. The longer wavelength components are centered on an absorption line of oxygen and thus readily absorbed, and the shorter wavelength components are moved away from that line and minimally absorbed. A polarization modulator alternately selects the set of the longer wavelength, or upshifted, components or the set of the shorter wavelength, or downshifted, components and passes the selected set to an environment of interest. After transmission over a path through that environment, the transmitted optical flux of the argon line varies as a result of the differential absorption. The system then determines the <span class="hlt">concentration</span> of oxygen in the environment based on the changes in the transmitted optical flux between the two sets of components. In alternative embodiments modulation is achieved by selectively reversing the polarity of the magnetic field or by selectively supplying the magnetic field to either the emitting plasma of the lamp or the environment of interest. 4 figs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/871064','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/871064"><span>Optical oxygen <span class="hlt">concentration</span> monitor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Kebabian, Paul</p> <p>1997-01-01</p> <p>A system for measuring and monitoring the <span class="hlt">concentration</span> of oxygen uses as a light source an argon discharge lamp, which inherently emits light with a spectral line that is close to one of oxygen's A-band absorption lines. In a preferred embodiment, the argon line is split into sets of components of shorter and longer wavelengths by a magnetic field of approximately 2000 Gauss that is parallel to the light propagation from the lamp. The longer wavelength components are centered on an absorption line of oxygen and thus readily absorbed, and the shorter wavelength components are moved away from that line and minimally absorbed. A polarization modulator alternately selects the set of the longer wavelength, or upshifted, components or the set of the shorter wavelength, or downshifted, components and passes the selected set to an environment of interest. After transmission over a path through that environment, the transmitted optical flux of the argon line varies as a result of the differential absorption. The system then determines the <span class="hlt">concentration</span> of oxygen in the environment based on the changes in the transmitted optical flux between the two sets of components. In alternative embodiments modulation is achieved by selectively reversing the polarity of the magnetic field or by selectively supplying the magnetic field to either the emitting plasma of the lamp or the environment of interest.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SPIE.7773E..15D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SPIE.7773E..15D"><span>Benchmarking <span class="hlt">concentrating</span> photovoltaic systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duerr, Fabian; Muthirayan, Buvaneshwari; Meuret, Youri; Thienpont, Hugo</p> <p>2010-08-01</p> <p>Integral to photovoltaics is the need to provide improved economic viability. To achieve this goal, photovoltaic technology has to be able to harness more light at less cost. A large variety of <span class="hlt">concentrating</span> photovoltaic concepts has provided cause for pursuit. To obtain a detailed profitability analysis, a flexible evaluation is crucial for benchmarking the cost-performance of this variety of <span class="hlt">concentrating</span> photovoltaic concepts. To save time and capital, a way to estimate the cost-performance of a complete solar energy system is to use computer aided modeling. In this work a benchmark tool is introduced based on a modular programming concept. The overall implementation is done in MATLAB whereas Advanced Systems Analysis Program (ASAP) is used for ray tracing calculations. This allows for a flexible and extendable structuring of all important modules, namely an advanced source modeling including time and local dependence, and an advanced optical system analysis of various optical designs to obtain an evaluation of the figure of merit. An important figure of merit: the energy yield for a given photovoltaic system at a geographical position over a specific period, can be calculated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5286212','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5286212"><span><span class="hlt">Variable</span> venturi type carburetor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tahata, M.</p> <p>1986-09-02</p> <p>A <span class="hlt">variable</span> venturi type carburetor is described comprising a carburetor body provided with a suction passage therein for flow of air through the passage, a slide valve supported by the body for slidable movement across the suction passage to serve as a <span class="hlt">variable</span> venturi, a butterfly throttle valve pivotably supported by the carburetor body downstream of the slide valve, interlocking means connecting the slide valve and the butterfly throttle valve together for operating in correspondence with one another, operating means connected to one of the valves for operating the same by application of an external force thereto. A low-speed fuel nozzle opens into the suction passage in the vicinity of the butterfly throttle valve, an intermediate and a high speed main fuel nozzle opens into the suction passage opposite the slide valve, and a low and intermediate-speed primary fuel nozzle opens into the suction passage between the slide valve and the butterfly throttle valve. The slide valve includes a bottom portion having a front side surface facing upstream in the suction passage and a rear side surface facing downstream in the suction passage, the front and rear side surfaces having lower edges which are located in the same horizontal plane, the rear side surface being provided with an inverted cutaway.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TDM.....3d1005A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TDM.....3d1005A"><span>Suspended graphene <span class="hlt">variable</span> capacitor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>AbdelGhany, M.; Mahvash, F.; Mukhopadhyay, M.; Favron, A.; Martel, R.; Siaj, M.; Szkopek, T.</p> <p>2016-12-01</p> <p>Electromechanical <span class="hlt">variable</span> capacitors, or varactors, find a wide range of applications including sensing applications and the tuning of electrical circuit resonance. We demonstrate a nano-electromechanical graphene varactor, a <span class="hlt">variable</span> capacitor wherein the capacitance is tuned by voltage controlled deflection of a dense array of suspended graphene membranes. The low flexural rigidity of graphene monolayers is exploited to achieve low actuation voltage and high tunable capacitance density in an ultra-thin structure. Large arrays comprising thousands of suspensions were fabricated to give a tunable capacitance of over 10 pF mm-2. This capacitance density suggests that graphene offers a potential solution to the challenge of reducing the size of micro-electromechanical systems (MEMS). A capacitance tuning of 55% was achieved with a 10 V actuating voltage, exceeding the 50% tuning limit of Hookean parallel plate pull-in without the use of complex mechanical schemes that occupy substrate area. Capacitor behavior was investigated experimentally, and described by a simple theoretical model. Mechanical properties of the graphene membranes were measured independently using atomic force microscopy. We present a comparison of state-of-the-art MEMS and graphene varactors. The quality factor of graphene varactors is limited by graphene sheet resistance, pull-in voltage can be improved with more aggressive scaling, while the power handling and cycling stability of graphene varactors remains unknown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3743360','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3743360"><span>Glycemic <span class="hlt">variability</span>: Clinical implications</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Satya Krishna, Surabhi Venkata; Kota, Sunil K.; Modi, Kirtikumar D.</p> <p>2013-01-01</p> <p>Glycemic control and its benefits in preventing microvascular diabetic complications are convincingly proved by various prospective trials. Diabetes control and complications trial (DCCT) had reported <span class="hlt">variable</span> glycated hemoglobin (HbA1C) as a cause of increased microvascular complications in conventional glycemic control group versus intensive one. However, in spite of several indirect evidences, its link with cardiovascular events or macrovascular complications is still not proved. Glycemic <span class="hlt">variability</span> (GV) is one more tool to explain relation between hyperglycemia and increased cardiovascular risk in diabetic patients. In fact GV along with fasting blood sugar, postprandial blood sugar, HbA1C, and quality of life has been proposed to form glycemic pentad, which needs to be considered in diabetes management. Postprandial spikes in blood glucose as well as hypoglycemic events, both are blamed for increased cardiovascular events in Type 2 diabetics. GV includes both these events and hence minimizing GV can prevent future cardiovascular events. Modern diabetes management modalities including improved sulfonylureas, glucagon like peptide-1 (GLP-1)-based therapy, newer basal insulins, and modern insulin pumps address the issue of GV effectively. This article highlights mechanism, clinical implications, and measures to control GV in clinical practice. PMID:23961476</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930074817&hterms=variables+Research&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dvariables%2BResearch','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930074817&hterms=variables+Research&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dvariables%2BResearch"><span><span class="hlt">Variable</span> gravity research facility</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1987-01-01</p> <p>Eight fourth-year engineering design students formed two teams to study methods of varying the perceived gravity level in a <span class="hlt">variable</span> gravity research facility. A tether system and an arm system were the chosen topics. Both teams have produced and built scale models of their design. In addition, a three-credit Special Topics Course (Aviation 370) was formed, as the project offers an excellent opportunity to build a multi-disciplinary program around the initial conceptualization process. Fifty students were registered in the Special Topics course. Each week during a three hour class, a guest lecturer covered one or more of the many areas associated with the concept of a <span class="hlt">variable</span>-gravity facility. The students formed small groups organized on a multi-disciplinary basis (there were twelve separate disciplines represented by one or more students) where they discussed among themselves the various issues involved. These groups also met outside class for three or more hours each week. During class each group presented oral reports on their findings during a one-hour general question and answer period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006SASS...25..167P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006SASS...25..167P"><span>Superhumps in Cataclysmic <span class="hlt">Variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Patterson, J.</p> <p>2006-05-01</p> <p>The individual telescopes of the CBA produce fast (<1 min) photometry of <span class="hlt">variable</span> stars. With runs of >5 hours and spliced data from many longitudes, we aim to assemble long light curves with nearly continuous coverage. This is an ideal data base for period and other timing studies. I have found it to be many times more effective than one large telescope proudly performing its hijinks on one mountaintop. I'll give a brief account of how this enterprise has evolved from one CCD in a tuna fish can to the world's leading supplier of periodic signals in cataclysmic <span class="hlt">variables</span>. The most interesting and productive research program has been the discovery and study of "superhumps", mysterious large-amplitude waves at a period slightly offset from the true orbital period of the binary. These result from the "precession" of the accretion disk. The disks appear to wobble and precess in a manner similar to the Moon's orbit, and we can use this as a tool for weighing the unseen secondary stars. I'll describe the superhumps, and their fascinating astrophysical uses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMED33B0774D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMED33B0774D"><span>Current Climate <span class="hlt">Variability</span> & Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diem, J.; Criswell, B.; Elliott, W. C.</p> <p>2013-12-01</p> <p>Current Climate <span class="hlt">Variability</span> & Change is the ninth among a suite of ten interconnected, sequential labs that address all 39 climate-literacy concepts in the U.S. Global Change Research Program's Climate Literacy: The Essential Principles of Climate Sciences. The labs are as follows: Solar Radiation & Seasons, Stratospheric Ozone, The Troposphere, The Carbon Cycle, Global Surface Temperature, Glacial-Interglacial Cycles, Temperature Changes over the Past Millennium, Climates & Ecosystems, Current Climate <span class="hlt">Variability</span> & Change, and Future Climate Change. All are inquiry-based, on-line products designed in a way that enables students to construct their own knowledge of a topic. Questions representative of various levels of Webb's depth of knowledge are embedded in each lab. In addition to the embedded questions, each lab has three or four essential questions related to the driving questions for the lab suite. These essential questions are presented as statements at the beginning of the material to represent the lab objectives, and then are asked at the end as questions to function as a summative assessment. For example, the Current Climate <span class="hlt">Variability</span> & Change is built around these essential questions: (1) What has happened to the global temperature at the Earth's surface, in the middle troposphere, and in the lower stratosphere over the past several decades?; (2) What is the most likely cause of the changes in global temperature over the past several decades and what evidence is there that this is the cause?; and (3) What have been some of the clearly defined effects of the change in global temperature on the atmosphere and other spheres of the Earth system? An introductory Prezi allows the instructor to assess students' prior knowledge in relation to these questions, while also providing 'hooks' to pique their interest related to the topic. The lab begins by presenting examples of and key differences between climate <span class="hlt">variability</span> (e.g., Mt. Pinatubo eruption) and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/993477','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/993477"><span><span class="hlt">Variable</span> Valve Actuation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jeffrey Gutterman; A. J. Lasley</p> <p>2008-08-31</p> <p>Many approaches exist to enable advanced mode, low temperature combustion systems for diesel engines - such as premixed charge compression ignition (PCCI), Homogeneous Charge Compression Ignition (HCCI) or other HCCI-like combustion modes. The fuel properties and the quantity, distribution and temperature profile of air, fuel and residual fraction in the cylinder can have a marked effect on the heat release rate and combustion phasing. Figure 1 shows that a systems approach is required for HCCI-like combustion. While the exact requirements remain unclear (and will vary depending on fuel, engine size and application), some form of substantially <span class="hlt">variable</span> valve actuation is a likely element in such a system. <span class="hlt">Variable</span> valve actuation, for both intake and exhaust valve events, is a potent tool for controlling the parameters that are critical to HCCI-like combustion and expanding its operational range. Additionally, VVA can be used to optimize the combustion process as well as exhaust temperatures and impact the after treatment system requirements and its associated cost. Delphi Corporation has major manufacturing and product development and applied R&D expertise in the valve train area. Historical R&D experience includes the development of fully <span class="hlt">variable</span> electro-hydraulic valve train on research engines as well as several generations of mechanical VVA for gasoline systems. This experience has enabled us to evaluate various implementations and determine the strengths and weaknesses of each. While a fully <span class="hlt">variable</span> electro-hydraulic valve train system might be the 'ideal' solution technically for maximum flexibility in the timing and control of the valve events, its complexity, associated costs, and high power consumption make its implementation on low cost high volume applications unlikely. Conversely, a simple mechanical system might be a low cost solution but not deliver the flexibility required for HCCI operation. After modeling more than 200 variations of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ACP....1111319M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ACP....1111319M"><span>A statistical proxy for sulphuric acid <span class="hlt">concentration</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mikkonen, S.; Romakkaniemi, S.; Smith, J. N.; Korhonen, H.; Petäjä, T.; Plass-Duelmer, C.; Boy, M.; McMurry, P. H.; Lehtinen, K. E. J.; Joutsensaari, J.; Hamed, A.; Mauldin, R. L., III; Birmili, W.; Spindler, G.; Arnold, F.; Kulmala, M.; Laaksonen, A.</p> <p>2011-11-01</p> <p>Gaseous sulphuric acid is a key precursor for new particle formation in the atmosphere. Previous experimental studies have confirmed a strong correlation between the number <span class="hlt">concentrations</span> of freshly formed particles and the ambient <span class="hlt">concentrations</span> of sulphuric acid. This study evaluates a body of experimental gas phase sulphuric acid <span class="hlt">concentrations</span>, as measured by Chemical Ionization Mass Spectrometry (CIMS) during six intensive measurement campaigns and one long-term observational period. The campaign datasets were measured in Hyytiälä, Finland, in 2003 and 2007, in San Pietro Capofiume, Italy, in 2009, in Melpitz, Germany, in 2008, in Atlanta, Georgia, USA, in 2002, and in Niwot Ridge, Colorado, USA, in 2007. The long term data were obtained in Hohenpeissenberg, Germany, during 1998 to 2000. The measured time series were used to construct proximity measures ("proxies") for sulphuric acid <span class="hlt">concentration</span> by using statistical analysis methods. The objective of this study is to find a proxy for sulfuric acid that is valid in as many different atmospheric environments as possible. Our most accurate and universal formulation of the sulphuric acid <span class="hlt">concentration</span> proxy uses global solar radiation, SO2 <span class="hlt">concentration</span>, condensation sink and relative humidity as predictor <span class="hlt">variables</span>, yielding a correlation measure (R) of 0.87 between observed <span class="hlt">concentration</span> and the proxy predictions. Interestingly, the role of the condensation sink in the proxy was only minor, since similarly accurate proxies could be constructed with global solar radiation and SO2 <span class="hlt">concentration</span> alone. This could be attributed to SO2 being an indicator for anthropogenic pollution, including particulate and gaseous emissions which represent sinks for the OH radical that, in turn, is needed for the formation of sulphuric acid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ACPD...1120141M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ACPD...1120141M"><span>A statistical proxy for sulphuric acid <span class="hlt">concentration</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mikkonen, S.; Romakkaniemi, S.; Smith, J. N.; Korhonen, H.; Petäjä, T.; Plass-Duelmer, C.; Boy, M.; McMurry, P. H.; Lehtinen, K. E. J.; Joutsensaari, J.; Hamed, A.; Mauldin, R. L., III; Birmili, W.; Spindler, G.; Arnold, F.; Kulmala, M.; Laaksonen, A.</p> <p>2011-07-01</p> <p>Gaseous sulphuric acid is a key precursor for new particle formation in the atmosphere. Previous experimental studies have confirmed a strong correlation between the number <span class="hlt">concentrations</span> of freshly formed particles and the ambient <span class="hlt">concentrations</span> of sulphuric acid. This study evaluates a body of experimental gas phase sulphuric acid <span class="hlt">concentrations</span>, as measured by Chemical Ionization Mass Spectrometry (CIMS) during six intensive measurement campaigns and one long-term observational period. The campaign datasets were measured in Hyytiälä, Finland, in 2003 and 2007, in San Pietro Capofiume, Italy, in 2009, in Melpitz, Germany, in 2008, in Atlanta, Georgia, USA, in 2002, and in Niwot Ridge, Colorado, USA, in 2007. The long term data were obtained in Hohenpeissenberg, Germany, during 1998 to 2000. The measured time series were used to construct proximity measures ("proxies") for sulphuric acid <span class="hlt">concentration</span> by using statistical analysis methods. The objective of this study is to find a proxy for sulfuric acid that is valid in as many different atmospheric environments as possible. Our most accurate and universal formulation of the sulphuric acid <span class="hlt">concentration</span> proxy uses global solar radiation, SO2 <span class="hlt">concentration</span>, condensation sink and relative humidity as predictor <span class="hlt">variables</span>, yielding a correlation measure (R) of 0.87 between observed <span class="hlt">concentration</span> and the proxy predictions. Interestingly, the role of the condensation sink in the proxy was only minor, since similarly accurate proxies could be constructed with global solar radiation and SO2 <span class="hlt">concentration</span> alone. This could be attributed to SO2 being an indicator for anthropogenic pollution, including particulate and gaseous emissions which represent sinks for the OH radical that, in turn, is needed for the formation of sulphuric acid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/862935','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/862935"><span>Non-tracking solar <span class="hlt">concentrator</span> with a high <span class="hlt">concentration</span> ratio</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Hinterberger, Henry</p> <p>1977-01-01</p> <p>A nontracking solar <span class="hlt">concentrator</span> with a high <span class="hlt">concentration</span> ratio is provided. The <span class="hlt">concentrator</span> includes a plurality of energy absorbers which communicate with a main header by which absorbed heat is removed. Undesired heat flow of those absorbers not being heated by radiant energy at a particular instant is impeded, improving the efficiency of the <span class="hlt">concentrator</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23816910','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23816910"><span><span class="hlt">Concentrating</span> solar thermal power.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Müller-Steinhagen, Hans</p> <p>2013-08-13</p> <p>In addition to wind and photovoltaic power, <span class="hlt">concentrating</span> solar thermal power (CSP) will make a major contribution to electricity provision from renewable energies. Drawing on almost 30 years of operational experience in the multi-megawatt range, CSP is now a proven technology with a reliable cost and performance record. In conjunction with thermal energy storage, electricity can be provided according to demand. To date, solar thermal power plants with a total capacity of 1.3 GW are in operation worldwide, with an additional 2.3 GW under construction and 31.7 GW in advanced planning stage. Depending on the <span class="hlt">concentration</span> factors, temperatures up to 1000°C can be reached to produce saturated or superheated steam for steam turbine cycles or compressed hot gas for gas turbine cycles. The heat rejected from these thermodynamic cycles can be used for sea water desalination, process heat and centralized provision of chilled water. While electricity generation from CSP plants is still more expensive than from wind turbines or photovoltaic panels, its independence from fluctuations and daily variation of wind speed and solar radiation provides it with a higher value. To become competitive with mid-load electricity from conventional power plants within the next 10-15 years, mass production of components, increased plant size and planning/operating experience will be accompanied by technological innovations. On 30 October 2009, a number of major industrial companies joined forces to establish the so-called DESERTEC Industry Initiative, which aims at providing by 2050 15 per cent of European electricity from renewable energy sources in North Africa, while at the same time securing energy, water, income and employment for this region. Solar thermal power plants are in the heart of this concept.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AJ....145...45H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AJ....145...45H"><span>Wind <span class="hlt">Variability</span> in BZ Camelopardalis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Honeycutt, R. K.; Kafka, S.; Robertson, J. W.</p> <p>2013-02-01</p> <p>Sequences of spectra of the nova-like cataclysmic <span class="hlt">variable</span> (CV) BZ Cam were acquired on nine nights in 2005-2006 in order to study the time development of episodes of wind activity known to occur frequently in this star. We confirm the results of Ringwald & Naylor that the P-Cygni absorption components of the lines mostly evolve from higher expansion velocity to lower velocity as an episode progresses. We also commonly find blueshifted emission components in the Hα line profile, whose velocities and durations strongly suggest that they are also due to the wind. Curiously, Ringwald & Naylor reported common occurrences of redshifted Hα emission components in their BZ Cam spectra. We have attributed these emission components in Hα to occasions when gas <span class="hlt">concentrations</span> in the bipolar wind (both front side and back side) become manifested as emission lines as they move beyond the disk's outer edge. We also suggest, based on changes in the P-Cygni profiles during an episode, that the progression from larger to smaller expansion velocities is due to the higher velocity portions of a wind <span class="hlt">concentration</span> moving beyond the edge of the continuum light of the disk first, leaving a net redward shift of the remaining absorption profile. We derive a new orbital ephemeris for BZ Cam, using the radial velocity of the core of the He I λ5876 line, finding P = 0.15353(4). Using this period, the wind episodes in BZ Cam are found to be <span class="hlt">concentrated</span> near the inferior conjunction of the emission line source. This result helps confirm that the winds in nova-like CVs are often phase dependent, in spite of the puzzling implication that such winds lack axisymmetry. We argue that the radiation-driven wind in BZ Cam receives an initial boost by acting on gas that has been lifted above the disk by the interaction of the accretion stream with the disk, thereby imposing flickering timescales onto the wind events, as well as leading to an orbital modulation of the wind due to the non</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22089691','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22089691"><span>WIND <span class="hlt">VARIABILITY</span> IN BZ CAMELOPARDALIS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Honeycutt, R. K.; Kafka, S.; Robertson, J. W. E-mail: skafka@dtm.ciw.edu</p> <p>2013-02-01</p> <p>Sequences of spectra of the nova-like cataclysmic <span class="hlt">variable</span> (CV) BZ Cam were acquired on nine nights in 2005-2006 in order to study the time development of episodes of wind activity known to occur frequently in this star. We confirm the results of Ringwald and Naylor that the P-Cygni absorption components of the lines mostly evolve from higher expansion velocity to lower velocity as an episode progresses. We also commonly find blueshifted emission components in the H{alpha} line profile, whose velocities and durations strongly suggest that they are also due to the wind. Curiously, Ringwald and Naylor reported common occurrences of redshifted H{alpha} emission components in their BZ Cam spectra. We have attributed these emission components in H{alpha} to occasions when gas <span class="hlt">concentrations</span> in the bipolar wind (both front side and back side) become manifested as emission lines as they move beyond the disk's outer edge. We also suggest, based on changes in the P-Cygni profiles during an episode, that the progression from larger to smaller expansion velocities is due to the higher velocity portions of a wind <span class="hlt">concentration</span> moving beyond the edge of the continuum light of the disk first, leaving a net redward shift of the remaining absorption profile. We derive a new orbital ephemeris for BZ Cam, using the radial velocity of the core of the He I {lambda}5876 line, finding P = 0.15353(4). Using this period, the wind episodes in BZ Cam are found to be <span class="hlt">concentrated</span> near the inferior conjunction of the emission line source. This result helps confirm that the winds in nova-like CVs are often phase dependent, in spite of the puzzling implication that such winds lack axisymmetry. We argue that the radiation-driven wind in BZ Cam receives an initial boost by acting on gas that has been lifted above the disk by the interaction of the accretion stream with the disk, thereby imposing flickering timescales onto the wind events, as well as leading to an orbital modulation of the wind</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70024396','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70024396"><span>Consistency of patterns in <span class="hlt">concentration</span>-discharge plots</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Chanat, Jeffrey G.; Rice, Karen C.; Hornberger, George M.</p> <p>2002-01-01</p> <p><span class="hlt">Concentration</span>-discharge (c-Q) plots have been used to infer how flow components such as event water, soil water, and groundwater mix to produce the observed episodic hydrochemical response of small catchments. Because c-Q plots are based only on observed streamflow and solute <span class="hlt">concentration</span>, their interpretation requires assumptions about the relative volume, hydrograph timing, and solute <span class="hlt">concentration</span> of the streamflow end-members. Evans and Davies [1998] present a taxonomy of c-Q loops resulting from three-component conservative mixing. Their analysis, based on a fixed template of end-member hydrograph volume, timing, and <span class="hlt">concentration</span>, suggests a unique relationship between c-Q loop form and the rank order of end-member <span class="hlt">concentrations</span>. Many catchments exhibit <span class="hlt">variability</span> in component contributions to storm flow in response to antecedent conditions or rainfall characteristics, but the effects of such variation on c-Q relationships have not been studied systematically. Starting with a "baseline" condition similar to that assumed by Evans and Davies [1998], we use a simple computer model to characterize the <span class="hlt">variability</span> in c-Q plot patterns resulting from variation in end-member volume, timing, and solute <span class="hlt">concentration</span>. <span class="hlt">Variability</span> in these three factors can result in more than one c-Q loop shape for a given rank order of end-member solute <span class="hlt">concentrations</span>. The number of resulting hysteresis patterns and their relative frequency depends on the rank order of solute <span class="hlt">concentrations</span> and on their separation in absolute value. In ambiguous cases the c-Q loop shape is determined by the relative "prominence" of the event water versus soil water components. This "prominence" is broadly defined as a capacity to influence the total streamflow <span class="hlt">concentration</span> and may result from a combination of end-member volume, timing, or <span class="hlt">concentration</span>. The modeling results indicate that plausible hydrological <span class="hlt">variability</span> in field situations can confound the interpretation of c-Q plots, even when</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.sciencemag.org/content/339/6117/277.full.pdf?sid=95070849-cf3e-40a5-a663-56462634de9a','USGSPUBS'); return false;" href="http://www.sciencemag.org/content/339/6117/277.full.pdf?sid=95070849-cf3e-40a5-a663-56462634de9a"><span>Essential biodiversity <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Pereira, H.M.; Ferrier, S.; Walters, M.; Geller, G.N.; Jongman, R.H.G.; Scholes, R.J.; Bruford, M.W.; Brummitt, N.; Butchart, S.H.M.; Cardoso, A.C.; Coops, N.C.; Dulloo, E.; Faith, D.P.; Freyhof, J.; Gregory, R.D.; Heip, C.; Höft, R.; Hurtt, G.; Jetz, W.; Karp, D.S.; McGeoch, M.A.; Obura, D.; Onada, Y.; Pettorelli, N.; Reyers, B.; Sayre, R.; Scharlemann, J.P.W.; Stuart, S.N.; Turak, E.; Walpole, M.; Wegmann, M.</p> <p>2013-01-01</p> <p>Reducing the rate of biodiversity loss and averting dangerous biodiversity change are international goals, reasserted by the Aichi Targets for 2020 by Parties to the United Nations (UN) Convention on Biological Diversity (CBD) after failure to meet the 2010 target (1, 2). However, there is no global, harmonized observation system for delivering regular, timely data on biodiversity change (3). With the first plenary meeting of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) soon under way, partners from the Group on Earth Observations Biodiversity Observation Network (GEO BON) (4) are developing—and seeking consensus around—Essential Biodiversity <span class="hlt">Variables</span> (EBVs) that could form the basis of monitoring programs worldwide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940021185','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940021185"><span><span class="hlt">Variable</span> speed controller</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Estes, Christa; Spiggle, Charles; Swift, Shannon; Vangeffen, Stephen; Younger, Frank</p> <p>1992-01-01</p> <p>This report details a new design for a <span class="hlt">variable</span> speed controller which can be used to operate lunar machinery without the astronaut using his or her upper body. In order to demonstrate the design, a treadle for an industrial sewing machine was redesigned to be used by a standing operator. Since the invention of an electrically powered sewing machine, the operator has been seated. Today, companies are switching from sit down to stand up operation involving modular stations. The old treadle worked well with a sitting operator, but problems have been found when trying to use the same treadle with a standing operator. Emphasis is placed on the ease of use by the operator along with the ergonomics involved. Included with the design analysis are suggestions for possible uses for the speed controller in other applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4313909','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4313909"><span>On Botulinum Neurotoxin <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2015-01-01</p> <p>ABSTRACT  The rapidly growing number of botulinum neurotoxin sequences poses the problem of the possible evolutionary significance of the <span class="hlt">variability</span> of these superpotent neurotoxins for toxin-producing Clostridium species. To progress in the understanding of this remarkable phenomenon, we suggest that researchers should (i) abandon an anthropocentric view of these neurotoxins as human botulism-causing agents or as human therapeutics, (ii) begin to investigate in depth the role of botulinum neurotoxins in animal botulism in the wilderness, and (iii) devote large efforts to next-generation sequencing of soil samples to identify novel botulinum neurotoxins. In order to compare the fitness of the different toxins, we suggest that assays of all the steps from toxin production to animal death should be performed. PMID:25564463</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15731438','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15731438"><span>Saturn's <span class="hlt">variable</span> magnetosphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gombosi, Tamas I; Hansen, Kenneth C</p> <p>2005-02-25</p> <p>Since the Cassini spacecraft reached Saturn's orbit in 2004, its instruments have been sending back a wealth of data on the planet's magnetosphere (the region dominated by the magnetic field of the planet). In this Viewpoint, we discuss some of these results, which are reported in a collection of reports in this issue. The magnetosphere is shown to be highly <span class="hlt">variable</span> and influenced by the planet's rotation, sources of plasma within the planetary system, and the solar wind. New insights are also gained into the chemical composition of the magnetosphere, with surprising results. These early results from Cassini's first orbit around Saturn bode well for the future as the spacecraft continues to orbit the planet.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10499130','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10499130"><span>Plasma lipid <span class="hlt">concentrations</span> during episodic occupational stress.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>McCann, B S; Benjamin, G A; Wilkinson, C W; Retzlaff, B M; Russo, J; Knopp, R H</p> <p>1999-01-01</p> <p>The possibility that stress affects plasma lipid <span class="hlt">concentrations</span> has been the subject of recent investigation, but the findings are equivocal in nonlaboratory settings. To determine whether psychological stress contributes to <span class="hlt">variability</span> in plasma lipid <span class="hlt">concentrations</span> and concomitant changes in health behaviors, the effect of increased work load on plasma lipids and apolipoproteins was examined in 173 lawyers. Plasma cholesterol, triglyceride, and apolipoprotein <span class="hlt">concentrations</span> were studied during periods of high work load (corresponding to impending tax deadlines) and during periods of usual work load. Self-reports of stress, work load, and time pressure, and cortisol, blood pressure, and heart rate were measured to verify that impending deadlines were associated with increased stress levels. Health behaviors which may affect plasma lipoprotein <span class="hlt">concentrations</span>, including dietary intake and exercise, were also examined. High work load was accompanied by increases in self-reported work load among lawyers most directly affected by the impending deadlines. Plasma apolipoprotein B and triglycerides increased during periods of high work load (M = 1.9 mg/dL, SD = 10.1 and M = 5.3, SD = 34.4, respectively). No changes in dietary intake and exercise were observed. Psychological stress (high work load) is associated with potentially atherogenic changes in plasma lipid <span class="hlt">concentrations</span>. While the lipoprotein effect of this short-term work stress is small, the effects of longer-term stress on multiple rise factors including triglycerides and apolipoprotein B could have significance for the development of coronary artery disease.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AtmEn..45.4025B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AtmEn..45.4025B"><span>Fine particulate <span class="hlt">concentrations</span> on sidewalks in five Southern California cities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boarnet, Marlon G.; Houston, Douglas; Edwards, Rufus; Princevac, Marko; Ferguson, Gavin; Pan, Hansheng; Bartolome, Christian</p> <p>2011-08-01</p> <p>This research provides an exploratory examination of the factors associated with fine particle <span class="hlt">concentrations</span> in intersection and sidewalk microenvironments in five study areas in the Los Angeles region. The study areas range from low-density, auto-oriented development patterns to dense urban areas with mid- and high-rise buildings. Average <span class="hlt">concentrations</span> of FP DT (fine particle <span class="hlt">concentrations</span> measured with DustTrak Aerosol Monitors) ranged from about 20 to 70 μg m -3 across study areas during stationary and mobile (walking) monitoring in morning, midday, and evening periods. Results suggest that fine particle <span class="hlt">concentrations</span> are highly <span class="hlt">variable</span> on urban sidewalks. A regression analysis shows that <span class="hlt">concentrations</span> are associated with traffic and the proximate built environment characteristics after accounting for meteorological factors, time of day, and location in the region. Regressions show higher <span class="hlt">concentrations</span> were associated with lower wind speeds and higher temperatures, higher adjacent passenger vehicle traffic, higher ambient <span class="hlt">concentrations</span>, and street canyons with buildings of over five stories. Locations in street canyons with 2-5 story buildings and with more paving and open space had lower <span class="hlt">concentrations</span> after accounting for other factors. The associations with traffic and built environment <span class="hlt">variables</span> explained a small amount of the variation in FP DT <span class="hlt">concentrations</span>, suggesting that future research should examine the relative role of localized traffic and built environment characteristics compared to regional ambient <span class="hlt">concentrations</span> and meteorology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/EJ1052931.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/EJ1052931.pdf"><span>Preservice Teachers' Understanding of <span class="hlt">Variable</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Brown, Sue; Bergman, Judy</p> <p>2013-01-01</p> <p>This study examines the research on middle school students' understanding of <span class="hlt">variables</span> and explores preservice elementary and middle school teachers' knowledge of <span class="hlt">variables</span>. According to research studies, middle school students have limited understanding of <span class="hlt">variables</span>. Many studies have examined the performance of middle school students and offered…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10146187','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10146187"><span>Photovoltaic solar <span class="hlt">concentrator</span> module</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chiang, C.J.</p> <p>1991-05-16</p> <p>This invention consists of a planar photovoltaic <span class="hlt">concentrator</span> module for producing an electrical signal from incident solar radiation which includes an electrically insulating housing having a front wall, an opposing back wall and a hollow interior. A solar cell having electrical terminals is positioned within the interior of the housing. A planar conductor is connected with a terminal of the solar cell of the same polarity. A lens forming the front wall of the housing is operable to direct solar radiation incident to the lens into the interior of the housing. A refractive optical element in contact with the solar cell and facing the lens receives the solar radiation directed into the interior of the housing by the lens and directs the solar radiation to the solar cell to cause the solar cell to generate an electrical signal. An electrically conductive planar member is positioned in the housing to rest on the housing back wall in supporting relation with the solar cell terminal of opposite polarity. The planar member is operable to dissipate heat radiated by the solar cell as the solar cell generates an electrical signal and further forms a solar cell conductor connected with the solar cell terminal to permit the electrical signal generated by the solar cell to be measured between the planar member and the conductor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4339103','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4339103"><span>Workplace <span class="hlt">Concentration</span> of Immigrants</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Andersson, Fredrik; García-Pérez, Mónica; Haltiwanger, John; McCue, Kristin; Sanders, Seth</p> <p>2014-01-01</p> <p>Casual observation suggests that in most U.S. urban labor markets, immigrants have more immigrant coworkers than native-born workers do. While seeming obvious, this excess tendency to work together has not been precisely measured, nor have its sources been quantified. Using matched employer–employee data from the U.S. Census Bureau Longitudinal Employer-Household Dynamics (LEHD) database on a set of metropolitan statistical areas (MSAs) with substantial immigrant populations, we find that, on average, 37% of an immigrant’s coworkers are themselves immigrants; in contrast, only 14% of a native-born worker’s coworkers are immigrants. We decompose this difference into the probability of working with compatriots versus with immigrants from other source countries. Using human capital, employer, and location characteristics, we narrow the mechanisms that might explain immigrant <span class="hlt">concentration</span>. We find that industry, language, and residential segregation collectively explain almost all the excess tendency to work with immigrants from other source countries, but they have limited power to explain work with compatriots. This large unexplained compatriot component suggests an important role for unmeasured country-specific factors, such as social networks. PMID:25425452</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1078311','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1078311"><span><span class="hlt">Concentric</span> tube support assembly</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Rubio, Mark F.; Glessner, John C.</p> <p>2012-09-04</p> <p>An assembly (45) includes a plurality of separate pie-shaped segments (72) forming a disk (70) around a central region (48) for retaining a plurality of tubes (46) in a <span class="hlt">concentrically</span> spaced apart configuration. Each segment includes a support member (94) radially extending along an upstream face (96) of the segment and a plurality of annularly curved support arms (98) transversely attached to the support member and radially spaced apart from one another away from the central region for receiving respective upstream end portions of the tubes in arc-shaped spaces (100) between the arms. Each segment also includes a radial passageway (102) formed in the support member for receiving a fluid segment portion (106) and a plurality of annular passageways (104) formed in the support arms for receiving respective arm portions (108) of the fluid segment portion from the radial passageway and for conducting the respective arm portions into corresponding annular spaces (47) formed between the tubes retained by the disk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25425452','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25425452"><span>Workplace <span class="hlt">concentration</span> of immigrants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Andersson, Fredrik; García-Pérez, Mónica; Haltiwanger, John; McCue, Kristin; Sanders, Seth</p> <p>2014-12-01</p> <p>Casual observation suggests that in most U.S. urban labor markets, immigrants have more immigrant coworkers than native-born workers do. While seeming obvious, this excess tendency to work together has not been precisely measured, nor have its sources been quantified. Using matched employer-employee data from the U.S. Census Bureau Longitudinal Employer-Household Dynamics (LEHD) database on a set of metropolitan statistical areas (MSAs) with substantial immigrant populations, we find that, on average, 37 % of an immigrant's coworkers are themselves immigrants; in contrast, only 14 % of a native-born worker's coworkers are immigrants. We decompose this difference into the probability of working with compatriots versus with immigrants from other source countries. Using human capital, employer, and location characteristics, we narrow the mechanisms that might explain immigrant <span class="hlt">concentration</span>. We find that industry, language, and residential segregation collectively explain almost all the excess tendency to work with immigrants from other source countries, but they have limited power to explain work with compatriots. This large unexplained compatriot component suggests an important role for unmeasured country-specific factors, such as social networks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/458339','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/458339"><span>Estimating whole-body fish PCB <span class="hlt">concentrations</span> from fillet data</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rigg, D.; Hohreiter, D.; Strause, K.; Brown, M.; Barnes, C.</p> <p>1995-12-31</p> <p>A study was designed to assess a potentially cost-effective method for generating both types of data from single fish specimens. The method is based on the testable hypothesis that whole-body PCE <span class="hlt">concentrations</span> are predictable from fillet PCB <span class="hlt">concentrations</span> and fillet and whole-body lipid <span class="hlt">concentrations</span>. The study involved the collection of small-mouth bass (Micropterus dolomieui) and carp (Cyprinus carpio) from several locations in the Kalamazoo River (Michigan) watershed to represent a range in PCB exposure. PCB and lipid <span class="hlt">concentrations</span> were determined in aliquots of homogenized fillets and remaining carcasses. Wet-weight total PCB <span class="hlt">concentrations</span> in carp ranged from 0.06 to 17 mg/kg in fillets, and from 0.11 to 14 mg/kg for remaining carcass; small-mouth bass ranged from 0.08 to 5.8 mg/kg in fillets, and from 0.21 to 13.2 mg/kg for remaining carcass. Whole-body PCB <span class="hlt">concentrations</span> predicted using fillet PCB <span class="hlt">concentrations</span> and fillet and carcass lipid <span class="hlt">concentrations</span> accounted for 94% and 88% of the <span class="hlt">variability</span> in measured whole-body small-mouth and whole-body carp <span class="hlt">concentrations</span>, respectively. Predicted and measured whole-body PCB <span class="hlt">concentrations</span> had a correlation of 91% for small-mouth bass, and 84% for carp. These results demonstrate that value of the lipid-based model in predicting whole-body PCB <span class="hlt">concentrations</span> from measured fillet PCB <span class="hlt">concentrations</span> and lipid <span class="hlt">concentrations</span> in fillet and remaining carcass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA086782','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA086782"><span>Design and Fabrication of an Aerosol <span class="hlt">Concentrator</span>.</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1980-05-08</p> <p>MBEran GpVt 08C IO NO 3. RECIPIENT’S CATALOG NUMBER 4. TITL S. VVIREOP ePORT A PERIOD COVERED Interim report on a continuing ~ESIGN AND ,BRICATION OF AN...electronic tachometer , and a <span class="hlt">variable</span> speed controller. Our motor is a hand-held router motor, model 90114, manufactured by the Stanley Power Tool Company (P.O...be obtained from Lordco Supply (Erie, PA 16505). Since the <span class="hlt">concentrator</span> is run at various speeds, we incorporated an electronic tachometer into the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28282914','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28282914"><span>Nitrate, Nitrite, and Ammonium <span class="hlt">Variability</span> in Drinking Water Distribution Systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schullehner, Jörg; Stayner, Leslie; Hansen, Birgitte</p> <p>2017-03-09</p> <p>Accurate assessments of exposure to nitrate in drinking water is a crucial part of epidemiological studies investigating long-term adverse human health effects. However, since drinking water nitrate measurements are usually collected for regulatory purposes, assumptions on (1) the intra-distribution system <span class="hlt">variability</span> and (2) short-term (seasonal) <span class="hlt">concentration</span> <span class="hlt">variability</span> have to be made. We assess <span class="hlt">concentration</span> <span class="hlt">variability</span> in the distribution system of nitrate, nitrite, and ammonium, and seasonal <span class="hlt">variability</span> in all Danish public waterworks from 2007 to 2016. Nitrate <span class="hlt">concentrations</span> at the exit of the waterworks are highly correlated with nitrate <span class="hlt">concentrations</span> within the distribution net or at the consumers' taps, while nitrite and ammonium <span class="hlt">concentrations</span> are generally lower within the net compared with the exit of the waterworks due to nitrification. However, nitrification of nitrite and ammonium in the distribution systems only results in a relatively small increase in nitrate <span class="hlt">concentrations</span>. No seasonal variation for nitrate, nitrite, or ammonium was observed. We conclude that nitrate measurements taken at the exit of the waterworks are suitable to calculate exposures for all consumers connected to that waterworks and that sampling frequencies in the national monitoring programme are sufficient to describe temporal variations in longitudinal studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5369112','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5369112"><span>Nitrate, Nitrite, and Ammonium <span class="hlt">Variability</span> in Drinking Water Distribution Systems</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Schullehner, Jörg; Stayner, Leslie; Hansen, Birgitte</p> <p>2017-01-01</p> <p>Accurate assessments of exposure to nitrate in drinking water is a crucial part of epidemiological studies investigating long-term adverse human health effects. However, since drinking water nitrate measurements are usually collected for regulatory purposes, assumptions on (1) the intra-distribution system <span class="hlt">variability</span> and (2) short-term (seasonal) <span class="hlt">concentration</span> <span class="hlt">variability</span> have to be made. We assess <span class="hlt">concentration</span> <span class="hlt">variability</span> in the distribution system of nitrate, nitrite, and ammonium, and seasonal <span class="hlt">variability</span> in all Danish public waterworks from 2007 to 2016. Nitrate <span class="hlt">concentrations</span> at the exit of the waterworks are highly correlated with nitrate <span class="hlt">concentrations</span> within the distribution net or at the consumers’ taps, while nitrite and ammonium <span class="hlt">concentrations</span> are generally lower within the net compared with the exit of the waterworks due to nitrification. However, nitrification of nitrite and ammonium in the distribution systems only results in a relatively small increase in nitrate <span class="hlt">concentrations</span>. No seasonal variation for nitrate, nitrite, or ammonium was observed. We conclude that nitrate measurements taken at the exit of the waterworks are suitable to calculate exposures for all consumers connected to that waterworks and that sampling frequencies in the national monitoring programme are sufficient to describe temporal variations in longitudinal studies. PMID:28282914</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5835952','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5835952"><span>Infinitely <span class="hlt">variable</span> steering transmission</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Reed, B.O.</p> <p>1989-04-04</p> <p>A steering transmission is described comprising: first and second drive units each driven at a substantially constant speed for producing respective first and second unidirectional, continuous outputs infinitely <span class="hlt">variable</span> between a minimum speed and a maximum speed; a first output planetary gear drivingly connected to a first transmission output; a second output planetary gear set drivingly connected to a second transmission output; an input gear set; means interconnecting the first and second output planetary gear sets; means connecting the first drive unit to the first output planetary gear set; means applying the second drive unit output to the second output planetary gear set; means applying a substantially constant speed input to the input gear set; means for selectively conditioning the input gear set to drive the one output planetary gear set at a speed having a first predetermined fixed ratio to the constant speed input, whereby to operate the transmission in one speed range; and means for selectively applying the first drive unit output to second output planetary gear set, whereby to operate the transmission in another speed range different from the one speed range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/450071','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/450071"><span><span class="hlt">Variable</span> depth core sampler</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bourgeois, P.M.; Reger, R.J.</p> <p>1994-12-31</p> <p>This invention relates to a sampling means, more particularly to a device to sample hard surfaces at varying depths. Often it is desirable to take samples of a hard surface wherein the samples are of the same diameter but of varying depths. Current practice requires that a full top-to-bottom sample of the material be taken, using a hole saw, and boring a hole from one end of the material to the other. The sample thus taken is removed from the hole saw and the middle of said sample is then subjected to further investigation. This paper describes a <span class="hlt">variable</span> depth core sampler comprimising a circular hole saw member, having longitudinal sections that collapse to form a point and capture a sample, and a second saw member residing inside the first hole saw member to support the longitudinal sections of the first member and prevent them from collapsing to form a point. The second hole saw member may be raised and lowered inside the the first hole saw member.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/7224634','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/7224634"><span><span class="hlt">Variable</span> camshaft timing system</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sapienza, S.J.</p> <p>1988-05-17</p> <p>A <span class="hlt">variable</span> camshaft timing system in combination with an internal combustion engine having at least one cylinder, a rotatable member such as a crankshaft, and an intake and exhaust valve coupled to an intake camshaft and an exhaust camshaft respectively, the system is described comprising: a pulley wheel fixedly attached at one end of each of the intake and exhaust camshafts and the crankshaft; belt means interconnecting each of the pulley wheels for transferring rotational motion from the crankshaft to the intake and exhaust camshafts; first and second idler arm means pivotally attached to the engine, each of the idler arm means having a pivoting arm, a cam follower arm and an idler wheel in operative contact with the belt means; positioning cam means operatively coupled to each of the cam follower arms of the idler arm means; a control means responsive to various engine operating parameters for generating motor control signals; and electric motor means responsive to the motor control signals and operatively coupled to rotate the positioning cams means for positioning each of the idler arm means for changing the relative rotational position between the input camshaft and the exhaust camshaft.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AIPC..752..175S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AIPC..752..175S"><span>Extragalactic Cataclysmic <span class="hlt">Variables</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shara, Michael M.; Neill, James D.</p> <p>2005-03-01</p> <p>SALT is uniquely poised to make major inroads in the study of extragalactic cataclysmic <span class="hlt">variables</span> (CVs) - novae and dwarf novae. The ability to search an external galaxy for erupting CVs night after night, for months at a time, AND to obtain confirmatory spectra within a night of discovery is unique and invaluable. We present several examples of multi-week to multi-month searches for extragalactic CVs with 1 to 4 meter-class telescopes. In particular, we have detected the first erupting dwarf novae in the LMC and placed a lower limit on the number of CVs in that galaxy. We have also observed the Local Group dwarf ellipticals M32 and NGC 205 in their entirety every clear night over a 4.5 month interval. In this survey we discovered one nova each in M32 and NGC 205, far more than previous nova surveys led us to expect. A similar search in M81 again reveals more novae than expected, and demonstrates, conclusively, that novae are predominantly a bulge population in spiral galaxies. Finally we report the detection of intergalactic tramp novae in the Fornax cluster, and emphasize that these are valuable tracers of stars stripped from their hosts during galaxy harassment. The insights gained during these preliminary studies illustrate how valuable SALT campaigns on extragalactic CVs will be.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950020650','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950020650"><span>Nova-like <span class="hlt">variables</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ladous, Constanze</p> <p>1993-01-01</p> <p>On grounds of different observable characteristics five classes of nova-like objects are distinguished: the UX Ursae Majoris stars, the antidwarf novae, the DQ Herculis stars, the AM Herculis stars, and the AM Canum Venaticorum stars. Some objects have not been classified specifically. Nova-like stars share most observable features with dwarf novae, except for the outburst behavior. The understanding is that dwarf novae, UX Ursae Majoris stars, and anti-dwarf novae are basically the same sort of objects. The difference between them is that in UX Ursae Majoris stars the mass transfer through the accretion disc always is high so the disc is stationary all the time; in anti-dwarf novae for some reason the mass transfer occasionally drops considerably for some time, and in dwarf novae it is low enough for the disc to undergo semiperiodic changes between high and low accretion events. DQ Herculis stars are believed to possess weakly magnetic white dwarfs which disrupt the inner disc at some distance from the central star; the rotation of the white dwarf can be seen as an additional photometric period. In AM Herculis stars, a strongly magnetic white dwarf entirely prevents the formation of an accretion disk and at the same time locks the rotation of the white dwarf to the binary orbit. Finally, AM Canum Venaticorum stars are believed to be cataclysmic <span class="hlt">variables</span> that consist of two white dwarf components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/125102','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/125102"><span><span class="hlt">Variable</span> angle correlation spectroscopy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lee, Young Kyo</p> <p>1994-05-01</p> <p>In this dissertation, a novel nuclear magnetic resonance (NMR) technique, <span class="hlt">variable</span> angle correlation spectroscopy (VACSY) is described and demonstrated with <sup>13</sup>C nuclei in rapidly rotating samples. These experiments focus on one of the basic problems in solid state NMR: how to extract the wealth of information contained in the anisotropic component of the NMR signal while still maintaining spectral resolution. Analysis of the anisotropic spectral patterns from poly-crystalline systems reveal information concerning molecular structure and dynamics, yet in all but the simplest of systems, the overlap of spectral patterns from chemically distinct sites renders the spectral analysis difficult if not impossible. One solution to this problem is to perform multi-dimensional experiments where the high-resolution, isotropic spectrum in one dimension is correlated with the anisotropic spectral patterns in the other dimensions. The VACSY technique incorporates the angle between the spinner axis and the static magnetic field as an experimental parameter that may be incremented during the course of the experiment to help correlate the isotropic and anisotropic components of the spectrum. The two-dimensional version of the VACSY experiments is used to extract the chemical shift anisotropy tensor values from multi-site organic molecules, study molecular dynamics in the intermediate time regime, and to examine the ordering properties of partially oriented samples. The VACSY technique is then extended to three-dimensional experiments to study slow molecular reorientations in a multi-site polymer system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26868026','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26868026"><span>Common <span class="hlt">Variable</span> Immunodeficiency.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Saikia, Biman; Gupta, Sudhir</p> <p>2016-04-01</p> <p>Common <span class="hlt">variable</span> immunodeficiency (CVID) is the most common primary immunodeficiency of young adolescents and adults which also affects the children. The disease remains largely under-diagnosed in India and Southeast Asian countries. Although in majority of cases it is sporadic, disease may be inherited in a autosomal recessive pattern and rarely, in autosomal dominant pattern. Patients, in addition to frequent sino-pulmonary infections, are also susceptible to various autoimmune diseases and malignancy, predominantly lymphoma and leukemia. Other characteristic lesions include lymphocytic and granulomatous interstitial lung disease, and nodular lymphoid hyperplasia of gut. Diagnosis requires reduced levels of at least two immunoglobulin isotypes: IgG with IgA and/or IgM and impaired specific antibody response to vaccines. A number of gene mutations have been described in CVID; however, these genetic alterations account for less than 20% of cases of CVID. Flow cytometry aptly demonstrates a disturbed B cell homeostasis with reduced or absent memory B cells and increased CD21(low) B cells and transitional B cell populations. Approximately one-third of patients with CVID also display T cell functional defects. Immunoglobulin therapy remains the mainstay of treatment. Immunologists and other clinicians in India and other South East Asian countries need to be aware of CVID so that early diagnosis can be made, as currently, majority of these patients still go undiagnosed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24188283','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24188283"><span>The contribution of intra- and interspecific tolerance <span class="hlt">variability</span> to biodiversity changes along toxicity gradients.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>De Laender, Frederik; Melian, Carlos J; Bindler, Richard; Van den Brink, Paul J; Daam, Michiel; Roussel, Helene; Juselius, Jonas; Verschuren, Dirk; Janssen, Colin R</p> <p>2014-01-01</p> <p>The worldwide distribution of toxicants is an important yet understudied driver of biodiversity, and the mechanisms relating toxicity to diversity have not been adequately explored. Here, we present a community model integrating demography, dispersal and toxicant-induced effects on reproduction driven by intraspecific and interspecific <span class="hlt">variability</span> in toxicity tolerance. We compare model predictions to 458 species abundance distributions (SADs) observed along <span class="hlt">concentration</span> gradients of toxicants to show that the best predictions occur when intraspecific <span class="hlt">variability</span> is five and ten times higher than interspecific <span class="hlt">variability</span>. At high <span class="hlt">concentrations</span>, lower settings of intraspecific <span class="hlt">variability</span> resulted in predictions of community extinction that were not supported by the observed SADs. Subtle but significant species losses at low <span class="hlt">concentrations</span> were predicted only when intraspecific <span class="hlt">variability</span> dominated over interspecific <span class="hlt">variability</span>. Our results propose intraspecific <span class="hlt">variability</span> as a key driver for biodiversity sustenance in ecosystems challenged by environmental change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2429973','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2429973"><span>Increased Brain Signal <span class="hlt">Variability</span> Accompanies Lower Behavioral <span class="hlt">Variability</span> in Development</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>McIntosh, Anthony Randal; Kovacevic, Natasa; Itier, Roxane J.</p> <p>2008-01-01</p> <p>As the brain matures, its responses become optimized. Behavioral measures show this through improved accuracy and decreased trial-to-trial <span class="hlt">variability</span>. The question remains whether the supporting brain dynamics show a similar decrease in <span class="hlt">variability</span>. We examined the relation between <span class="hlt">variability</span> in single trial evoked electrical activity of the brain (measured with EEG) and performance of a face memory task in children (8–15 y) and young adults (20–33 y). Behaviorally, children showed slower, more <span class="hlt">variable</span> response times (RT), and less accurate recognition than adults. However, brain signal <span class="hlt">variability</span> increased with age, and showed strong negative correlations with intrasubject RT <span class="hlt">variability</span> and positive correlations with accuracy. Thus, maturation appears to lead to a brain with greater functional <span class="hlt">variability</span>, which is indicative of enhanced neural complexity. This <span class="hlt">variability</span> may reflect a broader repertoire of metastable brain states and more fluid transitions among them that enable optimum responses. Our results suggest that the moment-to-moment <span class="hlt">variability</span> in brain activity may be a critical index of the cognitive capacity of the brain. PMID:18604265</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040050637','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040050637"><span>Greenland Glacier Albedo <span class="hlt">Variability</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p>The program for Arctic Regional Climate Assessment (PARCA) is a NASA-funded project with the prime goal of addressing the mass balance of the Greenland ice sheet. Since the formal initiation of the program in 1995, there has been a significant improvement in the estimates of the mass balance of the ice sheet. Results from this program reveal that the high-elevation regions of the ice sheet are approximately in balance, but the margins are thinning. Laser surveys reveal significant thinning along 70 percent of the ice sheet periphery below 2000 m elevations, and in at least one outlet glacier, Kangerdlugssuaq in southeast Greenland, thinning has been as much as 10 m/yr. This study examines the albedo <span class="hlt">variability</span> in four outlet glaciers to help separate out the relative contributions of surface melting versus ice dynamics to the recent mass balance changes. Analysis of AVHRR Polar Pathfinder albedo shows that at the Petermann and Jakobshavn glaciers, there has been a negative trend in albedo at the glacier terminus from 1981 to 2000, whereas the Stor+strommen and Kangerdlugssuaq glaciers show slightly positive trends in albedo. These findings are consistent with recent observations of melt extent from passive microwave data which show more melt on the western side of Greenland and slightly less on the eastern side. Significance of albedo trends will depend on where and when the albedo changes occur. Since the majority of surface melt occurs in the shallow sloping western margin of the ice sheet where the shortwave radiation dominates the energy balance in summer (e.g. Jakobshavn region) this region will be more sensitive to changes in albedo than in regions where this is not the case. Near the Jakobshavn glacier, even larger changes in albedo have been observed, with decreases as much as 20 percent per decade.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1324436','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1324436"><span>Droplet Number <span class="hlt">Concentration</span> Value Added Product</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chitra Sivaraman, PNNL</p> <p>2015-08-06</p> <p>Cloud droplet number <span class="hlt">concentration</span> is an important factor in understanding aerosol-cloud interactions. As aerosol <span class="hlt">concentration</span> increases, it is expected that droplet number <span class="hlt">concentration</span> (Nd) will increase and droplet size will decrease, for a given liquid water path. This will greatly affect cloud albedo as smaller droplets reflect more shortwave radiation; however, the magnitude and <span class="hlt">variability</span> of these processes under different environmental conditions is still uncertain.McComiskey et al. (2009) have implemented a method, based onBoers and Mitchell (1994), for calculating Nd from ground-based remote sensing measurements of optical depth and liquid water path. They show that the magnitude of the aerosol-cloud interactions (ACI) varies with a range of factors, including the relative value of the cloud liquid water path (LWP), the aerosol size distribution, and the cloud updraft velocity. Estimates of Nd under a range of cloud types and conditions and at a variety of sites are needed to further quantify the impacts of aerosol cloud interactions. In order to provide data sets for studying aerosol-cloud interactions, the McComiskey et al. (2009) method was implemented as the Droplet Number <span class="hlt">Concentration</span> (NDROP) value-added product (VAP).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5373004','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5373004"><span>The History of Clotting Factor <span class="hlt">Concentrates</span> Pharmacokinetics</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Morfini, Massimo</p> <p>2017-01-01</p> <p>Clotting factor <span class="hlt">concentrates</span> (CFCs) underwent tremendous modifications during the last forty years. Plasma-derived <span class="hlt">concentrates</span> made the replacement therapy feasible not only in the hospital but also at patients’ home by on-demand or prophylactic regimen. Virucidal methods, implemented soon after hepatitis and AIDS outbreak, and purification by Mabs made the plasma-derived <span class="hlt">concentrates</span> safer and purer. CFCs were considered equivalent to the other drugs and general rules and methods of pharmacokinetics (PK) were applied to their study. After the first attempts by graphical methods and calculation of In Vivo Recovery, compartment and non-compartment methods were applied also to the study of PK of CFCs. The bioequivalence of the new <span class="hlt">concentrates</span> produced by means of recombinant DNA biotechnology was evaluated in head-to-head PK studies. Since the beginning, the large inter-patient <span class="hlt">variability</span> of dose/response of replacement therapy was realized. PK allowed tailoring haemophilia therapy and PK driven prophylaxis resulted more cost effective. Unfortunately, the need of several blood samples and logistic difficulties made the PK studies very demanding. Recently, population PK (PopPK) has been applied to the prediction of CFCs dosing by Bayesian methodology. By PopPK also sparse data may allow evaluating the appropriateness of replacement therapy. PMID:28335525</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27681102','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27681102"><span>Tumor Static <span class="hlt">Concentration</span> Curves in Combination Therapy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cardilin, Tim; Almquist, Joachim; Jirstrand, Mats; Sostelly, Alexandre; Amendt, Christiane; El Bawab, Samer; Gabrielsson, Johan</p> <p>2017-03-01</p> <p>Combination therapies are widely accepted as a cornerstone for treatment of different cancer types. A tumor growth inhibition (TGI) model is developed for combinations of cetuximab and cisplatin obtained from xenograft mice. Unlike traditional TGI models, both natural cell growth and cell death are considered explicitly. The growth rate was estimated to 0.006 h(-1) and the natural cell death to 0.0039 h(-1) resulting in a tumor doubling time of 14 days. The tumor static <span class="hlt">concentrations</span> (TSC) are predicted for each individual compound. When the compounds are given as single-agents, the required <span class="hlt">concentrations</span> were computed to be 506 μg · mL(-1) and 56 ng · mL(-1) for cetuximab and cisplatin, respectively. A TSC curve is constructed for different combinations of the two drugs, which separates <span class="hlt">concentration</span> combinations into regions of tumor shrinkage and tumor growth. The more concave the TSC curve is, the lower is the total exposure to test compounds necessary to achieve tumor regression. The TSC curve for cetuximab and cisplatin showed weak concavity. TSC values and TSC curves were estimated that predict tumor regression for 95% of the population by taking between-subject <span class="hlt">variability</span> into account. The TSC concept is further discussed for different <span class="hlt">concentration</span>-effect relationships and for combinations of three or more compounds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JGRG..113.2010S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JGRG..113.2010S"><span>Spatiotemporal <span class="hlt">variability</span> in peatland subsurface methane dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Strack, M.; Waddington, J. M.</p> <p>2008-06-01</p> <p>Peatlands are large natural sources of atmospheric methane (CH4). While many studies have measured CH4 emissions to the atmosphere, less is known about the stock and residence time of subsurface CH4. In this study we examined dissolved CH4 <span class="hlt">concentration</span> in near-surface peatland pore waters of a poor fen near Québec City, Canada, in order to (1) investigate the <span class="hlt">variability</span> in and potential controls on these <span class="hlt">concentrations</span> and (2) combine measured dissolved CH4 <span class="hlt">concentration</span> with estimated bubble CH4 stock and measured CH4 fluxes to estimate the mean residence time of subsurface CH4. <span class="hlt">Concentrations</span> ranged from 1 to 450 μM during both study seasons. Depth profiles were generally consistent at one location within the peatland throughout the sampling period but varied between locations. Patterns with depth were not well correlated to pore water pH or EC; however, changes in CH4 <span class="hlt">concentration</span> through time in the upper 30 cm were related to temperature and water table at some locations. Depth profiles taken at 2- to 5-cm intervals revealed discrete <span class="hlt">concentration</span> "spikes" which were often maintained throughout the season and are likely related to bubble CH4 dynamics. Estimated subsurface CH4 stocks indicate that even when relatively low bubble volume (5% of peat volume) is assumed, bubble CH4 accounted for greater than half of total stocks. Calculated mean residence times were 28-120 days. This implies that CH4 flux may lag changes in water table and temperature which happen on shorter timescales (hours or days). To improve our description of subsurface CH4 stocks, links between dissolved and bubble CH4 stocks and peatland CH4 residence time, coincident measurement of pore water CH4 <span class="hlt">concentrations</span>, entrapped gas content and composition, diffusive CH4 flux, and ebullition are required.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27537548','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27537548"><span>Organic Wheat Farming Improves Grain Zinc <span class="hlt">Concentration</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Helfenstein, Julian; Müller, Isabel; Grüter, Roman; Bhullar, Gurbir; Mandloi, Lokendra; Papritz, Andreas; Siegrist, Michael; Schulin, Rainer; Frossard, Emmanuel</p> <p>2016-01-01</p> <p>Zinc (Zn) nutrition is of key relevance in India, as a large fraction of the population suffers from Zn malnutrition and many soils contain little plant available Zn. In this study we compared organic and conventional wheat cropping systems with respect to DTPA (diethylene triamine pentaacetic acid)-extractable Zn as a proxy for plant available Zn, yield, and grain Zn <span class="hlt">concentration</span>. We analyzed soil and wheat grain samples from 30 organic and 30 conventional farms in Madhya Pradesh (central India), and conducted farmer interviews to elucidate sociological and management <span class="hlt">variables</span>. Total and DTPA-extractable soil Zn <span class="hlt">concentrations</span> and grain yield (3400 kg ha-1) did not differ between the two farming systems, but with 32 and 28 mg kg-1 respectively, grain Zn <span class="hlt">concentrations</span> were higher on organic than conventional farms (t = -2.2, p = 0.03). Furthermore, multiple linear regression analyses revealed that (a) total soil zinc and sulfur <span class="hlt">concentrations</span> were the best predictors of DTPA-extractable soil Zn, (b) Olsen phosphate taken as a proxy for available soil phosphorus, exchangeable soil potassium, harvest date, training of farmers in nutrient management, and soil silt content were the best predictors of yield, and (c) yield, Olsen phosphate, grain nitrogen, farmyard manure availability, and the type of cropping system were the best predictors of grain Zn <span class="hlt">concentration</span>. Results suggested that organic wheat contained more Zn despite same yield level due to higher nutrient efficiency. Higher nutrient efficiency was also seen in organic wheat for P, N and S. The study thus suggests that appropriate farm management can lead to competitive yield and improved Zn <span class="hlt">concentration</span> in wheat grains on organic farms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4990241','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4990241"><span>Organic Wheat Farming Improves Grain Zinc <span class="hlt">Concentration</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Helfenstein, Julian; Müller, Isabel; Grüter, Roman; Bhullar, Gurbir; Mandloi, Lokendra; Papritz, Andreas; Siegrist, Michael; Schulin, Rainer; Frossard, Emmanuel</p> <p>2016-01-01</p> <p>Zinc (Zn) nutrition is of key relevance in India, as a large fraction of the population suffers from Zn malnutrition and many soils contain little plant available Zn. In this study we compared organic and conventional wheat cropping systems with respect to DTPA (diethylene triamine pentaacetic acid)-extractable Zn as a proxy for plant available Zn, yield, and grain Zn <span class="hlt">concentration</span>. We analyzed soil and wheat grain samples from 30 organic and 30 conventional farms in Madhya Pradesh (central India), and conducted farmer interviews to elucidate sociological and management <span class="hlt">variables</span>. Total and DTPA-extractable soil Zn <span class="hlt">concentrations</span> and grain yield (3400 kg ha-1) did not differ between the two farming systems, but with 32 and 28 mg kg-1 respectively, grain Zn <span class="hlt">concentrations</span> were higher on organic than conventional farms (t = -2.2, p = 0.03). Furthermore, multiple linear regression analyses revealed that (a) total soil zinc and sulfur <span class="hlt">concentrations</span> were the best predictors of DTPA-extractable soil Zn, (b) Olsen phosphate taken as a proxy for available soil phosphorus, exchangeable soil potassium, harvest date, training of farmers in nutrient management, and soil silt content were the best predictors of yield, and (c) yield, Olsen phosphate, grain nitrogen, farmyard manure availability, and the type of cropping system were the best predictors of grain Zn <span class="hlt">concentration</span>. Results suggested that organic wheat contained more Zn despite same yield level due to higher nutrient efficiency. Higher nutrient efficiency was also seen in organic wheat for P, N and S. The study thus suggests that appropriate farm management can lead to competitive yield and improved Zn <span class="hlt">concentration</span> in wheat grains on organic farms. PMID:27537548</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720000147','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720000147"><span>Conical electromagnetic radiation flux <span class="hlt">concentrator</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miller, E. R.</p> <p>1972-01-01</p> <p><span class="hlt">Concentrator</span> provides method of <span class="hlt">concentrating</span> a beam of electromagnetic radiation into a smaller beam, presenting a higher flux density. Smaller beam may be made larger by sending radiation through the device in the reverse direction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2253496','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2253496"><span>Quantifying <span class="hlt">Variability</span> of Avian Colours: Are Signalling Traits More <span class="hlt">Variable</span>?</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Delhey, Kaspar; Peters, Anne</p> <p>2008-01-01</p> <p>Background Increased <span class="hlt">variability</span> in sexually selected ornaments, a key assumption of evolutionary theory, is thought to be maintained through condition-dependence. Condition-dependent handicap models of sexual selection predict that (a) sexually selected traits show amplified <span class="hlt">variability</span> compared to equivalent non-sexually selected traits, and since males are usually the sexually selected sex, that (b) males are more <span class="hlt">variable</span> than females, and (c) sexually dimorphic traits more <span class="hlt">variable</span> than monomorphic ones. So far these predictions have only been tested for metric traits. Surprisingly, they have not been examined for bright coloration, one of the most prominent sexual traits. This omission stems from computational difficulties: different types of colours are quantified on different scales precluding the use of coefficients of variation. Methodology/Principal Findings Based on physiological models of avian colour vision we develop an index to quantify the degree of discriminable colour variation as it can be perceived by conspecifics. A comparison of <span class="hlt">variability</span> in ornamental and non-ornamental colours in six bird species confirmed (a) that those coloured patches that are sexually selected or act as indicators of quality show increased chromatic <span class="hlt">variability</span>. However, we found no support for (b) that males generally show higher levels of <span class="hlt">variability</span> than females, or (c) that sexual dichromatism per se is associated with increased <span class="hlt">variability</span>. Conclusions/Significance We show that it is currently possible to realistically estimate <span class="hlt">variability</span> of animal colours as perceived by them, something difficult to achieve with other traits. Increased <span class="hlt">variability</span> of known sexually-selected/quality-indicating colours in the studied species, provides support to the predictions borne from sexual selection theory but the lack of increased overall <span class="hlt">variability</span> in males or dimorphic colours in general indicates that sexual differences might not always be shaped by similar selective</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4226393','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4226393"><span><span class="hlt">VARIABLE</span> TIME-INTERVAL GENERATO