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1

Average Soil Water Retention Curves Measured by Neutron Radiography  

SciTech Connect

Water retention curves are essential for understanding the hydrologic behavior of partially-saturated porous media and modeling flow transport processes within the vadose zone. In this paper we report direct measurements of the main drying and wetting branches of the average water retention function obtained using 2-dimensional neutron radiography. Flint sand columns were saturated with water and then drained under quasi-equilibrium conditions using a hanging water column setup. Digital images (2048 x 2048 pixels) of the transmitted flux of neutrons were acquired at each imposed matric potential (~10-15 matric potential values per experiment) at the NCNR BT-2 neutron imaging beam line. Volumetric water contents were calculated on a pixel by pixel basis using Beer-Lambert s law after taking into account beam hardening and geometric corrections. To remove scattering effects at high water contents the volumetric water contents were normalized (to give relative saturations) by dividing the drying and wetting sequences of images by the images obtained at saturation and satiation, respectively. The resulting pixel values were then averaged and combined with information on the imposed basal matric potentials to give average water retention curves. The average relative saturations obtained by neutron radiography showed an approximate one-to-one relationship with the average values measured volumetrically using the hanging water column setup. There were no significant differences (at p < 0.05) between the parameters of the van Genuchten equation fitted to the average neutron radiography data and those estimated from replicated hanging water column data. Our results indicate that neutron imaging is a very effective tool for quantifying the average water retention curve.

Cheng, Chu-Lin [ORNL; Perfect, Edmund [University of Tennessee, Knoxville (UTK); Kang, Misun [ORNL; Voisin, Sophie [ORNL; Bilheux, Hassina Z [ORNL; Horita, Juske [Texas Tech University (TTU); Hussey, Dan [NIST Center for Neutron Research (NCRN), Gaithersburg, MD

2011-01-01

2

Water retention curves and thermal insulating properties of Thermosand  

NASA Astrophysics Data System (ADS)

The heat loss and the efficiency of isolating material surrounding heat supply pipes are essential issues for the energy budget of heat supply pipe lines. Until now heat loss from the pipe is minimized by enlarging the polyurethane (PU) - insulation thickness around the pipe. As a new approach to minimize the heat loss a thermally insulating bedding material was developed and investigated. Conventional bedding sands cover all necessary soil mechanical properties, but have a high thermal conductivity from ? =1,5 to 1,7 W/(m K). A newly developed embedding material 'Thermosand' shows thermal properties from ?=0,18 W/(m K) (dry) up to 0,88 W/(m K) (wet). The raw material originates from the waste rock stockpiles of a coal mine near Fohnsdorf, Austria. With high temperatures up to nearly 1000 ° C and a special mineral mixture, a natural burned reddish material resembling clinker arises. The soilmechanical properties of Thermosand has been thoroughly investigated with laboratory testing and in situ investigations to determine compaction-, permeability- and shear-behaviour, stiffness and corresponding physical parameters. Test trenches along operational heat pipes with temperature-measurement along several cross-sections were constructed to compare conventional embedding materials with 'Thermosand'. To investigate the influence of varying moisture content on thermal conductivity a 1:1 large scale model test in the laboratory to simulate real insitu-conditions was established. Based on this model it is planned to develop numerical simulations concerning varying moisture contents and unsaturated soil mechanics with heat propagation, including the drying out of the soil during heat input. These simulations require the knowledge about the water retention properties of the material. Thus, water retention curves were measured using both steady-state tension and pressure techniques and the simplified evaporation method. The steady-state method employs a tension table (sand box) at tensions below 100 hPa and a pressure extractor at tensions between 300 hPa and 15,000 hPa; the water content is measured by weighing after the sample has equilibrated at the tension value set on the table or plate. In the transient evaporation method two tensiometers with a measurement range between 0 and 850 hPa are installed at a depth of 1.25 cm and 3.75 cm in a sample of 5 cm in height; the mean values of the two tensiometers and the water contents measured by weighting are used to obtain the water retention curve. First results of both methods show that the Thermosand samples release water over the entire tension range measured above 10 hPa. Because of the limited measurement range of the tensiometers used for the evaporation method, the measured curve must be extrapolated between 850 hPa and 15,000 hPa, to allow comparison with the steady-state method. To this end, it was attempted to match the Van-Genuchten and a bimodal Van-Genuchten retention function to the data from the evaporation experiments. This involves a simultaneous fit of both the water-retention and the hydraulic-conductivity function. As one first result only the Van-Genuchten model was found to be able to produce satisfactorily fits to the data. The extrapolated water retention curves (above 850 hPa) however do not match the data from the steady-state method. This suggests that alternative soil hydraulic functions are needed to provide an adequate representation of the water retention characteristics of the Thermosand. It has to be considered that especially for the heat flow simulation water retention and hydraulic conductivity functions above 15,000 hPa have to be determined.

Leibniz, Otto; Winkler, Gerfried; Birk, Steffen

2010-05-01

3

Soil Water Thermodynamic to Unify Water Retention Curve by Pressure Plates and Tensiometer  

NASA Astrophysics Data System (ADS)

The pressure plate method is a standard method for measuring the pF curves, also called soil water retention curves, in a large soil moisture range from saturation to a dry state corresponding to a tension pressure of near 1500 kPa. However, the pressure plate can only provide discrete water retention curves represented by a dozen measured points. In contrast, the measurement of the soil water retention curves by tensiometer is direct and continuous, but limited to the range of the tensiometer reading: from saturation to near 70-80 kPa. The two methods stem from two very different concepts of measurement and the compatibility of both methods has never been demonstrated. The recently established thermodynamic formulation of the pedostructure water retention curve, will allow the compatibility of the two curves to be studied, both theoretically and experimentally. This constitutes the object of the present article. We found that the pressure plate method provides accurate measurement points of the pedostructure water retention curve h(W), conceptually the same as that accurately measured by the tensiometer. However, contrarily to what is usually thought, h is not equal to the applied air pressure on the sample, but rather, is proportional to its logarithm, in agreement with the thermodynamic theory developed in the article. The pF curve and soil water retention curve, as well as their methods of measurement are unified in a same physical theory. It is the theory of the soil medium organization (pedostructure) and its interaction with water. We show also how the hydrostructural parameters of the theoretical curve equation can be estimated from any measured curve, whatever the method of measurement. An application example using published pF curves is given.

Braudeau, Erik; Hovhannissian, Gaghik; Assi, Amjad; Mohtar, Rabi

2014-10-01

4

A Global Optimization Method to Calculate Water Retention Curves  

NASA Astrophysics Data System (ADS)

Water retention curves (WRC) have a key role for the hydraulic characterization of soils and rocks. The behaviour of the medium is defined by relating the unsaturated water content to the matric potential. The experimental determination of WRCs requires an accurate and detailed measurement of the dependence of matric potential on water content, a time-consuming and error-prone process, in particular for rocky media. A complete experimental WRC needs at least a few tens of data points, distributed more or less uniformly from full saturation to oven dryness. Since each measurement requires to wait to reach steady state conditions (i.e., between a few tens of minutes for soils and up to several hours or days for rocks or clays), the whole process can even take a few months. The experimental data are fitted to the most appropriate parametric model, such as the widely used models of Van Genuchten, Brooks and Corey and Rossi-Nimmo, to obtain the analytic WRC. We present here a new method for the determination of the parameters that best fit the models to the available experimental data. The method is based on differential evolution, an evolutionary computation algorithm particularly useful for multidimensional real-valued global optimization problems. With this method it is possible to strongly reduce the number of measurements necessary to optimize the model parameters that accurately describe the WRC of the samples, allowing to decrease the time needed to adequately characterize the medium. In the present work, we have applied our method to calculate the WRCs of sedimentary carbonatic rocks of marine origin, belonging to 'Calcarenite di Gravina' Formation (Middle Pliocene - Early Pleistocene) and coming from two different quarry districts in Southern Italy. WRC curves calculated using the Van Genuchten model by simulated annealing (dashed curve) and differential evolution (solid curve). The curves are calculated using 10 experimental data points randomly extracted from the full experimental dataset. Simulated annealing is not able to find the optimal solution with this reduced data set.

Maggi, S.; Caputo, M. C.; Turturro, A. C.

2013-12-01

5

Estimating water retention curves for sandy soils at the Doñana National Park, SW Spain  

Technology Transfer Automated Retrieval System (TEKTRAN)

The determination of soil water retention curves (SWRC) in the laboratory is a slow and tedious task, which is especially challenging for sandy soils due to their low water retention capacity and large water content changes for small pressure head differences. Due to spatial variability within larg...

6

Multiple pixel-scale soil water retention curves quantified by neutron radiography  

NASA Astrophysics Data System (ADS)

The soil water retention function is needed for modeling multiphase flow in porous media. Traditional techniques for measuring the soil water retention function, such as the hanging water column or pressure cell methods, yield average water retention data which have to be modeled using inverse procedures to extract relevant point parameters. In this study, we have developed a technique for directly measuring multiple point (pixel-scale) water retention curves for a repacked sand material using 2-D neutron radiography. Neutron radiographic images were obtained under quasi-equilibrium conditions at nine imposed basal matric potentials during monotonic drying of Flint sand at the High Flux Isotope Reactor (HFIR) Cold Guide (CG) 1D beamline at Oak Ridge National Laboratory. All of the images were normalized with respect to an image of the oven dry sand column. Volumetric water contents were computed on a pixel by pixel basis using an empirical calibration equation after taking into account beam hardening and geometric corrections. Corresponding matric potentials were calculated from the imposed basal matric potential and pixel elevations. Volumetric water content and matric potential data pairs corresponding to 120 selected pixels were used to construct 120 point water retention curves. Each curve was fitted to the Brooks and Corey equation using segmented non-linear regression in SAS. A 98.5% convergence rate was achieved resulting in 115 estimates of the four Brooks and Corey parameters. A single Brooks and Corey point water retention function was constructed for Flint sand using the median values of these parameter estimates. This curve corresponded closely with the point Brooks and Corey function inversely extracted from the average water retention data using TrueCell. Forward numerical simulations performed using HYDRUS 1-D showed that the cumulative outflows predicted using the point Brooks and Corey functions from both the direct (neutron radiography) and inverse (TrueCell) methods were in good agreement with independent measurements of cumulative outflow determined with a transducer. Our results indicate that neutron radiography can be used to quantify the point water retention curve of homogeneous mineral particles. Further research will be needed to extend this approach to more heterogeneous porous media.

Kang, M.; Perfect, E.; Cheng, C. L.; Bilheux, H. Z.; Lee, J.; Horita, J.; Warren, J. M.

2014-03-01

7

Extrapolative Capability of Two Models That Estimating Soil Water Retention Curve between Saturation and Oven Dryness  

PubMed Central

Accurate estimation of soil water retention curve (SWRC) at the dry region is required to describe the relation between soil water content and matric suction from saturation to oven dryness. In this study, the extrapolative capability of two models for predicting the complete SWRC from limited ranges of soil water retention data was evaluated. When the model parameters were obtained from SWRC data in the 0–1500 kPa range, the FX model (Fredlund and Xing, 1994) estimations agreed well with measurements from saturation to oven dryness with RMSEs less than 0.01. The GG model (Groenevelt and Grant, 2004) produced larger errors at the dry region, with significantly larger RMSEs and MEs than the FX model. Further evaluations indicated that when SWRC measurements in the 0–100 kPa suction range was applied for model establishment, the FX model was capable of producing acceptable SWRCs across the entire water content range. For a higher accuracy, the FX model requires soil water retention data at least in the 0- to 300-kPa range to extend the SWRC to oven dryness. Comparing with the Khlosi et al. (2006) model, which requires measurements in the 0–500 kPa range to reproduce the complete SWRCs, the FX model has the advantage of requiring less SWRC measurements. Thus the FX modeling approach has the potential to eliminate the processes for measuring soil water retention in the dry range. PMID:25464503

Lu, Sen; Ren, Tusheng; Lu, Yili; Meng, Ping; Sun, Shiyou

2014-01-01

8

Comparison of Optimization and Two-point Methods in Estimation of Soil Water Retention Curve  

NASA Astrophysics Data System (ADS)

Soil water retention curve (SWRC) is one of the soil hydraulic properties in which its direct measurement is time consuming and expensive. Since, its measurement is unavoidable in study of environmental sciences i.e. investigation of unsaturated hydraulic conductivity and solute transport, in this study the attempt is to predict soil water retention curve from two measured points. By using Cresswell and Paydar (1996) method (two-point method) and an optimization method developed in this study on the basis of two points of SWRC, parameters of Tyler and Wheatcraft (1990) model (fractal dimension and air entry value) were estimated and then water content at different matric potentials were estimated and compared with their measured values (n=180). For each method, we used both 3 and 1500 kPa (case 1) and 33 and 1500 kPa (case 2) as two points of SWRC. The calculated RMSE values showed that in the Creswell and Paydar (1996) method, there exists no significant difference between case 1 and case 2. However, the calculated RMSE value in case 2 (2.35) was slightly less than case 1 (2.37). The results also showed that the developed optimization method in this study had significantly less RMSE values for cases 1 (1.63) and 2 (1.33) rather than Cresswell and Paydar (1996) method.

Ghanbarian-Alavijeh, B.; Liaghat, A. M.; Huang, G.

2009-04-01

9

Soil water retention curve of agrogray soils: Influence of anisotropy and the scaling factor  

NASA Astrophysics Data System (ADS)

The soil water characteristic or soil water retention curve (WRC) of medium-loamy gray forest soil horizons was studied in cylinder-shaped samples of disturbed and undisturbed structure. The sample height varied within 2-4 cm and the diameter within 4.5-10 cm. The soil monoliths were sampled in three profiles: vertically, along the slope, and across the slope in accordance with the intrasoil paleorelief formed by the funnel-shaped surface of the second humus horizon. The experimental WRC were approximated with the van Genuchten equation. The statistical analysis of the WRc approximation parameters proved to differ significantly in filled soil samples and monoliths, and a number of parameters differ for samples of the maximal height and diameter. The reliable differences of the parameters were also noted for the different sampling directions, most often, for those across the paleorelief slope. The noted variation in the WRC approximation parameters may substantially influence the predictive estimation of the spring water reserve for example. This fact suggests the necessity to strictly indicate the sampling procedure, in particular, with respect to the soil profile, the asymmetry in the soil properties, and the sample sizes (scaling factor) used for analyzing the hydrological properties of structured soils.

Umarova, A. B.; Shein, E. V.; Kukharuk, N. S.

2014-12-01

10

Analysis of water retention curve as a potential tool in comparing the effect of different soil management in two olive orchard in southern Spain  

NASA Astrophysics Data System (ADS)

Water soil erosion is one of the major concerns in agricultural areas in Southern Spain, and the use of cover crops has been recommended as an alternative to tillage to prevent, or mitigate, soil erosion. This change of soil management implies a progressive modification of soil chemical, biological and physical properties which to date, have been documented by a limited number of studies. In this communication we describe a methodology based on the modification of the water retention curves of intact cores, present the results obtained in two olive orchards in Southern Spain, and compare them with several chemical and physical properties measured simultaneously in the orchards. The experimental areas were located in Benacazón and Pedrera, Seville province in Southern Spain, and at each location two experimental plots were established. One of the plots was under traditional tillage management and the other under cover crop soil management. The slope at the plots was 12 and 4% respectively. Soil samples were taken at both plots differentiating between the inter tree areas and the under the olive canopy areas, between two different depths: 0-10 cm and 10-20 cm. These resulted in eight different sampling areas (2x2x2). Samples were taken three year after establishing the experiments. Water retention curves of soils were obtained as the average of replications per and using the Eijkelkamp Sand and Sand/Kaolin suction tables (0-500 hPa) and a Decagon's WP4-T dewpoint potentiometer (0-300•106 hPa). The latest was used to determine the residual water content. Experimental water retention curves were to two different models: van Genuchten (1980) and Kosugi (1994). Once modeling was done, the slope value of the curves at the inflexion point, proposed by Dexter (2004a, b, c) to estimate physical quality of soils, was calculated. This study presents and discusses the advantages and problems of the different approaches for determining the water retention curves, the potential of these curves to evaluate physical modifications of the soils, and compares them with the other soil properties measured at the experiments. References: Dexter, A. R. 2004. a.- Soil physical quality. Part I. Theory, effects of soil texture, density, and organic matter, and effects on root growth. Geoderma 120 (2004) 201-214. Dexter, A. R. 2004. b.- Soil physical quality. Part II. Friability, tillage, tilth and hardsetting. Geoderma 120 (2004) 215-225. Dexter, A. R. 2004. c.- Soil physical quality. Part III: Unsaturated hydraulic conductivity and general conclusions about S-theory. Geoderma 120 (2004) 227-239. Kosugi, K. 1994. Three-parameter lognormal distribution model for soil water retention. Water Resour. Re. 30: 891-901. van Genutchen, M.Th. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils, Soil Science Society of America Journal, v.44, p.892-898,1980.

Guzmán, G.; Gómez, J. A.; Giráldez, J. V.

2010-05-01

11

High-resolution Land Cover Datasets, Composite Curve Numbers, and Storm Water Retention in the Tampa Bay, FL region  

EPA Science Inventory

Policy makers need to understand how land cover change alters storm water regimes, yet existing methods do not fully utilize newly available datasets to quantify storm water changes at a landscape-scale. Here, we use high-resolution, remotely-sensed land cover, imperviousness, an...

12

Formulation of soil hydraulic conductivity from water retention curve, based on data inversion results, interpreted in terms of tortuosity, connectivity and flow turbulence.  

NASA Astrophysics Data System (ADS)

In order to refine hydraulic conductivity determination from soil water retention curve, we calculated the correcting factors, by data inversion, using a generalised formulation issued from Burdine or Mualem hydraulic conductivity. These formulations use the laminar flow, obeying Poiseuille law, through a bundle of cylinders of different radii, and correcting factors traducing the gap with real flow and real soil geometry. A general correcting factor is supposed to be proportional to water content, with an exponent a. An inner correcting factor is a function of pore size and/or water content and is inside the integral. We did not presuppose any analytical form for this inner correcting function. We used soil data obtained from clayey Amazonian tropical ferralsols composed of around 7/8 of clay fraction and fine silt (mainly kaolinite with some gibbsite and goethite) and 1/8 of coarse sand (quartz and kaolinite aggregates), with 0,2 to 1,5 % organic carbon content. Data were obtained using three different techniques : high pressurized water extraction disposal, evaporation experiment (Wind method) and in situ infiltration. The explored pore size domain was very large, ranging from 2 micrometers to 2 mm, completed by some data around 0,1 micrometer, so three to four orders of magnitude. We precised pore distribution in the range from 4 nm to 2 micrometers with mercury injection porosimetry corrected from drying effects. The pore distribution is bimodal, with a very small pore volume around 0,25 micrometer pore size. Such pore distribution allows observing separately the effects of pore size and water content on hydraulic conductivity, as water content is not a regularly increasing function of largest filled pores size. The results showed that a general correcting factor as an exponent of water content over all the described domain is inappropriate, as we encountered the smallest spreading of the inner correcting function when the exponent a is zero. The general correcting factor was taken constant with respect to water content ; it decreased with increasing organic carbon content (decrease of a factor 2). For the inner correcting factor, we shall interpret separately two domains, pores smaller or greater than 0,1 mm. For pores greater than 0,1 mm, hydraulic conductivity increase was simply proportional to water content increase : Poiseuille law does no longer apply as flow gets turbulent. For pores smaller than 0,1 mm, Poiseuille law applies, hydraulic conductivity increase (6 orders of magnitude) was explained, the inner correcting function extreme values ratio was 50. The correcting function variations correlated with the poral volume of the two orders of magnitude smaller than the size of the largest pores filled with water, we interpreted this as the connectivity effect. The remaining correcting factor extreme values ratio was then 2.7, that we interpreted as the square of tortuosity variations, that should depend on soil mineralogy and must be defined by some hydraulic conductivity data. Then the whole hydraulic conductivity curve can be predicted from poral data and organic carbon content.

du Gardin, Béryl; Lucas, Yves

2014-05-01

13

Soil Water Retention Measurements Using a Combined Tensiometer-Coiled Time Domain Reflectometry Probe  

E-print Network

Soil Water Retention Measurements Using a Combined Tensiometer-Coiled Time Domain Reflectometry al., 1975; Arya et al.,that can be used to determine soil water retention curves in both 1975; Royer of a standard tensiometer. The combined tensiometer-coiled TDR probe was con- of soil water retention curves

Wildenschild, Dorthe

14

In-situ Field Capacity and Soil Water Retention Measurements in Two Contrasting Soil Textures  

Technology Transfer Automated Retrieval System (TEKTRAN)

Knowledge of the in-situ field capacity and soil-water retention curve for soils is important for effective irrigation management and scheduling. The primary objective of this study was to estimate in-situ field capacity and soil water retention curves in the field using continually monitoring soil ...

15

In-situ field capacity and soil water retention measurements in two contrasting soil textures  

Technology Transfer Automated Retrieval System (TEKTRAN)

Knowledge of the in-situ field capacity and soil-water retention curve for soils is important for effective irrigation management and scheduling. The primary objective of this study was to estimate in-situ field capacity and soil water retention curves in the field using continually monitoring soil ...

16

Modeling structural influences on soil water retention  

USGS Publications Warehouse

A new model quantities the effect of soil structure, considered as the arrangement of particles in the soil, on soil water retention. The model partitions the pore space into texture-related and structure-related components, the textural component being what can be deduced to exist if the arrangement of the particles were random, and the structural component being the remainder. An existing model, based on particle-size distributions, represents the textural component, and a new model, based on aggregate-size distributions, represents the structural component. This new model makes use of generalized properties that vary little from one medium to another, thereby eliminating any need for empirically tilted parameters. It postulates a particular character of the structural pore space that in same ways resembles texture-related pore space, but with pore shape related to the breadth of the aggregate-size distribution. To predict a soil water retention curve, this model requires the soil's porosity and particle- and aggregate-size distributions. Tested with measurements for 17 samples from two sources, it fits the data much better than does a model based on texture alone. Goodness of fit indicated by correlation coefficients ranged from 0.908 to 0.998 for the new model, compared with a range of 0.686 in 0.955 for the texture-based model.

Nimmo, J.R.

1997-01-01

17

Running heading: Water retention properties of the clay in clayey soils Water retention properties of the clay in soils developed  

E-print Network

1 Running heading: Water retention properties of the clay in clayey soils Water retention. E-mail: ary.bruand@orleans.inra.fr Summary We have investigated the water retention properties retention properties have been studied from -10 hPa to -15 000 hPa water potential using small clods

Paris-Sud XI, Université de

18

Three-fluid retention in porous media involving water, PCE and air  

Microsoft Academic Search

A classical way to obtain three-fluid retention curves in porous media from measured two-fluid retention curves is based on the Leverett concept, which states that the total volumetric liquid content in a water-wet porous medium, containing water, a nonaqueous-phase liquid (NAPL) and air, is a function of the capillary pressure across the interface between the continuous NAPL and air. This

C. Hofstee; J. H. Dane; W. E. Hill

1997-01-01

19

Wildfire impacts on soil-water retention in the Colorado Front Range, United States  

NASA Astrophysics Data System (ADS)

This work examined the plot-scale differences in soil-water retention caused by wildfire in the area of the 2010 Fourmile Canyon Fire in the Colorado Front Range, United States. We measured soil-water retention curves on intact cores and repacked samples, soil particle-size distributions, and organic matter content. Estimates were also made of plant-available water based on the soil-water retention curves. Parameters for use in soil-hydraulic property models were estimated; these parameters can be used in unsaturated flow modeling for comparing burned and unburned watersheds. The primary driver for measured differences in soil-water retention in burned and unburned soils was organic matter content and not soil-particle size distribution. The tendency for unburned south-facing soils to have greater organic matter content than unburned north-facing soils in this field area may explain why unburned south-facing soils had greater soil-water retention than unburned north-facing soils. Our results suggest that high-severity wildfire can "homogenize" soil-water retention across the landscape by erasing soil-water retention differences resulting from organic matter content, which for this site may be affected by slope aspect. This homogenization could have important implications for ecohydrology and plant succession/recovery in burned areas, which could be a factor in dictating the window of vulnerability of the landscape to flash floods and erosion that are a common consequence of wildfire.

Ebel, Brian A.

2012-12-01

20

Upscaled soil-water retention using van Genuchten's function  

USGS Publications Warehouse

Soils are often layered at scales smaller than the block size used in numerical and conceptual models of variably saturated flow. Consequently, the small-scale variability in water content within each block must be homogenized (upscaled). Laboratory results have shown that a linear volume average (LVA) of water content at a uniform suction is a good approximation to measured water contents in heterogeneous cores. Here, we upscale water contents using van Genuchten's function for both the local and upscaled soil-water-retention characteristics. The van Genuchten (vG) function compares favorably with LVA results, laboratory experiments under hydrostatic conditions in 3-cm cores, and numerical simulations of large-scale gravity drainage. Our method yields upscaled vG parameter values by fitting the vG curve to the LVA of water contents at various suction values. In practice, it is more efficient to compute direct averages of the local vG parameter values. Nonlinear power averages quantify a feasible range of values for each upscaled vG shape parameter; upscaled values of N are consistently less than the harmonic means, reflecting broad pore-size distributions of the upscaled soils. The vG function is useful for modeling soil-water retention at large scales, and these results provide guidance for its application.

Green, T.R.; Constantz, J.E.; Freyberg, D.L.

1996-01-01

21

Estimating soil water retention using soil component additivity model  

NASA Astrophysics Data System (ADS)

Soil water retention is a major soil hydraulic property that governs soil functioning in ecosystems and greatly affects soil management. Data on soil water retention are used in research and applications in hydrology, agronomy, meteorology, ecology, environmental protection, and many other soil-related fields. Soil organic matter content and composition affect both soil structure and adsorption properties; therefore water retention may be affected by changes in soil organic matter that occur because of both climate change and modifications of management practices. Thus, effects of organic matter on soil water retention should be understood and quantified. Measurement of soil water retention is relatively time-consuming, and become impractical when soil hydrologic estimates are needed for large areas. One approach to soil water retention estimation from readily available data is based on the hypothesis that soil water retention may be estimated as an additive function obtained by summing up water retention of pore subspaces associated with soil textural and/or structural components and organic matter. The additivity model and was tested with 550 soil samples from the international database UNSODA and 2667 soil samples from the European database HYPRES containing all textural soil classes after USDA soil texture classification. The root mean square errors (RMSEs) of the volumetric water content estimates for UNSODA vary from 0.021 m3m-3 for coarse sandy loam to 0.075 m3m-3 for sandy clay. Obtained RMSEs are at the lower end of the RMSE range for regression-based water retention estimates found in literature. Including retention estimates of organic matter significantly improved RMSEs. The attained accuracy warrants testing the 'additivity' model with additional soil data and improving this model to accommodate various types of soil structure. Keywords: soil water retention, soil components, additive model, soil texture, organic matter.

Zeiliger, A.; Ermolaeva, O.; Semenov, V.

2009-04-01

22

Estimation of hydraulic conductivities of Yucca Mountain tuffs from sorptivity and water retention measurements  

SciTech Connect

The hydraulic conductivity functions of the matrix rocks at Yucca Mountain, Nevada, are among the most important data needed as input for the site-scale hydrological model of the unsaturated zone. The difficult and time-consuming nature of hydraulic conductivity measurements renders it infeasible to directly measure this property on large numbers of cores. Water retention and sorptivity measurements, however, can be made relatively rapidly. The sorptivity is, in principle, a unique functional of the conductivity and water retention functions. It therefore should be possible to invert sorptivity and water retention measurements in order to estimate the conductivity; the porosity is the only other parameter that is required for this inversion. In this report two methods of carrying out this inversion are presented, and are tested against a limited data set that has been collected by Flint et al. at the USGS on a set of Yucca Mountain tuffs. The absolute permeability is usually predicted by both methods to within an average error of about 0.5 - 1.0 orders of magnitude. The discrepancy appears to be due to the fact that the water retention curves have only been measured during drainage, whereas the imbibition water retention curve is the one that is relevant to sorptivity measurements. Although the inversion methods also yield predictions of the relative permeability function, there are yet no unsaturated hydraulic conductivity data against which to test these predictions.

Zimmerman, R.W.; Bodvarsson, G.S.

1995-06-01

23

Soil water retention and maximum capillary drive from saturation to oven dryness  

USGS Publications Warehouse

This paper provides an alternative method to describe the water retention curve over a range of water contents from saturation to oven dryness. It makes two modifications to the standard Brooks and Corey [1964] (B-C) description, one at each end of the suction range. One expression proposed by Rossi and Nimmo [1994] is used in the high-suction range to a zero residual water content. (This Rossi-Nimmo modification to the Brooks-Corey model provides a more realistic description of the retention curve at low water contents.) Near zero suction the second modification eliminates the region where there is a change in suction with no change in water content. Tests on seven soil data sets, using three distinct analytical expressions for the high-, medium-, and low-suction ranges, show that the experimental water retention curves are well fitted by this composite procedure. The high-suction range of saturation contributes little to the maximum capillary drive, defined with a good approximation for a soil water and air system as H(cM) = {???)/(o) k(rw) dh(c), where k(rw) is relative permeability (or conductivity) to water and h(c) is capillary suction, a positive quantity in unsaturated soils. As a result, the modification suggested to describe the high-suction range does not significantly affect the equivalence between Brooks-Corey (B-C) and van Genuchten [1980] parameters presented earlier. However, the shape of the retention curve near 'natural saturation' has a significant impact on the value of the capillary drive. The estimate using the Brooks-Corey power law, extended to zero suction, will exceed that obtained with the new procedure by 25 to 30%. It is not possible to tell which procedure is appropriate. Tests on another data set, for which relative conductivity data are available, support the view of the authors that measurements of a retention curve coupled with a speculative curve of relative permeability as from a capillary model are not sufficient to accurately determine the (maximum) capillary drive. The capillary drive is a dynamic scalar, whereas the retention curve is of a static character. Only measurements of infiltration rates with time can determine the capillary drive with precision for a given soil.

Morel-Seytoux, H. J.; Nimmo, J.R.

1999-01-01

24

Determination of water retention in stratified porous materials  

USGS Publications Warehouse

Predicted and measured water-retention values, ??(??), were compared for repacked, stratified core samples consisting of either a sand with a stone-bearing layer or a sand with a clay loam layer in various spatial orientations. Stratified core samples were packed in submersible pressure outflow cells, then water-retention measurements were performed between matric potentials, ??, of 0 to -100 kPa. Predictions of ??(??) were based on a simple volume-averaging model using estimates of the relative fraction and ??(??) values of each textural component within a stratified sample. In general, predicted ??(??) curves resembled measured curves well, except at higher saturations in a sample consisting of a clay loam layer over a sand layer. In this case, the model averaged the air-entry of both materials, while the air-entry of the sample was controlled by the clay loam in contact with the cell's air-pressure inlet. In situ, avenues for air-entry generally exist around clay layers, so that the model should adequately predict air-entry for stratified formations regardless of spatial orientation of fine versus coarse layers. Agreement between measured and predicted volumetric water contents, ??, was variable though encouraging, with mean differences between measured and predicted ?? values in the range of 10%. Differences in ?? of this magnitude are expected due to variability in pore structure between samples, and do not indicate inherent problems with the volume averaging model. This suggets that explicit modeling of stratified formations through detailed characterization of the stratigraphy has the potential of yielding accurate ??(??) values. However, hydraulic-equilibration times were distinctly different for each variation in spatial orientation of textural layering, indicating that transient behavior during drainage in stratified formations is highly sensitive to the stratigraphic sequence of textural components, as well as the volume fraction of each textural component in a formation. This indicates that prolonged residence times of water, nutrients, and pollutants are likely within finer-textured layers, when ?? conditions have resulted in drainage of underlying coarser-textured strata. ?? 1995 Kluwer Academic Publishers.

Constantz, J.

1995-01-01

25

Water-Retention of Fractal Soil Models Using Continuum Percolation Theory: Tests of Hanford Site Soils  

Microsoft Academic Search

ABSTRACT,of percolation theory for flow in a fractal medium in- creases understanding of the steady-state hydraulic con- For 43 Hanford site soils, we use fractal analysis and assume propor- ductivity in the DOE Hanford Site soils. A related prob- tionality of pore radii to particle radii to generate water-retention curves, h(), from particle-size distributions. The air-entry head is lem, which

Allen G. Hunt; Glendon W. Gee

2002-01-01

26

Modelling Soil Water Retention Using Support Vector Machines with Genetic Algorithm Optimisation  

PubMed Central

This work presents point pedotransfer function (PTF) models of the soil water retention curve. The developed models allowed for estimation of the soil water content for the specified soil water potentials: –0.98, –3.10, –9.81, –31.02, –491.66, and –1554.78?kPa, based on the following soil characteristics: soil granulometric composition, total porosity, and bulk density. Support Vector Machines (SVM) methodology was used for model development. A new methodology for elaboration of retention function models is proposed. Alternative to previous attempts known from literature, the ?-SVM method was used for model development and the results were compared with the formerly used the C-SVM method. For the purpose of models' parameters search, genetic algorithms were used as an optimisation framework. A new form of the aim function used for models parameters search is proposed which allowed for development of models with better prediction capabilities. This new aim function avoids overestimation of models which is typically encountered when root mean squared error is used as an aim function. Elaborated models showed good agreement with measured soil water retention data. Achieved coefficients of determination values were in the range 0.67–0.92. Studies demonstrated usability of ?-SVM methodology together with genetic algorithm optimisation for retention modelling which gave better performing models than other tested approaches. PMID:24772030

Lamorski, Krzysztof; S?awi?ski, Cezary; Moreno, Felix; Barna, Gyöngyi; Skierucha, Wojciech; Arrue, José L.

2014-01-01

27

Biodestruction of strongly swelling polymer hydrogels and its effect on the water retention capacity of soils  

NASA Astrophysics Data System (ADS)

The biodestruction of strongly swelling polymer hydrogels (water adsorbing soil conditioners of the new generation) has been studied at the quantitative level using original mathematical models. In laboratory experiments, a relationship between the hydrogel degradation rate and the temperature has been obtained, and the effect of the biodestruction on the water retention curve of soil compositions with hydrogels (used as an index of their water retention capacity) has been assessed. From the automatic monitoring data of the temperature regime of soils, the potential biodestruction of hydrogels has been predicted for different climatic conditions. The loss of hydrogels during three months of the vegetation period because of destruction can exceed 30% of their initial content in irrigated agriculture under arid climatic conditions and more than 10% under humid climatic conditions. Thus, the biodestruction of hydrogels is one of the most important factors decreasing their efficiency under actual soil conditions.

Smagin, A. V.; Sadovnikova, N. B.; Smagina, M. V.

2014-06-01

28

Estimating hysteresis in the soil water retention function from cone permeameter experiments  

NASA Astrophysics Data System (ADS)

Data obtained from modified cone penetrometer experiments were used to estimate the hysteretic soil hydraulic properties with a parameter estimation technique which combined a numerical solution of the Richards equation with Marquardt-Levenberg optimization. The modified cone penetrometer was designed to inject water into a soil through a cylindrical screen, measure the infiltration rate with time, and track the movement of the wetting front using two tensiometer rings positioned above the screen. After reaching relatively stable tensiometer readings during the experiments, the source of water was cut off and pressure head readings measured while water in the soil profile redistributed. Cumulative inflow and pressure head readings for two experiments with different supply pressures were analyzed to obtain estimates of the soil water retention and hydraulic conductivity functions. Analysis of flow responses obtained during the infiltration period, and of those obtained during the combined infiltration and redistribution phases, demonstrated the importance of hysteresis of the soil hydraulic functions. We found that the redistribution phase could not be described accurately when hysteresis was neglected. Hysteresis in the soil hydraulic functions was modeled using a relatively simple empirical model in which wetting scanning curves are scaled from the main wetting curve and drying scanning curves are scaled from the main drying curve. This model was deemed adequate for our examples. Optimization results for various combinations of unknown soil hydraulic parameters were compared to results of standard laboratory and in situ methods. Estimates of the saturated hydraulic conductivity were well within the range of in situ measurements. The estimated main hysteretic loops of the soil water retention curve were for the most part situated between the wetting and drying curves obtained with standard methods.

Šim?nek, Ji?í; Kodešová, Radka; Gribb, Molly M.; van Genuchten, Martinus T.

29

Transport and Retention of Stabilized Silver Nanoparticles in Water-Saturated Porous Media  

NASA Astrophysics Data System (ADS)

Water-saturated column experiments were conducted to investigate the transport and retention of surfactant stabilized silver nanoparticles (AgNPs) in quartz sand. The mobility of AgNPs was enhanced with an increase in water velocity, sand grain size, and AgNP input concentration (Co), and a decrease in solution ionic strength (IS). Retention profiles (RPs) for AgNPs exhibited uniform, nonmonotonic, or hyperexponential shapes depending on physicochemical conditions. The experimental breakthrough curves (BTCs) and RPs were described using a numerical model that considers time/concentration- and depth-dependent retention. The simulated maximum retained concentration on the solid phase (Smax) and the retention rate coefficient (k1) increased with IS and as the grain size and/or Co decreased. The RPs were more hyperexponential in finer textured sand and at lower Co, were nonmonotonic or uniform at higher Co and in coarser sand, and tended to exhibit higher peak concentrations in the RPs at lower velocities and at higher solution IS. These observations indicate that uniform and nonmonotonic RPs occurred under conditions when Smax was approaching filled conditions. The sensitivity of the nonmonotonic RPs to IS and velocity in coarser textured sand indicates that AgNPs were partially interacting in a secondary minimum and largely irreversibly interacting in a primary minimum associated with microscopic heterogeneity. The competitive retention of AgNPs and surfactants close to the column inlet was observed when additional surfactants were added into the system. Nonmonotonic RPs had peak concentrations at a greater distance in the presence of larger amount of surfactant. This implies that the existence of natural occurring organic matter will likely facilitate NP transport deeper into the subsurface environment and increase the risk potential of ground water contamination. Y. Liang, S. A. Bradford, J. Simunek, H.Vereecken, E. Klumpp. Sensitivity of the Transport and Retention of Stabilized Silver Nanoparticles to Physicochemical Factors. Water Research. Submitted.

Liang, Yan; Bradford, Scott A.; Simunek, Jiri; Vereecken, Harry; Klumpp, Erwin

2013-04-01

30

EFFECT OF SOIL AGGREGATE SIZE DISTRIBUTION ON WATER RETENTION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Quantitative information on soil water retention is in demand in hydrology, agrometeorology, agronomy, contaminant transport, and other soil-related disciplines of earth and environmental sciences. Soil aggregate composition is an important characteristic of soil structure and, as such, has been exp...

31

USING FIELD TOPOGRAPHIC DESCRIPTORS TO ESTIMATE SOIL WATER RETENTION  

Technology Transfer Automated Retrieval System (TEKTRAN)

In field-, watershed-, and regional-scale projects, soil water retention is often estimated from soil textural classes shown in soil maps. Only the dominating textural class is often shown, cartographers routinely use error-prone field judgement of soil texture, and soil texture is known to vary alo...

32

Is the Water Heating Curve as Described?  

ERIC Educational Resources Information Center

We analysed the heating curve of water which is described in textbooks. An experiment combined with some simple heat transfer calculations is discussed. The theoretical behaviour can be altered by changing the conditions under which the experiment is modelled. By identifying and controlling the different parameters involved during the heating…

Riveros, H. G.; Oliva, A. I.

2008-01-01

33

LIGHTWEIGHT GREEN ROOF WATER RETENTION SYSTEM  

EPA Science Inventory

During Phase I, we have forged numerous necessary partnerships, which will allow us to begin our implementation tests. Working with the Philadelphia Water Department (PWD) and Drexel Smart House (DSH) we have 3 to 4 prime test sites for our system. We plan to execute our insta...

34

Water retention of biochar amended soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

We analyzed the water holding capacities of soils amended with biochars made from switchgrass, pecan shells, peanut hulls, poultry litter, and hardwood sawdust. Soils were amended with 20 g/kg (44 tonnes/ha) of each biochar produced at both high (>500 degrees C) and low (<400 degrees C) temperatures...

35

Correlated Moisture Content, Pressure and Temperature Data for Development of Hysteretic Moisture Retention Curves.  

NASA Astrophysics Data System (ADS)

This study was performed as the first part of an effort to collect high quality, repeatable, hydrologic data in a laboratory environment to provide a sound basis for future macropore model development, validation, and calibration. The objective of the experiment was to study the hysteretic function (drainage/wetting/scanning) of soils and the role of hysteresis in fluid transport. Our hysteretic dataset provides detailed information of coupled fluid transport behavior that includes temperature, moisture, and concentration. Hysteretic data collected has been further correlated with soil matric potential and temperature to define moisture-retention curves in replicates of a coarse-sandy, mixed, mesic Fluventic Hapludoll, loam soil (Eudora loam of the Kansas River Valley). Large (28 L-soil core) volume minimized statistical uncertainty that customarily accompany small cores and provided robust results in determining scanning curves (wetting and drying). Integration of a bromide tracer applied to the large cores at saturation indicated that macropore transport occurred within the range of 0-20 kPa thereafter, transport was via soil matrix flow. The tracer also provided further information about the physical and chemical properties of the soil, which can be utilized in the future development and calibration of robust, versatile computer models. Continuing research of these same cores will focus on macropore transport as it correlates to our existing research.

Little, J. J.; Tindall, J. A.; Friedel, M.

2004-12-01

36

Water retention curves and thermal insulating properties of Thermosand  

Microsoft Academic Search

The heat loss and the efficiency of isolating material surrounding heat supply pipes are essential issues for the energy budget of heat supply pipe lines. Until now heat loss from the pipe is minimized by enlarging the polyurethane (PU) - insulation thickness around the pipe. As a new approach to minimize the heat loss a thermally insulating bedding material was

Otto Leibniz; Gerfried Winkler; Steffen Birk

2010-01-01

37

Water Retention and Rheology of Ti-doped, Synthetic Olivine  

NASA Astrophysics Data System (ADS)

Upper mantle flow laws are currently based almost entirely on experiments with olivine from San Carlos in Arizona. Synthetically produced olivine enables the exploration of the effects of trace elements on the rheology. We have conducted a range of experiments in a gas medium apparatus with solution-gelation derived olivine that show that titanium is the most effective in binding water in the olivine structure. The FTIR signature of this structurally bound water is most similar to that of water-undersaturated natural olivine with absorption bands at 3575 and 3525 cm-1. Water added, titanium-free solgel contains little water after hotpressing and shows adsorption bands at wavenumbers near 3200 cm-1. Noble metal capsules such as Pt or AuPd, providing more oxidizing conditions, are more effective in retaining water. Experiments with NiFe-lined welded Pt capsules retain no more water than NiFe lined samples without Pt capsule. Water retention is, however, again dependent on trace element content, with Ti doped samples containing tens of ppm after hotpressing. By comparison undoped samples run under the same conditions contain little water, again with different FTIR spectra to Ti-doped samples. Our experiments suggest that Ti by itself, or with water contents at the FTIR detection limit enhances diffusion creep rates relative to undoped, dry solgel olivine. Water contents around 10 ppm in NiFe wrapped samples show an enhancement of strain rates of more than one order of magnitude. The addition of Ti, together with the presence of water, also enhances grain growth. For more coarse-grained samples in the dislocation creep regime the enhancement of the stain rate as a function of water content is approximately consistent with the flow laws of Hirth and Kohlstedt (2003).

Faul, U.; Jackson, I.; Fitz Gerald, J. D.

2012-12-01

38

Thermodynamic assessment of the effect of strongly swelling polymer hydrogels on the water retention capacity of model porous media  

NASA Astrophysics Data System (ADS)

The effect of different rates and fractions of strongly swelling polymer hydrogel (SSPH) based on radiation-grafted polyacrylamide on the water retention capacity and structural state of model porous media in the form of quartz sand fractions with different degrees of dispersion has been studied. The water retention curve (WRC) of sandy porous media obtained by the capillarimetric method has been used as a basic thermodynamic parameter. An original method has been proposed for the comparative study of the effect of SSPHs on the WRC based on the approximation of data by the nonlinear van Genuchten function followed by differential analysis. Equations are given for the calculation of capillary water capacity and structural curves of pore size distribution. SSPH concentrations in the range 0.05-0.2% of enclosing material weight reliably increase the water retention capacity of sandy fractions and the total, capillary, and field capacities (determined by the Voronin secant method) by 2-3 times; as well as the range of available water and the contents of fine macropores and mesopores. Factors limiting the swelling of SSPHs in model porous media have been revealed.

Sadovnikova, N. B.; Smagin, A. V.; Sidorova, M. A.

2014-04-01

39

Principles of water capture, evaporation, and soil water retention  

Technology Transfer Automated Retrieval System (TEKTRAN)

Successful dryland crop production in semiarid environments is dependent upon efficient storage of precipitation and use of stored soil water supplies. The objectives of this presentation are to: 1. Summarize information regarding the effects of time of year; environmental parameters; residue orient...

40

Marked differences between van Genuchten soil water-retention parameters for temperate and tropical soils: a new water-retention pedo-transfer functions developed for tropical soils  

Microsoft Academic Search

All of the physical, chemical and soil water-retention data suitable for the derivation of a Pedo-Transfer Functions (PTF) for water retention for tropical soils (771 suitable horizons) were extracted from the IGBP-DIS soil database. The parameters ?s, ?r, ? and n of the van Genuchten (vG) [Soil Sci. Soc. Am. J. 44 (1980) 892] equation were derived and compared with

M. G. Hodnett; J. Tomasella

2002-01-01

41

EVALUATION OF SOIL WATER RETENTION MODELS BASED ON BASIC SOIL PHYSICAL PROPERTIES  

EPA Science Inventory

Algorithms to model soil water retention are needed to study the response of vegetation and hydrologic systems to climate change. he objective of this study was to evaluate some soil water retention models to identify minimum input data requirements. ix models that function with ...

42

Enhancing the Effectiveness of Heuristic Rule Curves for Water  

E-print Network

Enhancing the Effectiveness of Heuristic Rule Curves for Water Supply Reservoir Operation Adebayo economic benefits from the ubiquitous water resources Raise international profile of the nation as world leader in water management practices Develop a water centre of expertise with international reach

Painter, Kevin

43

Validity of the centrifuge method for determining the water retention properties of tropical soils  

E-print Network

1 Validity of the centrifuge method for determining the water retention properties of tropical.Bruand@univ-orleans.fr (A. Bruand) ABSTRACT This study compared the centrifuge and pressure plate methods with appropriate retention recorded by using the pressure plate and centrifuge methods. The results showed good agreement (R2

Paris-Sud XI, Université de

44

Transparent hydrogel with enhanced water retention capacity by introducing highly hydratable salt  

E-print Network

Transparent hydrogel with enhanced water retention capacity by introducing highly hydratable salt 2014; published online 14 October 2014) Polyacrylamide hydrogels containing salt as electrolyte have of polyacrylamide hydrogel by introducing highly hydratable salts into the hydrogel. These hydrogels show enhanced

Suo, Zhigang

45

Primer on Condition Curves for Water Mains  

EPA Science Inventory

ABSTRACT The development of economical tools to prioritize pipe renewal based upon structural condition and remaining asset life is essential to effectively manage water infrastructure assets for both large and small diameter pipes. One tool that may facilitate asset management...

46

Soil-Water Characteristic Curve Modeling at Low Water Content: Empirical and Semi-Empirical Approaches  

E-print Network

Soil-Water Characteristic Curve Modeling at Low Water Content: Empirical and Semi model, the Modified Kovacs (MK) model for the determination of soil-water characteristic curve at the low water contents of two horizons of a soil from Burkina Faso. Combining terms from capillary state

Paris-Sud XI, Université de

47

Pore-Scale Effects of Soil Structure And Microbial EPS Production On Soil Water Retention  

NASA Astrophysics Data System (ADS)

Climate-induced changes to the hydrological cycle will increase the frequency of extreme weather events including powerful storms and prolonged droughts. Moving forward, one of the major factors limiting primary productivity in terrestrial ecosystems will be sub-optimal soil moisture. We focus here on the ability of soils to retain moisture under drying conditions. A soil's ability to retain moisture is influenced by many factors including its texture, its structure, and the activities of soil microbes. In soil microcosms, the addition of small amounts of microbially-produced extracellular polymeric substances (EPS) can dramatically shift moisture retention curves. The objective of this research is to better understand how soil structure and EPS may act together to retain moisture in unsaturated soils. Replicate micromodels with exactly-conserved 2-D physical geometry were initially filled with aqueous suspensions of one of two types of bacteria: one mutant was ultra- muccoid and the other was non-muccoid. Replicate micromodels were held at a fixed, external, relative humidity, and the position of the air-water interface was imaged over time as water evaporates. There was no forced convection of air or water inside the micromodels: drying was achieved by water evaporation and diffusion alone. We used a fully automated, inverted microscope to image replicate drying lanes each with dimensions of 1 mm x 10 mm. A complete set of images was collected every 30 minutes for 30 hours. The results show devices loaded with the highly muccoid strain remained >40% hydrated for 13 h, while devices loaded with the non-muccoid remained >40% hydrated for only 6 h, and were completely dry by 13 h. Current work is comparing interfacial water fluxes in structured and unstructured settings, and is attempting to model the synergistic effects of soil structure and EPS content on moisture retention in real soils. This research may allow more accurate description of naturally-occurring feedbacks between the soil carbon and water cycles, and may enable agriculture biotechnology that enhances natural soil processes for improved resiliency of terrestrial ecosystems.

Orner, E.; Anderson, E.; Rubinstein, R. L.; Chau, J. F.; Shor, L. M.; Gage, D. J.

2013-12-01

48

Soil water retention at varying matric potentials following repeated wetting with modestly saline-sodic water and subsequent air drying  

SciTech Connect

Coal bed natural gas (CBNG) development in the Powder River (PR) Basin produces modestly saline, highly sodic wastewater. This study assessed impacts of wetting four textural groups (0-11%, 12-22%, 23 -33%, and > 33% clay (g clay/100 g soil) x 100%))with simulated PR or CBNG water on water retention. Soils received the following treatments with each water quality: a single wetting event, five wetting and drying events, or five wetting and drying events followed by leaching with salt-free water. Treated samples were then resaturated with the final treatment water and equilibrated to -10, -33, -100, -500, or -1,500 kPa. At all potentials, soil water retention increased significantly with increasing clay content. Drought-prone soils lost water-holding capacity between saturation and field capacity with repeated wetting and drying, whereas finer textured soils withstood this treatment better and had increased water-retention capacity at lower matric potentials.

Browning, L.S.; Hershberger, K.R.; Bauder, J.W. [Montana State University, Bozeman, MT (United States). Dept. of Land Resources & Environmental Science

2007-07-01

49

Experimental Investigation on Role of Root Mucilage and Microbial Exudates on Soil Water Retention Dynamics  

NASA Astrophysics Data System (ADS)

The release of organic molecules by soil microbes and plant roots to adapt their surrounding represents a substantial portion of the energy use by these organisms. The hypothesis in this study is that the long-chain molecules and hydrophilic nature of the released organic compounds deposited on soil surfaces drastically alters the dynamism of the soil water retention curves (SWRC) of the rhizosphere relative to the bulk soil through direct effect besides the well-known indirect influence of the organic matter by modifying the soil structure and providing energy for the biogeochemical processes. The experiment was set up in such away that it suppresses the indirect effect of organic matter (OM) and rather it traces only its immediate effect on SWRC. To achieve this goal inert and uniform size (0.1-0.11 mm) glassbeads were used. We assumed that wet mixing of the glass beads with OM and slow drying the mixture (40-50oC) for 1-day will lead to deposition of the OM only at the surface of the glass beads, the short time being not enough for aggregate formation. This way we can simulate the natural deposition of OM on soil surfaces. Our argument is that this deposited OM has its own distinct time-dependent SWRC which is different from that of bulk soil. Model exudates including PGA, XA, and SPA are used to mimic the behavior of plant root mucilages, bacterial and fungal exudates respectively. These model exudates at varying concentration (0, 0.008, 0.04, and 0.2 gm/l) were wet mixed with glass beads. SWRC was determined using both water-hanging column and pressure plate for both low and high suction ranges respectively. We will present the effect of exudate type and level of concentration on the dynamic behavior of SWRC of the glassbeads by determining: i) the SWRC for each treatment; ii) the rate of drying and wetting at different intervals; iii) the hysteresis of the retention curves; iv) the saturated hydraulic conductivity.

Gebrenegus, T. B.; Ghezzehei, T.

2011-12-01

50

Post-retention Development of Curve of Spee in Pre-adjusted Edgewise Appliance Cases, Its Correlation to Dentoskeletal Parameters: An In vitro Study  

PubMed Central

Background: Curve of Spee was first described by Ferdin and Graf Von Spee in 1890. The curve of Spee is an important characteristic of the mandibular dental arch. One of the most frequently encountered problems in the treatment of orthodontic patients is an excessive overbite. Deep bite has been found to be associated with abnormal mandibular function. Temporomandibular joint disorders also have potentially detrimental effects on mandibular development. Andrews advocated leveling the curve of Spee to aflat curve, in order to facilitate construction of an optimal occlusion and that a flat plane should be given as a form of over treatment. There is no reliable information currently available from the literature about the long-term stability of the curve of Spee and the factors influencing the same. The objective of this study was to assess the post-retention development of the curve of Spee and to evaluate the dental and skeletal parameters as predictors of its post-retention stability. Materials and Methods: Pre-treatment (Tl), post-treatment (T2) and post-retention (T3) dental casts and lateral cephalograms of 24 orthodontically treated patients having a mean age of 14.5 years were evaluated. The mean period of the study group after retention was up to 2.6 years (range = 1-5 years). Pre-treatment T1, post-treatment T2, and post-retention T3 casts and radiographs were measured. The data were tabulated and statistically analyzed. Results: A highly significant positive correlation was observed between the changes in the curve of Spee during treatment (T2-T1) and the net result after retention (T3-T2). This means that much of the treatment results remained stable at T3. However, slight change was noticed in curve of Spee’s depth during the time interval T3-T2. This finding was very negligible and was not statistically significant. Conclusion: The leveling of the curve of Spee during the treatment is a stable treatment objective on long term basis. There was a mild correlation existing between the curve of Spee and the different dental and skeletal parameters. PMID:25395790

Ahammed, A R Yusuf; Ganiger, Channamallappa C; Shetty, Vikranth; Sunny, Sunil; Shetty, Sadashiva; Pawar, Renuka; Suresh, K V

2014-01-01

51

NMR investigations of water retention mechanism by cellulose ethers in cement-based materials  

E-print Network

1 NMR investigations of water retention mechanism by cellulose ethers in cement-based materials J of freshly-mixed white cement pastes. NMRD is useful to determine the surface diffusion coefficient of water, the specific surface area and the hydration kinetics of the cement-based material. In spite of modifications

Boyer, Edmond

52

Prediction of soil water retention properties after stratification by combining texture, bulk density and the type of horizon  

E-print Network

1 Prediction of soil water retention properties after stratification by combining texture, bulk water retention properties at continental and national scales because only very basic soils data (topsoil and subsoil). The performance of these class-PTFs was validated against water retained at -33

Paris-Sud XI, Université de

53

Nuclear magnetic relaxation dispersion investigations of water retention mechanism by cellulose ethers in mortars  

SciTech Connect

We show how nuclear magnetic spin-lattice relaxation dispersion of proton-water (NMRD) can be used to elucidate the effect of cellulose ethers on water retention and hydration delay of freshly-mixed white cement pastes. NMRD is useful to determine the surface diffusion coefficient of water, the specific area and the hydration kinetics of the cement-based material. In spite of modifications of the solution's viscosity, we show that the cellulosic derivatives do not modify the surface diffusion coefficient of water. Thus, the mobility of water present inside the medium is not affected by the presence of polymer. However, these admixtures modify significantly the surface fraction of mobile water molecules transiently present at solid surfaces. This quantity measured, for the first time, for all admixed cement pastes is thus relevant to explain the water retention mechanism.

Patural, Laetitia [Ecole Nationale Superieure des Mines de Saint-Etienne, Centre SPIN, LPMG FRE 3312, 158 Cours Fauriel, 42023 Saint-Etienne Cedex 2 (France)] [Ecole Nationale Superieure des Mines de Saint-Etienne, Centre SPIN, LPMG FRE 3312, 158 Cours Fauriel, 42023 Saint-Etienne Cedex 2 (France); Korb, Jean-Pierre, E-mail: jean-pierre.korb@polytechnique.fr [Physique de la Matiere Condensee, Ecole Polytechnique-CNRS, Route de Saclay, 91128 Palaiseau Cedex (France)] [Physique de la Matiere Condensee, Ecole Polytechnique-CNRS, Route de Saclay, 91128 Palaiseau Cedex (France); Govin, Alexandre; Grosseau, Philippe [Ecole Nationale Superieure des Mines de Saint-Etienne, Centre SPIN, LPMG FRE 3312, 158 Cours Fauriel, 42023 Saint-Etienne Cedex 2 (France)] [Ecole Nationale Superieure des Mines de Saint-Etienne, Centre SPIN, LPMG FRE 3312, 158 Cours Fauriel, 42023 Saint-Etienne Cedex 2 (France); Ruot, Bertrand; Deves, Olivier [Universite Paris-Est, Centre Scientifique et Technique du Batiment, Departement Enveloppe et Revetements/Division Enduits, Mortiers et Colles, 84 avenue Jean Jaures, 77447 Marne-la-Vallee Cedex 2 (France)] [Universite Paris-Est, Centre Scientifique et Technique du Batiment, Departement Enveloppe et Revetements/Division Enduits, Mortiers et Colles, 84 avenue Jean Jaures, 77447 Marne-la-Vallee Cedex 2 (France)

2012-10-15

54

Peat properties and water retention in boreal forested peatlands subject to wildfire  

NASA Astrophysics Data System (ADS)

Peat cores from a recently burned peatland and one over 75 years since fire in Alberta, Canada were analyzed for physical properties and water retention. Wildfire exposed denser peat at the peat surface, more so in hollow than hummock microforms. Water retention in peat has implications for postfire Sphagnum regeneration, as this more dense peat requires smaller volumes of water loss before a critical growth-inhibiting pore-water pressure of -100 mb is reached. Simulations of water retention after fire showed that hollow microforms are at a higher risk of losing low-density surface peat, which moderates water table (WT) declines via high specific yield. Exposure of dense peat to the surface after fire increases surface moisture under a constant WT. The net effect of decreasing specific yield and increasing water retention at the surface has implications on hydrologic stability and resilience of boreal peatlands to future wildfire risk under a changing climate. Earth system models incorporating wildfire disturbance in boreal peatlands would benefit from the inclusion of these hydrological feedbacks in this globally significant carbon reservoir.

Thompson, Dan K.; Waddington, James M.

2013-06-01

55

A Simple Approach for Demonstrating Soil Water Retention and Field Capacity  

ERIC Educational Resources Information Center

It is difficult to demonstrate the soil water retention relationship and related concepts because the specialized equipment required for performing these measurements is unavailable in most classrooms. This article outlines a low-cost, easily visualized method by which these concepts can be demonstrated in most any classroom. Columns (62.5 cm…

Howard, A.; Heitman, J. L.; Bowman, D.

2010-01-01

56

PREVENTING LOSS AND RESTORING WATER RETENTION VALUES TO PULP BY FIBER LOADING  

E-print Network

that at the lower lignin levels, irreversible bonding of cellulose components occurs within the fiber walls the irreversible bonding within the pulp fiber wall by preventing contact of cellulose components within the cellPREVENTING LOSS AND RESTORING WATER RETENTION VALUES TO PULP BY FIBER LOADING John H. Klungness

Abubakr, Said

57

Retention and release of water by sintered uranium dioxide  

NASA Astrophysics Data System (ADS)

The release of water and hydrogen upon heating sintered UO 2 pellets was measured by a direct mass spectrometric method of vacuum outgassing. The technique avoids water loss by sample transfer and measures, rather than the cumulative release, the rate of release with a sensitivity of 1 ?g of water (as D 2O) per hour. Exposure of high-density UO 2 pellets to water (liquid D 2O) results in negligible water adsorption. Water in pellets fabricated with especially high open porosity (5%) was driven off by a linear temperature ramp below 200°C. A drying model for this process was developed and applied to the data. Strongly bound water was introduced into high-density UO 2by sintering in an atmosphere of D 2O and D 2. Release of the water or hydrogen began at ~500°C and was complete only at the melting point of UO 2(2800°C). The release kinetics are not diffusion-controlled; rather the process is governed by the rates of desorption of bound hydrogen-bearing species from at least three binding sites in the solid characterized by interaction energies between 20 and 50 kcal/mol. The D 2O/D 2 ratio of the desorbed gas was > 1 and did not correspond to thermodynamic equilibrium with stoichiometric urania. Hydrogen and water release kinetics are comparable below 2˜000°C, suggesting a common bound precursor. The total hydrogen (as D 2O or D 2) absorbed in the specimens was between 2 and 4 ?g/g UO 2.

Olander, D. R.; Sherman, D.; Balooch, M.

1982-05-01

58

DEVELOPING JOINT PROBABILITY DISTRIBUTIONS OF SOIL WATER RETENTION CHARACTERISTICS  

EPA Science Inventory

A method is presented for developing probability density functions for parameters of soil moisture relationships of capillary head and hydraulic conductivity. These soil moisture parameters are required for the assessment of water flow and solute transport in unsaturated media. T...

59

MODELING SHALLOW GROUNDWATER TABLE CONTRIBUTION TO SOIL WATER RETENTION IN THE UNSATURATED ZONE OF A CALCAREOUS SOIL OF SOUTH  

E-print Network

1 MODELING SHALLOW GROUNDWATER TABLE CONTRIBUTION TO SOIL WATER RETENTION IN THE UNSATURATED ZONE. But specially for conferring me the opportunity of learning and developing my interests in water resources.............................................................................................................................15 Shallow Groundwater Capillarity

Migliaccio, Kati White

60

Soil Water Retention and Relative Permeability for Full Range of Saturation  

SciTech Connect

Common conceptual models for unsaturated flow often rely on the oversimplified representation of medium pores as a bundle of cylindrical capillaries and assume that the matric potential is attributed to capillary forces only. The adsorptive surface forces are ignored. It is often assumed that aqueous flow is negligible when a soil is near or at the residual water content. These models are successful at high and medium water contents but often give poor results at low water contents. These models do not apply to conditions at which water content is less than the residual water content. We extend the lower bound of existing water-retention functions and conductivity models from residual water content to the oven-dry condition (i.e., zero water content) by defining a state-dependent, residual-water content for a soil drier than a critical value. Furthermore, a hydraulic conductivity model for smooth uniform spheres was modified by introducing a correction factor to describe the film flow-induced hydraulic conductivity for natural porous media. The total unsaturated hydraulic conductivity is the sum of those due to capillary and film flow. The extended retention and conductivity models were verified with six datasets from the literature. Results show that, when the soil is at high and intermediate water content, there is no difference between the un-extended and the extended models; when the soil is at low water content, the un-extended models overestimate the water content but under-estimate the conductivity while the extended models match the retention and conductivity measurements well.

Zhang, Z. F.

2010-09-28

61

Soil Water Retention and Relative Permeability for Conditions from Oven-Dry to Full Saturation  

SciTech Connect

Common conceptual models for unsaturated flow often rely on the oversimplified representation of medium pores as a bundle of cylindrical capillaries and assume that the matric potential is attributed to the capillary force only. The adsorptive surface forces are ignored. It is often assumed that aqueous flow is negligible when a soil is near or at the residual water content. These models are successful at high and medium water contents but often give poor results at low water contents. These models do not apply to conditions at which the water content is less than the residual water content. We extend the lower bound of existing water-retention functions and conductivity models from residual water content to the oven-dry condition (i.e., zero water content) by defining a state-dependent, residual-water content for a soil drier than a critical value. Furthermore, a hydraulic conductivity model for smooth uniform spheres was modified by introducing a correction factor to describe the film flow-induced hydraulic conductivity for natural porous media. The total unsaturated hydraulic conductivity is the sum of those due to capillary and film flow. The extended retention and conductivity models were verified measurements. Results show that, when the soil is at high and intermediate water content, there is no difference between the un-extended and the extended models; when the soil is at low water content, the un-extended models overestimate the water content but underestimate the conductivity. The extended models match the retention and conductivity measurements well.

Zhang, Z. F.

2011-11-04

62

Submersible pressure outflow cell for measurement of soil water retention and diffusivity from 5 to 95oC.  

USGS Publications Warehouse

The technique is designed to measure soil water retention characteristics and to make transient outflow estimates of the soil water diffusivity at temperatures from 5 to 95oC. We also used the technique to determine the isobaric temperature dependence of water retention in soil. Results indicate that at constant capillary pressure, the relationship between moisture content and temperature is hysteretic.-from Authors

Constantz, J.; Herkelrath, W.N.

1984-01-01

63

Water retention and drainage in different brands of microcrystalline cellulose: effect of measuring conditions.  

PubMed

Interaction between water and microcrystalline cellulose (MCC) measured as retention and cumulative drainage of water (WR% and CDW%) is investigated for unmilled and micronized standard (Avicel and Emcocel) and silicified (Prosolv) MCC brands. A centrifuge method was applied with increasing duration and different porosity and thickness of cylindrical powder beds (specimens), in order to establish optimal determination conditions and quantify alterations in interaction between water and different MCC brands. Also, changes of specimen thickness due to presence of water (swelling) were followed. It was found that the effect of specimen porosity and thickness on water drainage (CDW%) appears to be opposite to that on water retention (WR%), while two patterns of WR% and CDW% change with specimen porosity and thickness can be distinguished depending on the centrifugation time. Also, WR% and CDW% are affected by the MCC brand and the micronization. Unmilled silicified MCC brand (Prosolv) shows significantly lower retention and higher drainage of water compared to standard unmilled brands (Avicel and Emcocel), while differences between the unmilled standard Avicel and Emcocel brands are not easily distinguished. Micronization, in general, increases greatly the WR% and decreases CDW% for all the tested MCC brands, and enhances their differences even between Avicel and Emcocel. Swelling of specimen due to presence of water was observed, which was significantly reduced with the micronization, the specimen porosity, and centrifugation as well, but showed slight variation between the different MCC brands. Values of specimen porosity between 60% and 70%, thickness/diameter ratio between 0.75 and 1.0, and centrifugation time between 5 and 20 min provide optimal measuring settings for comparison of MCC brands. PMID:16527466

Nikolakakis, Ioannis; Tsarvouli, Konstantina; Malamataris, Stavros

2006-07-01

64

A hydrologic retention system and water quality monitoring program for a human decomposition research facility: concept and design.  

PubMed

Forensic taphonomy is an essential research field; however, the decomposition of human cadavers at forensic science facilities may lead to nutrient loading and the introduction of unique biological compounds to adjacent areas. The infrastructure of a water retention system may provide a mechanism for the biogeochemical processing and retention of nutrients and compounds, ensuring the control of runoff from forensic facilities. This work provides a proof of concept for a hydrologic retention system and an autonomous water quality monitoring program designed to mitigate runoff from The Southeast Texas Applied Forensic Science (STAFS) Facility. Water samples collected along a sample transect were analyzed for total phosphorous, total nitrogen, NO3-, NO2-, NH4 , F(-) , and Cl(-) . Preliminary water quality analyses confirm the overall effectiveness of the water retention system. These results are discussed with relation to how this infrastructure can be expanded upon to monitor additional, more novel, byproducts of forensic science research facilities. PMID:25041409

Wozniak, Jeffrey R; Thies, Monte L; Bytheway, Joan A; Lutterschmidt, William I

2015-01-01

65

Development of a world data set of soil water retention properties using pedotransfer rules  

Microsoft Academic Search

The World Inventory of Soil Emission Potentials (WISE) database is used to compile a standardized and spatially explicit data set of soil water retention properties. WISE holds 4353 globally distributed profiles considered to be representative of the soil units shown on a 1\\/2° latitude by 1\\/2° longitude version of the corrected and digitized 1:5 M FAO-Unesco Soil Map of the

N. H. Batjes

1996-01-01

66

The role of proximal nephron in cyclophosphamide-induced water retention: preliminary data.  

PubMed

Cyclophosphamide is clinically useful in treating malignancy and rheumatologic disease, but has limitations in that it induces hyponatremia. The mechanisms by which cyclophosphamide induces water retention in the kidney have yet to be identified. This study was undertaken to test the hypothesis that cyclophosphamide may produce water retention via the proximal nephron, where aquaporin-1 (AQP1) and aquaporin-7 (AQP7) water channels participate in water absorption. To test this hypothesis, we gave a single dose of intraperitoneal cyclophosphamide to male Sprague-Dawley rats and treated rabbit proximal tubule cells (PTCs) with 4-hydroperoxycyclophosphamide (4-HC), an active metabolite of cyclophosphamide. In the short-term 3-day rat study, AQP1 protein expression was significantly increased in the whole kidney homogenates by cyclophosphamide administration at 48 (614 ± 194%, P < 0.005), and 96 (460 ± 46%, P < 0.05) mg/kg BW compared with vehicle-treated controls. Plasma sodium concentration was significantly decreased (143 ± 1 vs. 146 ± 1 mEq/L, P < 0.05) by cyclophosphamide 100 mg/kg BW in the long-term 6-day rat study. When primary cultured rabbit PTCs were treated with 4-HC for 24 hours, the protein expressions of AQP1 and AQP7 were increased in a dose-dependent manner. Quantitative polymerase chain reaction revealed no significant changes in the mRNA levels of AQP1 and AQP7 from cyclophosphamide-treated rat renal cortices. From these preliminary data, we conclude that the proximal nephron may be involved in cyclophosphamide-induced water retention via AQP1 and AQP7 water channels. Further studies are required to demonstrate intracellular mechanisms that affect the expression of AQP proteins. PMID:21998601

Kim, Sua; Jo, Chor Ho; Park, Joon-Sung; Han, Ho Jae; Kim, Gheun-Ho

2011-06-01

67

Retention of contaminants in northern natural peatlands treating mine waste waters  

NASA Astrophysics Data System (ADS)

The mining industry in Finland is growing, leading to an increasing number of working and proposed mine sites. As a consequence, the amount of mine waste waters created is likewise increasing. This poses a great challenge for water management and purification, as these mine waste waters can lead to severe environmental and health consequences when released to receiving water bodies untreated. In the past years, the use of natural peatlands for cost-effective passive waste water treatment has been increasing. In this study, the fate of mine water contaminants in a treatment peatland receiving process waters from the Kittilä gold mine was investigated. Special attention was paid to the fate of potentially harmful substances such as arsenic, antimony or nickel. During the 4 years of operation, the peatland removed contaminants from process waters at varying efficiencies. While arsenic, antimony and nickel were retained at high efficiencies (>80% retention), other contaminants such as zinc, sulfate or iron were not retained or even leaching from the peatland. Soil samples taken in 2013 showed a linear increase of arsenic, antimony and nickel concentration in the peatland as compared to earlier sampling times, in agreement with the good retention efficiencies for those contaminants. Measured concentrations exceeded guideline values for contaminated soils, indicating that the prolonged use of treatment peatlands leads to high soil contamination and restrict further uses of the peatlands without remediation measures. Soil and pore water samples were taken along a transect with varying distance from the process water distribution ditch and analyzed for total and more easily mobile concentrations of contaminants (peat soil) as well as total and dissolved contaminants (water samples). Concentrations of contaminants such as arsenic, manganese or antimony in peat and pore water samples were highest near the distribution ditch and decreased with increasing distance from the ditch. Moreover, ratios of dissolved and total concentrations in pore water and of mobile and total concentrations in peat changed along the transect. Higher ratios of dissolved contaminants in water in greater distance from the distribution ditch indicate a decrease of particulate matter. Additionally, higher ratios of mobile contaminants in peat at greater distance from the distribution ditch indicate efficient immobilization of contaminants by chemical adsorption or sedimentation of particulate contaminants near the distribution ditch. Other contaminants such as sulfur/sulfate, sodium, magnesium and zinc showed similar concentrations in peat and pore water at all points of the transect, as well as similar concentration ratios, indicating that there is only minor net retention of those contaminants. This is in good agreement with the low retention efficiencies obtained for those contaminants. In conclusion, the study revealed that (i) removal efficiencies are variable depending on the individual contaminant, (ii) major contaminants are enriched to a degree which exceeds guideline values for contaminated soils, (iii) concentrational changes with distance from the process water distribution ditch can give further insights on the fate of individual contaminants. Even though the dominant processes involved in contaminant removal are not clearly identified to date, further analysis of the data obtained in this study will provide new insights on the fate of mine water contaminants in treatment peatlands and help evaluate potential consequences of the use of peatlands for mine water treatment.

Palmer, Katharina; Ronkanen, Anna-Kaisa; Klöve, Björn

2014-05-01

68

Organic matter controls of soil water retention in an alpine grassland and its significance for hydrological processes  

NASA Astrophysics Data System (ADS)

Soil water retention influences many soil properties and soil hydrological processes. The alpine meadows and steppes of the Qilian Mountains on the northeast border of the Qinghai-Tibetan Plateau form the source area of the Heihe River, the second largest inland river in China. The soils of this area therefore have a large effect on water movement and storage of the entire watershed. In order to understand the controlling factors of soil water retention and how they affect regional eco-hydrological processes in an alpine grassland, thirty-five pedogenic horizons in fourteen soil profiles along two facing hillslopes in typical watersheds of this area were selected for study. Results show that the extensively-accumulated soil organic matter plays a dominant role in controlling soil water retention in this alpine environment. We distinguished two mechanisms of this control. First, at high matric potentials soil organic matter affected soil water retention mainly through altering soil structural parameters and thereby soil bulk density. Second, at low matric potentials the water adsorbing capacity of soil organic matter directly affected water retention. To investigate the hydrological functions of soils at larger scales, soil water retention was compared by three generalized pedogenic horizons. Among these soil horizons, the mattic A horizon, a diagnostic surface horizon of Chinese Soil Taxonomy defined specially for alpine meadow soils, had the greatest soil water retention over the entire range of measured matric potentials. Hillslopes with soils having these horizons are expected to have low surface runoff. This study promotes the understanding of the critical role of alpine soils, especially the vegetated surface soils in controlling the eco-hydrological processes in source regions of the Heihe River watershed.

Yang, Fei; Zhang, Gan-Lin; Yang, Jin-Ling; Li, De-Cheng; Zhao, Yu-Guo; Liu, Feng; Yang, Ren-Min; Yang, Fan

2014-11-01

69

'Sticky water' enables the retention of larvae in a reef mosaic  

NASA Astrophysics Data System (ADS)

To study retention of waterborn larvae in a reef matrix we used a finite-element unstructured numerical model with a minimum horizontal resolution of 150 m that can capture variability of currents on a spatial scale relevant to coral reefs in the Great Barrier Reef (GBR). Areas of high reef density (i.e. closely aggregated reefs) are poorly flushed because the prevailing currents are directed around and away from these regions, which is an oceanographic process called the 'sticky water' effect. The model showed that the sticky water effect leads to decreased flushing and a high exposure time in high reef density areas in the southern and central regions of the GBR matrix. In turn this generated hot spots of high self-seeding, and these hot spots existed under both calm weather conditions and wind conditions typical of those during the coral spawning season. Away from these areas, self-seeding was less likely to occur and larval replenishment would result mainly from connectivity between reefs located kilometres to tens of kilometres apart. The location of sticky water areas varied spatially within the reef matrix according to tidal and mean currents, local bathymetry and reef density (defined as the degree of aggregation by reefs). A simple analytical formula is presented that explains ˜70% of the variation in larval retention in both calm weather and windy conditions. Complex reef mosaics and the related sticky water effect may have significant implications on the fate of larvae, and thus on connectivity for coral reefs worldwide.

Andutta, Fernando P.; Kingsford, Michael J.; Wolanski, Eric

2012-04-01

70

Assessing the Use of Sunken Lanes for Water Retention in a Landscape  

NASA Astrophysics Data System (ADS)

Newly-designed structures and landscaping elements are often used for flood protection. This article assesses the use of existing sunken lanes for retaining water in a landscape and the sedimentation of washed-off soil. The article also describes ways how to preserve or, at least minimally disrupt, existing biotopes and landscape segments. Geodetic data from one specific sunken lane in South Moravia in the Czech Republic were transferred to a digital terrain model; 9 models were subsequently generated, each with a different longitudinal sunken lane bed slope. Retention dams consisting of gabions were placed in them. The number of dams, the volume of structures made of steel gabions, and the retention area volume behind the dams were determined for each model specifically. It was determined that the number of dams, as well as their total volume, increased with the average longitudinal slope of the sunken lane bed. It was also discovered that the retention volume remained almost the same, as it only very slightly decreases with an increasing longitudinal slope.

Zlatuška, Karel

2012-12-01

71

Regularities of Anthocyanins Retention in RP HPLC for “Water–Acetonitrile–Phosphoric Acid” Mobile Phases  

PubMed Central

The influence of exchange of HCOOH (System 2) by phosphoric acid (System 1) for acidification of the “acetonitrile–water” mobile phases for reversed-phase HPLC of anthocyanins was investigated in the framework of relative retention analysis. The differences and similarities of anthocyanins separation were revealed. It has been shown that some common features of the quantitative relationships may be used for preliminary anthocyanins structure differentiation, according to the number of OH-groups in anthocyanidin backbone as well as to a number of saccharide molecules in glycoside radicals in position 3 of the anthocyanin without MS detection.

Deineka, V. I.; Deineka, L. A.; Saenko, I. I.

2015-01-01

72

Investigating and simulating the impact of surface water retention potential in Western Siberia  

NASA Astrophysics Data System (ADS)

The Western Siberian lowland is characterised through an extreme climate with a yearly temperature difference of more than 60°C. An intensive growth period of five months follows the most important hydrological event of the year, the snowmelt, which defines more than 90% of the yearly runoff. The geophysical setting is mainly influenced through low hydraulic gradients, clayey soils, retention basins, landscape depressions and embankments that lead to a high water rentention potential on the surface and the soil. During snowmelt, this leads to a runoff delay. In hand with high evaporation, the described characteristics cause low runoff generation during the rest of the year, even after intense rainfall events. Within the scope of the project "Sustainable land management and adaptation stategies to climate change for the Western Siberian corn-belt" (SASCHA) the hydrological processes are simulated in three catchments, in a gradient from the pre-taiga to the forest steppe. The three catchments are Pyschma (16.762 km²), Vagai (2.851 km²) and Loktinka (334 km²). The special challenges in the simulations are: (1) the correct simulation of the half-year long snow cover and its melting, (2) the scarce historical flow data, which could only be extended in 2013 through own measurement campaings and (3) to quantify and simulate the impact of the water retention potential on the catchment hydrology using raw and filled digital elevation models and landscape characteristics. Against the background of these challenges, we present the hydrological simulations with the Soil and Water Assessment Tool (SWAT).

Kiesel, Jens; Kolychalow, Olga; Sheludkov, Artyom; Marciniak, Hasmik; Abramenko, Katya; Schmalz, Britta; Conrad, Yvonne; Pfannerstill, Matthias; Veshkurseva, Tatyana; Khoroshavin, Vitaliy; Tolstikov, Andrey; Fohrer, Nicola

2014-05-01

73

Influence of vegetative filter strips on heavy metal retention in runoff waters: a laboratory evaluation  

NASA Astrophysics Data System (ADS)

Point-polluted industrial sites can be exposed to water erosion, leading to a dispersion of, e.g., heavy metal contaminated soil particles. Sowing vegetative buffer strips could limit this problem. We therefore investigated the influence of different vegetative filter strips on heavy metal retention, for runoff water loaded with two different polluted sediments. An experimental flume was built in order to simulate sediment retention by short vegetative buffer strips for different runoff discharges, slopes and sediment concentrations. At the lower bound of the flume, a 0.58 m wide x 1 m long x 0.1 m deep cage filled with soil could be inserted. Three treatments were considered: bare soil and soil sown with either Trifolium repens or Lolium perenne. The plants were allowed to grow for 2 months after germination. The setup allowed characterizing the water and sediment discharge at the outlet of the vegetative strips by means of a tipping bucket with splitter device. Heavy metal-polluted soils were collected at two industrial sites highly polluted with 1) arsenic and lead (Ath), and 2) cadmium and zinc (Prayon). We investigated the effects of the three different covers for these two sediment types (4 replications by treatment), with a slope of 8%, a discharge of 1.7 m3/h and a sediment concentration of 10g/l. Besides sediment mass, we determined heavy metal concentrations and particle size of the sediments collected both at the outlet of the flume and in the sediment deposits upstream of the strips. Following these experiments, size separation of the initial soils was performed, to analyze heavy metal concentrations of each size class. Finally, selective extractions (water, CaCl2 and EDTA) were performed, allowing estimation of heavy metal soluble fractions not retained by vegetative filter strips. Ath Prayon As [%] Pb [%] Cd [%] Zn [%] Lolium perenne 24.1 21.5 23.7 21.2 Trifolium repens 47.8 40.5 55 52.4 Bare soil 20.5 10.9 26.5 22.1 Concentrations [mg/kg] 800 40000 42 2400 Heavy metal retention by vegetative filter strips and mean concentrations [mg/kg] of soils. Heavy metal concentrations increased at the outlet of the flume because of selective sedimentation. Vegetative filter strips with Trifolium repens were the most effective to trap sediments and heavy metals. These strips slowed significantly the flow, leading to important sediment deposits upstream. Lolium perenne were not more efficient than bare soil, because of its erected posture and its low number of tillers after 2 months.

Lambrechts, Thomas; de Braekeleer, Charlotte; Iserentant, Anne; Rentmeesters, Guido; Lutts, Stanley; Bielders, Charles

2010-05-01

74

Source or Sink: Investigating the role of storm water retention ponds in the urban landscape (Invited)  

NASA Astrophysics Data System (ADS)

The impact of human activities on surface water, groundwater and soil is nowhere more apparent than in urban and suburban systems. Dramatic changes to watersheds in urbanizing areas have led to changes in hydrology and an associated increase in the flux of sediment and contaminants to surface and ground waters. In an effort to mediate these impacts, Best Management Practices (BMP) have been established in order to increase infiltration of runoff and trap sediment and particulates derived from impervious surfaces before they enter surface waters. Perhaps the most ubiquitous BMP are storm water retention ponds. While these structures are designed to reduce runoff and particulate loading to urban streams, their addition to the urban landscape has created a large number of new wetland habitats. In the Red Run watershed, just outside of Baltimore, Maryland, 186 discrete natural or man-made wetland areas have been identified. Of these 186 wetland areas, 165 were created to manage stormwater and most were specifically designed as stormwater management ponds (i.e., human-created basins or depressions that hold runoff for some period during the annual hydrological year). Despite their abundance in the landscape, very little is known about how these systems impact the flux of stormwater pollutants or affect the organisms using these ponds as habitat. Results from a series of related projects in the Red Run watershed are presented here in an effort to summarize the range of issues associated with stormwater management ponds. The Red Run watershed is situated inside the Urban-Rural Demarcation Line (URDL) around Baltimore City and has been identified as a smart growth corridor by Baltimore County. This region is one of two areas in Baltimore County where new development is focused. In a series of investigations of soils, surface and ground waters, and amphibian and earthworm use of 68 randomly selected stormwater retention ponds from the Red Run watershed, a range of hydrologic, ecologic, and geochemical conditions have been identified. Results from these investigations suggest that pollutant conditions, specifically trace metals and chloride, limit the use of these ponds by amphibians and effect the distribution of earthworms within ponds. The soils in ponds associated with high use roadways contain elevated levels of PAHs, Zn and Cu and the groundwater beneath these same ponds tends to have elevated chloride levels year round. Pond and associated flood plain soils in these systems have been altered and exhibit elevated Na+ or Ca2+ concentrations suggesting years of interaction with road salt contaminated discharge. These Na+ and Ca2+ form soils affect the retention of dissolved trace metals with Ca-enriched soils potentially increasing the dissolved metal concentrations of surface and pore waters and enabling the transport of roadway derived metals to surface waters and Na-enriched soils scavenging trace metals from incoming runoff. The increase in dissolved metals may also increase the toxicity to amphibians and other organisms inhabiting the storm water ponds and ultimately, streams fed by ground water recharge from ponds. Our results to date suggest both the intended and unintended function of storm water ponds in urban landscapes are complicated and deserving of more attention.

Lev, S.; Casey, R.; Ownby, D.; Snodgrass, J.

2009-12-01

75

Preparation and properties of a double-coated slow-release and water-retention urea fertilizer.  

PubMed

A double-coated, slow-release, and water-retention urea fertilizer (DSWU) was prepared by cross-linked poly(acrylic acid)-containing urea (PAAU) (the outer coating), polystyrene (PS) (the inner coating), and urea granule (the core). Elemental analysis results showed that the nitrogen content of the product was 33.6 wt %. The outer coating (PAAU) regulated the nitrogen release rate and protected the inner coating from damage. The slow-release property of the product was investigated in water and in soil. The possible mechanism of nitrogen release was proposed. The influences of PS coating percentage, temperature, water absorbency, and pH on the release of nitrogen were also investigated. It was found that PS coating percentage, temperature, and water absorbency had a significant influence on the release of nitrogen. However, the pH had no effect. The water-retention property of the product was also investigated. The results showed that the product not only had a good slow-release property but also excellent water-retention capacity, which could effectively improve the utilization of fertilizer and water resources. The results of the present work indicated that the DSWU would find good application in agriculture and horticulture, especially in drought-prone areas where the availability of water is insufficient. PMID:16478265

Liang, Rui; Liu, Mingzhu

2006-02-22

76

Preparation and properties of a double-coated slow-release NPK compound fertilizer with superabsorbent and water-retention.  

PubMed

A double-coated slow-release NPK compound fertilizer with superabsorbent and water-retention was prepared by crosslinked poly(acrylic acid)/diatomite - containing urea (the outer coating), chitosan (the inner coating), and water-soluble granular fertilizer NPK (the core). The effects of the amount of crosslinker, initiator, degree of neutralization of acrylic acid, initial monomer and diatomite concentration on water absorbency were investigated and optimized. The water absorbency of the product was 75 times its own weight if it was allowed to swell in tap water at room temperature for 2 h. Atomic absorption spectrophotometer and element analysis results showed that the product contained 8.47% potassium (shown by K(2)O), 8.51% phosphorus (shown by P(2)O(5)), and 15.77% nitrogen. We also investigated the water-retention property of the product and the slow release behavior of N, P and K in the product. This product with excellent slow release and water-retention capacity, being nontoxic in soil and environment-friendly, could be especially useful in agricultural and horticultural applications. PMID:17320380

Wu, Lan; Liu, Mingzhu; Rui Liang

2008-02-01

77

Preparation and properties of a coated slow-release and water-retention biuret phosphoramide fertilizer with superabsorbent.  

PubMed

In this investigation, a novel water-insoluble slow-release fertilizer, biuret polyphosphoramide (BPAM), was formulated and synthesized from urea, phosphoric acid (H(3)PO(4)), and ferric oxide (Fe(2)O(3)). The structure of BPAM was characterized by Fourier transform infrared (FTIR) spectroscopy. Subsequently, a coated slow-release BPAM fertilizer with superabsorbent was prepared by ionic cross-linked carboxymethylchitosan (the core), acrylic acid, acrylamide, and active carbon (the coating). The variable influences on the water absorbency were investigated and optimized. Component analysis results showed that the coated slow-release BPAM contained 5.66% nitrogen and 11.7% phosphorus. The property of water retention, the behavior of slow release of phosphorus, and the capacity of adsorption of cations were evaluated, and the results revealed that the product not only had good slow-release property and excellent water retention capacity but also higher adsorption capacities of cations in saline soil. PMID:21155599

Jin, Shuping; Yue, Guoren; Feng, Lei; Han, Yuqi; Yu, Xinghai; Zhang, Zenghu

2011-01-12

78

Improved Soil and Water Assessment Tool (SWAT) Performance by Removal of the Curve Number Method  

Microsoft Academic Search

The Soil and Water Assessment Tool (SWAT) is a watershed model widely used to predict water quantity and quality under varying land and water use regimes. To determine the respective amounts of infiltration and surface runoff, SWAT uses the popular Curve Number (CN) method. While appropriate for engineering design in temperate climates, the CN is less than ideal when used

E. D. White; Z. M. Easton; D. R. Fuka; T. S. Steenhuis

2008-01-01

79

Evaluation of a computer program used to estimate water characteristic curve  

Technology Transfer Automated Retrieval System (TEKTRAN)

The soil water characteristic curve, h(theta), can be used to estimate a variety of parameters in unsaturated soils. One practical application of h(theta) is its use by DRAINMOD, a drainage model that has been widely used in shallow water table regions, to determine the water table depth–drainage v...

80

Determining factors for anodic polarization curves of typical structural materials of boiling water reactors in high temperature – high purity water  

Microsoft Academic Search

In order to examine the anodic polarization characteristics of typical structural materials of boiling water reactors (BWRs), the anodic polarization curves of type 316L stainless steel (316L SS) and Alloy 182 were measured in deaerated high purity water at 553 K using the previously reported measurement method which was confirmed suitable for high temperature – high purity water. In order to

Masahiko Tachibana; Kazushige Ishida; Yoichi Wada; Ryosuke Shimizu; Nobuyuki Ota; Nobuyoshi Hara

2012-01-01

81

Transport and retention of phosphorus in surface water in an urban slum area  

NASA Astrophysics Data System (ADS)

The transport of excessive phosphorus (P) discharged from unsewered informal settlements (slums) due to poor on-site sanitation is largely unknown. Hence, we investigated the processes governing P transport in a 28 km2 slum-dominated catchment in Kampala, Uganda. During high runoff events and a period of base flow, we collected hourly water samples (over 24 h) from a primary channel draining the catchment and from a small size tertiary channel draining one of the contributing slum areas (0.5 km2). Samples were analyzed for orthophosphate (PO4-P), particulate P (PP), total P (TP) and selected hydro-chemical parameters. Channel bed and suspended sediments were collected to determine their sorption potential, geo-available metals and dominant P forms. We found that P inputs in the catchment originated mainly from domestic wastewater as evidenced by high concentrations of Cl (36-144 mg L-1), HCO3 and other cations in the channels. Most P discharged during low flow conditions was particulate implying that much of it was retained in bed sediments. Retained P was mostly bound to Ca and Fe/Al oxides. Hence, we inferred that mineral precipitation and adsorption to Ca-minerals were the dominant P retention processes. Bed sediments were P-saturated and showed a tendency to release P to discharging waters. P released was likely due to Ca-bound P because of the strong correlation between Ca and total P in sediments (r2 = 0.9). High flows exhibited a strong flush of PP and SS implying that part of P retained was frequently flushed out of the catchment by surface erosion and resuspension of bed sediment. Our findings suggest that P accumulated in the channel bed during low flows and then was slowly released into surface water. Hence, it will likely take some time, even with improved wastewater management practices, before P loads to downstream areas can be significantly reduced.

Nyenje, P. M.; Meijer, L. M. G.; Foppen, J. W.; Kulabako, R.; Uhlenbrook, S.

2013-08-01

82

Utilization of wheat straw for the preparation of coated controlled-release fertilizer with the function of water retention.  

PubMed

With the aim of improving fertilizer use efficiency and minimizing the negative impact on the environment, a new coated controlled-release fertilizer with the function of water retention was prepared. A novel low water solubility macromolecular fertilizer, poly(dimethylourea phosphate) (PDUP), was "designed" and formulated from N,N'-dimethylolurea (DMU) and potassium dihydrogen phosphate. Simultaneously, an eco-friendly superabsorbent composite based on wheat straw (WS), acrylic acid (AA), 2-acryloylamino-2-methyl-1-propanesulfonic acid (AMPS), and N-hydroxymethyl acrylamide (NHMAAm) was synthesized and used as the coating to control the release of nutrient. The nitrogen release profile and water retention capacity of the product were also investigated. The degradation of the coating material in soil solution was studied. Meanwhile, the impact of the content of N-hydroxymethyl acrylamide on the degradation extent was examined. The experimental data showed that the product with good water retention and controlled-release capacities, being economical and eco-friendly, could be promising for applications in agriculture and horticulture. PMID:22730900

Xie, Lihua; Liu, Mingzhu; Ni, Boli; Wang, Yanfang

2012-07-18

83

Modeling gravity effects on water retention and gas transport characteristics in plant growth substrates  

NASA Astrophysics Data System (ADS)

Growing plants to facilitate life in outer space, for example on the International Space Station (ISS) or at planned deep-space human outposts on the Moon or Mars, has received much attention with regard to NASA’s advanced life support system research. With the objective of in situ resource utilization to conserve energy and to limit transport costs, native materials mined on Moon or Mars are of primary interest for plant growth media in a future outpost, while terrestrial porous substrates with optimal growth media characteristics will be useful for onboard plant growth during space missions. Due to limited experimental opportunities and prohibitive costs, liquid and gas behavior in porous substrates under reduced gravity conditions has been less studied and hence remains poorly understood. Based on ground-based measurements, this study examined water retention, oxygen diffusivity and air permeability characteristics of six plant growth substrates for potential applications in space, including two terrestrial analogs for lunar and Martian soils and four particulate substrates widely used in reduced gravity experiments. To simulate reduced gravity water characteristics, the predictions for ground-based measurements (1 - g) were scaled to two reduced gravity conditions, Martian gravity (0.38 - g) and lunar gravity (0.16 - g), following the observations in previous reduced gravity studies. We described the observed gas diffusivity with a recently developed model combined with a new approach that estimates the gas percolation threshold based on the pore size distribution. The model successfully captured measured data for all investigated media and demonstrated the implications of the poorly-understood shift in gas percolation threshold with improved gas percolation in reduced gravity. Finally, using a substrate-structure parameter related to the gaseous phase, we adequately described the air permeability under reduced gravity conditions.

Chamindu Deepagoda, T. K. K.; Jones, Scott B.; Tuller, Markus; de Jonge, Lis Wollesen; Kawamoto, Ken; Komatsu, Toshiko; Moldrup, Per

2014-08-01

84

QSPR models of boiling point, octanol- water partition coefficient and retention time index of polycyclic aromatic hydrocarbons  

Microsoft Academic Search

A Quantitative Structure - Property Relationship (QSPR) analysis and study of polycyclic aromatic hydrocarbons (PAHs) is presented. Three physicochemical properties related to their environmental impact are studied: boiling point (bp), octanol- water partition coefficient ðlog KowÞ and retention time index (RI) for reversed-phase liquid chromatography analysis. The geometry of all PAHs were optimized by the semi-empirical method AM1 and used

Fabiana Alves de Lima; Marcia Miguel Castro Ferreira

85

QSPR models of boiling point, octanol–water partition coefficient and retention time index of polycyclic aromatic hydrocarbons  

Microsoft Academic Search

A Quantitative Structure–Property Relationship (QSPR) analysis and study of polycyclic aromatic hydrocarbons (PAHs) is presented. Three physicochemical properties related to their environmental impact are studied: boiling point (bp), octanol–water partition coefficient (logKow) and retention time index (RI) for reversed-phase liquid chromatography analysis. The geometry of all PAHs were optimized by the semi-empirical method AM1 and used to calculate thermodynamic, electronic,

Fabiana Alves de Lima Ribeiro; Márcia Miguel Castro Ferreira

2003-01-01

86

StormWater Retention, Grain Production, and Aviation in the Southern Great Plains  

Microsoft Academic Search

How might grain-crop agriculture and stormwater-retention structures within FAA airport sighting criteria affect bird strike risk? We summarize over seven months of data (20 August 2007–31 March 2008) from an on-going wildlife hazard assessment at a General Aviation airport in north central Oklahoma, including concurrent observations at 10 stormwater-retention structures within the two-mile sighting criteria. The landscape within the 5-mile

Philip Robinson; Alicia Bernard; Bradley F. Blackwell

2008-01-01

87

Stiffness-Modulated Water Retention and Neovascularization of Dermal Fibroblast-Encapsulating Collagen Gel  

PubMed Central

There is increasing evidence that matrix stiffness modulates various phenotypic activities of cells surrounded by a three-dimensional (3D) matrix. These findings suggest that matrix stiffness can also regulate dermal fibroblasts activities to remodel, repair, and recreate skin dermis, but this has not yet been systematically demonstrated to date. This study examines the effects of matrix rigidity on the morphology, growth rates, and glycosaminoglycan (GAG) production of dermal fibroblasts cultured in collagen-based hydrogels with controlled elastic moduli. The elastic moduli (E) of collagen hydrogels were increased from 0.7 to 1.6 and 2.2?kPa by chemically cross-linking collagen fibrils with poly(ethylene glycol) disuccinimidylester. Increasing E of the hydrogel led to decreases in cellular spreading, nuclear aspect ratio, and growth rate. In contrast, the cellular GAG production level was elevated by increasing E from 0.7 to 1.6?kPa. The larger accumulation of GAG in the stiffer hydrogel led to increased water retention during exposure to air, as confirmed with magnetic resonance imaging. Additionally, in a chicken chorioallantoic membrane, a cell-encapsulating hydrogel with E of 1.6?kPa created dermis-like tissue with larger amount of GAG and density of blood vessels, while a cell–hydrogel construct with E of 0.7?kPa generated scar-like tissue. Overall, the results of this study will be highly useful for designing advanced tissue engineering scaffolds that can enhance the quality of a wide array of regenerated tissues including skin. PMID:23289622

Jeong, Jae Hyun; Liang, Youyun; Jang, Michelle; Cha, Chaenyung; Chu, Cathy; Lee, Haekwang; Jung, Woonggyu; Kim, Jin Woong; Boppart, Stephen A.

2013-01-01

88

EXPERIMENTAL STUDY OF CRITICAL HEAT FLUX WITH ALUMINA-WATER NANOFLUIDS IN DOWNWARD-FACING CHANNELS FOR IN-VESSEL RETENTION APPLICATIONS  

E-print Network

The Critical Heat Flux (CHF) of water with dispersed alumina nanoparticles was measured for the geometry and flow conditions relevant to the In-Vessel Retention (IVR) situation which can occur during core melting sequences ...

Park, R.J.

89

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

PubMed

Traditional community-based bioassessment is time-consuming because they rely on full species-abundance data of a community. To improve bioassessment efficiency, the feasibility of the diversity measures based on species accumulative curves for bioassessment of water quality status was studied based on a dataset of microperiphyton fauna. The results showed that: (1) the species accumulative curves well fitted the Michaelis-Menten equation; (2) the ?- and ?-diversity, as well as the number of samples to 50% of the maximum species number (Michaelis-Menten constant K), can be statistically estimated based on the formulation; (3) the rarefied ?-diversity represented a significant negative correlation with the changes in the nutrient NH4-N; and (4) the estimated ?-diversity and the K constant were significantly positively related to the concentration of NH4-N. The results suggest that the diversity measures based on species accumulative curves might be used as a potential bioindicator of water quality in marine ecosystems. PMID:25499181

Xu, Guangjian; Zhang, Wei; Xu, Henglong

2015-02-15

90

The infrared light curve of Periodic Comet Halley 1986 III and its relationship to the visual light curve, C2, and water production rates  

NASA Astrophysics Data System (ADS)

The near-IR light curve of Periodic Comet Halley 1986 III is analyzed and compared with C2 production, water production, and the visual light curve. This is the most complete IR light curve compiled to date for any comet. The scattering phase function at small sun-comet-earth angles is shown to affect the slope of near-IR light curve significantly. P/Halley's dust production, as inferred from the IR light curve showed an increased production rate near perihelion which appears to be correlated with the onset of significant jet activity. The near-IR light curve, visual light curve, C2, and water production rates displayed different heliocentric variations, suggesting that one parameter cannot be accurately estimated from another. This is particularly true of the early preperihelion visual light curve. A peak of 0.3-0.5 magnitude in the visual magnitude, representing the integrated brightness of the comet's visible coma, lagged the other parameters by about a day. The near-IR color, J-H, was less red during periods of strong dust activity.

Morris, C. S.; Hanner, M. S.

1993-04-01

91

Hamerschlag Hall Green Roof Storm Water Retention and Runoff Reduction Performance Lucheng Chen  

E-print Network

..................................................................................................... 23 5.3.2. Snow ...................................................................................................................... 26 5.3.3. Seasonal Effects water and plants that evapotranspire the stored water. Storm water runoff from two hydraulically

Andrews, Peter B.

92

A biokinetic model for predicting the retention of 3H in the human body after intakes of tritiated water.  

PubMed

Scarce published data on the long-term excretion of tritiated water from the human body have been re-evaluated in order to develop a biokinetic model describing the retention in the human body of 3H from tritiated water (HTO) that could be used for both prospective and retrospective radiation protection. A three-component exponential function is proposed to describe the elimination of 3H from HTO with biological half-times of 10 d (99.00%), 40 d (0.98%) and 350 d (0.02%) respectively. The model predicts a committed effective dose of 1.7 x 10(-11) Sv Bq(-1), comparable with that of the current ICRP Publication 56 and 72 models, and estimates the retention of 3H to within a factor of about 2 of the measured values up to 40 d after intake and about 5 at times longer than 100 d. The derivation of the model and the uncertainties associated with the various parameters are discussed. PMID:14526960

Taylor, D M

2003-01-01

93

A Nonparametric Instrumental Variable Approach to Estimating the Environmental Kuznets Curve for Water Pollutants at the Global Level  

E-print Network

for Water Pollutants at the Global Level Krishna P. Paudel1 , C.-Y. Cynthia Lin2 , Mahesh Pandit the Environmental Kuznets Curve for Water Pollutants at the Global Level Abstract We examine the relationship between income and water pollutants using country- level global water quality data over the period 1980

Lin, C.-Y. Cynthia

94

The disappearing Environmental Kuznets Curve: a study of water quality in the Lower Mekong Basin (LMB).  

PubMed

The literature is flush with articles focused on estimating the Environmental Kuznets Curve (EKC) for various pollutants and various locations. Most studies have utilized air pollution variables; far fewer have utilized water quality variables, all with mixed results. We suspect that mixed evidence of the EKC stems from model and error specification. We analyze annual data for four water quality indicators, three of them previously unstudied - total phosphorus (TOTP), dissolved oxygen (DO), ammonium (NH4) and nitrites (NO2) - from the Lower Mekong Basin region to determine whether an Environmental Kuznets Curve (EKC) is evident for a transboundary river in a developing country and whether that curve is dependent on model specification and/or pollutant. We build upon previous studies by correcting for the problems of heteroskedasticity, serial correlation and cross-sectional dependence. Unlike multi-country EKC studies, we mitigate for potential distortion from pooling data across geographically heterogeneous locations by analyzing data drawn from proximate locations within a specific international river basin in Southeast Asia. We also attempt to identify vital socioeconomic determinants of water pollution by including a broad list of explanatory variables alongside the income term. Finally, we attempt to shed light on the pollution-income relationship as it pertains to trans-boundary water pollution by examining data from an international river system. We do not find consistent evidence of an EKC for any of the 4 pollutant indicators in this study, but find the results are entirely dependent on model and error specification as well as pollutant. PMID:24211570

Wong, Yoon Loong Andrew; Lewis, Lynne

2013-12-15

95

Vortex shedding experiment with flat and curved bluff plates in water  

NASA Technical Reports Server (NTRS)

Vortex shedding experiments were conducted in a water flow facility in order to simulate the strong discrete 4000-Hz vibration detected in the Space Shuttle Main Engine (SSME) which is thought to be associated with the SSME LOX inlet tee splitter vanes on the Main Injector. For the case of a flat vane with a blunt trailing edge excited by flow induced vortex shedding, lock-in with the first bending mode of the plate was observed. A curved vane displayed similar behavior, with the lock-in being a more discrete higher amplitude response. Aluminum vanes were employed to decouple the first vane bending mode from the vortex shedding mode. The application of an asymmetric 30-deg trailing edge bevel to both the flat and curved vanes was found to greatly reduce the strength of the shed vortices.

Reed, D.; Nesman, T.; Howard, P.

1988-01-01

96

Surface-bubble-modulated liquid chromatography: a new approach for manipulation of chromatographic retention and investigation of solute distribution at water/hydrophobic interfaces.  

PubMed

In this paper, we present a new chromatographic method termed surface-bubble-modulated liquid chromatography (SBMLC), that has a hybrid separation medium incorporated with surface nanobubbles. Nanobubbles or nanoscale gas phases can be fixed at the interface between water and a hydrophobic material by delivering water into a dry column packed with a nanoporous material. The incorporation of a gas phase at the hydrophobic surface leads to the formation of the hybrid separation system consisting of the gas phase, hydrophobic moieties, and the water/hydrophobic interface or the interfacial water. One can change the volume of the gas phase by pressure applied to the column, which in turn alters the area of water/hydrophobic interface or the volume of the interfacial water, while the amount of the hydrophobic moiety remains constant. Therefore, this strategy provides a novel technique not only for manipulating the separation selectivity by pressure but also for elucidating the mechanism of accumulation or retention of solute compounds in aqueous solutions by a hydrophobic material. We evaluate the contributions of the interfacial water at the surface of an octadecyl bonded silica and the bonded layer itself to the retention of various solute compounds in aqueous solutions on the column packed with the material by SBMLC. The results show that the interfacial water formed at the hydrophobic surface has a key role in retention even though its volume is rather small. The manipulation of the separation selectivity of SBMLC for some organic compounds by pressure is demonstrated. PMID:25496068

Nakamura, Keisuke; Nakamura, Hiroki; Saito, Shingo; Shibukawa, Masami

2015-01-20

97

Surfactant and Irrigation Effects on Runoff, Erosion, and Water Retention of Three Wettable Soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

Surfactants are chemical compounds that change the contact angle of water on solid surfaces and are commonly used to increase infiltration into hydrophobic soil. Since production fields with water-repellent soil often contain areas of wettable soil, surfactants applied to such fields will likely be ...

98

Soil water repellency characteristic curves for soil profiles with natural organic carbon gradients  

NASA Astrophysics Data System (ADS)

Soil water repellency (SWR) is a phenomenon that influences many soil hydrologic processes such as reduction of infiltration, increase in overland flow, and enhanced preferential flow. SWR has been observed in various soil types and textures, and the degree of SWR is greatly controlled by soil moisture content and levels of organic matter and clay. One of the key topics in SWR research is how to describe accurately the seasonal and temporal variation of SWR with the controlling factors such as soil moisture, organic matter, and clay contents for soil profiles with natural organic carbon gradients. In the present study, we summarize measured SWR data for soil profiles under different land uses and vegetation in Japan and New Zealand, and compared these with literature data. We introduce the contact angle-based evaluation of SWR and predictive models for soil water repellency characteristic curves, in which the contact angle is a function of the moisture content. We also discuss a number of novel concepts, including i) the reduction in the contact angle with soil-water contact time to describe the time dependence of SWR, ii) the relationship between the contact angles from the measured scanning curves under controlled wetting and drying cycles, and iii) the initial contact angles measured by the sessile drop method.

Kawamoto, Ken; Müller, Karin; Moldrup, Per; de Jonge, Lis; Clothier, Brent; Hiradate, Syuntaro; Komatsu, Toshiko

2014-05-01

99

Importance of intercellular lipids in water-retention properties of the stratum corneum: induction and recovery study of surfactant dry skin  

Microsoft Academic Search

In order to further clarify the role of intercellular lipids in the water-retention properties of the stratum corneum, forearm skin of six healthy male volunteers was treated with 5% sodium dodecyl sulfate (SDS) for 1, 10, and 30 min. All treatment periods induced chapping and scaling of the stratum corneum without any inflammatory reaction, accompanied by a significant decrease in

G. Imokawa; S. Akasaki; Y. Minematsu; M. Kawai

1989-01-01

100

Going beyond the unitary curve: incorporating richer cognition into agent-based water resources models  

NASA Astrophysics Data System (ADS)

The increased availability and understanding of agent-based modeling technology and techniques provides a unique opportunity for water resources modelers, allowing them to go beyond traditional behavioral approaches from neoclassical economics, and add rich cognition to social-hydrological models. Agent-based models provide for an individual focus, and the easier and more realistic incorporation of learning, memory and other mechanisms for increased cognitive sophistication. We are in an age of global change impacting complex water resources systems, and social responses are increasingly recognized as fundamentally adaptive and emergent. In consideration of this, water resources models and modelers need to better address social dynamics in a manner beyond the capabilities of neoclassical economics theory and practice. However, going beyond the unitary curve requires unique levels of engagement with stakeholders, both to elicit the richer knowledge necessary for structuring and parameterizing agent-based models, but also to make sure such models are appropriately used. With the aim of encouraging epistemological and methodological convergence in the agent-based modeling of water resources, we have developed a water resources-specific cognitive model and an associated collaborative modeling process. Our cognitive model emphasizes efficiency in architecture and operation, and capacity to adapt to different application contexts. We describe a current application of this cognitive model and modeling process in the Arkansas Basin of Colorado. In particular, we highlight the potential benefits of, and challenges to, using more sophisticated cognitive models in agent-based water resources models.

Kock, B. E.

2008-12-01

101

Effect of the water content on the retention and enantioselectivity of albendazole and fenbendazole sulfoxides using amylose-based chiral stationary phases in organic-aqueous conditions.  

PubMed

Four commercially available immobilized amylose-derived CSPs (Chiralpak IA-3, Chiralpak ID-3, Chiralpak IE-3 and Chiralpak IF-3) were used in the HPLC analysis of the chiral sulfoxides albendazole (ABZ-SO) and fenbendazole (FBZ-SO) and their in vivo sulfide precursor (ABZ and FBZ) and sulfone metabolite (ABZ-SO2 and FBZ-SO2) under organic-aqueous mode. U-shape retention maps, established by varying the water content in the acetonitrile- and ethanol-water mobile phases, were indicative of two retention mechanisms operating on the same CSP. The dual retention behavior of polysaccharide-based CSPs was exploited to design greener enantioselective and chemoselective separations in a short time frame. The enantiomers of ABZ-SO and FBZ-SO were baseline resolved with water-rich mobile phases (with the main component usually being 50-65% water in acetonitrile) on the IF-3 CSP and ethanol-water 100:5 mixture on the IA-3 and IE-3 CSPs. A simultaneous separation of ABZ (or FBZ), enantiomers of the corresponding sulfoxide and sulfone was achieved on the IA-3 using ethanol-water 100:60 (acetonitrile-water 100:100 for FBZ) as a mobile phase. PMID:24411094

Materazzo, Sabrina; Carradori, Simone; Ferretti, Rosella; Gallinella, Bruno; Secci, Daniela; Cirilli, Roberto

2014-01-31

102

Sulfonated polyimide/acid-functionalized graphene oxide composite polymer electrolyte membranes with improved proton conductivity and water-retention properties.  

PubMed

Sulfonated polyimide (SPI)/sulfonated propylsilane graphene oxide (SPSGO) was assessed to be a promising candidate for polymer electrolyte membranes (PEMs). Incorporation of multifunctionalized (-SO3H and -COOH) SPSGO in SPI matrix improved proton conductivity and thermal, mechanical, and chemical stabilities along with bound water content responsible for slow dehydration of the membrane matrix. The reported SPSGO/SPI composite PEM was designed to promote internal self-humidification, responsible for water-retention properties, and to promote proton conduction, due to the presence of different acidic functional groups. Strong hydrogen bonding between multifunctional groups thus led to the presence of interconnected hydrophobic graphene sheets and organic polymer chains, which provides hydrophobic-hydrophilic phase separation and suitable architecture of proton-conducting channels. In single-cell direct methanol fuel cell tests, SPI/SPSGO-8 exhibited 75.06 mW·cm(-2) maximum power density (in comparison with commercial Nafion 117 membrane, 62.40 mW·cm(-2)) under 2 M methanol fuel at 70 °C. PMID:25207457

Pandey, Ravi P; Thakur, Amit K; Shahi, Vinod K

2014-10-01

103

INVESTIGATION OF PHASE AND EMULSION BEHAVIOR, SURFACTANT RETENTION, AND CONDENSATE RECOVERY FOR CONDENSATE/WATER/ETHANOL MIXTURES  

SciTech Connect

This semi-annual technical progress report describes work performed at Morehouse College under DOE Grant No. DE-FG26-02NT15447 during the period April 01, 2003 to September 30, 2003 which covers the second six months of the project. Presently work is in progress to characterize phase and emulsion behavior for ethylbenzene/water/ethanol system. During this reporting period, salinity scans were completed for 0, 5, 10, 20, 50, 100, 250, 500, and 1000 mM salt concentrations at room temperature to identify optimal salinity intervals in which all three phases coexist for this system. Temperature scans are in progress at Morehouse College to identify the optimal temperature, and the temperature intervals in which all three phases coexist for this system. Coreflooding experiments are being conducted by our industrial partner in this project, Surtek, CO, to measure the effectiveness for surfactant retention and condensate recovery in flooding processes. Review of the current literature in the subject area, and modeling efforts that were established in our previous studies to predict electrical conductivities and inversion phenomena was continued from the previous reporting period. Based on the review a computer model to predict electrical conductivities of the ethylbenzene (that has the equivalent carbon number of the condensate)/water/ethanol system is being developed.

Ramanathan Sampath

2003-10-01

104

Cathodic polarization curves of the oxygen reduction reaction on various structural materials of boiling water reactors in high temperature–high purity water  

Microsoft Academic Search

Cathodic polarization curves of the O2 reduction reaction were measured by using electrodes made from typical structural materials of boiling water reactors (BWRs) to evaluate the effects of kind of material on the electrochemical corrosion potential (ECP) calculation. To estimate ECPs at any region in the BWRs on the basis of the BWR environmental conditions, anodic and cathodic polarization curves

Masahiko Tachibana; Kazushige Ishida; Yoichi Wada; Ryosuke Shimizu; Nobuyuki Ota; Nobuyoshi Hara

2012-01-01

105

Water retention and internal accumulation in the percolation zone of the Greenland ice sheet  

NASA Astrophysics Data System (ADS)

In the lower accumulation area along the K-transect, Kangerlussuaq, West Greenland (67 °N 47 °W, 1850 m a.s.l.), a thermistor string installation including instrumentation for surface height, air temperature and radiation components captured the thermal changes during the extreme melt season of 2012 and the season of 2013. Firn cores were drilled in spring 2012 and 2013. The temperature variations in the firn reveal water percolation and refreezing in the uppermost 2.7 m during July and August 2012. Near melting-point temperatures at larger depths (approx. 6 m) recorded in autumn 2012 suggest the presence of liquid water, unable to penetrate the ice layers below. Comparing 2012 and 2013 firn cores reveal that refrozen melt water has filled most of the remaining pore space in the uppermost 7 meters. Below that depth there is no indication of melt water percolation and the temperature variations can be explained by conduction alone. The firn temperature measurements reveal a uniform 4 °C warming of the upper 10 meters from May 2012 to May 2013. This indicates that the firn/ice column gained 3629 kJ m-3 of energy. The formation of an impermeable ice layer along with the recorded albedo decrease is evidence of a rapidly changing area. If large melt events persist, the area will experience a transition towards a superimposed ice regime, or even turn into ablation area, drastically impacting melt and melt extent in the area.

Charalampidis, C.; van As, D.; Macferrin, M. J.; Machguth, H.; Pettersson, R.; Pohjola, V. A.

2013-12-01

106

Norepinephrine Infused into the Basolateral Amygdala Posttraining Enhances Retention in a Spatial Water Maze Task  

Microsoft Academic Search

Recent evidence indicates that the amygdala plays a role in modulating memory processes in other brain regions. For example, posttraining intra-amygdala infusions of amphetamine enhanced memory in both spatial and cued training water maze tasks; these tasks are known to depend on the integrity of the hippocampus and caudate nucleus, respectively. To determine whether this modulation is dependent on noradrenergic

Tammy Hatfield; James L. McGaugh

1999-01-01

107

Use of a storm water retention system for conservation of regionally endangered fishes  

USGS Publications Warehouse

Maintaining aquatic biodiversity in urban or suburban areas can be problematic because urban landscapes can be nearly devoid of aquatic habitats other than engineered basins for storm water management. These areas are usually of questionable value for fish, but we examined a case study in which five regionally imperiled fish species were reintroduced into an artificial storm water detention pond and subsequently thrived. Although not a formal experiment, postintroduction survey data suggested that three of the five species maintained high population densities for 10 years after initial stocking, and two persisted in lower numbers. Success was likely due to a combination of unique design features and prior habitat preparation that resulted in clear water conditions that supported dense vegetation. Stocked fish persisted despite occasional bouts of low dissolved oxygen and increased chloride levels resulting from road salt application within the watershed. Transplanted fish served as a source population for both research and further reintroduction experiments. We suggest that, for some fish species, habitat preservation has a middle ground between natural habitats and completely artificial environments that require constant husbandry and that storm water systems could be used to create engineered sanctuaries within the human landscape that have many potential benefits for both humans and fish.

Schaeffer, Jeffrey S.; Bland, James K.; Janssen, John

2012-01-01

108

Development of a quasi-adiabatic calorimeter for the determination of the water vapor pressure curve.  

PubMed

Progress in the knowledge of the water saturation curve is required to improve the accuracy of the calibrations in humidity. In order to achieve this objective, the LNE-CETIAT and the LNE-CNAM have jointly built a facility dedicated to the measurement of the saturation vapor pressure and temperature of pure water. The principle is based on a static measurement of the pressure and the temperature of pure water in a closed, temperature-controlled thermostat, conceived like a quasi-adiabatic calorimeter. A copper cell containing pure water is placed inside a temperature-controlled copper shield, which is mounted in a vacuum-tight stainless steel vessel immersed in a thermostated bath. The temperature of the cell is measured with capsule-type standard platinum resistance thermometers, calibrated with uncertainties below the millikelvin. The vapor pressure is measured by calibrated pressure sensors connected to the cell through a pressure tube whose temperature is monitored at several points. The pressure gauges are installed in a thermostatic apparatus ensuring high stability of the pressure measurement and avoiding any condensation in the tubes. Thanks to the employment of several technical solutions, the thermal contribution to the overall uncertainty budget is reduced, and the remaining major part is mainly due to pressure measurements. This paper presents a full description of this facility and the preliminary results obtained for its characterization. PMID:22852731

Mokdad, S; Georgin, E; Hermier, Y; Sparasci, F; Himbert, M

2012-07-01

109

Water flow and retention in coarse soil pockets in the shallow subsurface  

Microsoft Academic Search

Soil moisture processes in the near-land-surface subsurface, referred to here as the shallow subsurface, plays a crucial role in the hydrologic cycle and global water budget. In addition, this critical zone is associated with emerging problems in hydrology, climate, the environment and relates to multiple direct and tangential short- and long-term national security interests. Some of the problems associated with

T. Sakaki; A. Limsuwat; T. H. Illangasekare

2010-01-01

110

Role of air on local water retention behavior in the shallow heterogeneous vadose zone  

NASA Astrophysics Data System (ADS)

In the presence of a subsurface source, air flowing through the unsaturated soil can transport toxic vapor into subsurface structures due to pressure gradients created by, e.g., a pressure drop within the building. Development of dynamic air pathways in the subsurface are largely controlled by the geological heterogeneity and the spatial and temporal distribution of soil moisture. To better understand how these air pathways are developed, it is crucial to know how water is retained in heterogeneous medium at spatial resolutions that are finer than those adopted in typical hydrologic and soil physics applications. Although methods for soil water pressure measurement can be readily found in literature, a technique for measuring “air pressure” in wet soil is not well-established or documented. Hydrophobic porous ceramic cups have been used to measure non-wetting NAPL phase pressure in two-phase systems. However, our preliminary tests using the hydrophobic ceramic cups installed in highly wet soil showed that under conditions of fast drainage of the wetting fluid that is replaced by air, it typically took some time before the cups responded to register the air pressure. Therefore, an attempt was made to develop a more robust method where the time lag is minimized. The tested materials were; 1) ceramic porous cups, 2) sintered stainless steel cups, 3) porous glass discs, and 4) non-woven PTFE fabric. The ceramic cups, sintered stainless steel cups and sintered porous glass discs required hydrophobic treatment, whereas the non-woven PTFE fabric is hydrophobic by itself. To treat the ceramic porous cups, the method proposed by Parker and Lenhard [1988] was adopted. The sintered porous stainless steel cups and porous glass discs were treated by a commercially available water repellant compound. For those four materials, contact angle, water entry pressure, and time lag to respond to an imposed pressure were measured. The best performing material was then tested in a simple heterogeneous column. The column was packed using two sands to form three layers where the coarser sand was sandwitched by two layers of a finer sand. In each layer, soil moisture, water pressure and air pressure were monitored. The soil was initially saturated and suction at the bottom was gradually increased to induce wetting fluid drainage, and followed by a wetting cycle. In the drainage cycle, the coarse middle layer did not drain until air front reached the bottom of the top fine layer. Once the air front reached the fine-coarse interface, air was quickly pulled into the coarse layer. The results showed that the newly developed hydrophobic material showed very small time lag and captured the abrupt air pressure change in the wet soil. In the wetting cycle, we observed positive air pressure which indicated entrapment of air and its compression as wetting proceeded. This behavior cannot be evaluated properly without the rapid measurement of air pressure. The method is currently being applied in a large 2D vertical aquifer with a structured heterogeneity to investigate how air pathways are formed under various flux/temperature conditions at the soil surface.

Sakaki, T.; Limsuwat, A.; Illangasekare, T. H.

2009-12-01

111

Dramatic Improvement in Water Retention and Proton Conductivity in Electrically Aligned Functionalized CNT/SPEEK Nanohybrid PEM.  

PubMed

Nanohybrid membranes of electrically aligned functionalized carbon nanotube f CNT with sulfonated poly ether ether ketone (SPEEK) have been successfully prepared by solution casting. Functionalization of CNTs was done through a carboxylation and sulfonation route. Further, a constant electric field (500 V·cm(-2)) has been applied to align CNTs in the same direction during the membrane drying process. All the membranes are characterized chemically, thermally, and mechanically by the means of FTIR, DSC, DMA, UTM, SEM, TEM, and AFM techniques. Intermolecular interactions between the components in hybrid membranes are established by FTIR. Physicochemical measurements were done to analyze membrane stability. Membranes are evaluated for proton conductivity (30-90 °C) and methanol crossover resistance to reveal their potential for direct methanol fuel cell application. Incorporation of f CNT reasonably increases the ion-exchange capacity, water retention, and proton conductivity while it reduces the methanol permeability. The maximum proton conductivity has been found in the S-sCNT-5 nanohybrid PEM with higher methanol crossover resistance. The prepared membranes can be also used for electrode material for fuel cells and batteries. PMID:25513706

Gahlot, Swati; Kulshrestha, Vaibhav

2015-01-14

112

Superhydrophobic surfaces of the water bug Notonecta glauca: a model for friction reduction and air retention  

PubMed Central

Summary Superhydrophobic surfaces of plants and animals are of great interest for biomimetic applications. Whereas the self-cleaning properties of superhydrophobic surfaces have been extensively investigated, their ability to retain an air film while submerged under water has not, in the past, received much attention. Nevertheless, air retaining surfaces are of great economic and ecological interest because an air film can reduce friction of solid bodies sliding through the water. This opens perspectives for biomimetic applications such as low friction fluid transport or friction reduction on ship hulls. For such applications the durability of the air film is most important. While the air film on most superhydrophobic surfaces usually lasts no longer than a few days, a few semi-aquatic plants and insects are able to hold an air film over a longer time period. Currently, we found high air film persistence under hydrostatic conditions for the elytra of the backswimmer Notonecta glauca which we therefore have chosen for further investigations. In this study, we compare the micro- and nanostructure of selected body parts (sternites, upper side of elytra, underside of elytra) in reference to their air retaining properties. Our investigations demonstrate outstanding air film persistence of the upper side of the elytra of Notonecta glauca under hydrostatic and hydrodynamic conditions. This hierarchically structured surface was able to hold a complete air film under hydrostatic conditions for longer than 130 days while on other body parts with simple structures the air film showed gaps (underside of elytra) or even vanished completely after a few days (sternites). Moreover, the upper side of the elytra was able to keep an air film up to flow velocities of 5 m/s. Obviously the complex surface structure with tiny dense microtrichia and two types of larger specially shaped setae is relevant for this outstanding ability. Besides high air film persistence, the observation of a considerable fluid velocity directly at the air–water interface indicates the ability to reduce friction significantly. The combination of these two abilities makes these hierarchically structured surfaces extremely interesting as a biomimetic model for low friction fluid transport or drag reduction on ship hulls. PMID:21977425

Schneider, Erik S; Melskotte, Jan-Erik; Brede, Martin; Leder, Alfred

2011-01-01

113

On the Way to Determination of the Vapor-Pressure Curve of Pure Water  

NASA Astrophysics Data System (ADS)

The determination of the physical properties of pure water, especially the vapor-pressure curve of water, is one of the major issues identified by the Consultative Committee for Thermometry of the International Committee for Weights and Measures (CIPM) to improve the accuracy of the national references in humidity. At the present time the saturation-pressure data, corresponding to ice or liquid-vapor equilibrium, at low temperature are scarce and unreliable. This study presents new measurements of vapor and sublimation pressures of, respectively, water and ice, using a static apparatus. Prior to saturation-pressure measurements, the temperature and pressure sensors of the static apparatus were calibrated against reference gauges in use at the LNE- CETIAT laboratories. The effect of thermal transpiration has been studied. The explored temperature range lies between 250 K and 374 K, and the pressure range between 70 Pa and 105 Pa. An automatic data acquisition program was developed to monitor the pressure and temperature. The obtained results have been compared with available literature data. The preliminary uncertainty budget took into account several components: pressure measurements, temperature measurements, and environmental error sources such as thermal transpiration and hydrostatic correction.

Mokdad, S.; Georgin, E.; Mokbel, I.; Jose, J.; Hermier, Y.; Himbert, M.

2012-09-01

114

Light saturation curves show competence of the water splitting complex in inactive Photosystem II reaction centers.  

PubMed

Photosystem II complexes of higher plants are structurally and functionally heterogeneous. While the only clearly defined structural difference is that Photosystem II reaction centers are served by two distinct antenna sizes, several types of functional heterogeneity have been demonstrated. Among these is the observation that in dark-adapted leaves of spinach and pea, over 30% of the Photosystem II reaction centers are unable to reduce plastoquinone to plastoquinol at physiologically meaningful rates. Several lines of evidence show that the impaired reaction centers are effectively inactive, because the rate of oxidation of the primary quinone acceptor, QA, is 1000 times slower than in normally active reaction centers. However, there are conflicting opinions and data over whether inactive Photosystem II complexes are capable of oxidizing water in the presence of certain artificial electron acceptors. In the present study we investigated whether inactive Photosystem II complexes have a functional water oxidizing system in spinach thylakoid membranes by measuring the flash yield of water oxidation products as a function of flash intensity. At low flash energies (less that 10% saturation), selected to minimize double turnovers of reaction centers, we found that in the presence of the artificial quinone acceptor, dichlorobenzoquinone (DCBQ), the yield of proton release was enhanced 20±2% over that observed in the presence of dimethylbenzoquinone (DMBQ). We argue that the extra proton release is from the normally inactive Photosystem II reaction centers that have been activated in the presence of DCBQ, demonstrating their capacity to oxidize water in repetitive flashes, as concluded by Graan and Ort (Biochim Biophys Acta (1986) 852: 320-330). The light saturation curves indicate that the effective antenna size of inactive reaction centers is 55±12% the size of active Photosystem II centers. Comparison of the light saturation dependence of steady state oxygen evolution in the presence of DCBQ or DMBQ support the conclusion that inactive Photosystem II complexes have a functional water oxidation system. PMID:24415257

Nedbal, L; Gibas, C; Whitmarsh, J

1991-12-01

115

Improved Soil and Water Assessment Tool (SWAT) Performance by Removal of the Curve Number Method  

NASA Astrophysics Data System (ADS)

The Soil and Water Assessment Tool (SWAT) is a watershed model widely used to predict water quantity and quality under varying land and water use regimes. To determine the respective amounts of infiltration and surface runoff, SWAT uses the popular Curve Number (CN) method. While appropriate for engineering design in temperate climates, the CN is less than ideal when used for temporal hydrologic modeling, especially in monsoonal regions. The CN methodology is based on the assumption that moisture content distribution in the watershed is similar for each runoff event, a questionable assumption in many regions where rainfall is concentrated into distinct time periods. In monsoonal climates water balance models generally capture the runoff generation processes and thus the flux of water or transport of chemicals and sediments better than CN based models. In order to use SWAT in monsoonal climates, the CN routine to predict runoff was replaced with a simple water balance routine in the code base. Additionally, rather than determine the spatial distribution of runoff as a function of solely soil and landcover, as the CN method does, a soil topographic index (STI) was included in the derivation of hydrologic response units. To compare this new water balance based SWAT (SWAT-WB) to the original CN based SWAT (SWAT-CN), several watersheds in the headwaters of the Blue Nile in Ethiopia were modeled at a daily time step. While long term, daily data are largely non-existent for portions of the Blue Nile, data were available for one 1270 km2 subbasin of the Lake Tana watershed, northeast of Bahir Dar, Ethiopia, which was used to initialize both versions of SWAT. Prior to any calibration of the models, daily Nash-Sutcliffe model efficiencies improved from 0.01 with SWAT-CN to 0.50 with SWAT-WB, with a similar increase in R-squared values from 0.27 to 0.55, respectively. These initial results indicate that replacement of the CN with a water balance routine in SWAT significantly improves model predictions in monsoonal climates.

White, E. D.; Easton, Z. M.; Fuka, D. R.; Steenhuis, T. S.

2008-12-01

116

Effects of Solution Chemistry on the Retention and Dissolution of Silver Nanoparticles in Water-Saturated Porous Media  

NASA Astrophysics Data System (ADS)

Potential health and environmental effects have been attributed to both silver nanoparticles (nAg) and the silver ion (Ag+), necessitating a thorough understanding of mechanisms governing the fate and transport of nAg in natural systems. Batch and column experiments were conducted to assess nAg transport, retention and dissolution kinetics as a function of pH, electrolyte and dissolved oxygen (DO) content. Batch experiments were performed at pH 4, 5.5 and 7, DO levels of <0.15 mg/L, 2mg/L and 8.9 mg/L, and with 10mM nitrate, acetate or borate as the background electrolyte. Batch solutions containing ca. 2 mg/L nanosilver were monitored regularly for 48 hours and analyzed for mean particle diameter, zeta potential, nanoparticle concentration and silver ion concentration. Silver nanoparticle dissolution increased with decreasing pH and with dissolved oxygen content. Increased aggregation and less negative zeta potential values (tending closer to the point of zero charge) indicate that acetate causes greater instability in nAg suspensions as compared with nitrate at the same ionic strength. Column experiments were performed in glass columns (11 cm length x 2.7 cm diameter) packed with washed 40-50 mesh Ottawa sand and saturated with a background electrolyte solution. Following a non-reactive tracer test, a three pore volume pulse of nAg suspension (ca. 3 mg/L silver) was introduced at a flow rate of 1.0 ml/min (pore water velocity of ca. 7.0 m/d), followed by three pore volumes of nanoparticle-free solution. Column experiments were conducted with 10mM sodium nitrate at pH 4 and 7 and under oxygen rich (DO = 8.9 mg/L) and lean (DO < 0.15 mg/L) conditions. Hyper-exponential retention profiles were observed, with the highest attachment measured at the column inlet. Under oxygen rich conditions, approximately 85% of the input nAg was retained in sand at pH 4, compared with 25% at pH 7. Consistent with batch experimental results, dissolution of retained nanoparticles increased with DO and with decreasing pH. At pH 4 and 7, input suspensions initially contained 0.07 mg/L and 0.03 mg/L silver ion, respectively, while effluent samples contained a maximum of 0.17 mg/L and 0.04 mg/L Ag+, respectively. Batch and column experiments indicate that the retention and dissolution of silver nanoparticles are strongly dependent on solution chemistry. The release of silver ions from retained particles can be substantial under certain environmentally relevant conditions, namely saturated oxygen levels and lower pH values.

Mittelman, A.; Wang, Y.; Pennell, K. D.

2011-12-01

117

Modeling water retention of sludge simulants and actual saltcake tank wastes  

SciTech Connect

The Ferrocyanide Tanks Safety Program managed by Westinghouse hanford Company has been concerned with the potential combustion hazard of dry tank wastes containing ferrocyanide chemical in combination with nitrate salts. Pervious studies have shown that tank waste containing greater than 20 percent of weight as water could not be accidentally ignited. Moreover, a sustained combustion could not be propagated in such a wet waste even if it contained enough ferrocyanide to burn. Because moisture content is a key critical factor determining the safety of ferrocyanide-containing tank wastes, physical modeling was performed by Pacific Northwest National laboratory to evaluate the moisture-retaining behavior of typical tank wastes. The physical modeling reported here has quantified the mechanisms by which two main types of tank waste, sludge and saltcake, retain moisture in a tank profile under static conditions. Static conditions usually prevail after a tank profile has been stabilized by pumping out any excess interstitial liquid, which is not naturally retained by the waste as a result of physical forces such as capillarity.

Simmons, C.S.

1996-07-01

118

Wettability of poultry litter biochars at variable pyrolysis temperatures and their impact on soil wettability and water retention relationships  

NASA Astrophysics Data System (ADS)

To reduce the impact of poultry farming on greenhouse gas emissions, poultry farming waste - poultry litter - can be converted to biofuel and biochar through slow-pyrolysis, with the biochar added to agricultural soil for nutrient enrichment and carbon sequestration. While biochars from source materials other than poultry litter have been shown to sequester carbon and increase soil fertility, there is considerable variability in biochar behavior - even with biochars created from the same source material. This situation is exacerbated by our limited understanding of how biochars alter physical, chemical, and biological processes in agricultural soils. The focus of this work is to develop a mechanistic understanding of how poultry litter (PL) biochars affect the hydrology, microbial communities, N2O emissions, and nitrogen cycling in agricultural soils. The initial focus is on the impact of PL biochar on soil hydrology. PL from Perdue AgriRecycle, LLC (Seaford, Delaware) was used to produce biochars at pyrolysis temperatures from 300°C to 600°C. To explore the impact of these biochars on soil wettability, the PL biochars were mixed with a 30/40 Accusand in mass fractions from 0% to 100%. The water contact angle was then measured using a goniometer on these sand/biochar mixtures using the sessile drop method and a single layer of sample particles. The PL biochars produced at temperatures between 300°C to 400°C were hydrophobic, while those pyrolized at > 400°C were hydrophilic. Water contact angles for samples with 100% biochar varied systematically with pyrolysis temperature, decreasing from 101.12° to 20.57° as the pyrolysis temperature increased from 300 to 600°C. Even for small amounts of hydrophobic biochar added to the hydrophilic sand, the contact angle of the mixture was altered: for sand/biochar mixtures containing only 2% hydrophobic PL biochar by weight, the contact angle of the mixture increased from ~ 8° (0% biochar) to 20° (2% biochar). For higher mass fractions, the impact of hydrophobic PL biochar on the sand/mixture contact angle was more dramatic: for a sand/biochar mixture with 15% PL biochar, the contact angle was 40.12°. Water drop penetration tests were also performed on these samples, and results were consistent with contact angles measured with the sessile drop method. To further explore the cause of the varying contact angle with pyrolysis temperature, the PL biochars were vigorously rinsed with deionized water or heated for 24 hours at 105°C, and the contact angle measurements repeated. Both rinsing and heating samples rendered hydrophobic PL biochar hydrophilic. Rinsate samples were analyzed for total organic carbon and with GC-MS. These data suggest that bio-oils produced during slow-pyrolysis at temperatures < 400°C condensed on biochar and caused hydrophobicity. These bio-oils could be removed through vigorous washing with deionized water or heating to 105°C. The implication of these changes in water contact angle from PL biochar addition on water retention relationships for soil and on water distribution within pores will be discussed.

Yi, S. C.; Witt, B.; Guo, M.; Chiu, P.; Imhoff, P. T.

2012-12-01

119

Investigation of downward facing critical heat flux with water-based nanofluids for In-Vessel Retention applications  

E-print Network

In-Vessel Retention ("IVR") is a severe accident management strategy that is power limiting to the Westinghouse AP1000 due to critical heat flux ("CHF") at the outer surface of the reactor vessel. Increasing the CHF level ...

DeWitt, Gregory L

2011-01-01

120

Retention of ionizable compounds on HPLC. 4. Mobile-phase pH measurement in methanol/water  

PubMed

The different procedures used in HPLC to measure the pH of a mobile phase are evaluated in terms of the rigorous IUPAC definition of pH. The three procedures evaluated are as follows: measurement of the pH of the aqueous HPLC buffer before mixing it with the organic modifier, measurement of the pH of the HPLC buffer after mixing it with the organic modifier using a pH electrode system calibrated with aqueous buffers, and measurement of the pH of the HPLC buffer after mixing it with the organic modifier but calibrating the electrode system with reference buffers prepared in the same mixed solvent used as mobile phase. Following IUPAC definitions and recommendations, the three pH values can be related with the pH scales: w(w)pH, s(w)pH, and s(s)pH, respectively. The relationships between these three pH scales are also presented. The retention of several compounds with acid/base behavior in a C-18 and a polymeric column with buffered methanol/water as mobile phase is related to the mobile phase pH value measured in the three pH scales. It is demonstrated that the s(w)pH and s(s)pH scales give better relationships than the w(w)pH scale (pH measured in the aqueous buffer before mixing it with the organic modifier), commonly used on HPLC. The s(w)pH scale is specially recommended because of its simplicity of measurement: the pH is measured after mixing the aqueous buffer with the organic modifier, but the pH calibration is performed with the common aqueous reference buffers. PMID:10784145

Canals; Portal; Bosch; Roses

2000-04-15

121

In the Way of Peacemaker Guide Curve between Water Supply and Flood Control for Short Term Reservoir Operation  

NASA Astrophysics Data System (ADS)

Effective management of a controlled reservoir system where it involves multiple and sometimes conflicting objectives is a complex problem especially in real time operations. Yuvac?k Dam Reservoir, located in the Marmara region of Turkey, is built to supply annual demand of 142 hm3 water for Kocaeli city requires such a complex management strategy since it has relatively small (51 hm3) effective capacity. On the other hand, the drainage basin is fed by both rainfall and snowmelt since the elevation ranges between 80 - 1548 m. Excessive water must be stored behind the radial gates between February and May in terms of sustainability especially for summer and autumn periods. Moreover, the downstream channel physical conditions constraint the spillway releases up to 100 m3/s although the spillway is large enough to handle major floods. Thus, this situation makes short term release decisions the challenging task. Long term water supply curves, based on historical inflows and annual water demand, are in conflict with flood regulation (control) levels, based on flood attenuation and routing curves, for this reservoir. A guide curve, that is generated using both water supply and flood control of downstream channel, generally corresponds to upper elevation of conservation pool for simulation of a reservoir. However, sometimes current operation necessitates exceeding this target elevation. Since guide curves can be developed as a function of external variables, the water potential of a basin can be an indicator to explain current conditions and decide on the further strategies. Besides, releases with respect to guide curve are managed and restricted by user-defined rules. Although the managers operate the reservoir due to several variable conditions and predictions, still the simulation model using variable guide curve is an urgent need to test alternatives quickly. To that end, using HEC-ResSim, the several variable guide curves are defined to meet the requirements by taking inflow, elevation, precipitation and snow water equivalent into consideration to propose alternative simulations as a decision support system. After that, the releases are subjected to user-defined rules. Thus, previous year reservoir simulations are compared with observed reservoir levels and releases. Hypothetical flood scenarios are tested in case of different storm event timing and sizing. Numerical weather prediction data of Mesoscale Model 5 (MM5) can be used for temperature and precipitation forecasts that will form the inputs for a hydrological model. The estimated flows can be used for real time short term decisions for reservoir simulation based on variable guide curve and user defined rules.

Uysal, G.; Sensoy, A.; Yavuz, O.; Sorman, A. A.; Gezgin, T.

2012-04-01

122

Introducing Hysteresis in Snow Depletion Curves to Improve the Water Budget of a Land Surface Model in an Alpine Catchment  

E-print Network

Introducing Hysteresis in Snow Depletion Curves to Improve the Water Budget of a Land Surface Model), a distributed land surface model (LSM) with a multilayer, physically based snow model, has been applied of the accu- mulation and ablation of the snow cover using Moderate Resolution Imaging Spectroradiometer

123

THE SIGNIFICANCE OF "STAGNATION CURVES" FOR LEAD AND COPPER, AND WATER QUALITY FACTORS AFFECTING THEM  

EPA Science Inventory

"Stagnation curves" are the response of metal levels, particularly lead and copper, to time under conditions of no water flow. Research on lead pipe in the early 1980's in the United States, Germany, and in the United Kingdom suggested that they were characterized by rapid incre...

124

Multivariate Curve Resolution-Assisted Determination of Pseudoephedrine and Methamphetamine by HPLC-DAD in Water Samples.  

PubMed

In the present study, a simple strategy based on solid-phase extraction (SPE) with a cation exchange sorbent (Finisterre SCX) followed by fast high-performance liquid chromatography (HPLC) with diode array detection coupled with chemometrics tools has been proposed for the determination of methamphetamine and pseudoephedrine in ground water and river water. At first, the HPLC and SPE conditions were optimized and the analytical performance of the method was determined. In the case of ground water, determination of analytes was successfully performed through univariate calibration curves. For river water sample, multivariate curve resolution and alternating least squares was implemented and the second-order advantage was achieved in samples containing uncalibrated interferences and uncorrected background signals. The calibration curves showed good linearity (r(2) > 0.994).The limits of detection for pseudoephedrine and methamphetamine were 0.06 and 0.08 ?g/L and the average recovery values were 104.7 and 102.3% in river water, respectively. PMID:24920656

Vosough, Maryam; Mohamedian, Hadi; Salemi, Amir; Baheri, Tahmineh

2014-06-11

125

Distribution of Typical Freshwater Bacterial Groups Is Associated with pH, Temperature, and Lake Water Retention Time  

Microsoft Academic Search

The distribution of 15 typical freshwater bacterial groups in 15 diverse lakes in northern Europe was investigated using reverse line blot hybridization. Statistical evaluation of the data in relation to the charac- teristics of the lakes showed that pH, temperature, and the theoretical hydrological retention time of the lakes were most strongly related to variations in the distribution of bacterial

Eva S. Lindstrom; Miranda P. Kamst-Van Agterveld; Gabriel Zwart

2005-01-01

126

Retention Capacity of Random Surfaces  

NASA Astrophysics Data System (ADS)

We introduce a “water retention” model for liquids captured on a random surface with open boundaries and investigate the model for both continuous and discrete surface heights 0,1,…,n-1 on a square lattice with a square boundary. The model is found to have several intriguing features, including a nonmonotonic dependence of the retention on the number of levels: for many n, the retention is counterintuitively greater than that of an (n+1)-level system. The behavior is explained using percolation theory, by mapping it to a 2-level system with variable probability. Results in one dimension are also found.

Knecht, Craig L.; Trump, Walter; Ben-Avraham, Daniel; Ziff, Robert M.

2012-01-01

127

pH-responsive controlled-release fertilizer with water retention via atom transfer radical polymerization of acrylic acid on mussel-inspired initiator.  

PubMed

This work reports a polydopamine-graft-poly(acrylic acid) (Pdop-g-PAA)-coated controlled-release multi-element compound fertilizer with water-retention function by a combination of mussel-inspired chemistry and surface-initiated atom transfer radical polymerization (SI-ATRP) techniques for the first time. The morphology and composition of the products were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography (GPC), and inductively coupled plasma (ICP) emission spectrometry. The results revealed that the stimuli-responsive layer formed by a Pdop inner layer and a PAA outer corona exhibit outstanding selective permeability to charged nutrients and the release rate of encapsulated elements can be tailored by the pH values. At low pH, the Pdop-g-PAA layer can reduce nutrient loss, and at high pH, the coating restrains transportation of negative nutrients but favors the release of cations. Moreover, PAA brushes provide good water-retention property. This Pdop-graft-polymer brushes coating will be effective and promising in the research and development of multi-functional controlled-release fertilizer. PMID:23692274

Ma, Zhi-yuan; Jia, Xin; Zhang, Guo-xiang; Hu, Jia-mei; Zhang, Xiu-lan; Liu, Zhi-yong; Wang, He-yun; Zhou, Feng

2013-06-12

128

Enhancing water retention and low-humidity proton conductivity of sulfonated poly(ether ether ketone) composite membrane enabled by the polymer-microcapsules with controllable hydrophilicity-hydrophobicity  

NASA Astrophysics Data System (ADS)

Four kinds of polymer microcapsules (PMCs) with different hydrophilicity-hydrophobicity are synthesized via distillation-precipitation polymerization (polymer microcapsules form by self-crosslinking of monomers/crosslinkers in this process) and incorporated into sulfonated poly(ether ether ketone) (SPEEK) matrix to prepare composite membranes. To improve the water retention of the PMCs, the hydrophilicity-hydrophobicity of the PMCs is manipulated by regulating the proportion of hydrophilic ethylene glycol dimethacrylate (EGDMA) and hydrophobic divinylbenzene (DVB) crosslinkers in the synthesis formula. The hydrophilicity of the PMCs decreases with increasing the content of polyDVB in the PMCs. The four kinds of PMCs exhibit different water retention properties. The PMCs with appropriate hydrophilic/hydrophobic balance (EGDMA: DVB = 1:1) possess the best water retention properties. Incorporation of PMCs into SPEEK matrix enhances the water-retention properties, and consequently increases proton conductivity to 0.0132 S cm-1 under 20% relative humidity, about thirteen times higher than that of the SPEEK control membrane. Moreover, the incorporation of PMCs reduces the activation energy for proton conduction and the methanol permeability of the membranes. This study may be helpful to rational design of excellent water-retention materials.

He, Guangwei; Li, Yifan; Li, Zongyu; Nie, Lingli; Wu, Hong; Yang, Xinlin; Zhao, Yuning; Jiang, Zhongyi

2014-02-01

129

Properties of water along the liquid-vapor coexistence curve via molecular dynamics simulations using the polarizable TIP4P-QDP-LJ water model  

Microsoft Academic Search

We present an extension of the TIP4P-QDP model, TIP4P-QDP-LJ, that is designed to couple changes in repulsive and dispersive nonbond interactions to changes in polarizability. Polarizability is intimately related to the dispersion component of classical force field models of interactions, and we explore the effect of incorporating this connection explicitly on properties along the liquid-vapor coexistence curve of pure water.

Brad A. Bauer; Sandeep Patel

2009-01-01

130

REVERSED-PHASE SEPARATION OF ESTUARINE INTERSTITIAL WATER FRACTIONS AND THE CONSEQUENCES OF C18 RETENTION OF ORGANIC MATTER  

EPA Science Inventory

Data are presented on the application of the reversed-phase separation technique for the determination of dissolved organic compounds in estuarine interstitial water. hirty-seven neutral, nonpolar organic compounds were equilibrated with interstitial water, extracted by emulsion-...

131

Effects of a Long-Acting Ophthalmic Formulation of Carteolol Containing Alginic Acid on the Corneal Epithelial Barrier Function and Water Retentive Effect  

PubMed Central

Abstract Purpose Effects of a long-acting ophthalmic formulation of carteolol containing alginic acid on the corneal epithelial barrier function and its water retentive effect were investigated. Methods Using 10 healthy adult subjects, 2% Mikelan Ophthalmic Solution® (MK) was instilled in the eye once daily for 7 days (MK group) and then after a washout period of at least 28 days, 2% Mikelan LA Ophthalmic Solution® (MKLA) was instilled in the eye once daily for 7 days (LA group). As an index of the corneal epithelial barrier function, the fluorescein uptake was measured using Kowa FL-500. A Schirmer test was conducted to evaluate the tear dynamics. In another 10 subjects, 0.5% Timoptol® (TM) was instilled in the eye unilaterally twice daily for 7 days (TM group), and the tests were conducted in the same manner. Results Concerning the fluorescein uptake before and after initiation of instillation, the levels before and at 7 days after initiation of instillation were 20.7 and 26.5?ng/mL, respectively, in the LA group and 20.6 and 26.4?ng/mL, respectively, in the MK group, showing no significant difference between levels before and after initiation of instillation in either group. In the TM group, the levels were 21.4 and 65.5?ng/mL, respectively, showing a significant increase after initiation of instillation. In the Schirmer test, the values before and after initiation of instillation were 16.8 and 20.7?mm, respectively, in the LA group and 13.7 and 12.7?mm, respectively, in the MK group, showing a trend toward increase in the LA group. Conclusions The findings suggest that the long-acting ophthalmic formulation of carteolol containing alginic acid does not affect the corneal epithelial barrier function and that it may possess a water retentive action. PMID:22217390

Inoue, Jun; Yamazaki, Izumi; Ueno, Satoki; Fujisawa, Sigeki

2012-01-01

132

Evaluation of pollutant loads from stormwater BMPs to receiving water using load frequency curves with uncertainty analysis.  

PubMed

This study examined pollutant loads released to receiving water from a typical urban watershed in the Los Angeles (LA) Basin of California by applying a best management practice (BMP) performance model that includes uncertainty. This BMP performance model uses the k-C model and incorporates uncertainty analysis and the first-order second-moment (FOSM) method to assess the effectiveness of BMPs for removing stormwater pollutants. Uncertainties were considered for the influent event mean concentration (EMC) and the aerial removal rate constant of the k-C model. The storage treatment overflow and runoff model (STORM) was used to simulate the flow volume from watershed, the bypass flow volume and the flow volume that passes through the BMP. Detention basins and total suspended solids (TSS) were chosen as representatives of stormwater BMP and pollutant, respectively. This paper applies load frequency curves (LFCs), which replace the exceedance percentage with an exceedance frequency as an alternative to load duration curves (LDCs), to evaluate the effectiveness of BMPs. An evaluation method based on uncertainty analysis is suggested because it applies a water quality standard exceedance based on frequency and magnitude. As a result, the incorporation of uncertainty in the estimates of pollutant loads can assist stormwater managers in determining the degree of total daily maximum load (TMDL) compliance that could be expected from a given BMP in a watershed. PMID:22578429

Park, Daeryong; Roesner, Larry A

2012-12-15

133

The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water-air CO2 fluxes in a tropical hydropower reservoir  

NASA Astrophysics Data System (ADS)

Abundant research has been devoted to understanding the complexity of the biogeochemical and physical processes that are responsible for greenhouse gas (GHG) emissions from hydropower reservoirs. These systems may have spatially complex and heterogeneous GHG emissions due to flooded biomass, river inflows, primary production and dam operation. In this study, we investigated the relationships between the water-air CO2 fluxes and the phytoplanktonic biomass in the Funil Reservoir, which is an old, stratified tropical reservoir that exhibits intense phytoplankton blooms and a low partial pressure of CO2 (pCO2). Our results indicated that the seasonal and spatial variability of chlorophyll concentrations (Chl) and pCO2 in the Funil Reservoir are related more to changes in the river inflow over the year than to environmental factors such as air temperature and solar radiation. Field data and hydro-dynamic simulations revealed that river inflow contributes to increased heterogeneity during the dry season due to variations in the reservoir retention time and river temperature. Contradictory conclusions could be drawn if only temporal data collected near the dam were considered without spatial data to represent CO2 fluxes throughout the reservoir. During periods of high retention, the average CO2 fluxes were 10.3 mmol m-2 d-1 based on temporal data near the dam versus -7.2 mmol m-2 d-1 with spatial data from along the reservoir surface. In this case, the use of solely temporal data to calculate CO2 fluxes results in the reservoir acting as a CO2 source rather than a sink. This finding suggests that the lack of spatial data in reservoir C budget calculations can affect regional and global estimates. Our results support the idea that the Funil Reservoir is a dynamic system where the hydrodynamics represented by changes in the river inflow and retention time are potentially a more important force driving both the Chl and pCO2 spatial variability than the in-system ecological factors.

Pacheco, F. S.; Soares, M. C. S.; Assireu, A. T.; Curtarelli, M. P.; Abril, G.; Stech, J. L.; Alvalá, P. C.; Ometto, J. P.

2015-01-01

134

Remote community drinking water supply : mechanisms of uranium retention and adsorption by ultrafiltration, nanofiltration and reverse osmosis   

E-print Network

Worldwide, around 884 million people lack access to safe drinking water. To address this, groundwater sources such as boreholes and wells are often installed in remote locations especially in developing countries. However, ...

Schulte-Herbruggen, Helfrid Maria Albertina

2012-11-29

135

Low temperature sugar-water equilibrium curve by a rapid calorimetric method  

Microsoft Academic Search

A simple rapid enthalpic method based upon a unique calorimetric measurement was developed and applied to sugar solutions at low temperatures to determine the amount of unfreezable water. The experimental results were in good agreement with those obtained by the usual freezing point depression method. The experimental data were also used to test the validity of several literature semi-empirical models

V. Hoff; S CORRERA

1995-01-01

136

HOT-ATOM CHEMISTRY OF ARSENATES--EFFECT OF CATION, WATER OF CRYSTALLIZATION AND IRRADIATION TEMPERATURE ON THE RETENTION OF RADIOARSENIC IN NEUTRON-IRRADIATED SOLID ARSENATES  

Microsoft Academic Search

The effects of variables on retention of arsenic(V) were studied in ; arsenates of Li, NHâ, Na, K, Co(II), and Ba, using thermalized neutrons. ; For NaâHAsOâ 7 HâO, storage at -72 and -196 deg C after ; irradiation had little effect on the retention, while storage at room temperature ; showed a graduai increase in the retention with time.

Nobufusa Saito; Isao Tomita

1962-01-01

137

A time series approach to inferring groundwater recharge using the water table fluctuation method  

Microsoft Academic Search

The water table fluctuation method for determining recharge from precipitation and water table measurements was originally developed on an event basis. Here a new multievent time series approach is presented for inferring groundwater recharge from long-term water table and precipitation records. Additional new features are the incorporation of a variable specific yield based upon the soil moisture retention curve, proper

Russell S. Crosbie; Philip Binning; Jetse D. Kalma

2005-01-01

138

Effectiveness of using pedo-transfer functions to quantify the spatial variability of soil water retention characteristics  

Microsoft Academic Search

Accurate knowledge of soil hydraulic properties is of crucial importance for reliable applications of recently developed distributed models to environmental studies and land-use planning. To provide such information in a cost-effective way, indirect estimation of water transport parameters from easily measurable or already available soil data using pedo-transfer functions (PTFs) is becoming increasingly popular. However, distributed hydrological modeling requires that

Nunzio Romano; Alessandro Santini

1997-01-01

139

Investigation of Phase and Emulsion Behavior, Surfactant Retention and Condensate Recovery for Condensate/Water/Ethanol Mixtures  

SciTech Connect

This semi-annual technical progress report describes work performed at Morehouse College under DOE Grant No. DE-FG26-02NT15447 during the period October 01, 2003 to March 31, 2004 which covers the third six months of the project. Presently work is in progress to characterize phase and emulsion behavior for ethylbenzene/water/ethanol system. Ethylbenzene that has the equivalent carbon number is used as the model condensate. During this reporting period, temperature scans were performed mixing equal volumes of ethylbenzene and 10mM NaCl water with various concentrations of ethanol ranging from 2 to 70 vol%. For the range of temperatures tested (2 to 70 C), results indicate that temperature is invariant and produced a single phase for ethanol concentrations greater than 60 vol%. For ethanol concentrations less than 60 vol%, only two phases were obtained with aqueous rich bottom phase more in volume than that of the ethylbenzene rich top phase. Linear coreflooding experiments were completed by our industrial partner in this project, Surtek, CO, to measure the condensate recovery in flooding processes. It was found about 30% ethylbenzene recovery was obtained by the waterflooding, however, 2wt% ethanol flooding did not produce incremental recovery of the ethylbenzene. Radial coreflooding with ethanol injection prior to water injection is in progress to assess the effectiveness of the surfactant flooding in the recovery of condensate.

Ramanathan Sampath

2004-03-31

140

Investigation of Phase and Emulsion Behavior, Surfactant Retention and Condensate Recovery for Condensate/Water/Ethanol Mixtures  

SciTech Connect

This semi-annual technical progress report describes work performed at Morehouse College under DOE Grant No. DE-FG26-02NT15447 during the period April 01, 2004 to September 30, 2004 which covers the fourth six months of the project. Presently work is in progress to characterize phase and emulsion behavior for ethylbenzene/water/ethanol system. Ethylbenzene that has the equivalent carbon number is used as the model condensate. During this reporting period, work was under way and the electrical conductivity experimental system was set up at the Atlanta University Center. Following the set-up of the emulsion measurement system, the electronic instruments and data acquisition modules involved were tested for proper operation of the system. Then, the conductivity output was normalized with that obtained for 10mM NaCl water. Radial coreflooding experiments with ethanol injection prior to and after water injection were completed to assess the effectiveness of the surfactant flooding in the recovery of condensate by our industrial partner, Surtek, CO, in this reporting period. In Run 1, 10 mM NaCl without ethanol injection recovered 31.5% of the initial ethyl benzene saturation. Injection of ethanol following 10 mM NaCl produced a tertiary ethyl benzene bank with maximum ethyl benzene cuts of 32%. In Run 2, 50 vol% of pure (100%) ethanol was injected and flowed through the Berea sandstone after Ethyl Benzene Saturation. 69% of the initial ethyl benzene was recovered. Results of the radial corefloods are very encouraging. Emulsion conductivity measurements for conjugate pair phases are in progress at Morehouse.

Ramanathan Sampath

2004-09-30

141

Investigation of Phase and Emulsion Behavior, Surfactant Retention and Condensate Recovery for Condensate/Water/Ethanol Mixtures  

SciTech Connect

This semi-annual technical progress report describes work performed at Morehouse College under DOE Grant No. DE-FG26-02NT15447 during the period October 01, 2002 to April 01, 2003 which covers the first six months of the project. Presently work is in progress to characterize phase and emulsion behavior for condensate/water/ethanol system. Temperature and salinity scans are planned to identify the optimal salinity and temperature, and the temperature and salinity intervals in which all three phases coexist for this system. Test matrix to perform salinity and temperature scans has been established. Supply requests to obtain hydrocarbons, surfactant, etc., were processed and supplies obtained. Current literature in the subject area, and modeling efforts that were established in our previous studies to predict electrical conductivities and inversion phenomena were reviewed. Based on the review a computer model to predict electrical conductivities of the ethylbenzene (that has the equivalent carbon number of the condensate)/water/ethanol system is being developed. These activities resulted in one published conference abstract during this reporting period.

Ramanathan Sampath

2003-03-31

142

Investigation of Phase and Emulsion Behavior, Surfactant Retention and Condensate Recovery for Condensate/Water/Ethanol Mixtures  

SciTech Connect

This semi-annual technical progress report describes work performed at Morehouse College under DOE Grant No. DE-FG26-02NT15447 during the period October 01, 2004 to March 31, 2005 which covers the fifth six months of the project. Presently work is in progress to characterize phase and emulsion behavior for ethylbenzene/water/ethanol system. Ethylbenzene that has the equivalent carbon number is used as the model condensate. During this reporting period, electrical conductivity measurements for bottom, and top phases, as well as bottom/top, and top/bottom conjugate pair phases of the ethylbenzene/water/ethanol system were performed for various ethanol volume percentage of the mixtures starting from 2% to 60%. Preliminary findings are that electrical conductivity of the bottom phase decreased as ethanol volume fraction of the mixture increased. Conductivity of the top phase was small and remained almost the same for variations in ethanol volume fraction of the mixture. Conductivity of the emulsion of the conjugate pair phases decreased as the fraction of volume of the top phase was increased and vice versa. Also inversion phenomena was observed. Detailed analyses are in progress including the prediction of conductivity data using the theoretical model already developed in this project.

Ramanathan Sampath

2005-03-31

143

Investigation of Phase and Emulsion Behavior, Surfactant Retention and Condensate Recovery for Condensate/Water/Ethanol Mixtures  

SciTech Connect

This semi-annual technical progress report describes work performed at Morehouse College under DOE Grant No. DE-FG26-02NT15447 during the period April 01, 2005 to September 30, 2005 which covers the sixth six months of the project. Presently work is in progress to characterize phase and emulsion behavior for ethylbenzene/water/ethanol system. Ethylbenzene that has the equivalent carbon number is used as the model condensate. In the last reporting period, electrical conductivity measurements for bottom/top, and top/bottom conjugate pair phases of the ethylbenzene/water/ethanol system were performed for various ethanol volume percentage in the mixture: 2,10,20,33,43,50, and 56. During this reporting period, prediction of electrical conductivity data obtained in the past was conducted employing a theoretical model already developed in this project. Results of the comparisons for 2, and 10% ethanol volume in the mixture are presented here. A good agreement was obtained between the predicted emulsion conductivities and the measured values. To date about 99% of the proposed work has been completed. Conductivity prediction for 56% ethanol volume in the mixture is in progress. Following this prediction, a final report will be developed describing the research activities conducted through the entire project period including results and conclusions.

Ramanathan Sampath

2005-09-30

144

INVESTIGATION OF PHASE AND EMULSION BEHAVIOR, SURFACTANT RETENTION, AND CONDENSATE RECOVERY FOR CONDENSATE/WATER/ETHANOL MIXTURES  

SciTech Connect

This final technical report describes work performed at Morehouse College under DOE Grant No. DE-FG26-02NT15447 during the period October 01, 2002 to September 30, 2005, which covers the total performance period of the project. During this period, work was conducted to characterize phase and emulsion behavior for ethylbenzene/water/ethanol system. Ethylbenzene that has the equivalent carbon number was used as the model condensate. Salinity scans were performed for 0, 5, 10, 20, 50, 100, 250, 500, and 1000 mM salt concentrations at room temperature to identify the optimal salinity and salinity intervals in which all phases coexisted. It was found that only two phases formed, and salinity has no significant effect in the volumes of the phases formed. Experiments were repeated at 30 C and observed salinity has no effect at higher temperatures as well. Following the salinity experiments, measurements were made with 10mM NaCl water for surfactant concentrations from 2 to 70 volume percent at room temperature. It was found that only two phases were formed upto 60 vol% concentration of the surfactant. Above 60 vol% surfactant, the mixture produced only a single phase. Experiments were repeated from 2 to 70 C and observed that temperature has no significant effect on the number of phases formed. At the temperatures and surfactant concentration tested, volume fraction of the aqueous bottom phase was found to be larger than that of the top phase. Electrical conductivity measurements were then conducted for bottom/top, and top/bottom conjugate pair phases of the ethylbenzene/water/ethanol system formed by mixing ethanol at various volume percentages including 2,10,33,and 56% while keeping the volumes of ethylbenzene and water the same in the mixture. Electrical conductivity of the bottom phase decreased as ethanol volume fraction in the mixture increased. Conductivity of the top phase was found small and remained almost the same for variations in ethanol volume fraction in the mixture. Also inversion phenomena was observed. Prediction of the conductivity data obtained was then conducted employing a theoretical model developed in this project based on Maxwell relations. Results of the comparisons for 2, 10, 33, and 56% ethanol volume in the mixture are presented here. A good agreement was obtained between the predicted emulsion conductivities and the measured values. Work was also conducted at Surtek, Golden, CO, our industrial partner in this project, to measure the effectiveness for condensate recovery employing coreflooding techniques. In Run 1 of the radial coreflooding experiments conducted, 10 mM NaCl without ethanol injection recovered 31.5% of the initial ethyl benzene saturation. Injection of ethanol following 10 mM NaCl produced a tertiary ethyl benzene bank with maximum ethyl benzene cuts of 32%. In Run 2, 50 vol% of pure (100%) ethanol was injected and flowed through the Berea sandstone after Ethyl Benzene Saturation. 69% of the initial ethyl benzene was recovered. While 50 vol% of ethanol injection does not make economic sense when injecting a large fraction of a pore volume, injection of sufficient volume to remove water and condensate from around the near well bore area of a gas well could be economic.

Ramanathan Sampath

2005-12-01

145

Analytic fits to Monte Carlo calculated depth-dose curves of 1- to 50-MeV electrons in water  

NASA Astrophysics Data System (ADS)

An analytic expression is given for depth-dose curves of plane-parallel electron beams normally incident on semi-infinite water absorbers with initial energies from 1 to 50 MeV. The expression consists of two terms representing the main component due to collision energy-loss of primary electrons and the component via radiative process. To study the profile of the bremsstrahlung component, Monte Carlo calculations have been made with the MCEF code. The results show that this component has a maximum around 0.9 r0, where r0 is the csda (continuous slowing-down approximation) range of electrons in water. Values of the constants in the main term have been determined so as to minimize the deviations of the expression from the depth-dose data calculated with three Monte Carlo codes (MCEF, EGS4 and ITS). The maximum value of the deviations is from 0.7 to 3.5% of the maximum dose at each energy and is less than or comparable to the maximum deviations among the different Monte Carlo results.

Tatsuo, Tabata; Andreo, Pedro; Rinsuke, Ito

1991-06-01

146

Research of data retention in EEPROM cells  

NASA Astrophysics Data System (ADS)

This paper investigates date retention ability of EEPROM cells for a given voltage or temperature by theory and experiment. The expression of EEPROM date retention is derived. In the temperature acceleration experiment, the logarithm of device inactivation time have linear ratio with temperature according to Arrhenius formula and the device life retention was acquired in the various temperature. According to Arrhenius equation, lifetime curve is deduced. In the electric acceleration experiment, because of the charge leaking on the floating-gate, the threshold voltage would decrease gradually. In the log-log plot, the decrease efficiency of threshold voltage have linear ratio with time. Under the assumption that the charge loss mechanism is Fowler-Nordheim tunneling through the thin oxide, date retention time of EEPROM cells is derived and the experience formula is derived by experiment.

Cheng, Wei; Zhang, Ni; Hu, Cang-lu; Jiao, Gang-cheng; Miao, Zhuang; Fu, Ling-yun; Liu, Feng

2013-08-01

147

Stabilities of thiomolybdate complexes of iron; implications for retention of essential trace elements (Fe, Cu, Mo) in sulfidic waters.  

PubMed

In aquatic ecosystems, availabilities of Fe, Mo and Cu potentially limit rates of critical biological processes, including nitrogen fixation, nitrate assimilation and N2O decomposition. During long periods in Earth's history when large parts of the ocean were sulfidic, what prevented these elements' quantitative loss from marine habitats as insoluble sulfide phases? They must have been retained by formation of soluble complexes. Identities of the key ligands are poorly known but probably include thioanions. Here, the first determinations of stability constants for Fe(2+)-[MoS4](2-) complexes in aqueous solution are reported based on measurements of pyrrhotite (hexagonal FeS) solubility under mildly alkaline conditions. Two linear complexes, [FeO(OH)MoS4](3-) and [(Fe2S2)(MoS4)2](4-), best explain the observed solubility variations. Complexes that would be consistent with cuboid cluster structures were less successful, implying that such clusters probably are minor or absent in aqueous solution under the conditions studied. The new data, together with prior data on stabilities of Cu(+)-[MoS4](2-) complexes, are used to explore computationally how competition of Fe(2+) and Cu(+) for [MoS4](2-), as well as competition of [MoS4](2-) and HS(-) for both metals would be resolved in solutions representative of sulfidic natural waters. Thiomolybdate complexes will be most important at sulfide concentrations near the [MoO4](2-)-[MoS4](2-) equivalence point. At lower sulfide concentrations, thiomolybdates are insufficiently stable to be competitive ligands in natural waters and at higher sulfide concentrations HS(-) ligands out-compete thiomolybdates. PMID:24226648

Helz, George R; Erickson, Britt E; Vorlicek, Trent P

2014-06-01

148

Properties of water along the liquid-vapor coexistence curve via molecular dynamics simulations using the polarizable TIP4P-QDP-LJ water model  

NASA Astrophysics Data System (ADS)

We present an extension of the TIP4P-QDP model, TIP4P-QDP-LJ, that is designed to couple changes in repulsive and dispersive nonbond interactions to changes in polarizability. Polarizability is intimately related to the dispersion component of classical force field models of interactions, and we explore the effect of incorporating this connection explicitly on properties along the liquid-vapor coexistence curve of pure water. Parametrized to reproduce condensed-phase liquid water properties at 298 K, the TIP4P-QDP-LJ model predicts density, enthalpy of vaporization, self-diffusion constant, and the dielectric constant at ambient conditions to about the same accuracy as TIP4P-QDP but shows remarkable improvement in reproducing the liquid-vapor coexistence curve. TIP4P-QDP-LJ predicts critical constants of Tc=623 K, ?c=0.351 g/cm3, and Pc=250.9 atm, which are in good agreement with experimental values of Tc=647.1 K, ?c=0.322 g/cm3, and Pc=218 atm, respectively. Applying a scaling factor correction (obtained by fitting the experimental vapor-liquid equilibrium data to the law of rectilinear diameters using a three-term Wegner expansion) the model predicts critical constants (Tc=631 K and ?c=0.308 g/cm3). Dependence of enthalpy of vaporization, self-diffusion constant, surface tension, and dielectric constant on temperature are shown to reproduce experimental trends. We also explore the interfacial potential drop across the liquid-vapor interface for the temperatures studied. The interfacial potential demonstrates little temperature dependence at lower temperatures (300-450 K) and significantly enhanced (exponential) dependence at elevated temperatures. Terms arising from the decomposition of the interfacial potential into dipole and quadrupole contributions are shown to monotonically approach zero as the temperature approaches the critical temperature. Results of this study suggest that self-consistently treating the coupling of phase-dependent polarizability with dispersion interactions in classical water force fields may be an important effect for the extension of polarizable water force fields to reproduce properties along the liquid-vapor coexistence envelope as well as near critical conditions. More importantly, the present study demonstrates the rather remarkable transferability of a water model parametrized to a single state point to other thermodynamic states. Further studies are recommended.

Bauer, Brad A.; Patel, Sandeep

2009-08-01

149

Properties of water along the liquid-vapor coexistence curve via molecular dynamics simulations using the polarizable TIP4P-QDP-LJ water model  

PubMed Central

We present an extension of the TIP4P-QDP model, TIP4P-QDP-LJ, that is designed to couple changes in repulsive and dispersive nonbond interactions to changes in polarizability. Polarizability is intimately related to the dispersion component of classical force field models of interactions, and we explore the effect of incorporating this connection explicitly on properties along the liquid-vapor coexistence curve of pure water. Parametrized to reproduce condensed-phase liquid water properties at 298 K, the TIP4P-QDP-LJ model predicts density, enthalpy of vaporization, self-diffusion constant, and the dielectric constant at ambient conditions to about the same accuracy as TIP4P-QDP but shows remarkable improvement in reproducing the liquid-vapor coexistence curve. TIP4P-QDP-LJ predicts critical constants of Tc=623 K, ?c=0.351 g?cm3, and Pc=250.9 atm, which are in good agreement with experimental values of Tc=647.1 K, ?c=0.322 g?cm3, and Pc=218 atm, respectively. Applying a scaling factor correction (obtained by fitting the experimental vapor-liquid equilibrium data to the law of rectilinear diameters using a three-term Wegner expansion) the model predicts critical constants (Tc=631 K and ?c=0.308 g?cm3). Dependence of enthalpy of vaporization, self-diffusion constant, surface tension, and dielectric constant on temperature are shown to reproduce experimental trends. We also explore the interfacial potential drop across the liquid-vapor interface for the temperatures studied. The interfacial potential demonstrates little temperature dependence at lower temperatures (300–450 K) and significantly enhanced (exponential) dependence at elevated temperatures. Terms arising from the decomposition of the interfacial potential into dipole and quadrupole contributions are shown to monotonically approach zero as the temperature approaches the critical temperature. Results of this study suggest that self-consistently treating the coupling of phase-dependent polarizability with dispersion interactions in classical water force fields may be an important effect for the extension of polarizable water force fields to reproduce properties along the liquid-vapor coexistence envelope as well as near critical conditions. More importantly, the present study demonstrates the rather remarkable transferability of a water model parametrized to a single state point to other thermodynamic states. Further studies are recommended. PMID:19725623

Bauer, Brad A.; Patel, Sandeep

2009-01-01

150

Gastro retention using polymer cocoons.  

PubMed

Abstract A gastro-retentive capsule has been prepared which is retained in the stomach for a period of 24h, providing a vehicle for the controlled delivery to the upper intestines. These "gastro cocoons" can resist passage through the sphincter of the stomach, and can retain a high drug payload (30%). They are made from oppositely charged polyelectrolytes and can swell to twice their initial volume. They are strong and also can resist 550 N of compressive force. They are based on filled pharmaceutical capsules which are visible to X-rays. Using ambroxol hydrochloride as a model drug linear, zero-order, release curves were obtained. PMID:25078789

Arnold, Julien; Hunkeler, David

2015-02-01

151

Relating soil specific surface area, water film thickness, and water vapor adsorption  

NASA Astrophysics Data System (ADS)

of soil specific surface area (SSA) and dry-end water vapor adsorption are important for porous media characterization and for prediction of water and vapor fluxes in arid environments. The objective of the presented study was to model water adsorption, film thickness, and SSA based on the t-curve theory originally developed for N2 adsorption. Data from 21 source soils with clay contents ranging from 0.6 to 52.2% were used to estimate specific surface area based on water retention, a t-curve type method, the linear prediction method, and a simplified monolayer method. The water retention and the t-curve methods were found to be mathematically analogous and were among the most accurate with regard to correlation coefficient (r = 0.97) and root-mean-square error (RMSE = 11.36 × 103 m2/kg) when compared to measurements obtained with the standard ethylene glycol monoethyl ether (EGME) method. The corrected t-curve method significantly overestimated SSA when compared to EGME data. Comparison of all considered methods with N2-BET (BET) measurements disclosed lower correlation coefficients. For soil studies, the vapor adsorption in conjunction with the t-curve or water retention methods should be preferred for SSA estimation as they show much higher correlation with soil clay content and EGME measurements.

Leão, Tairone Paiva; Tuller, Markus

2014-10-01

152

Ogive Curves  

NSDL National Science Digital Library

This page contains a discussion of ogive curves, logistic regression curves, and architecture. Nice photographs of architectural applications are included. The classic Birthday Problems is included as an example of an ogive curve.

2008-01-01

153

The effect of dietary carbohydrate composition on apparent total tract digestibility, feed mean retention time, nitrogen and water balance in horses.  

PubMed

A total of four diets with different carbohydrate composition were investigated in a 4×4 Latin square design experiment with four Norwegian Coldblooded trotter horses. The objective of the present study was to increase the fermentable fibre content and reduce the starch intake of the total ration obtained by partly substituting mature hay and barley with sugar beet pulp (SBP), a soluble fibre source. The diets investigated were hay only (HAY), hay (85% of dry matter intake (DMI)) and molassed SBP (15% of DMI) (SBP), hay (68% of DMI) and barley (32% of DMI) (BAR), and hay (68% of DMI), barley (26% of DMI) and SBP (6% of DMI) (BAR+SBP). The feeding level was 18.5, 17.3, 15.7 and 15.7 g DM/kg BW per day for the HAY, SBP, BAR and BAR+SBP diets, respectively. Each diet was fed for 18 days followed by 10 days of data collection, where apparent total tract digestibility (ATTD), total mean retention time (TMRT) of ytterbium-labelled hay, water balance, digestible energy (DE) intake and nitrogen balance were measured. An enzymatic chemical dietary fibre (DF) method was used to get detailed information on the composition and ATTD of the fibre fraction. Inclusion of SBP in the diet increased the ATTD of the constituent sugars galactose and arabinose (P<0.01). Feeding the HAY and SBP diets resulted in a lower TMRT owing to a higher DF intake than the BAR and BAR+SBP diets (P<0.01). There was no difference in water intake between HAY and SBP, but faecal dry matter was lower for HAY than the other diets (P=0.017), indicating that water was more tightly bound to fibre in the HAY diet. The diets were iso-energetic and provided enough DE and protein for light to moderate exercise for a 550 kg horse. In conclusion, this study showed that the DF intake had a larger effect on TMRT than partly substituting hay or barley with SBP, and that highly fermentable pectin-rich soluble DF from SBP maintains high nutrient utilization in horses. PMID:25018093

Jensen, R B; Austbø, D; Bach Knudsen, K E; Tauson, A-H

2014-11-01

154

Optimized Delivery System Achieves Enhanced Endomyocardial Stem Cell Retention  

PubMed Central

Background Regenerative cell-based therapies are associated with limited myocardial retention of delivered stem cells. The objective of this study is to develop an endocardial delivery system for enhanced cell retention. Methods and Results Stem cell retention was simulated in silico using one and three-dimensional models of tissue distortion and compliance associated with delivery. Needle designs, predicted to be optimal, were accordingly engineered using nitinol – a nickel and titanium alloy displaying shape memory and super-elasticity. Biocompatibility was tested with human mesenchymal stem cells. Experimental validation was performed with species-matched cells directly delivered into Langendorff-perfused porcine hearts or administered percutaneously into the endocardium of infarcted pigs. Cell retention was quantified by flow cytometry and real time quantitative polymerase chain reaction methodology. Models, computing optimal distribution of distortion calibrated to favor tissue compliance, predicted that a 75°-curved needle featuring small-to-large graded side holes would ensure the highest cell retention profile. In isolated hearts, the nitinol curved needle catheter (C-Cath) design ensured 3-fold superior stem cell retention compared to a standard needle. In the setting of chronic infarction, percutaneous delivery of stem cells with C-Cath yielded a 37.7±7.1% versus 10.0±2.8% retention achieved with a traditional needle, without impact on biocompatibility or safety. Conclusions Modeling guided development of a nitinol-based curved needle delivery system with incremental side holes achieved enhanced myocardial stem cell retention. PMID:24326777

Behfar, Atta; Latere, Jean-Pierre; Bartunek, Jozef; Homsy, Christian; Daro, Dorothee; Crespo-Diaz, Ruben J.; Stalboerger, Paul G.; Steenwinckel, Valerie; Seron, Aymeric; Redfield, Margaret M.; Terzic, Andre

2014-01-01

155

Biochar from sugarcane filtercake reduces soil CO2 emissions relative to raw residue and improves water retention and nutrient availability in a highly-weathered tropical soil.  

PubMed

In Brazil, the degradation of nutrient-poor Ferralsols limits productivity and drives agricultural expansion into pristine areas. However, returning agricultural residues to the soil in a stabilized form may offer opportunities for maintaining or improving soil quality, even under conditions that typically promote carbon loss. We examined the use of biochar made from filtercake (a byproduct of sugarcane processing) on the physicochemical properties of a cultivated tropical soil. Filtercake was pyrolyzed at 575°C for 3 h yielding a biochar with increased surface area and porosity compared to the raw filtercake. Filtercake biochar was primarily composed of aromatic carbon, with some residual cellulose and hemicellulose. In a three-week laboratory incubation, CO2 effluxes from a highly weathered Ferralsol soil amended with 5% biochar (dry weight, d.w.) were roughly four-fold higher than the soil-only control, but 23-fold lower than CO2 effluxes from soil amended with 5% (d.w.) raw filtercake. We also applied vinasse, a carbon-rich liquid waste from bioethanol production typically utilized as a fertilizer on sugarcane soils, to filtercake- and biochar-amended soils. Total CO2 efflux from the biochar-amended soil in response to vinasse application was only 5% of the efflux when vinasse was applied to soil amended with raw filtercake. Furthermore, mixtures of 5 or 10% biochar (d.w.) in this highly weathered tropical soil significantly increased water retention within the plant-available range and also improved nutrient availability. Accordingly, application of sugarcane filtercake as biochar, with or without vinasse application, may better satisfy soil management objectives than filtercake applied to soils in its raw form, and may help to build soil carbon stocks in sugarcane-cultivating regions. PMID:24897522

Eykelbosh, Angela Joy; Johnson, Mark S; Santos de Queiroz, Edmar; Dalmagro, Higo José; Guimarães Couto, Eduardo

2014-01-01

156

Effects of Age and Calving Season on Lactation Curves of Milk Production Traits in Italian Water Buffaloes  

Microsoft Academic Search

Test day (TD) records of milk production traits (milk yield, fat, and protein percentages) of 534 Italian buf- falo cows were analyzed with a mixed linear model in order to estimate lactation curves pertaining to differ- ent ages at calving and different seasons of calving. Milk yield lactation curves of younger animals were lower than those of older animals until

G. Catillo; N. P. P. Macciotta; A. Carretta; A. Cappio-Borlino

2002-01-01

157

Curved Mirrors  

NSDL National Science Digital Library

This inquiry activity will be used before discussing curved mirrors in class. Students will discover how curved mirrors act and how the size and the orientation of the image are related to the distance from the mirror. Ray diagrams for curved mirrors are

Horton, Michael

2009-05-30

158

Improvement in the water retention characteristics of sandy loam soil using a newly synthesized poly(acrylamide-co-acrylic acid)/AlZnFe2O4 superabsorbent hydrogel nanocomposite material.  

PubMed

The use of some novel and efficient crop nutrient-based superabsorbent hydrogel nanocomposites (SHNCs), is currently becoming increasingly important to improve the crop yield and productivity, due to their water retention properties. In the present study a poly(Acrylamide-co-acrylic acid)/AlZnFe2O4 superabsorbent hydrogel nanocomposite was synthesized and its physical properties characterized using Energy Dispersive X-ray (EDX), FE-SEM and FTIR spectroscopic techniques. The effects of different levels of SHNC were studied to evaluate the moisture retention properties of sandy loam soil (sand 59%, silt 21%, clay 19%, pH 7.4, EC 1.92 dS/m). The soil amendment with 0.1, 0.2, 0.3 and 0.4 w/w% of SHNC enhanced the moisture retention significantly at field capacity compared to the untreated soil. Besides, in a separate experiment, seed germination and seedling growth of wheat was found to be notably improved with the application of SHNC. A delay in wilting of seedlings by 5-8 days was observed for SHNC-amended soil, thereby improving wheat plant growth and establishment. PMID:22864245

Shahid, Shaukat Ali; Qidwai, Ansar Ahmad; Anwar, Farooq; Ullah, Inam; Rashid, Umer

2012-01-01

159

Two-dimensional array of particles originating from dipole-dipole interaction as evidenced by potential curve measurements at vertical oil/water interfaces.  

PubMed

We propose a new method to evaluate the interaction potential energy between the particles adsorbed at an oil/water interface as a function of interparticle distance. The method is based on the measurement of the interparticle distance at a vertical oil/water interface, at which the gravitational force is naturally applied to compress the particle monolayer in the in-plane direction. We verified the method by examining whether we obtained the same potential curve upon varying the gravitational acceleration by tilting the interface. The present method is applicable in the force range from ?0.1 to ?100 pN, determined by the effective weight of the particles at the interface. The method gives a rather simple procedure to estimate a long range interaction among the particles adsorbed at oil/water interfaces. We applied this method to polystyrene particles at the decane/aqueous surfactant solution interface, and obtained the interparticle potential curves. All the potential curves obtained by the present method indicated that the interparticle repulsion is due to the electrical dipole-dipole interaction based on the negative charge of the particles. The mechanism of the dipole-dipole interaction is further discussed on the basis of the effects of surfactants. PMID:25005863

Sakka, Tetsuo; Kozawa, Daichi; Tsuchiya, Kiyoto; Sugiman, Nao; Øye, Gisle; Fukami, Kazuhiro; Nishi, Naoya; Ogata, Yukio H

2014-08-28

160

A Nonparametric Instrumental Variable Approach to Estimating the Environmental Kuznets Curve for Water Pollutants at the Global Level1  

E-print Network

for Water Pollutants at the Global Level1 C.-Y. Cynthia Lin,2 Krishna P. Paudel, Mahesh Pandit for Water Pollutants at the Global Level Abstract We examine the relationship between income and water pollutants using country- level global water quality data over the period 1980 to 2012. We include civil

Lin, C.-Y. Cynthia

161

Semiempirical model of soil water hysteresis  

USGS Publications Warehouse

In order to represent hysteretic soil water retention curves accurately using as few measurements as possible, a new semiempirical model has been developed. It has two postulates related to physical characteristics of the medium, and two parameters, each with a definite physical interpretation, whose values are determined empirically for a given porous medium. Tests of the model show that it provides high-quality optimized fits to measured water content vs. matric pressure wetting curves for a wide variety of media. A practical use of this model is to provide a complete simulated main wetting curve for a medium where only a main drying curve and two points on the wetting curve have been measured. -from Author

Nimmo, J.R.

1992-01-01

162

Drug Retention Times  

SciTech Connect

The purpose of this monograph is to provide information on drug retention times in the human body. The information provided is based on plausible illegal drug use activities that might be engaged in by a recreational drug user.

Center for Human Reliability Studies

2007-05-01

163

Drug Retention Times  

SciTech Connect

The purpose of this monograph is to provide information on drug retention times in the human body. The information provided is based on plausible illegal drug use activities that might be engaged in by a recreational drug user

Center for Human Reliability Studies

2007-05-01

164

Fuel retention in tokamaks  

NASA Astrophysics Data System (ADS)

Tritium retention constitutes an outstanding problem for ITER operation and future fusion reactors, particularly for the choice of the first wall materials. In present day tokamaks, fuel retention is evaluated by two complementary methods. The in situ gas balance allows evaluation of how much fuel is retained during a discharge and, typically, up to one day of experiments. Post-mortem analysis is used to determine where the fuel is retained, integrated over an experimental campaign. In all the carbon clad devices, using the two methods, the retention is demonstrated to be very closely related to the carbon net erosion. This results from plasma-wall interaction with ion and charge-exchange fluxes, ELMs and is proportional to the pulse duration. The fuel retention by implantation saturates at high wall temperatures and limits the D/C ratio in the deposited layers but, as far as a carbon source exists, the dominant retention process remains the co-deposition of carbon with deuterium. In full metallic device, in the absence of wall conditioning with boron, co-deposition is strongly reduced and fuel retention below 1% can be achieved. Extrapolation to ITER shows that removing the carbon from the plasma-facing components would increase the number of discharges to 2500 before reaching the maximum tritium limit of 700 g.

Loarer, T.

2009-06-01

165

Ultrasonic spectroscopy allows a rapid determination of the relative water content at the turgor loss point: a comparison with pressure-volume curves in 13 woody species.  

PubMed

The turgor loss point (TLP), which is considered a threshold for many physiological processes, may be useful in plant-breeding programs or for the selection of reforestation species. Obtaining TLP through the standard pressure-volume (p-v) curve method in a large set of species is highly time-consuming and somewhat subjective. To solve this problem, we present an objective and a less time-consuming technique based on the leaf resonance able to calculate the relative water content (RWC) at TLP (RWCTLP). This method uses air-coupled broadband ultrasonic spectroscopy to obtain the sigmoidal relation between RWC and the standardized resonant frequency (f/fo). For the 13 species measured, the inflexion point of the RWC-f/fo relationship ( ) was not statistically different from the value of RWC at the TLP obtained with the p-v curves (RWCTLP p-v). PMID:23933828

Sancho-Knapik, Domingo; Peguero-Pina, José Javier; Fariñas, María Dolores; Alvarez-Arenas, Tomás Gómez; Gil-Pelegrín, Eustaquio

2013-07-01

166

Laser induced desorption as tritium retention diagnostic method in ITER  

Microsoft Academic Search

Measurement and control of long term tritium retention is one of the most critical issues for ITER and future fusion devices. Since the measurement of the hydrogenic retention by post mortem tile analysis becomes more and more difficult in future devices due to active water cooling and tile activation, Laser Induced Desorption Spectroscopy (LIDS) is under development in TEXTOR to

M. Zlobinski; V. Philipps; B. Schweer; A. Huber; S. Brezinsek; Ch. Schulz; S. Möller; U. Samm

2011-01-01

167

Quality assessment of the multivariate curve resolution alternating least squares method for the investigation of environmental pollution patterns in surface water.  

PubMed

Multivariate curve resolution alternating least squares is shown to be a powerful chemometric tool for investigation of main surface water contamination patterns affecting a particular geographical area over a period of time. When environmental monitoring data tables are analyzed using this method, the identification of the main contamination patterns, and the description of their geographical and temporal distribution profiles, can be obtained. To show the potential of the proposed method, the investigation of the pesticide contamination affecting the Ebro River delta (Catalonia, NE Spain) during the rice-growing season in 2005, is selected as a case study in this work. Three different contamination patterns of pesticides with different spatial end temporal behaviors were identified. A method validation using simulated data is then proposed to evaluate the suitability of the proposed multivariate curve resolution method for the analysis of the different possible date structures currently occurring in environmental monitoring studies. In particular, different data structures previously encountered in the experimental study of the Ebro River have been investigated in detail. The importance of using either raw or scaled data is contrasted using the simulated data sets. Possible propagation of noise on resolved profiles is also investigated to establish the difference between its effects and the possible ambiguities inherent to multivariate curve resolution methods. PMID:19708360

Terrado, Marta; Barceló, Damià; Tauler, Roma

2009-07-15

168

Light Curves  

NSDL National Science Digital Library

This is a game about light curves that will test your ability to figure out things about an asteroid from just a graph of its brightness. Astronomers use telescopes to collect light curves - measurements of the brightness of distant asteroids over time. It is part of the Killer Asteroids Web Site. The site also features a background overview of the differences between asteroids and comets, information on different types of asteroids (rubble piles vs monoliths), a discussion of how at risk Earth really is to an asteroid or comet impact, and background information on light curves.

169

SCALING INFILTRATION AND OTHER SOIL WATER PROCESSES ACROSS DIVERSE SOIL TEXTURAL CLASSES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Our studies showed that the pore-size distribution index (lambda) can scale Brooks-Corey (B-C) formulation of the soil-water retention curves below the air-entry pressure head across dissimilar (Sandy to clayey) soils, and other key B-C hydraulic parameters ( Ksat, air-entry pressure head, and depen...

170

Liquid chromatography with diode array detection and multivariate curve resolution for the selective and sensitive quantification of estrogens in natural waters.  

PubMed

Following the green analytical chemistry principles, an efficient strategy involving second-order data provided by liquid chromatography (LC) with diode array detection (DAD) was applied for the simultaneous determination of estriol, 17?-estradiol, 17?-ethinylestradiol and estrone in natural water samples. After a simple pre-concentration step, LC-DAD matrix data were rapidly obtained (in less than 5 min) with a chromatographic system operating isocratically. Applying a second-order calibration algorithm based on multivariate curve resolution with alternating least-squares (MCR-ALS), successful resolution was achieved in the presence of sample constituents that strongly coelute with the analytes. The flexibility of this multivariate model allowed the quantification of the four estrogens in tap, mineral, underground and river water samples. Limits of detection in the range between 3 and 13 ng L(-1), and relative prediction errors from 2 to 11% were achieved. PMID:24952625

Pérez, Rocío L; Escandar, Graciela M

2014-07-01

171

Stubble retention and nitrogen fertilisation in a fallow-wheat rainfed cropping system. 1. Soil water and nitrogen conservation, crop growth and yield  

Microsoft Academic Search

In semi-arid environments where water supply is the factor usually limiting grain yield, fallowing provides a way to increase water and nitrogen supply. An experiment was maintained from 1980 to 1990 at the Wimmera Research Station, Dooen, Australia. In each year, water use, growth and yield of wheat (Triticum aestivum L.) were measured following three tillage methods of year-long fallow.

C. Cantero-Martinez; G. J. O'Leary; D. J. Connor

1995-01-01

172

Tritium retention in TFTR  

SciTech Connect

This report discusses the materials physics related to D-T operation in TFTR. Research activities are described pertaining to basic studies of hydrogenic retention in graphite, hydrogen recycling phenomena, first-wall and limiter conditioning, surface analysis of TFTR first-wall components, and estimates of the tritium inventory.

Dylla, H.F.; Wilson, K.L. (eds.)

1988-04-01

173

Secrets of Retention  

ERIC Educational Resources Information Center

Recruiting students is one thing, but keeping them in a chorus, orchestra, or band is another. Although a music director has no control over some variables, there is much that can be done to help students to stay. Several experts share their advice on retention. One expert said a teacher's own attitude and classroom strategies may be two of the…

Poliniak, Susan

2012-01-01

174

Principals Retention. Research Brief  

ERIC Educational Resources Information Center

Many districts are struggling with the problem of administrator retention. Hoffman (2004) identifies some of the reasons for this: (1) Increased accountability expectations; (2) Diminished or static levels of resources to support reform efforts; (3) Greater administrator vulnerability to sanctions; (4) The complex demands of government and the…

Muir, Mike

2005-01-01

175

Data Show Retention Disparities  

ERIC Educational Resources Information Center

New nationwide data collected by the U.S. Department of Education's civil rights office reveal stark racial and ethnic disparities in student retentions, with black and Hispanic students far more likely than white students to repeat a grade, especially in elementary and middle school. The contrast is especially strong for African-Americans. In the…

Adams, Caralee J.; Robelen, Erik W.; Shah, Nirvi

2012-01-01

176

Generic Recruitment and Retention Plan  

Cancer.gov

February 23, 2010 Version 3 Division of Cancer Prevention Recruitment Retention and Adherence Plan TemplateInstructions NCI DCP requires a study-specific recruitment, retention and adherence (RRA) plan for each cancer chemoprevention study. Each participating

177

DEVELOPMENT OF DURATION-CURVE BASED METHODS FOR QUALIFYING VARIABILITY AND CHANGE IN WATERSHED HYDROLOGY AND WATER QUALITY  

EPA Science Inventory

During the past decades, U.S. Environmental Protection Agency (EPA), U.S. Department of Agriculture (USDA) and other Federal program administrative and regulatory agencies spent considerable amounts of time and money to manage risks to surface waters associated with agricultural ...

178

Colloids transport, retention, and remobilization during two phase flow  

NASA Astrophysics Data System (ADS)

Colloidal particles transported by water through a porous medium can deposit on solid surfaces and are removed from water. But, it is known that adsorbed particles could be remobilized if hydraulic or hydro-chemical conditions change. The work presented here studied colloids transport under steady-state and wetting fronts of different surface tensions. Experiments were performed in a PDMS micro-model with dimensions of 1mm×10mm, with a mean pore size of 30 microns. Given the fact that the micro-model was hydrophobic, fluorinert was the wetting phase, water was the non-wetting phase. We used carboxylate-modified fluorescent microspheres with mean diameter of 300nm as model colloids. The colloids were dispersed in water phase. We directly observed colloids movement and fluids distribution within pores of the micro-model using a confocal laser scanning microscope. We also measured the effluent concentration. We performed experiments under both single-phase and two-phase flow conditions. In both cases, we conducted both steady-state and transient flow experiments. We conducted similar above mentioned experiments by adding surfactant in the wetting-phase. We need to address that the particles were dispersed in the non-wetting phase. Thus, we can make sure that the surfactant didn't change the Ionic strength and pH, only the fluid-fluid surface tension was reduced. The breakthrough curves showed that under steady-state flow, with the decrease of water saturation, more colloids were retained. Our visualization results suggested that the enhanced attachment was due to retention of colloids to fluorinert-water interfaces (FWIs) and fluorinert-water-solid contact lines (FWSCs). At the end of a steady-state two phase flow experiment, we imbibing the system. Measurement of the breakthrough curves showed that remobilization of colloids occurred during the imbibition events. Video images showed that colloids deposited on the solid-water interfaces (SWIs) were detached by the moving FWS contact lines. Lowering the surface tension resulted in less attachment under unsaturated steady-state flow and less remobilization. Mainly due to the decrease of surface tension reduced capillary forces. In the video images, less remobilization was observed.

Zhang, Q.; Hassanizadeh, S.

2013-12-01

179

Colloidal particle transport in unsaturated porous media: Influence of flow velocity and ionic strength on colloidal particle retention  

NASA Astrophysics Data System (ADS)

Recently, anthropogenic colloidal particles are increasingly present into the environment. They can carry contaminants or constitute themselves a risk for the environment. Several factors can influence the fate of colloidal particles in soils. This work presents the investigation of effects of flow velocity and ionic strength on colloidal particles retention in unsaturated porous media. Experiments were carried out in laboratory column (D = 10 cm, L = 30 cm) with compacted mixture sand-gravel from a fluvioglacial basin of Lyon, France. Fluorescents nanoparticles (D = 50 to 60 nm) of silica doped with fluorescent organic molecules (fluorescein) have been used to simulate colloid particle transport. A solution of a non-reactive tracer, Br-, was used to determine the water flow behavior. Three different unsaturated water flow velocities (i.e. V = 0.025, 0.064 and 0.127 cm/min) and five ionic strengths (i.e. IS = 1, 5, 50, 100 and 200 mM at pH=8.5) have been tested for the case of a pulse injection of a colloidal particle solution at a concentration of 2 mg/L. Breakthrough curves are modeled by the non-equilibrium transfer model MIM (mobile and immobile water fraction), taking into account a sink term to reflect the colloidal particles adsorption. Results show that, when the flow velocity increases, the colloidal particle retention decreases. The decrease in flow velocity allows a better homogenization of the flow. In addition, colloidal entrapment is favored by the fact that their pore velocity is reduced. The retention of colloidal particle is function of ionic strength as well. Indeed, when the ionic strength increases, the retention increases. However for ionic strength higher than 50 mM, the retention decreases suggesting that there is a threshold value for the ionic strength with respect to the retention of colloidal particles. The retention profiles at the end of experiments indicate that the colloidal particles are retained at the inlet of the columns. Experimental and simulation results can be used to understand the mechanisms that are responsible for the transfer of colloidal particles in the environment and then to improve remediation techniques for contaminated soils. Keys words: colloidal particles, flow velocity, ionic strength, unsaturated soil

Predelus, Dieuseul; Coutinho, Paiva Artur; Lassabatere, Laurent; Winiarsky, Thierry; Angulo Jaramillo, Rafael

2014-05-01

180

Curved Space or Curved Vacuum?  

E-print Network

While the simple picture of a spatially flat, matter plus cosmological constant universe fits current observation of the accelerated expansion, strong consideration has also been given to models with dynamical vacuum energy. We examine the tradeoff of ``curving'' the vacuum but retaining spatial flatness, vs. curving space but retaining the cosmological constant. These different breakdowns in the simple picture could readily be distinguished by combined high accuracy supernovae and cosmic microwave background distance measurements. If we allow the uneasy situation of both breakdowns, the curvature can still be measured to 1%, but at the price of degrading estimation of the equation of state time variation by 60% or more, unless additional information (such as weak lensing data or a tight matter density prior) is included.

Eric V. Linder

2005-08-15

181

An ATP-binding cassette subfamily G full transporter is essential for the retention of leaf water in both wild barley and rice  

PubMed Central

Land plants have developed a cuticle preventing uncontrolled water loss. Here we report that an ATP-binding cassette (ABC) subfamily G (ABCG) full transporter is required for leaf water conservation in both wild barley and rice. A spontaneous mutation, eibi1.b, in wild barley has a low capacity to retain leaf water, a phenotype associated with reduced cutin deposition and a thin cuticle. Map-based cloning revealed that Eibi1 encodes an HvABCG31 full transporter. The gene was highly expressed in the elongation zone of a growing leaf (the site of cutin synthesis), and its gene product also was localized in developing, but not in mature tissue. A de novo wild barley mutant named “eibi1.c,” along with two transposon insertion lines of rice mutated in the ortholog of HvABCG31 also were unable to restrict water loss from detached leaves. HvABCG31 is hypothesized to function as a transporter involved in cutin formation. Homologs of HvABCG31 were found in green algae, moss, and lycopods, indicating that this full transporter is highly conserved in the evolution of land plants. PMID:21737747

Chen, Guoxiong; Komatsuda, Takao; Ma, Jian Feng; Nawrath, Christiane; Pourkheirandish, Mohammad; Tagiri, Akemi; Hu, Yin-Gang; Sameri, Mohammad; Li, Xinrong; Zhao, Xin; Liu, Yubing; Li, Chao; Ma, Xiaoying; Wang, Aidong; Nair, Sudha; Wang, Ning; Miyao, Akio; Sakuma, Shun; Yamaji, Naoki; Zheng, Xiuting; Nevo, Eviatar

2011-01-01

182

Selenide retention by mackinawite.  

PubMed

The isotope (79)Se may be of great concern with regard to the safe disposal of nuclear wastes in deep geological repositories due to its long half-life and potential mobility in the geosphere. The Se mobility is controlled by the oxidation state: the oxidized species (Se(IV)) and (Se(VI)) are highly mobile, whereas the reduced species (Se(0) and Se(-II)) form low soluble solids. The mobility of this trace pollutant can be greatly reduced by interacting with the various barriers of the repository. Numerous studies report on the oxidized species retention by mineral phases, but only very scarce studies report on the selenide (Se(-II)) retention. In the present study, the selenide retention by coprecipitation with and by adsorption on mackinawite (FeS) was investigated. XRD and SEM analyses of the samples reveal no significant influence of Se on the mackinawite precipitate morphology and structure. Samples from coprecipitation and from adsorption are characterized at the molecular scale by a multi-edge X-ray absorption spectroscopy (XAS) investigation. In the coprecipitation experiment, all elements (S, Fe, and Se) are in a low ionic oxidation state and the EXAFS data strongly point to selenium located in a mackinawite-like sulfide environment. By contacting selenide ions with FeS in suspension, part of Se is located in an environment similar to that found in the coprecipitation experiment. The explanation is a dynamical dissolution-recrystallization mechanism of the highly reactive mackinawite. This is the first experimental study to report on selenide incorporation in iron monosulfide by a multi-edge XAS approach. PMID:22900520

Finck, N; Dardenne, K; Bosbach, D; Geckeis, H

2012-09-18

183

Hyperexponential and nonmonotonic retention of polyvinylpyrrolidone-coated silver nanoparticles in an Ultisol  

NASA Astrophysics Data System (ADS)

The increasing application of engineered nanoparticles (ENPs) has heightened the concern that these ENPs would eventually be released to the environment and may enter into life cycle of living beings. In this regard, it is essential to understand how these ENPs transport and retain in natural soils because they are considered to be a major repository for ENPs. Herein, transport and retention of polyvinylpyrrolidone (PVP)-coated silver nanoparticles (PVP-AgNPs) were investigated over a wide range of physicochemical factors in water-saturated columns packed with an Ultisol rich in clay-size particles. Higher mobility of PVP-AgNPs occurred at larger soil grain size, lower solution ionic strength and divalent cation concentration, higher flow rate, and greater PVP concentrations. Most breakthrough curves (BTCs) for PVP-AgNPs exhibited significant amounts of retardation in the soil due to its large surface area and quantity of retention sites. In contrast to colloid filtration theory, the shapes of retention profiles (RPs) for PVP-AgNPs were either hyperexponential or nonmonotonic (a peak in particle retention down-gradient from the column inlet). The BTCs and hyperexponential RPs were successfully described using a 1-species model that considered time- and depth-dependent retention. Conversely, a 2-species model that included reversibility of retained PVP-AgNPs had to be employed to better simulate the BTCs and nonmonotonic RPs. As the retained concentration of species 1 approached the maximum solid-phase concentration, a second mobile species (species 2, i.e., the same PVP-AgNPs that are reversibly retained) was released that could be retained at a different rate than species 1 and thus yielded the nonmonotonic RPs. Some retained PVP-AgNPs were likely to irreversibly deposit in the primary minimum associated with microscopic chemical heterogeneity (favorable sites). Transmission electron microscopy and energy-dispersive X-ray spectroscopy analysis suggested that these favorable sites were positively charged sites on montmorillonite edges and goethite surfaces in the soil. Overall, our study highlights that the transport and especially retention of PVP-AgNPs are highly sensitive to the physicochemical factors, but mathematical modeling can accurately predict the fate of these ENPs in porous media which is important for better understanding the fate of these ENPs in point of exit and in the environment.

Wang, Dengjun; Ge, Liqiang; He, Jianzhou; Zhang, Wei; Jaisi, Deb P.; Zhou, Dongmei

2014-08-01

184

RETENTION TIME EFFECT ON METAL REMOVAL BY PEAT COLUMNS  

SciTech Connect

The potential use of a peat bed to treat the H-12 Outfall discharge to bring it to new compliance limits was previously investigated and reported utilizing a 7 hour retention time. The influence of retention time (contact time) of water with peat moss on the removal of copper from the water was investigated under laboratory conditions using vertical flow peat moss columns. Reduction of the necessary retention time has a large influence on the design sizing of any peat bed that would be constructed to treat the H-12 discharge on a full scale basis. Retention times of 5 hours, 3 hours and 1 hour were tested to determine the copper removal by the peat columns using vertical flow. Water samples were collected after 4, 8, 12, and 16 water volumes had passed through the columns and analyzed for a suite of metals, with quantitative emphasis on copper. Laboratory results indicated that copper removal was very high at each of the 3 retention times tested, ranging from 99.6 % removal at 5 and 3 hours to 98.8% removal at 1 hour. All these values are much lower that the new compliance limit for the outfall. The results also indicated that most divalent metals were removed to their normal reporting detection limit for the analytical methods used, including zinc. Lead levels in the H-12 discharge used in this study were below PQL in all samples analyzed. While each of the retention times studied removed copper very well, there were indications that 1 hour is probably too short for an operational, long-term facility. At that retention time, there was about 6% compaction of the peat in the column due to the water velocity, and this may affect long term hydraulic conductivity of the peat bed. At that retention time, copper concentration in the effluent was higher than the other times tested, although still very low. Because of the potential compacting and somewhat reduced removal efficiency at a 1 hour retention time, it would be prudent to design to at least a 3 hour retention time for water in any peat bed system that is proposed for the H-12 Outfall. A scope to design and install a pilot level study at H-12 is currently under development. This study will be designed to examine some of the engineering issues that are of concern regarding the scaling of an actual peat bed to treat the volumes of water that are typically discharged through the H-12 Outfall. Different hydraulic paths and configurations are expected to be part of that scope.

Nelson, E

2007-02-28

185

Soluble reactive phosphorus transport and retention in tropical, rainforest streams draining a volcanic and geothermally active landscape in Costa Rica.: Long-term concentration patterns, pore water environment and response to ENSO events  

USGS Publications Warehouse

Soluble reactive phosphorus (SRP) transport/retention was determined at four sites in three rainforest streams draining La Selva Biological Station, Costa Rica. La Selva is located at the base of the last remaining intact rainforest transect from 30 m above sea level to 3000 m along the entire Caribbean slope of Central America. Steam SRP levels can be naturally high there due to regional, geothermal groundwater discharged at ambient temperature. Monitoring since 1988 has revealed distinctive long-term differences in background SRP and total P (TP) for three streams in close proximity, and identified the impact of ENSO (El Nino Southern Oscillation) events on SRP-enriched reaches. Mean interannual SRP concentrations (?? standard deviation) were 89 ?? 53??g/l in the Salto (1988-1996), 21 ?? 39??g/l in the Pantano (1988-1998), and 26 ?? 35??g/l in the Sabalo (1988-1996). After January, 1997 the separate upland-lowland contributions to discharge and SRP load were determined monthly in the Salto. SRP in Upper Salto was low (19 ?? 8??g/l, 1997-2002) until enriched at the upland-lowland transition by regional groundwater. Mean SRP concentration in Lower Salto (108 ?? 104??g/l) was typically highest February-April, the driest months, and lowest July-September, the wettest. SRP concentration was positively correlated to the inverse of discharge in Lower Salto when ENSO data were omitted (1992 and 1998-1999), but not in the Upper Salto, Pantano, or Sabalo. TP was positively correlated to the inverse of discharge in all three streams when ENSO data were omitted. High SRP springs and seeps along the Lower Salto contributed 36% of discharge but 85% of SRP export 1997-2001. Annual SRP flux from the total Salto watershed (1997-2001) averaged 2.9 kg/ha year, but only 0.6 kg/ha year from the Upper Salto. A dye tracer injection showed that pore water environments were distinctly different between Upper and Lower Salto. Upper Salto had high surface water-pore water exchange, high dissolved oxygen, low SRP, and low conductivity similar to surface water, and Lower Salto had low surface water-pore water exchange, low dissolved oxygen, high SRP, and high conductivity reflecting geothermal groundwater influence. SRP export from the Salto was controlled by regional groundwater transfer, which in similar volcanic settings could be a significant P source. However, ENSO events modified the SRP concentration in the Salto suggesting that long-term monitoring is required to understand underlying SRP dynamics and P flux to downstream communities. ?? 2006 Springer Science+Business Media, Inc.

Triska, F.J.; Pringle, C.M.; Duff, J.H.; Avanzino, R.J.; Ramirez, A.; Ardon, M.; Jackman, A.P.

2006-01-01

186

Application of the Green-Ampt infiltration equation with the Horton interception and surface retention equations to predict runoff  

E-print Network

storm interception and surface retention volumes (Linsley, 1982). These equations differ from the curve number procedure in many ways. The equations treat interception and surface retention as separate computations as opposed to one lump sum... the entire storm sequence, determines the 18 abstractions taken from the precipitation to determine direct runoff (Linsley, 1982). ALTERNATIVE METHODS TO COMPUTE RAINFALL INTERCEPTION AND SURFACE RETENTION LOSSES Several methods for determining rainfall...

Reedy, Michael Vincent

1991-01-01

187

Toward a Record Retention Policy  

ERIC Educational Resources Information Center

An academic library working group was charged in 2005 to create a records retention schedule and policy applicable to records containing personally identifiable information of library patrons. This group conducted a survey and extensive research, culminating in an adopted library records retention schedule and policy implemented in 2006.

Vaughan, Jason

2007-01-01

188

SULFUR RETENTION IN COAL ASH  

EPA Science Inventory

The report gives results of an analytical study to assess the potential for sulfur retention in various types of coal-fired boilers. Results of a field test of 10 industrial coal-fired boilers were used to evaluate the impact on sulfur retention of the operating variables (load a...

189

Geography Undergraduate Program Essentials: Retention  

ERIC Educational Resources Information Center

Following an integrative model that shows the complex connections of recruitment, retention, and placement, this second paper in a three-part series explores the exigent endeavor of retaining students who undertake geography as their undergraduate major. Survey data of graduating students are requisite in constructing successful retention plans.…

Estaville, Lawrence E.; Brown, Brock J.; Caldwell, Sally

2006-01-01

190

Flavor Retention During Drying1  

Microsoft Academic Search

The influence of spray dryer operating conditions (drying temperatures, extract solids content, nozzle orifice size, and in- feed spray pressure) and of variations in the proportions of individual skin~- milk components in the extract to be dried, upon flavor retention during drying, was investigated. The influence of those variables upon flavor retention was evalu- ated by adding either acetoin, acetone,

Gary A. Reineccius; S. T. Coulter

1969-01-01

191

5 CFR 351.404 - Retention register.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 false Retention register. 351.404 Section 351.404 ...Competition § 351.404 Retention register. (a) When a competing employee...agency shall establish a separate retention register for that competitive level. The...

2010-01-01

192

Characterization of retentivity of reversed phase liquid chromatography columns.  

PubMed

There are dozens of commercially available reversed phase columns, most marketed as C-8 or C-18 materials, but with no useful way of classifying their retentivity. A useful way of ranking these columns in terms of column "strength" or retentivity is presented. The method utilizes a value for ln k'(w), the estimated retention of a solute from a mobile phase of 100% water, and the slope of the plot of ln k' vsE(T)(30), the solvent polarity. The method is validated with 26 solutes varying in ln k'(w) from about 2 to over 20, on 14 different reversed phase columns. In agreement with previous work, it is found that the phase volume ratio of the column is the most important parameter in determining retentivity. It is strongly suggested that manufacturers adopt a uniform method of calculating this value and that it be made available in advertising, rather than the uninterpretable "% carbon". PMID:18965135

Ying, P T; Dorsey, J G

1991-03-01

193

Rational Curves 598 CHAPTER 22. RATIONAL CURVES  

E-print Network

Chapter 22 Rational Curves 597 #12;598 CHAPTER 22. RATIONAL CURVES 22.1 Rational Curves and Multiprojective Maps In this chapter, rational curves are investigated. After a quick review of the traditional parametric definition in terms of homogeneous polynomials, we explore the possibility of defining rational

Gallier, Jean

194

Data Retention and Anonymity Services  

NASA Astrophysics Data System (ADS)

The recently introduced legislation on data retention to aid prosecuting cyber-related crime in Europe also affects the achievable security of systems for anonymous communication on the Internet. We argue that data retention requires a review of existing security evaluations against a new class of realistic adversary models. In particular, we present theoretical results and first empirical evidence for intersection attacks by law enforcement authorities. The reference architecture for our study is the anonymity service AN.ON, from which we also collect empirical data. Our adversary model reflects an interpretation of the current implementation of the EC Directive on Data Retention in Germany.

Berthold, Stefan; Böhme, Rainer; Köpsell, Stefan

195

Nitrate-nitrogen retention in wetlands in the Mississippi River Basin  

Microsoft Academic Search

Nitrate-nitrogen retention as a result of river water diversions is compared in experimental wetland basins in Ohio for 18 wetland-years (9 years×2 wetland basins) and a large wetland complex in Louisiana (1 wetland basin×4 years). The Ohio wetlands had an average nitrate-nitrogen retention of 39g-Nm?2year?1, while the Louisiana wetland had a slightly higher retention of 46g-Nm?2year?1 for a similar loading

William J. Mitsch; John W. Day; Li Zhang

2005-01-01

196

EA Shuttle Document Retention Effort  

NASA Technical Reports Server (NTRS)

This slide presentation reviews the effort of code EA at Johnson Space Center (JSC) to identify and acquire databases and documents from the space shuttle program that are adjudged important for retention after the retirement of the space shuttle.

Wagner, Howard A.

2010-01-01

197

Parent lithology, surface-groundwater exchange, and nitrate retention in headwater streams  

Microsoft Academic Search

We address the ecological ramifications of variation in hydrologic interaction between streams and alluvial aquifers in catchments with alluvium derived from parent materials of contrasting geologic composition. We present a conceptual model in which solute retention in streams results from hydrologic retention (increased water residence time resulting from surface-groundwater exchange), biological nutrient cycling, and chemical processes. Solute injection experiments were

H. Maurice Valett; John A. Morrice; N. Dahm

1996-01-01

198

Record Retention Policy Page 1 of 3 10.7 Record Retention Policy  

E-print Network

Record Retention Policy Page 1 of 3 10.7 Record Retention Policy Policy Number & Name: 10.7 Record Retention #12;Record Retention Policy Page 2 of 3 Period for a Record does not change when a properly Retention Policy Approval Authority: Administrative Council Responsible Executive: Vice President

Yang, Eui-Hyeok

199

Long-Term Sodium Chloride Retention in a Rural Watershed  

E-print Network

Long-Term Sodium Chloride Retention in a Rural Watershed: Legacy Effects of Road Salt% of the input. Road salt use in the watershed did not increase during the study include road salt, oil field brine, water softeners, septic and sewage effluent, natural salt deposits

Weathers, Kathleen C.

200

Phosphorus Retention in Streams and Wetlands: A Review  

Microsoft Academic Search

Wetlands and streams buffer the interactions among uplands and adjacent aquatic systems. Phosphorus (P) is often the key nutrient found to be limiting in both estuarine and freshwater ecosystems. As such, the ability of wetlands and streams to retain P is key to determining downstream water quality. This article reviews the processes and factors regulating P retention in streams and

K. R. Reddy; R. H. Kadlec; E. Flaig; P. M. Gale

1999-01-01

201

Isolated Curves for Hyperelliptic Curve Cryptography  

E-print Network

We introduce the notion of isolated genus two curves. As there is no known efficient algorithm to explicitly construct isogenies between two genus two curves with large conductor gap, the discrete log problem (DLP) cannot be efficiently carried over from an isolated curve to a large set of isogenous curves. Thus isolated genus two curves might be more secure for DLP based hyperelliptic curve cryptography. We establish results on explicit expressions for the index of an endomorphism ring in the maximal CM order, and give conditions under which the index is a prime number or an almost prime number for three different categories of quartic CM fields. We also derived heuristic asymptotic results on the densities and distributions of isolated genus two curves with CM by any fixed quartic CM field. Computational results, which are also shown for three explicit examples, agree with heuristic prediction with errors within a tolerable range.

Wang, Wenhan

2012-01-01

202

Exploring particulate retention mechanisms through visualization of E. coli transport through a single, saturated fracture  

NASA Astrophysics Data System (ADS)

Groundwater is an extremely valuable resource; a large body of work has been conducted towards remediating, tracking and reducing its contamination. Even so, there are large gaps within the current understanding of groundwater flow and contaminant transport, particularly within fractured media. Fractured media has the ability transport contaminants over longer distances in less time relative to porous media. Furthermore, colloids display unique transport characteristics in comparison to dissolved constituents, including the fact that they typically exhibit earlier initial arrival times. Of particular concern to human health are pathogenic microorganisms, which often originate from fecal contamination. Escherichia coli is a common indicator for fecal contamination; some strains are pathogenic, causing acute illness and sometimes death, in humans. A comprehensive understanding of the transport and retention of E. coli in fractured media will improve our ability to accurately assess whether a site is at risk of becoming contaminated by pathogenic microorganisms. Therefore, the goal of this work is to expand our mechanistic understanding particulate retention, specifically E. coli, in fractures, and the influence of flow rate on these mechanisms. In order to achieve this goal, clear epoxy casts were fabricated of two dolomitic limestone fractures retrieved from a quarry in Guelph, Ontario. Each aperture field was characterized through hydraulic and tracer tests, and measured directly using the light transmission technique. E. coli RS2-GFP, which is a non-pathogenic strain of E. coli that has been tagged with a green fluorescent protein, was injected into the cast under three separate specific discharges ranging from 5 - 30 m/d. These experiments were conducted on an ultraviolet light source, and a high resolution charged-couple device (CCD) camera was employed to take photos at regular intervals in order to capture the dominant flow paths and the areas of retention within the epoxy fracture. Samples were drawn downstream to obtain the E. coli breakthrough curve and determine the percent retained within the fracture. This paper will present the dominant retention mechanisms of E. coli at various effective flow rates as determined from an analysis of the images showing trapped E. coli, together with the aperture field information from the direct measurement. This information will help to improve the robustness and of contaminant transport models in fractures, and will therefore improve the ability to assess the risk posed by using bedrock aquifers as drinking water sources.

Burke, M. G.; Dickson, S. E.; Schutten, M.

2011-12-01

203

SOIL MOISTURE RETENTION CHARACTERISTICS AND HYDRAULIC CONDUCTIVITY FOR DIFFERENT AREAS IN INDIA IN SELECTED STATES  

E-print Network

SOIL MOISTURE RETENTION CHARACTERISTICS AND HYDRAULIC CONDUCTIVITY FOR DIFFERENT AREAS IN INDIA systems require knowledge of the relationships between soil moisture content (), soil water pressure (h) and unsaturated hydraulic conductivity (K). This study involved field and laboratory determination of soil

Kumar, C.P.

204

Short-Term Effects of Grade Retention on the Growth Rate of Woodcock-Johnson III Broad Math and Reading Scores  

ERIC Educational Resources Information Center

We investigated the effects of grade retention in first grade on the growth of the Woodcock-Johnson broad mathematics and reading scores over three years using linear growth curve modeling on an academically at-risk sample. A large sample (n=784) of first grade children who were at risk for retention was initially identified based on low literacy…

Wu, Wei; West, Stephen G.; Hughes, Jan N.

2008-01-01

205

Maslow's Hierarchy and Student Retention.  

ERIC Educational Resources Information Center

Abraham Maslow's hierarchy of needs offers perspective on student motivation and a rationale for college retention programing. Student affairs and faculty interventions addressing student safety needs and engaging students' sense of purpose reinforce persistence. A mentor program is a possible cooperative effort between student personnel and…

Brookman, David M.

1989-01-01

206

Teacher Retention: An Appreciative Approach  

ERIC Educational Resources Information Center

Nationally, the problem of teacher retention compounds the unstable nature of the educational situation, especially in urban, high-needs schools. Much of the instability of urban schools is due to teacher movement, the migration of teachers from school to another school within or between school districts, particularly from high-needs schools.…

Pesavento-Conway, Jennifer Jean

2010-01-01

207

Academic Advising for Retention Purposes.  

ERIC Educational Resources Information Center

An effective academic advising system can assist in the retention of two-year college students; however, the institution and its faculty must be committed to providing such a system. Establishing a successful advising system would require the following: (1) a clear distinction must be made between academic advising and course scheduling; (2)…

Kazazes, Barbara A.

208

Course Retention Analysis. Focus Study.  

ERIC Educational Resources Information Center

A study was conducted at Mount San Antonio College (MSAC), California, to analyze patterns in credit course retention between fall 1986 and spring 1989. The study investigated the development of course prerequisites based on faculty perceptions of the skills necessary for success and minimal skill levels associated with success; student assessment…

Mount San Antonio Coll., Walnut, CA.

209

Retention-Oriented Curricular Design  

ERIC Educational Resources Information Center

This paper presents a retention-oriented approach to the educational value stream within the STEM undergraduate area. Faced with several strategic challenges and opportunities, a Flex Advantage Plan was developed to enhance the undergraduate engineering technology programs and better utilize the curricular flexibilities inherent in the current…

Milanovic, Ivana; Eppes, Tom A.; Girouard, Janice; Townsend, Lee

2010-01-01

210

Nuclear reactor melt-retention structure to mitigate direct containment heating  

DOEpatents

A light water nuclear reactor melt-retention structure to mitigate the extent of direct containment heating of the reactor containment building. The structure includes a retention chamber for retaining molten core material away from the upper regions of the reactor containment building when a severe accident causes the bottom of the pressure vessel of the reactor to fail and discharge such molten material under high pressure through the reactor cavity into the retention chamber. In combination with the melt-retention chamber there is provided a passageway that includes molten core droplet deflector vanes and has gas vent means in its upper surface, which means are operable to deflect molten core droplets into the retention chamber while allowing high pressure steam and gases to be vented into the upper regions of the containment building. A plurality of platforms are mounted within the passageway and the melt-retention structure to direct the flow of molten core material and help retain it within the melt-retention chamber. In addition, ribs are mounted at spaced positions on the floor of the melt-retention chamber, and grid means are positioned at the entrance side of the retention chamber. The grid means develop gas back pressure that helps separate the molten core droplets from discharged high pressure steam and gases, thereby forcing the steam and gases to vent into the upper regions of the reactor containment building.

Tutu, Narinder K. (Manorville, NY); Ginsberg, Theodore (East Setauket, NY); Klages, John R. (Mattituck, NY)

1991-01-01

211

High retention membrane bioreactors: challenges and opportunities.  

PubMed

Extensive research has focussed on the development of novel high retention membrane bioreactor (HR-MBR) systems for wastewater reclamation in recent years. HR-MBR integrates high rejection membrane separation with conventional biological treatment in a single step. High rejection membrane separation processes currently used in HR-MBR applications include nanofiltration, forward osmosis, and membrane distillation. In these HR-MBR systems, organic contaminants can be effectively retained, prolonging their retention time in the bioreactor and thus enhancing their biodegradation. Therefore, HR-MBR can offer a reliable and elegant solution to produce high quality effluent. However, there are several technological challenges associated with the development of HR-MBR, including salinity build-up, low permeate flux, and membrane degradation. This paper provides a critical review on these challenges and potential opportunities of HR-MBR for wastewater treatment and water reclamation, and aims to guide and inform future research on HR-MBR for fast commercialisation of this innovative technology. PMID:24996563

Luo, Wenhai; Hai, Faisal I; Price, William E; Guo, Wenshan; Ngo, Hao H; Yamamoto, Kazuo; Nghiem, Long D

2014-09-01

212

12 CFR 1026.25 - Record retention.  

Code of Federal Regulations, 2013 CFR

... false Record retention. 1026.25 Section 1026.25 Banks and Banking BUREAU OF CONSUMER FINANCIAL PROTECTION TRUTH IN LENDING (REGULATION Z) Miscellaneous § 1026.25 Record retention. (a) General rule. A...

2013-01-01

213

12 CFR 1026.25 - Record retention.  

... false Record retention. 1026.25 Section 1026.25 Banks and Banking BUREAU OF CONSUMER FINANCIAL PROTECTION TRUTH IN LENDING (REGULATION Z) Miscellaneous § 1026.25 Record retention. (a) General rule. A...

2014-01-01

214

Nitrogen retention in urban lawns and forests.  

PubMed

Lawns are a dominant cover type in urban ecosystems, and there is concern about their impacts on water quality. However, recent watershed-level studies suggest that these pervious areas might be net sinks, rather than sources, for nitrogen (N) in the urban environment. A 15N pulse-labeling experiment was performed on lawn and forest plots in the Baltimore (Maryland, U.S.A.) metropolitan area to test the hypothesis that lawns are a net sink for atmospheric-N deposition and to compare and contrast mechanisms of N retention in these vegetation types. A pulse of 15N-NO3-, simulating a precipitation event, was followed through mineral soils, roots, Oi-layer/thatch, aboveground biomass, microbial biomass, inorganic N, and evolved N2 gas over a one-year period. The 15N label was undetectable in gaseous samples, but enrichment of other pools was high. Gross rates of production and consumption of NO3- and NH4+ were measured to assess differences in internal N cycling under lawns and forests. Rates of N retention were similar during the first five days of the experiment, with lawns showing higher N retention than forests after 10, 70, and 365 days. Lawns had larger pools of available NO3- and NH4+; however, gross rates of mineralization and nitrification were also higher, leading to no net differences in NO3- and NH4+ turnover times between the two systems. Levels of 15N remained steady in forest mineral soils from day 70 to 365 (at 23% of applied 15N), but continued to accumulate in lawn mineral soils over this same time period, increasing from 20% to 33% of applied 15N. The dominant sink for N in lawn plots changed over time. Immobilization in mineral soils dominated immediately (one day) after tracer application (42% of recovered 15N); plant biomass dominated the short term (10 days; 51%); thatch and mineral-soil pools together dominated the medium term (70 days; 28% and 36%, respectively); and the mineral-soil pool alone dominated long-term retention (one year; 70% of recovered 15N). These findings illustrate the mechanisms whereby urban and suburban lawns under low to moderate management intensities are an important sink for atmospheric-N deposition. PMID:18839758

Raciti, S M; Groffman, P M; Fahey, T J

2008-10-01

215

Water relations of Robinia pseudoacacia?L.: do vessels cavitate and refill diurnally or are R-shaped curves invalid in Robinia?  

PubMed

Since 2005, an unresolved debate has questioned whether R-shaped vulnerability curves (VCs) might be an artefact of the centrifuge method of measuring VCs. VCs with R-shape show loss of stem conductivity from approximately zero tension, and if true, this suggests that some plants either refill embolized vessels every night or function well with a high percentage of vessels permanently embolized. The R-shaped curves occur more in species with vessels greater than half the length of the segments spun in a centrifuge. Many have hypothesized that the embolism is seeded by agents (bubbles or particles) entering the stem end and travelling towards the axis of rotation in long vessels, causing premature cavitation. VCs were measured on Robinia pseudoacacia?L. by three different techniques to yield three different VCs; R-shaped: Cavitron P50 ?=?0.30?MPa and S-shaped: air injection P50 ?=?1.48?MPa and bench top dehydration P50 ?=?3.57?MPa. Stem conductivity measured in the Cavitron was unstable and is a function of vessel length when measured repeatedly with constant tension, and this observation is discussed in terms of stability of air bubbles drawn into cut-open vessels during repeated Cavitron measurement of conductivity; hence, R-shaped curves measured in a Cavitron are probably invalid. PMID:24588635

Wang, Ruiqing; Zhang, Lingling; Zhang, Shuoxin; Cai, Jing; Tyree, Melvin T

2014-12-01

216

Sensitivity of the transport and retention of stabilized silver nanoparticles to physicochemical factors  

Technology Transfer Automated Retrieval System (TEKTRAN)

Saturated sand-packed column experiments were conducted to investigate the influence of physicochemical factors on the transport and retention of surfactant stabilized silver nanoparticles (AgNPs). The normalized concentration in breakthrough curves (BTCs) of AgNPs increased with a decrease in solut...

217

Reframing Retention Strategy: A Focus on Profile  

ERIC Educational Resources Information Center

Over 35 years of retention theory and literature have acknowledged the importance of institutional and student profiles in accounting for cross-sectional differences in retention and completion rates between types of colleges and universities. The first "P" within a 4 Ps framework of student retention--"profile"--recognizes that an institution's…

Kalsbeek, David H.; Zucker, Brian

2013-01-01

218

AN ORIENTATION COURSE AND COMMUNITY COLLEGE RETENTION  

Microsoft Academic Search

Orientation and retention programs are common in institutions of higher education. The potential association between orientation programs and student retention, particularly within the community college sector, has long been neglected. This study presents an institutional view of a potential associative relationship between an orientation course and student retention measures. A chi-square analysis revealed a significant association among orientation program, student

Dustin C. Derby; Thomas Smith

2004-01-01

219

Records retention in relational database systems  

Microsoft Academic Search

The recent introduction of several pieces of legislation man- dating minimum and maximum retention periods for cor- porate records has prompted the Enterprise Content Man- agement (ECM) community to develop various records re- tention solutions. Records retention is a significant subfield of records management, and legal records retention require- ments apply over corporate records regardless of their shape or form.

Ahmed A. Ataullah; Ashraf Aboulnaga; Frank Wm. Tompa

2008-01-01

220

New Freshman and Transfer Retention Study  

E-print Network

New Freshman and Transfer Retention Study Fall 2011 Institutional Research #12;1 Introduction, and persistence rates of new freshmen and transfer students entering Colorado State University (CSU). Combining the two previously separate studies (New Freshman Retention and Transfer Retention) was in response

221

Scale and Seasonal Controls on Nitrate and Sediment Retention in Freshwater Tidal Wetlands  

NASA Astrophysics Data System (ADS)

Channel networks in freshwater tidal wetlands convey water, sediment, and solutes into marsh interiors where sediment deposition and biogeochemical processes, such as denitrification and nitrogen uptake occur. Tidal inlets that connect these channel network systems to the main estuary define the initial solute or sediment load into these systems, but channel, soil, and vegetation characteristics influence nitrate and sediment retention. We used field measurements and remotely sensed images to determine marsh area, stream length, inlet morphology, and channel morphology for the 267 marshes in the freshwater tidal ecosystem. Discharge and water volume over high tidal cycles was measured at selected inlets representative of the range of inlet sizes in the ecosystem. Aquatic vegetation distribution and density was also measured at these inlets. These data were used to develop geomorphic-hydraulic relationships for the marshes for winter (no vegetation) and summer (vegetated) conditions. Nitrate and sediment retention were determined from field mass balance measurements based on water flux and concentration measurements taken over tidal cycle at inlets to selected marshes of varying size over a 3-year period. These mass balance data indicate that net nitrate retention is a simple function of tidal water volume for marshes of different sizes and for various vegetated conditions. These data suggest that nitrate retention is transport limited for the range of initial nitrate concentrations observed in this system. Although nitrate retention was a function of tidal water volume, it was also seasonally variable due to restrictions in water flow and volume caused by aquatic vegetation in summer months. Sediment retention is seasonally variable due to the strong controls exerted by emergent and submerged aquatic vegetation and decoupled from the water volume dependence observed for nitrate retention. Variations in sediment retention caused by vegetation resulted in channel morphology that oscillates between summer and winter conditions.

Prestegaard, K. L.; Seldomridge, E.; Statkiewicz, A.

2013-12-01

222

On nondegeneracy of curves  

Microsoft Academic Search

A curve is called nondegenerate if it can be modeled by a Laurent polynomial\\u000athat is nondegenerate with respect to its Newton polytope. We show that up to\\u000agenus 4, every curve is nondegenerate. We also prove that the locus of\\u000anondegenerate curves inside the moduli space of curves of fixed genus g > 1 is\\u000amin(2g+1,3g-3)-dimensional, except in case

Wouter Castryck; John Voight

2009-01-01

223

Water  

E-print Network

Explore Australia’s most comprehensive water information resource. The National Water Account provides the following information for nine nationally significant regions: • total water resource • water available for extraction • rights to abstract water • actual abstraction of water.

Quick Link

224

Measuring in-stream retention of copper by means of constant-rate additions.  

PubMed

Human practices entail inputs of nutrients and toxicants such as heavy metals to the fluvial ecosystems. While nutrient dynamics in fluvial ecosystems have been widely studied for over three decades, dynamics of toxicants still remain unclear. In this investigation, the nutrient spiraling concept and associated methodologies to quantify nutrient retention in streams were applied to study copper (Cu) dynamics in streams. The present study aimed to quantify total dissolved Cu retention using a simplified system of indoor channels colonized with fluvial biofilms. Cu retention was studied at sub-toxic concentrations to avoid negative/lethal effects on biota. In addition, Cu retention was compared with retention estimates of a macronutrient, phosphate (PO(4)(3-)), which has been widely studied within the context of the nutrient spiraling concept. The methodology used allowed a successful quantification of Cu and PO(4)(3-) retention. The results showed higher retention efficiency for PO(4)(3-) than for Cu. The biofilm played a key role in retaining both solutes. Although retention efficiency for both solutes was higher in the experiments with colonized substrata compared to uncolonized substrata, we found a positive relationship between uptake rate and chlorophyll-a only for PO(4)(3-). Finally, retention efficiency for both solutes was influenced by water discharge, showing lower retention efficiencies under higher flow conditions. These results suggest that the fate and toxic effects of copper on stream biota may be strongly influenced by the prevailing environmental conditions. Our results indicate that the experimental approach considered can provide new insights into the investigation of retention of toxic compounds in fluvial systems and their controlling mechanisms. PMID:19299001

Serra, A; Guasch, H; Martí, E; Geiszinger, A

2009-06-01

225

Modelling global nutrient retention by river damming: Phosphorus and silicon  

NASA Astrophysics Data System (ADS)

The phosphorus to silicon (P:Si) nutrient ratio is a key variable affecting ecosystem health in many aquatic environments. River damming represents a major anthropogenic perturbation of natural material flows along the aquatic continuum, with the potential to profoundly modify absolute and relative nutrient availabilities in surface waters. In this study, a multi-tiered approach for estimating global nutrient retention in man-made reservoirs is presented. We illustrate its application to the global riverine flux of reactive Si, using a database of dissolved reactive Si (DSi) budgets for 24 natural lakes and 22 artificial reservoirs. The database includes information on bedrock geology, surface water pH, water residence time, reservoir age and function, climate, and trophic status. Statistical analyses (ANOVA, t-test, PCA, linear plus non-linear regressions) are used to identify the best predictors of DSi retention and delineate how reservoir properties modulate nutrient dynamics. Results indicate that (1) reservoirs retain significantly less DSi than natural lakes, and (2) the water residence time, reservoir age and function (e.g., hydroelectrical production, irrigation, flood control) are the main system variables controlling DSi retention by dams. Next, a biogeochemical Si model is used to reproduce the previously derived statistical trends for DSi retention. Calibration of the model yields a relationship that enables one to predict annual in-reservoir siliceous productivity as a function of the external reactive Si supply. The model further accounts for the transition from reservoirs where reactive Si retention is primarily due to burial of allochtonous Si to those where in-reservoir DSi uptake by diatoms dominates. Finally, the statistical and mechanistic relationships are extrapolated to estimate that 25-28 Tg SiO2 yr-1 are retained worldwide by dams, or 7% of the annual reactive Si load to watersheds. We are currently applying the same multi-tiered approach to the global P cycle. Our goal is to predict not only the effect of dams on reactive P retention, but also to determine how they are changing the P:Si ratios in river systems. Our preliminary results indicate that reservoirs are more effective in retaining nutrient P than Si.

Maavara, Taylor; Dürr, Hans; Van Cappellen, Philippe

2014-05-01

226

Foundations of retention in partition chromatography.  

PubMed

The connection between the observable output in column chromatography (retention time, retention volume, retention factor, separation factor, etc.) and system properties (hold-up volume, pressure, temperature, isotherm behavior, etc.) is discussed from a practical and mechanistic perspective for gas-liquid chromatography, reversed-phase liquid chromatography, supercritical fluid chromatography, micellar electrokinetic chromatography, and capillary electrochromatography. The unifying feature of these techniques is that retention can be described by a partition model, although not always exclusively. When over simplistic system models are used to explain variation in retention parameters they frequently mask the true reasons for poor repeatability and difficulties in transfer between system. Methods employing relative retention afford higher precision but may contain residual uncorrected errors. For those systems with several separate mechanisms contributing to retention the effective retention parameters can no longer be interpreted by simple partition models. The broadly based and practically focused material in this article affords an illustration of the often complicated relationship between system properties and retention, and the dangers that lurk in simplified retention models if the validity of their underlining approximations is not appropriate for the system under study. PMID:19013576

Poole, Colin F; Poole, Salwa K

2009-03-01

227

The human body retention time of environmental organically bound tritium.  

PubMed

Tritium in the UK environment causes low radiation doses to the public, but uncertainty exists in the dose coefficient for the organically bound component of tritium (OBT). This can affect the assessment of effective doses to representative persons. Contributing to that uncertainty is poor knowledge of the body retention time of OBT and how this varies for different OBT compounds in food. This study was undertaken to measure the retention time of tritium by volunteers after eating sole from Cardiff Bay, which may contain OBT from discharges from the GE Healthcare Ltd plant. Five volunteers provided samples of excreta over periods up to 150 days after intake. The results, which are presented in raw form to allow independent analysis, suggest retention of total tritium with body half-times ranging from 4 to 11 days, with no evidence (subject to experimental noise) of a significant contribution due to retention with a longer half-time. This range covers the half-time of 10 days used by the ICRP for tritiated water. The short timescale could be due to rapid hydrolysis in body tissues of the particular form of OBT used in this study. Implications for the dose coefficient for OBT are that the use of the ICRP value of 4.2 x 10(-11) Sv Bq(-1) may be cautious in this specific situation. These observations on dose coefficients are separate from any implications of recent discussion on whether the tritium radiation weighting factor should be increased from 1 to 2. PMID:19225188

Hunt, John; Bailey, Trevor; Reese, Allan

2009-03-01

228

Phosphorus retention and remobilization along hydrological pathways in karst terrain.  

PubMed

Karst landscapes are often perceived as highly vulnerable to agricultural phosphorus (P) loss, via solution-enlarged conduits that bypass P retention processes. Although attenuation of P concentrations has been widely reported within karst drainage, the extent to which this results from hydrological dilution, rather than P retention, is poorly understood. This is of strategic importance for understanding the resilience of karst landscapes to P inputs, given increasing pressures for intensified agricultural production. Here hydrochemical tracers were used to account for dilution of P, and to quantify net P retention, along transport pathways between agricultural fields and emergent springs, for the karst of the Ozark Plateau, midcontinent USA. Up to ? 70% of the annual total P flux and ? 90% of the annual soluble reactive P flux was retained, with preferential retention of the most bioavailable (soluble reactive) P fractions. Our results suggest that, in some cases, karst drainage may provide a greater P sink than previously considered. However, the subsequent remobilization and release of the retained P may become a long-term source of slowly released "legacy" P to surface waters. PMID:24720609

Jarvie, Helen P; Sharpley, Andrew N; Brahana, Van; Simmons, Tarra; Price, April; Neal, Colin; Lawlor, Alan J; Sleep, Darren; Thacker, Sarah; Haggard, Brian E

2014-05-01

229

Curve Family Index (Visual Dictionary of Special Plane Curves)  

NSDL National Science Digital Library

A discussion of the many ways to classify curves, how they are named, a curve family tree, and interconnection between curves, with related Web sites about fractals and curves. Hosted by the Math Forum.

Lee, Xah

2007-12-20

230

Retention behavior of proton pump inhibitors using immobilized polysaccharide-derived chiral stationary phases with organic-aqueous mobile phases.  

PubMed

In the present study, the chromatographic behavior of two immobilized polysaccharide-derived chiral stationary phases (CSPs), the Chiralpak ID-3 and Chiralpak IE-3, under aqueous mobile phases conditions is presented. Four proton pump inhibitors (PPIs) (omeprazole, lansoprazole, pentaprazole and rabeprazole) were selected as test compounds. The effect of the concentration of water in the mobile phase was investigated with respect to its contribution to enantioselectivity and retention. Under acetonitrile-water mobile phase conditions, retention behavior evidenced an interesting pattern. At lower water content, the retention factors decreased with increasing water and at higher water content a reversed trend was observed. These findings support the hypothesis that two retention mechanisms operated successively on the same CSP: the HILIC (with water-poor eluents) and RPLC (with water-rich eluents) modes. The retention factors were minimum in the intermediate region, corresponding to a water concentration of about 20%. Interestingly, the baseline separation of all PPIs investigated was optimized under organic-aqueous mobile phases containing a high water content (from about 50 to 65%). Thus, the dual retention behavior of the PPIs on the Chiralpak ID-3 and Chiralpak IE-3 made it possible to reach greener and harmless enantioselective conditions in a short analysis time. PMID:23880466

Cirilli, Roberto; Ferretti, Rosella; Gallinella, Bruno; Zanitti, Leo

2013-08-23

231

Dissecting the ecosystem service of large-scale pollutant retention: The role of wetlands and other landscape features.  

PubMed

Various features of a landscape contribute to the regulating ecosystem service of reducing waterborne pollutant loading to downstream environments. At local scales, wetlands have been shown to be effective in retaining pollutants. Here, we investigate the landscape-scale contribution to pollutant retention provided by multiple wetlands. We develop a general analytical model which shows that the retention contribution of wetlands and other landscape features is only significant if a large fraction of the total waterborne pollutant transport passes through them. Next, by means of a statistical analysis of official data, we quantify the nutrient retention contribution of wetlands for multiple sub-catchments in two Swedish Water Management Districts. We compare this with the retention contribution of two other landscape features: the waterborne transport distance and major lakes. The landscape-scale retention contribution of wetlands is undetectable; rather, the other two landscape features account for much of the total nutrient retention. PMID:25576287

Quin, Andrew; Jaramillo, Fernando; Destouni, Georgia

2015-01-01

232

Retention at Departments of Physics  

NASA Astrophysics Data System (ADS)

A thriving physics department is the end result of many actions, taken over time, that results in the development of a sense of community between the faculty and the students. As part of this sense of community, gifted students must receive special attention and innovative ideas must be incorporated to successfully accommodate the needs of these students. We have found that the best retention strategy for gifted undergraduates is the total involvement of them in undergraduate research projects and also the development of leadership in extracurricular activities within the department. A careful employment strategy is needed to secure a faculty committed to the goals of the community.

Muller, Rafael; Rosa, Luis

2013-03-01

233

NASA's Potential Contributions for Remediation of Retention Ponds Using Solar Ultraviolet Radiation and Photocatalysis  

NASA Technical Reports Server (NTRS)

This Candidate Solution uses NASA Earth science research on atmospheric ozone and aerosols data (1) to help improve the prediction capabilities of water runoff models that are used to estimate runoff pollution from retention ponds, and (2) to understand the pollutant removal contribution and potential of photocatalytically coated materials that could be used in these ponds. Models (the EPA's SWMM and the USGS SLAMM) exist that estimate the release of pollutants into the environment from storm-water-related retention pond runoff. UV irradiance data acquired from the satellite mission Aura and from the OMI Surface UV algorithm will be incorporated into these models to enhance their capabilities, not only by increasing the general understanding of retention pond function (both the efficacy and efficiency) but additionally by adding photocatalytic materials to these retention ponds, augmenting their performance. State and local officials who run pollution protection programs could then develop and implement photocatalytic technologies for water pollution control in retention ponds and use them in conjunction with existing runoff models. More effective decisions about water pollution protection programs could be made, the persistence and toxicity of waste generated could be minimized, and subsequently our natural water resources would be improved. This Candidate Solution is in alignment with the Water Management and Public Health National Applications.

Underwood, Lauren W.; Ryan, Robert E.

2007-01-01

234

Supply Curves of Conserved Energy  

SciTech Connect

Supply curves of conserved energy provide an accounting framework that expresses the potential for energy conservation. The economic worthiness of a conservation measure is expressed in terms of the cost of conserved energy, and a measure is considered economical when the cost of conserved energy is less than the price of the energy it replaces. A supply curve of conserved energy is independent of energy prices; however, the economical reserves of conserved energy will depend on energy prices. Double-counting of energy savings and error propagation are common problems when estimating conservation potentials, but supply curves minimize these difficulties and make their consequences predictable. The sensitivity of the cost of conserved energy is examined, as are variations in the optimal investment strategy in response to changes in inputs. Guidelines are presented for predicting the consequences of such changes. The conservation supply curve concept can be applied to peak power, water, pollution, and other markets where consumers demand a service rather than a particular good.

Meier, Alan Kevin

1982-05-01

235

Advancing the physical basis of depletion curves to improve curve estimation and snowmelt modeling  

NASA Astrophysics Data System (ADS)

The spatial distribution of snow on the landscape is a fundamental control on meltwater inputs to basins. The effects of the spatial variability in snow accumulation and melt are commonly parameterized through the use of some version of a depletion curve, relating the snow covered area to time, accumulated melt, or the remaining snowpack on the ground. Depletion curves are generally estimated empirically through calibration against basin outflows, limiting their application in ungaged basins. Understanding the physical basis of depletion curves can provide valuable insights to improve curve estimation; provide utility for remote sensing of snow water equivalent; and improve the parameterizations in physically based models. To a first approximation, depletion curves can be derived as a function of the variability of snow water equivalent in the basin. In this respect, the coefficient of variation of spatially sampled snow water equivalent at peak accumulation is a good predictor of the depletion curve. A second approximation to the depletion curve can be derived from the spatial covariation of snow water equivalent at peak accumulation with energy inputs for snowmelt. While both approximations can be derived from spatially sampled snow water equivalent, such data are rarely available over large areas. Temporal sampling of remotely sensed snow covered area combined with estimates of snowmelt is an alternative that remains true to the second approximation. This approach opens the possibility to large scale estimation of depletion curves, with the potential for estimating the fraction of the seasonal maximum snow water equivalent remaining on the ground for a given remote sensing scene or to improve data assimilation procedures. Both of these approaches only estimate the snow covered fraction of a given unit. Further using the correlation between snow water equivalent and exposure to melt energy, we can estimate the relative energy exposure of the remaining patches, providing greater utility of the depletion curve concept for hydrologic modeling applications.

Luce, C.; Tarboton, D.; McNamara, J.

2006-12-01

236

Fission-product retention in HTGR fuels  

SciTech Connect

Retention data for gaseous and metallic fission products are presented for both Triso-coated and Biso-coated HTGR fuel particles. Performance trends are established that relate fission product retention to operating parameters, such as temperature, burnup, and neutron exposure. It is concluded that Biso-coated particles are not adequately retentive of fission gas or metallic cesium, and Triso-coated particles which retain cesium still lose silver. Design implications related to these performance trends are identified and discussed.

Homan, F.J.; Kania, M.J.; Tiegs, T.N.

1982-01-01

237

Mathematical Curve Conjectures  

NSDL National Science Digital Library

In this activity, a six-foot length of nylon rope is suspended at both ends to model a mathematical curve known as the hyperbolic cosine. In a write-pair-share activity, students are asked to make a conjecture concerning the nature of the curve and then embark on a guided discovery in which they attempt to determine a precise mathematical description of the curve using function notation.

James Rutledge

238

Radionuclide Retention in Concrete Wasteforms  

SciTech Connect

Assessing long-term performance of Category 3 waste cement grouts for radionuclide encasement requires knowledge of the radionuclide-cement interactions and mechanisms of retention (i.e., sorption or precipitation); the mechanism of contaminant release; the significance of contaminant release pathways; how wasteform performance is affected by the full range of environmental conditions within the disposal facility; the process of wasteform aging under conditions that are representative of processes occurring in response to changing environmental conditions within the disposal facility; the effect of wasteform aging on chemical, physical, and radiological properties; and the associated impact on contaminant release. This knowledge will enable accurate prediction of radionuclide fate when the wasteforms come in contact with groundwater. Data collected throughout the course of this work will be used to quantify the efficacy of concrete wasteforms, similar to those used in the disposal of LLW and MLLW, for the immobilization of key radionuclides (i.e., uranium, technetium, and iodine). Data collected will also be used to quantify the physical and chemical properties of the concrete affecting radionuclide retention.

Wellman, Dawn M.; Jansik, Danielle P.; Golovich, Elizabeth C.; Cordova, Elsa A.

2012-09-24

239

Simulation of optically conditioned retention and mass occurrences of Periphylla periphylla  

PubMed Central

Jellyfish blooms are of increasing concern in many parts of the world, and in Norwegian fjords an apparent increase in mass occurrences of the deep water jellyfish Periphylla periphylla has attracted attention. Here we investigate the hypothesis that changes in the water column light attenuation might cause local retention and thereby facilitate mass occurrences. We use a previously tested individual-based model of light-mediated vertical migration in P. periphylla to simulate how retention is affected by changes in light attenuation. Our results suggest that light attenuation, in combination with advection, has a two-sided effect on retention and that three fjord categories can be defined. In category 1, increased light attenuation turns fjords into dark “deep-sea” environments which increase the habitat and retention of P. periphylla. In category 2, an optimal light attenuation facilitates the maximum retention and likelihood for mass occurrences. In category 3, further increase in light attenuation, however, shoals the habitat so that individuals are increasingly exposed to advection and this results in loss of individuals and decreased retention. This classification requires accurate determinations of the organism's light preference, the water column light attenuation and topographical characteristics affecting advection. PMID:20454515

Dupont, Nicolas; Aksnes, Dag L.

2010-01-01

240

Nonequilibrium water dynamics in the rhizosphere: How mucilage affects water flow in soils  

NASA Astrophysics Data System (ADS)

flow of water from soil to plant roots is controlled by the properties of the narrow region of soil close to the roots, the rhizosphere. In particular, the hydraulic properties of the rhizosphere are altered by mucilage, a polymeric gel exuded by the roots. In this paper we present experimental results and a conceptual model of water flow in unsaturated soils mixed with mucilage. A central hypothesis of the model is that the different drying/wetting rate of mucilage compared to the bulk soil results in nonequilibrium relations between water content and water potential in the rhizosphere. We coupled this nonequilibrium relation with the Richards equation and obtained a constitutive equation for water flow in soil and mucilage. To test the model assumptions, we measured the water retention curve and the saturated hydraulic conductivity of sandy soil mixed with mucilage from chia seeds. Additionally, we used neutron radiography to image water content in a layer of soil mixed with mucilage during drying and wetting cycles. The radiographs demonstrated the occurrence of nonequilibrium water dynamics in the soil-mucilage mixture. The experiments were simulated by numerically solving the nonequilibrium model. Our study provides conceptual and experimental evidences that mucilage has a strong impact on soil water dynamics. During drying, mucilage maintains a greater soil water content for an extended time, while during irrigation it delays the soil rewetting. We postulate that mucilage exudation by roots attenuates plant water stress by modulating water content dynamics in the rhizosphere.

Kroener, Eva; Zarebanadkouki, Mohsen; Kaestner, Anders; Carminati, Andrea

2014-08-01

241

Automated solid-phase extraction of herbicides from water for gas chromatographic-mass spectrometric analysis  

USGS Publications Warehouse

An automated solid-phase extraction (SPE) method was developed for the pre-concentration of chloroacetanilide and triazine herbicides, and two triazine metabolites from 100-ml water samples. Breakthrough experiments for the C18 SPE cartridge show that the two triazine metabolites are not fully retained and that increasing flow-rate decreases their retention. Standard curve r2 values of 0.998-1.000 for each compound were consistently obtained and a quantitation level of 0.05 ??g/l was achieved for each compound tested. More than 10,000 surface and ground water samples have been analyzed by this method.

Meyer, M.T.; Mills, M.S.; Thurman, E.M.

1993-01-01

242

Water balance of sandy soils of Niger, West Africa  

E-print Network

. Summary of Valet's (1975, 1976) results: physical properties 65 4. Dates of 1985 rain events and amounts (mm). . 71 5. Data points used in calibration of probe: Surface reading with water content at 0. 05 m 6. Data points used in calibration of probe... at experimental sites 51 6. Root counts of two millet plants at N'Dounga 54 7. Root counts of two millet plants at Kala Pate ' 55 8. Root counts of two millet plants at Chikal 56 9. Moisture retention curve for surface horizon at N'Dounga 57 10...

Payne, William Albert

1987-01-01

243

Juvenile densities relative to water regime in mainstem reservoirs of the Tennessee River, USA  

USGS Publications Warehouse

Successful reproduction and development of strong year classes of fish in storage reservoirs are commonly associated with reproductive seasons of high water level and extensive flooding. Responses to flooding are likely to be less pronounced or altogether different in mainstem navigation reservoirs that experience limited water level fluctuation. In these reservoirs, water regime characteristics such as timing of flooding, instability of water level, and water retention could supersede the effects of water level. We examined existing data to identify aspects of the water regime that have detectable consequence on juveniles of selected taxa in a sequence of four reservoirs of the Tennessee River that exhibited relatively small annual rises. Empirical models relating density of selected age-0 centrarchids to water regime suggested that descriptors of spring and summer flow through the reservoirs, water level instability, and summer water level were better related to juvenile densities than was spring water level. Different water regimes had different effects on the study species, and presumably other species in the fish communities. Therefore, a diversity of water regimes rather than a rigid rule curve is likely most beneficial to the long-term permanence of the fish assemblages of the study reservoirs. Fixed rule curves produce drawdown zones devoid of vegetation consisting primarily of mudflats of limited ecological value to floodplain species, and maintenance of water levels within the rule curve force operational drops and rises that adversely affect littoral spawners. In developing water management plans, regulatory agencies should consider incorporating managed randomness into rule curves. ?? 2007 Blackwell Publishing Asia Pty Ltd.

Miranda, L.E.; Lowery, D.R.

2007-01-01

244

Anodic Polarization Curves Revisited  

ERIC Educational Resources Information Center

An experiment published in this "Journal" has been revisited and it is found that the curve pattern of the anodic polarization curve for iron repeats itself successively when the potential scan is repeated. It is surprising that this observation has not been reported previously in the literature because it immediately brings into…

Liu, Yue; Drew, Michael G. B.; Liu, Ying; Liu, Lin

2013-01-01

245

The Curved Cube  

NSDL National Science Digital Library

Take a solid cube with rods attached at diagonally opposite vertices. Hold the rods horizontally and rapidly spin the cube. (See Figure 1.) You should see a curved outline formed by the spinning cube. The objective of this demos is to discover how the straight edges of the cube become curved. The demo is physically based, but can be simulated within various software packages.

Hill, David R.

2003-02-24

246

Electrostatic curved electrode actuators  

Microsoft Academic Search

In this paper, the design, fabrication, and first experimental results of electrostatic curved electrode actuators are addressed. The actuator design is based upon the deformation of a movable micromechanical structure by electrostatic forces using a fixed curved electrode. When a voltage is applied, an electrostatic force is created that will deform the free structure along the outline of the fixed

Rob Legtenberg; Erwin Berenschot; Miko Elwenspoek; J. H. J. Fluitman

1995-01-01

247

Tails of Lorenz curves  

Microsoft Academic Search

The Lorenz dominance criterion is the centre piece of inequality analysis. Yet, the appeal of this criterion, which requires considering Lorenz curves in their entirety, is undermined by the practical problem that many sample Lorenz curves intersect in the tails. The commonly used inferential methods, based on central limit theorem arguments, do not apply to the tails since these contain

Christian Schluter; Mark Trede

2002-01-01

248

Enhanced retention of linuron, alachlor and metalaxyl in sandy soil columns intercalated with wood barriers.  

PubMed

A study has been made of the effect a reactive barrier made of pine (softwood) or oak (hardwood) wood intercalated in a sandy soil column has on the retention of linuron, alachlor and metalaxyl (pesticides with contrasting physicochemical characteristics). The leaching of pesticides has been carried out under a saturated flow regime and breakthrough curves (BTCs) have been obtained at flow rates of 1 m Lmin(-1) (all pesticides) and 3 m Lmin(-1) (linuron). The cumulative curves in the unmodified soil indicate a leaching of pesticides >80% of the total amount of compound added. After barrier intercalation, linuron leaching decreases significantly and a modification of the leaching kinetics of alachlor and metalaxyl has been observed. The theoretical R factors increased ?2.6-3.3, 1.2-1.6-fold, and 1.4-1.7-fold and the concentration of the maximum peak decreased ?6-12-fold, 2-4-fold and 1.2-2-fold for linuron, alachlor and metalaxyl, respectively. When considering the three pesticides, significant correlations have been found between the theoretical retardation factor (R) and the pore volume corresponding to the maximum peaks of the BTCs (r=0.77; p<0.05) or the total volume leached (r=-0.78; p<0.05). The results reveal the efficacy of reactive wood barriers to decrease the leaching of pesticides from point sources of pollution depends on the type of wood, the hydrophobicity of the pesticide and the adopted water flow rate. Pine was more effective than oak in decreasing the leaching of hydrophobic pesticide linuron or in decreasing the maximum peak concentration of the less hydrophobic pesticides in soils. Efficacy of these wood barriers was limited for the least hydrophobic pesticide metalaxyl. PMID:21183199

Rodríguez-Cruz, M S; Ordax, J M; Arienzo, M; Sánchez-Martín, M J

2011-03-01

249

DIN retention-transport through four hydrologically connected zones in a headwater catchment of the Upper Mississippi River  

USGS Publications Warehouse

Dissolved inorganic nitrogen (DIN) retention-transport through a headwater catchment was synthesized from studies encompassing four distinct hydrologic zones of the Shingobee River Headwaters near the origin of the Mississippi River. The hydrologic zones included: (1) hillslope ground water (ridge to bankside riparian); (2) alluvial riparian ground water; (3) ground water discharged through subchannel sediments (hyporheic zone); and (4) channel surface water. During subsurface hillslope transport through Zone 1, DIN, primarily nitrate, decreased from ???3 mg-N/l to <0.1 mg-N/l. Ambient seasonal nitrate:chloride ratios in hillslope flow paths indicated both dilution and biotic processing caused nitrate loss. Biologically available organic carbon controlled biotic nitrate retention during hillslope transport. In the alluvial riparian zone (Zone 2) biologically available organic carbon controlled nitrate depletion although processing of both ambient and amended nitrate was faster during the summer than winter. In the hyporheic zone (Zone 3) and stream surface water (Zone 4) DIN retention was primarily controlled by temperature. Perfusion core studies using hyporheic sediment indicated sufficient organic carbon in bed sediments to retain ground water DIN via coupled nitrification-denitrification. Numerical simulations of seasonal hyporheic sediment nitrification-denitrification rates from perfusion cores adequately predicted surface water ammonium but not nitrate when compared to 5 years of monthly field data (1989-93). Mass balance studies in stream surface water indicated proportionally higher summer than winter N retention. Watershed DIN retention was effective during summer under the current land use of intermittently grazed pasture. However, more intensive land use such as row crop agriculture would decrease nitrate retention efficiency and increase loads to surface water. Understanding DIN retention capacity throughout the system, including special channel features such as sloughs, wetlands and floodplains that provide surface water-ground water connectivity, will be required to develop effective nitrate management strategies. ?? 2007 American Water Resources Association.

Triska, F.J.; Duff, J.H.; Sheibley, R.W.; Jackman, A.P.; Avanzino, R.J.

2007-01-01

250

Characterization and radionuclide retention properties of heat-treated concrete  

NASA Astrophysics Data System (ADS)

This study was performed to obtain insight into the characteristics of contaminated cementitious materials which may result from a light water reactor core melt down accident. Such material arose in a huge amount from the Fukushima disaster. We analyzed the elemental and mineralogical composition of similar, heat-treated material and investigated its radionuclide retention properties. We present the radionuclide retention properties of concrete samples which originally were part of an experiment using a thick-walled concrete recipient that had been heated by simulating a reactor melt down. Batch sorption experiments have been performed with the elements Cs(I), Co(II), and Eu(III) in seawater under aerobic conditions. Sorption coefficients were measured: Rs(Eu) ?5800 ml g-1 and Rs(Co) ?110 ml g-1. A tentative value for Cs was determined, adulterated by the relatively high release of Cs from the concrete itself.

Kienzler, B.; Borkel, C.; Finck, N.; Heck, S.; Hilpp, S.; Schlieker, M.; Metz, V.; Plaschke, M.; Soballa, E.; Cron, T.; Miassoedov, A.

251

Retention and transport of nutrients in a mature agricultural impoundment  

NASA Astrophysics Data System (ADS)

Small impoundments intended for irrigation, livestock watering, and hydropower are numerous in agricultural regions of the world. Many of these artificial water bodies are well positioned to intercept fertilizer runoff and pollutants but could be vulnerable to long-term sedimentation, management intervention, or failure. We examined solute retention in a mature, sediment-filled, run-of-river impoundment created by a small, >100 year old dam in agricultural Wisconsin, United States. To do so, we measured instantaneous net fluxes of inorganic and organic solutes through the system, which contained wetlands. The impoundment was a persistent net sink for sulfate and, during the warm season only, a net sink for nitrate, ammonium, and soluble reactive phosphorus. There was also a negative relationship between nitrate and sulfate retention, suggestive of nitrate-stimulated sulfate production. Impoundment hydraulics were then altered by a management manipulation (dam removal) that caused mean water travel time to decrease by approximately 40%. Following manipulation, autoregressive modeling of solute time series indicated a decrease in mean net retention of nitrate, sulfate, ammonium, and soluble reactive phosphorus. There was also a decrease in the variability (coefficient of variation) of instantaneous net exports of dissolved organic nitrogen and dissolved organic phosphorus. These biogeochemical changes were consistent with predictions based on hydraulics (reduced water travel time), with the exception of ammonium release immediately following reservoir dewatering. Our results emphasize the biogeochemical importance of reservoir-wetland ecosystems, which are expanding with impoundment sedimentation but are threatened by infrastructure aging. We suggest that reservoir wetlands be considered in the management of dams and surface water pollution.

Powers, S. M.; Julian, J. P.; Doyle, M. W.; Stanley, E. H.

2013-03-01

252

A wave propagation algorithm for hyperbolic systems on curved manifolds  

Microsoft Academic Search

An extension of the wave propagation algorithm first introduced by LeVeque [J. Comput. Phys. 131 (1997) 327] is developed for hyperbolic systems on a general curved manifold. This extension is important in a variety of applications, including the propagation of sound waves on a curved surface, shallow water flow on the surface of the Earth, shallow water magnetohydrodynamics in the

James A. Rossmanith; Derek S. Bale; Randall J. LeVeque

2004-01-01

253

Black Student Retention in Higher Education.  

ERIC Educational Resources Information Center

This collection focuses on problems in the recruitment, enrollment and retention of Blacks in higher education in America. The following chapters are provided: "The Black Student Retention Problem in Higher Education: Some Introductory Perspectives" (Marvel Lang); "Early Acceptance and Institutional Linkages in a Model Program of Recruitment,…

Lang, Marvel, Ed.; Ford, Clinita A., Ed.

254

Minority Teacher Recruitment and Retention Strategies  

ERIC Educational Resources Information Center

The tools and resources in this book help school leaders seamlessly incorporate minority teacher recruitment and retention programs into current human-resources activities. With details about exemplary minority teacher recruitment and retention programs, this book also showcases strategies for how to replicate such programs in your own school or…

Kearney-Gissendaner, Janet E.

2010-01-01

255

Enrollment and Retention: A Private College Consortium.  

ERIC Educational Resources Information Center

A consortium program of eight private colleges in Southern California that focuses on student retention efforts is described. Each college has a retention task force consisting of faculty, administrators, student affairs staff, and students. A steering committee with one representative from each college, generally the dean of students, coordinates…

Green, Kenneth C.

256

Novel Word Retention in Sequential Bilingual Children  

ERIC Educational Resources Information Center

Children's ability to learn and retain new words is fundamental to their vocabulary development. This study examined word retention in children learning a home language (L1) from birth and a second language (L2) in preschool settings. Participants were presented with sixteen novel words in L1 and in L2 and were tested for retention after…

Kan, Pui Fong

2014-01-01

257

African Retentions in Blues and Jazz.  

ERIC Educational Resources Information Center

The perseverance of African musical characteristics among American Blacks is an historic reality. African retentions have been recorded in Black music of the antebellum period. Various African scales and rhythms permeate Black American music today as evidenced in the retentions found in blues and jazz. (RLV)

Meadows, Eddie S.

1979-01-01

258

How “Good” is Your Institution's Retention Rate?  

Microsoft Academic Search

Attempts to assess institutional performance by means of retention rates, student performance on standardized tests, and other raw outcome measures are seriously flawed because such measures fail to take into account the powerful effect of student inputs. In this study, national longitudinal retention data on 52,898 students attending 365 baccalaureate-granting colleges and universities are used to generate formulas for estimating

Alexander W. Astin

1997-01-01

259

Spoon River College Student Retention Project.  

ERIC Educational Resources Information Center

As part of a student retention project conducted at Spoon River College (SRC), specific populations served by SRC were identified; strategies to increase retention of particular student populations were developed; students in need of assistance were identified; and a transfer graduate follow-up study and two cohort tracking studies involving all…

Gardner, Janet L.

260

Healthcare Learning Community and Student Retention  

ERIC Educational Resources Information Center

Teaching, learning, and retention processes have evolved historically to include multifaceted techniques beyond the traditional lecture. This article presents related results of a study using a healthcare learning community in a southwest Georgia university. The value of novel techniques and tools in promoting student learning and retention

Johnson, Sherryl W.

2014-01-01

261

Radionuclide Retention in Concrete Wasteforms  

SciTech Connect

Assessing long-term performance of Category 3 waste cement grouts for radionuclide encasement requires knowledge of the radionuclide-cement interactions and mechanisms of retention (i.e., sorption or precipitation); the mechanism of contaminant release; the significance of contaminant release pathways; how wasteform performance is affected by the full range of environmental conditions within the disposal facility; the process of wasteform aging under conditions that are representative of processes occurring in response to changing environmental conditions within the disposal facility; the effect of wasteform aging on chemical, physical, and radiological properties; and the associated impact on contaminant release. This knowledge will enable accurate prediction of radionuclide fate when the wasteforms come in contact with groundwater. The information present in the report provides data that (1) measures the effect of concrete wasteform properties likely to influence radionuclide migration; and (2) quantifies the rate of carbonation of concrete materials in a simulated vadose zone repository.

Bovaird, Chase C.; Jansik, Danielle P.; Wellman, Dawn M.; Wood, Marcus I.

2011-09-30

262

Headwaters Retention Potential Assessment with Respect to Hydrological Extremes  

NASA Astrophysics Data System (ADS)

Urgent need of solving of issues dealing with protection against hydrological extremes calls also for detailed clarification of runoff generation mechanisms. The topicality of this subject is associated with recent climate change and the intensification of hydrometeorological extremes, taking place in Central Europe as well. Suitable conditions for the research realization at present is related to the highly peaty Otava River headwaters, sw. Czechia. To understand and clarify the runoff generation process and the effect of various physical-geographic factors on its dynamics, the analyses of runoff regime in chosen experimental catchments were done. In order to evaluate the study area retention potential peat bogs hydrological function assessment had to be carried out. Attention was also focused on findings of a runoff dynamics dependence on the ground water table in the peatland. Hydrochemical and geochemical approaches including isotope hydrology principles were used to explain the mechanisms of streamflow generation processes in the highly peaty catchments. On the base of acquired results and time series statistical analyses it could be stated that more distinct runoff variability is typical for streams draining catchments with the significant proportion of peatland. The fact that the existence of bogs has the negative effect on the runoff process, especially during extreme hydrological situations, was confirmed by hydropedological, hydrochemical and geochemical approaches. Implementation of unforceable measures, such as the use of potential accumulation and retention spaces in the catchment area, could contribute significantly to reduction of peak flows and to increase of water resources during eventual extreme droughts in future. Key words: hydrological extremes, runoff formation, retention potential, Otava River, automatic stations, experimental catchment, peat bogs hydrological function, oxygen isotopes, snow cover, retention and accumulation spaces, climate change

Kocum, Jan; Jansky, Bohumir; Vlcek, Lukas

2014-05-01

263

A comparison of the retention of pathogenic Escherichia coli?O157 by sprouts, leaves and fruits  

PubMed Central

The retention (binding to or association with the plant) of Escherichia coli by cut leaves and fruits after vigorous water washing was compared with that by sprouts. Retention by fruits and leaves was similar but differed from retention by sprouts in rate, effect of wounding and requirement for poly-?,1-6-N-acetyl-D-glucosamine. Escherichia coli was retained by cut ends of lettuce leaves within 5 min while more than 1 h was required for retention by the intact epidermis of leaves and fruits, and more than 1 day for sprouts. Retention after 5 min at the cut leaf edge was specific for E. coli and was not shown by the plant-associated bacteria Agrobacterium tumefaciens and Sinorhizobium meliloti.?Escherichia coli was retained by lettuce, spinach, alfalfa, bean, tomato, Arabidopsis thaliana, cucumber, and pepper leaves and fruits faster than by sprouts. Wounding of leaves and fruits but not sprouts increased bacterial retention. Mutations in the exopolysaccharide synthesis genes yhjN and wcaD reduced the numbers of bacteria retained. PgaC mutants were retained by cut leaves and fruits but not by sprouts. There was no significant difference in the retention of an O157 and a K12 strain by fruits or leaves. However, retention by sprouts of O157 strains was significantly greater than K12 strains. These findings suggest that there are differences in the mechanisms of E coli retention among sprouts, and leaves and fruits. PMID:25351040

Mathews, Stephanie L; Smith, Rachel B; Matthysse, Ann G

2014-01-01

264

A comparison of the retention of pathogenic Escherichia coli?O157 by sprouts, leaves and fruits.  

PubMed

The retention (binding to or association with the plant) of Escherichia coli by cut leaves and fruits after vigorous water washing was compared with that by sprouts. Retention by fruits and leaves was similar but differed from retention by sprouts in rate, effect of wounding and requirement for poly-?,1-6-N-acetyl-D-glucosamine. Escherichia coli was retained by cut ends of lettuce leaves within 5?min while more than 1?h was required for retention by the intact epidermis of leaves and fruits, and more than 1 day for sprouts. Retention after 5?min at the cut leaf edge was specific for E.?coli and was not shown by the plant-associated bacteria Agrobacterium tumefaciens and Sinorhizobium meliloti.?Escherichia coli was retained by lettuce, spinach, alfalfa, bean, tomato, Arabidopsis thaliana, cucumber, and pepper leaves and fruits faster than by sprouts. Wounding of leaves and fruits but not sprouts increased bacterial retention. Mutations in the exopolysaccharide synthesis genes yhjN and wcaD reduced the numbers of bacteria retained. PgaC mutants were retained by cut leaves and fruits but not by sprouts. There was no significant difference in the retention of an O157 and a K12 strain by fruits or leaves. However, retention by sprouts of O157 strains was significantly greater than K12 strains. These findings suggest that there are differences in the mechanisms of E? coli retention among sprouts, and leaves and fruits. PMID:25351040

Mathews, Stephanie L; Smith, Rachel B; Matthysse, Ann G

2014-11-01

265

12 CFR Appendix A to Part 749 - Record Retention Guidelines  

Code of Federal Regulations, 2010 CFR

...false Record Retention Guidelines A Appendix A to Part 749 Banks and Banking ...UNIONS RECORDS PRESERVATION PROGRAM AND APPENDICES-RECORD RETENTION GUIDELINES; CATASTROPHIC...PREPAREDNESS GUIDELINES Pt. 749, App. A Appendix A to Part 749—Record Retention...

2010-01-01

266

GENERALIZED MORDELL CURVES, GENERALIZED FERMAT CURVES, AND THE HASSE PRINCIPLE  

E-print Network

GENERALIZED MORDELL CURVES, GENERALIZED FERMAT CURVES, AND THE HASSE PRINCIPLE NGUYEN NGOC DONG. The descending chain condition on sequences of curves 18 6. Certain generalized Fermat curves violating the Hasse of generalized Fermat curves 33 9. Epilogue 35 Acknowledgements 45 References 45 Abstract. A generalized Mordell

Nguyen, Dong Quan Ngoc

267

Water quality beneath urban runoff water management basins  

Microsoft Academic Search

The chemical impact of urban runoff water on water quality beneath five retention\\/recharge basins was investigated as part of the US EPA's Nationwide Urban Runoff Program in Fresno, California. Soil water percolating through alluvium soils and the ground water at the top of the water table were sampled with ceramic\\/Teflon vacuum water extractors at depths up to 26 m during

Harry I. Nightingale

1987-01-01

268

Estimating steady-state evaporation rates from bare soils under conditions of high water table  

USGS Publications Warehouse

A procedure that combines meteorological and soil equations of water transfer makes it possible to estimate approximately the steady-state evaporation from bare soils under conditions of high water table. Field data required include soil-water retention curves, water table depth and a record of air temperature, air humidity and wind velocity at one elevation. The procedure takes into account the relevant atmospheric factors and the soil's capability to conduct 'water in liquid and vapor forms. It neglects the effects of thermal transfer (except in the vapor case) and of salt accumulation. Homogeneous as well as layered soils can be treated. Results obtained with the method demonstrate how the soil evaporation rates·depend on potential evaporation, water table depth, vapor transfer and certain soil parameters.

Ripple, C.D.; Rubin, J.; Van Hylckama, T. E. A.

1970-01-01

269

Logistic Curve Demo  

NSDL National Science Digital Library

This interactive demo illustrates the generation of a logistic curve. This demo is appropriate for a pre-calculus course, but is quite effective in a calculus class immediately after a discussion of inflection points.

Roberts, Lila F.; Hill, David R.

2002-02-03

270

Crude oil supply curves  

E-print Network

Short-run cost curves shift over time as depletion counters increasing knowledge. Under competition, a rightward (leftward) shift indicates lower (higher) cost and greater (lesser) productivity. A simple coefficient captures ...

Adelman, Morris Albert

1998-01-01

271

Enhancing Nitrification at Low Temperature with Zeolite in a Mining Operations Retention Pond  

PubMed Central

Ammonium nitrate explosives are used in mining operations at Diavik Diamond Mines Inc. in the Northwest Territories, Canada. Residual nitrogen is washed into the mine pit and piped to a nearby retention pond where its removal is accomplished by microbial activity prior to a final water treatment step and release into the sub-Arctic lake, Lac de Gras. Microbial removal of ammonium in the retention pond is rapid during the brief ice-free summer, but often slows under ice cover that persists up to 9?months of the year. The aluminosilicate mineral zeolite was tested as an additive to retention pond water to increase rates of ammonium removal at 4°C. Water samples were collected across the length of the retention pond monthly over a year. The structure of the microbial community (bacteria, archaea, and eukarya), as determined by denaturing gradient gel electrophoresis of PCR-amplified small subunit ribosomal RNA genes, was more stable during cold months than during July–September, when there was a marked phytoplankton bloom. Of the ammonia-oxidizing community, only bacterial amoA genes were consistently detected. Zeolite (10?g) was added to retention pond water (100?mL) amended with 5?mM ammonium and incubated at 12°C to encourage development of a nitrifying biofilm. The biofilm community was composed of different amoA phylotypes from those identified in gene clone libraries of native water samples. Zeolite biofilm was added to fresh water samples collected at different times of the year, resulting in a significant increase in laboratory measurements of potential nitrification activity at 4°C. A significant positive correlation between the amount of zeolite biofilm and potential nitrification activity was observed; rates were unaffected in incubations containing 1–20?mM ammonium. Addition of zeolite to retention ponds in cold environments could effectively increase nitrification rates year-round by concentrating active nitrifying biomass. PMID:22866052

Miazga-Rodriguez, Misha; Han, Sukkyun; Yakiwchuk, Brian; Wei, Kai; English, Colleen; Bourn, Steven; Bohnert, Seth; Stein, Lisa Y.

2012-01-01

272

The Bell Curve  

NSDL National Science Digital Library

This lesson is designed to introduce students to the normal distribution or bell curve. The lesson also discusses controversy behind the interpretation of the bell curve. This lesson provides links to discussions and activities related to the normal distribution as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with the current one.

2011-05-23

273

Water  

MedlinePLUS

... the 1986 and 1996 amendments to the Safe Drinking Water Act ( http://www.epa.gov/safewater/sdwa/index. ... You cannot see, taste, or smell lead in drinking water. Therefore, you must ask your water provider whether ...

274

Water  

MedlinePLUS

... to groundwater (the fresh water found under the Earth’s surface that supplies wells and springs). Everything that ... body is water. 4. How much of the earth’s surface is water? About 80 percent of the ...

275

Highly curved microchannel plates  

NASA Technical Reports Server (NTRS)

Several spherically curved microchannel plate (MCP) stack configurations were studied as part of an ongoing astrophysical detector development program, and as part of the development of the ALEXIS satellite payload. MCP pairs with surface radii of curvature as small as 7 cm, and diameters up to 46 mm have been evaluated. The experiments show that the gain (greater than 1.5 x 10 exp 7) and background characteristics (about 0.5 events/sq cm per sec) of highly curved MCP stacks are in general equivalent to the performance achieved with flat MCP stacks of similar configuration. However, gain variations across the curved MCP's due to variations in the channel length to diameter ratio are observed. The overall pulse height distribution of a highly curved surface MCP stack (greater than 50 percent FWHM) is thus broader than its flat counterpart (less than 30 percent). Preconditioning of curved MCP stacks gives comparable results to flat MCP stacks, but it also decreases the overall gain variations. Flat fields of curved MCP stacks have the same general characteristics as flat MCP stacks.

Siegmund, O. H. W.; Cully, S.; Warren, J.; Gaines, G. A.; Priedhorsky, W.; Bloch, J.

1990-01-01

276

Knowledge Retention after an Online Tutorial: A Randomized Educational Experiment among Resident Physicians  

PubMed Central

BACKGROUND The time course of physicians’ knowledge retention after learning activities has not been well characterized. Understanding the time course of retention is critical to optimizing the reinforcement of knowledge. DESIGN Educational follow-up experiment with knowledge retention measured at 1 of 6 randomly assigned time intervals (0–55 days) after an online tutorial covering 2 American Diabetes Association guidelines. PARTICIPANTS Internal and family medicine residents. MEASUREMENTS Multiple-choice knowledge tests, subject characteristics including critical appraisal skills, and learner satisfaction. RESULTS Of 197 residents invited, 91 (46%) completed the tutorial and were randomized; of these, 87 (96%) provided complete follow-up data. Ninety-two percent of the subjects rated the tutorial as “very good” or “excellent.” Mean knowledge scores increased from 50% before the tutorial to 76% among those tested immediately afterward. Score gains were only half as great at 3–8 days and no significant retention was measurable at 55 days. The shape of the retention curve corresponded with a 1/4-power transformation of the delay interval. In multivariate analyses, critical appraisal skills and participant age were associated with greater initial learning, but no participant characteristic significantly modified the rate of decline in retention. CONCLUSIONS Education that appears successful from immediate posttests and learner evaluations can result in knowledge that is mostly lost to recall over the ensuing days and weeks. To achieve longer-term retention, physicians should review or otherwise reinforce new learning after as little as 1 week. Electronic supplementary material The online version of this article (doi:10.1007/s11606-008-0604-2) contains supplementary material, which is available to authorized users. PMID:18446414

Harless, Charles E.; Higa, Jerilyn K.; Bjork, Elizabeth L.; Bjork, Robert A.; Bazargan, Mohsen; Mangione, Carol M.

2008-01-01

277

Rigidity and retention of ceramic root canal posts.  

PubMed

Ceramic root-canal posts offer potential advantages over other types with respect to aesthetics and biocompatibility. Any post must be sufficiently rigid and retentive to withstand functional forces. Ceraposts (1.2 mm coronal diameter, ceramic, tapering, smooth posts) and Paraposts (1.25 mm, stainless-steel, parallel, serrated posts) were tested for rigidity by means of a three-point bending test. To test retention in roots, ceramic posts were cemented using one of three protocols: (1) glass-ionomer cement, (2) silane coupling agent and resin cement, or (3) sandblasted post surface, silane coupling agent, and resin cement. Stainless-steel posts were cemented with resin. The tensile force required to dislodge the posts, following four weeks of storage in water, was recorded. Data were compared using Student's t-test and Mann-Whitney U analysis. Ceraposts were significantly more rigid than Paraposts (p < 0.001). Paraposts cemented with resin were significantly more strongly retained than Ceraposts following any cementation protocol (p < 0.001). Retention of the ceramic posts was significantly greater with a silane coupling agent and resin cement than with glass-ionomer cement (p < 0.001). Sandblasting the ceramic posts produced variable results and needs further investigation before it could be recommended. PMID:11203820

Purton, D G; Love, R M; Chandler, N P

2000-01-01

278

Evaluation of the retention of endodontic implants.  

PubMed

The study investigated the retentive strength of endodontic implants measured by forced removal (pull-out or push-out tests) as a function of implant design and cement type. Smooth-tapered, threaded, and an innovative porous-surfaced implant were evaluated. Specimens were cemented in single-rooted human teeth with five different cements: zinc phosphate, polycarboxylate, glass ionomer, silicophosphate, or AH-26. The results indicated superior retention for the threaded and porous-surfaced implants, and stronger retention with glass-ionomer and AH-26 cements. PMID:3162990

Maniatopoulos, C; Pilliar, R M; Smith, D C

1988-04-01

279

VAPOR-PHASE TRANSPORT OF TRICHLOROETHENE IN AN INTERMEDIATE-SCALE VADOSE-ZONE SYSTEM: RETENTION PROCESSES AND TRACER-BASED PREDICTION  

PubMed Central

Gas-phase miscible-displacement experiments were conducted using a large weighing lysimeter to evaluate retention processes for volatile organic compounds (VOCs) in water-unsaturated (vadoze-zone) systems, and to test the utility of gas-phase tracers for predicting VOC retardation. Trichloroethene (TCE) served as a model VOC, while trichlorofluoromethane (CFM) and heptane were used as partitioning tracers to independently characterize retention by water and the air-water interface, respectively. Retardation factors for TCE ranged between 1.9 and 3.5, depending on water content. The results indicate that dissolution into the bulk water was the primary retention mechanism for TCE under all conditions studied, contributing approximately two thirds of the total measured retention. Accumulation at the air-water interface comprised a significant fraction of the observed retention for all experiments, with an average contribution of approximately 24%. Sorption to the solid phase contributed approximately 10% to retention. Water contents and air-water interfacial areas estimated based on the CFM and heptane tracer data, respectively, were similar to independently measured values. Retardation factors for TCE predicted using the partitioning-tracer data were in reasonable agreement with the measured values. These results suggest that gas-phase tracer tests hold promise for characterizing the retention and transport of VOCs in the vadose-zone. PMID:23333418

Costanza-Robinson, Molly S.; Carlson, Tyson D.; Brusseau, Mark L.

2013-01-01

280

Understanding mixed-mode retention mechanisms in liquid chromatography with hydrophobic stationary phases.  

PubMed

The chromatographic retention mechanisms of two hydrophobic bonded phases, octadecyl ethyl-bridged organic/inorganic (BEH-C18) and straight-chain perfluorohexylpropyl silica (C6F13), have been investigated by using a homologous series of alkyl-benzenes and perfluoroalkyl acids as test compounds in a variety of acetonitrile/water mobile phases and at different temperatures. On both columns, polar compounds exhibited a characteristic U-shape retention behavior in function of acetonitrile amount in the eluent, whereas retention of neutral molecules decreased continuously, following an increase of organic modifier, over the entire mobile phase range. The dependence of perfluoromethylene selectivity upon eluent composition explains the typical reversed-phase behavior (decreasing in retention following an increase of acetonitrile in mobile phase) initially exhibited by perfluoroalkyl acids, but alone it cannot justify their increasing of retention at organic-rich mobile phases (approximately >90% v/v for acetonitrile with the C6F13 column and acetonitrile >80% v/v for the BEH-C18 one). It actually predicts an opposite trend, indicating thus the presence of mixed-mode retention mechanisms. Indeed it was found that, at organic-rich mobile phases, the transfer from the mobile to the stationary phase of the polar moiety of molecules drives retention. This finding has been correlated to the excess adsorption isotherm of acetonitrile/water binary mixtures and thus to the composition of the stationary phase. At organic-rich mobile phases, in fact, stationary phases are characterized by a positive excess of adsorbed water that creates an "environment" suitable to the transfer herein of polar groups. PMID:24725093

Cavazzini, Alberto; Marchetti, Nicola; Guzzinati, Roberta; Pasti, Luisa; Ciogli, Alessia; Gasparrini, Francesco; Laganà, Aldo

2014-05-20

281

Short-Term Effects of Grade Retention on the Growth Rate of Woodcock-Johnson III Broad Math and Reading Scores  

PubMed Central

We investigated the effects of grade retention in first grade on the growth of the Woodcock-Johnson broad mathematics and reading scores over three years using linear growth curve modeling on an academically at-risk sample. A large sample (n = 784) of first grade children who were at risk for retention were initially identified based on low literacy scores. Scores representing propensity for retention were constructed based on 72 variables collected in comprehensive baseline testing in first grade. We closely matched 97 pairs of retained and promoted children based on their propensity scores using optimal matching procedures. This procedure adjusted for baseline differences between the retained and promoted children. We found that grade retention decreased the growth rate of mathematical skills but had no significant effect on reading skills. In addition, several potential moderators of the effect of retention on growth of mathematical and reading skills were identified including limited English language proficiency and children's conduct problems. PMID:19083352

Wu, Wei; West, Stephen G.; Hughes, Jan N.

2008-01-01

282

5 CFR 293.404 - Retention schedule.  

Code of Federal Regulations, 2011 CFR

...Service accepts a Presidential appointment pursuant to 5 U.S.C...employed under that Presidential appointment. When the appointment ends, and the individual...necessary beyond the retention schedules identified in...

2011-01-01

283

5 CFR 293.404 - Retention schedule.  

Code of Federal Regulations, 2010 CFR

...Service accepts a Presidential appointment pursuant to 5 U.S.C...employed under that Presidential appointment. When the appointment ends, and the individual...necessary beyond the retention schedules identified in...

2010-01-01

284

Tritium retention and removal on TFTR  

SciTech Connect

Tritium retention and removal are critical issues for the success of ITER or any DT fusion reactor. The Tokamak Fusion Test Reactor, TFTR, is the first fusion facility to afford the opportunity to study the tritium retention and removal over an extended period. In TFTR, tritium accumulates on all surfaces with line of sight to the plasma by codeposition of tritium with carbon. Measurements of both deuterium and tritium retention fractions have yielded retention between 0.2 and 0.6 of the injected fuel in the torus. Tritium has been successfully removed from TFTR by glow discharge cleaning and by air purges. The in-vessel inventory was reduced by a factor of 2, facilitating machine maintenance. In TFTR, the amount of dust recovered from the TFTR vacuum vessel has varied from several grams to a few kilograms.

Mueller, D.; Blanchard, W. [Princeton Plasma Physics Lab., NJ (United States); Doyle, B.L. [Sandia National Labs., Albuquerque, NM (United States)] [and others

1997-10-01

285

7 CFR 4280.136 - Minimum retention.  

Code of Federal Regulations, 2010 CFR

...BUSINESS-COOPERATIVE SERVICE AND RURAL UTILITIES SERVICE, DEPARTMENT OF AGRICULTURE LOANS AND GRANTS Renewable Energy Systems and Energy Efficiency Improvements Program Section B. Guaranteed Loans § 4280.136 Minimum retention....

2010-01-01

286

12 CFR 226.25 - Record retention.  

Code of Federal Regulations, 2011 CFR

...Section 226.25 Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM TRUTH IN LENDING (REGULATION Z) Miscellaneous § 226.25 Record retention. (a) General rule. A creditor...

2011-01-01

287

12 CFR 226.25 - Record retention.  

Code of Federal Regulations, 2010 CFR

...Section 226.25 Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM TRUTH IN LENDING (REGULATION Z) Miscellaneous § 226.25 Record retention. (a) General rule. A creditor...

2010-01-01

288

12 CFR 226.25 - Record retention.  

Code of Federal Regulations, 2013 CFR

... Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM (CONTINUED) TRUTH IN LENDING (REGULATION Z) Miscellaneous § 226.25 Record retention. (a) General rule. A creditor...

2013-01-01

289

21 CFR 107.280 - Records retention.  

Code of Federal Regulations, 2010 CFR

...HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION INFANT FORMULA Infant Formula Recalls § 107.280 Records retention. Each manufacturer of an infant formula shall make and retain such records respecting the...

2010-04-01

290

19 CFR 10.308 - Records retention.  

Code of Federal Regulations, 2013 CFR

...CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Canada Free Trade Agreement § 10.308 Records retention. ...or who knowlingly causes to be exported, any merchandise to Canada shall make, keep, and render for examination and...

2013-04-01

291

19 CFR 10.308 - Records retention.  

...CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Canada Free Trade Agreement § 10.308 Records retention. ...or who knowlingly causes to be exported, any merchandise to Canada shall make, keep, and render for examination and...

2014-04-01

292

19 CFR 10.308 - Records retention.  

Code of Federal Regulations, 2011 CFR

...CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Canada Free Trade Agreement § 10.308 Records retention. ...or who knowlingly causes to be exported, any merchandise to Canada shall make, keep, and render for examination and...

2011-04-01

293

10 CFR 490.810 - Record retention.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Record retention. 490.810 Section 490.810 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ALTERNATIVE FUEL TRANSPORTATION PROGRAM Alternative Compliance § 490.810 Record...

2012-01-01

294

10 CFR 490.810 - Record retention.  

...2014-01-01 2014-01-01 false Record retention. 490.810 Section 490.810 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ALTERNATIVE FUEL TRANSPORTATION PROGRAM Alternative Compliance § 490.810 Record...

2014-01-01

295

10 CFR 490.810 - Record retention.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Record retention. 490.810 Section 490.810 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ALTERNATIVE FUEL TRANSPORTATION PROGRAM Alternative Compliance § 490.810 Record...

2013-01-01

296

10 CFR 490.810 - Record retention.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Record retention. 490.810 Section 490.810 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ALTERNATIVE FUEL TRANSPORTATION PROGRAM Alternative Compliance § 490.810 Record...

2011-01-01

297

10 CFR 490.810 - Record retention.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Record retention. 490.810 Section 490.810 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ALTERNATIVE FUEL TRANSPORTATION PROGRAM Alternative Compliance § 490.810 Record...

2010-01-01

298

Nitrogen inputs, ouptut, and retention in a coastal suburban basin  

NASA Astrophysics Data System (ADS)

Understanding the biogeochemistry of suburban basins is becoming increasingly important due to the rapidly accelerating suburban sprawl in many parts of the US. In southeastern New Hampshire, population density is expected to increase by 50% over 20 years, and most of the development will occur as low-density suburban home lots with wells and on-site waste disposal. We measured the N inputs, outputs, and loss/storage in a 470 sq km basin, the Lamprey River of coastal New Hampshire. Atmospheric deposition and food imported into the basin were both significant inputs, and totaled 13 kg/ha/yr. Output was 0.6 kg/ha/yr, for a net loss/retention of 95% of inputs. Net retention among various sub-watersheds of the Lamprey ranged from 50 to 98%. Because the Lamprey river basin contains a high proportion of wetlands (14% wetlands and open water), has some water courses that undergo periodic oxygen depletion, and has high levels of dissolved organic carbon in surface waters (6 mg/l), in-stream and wetland denitrification may be a major loss pathway for N in the basin. Results from a study of riparian zone biogeochemistry suggest that riparian denitrification may also be a significant loss pathway. Accelerating suburbanization may greatly increase N delivery to the coast if it shortens hydrologic flow paths and decreases wetland coverage while increasing N inputs.

McDowell, W. H.; Daley, M. L.; Gettel, G.

2005-12-01

299

Molecular Mechanisms Controlling GLUT4 Intracellular Retention  

Microsoft Academic Search

ABSTRACT In basal adipocytes GLUT4 is sequestered intracellularly by an insulin-reversible retention mechanism. Here we analyze the roles of three GLUT4 trafficking motifs (FQQI, TELEY and LL), providing molecular links between insulin signaling, cellular trafficking machinery and the motifs in the specialized trafficking of GLUT4. Our resultssupport a GLUT4 retention model that involves two linked intracellular cycles: one between endosomes

Vincent Blot; Timothy E. McGraw

2008-01-01

300

Vermicompost for Tinted Organic Cationic Dyes Retention  

Microsoft Academic Search

The use of vermicompost was expanded as natural adsorbent for cationic dyes retention. The adsorption profiles in batch and\\u000a flow modes for crystal violet and methylene blue on vermicompost material were evaluated. In batch mode, a retention index\\u000a higher than 97% was obtained for both compounds, while in flow condition, 40 g of dried adsorbent material were enough to\\u000a remove 100 mg

Madson de Godoi Pereira; Mauro Korn; Bruno Barros Santos; Marcia Guia Ramos

2009-01-01

301

Transport along null curves  

NASA Astrophysics Data System (ADS)

Fermi transport is useful for describing the behaviour of spins or gyroscopes following non-geodesic, timelike worldlines. However, Fermi transport breaks down for null worldlines. We introduce a transport law for polarization vectors along non-geodesic null curves. We show how this law emerges naturally from the geometry of null directions by comparing polarization vectors associated with two distinct null directions. We then give a spinorial treatment of this topic and make contact with the geometric phase of quantum mechanics. There are two significant differences between the null and timelike cases. In the null case (a) the transport law does not approach a unique smooth limit as the null curve approaches a null geodesic and (b) the transport law for vectors is integrable, i.e. the result depends only on the local properties of the curve and not on the entire path taken. However, the transport of spinors is not integrable: there is a global sign of topological origin.

Samuel, Joseph; Nityananda, Rajaram

2000-04-01

302

Retention time and flow patterns in Lake Marion, South Carolina, 1984  

USGS Publications Warehouse

In 1984, six dye tracer tests were made on Lake Marion to determine flow patterns and retention times under conditions of high and low flow. During the high-flow tests, with an average inflow of about 29,000 cubic feet per second, the approximate travel time through the lake for the peak tracer concentration was 14 days. The retention time was about 20 days. During the low-flow tests, with an average inflow of about 9,000 cubic feet per second, the approximate travel time was 41 days, and the retention time was about 60 days. The primary factors controlling movement of water in the lake are lake inflow and outflow. The tracer cloud moved consistently downstream, slowing as the lake widened. Flow patterns in most of the coves, and in some areas along the northeastern shore, are influenced more by tributary inflow than by factors attributable to water from the main body of the lake.

Patterson, G.G.; Harvey, R.M.

1995-01-01

303

Effects of bioreactor retention time on aerobic microbial decomposition of CELSS crop residues  

NASA Astrophysics Data System (ADS)

The focus of resource recovery research at the KSC-CELSS Breadboard Project has been the evaluation of microbiologically mediated biodegradation of crop residues by manipulation of bioreactor process and environmental variables. We will present results from over 3 years of studies that used laboratory- and breadboard-scale (8 and 120 L working volumes, respectively) aerobic, fed-batch, continuous stirred tank reactors (CSTR) for recovery of carbon and minerals from breadboard grown wheat and white potato residues. The paper will focus on the effects of a key process variable--bioreactor retention time--on response variables indicative of bioreactor performance. The goal is to determine the shortest retention time that is feasible for processing CELSS crop residues, thereby reducing bioreactor volume and weight requirements. Pushing the lower limits of bioreactor retention times will provide useful data for engineers who need to compare biological and physicochemical components. Bioreactor retention times were manipulated to range between 0.25 and 48 days. Results indicate that increases in retention time lead to a 4-fold increase in crop residue biodegradation, as measured by both dry weight losses and CO_2 production. A similar overall trend was also observed for crop residue fiber (cellulose and hemicellulose), with a noticeable jump in cellulose degradation between the 5.3 day and 10.7 day retention times. Water-soluble organic compounds (measured as soluble TOC) were appreciably reduced by more than 4-fold at all retention times tested. Results from a study of even shorter retention times (down to 0.25 days), in progress, will also be presented.

Strayer, R. F.; Finger, B. W.; Alazraki, M. P.

1997-01-01

304

New Curves from Branes  

E-print Network

We consider configurations of Neveu-Schwarz fivebranes, Dirichlet fourbranes and an orientifold sixplane in type IIA string theory. Upon lifting the configuration to M-theory and proposing a description of how to include the effects of the orientifold sixplane we derive the curves describing the Coulomb branch of N=2 gauge theories with orthogonal and symplectic gauge groups, product gauge groups of the form SU(k_1)...SU(k_i) x SO(N) and SU(k_1)...SU(k_i) x Sp(N). We also propose new curves describing theories with unitary gauge groups and matter in the symmetric or antisymmetric representation.

Karl Landsteiner; Esperanza Lopez

1997-08-22

305

New Curves from Branes  

E-print Network

We consider configurations of Neveu-Schwarz fivebranes, Dirichlet fourbranes and an orientifold sixplane in type IIA string theory. Upon lifting the configuration to M-theory and proposing a description of how to include the effects of the orientifold sixplane we derive the curves describing the Coulomb branch of N=2 gauge theories with orthogonal and symplectic gauge groups, product gauge groups of the form SU(k_1)...SU(k_i) x SO(N) and SU(k_1)...SU(k_i) x Sp(N). We also propose new curves describing theories with unitary gauge groups and matter in the symmetric or antisymmetric representation.

Landsteiner, K; Landsteiner, Karl; Lopez, Esperanza

1998-01-01

306

Exploring Area between Curves  

NSDL National Science Digital Library

Calculus texts have problems on finding the Areas between Curves in the chapters on applications of Integration. The NCB suggests finding some of these examples in a text and trying them in Harumi's graph. Experimenting on a computer with the approximation for finding the area using rectangles is fascinating. As the number of rectangles increases, the approximation improves. Therefore, mathematicians define the area A between the two curves as the limit of the sum of the areas of these approximating rectangles where n is the number of rectangles bounded between a and b.

Monroy, Harumi

2006-01-01

307

Transport and retention from single to multiple fractures in crystalline rock at Äspö (Sweden): 2. Fracture network simulations and generic retention model  

NASA Astrophysics Data System (ADS)

Hydrogeologic characterization of crystalline rock formations on the field scale is important for many applications but still presents a multitude of challenges. In this work we use comprehensive hydrostructural information and present a detailed simulation study of flow and advective transport in a discrete fracture network (DFN) that replicates the Tracer Retention Understanding Experiments (TRUE) Block Scale rock volume at the Äspö Hard Rock Laboratory (Sweden). Simulated water residence time ? and hydrodynamic retention parameter ? are used as independent constraints for estimating material retention properties as presented in paper 1 of this series, whereas simulated mean water residence times are compared with observed values. We find that the DFN simulations reproduce water residence times reasonably well, indicating that the characterization data are sufficient and that the DFN model does capture dominant features of the flow paths analyzed. The empirical quadratic law that relates aperture and transmissivity seems to better reproduce calibrated mean water residence times than the theoretical cubic law for the five flow paths. The active specific surface area (?/?) [1/L] as inferred from simulations is used for defining a generic retention model for the dominant rock type (Äspö diorite) that matches fairly well the entire range of calibrated retention parameters of the TRUE tests. The combination of paper 1 and this work provides a general, comprehensive methodology for evaluating tracer test results in crystalline rock where a comparable amount of information is available; critical to this methodology is that tracer tests are carried out using tracers with sufficiently different sorption affinities (of factor 10-100).

Cvetkovic, V.; Frampton, A.

2010-05-01

308

Factorization with genus 2 curves  

NASA Astrophysics Data System (ADS)

The elliptic curve method (ECM) is one of the best factorization methods available. It is possible to use hyperelliptic curves instead of elliptic curves but it is in theory slower. We use special hyperelliptic curves and Kummer surfaces to reduce the complexity of the algorithm. Our implementation GMP-HECM is faster than GMP-ECM for factoring large numbers.

Cosset, Romain

2010-04-01

309

Uncertainty propagation: Curve fitting  

NSDL National Science Digital Library

Students will learn a sample-variance curve fitting method that can be used to determine whether a set of experimental data appears to have been generated by a model. This method is based on minimizing the reduced chi-squared value. This video includes a reminder to inspect normalized residuals before reporting fitted parameters.

2013-06-21

310

New Curves from Branes  

Microsoft Academic Search

We consider configurations of Neveu-Schwarz fivebranes, Dirichlet fourbranes and an orientifold sixplane in type IIA string theory. Upon lifting the configuration to M-theory and proposing a description of how to include the effects of the orientifold sixplane we derive the curves describing the Coulomb branch of N = 2 gauge theories with orthogonal and symplectic gauge groups, product gauge groups

Karl Landsteiner; Esperanza Lopez

311

New curves from branes  

Microsoft Academic Search

We consider configurations of Neveu-Schwarz fivebranes, Dirichlet fourbranes and an orientifold sixplane in type IIA string theory. Upon lifting the configuration to M-theory and proposing a description of how to include the effects of the orientifold sixplane we derive the curves describing the Coulomb branch of N = 2 gauge theories with orthogonal and symplectic gauge groups, product gauge groups

Karl Landsteiner; Esperanza Lopez

1998-01-01

312

Electrostatic curved electrode actuators  

Microsoft Academic Search

This paper presents the design and performance of an electrostatic actuator consisting of a laterally compliant cantilever beam and a fixed curved electrode, both suspended above a ground plane. A theoretical description of the static behavior of the cantilever as it is pulled into contact with the rigid fixed-electrode structure is given. Two models are presented: a simplified semi-analytical model

Rob Legtenberg; John Gilbert; Stephen D. Senturia; Miko Elwenspoek

1997-01-01

313

The Bacterial Growth Curve.  

ERIC Educational Resources Information Center

A procedure that allows students to view an entire bacterial growth curve during a two- to three-hour student laboratory period is described. Observations of the lag phase, logarithmic phase, maximum stationary phase, and phase of decline are possible. A nonpathogenic, marine bacterium is used in the investigation. (KR)

Paulton, Richard J. L.

1991-01-01

314

The Snowflake Curve.  

ERIC Educational Resources Information Center

An unusual shape is considered, and properties and steps in drawing it are detailed. The focus is on development and presentation of a computer program that will draw the curve. The program is written in BASIC with special plotting commands for a Techtronix computer, but is adaptable to other systems. (MP)

Lambert, Tim

1982-01-01

315

Vegetable Light Curves  

NSDL National Science Digital Library

In this activity, students will observe the surface of rotating potatoes to help them understand how astronomers can sometimes determine the shape of asteroids from variations in reflective brightness. When astronomers graph data relating to reflective brightness as a function of time, the resulting graph is called a "light curve."

2009-04-22

316

Graphing Polar Curves  

ERIC Educational Resources Information Center

Graphing polar curves typically involves a combination of three traditional techniques, all of which can be time-consuming and tedious. However, an alternative method--graphing the polar function on a rectangular plane--simplifies graphing, increases student understanding of the polar coordinate system, and reinforces graphing techniques learned…

Lawes, Jonathan F.

2013-01-01

317

Water & Energy Conservation Plan  

E-print Network

Water & Energy Conservation Plan View of PGI construction and retention pond, Sitapura Industrial of Colleges (PGC) in Rajasthan, India suggests measures to mitigate the impending water and energy crisis that India and the college both face. Within, plans are made for the conservation of water and energy

Illinois at Chicago, University of

318

Retention through Intervention: A Strategic Plan for Retention of High-Risk Students.  

ERIC Educational Resources Information Center

In an effort to increase the retention rates of high-risk students in allied health programs, the Medical Campus of Miami-Dade Community College has developed a strategic plan for retention that employs a systems approach to the integration of academic support services, emotional and social supports, and personalized communication. The assumptions…

Mese, Janice H.; Spano, Carleen M.

319

Determining the Chemical and Biological Availability of Zinc in Urban Stormwater Retention Ponds  

Microsoft Academic Search

Highway runoff has the potential to negatively impact receiving systems due to transport of contaminants that accumulate on road surfaces. Metals such as copper and zinc are major components of automobile brake pads and tires, respectively. As these automobile parts are degraded, these metal containing particulates are deposited on the roadway and are washed into storm water retention ponds and

K. Camponelli; R. Casey; S. M. Lev; E. R. Landa; J. Snodgrass

2005-01-01

320

Temporal determinants of long-term retention of olfactory memory in the cricket Gryllus bimaculatus  

Microsoft Academic Search

Temporal determinants of olfactory long-term memory retention in the cricket Gryllus bimaculatus were studied. Elementary appetitive and aversive conditioning procedures, as well as a differential conditioning procedure, were applied. In appetitive conditioning, peppermint odour was paired with a water reward. In aversive conditioning, vanilla odour was paired with saline solution. In differential conditioning, an appetitive conditioning trial was followed by

Yukihisa Matsumoto; Makoto Mizunami

2002-01-01

321

AIRWAY RETENTION OF MATERIALS OF DIFFERENT SOLUBILITY FOLLOWING LOCAL INTRABRONCHIAL DEPOSITION IN DOGS  

EPA Science Inventory

We used a gamma camera to monitor the retention and clearance of radiolabeled human serum albumin (HSA), a water-soluble material with molecular weight of 66,000 Daltons, and radiolabeled sulfur colloid (SC), an insoluble submicron (0.22 microm) particle, following localized depo...

322

Trends in nutrient and sediment retention in Great Plains reservoirs (USA)  

E-print Network

between rivers and lakes. Greater water reten- tion time in reservoirs provides conditions for cycling in the Great Plains (Kansas, USA), an area where little is known about these dominant hydrologic features. We . Multipurpose reservoirs . Nutrient removal . Solids retention Introduction Reservoirs dominate most river

Dodds, Walter

323

Liquid Drops on an Inclined Plane: The Relation between Contact Angles, Drop Shape, and Retentive Force  

Microsoft Academic Search

Contact angle hysteresis, drop shape, and drop retention were studied with a tiltable plane. Contact liquids were water and ethylene glycol. Four polymers and silicon wafers were used as substrates. When the plane was inclined, the shape of drops distorted, exhibiting advancing and receding contact angles. Drops remained stationary until a critical angle of tilt was exceeded, and then they

Charles W. Extrand; Y. Kumagai

1995-01-01

324

Retention of Antioxidant Activity in Minimally Processed Mandarin and Satsuma Fruits  

Microsoft Academic Search

Changes in overall antioxidant activity of the water-soluble fraction of some mandarin derivatives were studied. In particular, fresh juices and segments packaged with two plastic films having different permeability were considered. The evolution of antioxidant properties as affected by processing and storage conditions were not entirely related to ascorbic acid changes. Mandarin juices showed good retention of the original antioxidant

A. Piga; M. Agabbio; F. Gambella; M. C. Nicoli

2002-01-01

325

Multivariate curve resolution in liquid chromatography  

SciTech Connect

Self-modeling curve resolution has been shown to allow resolution of two co-eluting chromatographic peaks without requiring any assumption of an underlying peak shape. The subsequent problem of quantitation of these co-eluting peaks is limited by both the chromatographic resolution (separation in time and difference in elution profile) and by the degree of spectral uniqueness. An experimental system of two water-soluble vitamins has been used to examine the effects of varying chromatographic resolution on the quantitative accuracy of the curve resolution method.

Osten, D.W.; Kowalski, B.R.

1983-12-01

326

Trishear for curved faults  

NASA Astrophysics Data System (ADS)

Fault-propagation folds form an important trapping element in both onshore and offshore fold-thrust belts, and as such benefit from reliable interpretation. Building an accurate geologic interpretation of such structures requires palinspastic restorations, which are made more challenging by the interplay between folding and faulting. Trishear (Erslev, 1991; Allmendinger, 1998) is a useful tool to unravel this relationship kinematically, but is limited by a restriction to planar fault geometries, or at least planar fault segments. Here, new methods are presented for trishear along continuously curved reverse faults defining a flat-ramp transition. In these methods, rotation of the hanging wall above a curved fault is coupled to translation along a horizontal detachment. Including hanging wall rotation allows for investigation of structures with progressive backlimb rotation. Application of the new algorithms are shown for two fault-propagation fold structures: the Turner Valley Anticline in Southwestern Alberta, and the Alpha Structure in the Niger Delta.

Brandenburg, J. P.

2013-08-01

327

Water  

NSDL National Science Digital Library

This tutorial examines the importance of water to Earth's ecosystems. Topics include the sources and distribution of water, the water cycle, and how snow and rain occur. There is a discussion of the phases in which it can exist (solid, liquid, or vapor), and a description of how animals adapt to cold snowy environments in the winter. Examples include burrowing, hibernation, migration, and thick fur. A quiz and glossary are included.

328

The laparoscopic learning curve.  

PubMed

To characterize the learning curve for laparoscopic cholecystectomy, we compared the first 47 cases (group A), which were performed by two senior attending surgeons who assisted each other when the procedure was introduced into clinical practice (1990-1991), with the first 46 cases (group R) performed by two surgical chief residents who were assisted by members of the teaching faculty in 1992-1993. The patient groups were comparable in terms of age, sex, and anesthetic class, but pathologically proven acute cholecystitis was more common in group R (33% vs. 9%; p < 0.005). To analyze operative procedures and outcomes, we compared operative time, frequency of successful operative cholangiography (attempted in all cases), frequency of conversion to open cholecystectomy, major complication rate, and days of postoperative stay for all patients and for those without complications. Of these parameters, only operative time for nonacute cases differed significantly between the groups (144 min for group A vs. 114 min for group R; p < 0.05). Complications in group A included one ductal injury and one case of postoperative pancreatitis; group R had one ductal injury and two cases of postoperative bleeding. We conclude that (a) the learning curve has similar structure for senior surgeons and resident trainees; and (b) the resident learning curve is not hazardous when teaching assistants are trained in the procedure, which has implications for safe instruction and proctoring of residents and staff. PMID:8611992

Lekawa, M; Shapiro, S J; Gordon, L A; Rothbart, J; Hiatt, J R

1995-12-01

329

Tritium recycling and retention in JET  

NASA Astrophysics Data System (ADS)

JET's 1997 Deuterium Tritium Experiment (DTE1) allows a detailed study of hydrogenic isotope recycling and retention in a pumped divertor configuration relevant to ITER. There appear to be two distinct forms of retained tritium. (1) A dynamic inventory which controls the fueling behaviour of a single discharge, and in particular determines the isotopic composition. This is shown to be consistent with neutral particle implantation over the whole vessel surface area. (2) A continually growing inventory, which plays a small role in the particle balance of a single discharge, but ultimately dominates the hydrogenic inventory for an experimental campaign comprising thousands of pulses. This will be the dominant retention mechanism in long-pulse devices like ITER. The JET retention scaled-up to ITER proportions suggests that ITER may reach its tritium inventory limit in less than 100 pulses.

Andrew, P.; Brennan, D.; Coad, J. P.; Ehrenberg, J.; Gadeberg, M.; Gibson, A.; Groth, M.; How, J.; Jarvis, O. N.; Jensen, H.; Lässer, R.; Marcus, F.; Monk, R.; Morgan, P.; Orchard, J.; Peacock, A.; Pearce, R.; Pick, M.; Rossi, A.; Schunke, B.; Stamp, M.; von Hellermann, M.; Hillis, D. L.; Hogan, J.

330

Nitrogen Saturation in Highly Retentive Watersheds?  

NASA Astrophysics Data System (ADS)

Watershed managers are often concerned with minimizing the amount of N delivered to N-limited estuaries and coastal zones. A major concern is that watersheds might reach N saturation, in which N delivered to coastal zones increases due to declines in the efficiency of N retention despite constant or even reduced N inputs. We have quantified long-term changes in N inputs (atmospheric deposition, imported food and agricultural fertilizers), outputs (N concentration and export) and retention in the urbanizing Lamprey River watershed in coastal NH. Overall, the Lamprey watershed is 70% forested, receives about 13.5 kg N/ha/yr and has a high rate of annual N retention (85%). Atmospheric deposition (8.7 kg/ha/yr) is the largest N input to the watershed. Of the 2.2 kg N/ha/yr exported in the Lamprey River, dissolved organic N (DON) is the dominant form (50% of total) and it varies spatially throughout the watershed with wetland cover. Nitrate accounts for 30% of the N exported, shows a statistically significant increase from 1999 to 2009, and its spatial variability in both concentration and export is related to human population density. In sub-basins throughout the Lamprey, inorganic N retention is high (85-99%), but the efficiency of N retention declines sharply with increased human population density and associated anthropogenic N inputs. N assimilation in the vegetation, denitrification to the atmosphere and storage in the groundwater pool could all be important contributors to the current high rates of N retention. The temporal and spatial patterns that we have observed in nitrate concentration and export are driven by increases in N inputs and impervious surfaces over time, but the declining efficiency of N retention suggests that the watershed may also be reaching N saturation. The downstream receiving estuary, Great Bay, already suffers from low dissolved oxygen levels and eelgrass loss in part due to N loading from the Lamprey watershed. Targeting and reducing anthropogenic sources of N that are not retained in the watershed and maintaining high rates of N retention will be of utmost concern for coastal managers.

Daley, M. L.; McDowell, W. H.

2009-12-01

331

Laparoscopic Treatment of Ovarian Retention Pathology  

PubMed

We define ovarian retention pathology as the complications (cystic, degenerative, adhesions, endometriosis, pain, etc.) attributed to ovaries deliberately retained at the time of hysterectomy. We established a protocol for laparoscopy in these women. During 14 laparoscopic procedures for ovarian retention pathology, only one intraoperative complication occurred, a small bowel injury requiring minilaparotomy. One woman required repeat surgery for ovarian remnant syndrome. Published experience with laparotomy suggests that significant injuries to or resections of bowel, bladder, or ureters can occur, but the limited experience with laparoscopic surgery has not shown significant complications. PMID:9074105

Dionisi; Dionisi; Dionisi

1996-08-01

332

Modeling of Tritium Retention in TFTR  

SciTech Connect

The Tokamak Fusion Test Reactor (TFTR) tritium retention experience is reviewed and the data related to models of plasma surface interactions. Over 3.5 years of TFTR deuterium-tritium operations, approximately 51% of the tritium injected into TFTR was retained in the torus. Most of this was subsequently recovered by glow discharges and air ventilation. Co-deposition rates for representative conditions in tritium operation were modeled with the BBQ code. The calculations indicate that known erosion mechanisms and subsequent co-deposition are sufficient to account for the order of magnitude of retention.

Blanchard, W.; Brooks, J.N.; Budny, R.V.; Hogan, J.T.; Hosea, J.; Skinner, C.H.; et al.

1998-08-19

333

Water  

NSDL National Science Digital Library

This video segment from IdahoPTV's D4K shows us from where we get water, how it's stored and how powerful it can be. We learn how important it is to conserve the .3% of usable fresh water available on earth.

Idaho PTV

2011-10-06

334

Water  

NSDL National Science Digital Library

The same water that has existed on Earth for millions of years travels through a series of steps in a cycle from mountains to the sea, flows in and out of the cells in your body, and comprises 95% of the mass of a jellyfish. In short, water is the connect

Frederick, J. A.; Blake Jr., Robert W.; Haines, Sarah; Lee, Stephanie C.

2010-02-01

335

Least Limiting Water Range of soils in the Colonia Agrícola de Turen, Venezuela  

NASA Astrophysics Data System (ADS)

Soil physical degradation is a major problem affecting the soil quality for crops production in Venezuelan agricultural areas. The least limiting water range (LLWR) is considered a soil physical quality index defined as the range in soil water content within which the limitations to plant response associated with water potential, poor aeration and high mechanical resistance are minimal. The study was carried out to characterize the LLWR and to determine the LLWR response to structural changes on soils of the Colonia Agricola de Turen, Venezuela. The soils were cropped with maize under different tillage systems (no tillage, conventional and conventional - fallow) and non-cropped under native forest. Hundred and seventy undisturbed samples were taken from specific sites under each of the above soil conditions to determine the water retention curve, the soil resistance curve and bulk density. Disturbed samples were also taken from each site to determine particle size and organic matter content. Pedotransfer functions relating the water retention curve and soil resistance curve with particle size distribution, organic matter content and bulk density were developed and use to calculate the LLWR for each site. According to the results, soil physical degradation under conventional tillage and high clay content had the highest negative impact on the LLWR. For this case (silty clay loam soil), the LLWR became narrower due to the lower water content associated with poor aeration and the higher water content associated with high mechanical resistance. In contrast, for non degraded soils with high sand content (sandy loam) the LLWR showed the highest values associated with the water content at field capacity and the water content at permanent wilting point, both the upper and lower critical limits of LLWR. For silty loam and loam soils the LLWR declined with increasing bulk density and clay content associated with water content at field capacity and water content at high mechanical resistance. Soil resistance to root penetration determined the lower limit of LLWR in 41 % of the soils and the water content at field capacity determined the upper limit of LLWR in 94% of the soils. Further studies are recommended to determine the nature and magnitude of the association between the LLWR and crop yield under different soils and climate conditions.

Perez, Maiby Yolanda; Florentino de Andreu, Adriana

2013-04-01

336

Retention and remobilization dynamics of fine particles and microorganisms in pastoral streams.  

PubMed

Both microbial metabolism and pathogen retention and remobilization are dependent on downstream transport of fine particles, which migrate in a series of deposition and resuspension events. All fine particles, including clay minerals, particulate organic carbon, nutrients and microbes, are often considered to be transported similarly in the environment because of a lack of specific observations comparing their relative transport. We conducted a tracer injection study to compare the transport and retention of the fecal indicator bacterium Escherichia coli, synthetic inert fluorescent fine particles, and a dissolved conservative tracer. We found that the fluorescent fine particles and bacteria were transported similarly, with both having greater retention than the solute tracer. We used a stochastic model to evaluate in-stream retention and migration of the solute, fluorescent particles, and E. coli. The best-fit model parameters indicate that different stream reaches had varied retention characteristics, but always showed greater retention of fluorescent particles and E. coli compared to the solute tracer. Direct measurements within known retention areas after the injection showed that the majority of the fluorescent particles and E. coli were retained near the sediment-water interface in macrophyte stands or filtered within the top 3 cm of the streambed sediment. Both the tracer particles and E. coli were retained within these regions for multiple months following the injection experiment. The stochastic model properly captured the wide range of storage timescales and processes we observed in the stream. Our results demonstrate the importance of the streambed sediment and in-stream macrophytes as short- and long-term reservoirs for fine organic particles and microbes in streams. PMID:25243658

Drummond, J D; Davies-Colley, R J; Stott, R; Sukias, J P; Nagels, J W; Sharp, A; Packman, A I

2014-12-01

337

Grazing and no-till cropping impacts on nitrogen retention in dryland agroecosystems.  

PubMed

As the world's population increases, marginal lands such as drylands are likely to become more important for food production. One proven strategy for improving crop production in drylands involves shifting from conventional tillage to no-till to increase water use efficiency, especially when this shift is coupled with more intensive crop rotations. Practices such as no-till that reduce soil disturbance and increase crop residues may promote C and N storage in soil organic matter, thus promoting N retention and reducing N losses. By sampling soils 15 yr after a N tracer addition, this study compared long-term soil N retention across several agricultural management strategies in current and converted shortgrass steppe ecosystems: grazed and ungrazed native grassland, occasionally mowed planted perennial grassland, and three cropping intensities of no-till dryland cropping. We also examined effects of the environmental variables site location and topography on N retention. Overall, the long-term soil N retention of >18% in these managed semiarid ecosystems was high compared with published values for other cropped or grassland ecosystems. Cropping practices strongly influenced long-term N retention, with planted perennial grass systems retaining >90% of N in soil compared with 30% for croplands. Grazing management, topography, and site location had smaller effects on long-term N retention. Estimated 15-yr N losses were low for intact and cropped systems. This work suggests that semiarid perennial grass ecosystems are highly N retentive and that increased intensity of semiarid land management can increase the amount of protein harvested without increasing N losses. PMID:25602213

Mobley, Megan L; McCulley, Rebecca L; Burke, Ingrid C; Peterson, Gary; Schimel, David S; Cole, C Vernon; Elliott, Edward T; Westfall, Dwayne G

2014-11-01

338

Digital Jordan Curve Theorems Christer O. Kiselman  

E-print Network

Digital Jordan Curve Theorems Christer O. Kiselman's digital Jordan curve theorem states that the complement of a Jordan curve in the digital plane of Jordan curves. 1 Introduction The classical Jordan curve theorem says that the complement

Kiselman, Christer

339

Correlated Moisture Content, Pressure and Temperature Data for Development of Hysteretic Moisture Retention Curves  

Microsoft Academic Search

This study was performed as the first part of an effort to collect high quality, repeatable, hydrologic data in a laboratory environment to provide a sound basis for future macropore model development, validation, and calibration. The objective of the experiment was to study the hysteretic function (drainage\\/wetting\\/scanning) of soils and the role of hysteresis in fluid transport. Our hysteretic dataset

J. J. Little; J. A. Tindall; M. Friedel

2004-01-01

340

Seed Implant Retention Score Predicts the Risk of Prolonged Urinary Retention After Prostate Brachytherapy  

SciTech Connect

Purpose: To risk-stratify patients for urinary retention after prostate brachytherapy according to a novel seed implant retention score (SIRS). Patients and Methods: A total of 835 patients underwent transperineal prostate seed implant from March 1993 to January 2007; 197 patients had {sup 125}I and 638 patients had {sup 103}Pd brachytherapy. Four hundred ninety-four patients had supplemental external-beam radiation. The final downsized prostate volume was used for the 424 patients who had neoadjuvant hormone therapy. Retention was defined as reinsertion of a Foley catheter after the implant. Results: Retention developed in 7.4% of patients, with an average duration of 6.7 weeks. On univariate analysis, implant without supplemental external-beam radiation (10% vs. 5.6%; p = 0.02), neoadjuvant hormone therapy (9.4% vs. 5.4%; p = 0.02), baseline alpha-blocker use (12.5% vs. 6.3%; p = 0.008), and increased prostate volume (13.4% vs. 6.9% vs. 2.9%, >45 cm{sup 3}, 25-45 cm{sup 3}, <25 cm{sup 3}; p = 0.0008) were significantly correlated with increased rates of retention. On multivariate analysis, implant without supplemental external-beam radiation, neoadjuvant hormone therapy, baseline alpha-blocker use, and increased prostate volume were correlated with retention. A novel SIRS was modeled as the combined score of these factors, ranging from 0 to 5. There was a significant correlation between the SIRS and retention (p < 0.0001). The rates of retention were 0, 4%, 5.6%, 9%, 20.9%, and 36.4% for SIRS of 0 to 5, respectively. Conclusions: The SIRS may identify patients who are at high risk for prolonged retention after prostate brachytherapy. A prospective validation study of the SIRS is planned.

Lee, Hoon K., E-mail: Dr.Hoon@gmail.co [Regional Radiation Oncology, Staten Island, NY (United States); Department of Radiation Oncology, Richmond University Medical Center, Staten Island, NY (United States); Adams, Marc T. [Regional Radiation Oncology, Staten Island, NY (United States); Department of Radiation Oncology, Richmond University Medical Center, Staten Island, NY (United States); Shi, Qiuhu [Department of Biostatistics, School of Public Health, New York Medical School, Valhalla, NY (United States); Basillote, Jay; LaMonica, Joanne; Miranda, Luis; Motta, Joseph [Department of Urology, Richmond University Medical Center, Staten Island, NY (United States)

2010-04-15

341

Influence of pH on Phosphorus Retention in Oxidized Lake Sediments O. G. Olila* and K. R. Reddy  

E-print Network

Influence of pH on Phosphorus Retention in Oxidized Lake Sediments O. G. Olila* and K. R. Reddy ABSTRACT Diel pH changes in lake waters resulting from high photosynthetic activity may regulate water studies were conducted to determine the pH effect on P fractions and P sorption kinetics in oxidized

Florida, University of

342

Effect of polymers on the retention and aging of enzyme on bioactive papers.  

PubMed

The effect of polymer on the retention and the thermal stability of bioactive enzymatic papers was measured using a colorimetric technique quantifying the intensity of the enzyme-substrate product complex. Alkaline phosphatase (ALP) was used as model enzyme. Three water soluble polymers: a cationic polyacrylamide (CPAM), an anionic polyacrylic acid (PAA) and a neutral polyethylene oxide (PEO) were selected as retention aids. The model polymers increased the enzyme adsorption on paper by around 50% and prevented enzyme desorption upon rewetting of the papers. The thermal deactivation of ALP retained on paper with polymers follows two sequential first order reactions. This was also observed for ALP simply physisorbed on paper. The retention aid polymers instigated a rapid initial deactivation which significantly decreased the longevity of the enzymatic papers. This suggests some enzyme-polymer interaction probably affecting the enzyme tertiary structure. A deactivation mathematical model predicting the enzymatic paper half-life was developed. PMID:20417074

Khan, Mohidus Samad; Haniffa, Sharon B M; Slater, Alison; Garnier, Gil

2010-08-01

343

WATER AND ATRAZINE MOVEMENT IN A CALCAREOUS COMPOST APPLIED SOIL DURING SIMULATED MULTIPLE STORM EVENTS.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Agricultural soils in the region are mainly composed of crushed limestone, which has a low water and chemical retention capacity. Therefore, sustaining a profitable agricultural system requires appropriate applications of fertilizer, pesticides and irrigation. The retention and transport of atrazi...

344

Strong Agreement of Nationally Recommended Retention Measures from the Institute of Medicine and Department of Health and Human Services  

PubMed Central

Objective We sought to quantify agreement between Institute of Medicine (IOM) and Department of Health and Human Services (DHHS) retention indicators, which have not been compared in the same population, and assess clinical retention within the largest HIV cohort collaboration in the U.S. Design Observational study from 2008–2010, using clinical cohort data in the North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD). Methods Retention definitions used HIV primary care visits. The IOM retention indicator was: ?2 visits, ?90 days apart, each calendar year. This was extended to a 2-year period; retention required meeting the definition in both years. The DHHS retention indicator was: ?1 visit each semester over 2 years, each ?60 days apart. Kappa statistics detected agreement between indicators and C statistics (areas under Receiver-Operating Characteristic curves) from logistic regression analyses summarized discrimination of the IOM indicator by the DHHS indicator. Results Among 36,769 patients in 2008–2009 and 34,017 in 2009–2010, there were higher percentages of participants retained in care under the IOM indicator than the DHHS indicator (80% vs. 75% in 2008–2009; 78% vs. 72% in 2009–2010, respectively) (p<0.01), persisting across all demographic and clinical characteristics (p<0.01). There was high agreement between indicators overall (??=?0.83 in 2008–2009; ??=?0.79 in 2009–2010, p<0.001), and C statistics revealed a very strong ability to predict retention according to the IOM indicator based on DHHS indicator status, even within characteristic strata. Conclusions Although the IOM indicator consistently reported higher retention in care compared with the DHHS indicator, there was strong agreement between IOM and DHHS retention indicators in a cohort demographically similar to persons living with HIV/AIDS in the U.S. Persons with poorer retention represent subgroups of interest for retention improvement programs nationally, particularly in light of the White House Executive Order on the HIV Care Continuum. PMID:25375099

Rebeiro, Peter F.; Horberg, Michael A.; Gange, Stephen J.; Gebo, Kelly A.; Yehia, Baligh R.; Brooks, John T.; Buchacz, Kate; Silverberg, Michael J.; Gill, John; Moore, Richard D.; Althoff, Keri N.

2014-01-01

345

Modeling the Keeling Curve  

NSDL National Science Digital Library

In this problem set, learners will refer to the tabulated data used to create the Keeling Curve of atmospheric carbon dioxide to create a mathematical function that accounts for both periodic and long-term changes. They will use this function to answer a series of questions, including predictions of atmospheric concentration in the future. A link to the data, which is in an Excel file, as well as the answer key are provided. This is part of Earth Math: A Brief Mathematical Guide to Earth Science and Climate Change.

346

Crystallography on curved surfaces  

PubMed Central

We study static and dynamical properties that distinguish 2D crystals constrained to lie on a curved substrate from their flat-space counterparts. A generic mechanism of dislocation unbinding in the presence of varying Gaussian curvature is presented in the context of a model surface amenable to full analytical treatment. We find that glide diffusion of isolated dislocations is suppressed by a binding potential of purely geometrical origin. Finally, the energetics and biased diffusion dynamics of point defects such as vacancies and interstitials are explained in terms of their geometric potential. PMID:16894160

Vitelli, Vincenzo; Lucks, J. B.; Nelson, D. R.

2006-01-01

347

Continuity of discrete curve evolution  

Microsoft Academic Search

Recently Latecki and Lakamper reported a process called discrete curve evolution. This process has various application possibilities, in particular, for noise removal and shape simplification of boundary curves in digital images. In this paper we prove that the process of the discrete curve evolution is continuous: if polygon Q is close to polygon P, then the polygons obtained by their

Longin Jan Latecki; R. R. Ghadially; Rolf Lakaemper; Ulrich Eckhardt

2000-01-01

348

Guide to Elliptic Curve Cryptography  

E-print Network

Guide to Elliptic Curve Cryptography Darrel Hankerson Alfred Menezes Scott Vanstone Springer #12;Guide to Elliptic Curve Cryptography Springer New York Berlin Heidelberg Hong Kong London Milan Paris Tokyo #12;#12;Darrel Hankerson Alfred Menezes Scott Vanstone Guide to Elliptic Curve Cryptography

Babinkostova, Liljana

349

Confronting the Environmental Kuznets Curve  

Microsoft Academic Search

he environmental Kuznets curve posits an inverted-U relationship be- tween pollution and economic development. Kuznets's name was appar- ently attached to the curve by Grossman and Krueger (1993), who noted its resemblance to Kuznets's inverted-U relationship between income inequality and development. In the first stage of industrialization, pollution in the environ- mental Kuznets curve world grows rapidly because people are

Susmita Dasgupta; Benoit Laplante; Hua Wang; David Wheeler

2002-01-01

350

Student Responses to Merit Scholarship Retention Rules  

ERIC Educational Resources Information Center

A common justification for state-sponsored merit scholarships like Georgia's HOPE program is to promote academic achievement. However, grade-based retention rules encourage other behavioral responses. Using longitudinal records of enrolled undergraduates at the University of Georgia between 1989 and 1997, we estimate the effects of HOPE on…

Cornwell, Christopher M.; Lee, Kyung Hee; Mustard, David B.

2005-01-01

351

COMPARTMENTAL MODEL OF NITRATE RETENTION IN STREAMS  

EPA Science Inventory

A compartmental modeling approach is presented to route nitrate retention along a cascade of stream reach sections. A process transfer function is used for transient storage equations with first order reaction terms to represent nitrate uptake in the free stream, and denitrifica...

352

Online Student Retention: Can It Be Done?  

ERIC Educational Resources Information Center

Retention has been indicated as one of the greatest weaknesses in online instruction. While a preponderance of literature about online instruction is available, concrete ideas about how to retain students are lacking. A DHHS grant for over one million dollars made it possible for the Wright State University College of Nursing and Health (Dayton,…

O'Brien, Barbara S.; Renner, Alice L.

353

Attrition and Retention among Special Education Paraprofessionals  

ERIC Educational Resources Information Center

The purpose of the study was to obtain information about issues of turnover and retention among former and current special education paraprofessionals in one school district. Survey data and findings indicated ways to retain staff and reduce turnover. Information from this study was shared within the district and will be considered in creating…

Hall, Kimberly D.

2009-01-01

354

Residential Refrigerator Recycling Ninth Year Retention Study  

E-print Network

Residential Refrigerator Recycling Ninth Year Retention Study Study ID Nos. 546B, 563 Prepared RECYCLING PROGRAMS Study ID Nos. 546B and 563 Prepared for Southern California Edison Rosemead, California Prepared by KEMA Inc. Madison, Wisconsin July 22, 2004 Copyright © 2004 by KEMA Inc. All rights reserved

355

Retention of Electronic Fundamentals: Differences Among Topics.  

ERIC Educational Resources Information Center

Criterion-referenced tests were used to measure the learning and retention of a sample of material taught by means of programed instruction in the Avionics Fundamentals Course, Class A. It was found that the students knew about 30 percent of the material before reading the programs, that mastery rose to a very high level on the immediate posttest,…

Johnson, Kirk A.

356

Customer satisfaction and retention in transition economies  

Microsoft Academic Search

Customer Satisfaction Index studies have become standard practice in many industries and individual companies for improving performance through increased customer loyalty. However, customer decision-making and satisfaction in transitional economies have so far been studied less extensively in systematic ways. This paper reports on major empirical research focusing on customer perceived quality, satisfaction, retention and loyalty measurements taken in North-West Russia.

L. Murgulets; J. Eklöf; I. Dukeov; I. Selivanova

2001-01-01

357

Effects of Emotional Intelligence on Teacher Retention  

ERIC Educational Resources Information Center

This mixed methods, explanatory design study focused on determining if the emotional intelligence of principals affects the retention of new teachers. In phase one, a non-random cluster sample of 138 public school principals in the state of Louisiana was surveyed using a quantitative instrument. A Factor Analysis, Analysis of Variance (ANOVA), and…

Gerald, Grant Ronald

2010-01-01

358

Retention of Nontraditional Students in Postsecondary Education.  

ERIC Educational Resources Information Center

Two recent studies proved the usefulness of predictors of academic performance and conceptual models that were developed primarily from research on traditional college students for the study of retention among nontraditional adult students in conventional postsecondary programs. Some modifications and extensions were suggested. The first study…

Weidman, John C.

359

Relationship of Personality Traits to Student Retention  

ERIC Educational Resources Information Center

Carl Jung's theory of psychological types has been the basis for the development of personality categorization, including tests such as Myers-Briggs Type Indicator (MBTI). This study analyzed the extent of the relationship between MBTI and Tinto (1993) retention factors that influence Oriental medicine students' choice of staying or dropping out…

Liang, John Paul

2010-01-01

360

Hydrogen isotope retention and release from copper  

Microsoft Academic Search

The Tokamak Fusion Test Reactor (TFTR) at the Princeton Plasma Physics Laboratory is considering the use of tritium neutral beams during the deuterium--tritium phase of operation in 1990. A concern is the tritium inventory that will develop in neutral beam components such as the copper calorimeter. In this paper we report on measurements and calculations of hydrogen isotope retention and

K. L. Wilson; R. A. Causey; M. I. Baskes; J. Kamperschroer

1987-01-01

361

Testing to Enhance Retention in Human Anatomy  

ERIC Educational Resources Information Center

Recent work in cognitive psychology has shown that repeatedly testing one's knowledge is a powerful learning aid and provides substantial benefits for retention of the material. To apply this in a human anatomy course for medical students, 39 fill-in-the-blank quizzes of about 50 questions each, one for each region of the body, and four about the…

Logan, Jessica M.; Thompson, Andrew J.; Marshak, David W.

2011-01-01

362

Work Retention and Nonspecific Low Back Pain  

Microsoft Academic Search

and Introduction Abstract Study Design: A cohort study of patients with nonspecific low back pain (LBP) participated in a 4-week multidisciplinary rehabilitation program. Objective: To identify factors that predict work retention 24 months after treatment in patients with nonspecific LBP. Summary of Background Data: There is evidence that select physical, psychologic, and psychosocial factors are related to positive outcome for

Marco A. Campello; Sherri R. Weiser; Margareta Nordin; Rudi Hiebert

2006-01-01

363

Recruitment and Retention with a Spin  

ERIC Educational Resources Information Center

Strategic planning and innovation at Bismarck State College (BSC) found common ground in the college's goal to recruit and retain employees in an environment of low unemployment and strong competition for skilled employees. BSC's strategic plan for 2007-09 included the objective "to increase retention of employees." One of the strategies connected…

Lindgren, Rita; Hixson, Carla Braun

2010-01-01

364

Comprehensive Retention and Attrition Model (CRAM).  

ERIC Educational Resources Information Center

A continuing concern in a number of teaching fields is the shortage of fully qualified teachers. The decisions of fully qualified teachers to continue in their teaching assignments (retention), to transfer to another assignment (transfer), or to leave the profession for some other activity (exit attrition) are the major determinants of the degree…

Boe, Erling E.

365

Making Student Retention an Institutional Priority.  

ERIC Educational Resources Information Center

Describes a study conducted to determine the reasons behind the high rate of student attrition at Mountain Empire Community College in Virginia. Work demands and family conflicts were found to be the primary causes of drop out, conclusions that led to the formation of a task force and a student retention plan to improve persistence. (KC)

Sydow, Debbie L.; Sandel, Robert H.

1998-01-01

366

Systems Thinking Can Improve Teacher Retention.  

ERIC Educational Resources Information Center

Discusses the challenges of teacher retention and proposes that systems thinking can be used to address those challenges. Considers five strategies for retaining teachers. Suggests that the five strategies discussed can provide comprehensive programs to reduce teacher attrition and create stable teacher teams. (SG)

Minarik, Melanie M.; Thornton, Bill; Perreault, George

2003-01-01

367

Factors Contributing to Teacher Retention in Georgia  

ERIC Educational Resources Information Center

The purpose of this mixed method, survey-based inquiry was to determine how Georgia public high school faculty members perceive various pressures and experiences associated with a career in education. These perceptions were then analyzed as possible indicators of teacher attrition in order to improve retention rates. The independent demographic…

Locklear, Tina M.

2010-01-01

368

Structural Information Retention in Visual Art Processing.  

ERIC Educational Resources Information Center

The accuracy of non-art college students' longterm retention of structural information presented in Leonardo da Vinci's "Mona Lisa" was tested. Seventeen female undergraduates viewed reproductions of the painting and copies that closely resembled structural attributes of the original. Only 3 of the 17 subjects reported having viewed a reproduction…

Koroscik, Judith Smith

369

49 CFR 219.901 - Retention of alcohol testing records.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Retention of alcohol testing records. 219.901 Section...DEPARTMENT OF TRANSPORTATION CONTROL OF ALCOHOL AND DRUG USE Recordkeeping Requirements § 219.901 Retention of alcohol testing records. (a) General...

2010-10-01

370

Retention of Undergraduate Black Men Executive Summary of Preliminary Research  

E-print Network

1 Retention of Undergraduate Black Men Executive Summary of Preliminary and retention rates for undergraduate Black men to bring them to parity with all to an increase in the graduation rate of undergraduate Black men. Specifically, the task

Chen, Tsuhan

371

49 CFR 229.215 - Retention and inspection of designs.  

Code of Federal Regulations, 2010 CFR

...Retention and inspection of designs. (a) Retention of records—original designs. Each manufacturer or...of the original locomotive designs, including supporting...inspection and duplication within 7 days, any records referred...

2010-10-01

372

21 CFR 878.4930 - Suture retention device.  

Code of Federal Regulations, 2010 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4930 Suture retention device. (a) Identification. A suture retention...

2010-04-01

373

21 CFR 878.4930 - Suture retention device.  

Code of Federal Regulations, 2012 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4930 Suture retention device. (a) Identification. A suture retention...

2012-04-01

374

21 CFR 878.4930 - Suture retention device.  

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4930 Suture retention device. (a) Identification. A suture retention...

2014-04-01

375

21 CFR 878.4930 - Suture retention device.  

Code of Federal Regulations, 2011 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4930 Suture retention device. (a) Identification. A suture retention...

2011-04-01

376

21 CFR 878.4930 - Suture retention device.  

Code of Federal Regulations, 2013 CFR

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4930 Suture retention device. (a) Identification. A suture retention...

2013-04-01

377

49 CFR 219.901 - Retention of alcohol testing records.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Retention of alcohol testing records. 219.901 Section...DEPARTMENT OF TRANSPORTATION CONTROL OF ALCOHOL AND DRUG USE Recordkeeping Requirements § 219.901 Retention of alcohol testing records. (a) General...

2013-10-01

378

49 CFR 219.901 - Retention of alcohol testing records.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Retention of alcohol testing records. 219.901 Section...DEPARTMENT OF TRANSPORTATION CONTROL OF ALCOHOL AND DRUG USE Recordkeeping Requirements § 219.901 Retention of alcohol testing records. (a) General...

2011-10-01

379

49 CFR 219.901 - Retention of alcohol testing records.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Retention of alcohol testing records. 219.901 Section...DEPARTMENT OF TRANSPORTATION CONTROL OF ALCOHOL AND DRUG USE Recordkeeping Requirements § 219.901 Retention of alcohol testing records. (a) General...

2012-10-01

380

Disk galaxy rotation curves  

NASA Astrophysics Data System (ADS)

We show that simple axisymmetric Newtonian calculation suffices to consistently connect disk galaxy rotation curves to underlying mass distribution and vice versa, without need for any dark matter. To this end, we connect mass density profiles of five galaxies of varying sizes with observed galaxy rotation curves. The five galaxies are: NGC6822 (4.8 kpc), Large Magellanic Cloud (9 kpc), The Milky Way (17 kpc), NGC3198 (30 kpc) and UGC9133 (102.5 kpc). The mass and mass density profiles of these galaxies have been computed using the scientific computing s/w package MATLAB taking the already available velocity profiles of the galaxies as the input, and without considering any dark matter contribution. We have plotted these profiles after computing them according to three different theories of gravity (and dynamics): Newtonian, Modified Newtonian Dynamics (MOND) and Vacuum Modified Gravity. We also consider how the profile due to the Newtonian theory would modify if we use a cosmological constant = 5 × 10^{-56} cm^{-2}. Comparing these mass and mass density profiles, we try to form an idea regarding what could be a realistic theory of gravity and whether we need dark matter to explain the results.

Banhatti, Dilip G.; Datta, Rahul

381

Retention mechanisms in micellar liquid chromatography.  

PubMed

Micellar liquid chromatography (MLC) is a reversed-phase liquid chromatographic (RPLC) mode with mobile phases containing a surfactant (ionic or non-ionic) above its critical micellar concentration (CMC). In these conditions, the stationary phase is modified with an approximately constant amount of surfactant monomers, and the solubilising capability of the mobile phase is altered by the presence of micelles, giving rise to diverse interactions (hydrophobic, ionic and steric) with major implications in retention and selectivity. From its beginnings in 1980, the technique has evolved up to becoming a real alternative in some instances (and a complement in others) to classical RPLC with hydro-organic mixtures, owing to its peculiar features and unique advantages. This review is aimed to describe the retention mechanisms (i.e. solute interactions with both stationary and mobile phases) in an MLC system, revealed in diverse reports where the retention behaviour of solutes of different nature (ionic or neutral exhibiting a wide range of polarities) has been studied in a variety of conditions (with ionic and non-ionic surfactants, added salt and organic solvent, and varying pH). The theory is supported by several mechanistic models that describe satisfactorily the retention behaviour, and allow the measurement of the strength of solute-stationary phase and solute-micelle interactions. Suppression of silanol activity, steric effects in the packing pores, anti-binding behaviour, retention of ionisable compounds, compensating effect on polarity differences among solutes, and the contribution of the solvation parameter model to elucidate the interactions in MLC, are commented. PMID:18838142

Ruiz-Angel, M J; Carda-Broch, S; Torres-Lapasió, J R; García-Alvarez-Coque, M C

2009-03-01

382

A Simple Calorimetric Experiment that Highlights Aspects of Global Heat Retention and Global Warming  

ERIC Educational Resources Information Center

In this laboratory experiment, general chemistry students measure the heating curves for three different systems: (i) 500 g of room-temperature water heated by a small desk lamp, (ii) 500 g of an ice-water mixture warmed by conduction with room-temperature surroundings, and (iii) 500 g of an ice-water mixture heated by a small desk lamp and by…

Burley, Joel D.; Johnston, Harold S.

2007-01-01

383

Education for Sustainable Development and Retention: Unravelling a Research Agenda  

ERIC Educational Resources Information Center

This paper considers the question of what education for sustainable development (ESD) research might signify when linked to the concept of "retention", and how this relation (ESD and retention) might be researched. It considers two different perspectives on retention, as revealed through educational research trajectories, drawing on existing…

Lotz-Sisitka, Heila

2010-01-01

384

The Tennessee Lottery Scholarship Program: Impact on Retention  

ERIC Educational Resources Information Center

This study examined if the Tennessee Education Lottery Scholarship (TELS), which began in 2004, was related to student retention at the six Tennessee Board of Regents four-year institutions. This study investigated the impact of the TELS on student retention at TBR universities and general knowledge regarding retention. Post-facto data were…

Puryear, Carol G.

2009-01-01

385

Framing Retention for Institutional Improvement: A 4 Ps Framework  

ERIC Educational Resources Information Center

A 4 Ps framework for student retention strategy is a construct for reframing the retention discussion in a way that enables institutional improvement by challenging some conventional wisdom and prevailing perspectives that have characterized retention strategy for years. It opens new possibilities for action and improvement by suggesting that…

Kalsbeek, David H.

2013-01-01

386

Advances--and a Retreat--in Student Retention.  

ERIC Educational Resources Information Center

Because of a 50% drop-out rate of first-year to second-year students at Mountain Empire Community College, retention was identified as a priority. Students and faculty were surveyed to determine causes of student withdrawals, a summer retreat was held, and a retention task force was created to develop a comprehensive retention plan for the fall of…

Sandel, Robert H.; Sydow, Debbie

1997-01-01

387

California Institute of Technology Records Retention and Disposition Policy  

E-print Network

of the Records Retention and Disposition Policy is to establish and maintain a uniform records management policy activities and are subject to records management review and evaluation prior to any decisions regarding of Technology Records Retention Schedule ("Retention Schedule"). Department and division management should

388

Within-river phosphorus retention: accounting for a missing piece in the watershed phosphorus puzzle.  

PubMed

The prevailing "puzzle" in watershed phosphorus (P) management is how to account for the nonconservative behavior (retention and remobilization) of P along the land-freshwater continuum. This often hinders our attempts to directly link watershed P sources with their water quality impacts. Here, we examine aspects of within-river retention of wastewater effluent P and its remobilization under high flows. Most source apportionment methods attribute P loads mobilized under high flows (including retained and remobilized effluent P) as nonpoint agricultural sources. We present a new simple empirical method which uses chloride as a conservative tracer of wastewater effluent, to quantify within-river retention of effluent P, and its contribution to river P loads, when remobilized under high flows. We demonstrate that within-river P retention can effectively mask the presence of effluent P inputs in the water quality record. Moreover, we highlight that by not accounting for the contributions of retained and remobilized effluent P to river storm-flow P loads, existing source apportionment methods may significantly overestimate the nonpoint agricultural sources and underestimate wastewater sources in mixed land-use watersheds. This has important implications for developing effective watershed remediation strategies, where remediation needs to be equitably and accurately apportioned among point and nonpoint P contributors. PMID:23106359

Jarvie, Helen P; Sharpley, Andrew N; Scott, J Thad; Haggard, Brian E; Bowes, Michael J; Massey, Lesley B

2012-12-18

389

Multipulse phase resetting curves.  

PubMed

In this paper, we introduce and study systematically, in terms of phase response curves, the effect of dual-pulse excitation on the dynamics of an autonomous oscillator. Specifically, we test the deviations from linear summation of phase advances resulting from two small perturbations. We analytically derive a correction term, which generally appears for oscillators whose intrinsic dimensionality is >1. The nonlinear correction term is found to be proportional to the square of the perturbation. We demonstrate this effect in the Stuart-Landau model and in various higher dimensional neuronal models. This deviation from the superposition principle needs to be taken into account in studies of networks of pulse-coupled oscillators. Further, this deviation could be used in the verification of oscillator models via a dual-pulse excitation. PMID:24229244

Krishnan, Giri P; Bazhenov, Maxim; Pikovsky, Arkady

2013-10-01

390

Multipulse phase resetting curves  

PubMed Central

In this paper, we introduce and study systematically, in terms of phase response curves, the effect of dual-pulse excitation on the dynamics of an autonomous oscillator. Specifically, we test the deviations from linear summation of phase advances resulting from two small perturbations. We analytically derive a correction term, which generally appears for oscillators whose intrinsic dimensionality is >1. The nonlinear correction term is found to be proportional to the square of the perturbation. We demonstrate this effect in the Stuart-Landau model and in various higher dimensional neuronal models. This deviation from the superposition principle needs to be taken into account in studies of networks of pulse-coupled oscillators. Further, this deviation could be used in the verification of oscillator models via a dual-pulse excitation. PMID:24229244

Krishnan, Giri P.; Bazhenov, Maxim; Pikovsky, Arkady

2014-01-01

391

Ironing Out Curves  

NSDL National Science Digital Library

In this activity, students graph second and third order functions, discovering an inverse relationship between squares and square roots and between cubes and cube roots. Students graph these functions on both linear grid (evenly spaced numbers), and a log-log grid (evenly space exponents). Graph lines that curve on linear grids transform into straight lines on the log-log grids, with slopes equal to their exponential powers. This activity is activity E3 in the "Far Out Math" educator's guide. Lessons in the guide include activities in which students measure, compare quantities as orders of magnitude, become familiar with scientific notation, and develop an understanding of exponents and logarithms using examples from NASA's GLAST mission. These are skills needed to understand the very large and very small quantities characteristic of astronomical observations. Note: In 2008, GLAST was renamed Fermi, for the physicist Enrico Fermi.

392

Curved nanostructured materials  

NASA Astrophysics Data System (ADS)

Graphite is a layered material that is very flexible, in which each layer is able to curve in order to form cages, nanotubes, nanocoils, nanocones, etc. In this paper, we demonstrate that various synthetic routes are capable of producing graphite-like nanomaterials with fascinating electronic and mechanical properties. There are other layered systems, which could curl and bend, thus generating novel nanostructures with positive and negative Gaussian curvature. In this context, we will also demonstrate that hexagonal boron nitride, tungsten disulfide (WS2), molybdenum disulfide (MoS2) and rhenium disulfide (ReS2) are also able to create nanocages, nanotubes and nano-arrangements exhibiting novel physico-chemical properties that could revolutionize materials science in the 21st century.

Terrones, Humberto; Terrones, Mauricio

2003-10-01

393

Sensitivity and uncertainty analysis of estimated soil hydraulic parameters for simulating soil water content  

NASA Astrophysics Data System (ADS)

The sensitivity and uncertainty analysis has been carried out for the scalar parameters (soil hydraulic parameters (SHPs)), which govern the simulation of soil water content in the unsaturated soil zone. The study involves field experiments, which were conducted in real field conditions for wheat crop in Roorkee, India under irrigated conditions. Soil samples were taken for the soil profile of 60 cm depth at an interval of 15 cm in the experimental field to determine soil water retention curves (SWRCs). These experimentally determined SWRCs were used to estimate the SHPs by least square optimization under constrained conditions. Sensitivity of the SHPs estimated by various pedotransfer functions (PTFs), that relate various easily measurable soil properties like soil texture, bulk density and organic carbon content, is compared with lab derived parameters to simulate respective soil water retention curves. Sensitivity analysis was carried out using the monte carlo simulations and the one factor at a time approach. The different sets of SHPs, along with experimentally determined saturated permeability, are then used as input parameters in physically based, root water uptake model to ascertain the uncertainties in simulating soil water content. The generalised likelihood uncertainty estimation procedure (GLUE) was subsequently used to estimate the uncertainty bounds (UB) on the model predictions. It was found that the experimentally obtained SHPs were able to simulate the soil water contents with efficiencies of 70-80% at all the depths for the three irrigation treatments. The SHPs obtained from the PTFs, performed with varying uncertainties in simulating the soil water contents. Keywords: Sensitivity analysis, Uncertainty estimation, Pedotransfer functions, Soil hydraulic parameters, Hydrological modelling

Gupta, Manika; Garg, Naveen Kumar; Srivastava, Prashant K.

2014-05-01

394

A record-retention program can protect group practices.  

PubMed

Group practices can benefit from having a systematic record-retention program that includes a formal record-retention policy. While state and Federal laws require the retention of some types of business records, many other records should be retained in the event of an audit or litigation. Having a record-retention program in place can help group practices respond cost-effectively and efficiently when called upon to produce documentation. The record-retention program should include a policy that stipulates not only which records should be kept but also for how long. Group practices should retain records relating to patient care, taxes, payroll, and contracts. PMID:10557981

Stewart, E E

1999-04-01

395

Early fluid retention and severe acute mountain sickness.  

PubMed

Field studies of acute mountain sickness (AMS) usually include variations in exercise, diet, and environmental conditions over days and development of clinically apparent edemas. The purpose of this study was to clarify fluid status in persons developing AMS vs. those remaining without symptoms during simulated altitude with controlled fluid intake, diet, temperature, and without exercise. Ninety-nine exposures of 51 men and women to reduced barometric pressure (426 mmHg = 16,000 ft. = 4,880 m) were carried out for 8-12 h. AMS was evaluated by Lake Louise (LL) and AMS-C scores near the end of exposure. Serial measurements included fluid balance, electrolyte excretions, and plasma concentrations, regulating hormones, and free water clearance. Comparison between 16 subjects with the lowest AMS scores near the end of exposure ("non-AMS": mean LL = 1.0, range = 0-2.5) and 16 others with the highest AMS scores ("AMS": mean LL = 7.4, range = 5-11) demonstrated significant fluid retention in AMS beginning within the first 3 h, resulting from reduced urine flow. Plasma Na+ decreased significantly after 6 h, indicating dilution throughout the total body water. Excretion of Na+ and K+ trended downward with time in both groups, being lower in AMS after 6 h, and the urine Na+-to-K+ ratio was significantly higher for AMS after 6 h. Renal compensation for respiratory alkalosis, plasma renin activity, aldosterone, and atrial natriuretic peptide were not different between groups, with the latter tending to rise and aldosterone falling with time of exposure. Antidiuretic hormone fell in non-AMS and rose in AMS within 90 min of exposure and continued to rise in AMS, closely associated with severity of symptoms and fluid retention. PMID:15501929

Loeppky, Jack A; Icenogle, Milton V; Maes, Damon; Riboni, Katrina; Hinghofer-Szalkay, Helmut; Roach, Robert C

2005-02-01

396

Analysing the form of the confined uniaxial compression curve of various soils  

E-print Network

at high stresses. In the present work, uniaxial confined compression tests were performed on four soils compression curve at higher stresses; (ii) the S-shaped curve having deviation of the virgin compression curve the compression of air-filled pores and that of meso-pores storing water subjected to high capillary forces could

Paris-Sud XI, Université de

397

Retentive characteristics of dental cementation materials.  

PubMed

Glass ionomer, polycarboxylate, zinc phosphate, and two resin cements were tested in vitro to cement base and noble metal crowns to prepared extracted teeth. The cements had different retentive characteristics. Among cements, statistically significant tensile resistance to dislodgment in order of decreasing strength was: (1) C & B Metabond (resin); (2) Panavia (resin); (3) Fuji I (glass ionomer); (4) Durelon (polycarboxylate); and (5) Fleck's (zinc phosphate). Tensile resistance to dislodgment did not differ statistically among base and noble metal crowns cemented with glass ionomer, polycarboxylate, or zinc phosphate cements. Tensile resistance to dislodgment differed statistically among base and noble crowns cemented with the resin cements (C & B Metabond and Panavia); the base metal crowns had the highest rate of retention. PMID:23087930

Hunsaker, K J; Christensen, G J; Christensen, R P; Cao, D; Lewis, R G

1993-11-01

398

Staff retention and empowerment: functions of leadership.  

PubMed

Regardless of any organization's structure and technology, the most potent leverage for exceptional performance and quality assurance resides within personnel. Retention of empowered, committed staff who believe in their organization's purpose and leadership is important to an organization's success. The Clinical Laboratory Sciences (CLS) profession faces a different kind of crisis, not only one of economics, but also one of quality because of lost professional expertise. This dilemma is because of profound neglect of the organization's greatest asset--its CLS professionals. Retention of expert CLS professionals requires a dramatic change in management's belief system regarding the value of their assets. Laboratory leaders must create a culture of empowered people with the freedom to exhibit self-direction toward achieving the organization's mission and goals. Managers must consider employees valuable enough to invest in their professional growth. A laboratory's long-term sustainability and economic performance will depend on a committed workforce. PMID:12506831

Mass, Diana

2002-01-01

399

Science Teacher Retention: Mentoring and Renewal  

NSDL National Science Digital Library

"Some forty percent of all new science teachers leave the profession within five years, and too many science teachers are wedded to their textbooks and the routines they acquired during their collegiate years." What can be done to retain new science teachers and reinvigorate more experienced science teachers? Allow Science Teacher Retention: Mentoring and Renewal to "mentor" you as you reach toward this lofty but attainable goal. For this book, Jack Rhoton and Patricia Bowers assembled some of the country's most noted science educators and asked them to offer ideas to resolve the problems of science teacher retention and renewal. Their suggestions are designed to keep the brightest and most motivated new teachers in the profession and help all science teachers to continue to learn and to treat their own profession like science itself--that is, by basing it on questions, suggesting answers, and using their interests and abilities to test the validity of these answers.

2003-01-01

400

Deterministic contact mechanics model applied to electrode interfaces in polymer electrolyte fuel cells and interfacial water accumulation  

NASA Astrophysics Data System (ADS)

An elastic deterministic contact mechanics model is applied to the compressed micro-porous (MPL) and catalyst layer (CL) interfaces in polymer electrolyte fuel cells (PEFCs) to elucidate the interfacial morphology. The model employs measured two-dimensional surface profiles and computes local surface deformation and interfacial gap, average contact resistance, and percent contact area as a function of compression pressure. Here, we apply the model to one interface having a MPL with cracks and one with a crack-free MPL. The void size distributions and water retention curves for the two sets of CL|MPL interfaces under compression are also computed. The CL|MPL interfaces with cracks are observed to have higher roughness, resulting in twice the interfacial average gap compared to the non-cracked interface at a given level of compression. The results indicate that the interfacial contact resistance is roughly the same for cracked or non-cracked interfaces due to cracks occupying low percentage of overall area. However, the cracked CL|MPL interface yields higher liquid saturation levels at all capillary pressures, resulting in an order of magnitude higher water storage capacity compared to the smooth interface. The van Genuchten water retention curve correlation for log-normal void size distributions is found to fit non-cracked CL|MPL interfaces well.

Zenyuk, I. V.; Kumbur, E. C.; Litster, S.

2013-11-01

401

Auditing a Database under Retention Restrictions  

Microsoft Academic Search

Abstract—Auditing,the changes,to a database,is critical for identifying malicious behavior, maintaining data quality, and improving,system,performance.,But an accurate,audit log is a historical record of the past that can also pose a serious threat to privacy. Policies which,limit data retention conflict with the goal of accurate auditing, and data owners have to carefully balance the need for policy compliance,with the goal of accurate

Wentian Lu; Gerome Miklau

2009-01-01

402

Inquiry-Based Learning and Student Retention  

Microsoft Academic Search

The purpose of the study was to evaluate the benefits of inquiry based hands-on education, engage students in their own learning, and increase retention of knowledge. Research supports the connection between this process and the learning in a science curriculum. Four topics to be discussed in the following chapter are hands-on learning and inquiry-based instruction, hands-on learning beyond the classroom,

Shelly Marie Lamanna

2010-01-01

403

Continuous columns for determining moisture characteristic curves of soilless substrates  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sound water management is essential for effectively producing nursery crops. Understanding substrate water availability is a critical component to managing irrigation properly. The objective of this paper is to report a method for generating moisture characteristic curves of soilless substrate tha...

404

Maternal stress predicts postpartum weight retention.  

PubMed

Postpartum weight retention (PPWR) is a significant contributor to the development of overweight and obesity in women of childbearing age. Stress may be a key mechanism making it more difficult for mothers to lose weight in the year following delivery. The aim of this study was to assess whether specific aspects of parenting stress and life stress influence postpartum weight retention in new mothers. Women in late pregnancy or up to 2 months postpartum (n = 123) were enrolled in the study and followed through the first year postpartum. Linear regression models evaluated the associations of parenting stress (isolation, attachment and depressive symptoms) as well as overall life stress at 2, 6, and 12 months postpartum with PPWR at 6 and 12 months. During the first year postpartum, higher depression and life stress were significantly associated with greater PPWR. As the effect of depression diminished, the effect of life stress became significant. Contrary to hypothesized relationships, fewer problems with attachment and less social isolation were significantly associated with greater PPWR. Higher gestational weight gain and African American race were also significantly associated with greater PPWR at both 6 and 12 months. Different types of stress predict weight retention in first time mothers during the first year postpartum. Understanding the relationships between parenting stress, concurrent life stress and PPWR can enhance the development of future interventions that specifically target self-identified stressors, leading to improved weight related outcomes. PMID:24760321

Whitaker, Kara; Young-Hyman, Deborah; Vernon, Marlo; Wilcox, Sara

2014-11-01

405

Testing to enhance retention in human anatomy.  

PubMed

Recent work in cognitive psychology has shown that repeatedly testing one's knowledge is a powerful learning aid and provides substantial benefits for retention of the material. To apply this in a human anatomy course for medical students, 39 fill-in-the-blank quizzes of about 50 questions each, one for each region of the body, and four about the nervous system, were developed. The quizzes were optional, and no credit was awarded. They were posted online using Blackboard, which provided feedback, and they were very popular. To determine whether the quizzes had any effect on retention, they were given in a controlled setting to 21 future medical and dental students. The weekly quizzes included questions on regional anatomy and an expanded set of questions on the nervous system. Each question about the nervous system was given three times, in a slightly different form each time. The second quiz was given approximately half an hour after the first one, and the third was given one week after the second to assess retention. The quizzes were unpopular, but students showed robust improvement on the questions about the nervous system. The scores increased by almost 9% on the second quiz, with no intervention except viewing the correct answers. The scores were 29% higher on the third quiz than on the first, and there was also a positive correlation between the grades on the quizzes and the final examination. Thus, repeated testing is an effective strategy for learning and retaining information about human anatomy. PMID:21805688

Logan, Jessica M; Thompson, Andrew J; Marshak, David W

2011-01-01

406

High Efficiency Diffusion Molecular Retention Tumor Targeting  

PubMed Central

Here we introduce diffusion molecular retention (DMR) tumor targeting, a technique that employs PEG-fluorochrome shielded probes that, after a peritumoral (PT) injection, undergo slow vascular uptake and extensive interstitial diffusion, with tumor retention only through integrin molecular recognition. To demonstrate DMR, RGD (integrin binding) and RAD (control) probes were synthesized bearing DOTA (for 111 In3+), a NIR fluorochrome, and 5 kDa PEG that endows probes with a protein-like volume of 25 kDa and decreases non-specific interactions. With a GFP-BT-20 breast carcinoma model, tumor targeting by the DMR or IV methods was assessed by surface fluorescence, biodistribution of [111In] RGD and [111In] RAD probes, and whole animal SPECT. After a PT injection, both probes rapidly diffused through the normal and tumor interstitium, with retention of the RGD probe due to integrin interactions. With PT injection and the [111In] RGD probe, SPECT indicated a highly tumor specific uptake at 24 h post injection, with 352%ID/g tumor obtained by DMR (vs 4.14%ID/g by IV). The high efficiency molecular targeting of DMR employed low probe doses (e.g. 25 ng as RGD peptide), which minimizes toxicity risks and facilitates clinical translation. DMR applications include the delivery of fluorochromes for intraoperative tumor margin delineation, the delivery of radioisotopes (e.g. toxic, short range alpha emitters) for radiotherapy, or the delivery of photosensitizers to tumors accessible to light. PMID:23505478

Guo, Yanyan; Yuan, Hushan; Cho, Hoonsung; Kuruppu, Darshini; Jokivarsi, Kimmo; Agarwal, Aayush; Shah, Khalid; Josephson, Lee

2013-01-01

407

Deuterium retention in NSTX with lithium conditioning  

NASA Astrophysics Data System (ADS)

High (?90%) deuterium retention was observed in NSTX gas balance measurements both with- and without lithiumization of the carbon plasma-facing components. The gas retained in ohmic discharges was measured by comparing the vessel pressure rise after a discharge to that of a gas-only pulse with the pumping valves closed. For neutral beam heated discharges the gas input and gas pumped by the NB cryopanels were tracked. The discharges were followed by outgassing of deuterium that reduced the retention. The relationship between retention and surface chemistry was explored with a new plasma-material interface probe connected to an in vacuo surface science station that exposed four material samples to the plasma. XPS and TDS analysis demonstrated that binding of D atoms in graphite is fundamentally changed by lithium - in particular atoms are weakly bonded in regions near lithium atoms bound to either oxygen or the carbon matrix. This is in contrast to the strong ionic bonding that occurs between D and pure Li.

Skinner, C. H.; Allain, J. P.; Blanchard, W.; Kugel, H. W.; Maingi, R.; Roquemore, L.; Soukhanovskii, V.; Taylor, C. N.

2011-08-01

408

Improved motor sequence retention by motionless listening.  

PubMed

This study examined the effect of listening to a newly learned musical piece on subsequent motor retention of the piece. Thirty-six non-musicians were trained to play an unfamiliar melody on a piano keyboard. Next, they were randomly assigned to participate in three follow-up listening sessions over 1 week. Subjects who, during their listening sessions, listened to the same initial piece showed significant improvements in motor memory and retention of the piece despite the absence of physical practice. These improvements included increased pitch accuracy, time accuracy, and dynamic intensity of key pressing. Similar improvements, though to a lesser degree, were observed in subjects who, during their listening sessions, were distracted by another task. Control subjects, who after learning the piece had listened to nonmusical sounds, showed impaired motoric retention of the piece at 1 week from the initial acquisition day. These results imply that motor sequences can be established in motor memory without direct access to motor-related information. In addition, the study revealed that the listening-induced improvements did not generalize to the learning of a new musical piece composed of the same notes as the initial piece learned, limiting the effects to musical motor sequences that are already part of the individual's motor repertoire. PMID:22434336

Lahav, Amir; Katz, Tal; Chess, Roxanne; Saltzman, Elliot

2013-05-01

409

Water  

Microsoft Academic Search

Water is an essential nutrient required for life. To be well hydrated, the average sedentary adult man must consume at least 2,900 mL (12 c) fluid per day, and the average sedentary adult woman at least 2,200 mL (9 c) fluid per day, in the form of noncaffeinated, nonalcoholic beverages, soups, and foods. Solid foods contribute approximately 1,000 mL (4

SUSAN M KLEINER

1999-01-01

410

DESICCATION TOLERANCE AND WATER-RETENTIVE MECHANISMS IN TARDIGRADES  

Microsoft Academic Search

Summary Tardigrades entering a state of anhydrobiosis (cryptobiosis) show considerable interspecific variation in desiccation tolerance, lower lethal humidities for initial desiccation ranging from 78 to 53 %. Species most tolerant of rapid initial drying also show the most rapid acquisition of tolerance to low humidities (25-31 %) following drying in high humidity. Surface area reduction during tun formation shows a

JONATHAN C. WRIGHT

1989-01-01

411

Nonlinear Curve-Fitting Program  

NASA Technical Reports Server (NTRS)

Nonlinear optimization algorithm helps in finding best-fit curve. Nonlinear Curve Fitting Program, NLINEAR, interactive curve-fitting routine based on description of quadratic expansion of X(sup 2) statistic. Utilizes nonlinear optimization algorithm calculating best statistically weighted values of parameters of fitting function and X(sup 2) minimized. Provides user with such statistical information as goodness of fit and estimated values of parameters producing highest degree of correlation between experimental data and mathematical model. Written in FORTRAN 77.

Everhart, Joel L.; Badavi, Forooz F.

1989-01-01

412

Inference and analysis of xenon outflow curves under multi-pulse injection in two-dimensional chromatography.  

PubMed

Multidimensional gas chromatography is widely applied to atmospheric xenon monitoring for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). To improve the capability for xenon sampling from the atmosphere, sampling techniques have been investigated in detail. The sampling techniques are designed by xenon outflow curves which are influenced by many factors, and the injecting condition is one of the key factors that could influence the xenon outflow curves. In this paper, the xenon outflow curves of single-pulse injection in two-dimensional gas chromatography has been tested and fitted as a function of exponential modified Gaussian distribution. An inference formula of the xenon outflow curve for six-pulse injection is derived, and the inference formula is also tested to compare with its fitting formula of the xenon outflow curve. As a result, the curves of both the one-pulse and six-pulse injections obey the exponential modified Gaussian distribution when the temperature of the activated carbon column's temperature is 26°C and the flow rate of the carrier gas is 35.6mLmin(-1). The retention time of the xenon peak for one-pulse injection is 215min, and the peak width is 138min. For the six-pulse injection, however, the retention time is delayed to 255min, and the peak width broadens to 222min. According to the inferred formula of the xenon outflow curve for the six-pulse injection, the inferred retention time is 243min, the relative deviation of the retention time is 4.7%, and the inferred peak width is 225min, with a relative deviation of 1.3%. PMID:24007686

Shu-Jiang, Liu; Zhan-Ying, Chen; Yin-Zhong, Chang; Shi-Lian, Wang; Qi, Li; Yuan-Qing, Fan

2013-10-11

413

Reflectometry on curved interfaces  

NASA Astrophysics Data System (ADS)

Reflectometry is known since long as an interferometric method which can be used to characterize surfaces and thin films regarding their structure and, to a certain degree, composition as well. Properties like layer structures, layer thickness, density, and interface roughness can be determined by fitting the obtained reflectivity data with an appropriate model using a recursive fitting routine. However, one major drawback of the reflectometric method is its restriction to planar surfaces. In this article we demonstrate an approach to apply X-ray and neutron reflectometry to curved surfaces by means of the example of bent bare and coated glass slides. We prove the possibility to observe all features like Fresnel decay, Kiessig fringes, Bragg peaks and off-specular scattering and are able to interpret the data using common fitting software and to derive quantitative results about roughness, layer thickness and internal structure. The proposed method has become practical due to the availability of high quality 2D-detectors. It opens up the option to explore many kinds and shapes of samples, which, due to their geometry, have not been in the focus of reflectometry techniques until now.

Früh, Johannes; Rühm, Adrian; Möhwald, Helmuth; Krastev, Rumen; Köhler, Ralf

2015-01-01

414

Study on retention factor and resolution of tocopherols by supercritical fluid chromatography.  

PubMed

To develop a process for separation of natural alpha-tocopherol from gamma- and delta-tocopherols by supercritical fluid chromatography, the effects of pressure, temperature and the ethanol concentration in the mobile phase on the retention factor and resolution of tocopherols were studied comprehensively. The ranges of the studied pressure, temperature and ethanol concentration were 12 to 20 MPa, 30 to 90 degrees C and 0 to 6.54 wt% respectively. It was found that the retention factors of the tocopherols decrease as the ethanol concentration in the mobile phase increases. The resolution of tocopherols increases as the temperature increases and as the pressure decreases, and there is a maximum of the ethanol concentration curve at a definite temperature and pressure. A simplified model of the retention factor ln k' = A + B/T + C rho - D(rho/T) + E(rho2/T) based on the unified molecular theory was proposed. The experimental data were correlated by the model with the AARD% less than 14.70%. PMID:12924790

Jiang, Chongwen; Ren, Qilong; Wu, Pingdong

2003-07-11

415

Retention of Oxytetracycline-Induced Marks on Sagittae of Red Drum  

Microsoft Academic Search

In a pilot-scale stocking program, juvenile red drum Sciaenops ocellatus were immersed for 4 h in a 500-mg\\/L active solution of oxytetracycline hydrochloride (OTC) and 15-g\\/L salinity water at a temperature of 26.2°C to mark the otoliths before release. A portion of the treated fish was retained to determine marking success and mark retention. Retained fish were held in outdoor

Wallace E. Jenkins; Michael R. Denson; Charles B. Bridgham; Mark R. Collins; Theodore I. J. Smith

2002-01-01

416

Retention and separation studies of cholesterol and bile acids using thermostated thin-layer chromatography  

Microsoft Academic Search

The influence of temperature on retention and separation of cholesterol and bile acids, using reversed-phase thin-layer chromatography, was studied. As mobile phases methanol–water mixtures of various compositions were used. Chromatographic experiments were performed using vapor-saturated chambers at temperatures ranging from 5 to 60°C. A linear relationship between RM values and temperature (1\\/T) as well as mobile phase composition was observed.

P. K Zarzycki; M Wierzbowska; H Lamparczyk

1999-01-01

417

Retention of Vibrio parahaemolyticus in oyster tissues after chlorine dioxide treatment  

Microsoft Academic Search

Vibrio parahaemolyticus is an important food-borne bacterium that is closely related to food poisoning from consumption of raw or lightly-cooked oysters. Therefore, intensive efforts must be taken to depurate the contaminated oysters. Chlorine dioxide (ClO2) is considered to be a safe and effective disinfectant and is routinely applied for treatment of drinking water and seafood. However, the retention of V.

Dapeng Wang; Dandan Zhang; Wanyi Chen; Shuijing Yu; Xianming Shi

2010-01-01

418

Trends in nutrient and sediment retention in Great Plains reservoirs (USA).  

PubMed

Reservoirs are artificial ecosystems with physical, chemical, and biological transitional characteristics between rivers and lakes. Greater water retention time in reservoirs provides conditions for cycling materials inputs from upstream waters through sedimentation, biological assimilation and other biogeochemical processes. We investigated the effects of reservoirs on the water quantity and quality in the Great Plains (Kansas, USA), an area where little is known about these dominant hydrologic features. We analyzed a 30-year time-series of discharge, total phosphorus (TP), nitrate (NO3(-)), and total suspended solids (TSS) from six reservoirs and estimated overall removal efficiencies from upstream to downstream, testing correlations among retention, discharge, and time. In general, mean removal of TP (42-74%), TSS (0-93%), and NO3(-) (11-56%) from upstream to downstream did not change over 30 years. TP retention was associated with TSS removal, suggesting that nutrient substantial portion of P was adsorbed to solids. Our results indicated that reservoirs had the effect of lowering variance in the water quality parameters and that these reservoirs are not getting more or less nutrient-rich over time. We found no evidence of temporal changes in the yearly mean upstream and downstream discharges. The ratio upstream/downstream discharge was analyzed because it allowed us to assess how much contribution of additional unsampled tributaries may have biased our ability to calculate retention. Nutrient and sediment removal was less affected by hydraulic residence time than expected. Our study demonstrates that reservoirs can play a role in the removal and processing of nutrient and sediments, which has repercussions when valuing their ecological services and designing watershed management plans. PMID:24061791

Cunha, Davi Gasparini Fernandes; do Carmo Calijuri, Maria; Dodds, Walter Kennedy

2014-02-01

419

Cp* Iridium Complexes Give Catalytic Alkane Hydroxylation with Retention of Stereochemistry  

SciTech Connect

A series of Cp*Ir complexes can catalyze C?H oxidation, with ceric ammonium nitrate as the terminal oxidant and water as the source of oxygen. Remarkably the hydroxylation of cis-decalin and 1,4-dimethylcyclohexane proceeds with retention of stereochemistry. With H{sub 2}O{sup 18}, cis-decalin oxidation gave {sup 18}O incorporation into the product cis-decalol.

Zhou, Meng; Schley, Nathan D; Crabtree, Robert H

2010-01-01

420

Use of ultrasound imaging and fluoroscopic imaging to study gastric retention of enzyme-digestible hydrogels.  

PubMed

Ultrasound and fluoroscopic imaging techniques were used to monitor the gastric retention of enzyme-digestible hydrogels in the canine stomach. When water was present in the stomach, ultrasound imaging was very effective in monitoring the position of the hydrogel in the stomach, solvent penetration into the gel, and the gastric tissue-gel interactions during peristalsis. Rubbery or fully swollen hydrogels appeared as sonolucent objects with ultrasound imaging. Partially swollen hydrogels displayed a sonolucent outer layer due to solvent penetration and a centrally located bright echo resulting from the acoustic impedance mismatch at the glassy/rubbery interface. The degree of gastric tissue-gel interactions during peristalsis was inversely related to the extent of lumenal distention with water. The effectiveness of peristaltic contractions in driving the hydrogel toward the pyloric sphincter increased as the water was emptied from the stomach. In the absence of water, imaging of the gel with ultrasound became difficult. For this reason, gels were loaded with diatrizoate meglumine/sodium diatrizoate to visualize in real-time using fluoroscopic imaging. Fluoroscopic imaging allowed only indirect assessment of the hydrogel movement during peristalsis and the degree of hydrogel swelling. The gastric retention of the hydrogel under fasted conditions was influenced by the degree of gel deformation in response to peristaltic contractions. Hydrogels with a low degree of deformation during peristalsis showed long gastric retention times. The utilization of ultrasound imaging and fluoroscopic imaging for monitoring dynamic events in the stomach provided information on hydrogel properties which are important to gastric retention. The use of these imaging techniques in the development of long-term oral drug delivery systems is described. PMID:1600031

Shalaby, W S; Blevins, W E; Park, K

1992-01-01

421

Random Curves by Conformal Welding  

E-print Network

We construct a conformally invariant random family of closed curves in the plane by welding of random homeomorphisms of the unit circle given in terms of the exponential of Gaussian Free Field. We conjecture that our curves are locally related to SLE$(\\kappa)$ for $\\kappa<4$.

Astala, K; Kupiainen, A; Saksman, E

2009-01-01

422

Random Curves by Conformal Welding  

E-print Network

We construct a conformally invariant random family of closed curves in the plane by welding of random homeomorphisms of the unit circle given in terms of the exponential of Gaussian Free Field. We conjecture that our curves are locally related to SLE$(\\kappa)$ for $\\kappa<4$.

K. Astala; P. Jones; A. Kupiainen; E. Saksman

2009-12-17

423

Increased local retention of reef coral larvae as a result of ocean warming  

NASA Astrophysics Data System (ADS)

Climate change will alter many aspects of the ecology of organisms, including dispersal patterns and population connectivity. Understanding these changes is essential to predict future species distributions, estimate potential for adaptation, and design effective networks of protected areas. In marine environments, dispersal is often accomplished by larvae. At higher temperatures, larvae develop faster, but suffer higher mortality, making the effect of temperature on dispersal difficult to predict. Here, we experimentally calibrate the effect of temperature on larval survival and settlement in a dynamic model of coral dispersal. Our findings imply that most reefs globally will experience several-fold increases in local retention of larvae due to ocean warming. This increase will be particularly pronounced for reefs with mean water residence times comparable to the time required for species to become competent to settle. Higher local retention rates strengthen the link between abundance and recruitment at the reef scale, suggesting that populations will be more responsive to local conservation actions. Higher rates of local retention and mortality will weaken connectivity between populations, and thus potentially retard recovery following severe disturbances that substantially deplete local populations. Conversely, on isolated reefs that are dependent on replenishment from local broodstock, increases in local retention may hasten recovery.

Figueiredo, Joana; Baird, Andrew H.; Harii, Saki; Connolly, Sean R.

2014-06-01

424

Impact of phosphorus control measures on in-river phosphorus retention associated with point source pollution  

NASA Astrophysics Data System (ADS)

In-river phosphorus retention alters the quantity and timings of phosphorus delivery to downstream aquatic systems. Many intensive studies of in-river phosphorus retention have been carried out but generally on a short time scale (2-4 years). In this paper, monthly water quality data, collected by the Environment Agency of England and Wales over 12 years (1990-2001), were used to model daily phosphorus fluxes and monthly in-river phosphorus retention in the lowland calcareous River Wensum, Norfolk, UK. The effectiveness of phosphorus stripping at two major sewage treatment works was quantified over different hydrological conditions. The model explained 78% and 88% of the observed variance before and after phosphorus control, respectively. During relatively dry years, there was no net export of phosphorus from the catchment. High retention of phosphorus occurred, particularly during the summer months, which was not compensated for, by subsequent higher flow events. The critical discharge (Q) above which net remobilisation would occur, was only reached during few, high flow events Q25-Q13. Phosphorus removal from the effluent at two major STWs (Sewage Treatment Works) reduced the phosphorus catchment mass balance variability by 20-24% under the Q99-Q1. range of flow conditions. Although the absorbing capacity of the catchment against human impact was remarkable, further phosphorus remedial strategies will be necessary to prevent downstream risks of eutrophication occuring independently of the unpredictable variability in weather conditions.

Demars, B. O. L.; Harper, D. M.; Pitt, J.-A.; Slaughter, R.

2005-01-01

425

Microbes mediate carbon and nitrogen retention in shallow photic sediments  

NASA Astrophysics Data System (ADS)

Sediments in shallow coastal bays are sites of intense biogeochemical cycling facilitated by a complex microbial consortium. Unlike deeper coastal environments, much of the benthos is illuminated by sunlight in these bays. As a result, benthic autotrophs such as benthic microalgae (BMA) and macroalgae play an integral role in nutrient cycling. Investigating pathways of carbon (C) and nitrogen (N) flow through individual compartments within the sediment microbial community has previously proved challenging due to methodological difficulties. However, it is now possible using stable isotopes and microbial biomarkers such as fatty acids and amino acids to track C and N flow through individual microbial pools. We investigated the uptake and retention of C and N by bacteria and BMA in a shallow subtidal system. Using bulk and compound specific isotopic analysis, we traced the pathways of dissolved inorganic 13C and 15N under various treatments: 1) in ambient light or dark, 2) from porewater or water column sources, and 3) in the presence or absence of bloom forming nuisance macroalgae. Excess 13C and 15N in THAAs and excess 13C in total PLFAs showed a strong dependence on light. Enrichment of these pools represents uptake by the microbial community, which can include both autotrophic and heterotrophic components. Higher excess 13C in benthic microalgal fatty acids (C20, C22 PUFAs) provides evidence that benthic microalgae were fixing 13C. Aditionally, the ratio of excess 13C in branched fatty acids to microbial fatty acids (BAR) and excess 13C and 15N in D-Ala to L-Ala (D/L-Ala) were low, suggesting dominance by benthic microalgae over bacteria to total label incorporation. Our results support uptake and retention of C and N by the sediment microbial community and indicate a tight coupling between BMA and bacteria in shallow illuminated systems. This uptake is diminished in the presence of macroalgae, likely due to shading and/or nutrient competition. Therefore, macroalgae reduce the retention of C and N within surface sediments, diminishing the role of the microbial community in nutrient cycling processes.

Hardison, A.; Anderson, I.; Canuel, E. A.; Tobias, C.; Veuger, B.

2009-12-01

426

Exchange of phosphorus across the sediment-water interface  

Microsoft Academic Search

In this article, principles of phosphorus retention and phosphorus release at the sediment-water interface in lakes are reviewed. New results and hypotheses are discussed in relation to older models of phosphorus exchange between sediments and water. The fractional composition of sedimentary phosphorus is discussed as a tool for interpretation of different retention mechanisms. Special emphasis is given to the impact

Bengt Boström; Jens M. Andersen; Siegfried Fleischer; Mats Jansson

1988-01-01

427

Antiretroviral Treatment Program Retention among HIV-Infected Children in the Democratic Republic of Congo  

PubMed Central

Background Retaining patients with HIV infection in care is still a major challenge in sub- Saharan Africa, particularly in the Democratic Republic of Congo (DRC) where the antiretroviral treatment (ART) coverage is low. Monitoring retention is an important tool for evaluating the quality of care. Methods and Findings A review of medical records of HIV -infected children was performed in three health facilities in the DRC: the Amo-Congo Health center, the Monkole Clinic in Kinshasa, and the HEAL Africa Clinic in Goma. Medical records of 720 children were included. Kaplan Meier curves were constructed with the probability of retention at 6 months, 1 year, 2 years and 3 years. Retention rates were: 88.2% (95% CI: 85.1%–90.8%) at 6 months; 85% (95% CI: 81.5%–87.6%) at one year; 79.4% (95%CI: 75.5%–82.8%) at two years and 74.7% (95% CI: 70.5%–78.5%) at 3 years. The retention varied across study sites: 88.2%, 66.6% and 92.5% at 6 months; 84%, 59% and 90% at 12 months and 75.7%, 56.3% and 85.8% at 24 months respectively for Amo-Congo/Kasavubu, Monkole facility and HEAL Africa. After multivariable Cox regression four variables remained independently associated with attrition: study site, CD4 cell count <350 cells/µL, children younger than 2 years and children whose caregivers were member of an independent church. Conclusions Attrition remains a challenge for pediatric HIV positive patients in ART programs in DRC. In addition, the low coverage of pediatric treatment exacerbates the situation of pediatric HIV/AIDS. PMID:25541707

Ditekemena, John; Luhata, Christophe; Bonane, William; Kiumbu, Modeste; Tshefu, Antoinette; Colebunders, Robert; Koole, Olivier

2014-01-01

428

Toxicity of Karlodinium micrum (Dinophyceae) associated with a fish kill in a South Carolina brackish retention pond  

Microsoft Academic Search

A dinoflagellate bloom was found associated with a fish kill event in a South Carolina brackish water retention pond. A multi-analytical approach was used to confirm the identity of the bloom dinoflagellate and evaluate its potential toxicity. Karlodinium micrum was confirmed through light microscopy, pigment profile comparisons, species-specific PCR, and gene sequence data. Necropsy findings on several fish were suggestive

Jason W. Kempton; Alan J. Lewitus; Jonathan R. Deeds; J. McHugh Law

2002-01-01

429

The solids retention time—a suitable design parameter to evaluate the capacity of wastewater treatment plants to remove micropollutants  

Microsoft Academic Search

Micropollutants as endocrine disrupting compounds (EDC) or pharmaceuticals are of increased interest in water pollution control. Wastewater treatment plant (WWTP) effluents are relevant point sources for residues of these compounds in the aquatic environment. The solids retention time (SRT) is one important parameter for the design of WWTPs, relating to growth rate of microorganisms and to effluent concentrations. If a

M. Clara; N. Kreuzinger; B. Strenn; O. Gans; H. Kroiss

2005-01-01

430

Uptake and Retention of Cs137 by a Blue-Green Alga in Continuous Flow and Batch Culture Systems  

SciTech Connect

Since routine monitoring data show that blue-green algae concentrate radioactivity from water by factors as great as 10,000, this study was initiated to investigate the uptake and retention patterns of specific radionuclides by the dominant genera of blue-green algae in the reactor effluents. Plectonema purpureum was selected for this study.

Watts, J.R.

2003-02-18

431

Processes controlling retention of spring-spawned Atlantic cod (Gadus morhua) in the western Gulf of Maine and their  

E-print Network

Processes controlling retention of spring-spawned Atlantic cod (Gadus morhua) in the western Gulf ABSTRACT Atlantic cod, Gadus morhua, harvested in US waters are currently managed as a Gulf of Maine stock. To investigate the hypothesis that this variation is related to variation in the transport of larval cod

Chen, Changsheng

432

Darwin curves and galaxy arms  

NASA Astrophysics Data System (ADS)

In the natural world, there exists one kind of structure which is beyond the scope of human laboratorial experiment. It is the structure of galaxies which is usually composed of billions of stars. Spiral galaxies are flat disk-shaped. There are two types of spiral galaxies. The spiral galaxies with some bar-shaped pattern are called barred spirals, and the ones without the pattern are called ordinary spirals. Longer-wavelength galaxy images (infrared, for example) show that ordinary spiral galaxies are basically an axi-symmetric disk that is called exponential disk. For a planar distribution of matter, Jin He defined Darwin curves in the plane as such that the ratio of the matter densities at both sides of the curve is constant along the curve. Therefore, the arms of ordinary spiral galaxies are Darwin curves. Now an important question is that: Are the arms of barred spiral galaxies the Darwin curves too? Fortunately, Jin He designed a piece of Galaxy Anatomy graphic software. With the software, not only can people simulate the stellar density distribution of barred spiral galaxies but also can draw the Darwin curves of the simulated galaxy structure. This paper shows partial evidence that the arms of galaxy NGC 3275, 4548 and 5921 follow Darwin curves.

He, Jin

2014-07-01

433

Football and Freshmen Retention: Examining the Impact of College Football on Institutional Retention Rates  

ERIC Educational Resources Information Center

Student retention has been one of the more researched topics in the study of American higher education over the past 20 years (Braxton, Hirschy, & McClendon, 2004; Pascarella & Terenzini, 2005). Very little of this research, however, has attempted to examine the impact of college athletics on an institution's ability to retain students. This…

Jones, Willis A.

2010-01-01

434

Mate retention in marriage: Further evidence of the reliability of the Mate Retention Inventory  

E-print Network

Todd K. Shackelford a,*, Aaron T. Goetz a , David M. Buss b a Department of Psychology, Florida Atlantic University, 2912 College Avenue, Davie, FL 33314, USA b Department of Psychology, The University rights reserved. Keywords: Mate retention; Marriage; Evolutionary psychology 1. Introduction Maintaining

Pillow, Jonathan

435

Water quality beneath urban runoff water management basins  

SciTech Connect

The chemical impact of urban runoff water on water quality beneath five retention/recharge basins was investigated as part of the US EPA's Nationwide Urban Runoff Program in Fresno, California. Soil water percolating through alluvium soils and the ground water at the top of the water table were sampled with ceramic/Teflon vacuum water extractors at depths up to 26 m during the two-year investigation. Inorganic and organic pollutants are present in the runoff water delivered to the basins. No significant contamination of percolating soil water or ground water underlying any of the five retention/recharge basins has occurred for constituents monitored in the study. The oldest basin was constructed in 1962. The concentration of selected trace elements in the ground water samples was similar to the levels reported in the regional ground water. None of the pesticides or other organic priority pollutants, for which water samples were analyzed, was detected except diazinon which was found in trace amounts (0.3 g/L or less) in only three soil water samples. These results are important to the continued conservation of storm water and the development of a best management practice for storm-water management using retention/recharge basins in a semi-arid climate.

Nightingale, H.I.

1987-04-01

436

Exploring Changes in Nitrogen and Phosphorus Retention in Global Rivers in the Twentieth Century  

NASA Astrophysics Data System (ADS)

Nutrients are transported from land to sea through the continuum formed by components of river basins (soils, groundwater, riparian zones, streams, rivers, lakes, and reservoirs). The hydrology, ecology and biogeochemical processing in each of these components are strongly coupled and result in retention of a significant fraction of the nutrients transported. For analyzing the impact of multiple changes and disturbances at the global scale, we use a distributed approach to describe the nitrogen (N) and phosphorus (P) transport and retention in all the above river basin components. A hydrological model is used to describe the water flow through the respective compartments. We analyze the changes in retention during the past century (1900-2000), as this period encompasses dramatic increases in human population and economic human activities that have resulted in global changes, such as climate change, land use change, changes in the hydrology by dam construction, irrigation, and consumptive water use. In the period 1900-2000, the global soil N budget surplus (inputs minus withdrawal by plants) for agricultural and natural ecosystems increased from 118 to 202 Tg yr-1, and the global P budget increased from < 0.5 to 11 Tg P yr-1. Our model for surface runoff accounts for residual P in soils resulting from past surpluses during the 1900-2000 period. For in-stream retention, we use the nutrient spiraling concept. We concentrate on the flows of total N and total P, because of the importance of the ratios between these two elements for biogeochemistry and the functioning of aquatic ecosystems. Since the various processes in the different compartments in terms of delivery to surface water are poorly known, we present a sensitivity analysis of the modeled river export for a number of key variables.

Beusen, A.; Bouwman, L.; Van Beek, R.; Wisser, D.; Hartmann, J.

2012-12-01

437

Rational curves on Fermat hypersurfaces  

E-print Network

In this note we study rational curves on degree $p^r+1$ Fermat hypersurface in $\\PP^{p^r+1}_k$, where $k$ is an algebraically closed field of characteristic $p$. The key point is that the presence of Frobenius morphism makes the behavior of rational curves to be very different from that of charateristic 0. We show that if there exists $N_0$ such that for all $e\\geq N_0$ there is a degree $e$ very free rational curve on $X$, then $N_0> p^r(p^r-1)$.

Shen, Mingmin

2011-01-01

438

Curved conveyor section guide assembly  

SciTech Connect

A guide assembly for a curved conveyor section of a scraperchain conveyor guides the scraper assembly from a first straight conveyor portion round the curved conveyor section to a second straight conveyor portion. This guiding is accomplished by a pair of independently rotatable pulley wheels. A further pair of independently rotatable pulley wheels are provided to guide the drive chain of a plough round the curved conveyor section. This enables the plough to be driven to and fro along the first straight conveyor portion by a drive station attached to the second straight conveyor portion adjacent to the guide assembly.

Truszczinski, H.

1981-02-03

439

The global landscape of intron retentions in lung adenocarcinoma  

PubMed Central

Background The transcriptome complexity in an organism can be achieved by alternative splicing of precursor messenger RNAs. It has been revealed that alternations in mRNA splicing play an important role in a number of diseases including human cancers. Methods In this study, we exploited whole transcriptome sequencing data from five lung adenocarcinoma tissues and their matched normal tissues to interrogate intron retention, a less studied alternative splicing form which has profound structural and functional consequence by modifying open reading frame or inserting premature stop codons. Results Abundant intron retention events were found in both tumor and normal tissues, and 2,340 and 1,422 genes only contain tumor-specific retentions and normal-specific retentions, respectively. Combined with gene expression analysis, we showed that genes with tumor-specific retentions tend to be over-expressed in tumors, and the abundance of intron retention within genes is negatively related with gene expression, indicating the action of nonsense mediated decay. Further functional analysis demonstrated that genes with tumor-specific retentions include known lung cancer driver genes and are found enriched in pathways important in carcinogenesis. Conclusions We hypothesize that intron retentions and consequent nonsense mediated decay may collectively counteract the over-expression of genes promoting cancer development. Identification of genes with tumor-specific retentions may also help develop targeted therapies. PMID:24646369

2014-01-01

440

Prediction of protein retention in hydrophobic interaction chromatography .  

E-print Network

??Hydrophobic interaction chromatography (HIC) is a powerful technique for protein separation. This review examines methodologies for predicting protein retention time in HIC involving elution with… (more)

Mahn, Andrea

2005-01-01

441

Radionuclide Retention in Concrete Wasteforms - FY13  

SciTech Connect

Assessing long-term performance of Category 3 waste cement grouts for radionuclide encasement requires knowledge of the radionuclide-cement interactions and mechanisms of retention (i.e., sorption or precipitation); the mechanism of contaminant release; the significance of contaminant release pathways; how wasteform performance is affected by the full range of environmental conditions within the disposal facility; the process of wasteform aging under conditions that are representative of processes occurring in response to changing environmental conditions within the disposal facility; the effect of wasteform aging on chemical, physical, and radiological properties; and the associated impact on contaminant release. This knowledge will enable accurate prediction of radionuclide fate when the wasteforms come in contact with groundwater. Data collected throughout the course of this work will be used to quantify the efficacy of concrete wasteforms, similar to those used in the disposal of low-level waste and mixed low-level waste, for the immobilization of key radionuclides (i.e., uranium, technetium, and iodine). Data collected will also be used to quantify the physical and chemical properties of the concrete affecting radionuclide retention.

Snyder, Michelle MV; Golovich, Elizabeth C.; Wellman, Dawn M.; Crum, Jarrod V.; Lapierre, Robert; Dage, Denomy C.; Parker, Kent E.; Cordova, Elsa A.

2013-10-15

442

Radionuclide Retention in Concrete Waste Forms  

SciTech Connect

Assessing long-term performance of Category 3 waste cement grouts for radionuclide encasement requires knowledge of the radionuclide-cement interactions and mechanisms of retention (i.e., sorption or precipitation); the mechanism of contaminant release; the significance of contaminant release pathways; how waste form performance is affected by the full range of environmental conditions within the disposal facility; the process of waste form aging under conditions that are representative of processes occurring in response to changing environmental conditions within the disposal facility; the effect of waste form aging on chemical, physical, and radiological properties; and the associated impact on contaminant release. This knowledge will enable accurate prediction of radionuclide fate when the waste forms come in contact with groundwater. The information presented in the report provides data that 1) quantify radionuclide retention within concrete waste form materials similar to those used to encapsulate waste in the Low-Level Waste Burial Grounds (LLBG); 2) measure the effect of concrete waste form properties likely to influence radionuclide migration; and 3) quantify the stability of uranium-bearing solid phases of limited solubility in concrete.

Mattigod, Shas V.; Bovaird, Chase C.; Wellman, Dawn M.; Wood, Marcus I.

2010-09-30

443

Retention of Halogens in Waste Glass  

SciTech Connect

In spite of their potential roles as melting rate accelerators and foam breakers, halogens are generally viewed as troublesome components for glass processing. Of five halogens, F, Cl, Br, I, and At, all but At may occur in nuclear waste. A nuclear waste feed may contain up to 10 g of F, 4 g of Cl, and ?100 mg of Br and I per kg of glass. The main concern is halogen volatility, producing hazardous fumes and particulates, and the radioactive iodine 129 isotope of 1.7x10^7-year half life. Because F and Cl are soluble in oxide glasses and tend to precipitate on cooling, they can be retained in the waste glass in the form of dissolved constituents or as dispersed crystalline inclusions. This report compiles known halogen-retention data in both high-level waste (HLW) and low-activity waste (LAW) glasses. Because of its radioactivity, the main focus is on I. Available data on F and Cl were compiled for comparison. Though Br is present in nuclear wastes, it is usually ignored; no data on Br retention were found.

Hrma, Pavel R.

2010-05-01

444

Hydrogen retention and diffusion in tungsten beryllide.  

PubMed

Beryllide compounds are often used in various domains because they are more resilient to oxidation than pure beryllium and at the same time they keep some of the properties of this metal. Nevertheless, the data about their properties during atomic hydrogen exposure are very scarce: numerous experiments have been conducted in the past few years on solid hydride deposition under beryllium-seeded plasma action or on energetic hydrogen implantation into metallic beryllium; many others have been devoted to hydrogen retention and diffusion in tungsten. There have been fewer studies about hydrogen interaction with the alloys of these metals, although the beryllium-tungsten mixed compounds have been experimentally detected in laboratory experiments. This article reports on calculations carried out using first-principles density functional theory (DFT) on tungsten beryllide crystal (Be12W) taken as a model alloy. The formation and reactivity of atomic vacancies are investigated in the domain of temperature ranging from 0 to 500?K, together with atomic hydrogen retention and diffusivity in the bulk and in/out vacancies. PMID:25017090

Allouche, A; Fernandez, N; Ferro, Y

2014-08-01

445

Nutrient retention efficiency in streams receiving inputs from wastewater treatment plants.  

PubMed

We tested the effect of nutrient inputs from wastewater treatment plants (WWTPs) on stream nutrient retention efficiency by examining the longitudinal patterns of ammonium, nitrate, and phosphate concentrations downstream of WWTP effluents in 15 streams throughout Catalonia (Spain). We hypothesized that large nutrient loadings would saturate stream communities, lowering nutrient retention efficiency (i.e., nutrient retention relative to nutrient flux) relative to less polluted streams. Longitudinal variation in ambient nutrient concentration reflected the net result of physical, chemical, or biological uptake and release processes. Therefore, gradual increases in nutrient concentration indicate that the stream acts as a net source of nutrients to downstream environments, whereas gradual declines indicate that the stream acts as a net sink. In those streams where gradual declines in nutrient concentration were observed, we calculated the nutrient uptake length as an indicator of the stream nutrient retention efficiency. No significant decline was found in dilution-corrected concentrations of dissolved inorganic nitrogen (DIN) and phosphate in 40 and 45% of streams, respectively. In the remaining streams, uptake length (estimated based on the decline of nutrient concentrations at ambient levels) ranged from 0.14 to 29 km (DIN), and from 0.14 to 14 km (phosphate). Overall, these values are longer (lower retention efficiency) than those from nonpolluted streams of similar size, supporting our hypothesis, and suggest that high nutrient loads affect fluvial ecosystem function. This study demonstrates that the efficiency of stream ecosystems to remove nutrients has limitations because it can be significantly altered by the quantity and quality of the receiving water. PMID:14964383

Marti, Eugènia; Aumatell, Jordi; Godé, Lluís; Poch, Manel; Sabater, Francesc

2004-01-01

446

Impact of phosphorus control measures on in-river phosphorus retention associated with point source pollution  

NASA Astrophysics Data System (ADS)

In-river phosphorus retention alters the quantity and timings of phosphorus delivery to downstream aquatic systems. Many intensive studies of in-river phosphorus retention have been carried out but generally on a short time scale (2-4 years). In this paper, monthly water quality data, collected by the Environment Agency of England and Wales over 12 years (1990-2001), were used to model daily phosphorus fluxes and monthly in-river phosphorus retention in the lowland calcareous River Wensum, Norfolk, UK. The calibrated model explained 79% and 89% of the observed variance before and after phosphorus control, respectively. A split test revealed that predicted TP loads were in good agreement with observed TP loads (r2=0.85), although TP loads were underestimated under high flow conditions. During relatively dry years, there was no net export of phosphorus from the catchment. High retention of phosphorus occurred, particularly during the summer months, which was not compensated for, by subsequent higher flow events. This was despite a relatively modest critical discharge (Q) above which net remobilisation occur. Phosphorus removal from the effluent at two major STWs (Sewage Treatment Works) reduced phosphorus retention but not the remobilisation. This may indicate that the presence of impoundments and weirs, or overbank flows may have more control on the phosphorus dynamics under high flow conditions. Further phosphorus remedial strategies will be necessary to prevent downstream risks of eutrophication occurring independently of the unpredictable variability in weather conditions. More research is also needed to quantify the impact of the weir and overbank flows on phosphorus dynamics.

Demars, B. O. L.; Harper, D. M.; Pitt, J.-A.; Slaughter, R.

2005-06-01

447

Variations in retention efficiency of bivalves to different concentrations and organic content of suspended particles  

NASA Astrophysics Data System (ADS)

Retention efficiencies (RE) of scallop ( Chlamys farreri), oyster ( Crassostrea gigas) and mussel ( Mytilus edulis) in a flow-through system were measured to understand the short-term response to various particle and organic matter concentrations. By comparing the RE of C. farreri with that of C. gigas and M. edulis, we gained further knowledge on the feeding physiological characteristics of C. farreri and ascertained the possible cause of high summer mortalities of this species. The experimental feeding conditions included natural differences in the abundance and composition of suspended seston, as well as conditions in which seston abundance and composition were manipulated by adding natural silt or cultured microalgae. The results show that in natural sea water, the minimum particle size for maximal retention in M. edulis, C. gigas and C. farreri was approximately 4, 6, and 8 ?m, respectively; the RE of 2-?m (equivalent spherical diameter) particles was 17%, 19%, and 8%, respectively; and the relative standardized RE was 58%, 49%, and 18%, respectively. In C. gigas and M. edulis, the minimal particle size for maximal retention did not change with food quality (organic content). C. farreri was more sensitive to fluctuations in particle concentration and organic content. With particle concentration increase, the minimal particle size for maximal retention in scallop shifted to large particles and the RE for 2-?m particle decreased from 8% in natural seawater to 1.6%-6% in silt-enriched groups. With organic content increase, the minimal particle size for maximal retention shifted from 8 to 5 ?m in natural seawater.Variation in RE of C. farreri with food conditions and the relationship between lower RE and smaller particle size may hamper C. farreri from food taking due to the decrease in the size distribution of phytoplankton in Sungo Bay.

Zhang, Jihong; Fang, Jianguang; Liang, Xingming

2010-01-01

448

Geoecological controls on net mercury retention in northern peatlands  

NASA Astrophysics Data System (ADS)

Peatlands, which receive much or all of their element inputs (e.g. nutrients or trace metals) via the atmosphere, are considered an ideal archive for studying past changes in mercury (Hg) deposition. These archives potentially contain information not only on important anthropogenic contributions to the environment over the past few centuries, but also on the natural antecedent conditions over the past several millennia. However, the assumption that Hg accumulation rates in peat represent an absolute record of past atmospheric deposition has proved problematic. In on-going studies of Hg retention in northern peatlands (bogs and oligotrophic fens) we find that net Hg accumulation is influenced by a range of geoecological factors in addition to actual changes in atmospheric deposition. Factors that influence the interception and net retention of Hg include differences in vegetation and microtopography - both of which may enhance dry deposition, and properties and processes within the peat such as decomposition that might influence long-term retention. Wetness, too, may play an important role in net retention in the surface peat through increased evasive losses of Hg. Differences between Hg concentrations in vascular plants and mosses are well established (at our site: 5-15 ng/g for leaves/needles of cottongrass, heather, Labrador tea and pine; 15-45 ng/g for mosses Sphagnum centrale and S. rubellum), but we also measured significant differences between different mosses within the same plots (S. rubellum, 24±3 ng/g; S. centrale, 18±2 ng/g). Further differences in Hg concentrations occur for single moss species in different settings; for example, Hg concentrations in S. centrale in open Sphagnum-only plots relative to plots including a mixture of vascular plants that form a field-layer canopy are 18±2 and 32±6 ng/g, respectively. As a result, sampling sites consisting of both Sphagnum and vascular plants have long-term cumulative inventories of mercury in the peat that are >60% greater than in areas characterized only by a mixture of Sphagnum species (where the water table is also relatively highest). However, comparisons of Pb-210 inventories, an independent proxy for atmospheric deposition, indicate that this increase in interception should be ?40%. Based on data also from other sites, where Hg inventories may vary between cores by 2-4 times, we have observed that wetter sites invariably have the lowest cumulative Hg inventories and hypothesize greater evasive loss from wetter sites, which has been shown for soils. We will investigate this during fall 2010. Although we have identified a number of factors that complicate the use of peat records as absolute records of mercury deposition, these problems can be circumvented by multi-core studies that provide a more robust estimate of mean net accumulation rates in peatlands.

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