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1

Water retention curve for hydrate-bearing sediments  

NASA Astrophysics Data System (ADS)

water retention curve plays a central role in numerical algorithms that model hydrate dissociation in sediments. The determination of the water retention curve for hydrate-bearing sediments faces experimental difficulties, and most studies assume constant water retention curves regardless of hydrate saturation. This study employs network model simulation to investigate the water retention curve for hydrate-bearing sediments. Results show that (1) hydrate in pores shifts the curve to higher capillary pressures and the air entry pressure increases as a power function of hydrate saturation; (2) the air entry pressure is lower in sediments with patchy rather than distributed hydrate, with higher pore size variation and pore connectivity or with lower specimen slenderness along the flow direction; and (3) smaller specimens render higher variance in computed water retention curves, especially at high water saturation Sw > 0.7. Results are relevant to other sediment pore processes such as bioclogging and mineral precipitation.

Dai, Sheng; Santamarina, J. Carlos

2013-11-01

2

A conceptual model of the soil water retention curve  

NASA Astrophysics Data System (ADS)

A conceptual model based on the assumption that soil structure evolves from a uniform random fragmentation process is proposed to define the water retention function. The fragmentation process determines the particle size distribution of the soil. The transformation of particles volumes into pore volumes via a power function and the adoption of the capillarity equation lead to an expression for the water retention curve. This expression presents two fitting parameters only. The proposed model is tested on water retention data sets of 12 soils representing a wide range of soil textures, from sand to clay. The agreement between the fitted curves and the measured data is very good. The performances of the model are also compared with those of the two-parameter models of van Genuchten [1980] and Russo [1988] for the water retention function. In general, the proposed model exhibits increased flexibility and improves the fit at both the high and the low water contents range.

Assouline, S.; Tessier, D.; Bruand, A.

1998-02-01

3

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

4

Aerodynamic method for obtaining the soil water retention curve  

NASA Astrophysics Data System (ADS)

A new method for the rapid plotting of the soil water retention curve (SWRC) has been proposed that considers the soil water as an environment limited by the soil solid phase on one side and by the soil air on the other side. Both contact surfaces have surface energies, which play the main role in water retention. The use of an idealized soil model with consideration for the nonequilibrium thermodynamic laws and the aerodynamic similarity principles allows us to estimate the volumetric specific surface areas of soils and, using the proposed pedotransfer function (PTF), to plot the SWRC. The volumetric specific surface area of the solid phase, the porosity, and the specific free surface energy at the water-air interface are used as the SWRC parameters. Devices for measuring the parameters are briefly described. The differences between the proposed PTF and the experimental data have been analyzed using the statistical processing of the data.

Alekseev, V. V.; Maksimov, I. I.

2013-07-01

5

A new model for predicting relative nonwetting phase permeability from soil water retention curves  

E-print Network

A new model for predicting relative nonwetting phase permeability from soil water retention curves by combining soil water retention curves with relative nonwetting phase permeability models. Experimental permeability from soil water retention curves is proposed in this paper. A closed form expression can

Jiao, Jiu Jimmy

6

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

7

Hysteresis and uncertainty in soil water-retention curve parameters  

USGS Publications Warehouse

Accurate estimates of soil hydraulic parameters representing wetting and drying paths are required for predicting hydraulic and mechanical responses in a large number of applications. A comprehensive suite of laboratory experiments was conducted to measure hysteretic soil-water characteristic curves (SWCCs) representing a wide range of soil types. Results were used to quantitatively assess differences and uncertainty in three simplifications frequently adopted to estimate wetting-path SWCC parameters from more easily measured drying curves. They are the following: (1) ?w=2?d, (2) nw=nd, and (3) ?ws=?ds, where ?, n, and ?s are fitting parameters entering van Genuchten’s commonly adopted SWCC model, and the superscripts w and d indicate wetting and drying paths, respectively. The average ratio ?w/?d for the data set was 2.24±1.25. Nominally cohesive soils had a lower ?w/?d ratio (1.73±0.94) than nominally cohesionless soils (3.14±1.27). The average nw/nd ratio was 1.01±0.11 with no significant dependency on soil type, thus confirming the nw=nd simplification for a wider range of soil types than previously available. Water content at zero suction during wetting (?ws) was consistently less than during drying (?ds) owing to air entrapment. The ?ws/?ds ratio averaged 0.85±0.10 and was comparable for nominally cohesive (0.87±0.11) and cohesionless (0.81±0.08) soils. Regression statistics are provided to quantitatively account for uncertainty in estimating hysteretic retention curves. Practical consequences are demonstrated for two case studies.

Likos, William J.; Lu, Ning; Godt, Jonathan W.

2014-01-01

8

A physically-based model to predict the water retention curve from basic geotechnical properties  

E-print Network

A physically-based model to predict the water retention curve from basic geotechnical properties M author: Michel Aubertin (michel.aubertin@polymtl.ca) #12;1 A physically-based model to predict the water means to estimate the water retention curve from basic geotechnical properties. A discussion follows

Aubertin, Michel

9

Chemical migration during soil water retention curve evaluation.  

PubMed

Wetting and drying (W-D) cycles can induce important elemental migrations in soils. The main purpose of this work was to study the possible existence of soil chemical elemental migrations in samples submitted to repeated W-D cycles during evaluations of soil water retention curve (SWRC). The experimental measurements were carried out by Atomic Absorption Spectrometry (AAS) for Ca(2+), Mg(2+) and K(+) on samples of three different Brazilian tropical soils (Geric Ferralsol, Eutric Nitosol and Rhodic Ferralsol). Results demonstrate an increase in the electrical conductivity of the water extracted from the samples and significant losses of Ca(2+), Mg(2+) and K(+) during the applications of up to nine W-D cycles. It was also observed differences in SWRC for all soils when samples submitted to the application of several W-D cycles were compared with samples not submitted to it. These differences occurred at the region of both structural and textural pores. A possible explanation for these results could be the soil chemical migration during the sequences of W-D cycles, which can affect the soil structure development. PMID:21830003

Pires, Luiz F; Villanueva, Felipe C A; Dias, Nivea M P; Bacchi, Osny O Santos; Reichardt, Klaus

2011-09-01

10

Measurement errors of water retention curve using pressure plates: consequences on parameterization  

NASA Astrophysics Data System (ADS)

Pressure plates are very common experimental devices to measure the soil water retention curve. However, recent studies have demonstrated the lack of reliability of pressure plates when measuring the soil water retention curve in the dry range, due to low plate and soil conductance, lack of soil-plate contact and soil dispersion. In a recent investigation on a silt loam soil, water retention data were determined using pressure plates only and a combination of pressure plates and a dew point meter, showing errors in the measurement of the soil water retention curve at potentials less than 20 m-H2O. This error led to unreliable evaluation of soil hydraulic properties and their parameterization. We extended the investigation on the effects of water retention measurement error to eighteen soils having different textural properties, by comparing measurements of soil water retention curves obtained with a combination of Stackman's beds and pressure plates and soil water retention curves obtained with the chilled-mirror dew point technique. The aim of this research was to investigate the differences between the soil water retention curves as function of different soil textural properties and their effect of soil hydraulic properties and water drainage. Comparison between retention curves and fitting van Genuchten parameters, showed an error in measurements made by the combination Stackman's beds and Richards' pressure plates, for potential values below 1 m-H2O to 57 m-H2O. By characterizing textural properties by using geometric mean diameters, a clear relationship between texture and errors in water retention was established. In particular coarser soil displayed errors at lower potential (in absolute value) with respect to finer textures. The occurrence of these errors in the water retention measurement performed with pressure plates showed that it is advisable to use a combination of methodologies to correctly measure an entire soil retention curve and current parameters database should be used with caution.

Bittelli, M.; Solone, R.

2012-04-01

11

Errors in water retention curves determined with pressure plates: Effects on the soil water balance  

NASA Astrophysics Data System (ADS)

Pressure plates apparatus are very common experimental devices utilized to measure the soil water retention curve. Many studies have demonstrated the lack of reliability of pressure plates apparatus when they are used to measure the soil water retention curve in the dry range, due to low plate and soil conductance, lack of hydrostatic equilibrium, lack of soil-plate contact and soil dispersion. In this research, we investigated measurements of soil water retention curves obtained with a combination of Stackman's tables, pressure plates apparatus and the chilled-mirror dew point technique. Specifically, the aim of this research was: (a) to investigate the differences in the measured soil water retention curves by the different experimental methods, (b) evaluate relationships between the experimental differences and soil texture, (c) analyze the effect of experimental differences on hydraulic properties parameterization and (d) investigate the effects of the different parameters set on water transport computation. The results showed differences in measurements made by the combination of Stackman's tables and Richards' pressure plates apparatus as compared to the dew point method, for fine textured soils, while no significant differences were detected for coarse textured soils. Computed cumulative drainage and evaporation displayed lower values if soil water retention curves were obtained from data obtained with the Stackman's tables and Richards' pressure plates apparatus instead of the dew point method. In soils, where the soil water retention curve was measured with traditional methods (Stackman's tables and Richards' pressure plates apparatus) average cumulative drainage was 173 mm, with respect to a combination of methods including the dew point methods, where the average cumulative drainage was 184 mm. Average cumulative evaporation was 77 mm for the traditional methods, while it was 91 mm, for the combination of methods. Overall, when simulation models are used for studies related to solute transport, polluted soil remediation, irrigation management and others, erroneous measurement of the SWRC for fine textured soils, may lead to erroneous computation of the soil water balance.

Solone, R.; Bittelli, M.; Tomei, F.; Morari, F.

2012-11-01

12

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

Microsoft Academic Search

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 larger areas and difficulties to obtain minimally disturbed soil samples, especially under dry conditions,

M. Luisa Prados Garcia; Karl Vanderlinden; Carolina Guardiola-Albert; Juan Vicente Giraldez Cervera; Andrey K. Guber; Yakov A. Pachepsky

2010-01-01

13

Estimating the water retention curve from soil properties: comparison of linear, nonlinear and concomitant variable methods  

Microsoft Academic Search

The unsaturated soil hydraulic functions involving the soil–water retention curve (SWRC) and the hydraulic conductivity provide useful integrated indices of soil quality. Existing and newly devised methods were used to formulate pedotransfer functions (PTFs) that predict the SWRC from readily available soil data. The PTFs were calibrated using a large soils database from Hungary. The database contains measured soil–water retention

Kálmán Rajkai; Sándor Kabos; M. Th. van Genuchten

2004-01-01

14

Water Repellency of Organic Growing Media and Its Consequences on Hysteretic Behaviours of the Water Retention Curve  

E-print Network

of the Water Retention Curve R. Naasz1, 2 , J.-C. Michel1 * and S. Charpentier1 * *Unit A462 1 Joint Research of this study was to estimate the influence of changes in wettability on the water retention properties of the two organic materials studied were observed. For peat, hysteresis was found in the water retention

Paris-Sud XI, Université de

15

A mathematical model for variation in water-retention curves among sandy soils  

E-print Network

@nrel.colostate.edu Abstract: Equations were developed to predict soil matric potential as a function of soil water content in that it embodies three basic properties of water-retention curves: a) matric potential is zero at saturation water content, b) matric potential approaches -1 as water content approaches zero, and c) volumetric water

Wall, Diana

16

An innovative device for determining the soil water retention curve under high suction at different temperatures  

Microsoft Academic Search

To characterise the water retention behaviour of fine soils, high suction values are applied. In this range of values, the\\u000a vapour equilibrium technique is usually used. This paper presents an innovative device, a sorption bench that permits the\\u000a determination of the water retention curve of soil. With this new testing method, the time required for testing is significantly\\u000a reduced. In

Simon Salager; Marta Rizzi; Lyesse Laloui

17

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

18

A physically based model for the water retention curve of clay pastes  

NASA Astrophysics Data System (ADS)

Available approaches for modeling the soil water retention curve are based on parameters to be fitted using observed data. Due to the formal fitting to the data the soil water retention curves of nonswelling and swelling soils are frequently considered on equal grounds, and the data of both soil types are used as examples in validation. The objective of this work is to construct and validate a new physical model of the water retention curve (the drying branch) of a swelling clay paste (as the simplest case of swelling soils) in the broad area of water content and suction values where the effect of adsorption against capillarity is negligible. The approach is based on a unitary description of pore-dimension, pore-shape, and pore-water distributions, using the case of swell-shrink clay pastes as an example. The general expression of suction is factorized. The first factor depends on the characteristic dimensions of water-containing pores and, indirectly, on shrinkage-swelling. The second depends on the soil-porosity variation at shrinkage-swelling. The case of clay paste allows a number of specific simplifications that lead to a final expression for matric suction. The consideration as a whole is based on a recently suggested model connecting the microstructure, pore size distribution, and shrinkage curve of a clay paste. The four parameters of the constructed retention curve have a clear physical meaning and can be measured independently of the model to be developed. These parameters include the density of the solid phase, the volume fraction of the solid phase at maximum water content (at the liquid limit), the minimum relative volume of the clay paste, and the maximum external dimension of 3D pores of the clay matrix at maximum water content. The physical model explains the qualitative differences to be observed between the retention curves of the swelling clay soil pastes and soils with a rigid matrix. For model validation data on the properties and the water retention curve of two clay pastes are compared to a data analysis using the suggested approach. The data and model prediction are in satisfactory agreement.

Chertkov, V. Y.

2004-01-01

19

A physically based model for the water retention curve of clay pastes  

NASA Astrophysics Data System (ADS)

Available approaches for modeling the soil water retention curve are based on parameters to be fitted using observed data. Due to the formal fitting to the data the soil water retention curves of nonswelling and swelling soils are frequently considered on equal grounds, and the data of both soil types are used as examples in validation. The objective of this work is to construct and validate a new physical model of the water retention curve (the drying branch) of a swelling clay paste (as the simplest case of swelling soils) in the broad area of water content and suction values where the effect of adsorption against capillarity is negligible. The approach is based on a unitary description of pore-dimension, pore-shape, and pore-water distributions, using the case of swell-shrink clay pastes as an example. The general expression of suction is factorized. The first factor depends on the characteristic dimensions of water-containing pores and, indirectly, on shrinkage-swelling. The second depends on the soil-porosity variation at shrinkage-swelling. The case of clay paste allows a number of specific simplifications that lead to a final expression for matric suction. The consideration as a whole is based on a recently suggested model connecting the microstructure, pore size distribution, and shrinkage curve of a clay paste. The four parameters of the constructed retention curve have a clear physical meaning and can be measured independently of the model to be developed. These parameters include the density of the solid phase, the volume fraction of the solid phase at maximum water content (at the liquid limit), the minimum relative volume of the clay paste, and the maximum external dimension of 3D pores of the clay matrix at maximum water content. The physical model explains the qualitative differences to be observed between the retention curves of the swelling clay soil pastes and soils with a rigid matrix. For model validation I use the available data on the properties and the water retention curve of two clay pastes and conduct a data analysis using the suggested approach. The data and model prediction are in satisfactory agreement.

Chertkov, V. Y.

2003-04-01

20

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

NASA Astrophysics Data System (ADS)

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 larger areas and difficulties to obtain minimally disturbed soil samples, especially under dry conditions, laboratory measurements of the SWRCs are only suitable for guidance, as a consequence of their low representativity and accuracy. This work was developed within the framework of a research project on the ecohydrological behaviour of the soil-plant-atmosphere system within the Doñana National Park (SW Spain). In order to characterise the hydrological behaviour of the soils, a good estimation of water retention curves and hydraulic parameters is needed. Ten locations within the study area were equipped with soil moisture sensors (ECH2O-EC20, Decagon Devices Inc.) to monitor volumetric water content at different depths throughout the vadose zone. These data allow the estimation of water fluxes and recharge of the underlying aquifer, which plays a crucial role in the wetland system of the Park, declared by UNESCO as Biosphere Reserve. In this work three methods for estimating SWRCs were developed and compared. First, sand and kaolin suction tables were used to obtain SWRCs for both minimally disturbed and disturbed samples. Second, SWRC were estimated with HYDRUS-1D using the monitored volumetric soil water content data. Finally, SWRCs were estimated using the additivity hypothesis, based on the idea that SWRCs can be approximated by summing up SWRCs corresponding to different particle-size and pore-space classes of which the soil is composed. Particle-size distributions were determined in the laboratory while water retention data for the different particle-size classes were taken from literature. The comparison of these three methods allowed us to define their strengths and weaknesses with respect to accurate estimation of SWRCs in sandy soils and to improve the estimation of water fluxes and recharge.

Prados Garcia, M. Luisa; Vanderlinden, Karl; Guardiola-Albert, Carolina; Giraldez Cervera, Juan Vicente; Guber, Andrey K.; Pachepsky, Yakov A.

2010-05-01

21

Identifying a parameterisation of the soil water retention curve from on-ground GPR measurements  

NASA Astrophysics Data System (ADS)

We show the potential of on-ground Ground-Penetrating Radar (GPR) to identify the parameterisation of the soil water retention curve, i.e. its functional form, with a semi-quantitative analysis based on numerical simulations of the radar signal. An imbibition and drainage experiment has been conducted at the ASSESS-GPR site to establish a fluctuating water table, while an on-ground GPR antenna recorded traces over time at a fixed location. These measurements allow to identify and track the capillary fringe in the soil. The typical dynamics of soil water content with a transient water table can be deduced from the recorded radargrams. The characteristic reflections from the capillary fringes in model soils that are described by commonly used hydraulic parameterisations are investigated by numerical simulations. The parameterisations used are (i) full van Genuchten, (ii) simplified van Genuchten with m = 1 - 1/n and (iii) Brooks-Corey. All three yield characteristically different reflections, which allows the identification of an appropriate parameterisation by comparing to the measured signals. We show that for the sand used here, these signals are not consistent with the commonly used simplified van Genuchten parameterisation with m = 1 - 1/n.

Dagenbach, A.; Buchner, J. S.; Klenk, P.; Roth, K.

2013-02-01

22

Modeling the relationships between particle and pore size distributions in multicomponent sphere packs: application to the water retention curve  

Microsoft Academic Search

A probabilistic approach that computes the distribution of the volume of the voids in packed spheres given their size distribution is applied to determine the corresponding water retention curves. The assumption of dense random packing is adopted. The volume of the void determined by four spheres mutually in contact is approximated by the volume of the osculatory sphere. Every void

S. Assouline; Y. Rouault

1997-01-01

23

Relationship between specific surface area and the dry end of the water retention curve for soils with varying clay and organic carbon contents  

NASA Astrophysics Data System (ADS)

Accurate description of the soil water retention curve (SWRC) at low water contents is important for simulating water dynamics and biochemical vadose zone processes in arid environments. Soil water retention data corresponding to matric potentials of less than -10 MPa, where adsorptive forces dominate over capillary forces, have also been used to estimate soil specific surface area (SA). In the present study, the dry end of the SWRC was measured with a chilled-mirror dew point psychrometer for 41 Danish soils covering a wide range of clay (CL) and organic carbon (OC) contents. The 41 soils were classified into four groups on the basis of the Dexter number (n = CL/OC), and the Tuller-Or (TO) general scaling model describing water film thickness at a given matric potential (<-10 MPa) was evaluated. The SA estimated from the dry end of the SWRC (SA_SWRC) was in good agreement with the SA measured with ethylene glycol monoethyl ether (SA_EGME) only for organic soils with n > 10. A strong correlation between the ratio of the two surface area estimates and the Dexter number was observed and applied as an additional scaling function in the TO model to rescale the soil water retention curve at low water contents. However, the TO model still overestimated water film thickness at potentials approaching ovendry condition (about -800 MPa). The semi-log linear Campbell-Shiozawa-Rossi-Nimmo (CSRN) model showed better fits for all investigated soils from -10 to -800 MPa and yielded high correlations with CL and SA. It is therefore recommended to apply the empirical CSRN model for predicting the dry part of the water retention curve (-10 to -800 MPa) from measured soil texture or surface area. Further research should aim to modify the more physically based TO model to obtain better descriptions of the SWRC in the very dry range (-300 to -800 MPa).

Resurreccion, Augustus C.; Moldrup, Per; Tuller, Markus; Ferré, T. P. A.; Kawamoto, Ken; Komatsu, Toshiko; de Jonge, Lis Wollesen

2011-06-01

24

Evolution of water repellency of organic growing media used in Horticulture and consequences on hysteretic behaviours of the water retention curve  

NASA Astrophysics Data System (ADS)

Most of growing media used in horticulture (particularly peat substrates) shows hysteresis phenomena during desiccation and rehydration cycles, which greatly affects their hydraulic properties. The origins of these properties have often been related to one or several of the specific mechanisms such as the non-geometrical uniformity of the pores (also called ‘ink bottle' effect), presence of trapped air, shrinkage-swelling phenomena, and changes in water repellency. However, recent results showed that changes in wettability during desiccation and rehydration could be considered as one of the main factors leading to hysteretic behaviour in these materials with high organic matter contents (Naasz et al., 2008). The general objective was to estimate the evolutions of changes in water repellency on the water retention properties and associated hysteresis phenomena in relation to the intensity and the number of drying/wetting cycles. For this, simultaneous shrinkage/swelling and water retention curves were obtained using method previously developed for soil shrinkage analysis by Boivin (2006) that we have adapted for growing media and to their physical behaviours during rewetting. The experiment was performed in a climatic chamber at 20°C. A cylinder with the growing medium tested was placed on a porous ceramic disk which is used to control the pressure and to full/empty water of the sample. The whole of the device was then placed on a balance to record the water loss/storage with time; whereas linear displacement transducers were used to measure the changes in sample height and diameter upon drying and wetting in the axial and radial directions. Ceramic cups (2 cm long and 0.21 cm diameter) connected to pressure transducers were inserted in the middle of the samples to record the water pressure head. In parallell, contact angles were measured by direct droplet method at different steps during the drying/rewetting cycles. First results obtained on weakly decomposed peat samples with or without surfactants showed isotropic shrinkage and swelling, and highlighted hysteresis phenomena in relation to the intensity of drying/wetting cycle. Contact angle measurements are in progress. Other measurements on highly decomposed peat (more repellent than weakly decomposed), composted pine bark (without volume change during dryin/wetting cycles), and coco fiber (expected as non repellent organic growing media) are also in progress.

Michel, Jean-Charles; Qi, Guifang; Charpentier, Sylvain; Boivin, Pascal

2010-05-01

25

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...

26

Retention Curve Measurement for Sands Using a TDR-based Long Column and Modified Tempe Cell  

Microsoft Academic Search

Long column and Tempe cell are typical methods for measuring the water retention curves for soils. In the conventional long column method utilizing a stack of rings, water saturation profile is determined gravimetrically. X-ray or gamma ray attenuation are non-destructive methods but require complex and expensive devices and involve the use of photon sources. Time domain reflectometry (TDR) is an

T. Sakaki; T. H. Illangasekare

2006-01-01

27

Water retention and gas relative permeability of two industrial concretes  

SciTech Connect

This experimental study aims at identifying the water retention properties of two industrial concretes to be used for long term underground nuclear waste storage structures. Together with water retention, gas transfer properties are identified at varying water saturation level, i.e. relative gas permeability is assessed directly as a function of water saturation level S{sub w}. The influence of the initial de-sorption path and of the subsequent re-saturation are analysed both in terms of water retention and gas transfer properties. Also, the influence of concrete microstructure upon water retention and relative gas permeability is assessed, using porosity measurements, analysis of the BET theory from water retention properties, and MIP. Finally, a single relative gas permeability curve is proposed for each concrete, based on Van Genuchten-Mualem's statistical model, to be used for continuous modelling approaches of concrete structures, both during drying and imbibition.

Chen Wei; Liu Jian; Brue, Flore; Skoczylas, Frederic [Univ Lille Nord de France, F-59000 Lille (France); ECLille, LML, BP 48, F-59650 Villeneuve d'Ascq (France); CNRS, UMR 8107, F-59650 Villeneuve d'Ascq (France); Davy, C.A., E-mail: catherine.davy@ec-lille.fr [Univ Lille Nord de France, F-59000 Lille (France); ECLille, LML, BP 48, F-59650 Villeneuve d'Ascq (France); CNRS, UMR 8107, F-59650 Villeneuve d'Ascq (France); Bourbon, Xavier; Talandier, Jean [Andra, 1-7 rue Jean Monnet, F-92298 Chatenay-Malabry Cedex (France)

2012-07-15

28

On the influence of coarse fragments on soil water retention  

Microsoft Academic Search

The classical determination of the soil water retention curve (SWRC) by measuring soil water content $\\\\theta$ at different matric potentials ? using undisturbed soil samples is time consuming and expensive. Furthermore, undisturbed soil sampling can be an intricate task when coarse soil fragments (>2 mm) are present. The objective of this study was to test whether tension infiltrometry could be

J. M. Baetens; K. Verbist; W. M. Cornelis; D. Gabriels; G. Soto

2009-01-01

29

Comparison of Predicted and Measured Soil Retention Curve in Lombardy Region Northern of Italy  

NASA Astrophysics Data System (ADS)

Water retention characteristics are crucial input parameters in any modeling study on water flow and solute transport. These properties are difficult to measure and therefore the use of both direct and indirect methods is required in order to adequately describe them with sufficient accuracy. Several field methods, laboratory methods and theoretical models for such determinations exist, each having their own limitations and advantages (Stephens, 1994). Therefore, extensive comparisons between estimated, field and laboratory results to determine it still requires their validity for a range of different soils and specific cases. This study attempts to make a contribution specifically in this connection. The soil water retention characteristics were determined in two representative sites (PMI-1 and PMI-5) located in Landriano field, in Lombardy region, northern Italy. In the laboratory, values of both volumetric water content (?) and soil water matric potential (h) are measured in the same sample using the tensiometric box and pressure plate apparatus. Field determination of soil water retention involved measurements of soil water content with SENTEK probes, and matric potential with tensiometers. The retention curve characteristics were also determined using some of the most commonly cited and some recently developed PTFs that use soil properties such as particle-size distribution (sand, silt, and clay content), organic matter or organic Carbon content, and dry bulk density. Field methods are considered to be more representative than laboratory and estimation methods for determining water retention characteristics (Marion et al., 1996). Therefore, field retention curves were compared against retention curves obtained from laboratory measurements and PTFs estimations. The performances of laboratory and PTFs in predicting field measured data were evaluated using root mean square error (RMSE) and bias. The comparison showed that laboratory measurements were the most accurate. They had the highest ranking for the validation indices (RMSE ranging between 2.4 and 7.7% and bias between 0.1 and 6.4%). The second best technique was the PTF Rosetta (Schaap et al. 2001). They perform only slightly poorer than the laboratory measurements (RMSE ranging between 2.7 and 10% and bias between 0.3 and 7.7%). The lowest prediction accuracy is observed for the Rawls and Brakensiek (1985) PTF (RMSE ranging between 6.3 and 17% and bias between 5 and 10%) which is in contradiction with previous finding (Calzolari et al., 2001), showing that this function is well representing the retention characteristics of the area. We conclude that the Rosetta PTF developed by Schaap et al (2001) appears to be well suited to predict the soil moisture retention curve from easily available soil properties in the Lombardy area and further field investigations would be useful to reinforce this finding. Keywords: water retention curve; laboratory measurements; field measurements; pedotransfert functions; comparison.

Wassar, Fatma; Rienzner, Michele; Chiaradia, Enrico Antonio; Gandolfi, Claudio

2013-04-01

30

A new Approach to Soil Water Retention (Drying Branch)  

NASA Astrophysics Data System (ADS)

Available models of soil water retention for both swelling and non-swelling cases with all essential differences between them are, in part or totally, based on curve-fitting to relevant experimental soil water retention data. The models use either parameters of a pore-size distribution in the fitting or parameters of some mathematical approximation (different for different models) of a retention curve. At least a part of the parameters have no clear physical meaning and can only be found by fitting. As a consequence, although the models can be of practical use for engineering applications, their possibilities from the viewpoint of advancement in the physical understanding and knowledge of the links between inter- and intra-aggregate soil structure and soil water retention as a function of the structure, are, even in the best case, limited. Recently the possibility of the physical prediction of another key soil characteristic - the shrinkage curve - was shown (Chertkov, 2007a, b, 2008a, b). These works permit one to explain soil shrinkage from inter- and intra-aggregate soil structures and without fitting (after many years of the domination of curve-fitting approaches). The results of these works strengthen the certainty that the physical prediction of soil characteristics is not hopeless, but just a difficult problem. The objective of this work is to slightly "dilute" the curve-fitting domination and to suggest some physical alternative as applied to the consideration of soil water retention (drying branch) in the general case, i.e., for swell-shrink soils. The attempt to be proposed relies on the concepts and results of recent works devoted to pure clay water retention (Chertkov, 2004) and soil shrinkage (Chertkov, 2007a, b, 2008a, b). The physical model to be presented includes three parts. We consider: (i) how in the general case a soil water retention curve can be presented through water retention curves of a contributive clay, an intra-aggregate matrix, and a system of internally saturated aggregates; (ii) essential improvement of the available clay water retention model (Chertkov, 2004); and (iii) water retention of a rigid matrix that can consist of sand grains or rigid water saturated aggregates. Then, using the model, we analyze available data to substantiate it. Chertkov V.Y. 2004. A physically based model for the water retention curve of clay pastes. Journal of Hydrology. 286, 203-226. Chertkov V.Y. 2007a. The reference shrinkage curve at higher than critical soil clay content. Soil Sci. Soc. Am. J. 71(3), 641-655. Chertkov V.Y. 2007b. The soil reference shrinkage curve. Open Hydrology Journal. 1, 1-18. Chertkov V.Y. 2008a. Estimating the aggregate/intraaggregate mass ratio of a shrinking soil. Open Hydrology Journal. 2, 7-14. Chertkov V.Y. 2008b. The physical effects of an intra-aggregate structure on soil shrinkage. Geoderma. 146, 147-156.

Chertkov, V. Y.

2008-12-01

31

Water retention of rigid soils from a two-factor model for clay  

E-print Network

Water retention is one of the key soil characteristics. Available models of soil water retention relate to the curve-fitting type. The objective of this work is to suggest a physical model of water retention (drying branch) for soils with a rigid matrix. "Physical" means the prediction based on the a priori measured or estimated soil parameters with a clear physical meaning. We rely on the two-factor model of clay that takes into account the factors of capillarity and shrinkage. The key points of the model to be proposed are some weak pseudo shrinkage that the rigid soils demonstrate according to their experimental water retention curves, and some specific properties of the rigid grain matrix. The three input parameters for prediction of soil water retention with the rigid grain matrix include inter-grain porosity, as well as maximum and minimum grain sizes. The comparison between measured and predicted sand water retention curves for four different sands is promising.

Chertkov, V Y

2014-01-01

32

2.5 SOIL WATER POTENTIAL ESTIMATES Soil moisture retention curves were evaluated for representative A, AE, and EB horizon soils  

E-print Network

measurements of soil water content (Fig. 5). Thermocouple psychrometers (SC-10, Decagon Devices, Inc., Pullman thermometers (NT-3, Decagon Devices) were used to derive µV and temperature readings for conversion into water#12;#12;#12;#12;#12;#12;#12;#12;#12;#12;#12;#12;#12;#12;#12;#12;#12;2.5 SOIL WATER POTENTIAL

33

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

34

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

35

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

36

The water retention properties of a natural unsaturated loess from Northern France J. A. Muoz-Castelblanco, J. M. Pereira, P. Delage and Y. J. Cui  

E-print Network

1 The water retention properties of a natural unsaturated loess from Northern France J. A. Muñoz The water retention properties of a natural loess from Northern France were investigated on intact block high capacity tensiometer (HCT) so as to determine the water retention curve of the loess. The results

Paris-Sud XI, Université de

37

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

38

Estimating Dry-Range Water Retention Properties Using Specific Surface Area and Particle-Size Measurements  

Microsoft Academic Search

To test whether the slope of the dry-range water retention curve can be correlated directly with particle size and specific surface area, measurements were completed for core samples from the Mojave Desert and the Idaho National Engineering and Environmental Laboratory. Samples ranged in texture from gravelly sands to silt loams. Each core sample was split into representative, 1-3 g subsamples,

K. A. Winfield; J. R. Nimmo

2001-01-01

39

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

40

Is the water heating curve as described?  

Microsoft Academic Search

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 process, we calculated that radiation, convection and evaporation are the

H. G. Riveros; A. I. Oliva

2008-01-01

41

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

42

Nitrogen surface water retention in the Baltic Sea drainage basin  

NASA Astrophysics Data System (ADS)

In this paper, we estimate the surface water retention of nitrogen (N) in all the 117 drainage basins to the Baltic Sea with the use of a statistical model (MESAW) for source apportionment of riverine loads of pollutants. Our results show that the MESAW model was able to estimate the N load at the river mouth of 88 Baltic Sea rivers, for which we had observed data, with a sufficient degree of precision and accuracy. The estimated retention parameters were also statistically significant. Our results show that around 380 000 t of N are annually retained in surface waters draining to the Baltic Sea. The total annual riverine load from the 117 basins to the Baltic Sea was estimated to 570 000 t of N, giving a total surface water N retention of around 40%. In terms of absolute retention values, three major river basins account for 50% of the total retention in the 117 basins; i.e. around 104 000 t of N is retained in Neva, 55 000 t in Vistula and 32 000 t in Oder. The largest retention was found in river basins with a high percentage of lakes as indicated by a strong relationship between N retention (%) and share of lake area in the river drainage areas. For example in Göta älv, we estimated a total N retention of 72%, whereof 67% of the retention occurred in the lakes of that drainage area (Lake Vänern primarily). The obtained results will hopefully enable the Helsinki Commission (HELCOM) to refine the nutrient load targets in the Baltic Sea Action Plan (BSAP), as well as to better identify cost-efficient measures to reduce nutrient loadings to the Baltic Sea.

Stålnacke, P.; Pengerud, A.; Vassiljev, A.; Smedberg, E.; Mörth, C.-M.; Hägg, H. E.; Humborg, C.; Andersen, H. E.

2014-09-01

43

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

44

A physical-chemical model for the static water retention characteristic of unsaturated porous media  

NASA Astrophysics Data System (ADS)

Water retention characteristic or water retention curve (WRC) is an important constitutive feature of porous media, and also meanwhile is an indispensable requirement in hydraulic transport modelling. Previous experiments have indicated that the specific surface area of porous media has effects on the WRC. It has also been observed that a linear relationship generally exists between the air-water interface area and the water saturation within unsaturated porous media. However it seems that no detailed study on their internal linkage with the WRC has been reported yet. This paper, at first gives a review of the development of WRC modelling, then it tries to explain the water retention characteristic according to the physical and chemical behaviours of the phases involved in unsaturated porous media. Using the traditional capillary theory, the volume averaging theorem and the advances in physical chemistry of interfacial surfaces, this paper then derives out a formula which represents the water retention characteristic of porous media. This formula demonstrates the internal linkage of the WRC to the specific surface area of porosities. It also shows agreements with the experimental observations mathematically. Based on this formula, a fitting model is proposed for the static WRC of porous media. Finally, this model is tested to fit the WRC measurements of a wide range of porous materials. Comparison with other main models is presented.

Wang, Y.; Grove, S. M.; Anderson, M. G.

45

Evaluation of the Arya-Paris model for estimating water retention characteristics of lignitic mine soils  

SciTech Connect

Mine soil materials may be viewed as man-made systems that consist of spatially disordered soil and sediment components, which are in an initial stage of soil development. A question is whether methods and approaches developed for natural soils, may also be used for such artificially created soil materials. The applicability of the Arya and Paris pedotransfer function to obtain hydraulic properties from the particle size distribution and bulk density was tested for lignitic mine soil material of the Lusatian Lignite Mining District in eastern Germany. The scaling factor a in this model was evaluated by (I) fitting of the water retention curves estimated with the Arya-Paris model (APM) to measured water retention data and (ii) interpretation of a as a fractal dimension of the pore channels and derivation of this fractal dimension from the fractal dimension of the particle size distribution. The two tested fractal approaches resulted in relatively inaccurate predictions of the water content. The use of a single fitted a value for each depth yielded a values between 1.05 and 1.47. Because of the inability of the APM to account for residual water contents in this sandy soil material, a correction was applied. The cumulative mass fraction fractal method did not improve the estimation in comparison with the retention curves calculated with a constant a value of 1.38. The closest fits with the data were obtained by using a variable a value that depended on the particle size. The accuracy of the predictions of the APM in the higher suction range could be improved (lower mean deviations and root mean square deviations of water content) by using a linear water content-dependent correction factor. Better estimates of water retention in the relatively dry range may be significant for simulation of water budgets of mine spoil sites in the Lusatian Mining District.

Buczko, U.; Gerke, H.H. [Brandenburg University of Technology, Cottbus (Germany)

2005-07-01

46

Variation of Retention Curves in the Past 70 years in the Tatsunokuchi-yama Forested Experimental Watershed  

NASA Astrophysics Data System (ADS)

Long-term variation of the retention curves were examined for better understanding of forest and water interaction in the Kita-tani catchment (17 ha) and the Minami-tani catchment (23 ha) in the Tatsunokuchi-yama experimental watershed (34°42'N, 133°58'E, 36-257 m) where rainfall and runoff observations started in 1937. The retention curve in watershed basis is expressed as relationship between rainfall (P) and loss of rainfall (L); L=S{1-exp(-KP)}. L is the difference between P and direct runoff. When P is infinity, L equals S. Hence S is sometimes called maximum water-holding capacity of watershed. As K gets larger, L becomes larger at same P when S is same. Unit flood hydrographs (peak runoff ≥ 1 mm/d) were extracted from daily runoff data, then P and L were estimated for each unit hydrograph. P and L were regressed in every five years with yearly step. Consequently, annual S and K were obtained. Coefficients of correlation were greater than 0.8 except 2005-2009 in the Kita-tani (r>0.7). Relationship between variation of moving median of these regression parameters and changes of vegetation cover condition were summarized as follows; S approximately ranged from 50 to 400 mm. S became larger when forest was thickly growing. In contrast, S became smaller when clearcut was conducted, forest fire occurred, or pine wilt disease occurred. If these variation of S were brought mainly by changes of canopy interception loss, it is not suitable to call S as water-holding capacity. K ranged from about 0.002 to 0.018. K showed antiphase that K becomes lager when S becomes smaller. Each catchment has individual variation of S and K as they have different history of vegetation cover. Annual rainfall in Tatsunokuchi-yama is about 1200 mm in average, but there is interannual fluctuation about 1000 mm (ranges about 600 to 1600 mm). In addition, direct runoffs' fluctuation influenced by antecedent rainfall condition is quite large because of seasonal deviation of rainfall and geology that is primarily underlain by crack rich Paleozoic sedimentary rocks of forearc accretionary prism. Although these circumstances exist, it is thought that vegetation cover condition can be explained by annual S and K.

Hosoda, I.

2010-12-01

47

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; Slawinski, Cezary; Moreno, Felix; Barna, Gyongyi; Skierucha, Wojciech; Arrue, Jose L.

2014-01-01

48

Modelling soil water retention using support vector machines with genetic algorithm optimisation.  

PubMed

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

49

Modeling of soil water retention from saturation to oven dryness  

Microsoft Academic Search

Most analytical formulas used to model moisture retention in unsaturated porous media have been developed for the wet range and are unsuitable for applications in which low water contents are important. We have developed two models that fit the entire range from saturation to oven dryness in a practical and physically realistic way with smooth, continuous functions that have few

Cinzia Rossi; John R. Nimmo

1994-01-01

50

Pathophysiology of Sodium and Water Retention in Heart Failure  

Microsoft Academic Search

Heart failure is a leading cause of morbidity and mortality. In the United States, there are more than 5 million patients with heart failure and over 500,000 newly diagnosed cases each year. Numerous advances have been made in our understanding of the pathophysiologic mechanisms contributing to sodium and water retention in this condition. Important alterations in the sympathetic nervous system

Melissa A. Cadnapaphornchai; Andrei K. Gurevich; Howard D. Weinberger; Robert W. Schrier

2001-01-01

51

Assessment of Stormwater Retention Basin Water Quality in Winnipeg, Canada  

Microsoft Academic Search

The water quality behaviour of 58 stormwater retention basins in Winnipeg, Canada, was intensively studied during a 5-month summer period (May to September). Dissolved oxygen (DO), temperature, turbidity, transparency and depth were measured onsite. Samples analyzed in the laboratory included: total suspended solids (TSS), pH, chlorophyll a, fecal coliforms (FC), total kjeldahl nitrogen (TKN), ammonia, nitrate, total phosphorus (TP) and

SARAH C. WAKELIN; PANAGIOTIS ELEFSINIOTIS; DAVID G. WAREHAM

2003-01-01

52

INFLUENCE OF CATION LEACHING ON WATER RETENTIVITY OF DRINKING WATER SLUDGE  

NASA Astrophysics Data System (ADS)

It is important for waste management and sound material-cycle society to clarify the change of the physico-chemical properties of reusable material. In this study, the influence of cation leaching on water retentivity of drinking water sludge was investigated. The column leaching test was executed using drinking water sludge to simulate rainwater percolation, and the water retentivity test of the degraded sludge was executed. As a result, the water retentivity of drinking water sludge decreased after cation leaching. The cation exchangeable capacity of drinking water sludge and its microscopic structure were almost stable during the leaching test. The results indicate a possibility that Al leaching decreases the hydrophilic part of flocculating agent which relates to water retention of drinking water sludge.

Watanabe, Yasutaka; Komine, Hideo; Yasuhara, Kazuya; Murakami, Satoshi; Toyoda, Kazuhiro

53

Water retention, hydraulic conductivity of hydrophilic polymers in sandy soil as affected by temperature and water quality  

NASA Astrophysics Data System (ADS)

SummaryHydrophilic polymers can swell by absorbing huge volumes of water or aqueous solutions. This property has led to many practical applications of these new materials, particularly in arid regions for improving water retention in sandy soils and the water supply to plants grown on them. The effects of two hydrophilic polymers, carboxymethylcellulose (RF) and isopropyl acrylamide (BF) on the water holding capacity and saturated hydraulic conductivity ( KS) of a sandy soil at varying soil temperature and water quality were evaluated. The RF was less efficient in absorbing water than BF, but the efficiency of BF in retaining water was negatively affected by its thermo-sensitivity and the quality of water. The temperature dependence of the water absorption was not clear for the soils treated with RF, whereas, the efficiency of BF treatment in absorbing water decreased significantly ( P < 0.05) with increasing soil temperature. The dependence of the KS on soil temperature differed with the type of hydrophilic polymer used. The KS of the control soil remained nearly constant as the soil temperature increased. The KS of the BF treated soil increased significantly ( P < 0.05) and linearly with increasing soil temperature, while that of soil treated with RF showed a quadratic response. The soil-absorbent mixtures exhibited different water retention characteristics under different soil temperature conditions. The increase in soil temperature did not affect the water retention characteristics curve of the control. The effect of soil temperature on the water potential curve of the soil treated with RF was not clear particularly when the temperature increased from 25 to 35 °C. The water potential curve for soil-BF mixtures showed that the water content value at field capacity shifted from 0.21 to 0.10 cm 3 cm -3 for 0.1% and from 0.27 to 0.12 cm 3 cm -3 for 0.2%, as the soil temperature increased from 15 to 35 °C. This implies that the soil-BF absorbent mixtures would release some moisture as the soil temperature would increase from 15 to 35 °C, and this water could be lost by percolation or taken up by plant. It was found that available water content increased up to four times with RF as compared to control soil whereas it increased up to five times with BF treatment. At high temperature, the difference was much reduced except for RF at 0.2%. This understanding of the characteristics of the absorbents and the interactions among absorbents, soil, and temperature would be of help in water management in sandy soil.

Andry, H.; Yamamoto, T.; Irie, T.; Moritani, S.; Inoue, M.; Fujiyama, H.

2009-06-01

54

A model for soil surface evaporation based on Campbell's retention curve  

NASA Astrophysics Data System (ADS)

SummaryThe objective of this study was to develop and verify a simple analytical model for one-dimensional non-steady upward flow from shallow and falling water table with minimum input data. Consequently, an analytical model was derived based on the Richards' equation with the Campbell's parametric retention model. This study proposes a model that uses the measurement of water table depth drawdown and some soil physical properties to estimate evaporation, instead of measuring evaporation rate itself. Nine relatively large lysimeters were packed with sandy loam, silty clay loam, and silty clay soil textures to obtain the data needed for evaluating the proposed model. The results indicate a reasonable agreement between the experimental data and the proposed model (root mean square error, RMSE = 2.11-4.22 mm/day). For the experimental period (64 days), however, there is some discrepancy between observation and simulation data. The reasons for this discrepancy may be attributed to vapor upward flow, evaporation which takes place from the lysimeters side gaps resulting from soil shrinkage and collapse of macropores resulting from soil packing.

Zarei, Ghasem; Homaee, Mehdi; Liaghat, Abdol Majid; Hoorfar, Abdol Hosain

2010-01-01

55

INFLUENCE OF CELLULOSE ETHER PARTICLE SIZE ON WATER RETENTION OF FRESHLY-MIXED  

E-print Network

INFLUENCE OF CELLULOSE ETHER PARTICLE SIZE ON WATER RETENTION OF FRESHLY-MIXED MORTARS By L on water retention of freshly-mixed mortars By L. Patural 1 , A. Govin 1 , P. Grosseau 1 , B. Ruot 2 , O to improve water retention capacity and workability of the freshly mixed materials. Cellulose derivatives can

Paris-Sud XI, Université de

56

Definition and experimental determination of a soil-water retention surface  

E-print Network

Definition and experimental determination of a soil-water retention surface S. Salager, M.S. El-water retention surface (SWRS), which is the tool used to present the hydromechanical behaviour of soils with respect to the water retention capability. An experi- mental method is introduced to determine the SWRS

Paris-Sud XI, Université de

57

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 to supply based on consideration of demand and available water: Best achieved using operating policies (OPs (surface- & ground-water) Water supply reservoirs planning and operation Assessment of climate change

Painter, Kevin

58

Applied Budyko curve analysis for county level water resources management  

NASA Astrophysics Data System (ADS)

Human population growth and urbanization exert significant controls on the water and energy balance of many watersheds. The framework of Budyko curve analysis provides a systematic approach to distinguish the local human influences such as surface water regulation, groundwater pumping and land cover change from global climate variation in such watersheds. Two indices, Budyko curve distance (?BC, the distance between a-ratios to the origin on the Budyko diagram) and Budyko curve deviation (?BC, the distance between a-ratios to the original Budyko curve on the Budyko diagram), are computed from the Budyko curve for McHenry County, Illinois (USA), and we test the hypothesis that these indices represent the impact of climate variation and human influences, respectively. Spatial and temporal analysis of the Budyko curve demonstrates that the dominant land cover within a watershed affects the shape and position of the Budyko curve and, therefore, the slope and intercept of the logarithmic regression function defining the curve (i.e., the water and energy characteristics of the watershed). Correlations between per capita water use and ?BC and between farm proprietors’ income and ?BC may explain how climate and human control factors affect these socioeconomic phenomena. Further studies are required to reduce the uncertainties of these correlations.

Yang, Y. E.; Lin, Y. F.

2010-12-01

59

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...

60

Background: Subsurface Water Retention Technology (SWRT) Durable and easy to install: Water  

E-print Network

Background: Subsurface Water Retention Technology (SWRT) Benefits Durable and easy to install: Water retaining membranes can last at least 40 years and can be installed quickly and costeffectively permeable marginal soils converting them to much higher production levels of food crops. Better water

61

Estimation of water retention parameters from nuclear magnetic resonance relaxation time distributions  

PubMed Central

[1] For characterizing water flow in the vadose zone, the water retention curve (WRC) of the soil must be known. Because conventional WRC measurements demand much time and effort in the laboratory, alternative methods with shortened measurement duration are desired. The WRC can be estimated, for instance, from the cumulative pore size distribution (PSD) of the investigated material. Geophysical applications of nuclear magnetic resonance (NMR) relaxometry have successfully been applied to recover PSDs of sandstones and limestones. It is therefore expected that the multiexponential analysis of the NMR signal from water-saturated loose sediments leads to a reliable estimation of the WRC. We propose an approach to estimate the WRC using the cumulative NMR relaxation time distribution and approximate it with the well-known van-Genuchten (VG) model. Thereby, the VG parameter n, which controls the curvature of the WRC, is of particular interest, because it is the essential parameter to predict the relative hydraulic conductivity. The NMR curves are calibrated with only two conventional WRC measurements, first, to determine the residual water content and, second, to define a fixed point that relates the relaxation time to a corresponding capillary pressure. We test our approach with natural and artificial soil samples and compare the NMR-based results to WRC measurements using a pressure plate apparatus and to WRC predictions from the software ROSETTA. We found that for sandy soils n can reliably be estimated with NMR, whereas for samples with clay and silt contents higher than 10% the estimation fails. This is the case when the hydraulic properties of the soil are mainly controlled by the pore constrictions. For such samples, the sensitivity of the NMR method for the pore bodies hampers a plausible WRC estimation. Citation: Costabel, S., and U. Yaramanci (2013), Estimation of water retention parameters from nuclear magnetic resonance relaxation time distributions, Water Resour. Res., 49, 2068-2079, doi:10.1002/wrcr.20207. PMID:23935225

Costabel, Stephan; Yaramanci, Ugur

2013-01-01

62

Neural Network-Based Multi-scale Pedo-Transfer Functions for Soil Water Retention  

NASA Astrophysics Data System (ADS)

Pedo Transfer Functions (PTFs) based on Artificial Neural Networks (ANNs) have been used in the field of hydrology for some time. However, while most previous studies derive and adopt these parameters at matching spatial scales (1:1) of input and output data, here we present two methodologies to derive the soil water retention function at the point or local scale using PTFs trained with coarser scale input data. In the first study, a conventional ANN was trained using soil texture and bulk density data from the SSURGO database (scale 1:24,000) and then used for predicting the soil water contents at different pressure heads with point scale data (1:1) inputs. Suitable bias correction was applied to the resulting output and used to construct the van Genuchten soil water characteristic curve. The results show good agreement between the soil water retention curves constructed from the ANN-based PTFs and the field observations at the local scale. In the second study we employed a Markov Chain Monte Carlo (MCMC) based Bayesian Neural Network to derive the soil water content values. While conventional ANN training attempts to describe the target variable as a function of the input vector and the training weights, Bayesian training attempts to update the weight vector with information available in the data. Comparisons of the outputs from the two methodologies are presented and their respective advantages and disadvantages are highlighted. These methods have potential as suitable tools to tackle the dual problems of parameter estimation and their scaling in one simple package.

Jana, R. B.; Mohanty, B. P.

2006-12-01

63

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

64

Solute-free water retention in preascitic cirrhotic rats following intravenous water loading.  

PubMed

Increased extracellular fluid volume (ECF) characterizes compensated cirrhosis. To identify the mechanisms of fluid retention in cirrhosis through clearance methods, 10 control and 10 preascitic rats with CCl(4)-induced cirrhosis were studied following i.v. loading with 1 ml 5% glucose solution. Glomerular filtration rate and renal plasma flow were evaluated through inulin and para-aminohippurate clearances; water and electrolyte handling was assessed measuring urine and plasma osmolarity, electrolyte excretions, and tubular solute-free water reabsorption (TFWR = osmolar clearance minus urinary output); ECF was assessed through hormonal status determination. After water loading, cirrhotic rats had increased ECF (lower plasma renin activity and aldosterone and higher atrial natriuretic peptide levels, all P<0.03), solute-free water retention (increased TFWR and decreased plasma osmolarity, all P<0.05), reduced absolute and fractional sodium excretions (P<0.05). Cirrhotic rats showed sodium retention in the medullary thick ascending limb of Henle's loop (i.e. increased values of TFWR for any given value of osmolar clearance). Trans-tubular potassium gradient in medullary collecting duct was similar in the two groups (P=0.55), ruling out aldosterone-dependent sodium retention and potassium hyper-secretion. In experimental preascitic cirrhosis NaCl retention in the ascending limb of Henle's loop increases medullary interstitial tonicity leading to vasopressin-independent water back-diffusion in thin descending limb of Henle's loop and collecting duct. PMID:20065504

Sansoe, G; Aragno, M; Smedile, A; Rizzetto, M; Rosina, F

2009-12-01

65

Statistical evaluation and choice of soil water retention models  

NASA Astrophysics Data System (ADS)

This paper presents the results of statistical investigations for the evaluation of soil water retention models (SWRMs). We employed three different methods developed for model selection in the field of nonlinear regression, namely, simulation studies, analysis of nonlinearity measures, and resampling strategies such as cross validation and bootstrap methods. Using these methods together with small data sets, we evaluated the performance of three exemplarily chosen types of SWRMs with respect to their parameter properties and the reliability of model predictions. The resulting rankings of models show that the favorable models are characterized by few parameters with an almost linear estimation behavior and close to symmetric distributions. To further demonstrate the potential of the statistical methods in the field of model selection, a modification of the four-parameter van Genuchten model is proposed which shows significantly improved and robust statistical properties.

Lennartz, Franz; Müller, Hans-Otfried; Nollau, Volker; Schmitz, Gerd H.; El-Shehawy, Shaban A.

2008-12-01

66

Influence of Soil Management on Water Retention from Saturation to Oven Dryness and Dominant Soil Water States in a Vertisol under Crop Rotation  

NASA Astrophysics Data System (ADS)

Unique water transfer and retention properties of Vertisols strongly affect their use in rainfed agriculture in water-limited environments. Despite the agricultural importance of the hydraulic properties of those soils, water retention data dryer than the wilting point are generally scarce, mainly as a result of practical constraints of traditional water retention measurement methods. In this work we provide a detailed description of regionalized water retention data from saturation to oven dryness, obtained from 54 minimally disturbed topsoil (0-0.05m) samples collected at a 3.5-ha experimental field in SW Spain where conventional tillage (CT) and direct drilling (DD) is compared in a wheat-sunflower-legume crop rotation on a Vertisol. Water retention was measured from saturation to oven dryness using sand and sand-kaolin boxes, a pressure plate apparatus and a dew point psychrometer, respectively. A common shape of the water retention curve (WRC) was observed in both tillage systems, with a strong discontinuity in its slope near -0.4 MPa and a decreasing spread from the wet to the dry end. A continuous function, consisting of the sum of a double exponential model (Dexter et al, 2008) and the Groenevelt and Grant (2004) model could be fitted successfully to the data. Two inflection points in the WRC were interpreted as boundaries between the structural and the textural pore spaces and between the textural and the intra-clay aggregate pore spaces. Water retention was significantly higher in DD (p<0.05) for pressure heads ranging from -0.006 to -0.32 MPa, and from -1.8 to -3.3 MPa. The magnitude of these differences ranged from 0.006 to 0.015 kg kg-1. The differential water capacity and associated equivalent pore-size distribution showed that these differences could be attributed to a combined effect of tillage and compaction, increasing and decreasing the amount of the largest pores in CT and DD, respectively, but resulting in a proportionally larger pore space with relevant pore-sizes for water dynamics and agronomic performance. Significant differences in water retention and equivalent pore-sizes at the dry end of the WRC could be associated with the higher organic matter content found in DD. These results explain the superior performance of DD over CT in satisfying high crop water demands, especially at the end of spring when atmospheric water demands become very high, resulting in an extension of the growing period under DD. The results provide also an explanation for the observed soil water dynamics pattern in the field, with rapid transitions between persistent wet and dry water content states. References Dexter, A.R., E.A. Czy?, G. Richard, A. Reszkowska, 2008. A user-friendly water retention function that takes account of the textural and structural pore spaces in soil. Geoderma, 143:243-253. Groenevelt, P.A., C.D. Grant, 2004. A new model for the soil-water retention curve that solves the problem of residual water contents. Eur. J. Soil Sci. 55:479-485.

Vanderlinden, Karl; Pachepsky, Yakov; Pederera, Aura; Martinez, Gonzalo; Espejo, Antonio Jesus; Giraldez, Juan Vicente

2014-05-01

67

REGIONAL SOIL WATER RETENTION IN THE CONTIGUOUS US: SOURCES OF VARIABILITY AND VOLCANIC SOIL EFFECTS  

EPA Science Inventory

Water retention of mineral soil is often well predicted using algorithms (pedotransfer functions) with basic soil properties but the spatial variability of these properties has not been well characterized. A further source of uncertainty is that water retention by volcanic soils...

68

Resolving structural influences on water-retention properties of alluvial deposits  

USGS Publications Warehouse

With the goal of improving property-transfer model (PTM) predictions of unsaturated hydraulic properties, we investigated the influence of sedimentary structure, defined as particle arrangement during deposition, on laboratory-measured water retention (water content vs. potential [??(??)]) of 10 undisturbed core samples from alluvial deposits in the western Mojave Desert, California. The samples were classified as having fluvial or debris-flow structure based on observed stratification and measured spread of particle-size distribution. The ??(??) data were fit with the Rossi-Nimmo junction model, representing water retention with three parameters: the maximum water content (??max), the ??-scaling parameter (??o), and the shape parameter (??). We examined trends between these hydraulic parameters and bulk physical properties, both textural - geometric mean, Mg, and geometric standard deviation, ??g, of particle diameter - and structural - bulk density, ??b, the fraction of unfilled pore space at natural saturation, Ae, and porosity-based randomness index, ??s, defined as the excess of total porosity over 0.3. Structural parameters ??s and Ae were greater for fluvial samples, indicating greater structural pore space and a possibly broader pore-size distribution associated with a more systematic arrangement of particles. Multiple linear regression analysis and Mallow's Cp statistic identified combinations of textural and structural parameters for the most useful predictive models: for ??max, including Ae, ??s, and ??g, and for both ??o and ??, including only textural parameters, although use of Ae can somewhat improve ??o predictions. Textural properties can explain most of the sample-to-sample variation in ??(??) independent of deposit type, but inclusion of the simple structural indicators Ae and ??s can improve PTM predictions, especially for the wettest part of the ??(??) curve. ?? Soil Science Society of America.

Winfield, K. A.; Nimmo, J. R.; Izbicki, J. A.; Martin, P. M.

2006-01-01

69

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

70

SOIL HYDRAULIC CONDUCTIVITY AND RETENTION CURVES FROM TENSION INFILTROMETER AND LABORATORY DATA  

Microsoft Academic Search

Long term tillage effects may be characterized on the basis of changes in soil surface hydraulic properties. These properties directly influence infiltration as well as the movement of soil water to the surface during drying. We measured surface soil hydraulic properties on no-till (NT) and conventional (stubble mulch) tillage (CT) plots, each of which was farmed with either a wheat-sorghum-fallow

S. R. Evett; F. H. Peters; O. R. Jones; P. W. Unger

71

DIVISION S-6—SOIL & WATER MANAGEMENT & CONSERVATION Soil Water Retention as Related to Topographic Variables  

Microsoft Academic Search

long been routinely used in soil mapping (Northcote, 1954). Geomorphometry was proposed as a data source Digital elevation models were proposed and used as a data source to predict soil properties (Moore et al., 1993; McKenzie to estimate soil properties. This study evaluated variability of texture and water retention of soils for a gently sloping 3.7-ha field located and Austin,

A. Pachepsky; D. J. Timlin; W. J. Rawls

72

Water films and scaling of soil characteristic curves at low water contents  

Microsoft Academic Search

Individual contributions of capillarity and adsorptive surface forces to the matric potential are seldom differentiated in determination of soil water characteristic (SWC) curves. Typically, capillary forces dominate at the wet end, whereas adsorptive surface forces dominate at the dry end of a SWC where water is held as thin liquid films. The amount of adsorbed soil water is intimately linked

Markus Tuller

2005-01-01

73

Effects of sodium polyacrylate on water retention and infiltration capacity of a sandy soil.  

PubMed

Based on the laboratory study, the effects of sodium polyacrylate (SP) was investigated at 5 rates of 0, 0.08, 0.2, 0.5, and 1%, on water retention, saturated hydraulic conductivity(Ks), infiltration characteristic and water distribution profiles of a sandy soil. The results showed that water retention and available water capacity effectively increased with increasing SP rate. The Ks and the rate of wetting front advance and infiltration under certain pond infiltration was significantly reduced by increasing SP rate, which effectively reduced water in a sandy soil leaking to a deeper layer under the plough layer. The effect of SP on water distribution was obviously to the up layer and very little to the following deeper layers. Considering both the effects on water retention and infiltration capacity, it is suggested that SP be used to the sandy soil at concentrations ranging from 0.2 to 0.5%. PMID:24701379

Zhuang, Wenhua; Li, Longguo; Liu, Chao

2013-01-01

74

Impact of Natural Conditioners on Water Retention, Infiltration and Evaporation Characteristics of Sandy Soil  

Microsoft Academic Search

Soil conditioners i.e., natural deposits and organic fertilizer are used for alleviate some of poor physical properties of sandy soils such as low water retention and inefficient water use, especially in arid and semi-arid regions such as in Saudi Arabia conditions. The present study aims to investigate the impact of clay deposits and organic fertilizer on water characteristics, cumulative infiltration

G. Abdel-Nasser; A. M. Al-Omran; A. M. Falatah; A. S. Sheta; A. R. Al-Harbi

2007-01-01

75

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

E-print Network

Hamerschlag Hall Green Roof Storm Water Retention and Runoff Reduction Performance performance in reducing storm water runoff and extending the runoff duration. Green roofs can reduce the amount and rate of storm water runoff by covering the impervious roof with porous soils that can retain

Andrews, Peter B.

76

Flux-gradient relationships and soil-water diffusivity from curves of water content versus time  

Microsoft Academic Search

Direct analysis of a family of curves of soil-water content vs. time at different fixed positions enables assessment of the flux-gradient relationship prior to the calculations of soil-water diffusivity. The method is evaluated on both smooth and random-error data generated from the solution of the horizontal soil-water intake problem with a known diffusivity function. Interpolation, differentiation, and intergration are carried

D. L. Nofziger; L. R. Ahuja; D. Swartzendruber

2009-01-01

77

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

Microsoft Academic Search

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

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

2010-01-01

78

Predicting the water retention characteristic of Sicilian soils by pedotransfer functions  

Microsoft Academic Search

The accuracy in predicting the water retention characteristics of some widely used pedotransfer functions (PTFs) was tested using a database of 149 soil samples collected in three Sicilian areas. The PTFs performance was assessed in terms of maximum error (ME), average error (AE) and root mean square error (RMSE) between predicted and measured water content data. The influence of pressure

C. Antinoro; V. Bagarello; M. Castellini; A. Giangrosso; G. Giordano; M. Iovino; A. Sgroi

79

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

80

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

81

Retention of radium from thermal waters on sand filters and adsorbents.  

PubMed

This study was focussed on laboratory experiences of retention of radium from one thermal water on sand filters and adsorbents, trying to find an easy method for the elimination in drinkable waters polluted with this natural radio-nuclide. A thermal water from Cantabria (Spain) was selected for this work. Retention experiences were made with columns of 35 mm of diameter containing 15 cm layers of washed river sand or 4 cm layers of zeolite A3, passing known volumes of thermal water at flows between 4 and 40 ml/min with control of the retained radium by determining the amount in the water after the treatment. The statistical analysis of data suggests that retention depends on the flow and the volume passed through the columns. As additional adsorbents were used kaolin and a clay rich in illite. Jar-test experiences were made agitating known weights of adsorbents with the selected thermal water, with addition of flocculants and determination of radium in filtrated water after the treatment. Data suggest that retention is related to the weight of adsorbent used, but important quantities of radium seem remain in solution for higher amounts of adsorbents, according to the statistical treatment of data. The elution of retained radium from columns or adsorbents, previously used in experiences, should be the aim of a future research. PMID:17346877

Elejalde, C; Herranz, M; Idoeta, R; Legarda, F; Romero, F; Baeza, A

2007-06-18

82

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...

83

Water retention of prefractal porous media generated with the homogeneous and heterogeneous algorithms  

E-print Network

neglect pore connectivity [Bird et al., 1996; Rieu and Perrier, 1998]. One way that this limitation canWater retention of prefractal porous media generated with the homogeneous and heterogeneous models of porous media are of interest in numerous scientific disciplines, including hydrology and soil

Sukop, Mike

84

Neural Network-Based Multi-scale Pedo-Transfer Functions for Soil Water Retention  

Microsoft Academic Search

Pedo Transfer Functions (PTFs) based on Artificial Neural Networks (ANNs) have been used in the field of hydrology for some time. However, while most previous studies derive and adopt these parameters at matching spatial scales (1:1) of input and output data, here we present two methodologies to derive the soil water retention function at the point or local scale using

R. B. Jana; B. P. Mohanty

2006-01-01

85

Wavelet-based multifractal analysis of field scale variability in soil water retention  

NASA Astrophysics Data System (ADS)

Better understanding of spatial variability of soil hydraulic parameters and their relationships to other soil properties is essential to scale-up measured hydraulic parameters and to improve the predictive capacity of pedotransfer functions. The objective of this study was to characterize scaling properties and the persistency of water retention parameters and soil physical properties. Soil texture, bulk density, organic carbon content, and the parameters of the van Genuchten water retention function were determined on 128 soil cores from a 384-m transect with a sandy loam soil, located at Smeaton, SK, Canada. The wavelet transform modulus maxima, or WTMM, technique was used in the multifractal analysis. Results indicate that the fitted water retention parameters had higher small-scale variability and lower persistency than the measured soil physical properties. Of the three distinct scaling ranges identified, the middle region (8-128 m) had a multifractal-type scaling. The generalized Hurst exponent indicated that the measured soil properties were more persistent than the fitted soil hydraulic parameters. The relationships observed here imply that soil physical properties are better predictors of water retention values at larger spatial scales than at smaller scales.

Zeleke, Takele B.; Si, Bing C.

2007-07-01

86

Pilot Scale Microfiltration–Coagulation for Treatment of Retention Pond Water  

Microsoft Academic Search

An evaluation of two commonly used coagulants, alum and ferric chloride was conducted to treat retention pond water using microfiltration. To determine the effectiveness of these coagulants in removing turbidity, color, and total suspended solids two different sets of the experiments were performed. Preliminary test was carried out to evaluate the optimum dosages of coagulants. Optimum turbidity removal was achieved

Katayon Saed; Megat Johari Megat Mohd Noor; Abdul Ghani Liew Abdullah; Mohd Razman Salim; Hiroshi Nagaoka; Hidenori Aya

2004-01-01

87

Resolving Structural Influences on Water-Retention Properties of Alluvial Deposits  

Microsoft Academic Search

With the goal of improving property-transfer model (PTM) predic- tions of unsaturated hydraulic properties, we investigated the influ- ence of sedimentary structure, defined as particle arrangement during deposition, on laboratory-measured water retention (water content vs. potential (u(c))) of 10 undisturbed core samples from alluvial deposits in the western Mojave Desert, California. The samples were classified as having fluvial or debris-flow

Kari A. Winfield; John R. Nimmo; John A. Izbicki; Peter M. Martin

2006-01-01

88

Integrated vegetation designs for enhancing water retention and recycling in agroecosystems  

Microsoft Academic Search

Long term studies have shown strong links between vegetation clearing and rainfall declines and more intense droughts. Many\\u000a agroecosystems are exposed to more extreme weather and further declines in rainfall under climate change unless adaptations\\u000a increase the retention of water in landscapes, and its recycling back to the lower atmosphere. Vegetation systems provide\\u000a vital feedbacks to mechanisms that underpin water

Justin G. RyanClive; Clive A. McAlpine; John A. Ludwig

2010-01-01

89

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

90

Developing joint probability distributions of soil water retention characteristics  

Microsoft Academic Search

A method is presented for developing probability density functions for parameters of soil moisture relationships of capillary head (h(Phi)) and hydraulic conductivity (K(Phi)). These soil moisture parameters are required for the assessment of water flow and solute transport in unsaturated media. The method employs a statistical multiple regression equations proposed in the literature for estimating (h(Phi)) or (K(Phi)) relationships using

Robert F. Carsel; Rudolph S. Parrish

1988-01-01

91

Applying application of aerial photos to estimate a retention volume of Chi-Shui river water in Taiwan  

NASA Astrophysics Data System (ADS)

In groundwater hydrology, retention volume of water is an important parameter for recharge. However, get value of retention volume of river water is not efficiency. In this paper, we used the fixed wing Unmanned Aerial Vehicles(UAVs) (swinglet CAM; senseFly Ltd., Switzerland) to collect images of Chi-Shui river in Taiwan. We also used these images to make aerial photos to estimate retention volume of river. Our interesting area is channel of Chi-Shui river located in Changhua and Yuunlin regions, Taiwan. We find the change obviously at river of terrain features. Taking aerial photo with Geographic Information System(GIS) together can make relief map of river landforms. Because we can get the information from this relief map, we estimate retention volume by three steps. Firstly, we build a relief map before retention. Secondly, building other one after retention. Finally, to compare with two period of relief map and get the retention volume of river water by GIS. In conclusion, we found a retention volume in this method. We can take advantage to the data, which is in used our study, can get a new retention volume immediately.

Chang, I.; Zheng, Y.; Huang, Y.; Huang, S.; Wen, J.

2013-12-01

92

Phosphorus retention in a newly constructed wetland receiving agricultural tile drainage water.  

PubMed

One measure used in Sweden to mitigate eutrophication of waters is the construction of small wetlands (free water surface wetland for phosphorus retention [P wetlands]) to trap particulate phosphorus (PP) transported in ditches and streams. This study evaluated P retention dynamics in a newly constructed P wetland serving a 26-ha agricultural catchment with clay soil. Flow-proportional composite water samples were collected at the wetland inlet and outlet over 2 yr (2010-2011) and analyzed for total P (TP), dissolved P (DP), particulate P (PP), and total suspended solids (TSS). Both winters had unusually long periods of snow accumulation, and additional time-proportional water samples were frequently collected during snowmelt. Inflow TP and DP concentrations varied greatly (0.02-1.09 mg L) during the sampling period. During snowmelt in 2010, there was a daily oscillation in P concentration and water flow in line with air temperature variations. Outflow P concentrations were generally lower than inflow concentrations, with net P losses observed only in August and December 2010. On an annual basis, the wetland acted as a net P sink, with mean specific retention of 69 kg TP, 17 kg DP, and 30 t TSS ha yr, corresponding to a reduction in losses of 0.22 kg TP ha yr from the agricultural catchment. Relative retention was high (36% TP, 9% DP, and 36% TSS), indicating that small constructed wetlands (0.3% of catchment area) can substantially reduce P loads from agricultural clay soils with moderately undulating topography. PMID:23673852

Kynkäänniemi, Pia; Ulén, Barbro; Torstensson, Gunnar; Tonderski, Karin S

2013-01-01

93

Epiphyte Water Retention and Evaporation in Native and Invaded Tropical Montane Cloud Forests in Hawaii  

NASA Astrophysics Data System (ADS)

Epiphyte water retention was quantified at two montane cloud forest sites in Hawai'i Volcanoes National Park, one native and the other invaded by an alien tree species. Water storage elements measured included all epiphytic mosses, leafy liverworts, and filmy ferns. Tree surface area was estimated and a careful survey was taken to account for all epiphytes in the sample area of the forest. Samples were collected and analyzed in the lab for epiphyte water retention capacity (WRC). Based on the volume of the different kinds of epiphytes and their corresponding WRC, forest stand water retention capacity for each survey area was estimated. Evaporation from the epiphyte mass was quantified using artificial reference samples attached to trees that were weighed at intervals to determine changes in stored water on days without significant rain or fog. In addition, a soil moisture sensor was wrapped in an epiphyte sample and left in the forest for a 6-day period. Epiphyte biomass at the Native Site and Invaded Site were estimated to be 2.89 t ha-1 and 1.05 t ha-1, respectively. Average WRC at the Native Site and Invaded Site were estimated at 1.45 mm and 0.68 mm, respectively. The difference is likely due to the presence of the invasive Psidium cattleianum at the Invaded Site because its smooth stem surface is unable to support a significant epiphytic layer. The evaporation rate from the epiphyte mass near WSC for the forest stand at the Native Site was measured at 0.38 mm day-1, which represented 10.6 % of the total ET from the forest canopy at the Native Site during the period. The above research has been recently complemented by a thorough investigation of the WSC of all water storage elements (tree stems, tree leaves, shrubs, grasses, litter, fallen branches, and epiphytes) at six forested sites at different elevations within, above, and below the zone of frequent cloud-cover. The goal of this study was to create an inexpensive and efficient methodology for acquiring estimates of above-ground water retention in different types of forests by means of minimally-destructive sampling and surveying. The results of this work serve as baseline data providing a range of possible values of the water retention of specific forest elements and the entire above-ground total where no values have been previously recorded.

Mudd, R. G.; Giambelluca, T. W.

2006-12-01

94

Estimating Soil Water Retention and Unsaturated Soil Hydraulic Conductivity of Aggregated Soils Using the Additivity Model  

NASA Astrophysics Data System (ADS)

Soil-water potential and hydraulic conductivity relationships with soil water content are needed for many plant and soil-water studies. Conventional soil pore space model lying in the base of "one pore region - one continuum", described by pair of water retention and unsaturated soil hydraulic functions, often oversimplifies representation of variably saturated porous media as a homogeneous textural pore space. Soil structure has a major effect on soils ability to retain and to conduct water. This is especially right for aggregated soils in which pore space consists of interconnected intra- and inter-aggregate pores with distinct hydraulic properties. When a proportion of the inter-aggregate pore space is significant, in many cases the conventional description of water flow provides results that don't much an experimental data. In case of developed "aggregated soil" based on the concept "two pore regions - two continuums" soil pore space is described by two pair of both unsaturated soil hydraulic functions. A special model to estimate these functions is developed based on input data of bulk and aggregate density, structural and textural component distributions. This model was tested with experimental data measured of water retention and hydraulic conductivity of soil cores consisting of aggregates with sizes within narrow ranges. Cores were fabricated from separated individual aggregate fractions of Halpic Chernozem, Podzoluvisol, Halpic Kastanozem soils and artificially prepared aggregates. The obtained results demonstrate the sensitivity of the "additivity" model to estimate both unsaturated soil hydraulic functions for each pore regions. Keywords: aggregated soil, soil structure, soil water retention, additivity model

Zeiliger, A.; Ermolaeva, O.

2009-04-01

95

Heat island mitigation using water retentive pavement sprinkled with reclaimed wastewater.  

PubMed

In Japan, reclaimed wastewater has been recycled widely for non-potable urban applications and it is to be used for sprinkling roads to mitigate heat island in urban areas. To assess the heat island mitigation effects of the sprinkling reclaimed wastewater on water retentive pavement, we carried out a survey at Shiodome-District, Tokyo. The temperatures of air and roads, humidity, and WBGT (Wet-bulb globe temperature) were measured and heat flux was estimated to compare the condition of the areas with/without sprinkling. The following results were obtained. 1) Sprinkling reclaimed wastewater decreased the road surface temperature by 8 degrees during the daytime and by 3 degrees at night: temperatures equal to those on planting zones. Nevertheless sprinkling was done only in the daytime, the temperature decrease effect was not only obtained during the daytime: it continued through the night, due to the water retentive pavement. 2) Sprinkling reclaimed wastewater reduced the amount of sensible heat flux and increased that of latent heat flux. These results suggest that sprinkling reclaimed wastewater on water retentive pavement can effectively mitigate the heat island phenomenon. PMID:18401150

Yamagata, H; Nasu, M; Yoshizawa, M; Miyamoto, A; Minamiyama, M

2008-01-01

96

A new water retention and hydraulic conductivity model accounting for contact angle  

NASA Astrophysics Data System (ADS)

The description of soil water transport in the unsaturated zone requires the knowledge of the soil hydraulic properties, i.e. the water retention and the hydraulic conductivity function. A great amount of parameterizations for this can be found in the literature, the majority of which represent the complex pore space of soils as a bundle of cylindrical capillary tubes of various sizes. The assumption of zero contact angles between water and surface of the grains is also made. However, these assumptions limit the predictive capabilities of these models, leading often to enormous errors in the prediction of water dynamics in soils. We present a pore scale analysis for equilibrium liquid configurations (retention) in angular pores taking the effect of contact angle into account. Furthermore, we propose an alternative derivation of the hydraulic conductivity function, again as a function of the contact angle, assuming flow perpendicular to pore cross sections. Finally, we upscale our model from the pore to the sample scale by assuming a gamma statistical distribution of the pore sizes. Closed form expressions are derived for both sample water retention and conductivity functions. The new model was tested against experimental data from multistep inflow/outflow (MSI/MSO) experiments for a sandy material. They were conducted using ethanol and water as the wetting liquid. Ethanol was assumed to form a zero contact angle with the soil grains. The proposed model described both imbibition and drainage of water and ethanol very well. Lastly, the consideration of the contact angle allowed the description of the observed hysteresis.

Diamantopoulos, Efstathios; Durner, Wolfgang

2013-04-01

97

ESTIMATING WATER TREATMENT COSTS. VOLUME 2. COST CURVES APPLICABLE TO 1 TO 200 MGD TREATMENT PLANTS  

EPA Science Inventory

This report discusses unit processes and combinations of unit processes that are capable of removing contaminants included in the National Interim Primary Drinking Water Regulations. Construction and operation and maintenance cost curves are presented for 99 unit processes that a...

98

Investigation of the use of nanofluids to enhance the In-Vessel Retention capabilities of Advanced Light Water Reactors  

E-print Network

Nanofluids at very low concentrations experimentally exhibit a substantial increase in Critical Heat Flux (CHF) compared to water. The use of a nanofluid in the In-Vessel Retention (IVR) severe accident management strategy, ...

Hannink, Ryan Christopher

2007-01-01

99

Nutrient Cycling and Retention Along a Littoral Gradient in a Dutch Shallow Lake in Relation to Water Level Regime  

Microsoft Academic Search

Littoral zones are characterized by gradients in depth and vegetation biomass, influencing nutrient retention capacity. A\\u000a field experiment was conducted in a Phragmites australis dominated littoral zone to investigate nutrient retention and its effect on surface water quality. Measurements were done\\u000a in mesocosms where water levels could be manipulated. Nutrient status was investigated along a gradient perpendicular to the\\u000a shore

S. Sollie; J. T. A. Verhoeven

2008-01-01

100

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

101

Ecological effects of water retention in the River Rhine valley: a review assisting future retention basin classification  

Microsoft Academic Search

This review paper summarizes the ecological effects of the use of floodplains and flood retention basins to control river flow in the River Rhine (Rhein) valley. Early River Rhine regulation strategies including channel straightening are assessed. The subsequent disappearance of alluvial hardwood forests has been highlighted as the major disadvantage. The response of trees to more recent strategies such as

M. Scholz

2007-01-01

102

Water absorption, retention and the swelling characteristics of cassava starch grafted with polyacrylic acid.  

PubMed

An important application of starch grafted with copolymers from unsaturated organic acids is the use as water absorbent. Although much research has been published in recent years, the kinetics of water absorption and the swelling behavior of starch based superabsorbents are relatively unexplored. Also, water retention under mechanical strain is usually not reported. Cassava starch was used since it has considerable economic potential in Asia. The gelatinized starch was grafted with acrylic acid and Fenton's initiator and crosslinked with N,N'-methylenebisacrylamide (MBAM). Besides a good initial absorption capacity, the product could retain up to 63 g H2O/g under severe suction. The material thus combines a good absorption capacity with sufficient gel strength. The mathematical analysis of the absorption kinetics shows that at conditions of practical interest, the rate of water penetration into the gel is determined by polymer chain relaxations and not by osmotic driven diffusion. PMID:24528736

Witono, J R; Noordergraaf, I W; Heeres, H J; Janssen, L P B M

2014-03-15

103

Gastric emptying of water in children with severe functional fecal retention.  

PubMed

The objective of this study was to evaluate gastric emptying (GE) in pediatric patients with functional constipation. GE delay has been reported in adults with functional constipation. Gastric emptying studies were performed in 22 children with chronic constipation, fecal retention and fecal incontinence, while presenting fecal retention and after resuming regular bowel movements. Patients (18 boys, median age: 10 years; range: 7.2 to 12.7 years) were evaluated in a tertiary pediatric gastroenterology clinic. Gastric half-emptying time of water (reference range: 12 ± 3?min) was measured using a radionuclide technique immediately after first patient evaluation, when they presented fecal impaction (GE1), and when they achieved regular bowel movements (GE2), 12 ± 5 weeks after GE1. At study admission, 21 patients had reported dyspeptic symptoms, which were completely relieved after resuming regular bowel movements. Medians (and interquartile ranges) for GE1 and GE2 were not significantly different [27.0 (16) and 27.5 (21) min, respectively (P = 0.10)]. Delayed GE seems to be a common feature among children with chronic constipation and fecal retention. Resuming satisfactory bowel function and improvement in dyspeptic symptoms did not result in normalization of GE data. PMID:23532267

Fernandes, V P I; Lima, M C L; Camargo, E E; Collares, E F; Bustorff-Silva, J M; Lomazi, E A

2013-03-01

104

Gastric emptying of water in children with severe functional fecal retention  

PubMed Central

The objective of this study was to evaluate gastric emptying (GE) in pediatric patients with functional constipation. GE delay has been reported in adults with functional constipation. Gastric emptying studies were performed in 22 children with chronic constipation, fecal retention and fecal incontinence, while presenting fecal retention and after resuming regular bowel movements. Patients (18 boys, median age: 10 years; range: 7.2 to 12.7 years) were evaluated in a tertiary pediatric gastroenterology clinic. Gastric half-emptying time of water (reference range: 12 ± 3?min) was measured using a radionuclide technique immediately after first patient evaluation, when they presented fecal impaction (GE1), and when they achieved regular bowel movements (GE2), 12 ± 5 weeks after GE1. At study admission, 21 patients had reported dyspeptic symptoms, which were completely relieved after resuming regular bowel movements. Medians (and interquartile ranges) for GE1 and GE2 were not significantly different [27.0 (16) and 27.5 (21) min, respectively (P = 0.10)]. Delayed GE seems to be a common feature among children with chronic constipation and fecal retention. Resuming satisfactory bowel function and improvement in dyspeptic symptoms did not result in normalization of GE data. PMID:23532267

Fernandes, V.P.I.; Lima, M.C.L.; Camargo, E.E.; Collares, E.F.; Bustorff-Silva, J.M.; Lomazi, E.A.

2013-01-01

105

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

106

Concentration polarization with monopolar ion exchange membranes: current–voltage curves and water dissociation  

Microsoft Academic Search

Concentration polarization is studied using a commercial anion and cation exchange membrane. Current–voltage curves show the occurrence of an overlimiting current. The nature of this overlimiting current is investigated in more detail, especially with respect to the contribution of water dissociation. pH measurements reveal that water dissociation is more pronounced in case of the anion exchange membrane than with the

J. J. Krol; M. Wessling; H. Strathmann

1999-01-01

107

Water retention properties of porous geopolymers for use in cooling applications  

Microsoft Academic Search

A series of geopolymers were prepared with varying ratios of sodium silicate, metakaolinite, NaOH and H2O and their porous properties, water retention and mechanical properties were determined, to develop materials for counteracting heat island effects. Samples were prepared with the molar ratios SiO2:Al2O3:Na2O:H2O of 3.66:1:x:y, where x=0.92–1.08 and y=14.2–19.5. The porous and mechanical properties of the geopolymers showed a good

Kiyoshi Okada; Asami Ooyama; Toshihiro Isobe; Yoshikazu Kameshima; Akira Nakajima; Kenneth J. D. MacKenzie

2009-01-01

108

Impact of storm water on groundwater quality below retention/detention basins.  

PubMed

Groundwater from 33 monitoring of peripheral wells of Karachi, Pakistan were evaluated in terms of pre- and post-monsoon seasons to find out the impact of storm water infiltration, as storm water infiltration by retention basin receives urban runoff water from the nearby areas. This may increase the risk of groundwater contamination for heavy metals, where the soil is sandy and water table is shallow. Concentration of dissolved oxygen is significantly low in groundwater beneath detention basin during pre-monsoon season, which effected the concentration of zinc and iron. The models of trace metals shown in basin groundwater reflect the land use served by the basins, while it differed from background concentration as storm water releases high concentration of certain trace metals such as copper and cadmium. Recharge by storm water infiltration decreases the concentration and detection frequency of iron, lead, and zinc in background groundwater; however, the study does not point a considerable risk for groundwater contamination due to storm water infiltration. PMID:19241126

Zubair, Arif; Hussain, Asif; Farooq, Mohammed A; Abbasi, Haq Nawaz

2010-03-01

109

Free water content and sludge retention time: impact on oxygen transfer in activated sludge.  

PubMed

To investigate the effect of sludge retention time (SRT) and the concentration of mixed liquid volatile suspended solids (MLVSS) on oxygen transfer in activated sludge, we studied mass transfer coefficients (k(L)a) in a pilot-scale membrane bioreactor, which treated synthetic greywater. Additionally, experiments with iron hydroxide flocs were performed to examine the role of free water content in oxygen transfer. The results demonstrate that the alpha-factor is reduced when free water content decreases and floc volume increases. Because the MLVSS concentration in activated sludge mainly regulates floc volume, a reduction of oxygen transfer with increasing MLVSS concentration was observed. If the floc volume remains unchanged, oxygen transfer increases with increasing SRT. PMID:20028052

Henkel, Jochen; Cornel, Peter; Wagner, Martin

2009-11-15

110

Studies on Microbial Heavy Metal Retention from Uranium Mine Drainage Water with Special Emphasis on Rare Earth Elements  

Microsoft Academic Search

Microbial heavy metal retention was studied using seepage water sampled from a former uranium mining site in Eastern Thuringia, Germany. The seepage water has a low pH and contains high concentrations of metals, including uranium, rare earth elements (REE), and other heavy metals. Microbial influence on sorption and\\/or active uptake of heavy metals was studied using REE patterns. Incubation of

D. Merten; E. Kothe; G. Büchel

2004-01-01

111

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

112

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

113

Shor Lab "Soil Water" Project Undergraduate Research Opportunity  

E-print Network

biofilm EPS level, drying condition and water retention. 5. Use microfluidic devices to systematically the water retention curve for whole soils. Bacteria can produce up to five times their mass in EPS, to characterize the affects of EPS on soil water retention. To achieve that, we need to first understand effect

Shor, Leslie McCabe

114

Note: curve fit models for atomic force microscopy cantilever calibration in water.  

PubMed

Atomic force microscopy stiffness calibrations performed on commercial instruments using the thermal noise method on the same cantilever in both air and water can vary by as much as 20% when a simple harmonic oscillator model and white noise are used in curve fitting. In this note, several fitting strategies are described that reduce this difference to about 11%. PMID:22129023

Kennedy, Scott J; Cole, Daniel G; Clark, Robert L

2011-11-01

115

Assessment of retention basin volume and outlet capacity in urban stormwater drainage systems with respect to water quality  

Microsoft Academic Search

The quality of river water or other surface waters is detrimentally affected by the contaminants carried by the rainfall runoff\\u000a in urban areas. The control of pollution moved by rainfall runoff is achieved by installing outlets and small retention basins\\u000a in stormwater collection systems, thereby allowing only a certain amount of rainfall water to overflow and leading the remaining\\u000a to

Mehmet A. Yurdusev; Ahmet A. Kumanlio?lu; Bekir Solmaz

2005-01-01

116

Free water clearance curves during saline, mannitol, glucose and urea diuresis in the rat  

PubMed Central

1. Free water clearances were measured during infusion of hypotonic saline, glucose, urea, and mannitol in Brattleboro rats. For each solute the free water clearances were plotted using either V or (CH2O + CNa) as the distal tubular delivery term. 2. In all cases the use of (CH2O + CNa) as distal delivery term yielded a steeper relationship than when V was used. There were no significant differences in the CH2O to V relationship when saline, glucose and mannitol was the solute infused. Urea, however, resulted in a curve with a slope significantly less than that for the other solutes. 3. When CH2O was plotted against (CH2O + CNa) there was still no significant difference between the slopes of the curves during saline or mannitol infusion. Use of this delivery term, however, resulted in a slope during glucose infusion which was significantly greater than that during saline or mannitol infusion. The slope for urea infusion remained lower than that for any other solute. 4. Regardless of the delivery term used, there was no significant difference in the slopes of the curves for awake Wistar and awake Brattleboro rats during mannitol infusion. This indicates that the awake rat is a suitable model for free water clearance studies. 5. The results indicate that NaCl and mannitol are both adequate for free water clearance and that (CH2O + CNa) is a better index of distal delivery than V. PMID:690907

Martinez-Maldonado, Manuel; Opava-Stitzer, Susan

1978-01-01

117

Characterizing Scale and Location-Dependent Correlation of Water Retention Parameters with Soil Physical Properties Using Wavelet Techniques  

Microsoft Academic Search

Understanding the correlation between soil hydraulic parameters and soil physical properties is a prerequisite for the prediction of soil hydraulic properties from soil physical properties. Th e objective of this study was to examine the scale- and location-dependent correlation between two water retention parameters (? and n) in the van Genuchten (1980) function and soil physical properties (sand content, bulk

Qiaosheng Shu; Zuoxin Liu; Bingcheng Si

2008-01-01

118

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

119

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 the approximate soil moisture retention curve at the places where only saturated hydraulic conductivity data

Kumar, C.P.

120

Factors affecting drying and wetting soil-water characteristic curves of sandy soils  

Microsoft Academic Search

Drying and wetting soil-water characteristic curves (SWCCs) for five sandy soils are investigated using a Tempe pressure cell and capillary rise open tube. The test data are fitted to two SWCC equations using a least-squares algorithm. The obtained fitting parameters and some hysteretic behaviour are discussed and correlated with grain-size distribution parameters. A concept of total hysteresis is proposed to

Hong Yang; Harianto Rahardjo; Eng-Choon Leong; D. G. Fredlund

2004-01-01

121

Characterization of subcritical water oxidation with in situ monitoring and self-modeling curve resolution  

Microsoft Academic Search

In this paper, a subcritical water oxidation (SBWO) process was monitored using self-modeling curve resolution (SMCR) of in situ UV-Vis measurements to estimate time-dependant composition profiles of reactants, intermediates and products. A small laboratory scale reactor with UV-Vis fiber-optic probes and a flow cell was used to demonstrate the usefulness of SMCR for monitoring the destruction of model compounds phenol,

Paul J. Gemperline; Yu Yang; Zhihui Bian

2003-01-01

122

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

123

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

124

Dynamic Oil-Water and Air-Water Capillary Pressure-Saturation Curves: Experiments and Lattice-Boltzmann Simulations  

NASA Astrophysics Data System (ADS)

Capillary pressure plays a significant role in multiphase flow and transport in porous media. Although capillary forces occur at the pore-scale, many mathematical models require a macro-scale relationship between capillary pressure and other properties of the system. The capillary pressure-saturation curve is the most widely used relationship to characterize hydraulic properties of multiphase flow in porous media. These curves are most commonly obtained from quasi-static drainage and imbibition experiments. It is then often assumed that the quasi-static curves can be applied to modeling transient flow conditions. In these models, the time it takes to reach a quasi-static state is completely ignored, which can be on the order of hours to months. Experimental evidence suggests that capillary pressure-saturation curves are not unique and that they exhibit dynamic effects depending on the flow conditions in the the system prior to and during the time of measurement. The extent to which dynamic flow conditions effect the measured capillary pressure is currently debated and the exact cause of the observed dynamic effects is not fully understood. In this study various drainage and imbibition experiments were conducted to further investigate the role dynamic effects play in the capillary pressure-saturation curve. Oil-water and air-water experiments were conducted on the same porous medium to compare the dynamic effects resulting from density and viscosity differences. Lattice-Boltzmann simulations of the dynamic effects were carried out to provide a comparison to the experimental results. The simulation results were then analyzed in an effort to identify the pore-scale mechanisms responsible for the dynamic effects observed in the macro-scale experiments.

Porter, M. L.; Schaap, M. G.; Wildenschild, D.

2006-12-01

125

Effects of organic and inorganic lead on the oxygen equilibrium curves of the fresh water field crab, Barytelphusa guerini  

SciTech Connect

Haemocyanin serves as normal transporter of oxygen in many Arthropods. The oxygen equilibrium curves have been described for the haemocyanins of many Arthropods and Molluscs. Oxygen equilibrium curves of the blood reveal the relationship between the oxygen tension and the percentage saturation of the haemocyanin. The shape of the oxygen equilibrium curves vary in position from sigmoid to hyperbolic in different animals or even undulatory as shown in some chitons. Oxygen equilibrium curves are known to be influenced by pH, temperature and inorganic ions. The effect of environmental pollutants like the heavy metals on the oxygen equilibrium curves of the fresh water crab has not been previously reported. One of the toxic heavy metals with regard to aquatic organisms is lead. Hence the present study was designed to determine the effect of organic and inorganic lead on the oxygen equilibrium curve of the fresh water crab, Barytelphusa guerini.

Tulasi, S.J.; Ramana Rao, J.V.

1989-02-01

126

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

127

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

128

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

129

Turbulent heat transfer to near-critical water in a heated curved pipe under the conditions of mixed convection  

Microsoft Academic Search

Numerical modeling was performed to investigate the developing turbulent flow and heat transfer characteristics of water near the critical point in a curved pipe. The renormalization group (RNG) ?–? model was used to account for the turbulent flow and heat transfer in the curved pipe at a constant wall temperature with or without buoyancy force effect. A control volume finite

L. J. Li; C. X. Lin; M. A. Ebadian

1999-01-01

130

International Equations for the Pressure Along the Melting and Along the Sublimation Curve of Ordinary Water Substance  

Microsoft Academic Search

In order to define the phase boundary between the solid phase (ice) and the fluid phase (liquid and gas) of ordinary (light) water substance in pressure-temperature coordinates, correlation equations for the pressure along the melting curve of the various modifications of ice as well as for the pressure along the sublimation curve are presented. The five equations for the melting

Wolfgang Wagner; A. Saul; A. Pruss

1994-01-01

131

A nanofiltration retention model for trace contaminants in drinking water sources  

Microsoft Academic Search

A diffusion-convection controlled mass transfer model was developed for predicting the retention behaviour of full-scale nanofiltration (NF) plants. The model is based upon a previous diffusion-only-controlled transport model and is described by an analytical equation in which the retention can be calculated as a function of the recovery. The three main parameters in the model are Kw, Ks, and Kc,

Emile R. Cornelissen; Jil Verdouw; Anneke J. Gijsbertsen-Abrahamse; Jan A. M. H. Hofman

2005-01-01

132

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

133

Soil-Water Characteristic Curves of Red Clay treated by Ionic Soil Stabilizer  

NASA Astrophysics Data System (ADS)

The relationship of red clay particle with water is an important factor to produce geological disaster and environmental damage. In order to reduce the role of adsorbed water of red clay in WuHan, Ionic Soil Stabilizer (ISS) was used to treat the red clay. Soil Moisture Equipment made in U.S.A was used to measure soil-water characteristic curve of red clay both in natural and stabilized conditions in the suction range of 0-500kPa. The SWCC results were used to interpret the red clay behavior due to stabilizer treatment. In addition, relationship were compared between the basic soil and stabilizer properties such as water content, dry density, liquid limit, plastic limit, moisture absorption rate and stabilizer dosages. The analysis showed that the particle density and specific surface area increase, the dehydration rate slows and the thickness of water film thins after treatment with Ionic Soil Stabilizer. After treatment with the ISS, the geological disasters caused by the adsorbed water of red clay can be effectively inhibited.

Cui, D.; Xiang, W.

2009-12-01

134

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

135

Impact of Natural Conditioners on Water Retention, Infiltration and Evaporation Characteristics of Sandy Soil  

NASA Astrophysics Data System (ADS)

Soil conditioners i.e., natural deposits and organic fertilizer are used for alleviate some of poor physical properties of sandy soils such as low water retention and inefficient water use, especially in arid and semi-arid regions such as in Saudi Arabia conditions. The present study aims to investigate the impact of clay deposits and organic fertilizer on water characteristics, cumulative infiltration and intermittent evaporation of loamy sand soil. Soil sample was collected from surface layer (0-30 cm depth) of the Agricultural Experiment and Research Station at Dierab, 40 km south west of Riyadh, Saudi Arabia. Two samples of clay deposits (CD#22 and CD#23) collected from Khyleis area, Jeddah-Madina road in addition of commercial Organic Fertilizer (OF) were used in the present study. The experiments were done during August to December 2005 in soil physics laboratory, the soil was mixed with clay deposits and organic fertilizer at rates of 0, 1, 2.5, 5.0 and 10.0% (w/w). The transparent PVC columns were packed with soil to depth of 30 cm every 5.0 cm intervals to insure a homogeneity of soil in columns. The clay deposits (CD#22 and CD#23) and Organic Fertilizer (OF) mixed with the soil were packed in the upper 0-5.0 cm of each soil column. The infiltration experiment was done using a flooding apparatus (Marriot device) with constant head of 3.0 cm over the soil surface. The cumulative infiltration and wetting front depth as a function of time were recorded. The evaporation experiment was conducted in 40 cm long transparent sectioned Lucite cylinders (5.0 cm ID). Fifty millimeters of tap water were applied weekly for three wetting/drying cycles. Cumulative evaporation against time was measured daily by weighing each soil column. The soil moisture distribution at the end of the experiment was determined gravimetrically for each 5.0 cm interval. The results indicated that the three conditioners significantly increased the water constants of mixed soil (i.e., SWC, FC, PWP and AW), but the CD#22 has a superior effect. The results clearly indicated that increasing the application rate of conditioners significantly decreased the cumulative infiltration (D). The decrease in D more pronounced at higher rates. The CD#22 was more effective in reducing the cumulative infiltration. The relationship between (D) as a function of Time (T) was done by fitting the data to the Kostiakov and Philip equations. Increasing the application rate of natural conditioners restricted the wetting front movement and need more time to reach 30 cm depth. The natural conditioners significantly reduced the cumulative evaporation throughout the 3 evaporation cycles. The reduction significantly increased with increasing the application rate, except for the higher rate (10%), which increases the cumulative evaporation under the present conditions. The improvement of soil hydro-physical properties and reduction in water infiltration and cumulative evaporation are good practices for plant growth in region limited in water such as most regions in Saudi Arabia.

Abdel-Nasser, G.; Al-Omran, A. M.; Falatah, A. M.; Sheta, A. S.; Al-Harbi, A. R.

136

ESTIMATING WATER TREATMENT COSTS. VOLUME 3. COST CURVES APPLICABLE TO 2,500 GPD TO 1 MGD TREATMENT PLANTS  

EPA Science Inventory

This report discusses unit processes and combinations of unit processes that are capable of removing contaminants included in the National Interim Primary Drinking Water Regulations. Construction and operation and maintenance cost curves are presented for 99 unit processes that a...

137

Water-soluble peptides in Cheddar cheese: isolation and identification of peptides in the diafiltration retentate of the water-soluble fraction.  

PubMed

The water-soluble extract of Cheddar cheese was fractionated by diafiltration using 10 kDa cut-off membranes. Peptides were isolated from the diafiltrate retentate by chromatography on DEAE-cellulose with a linear NaCl gradient in 50 mM-Tris-HCl. pH 8.6, and reversed-phase HPLC or electroblotting from urea-PAGE gels. Peptides were identified by determining N-terminal amino acid sequences and mass spectrometry. Most (45) of the total 51 peptides identified in the diafiltrate retentate originated from beta-casein, especially from a short region in the N-terminal half of the molecule. Only six peptides originated from alpha s1-casein; beta-lactoglobulin was also identified in the retentate. The origin of most of these peptides could be explained on the basis of known specificities of lactococcal cell envelope proteinases. PMID:8568032

Singh, T K; Fox, P F; Healy, A

1995-11-01

138

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.

139

Determination of n-octanol\\/water partition coefficient for DDT-related compounds by RP-HPLC with a novel dual-point retention time correction  

Microsoft Academic Search

n-Octanol\\/water partition coefficients (P) for DDTs and dicofol were determined by reversed-phase high performance liquid chromatography (RP-HPLC) on a C18 column using methanol–water mixture as mobile phase. A dual-point retention time correction (DP-RTC) was proposed to rectify chromatographic retention time (tR) shift resulted from stationary phase aging. Based on this correction, the relationship between logP and logkw, the logarithm of

Shu-ying Han; Jun-qin Qiao; Yun-yang Zhang; Li-li Yang; Hong-zhen Lian; Xin Ge; Hong-yuan Chen

2011-01-01

140

Deriving Short-Run, Multistage Demand Curves and Simulating Market Prices for Reservoir Water Under Weather Uncertainty  

Microsoft Academic Search

\\u000a Traditional deterministic mathematical programming methods for deriving normative irrigation-water demand curves are quite\\u000a suitable when water supplies and demands are free from climate-based uncertainty, but are unsuitable for summer rainfall irrigation\\u000a areas with highly variable and uncertain irrigation water supplies and demands. The marginal value of irrigation water, and\\u000a hence its opportunity cost for alternative uses, becomes highly variable and

Norman Dudley; Bradley Scott

141

Regional water balance modelling using flow-duration curves with observational uncertainties  

NASA Astrophysics Data System (ADS)

Robust and reliable water-resource mapping in ungauged basins requires estimation of the uncertainties in the hydrologic model, the regionalisation method, and the observational data. In this study we investigated the use of regionalised flow-duration curves (FDCs) for constraining model predictive uncertainty, while accounting for all these uncertainty sources. A water balance model was applied to 36 basins in Central America using regionally and globally available precipitation, climate and discharge data that were screened for inconsistencies. A rating-curve analysis for 35 Honduran discharge stations was used to estimate discharge uncertainty for the region, and the consistency of the model forcing and evaluation data was analysed using two different screening methods. FDCs with uncertainty bounds were calculated for each basin, accounting for both discharge uncertainty and, in many cases, uncertainty stemming from the use of short time series, potentially not representative for the modelling period. These uncertain FDCs were then used to regionalise a FDC for each basin, treating it as ungauged in a cross-evaluation, and this regionalised FDC was used to constrain the uncertainty in the model predictions for the basin. There was a clear relationship between the performance of the local model calibration and the degree of data set consistency - with many basins with inconsistent data lacking behavioural simulations (i.e. simulations within predefined limits around the observed FDC) and the basins with the highest data set consistency also having the highest simulation reliability. For the basins where the regionalisation of the FDCs worked best, the uncertainty bounds for the regionalised simulations were only slightly wider than those for a local model calibration. The predicted uncertainty was greater for basins where the result of the FDC regionalisation was more uncertain, but the regionalised simulations still had a high reliability compared to the locally calibrated simulations and often encompassed them. The regionalised FDCs were found to be useful on their own as a basic signature constraint; however, additional regionalised signatures could further constrain the uncertainty in the predictions and may increase the robustness to severe data inconsistencies, which are difficult to detect for ungauged basins.

Westerberg, I. K.; Gong, L.; Beven, K. J.; Seibert, J.; Semedo, A.; Xu, C.-Y.; Halldin, S.

2014-08-01

142

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

143

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...

144

Fate of Nitrogenand Phosphorus in a Waste-water RetentionReservoir Containing Aquatic Macrophytes1  

E-print Network

, cattails, elodea, aquatic system. Reddy, K. R. 1983. Fate of nitrogenand phosphorusin a waste water (Reddy et al., 1982). The capacity of vascular plants to assimilate nutrients from polluted waters has water, they provide very little understanding on the rate of N and P removal in these systems. Presence

Florida, University of

145

Nitrate Retention in Riparian Ground Water at Natural and Elevated Nitrate Levels in North Central Minnesota  

Microsoft Academic Search

The relationship between local ground water flows and NO3 2 transport to the channel was examined in three well transects from a natural, wooded riparian zone adjacent to the Shingobee River, MN. The hillslope ground water originated as recharge from intermittently grazed pasture up slope of the site. In the hillslope transect perpen- dicular to the stream, ground water NO3

John H. Duff; Alan P. Jackman; Frank J. Triska; Richard W. Sheibley; Ronald J. Avanzino

2007-01-01

146

Phosphorus Retention at the Redox Interface of Peatlands Adjacent to Surface Waters in Northeast Germany  

Microsoft Academic Search

It is demanded currently in public discussions to rewet peatlands and re-establish their function as nutrient sinks. But due to high phosphorus (P) concentrations in the pore water of rewetted peatlands (40–420 ?M) it is hypothesized that they can act as a surplus P source for adjacent surface waters and consequently support the eutrophication of such waters. Our detailed investigations

D. Zak; J. Gelbrecht; C. E. W. Steinberg

2004-01-01

147

Literature Review of the Potential Energy Savings and Retention Water from Green Roofs in Comparison with Conventional Ones  

NASA Astrophysics Data System (ADS)

The objective of this study is the comparison of green roof systems with conventional isolated and non-isolated ones in order to identify the potential energy savings of green roofs and the benefits provided in comparison with the cost of construction to the buildings. The region of interest is the Watergraafsmeer area in the city of Amsterdam. The method evaluates literature reports - mostly from 2003 to 2010 - that present the advantages of green roofs. Examples in real implementation of green roofs in USA, UK and Germany, retention of rainfall and a Life Cycle Assessment from a residential construction in Madrid will be introduced, showing the energy savings from insulation and heating/cooling that can be gained. All the reports have shown a reduction in energy costs and in runoff of water. Hence, costs and retrofitting potential completes the research. The age of buildings and the absence of insulation make green roofs an ideal alternative project for the retrofit of Watergraafsmeer.

Tselekis, Kyriakoulis

2012-09-01

148

Predicting the soil moisture retention curve, from soil particle size distribution and bulk density data using a packing density scaling factor  

NASA Astrophysics Data System (ADS)

A substantial number of models predicting the soil moisture characteristic curve (SMC) from particle size distribution (PSD) data underestimate the dry range of the SMC especially in soils with high clay and organic matter contents. In this study, we applied a continuous form of the PSD model to predict the SMC, and subsequently we developed a physically based scaling approach to reduce the model's bias at the dry range of the SMC. The soil particle packing density was considered as a metric of soil structure and used to define a soil particle packing scaling factor. This factor was subsequently integrated in the conceptual SMC prediction model. The model was tested on 82 soils, selected from the UNSODA database. The results show that the scaling approach properly estimates the SMC for all soil samples. In comparison to the original conceptual SMC model without scaling, the scaling approach improves the model estimations on average by 30%. Improvements were particularly significant for the fine- and medium-textured soils. Since the scaling approach is parsimonious and does not rely on additional empirical parameters, we conclude that this approach may be used for estimating SMC at the larger field scale from basic soil data.

Meskini-Vishkaee, F.; Mohammadi, M. H.; Vanclooster, M.

2014-10-01

149

Potential Water Retention Capacity as a Factor in Silage Effluent Control: Experiments with High Moisture By-product Feedstuffs.  

PubMed

The role of moisture absorptive capacity of pre-silage material and its relationship with silage effluent in high moisture by-product feedstuffs (HMBF) is assessed. The term water retention capacity which is sometimes used in explaining the rate of effluent control in ensilage may be inadequate, since it accounts exclusively for the capacity of an absorbent incorporated into a pre-silage material prior to ensiling, without consideration to how much the pre-silage material can release. A new terminology, 'potential water retention capacity' (PWRC), which attempts to address this shortcoming, is proposed. Data were pooled from a series of experiments conducted separately over a period of five years using laboratory silos with four categories of agro by-products (n = 27) with differing moisture contents (highest 96.9%, lowest 78.1% in fresh matter, respectively), and their silages (n = 81). These were from a vegetable source (Daikon, Raphanus sativus), a root tuber source (potato pulp), a fruit source (apple pomace) and a cereal source (brewer's grain), respectively. The pre-silage materials were adjusted with dry in-silo absorbents consisting wheat straw, wheat or rice bran, beet pulp and bean stalks. The pooled mean for the moisture contents of all pre-silage materials was 78.3% (±10.3). Silage effluent decreased (p<0.01), with increase in PWRC of pre-silage material. The theoretical moisture content and PWRC of pre-silage material necessary to stem effluent flow completely in HMBF silage was 69.1% and 82.9 g/100 g in fresh matter, respectively. The high correlation (r = 0.76) between PWRC of ensiled material and silage effluent indicated that the latter is an important factor in silage-effluent relationship. PMID:25049587

Razak, Okine Abdul; Masaaki, Hanada; Yimamu, Aibibula; Meiji, Okamoto

2012-04-01

150

Transfer and water-retention properties of seed-pelleting materials  

Microsoft Academic Search

Until now, the choice of materials for seed pelleting has been mostly empirical. We have analysed coating materials (silicate powder A, clay B and hydrophobic clay C) and their water-transfer properties. Seed-pelleting materials were studied with conventional soil-analysis techniques. An original device for studying water transfer through a thin layer of powder was designed to simulate the transfer of water

P. Grellier; L. M. Riviere; P. Renault

1999-01-01

151

Biobased polymer composites derived from corn stover and feather meals as double-coating materials for controlled-release and water-retention urea fertilizers.  

PubMed

In this paper, we synthesized a biobased polyurethane using liquefied corn stover, isocyanate, and diethylenetriamine. The synthesized polyurethane was used as a coating material to control nitrogen (N) release from polymer-coated urea. A novel superabsorbent composite was also formulated from chicken feather protein (CFP), acrylic acid, and N,N'-methylenebisacrylamide and used as an outer coating material for water retention. We studied the N release characteristics and water-retention capability of the double-layer polymer-coated urea (DPCU) applied in both water and soils. The ear yields, dry matter accumulation, total N use efficiency and N leaching from a sweet corn soil-plant system under two different irrigation regimes were also investigated. Comparison of DPCU treatments with conventional urea fertilizer revealed that DPCU treatments reduced the N release rate and improved water retention capability. Evaluation of soil and plant characteristics within the soil-plant system revealed that DPCU application effectively reduced N leaching loss, improved total N use efficiency, and increased soil water retention capability. PMID:23923819

Yang, Yuechao; Tong, Zhaohui; Geng, Yuqing; Li, Yuncong; Zhang, Min

2013-08-28

152

Climate Change Adaptation in the Western U.S.: the Case for Dynamic Rule Curves in Water Resources Management  

NASA Astrophysics Data System (ADS)

Climate change in the Western U.S. will bring systematic hydrologic changes affecting many water resources systems. Successful adaptation to these changes, which will be ongoing through the 21st century, will require the 'rebalancing' of competing system objectives such as water supply, flood control, hydropower production, and environmental services in response to hydrologic (and other) changes. Although fixed operating policies for the operation of reservoirs has been a traditional approach to water management in the 20th century, the rapid pace of projected climate shifts (~0.5 F per decade), and the prohibitive costs of recursive policy intervention to mitigate impacts, suggest that more sophisticated approaches will be needed to cope with climate change on a long term basis. The use of 'dynamic rule curves' is an approach that maintains some of the key characteristics of current water management practice (reservoir rule curves) while avoiding many of the fundamental drawbacks of traditional water resources management strategies in a non-stationary climate. In this approach, water resources systems are optimized for each operational period using ensemble streamflow and/or water demand forecasts. The ensemble of optimized reservoir storage traces are then analyzed to produce a set of unique reservoir rule curves for each operational period reflecting the current state of the system. The potential advantage of this approach is that hydrologic changes associated with climate change (such as systematically warmer temperatures) can be captured explicitly in operational hydrologic forecasts, which would in turn inform the optimized reservoir management solutions, creating water resources systems that are largely 'self tending' as the climate system evolves. Furthermore, as hydrologic forecasting systems improve (e.g. in response to improved ENSO forecasting or other scientific advances), so does the performance of reservoir operations. An example of the approach is given for flood control in the Columbia River basin.

Lee, S.; Hamlet, A. F.; Burges, S. J.

2008-12-01

153

Water Retention Properties of Soil in a Tropical Pre-Montane Transitional Forest  

E-print Network

to saprolite Storage mm H2O Plant-available water mm H2O 1 1160 563 365 2 590 294 250 3 650 336 263 Water and vertical distance from watershed stream Site Slope Position Depth to saprolite 1 25° Middle (trail cut) 116

154

Soil Formation & Retention Stores and buffers  

E-print Network

Soil Formation & Retention· Stores and buffers soil nutrients · Stores water · Drives soil ecosystem #12;Flood control · Water filtration, retention and flow · Protection from tsunamis and hurricanes

Gottgens, Hans

155

Water Retention of Extremophiles and Martian Soil Simulants Under Close to Martian Environmental Conditions  

NASA Astrophysics Data System (ADS)

We report data about interaction of moisture with soil simulants and extremophiles under Martian environmental conditions contributing on atmosphere/surface modelling and on effects determining the water inventory of the upper soil layer of Mars.

Jänchen, J.; Bauermeister, A.; Feyh, N.; deVera, J.-P.

2012-05-01

156

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

157

Linking the management of urban watersheds with the impacts on the receiving water bodies: the use of flow duration curves.  

PubMed

There is growing evidence that changes in the current hydrological behaviour of urbanising catchments are a major source of impacts on the downstream water bodies. However, current flow-rates are rarely considered in studies on urban stormwater management, usually focused on extreme flow-rates. We argue that taking into account receiving water bodies is possible with relatively small modifications in current practices of urban stormwater modelling, through the use of Flow duration curves (FDCs). In this paper, we discuss advantages and requirements of the use of FDCs. Then, we present an example of application comparing source control regulations over an urbanised catchment (178 ha) in Nantes, France. PMID:25026590

Petrucci, Guido; Rodriguez, Fabrice; Deroubaix, José-Frédéric; Tassin, Bruno

2014-01-01

158

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

159

THE EFFECT OF TOTAL WATER REUSE AND ALUM CONTROL ON FIRST PASS RETENTION  

EPA Science Inventory

Product quality deterioration, caused by poor wet end control and the resulting build up of dissolved inorganic and organic contaminants, has hampered achieving complete water reuse in paper manufacturing. By using pulp-derived dissolved organic material, the study makes use of a...

160

Prediction of Key Points of Water-oil Relative Permeability Curves Using the Linear Regression Technique  

Microsoft Academic Search

Relative permeability is among the most critical parameters in reservoir performance evaluation and EOR projects. It reflects the ease of movement and trapping of different phases and affects the production rate and ultimate recovery from reservoirs. Experimental measurement of relative permeability curves is complicated, costly, time consuming, and the results can easily be influenced by test conditions and interpretation methods.

R. Roghanian; M. Reza Rasaei; M. Haghighi

2012-01-01

161

Trinarization of ?X-ray CT images of partially saturated sand at different water-retention states using a region growing method  

NASA Astrophysics Data System (ADS)

The trinarization of micro-computed tomography (CT) images for partially saturated soils at different water-retention states has been performed to clearly identify the three phases, i.e., the soil particles, the pore water and the pore air. We have proposed a trinarization technique for partially saturated soils whose histograms of the gray values for the three phases overlap each other. The segmentation method used in this study is the region growing method that ensures the spatial continuity of the phases extracted by the segmentation. Micro CT images of a dense sand specimen during the wetting process in a water retention test have been obtained. It has been found that the trinarization of the CT images in a high pore saturation regime provides reasonable results, while that in a low pore saturation regime overestimates the local void ratio. This is because the gray values of the mixels of the soil particle phase and the air phase, due to the partial volume effect, are similar to those of the water phase. It is necessary, therefore, to validate the trinarization results, by a comparison with the test results, because it is difficult to theoretically evaluate the partial volume effect. The correction of the tolerance value for the low pore saturation case with validation has provided better trinarization results. Through the trinarized CT images, the form of the existing pore water at different water-retention states has been discussed.

Higo, Yosuke; Oka, Fusao; Morishita, Ryoichi; Matsushima, Yoshiki; Yoshida, Tatsuya

2014-04-01

162

Effect of Cropping History on Water Retention Characteristics of Clayey Paddy Soil under Low Water Potential Conditions  

NASA Astrophysics Data System (ADS)

The water content and water potential of soil samples from paddy fields with varied cropping histories were measured under low water potential conditions. The relationships between the water content and the water potential were fitted to power equations. Analyses of the results for the fresh soils showed that the coefficient a (the water content at water potential of -1MPa) (CA) and the absolute value of the exponential index b (AB) of the fitted power equation was smaller in the soils under the cultivation of upland crops than the wetland rice. On the other hand, the difference in CA and AB for air-dried soil was not revealed between the soils under the upland crop cultivation and the soils under the wetland rice cultivation. The difference in CA for the fresh soil and for the air-dried soil and the difference in AB for the fresh soil and for air-dried soil were found to increase with continuous cropping of wetland rice, and decrease in response to continuous cropping of upland crops. These finding suggest these indices can presume cropping histories of rotational paddy fields.

Adachi, Kazuhide; Yoshida, Shuichiro; Ohno, Satoshi; Obara, Hiroshi

163

Stubble retention and tillage in a semi-arid environment: 1. Soil water accumulation during fallow  

Microsoft Academic Search

A study was carried out over 4 years at two sites in semi-arid, north-west Victoria, Australia, to examine the effect of soil surface management during fallow on water and nitrogen accumulation and their effect on the growth and yield of the subsequent wheat crop. The fallow treatments comprised four combinations of stubble management and tillage in 18-month-long fallows of a

G. J. O'Leary; D. J. Connor

1997-01-01

164

Retention and transport of silver nanoparticles in a ceramic porous medium used for point-of-use water treatment.  

PubMed

The retention and transport of silver nanoparticles (Ag-NPs) through a ceramic porous medium used for point-of-use drinking water purification is investigated. Two general types of experiments were performed: (i) pulse injections of suspensions of Ag-NPs in aqueous MgSO4 solutions were applied to the ceramic medium, and effluent silver was quantified over time; (ii) Ag-NPs were applied directly to the porous medium during fabrication using a paint-on, dipping, or fire-in method, a synthetic, moderately hard water sample with monovalent and divalent inorganic ions was applied to the ceramic medium, and effluent silver was quantified over time. These latter experiments were performed to approximate real-world use of the filter medium. For experiments with Ag-NPs suspended in the inflow solution, the percentage of applied Ag-NPs retained in the ceramic porous medium ranged from about 13 to 100%. Ag-NP mobility decreased with increasing ionic strength for all cases and to a lesser extent with increasing nanoparticle diameter. Citrate-capped particles were slightly less mobile than proteinate-capped particles. For ceramic disks fabricated with Ag-NPs by the paint-on and dipping methods (where the Ag-NPs are applied to the disks after firing), significant release of nanoparticles into the filter disk effluent was observed relative to the fire-in method (where the nanoparticles are combined with the clay, water, grog, and flour before firing). These results suggest that the fire-in method may be a new and significant improvement to ceramic filter design. PMID:23496137

Ren, Dianjun; Smith, James A

2013-04-16

165

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

166

Retention and loss of water extractable carbon in soils: effect of clay properties.  

PubMed

Clay sorption is important for organic carbon (C) sequestration in soils, but little is known about the effect of different clay properties on organic C sorption and release. To investigate the effect of clay content and properties on sorption, desorption and loss of water extractable organic C (WEOC), two experiments were conducted. In experiment 1, a loamy sand alone (native) or mixed with clay isolated from a surface or subsoil (78 and 96% clay) resulting in 90, 158 and 175 g clay kg(-1) soil. These soil treatments were leached with different WEOC concentrations, and then CO2 release was measured for 28 days followed by leaching with reverse osmosis water at the end of experiment. The second experiment was conducted to determine WEOC sorption and desorption of clays isolated from the loamy sand (native), surface soil and subsoil. Addition of clays isolated from surface and subsoil to sandy loam increased WEOC sorption and reduced C leaching and cumulative respiration in percentage of total organic C and WEOC added when expressed per g soil and per g clay. Compared to clays isolated from the surface and subsoil, the native clay had higher concentrations of illite and exchangeable Ca(2+), total organic C and a higher CEC but a lower extractable Fe/Al concentration. This indicates that compared to the clay isolated from the surface and the subsoil, the native clay had fewer potential WEOC binding sites because it had lower Fe/Al content thus lower number of binding sites and the existing binding sites are already occupied native organic matter. The results of this study suggest that in the soils used here, the impact of clay on WEOC sorption and loss is dependent on its indigenous organic carbon and Fe and/or Al concentrations whereas clay mineralogy, CEC, exchangeable Ca(2+) and surface area are less important. PMID:24144942

Nguyen, Trung-Ta; Marschner, Petra

2014-02-01

167

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

168

Retention capacity of correlated surfaces.  

PubMed

We extend the water retention model [C. L. Knecht et al., Phys. Rev. Lett. 108, 045703 (2012)] to correlated random surfaces. We find that the retention capacity of discrete random landscapes is strongly affected by spatial correlations among the heights. This phenomenon is related to the emergence of power-law scaling in the lake volume distribution. We also solve the uncorrelated case exactly for a small lattice and present bounds on the retention of uncorrelated landscapes. PMID:25019758

Schrenk, K J; Araújo, N A M; Ziff, R M; Herrmann, H J

2014-06-01

169

Urinary Retention  

MedlinePLUS

... Kavoussi LR, Novick AC, et al. Campbell-Walsh Urology. 10th ed. Philadelphia: Saunders; 2011. 4 Mevcha A, ... of urinary retention in women. Indian Journal of Urology. 2010;26(2):230–235. [ Top ] What are ...

170

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

171

Retention of heavy metals and poly-aromatic hydrocarbons from road water in a constructed wetland and the effect of de-icing.  

PubMed

A full-scale remediation facility including a detention basin and a wetland was tested for retention of heavy metals and Poly-Aromatic Hydrocarbons (PAHs) from water drained from a motorway in The Netherlands. The facility consisted of a detention basin, a vertical-flow reed bed and a final groundwater infiltration bed. Water samples were taken of road water, detention basin influent and wetland effluent. By using automated sampling, we were able to obtain reliable concentration averages per 4-week period during 18 months. The system retained the PAHs very well, with retention efficiencies of 90-95%. While environmental standards for these substances were surpassed in the road water, this was never the case after passage through the system. For the metals the situation was more complicated. All metals studied (Cu, Zn, Pb, Cd and Ni) had concentrations frequently surpassing environmental standards in the road water. After passage through the system, most metal concentrations were lower than the standards, except for Cu and Zn. There was a dramatic effect of de-icing salts on the concentrations of Cu, Zn, Cd and Ni, in the effluent leaving the system. For Cu, the concentrations even became higher than they had ever been in the road water. It is advised to let the road water bypass the facility during de-icing periods. PMID:22226719

Tromp, Karin; Lima, Ana T; Barendregt, Arjan; Verhoeven, Jos T A

2012-02-15

172

Physically based estimation of soil water retention from textural data: General framework, new models, and streamlined existing models  

USGS Publications Warehouse

Numerous models are in widespread use for the estimation of soil water retention from more easily measured textural data. Improved models are needed for better prediction and wider applicability. We developed a basic framework from which new and existing models can be derived to facilitate improvements. Starting from the assumption that every particle has a characteristic dimension R associated uniquely with a matric pressure ?? and that the form of the ??-R relation is the defining characteristic of each model, this framework leads to particular models by specification of geometric relationships between pores and particles. Typical assumptions are that particles are spheres, pores are cylinders with volume equal to the associated particle volume times the void ratio, and that the capillary inverse proportionality between radius and matric pressure is valid. Examples include fixed-pore-shape and fixed-pore-length models. We also developed alternative versions of the model of Arya and Paris that eliminate its interval-size dependence and other problems. The alternative models are calculable by direct application of algebraic formulas rather than manipulation of data tables and intermediate results, and they easily combine with other models (e.g., incorporating structural effects) that are formulated on a continuous basis. Additionally, we developed a family of models based on the same pore geometry as the widely used unsaturated hydraulic conductivity model of Mualem. Predictions of measurements for different suitable media show that some of the models provide consistently good results and can be chosen based on ease of calculations and other factors. ?? Soil Science Society of America. All rights reserved.

Nimmo, J. R.; Herkelrath, W. N.; Laguna, Luna, A. M.

2007-01-01

173

Evolution of water repellency of organic growing media used in Horticulture and consequences on hysteretic behaviours of the water retention curve  

Microsoft Academic Search

Most of growing media used in horticulture (particularly peat substrates) shows hysteresis phenomena during desiccation and rehydration cycles, which greatly affects their hydraulic properties. The origins of these properties have often been related to one or several of the specific mechanisms such as the non-geometrical uniformity of the pores (also called `ink bottle' effect), presence of trapped air, shrinkage-swelling phenomena,

Jean-Charles Michel; Guifang Qi; Sylvain Charpentier; Pascal Boivin

2010-01-01

174

Prediction of relative and absolute permeabilities for gas and water from soil water retention curves using a pore-scale network model  

Microsoft Academic Search

Functional relationships for unsaturated flow in soils, including those between capillary pressure, saturation, and relative permeabilities, are often described using analytical models based on the bundle-of-tubes concept. These models are often limited by, for example, inherent difficulties in prediction of absolute permeabilities, and in incorporation of a discontinuous nonwetting phase. To overcome these difficulties, an alternative approach may be formulated

Ulrich Fischer; Michael A. Celia

1999-01-01

175

Effective improvement of water-retention in nanocomposite membranes using novel organo-modified clays as fillers for high temperature PEMFCs.  

PubMed

Toward an enhanced water-retention of polymer electrolyte membranes at high temperatures, novel organo-modified clays were prepared and tested as fillers for the creation of hybrid Nafion nanocomposites. Two smectite clays (Laponite and montmorillonite), with different structural and physical parameters, were loaded with various cationic organic molecules bearing several hydrophilic functional groups (-NH(2), -OH, -SO(3)H) and incorporated in Nafion by solution intercalation. The resulted hybrid membranes were characterized by a combination of powder X-ray diffraction, FTIR spectroscopy, and thermal analysis (DTA/TGA) showing that highly homogeneous exfoliated nanocomposites were created where the individual organoclay layers are uniformly dispersed in the continuous polymeric matrix. In this paper, water-transport properties were investigated by NMR spectroscopy, including pulsed-field-gradient spin-echo diffusion and spectral measurements conducted under variable temperature. Organo-montmorillonite nanofillers demonstrate a considerable effect on the Nafion polymer in terms both of water absorption/retention and water mobility with a remarkable behavior in the region of high temperatures (100-130 °C), denoting that the surface modifications of this clay with acid organic molecules significantly improve the performance of the final composite membrane. (1)H NMR spectral analysis allowed a general description of the water distribution in the system and an estimation of the number of water molecules involved in the hydration shell of the sulfonic groups as well as that absorbed on the organoclay particles. PMID:21671588

Nicotera, Isabella; Enotiadis, Apostolos; Angjeli, Kristina; Coppola, Luigi; Ranieri, Giuseppe A; Gournis, Dimitrios

2011-07-28

176

The influence of acid mist upon transpiration, shoot water potential and pressure—volume curves  

E-print Network

The influence of acid mist upon transpiration, shoot water potential and pressure and night transpiration rates were determined on 16/11/87 for 10 entire seedlings, of pH 2.5 and pH 5 transpiration rates were 1.19 ± 0.06 mmol's-1.tree-1 (day) and 0.54 ± 0.06 mmol's-1.tree-1 (night) for whole

Paris-Sud XI, Université de

177

Role of mixed boundaries on flow in open capillary channels with curved air-water interfaces.  

PubMed

Flow in unsaturated porous media or in engineered microfluidic systems is dominated by capillary and viscous forces. Consequently, flow regimes may differ markedly from conventional flows, reflecting strong interfacial influences on small bodies of flowing liquids. In this work, we visualized liquid transport patterns in open capillary channels with a range of opening sizes from 0.6 to 5.0 mm using laser scanning confocal microscopy combined with fluorescent latex particles (1.0 ?m) as tracers at a mean velocity of ?0.50 mm s(-1). The observed velocity profiles indicate limited mobility at the air-water interface. The application of the Stokes equation with mixed boundary conditions (i.e., no slip on the channel walls and partial slip or shear stress at the air-water interface) clearly illustrates the increasing importance of interfacial shear stress with decreasing channel size. Interfacial shear stress emerges from the velocity gradient from the adjoining no-slip walls to the center where flow is trapped in a region in which capillary forces dominate. In addition, the increased contribution of capillary forces (relative to viscous forces) to flow on the microscale leads to increased interfacial curvature, which, together with interfacial shear stress, affects the velocity distribution and flow pattern (e.g., reverse flow in the contact line region). We found that partial slip, rather than the commonly used stress-free condition, provided a more accurate description of the boundary condition at the confined air-water interface, reflecting the key role that surface/interface effects play in controlling flow behavior on the nanoscale and microscale. PMID:22867425

Zheng, Wenjuan; Wang, Lian-Ping; Or, Dani; Lazouskaya, Volha; Jin, Yan

2012-09-01

178

Design and implementation of a simple on-line time-activity curve detector for [O-15] water PET studies  

SciTech Connect

A simple, automated on-line detector system has been fabricated and implemented to detect the arterial time-activity curve (TAC) for water PET studies. This system offers two significant improvements over existing systems: a pump mechanism is not required to control arterial blood flow through the detector and dispersion correction of the time-activity curve is unnecessary. The positrons emanating from a thin-walled, 0.134 cm inner-diameter plastic tube are detected by a 0.5 cm wide by 1.0 cm long by 0.1 cm thick plastic scintillator mounted to a miniature PMT. Photon background is shielded by a 2.0 cm thick cylindrical lead shield. Mean cerebral blood flow (mCBF) calculated from the TAC determined by 1-second automated sampling was compared to that calculated from every 5-second integrated manual samples. Improvements in timing resolution (1-sec vs. 5-sec) cause small but significant differences between the two sampling methods. Dispersion is minimized due to small tubing diameters, short lengths of tubing between the radial arterial sampling site and the detector and the presence of a 3-way valve 10 cm proximal to the detector.

Wollenweber, S.D.; Hichwa, R.D.; Ponto, L.L.B. [Univ. of Iowa Hospitals & Clinics, Iowa City, IA (United States)

1996-12-31

179

Estimation of the gelatinization temperature of noodles from water sorption curves under temperature-programmed heating conditions.  

PubMed

A novel method in which the water sorption curve is observed under linearly temperature-raising conditions was proposed to estimate the gelatinization temperature of starch-containing foods, it was applied in an estimation of the gelatinization temperatures of dried noodles. The gelatinization temperatures of two kinds of spaghetti, dried at high and low temperature, were 52.3 and 53.1 °C, and those of udon, kishimen, juwari-soba, hachiwari-soba, so-called common soba, Malony(®), and kuzukiri were 57.0, 57.8, 61.1, 59.6, 57.4, 48.4, and 49.1 °C. The gelatinization temperatures estimated by the method were between the onset and peak temperatures obtained by differential scanning calorimetric measurement. PMID:23132576

Hasegawa, Ayako; Ogawa, Takenobu; Adachi, Shuji

2012-01-01

180

Retention Checklist.  

ERIC Educational Resources Information Center

Designed to improve student retention at Bronx Community College (BCC), this workbook is comprised of sets checklists for use by students in evaluating their progress toward a number of academic, personal, and work-related goals. The workbook is divided into five sections, each containing a set of goals and associated checklists. Part I deals with…

Santa Rita, Emilio

181

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

182

Development of Web-based Load Duration Curve system for analysis of total maximum daily load and water quality characteristics in a waterbody.  

PubMed

In many states of the US, the total maximum daily load program has been widely developed for watershed water quality restoration and management. However, the total maximum daily load is often represented as an average daily pollutant load based on average long-term flow conditions, and as such, it does not adequately describe the problems they aim to address. Without an adequate characterization of water quality problems, appropriate solutions cannot be identified and implemented. The total maximum daily load approach should consider adequate water quality characterizations based on overall flow conditions rather than on a single flow event such as average daily flow. The Load Duration Curve, which provides opportunities for enhanced pollutant source and best management practice targeting both in the total maximum daily load development and in water quality restoration efforts, has been used for the determination of appropriate total maximum daily load targets. However, at least 30 min to an hour is needed for unskilled people based on our experiences to generate the Load Duration Curve using a desktop-based spreadsheet computer program. Therefore, in this study, the Web-based Load Duration Curve system (https://engineering.purdue.edu/?ldc/) was developed and applied to a study watershed for an analysis of the total maximum daily load and water quality characteristics in the watershed. This system provides diverse options for Flow Duration Curve and Load Duration Curve analysis of a watershed of interest in a brief time. The Web-based Load Duration Curve system is useful for characterizing the problem according to flow regimes, and for providing a visual representation that enables an easy understanding of the problem and the total maximum daily load targets. In addition, this system will be able to help researchers identify appropriate best management practices within watersheds. PMID:22325582

Kim, Jonggun; Engel, Bernard A; Park, Youn Shik; Theller, Larry; Chaubey, Indrajeet; Kong, Dong Soo; Lim, Kyoung Jae

2012-04-30

183

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

184

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

185

Parametric Curves parametric curves (Splines)  

E-print Network

curves (Splines) · polygonal meshes #12;2 Roller coaster · Next programming assignment involves creating a 3D roller coaster animation · We must model the 3D curve describing the roller coaster, but how

Treuille, Adrien

186

Retention capacity of correlated surfaces  

E-print Network

We investigate the water retention model [C. L. Knecht \\emph{et al.}, Phys. Rev. Lett. {\\bf 108}, 045703 (2012)] on correlated and uncorrelated random surfaces. We find that the retention capacity of discrete random landscapes is strongly affected by spatial correlations among the heights. This phenomenon is related to the emergence of power-law scaling in the lake volume distribution. We also solve the uncorrelated case exactly for a small lattice.

Schrenk, K J; Ziff, R M; Herrmann, H J

2014-01-01

187

Evaluation of the physical properties of water treatment residue for use as a soil substitute compared with decomposed granite soil  

Microsoft Academic Search

To evaluate water treatment residue (WTR) as a soil substitute material, its physical properties were investigated and compared with decomposed granite soil (DGS). For comparison purposes, relative gas diffusivity (D\\/D0), saturated hydraulic conductivity (Ks), water retention curve, porosity and readily available water were measured for both the WTR and the DGS. The measured D\\/D0, Ks, water retention ability and porosity

Seok-Gon Park; Mizue Ohashi; Kiyoshi Kurosawa; Young-Jin Kim; Hisashi Yahata

2010-01-01

188

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-...

189

On the Investigation of Coarse-Grained Models for Water: Balancing Computational Efficiency and the Retention of Structural Properties  

PubMed Central

Developing accurate models of water for use in computer simulations is important for the study of many chemical and biological systems, including lipid bilayer self-assembly. The large temporal and spatial scales needed to study such self-assembly have led to the development and application of coarse-grained models for the lipid-lipid, lipid-solvent and solvent-solvent interactions. Unfortunately, popular center-of-mass-based coarse-graining techniques are limited to modeling water with one-water per bead. In this work, we have utilized the K-means algorithm to determine the optimal clustering of waters to allow the mapping of multiple waters to single coarse-grained beads. Through the study of a simple mixture between water and an amphiphilic solute (1-pentanol), we find a 4-water bead model has the optimal balance between computational efficiency and accurate solvation and structural properties when compared to water models ranging from 1 to 9 waters per bead. The 4-water model was subsequently utilized in studies of the solvation of hexadecanoic acid and the structure, as measured via radial distribution functions, for the hydrophobic tails and the bulk water phase were found to agree well with experimental data and their atomistic targets. PMID:20230012

Hadley, Kevin R.; McCabe, Clare

2010-01-01

190

Uptake and Retention of Mirex by Fish Maintained on Formulated and Natural Diets in Lake Ontario Waters  

Microsoft Academic Search

Fish with no detectable levels of the contaminant mirex were grown in Lake Ontario waters under conditions simulating commercial aquaculture. Benthic black bullheads (Ameiurus melas) were grown in cages placed in a bay of the lake. Pelagic rainbow trout (Oncorhynchus mykiss) were grown in terrestrial raceways served with Lake Ontario waters. Contaminant-free fingerlings were reared to a large size on

Joseph C. Makarewicz; Joseph K. Buttner; Theodore W. Lewis

1993-01-01

191

Retention Study Institutional Research  

E-print Network

Retention Study Fall 2012 Institutional Research #12;1 Introduction The Freshman and Transfer Retention Study conducted by Institutional Research (IR) tracks graduation, and persistence rates of new separate studies (New Freshman Retention and Transfer Retention) was in response to campus feedback

192

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

193

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

194

Linear viscoelastic master curves of neat and laponite-filled poly(ethylene oxide)–water solutions  

Microsoft Academic Search

Aqueous solutions composed of dispersed nanoparticles and entangled polymers are shown to exhibit common viscoelasticity over a range of particle and polymer concentrations. Time–temperature superposition and time–concentration superposition are applied to generate rheological master curves for neat and laponite-filled aqueous solutions of poly(ethylene oxide). The shift factors were correlated in terms of temperature and concentration and are found to differ

Vikram K. Daga; Norman J. Wagner

2006-01-01

195

Validation of a hyperspectral curve-fitting model for the estimation of plant water content of agricultural canopies  

Microsoft Academic Search

The estimation of plant water content is essential to the integration of remote sensing into precision agriculture. Hyperspectral models developed to estimate plant water content have had limited application under field conditions and have not been rigorously validated. A physical model using a spectrum matching technique was applied to hyperspectral data to directly calculate the canopy equivalent water thickness (EWT)

Catherine M Champagne; Karl Staenz; Abdou Bannari; Heather McNairn; Jean-Claude Deguise

2003-01-01

196

Preliminary analysis of water discharge and suspended sediment data from the Columbia River Basin: shifting rating curves and diminishing sediment loads  

NASA Astrophysics Data System (ADS)

Significant erosion along the coastlines of southwestern Washington in the last decade has motivated increased studies of sediment sources, sinks, and transport dynamics in the region. A key question is whether a reduction in sediment supply is responsible for the recent shift from a depositional regime. Because the Columbia River is the major fluvial system in the littoral cell, it is important to quantify sediment flux from the Columbia River to the coastal environment. We examine historical records of water discharge and suspended sediment transport along the Columbia main stem and in three subbasins in an attempt to quantify changes in total sediment transport and total load, and examine possible shifts in sediment sources over time. Suspended sediment data from the main stem near Vancouver, WA demonstrate a 3 to 5 fold downward shift in the rating curve in the last 90 years. The same trend is visible in data from the Snake River, with a decrease of almost an order of magnitude in sediment transport since the 1950's. Grain size data from the Kootenai River show a clear fining trend in the suspended load. The John Day River is the only long-term record we examined with no change in the rating curve over time; it is also the largest undammed river in the basin. Calculations of sediment load in the main stem were made using actual water discharge, estimated discharge (assuming no dams), and calculated `virgin' flow (Naik and Jay, in review). Preliminary results suggest that changes in the hydrograph (assuming a uniform rating curve) would diminish sediment transport to the coast by up to 20% over the last century; changes in the rating curve are responsible for at least that change, possibly more.

MacGregor, K. R.; Gelfenbaum, G.; Rubin, D.

2003-12-01

197

Bradford Curves.  

ERIC Educational Resources Information Center

Discussion of informetric distributions shows that generalized Leimkuhler functions give proper fits to a large variety of Bradford curves, including those exhibiting a Groos droop or a rising tail. The Kolmogorov-Smirnov test is used to test goodness of fit, and least-square fits are compared with Egghe's method. (Contains 53 references.) (LRW)

Rousseau, Ronald

1994-01-01

198

Curved Knives  

Microsoft Academic Search

IT may interest your correspondent, Dr. Otis T. Mason, to know that the curved ``drawing-knife'' described by him has representatives in Western (British) India. The Kolis (fishing races) of the Bombay coast wore lately, and some still wear, knives made by local blacksmiths, of which the blade, 2 to 3 inches long, was shaped and edged like that of an

W. F. Sinclair

1897-01-01

199

Ultrafast quantitation of six quinolones in water samples by second-order capillary electrophoresis data modeling with multivariate curve resolution-alternating least squares.  

PubMed

This paper presents the development of a capillary electrophoresis method with diode array detector coupled to multivariate curve resolution-alternating least squares (MCR-ALS) to conduct the resolution and quantitation of a mixture of six quinolones in the presence of several unexpected components. Overlapping of time profiles between analytes and water matrix interferences were mathematically solved by data modeling with the well-known MCR-ALS algorithm. With the aim of overcoming the drawback originated by two compounds with similar spectra, a special strategy was implemented to model the complete electropherogram instead of dividing the data in the region as usually performed in previous works. The method was first applied to quantitate analytes in standard mixtures which were randomly prepared in ultrapure water. Then, tap water samples spiked with several interferences were analyzed. Recoveries between 76.7 and 125 % and limits of detection between 5 and 18 ?g L(-1) were achieved. PMID:24566760

Alcaráz, Mirta R; Vera-Candioti, Luciana; Culzoni, María J; Goicoechea, Héctor C

2014-04-01

200

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

201

freshman retention study Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1  

E-print Network

freshman retention study fall 2010 #12; #12;Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Retention Trends New Freshmen Persistance and Graduation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 Retention by Semester Semester Persistence - New Freshmen

Stephens, Graeme L.

202

On the Fluid Retention Properties of Shales , A. Ferrari1  

E-print Network

On the Fluid Retention Properties of Shales V. Favero1 , A. Ferrari1 and L. Laloui1 1 Laboratory understanding of the hydro-mechanical behaviour of shales is of primary significance. The water retention methodologies that have been developed by the authors for the analysis of the retention behaviour of shales

Dalang, Robert C.

203

The effects of water replacement by oral rehydration fluids with or without betaine supplementation on performance, acid-base balance, and water retention of heat-stressed broiler chickens.  

PubMed

Exposing broilers to a high temperature increases water and electrolyte K(+) and Na(+) excretion, which negatively affects the heat dissipation capacity and acid-base homeostasis, resulting in losses in growth performance. In this experiment, the efficacy of providing oral rehydration therapy and betaine on growth performance, acid-base balance, and water and electrolyte retention was evaluated. A total of 432 one-day-old broiler chicks (Cobb) were allocated to 72 metabolic cages and reared to 31 d of age under standard conditions. From 32 to 41 d of age, chicks were exposed to heat stress (ambient temperature, 32°C) and high RH (80 to 100% RH) for 9 h daily. The ameliorative effects of a 3 × 3 factorial array of treatments administered via drinking water were evaluated in 8 replicates of 6 chicks per cage for each treatment. Two oral rehydration therapy (ORT) fluids, based on either citrate or bicarbonate salts, were added to tap water. In addition, betaine was added to tap water at an inclusion rate of 0, 500, or 1,000 mg/L to complete the array of 9 liquid-based treatments. Growth performance was assessed at 32, 35, and 41 d of age. From 32 to 35 d of age, chicks receiving ORT fluids exhibited improved growth performance, water balance, and electrolyte (K(+), Na(+)) retention. In addition, the physiological response to stress was attenuated, as indicated by lower heterophil-to-lymphocyte ratios and blood glucose concentrations relative to the negative controls. The addition of betaine at an inclusion rate of 500 mg/L improved BW gain. From d 36 to 41, treatments did not significantly influence growth performance, which suggests that chicks receiving tap water were able to compensate and adapt to the heat-stress conditions. The results demonstrate that the beneficial effects of providing ORT fluids and 500 mg of betaine/L were observed only during the first 4 d of heat exposure. After this period, adaptation to the heat appears to occur, and none of the treatments was successful in improving growth performance. PMID:21177455

Sayed, M A M; Downing, J

2011-01-01

204

Improvement of methods for reconstructing water heating aggregated load curves and evaluating demand-side control benefits  

Microsoft Academic Search

Electric water heating represents a substantial share of electricity consumption, and can be a significant part in utility system peak. Storage water heaters with limited capacity have been a useful tool for some utilities to manage the electrical load, generally promoted by attractive tariff structure. The present paper proposes a method to estimate the results of such a strategy. A

M. Orphelin; J. Adnot

1999-01-01

205

Climate Change Adaptation in the Western U.S.: the Case for Dynamic Rule Curves in Water Resources Management  

Microsoft Academic Search

Climate change in the Western U.S. will bring systematic hydrologic changes affecting many water resources systems. Successful adaptation to these changes, which will be ongoing through the 21st century, will require the 'rebalancing' of competing system objectives such as water supply, flood control, hydropower production, and environmental services in response to hydrologic (and other) changes. Although fixed operating policies for

S. Lee; A. F. Hamlet; S. J. Burges

2008-01-01

206

Transport and retention of multi-walled carbon nanotubes in saturated porous media: effects of input concentration and grain size.  

PubMed

Water-saturated column experiments were conducted to investigate the effect of input concentration (C?) and sand grain size on the transport and retention of low concentrations (1, 0.01, and 0.005 mg L?¹) of functionalized ¹?C-labeled multi-walled carbon nanotubes (MWCNT) under repulsive electrostatic conditions that were unfavorable for attachment. The breakthrough curves (BTCs) for MWCNT typically did not reach a plateau, but had an asymmetric shape that slowly increased during breakthrough. The retention profiles (RPs) were not exponential with distance, but rather exhibited a hyper-exponential shape with greater retention near the column inlet. The collected BTCs and RPs were simulated using a numerical model that accounted for both time- and depth-dependent blocking functions on the retention coefficient. For a given C?, the depth-dependent retention coefficient and the maximum solid phase concentration of MWCNT were both found to increase with decreasing grain size. These trends reflect greater MWCNT retention rates and a greater number of retention locations in the finer textured sand. The fraction of the injected MWCNT mass that was recovered in the effluent increased and the RPs became less hyper-exponential in shape with higher C? due to enhanced blocking/filling of retention locations. This concentration dependency of MWCNT transport increased with smaller grain size because of the effect of pore structure and MWCNT shape on MWCNT retention. In particular, MWCNT have a high aspect ratio and we hypothesize that solid phase MWCNT may create a porous network with enhanced ability to retain particles in smaller grain sized sand, especially at higher C?. Results demonstrate that model simulations of MWCNT transport and fate need to accurately account for observed behavior of both BTCs and RPs. PMID:23228890

Kasel, Daniela; Bradford, Scott A; Šim?nek, Ji?í; Heggen, Marc; Vereecken, Harry; Klumpp, Erwin

2013-02-01

207

Rapid and specific detection of Salmonella in water samples using real-time PCR and High Resolution Melt (HRM) curve analysis.  

PubMed

A real-time PCR assay combined with a pre-enrichment step for the specific and rapid detection of Salmonella in water samples is described. Following amplification of the invA gene target, High Resolution Melt (HRM) curve analysis was used to discriminate between products formed and to positively identify invA amplification. The real-time PCR assay was evaluated for specificity and sensitivity. The assay displayed 100% specificity for Salmonella and combined with a 16-18 h non-selective pre-enrichment step, the assay proved to be highly sensitive with a detection limit of 1.0 CFU/ml for surface water samples. The detection assay also demonstrated a high intra-run and inter-run repeatability with very little variation in invA amplicon melting temperature. When applied to water samples received routinely by the laboratory, the assay showed the presence of Salmonella in particularly surface water and treated effluent samples. Using the HRM based assay, the time required for Salmonella detection was drastically shortened to less than 24 h compared to several days when using standard culturing methods. This assay provides a useful tool for routine water quality monitoring as well as for quick screening during disease outbreaks. PMID:22170841

van Blerk, G N; Leibach, L; Mabunda, A; Chapman, A; Louw, D

2011-01-01

208

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

209

Retention and mitigation of metals in sediment, soil, water, and plant of a newly constructed root-channel wetland (China) from slightly polluted source water.  

PubMed

Constructed root-channel wetland (CRCW) is a term for pre-pond/wetland/post-pond complexes, where the wetland includes plant-bed/ditch landscape and root-channel structure. Source water out of pre-ponds flows through alternate small ditches and plant beds with root-channels via a big ditch under hydraulic regulation. Then source water flows into post-ponds to finish final polishing. This article aims to explore the potential of components of a pilot CRCW in China on mitigating metals in micro-polluted source water during its initial operation stage. We investigated six heavy metals (Cd, Cr, Cu, Ni, Zn, and Pb) in surface sediment, plant-bed subsurface soil, water, and aquatic plants during 2012-2013. Monitoring results showed that pond/ditch sediments and plant-bed soil retained a significant amount of Cr, Ni, and Zn with 93.1%, 72.4%, and 57.5% samples showing contamination factor above limit 1 respectively. Remarkably the high values of metal enrichment factor (EF) occurred in root-channel zones. Water monitoring results indicated that Ni, Zn, and Pb were removed by 78.5% (66.7%), 57.6% (59.6%), and 26.0% (7.5%) in east (west) wetland respectively. Mass balance estimation revealed that heavy metal mass in the pond/ditch sediments accounted for 63.30% and that in plant-bed soil 36.67%, while plant uptake occupied only 0.03%. The heavy metal accretion flux in sediments was 0.41?-?211.08 ?g?·?cm(-2)?·?a(-1), less than that in plant-bed soil (0.73?-?543.94 ?g?·?cm(-2)?·?a(-1)). The 1.83 ha wetland has retained about 86.18 kg total heavy metals within 494 days after operation. This pilot case study proves that constructed root-channel wetland can reduce the potential ecological risk of purified raw water and provide a new and effective method for the removal of heavy metals from drinking water sources. PMID:25032090

Wang, Baoling; Wang, Yu; Wang, Weidong

2014-01-01

210

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 Central

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 Jose; Guimaraes Couto, Eduardo

2014-01-01

211

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

212

A new Automated Laboratory Instrument for Soil Water Characteristic Determination. System Validation at Oregon State University  

Microsoft Academic Search

The soil water characteristic (SWC) is a fundamental descriptor of soil water retention properties. While tension table apparatus for defining drainage curves in the near-saturated region (0 to -100 cm H20) has been available for many decades, there has been little advance in automating the process, particularly when measurements of wetting, drying are combined. We describe a new automated tension

K. Vache; J. J. McDonneIl; C. Graham; J. Ekanayake; T. Davie

213

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

214

Curved microchannels and bacterial streamers  

NASA Astrophysics Data System (ADS)

Bacterial biofilms are commonly identified as microbial communities attached to a surface and encased in a self-secreted extracellular matrix. Due to their increased resistance to antimicrobial agents, biofilms have an enormous impact on health and medicine (e.g., wound healing, implant-associated infections, disease transmission). On the other hand, they constitute a major component of the stream ecosystem by increasing transport of nutrients and retention of suspended particles. In this talk, we present an experimental study of bacterial biofilm development in a microfluidic device. In particular, we show the formation of filamentous structures, or streamers, in curved channels and how these suspended biofilms are linked to the underlying hydrodynamics.

Rusconi, Roberto; Lecuyer, Sigolene; Guglielmini, Laura; Stone, Howard

2010-03-01

215

Neurogenic urinary retention  

Microsoft Academic Search

This review article on neurogenic urinary retention is divided into three main sections. The first covers the neuroanatomy of the bladder and urethral sphincters, developing the peripheral innervation as well as the spinal cord organization and the cortical and subcortical brain control of micturition. The second discusses the main central and peripheral neurological lesions and diseases causing urinary retention. The

A. G. Herbaut

1993-01-01

216

Clay particle retention in small constructed wetlands.  

PubMed

Constructed wetlands (CWs) can be used to mitigate non-point source pollution from arable fields. Previous investigations have shown that the relative soil particle retention in small CWs increases when hydraulic load increases. This paper investigates why this phenomenon occurs, even though common retention models predict the opposite, by studying clay and silt particle retention in two Norwegian CWs. Retention was measured with water flow proportional sampling systems in the inlet and outlet of the wetlands, and the texture of the suspended solids was analyzed. The surface area of the CWs was small compared to the watershed area (approximately 0.07%), giving high average hydraulic loads (1.1 and 2.0 md(-1)). One of the watersheds included only old arable land, whereas the other included areas with disturbed topsoil after artificial land leveling. Clay particle retention was 57% for the CW in the first watershed, and 22% for the CW in the disturbed watershed. The different behavior of the wetlands could be due to differences in aggregate size and stability of the particles entering the wetlands. Results showed that increased hydraulic loads did affect CW retention negatively. However, as runoff increased, soil particles/aggregates with higher sedimentation velocities entered the CWs (e.g., the clay particles behaved as silt particles). Hence, clay particle settling velocity is not constant as assumed in many prediction models. The net result was increased retention. PMID:12909097

Braskerud, B C

2003-09-01

217

Curves and Their Properties.  

ERIC Educational Resources Information Center

This volume, a reprinting of a classic first published in 1952, presents detailed discussions of 26 curves or families of curves, and 17 analytic systems of curves. For each curve the author provides a historical note, a sketch or sketches, a description of the curve, a discussion of pertinent facts, and a bibliography. Depending upon the curve,…

Yates, Robert C.

218

Freshman Inquiry Retention Preliminary Findings  

E-print Network

Freshman Inquiry Retention Preliminary Findings Sukhwant Jhaj, Rowanna Carpenter University Studies Student Data Warehouse - Student Retention - Academic Performance #12;Evolving Assessment Structure intending to graduate from PSU had a higher fall-to- fall retention rate than others. · First

219

Assessing Chemical Retention Process Controls in Ponds  

NASA Astrophysics Data System (ADS)

Small ponds are a ubiquitous component of the landscape and have earned a reputation as effective chemical retention devices. The most common characterization of pond chemical retention is the retention coefficient, Ri= ([Ci]inflow-[Ci] outflow)/[Ci]inflow. However, this parameter varies widely in one pond with time and among ponds. We have re-evaluated literature reported (Borden et al., 1998) monthly average retention coefficients for two ponds in North Carolina. Employing a simple first order model that includes water residence time, the first order process responsible for species removal have been separated from the water residence time over which it acts. Assuming the rate constant for species removal is constant within the pond (arguable at least), the annual average rate constant for species removal is generated. Using the annual mean rate constant for species removal and monthly water residence times results in a significantly enhanced predictive capability for Davis Pond during most months of the year. Predictive ability remains poor in Davis Pond during winter/unstratified periods when internal loading of P and N results in low to negative chemical retention. Predictive ability for Piedmont Pond (which has numerous negative chemical retention periods) is improved but not to the same extent as Davis Pond. In Davis Pond, the rate constant for sediment removal (each month) is faster than the rate constant for water and explains the good predictability for sediment retention. However, the removal rate constant for P and N is slower than the removal rate constant for sediment (longer water column residence time for P,N than for sediment). Thus sedimentation is not an overall control on nutrient retention. Additionally, the removal rate constant for P is slower than for TOC (TOC is not the dominate removal process for P) and N is removed slower than P (different in pond controls). For Piedmont Pond, sediment removal rate constants are slower than the removal rate constant for water indicating significant sediment resuspension episodes. It appears that these sediment resuspension events are aperiodic and control the loading and the chemical retention capability of Piedmont Pond for N,P,TOC. These calculated rate constants reflect the differing internal loading processes for each component and suggest means and mechanisms for the use of ponds in water quality management.

Torgersen, T.; Branco, B.; John, B.

2002-05-01

220

Quotient curves of the GK curve  

E-print Network

For every $q=l^3$ with $l$ a prime power greater than 2, the GK curve $X$ is an $F_{q^2}$-maximal curve that is not $F_{q^2}$-covered by any $F_{q^2}$-maximal Deligne-Lusztig curve. Interestingly, $X$ has a very large $F_{q^2}$-automorphism group with respect to its genus. In this paper we compute the genera of a large variety of curves that are Galois-covered by the GK curve, thus providing several new values in the spectrum of genera of $F_{q^2}$-maximal curves.

Giulietti, Stefania Fanali; Massimo

2009-01-01

221

THE UCF RETENTION PLAN THE UCF RETENTION PLAN  

E-print Network

1 THE UCF RETENTION PLAN June, 1994 #12;2 THE UCF RETENTION PLAN STATEMENT OF THE PROBLEM An effective program of academic development and retention is marked by a continual process of interaction (UCF) community in academic development and retention is essential to program effectiveness and student

Wu, Shin-Tson

222

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

223

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

224

Drug Retention Times.  

National Technical Information Service (NTIS)

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.

2007-01-01

225

Retention in Tough Times.  

ERIC Educational Resources Information Center

Interviews with 25 global talent leaders discuss keeping good people and the challenges and emerging practices for retaining employees. Sidebars discuss retention tips and what keeps people on the job. (JOW)

Kaye, Beverly; Jordan-Evans, Sharon

2002-01-01

226

Standard Mastery Curves and Skew Curves.  

ERIC Educational Resources Information Center

The objective of the study is to convince educational researchers of the necessity for "standard mastery curves" for the graphical representation of scores on summative tests for a group of students. Attention is drawn to the study of theoretical and empirical skew curves in education and biology. Use of standard mastery curves and study of skew…

Warries, Egbert

227

Interactive aesthetic curve segments  

Microsoft Academic Search

To meet highly aesthetic requirements in in- dustrial design and styling, we propose a new category of aesthetic curve segments. To achieve these aesthetic requirements, we use curves whose logarithmic curvature histograms(LCH) are represented by straight lines. We call such curves aesthetic curves. We identify the overall shapes of aesthetic curves depending on the slope of LCH ?, by imposing

Norimasa Yoshida; Takafumi Saito

2006-01-01

228

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

229

Comparison of soil moisture retention characteristics obtained by the extended evaporation method and the pressure plate/sand box apparatus  

NASA Astrophysics Data System (ADS)

The water retention curve (WRC) characterizes the capacity of soil to hold water at specified soil matric potentials. It is a key property in any soil hydrologic application. To determine water retention data accurately and in turn use them to draw the whole curve by optimizing parameters of a proper soil hydraulic equation, it is of crucial importance to choose a suitable measurement procedure. For many years, the sand box-pressure plate apparatus are widely accepted as a reference laboratory procedure. To overcome shortcomings of the pressure plate, the evaporation method was introduced, besides many others. The method is not dependent on hydrostatic equilibrium conditions, thus allowing much quicker measurements, and yields the WRC in very high resolution. The method furthermore enables to quantify the unsaturated hydraulic conductivity function. We investigated a set of 40 fine-textured soils with both methods. The samples were packed from aggregated, dried and sieved material. Eight (-5, -10, -33, -100, -400, -700,-1000 and -1500kPa) water retention data points were obtained from sand box-pressure plate apparatus. Evaporation measurements were performed with the commercial apparatus HYPROP by UMS GmbH, Munich, applying the extended method, which yields water retention data in the range from 0 to -500kPa. We found that the sand box-pressure plate method lead to immediate drainage of water, whereas in HYPROP water started to drain only after reaching an air-entry point of pF 1.2-1.3. Accordingly, HYPROP gave higher water contents until pF 2, compared to the sand box/pressure plate apparatus, but from this point on both curves begin to be close and around the field capacity (pF 2.5) they overlap. Both methods show that the textural pore system starts to drain much later, around pF 3.5. We hypothesize that the reason for the different drainage behaviour of the interaggrate pore system lies in the saturation procedure. For HYPROP, samples were saturated under vacuum, yielding 100% saturation, whereas for the traditional method saturation took place by capillary uptake.

Öztürk, Hasan S.; Durner, Wolfgang; Haghverdi, Amir; Walter, Birgit

2013-04-01

230

Curves of constant width  

Microsoft Academic Search

Curves of constant width have the same breadth regardless of how they are rotated. Highly noncircular curves with this property may be constructed geometrically. Such curves make good rollers, manhole covers, and allow one to drill nearly square holes.

James A. Flaten

1999-01-01

231

Curves of constant width  

NASA Astrophysics Data System (ADS)

Curves of constant width have the same breadth regardless of how they are rotated. Highly noncircular curves with this property may be constructed geometrically. Such curves make good rollers, manhole covers, and allow one to drill nearly square holes.

Flaten, James A.

1999-10-01

232

Retention Time Effect on Metal Removal by Peat Columns (U).  

National Technical Information Service (NTIS)

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 ...

E. A. Nelson

2007-01-01

233

Middle to late Miocene stepwise climate cooling: Evidence from a high-resolution deep water isotope curve spanning 8 million years  

NASA Astrophysics Data System (ADS)

present high-resolution (2-3 kyr) benthic foraminiferal stable isotopes in a continuous, well-preserved sedimentary archive from the West Pacific Ocean (Ocean Drilling Program Site 1146), which track climate evolution in unprecedented resolution over the period 12.9 to 8.4 Ma. We developed an astronomically tuned chronology over this interval and integrated our new records with published isotope data from the same location to reconstruct long-term climate and ocean circulation development between 16.4 and 8.4 Ma. This extended perspective reveals that the long eccentricity (400 kyr) cycle is prominently encoded in the ?13C signal over most of the record, reflecting long-term fluctuations in the carbon cycle. The ?18O signal closely follows variations in short eccentricity (100 kyr) and obliquity (41 kyr). In particular, the obliquity cycle is prominent from ~14.6 to 14.1 Ma and from ~9.8 to 9.2 Ma, when high-amplitude variability in obliquity is congruent with low-amplitude variability in short eccentricity. The ?18O curve is additionally characterized by a series of incremental steps at ~14.6, 13.9, 13.1, 10.6, 9.9, and 9.0 Ma, which we attribute to progressive deep water cooling and/or glaciation episodes following the end of the Miocene climatic optimum. On the basis of ?18O amplitudes, we find that climate variability decreased substantially after ~13 Ma, except for a remarkable warming episode at ~10.8-10.7 Ma at peak insolation during eccentricity maxima (100 and 400 kyr). This transient warming, associated with a massive negative carbon isotope shift, is reminiscent of intense global warming events at eccentricity maxima during the Miocene climatic optimum.

Holbourn, Ann; Kuhnt, Wolfgang; Clemens, Steven; Prell, Warren; Andersen, Nils

2013-12-01

234

The soil reference shrinkage curve  

E-print Network

A recently proposed model showed how a clay shrinkage curve is transformed to the soil shrinkage curve at the soil clay content higher than a critical one. The objective of the present work was to generalize this model to the soil clay content lower a critical one. I investigated (i) the reference shrinkage curve, that is, one without cracks; (ii) the superficial layer of aggregates, with changed pore structure compared with the intraaggregate matrix; and (iii) soils with sufficiently low clay content where there are large pores inside the intraaggregate clay (so-called lacunar pores). The methodology is based on detail accounting for different contributions to the soil volume and water content during shrinkage. The key point is the calculation of the lacunar pore volume variance at shrinkage. The reference shrinkage curve is determined by eight physical soil parameters: (1) oven-dried specific volume; (2) maximum swelling water content; (3) mean solid density; (4) soil clay content; (5) oven-dried structural porosity; (6) the ratio of aggregate solid mass to solid mass of intraaggregate matrix; (7) the lacunar factor that characterizes the rate of the lacunar pore volume change with water content; and (8) oven-dried lacunar pore volume. The model was validated using available data. The model predicted value of the slope of the reference shrinkage curve in the basic shrinkage area is equal to unity minus the lacunar factor value, and is between unity and zero in the agreement with observations.

V. Y. Chertkov

2014-03-11

235

Water Quality, Streamflow Conditions, and Annual Flow-Duration Curves for Streams of the San Juan-Chama Project, Southern Colorado and Northern New Mexico, 1935-2010.  

National Technical Information Service (NTIS)

The Albuquerque-Bernalillo County Water Utility Authority supplements the municipal water supply for the Albuquerque metropolitan area, in central New Mexico, with water diverted from the Rio Grande. Water diverted from the Rio Grande for municipal use is...

K. A. Hafich, S. E. Falk, S. K. Anderholm

2013-01-01

236

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

237

National Curve Bank  

NSDL National Science Digital Library

The National Curve Bank displays representations of two- and three-dimensional curves. Geometrical, algebraic, and historical aspects of curves are included. Educators and students have access to animations, interactions, java applets, Mathematica code, and more. Users may submit curves. Materials are reveiwed and selected by faculty at Cal State Los Angeles.

2009-03-01

238

Characterizations of Special Curves  

E-print Network

In this study, the new characterizations of special curves are investigated without using the curvatures of these special curves: general helices, slant helices, Bertrand curves, Mannheim curves. The curvatures are given by the help of the norms of the derivatives of Frenet vectors.

Yayli, Yusuf

2012-01-01

239

Understanding curved detonation waves  

SciTech Connect

A wave curve is the set of final states to which an initial state may be connected by a traveling wave. In gas dynamics, for example, the wave curve consists of the shock Hugoniot curve for compressive waves and the rarefaction curve for expansive waves. In this paper, we discuss the wave curve for an undriven planar detonation and for general planar detonations. We then extend the wave curve concept to detonations in converging and diverging geometry. We also discuss the application of these wave curves to the numerical computation of detonation problems.

Bukiet, B.G. [New Jersey Inst. of Tech., Newark, NJ (United States). Dept. of Mathematics; Menikoff, R. [Los Alamos National Lab., NM (United States)

1992-10-01

240

Understanding curved detonation waves  

SciTech Connect

A wave curve is the set of final states to which an initial state may be connected by a traveling wave. In gas dynamics, for example, the wave curve consists of the shock Hugoniot curve for compressive waves and the rarefaction curve for expansive waves. In this paper, we discuss the wave curve for an undriven planar detonation and for general planar detonations. We then extend the wave curve concept to detonations in converging and diverging geometry. We also discuss the application of these wave curves to the numerical computation of detonation problems.

Bukiet, B.G. (New Jersey Inst. of Tech., Newark, NJ (United States). Dept. of Mathematics); Menikoff, R. (Los Alamos National Lab., NM (United States))

1992-01-01

241

Modelling of arsenic retention in constructed wetlands.  

PubMed

A new model was developed in order to simulate the most significant arsenic retention processes that take place in constructed wetlands (CWs) treating high arsenic waters. The present contribution presents the implementation phases related to plants (arsenic uptake and accumulation, root arsenic adsorption, and root oxygen release), showing the first simulation results of the complete model. Different approaches with diverse influent configurations were simulated. In terms of total arsenic concentrations in effluent, the simulated data closely matched the data measured in all evaluated cases. The iron and arsenic species relationships, and the arsenic retention percentages obtained from simulations, were in agreement with the experimental data and literature. The arsenic retention efficiency increased whenever a new phase was implemented, reaching a maximum efficiency range of 85-95%. According to the quality of the obtained results, it can be considered that the implementation of all steps of RCB-ARSENIC provided reasonably good response values. PMID:23994963

Llorens, Esther; Obradors, Joshua; Alarcón-Herrera, María Teresa; Poch, Manel

2013-11-01

242

DRAM variable retention time  

Microsoft Academic Search

A DRAM bit has variable retention time (VRT) when the memory cell leakage, which determines how long a cell can retain information, varies with time. This paper reports on a study of VRT in cells from 4Mbit and 16 Mbit DRAM chips produced by a variety of manufacturers and in a number of technologies including trench capacitor and stacked capacitor

P. J. Restle; J. W. Park; B. F. Lloyd

1992-01-01

243

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

244

Promoting Employment Retention.  

ERIC Educational Resources Information Center

This document examines policy and program issues related to promoting employment retention among recipients of Temporary Assistance for Needy Families (TANF) who have moved from welfare into employment. The document begins with background information about the work requirements and time limits affecting TANF recipients. The second section…

Relave, Nanette

2000-01-01

245

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

246

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

247

Financial Literacy and Retention  

ERIC Educational Resources Information Center

Higher education administrators know it is more cost-effective to keep students than to recruit them. Understanding financial literacy--and how it impacts student retention and persistence on the campuses--is an important concept for administrators to comprehend. Most students are not financially literate when they enter the world of higher…

Adams, Ruth L.

2006-01-01

248

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

249

Biofilm Roughness Determines Cryptosporidium parvum Retention in Environmental Biofilms  

PubMed Central

The genus Cryptosporidium is a group of waterborne protozoan parasites that have been implicated in significant outbreaks of gastrointestinal infections throughout the world. Biofilms trap these pathogens and can contaminate water supplies through subsequent release. Biofilm microbial assemblages were collected seasonally from three streams in eastern Pennsylvania and used to grow biofilms in laboratory microcosms. Daily oocyst counts in the influx and efflux flow allowed the calculation of daily oocyst retention in the biofilm. Following the removal of oocysts from the influx water, oocyst attachment to the biofilm declined to an equilibrium state within 5 days that was sustained for at least 25 days. Varying the oocyst loading rate for the system showed that biofilm retention could be saturated, suggesting that discrete binding sites determined the maximum number of oocysts retained. Oocyst retention varied seasonally but was consistent across all three sites; however, seasonal oocyst retention was not consistent across years at the same site. No correlation between oocyst attachment and any measured water quality parameter was found. However, oocyst retention was strongly correlated with biofilm surface roughness and roughness varied among seasons and across years. We hypothesize that biofilm roughness and oocyst retention are dependent on environmentally driven changes in the biofilm community rather than directly on water quality conditions. It is important to understand oocyst transport dynamics to reduce risks of human infection. Better understanding of factors controlling biofilm retention of oocysts should improve our understanding of oocyst transport at different scales. PMID:22492449

Hargreaves, B. R.; Jellison, K. L.

2012-01-01

250

Samples: Minimum Retention Times APPENDIX L APPENDIX L (Sample Retention) page 1 of 1 APPENDIX L (Sample Retention)  

E-print Network

Samples: Minimum Retention Times APPENDIX L APPENDIX L (Sample Retention) page 1 of 1 APPENDIX L (Sample Retention) Updated Aug 2, 2011 Samples: Minimum Retention Times* (Calendar days starting from date

Keinan, Alon

251

Mobile Learning and Student Retention  

ERIC Educational Resources Information Center

Student retention in open and distance learning (ODL) is comparatively poor to traditional education and, in some contexts, embarrassingly low. Literature on the subject of student retention in ODL indicates that even when interventions are designed and undertaken to improve student retention, they tend to fall short. Moreover, this area has not…

Fozdar, Bharat Inder; Kumar, Lalita S.

2007-01-01

252

4, 26412665, 2007 Nitrogen retention  

E-print Network

BGD 4, 2641­2665, 2007 Nitrogen retention patterns and controlling factors X. Xu et al. Title Page Nitrogen retention patterns and their controlling factors in an alpine meadow: implications for carbon;BGD 4, 2641­2665, 2007 Nitrogen retention patterns and controlling factors X. Xu et al. Title Page

Paris-Sud XI, Université de

253

Email Archiving and Retention at  

E-print Network

Email Archiving and Retention at Old Dominion University Deleted Items When an item is deleted yourself with the retention requirements. Talk with your supervisor, and decide. 2. Even within a folder Retention periods? Decide what is unnecessary, and delete those. Decide what is the longest you'll need

254

Principal curves revisited  

Microsoft Academic Search

A principal curve (Hastie and Stuetzle, 1989) is a smooth curve passing through the ‘middle’ of a distribution or data cloud, and is a generalization of linear principal components. We give an alternative definition of a principal curve, based on a mixture model. Estimation is carried out through an EM algorithm. Some comparisons are made to the Hastie-Stuetzle definition.

Robert Tibshirani

1992-01-01

255

Ammonia-water mixtures at high pressures - Melting curves of ammonia dihydrate and ammonia monohydrate and a revised high-pressure phase diagram for the water-rich region. [in primordial solar system ices  

NASA Technical Reports Server (NTRS)

The phase relations of some mixtures of ammonia and water are investigated to create a phase diagram in pressure-temperature-composition space relevant to the geophysical study of bodies in the outer solar system. The mixtures of NH3(x)H2O(1-x), where x is greater than 0.30 but less than 0.51, are examined at pressures and temperatures ranging from 0-6.5 GPa and 125-400 K, respectively. The ruby luminescence technique monitors the pressure and a diamond-anvil cell compresses the samples, and the phases are identified by means of normal- and polarized-light optical microscopy. The melting curve for NH3H2O(2) is described by the equation T = 176 + 60P - 8.5P squared for the ranges of 0.06-1.4 GPa and 179-243 K. The equation for NH3H2O is T = 194 + 37P - P squared, which represents a minor correction of a previous description by Johnson et al. (1985). Observed phase transitions are consistent with the high-pressure stability limit of NH3H2O(2), and the transition boundary is found to be linear.

Boone, S.; Nicol, M. F.

1991-01-01

256

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

PubMed

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 solution ionic strength (IS), and an increase in water velocity, sand grain size, and input concentration (Co). In contrast to conventional filtration theory, retention profiles (RPs) for AgNPs exhibited uniform, nonmonotonic, or hyperexponential shapes that were sensitive to physicochemical conditions. The experimental BTCs and RPs with uniform or hyperexponential shape were well described using a numerical model that considers time- 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 because of their higher values of Smax. Conversely, RPs were nonmonotonic or uniform at higher Co and in coarser sand that had lower values of Smax, 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. Nonmonotonic RPs had peak concentrations at greater distances in the presence of excess amounts of surfactant, suggesting that competition between AgNPs and surfactant diminished Smax close to the column inlet. The sensitivity of the nonmonotonic RPs to IS and velocity in coarser textured sand indicates that AgNPs were partially interacting in a secondary minimum. However, elimination of the secondary minimum only produced recovery of a small portion (<10%) of the retained AgNPs. These results imply that AgNPs were largely irreversibly interacting in a primary minimum associated with microscopic heterogeneity. PMID:23490100

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

2013-05-01

257

The soil reference shrinkage curve  

E-print Network

A recently proposed model showed how a clay shrinkage curve is transformed to the soil shrinkage curve at the soil clay content higher than a critical one. The objective of the present work was to generalize this model to the soil clay content lower a critical one. I investigated (i) the reference shrinkage curve, that is, one without cracks; (ii) the superficial layer of aggregates, with changed pore structure compared with the intraaggregate matrix; and (iii) soils with sufficiently low clay content where there are large pores inside the intraaggregate clay (so-called lacunar pores). The methodology is based on detail accounting for different contributions to the soil volume and water content during shrinkage. The key point is the calculation of the lacunar pore volume variance at shrinkage. The reference shrinkage curve is determined by eight physical soil parameters: (1) oven-dried specific volume; (2) maximum swelling water content; (3) mean solid density; (4) soil clay content; (5) oven-dried structural...

Chertkov, V Y

2014-01-01

258

ENHANCED RETENTION AND SENSITIVITY IN THE ANALYSIS OF CYANURIC ACID IN WATER USING POROUS GRAPHITIC CARBON AND UV DETECTION IN HIGH PRESSURE LIQUID CHROMATOGRAPHY  

EPA Science Inventory

Cyanuric acid (CA) has found application as a chlorine stabilizer in pool waters. The National Swimming Pool Foundation recommends CA levels between 30-50 ppm and a chlorine residual of 1.0-3.0 ppm. These chlorine levels are needed to destroy harmful pathogenic organisms. Develo...

259

ENHANCED RETENTION AND SENSITIVITY IN THE ANALYSIS OF CYANURIC ACID IN WATER USING POROUS GRAPHITIC CARBON AND UV DETECTION IN HPLC  

EPA Science Inventory

Cyanuric acid (CA) has found application as a chlorine stabilizer in pool waters. The National Swimming Pool Foundation recommends CA levels between 30-50 ppm and a chlorine residual of 1.0-3.0 ppm. These chlorine levels are needed to destroy harmful pathogenic organisms. Develo...

260

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

261

Nutrient retention in plant biomass and sediments from the salt marsh in Hangzhou Bay estuary, China.  

PubMed

Nutrient load into the ocean can be retained during the process of plant uptake and sedimentation in marshes along the bay zone. Seasonal variations of biomass and nutrient concentration in three dominated plant assemblages and associated sediments were monitored in this study area to determine effects of salt marsh on nutrient retention. Results showed that plant aboveground biomass displayed a unimodal curve with nutrient concentration generally decreased from spring to winter. Belowground biomass was relatively low during the rapid growth period with nutrient concentration tending to decrease and then increase during this period. Plant total nitrogen (TN) pools are higher than total phosphorus (TP) pools, and both pools showed significant seasonal variations. Water purification coefficients (WPC) of nutrients by plant assimilation were 34.4/17.3, 19.3/24.0, and 5.14/6.04 t/(m(2) year) (TN/TP) for Phragmites australis, Spartina alterniflora, and Scirpus mariqueter, respectively. Overall, these results suggest that higher annual plant biomass and nutrient assimilation contribute to greater nutrient retention capacity and accumulation in sediments, thereby enabling reduced eutrophication in transitional waters. PMID:23589271

Shao, Xuexin; Wu, Ming; Gu, Binhe; Chen, Yinxu; Liang, Xinqiang

2013-09-01

262

Factors affecting water coning  

E-print Network

. The interpolated curve was essentially the same as the simulation curve during the later production history. The values of the interpolated curve during the transition period had lower water oil ratios than the simulation curve. This is due to using linear.... The interpolated curve was essentially the same as the simulation curve during the later production history. The values of the interpolated curve during the transition period had lower water oil ratios than the simulation curve. This is due to using linear...

Parker, Randy Keith

2012-06-07

263

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

264

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

265

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

266

Retention through redemption.  

PubMed

Corporate America and the U.S. Navy share one big problem: employee retention. Today's knowledge workers hop from start-up to start-up. And 40% of the navy's new recruits leave the service before their four-year tours of duty are up. D. Michael Abrashoff came face to face with the navy's retention problem when he took command of the USS Benfold. Before he became captain, sailors couldn't get away from the ship fast enough. Today the vessel is the pride of the Pacific fleet, and sailors from other ships are clamoring to join its crew. In this firsthand account, Abrashoff explains how he got the ship and its crew back on course by breaking bad habits--personal and professional ones--and jettisoning old attitudes. During his 21 months aboard the Benfold, Abrashoff came to realize that in today's technology-intensive U.S. Navy, the traditional command-and-control style wouldn't work. And it hadn't--the Benfold's 310 sailors had cheered derisively when Abrashoff's predecessor had left the ship. So he defied 225 years of navy tradition in his quest to engage the sailors in their work, increase their performance, and keep them around for their entire tours of duty. He retained his crew by redeeming them--showing them how to be not just better sailors but better people, too. That meant breaking them down when they were at their worst and then building them up to reach their best. It also meant personal redemption for Abrashoff; he resolved to really listen to what his sailors were saying. The result? Cost-saving ideas for the entire navy and surging confidence and commitment among crew members. PMID:11213688

Abrashoff, D M

2001-02-01

267

Retention and Students with Disabilities  

ERIC Educational Resources Information Center

The purpose of this article is to identify the factors affecting retention of college students with disabilities, examine the issues related to transition planning from secondary to postsecondary education, and explore the utility of the universal design concept to the retention of students. Further, promising practices will be shared along with…

Belch, Holley A.

2004-01-01

268

12 CFR 202.12 - Record retention.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 false Record retention. 202.12 Section 202...REGULATION B) § 202.12 Record retention. (a) Retention of prohibited information...the matter, unless an earlier time is allowed by order of the...

2011-01-01

269

12 CFR 202.12 - Record retention.  

...2014-01-01 false Record retention. 202.12 Section 202...REGULATION B) § 202.12 Record retention. (a) Retention of prohibited information...the matter, unless an earlier time is allowed by order of the...

2014-01-01

270

12 CFR 202.12 - Record retention.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Record retention. 202.12 Section 202...REGULATION B) § 202.12 Record retention. (a) Retention of prohibited information...the matter, unless an earlier time is allowed by order of the...

2010-01-01

271

12 CFR 202.12 - Record retention.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Record retention. 202.12 Section 202...REGULATION B) § 202.12 Record retention. (a) Retention of prohibited information...the matter, unless an earlier time is allowed by order of the...

2012-01-01

272

12 CFR 1002.12 - Record retention.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Record retention. 1002.12 Section 1002...REGULATION B) § 1002.12 Record retention. (a) Retention of prohibited information...the matter, unless an earlier time is allowed by order of the...

2012-01-01

273

5 CFR 9701.356 - Pay retention.  

Code of Federal Regulations, 2010 CFR

...regarding the application of pay retention. Pay retention prevents a reduction in basic...of the new band. (b) Pay retention must be based on the employee's...pay increases provided at the time of a rate range adjustment...

2010-01-01

274

5 CFR 9701.356 - Pay retention.  

Code of Federal Regulations, 2012 CFR

...regarding the application of pay retention. Pay retention prevents a reduction in basic...of the new band. (b) Pay retention must be based on the employee's...pay increases provided at the time of a rate range adjustment...

2012-01-01

275

12 CFR 1002.12 - Record retention.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Record retention. 1002.12 Section 1002...REGULATION B) § 1002.12 Record retention. (a) Retention of prohibited information...the matter, unless an earlier time is allowed by order of the...

2013-01-01

276

5 CFR 9701.356 - Pay retention.  

...regarding the application of pay retention. Pay retention prevents a reduction in basic...of the new band. (b) Pay retention must be based on the employee's...pay increases provided at the time of a rate range adjustment...

2014-01-01

277

5 CFR 9701.356 - Pay retention.  

Code of Federal Regulations, 2013 CFR

...regarding the application of pay retention. Pay retention prevents a reduction in basic...of the new band. (b) Pay retention must be based on the employee's...pay increases provided at the time of a rate range adjustment...

2013-01-01

278

5 CFR 9701.356 - Pay retention.  

Code of Federal Regulations, 2011 CFR

...regarding the application of pay retention. Pay retention prevents a reduction in basic...of the new band. (b) Pay retention must be based on the employee's...pay increases provided at the time of a rate range adjustment...

2011-01-01

279

12 CFR 202.12 - Record retention.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Record retention. 202.12 Section 202...REGULATION B) § 202.12 Record retention. (a) Retention of prohibited information...the matter, unless an earlier time is allowed by order of the...

2013-01-01

280

12 CFR 1002.12 - Record retention.  

...2014-01-01 false Record retention. 1002.12 Section 1002...REGULATION B) § 1002.12 Record retention. (a) Retention of prohibited information...the matter, unless an earlier time is allowed by order of the...

2014-01-01

281

49 CFR 576.7 - Retention.  

Code of Federal Regulations, 2012 CFR

... 7 2012-10-01 2012-10-01 false Retention. 576.7 Section 576.7 Transportation...DEPARTMENT OF TRANSPORTATION (CONTINUED) RECORD RETENTION § 576.7 Retention. Duplicate copies need not be retained....

2012-10-01

282

49 CFR 576.7 - Retention.  

Code of Federal Regulations, 2011 CFR

... 7 2011-10-01 2011-10-01 false Retention. 576.7 Section 576.7 Transportation...DEPARTMENT OF TRANSPORTATION (CONTINUED) RECORD RETENTION § 576.7 Retention. Duplicate copies need not be retained....

2011-10-01

283

49 CFR 576.7 - Retention.  

Code of Federal Regulations, 2013 CFR

... 7 2013-10-01 2013-10-01 false Retention. 576.7 Section 576.7 Transportation...DEPARTMENT OF TRANSPORTATION (CONTINUED) RECORD RETENTION § 576.7 Retention. Duplicate copies need not be retained....

2013-10-01

284

7 CFR 3015.21 - Retention period.  

...2014-01-01 2014-01-01 false Retention period. 3015.21 Section 3015.21...UNIFORM FEDERAL ASSISTANCE REGULATIONS Record Retention and Access Requirements § 3015.21 Retention period. (a) Except as provided...

2014-01-01

285

RECORD RETENTION FOR UNIVERSITY DEPARTMENTS Introduction  

E-print Network

RECORD RETENTION FOR UNIVERSITY DEPARTMENTS Introduction The General Records Disposition Schedule. The authorized dispositions listed in the Records Disposition Schedule prescribe the minimum retention supersede all previously approved retention periods established for the records listed. A Quick Reference

Oklahoma, University of

286

7 CFR 70.54 - Retention authorities.  

...2014-01-01 2014-01-01 false Retention authorities. 70.54 Section 70.54...Identifying and Marking Products § 70.54 Retention authorities. A grader may use retention tags or other devices and methods...

2014-01-01

287

7 CFR 3015.21 - Retention period.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Retention period. 3015.21 Section 3015.21...UNIFORM FEDERAL ASSISTANCE REGULATIONS Record Retention and Access Requirements § 3015.21 Retention period. (a) Except as provided...

2011-01-01

288

7 CFR 3015.21 - Retention period.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Retention period. 3015.21 Section 3015.21...UNIFORM FEDERAL ASSISTANCE REGULATIONS Record Retention and Access Requirements § 3015.21 Retention period. (a) Except as provided...

2012-01-01

289

7 CFR 3015.21 - Retention period.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Retention period. 3015.21 Section 3015.21...UNIFORM FEDERAL ASSISTANCE REGULATIONS Record Retention and Access Requirements § 3015.21 Retention period. (a) Except as provided...

2013-01-01

290

7 CFR 56.38 - Retention authorities.  

...2014-01-01 2014-01-01 false Retention authorities. 56.38 Section 56.38...Identifying and Marking Products § 56.38 Retention authorities. A grader may use retention tags or other devices and methods...

2014-01-01

291

transfer retention study Introduction and Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .i  

E-print Network

transfer retention study fall 2009 #12;#12;Introduction and Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 The Transfer Profile and Retention Study Table of Contents #12;Semester-to-Semester Persistence

Rutledge, Steven

292

Transport and retention of TiO2 rutile nanoparticles in saturated porous media under low-ionic-strength conditions: measurements and mechanisms.  

PubMed

The mechanisms governing the transport and retention kinetics of titanium dioxide (TiO(2), rutile) nanoparticle (NP) aggregates were investigated in saturated porous media. Experiments were carried out under a range of well-controlled ionic strength (from DI water up to 1 mM) and ion valence (NaCl vs CaCl(2)) comparable to the low end of environmentally relevant solution chemistry conditions. Solution chemistry was found to have a marked effect on the electrokinetic properties of NP aggregates and the sand and on the resulting extent of NP aggregate transport and retention in the porous media. Comparable transport and retention patterns were observed for NP aggregates in both NaCl and CaCl(2) solutions but at much lower ionic strength with CaCl(2). Transport experimental results showed temporal and spatial variations of NP aggregate deposition in the column. Specifically, the breakthrough curves displayed a transition from blocking to ripening shapes, and the NP retention profiles exhibited a shift of the maximum NP retention segment from the end toward the entrance of the column gradually with increasing ionic strength. Additionally, the deposition rates of the NP aggregates in both KCl and CaCl(2) solutions increased with ionic strength, a trend consistent with traditional Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Upon close examination of the results, it was found that the characteristics of the obtained transport breakthrough curves closely followed the general trends predicted by the DLVO interaction-energy calculations. However, the obtained NP retention profiles were found to deviate severely from the theory. We propose that a NP aggregate reconformation through collision between NP aggregates and sand grains reduced the repulsive interaction energies of NP-NP and NP-sand surfaces, consequently accelerating NP deposition with transport distance and facilitating approaching NP deposition onto NPs that had already been deposited. It is further suggested that TiO(2) NP transport and retention are determined by the combined influence of NP aggregate reconformation associated with solution chemistry, travel distance, and DLVO interactions of the system. PMID:21446737

Chen, Gexin; Liu, Xuyang; Su, Chunming

2011-05-01

293

Terrestrial Exoplanet Light Curves  

E-print Network

The phase or orbital light curves of extrasolar terrestrial planets in reflected or emitted light will contain information about their atmospheres and surfaces complementary to data obtained by other techniques such as spectrosopy. We show calculated light curves at optical and thermal infrared wavelengths for a variety of Earth-like and Earth-unlike planets. We also show that large satellites of Earth-sized planets are detectable, but may cause aliasing effects if the lightcurve is insufficiently sampled.

Eric Gaidos; Nicholas Moskovitz; Darren M. Williams

2005-11-23

294

The effect of resin cements and primer on retentive force of zirconia copings bonded to zirconia abutments with insufficient retention  

PubMed Central

PURPOSE The purpose of this study was to investigate the effect of resin cements and primer on the retentive force of zirconia copings bonded to zirconia abutments with insufficient retention. MATERIALS AND METHODS Zirconia blocks (Lava, 3M ESPE, St. Paul, MN, USA) were obtained and forty sets of zirconia abutments and copings were fabricated using CAD/CAM technology. They were grouped into 4 categories as follows, depending on the types of resin cements used, and whether the primer is applied or not:Panavia F2.0 (P), Panavia F2.0 using Primer (PRIME Plus, Bisco Inc, Schaumburg, IL, USA) (PZ), Superbond C&B (S), and Superbond C&B using Primer (SZ). For each of the groups, the cementation was conducted. The specimens were kept in sterilized water (37?) for 24 hours. Retentive forces were tested and measured, and a statistical analysis was carried out. The nature of failure was recorded. RESULTS The means and standard deviations of retentive force in Newton for each group were 265.15 ± 35.04 N (P), 318.21 ± 22.24 N (PZ), 445.13 ± 78.54 N (S) and 508.21 ± 79.48 N (SZ). Superbond C&B groups (S & SZ) showed significantly higher retentive force than Panavia F2.0 groups (P & PZ). In Panavia F2.0 groups, the use of primer was found to contribute to the increase of retentive force. On the other hand, in Superbond C&B groups, the use of primer did not influence the retention forces. Adhesive failure was observed in all groups. CONCLUSION This study suggests that cementation of the zirconia abutments and zirconia copings with Superbond C&B have a higher retentive force than Panavia F2.0. When using Panavia F2.0, the use of primer increases the retentive force. PMID:23755347

Kim, Seung-Mi; Yoon, Ji-Young; Lee, Myung-Hyun

2013-01-01

295

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

296

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

297

Pulmonary retention of coal dusts  

SciTech Connect

The principal objectives of this study were: to determine, quantitatively, coal dust retention times in the dog lung; to test the appropriateness of a pulmonary retention model which incorporates first order rate coefficients obtained from in vitro and in vivo experiments on neutron-activated coal; to acquire a temporal description of the pulmonary disposition of the retained coal dust, and to compare the behavior of two different Pennsylvania coals in the foregoing regards. The principal findings include: retention half-times for both coals of approximately 2 years following single, hour-long exposures; a vivid association of the retained coal dust with the pulmonic lymphatics; and a general validation of the retention model.

Morrow, P.E.; Gibb, F.R.; Beiter, H.; Amato, F.; Yuile, C.; Kilpper, R.W.

1980-01-01

298

Retention in Florida community colleges.  

E-print Network

??This study examined the relationship between selected student and institutional characteristics and the retention rates of first-time, degree seeking, full-time and parttime, freshman student cohorts… (more)

DeLuz, Ancil.

2011-01-01

299

Fractal processes in soil water retention  

Microsoft Academic Search

The authors propose a physical conceptual model for soil texture and pore structure that is based on the concept of fractal geometry. The motivation for a fractal model of soil texture is that some particle size distributions in granular soils have already been shown to display self-similar scaling that is typical of fractal objects. Hence it is reasonable to expect

Scott W. Tyler; Stephen W. Wheatcraft

1990-01-01

300

College Counseling and Student Retention  

Microsoft Academic Search

Although it is commonly believed that college counseling positively affects student retention and further, that there are convincing data and evidence to support such a belief, an extensive literature search found no objective evidence at all on the relationship of a counseling center's conventional one-to-one counseling and therapy activities with short-term student retention. Two program evaluations which attempt to relate

Norman S Giddan; David M Levy; Ronald M Estroff; John C Cline; Erika B Altman; Karen A Isham; Steven J Weiss

1987-01-01

301

Data Retention and Anonymity Services  

Microsoft Academic Search

The recently introduced legislation on data retention to aid prosecuting cyber-related crime in Europe also affects the achievable\\u000a security of systems for anonymous communication on the Internet. We argue that data retention requires a review of existing\\u000a security evaluations against a new class of realistic adversary models. In particular, we present theoretical results and\\u000a first empirical evidence for intersection attacks

Stefan Berthold; Rainer Böhme; Stefan Köpsell

2009-01-01

302

Retention Rate by Ethnicity. Information Capsule.  

ERIC Educational Resources Information Center

This document discusses retention rate based on ethnicity for Miami-Dade Community College (M-DCC) for December 2002. The study found that the 2001 Fall-Spring retention rates increased among all ethnic groups. The total college retention rate rose by 2.7 percentage points to 75.2%. Among individual groups, the highest retention rate of 76.9% was…

Baldwin, Anne

303

New Freshman and Transfer Retention Study  

E-print Network

New Freshman and Transfer Retention Study Fall 2011 Institutional Research #12;1 Introduction The Freshman and Transfer Retention Study conducted by Institutional Research (IR) tracks graduation the two previously separate studies (New Freshman Retention and Transfer Retention) was in response

304

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

305

Liquefaction Probability Curves for Surficial Geologic Units  

NASA Astrophysics Data System (ADS)

Liquefaction probability curves that predict the probability of surface manifestations of earthquake-induced liquefaction are developed for 14 different surficial geologic deposits. The geologic units include alluvial fan, beach ridge, river delta, eolian dune, point bar, floodbasin, natural river levee, abandoned river channel, deep-water lake, lagoonal, sandy artificial fill, and valley train deposits. Probability is conditioned on earthquake magnitude and peak ground acceleration. Curves are developed for water table depths of 1.5 and 5.0 m. Probabilities were derived from complementary cumulative frequency distributions of the liquefaction potential index (LPI) that were computed from 935 cone penetration tests. Most of the curves can be fit with a 3-parameter logistic function, which facilitates computations of probability. For natural deposits with a water table at 1.5 m depth and subjected to an M7.5 earthquake with a PGA = 0.25 g, probabilities range from <0.03 for alluvial fan and lacustrine deposits to >0.5 for fluvial point bar, barrier island beach ridge, and deltaic deposits. Retrospective predictions of liquefaction during historical earthquakes based on the curves compare favorably to post-earthquake observations. We also have used the curves to assign ranges of liquefaction probabilities to the susceptibility categories proposed by Youd and Perkins (1978) for different geologic deposits. For the earthquake loading and conditions described above, probabilities range from 0-0.08 for low, 0.09-0.30 for moderate, 0.31-0.62 for high, to 0.63-1.00 for very high susceptibility. Liquefaction probability curves have two primary practical applications. First, the curves can be combined with seismic source characterizations to transform surficial geologic maps into probabilistic liquefaction hazard maps. Geographic specific curves are clearly desirable, but in the absence of such information, generic liquefaction probability curves provide a first approximation of liquefaction hazard. Such maps are useful both to delineate regional liquefaction hazard and to develop regulatory hazard zones. Second, the curves enable preliminary estimates of liquefaction hazard along paths of lifelines. Lifelines typically cross multiple types of surficial geologic deposits. Liquefaction probability curves can be used to estimate the likelihood of liquefaction during the lifetimes of these structures.

Holzer, T. L.; Noce, T. E.; Bennett, M. J.

2009-12-01

306

Quantifying flow retention due to vegetation in an earthen experimental channel using the Aggregated Dead Zone (ADZ) dilution approach  

NASA Astrophysics Data System (ADS)

Understanding of flow resistance of forested floodplains is essential for floodplain flow routing and floodplain reforestation projects. Although the flow resistance of grass-lined channels is well-known, flow retention due to flow-blocking by trees is poorly understood. Flow behaviour through tree-filled channels or over forested floodplain surfaces has largely been addressed using laboratory studies of artificial surfaces and vegetation. Herein we take advantage of a broad, shallow earthen experimental outdoor channel with headwater and tailwater controls. The channel was disused and left undisturbed for more than 20 years. During this time period, small deciduous trees and a soil cover of grass, herbs and leaf-litter established naturally. We measured flow resistance and fluid retention in fifteen controlled water discharge experiments for the following conditions: (a) natural cover of herbs and trees; (b) trees only and; (c) earthen channel only. In the b-experiments the herbaceous groundcover was first removed carefully and in the c-experiments the trees were first cut flush with the earthen channel floor. Rhodamine-B dye was used to tag the flow and the resultant fluorescence of water samples were systematically assayed through time at two stations along the length of the channel. Dilution-curve data were analysed within the Aggregated Dead Zone (ADZ) framework to yield bulk flow parameters including dispersion, fluid retention and flow resistance parameters after the procedure of Richardson & Carling (2006). The primary response of the bulk flow to vegetation removal was an increase in bulk velocity, with depth and wetted width decreasing imperceptibly at the resolution of measurement. An overall reduction in flow resistance and retention occurred as discharge increased in all experiments and flow retention. Retentiveness was more prominent during low flow and for all three experimental conditions tended to converge on a constant low value for high discharges. Reach mean travel times and the advective time delays decreased very slightly from experiments (a) to (b) which is not surprising given the sparse nature of the herbaceous soil cover. Thus in these two initial experiments, the trees provided the majority of the resistance in contrast to the aggregate effect of grass, herbs and litter. Removing the trees leaving an earthen channel further decreased travel times such that the ADZ residence time was more than halved moving from (a) to (c). The overall bulk flow effect of tree cover on retention is here expressed by the dispersive fraction parameter, indicating retention volume and time, which reduced from typically 0.4 to closer to 0.2 when vegetation was removed. The Darcy-Weisbach friction factor during low discharges was higher for experiments (a) compared with (b) but the friction factors converged on the low earthen channel value as discharge increased. In conclusion the effect of vegetation on hydraulic retention compared with an unvegetated channel is prominent during low discharges but becomes negligible during high discharges as momentum increasingly dominates the flow.

Carling, Paul; Kleinhans, Maarten; Leyland, Julian; Besozzi, Louison; Duranton, Pierre; Trieu, Hai; Teske, Roy

2014-05-01

307

Predicting changes in hydrologic retention in an evolving semi-arid alluvial stream  

Microsoft Academic Search

Hydrologic retention of solutes in hyporheic zones or other slowly moving waters of natural channels is thought to be a significant control on biogeochemical cycling and ecology of streams. To learn more about factors affecting hydrologic retention, we repeated stream-tracer injections for 5 years in a semi-arid alluvial stream (Pinal Creek, Ariz.) during a period when streamflow was decreasing, channel

Judson W. Harvey; Martha H. Conklin; Roger S. Koelsch

2003-01-01

308

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

309

Study on optimization of moisture retention for golf green rootzone soil mixtures  

Microsoft Academic Search

Most golf course green have been constructed with pure sand or sand-based rootzone mixes. As we know, high sand content provides rapid drainage despite sand’s inefficiency in retaining moisture. However, drainage capability and water retention are both essential elements to the golf course green, and the addition of peat could increase the soil moisture retention, therefore, the research on the

Shao-Hua Yin; Zhi-Hui Chang; Lie-Bao Han; Xin-Shi Lu

310

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

311

Atlas of fatigue curves  

Microsoft Academic Search

This Atlas was developed to serve engineers who are looking for fatigue data on a particular metal or alloy. Having these curves compiled in a single book will also facilitate the computerization of the involved data. It is pointed out that plans are under way to make the data in this book available in ASCII files for analysis by computer

1986-01-01

312

Characteristic Curves of PEMFC  

NSDL National Science Digital Library

This in-class exercise will allow students hands-on experience working with a proton exchange membrane fuel cell, or PEMFC. The class will examine the characteristic curve of one of these fuel cells and measure the voltage and current output of the cell. Step by step instructions are provided for the experiment. This document may be downloaded in PDF file format.

2012-07-11

313

Econophysics Master curve for  

E-print Network

-curve collapse of the price-impact function suggests that fluctuations from the supply- and-demand equilibrium this separately for buying and selling. The transactions are classified as being initiated by a buyer or seller is the liq- uidity and sign( ) is +1 or 1 for buying and selling, respectively. For all four years

314

Principal curve time warping  

Microsoft Academic Search

Time warping finds use in many fields of time series analysis, and it has been effectively implemented in many different application areas. Rather than focusing on a particular application area we approach the general problem definition, and employ principal curves, a powerful machine learning tool, to improve the noise robustness of existing time warping methods. The increasing noise level is

Umut Ozertem; Deniz Erdogmus

2009-01-01

315

Extinction curves in AGN  

E-print Network

The presence of the dust in the circumnuclear region strongly affects our view of the nucleus itself. The effect is strong in type 2 objects but weaker effect is likely to be present in type 1 objects as well. In these objects a correction to the observed optical/UV spectrum must be done in order to recover the intrinsic spectrum of a nucleus. The approach based on the extinction curve is convenient for that purpose so significant effort has been recently done in order to determine the extinction curve for the circumnuclear material. It seems clear that the circumnuclear dust is different from the average properties of the dust in the Interstellar Medium in our galaxy: the well known 2175 A feature is weak or absent in AGN nuclear dust, and the extinction curve at shorter wavelength does not seem to be rising as steeply. The circumnuclear dust is therefore more similar to SMC dust, or more likely, to the dust in very dense molecular clouds in our Galaxy. However, the exact shape of the extinction curve in the far UV is still a matter of debate, and various effects are difficult to disentangle.

B. Czerny

2006-12-16

316

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

317

Derivation of Soil Moisture Retention Characteristics from Saturated Hydraulic Conductivity  

E-print Network

1 Derivation of Soil Moisture Retention Characteristics from Saturated Hydraulic Conductivity C. P systems require knowledge of the relationships between soil moisture content (), soil water pressure (h involved field and laboratory determination of soil moisture characteristics along the Hindon river in its

Kumar, C.P.

318

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.

319

Effect of adhesive system on retention in posts comprising fiber post and core resin.  

PubMed

The purpose of this study was to compare the retention of fiber-reinforced composite (FRC) posts luted with either conventional or self-adhesive resin cement. The FRC posts and core resin were built up in bovine teeth. The posts were luted with standard etch-andrinse cement, self-etch cement, or one of two self-adhesive cements. The samples were stored in water for 1 or 14 days or subjected to thermal cycling (TC). Retention value was measured with the pull-out test using a universal testing machine. Conventional adhesive resin cement yielded significantly greater retention than self-adhesive resin cement at 1 day. No significant difference was observed in retention among the adhesive systems tested at 14 days or after TC. During the early luting stage, self-adhesive resin cement yielded lower retention value than conventional resin cement. After 14 days storage or TC, retention was comparable to that with conventional resin cement. PMID:23903651

Soejima, Hirotaka; Takemoto, Shinji; Hattori, Masayuki; Yoshinari, Masao; Kawada, Eiji; Oda, Yutaka

2013-01-01

320

A study of Dykstra-Parsons curves  

SciTech Connect

The Dykstra-Parsons method for prediction of oil recovery by water flooding is a well known technique which has been used by the petroleum industry since 1945. The present work carries their study further, solving the same problem of calculating coverage for certain values of permeability variation having water-oil-ratio and mobility ratio as fixed parameters. The work herein, instead of using 50 layers, uses 200. Also a more precise theoretical approach to the problem is given. Because of these differences the resulting curves are slightly modified. In a second part, the authors deal with empirical simplifications with considerable success. The idea was to collapse the data and curves obtained in the first part into a single curve which covers most of the range of variables commonly seen in reservoir displacements.

Souza, A.O. de; Brigham, W.E.

1995-02-01

321

Atlas of fatigue curves  

SciTech Connect

This Atlas was developed to serve engineers who are looking for fatigue data on a particular metal or alloy. Having these curves compiled in a single book will also facilitate the computerization of the involved data. It is pointed out that plans are under way to make the data in this book available in ASCII files for analysis by computer programs. S-N curves which typify effects of major variables are considered along with low-carbon steels, medium-carbon steels, alloy steels, HSLA steels, high-strength alloy steels, heat-resisting steels, stainless steels, maraging steels, cast irons, and heat-resisting alloys. Attention is also given to aluminum alloys, copper alloys, magnesium alloys, molybdenum, tin alloys, titanium and titanium alloys, zirconium, steel castings, closed-die forgings, powder metallurgy parts, composites, effects of surface treatments, and test results for component parts.

Boyer, H.E.

1986-01-01

322

Curve parametrization by moments.  

PubMed

We present a method for deriving a parametric description of a conic section (quadratic curve) in an image from the moments of the image with respect to several specially-constructed kernel functions. In contrast to Hough-transform-type methods, the moment approach requires no large accumulator array. Judicious implementation allows the parameters to be determined using five multiplication operations and six addition operations per pixel. The use of moments renders the calculation robust in the presence of high-frequency noise or texture and resistant to small-scale irregularities in the edge. Our method is generalizable to more complex classes of curves with more parameters as well as to surfaces in higher dimensions. PMID:19029543

Popovici, Irina; Withers, William Douglas

2009-01-01

323

Forced convective heat transfer in curved diffusers  

Microsoft Academic Search

Measurements of the velocity characteristics of the flows in two curved diffusers of rectangular cross section with C and S-shaped centerlines are presented and related to measurements of wall heat transfer coefficients along the heated flat walls of the ducts. The velocity results were obtained by laser-Doppler anemometry in a water tunnel and the heat transfer results by liquid crystal

J. Rojas; J. H. Whitelaw; M. Yianneskis

1987-01-01

324

Curve-Skeleton Applications  

Microsoft Academic Search

Curve-skeletons are a 1D subset of the medial surface of a 3D object and are useful for many visualization tasks including virtual navigation, reduced-model formulation, visualization improvement, mesh repair, animation, etc. There are many algorithms in the literature describing extraction methodologies for different applications; however, it is unclear how general and robust they are. In this paper, we provide an

Nicu D. Cornea; Deborah Silver; Patrick Min

2005-01-01

325

Diffusion in Curved Spacetimes  

E-print Network

Using simple kinematical arguments, we derive the Fokker-Planck equation for diffusion processes in curved spacetimes. In the case of Brownian motion, it coincides with Eckart's relativistic heat equation (albeit in a simpler form), and therefore provides a microscopic justification for his phenomenological heat-flux ansatz. Furthermore, we obtain the small-time asymptotic expansion of the mean square displacement of Brownian motion in static spacetimes. Beyond general relativity itself, this result has potential applications in analogue gravitational systems.

Matteo Smerlak

2011-04-17

326

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

327

Odonata, Amphibia and Environmental Characteristics in Motorway Stormwater Retention Ponds (Southern France)  

Microsoft Academic Search

Water and its protection against pollution is an urgent priority for all countries around the world. In that context, France, through its Water Law in 1992 obliged the motorway companies to build stormwater retention ponds along roads in order to protect the water resource from transport pollution and to control water flow during rainstorms. We propose to evaluate how much

Olivier Scher; Alain Thièry

2005-01-01

328

BIOGEOCHEMICAL INDICES OF PHOSPHORUS RETENTION AND RELEASE BY WETLAND SOILS AND ADJACENT STREAM SEDIMENTS  

E-print Network

. Phosphorus sorption under ambient P conditions (soil equilibrated with ambient site water) covaried best with P concentrations in site surface water and, as concentrations increased, P sorption also increased, indices, sorption, retention, and release INTRODUCTION Water quality is still a problem in many water

Florida, University of

329

Improving GNVQ Retention and Completion.  

ERIC Educational Resources Information Center

This booklet, which draws heavily on the findings of a major study of the causes of student withdrawal from General National Vocational Qualifications (GNVQ) courses in Britain, explains how student retention and completion can be improved at each stage of students' progress through a further education college. The booklet begins with background…

Davies, Peter; Mullaney, Lorraine; Sparkes, Pauline

330

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

331

Three Recruitment and Retention Surveys.  

ERIC Educational Resources Information Center

This three-part report summarizes methodology and findings of three recruitment and retention studies conducted by the Bronx Community College (BCC) during 1979-1980. Part I examines a survey of enrolled students conducted to determine student attitudes toward BCC, the services that were most in demand, the reasons for attending BCC, and student…

Bronx Community Coll., NY.

332

Retention of Adult College Students.  

ERIC Educational Resources Information Center

In a review of the literature, some of the reasons traditional college-age students withdraw are applied to adults. Conclusions regarding adults who persist versus those who drop out are offered and suggestions for increasing the retention of adult students are presented. (Author/MLW)

Swift, John Stewart, Jr.

1987-01-01

333

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.

334

Kindergarten Retention. Burning Issues [Series].  

ERIC Educational Resources Information Center

This information packet contains nine articles that outline current trends in kindergarten retention/exclusion and their negative impact on student outcomes, particularly for high risk students. The 1980s saw increasing numbers of children required to repeat kindergarten, attend a transitional grade before first grade, or wait an extra year before…

San Diego County Office of Education, CA.

335

Enhancing student retention and employability  

Microsoft Academic Search

Retention of first year students in the Faculty of Engineering is a significant problem. There appears to be a pattern of loss of students early in Semester 1 with students failing to engage with their program of learning and again in Semester 2 after the publication of results of the January exam diet. This project aimed to address these problems

D. Ballance; A. Browitt; J. Davies; J. Pritchard; S. Roy; W. Stewart; M. Vezza; L. Walker; A. Whittaker

336

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

337

[Volume retention in heart failure, nephrotic syndrome, and liver cirrhosis].  

PubMed

Volume retention in heart failure, nephrotic syndrome, and liver cirrhosis reflects pathological changes in homeostatic mechanisms that regulate the extracellular volume (sympathetic activity, renin-angiotensin-aldosterone system [RAAS], natriuretic peptides) and plasma osmolality (antidiuretic hormone [ADH]). In heart failure and liver cirrhosis, these changes are induced by a reduction of the effective circulating volume, which is the part of the extracellular fluid that is within the arterial system and effectively perfusing the tissues. This reduction in the effective circulating volume is caused by reduced cardiac output (heart failure), or by splanchnic vasodilatation with arterial underfilling (liver cirrhosis). In both cases, baroreceptors in both the carotid sinuses and in the glomerular afferent arterioles upregulate RAAS- and sympathetic activity, resulting in systemic vasoconstriction and renal sodium (and volume) retention. More severe reductions in the effective circulating volume may additionally stimulate ADH release, thus increasing the reabsorption of free water with subsequent hyponatriemia. In nephrotic syndrome, volume retention results either directly from the primary renal disease, which induces renal sodium and volume retention ("overfilling"), or indirectly from the reduced plasma oncotic pressure due to hypoalbuminemia, which induces a fluid shift from the intravascular to the interstitial space ("underfilling") with subsequent acitivation of baroreceptors and secondary sodium and volume retention. PMID:17009041

Heine, G H; Sester, U; Köhler, H

2006-11-01

338

Planar dimers and Harnack curves  

E-print Network

In this paper we study the connection between dimers and Harnack curves discovered in math-ph/0311005. We prove that every Harnack curve arises as a spectral curve of some dimer model. We also prove that the space of Harnack curve of given degree is homeomorphic to a closed octant and that the areas of the amoeba holes and the distances between the amoeba tentacles give these global coordinates. We characterize Harnack curves of genus zero as spectral curves of isoradial dimers and also as minimizers of the volume under their Ronkin function with given boundary conditions.

Richard Kenyon; Andrei Okounkov

2003-11-05

339

Willing Retention of Misbelief  

NASA Astrophysics Data System (ADS)

Students also ought to get a better picture of how useful chemistry is and what insights it can provide regarding crucial problems that face society. A student who has completed a general chemistry course ought to have some understanding of how chemists are addressing major problems involving energy resources, adequate supplies of pure food and water, degradation of the environment, poverty, disease, and terrorism. Even better, the student should be aware that these problems are intertwined and solving one of them at the expense of any or all of the others is not a true solution. Better yet, the student should realize that with appropriate education and experience, the student could contribute significantly to society’s efforts to solve these problems. Former ACS President Ronald Breslow has suggested on numerous occasions that students are more likely to be attracted to a field in which the student can participate in solving important problems, but we persist in teaching chemistry as if it is a dead science, where everything is already known. Both learning and the unknown are powerful challenges that can motivate students to put forth their best efforts. We ought to make better use of them.

Moore, John W.

2003-12-01

340

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

341

Award-Winning Approaches to Retention.  

ERIC Educational Resources Information Center

Describes retention programs for at-risk freshmen that have been recognized as successful in a study by the consulting firm Noel-Levitz. Provides details about the retention efforts at 10 colleges and universities. (SLD)

Hammer, Ben

2003-01-01

342

12 CFR 609.945 - Records retention.  

Code of Federal Regulations, 2010 CFR

...retention. 609.945 Section 609.945 Banks and Banking FARM CREDIT ADMINISTRATION FARM CREDIT SYSTEM ELECTRONIC COMMERCE Standards for Boards and Management § 609.945 Records retention. Records stored electronically must...

2010-01-01

343

27 CFR 27.137 - Retention.  

Code of Federal Regulations, 2011 CFR

...ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS IMPORTATION OF DISTILLED SPIRITS, WINES, AND BEER Importer's Records and Reports Filing and Retention of Records and Reports § 27.137 Retention....

2011-04-01

344

27 CFR 27.137 - Retention.  

Code of Federal Regulations, 2013 CFR

...ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL IMPORTATION OF DISTILLED SPIRITS, WINES, AND BEER Importer's Records and Reports Filing and Retention of Records and Reports § 27.137 Retention....

2013-04-01

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

Lenses on curved surfaces.  

PubMed

This Letter presents a theory that allows graded index lenses to be mapped onto arbitrary rotationally symmetric curved surfaces. Examples of the Luneburg and Maxwell fish-eye lens are given, for numerous surfaces, always resulting in isotropic permittivity requirements. The performance of these lenses is initially illustrated with full-wave simulations utilizing a waveguide structure. A transformation of the refractive index profiles is then performed to design surface-wave lenses, where the dielectric layer is not only isotropic but also homogenous, demonstrating the applicability and ease of fabrication. PMID:24978534

Mitchell-Thomas, R C; Quevedo-Teruel, O; McManus, T M; Horsley, S A R; Hao, Y

2014-06-15

348

Curved cap corrugated sheet  

NASA Technical Reports Server (NTRS)

The report describes a structure for a strong, lightweight corrugated sheet. The sheet is planar or curved and includes a plurality of corrugation segments, each segment being comprised of a generally U-shaped corrugation with a part-cylindrical crown and cap strip, and straight side walls and with secondary corrugations oriented at right angles to said side walls. The cap strip is bonded to the crown and the longitudinal edge of said cap strip extends beyond edge at the intersection between said crown and said side walls. The high strength relative to weight of the structure makes it desirable for use in aircraft or spacecraft.

Davis, R. C.; Bales, T. T.; Royster, D. M.; Jackson, L. R. (inventors)

1984-01-01

349

Data Plotting and Curve Fitting in MATLAB Curve Fitting  

E-print Network

Data Plotting and Curve Fitting in MATLAB Curve Fitting Get the file pwl.dat from the class web(1)*pwl(:,1)+fit1(2)) If you're getting tired of typing pwl(:,1), etc., create new variables with shorter]') ylabel(`Output Current [mA]') title(`Curve Fitting Exercise') It is very important to always label your

Harrison, Reid R.

350

Assessing Chemical Retention Process Controls in Ponds  

Microsoft Academic Search

Small ponds are a ubiquitous component of the landscape and have earned a reputation as effective chemical retention devices. The most common characterization of pond chemical retention is the retention coefficient, Ri= ([Ci]inflow-[Ci] outflow)\\/[Ci]inflow. However, this parameter varies widely in one pond with time and among ponds. We have re-evaluated literature reported (Borden et al., 1998) monthly average retention coefficients

T. Torgersen; B. Branco; B. John

2002-01-01

351

On planar rational cuspidal curves  

E-print Network

This thesis studies rational curves in the complex projective plane that are homeomorphic to their normalizations. We derive some combinatorial constraints on such curves from a result of Borodzik-Livingston in Heegaard-Floer ...

Liu, Tiankai

2014-01-01

352

Curve walking in crayfish  

PubMed

Curve walking of crayfish Astacus leptodactylus was investigated by exploiting their optomotor response. The animal walked while spatially fixed on a motor-driven treadmill and turning behaviour was induced by an optical stimulus, a pattern consisting of vertical stripes moving in a horizontal direction. In this open-loop situation, the crayfish maintains the same step frequency for the legs on both sides of the body for low and intermediate turning speeds, but increases the step amplitude of the outer legs 2, 3 and 4 by shifting the posterior extreme position (PEP) of these legs in a posterior direction and reduces the step amplitude of inner leg 5 by shifting the PEP of this leg in an anterior direction. Furthermore, the main movement direction of the legs can change relative to the body. This was observed for outer leg 5 and also, at higher turning speeds, for outer leg 2. As coordinating influences between contra- and ipsilateral legs were found directly to influence only the anterior extreme position of the legs, these results indicate that the mechanisms controlling curve walking may be different from those controlling normal leg coordination. PMID:9319377

Cruse; Saavedra

1996-01-01

353

5 CFR 351.404 - Retention register.  

Code of Federal Regulations, 2012 CFR

...the agency shall enter on the retention register, in the order of retention standing, the name of each...each employee serving under a time limited appointment or promotion...entered on a list apart from the retention register for that...

2012-01-01

354

5 CFR 351.404 - Retention register.  

Code of Federal Regulations, 2011 CFR

...the agency shall enter on the retention register, in the order of retention standing, the name of each...each employee serving under a time limited appointment or promotion...entered on a list apart from the retention register for that...

2011-01-01

355

5 CFR 351.404 - Retention register.  

Code of Federal Regulations, 2010 CFR

...the agency shall enter on the retention register, in the order of retention standing, the name of each...each employee serving under a time limited appointment or promotion...entered on a list apart from the retention register for that...

2010-01-01

356

7 CFR 1409.7 - Records retention.  

...2014-01-01 false Records retention. 1409.7 Section 1409...CORPORATION § 1409.7 Records retention. (a) The Secretary...officer which sets forth the time and place of the closed meeting...such minutes. (b) The retention period for the records...

2014-01-01

357

5 CFR 351.404 - Retention register.  

Code of Federal Regulations, 2013 CFR

...the agency shall enter on the retention register, in the order of retention standing, the name of each...each employee serving under a time limited appointment or promotion...entered on a list apart from the retention register for that...

2013-01-01

358

5 CFR 351.404 - Retention register.  

...the agency shall enter on the retention register, in the order of retention standing, the name of each...each employee serving under a time limited appointment or promotion...entered on a list apart from the retention register for that...

2014-01-01

359

7 CFR 1409.7 - Records retention.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 false Records retention. 1409.7 Section 1409...CORPORATION § 1409.7 Records retention. (a) The Secretary...officer which sets forth the time and place of the closed meeting...such minutes. (b) The retention period for the records...

2012-01-01

360

7 CFR 1409.7 - Records retention.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Records retention. 1409.7 Section 1409...CORPORATION § 1409.7 Records retention. (a) The Secretary...officer which sets forth the time and place of the closed meeting...such minutes. (b) The retention period for the records...

2013-01-01

361

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

362

Designing Online Courses to Promote Student Retention  

ERIC Educational Resources Information Center

Although the issue of student retention is a campus-wide one, it is of special interest in online distance learning courses, where retention rates are reported to be lower than in face-to-face classes. Among the explanations and theories of retention rates in online courses, one that struck us as most useful is a structural one, namely, course…

Dietz-Uhler, Beth; Fisher, Amy; Han, Andrea

2008-01-01

363

Toward a Political Explanation of Grade Retention  

ERIC Educational Resources Information Center

Policies that mandate in-grade retention of low-performing students have become central components of standards-based reforms across the country. While educational researchers have extensively studied the student-level correlates of retention and the consequences of retention for student achievement, little attention has been focused on…

Bali, Valentina A.; Anagnostopoulos, Dorothea; Roberts, Reginald

2005-01-01

364

Selective retention of soluble radioisotopes by fabrics  

SciTech Connect

Wide-area buildup of contamination on laundered protective clothing led the investigators to examine differences in the retention of soluable radioisotopes by selected fabrics. In this paper experimental evidence is provided which suggests selectivity in isotopic retention. Supported by variation in retention between different colors of a fabric, it appears that dyes play a role in controlling the ion selection mechanism.

Wilson, G.R.; Fanelli, S.L. (INS Corp. (US))

1989-06-01

365

2014 Action Plan for Retention and  

E-print Network

2014 Action Plan for Retention and Graduation #12;1 Background Provost Jeffrey Hecker assembled the Advisory Group on Retention and Graduation in fall 2013 and charged it with collecting data and evaluating best practices leading to incremental improvement of retention rates, graduation rates, and student

Thomas, Andrew

366

University Record Retention Policy Policy # FA-002  

E-print Network

University Record Retention Policy Policy # FA-002 Effective Date: June 1, 2009 Policy Statement that are outlined in this document. Reason for Policy Boston University is committed to effective records retention requirements, optimize the use of space, minimize the cost of record retention, and ensure that outdated

Xia, Yu "Brandon"

367

12 CFR 1026.25 - Record retention.  

...2014-01-01 2014-01-01 false Record retention. 1026.25 Section 1026.25 ...Miscellaneous § 1026.25 Record retention. (a) General rule. A...forth as follows: § 1026.25 Record retention. (a) General rule. A...

2014-01-01

368

Entering Fall One Year Retention 2006 Cohort  

E-print Network

Entering Fall One Year Retention 2011 88% 2006 Cohort Total Entering 2,913 % Graduating in Six Students 80% Sources: CSRDE-Consortium for Student Retention Data Exchange; Financial Aid Office Note-Year Graduation Rate by Gender, by Ethnicity and by Financial Aid Status Retention and Graduation Rates Six

369

Issued June 1, 2012 FACULTY RETENTION FUND  

E-print Network

Issued June 1, 2012 FACULTY RETENTION FUND Office of the Provost FY 2012-2013 The Office of the Provost will continue to allocate Faculty Retention Funds in 2012-13 in an effort to retain Purdue's most enhancements, counter-offers or salary equity adjustments when retention is of concern. Although this program

Holland, Jeffrey

370

Recruitment and Retention in Clinical Research  

E-print Network

Recruitment and Retention in Clinical Research June 24, 2011 Linda Ziegahn, Ph.D. Sergio Aguilar.womancando.org; Mills, 2004 #12;Main Goal of Recruitment and Retention of Underrepresented Groups: Study patients who://www.dfhcc.harvard.edu/minority_initiatives/index.asp #12;Challenges to Recruitment, Retention . . . #12;Attitudes of Minority Participants Towards

Carmichael, Owen

371

Retention Implementation Task Force Final Report  

E-print Network

1 Retention Implementation Task Force Final Report December 2010 Ronald Brown, Chair Provost Rapport Matthew Seeger Howard Shapiro Robert Thomas Phyllis Vroom Paula Wood #12;2 Retention Implementation Task Force Report December 2010 Executive Summary Undergraduate student retention and graduation

Cinabro, David

372

3, 10811119, 2006 Nitrogen retention in  

E-print Network

BGD 3, 1081­1119, 2006 Nitrogen retention in a tidal freshwater marsh B. Gribsholt et al. Title Nitrogen assimilation and short term retention in a nutrient-rich tidal freshwater marsh ­ a whole 3, 1081­1119, 2006 Nitrogen retention in a tidal freshwater marsh B. Gribsholt et al. Title Page

Boyer, Edmond

373

RETENTION OF UNIVERSITY RECORDS Policy Statement  

E-print Network

Page 1 RETENTION OF UNIVERSITY RECORDS Policy Statement Northwestern University and various federal. The University has designated official repositories and a retention schedule for maintenance of these records/Purpose The University is committed to effective records retention to meet business needs, preserve its history, comply

Shahriar, Selim

374

Logit analysis of graduate student retention  

Microsoft Academic Search

A logit model is developed to predict the retention of graduate students. The use of the BMDP4F procedure to develop a logit model for graduation student retention is outlined, and the model is applied to data from a major university. In this study, predicted retention rates for master's students were independent of age and sex, but were a function of

Mary Diederich Ott; Theodore S. Markewich; Nancy L. Ochsner

1984-01-01

375

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 Policy Approval Authority: Administrative Council Responsible Executive: Vice President and Summary of Policy This Policy sets forth the standards and procedures for the systematic review, retention

Yang, Eui-Hyeok

376

Retention and Graduation InitiativeRetention and Graduation Initiative 4 May 2011y  

E-print Network

#12;Status fof Retention and Graduation InitiativeRetention and Graduation Initiative 4 May 2011y #12;Purpose of the Task Force · "It is the purpose of the Task Force on Undergraduate Retention and Graduation to complete an analysis ofRetention and Graduation to complete an analysis of undergraduate

Bieber, Michael

377

NAAP Retention of an Atmosphere 1/7 Atmospheric Retention Student Guide  

E-print Network

Name: NAAP ­ Retention of an Atmosphere 1/7 Atmospheric Retention ­ Student Guide Background ­ Retention of an Atmosphere 2/7 Question 3: Experiment with the Maxwell Distribution Simulator. Then a) draw corresponding to the fastest moving 3% of the gas particles. Maxwell Speed Distribution #12;NAAP ­ Retention

Farritor, Shane

378

Retention of phytoplankton by an eddy  

NASA Astrophysics Data System (ADS)

A patch of high phytoplankton biomass, approximately 10 9 m 2 in area, remained apparently stationary off King George Island, South Shetland Islands, over a period of at least 11 days. The patch was centred on an eddy at the apex of a tight meander formed by water passing round the eastern end of King George Island and being turned back immediately by the strong northeastern flow of water within the Bransfield Strait. Chlorophyll a biomass approached 1 g m 2 and was concentrated within the top 50-75 m of water. The community consisted mainly of diatoms, which were growing actively. Growth in situ might have been sufficient to generate the observed high biomass from the general concentration of phytoplankton observed locally but only if all production had been retained within the patch. However, elevated biomass downcurrent of the patch suggested that physical retention was only about 50% efficient. It is concluded that the patch was derived from a pulse of high biomass which had been transported into the area and partially retained by the horizontal recirculation of water within the eddy. Dominant diatom species, Odontella weissflogii, Proboscia 'alata', Chaetoceros curvisetum and Thalassiosira tumida, were also predominant in a phytoplankton maximum off Brabant Island, upcurrent of the study site. This may have provided the seed population for the patch off King George Island. Vertical migration may have prevented krill accumulation within the eddy and it is concluded that some shallow eddies may partially insulate phytoplankton communities from heavy grazing pressure.

Heywood, R. B.; Priddle, J.

1987-08-01

379

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

380

5 CFR 536.204 - Period of grade retention.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Period of grade retention. 536.204 Section 536.204 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.204 Period of grade retention....

2013-01-01

381

48 CFR 4.704 - Calculation of retention periods.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Calculation of retention periods. 4.704 Section 4.704 Federal...ADMINISTRATIVE MATTERS Contractor Records Retention 4.704 Calculation of retention periods. (a) The retention...

2011-10-01

382

5 CFR 536.202 - Optional grade retention.  

...2014-01-01 2014-01-01 false Optional grade retention. 536.202 Section 536.202 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.202 Optional grade retention....

2014-01-01

383

5 CFR 536.302 - Optional pay retention.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Optional pay retention. 536.302 Section 536.302 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Pay Retention § 536.302 Optional pay retention....

2011-01-01

384

5 CFR 536.201 - Mandatory grade retention.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Mandatory grade retention. 536.201 Section 536.201 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.201 Mandatory grade retention....

2012-01-01

385

5 CFR 536.302 - Optional pay retention.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Optional pay retention. 536.302 Section 536.302 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Pay Retention § 536.302 Optional pay retention....

2013-01-01

386

48 CFR 4.704 - Calculation of retention periods.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Calculation of retention periods. 4.704 Section 4.704 Federal...ADMINISTRATIVE MATTERS Contractor Records Retention 4.704 Calculation of retention periods. (a) The retention...

2013-10-01

387

5 CFR 536.204 - Period of grade retention.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Period of grade retention. 536.204 Section 536.204 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.204 Period of grade retention....

2011-01-01

388

5 CFR 536.301 - Mandatory pay retention.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Mandatory pay retention. 536.301 Section 536.301 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Pay Retention § 536.301 Mandatory pay retention....

2012-01-01

389

5 CFR 536.202 - Optional grade retention.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Optional grade retention. 536.202 Section 536.202 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.202 Optional grade retention....

2013-01-01

390

5 CFR 536.204 - Period of grade retention.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Period of grade retention. 536.204 Section 536.204 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.204 Period of grade retention....

2012-01-01

391

5 CFR 536.301 - Mandatory pay retention.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Mandatory pay retention. 536.301 Section 536.301 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Pay Retention § 536.301 Mandatory pay retention....

2013-01-01

392

5 CFR 536.301 - Mandatory pay retention.  

...2014-01-01 2014-01-01 false Mandatory pay retention. 536.301 Section 536.301 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Pay Retention § 536.301 Mandatory pay retention....

2014-01-01

393

5 CFR 536.204 - Period of grade retention.  

...2014-01-01 2014-01-01 false Period of grade retention. 536.204 Section 536.204 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.204 Period of grade retention....

2014-01-01

394

5 CFR 536.201 - Mandatory grade retention.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Mandatory grade retention. 536.201 Section 536.201 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.201 Mandatory grade retention....

2011-01-01

395

5 CFR 536.302 - Optional pay retention.  

...2014-01-01 2014-01-01 false Optional pay retention. 536.302 Section 536.302 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Pay Retention § 536.302 Optional pay retention....

2014-01-01

396

5 CFR 536.201 - Mandatory grade retention.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Mandatory grade retention. 536.201 Section 536.201 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.201 Mandatory grade retention....

2013-01-01

397

48 CFR 4.704 - Calculation of retention periods.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Calculation of retention periods. 4.704 Section 4.704 Federal...ADMINISTRATIVE MATTERS Contractor Records Retention 4.704 Calculation of retention periods. (a) The retention...

2012-10-01

398

5 CFR 536.201 - Mandatory grade retention.  

...2014-01-01 2014-01-01 false Mandatory grade retention. 536.201 Section 536.201 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.201 Mandatory grade retention....

2014-01-01

399

5 CFR 536.301 - Mandatory pay retention.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Mandatory pay retention. 536.301 Section 536.301 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Pay Retention § 536.301 Mandatory pay retention....

2011-01-01

400

5 CFR 536.202 - Optional grade retention.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Optional grade retention. 536.202 Section 536.202 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.202 Optional grade retention....

2012-01-01

401

5 CFR 536.302 - Optional pay retention.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Optional pay retention. 536.302 Section 536.302 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Pay Retention § 536.302 Optional pay retention....

2012-01-01

402

5 CFR 536.202 - Optional grade retention.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Optional grade retention. 536.202 Section 536.202 Administrative...MANAGEMENT CIVIL SERVICE REGULATIONS GRADE AND PAY RETENTION Grade Retention § 536.202 Optional grade retention....

2011-01-01

403

Recession curve analysis for groundwater levels: case study in Latvia  

NASA Astrophysics Data System (ADS)

Recession curve analysis is powerful and effective analysis technique in many research areas related with hydrogeology where observations have to be made, such as water filtration and absorption of moisture, irrigation and drainage, planning of hydroelectric power production and chemical leaching (elution of chemical substances) as well as in other areas. The analysis of the surface runoff hydrograph`s recession curves, which is performed to conceive the after-effects of interaction of precipitation and surface runoff, has approved in practice. The same method for analysis of hydrograph`s recession curves can be applied for the observations of the groundwater levels. There are manually prepared hydrograph for analysis of recession curves for observation wells (MG2, BG2 and AG1) in agricultural monitoring sites in Latvia. Within this study from the available monitoring data of groundwater levels were extracted data of declining periods, splitted by month. The drop-down curves were manually (by changing the date) moved together, until to find the best match, thereby obtaining monthly drop-down curves, representing each month separately. Monthly curves were combined and manually joined, for obtaining characterizing drop-down curves of the year for each well. Within the process of decreased recession curve analysis, from the initial curve was cut out upward areas, leaving only the drops of the curve, consequently, the curve is transformed more closely to the groundwater flow, trying to take out the impact of rain or drought periods from the curve. Respectively, the drop-down curve is part of the data, collected with hydrograph, where data with the discharge dominates, without considering impact of precipitation. Using the recession curve analysis theory, ready tool "A Visual Basic Spreadsheet Macro for Recession Curve Analysis" was used for selection of data and logarithmic functions matching (K. Posavec et.al., GROUND WATER 44, no. 5: 764-767, 2006), as well as functions were developed by manual processing of data. For displaying data the mathematical model of data equalization was used, finding the corresponding or closest logarithmic function of the recession for the graph. Obtained recession curves were similar but not identical. With full knowledge of the fluctuations of ground water level, it is possible to indirectly (without taking soil samples) determine the filtration coefficient: more rapid decline in the recession curve correspond for the better filtration conditions. This research could be very useful in construction planning, road constructions, agriculture etc. Acknowledgments The authors gratefully acknowledge the funding from ESF Project "Establishment of interdisciplinary scientist group and modeling system for groundwater research" (Agreement No. 2009/0212/1DP/1.1.1.2.0/09/APIA/VIAA/060EF7)

Gailuma, A.; VÄ«tola, I.; Abramenko, K.; Lauva, D.; Vircavs, V.; Veinbergs, A.; Dimanta, Z.

2012-04-01

404

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.

405

Removal of pharmaceutical and personal care products from reverse osmosis retentate using advanced oxidation processes.  

PubMed

The application of reverse osmosis (RO) in water intended for reuse is promising for assuring high water quality. However, one significant disadvantage is the need to dispose of the RO retentate (or reject water). Studies focusing on Pharmaceutical and Personal Care Products (PPCPs) have raised questions concerning their concentrations in the RO retentate. Advanced oxidation processes (AOPs) are alternatives for destroying these compounds in retentate that contains high concentration of effluent organic matter (EfOM) and other inorganic constituents. Twenty-seven PPCPs were screened in a RO retentate using solid phase extraction (SPE) and UPLC-MS/MS, and detailed degradation studies for 14 of the compounds were obtained. Based on the absolute hydroxyl radical (HO•) reaction rate constants for individual pharmaceutical compounds, and that of the RO retentate (EfOM and inorganic constituents), it was possible to model their destruction. Using excitation-emission matrix (EEM) fluorescence spectroscopy, the HO• oxidation of the EfOM could be observed through decreases in the retentate fluorescence. The decrease in the peak normally associated with proteins correlated well with the removal of the pharmaceutical compounds. These results suggest that fluorescence may be a suitable parameter for monitoring the degradation of PPCPs by AOPs in RO retentates. PMID:21384915

Abdelmelek, Sihem Ben; Greaves, John; Ishida, Kenneth P; Cooper, William J; Song, Weihua

2011-04-15

406

Combined use of rosiglitazone and fenofibrate in patients with type 2 diabetes: prevention of fluid retention.  

PubMed

Elevated plasma free fatty acid (FFA) levels are responsible for much of the insulin resistance in obese patients with type 2 diabetes. To lower plasma FFA levels effectively and long term, we have treated eight obese patients with type 2 diabetes for 2 months with placebo followed by 2 months of treatment with a combination of rosiglitazone (RGZ) (8 mg/day) and fenofibrate (FFB) (160 mg/day) in a single-blind placebo-controlled study design. Compared with placebo, RGZ/FFB lowered mean 24-h plasma FFA levels 30% (P < 0.03) and mean 24-h glucose levels 23% (P < 0.03) and increased insulin-stimulated glucose uptake (glucose rate of disappearance [G(R)(d)], determined using euglycemic-hyperinsulinemic clamp) 442% (P < 0.01), oral glucose tolerance (area under the curve for 3-h oral glucose tolerance test) 28% (P < 0.05), and plasma adiponectin levels 218% (P < 0.01). These RGZ/FFB results were compared with results obtained in five patients treated with RGZ alone. RGZ/FFB prevented the fluid retention usually associated with RGZ (-1.6 vs. 5.6%, P < 0.05), lowered fasting plasma FFA more effectively than RGZ alone (-22 vs. 5%, P < 0.05), and tended to be more effective than RGZ alone in lowering A1C (-0.9 vs. -0.4%) and triglyceride levels (-38 vs. -5%) and increasing G(Rd) (442 vs. 330%). We conclude that RGZ/FFB is a promising new therapy for type 2 diabetes that lowers plasma FFA more than RGZ alone and in contrast to RGZ does not cause water retention and weight gain. PMID:17192489

Boden, Guenther; Homko, Carol; Mozzoli, Maria; Zhang, Meijuan; Kresge, Karen; Cheung, Peter

2007-01-01

407

ALMOST-COMPLEX CURVES IN S6 AND SPECTRAL CURVES  

Microsoft Academic Search

There are three types of almost-complex curves in the nearly-Kahler 6- sphere: they are totally geodesic, pseudo-holomorphic or superconformal, the last case being generic. This paper concerns superconformal almost-complex curves. We begin by giving a geometric construction of a particularly natural G2-framing for such curves. This framing can easily be shown to agree with that in (6); the exposition here

EMMA CARBERRY

408

Curve Matching by using B-spline Curves  

Microsoft Academic Search

This paper presents an algorithm for estimating the control points of the B-spline and curve matching which is achieved by using the dissimilarity measure based on the knot associated with the B-spline curves. The B-splines stand as one of the most efficient curve representations and possess very attractive properties such as spatial uniqueness, boundedness and continuity, local shape controllability, and

Tet Toe; Tang Van To

409

Effects of a novel poly (AA-co-AAm)/AlZnFe?O?/potassium humate superabsorbent hydrogel nanocomposite on water retention of sandy loam soil and wheat seedling growth.  

PubMed

A novel poly(acrylic acid-co-acrylamide)AlZnFe?O?/potassium humate( )superabsorbent hydrogel nanocomposite (PHNC) was synthesized and its physical properties characterized using SEM, Energy Dispersive X-ray (EDX) and FTIR spectroscopic techniques. Air dried sandy loam soil was amended with 0.1 to 0.4 w/w% of PHNC to evaluate its soil moisture retention attributes. Effect of PHNC amendment on pH, electrical conductivity (EC), porosity, bulk density and hydraulic conductivity of sandy loam soil was also studied. The soil amendment with 0.1 to 0.4 w/w% of PHNC remarkably enhanced the moisture retention at field capacity as compared to the un-amended soils. Seed germination and seedling growth of wheat (Triticum aestivum L.) was considerably increased and a delay by 6-9 days in wilting of seedlings was observed in the soil amended with PHNC, resulting in improved wheat plant establishment and growth. PMID:23099615

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

2012-01-01

410

Connecting curves in higher dimensions  

NASA Astrophysics Data System (ADS)

Connecting curves have been shown to organize the rotational structure of strange attractors in three-dimensional dynamical systems. We extend the description of connecting curves and their properties to higher dimensions within a special class of differential dynamical systems. The general properties of connecting curves are derived and selection rules stated. Examples are presented to illustrate these properties for dynamical systems of dimension n = 3, 4, 5.

Byrne, Greg; Gilmore, Robert; Cebral, Juan

2014-05-01

411

Langevin Equation on Fractal Curves  

E-print Network

We analyse a random motion of a particle on a fractal curve, using Langevin approach. This involves defining a new velocity in terms of mass of the fractal curve, as defined in recent work. The geometry of the fractal curve, hence plays an important role in this analysis. A Langevin equation with a particular noise model is thus proposed and solved using techniques of the newly developed $F^\\alpha$-Calculus .

Seema Satin; A. D. Gangal

2014-04-28

412

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

413

The CARIACO (CArbon Retention In A Colored Ocean) Time Series Program University of South Florida, College of Marine Science  

E-print Network

The CARIACO (CArbon Retention In A Colored Ocean) Time Series Program University of South Florida of the CARIACO (CArbon Retention In A Colored Ocean) Time-Series Program conducted by the University of South, to collect hydrographic and biogeochemical data throughout the water column. The CARIACO time-series program

Meyers, Steven D.

414

ReproducedfromVadoseZoneJournal.PublishedbySoilScienceSocietyofAmerica.Allcopyrightsreserved. Pore-Scale Visualization of Colloid Transport and Retention  

E-print Network

-crospheres provides compelling visual evidence that colloid retention uted to sorption at the AW interface and film straining.in sandy porous media occurs via trapping in the thin film of water In one case retentionCarthy and Zachara, 1989). Scientific reviews em- positively charged particles attached to the negatively phasize

McCarthy, John F.

415

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

416

Organ retention and return: problems of consent  

PubMed Central

This paper explores difficulties around consent in the context of organ retention and return. It addresses the proposals of the Independent Review Group in Scotland on the Retention of Organs at Post Mortem to speak of authorisation rather than consent. Practical problems about whose consent determines disputes in relation to organ retention are explored. If a young child dies and his mother refuses consent but his father agrees what should ensue? Should the expressed wishes of a deceased adult override the objections of surviving relatives? The paper suggests much broader understanding of the issues embedded in organ retention is needed to provide solutions which truly meet families' and society's needs. PMID:12569192

Brazier, M

2003-01-01

417

REGIONAL CURVE DEVELOPMENT FOR KANSAS  

Microsoft Academic Search

In 1999, a study to establish a baseline database of fluvial geomorphology characteristics for Kansas streams began. Data were employed to apply a uniform stream classification system and develop regional runoff curves. Regional runoff curve data are essential for estimating the discharge and dimensions of bankfull elevations in ungaged watersheds. The study has used the Rosgen (1994) stream classification. To

Brock A. Emmert

418

Conic approximation of planar curves  

Microsoft Academic Search

An upper bound of the Hausdorff distance between planar curve and conic section can be expressed by the maximum norm of error function from the conic section to the planar curve (Comput. Aided Geomet. Design, 14 (1997) 135–151). With respect to the maximum norm we characterize the necessary and sufficient condition for the conic section to be optimal approximation of

Young Joon Ahn

2001-01-01

419

Melting curve of black phosphorous  

NASA Astrophysics Data System (ADS)

The melting curve of black phosphorus has been determined up to 5 GPa by a high-pressure high-temperature X-ray system using synchrotron radition. The curve has a maximum at 1 GPa and joins the orthorhombic-rhombohedral phase boundary at a triple point around 2.7 GPa and 900°C.

Akahama, Y.; Utsumi, W.; Endo, S.; Kikegawa, T.; Iwasaki, H.; Shimomura, O.; Yagi, T.; Akimoto, S.

1987-06-01

420

Random curves by conformal welding  

Microsoft Academic Search

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(?) for ?4.

Kari Astala; Peter Jones; Antti Kupiainen; Eero Saksman

2010-01-01

421

Random Curves by Conformal Welding  

Microsoft Academic Search

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

2009-01-01

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 $\\kappa<4$.

Astala, K; Kupiainen, A; Saksman, E

2009-01-01

423

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

424

Linear systems on tropical curves  

Microsoft Academic Search

A tropical curve ? is a metric graph with possibly unbounded edges, and tropical rational functions are continuous piecewise\\u000a linear functions with integer slopes. We define the complete linear system |D| of a divisor D on a tropical curve ? analogously to the classical counterpart. We investigate the structure of |D| as a cell complex and show that linear systems

Christian Haase; Gregg Musiker; Josephine Yu

425

Design fire curves for tunnels  

Microsoft Academic Search

Various ways exist to represent a design fire curve for tunnels. These can include different fire growth rates or combinations of fire growth rates with constant levels of heat release rate (HRR) coupled to a decay period. This means that the curve has to be represented with different mathematical expressions for different time periods. A more convenient way is to

Haukur Ingason

2009-01-01

426

Aligning LC peaks by converting gradient retention times to retention index of peptides in proteomic experiments  

Microsoft Academic Search

Motivation: Liquid chromatography-tandem mass spectrometry (LC-MS\\/MS) is a powerful tool in proteomics studies, but when peptide retention information is used for identification purposes, it remains challenging to compare multiple LC-MS\\/MS runs or to match observed and predicted retention times, because small changes of LC conditions unavoidably lead to variability in retention times. In addition, noncontiguous retention data obtained with different

Kosaku Shinoda; Masaru Tomita; Yasushi Ishihama

2008-01-01

427

Adult Student Retention: A Practical Approach to Retention Improvement Through Learning Enhancement  

Microsoft Academic Search

Adult student retention is an issue of growing concern for many institutions. It differs from traditional retention much like traditional students differ from adult students. As the majority of student body growth comes from adult students, adult student retention management will become critical to the majority of colleges and universities. To support this end, this article explores the forces producing

Mark Fincher

2010-01-01

428

Retention of probabilistic cue-criterion relations as a function of cue validity and retention interval  

Microsoft Academic Search

Studied retention of a probabilistic cue-criterion task with scaled cue and criterion variables in a 3 * 2 factorial experiment with 3 levels of cue validity; .45, .70, and .90; and 2 retention intervals, immediately after the completion of the learning stage, and 1 wk. later. The retention tests were performed without feedback with 54 undergraduates. Response consistency was higher

Berndt Brehmer; Lars-AKe Lindberg

1970-01-01

429

Mechanisms affecting the transport and retention of bacteria, bacteriophage and microspheres in laboratory-scale saturated fractures  

NASA Astrophysics Data System (ADS)

Groundwater is becoming an increasingly important water source due to the ever-increasing demands from agricultural, residential and industrial consumers. In search of more secure sources, wells are routinely finished over large vertical depths in bedrock aquifers, creating new hydraulic pathways and thus increasing the risk of cross contamination. Moreover, hydraulic pathways are also being altered and created by increasing water withdrawal rates from these wells. Currently, it is not well understood how biological contaminants are transported through, and retained in, fractured media thereby making risk assessment and land use decisions difficult. Colloid transport within fractured rock is a complex process with several mechanisms affecting transport and retention, including: advection, hydrodynamic dispersion, diffusion, size exclusion, adsorption, and decay. Several researchers have investigated the transport of bacteria, bacteriophage, and microspheres (both carboxylated and plain) to evaluate the effects of surface properties and size on transport and retention. These studies have suggested that transport is highly dependent on the physico-chemical properties of the particle, the fracture, and the carrying fluid. However, these studies contain little detail regarding the specific mechanisms responsible for transport beyond speculating about their existence. Further, little work has been done to compare the transport of these particulate materials through the same fracture, allowing for direct observations based on particulate size and surface properties. This research examines the similarities and differences in transport and retention between four different particles through two different laboratory-scale, saturated fractures. This work is designed to explore the effects of particle size, surface properties, ionic strength of the carrying solution, and aperture field characteristics on transport and retention in single, saturated fractures. The particulates chosen for this work include E.coli RS2-GFP, MS2, and carboxylated microspheres with diameters of 0.0425 ?m and 0.525 ?m. The results of this work will contribute to the understanding of risk posed by contaminants to bedrock aquifer sources. Dolomite rock samples were collected from the DoLime quarry in Guelph, Ontario. A single fracture was induced in the sample by applying a uniaxial force. Lengthwise edges were sealed to create no-flow boundaries, and flow cells were fitted on the up- and down-stream ends of the fracture. Aperture size and variability were characterized using hydraulic and solute tracer tests. Particulate tracer tests were conducted by injecting a pulse of particles (E.coli RS2-GFP, MS2, or microspheres) into the upstream flow cell, and measuring the subsequent effluent concentration profile. From these tests, the percent recovery and mean residence time of the particulate were analyzed. Generally, it was found that microspheres are a poor indication of biological particulate transport, likely due to differences in surface properties affecting the retention mechanisms. This talk will provide an analysis of the breakthrough curves, with specific details regarding the transport and retention mechanisms for the various types and sizes of particles employed in these experiments.

Seggewiss, G.; Dickson, S. E.

2013-12-01

430

The Reference Shrinkage Curve of an Aggregated Soil  

NASA Astrophysics Data System (ADS)

Two fundamental problems of soil shrinkage are the subject of this work. The first is the qualitative differences between the shrinkage curve of an aggregated soil and that of the clay contributing to the soil even though the clay is the only shrink-swell component of the soil. These differences and their origin require a scientific explanation based on both inter- and, especially, intra-aggregate soil structure. The second problem is the cracking that accompanies shrinkage and depends on shrinkage conditions (sampling, sample preparation, sample size, drying regime). In general, because of the crack volume contribution, the measured shrinkage curve is not the single-valued feature of a soil. In addition to the measured shrinkage curve one needs know the crack volume contribution at any water content for the given conditions. To solve both problems we introduce the concept of the shrinkage curve that is only stipulated by soil shrinkage without cracking (the reference shrinkage curve). The difference between the observed shrinkage curve and the reference shrinkage curve estimates the crack volume evolution at shrinkage, solving the second problem. In addition, the reference shrinkage curve of the soil can only differ from the observed shrinkage curve quantitatively, but not qualitatively. That is, the derivation of the reference shrinkage curve from the inter- and intra-aggregate soil structure should also shed light upon the origin of the qualitative differences between the shrinkage curves of the soil and the corresponding clay, solving the first problem. The contemporary approaches to shrinkage curve presentation are based on the approximation of experimental data by fitted curves that include the crack volume contribution. That is, the approaches are not suitable for finding the reference shrinkage curve. The objective of the work is to develop the reference shrinkage curve model and validate it. In addition to solving the above problems, the model can have numerous applications. The modeling methods of the reference shrinkage curve are based on the new concepts of: (i) the rigid superficial layer of aggregates with changed pore-size range and pore-size distribution, compared to the intra-aggregate matrix; (ii) the evolution of large pores inside the clay (so-called lacunar pores) with shrinkage; and (iii) the critical clay content value that separates between the soils with the higher than critical clay content without lacunar pores and the soils with the lower than critical clay content with lacunar pores. In general, the reference shrinkage curve is determined by the nine physical non-fitted parameters of soil solids, clay component, silt-sand component, and inter-aggregate structure. The obtained results, using numerical modeling and available data, show the feasibility of the model.

Chertkov, V. Y.

2006-12-01

431

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

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

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

434

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.

435

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

436

Increasing Retention without Increasing Study Time  

ERIC Educational Resources Information Center

Because people forget much of what they learn, students could benefit from learning strategies that provide long-lasting knowledge. Yet surprisingly little is known about how long-term retention is most efficiently achieved. Here we examine how retention is affected by two variables: the duration of a study session and the temporal distribution…

Rohrer, Doug; Pashler, Hal

2007-01-01

437

16 CFR 437.7 - Record retention.  

...2014-01-01 2014-01-01 false Record retention. 437.7 Section 437.7 Commercial...OPPORTUNITY RULE § 437.7 Record retention. To prevent the unfair and deceptive...relies for each earnings claim from the time each such claim is...

2014-01-01

438

5 CFR 353.209 - Retention protections.  

...2014-01-01 2014-01-01 false Retention protections. 353.209 Section 353...INJURY Uniformed Service § 353.209 Retention protections. (a) During uniformed...Except in the case of an employee under time-limited appointment who finishes...

2014-01-01

439

12 CFR 219.24 - Retention period.  

... 2014-01-01 false Retention period. 219.24 Section...Transmittals of Funds § 219.24 Retention period. All records...within a reasonable period of time, taking into consideration...the record and the amount of time that has expired since...

2014-01-01

440

Factors Affecting Students' Retention at Kuwait University  

ERIC Educational Resources Information Center

This article addresses the factors that affect students' retention at Kuwait University. Five hundred seventy students participated in the study. A survey of 22 retention factors was designed to measure student perceptions. Students presented their agreement on factors which included: achieving personal aspiration, getting jobs, free-of-charge…

AlKandari, Nabila

2008-01-01

441

Measuring Up: Benchmarking Graduate Retention. IES Report.  

ERIC Educational Resources Information Center

Retention of college graduates by employers across the United Kingdom was examined. Data were collected through a survey of 362 organizations and interviews with 36 employers and their graduate employees. Most employers were unworried by their levels of graduate retention; two-thirds expected to keep new recruits for the foreseeable future. Rates…

Tyers, C.; Perryman, S.; Barber, L.

442

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

443

The Generality of the Retention Interval Model  

Microsoft Academic Search

Elaborations and refinements were made for core constructs of the retention interval (RI) model that specified a major difference between anticipation and study-test methods to be short-term memory (STM) processes in differential retention intervals. Subsequent developments reinforce the model and suggest that basic processes per each type of event are, respectively, the same for both methods (except for quantitatively differential

Chizuko Izawa

1983-01-01

444

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

445

9 CFR 354.73 - Retention labels.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Retention labels. 354.73 Section 354.73 Animals and Animal Products FOOD SAFETY AND...PRODUCTS THEREOF Supervision of Marking and Packaging § 354.73 Retention labels. An inspector may use...

2010-01-01

446

Grade Retention: A History of Failure.  

ERIC Educational Resources Information Center

As this historical overview shows, viewing grade retention as a panacea for education woes ignores its negative effects on children. Today's retention rate is high, matching that of the early 1900s. Retained students are more likely to drop out, have underprivileged backgrounds, be male and African American, and have less educated parents.…

Owings, William A.; Magliaro, Susan

1998-01-01

447

The CADRE Project: A Retention Study  

Microsoft Academic Search

I his article describes the findings of a study of leachcr retention and the effectiveness of one induction program, the Career Advancement and Development for Recruits and Experienced teachers (CADRE) Project, in helping teachers remain in the profession. National statistics report teacher attrition rate to be 40 percent over five years. CADRE participants have a retention rule ol 89 percent

Sheryl McGlamery; Edick Nancy A

2004-01-01

448

The Grade Retention/Social Promotion Debate.  

ERIC Educational Resources Information Center

This publication focuses on the retention/promotion debate regarding failing and low-achieving students. An introductory essay describes the inherent limitation in the research done on this issue--the impossibility of obtaining an appropriate control group--and suggests that the retention/promotion quandary can best be resolved by accommodating…

Lindelow, John

1985-01-01

449

Improving Student Athlete Academic Success and Retention.  

ERIC Educational Resources Information Center

This study examined a program to improve the academic success and retention of student athletes at a target community college in central Illinois. The problem of academic success and retention was identified through use of document analysis, surveys, and interviews. Analysis of probable cause data revealed that varied perceptions of student…

Hobneck, Cheryl; Mudge, Linda; Turchi, Mary

450

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.

451

Center for Academic Retention and Enhancement  

E-print Network

: Registered Student Organizations FROM: Center for Academic Retention and Enhancement (CARE) RE: CARE Summer is a chance to introduce these new students to various engagement opportunities throughout the FSU communityCenter for Academic Retention and Enhancement Summer Bridge Program May 2, 2012 ATTENTION TO

Sura, Philip

452

Student retention: Moving from numbers to action  

Microsoft Academic Search

We describe a multifaceted approach to providing information to improve student retention at an urban public university. Many students at this institution are older, working people; few live on campus and participate in “traditional” student experiences. A Retention Task Force, using qualitative as well as quantitative methods, identified problems that were barriers to student success or that contributed to student

Mary K. Kinnick; Mary F. Ricks

1993-01-01

453

A QUANTITATIVE COMPARISON OF SEDIMENT RETENTION DEVICES UNDER STANDARDIZED TEST CONDITIONS  

Microsoft Academic Search

Interest in Sediment Retention Devices (SRDs) and Storm Water Treatment Devices (SWTDs) has grown as more stringent storm water and environmental regulations have been enacted. Increased monitoring and enforcement activities have stimulated demand for more advanced and cost effective methods to control sediment and treat stormwater being discharged from construction related activities. One of the greatest problems facing specifiers in

Marc S. Theisen; TN Kevin Spittle

454

An evaluation of retention and disposal options for tritium in fuel reprocessing  

SciTech Connect

This report assesses the possible options for retention of tritium and its ultimate disposal during future reprocessing of irradiated oxide fuels discharged from light water reactors (LWRs) and liquid metal fast breeder reactors (LMFBRs). The assessment includes an appraisal of the state of the retention and disposal options, an estimate of the dose commitments to the general public, an estimation of the incremental costs of the several retention and disposal options, and the potential reduction of the dose commitments resulting from retention and disposal of the tritium. The assessment is based upon an extensive study of tritium retention in reprocessing completed in 1982 by Grimes et al. Two plants were assumed, one to process LWR oxide fuel and the other to process LMFBR fuel. In each base case plant the tritium was vaporized to the atmosphere. Each of the hypothetical plants was assumed to be constructed during the 1990`s and to operate for a 20-year lifetime beginning in the year 2000 at a rate of 1,500 metric tons of heavy metal (MTHM) per 300-d year. In addition to the base case (Case 1), six other cases which included tritium retention options were examined. Although many of the features of the base-case plants remain unchanged in the tritium retention options, each case requires some additions, deletions, and modifications of portions of the plants. The retained tritium must also be managed and disposed of in a manner that is environmentally acceptable.

Benjamin, R.W. [E.I. du Pont de Nemours and Co., Aiken, SC (United States). Savannah River Lab.; Hampson, D.C. [Oak Ridge National Lab., TN (United States)

1987-12-31

455

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

456

Rainwater runoff retention on an aged intensive green roof.  

PubMed

Urban areas are characterised by large proportions of impervious surfaces which increases rainwater runoff and the potential for surface water flooding. Increased precipitation is predicted under current climate change projections, which will put further pressure on urban populations and infrastructure. Roof greening can be used within flood mitigation schemes to restore the urban hydrological balance of cities. Intensive green roofs, with their deeper substrates and higher plant biomass, are able to retain greater quantities of runoff, and there is a need for more studies on this less common type of green roof which also investigate the effect of factors such as age and vegetation composition. Runoff quantities from an aged intensive green roof in Manchester, UK, were analysed for 69 rainfall events, and compared to those on an adjacent paved roof. Average retention was 65.7% on the green roof and 33.6% on the bare roof. A comprehensive soil classification revealed the substrate, a mineral soil, to be in good general condition and also high in organic matter content which can increase the water holding capacity of soils. Large variation in the retention data made the use of predictive regression models unfeasible. This variation arose from complex interactions between Antecedant Dry Weather Period (ADWP), season, monthly weather trends, and rainfall duration, quantity and peak intensity. However, significantly lower retention was seen for high rainfall events, and in autumn, which had above average rainfall. The study period only covers one unusually wet year, so a longer study may uncover relationships to factors which can be applied to intensive roofs elsewhere. Annual rainfall retention for Manchester city centre could be increased by 2.3% by a 10% increase in intensive green roof construction. The results of this study will be of particular interest to practitioners implementing greenspace adaptation in temperate and cool maritime climates. PMID:23712113

Speak, A F; Rothwell, J J; Lindley, S J; Smith, C L

2013-09-01

457

Parabolic curves in Lie groups  

SciTech Connect

To interpolate a sequence of points in Euclidean space, parabolic splines can be used. These are curves which are piecewise quadratic. To interpolate between points in a (semi-)Riemannian manifold, we could look for curves such that the second covariant derivative of the velocity is zero. We call such curves Jupp and Kent quadratics or JK-quadratics because they are a special case of the cubic curves advocated by Jupp and Kent. When the manifold is a Lie group with bi-invariant metric, we can relate JK-quadratics to null Lie quadratics which arise from another interpolation problem. We solve JK-quadratics in the Lie groups SO(3) and SO(1,2) and in the sphere and hyperbolic plane, by relating them to the differential equation for a quantum harmonic oscillator00.

Pauley, Michael [School of Mathematics and Statistics, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009 (Australia)

2010-05-15

458

Homotopy curves of eigenvalue problems  

SciTech Connect

In this paper, the homotopy curves of eigenvalue problems axe studied. Some results which guarantee the safety of choosing a starting problem of homotopy method for a eigenvalue problem are presented.

Li, K. [Univ. of West Florida, Pensacola, FL (United States)

1994-12-31

459

28 CFR 345.67 - Retention of benefits.  

Code of Federal Regulations, 2012 CFR

...Benefits § 345.67 Retention of benefits. (a) Job retention. Ordinarily...significant period of time, the SOI will fill...reimbursed for the time spent in detention...may approve pay grade retention when an inmate is...

2012-07-01

460

22 CFR 50.20 - Retention of nationality.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Retention of nationality. 50...NATIONALITY PROCEDURES Retention and Resumption of Nationality § 50.20 Retention of nationality. (a...Nationality Act must, within the time period specified in...

2013-04-01

461

49 CFR 655.71 - Retention of records.  

Code of Federal Regulations, 2012 CFR

...Requirements § 655.71 Retention of records. (a) General...access. (b) Period of retention. In determining compliance with the retention period requirement, each...specified minimum period of time as measured from the...

2012-10-01

462

19 CFR 111.23 - Retention of records.  

...Customs Brokers § 111.23 Retention of records. (a) Place of retention. A licensed customs...calendar days, or such longer time as spec