bluuebunny/crossref_metadata_2025 huggingface dataset:
Demand Routing with ASE Impairment Consideration in Long Distance Optical Networks
Authors: Dai Rui , Yang Hongchang , Xu Liang
Published: April 2015

In this paper, a heuristic algorithm that considers ASE (Amplified Spontaneous Emission) noise impairment is developed for demand routing in long distance optical networks. Amplifier span constraints, determined by ASE noise impairment, are presented to constrain the maximal transparent reach of a lightpath. Problem formulation and heuristic algorithms are given. Simulation demonstrates that each demand stream is guaranteed to be successfully routed, and network resources (wavelength channels and transceivers) are effectively utilized.
Development of biomaterial surfaces with and without microbial nanosegments
Authors: Alarfaj Abdullah A. , Lee Henry Hsin-chung , Munusamy Murugan A. , Ling Qing-Dong , Kumar Suresh , Chang Yung , Chen Yen-Ming , Lin Hong-Ren , Lu Yi-Tung , Wu Gwo-Jang , Higuchi Akon
Published: April 2015

Infections by microorganisms are a major problem in public health throughout the world. Artificial materials, including biomedical goods, inherently lack defense against microbial development. Therefore, microbial cells can adhere on any type of artificial surface, particularly in a moist environment, and start to multiply to form a huge population. In this review, we will discuss a strategy for designing antimicrobial polymers and antimicrobial surfaces. Generally, there are five types of antimicrobial polymers: (a) polymeric biocides, (b) biocidal polymers, (c) biocide-releasing polymers, (d) bioactive oligopeptides, and (e) antimicrobial surfaces. Antimicrobial surfaces preventing the growth of microorganisms are a promising method to inhibit the spread of microbial infections. The antimicrobial surfaces can reject the attachment of microbes and/or kill microbes in the vicinity and can be designed to kill microbes on contact. It is recommended that the material surface not release biocidal substances, therefore preventing exhaustion of biocide release to kill microbes. Furthermore, the antimicrobial surfaces are desired to be nontoxic to human cells. The development of contact-active antimicrobial surfaces by grafting antimicrobial nanosegments onto the material surface will be an important topic in the future.
Influence of tire cord layers and arrangement direction on mechanical properties and vibration isolation of chloroprene rubber composite materials reinforced with polyester tire cord
Authors: Tsai Peir-An , Wu Jyh-Horng
Published: April 2015

Polyester tire cord is often used as reinforcement in the production of chloroprene rubber (CR) composite materials. This study investigated the influences of polyester tire cord layers and arrangement directions on the mechanical properties and vibration isolation of CR composite materials. The experimental results indicate that the optimal molding condition for bonding tire cord with CR composites is 170°C for 30 min, which enables tire cord-reinforced CR composites to exhibit maximum pull-out strength. The compression set, tensile strength, and tear strength of CR composites increased with the increasing number of tire cord layers, and the stretching direction parallel to the arrangement direction of the tire cord produced optimal reinforcement effect. Moreover, the storage modulus of CR composites is better than that of pure CR at low temperature, although it reduced the tan delta at glass transition temperature. Regarding the vibration isolation properties, the transmissibility ratio decreased at resonance frequency, while the damping ratio increased when the CR is reinforced with increasing number of tire cord layers.
Material parameter identification in functionally graded structures using isoparametric graded finite element model
Authors: Huang Lixin , Yang Ming , Zhou Xiaojun , Yao Qi , Wang Lin
Published: April 2015

An identification algorithm based on an isoparametric graded finite element model is developed to identify the material parameters of the plane structure of functionally graded materials (FGMs). The material parameter identification problem is formulated as the problem of minimizing the objective function, which is defined as a square sum of differences between measured displacement and calculated displacement by the isoparametric graded finite element approach. The minimization problem is solved by using the Levenberg-Marquardt method, in which the sensitivity calculation is based on the differentiation of the governing equations of the isoparametric graded finite element model. The validity of this algorithm is illustrated by some numerical experiments. The numerical results reveal that the proposed algorithm not only has high accuracy and stable convergence, but is also robust to the effects of measured displacement noise.
Soliton Solutions, Bäcklund Transformation and Lax Pair for Coupled Burgers System via Bell Polynomials
Authors: Ünsal Ömer , Taşcan Filiz
Published: April 2015

In this work, we apply the binary Bell polynomial approach to coupled Burgers system. In other words, we investigate possible integrability of referred system. Bilinear form and soliton solutions are obtained, some figures related to these solutions are given. We also get Bäcklund transformations in both binary Bell polynomial form and bilinear form. Based on the Bäcklund transformation, Lax pair is obtained. Namely, this is a study in which integrabilitiy of coupled burgers system is investigated.
Comparative efficacy of biofeedback interventions in predicting improvements in soccer shooting performance
Authors: Saha Soumendra
Published: April 2015

The beneficial impact of the differential biofeedback intervention technique on modification in autonomic competence, as well as the ultimate impact on bilateral shooting ability, were studied on young and competitive male soccer players.  A total of 45 young high-performing soccer players in the age range of 18 to 24 years were recruited. At first, the players were subjected to baseline evaluation of psychomotor (i.e., reaction time – RT), physiological (viz. resting heart-rate; VO2Max, electrical muscle potentiality, etc.), and psychobiological indices (such as skin conductance components – latency, amplitude and recovery time). Thereafter, they were equally categorized into: Control Group, Experimental Group I [who received skin conductance (Sc) biofeedback training], and Experimental Group II [who received electromyography (EMG) biofeedback intervention training]. Participants of the experimental groups were subjected to their respective interventions (Sc & EMG biofeedback intervention training), which were imparted for 24 sessions (15 mins/day; 2 days/week for 12 weeks). After six weeks of intervention, mid-term evaluation of all of the aforementioned parameters (assessed during baseline evaluation) was performed. Thereafter, intervention sessions continued following the identical protocol for six weeks. At the end of the 12th week, a post-intervention assessment on all of the psychological, psychomotor and psychobiological variables was carried out on all of the participants to verify the effect of training on dependent measures. Post-intervention analyses revealed improvements in physiological, psychobiological and performance parameters, which could be rationally attributed to the differential biofeedback therapeutic interventions introduced to the experimental groups. The outcome suggested that both interventions facilitated improvement in bilateral shooting ability, while in-depth analyses clarified that a higher extent of autonomic recovery emerged as the most significant factor facilitating shooting ability in the experimental groups. 
Caenorhabditis elegansTBX-2 Directly Regulates Its Own Expression in a Negative Autoregulatory Loop
Authors: Milton Angenee C , Okkema Peter G
Published: April 2015

T-box genes often exhibit dynamic expression patterns, and their expression levels can be crucial for normal function. Despite the importance of these genes, there is little known about T-box gene regulation. We have focused on the Caenorhabditis elegans gene tbx-2 to understand how T-box gene expression is regulated, and here we demonstrate TBX-2 itself directly represses its own expression in a negative autoregulatory loop. tbx-2 is essential for normal pharyngeal muscle development, and a tbx-2 promoter gfp fusion (Ptbx-2::gfp) is transiently expressed in the pharynx during embryogenesis and in a small number of head neurons in larvae and adults. Reduced tbx-2 function resulted in ectopic Ptbx-2::gfp expression in the seam cells and gut in larvae and adults. Mutation of potential T-box binding sites within the tbx-2 promoter resulted in a similar pattern of ectopic Ptbx-2::gfp expression, and chromatin immunoprecipitation analyses show TBX-2 binds these sites in vivo. This pattern of ectopic Ptbx-2::gfp expression in tbx-2 mutants was very similar to that observed in mutants affecting the NF-Y complex, and our results comparing tbx-2 and nfyb-1 single- and double mutants suggest TBX-2 and NF-Y function in a single pathway to repress the tbx-2 promoter. The tbx-2 promoter is the first direct target identified for TBX-2, and we used it to ask whether SUMOylation is essential for TBX-2 repression. RNAi knockdown of SUMOylation pathway components led to ectopic Ptbx-2::gfp expression in the seam cells and gut. Ectopic Ptbx-2::gfp also was observed in the syncytial hypodermis, suggesting either the tbx-2 promoter is repressed by other SUMOylation dependent mechanisms, or that decreased SUMOylation leads to stable changes in seam cell nuclei as they fuse with the syncytial hypodermis. We suggest negative autoregulation is an important mechanism that allows precise control of tbx-2 expression levels and may allow rapid changes in gene expression during development.
Prospective Comprehensive Genomic Profiling of Advanced Gastric Carcinoma Cases Reveals Frequent Clinically Relevant Genomic Alterations and New Routes for Targeted Therapies
Authors: Ali Siraj M. , Sanford Eric M. , Klempner Samuel J. , Rubinson Douglas A. , Wang Kai , Palma Norma A. , Chmielecki Juliann , Yelensky Roman , Palmer Gary A. , Morosini Deborah , Lipson Doron , Catenacci Daniel V. , Braiteh Fadi , Erlich Rachel , Stephens Philip J. , Ross Jeffrey S. , Ou Sai-Hong Ignatius , Miller Vincent A.
Published: April 2015

Background.

Gastric cancer (GC) is a major global cancer burden and the second most common cause of global cancer-related deaths. The addition of anti-ERBB2 (HER2) targeted therapy to chemotherapy improves survival for ERBB2-amplified advanced GC patients; however, the majority of GC patients do not harbor this alteration and thus cannot benefit from targeted therapy under current practice paradigms.

Materials and Methods.

Prospective comprehensive genomic profiling of 116 predominantly locally advanced or metastatic (90.0%) gastric cancer cases was performed to identify genomic alterations (GAs) associated with a potential response to targeted therapies approved by the U.S. Food and Drug Administration or targeted therapy-based clinical trials.

Results.

Overall, 78% of GC cases harbored one clinically relevant GA or more, with the most frequent alterations being found in TP53 (50%), ARID1A (24%), KRAS (16%), CDH1 (15%), CDKN2A (14%), CCND1 (9.5%), ERBB2 (8.5%), PIK3CA (8.6%), MLL2 (6.9%), FGFR2 (6.0%), and MET (6.0%). Receptor tyrosine kinase genomic alterations were detected in 20.6% of cases, primarily ERBB2, FGFR2, and MET amplification, with ERBB2 alterations evenly split between amplifications and base substitutions. Rare BRAF mutations (2.6%) were also observed. One MET-amplified GC patient responded for 5 months to crizotinib, a multitargeted ALK/ROS1/MET inhibitor.

Conclusion.

Comprehensive genomic profiling of GC identifies clinically relevant GAs that suggest benefit from targeted therapy including MET-amplified GC and ERBB2 base substitutions.
Flood risk in Saint Petersburg, Russia: history and modern times
Authors: Lavrov Leonid , Sementsov Sergey
Published: April 2015

Situated in the low-lying Neva delta region, Saint Petersburg has always been at risk from flooding. The primary cause is strong winds from the Gulf of Finland pushing the Neva River flow back over the ice fields, predominantly in autumn and winter. In the eighteenth and nineteenth centuries, the city developed along the Neva River channels by raising ground levels and building embankments. In the twentieth century, the city moved towards and out into the Baltic, reclaiming large areas along the shoreline for new development. In 2011 a 25 km long, £2 billion flood embankment across the Gulf of Finland was finally completed and has already protected the city from storm surges. This paper describes the city's 300 year battle with flood waters, which now at last appears to have been won – but at a potentially huge ecological cost.
Integrated foresight urban planning in Singapore
Authors: Meng Meng , Zhang Jie , Wong Yiik Diew
Published: April 2015

How to optimise urban planning for sustainable development within finite land resources and growing urban population is an important global issue. This paper introduces a range of successful experiences of Singapore's integrated foresight urban planning to provide thought and guidance on urban planning. The whole planning framework follows three steps: concept plan, master plan and detailed plan. The core planning model is to divide the planning area into mass rapid transit-orientated new towns with a similar prototype. A multi-level transportation system forms Singapore's urban skeleton and enhances the connectivity among new towns. As a garden city, Singapore's green space planning methodology and white site concept are also advanced and worth learning.
Advanced Torque and Drag Considerations in Extended-Reach Wells
Authors: Payne M. L. , Abbassian F.
Published: April 2015

Excessive torque and drag can be critical limitations in Extended-Reach Drilling (ERD). This paper details issues related to torque and drag prediction, monitoring, and management in ERD wells. Results are presented from sensitivity analyses of extreme ERD trajectories such as 7 to 8 km departures at 1600 m TVD. Several such wells have now been successfully drilled at BP's Wytch Farm oil-field using results from these studies. In such high-angle ERD wells, compression generated in the drillpipe during tripping and sliding operations can exceed the critical buckling load and cause the drillpipe to buckle. As a result, buckling initiation and post-buckling analyses are used to quantify the extent and severity of buckling and the associated increases in drag forces and pipe stresses. The paper addresses the importance of drilling data in calibrating torque/drag models in order to capture the continual changes in drilling parameters and operating conditions. The paper presents a number of field case studies where analyses have been conducted to directly assist drilling operations. This paper should be of high interest to engineers executing, planning, or evaluating ERD operations.
Strip Tillage and High‐Efficiency Irrigation Applied to a Sugarbeet–Barley Rotation
Authors: Stevens William B. , Evans Robert G. , Iversen William M. , Jabro Jalal D. , Sainju Upendra M. , Allen Brett L.
Published: April 2015

Strip tillage (ST) and high‐efficiency overhead irrigation methods reduce fuel and water inputs compared to conventional practices, but have not been extensively evaluated in sugarbeet (Beta vulgaris L.)–malt barley (Hordeum vulgare L.) cropping systems. A field study comparing conventional tillage (CT) and ST systems and two sprinkler irrigation methods (mid‐elevation spray application, MESA; low‐energy precision application, LEPA) was conducted near Sidney, MT, from 2004 to 2008. Strip tillage was performed (for sugarbeet only) using a single operation that left alternating 30‐cm wide strips of tilled and untilled soil while fertilizer was simultaneously banded 10 cm below the seed row. Conventional tillage for sugarbeet consisted of six separate tillage operations following a broadcast application of fertilizer. Tillage preceding malt barley consisted of one pass each with a disk and a field cultivator following a broadcast application of fertilizer. Sugarbeet grown with ST yielded as well as when grown with CT. Irrigation method did not affect sugarbeet yield. Malt barley yield was not affected by irrigation method but was 5.4% lower following ST sugarbeet than when following CT sugarbeet. Tillage and fertilizer application costs for the sugarbeet phase of the 2‐yr rotation were estimated to be approximately $141 ha−1 less with ST than with CT representing reductions of 66% for the sugarbeet phase alone and 47% for the 2‐yr cropping system. It was concluded that both ST and LEPA are applicable to irrigated sugarbeet–malt barley cropping systems and may provide substantial cost savings compared to conventional practices.
Foliar Fertilization Does Not Reduce Soybean Aphid Populations, Change Plant Nitrogen and Potassium, or Protect Yield from Aphid Feeding, under Non‐limiting Nutrient Conditions
Authors: DiFonzo Christina , Jewett Michael R. , Nagelkirk Martin L.
Published: April 2015

The soybean aphid (Aphis glycines Matsumura) is a key pest of soybean [Glycine max (L.) Merr] in the Midwest. In the early 2000s, foliar fertilization was sometimes recommended to reduce aphid populations, regardless of soil or plant nutrient levels in fields. Nitrogen (N) fertilization or potassium (K) deficiency can increase aphid populations, so the impact of foliar fertilization on soybean aphid was not clear. This study measured percent N and K in leaf tissue, cumulative aphid days, and yield in aphid‐free (insecticide treated) and aphid‐infested soybean plots, with or without a foliar fertilizer timed at the R3 and R5 growth stages during typical peak aphid infestation. Five separate trials were done over 2 years in non‐deficient fields. In a low aphid year (2004), fertilization did not increase percent N and K in leaf tissue, change aphid numbers, or effect yield. In an aphid outbreak year (2005), percent N and K was significantly lower on three occasions in aphid‐infested treatments. Significant reductions in aphid number and increases in yield were measured at all locations in 2005, the result of insecticide (not fertilizer) application. In a laboratory assay, aphid survival and nymph production was not affected by direct exposure to fertilizer diluted to a field rate. This study cannot rule out the possibility that in nutrient‐deficient fields, foliar fertilization may alleviate stress on aphid‐infested plants. However, given the high reproductive potential of soybean aphid, it is an insecticide application that will significantly reduce aphid numbers and protect soybean yield during an outbreak, under non‐limiting nutrient conditions.
Laboratory Investigation of Boundary Condition Impacts on Nitrate Anion Exclusion in an Unsaturated Soil
Authors: Allred Barry J. , Brown Glenn O. , Martinez Luis R.
Published: April 2015

Transient unsaturated horizontal column experiments were conducted with a loam soil, under variable boundary conditions, to obtain added insight on nitrate (NO3−) anion exclusion processes. The boundary conditions evaluated were column inlet soil water content (θ0), initial soil water content (θi), column inlet soil solution NO3−–N concentration (C0), and the initial soil solution NO3− concentration (Ci). Results consistent with significant anion exclusion of NO3− were exhibited in all experiments. For tests with NO3− solution injected at the column inlet, the soil solution NO3− concentration at the inlet was found to be 12 to 19% less than the injected NO3− concentration. For these same tests, where initial soil conditions were dry with no NO3− originally present, the NO3− concentrations at the wetting front edge were substantially greater than the injected NO3− concentration, while for initially wetter conditions, with or without NO3− originally present, the NO3− front was found to extend well beyond the theoretical “piston front” separating the injected solution from displaced initial soil water. For displacement tests, in which water was injected at the inlet of a column initially wetted with a NO3− solution, the soil solution NO3− front also extended beyond the piston front. Inlet NO3− excluded water content ranged from 0.03 to 0.06 and was not affected by pore water velocity, but did have a modest positive correlation with total water content (r = 0.60 and r = 0.67). The findings of this investigation provide a better overall understanding of nitrate movement through the soil profile.
Thermal Property Measurement Errors with Heat‐Pulse Sensors Positioned near a Soil–Air Interface
Authors: Xiao X. , Zhang X. , Ren T. , Horton R. , Heitman J.L.
Published: April 2015

Heat‐pulse sensor measurements analyzed with pulsed infinite line source (PILS) theory have been widely used to measure soil properties. The PILS theory assumes that the measured soil medium is uniform and infinite. When the sensors are positioned near the soil surface, the effects of the heterogeneity associated with the soil–air interface should not be ignored. In 1999, Philip and Kluitenberg (PK99) proposed an analytical solution using an instantaneous heating model to analyze the effects of the soil–air interface on soil thermal property measurements with heat‐pulse sensors. The purpose of this study is to test the PK99 instantaneous heat source solution under controlled laboratory conditions. Soil thermal properties including volumetric heat capacity, thermal diffusivity, and thermal conductivity were measured with a commercially available dual‐needle heat‐pulse sensor buried at different depths beneath the soil surface. Three soil materials, sand, loamy sand, and sandy clay loam, were tested at both air‐dry and saturated moisture conditions. With shallow sensor burial, measured thermal properties were underestimated by up to 50%, similar to the predicted thermal properties from the PK99 analytical solution, due to the effects of the soil–air interface. Using PK99 to adjust thermal property values obtained from shallow sensors has potential to improve estimates of water content, evaporation, and other soil measurements derived from heat‐pulse sensors.
Soil Organic Matter Functional Group Composition in Relation to Organic Carbon, Nitrogen, and Phosphorus Fractions in Organically Managed Tomato Fields
Authors: Margenot Andrew J. , Calderón Francisco J. , Bowles Timothy M. , Parikh Sanjai J. , Jackson Louise E.
Published: April 2015

The objectives of this study were to examine soil organic matter (SOM) functional group composition and its relationship to labile SOM fractions with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). We analyzed soils from 13 organically managed tomato (Solanum lycopersicum) fields in northern California for labile organic C, N, and P fractions and by DRIFTS for bands representing organic functional groups, including aliphatic C‐H (2924, 2850, 1470, 1405, 1390 cm‐1), aromatic C=C (1650 cm‐1) and C‐H (920, 840 cm‐1), polysaccharide and phenol C‐O (1270, 1110, 1080 cm‐1), and amine and amide N‐H (3400, 1575 cm‐1). Significant differences in relative band intensities occurred among the 13 organic tomato fields, in particular a relative increase in absorbance of bands representing aliphatic C‐H positively associated with soil organic carbon (SOC), as well as permanganate‐oxidizable carbon (POXC), extractable organic carbon (EOC) and nitrogen (EON), and potentially mineralizable N (PMN). In comparison, organic P fractions like sodium bicarbonate extractable (NaHCO3–Po) and sodium hydroxide extractable organic P (NaOH‐Po) were poorly associated with SOC and functional groups represented by bands, including aliphatic C‐H. This could reflect limitations of DRIFTS, but is consistent with hypotheses of greater decoupling of C and P vs. C and N in soils. This study implicates relative differences in organic functional groups with differences in SOC and labile SOM fractions, and in agreement with previous studies, identifies absorbance of infrared bands representing aliphatic C‐H functional groups in these systems as a potential indicator of SOM transformations related to changes in its labile fractions.
Diffusion‐Limited Mobilization and Transport of Natural Colloids in Macroporous Soil
Authors: Schelde Kirsten , Moldrup Per , Jacobsen Ole Hørbye , de Jonge Hubert , de Jonge Lis Wollesen , Komatsu Toshiko
Published: April 2015

This study examines the dynamics of colloid mobilization and leaching from macroporous soil columns by means of laboratory experiments and numerical modeling. On the basis of a previous column study involving high and low water flow rates in structured soil, we designed a novel experiment emphasizing the time‐dependence of the colloid release process. Intact macroporous soil columns were exposed to variable pauses in irrigation (flow interruption for 30 min, 1 d, or 7 d) followed by resumed infiltration. The experiments showed that (i) there was a seemingly unlimited source of in situ colloids even after prolonged leaching and (ii) the peak concentration of colloids in the effluent after the flow interruption increased with increasing length of the preceding pause. The results demonstrated that colloid mobilization is not controlled by hydrodynamic shear induced by the flowing water but is a time‐dependent and possibly diffusion‐limited process. We developed a simple, equivalent macropore model to investigate the hypothesis that colloid release to the flowing water is governed by two diffusion processes, one in a uniform water film lining the macropore and one in the crust of the macropore. The model was capable of reproducing and explaining the characteristic results of our soil column experiments and required no recalibration of exchange process parameters to simulate the particle mobilization after a flow interruption. However, model calibration yielded unexpected results with respect to the size of the diffusion coefficient of the crust and did not warrant accepting the dual diffusion model hypothesis. Using a simpler mass transfer concept to quantify the mobilization of colloids in 21 soil columns, we found mass transfer coefficients to be about 30 times higher in the water film than in the crust.
Unsaturated Hydraulic Conductivity of Structured Porous Media: A Review of Liquid Configuration–Based Models
Authors: Tuller Markus , Or Dani
Published: April 2015

Common approaches for modeling hydraulic functions of unsaturated structured porous media (SPM) rely on macroscopic continuum representation, where parameterization schemes and constitutive relationships originally developed for homogeneous porous media are extended to represent hydraulic behavior of dual (or multi) continuum SPM. Such models often result in inconsistencies due to lack of consideration of structural pore space geometry and the neglect of underlying physical processes governing liquid retention and flow under unsaturated conditions. We review a new framework that considers equilibrium liquid configurations in dual continuum pore space as the basis for calculation of liquid saturation and subsequent introduction of hydrodynamic considerations. The SPM pore space is represented by a bimodal distribution of pore sizes, reflecting two disparate populations of matrix and structural pores. Three steady‐state and laminar flow regimes are considered to derive unsaturated hydraulic conductivity functions: (i) flow in completely filled pore spaces, (ii) corner flow in partially filled pores and grooves, and (iii) film flow on solid surfaces. Two key assumptions are used in deriving the average cross‐sectional flow velocities in these regimes: (i) that equilibrium liquid–vapor interfaces remain stable under slow laminar flows and (ii) that flow pathways are parallel. Liquid–vapor interfacial configurations for different matric potentials are calculated and statistically upscaled to derive sample‐scale saturated and unsaturated hydraulic conductivity from velocity expressions weighted by the appropriate liquid‐occupied cross‐sectional areas, neglecting three‐dimensional (3‐D) network effects. Similarly, the hydraulic functions for matrix and structural pores are derived separately and later combined by weighting the individual contributions by the porosities of the associated pore spaces. A parameter estimation scheme was developed to calculate liquid saturation and to predict sample‐scale unsaturated hydraulic conductivity. Model evaluation using measured data for homogeneous porous media, fractured welded tuff, and macroporous and aggregated soils shows favorable agreement (within the limitations of model assumptions). Effects of nonequilibrium conditions between matrix and structural pore domains on the hydraulic conductivity and approximate consideration of 3‐D network effects are discussed.
Chloride Distributions as Indicators of Vadose Zone Stratigraphy in Palouse Loess Deposits
Authors: O'Geen A. T. , McDaniel P. A. , Boll J.
Published: April 2015

Chloride is often used as a conservative tracer to estimate groundwater recharge rates in arid and semiarid regions. Relationships between Cl− depth profiles and vadose zone stratigraphy have revealed new information on the behavior of this dissolved constituent in pore waters of heterogeneous materials. We measured pore‐water Cl− in loess deposits of the eastern Palouse region in northern Idaho, where multiple sequences of buried soils extend to ∼20 m depth. Three cores were collected to bedrock at summit, side slope, and valley positions. Pore‐water Cl− distribution, clay content, soil strength, and secondary Mnd/Fed ratios were measured to identify relationships between natural tracer migration and vadose zone stratigraphy. Characterization of deep strata revealed complex sequences of extremely dense paleosol fragipans interstratified with less dense leached horizons. Abrupt changes in Cl− concentration reflect boundaries between these stratigraphic units that display contrasting physical and morphological properties. Results illustrate that loess stratigraphy influences vadose zone water movement in the Palouse. In addition, Cl− depth profiles can be used as indicators of deep stratigraphy across various landscape positions.
Analytical Model for Vadose Zone Solute Transport with Root Water and Solute Uptake
Authors: Schoups G. , Hopmans J. W.
Published: April 2015

An efficient method is presented for calculating one‐dimensional solute transport through the vadose zone in the presence of vertically distributed root water and solute uptake. The method is based on an analytical solution of the convective transport equation, which is solved by the method of characteristics. The solution requires a time‐invariant leaching fraction, and assumes that transport occurs by convection alone; that is, hydrodynamic dispersion and molecular diffusion are neglected. From this solution, two variables of practical importance are calculated, (i) the average solute concentration in the root zone, weighted by the root distribution, and (ii) the cumulative solute flux to the groundwater. Model parameters are related to water management, crop type, and soil type, through the following parameters: leaching fraction, root distribution, and soil hydraulic properties. Simulation results are presented for both downward and upward flow scenarios. Simulations with a nonuniform moisture profile indicate that nearly identical results are obtained by replacing the profile by a uniform moisture content equal to the arithmetic average or the uptake‐weighted average moisture content, so that closed‐form analytical expressions for travel time and travel depth can be obtained. A sensitivity analysis of the relevant model parameters shows that solute concentrations are largely determined by the magnitude of the effective water application ratio, defined by the fraction of infiltrated water that is removed by evapotranspiration. We present suggestions of how dispersive mixing and temporal changes in leaching fraction are readily incorporated into the current model. Although potentially simplistic, the presented methodology can be extremely useful for longer‐term and field‐to‐regional scale characterization of contaminant movement.
Modeling Heat, Water Vapor, and Carbon Dioxide Flux Distribution Inside Canopies Using Turbulent Transport Theories
Authors: Katul Gabriel , Siqueira Mario
Published: April 2015

This study reports recent developments in mulitlayer turbulent transport methods to compute distributions of strengths of scalar sources and sinks Sc as well as turbulent fluxes Fc within the plant–atmosphere continuum. In particular, we focus on the so‐called “inverse methods” that estimate Sc from measured mean scalar concentration (or temperature) distribution within the canopy without resorting to any ecophysiologically based input. These approaches are able to reproduce measured turbulent fluxes above and within the canopy without relying on gradient diffusion formulation. Comparison between measured and modeled sensible heat flux vertical attenuation within the canopy suggests that all three methods provided comparable root‐mean squared error (RMSE) (∼50 W m−2). Furthermore, correcting for local atmospheric stability significantly improved the agreement between model calculations and measurements. Comparisons between measured and modeled land surface fluxes of sensible heat, latent heat, and CO2 above the canopy are conducted using wavelet spectral methods applied to a wide range of temporal scales (30 min–2 yr). This study is the first to rigorously assess the performance of several inverse methods for such a broad range of time scales. We found that the three inverse modeled flux spectra bound the measured one. Hence, spectral agreement among the three models provides the necessary confidence in calculated fluxes and scalar sources. Conversely, large disagreement between the inverse models “flags” large uncertainties at those particular time scales.
Temperature‐Profile Methods for Estimating Percolation Rates in Arid Environments
Authors: Constantz Jim , Tyler Scott W. , Kwicklis Edward
Published: April 2015

Percolation rates are estimated using vertical temperature profiles from sequentially deeper vadose environments, progressing from sediments beneath stream channels, to expansive basin‐fill materials, and finally to deep fractured bedrock underlying mountainous terrain. Beneath stream channels, vertical temperature profiles vary over time in response to downward heat transport, which is generally controlled by conductive heat transport during dry periods, or by advective transport during channel infiltration. During periods of stream‐channel infiltration, two relatively simple approaches are possible: a heat‐pulse technique, or a heat and liquid‐water transport simulation code. Focused percolation rates beneath stream channels are examined for perennial, seasonal, and ephemeral channels in central New Mexico, with estimated percolation rates ranging from 100 to 2100 mm d−1. Deep within basin‐fill and underlying mountainous terrain, vertical temperature gradients are dominated by the local geothermal gradient, which creates a profile with decreasing temperatures toward the surface. If simplifying assumptions are employed regarding stratigraphy and vapor fluxes, an analytical solution to the heat transport problem can be used to generate temperature profiles at specified percolation rates for comparison to the observed geothermal gradient. Comparisons to an observed temperature profile in the basin‐fill sediments beneath Frenchman Flat, Nevada, yielded water fluxes near zero, with absolute values <10 mm yr−1. For the deep vadose environment beneath Yucca Mountain, Nevada, the complexities of stratigraphy and vapor movement are incorporated into a more elaborate heat and water transport model to compare simulated and observed temperature profiles for a pair of deep boreholes. Best matches resulted in a percolation rate near zero for one borehole and 11 mm yr−1 for the second borehole.
A Time Domain Transmission Method for Determining the Dependence of the Dielectric Permittivity on Volumetric Water Content: An Application to Municipal Landfills
Authors: Masbruch K. , Ferré T. P. A.
Published: April 2015

A method for determining the dependence of the dielectric permittivity of municipal refuse on its volumetric water content is developed and tested. The method is based on time domain transmission (TDT) measurements collected with an automated network analyzer (ANA). Measurements in variably saturated sand were first made to test the method's ability to measure the apparent dielectric permittivity. The method was then extended to samples of municipal refuse to determine whether a single calibration can be used to describe the relationship between the dielectric permittivity and the volumetric water content of refuse. The results show that the relationship between the dielectric permittivity and the volumetric water content within the refuse shows significant spatial variability. The results do show, however, that a calibration based on multiple samples collected throughout the landfill can be used to measure the volumetric water content with a root mean square volumetric water content measurement error of <0.04 cm3 cm−3 Deviations from the common calibration are not explained by variations in bulk density or porosity among samples. It is recommended that a calibration be derived from samples collected throughout a municipal landfill before a water content monitoring method based on dielectric permittivity measurements is used.
Numerical Simulations of One‐Dimensional Infiltration into Layered Soils with the Richards Equation Using Different Estimates of the Interlayer Conductivity
Authors: Brunone B. , Ferrante M. , Romano N. , Santini A.
Published: April 2015

Transient water flow processes in unsaturated soils are usually modeled using the Richards equation. This paper compares several numerical approximations to this equation for vertical infiltration in layered soil profiles. Three formulations of the governing flow equation (i.e., the h‐based, θ‐based, and mixed forms) are compared for the critical test problem of infiltration into a layered soil profile with initially relatively low soil water contents. An efficient, yet relatively simple weighting algorithm is employed that improves the estimation of the interlayer hydraulic conductivity in an h‐based finite‐difference formulation. Results highlight improvements in the mass conservative properties of this model, which is termed the H‐IL model A comparison is then performed between the finite‐difference H‐IL model and a finite‐element model for infiltration toward a water table. The H‐IL model was found to be computationally very efficient for this test problem. For both illustrative flow examples, the different numerical models were evaluated in terms of their ability to reproduce an exact solution developed by Srivastava and Yeh (1991) in their work on one‐dimensional, transient infiltration toward the water table in homogeneous and layered soils.
Endosulfan Losses through Runoff and Leaching from Calcareous Gravelly or Marl Soils
Authors: Zhou M. , Li Y. C. , Nkedi‐Kizza P. , O'Hair S. K.
Published: April 2015

The non‐point loss of a pesticide through runoff and leaching from agricultural fields depends not only on its chemical properties but also on environmental factors such as soil type, rainfall intensity, and water table level. Two major agricultural calcareous soils in South Florida, Krome (loamy‐skeletal, carbonatic, hyperthermic Lithic Udorthents) very gravelly loam (Krome) and Biscayne (loamy, carbonatic, hyperthermic, shallow Typic Fluvaquents) marl (marl), were packed in tilted stainless‐steel runoff–leaching chambers for measuring the transport of endosulfan (6,7,8,9,10,10‐hexachloro‐1,5,5a,6,9,9a‐hexahydro‐6,9‐methano‐2,4,3‐benzadioxathiepin 3‐oxide) isomers in leachates and surface runoff. Endosulfan loss was the greatest in runoff sediment, followed by loss in runoff water, and finally in the leachate. At a rainfall intensity of 75 mm h−1, the infiltration rate in the Krome soil was higher than in the marl soil. Endosulfan movement with infiltration water in Krome soil is a nonequilibrium process. Increasing rainfall intensity to 150 mm h−1 significantly decreased endosulfan leaching and increased runoff. High rainfall intensity and/or water table dramatically increased the endosulfan loss through the sediments in runoff. Marl soil has a higher endosulfan runoff potential than Krome soil. Endosulfan α had a lower average experimental distribution coefficient, KD, than endosulfan β (265 vs. 472). Loss of endosulfan α dissolved in runoff water and through leaching was higher than that of endosulfan β, while loss of endosulfan α from runoff sediments was lower than that of endosulfan β. Endosulfan concentrations in runoff water decreased exponentially with cumulative rainfall and runoff sediment.
Near‐Surface Water Content Estimation with Borehole Ground Penetrating Radar Using Critically Refracted Waves
Authors: Rucker Dale F. , Ferré Ty P. A.
Published: April 2015

Zero‐offset profiling (ZOP) with borehole ground penetrating radar (BGPR) is a promising tool for profiling water contents in the subsurface to great depths with high spatial and temporal resolution. The ZOP method relies on determining the velocity of an electromagnetic (EM) wave that follows a direct path from the transmitter to the receiver. However, near the ground surface, critically refracted energy that travels along the ground surface at the velocity of an EM wave in air may arrive before direct waves that travel through the subsurface. If the critically refracted waves are mistakenly interpreted to be direct waves, the water content will be underestimated. As a result, the water content near the ground surface cannot be determined using standard BGPR analysis. We refer to the depth below which direct waves are the first to arrive as the refraction termination depth An alternative analysis is presented to determine the water content above the refraction termination depth using the slope of the travel time vs. depth profile. Additionally, guidelines are presented to predict the refraction termination depth for known near‐surface water contents.
Carbon Tetrachloride Flow Behavior in Unsaturated Hanford Caliche Material: An Investigation of Residual Nonaqueous Phase Liquids
Authors: Oostrom M. , Lenhard R. J.
Published: April 2015

At many contaminated sites, nonaqueous phase liquids (NAPLs) persist in the vadose zone for long periods of time. This occurs because the permeability of the NAPL becomes negligible at some saturation and downward movement ceases, resulting in residual NAPL. To obtain data that can be used to study the development of a residual NAPL saturation and to test corresponding models, a detailed transient experiment was conducted in a 170 cm long by 90 cm high by 5.5 cm wide flow cell. Fluid saturation measurements were obtained with a dual‐energy γ radiation system. The experimental conditions reflected those at the Hanford Site in Washington State, where an estimated 363 to 580 m3 of carbon tetrachloride (CCl4) was disposed to the subsurface. A key subsurface feature at the Hanford Site is a sloped Plio‐Pleistocene caliche layer, which was reproduced in the experiment as a sloped lens in a medium‐grained, uniform, sand matrix. The caliche contains considerable amounts of CaCO3 and may have fluid wettability properties other than strongly water wet. A total of 800 mL of CCl4 was injected into the experimental domain at a rate of 0.5 mL min−1 from a small source area located at the surface. After apparent static conditions were obtained with respect to CCl4 redistribution, saturation measurements indicated that all of the dense nonaqueous phase liquids (DNAPL) that had initially moved into the caliche remained in this layer. Water was subsequently applied to the surface at a constant rate over the full length of the caliche layer to study CCl4 displacement as a result of changing water saturations. Water saturation in the caliche layer rose to as high as 0.91 during water infiltration. Results show that 25% of the DNAPL present in the caliche migrated from this layer as a consequence of water infiltration, while 75% remained in the caliche layer. The experimental results could not be reproduced with numerical multifluid flow simulations based on common constitutive theory. This indicates that improvements in constitutive theory may be needed to accurately model air−DNAPL−water flow behavior.
The Active Fracture Model: Its Relation to Fractal Flow Patterns and an Evaluation Using Field Observations
Authors: Liu Hui‐Hai , Zhang Guoxiang , Bodvarsson Gudmundur S.
Published: April 2015

The active fracture model (AFM) (Liu et al., 1998) has been widely used in modeling flow and transport in the unsaturated zone of Yucca Mountain, Nevada, a proposed repository of high‐level nuclear wastes. This study presents an in‐depth evaluation of the AFM, based on both theoretical arguments and field observations. We first argue that flow patterns observed from different unsaturated systems (including the unsaturated zone of Yucca Mountain) may be fractals. We derive an interesting relation between the AFM and the fractal flow behavior, indicating that the AFM essentially captures this important flow behavior at a subgrid scale. Finally, the validity of the AFM is demonstrated by the favorable comparison between simulation results based on the AFM and 14C age and fracture coating data collected from the unsaturated zone at Yucca Mountain. These data sets independently provide important insight into flow and transport processes at the Yucca Mountain site. Potential future improvements of the AFM include expanding it to consider film flow and multifractal concepts.
Using Simple Bucket Models to Analyze Solute Export to Subsurface Drains by Preferential Flow
Authors: Kohler A. , Abbaspour K. C. , Fritsch M. , Schulin R.
Published: April 2015

Leaching of fertilizer and pesticide compounds from agricultural lands into ground and surface waters is a major environmental problem. To study this phenomenon, a bromide tracer experiment was performed on a 1.6‐ha area of a tile‐drained arable field to determine the contribution of preferential flow to solute leaching, and to investigate the factors triggering the onset of such events. During the 2 yr following the application of Br−, concentration of the drainage effluent exhibited a pattern of peaks coinciding with the discharge peaks. The concentration peaks, on top of a smooth base flow, were interpreted as being the contribution of preferential flow. The separation of peak and base flow indicated that 73% of the Br− leached during the 2 yr of study was exported through preferential flow. A simple leaching bucket model was able to accurately predict the occurrence of solute peaks in the drain discharge. The analyses indicated that preferential flow originated primarily at the boundary between top‐ and subsoil as soon as the topsoil became sufficiently saturated. Thus, low intensity, high duration events could also trigger preferential flow.