bluuebunny/crossref_metadata_2025 huggingface dataset:
Light Profile Microscopy Based on Raman and Wavelength Resolved Luminescence Contrast
Authors: Power J. F. , Fu S. W.
Published: May 2006

Light profile microscopy based on contrast from wavelength resolved Raman and luminescence measurements is demonstrated experimentally for the first time. A Raman/multispectral light profile microscope (RMS-LPM) has been constructed based on a line profiling geometry in which the sample is irradiated with a tightly focused laser beam (of ten micrometers radius or less) behind a polished view surface and the resulting line image is dispersed over the wavelength using an imaging spectrograph. The instrumentation developed in this laboratory has a spectral resolution approaching 10 cm−1 and an (actual) depth independent spatial resolution of 6–8 times the Rayleigh diffraction limit, limited at present by optical aberrations and alignment. The technique has the potential to image at approximately twice the Rayleigh diffraction limit. The spectral signatures reconstructed from a variety of common industrial polymers show excellent agreement with reference spectra from the literature, and may be used to identify individual layers in depth images of unknown materials. RMS-LPM image data based on luminescence contrast have also been used to provide concentration depth profiles of additives and degradation products in injection molded samples of high-density poly(ethylene) (HDPE).
Insight into the Molecular Arrangement of High-Density Polyethylene Polymer Chains in Blends of Polystyrene/High-Density Polyethylene from Differential Scanning Calorimetry and Raman Techniques
Authors: Joshi Jayant , Lehman Richard , Hall Gene S.
Published: May 2006

Polystyrene/high-density polyethylene (PS/HDPE) blends were synthesized by melt blending in a single screw extruder. Co-continuity measurements using solvent extraction and scanning electron (SEM) micrographs showed that co-continuity was obtained around 35% PS. Thermal analyses measurements revealed a reduction in crystallinity of the HDPE phase around the co-continuous composition. Raman analyses across the entire composition range of these blends showed an increase in the normalized integral intensities of the 1128 cm−1 and 1061 cm−1 stretching vibrations of the HDPE molecules. The presence of all-trans HDPE chains that are not packed into an orthorhombic structure is used to explain the simultaneous occurrence of reduced crystallinity and increased intensity of all-trans HDPE stretch vibrations.
Stress Characterization of Si by Near-Field Raman Microscope Using Resonant Scattering
Authors: Yoshikawa Masanobu , Murakami Masataka
Published: May 2006

We have developed a tapping-mode scanning near-field optical Raman microscope (SNORM) with a caved and pyramidical probe, using resonant Raman scattering, and have measured the stress distribution of Si. The peak frequency shifts to a lower frequency by 0–0.5 cm−1 in the area covered by silicon dioxide, whereas it shifts to a higher frequency by 0–0.3 cm−1 in the area uncovered by silicon dioxide, showing that the areas covered and uncovered by silicon dioxide are under tensile and compressive stresses, respectively. It has been found that compressive stresses of about 0.69 GPa/cm2 are concentrated on the corner of the area uncovered by silicon dioxide. The comparison of stress distributions measured with and without the cantilever shows that the SNORM we developed has a spatial resolution of at least less than 250 nm.
Integrating X-Ray Fluorescence and Infrared Imaging Microspectroscopies for Comprehensive Characterization of an Acetaminophen Model Pharmaceutical
Authors: Patterson Brian M. , Havrilla George J.
Published: May 2006

The integration of full spectral images using the complementary microspectroscopic imaging techniques X-ray fluorescence and Fourier transform infrared is demonstrated. This effort surpasses previous work in that a single chemometric software package is used to elicit chemical information from the integrated spectroscopic images. Integrating these two complementary spectroscopic methods provides both elemental and molecular spatial distribution within a specimen. The critical aspect in this work is using full spectral maps from each pixel within the image and subsequent processing with chemometric tools to provide integrated chemical information. This integration enables a powerful approach to more comprehensive materials characterization. Issues addressed include sample registration and beam penetration depth and how each affects post-processing. An inorganic salt and an acetaminophen pharmaceutical model mixture demonstrate the power of integrating these techniques with chemometric software.
Modified Coin Cells for In situ Raman Spectroelectrochemical Measurements of LixV2O5 for Lithium Rechargeable Batteries
Authors: Burba Christopher M. , Frech Roger
Published: May 2006

In situ Raman spectroscopy is an extremely valuable technique for investigating fundamental reactions that occur inside lithium rechargeable batteries. However, specialized in situ Raman spectroelectrochemical cells must be constructed to perform these experiments. These cells are often quite different from the cells used in normal electrochemical investigations. More importantly, the number of cells is usually limited by construction costs; thus, routine usage of in situ Raman spectroscopy is hampered for most laboratories. This paper describes a modification to industrially available coin cells that facilitates routine in situ Raman spectroelectrochemical measurements of lithium batteries. To test this strategy, in situ Raman spectroelectrochemical measurements are performed on Li//V2O5 cells. Various phases of Li xV2O5 could be identified in the modified coin cells with Raman spectroscopy, and the electrochemical cycling performance between in situ and unmodified cells is nearly identical.
Application of Band-Target Entropy Minimization to Infrared Emission Spectroscopy and the Reconstruction of Pure Component Emissivities from Thin Films and Liquid Samples
Authors: Cheng Shuying , Rajarathnam D. , Meiling Tan , Garland Marc
Published: May 2006

Thermal emission spectral data sets were collected for a thin solid film (parafilm) and a thin liquid film (isopropanol) on the interval of 298–348 K. The measurements were performed using a conventional Fourier transform infrared (FT-IR) spectrometer with external optical bench and in-house-designed emission cell. Both DTGS and MCT detectors were used. The data sets were analyzed with band-target entropy minimization (BTEM), which is a pure component spectral reconstruction program. Pure component emissivities of the parafilm, isopropanol, and thermal background were all recovered without any a priori information. Furthermore, the emissivities were obtained with increased signal-to-noise ratios, and the signals due to absorbance of thermal radiation by gas-phase moisture and CO2 were significantly reduced. As expected, the MCT results displayed better signal-to-noise ratios than the DTGS results, but the latter results were still rather impressive given the low temperatures used in this study. Comparison is made with spectral reconstruction using the orthogonal projection approach–alternating least squares (OPA-ALS) technique. This contribution introduces the primary equation for emission spectral reconstruction using BTEM and discusses some of the unusual characteristics of thermal emission and their impact on the analysis.
Quantitative Analysis of Cotton—Polyester Textile Blends from Near-Infrared Spectra
Authors: Ruckebusch C. , Orhan F. , Durand A. , Boubellouta T. , Huvenne J. P.
Published: May 2006

Quantitative analysis of textile blends and textile fabrics is currently of particular interest in the industrial context. In this frame, this work investigates whether the use of Fourier transform (FT) near-infrared (NIR) spectroscopy and chemometrics is powerful for rapid and accurate quantitative analysis of cotton–polyester content in blend products. As samples of the same composition have many sources of variability that affect NIR spectra, indirect prediction is particularly challenging and a large sample population is required to design robust calibration models. Thus, a total of more than three-hundred cotton–polyester samples were selected covering the range from the 0% to 100% cotton and the corresponding NIR reflectance spectra were measured on raw fabrics. The data set obtained was used to develop multivariate models for quantitative prediction from reference measurements. A successful approach was found to rely on partial least squares (PLS) regression combined with genetic algorithms (GAs) for wavelength selection. It involved evaluating a set of calibration models considering different spectral regions. The results obtained considering 27.5% of the original variables yielded a prediction error (RMSEP) of 2.3 in percent cotton content. It demonstrates that FT-NIR spectroscopy has the potential to be used in the textile industry for the prediction of the composition of cotton– polyester blends. As a further consequence, it was observed that the spectral preprocessing and the complexity of the model are simplified compared to the full-spectrum approach. Also, the relevancy of the spectral intervals retained after variable selection can be discussed.
Investigation of the Mixing Efficiency of a Chaotic Micromixer Using Thermal Lens Spectrometry
Authors: Ghaleb Khalil Abbas , Stephan Khaled , Pittet Patrick , Ferrigno Rosaria , Georges Joseph
Published: May 2006

This work investigates the efficiency of a chaotic micromixer using thermal lens spectrometry. The outlet of the mixing device was connected to a thermal lens detection head integrating the probe beam optical fibers and the sample capillary. The chaotic micromixer consisted of a Y-shaped poly(dimethylsiloxane) (PDMS) microchip in which ribbed herringbone microstructures were etched on the floor of the main channel. Due to the solvent composition dependence of the thermal lens response, the photothermal method was shown to be highly sensitive to nonhomogeneous mixing compared to fluorescence detection. The apparatus was applied to the determination of Fe2+ with 1,10-phenanthroline using flow injection analysis; a limit of detection of 11 μg L−1 of iron was obtained.
Probability-Based Differential Normalized Fluorescence Bivariate Analysis for the Classification of Tissue Autofluorescence Spectra
Authors: Wang Gufeng , Platz Charles P. , Geng M. Lei
Published: May 2006

Differential normalized fluorescence (DNF) is an efficient and effective method for the differentiation of normal and cancerous tissue fluorescence spectra. The diagnostic features are extracted from the difference between the averaged cancerous and averaged normal tissue spectra and used as indices in tissue classification. In this paper, a new method, probability-based DNF bivariate analysis, is introduced based on the univariate DNF method. Two differentiation features are used concurrently in the new method to achieve better classification accuracy. The probability of each sample belonging to a disease state is determined with Bayes decision theory. This probability approach classifies the tissue spectra according to disease states and provides uncertainty information on classification. With a data set of 57 colonic tissue sites, probability-based DNF bivariate analysis is demonstrated to improve the accuracy of cancer diagnosis. The bivariate DNF analysis only requires the collection of a few data points across the entire emission spectrum and has the potential of improving data acquisition speed in tissue imaging.
Fiber-Optic Infrared Reflection Absorption Spectroscopy for Trace Analysis on Surfaces of Varying Roughness: Sodium Dodecyl Sulfate on Stainless Steel
Authors: Hamilton Michelle L. , Perston Benjamin B. , Harland Peter W. , Williamson Bryce E. , Thomson Mary A. , Melling Peter J.
Published: May 2006

The effect of surface roughness on the analytical performance of a fiber-optic grazing-angle infrared reflection absorption spectroscopy (IRRAS) system has been investigated. The instrument was used to develop calibrations to quantify trace surface loadings for sodium dodecyl sulfate (SDS) on 316 stainless steel with three different surface finishes. Partial least squares (PLS) calibrations were developed for both individual finishes and combinations of finishes. For SDS on individual surface finishes, the root mean square (rms) error of cross-validation (RMSECV) varied between 0.08 and 0.12 μg cm−2 with values of R2 between 0.89 and 0.96. A combined model for SDS on all surfaces gave an RMSECV of 0.18 μg cm−2 with an R2 of 0.85.
Practical Calibration Correction Method for the Maintenance of an On-Line Near-Infrared Monitoring System for Molten Polymers
Authors: Watari Masahiro , Ozaki Yukihiro
Published: May 2006

The present study has investigated a practical calibration correction method for an on-line monitoring system for molten polymers using a near-infrared (NIR) spectrometer. A partial least squares (PLS) calibration model for the ethylene (C2) content in melt polypropylene (PP) was developed for the investigation of changes in the performance of the on-line system before and after maintenance necessitated by the relocation. The predicted values for the C2 content from the spectra measured after maintenance by using the calibration model developed from the spectra collected before maintenance showed that there were some differences between the spectra obtained by the NIR spectrometer system before and after maintenance. The loadings from factor analysis suggested that the main cause for the differences in the system performance before and after maintenance was wavenumber shifts in the NIR spectra of PP in the melt state. Six popular standardization or calibration transfer methods (direct standardization (DS), piecewise direct standardization (PDS), additive correction (AD), multiplicative correction (MP), slope and bias (SB), and difference spectrum with interpolation (DSI)) were evaluated for the calibration correction of the on-line NIR monitoring system. However, the results of the evaluation showed that these standardization methods need more than two samples to obtain the high accuracy for the nonlinearity contained in the spectra set. From the standpoint of practical calibration in a real plant, the acceptable number of samples for the calibration is one or two. Moreover, recalibration using transferred spectra is not preferable because of the traceability for a calibration model. As a practical solution for a calibration correction in a real plant, a method considering wavenumber shift and path-length correction has been proposed in this study. The predicted results for the C2 content in the melt-state PP from the spectra measured after maintenance by using the proposed method have shown that the proposed method is useful for calibration correction in a real plant in spite of using only one sample.
Evidence-based policy-making
Authors: Moore R. Andrew
Published: May 2006

There is no large literature on evidence-based policy-making. We do know that one of the most difficult decisions is about the dependability of evidence we use to make policy. Unless the evidence can fulfil the criteria of quality, validity, and size, then it has the potential to mislead us, whatever study designs or methods have been used. The best examples of evidence-based policy-making come from development of care pathways, in which multidisciplinary groups merge best-available evidence with what is possible in local circumstances. These care pathways almost always have the ability to deliver better care for patients, with less fuss for professionals and at lower cost to the community. They may be the single best way of improving healthcare.
Integration between the Tele-Cardiology Unit and the central laboratory: methodological and clinical evaluation of point-of-care testing cardiac marker in the ambulance
Authors: Di Serio Francesca , Lovero Roberto , Leone Massimo , De Sario Rosalia , Ruggieri Vincenzo , Varraso Lucia , Pansini Nicola
Published: May 2006

The aim of this study was to identify patients with myocardial necrosis in pre-hospital phase during transport by ambulance, without ST-segment elevation (NSTE) on the ambulance ECG. The analytical performance of the i-STAT
ISO 15189:2003 – Quality management, evaluation and continual improvement
Authors: Burnett David
Published: May 2006

The requirements of ISO 15189:2003 are discussed in the context of a process- and outcome-based quality management model in which the user's needs are the central focus. The requirements of ISO 15189:2003 are examined in terms of organisation and a quality management system, stressing the importance of evidence, document control, and control of records and clinical material. Examples are provided from the areas of resource management, and pre-examination, examination and post-examination processes. In the final section the importance of evaluation and continual improvement is presented in relation to internal audit and external assessment, non-conformity, corrective and preventative action and management review.
Clinical Governance: from clinical risk management to continuous quality improvement
Authors: Chiozza Maria Laura , Plebani Mario
Published: May 2006

Reducing medical errors has become an international concern. Population-based studies from a number of nations around the world have consistently demonstrated unacceptably high rates of medical injury and preventable deaths. The introduction of effective reporting systems is a cornerstone of safe practice within hospitals and other healthcare organisations. Reporting can help to identify hazards and risks. However, reporting in itself does not improve safety. It is the response to reports that leads to change. Clinical teams must feel empowered to change the way in which they deliver their services, promoting effective clinical risk management. Process analysis, implementation of evidence-based practices, and a clear accountability system are effective tools not only for decreasing error rates, but also for improving effectiveness. Clinical Governance represents the context in which effective clinical risk management should be promoted and continuously improved. It should not be regarded as a separate activity, but should form part of the everyday practice of all healthcare professionals. It requires good multidisciplinary working and a willingness to reflect on and learn from errors to achieve a patient-centred and safer system.
Clinical Governance – from rhetoric to reality?
Authors: Lugon Myriam
Published: May 2006

Although Clinical Governance now has a strong structural base in the National Health Service (NHS), its actual application in terms of service delivery is more inconsistent. Cross-agency and boundary working are still underdeveloped and true patient involvement remains the province of a minority of enthusiasts. Despite this, there have been some significant moves forward, in that quality is now intrinsically linked to service delivery, and managers and clinicians are more explicitly accountable for the care they provide. This article examines the introduction of Clinical Governance to the NHS and discusses what practical applications have been made. Case studies drawn from those who are working at the frontline are used to illustrate the impact that Clinical Governance components have had on service delivery and patient experience.
Forschen für die Internetgesellschaft – Trends, Technologien, Anwendungen: Der Feldafinger Kreis (Research for the Internet Society: Trends, Technologies, Applications)
Authors: Raffler Hartmut , Wahlster Wolfgang
Published: May 2006

Der Feldafinger Kreis wurde durch eine Initiative von Repräsentanten der deutschen Wissenschaftsorganisationen und dem Bundesverband der deutschen Industrie (BDI) im August 2001 gegründet. Er hat sich zum Ziel gesetzt, den Dialog zwischen Wissenschaft und Wirtschaft auf dem Gebiet ‚Forschung für die Internetgesellschaft‘ zu intensivieren, die Internetforschung in Deutschland zu stimulieren und Impulse zu geben zur besseren Nutzung der Innovationspotenziale, die das Internet bietet.
Effizienz und Dienstgüte von IP Netzwerken (Efficiency and Quality of Service of IP Networks)
Authors: Heckmann Oliver
Published: May 2006

Effizienz und Dienstgüte sind zwei sehr wichtige Eigenschaften von IP Netzwerken. Aus der Sicht eines Internet Netzwerkbetreibers (engl.: Internet Service Provider, ISP) untersuchen wir in dieser Arbeit, wie man die Effizienz und Dienstgüte verbessern kann. Hierzu betrachten wir die Netzwerkarchitektur, die Interkonnektion und die Verkehrs- und Netzwerkanpassungsmaßnahmen (engl.: network & traffic engineering).
Estimation of the Unsaturated Hydraulic Conductivity of Peat Soils: Laboratory versus Field Data
Authors: Schwärzel K. , Šimůnek J. , Stoffregen H. , Wessolek G. , van Genuchten M. Th.
Published: May 2006

As compared with mineral soils, there are few in situ measurements of the unsaturated hydraulic properties of peat soils available. We used parameter estimation (inverse) methods to estimate the water retention and hydraulic conductivity functions of drained peat soils from both laboratory and field data. The laboratory data were obtained on small cores using the traditional evaporation method, while the field data were obtained by means of evaporation experiments using groundwater lysimeters with and without vegetation. The field experiments without vegetation produced highly uncertain parameters and were limited to a relatively small pressure head range. Better results were obtained for the lysimeter with a grass cover that caused the peat soil to dry out more. However, a physically realistic minimum in the objective function for the plant‐covered lysimeter could be found only when prior information about several parameters was included in the optimization. Good agreement was obtained between the laboratory and field measurements. The hydraulic functions were subsequently tested by comparing forward simulations with independently measured pressure heads and water contents of an additional lysimeter experiment under grass. The dynamics of the drying process was described well using the optimized soil hydraulic properties.
Fault Zone Deformation Overprints Permeability of Nonwelded Ignimbrite: Chalk Cove Fault, Bishop Tuff, Bishop, California
Authors: Dinwiddie Cynthia L. , Bradbury Kelly Keighley , McGinnis Ronald N. , Fedors Randall W. , Ferrill David A.
Published: May 2006

Deformation‐induced secondary heterogeneities associated with a steeply‐dipping normal fault in the nonwelded Bishop Tuff were examined in a multidisciplinary study using in situ gas permeability tests, structural mapping, and laboratory analyses as analogs for fault deformation features within the poorly exposed Paintbrush nonwelded hydrogeologic unit at Yucca Mountain, Nevada. Three features of fault‐zone deformation were identified that may act to constrain lateral flow in unsaturated nonwelded ignimbrites. First, development of a fault gouge, with a decrease in grain size caused by grain comminution, decreases the permeability of this element with respect to the host rock. Second, long open fractures paralleling the fault have an increased permeability with respect to the host rock. Third, small‐scale fractures and grain rotation in adjacent matrix blocks induce an interconnected porosity not seen in host rock. Intrinsic permeability variation beyond what is observed in the host rock reflects the effect of small‐scale deformation in the matrix adjacent the fault. These features can reduce the continuity of potential capillary or permeability barriers, and thus limit any redistribution of percolation that would result from lateral flow diversion.
Characterizing Pore‐Scale Configuration of Organic Immiscible Liquid in Multiphase Systems With Synchrotron X‐Ray Microtomography
Authors: Schnaar G. , Brusseau M. L.
Published: May 2006

The objective of this study was to examine the pore‐scale distribution and morphology of organic immiscible liquid in natural porous media containing three immiscible fluids. High‐resolution, three‐dimensional images of an organic liquid (tetrachloroethene) in both three‐phase (water–air–organic liquid) and two‐phase (water–organic liquid) systems were obtained using synchrotron X‐ray microtomography. These data were used to quantitatively characterize the morphology of the organic liquid residing within columns packed with one of three natural, sandy porous media. Organic‐liquid blobs varied greatly in both size and shape, ranging from small, single spheres (≥0.03 mm in diameter) to large, amorphous ganglia with mean lengths of 4 to 5 mm. Singlets comprised the greatest number of blobs, whereas the large ganglia, while much fewer in number, comprised the majority of the organic‐liquid surface area and volume. A significant portion of the organic liquid in the three‐phase systems was observed to exist as lenses and films in contact with air. These features were not observed in the two‐phase water–organic liquid systems. The median of the blob‐frequency distributions was smaller and the variance larger for the three‐phase systems. In addition, the global specific surface areas of the organic liquid were greater for the three‐phase systems. These differences are attributed to the presence of the organic‐liquid lenses and films for the three‐phase systems.
Colloid and Bromide Transport in Undisturbed Soil Columns: Application of Two‐Region Model
Authors: Poulsen Tjalfe G. , Moldrup Per , de Jonge Lis W. , Komatsu Toshiko
Published: May 2006

Bromide tracer breakthrough and natural soil colloid leaching curves for undisturbed soil columns were used to characterize dissolved and suspended matter transport at the field scale. Data from 33 columns of 20‐cm diameter and 20‐cm height were used. Columns were collected in a grid of 25 by 30 m at an agricultural field. A two‐region (mobile–immobile water phase, MIM) solute transport model was fitted to data. The model was used to estimate bromide and colloid transport parameters including mobile and immobile water contents (θm, θim), bromide and colloid advective velocities (vBr, vColl), and mobile–immobile mass transfer coefficients (αbr, αcoll). Both soil physical properties and transport parameters were highly variable across the sampling field. Comparison of bromide transport parameters with basic soil physical properties revealed that vBr was proportional to soil clay content and bulk density (ρb), but αBr was inversely proportional to these parameters. Colloid transport parameters, vColl and αColl, however, showed only a weak correlation with clay content and ρb. Also, vColl was typically three to four times higher than vBr. The colloid velocity was generally higher than the bromide velocity, implying size exclusion of colloids. The spatial distributions of soil physical properties, bromide and colloid transport parameters, and leached quantities of particles were compared. The results suggested that bromide and colloid mass transfer (diffusion) were not controlled by the same soil physical conditions, and that soil structure and macropore flow are more important than the quantity of dispersible colloids in controlling colloid leaching.
The Impact of Fracture–Matrix Interaction on Thermal–Hydrological Conditions in Heated Fractured Rock
Authors: Birkholzer Jens T. , Zhang Yingqi
Published: May 2006

Dual‐continuum models have been widely used in modeling flow and transport in fractured porous rocks. Among many other applications, dual‐continuum approaches were used in predictive models of the thermal–hydrological conditions near emplacement tunnels (drifts) at Yucca Mountain, NV, the proposed site for a radioactive waste repository in the USA. In unsaturated formations such as those at Yucca Mountain, the magnitude of mass and heat exchange between the two continua—fracture network and rock matrix—depends on the small‐scale flow characteristics in the fractures, because channelized finger‐type flow strongly reduces the interface area between the matrix surfaces and the flowing liquid. This effect may have important implications, for example, during the time period that the fractured rock near the repository drifts would be heated above the boiling point of water. Depending on the magnitude of heat transfer from the matrix, water percolating down the fractures will either boil off in the rock region above drifts or may penetrate all the way to the drift walls and possibly seep into the open cavities. In this study, we conducted a sensitivity analysis using different approaches to treat fracture–matrix interaction in a three‐dimensional dual‐continuum setting. Our simulation example was a laboratory heater experiment described in the literature that provides evidence of rapid water flow in fractures, leading to seepage into the heater hole despite above‐boiling conditions in the adjacent fractured rock. We showed that the experimental finding can only be reproduced when the interface area for heat transfer between the matrix and fracture continua is reduced to account for flow channeling. Our analysis also suggests that the conditions in the laboratory experiment are unique and not representative of the expected thermal–hydrological conditions near emplacement drifts at Yucca Mountain.
Correction of Lightning Effects on Water Content Reflectometer Soil Moisture Data
Authors: McCartney John S. , Zornberg Jorge G.
Published: May 2006

Soil moisture monitoring systems involving correlations with soil dielectric content measured using WCR (water content reflectometer) probes are susceptible to lightning‐induced errors during field monitoring programs. These errors must be understood and corrected to use moisture data in geoenvironmental or hydrological applications. This study evaluated the effect of lightning on WCR measurements observed during the monitoring of four evapotranspirative landfill test covers. Several lightning strikes at the site caused unrealistic shifts in the inferred moisture content (from 0.001 to 3.900 m3 m−3), which showed a time‐dependent decay. A conceptual model for lightning strike effects was developed that allowed correction of affected WCR data. Because duplicate probes were available in this project, WCR corrections could be calibrated by minimizing the difference between the data from affected probes with data from unaffected probes to within ±5 m3 m−3. This led to a correlation useful in other cases where duplicate probes were not available. Assessment of the consistency of the corrected data included evaluation of wetting fronts, comparison of moisture changes against meteorological patterns, and comparison of the corrected moisture content with upper‐ and lower‐bound moisture content values.
Estimation of Soil Hydraulic Properties from Numerical Inversion of Tension Disk Infiltrometer Data
Authors: Ramos T. B. , Gonçalves M. C. , Martins J. C. , van Genuchten M. Th. , Pires F. P.
Published: May 2006

Many applications involving variably saturated flow and transport require estimates of the unsaturated soil hydraulic properties. Numerical inversion of cumulative infiltration data during transient flow, complemented with initial or final soil water content data, is an increasingly popular approach for estimating the hydraulic curves. In this study, we compared Mualem–van Genuchten (MVG) soil hydraulic parameters obtained from direct laboratory and in situ unsaturated hydraulic conductivity measurements with estimates using numerical inversion of tension infiltration data of four coarse‐ to medium‐textured soils in Alentejo (Portugal). The laboratory methods used were suction tables, pressure plates, and the evaporation method as applied to undisturbed soil samples collected from the surface horizons of four different soil profiles. Field measurements were taken with a tension disk infiltrometer using consecutive supply pressure heads of −15, −6, −3, and 0 cm. Six MVG parameters (residual soil water content [θr], saturated soil water content [θs], empirical shape factorsα, η, and ℓ, and saturated hydraulic conductivity [Ks]) were estimated from the field data by numerical inversion using the HYDRUS‐2D software package, and compared with values estimated from the laboratory data. Macroporosity was also determined. The laboratory‐ and field‐measured water retention curves were found to agree closely for most experiments as reflected by relatively high values of the coefficient of determination, the modified coefficient of efficiency, and the modified index of agreement (always >0.9949, 0.8412, and 0.8931, respectively). The unsaturated hydraulic conductivity curves were predicted less accurately, although good estimates ofKswere obtained.
Modeling the Relationship between Soil Bulk Density and the Hydraulic Conductivity Function
Authors: Assouline S.
Published: May 2006

A model is presented that could quantify and predict the effect of an increase in soil bulk density on the hydraulic conductivity function (HCF). Two approaches are formulated to predict the saturated hydraulic conductivity of compacted soils. The first approach is a general expression based on the Kozeny equation that requires only information on the bulk density. The second approach exploits information contained in the water retention curve (WRC). This approach, which relies on Assouline's model for soil HCFs, also provides a basis for a proposed expression to predict the unsaturated HCF of compacted soils. It is shown that a relationship between η, the power parameter in the expression for the HCF, and ε, the coefficient of variation of the WRC, is applicable to a large number of both compacted and uncompacted soils. The model was verified against measured HCFs for soils at different bulk density values. Both the saturated and unsaturated hydraulic conductivities were well reproduced by the suggested expressions.
Resolving Structural Influences on Water‐Retention Properties of Alluvial Deposits
Authors: Winfield Kari A. , Nimmo John R. , Izbicki John A. , Martin Peter M.
Published: May 2006

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 [θ(ψ)]) 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 θ(ψ) data were fit with the Rossi–Nimmo junction model, representing water retention with three parameters: the maximum water content (θmax), the ψ‐scaling parameter (ψo), and the shape parameter (λ). We examined trends between these hydraulic parameters and bulk physical properties, both textural—geometric mean, Mg, and geometric standard deviation, σg, of particle diameter—and structural—bulk density, ρb, the fraction of unfilled pore space at natural saturation, Ae, and porosity‐based randomness index, Φs, defined as the excess of total porosity over 0.3. Structural parameters Φs 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 θmax, including Ae, Φs, and σg, and for both ψo and λ, including only textural parameters, although use of Ae can somewhat improve ψo predictions. Textural properties can explain most of the sample‐to‐sample variation in θ(ψ) independent of deposit type, but inclusion of the simple structural indicators Ae and Φs can improve PTM predictions, especially for the wettest part of the θ(ψ) curve.
Estimating the Fine Soil Fraction of Desert Pavements Using Ground Penetrating Radar
Authors: Meadows Darren G. , Young Michael H. , McDonald Eric V.
Published: May 2006

A reconnaissance tool that can estimate the clay content and saturated hydraulic conductivity (Ks) of well‐developed desert pavements has immediate applications for researchers and practitioners who work in arid environments. We examined the use of surface‐based ground penetrating radar (GPR) to rapidly approximate these properties on six, 100‐m‐long transects for two different aged (∼100 000 vs. 4000 yr) desert pavement surfaces. We determined early‐time amplitudes from GPR transects, ground electrical conductivity, hydraulic properties, clay content, water content, and soil salinity at regular intervals along each transect. Both surfaces were low in water content and salinity; however, the older pavement contained substantial amounts of silt and clay in the surficial soil horizon. Using multivariate linear regression, which included GPR amplitude and a nominal measure of soil structure ascertained by visual field inspection, we show significant correlations between measured and predicted values of both silt plus clay content (r = 0.84, P < 0.0001) and Ks (r = 0.73, P < 0.0001) for the older surface. No significant correlations were found on the younger surface. This is probably due to the low concentrations of clays in the young soil. Including the metric of soil structure improved the predictive capabilities on the older surface. The GPR method provides higher spatial resolution than electromagnetic measurements. The results suggest that, at this location, the approach is not influenced by heterogeneities in lower soil horizons. The method can be used for reconnaissance surveys as a means of estimating the clay content, and in some cases Ks, of surficial soils on certain well‐developed desert pavements.
Dependence of the Electrical Conductivity on Saturation in Real Porous Media
Authors: Ewing R. P. , Hunt A. G.
Published: May 2006

Archie's Law for the porosity and saturation dependence of electrical conductivity, σ(θ) = aσbϕm(θ/ϕ)n (where σ is electrical conductivity, the subscript b denotes the brine or bulk solution, ϕ is porosity, θ is volume wetness, and a, m, and n are fitting parameters) was recently derived by applying continuum percolation theory to fractal porous media. We have recast Archie's Law in terms of saturation alone to obtain σ(θ) = σ0 (θ − θc)μ, where θc is the critical volume fraction for percolation, and σ0 = aσb/(1 − θc)μ. The value of the exponent, μ = 2.0 for three‐dimensional systems and 1.28 for two, is consistent with theory and simulations. We examined the universality of the exponent's value, and the range of validity of our expression. Drawing on published data, we compared predicted and measured values of σ(θ) across the full range of saturation, and found that the newly derived expression provides good predictions, is robust with respect to secondary effects such as residual salinity and contact resistance, and yields meaningful physical parameters.
Modeling the Impact of Clustered Septic Tank Systems on Groundwater Quality
Authors: Pang Liping , Nokes Chris , Šimůnek Jirka , Kikkert Heather , Hector Ross
Published: May 2006

Contamination of groundwater from onsite disposal of septic tank effluent is an increasing concern. In this study, HYDRUS‐2D simulated the impact of clustered disposal systems on NO3− and fecal coliforms in groundwater in a rural community near Christchurch, New Zealand. The model included nine disposal boulder pits, embedded 4 m below the surface in alluvial gravel media, in a domain of 3.3 km by 30 m (including both unsaturated and saturated zones). Water movement between the ground surface and the disposal pits was simulated using HYDRUS‐1D. The performance of the two‐dimensional model was evaluated using monitoring data obtained from a 1977 study. Applying the daily climate data for 1974 to 1977, the simulated NO3− and bacteria concentrations in the groundwater were similar to those observed. Both observed and simulated results showed that clustered disposal systems have a significant cumulative impact on NO3− concentrations in groundwater, but the impact of fecal coliforms from individual systems is localized. This study further demonstrates that groundwater has a limited ability to dilute NO3−, requiring at least 2.9 km for NO3− to be reduced to near background levels. Therefore, disposal systems must treat effluent efficiently and water wells downgradient of closely clustered disposal systems must be deep enough to avoid the adverse health effects of NO3−. Sensitivity analysis suggests that the model results are most sensitive to changes in hydraulic conductivity, effluent concentrations and discharge rate, and the removal rate of bacteria in the unsaturated zone. Therefore, the accurate estimation of these parameters is a fundamental requirement for the model to produce realistic results.
Incorporating Parametric Uncertainty in the Design of Alternative Landfill Covers in Arid Regions
Authors: Young Michael H. , Albright William , Pohlmann Karl F. , Pohll Greg , Zachritz Walter H. , Zitzer Stephen , Shafer David S. , Nester Irene , Oyelowo Layi
Published: May 2006

Monte Carlo simulations and a combination of site‐specific data (e.g., soil properties, climatic conditions, and native vegetation) were used to design alternative (evapotranspiration) landfill covers at Edwards Air Force Base, located near Lancaster, CA. Laboratory analyses of site soils indicated the presence of three distinct surface soils, from which statistical distributions were generated. A 10‐yr climate sequence (precipitation and potential evapotranspiration) was used for the upper boundary. Potential evapotranspiration was partitioned into potential evaporation and potential transpiration using the phenology of a Mojave Desert plant community. Nearly 1000 realizations were run for each of 72 different combinations of soil type, cover thickness, and plant cover percentage. The results indicate that threshold design parameters, needed to limit deep flux to <0.5 cm yr−1, differ based on the relationship between the Ks (saturated hydraulic conductivity) of the surface soil, cover thickness, and plant cover percentage. In the lower conductivity soils (mean Ks = 20 cm d−1), deep flux was ≤0.2 cm yr−1 for a cover thickness >80 cm with a plant cover >10%. Higher conductivity soils (Ks = 250 cm d−1) required thicker soils covers (>100 cm) and greater plant cover (>20%) to achieve similar fluxes. In all cases, variations in both cover thickness and plant cover percentage indicated threshold values, above which incremental additions added little to cover performance. The methods developed here could be implemented at other sites where conditions are known. Designs can account for uncertainties in site parameters and contribute to improved decision making.
Comparing Ambient Temperature Effects on Heat Pulse and Time Domain Reflectometry Soil Water Content Measurements
Authors: Olmanson Ole K. , Ochsner Tyson E.
Published: May 2006

Time domain reflectometry (TDR) and the heat pulse method are both used to measure soil water content. Changes in ambient temperature have been shown to affect TDR measurements, but less is known about the behavior of heat pulse sensors in response to changes in temperature. This study directly measured and compared the temperature sensitivity of the TDR and heat pulse methods. Both methods were used to estimate water content in silt loam and sand at two fixed water contents across a wide temperature range. An increase in temperature led to an increase in measured water content in most cases. Across the 40°C temperature range, changes in measured water content were generally 0.04 m3 m−3 or less for both methods. Weighted linear regression showed that in these soils the heat pulse method exhibited greater temperature sensitivity than the TDR method, although the differences were not statistically significant. A previously proposed correction for the temperature sensitivity of the TDR method produced mixed results. The temperature sensitivity of the heat pulse method was attributed to the changes in the density and specific heat of water and specific heat of soil with respect to temperature. When the changes in these parameters were accounted for, the temperature sensitivity was eliminated in three out of four cases.
Electrical Conductivity of a Failed Septic System Soil Absorption Field
Authors: Lee Brad D. , Jenkinson Byron J. , Doolittle James A. , Taylor Richard S. , Tuttle J. Wes
Published: May 2006

Locating existing septic systems and determining the extent of soil contamination after septic system failure can be destructive, time consuming, and a nuisance to homeowners. The objective of this study was to determine the effectiveness of noninvasive electromagnetic induction (EMI) for locating a failed septic system in fine‐textured glacial‐till‐derived soils. Components of a failed septic system were located with a push probe, georeferenced with a theodolite, and surveyed with a dual receiver EMI sensor (DUALEM‐2) in December 2001 (wet soil moisture condition) and July 2002 (dry soil moisture condition). Three transects located perpendicular to the soil absorption field trenches were sampled to a depth of 1.2 m and used to ground reference the EMI survey. Near‐surface (1‐m depth) apparent conductivity (ECa) was significantly correlated to unweighted average electrical conductivity from soil saturated paste extracts (ECsat; r = 0.79). The ECa below the soil absorption field was higher than the surrounding native soil under both dry and wet soil moisture conditions. Individual soil absorption trenches had a higher ECa than background ECa under both soil moisture conditions. A higher ECa pattern that was apparent in December 2001 associated with discharge of wastewater at shallow depths was not evident in July 2002 after the system had been abandoned for 6 mo. While more research is warranted, results from this study suggest that electromagnetic induction is a promising technique to identify the location of septic system components, failed septic systems, and their associated effluent plumes.
A Review of Multidimensional, Multifluid Intermediate‐Scale Experiments: Nonaqueous Phase Liquid Dissolution and Enhanced Remediation
Authors: Oostrom M. , Dane J. H. , Wietsma T. W.
Published: May 2006

A review is presented of original multidimensional, intermediate‐scale experiments involving NAPLs (nonaqueous phase liquids). The experimental approach at this scale can be viewed as an important intermediary between column studies and field trials. The primary advantage of intermediate‐scale flow cell experiments is that field‐scale processes can be simulated under controlled conditions. The experiments are frequently conducted to provide data sets to test and verify numerical and analytical flow and transport models. The controlled setting and laboratory instrumentation reduces the uncertainty in parameter estimation, allowing comparisons between simulation and experimental results to focus on flow and transport processes. A total of about 125 original contributions were identified and reviewed. Depending on the main topic of NAPL experimental research, the papers were divided into the following sections: (i) aqueous dissolution, (ii) enhanced remediation, (iii) flow behavior, (iv) quantification, and (v) imaging. In this review, the first two categories are discussed and suggestions for future research are provided. In a companion review, experimental work related to the other three categories is investigated. The aqueous dissolution category includes experiments in which pooled and entrapped NAPL removal occurs due to water flushing. The enhanced remediation section contains experimental contributions investigating surfactant flushing, alcohol flushing, surfactant and alcohol flushing combinations, dense brine strategies, hydraulic NAPL recovery, soil vapor extraction, air sparging, heat‐based remediation, bioremediation, and other techniques.