bluuebunny/crossref_metadata_2025 huggingface dataset:
Vadose Zone Characterization and Monitoring Beneath Waste Disposal Pits Using Horizontal Boreholes
Authors: McLin Stephen G. , Newman Brent D. , Broxton David E.
Published: August 2005

Vadose zone characterization and monitoring immediately below landfills using horizontal boreholes is an emerging technology. However, this topic has received little attention in the peer‐reviewed literature. The value of this approach is that activities are conducted below the waste, providing clear and rapid verification of containment. Here we report on two studies that examined the utility of horizontal boreholes for environmental characterization and monitoring under radioactive waste disposal pits. Both studies used core sample analyses to determine the presence of various radionuclides, organic compounds, or metals. At one borehole site, water content and pore‐water chloride concentrations were also used to interpret vadose zone behavior. At another site, we examined the feasibility of using flexible membrane liners in uncased boreholes for periodic monitoring. For this demonstration, these retrievable liners were air‐injected into boreholes on multiple occasions carrying different instrument packages for environmental surveillance. These included a neutron logging device to measure volumetric water at regular intervals, high‐absorbency collectors that wicked available water from borehole walls, or vent tubes that were used to measure air permeability and collect air samples. The flexible and retrievable liner system was an effective way to monitor water content and measure in situ air permeability. The high‐absorbency collectors were efficient at extracting liquid water for contaminant analyses even at volumetric water contents below 10%, and revealed tritium migration below one disposal pit. Both demonstration studies proved that effective characterization and periodic monitoring in horizontal boreholes is both feasible and adaptable to many waste disposal problems and locations.
Mini Suction Cups and Water‐Extraction Effects on Preferential Solute Transport
Authors: Köhne J. Maximilian
Published: August 2005

Soil water suction cups used in laboratory solute transport studies may cause undesired perturbations of the flow field. The twofold objective of this study was to test mini suction cups, and to assess the effects of pore water‐extraction rate and cup size on preferential water flow and bromide (Br−) breakthrough. Porous ceramic cups of 0.25‐cm outer diameter and 1‐cm length could extract 1 cm3 of pore water within 17 (34, 38) min from 100% (85%, 70%) saturated loam soil by applying 0.1 (0.3, 0.5) bar suction. The corresponding sampling times for larger cups (0.6‐cm diam., 2‐cm length) were 3.3, 4.6, and 5.7 min. The smaller cups were subsequently tested for solution extraction of 1‐cm3 samples every 20 min out of the matrix and preferential flow path (PFP) of a large soil column (24‐cm diam., 80‐cm high) during a Br− transport experiment. Numerical simulations were used (i) to describe the Br− transport experiment and (ii) to evaluate how preferential Br− transport would be affected by pore solution extraction at different locations in the matrix and the PFP of a loam soil block (20 by 20 by 20 cm3) subject to wet and dry initial conditions. Three‐dimensional water flow and solute transport were simulated using the Richards and convection–dispersion equations. The experimental and simulation results revealed a dilemma: while fast solution extraction using larger cups altered the flow field and preferential Br− breakthrough for wet and particularly for dry initial conditions, slower solution extraction using small cups caused negligible perturbation of the flow field, but yielded insufficient resolution of the preferential Br− breakthrough. Sampling in the matrix did not considerably affect Br− transport, and gave sufficient resolution of the matrix Br− peak. This study showed that the use of suction cups for measuring solute transport may be problematic in case of preferential flow.
Vadose Zone Transport of 1,1,1‐Trichloroethane: Conceptual Model Validation through Numerical Simulation
Authors: Stauffer Philip H. , Birdsell Kay H. , Witkowski Marc S. , Hopkins John K.
Published: August 2005

A conceptual model is developed to better understand vadose zone vapor‐phase diffusion within the mesas of the Pajarito Plateau at Los Alamos National Laboratory. We focus on 1,1,1‐trichloroethane (TCA) vapor transport from a liquid‐waste disposal site. The conceptual model incorporates several physical processes, including partitioning of TCA into the liquid phase, saturation‐dependent diffusion, diffusion through asphalt, and interaction with the atmosphere. Three‐dimensional numerical simulations that use the conceptual model of TCA transport are then calibrated to pore‐gas monitoring data. Adjustable parameters in the numerical simulations are limited to (i) the vapor‐phase diffusion coefficients for the different geologic units, asphalt cover, and land–atmosphere boundary layer and (ii) the fixed concentrations in the two shaft clusters. By including all of the components of the conceptual model in our numerical simulations we were able to achieve a reasonable match between the simulated plume and site data for two alternate conceptual models of asphalt, one with asphalt as a diffusive barrier and one without asphalt as a diffusive barrier. A goodness‐of‐fit analysis shows that the best‐fit simulations are highly correlated to 132 data points from 21 boreholes. The simulations demonstrate that diffusive behavior describes the general characteristics of the current subsurface vapor plume. Effective vapor‐phase diffusion coefficients used in the simulations that best fit the data suggest that barometric pumping is not contributing to diffusion in the deep vadose zone; however, it is likely that barometric pumping is occurring in fractures near the mesa edge. We conclude that asphalt is most likely acting as a barrier to diffusion at this site. The numerical simulations validate that the conceptual model developed for this study is a useful tool for analyzing TCA transport within the mesas of the Pajarito Plateau.
Surface Water–Groundwater Connection at the Los Alamos Canyon Weir Site: Part 2. Modeling of Tracer Test Results
Authors: Stauffer Philip H. , Stone William J.
Published: August 2005

Field observations of bromide transport in the unsaturated zone are used to constrain simulations that provide estimates of bulk porosity and permeability for the Cerros del Rio. The Cerros del Rio basalt is of particular interest because it underlies many of the potential waste sites at the Los Alamos National Laboratory. A highly simplified model is able to capture the general behavior of the breakthrough data. The simplifying assumption is that the basalt can be modeled as a homogeneous continuum with high permeability and low porosity. We estimate that the permeability of the bulk rock is 10−11 to 10−12 m2, whereas the porosity is estimated to lie between 0.001 and 0.01. The porosity estimates from this study are particularly useful for kilometer‐scale simulations that include flow and transport through the Cerros del Rio basalt because estimates based on other methods, such as core testing, are highly scale dependent and should not be extrapolated to larger scales. Although this model does not include the complex physics of flow in the fractured basalt, it is useful for simulations on the kilometer scale that require averaging of rock properties and optimization of computational speed. The porosity and permeability values obtained from this analysis will help to weight probability distributions used in the kilometer‐scale simulations of contaminant transport.
Solute Transport Dynamics by High‐Resolution Dye Tracer Experiments—Image Analysis and Time Moments
Authors: Persson Magnus , Haridy Sahar , Olsson Jonas , Wendt Johan
Published: August 2005

Accurate measurements of solute concentration are needed to conduct studies of solute transport process in unsaturated soil. In this paper we present a method of obtaining accurate measurements in time and space using dye infiltration and image analysis. The soil color was related to the dye concentration in the soil (Cs) using 74 small calibration samples. The overall root mean square error (RMSE) was 0.057 g dm−3, however, for Cs <0.75 g dm−3, the RMSE was only 0.032 g dm−3. Variability of the concentration estimates at the pixel scale could be reduced by using an average filter. We used the calibration relationship during four infiltration experiments in a 0.95 by 0.975 m large Plexiglas Hele‐Shaw cell to calculate dye concentration patterns. Using the first and second order time moments, the dispersivity λ was calculated for nine different artificial column widths, from 0.0014 (local‐scale) to 0.72 m (meso‐scale). The horizontally averaged λ proved to be identical for column widths from 0.0014 to 0.045 m. For larger scales, λ gradually increased. We noticed that the two experiments with higher flow (1 and 2) and the two experiments with lower flow (3 and 4) showed an almost identical variation of meso‐scale λ with depth. We concluded that above a specific critical value of θ (∼0.22 m3 m−3), solute mixing is enhanced, leading to a lower λ, and that solute transport can be described as a convective‐dispersive process. When θ is lower than this critical level, part of the porosity is deactivated and mixing between individual stream tubes decreases, which implies that transport then occurs as a stochastic‐convective process.
Improved Tension Infiltrometer for Measuring Low Fluid Flow Rates in Unsaturated Fractured Rock
Authors: Castiglione Paolo , Shouse Peter J. , Mohanty Binayak , Hudson David , van Genuchten Martinus Th.
Published: August 2005

The search for a permanent storage facility for the geological disposal of high‐level nuclear waste has motivated extensive research during the past several decades to characterize and predict fluid flow into and through unsaturated fractured rock. Tension infiltrometer experiments are extremely useful to investigate infiltration into fracture networks, but are difficult to perform using commercially available equipment developed mostly for soils. Our objective was to develop a tension infiltrometer suited for accurate measurements of infiltration into fractured rock at very low flow rates and for long equilibration times. We constructed several prototype instruments from porous stainless‐steel membrane, stainless‐steel casing, acrylic tubing, several temperature‐compensated pressure transducers, solenoid valves, and a data logger for automated control and data acquisition. An automated refill system was also developed to facilitate long unattended equilibration periods typical in infiltration experiments on unsaturated fractured rock. Results show that the improved design reduces temperature effects on the infiltration rate, allows for much longer periods of unattended operation (auto‐refill), and reduces evaporation from the infiltrometer. The estimated upper flow‐rate limit of our new infiltrometer is about 1 mm d−1, based on the conductance of the porous steel membrane (11 mm d−1). We were able to make measurements of the fluid flux as low as 10 mm yr−1 at a pressure head of about −110 cm.
Gas‐Phase Partitioning Tracer Test Method for Water Content Measurement: Evaluating Efficacy for a Range of Porous‐Medium Textures
Authors: Peng Sheng , Brusseau Mark L.
Published: August 2005

Gas‐phase partitioning tracer tests were conducted to measure water content for several porous media with different mean particle diameters and particle‐size distributions. Methane was used as the nonreactive tracer and difluoromethane was used as the water‐partitioning tracer. Water contents determined from the tracer‐test results were similar to values measured gravimetrically. These results support the utility of the gas‐phase tracer method for measuring water content in a variety of porous media.
Numerical Analysis of Flow and Transport from Trickle Sources on a Spatially Heterogeneous Hillslope
Authors: Russo David , Zaidel Jacob , Laufer Asher
Published: August 2005

The purpose of the present study was to analyze movement and spreading of water and a passive solute (chloride) on a hillslope under surface drip irrigation, taking into account the texture of the soil, the slope of the terrain, the spatial heterogeneity of the soil hydraulic properties, and water extraction by plant roots. Results of the present investigation suggest that under surface drip irrigation, the movement and spread of water and solutes are affected mostly by the soil texture and less by the terrain slope. Increasing terrain slope is shown to increase the deflection of the trajectories of the centroid of the solute mass from the vertical axis, particularly in fine‐textured soils associated with low saturated conductivity and considerable capillary forces, in which the interaction between adjacent drip line laterals may be appreciable. Transient flows originating from periodic water application and water uptake by plant roots are shown to enhance the effect of the terrain slope on water flow and solute movement, particularly in fine‐textured soils. Implications regarding the problem of sensor placement with respect to drip irrigation management are briefly discussed.
Surface Water–Groundwater Connection at the Los Alamos Canyon Weir Site: Part 1. Monitoring Site Installation and Tracer Tests
Authors: Levitt Daniel G. , Newell Dennis L. , Stone William J. , Wykoff David S.
Published: August 2005

Following the May 2000 Cerro Grande fire at Los Alamos, NM, surface water control structures were constructed near Los Alamos to mitigate the transport of contaminant‐bearing sediment toward the Rio Grande river due to increased runoff caused by the removal of vegetation by the fire. A low‐head weir was constructed in Los Alamos Canyon, 5 km to the east of Los Alamos, to capture contaminant‐bearing sediments and to allow runoff to pass downstream without significant ponding behind the weir. During construction of the weir, channel alluvium was removed and the underlying fractured basalt was exposed. To monitor any downward transport of contaminants into fractured basalt, and potentially downward to the regional groundwater, three boreholes (one vertical, and two angled) were installed for environmental monitoring. An innovative monitoring system was installed using FLUTe (Santa Fe, NM) liners for both vadose zone and perched groundwater zones. The vertical borehole intersects several perched water zones, and groundwater can be sampled from four ports. One angled borehole has an inflatable liner with sensors to measure relative water content. The second angled borehole was abandoned. Tracer tests were initiated in April 2002 and June 2003 with the application of solutions of potassium bromide and potassium iodide, respectively, onto the basin floor above the weir. The hydrogeologic characterization from drilling the boreholes, in conjunction with groundwater elevation and vadose zone moisture monitoring, and results from the tracer tests show that the subsurface hydrogeology is complex, and surface water and perched groundwater systems are in apparent close communication. Infiltration is rapid, and movement from the surface to the deepest perched zone (at a depth of 78 m) occurs within 8 to 14 d. Downward flow occurs predominantly via fracture flow.
Observations and Modeling of Deep Perched Water Beneath the Pajarito Plateau
Authors: Robinson Bruce A. , Broxton David E. , Vaniman David T.
Published: August 2005

Geologic characterization of the Pajarito Plateau, in support of environmental investigations of potential groundwater contamination at Los Alamos National Laboratory, has provided the opportunity to examine the nature and extent of deep perched groundwater in this semiarid setting. Deep perched groundwater occurs at widely dispersed locations across the Pajarito Plateau. A total of 33 perched‐zone occurrences were identified in 29 wells. The saturated thickness of perched zones is highly variable, ranging from about 1 to >122 m (>400 ft). Observations are consistent with a conceptual model of low‐permeability horizons on which infiltrating water sits. Deep perched groundwater is most often found beneath wet canyons, suggesting that in addition to perching horizons, locally high percolation rates are required to yield saturated conditions. Two conceptual models of perching systems are considered, one relatively stagnant and one more dynamic. To simulate deep perched groundwater in vadose zone flow models, a new method is developed that considers the interfaces between hydrogeologic units to be the horizons where the saturated permeability is lower than either of the units above or below the interface. A constant multiplier called the permeability reduction factor is applied at the interface between two hydrostratigraphic units to simulate the perching horizon. We demonstrate the method with two‐dimensional numerical simulations performed for Los Alamos Canyon, replicating perched saturation as observed and showing how contaminant dispersal may be enhanced in certain perched systems compared with dispersion in the underlying zone of regional saturation.
A Vadose Zone Flow and Transport Model for Los Alamos Canyon, Los Alamos, New Mexico
Authors: Robinson Bruce A. , Cole Gregory , Carey James W. , Witkowski Marc , Gable Carl W. , Lu Zhiming , Gray Robert
Published: August 2005

A vadose zone flow and transport model for Los Alamos Canyon is presented that demonstrates that a comprehensive understanding of vadose zone hydrologic processes can be obtained by integrating data from geologic, hydrologic, and site characterization sources. The complex hydrostratigraphy of the canyon is captured using geologic characterization of extensive deep‐well drilling samples, along with surface mapping. A water budget study for the surface and shallow subsurface hydrology is used to estimate spatially varying infiltration rates along the canyon. Three‐dimensional flow model results show that mesa‐top infiltration rates on the order of 1 mm yr−1, and canyon‐bottom rates several orders of magnitude higher, capture the water content profiles from available wells within the model domain. However, a range of a factor of three higher and lower than these mean values is also consistent with the data. Transient flow simulations show that episodic infiltration events can be effectively averaged in steady‐state flow modeling, but transients that last on the order of a decade or more, such as climate related or anthropogenically induced transients, significantly change the predicted water content. Modeling of tritium transport through the vadose zone indicates that even for a nonsorbing contaminant, most, but not all, of the contaminant released since in the past 40 yr should still be present in the vadose zone. The mass predicted to reach the water table is primarily in locations in the canyon where the Bandelier Tuff is not present. Available groundwater surveillance data for regional aquifer water are consistent with this result.
Comparison of the Water Balance of an Asphalt Cover and an Evapotranspiration Cover at Technical Area 49 at the Los Alamos National Laboratory
Authors: Levitt Daniel G. , Hartmann Matthew J. , Kisiel Kenneth C. , Criswell C. W. , Farley P. Dwain , Christensen Candace
Published: August 2005

Two different types of waste covers, an asphalt cap and an evapotranspiration (ET) cover, have been used to contain a contaminated site at Technical Area (TA) 49 at the Los Alamos National Laboratory (LANL). In 1961, a 2.5‐ to 20‐cm‐thick asphalt cap and gravel and clay cover was constructed to isolate contamination of surface soils associated with subcritical hydronuclear safety experiments conducted at TA‐49 between 1959 and 1961. The asphalt cap remained in place for 37 yr until 1998 when it was replaced with an ET cover. Cracks and subsidence features in the asphalt cap were periodically filled during that time. The thickness of the ET cover is 2.1 m at its center, tapering to zero thickness at its edges. The ET cover is instrumented with three neutron logging access tubes, and four time domain reflectometry (TDR) probes, and covered by a galvanized steel mesh bio‐intrusion layer. Soil moisture monitoring was conducted immediately after the removal of the asphalt cap in 1998, and continuously since 1999 within the ET cover, providing a unique comparison of the performance of these cap and cover types at a semiarid site. Soil moisture monitoring results indicate that the soils within and beneath the ET cover have been drying since its installation, and infiltration of precipitation and snowmelt has been minimized. The replacement of the asphalt cap with the ET cover has significantly decreased shallow subsurface moisture contents. With continued growth of vegetation and increased transpiration, the site should continue its return to native conditions where net infiltration and associated groundwater recharge rates are <7 mm yr−1
Conceptual Models of Vadose Zone Flow and Transport beneath the Pajarito Plateau, Los Alamos, New Mexico
Authors: Birdsell Kay H. , Newman Brent D. , Broxton David E. , Robinson Bruce A.
Published: August 2005

The Pajarito Plateau in northern New Mexico, on which the Los Alamos National Laboratory is situated, is characterized by a thick vadose zone overlying the regional aquifer of the western Espanola Basin. In this study, conceptual models of vadose zone flow and transport processes are presented and then supported through the interpretation of field data, including synthesis with numerical models. The conceptual models differentiate the rate of percolation by their location and surface hydrologic setting, including wet and dry canyons, and wet, dry, and disturbed mesas. Net infiltration beneath wet canyons is the highest, with rates on the order of a meter per year (100–1000 mm yr−1). Transport to the regional aquifer beneath the wettest canyons is likely on the order of several years to several decades, depending on the thicknesses of the various hydrostratigraphic layers. Perched water is sometimes found beneath wetter canyons and is associated with near‐surface alluvial systems and at intermediate depths along low‐permeability interfaces such as buried soils or unfractured regions of basalt flows. Percolation through the volcanic tuffs is generally considered to be via matrix‐dominated flow, whereas fracture flow may play a key role in contaminant transport through densely welded tuffs or basalt units beneath wet canyons. Infiltration beneath dry canyons and dry mesas is much slower (10 mm yr−1 or less), yielding transport times to the aquifer of hundreds to several thousands of years. However, long‐term surface disturbances at mesa‐top locations may alter infiltration rates such that at a local scale, the infiltration rates temporarily approach those of wetter canyons.
Barium and High Explosives in a Semiarid Alluvial System, Cañon de Valle, New Mexico
Authors: Reid Kevin D. , Reneau Steven L. , Newman Brent D. , Hickmott Donald D.
Published: August 2005

Concentrations and distributions of Ba, a component of the high explosive baritol, and RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine), a high explosive, were evaluated from 1996 to 2002 within a semiarid alluvial system in Cañon de Valle, New Mexico. A high explosive machining facility discharged effluent containing these chemicals to the canyon from 1951 to 1996. The connectivity between alluvial groundwater, surface water, and sediment was specifically addressed to understand the distributions and dynamics of Ba and RDX in the alluvial system. Surface water, groundwater, and sediment were characterized by conducting hydrologic measurements, geomorphic mapping, and collecting samples. Barium and RDX in sediment preferentially reside in fine‐grained deposits that represent the suspended load redeposited on floodplains following channel scour. However, RDX and Ba show markedly different behaviors in surface water and alluvial groundwater because of contrasting geochemical characteristics and transport mechanisms. Barium precipitates in sediments as barite and witherite and readily sorbs to sediment minerals. Therefore, sediment transport is an important control on its distribution in the canyon. In contrast, RDX appears to occur predominantly in the dissolved phase, behaves conservatively, and is most significant in groundwater. There is a strong correlation between RDX concentrations in water and the saturated thickness of the alluvial aquifer. During prolonged wet periods, the alluvial aquifer enlarges, causing more RDX to be mobilized within the alluvial system. Subsurface processes in the alluvial aquifer are therefore most important in controlling present RDX transport, whereas surface processes associated with floods are most important in controlling Ba transport.
Development of an Infiltration Map for the Los Alamos Area, New Mexico
Authors: Kwicklis Edward , Witkowski Marc , Birdsell Kay , Newman Brent , Walther Douglas
Published: August 2005

Using new and previously published estimates of point infiltration in upland areas and estimates of stream‐flow losses and gains along canyon bottoms, we created a map of net infiltration for the Los Alamos area, New Mexico for the pre‐Cerro Grande fire period. The point infiltration estimates are based on a combination of techniques that include the use of the Richards equation, the chloride mass‐balance method, and numerical modeling. The infiltration rates estimated with these techniques were extrapolated to uncharacterized parts of the study area using maps of environmental variables that are correlated with infiltration (such as topography, vegetation cover, and surficial geology and structure) and spatial algorithms implemented with GIS software that use the mapped variables. The map indicates that infiltration rates on mesas of the Pajarito Plateau are generally <2 mm yr−1, except near faults, where infiltration rates may be several tens to hundreds of millimeters per year. Infiltration rates at higher elevations in the Sierra de los Valles are typically >25 mm yr−1 in mixed conifer areas and >200 mm yr−1 in areas vegetated by aspen. An irregular transition zone with infiltration rates between 2 to 25 mm yr−1 exists near the western edge of the Pajarito Plateau adjacent to the Sierra de los Valles. This transition zone extends to lower elevations on the north‐facing slopes of deeply incised canyons. Canyon‐bottom infiltration rates are highly variable, ranging from several hundred millimeters per year in canyons with large watersheds that have their headwaters in the Sierra de los Valles or in canyons that receive effluent from Laboratory operations, to several millimeters per year in canyons that have their headwaters on the Pajarito Plateau but do not receive Laboratory effluent. The total net infiltration of approximately 10.6 × 106 m3 yr−1 (8600 acre‐ft yr−1) is consistent with estimates of the steady‐state groundwater discharge to perennial streams in the study area, whereas the relative rates of infiltration within the study area are consistent with the distribution of natural and anthropogenic tracers such as tritium in perched and regional groundwaters. Limitations of the study are that it does not address the effects of the Cerro Grande fire on the hydrology of the study area, nor does it completely capture the complex and sometimes incompletely documented history of Laboratory generated discharges during its 60‐yr history.
Simulation of Unsaturated Flow in Complex Fractures Using Smoothed Particle Hydrodynamics
Authors: Tartakovsky Alexandre M. , Meakin Paul
Published: August 2005

Smoothed particle hydrodynamics (SPH) models were used to simulate unsaturated flow in fractures with complex geometries. The SPH is a fully Lagrangian particle‐based method that allows the dynamics of interfaces separating fluids to be modeled without employing complex front tracking schemes. In SPH simulations, the fluid density field is represented by a superposition of weighting functions centered on particles which represent the fluids. The pressure is related to the fluid density through an equation of state, and the particles move in response to the pressure gradient. The SPH does not require the construction of grids that would otherwise introduce numerical dispersion. The model can be used to simulate complex free‐surface flow phenomenon such as invasion of wetting and nonwetting fluids into three‐dimensional fractures. These processes are a severe challenge for grid‐based methods. Surface tension was simulated by using a van der Waals equation of state and a combination of short‐range repulsive and longer‐range attractive interactions between fluid particles. The wetting behavior was simulated using similar interactions between mobile fluid particles and stationary boundary particles. The fracture geometry was generated from self‐affine fractal surfaces. The fractal model was based on a large body of experimental work, which indicates that fracture surfaces have a self‐affine fractal geometry characterized by a material independent (quasi universal) Hurst exponent of about 0.75.
Plant‐Based Plume‐Scale Mapping of Tritium Contamination in Desert Soils
Authors: Andraski B. J. , Stonestrom D. A. , Michel R. L. , Halford K. J. , Radyk J. C.
Published: August 2005

Plant‐based techniques were tested for field‐scale evaluation of tritium contamination adjacent to a low‐level radioactive waste (LLRW) facility in the Amargosa Desert, Nevada. Objectives were to (i) characterize and map the spatial variability of tritium in plant water, (ii) develop empirical relations to predict and map subsurface contamination from plant‐water concentrations, and (iii) gain insight into tritium migration pathways and processes. Plant sampling [creosote bush, Larrea tridentata (Sessé & Moc. ex DC.) Coville] required one‐fifth the time of soil water vapor sampling. Plant concentrations were spatially correlated to a separation distance of 380 m; measurement uncertainty accounted for <0.1% of the total variability in the data. Regression equations based on plant tritium explained 96 and 90% of the variation in root‐zone and sub‐root‐zone soil water vapor concentrations, respectively. The equations were combined with kriged plant‐water concentrations to map subsurface contamination. Mapping showed preferential lateral movement of tritium through a dry, coarse‐textured layer beneath the root zone, with concurrent upward movement through the root zone. Analysis of subsurface fluxes along a transect perpendicular to the LLRW facility showed that upward diffusive‐vapor transport dominates other transport modes beneath native vegetation. Downward advective‐liquid transport dominates at one endpoint of the transect, beneath a devegetated road immediately adjacent to the facility. To our knowledge, this study is the first to document large‐scale subsurface vapor‐phase tritium migration from a LLRW facility. Plant‐based methods provide a noninvasive, cost‐effective approach to mapping subsurface tritium migration in desert areas.
The Hydrogeology of Los Alamos National Laboratory: Site History and Overview of Vadose Zone and Groundwater Issues
Authors: Newman Brent D. , Robinson Bruce A.
Published: August 2005

This summary paper describes the hydrogeologic setting and site history for the Los Alamos National Laboratory (LANL), and as such, serves as an introduction to this special section in Vadose Zone Journal on the LANL site. Since 1943, LANL has operated on the Pajarito Plateau of north‐central New Mexico, performing national security research and development, particularly involving nuclear weapons design and engineering. There is an ongoing environmental characterization and remediation program as a result of the legacy of these operations. The flow and transport processes in the thick vadose zone in this semiarid region have been examined extensively at this site, and significant scientific findings have advanced our understanding and predictive abilities. This special section highlights the noteworthy field and modeling investigations conducted at LANL. The authors believe that these articles will be of benefit to the community of hydrologists working on vadose zone flow and transport by providing complex observational data sets and accompanying modeling studies to interpret the field data.
Severe Mincer Injuries of the Hand in Children in Saudi Arabia
Authors: AL-ARABI K. M. , SABET N. A.
Published: August 2005

A review of twenty-two children with a mean age of 1.9 ± 0.3 years who sustained injuries to the fingers and hand by domestic mincer machine. In each case the child inserted his hand in the machine while in motion. The pattern of injury is discussed and recommendations to avoid these mutilating injuries are made.
Dupuytren’s Disease Arising from the Abductor Digiti Minimi
Authors: BARTON N. J.
Published: August 2005

Twenty patients with Dupuytren’s disease arising from the abductor digiti minimi have been studied. The different patterns of origin, course, and termination of the diseased cord are described, and the clinical implications discussed.
Primary Flexor Tendon Repair in “No Man’s Land”
Authors: NIELSEN A. B. , JENSEN P. Ø.
Published: August 2005

Fifty-eight patients with 67 fingers with flexor tendon injuries in Bunnell’s “no man’s land” treated with primary repair were re-examined 14–84 months after surgery. Thirty-five fingers had repair of both tendons, and in thirty-two fingers the superficialis tendon was excised and only the profundus tendon was repaired. Postoperatively thirty-one fingers were treated by Kleinert’s rubber band traction, and in thirty-six fingers a dorsal plaster of Paris was applied. The functional end-result was evaluated according to the method of Buck-Gramcko. Seventy-four per cent of fingers with suture of both tendons and 47 per cent of fingers with suture of only the profundus tendon attained an excellent or good result. The fingers treated by Kleinert’s rubber band traction achieved the most favourable functional result, but many inconstant factors had influence upon this evaluation. The number of re-operations were significantly higher after repair of only the profundus tendon.
Combined Reconstruction of Volar and Radial Instability of a Thumb Metacarpo-Phalangeal Joint
Authors: BREWOOD A. F. M. , MENON T. J.
Published: August 2005

The purpose of this paper is to present a case of the combined volar and radial ligament instability of a thumb metacarpophalangeal joint secondary to trauma. A successful reconstruction of the volar capsule and the radial collateral ligament was achieved using the tendon of the extensor pollicis brevis.
Myocardial biopsy findings and gadolinium enhanced cardiovascular magnetic resonance in dilated cardiomyopathy
Authors: Zimmermann Oliver , Grebe Olaf , Merkle Nico , Nusser Thorsten , Kochs Matthias , Bienek‐Ziolkowski Magdalena , Hombach Vinzenz , Torzewski Jan
Published: August 2005

Background:

In some patients suffering from dilated cardiomyopathy (DCM) magnetic resonance imaging (MRI) shows late gadolinium enhancement with variable distribution. Myocardial biopsies in DCM reveal a chronic myocardial inflammatory process in almost 50% and myocardial persistence of adenoviral or enteroviral genome in about 15% of the patients.

Aims:

We prospectively investigated whether the pattern of late gadolinium enhancement correlates with myocardial biopsy findings.

Methods and results:

42 patients with DCM and 42 control subjects underwent contrast MRI. In the DCM group, endomyocardial biopsies were performed and evaluated for inflammation and viral genome.

None of the control subjects showed late gadolinium enhancement whereas in 29 DCM patients (69%) gadolinium enhancement was detectable (p<0.001). 21 of the DCM patients (50%) showed midwall septal enhancement, 7 patients (17%) showed a patchy distribution of hyperenhancement and 1 patient (2%) showed enhancement typical for ischemic heart disease. In myocardial biopsy analysis, 2 patients (5%) showed persistence of viral genome, 18 patients (43%) showed inflammation and in 22 patients (52%) neither virus nor inflammation was detected. The pattern of late gadolinium enhancement and myocardial biopsy findings were not significantly correlated (p=0.854).

Conclusion:

MRI as a non‐invasive technique cannot replace myocardial biopsy for the differential diagnosis of DCM.
Psychoeducation: improving outcomes in bipolar disorder
Authors: Colom Francesc , Lam Dominic
Published: August 2005

Background

A relevant paradigm shift in the treatment of bipolar disorder started a few years ago; crucial findings on the usefulness of psychological interventions clearly support switching from an exclusively pharmacological therapeutic approach to a combined yet hierarchical model in which pharmacotherapy plays a central role, but psychological interventions may help cover the gap that exists between theoretical efficacy and “real world” effectiveness. Hereby we review the efficacy of several adjunctive psychotherapies in the maintenance treatment of bipolar patients.

Methods

A systematic review of the literature on the issue was performed, using MEDLINE and CURRENT CONTENTS databases. “Bipolar”, “Psychotherapy”, “Psychoeducation”, “Cognitive-behavioral” and “Relapse prevention” were entered as keywords.

Results

Psychological treatments specifically designed for relapse prevention in bipolar affective disorder are useful tools in conjunction with mood stabilizers. Most of the psychotherapy studies recently published report positive results on maintenance as an add-on treatment, and efficacy on the treatment of depressive episodes. Interestingly, several groups from all over the world reported similar positive results and reached very similar conclusions; almost every intervention tested contains important psychoeducative elements including both compliance enhancement and early identification of prodromal signs — stressing the importance of life-style regularity — and exploring patients' health beliefs and illness-awareness.

Conclusions

The usefulness of psychotherapy for improving treatment adherence and clinical outcome of bipolar patients is nowadays unquestionable, and future treatment guidelines should promote its regular use amongst clinicians. As clinicians, it is our major duty, to offer the best treatment available to our patients and this includes both evidence-based psychoeducation programs and newer pharmacological agents.
SNX9 as an adaptor for linking synaptojanin‐1 to the Cdc42 effector ACK1
Authors: Yeow-Fong Lee , Lim Louis , Manser Ed
Published: August 2005

Sorting nexin 9 (SNX9, also referred to as SH3PX1) is a binding partner for the non‐receptor and Cdc42‐associated kinase (ACK) in Drosophila and mammals. ACK1 is known to bind clathrin and influence EGF receptor endocytosis. SNX9 comprises an N‐terminal Src homology domain 3 (SH3), a central PHOX homology (PX) domain, and a carboxyl‐terminal coiled‐coil region. In order to investigate SNX9 further we have made use of a novel in vivo biotinylation system to label various GST‐SH3 domains and perform blot overlays, thereby identifying synaptojanin‐1 as a partner for SNX9. Biotinylated SH3 domains were also used for specific identification of target proline‐rich sequences in synaptojanin and ACK1 on synthetic peptides arrays. Direct assessment of SH3 binding efficiencies at different positions within the extensive proline‐rich regions of these proteins were thus determined. While SNX9 targets a number of sequences within the proline‐rich regions of synaptojanin, a single site was identified in human ACK1. By testing the association of various truncations of ACK1 with SNX9 we confirmed the dominant SNX9 binding domain in human ACK1 (residues 920–955). In the presence of SNX9 we find that synaptojanin is able to colocalize with distinct ACK1 containing vesicles, indicating that this tyrosine kinase is linked to many components involved in vesicle dynamics including clathrin, AP2 and synaptojanin‐1.
The tumor suppressor Scrib selectively interacts with specific members of the zyxin family of proteins
Authors: Petit Marleen M.R. , Crombez Koen R.M.O. , Vervenne Hilke B.V.K. , Weyns Nancy , Van de Ven Wim J.M.
Published: August 2005

The zyxin family of proteins consists of five members, ajuba, LIMD1, LPP, TRIP6 and zyxin, which localize at cell adhesion sites and shuttle to the nucleus. Previously, we established that LPP interacts with the tumor suppressor Scrib, a member of the leucine‐rich repeat and PDZ (LAP) family of proteins. Here, we demonstrate that Scrib also interacts with TRIP6, but not with zyxin, ajuba, or LIMD1. We show that TRIP6 directly binds to the third PDZ domain of Scrib via its carboxy‐terminus. Both proteins localize in cell–cell contacts but are not responsible to target each other to these structures. In the course of our experiments, we also characterized the nuclear export signal of human TRIP6, and show that LIMD1 is localized in focal adhesions. The binding between two of zyxin's family members and Scrib links Scrib to a communication pathway between cell–cell contacts and the nucleus, and implicates these zyxin family members in Scrib‐associated functions.
The flow of Atlantic water to the North Icelandic Shelf and its relation to the drift of cod larvae
Authors: Jónsson Steingrímur , Valdimarsson Héðinn
Published: August 2005

The amount of Atlantic water (AW) present on the shelf north of Iceland is highly variable and influences the local biological productivity. Estimates of the volume and heat transports of AW to the North Icelandic Shelf between 1994 and 2000 are presented here. On average, 66% of the eastward flow on the Hornbanki section consists of AW with a transport of AW of approximately 0.75 Sv. The associated heat transport is 19 TW. There are large interannual variations in the transports, from over 1 Sv in the summers of 1997, 1999, and 2000 to almost no AW transport in February/March 1995. The seasonal variation in the transport has an amplitude of 0.2 Sv with a minimum in February/March and maximum during late spring and summer. Larval cod are carried by this flow from the main spawning grounds south of Iceland to the nursery grounds on the North Icelandic Shelf. The increasing abundance and the better condition of cod larvae after 1997 are related to the increase of the AW inflow then.
Three-dimensional simulation on current-density distribution in flip-chip solder joints under electric current stressing
Authors: Shao T. L. , Liang S. W. , Lin T. C. , Chen Chih
Published: August 2005

Three-dimensional simulations on current-density distribution in solder joints under electric current stressing were carried out by finite element method. Five underbump metallization (UBM) structures were simulated, including Ti∕Cr–Cu∕Cu thin-film UBM, Al∕Ni(V)∕Cu thin-film UBM, Cu thick-film UBM, Ni thick-film UBM, and Cu∕Ni thick-film UBM. The maximum current density inside the solder occurs in the vicinity of the entrance of the Al trace into the solder joint, while there is no obvious current crowding effect in the substrate side of the joint. The crowding ratio, which is defined as the maximum current density inside the solder divided by the average value in the UBM opening, is as high as 24.7 for the solder with the Ti∕Cr–Cu∕Cu UBM. However, it decreases to 23.4, 13.5, 8.7, and 7.2 for the rest of the UBM structures, respectively. Solder joints with thick UBMs were found to have a better ability to relieve the current crowding effect. The simulation results are in reasonable agreement with limited published data. The solder joints with higher current crowding ratios have a shorter electromigration failure time.
Field emission from coated nanowires
Authors: Marinov T. , Buldum A. , Clemons C. B. , Kreider K. L. , Young G. W. , Hariharan S. I.
Published: August 2005

This work investigates radial field emission from an Al-coated nanowire due to a time harmonic incident electromagnetic field. An analytical expression for the electric field inside and outside a smooth nanowire is derived. Through the boundary perturbation technique, this expression is corrected to include the effects of roughness of the nanowire surface. The corrected electric field is used to calculate the potential energy of the electromagnetic field in order to estimate the resulting current density. The Wentzel-Krammers-Brillouin approximation is employed in order to estimate the tunneling probability of the electrons in the metal due to the external electromagnetic potential. For the field-emission calculations, the free-electron model is invoked. The results indicate that at sufficiently low frequencies, the perturbative corrections do not influence the critical conditions for emission or the current density.
Vanishing of the negative anode sheath in a Hall thruster
Authors: Ahedo E. , Rus J.
Published: August 2005

The transition on a Hall thruster discharge from negative to zero anode sheaths is studied with a macroscopic, stationary model. Since electron drift velocities become of the order of the thermal velocity, inertial effects on electrons must be included in the model. For thrusters with the Hall parameter still large at the anode, these effects appear only in a thin region and bound the electron azimuthal velocity at the anode to values of the order of the thermal velocity. The no-sheath regime is reached when the discharge voltage is decreased and corresponds to a small and nonmonotonic portion of the voltage-current curve. Possible connections of this behavior with experimental results are suggested. Modifications on the discharge characteristics at the regime transition are analyzed. Energy losses at the lateral walls decrease with the discharge voltage, due to the changes on the temperature profile, whereas energy losses at the anode increase only moderately. The thrust efficiency presents a maximum within the negative-sheath regime.
Photoluminescence and electroluminescence of size-controlled silicon nanocrystallites embedded in SiO2 thin films
Authors: Jambois O. , Rinnert H. , Devaux X. , Vergnat M.
Published: August 2005

Silicon nanocrystallites (nc-Si) were obtained by thermal annealing treatments of SiO∕SiO2 multilayers, prepared by evaporation. The nc-Si size was controlled by the SiO thickness. In this study the SiO2 thickness was maintained at 5nm and the SiO thickness was varied from 2to6nm. The film’s microstructure was studied by transmission electron microscopy. A strong photoluminescence was obtained in the visible range which corresponds to the radiative recombination of electron-hole pairs in the nc-Si. The electroluminescence signal is weaker and broader than the photoluminescence one. A model taking into account SiO2 defects and nc-Si is proposed to explain the electroluminescence results.
Influence of electrode, buffer gas and control gear on metal halide lamp performance
Authors: Lamouri A , Naruka A , Sulcs J , Varanasi C V , Brumleve T R
Published: August 2005

In this paper the influence of electrode composition, buffer gas fill pressure and control gear on the performance of metal halide lamps is investigated. It is shown that pure tungsten electrodes improve lumen maintenance and reduce voltage rise over lamp life. An optimum buffer gas fill pressure condition is discovered which allows for reduced electrode erosion during lamp starting as well as under normal operating conditions. Use of electronic control gear is shown to improve the performance of metal halide lamps.