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Approximately 190 kg of 2 μm-diameter zero-valent iron (ZVI) particles were injected into a test zone in the top 2 m of an unconfined aquifer within a trichloroethene (TCE) source area. A shear-thinning fluid was used to enhance ZVI delivery in the subsurface to a radial distance of up to 4 m from a single injection well. The ZVI particles were mixed in-line with the injection water, shear-thinning fluid, and a low concentration of surfactant. ZVI was observed at each of the seven monitoring wells within the targeted radius of influence during injection. Additionally, all wells within the targeted zone showed low TCE concentrations and primarily dechlorination products present 44 d after injection. These results suggest that ZVI can be directly injected into an aquifer with shear-thinning fluids to induce dechlorination and extends the applicability of ZVI to situations where other emplacement methods may not be viable. [ABSTRACT FROM AUTHOR]

Kromhout D (Division of Public Health Research, National Institute of Public Health and Environmental Protection, PO Box 1, 3720 BA Bilthoven, The Netherlands), Nedeljkovic S I, Grujic M Z, Ostojic M C, Keys A, Menotti A, Katan M B, van Oostrom M A and Bloemberg B P M. Changes in major risk factors for cardiovascular diseases over 25 years in the Serbian cohorts of the Seven Countries Study. 1994; 23: 5–11. The Serbian cohorts of the Seven Countries Study were examined four times during a 25-year period. Large changes were observed in average serum cholesterol, blood pressure and the prevalence of smoking in these ageing cohorts. Comparison of men of the same age strata e.g. men aged 50–59 examined at baseline and after 10 years of follow-up and of men aged 65–69 examined after 10 and 25 years of follow-up showed that serum cholesterol increased by about 45% in Zrenjanin, 35% in Velika Krsna and 15% in Belgrade over the last 25 years. Systolic blood pressure increased by 9% in Zrenjanin and 7% in Velika Krsna. No significant increase in systolic blood pressure was observed in Belgrade. There was no major secular trend in smoking and the changes observed during 25 years were mainly due to ageing. No major change was observed in body mass index. The increases in serum cholesterol and blood pressure observed in the Serbian cohorts during the last 25 years are compatibile with the increase in cardiovascular disease mortality observed in Yugoslavian men aged 30–69 during the period 1970–1984. [ABSTRACT FROM PUBLISHER]

A method termed vapor-phase tomography has recently been proposed to characterize the distribution of volatile organic contaminant mass in vadose-zone source areas, and to measure associated three-dimensional distributions of local contaminant mass discharge. The method is based on measuring the spatial variability of vapor flux, and thus inherent to its effectiveness is the premise that the magnitudes and temporal variability of vapor concentrations measured at different monitoring points within the interrogated area will be a function of the geospatial positions of the points relative to the source location. A series of flow-cell experiments was conducted to evaluate this premise. A well-defined source zone was created by injection and extraction of a non-reactive gas (SF 6 ). Spatial and temporal concentration distributions obtained from the tests were compared to simulations produced with a mathematical model describing advective and diffusive transport. Tests were conducted to characterize both areal and vertical components of the application. Decreases in concentration over time were observed for monitoring points located on the opposite side of the source zone from the local-extraction point, whereas increases were observed for monitoring points located between the local-extraction point and the source zone. The results illustrate that comparison of temporal concentration profiles obtained at various monitoring points gives a general indication of the source location with respect to the extraction and monitoring points. [ABSTRACT FROM AUTHOR]

Light-sheet microscopy has made possible the 3D imaging of both fixed and live biological tissue, with samples as large as the entire mouse brain. However, segmentation and quantification of that data remains a time-consuming manual undertaking. Machine learning methods promise the possibility of automating this process. This study seeks to advance the performance of prior models through optimizing transfer learning. We fine-tuned the existing TrailMap model using expert-labeled data from noradrenergic axonal structures in the mouse brain. By changing the cross-entropy weights and using augmentation, we demonstrate a generally improved adjusted F1-score over using the originally trained TrailMap model within our test datasets., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Light-sheet microscopy has made possible the 3D imaging of both fixed and live biological tissue, with samples as large as the entire mouse brain. However, segmentation and quantification of that data remains a time-consuming manual undertaking. Machine learning methods promise the possibility of automating this process. This study seeks to advance the performance of prior models through optimizing transfer learning. We fine-tuned the existing TrailMap model using expert-labeled data from noradrenergic axonal structures in the mouse brain. By fine-tuning the final two layers of the neural network at a lower learning rate of the TrailMap model, we demonstrate an improved recall and an occasionally improved adjusted F1-score within our test dataset over using the originally trained TrailMap model.

To advance our ability to predict impacts of the protein scaffold on catalysis, robust classification schemes to define features of proteins that will influence reactivity are needed. One of these features is a protein's metal-binding ability, as metals are critical to catalytic conversion by metalloenzymes. As a step toward realizing this goal, we used convolutional neural networks (CNNs) to enable the classification of a metal cofactor binding pocket within a protein scaffold. CNNs enable images to be classified based on multiple levels of detail in the image, from edges and corners to entire objects, and can provide rapid classification. First, six CNN models were fine-tuned to classify the 20 standard amino acids to choose a performant model for amino acid classification. This model was then trained in two parallel efforts: to classify a 2D image of the environment within a given radius of the central metal binding site, either an Fe ion or a [2Fe-2S] cofactor, with the metal visible (effort 1) or the metal hidden (effort 2). We further used two sub-classifications of the [2Fe-2S] cofactor: (1) a standard [2Fe-2S] cofactor and (2) a Rieske [2Fe-2S] cofactor. The accuracy for the model correctly identifying all three defined features was >95%, despite our perception of the increased challenge of the metalloenzyme identification. This demonstrates that machine learning methodology to classify and distinguish similar metal-binding sites, even in the absence of a visible cofactor, is indeed possible and offers an additional tool for metal-binding site identification in proteins., (© 2023 Battelle Memorial Institute. Protein Science published by Wiley Periodicals LLC on behalf of The Protein Society.)

Artificial intelligence (AI) promises to reshape scientific inquiry and enable breakthrough discoveries in areas such as energy storage, quantum computing, and biomedicine. Scanning transmission electron microscopy (STEM), a cornerstone of the study of chemical and materials systems, stands to benefit greatly from AI-driven automation. However, present barriers to low-level instrument control, as well as generalizable and interpretable feature detection, make truly automated microscopy impractical. Here, we discuss the design of a closed-loop instrument control platform guided by emerging sparse data analytics. We hypothesize that a centralized controller, informed by machine learning combining limited a priori knowledge and task-based discrimination, could drive on-the-fly experimental decision-making. This platform may unlock practical, automated analysis of a variety of material features, enabling new high-throughput and statistical studies.

Background: Spatiotemporal perturbation of signaling pathways in vivo remains challenging and requires precise transgenic control of signaling effectors. Fibroblast growth factor (FGF) signaling guides multiple developmental processes, including body axis formation and cell fate patterning. In zebrafish, mutants and chemical perturbations affecting FGF signaling have uncovered key developmental processes; however, these approaches cause embryo-wide perturbations, rendering assessment of cell-autonomous vs. non-autonomous requirements for FGF signaling in individual processes difficult., Results: Here, we created the novel transgenic line fgfr1-dn-cargo, encoding dominant-negative Fgfr1a with fluorescent tag under combined Cre/lox and heatshock control to perturb FGF signaling spatiotemporally. Validating efficient perturbation of FGF signaling by fgfr1-dn-cargo primed with ubiquitous CreERT2, we established that primed, heatshock-induced fgfr1-dn-cargo behaves similarly to pulsed treatment with the FGFR inhibitor SU5402. Priming fgfr1-dn-cargo with CreERT2 in the lateral plate mesoderm triggered selective cardiac and pectoral fin phenotypes without drastic impact on overall embryo patterning. Harnessing lateral plate mesoderm-specific FGF inhibition, we recapitulated the cell-autonomous and temporal requirement for FGF signaling in pectoral fin outgrowth, as previously inferred from pan-embryonic FGF inhibition., Conclusions: As a paradigm for rapid Cre/lox-mediated signaling perturbations, our results establish fgfr1-dn-cargo as a genetic tool to define the spatiotemporal requirements for FGF signaling in zebrafish. Developmental Dynamics 247:1146-1159, 2018. © 2018 Wiley Periodicals, Inc., (© 2018 Wiley Periodicals, Inc.)

Two-phase immiscible displacement in porous media is controlled by capillary and viscous forces when gravitational effects are negligible. The relative importance of these forces is quantified through the dimensionless capillary number Ca and the viscosity ratio M between fluid phases. When the displacing fluid is Newtonian, the effects of Ca and M on the displacement patterns can be evaluated independently. However, when the injecting fluids exhibit shear-thinning viscosity behaviour the values of M and Ca are interdependent. Under these conditions, the effects on phase entrapment and the general displacement dynamics cannot be dissociated. In the particular case of shear-thinning aqueous polymer solutions, the degree of interdependence between M and Ca is determined by the polymer concentration. In this work, two-phase immiscible displacement experiments were performed in micromodels, using shear-thinning aqueous polymer solutions as displacing fluids, to investigate the effect of polymer concentration on the relationship between Ca and M, the recovery efficiency, and the size distribution of the trapped non-wetting fluid. Our results show that the differences in terms of magnitude and distribution of the trapped phase are related to the polymer concentration which influences the values of Ca and M., (Copyright © 2016 Elsevier Inc. All rights reserved.)

For sites with a contaminant source located in the vadose zone, the nature and extent of groundwater contaminant plumes are a function of the contaminant flux from the vadose zone to groundwater. Especially for thick vadose zones, transport may be relatively slow making it difficult to directly measure contaminant flux. An integrated assessment approach, supported by site characterization and monitoring data, is presented to explain current vadose zone contaminant distributions and to estimate future contaminant flux to groundwater in support of remediation decisions. The U.S. Department of Energy Hanford Site (WA, USA) SX Tank Farm was used as a case study because of a large existing contaminant inventory in its deep vadose zone, the presence of a limited-extent groundwater plume, and the relatively large amount of available data for the site. A predictive quantitative analysis was applied to refine a baseline conceptual model through the completion of a series of targeted simulations. The analysis revealed that site recharge is the most important flux-controlling process for future contaminant flux. Tank leak characteristics and subsurface heterogeneities appear to have a limited effect on long-term contaminant flux into groundwater. The occurrence of the current technetium-99 groundwater plume was explained by taking into account a considerable historical water-line leak adjacent to one of the tanks. The analysis further indicates that the vast majority of technetium-99 is expected to migrate into the groundwater during the next century. The approach provides a template for use in evaluating contaminant flux to groundwater using existing site data and has elements that are relevant to other disposal sites with a thick vadose zone., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The risk of acute cardiovascular events is highest during morning hours, and platelet activity peaks during morning hours. The effect of timing of aspirin intake on circadian rhythm and morning peak of platelet reactivity is not known. It was our objective to evaluate the effect of timing of aspirin intake on circadian rhythm and morning peak of platelet reactivity. A randomised open-label cross-over trial in healthy subjects (n=14) was conducted. Participants used acetylsalicylic acid (80 mg) on awakening or at bedtime for two periods of two weeks, separated by a four-week wash-out period. At the end of both periods blood was drawn every 3 hours to measure COX-1-dependent (VerifyNow-Aspirin; Serum Thromboxane B2 [STxB2]) and COX-1-independent (flow cytometry surface CD62p expression; microaggregation) platelet activity. VerifyNow platelet reactivity over the whole day was similar with intake on awakening and at bedtime (mean difference: -9 [95 % confidence interval (CI) -21 to 4]). However, the morning increase in COX-1-dependent platelet activity was reduced by intake of aspirin at bedtime compared with on awakening (mean difference VerifyNow: -23 Aspirin Reaction Units [CI -50 to 4]; STxB2: -1.7 ng/ml [CI -2.7 to -0.8]). COX-1-independent assays were not affected by aspirin intake or its timing. Low-dose aspirin taken at bedtime compared with intake on awakening reduces COX-1-dependent platelet reactivity during morning hours in healthy subjects. Future clinical trials are required to investigate whether simply switching to aspirin intake at bedtime reduces the risk of cardiovascular events during the high risk morning hours.

Carbon sequestration in saline aquifers involves displacing brine from the pore space by supercritical CO(2) (scCO(2)). The displacement process is considered unstable due to the unfavorable viscosity ratio between the invading scCO(2) and the resident brine. The mechanisms that affect scCO(2)-water displacement under reservoir conditions (41 °C, 9 MPa) were investigated in a homogeneous micromodel. A large range of injection rates, expressed as the dimensionless capillary number (Ca), was studied in two sets of experiments: discontinuous-rate injection, where the micromodel was saturated with water before each injection rate was imposed, and continuous-rate injection, where the rate was increased after quasi-steady conditions were reached for a certain rate. For the discontinuous-rate experiments, capillary fingering and viscous fingering are the dominant mechanisms for low (logCa ≤ -6.61) and high injection rates (logCa ≥ -5.21), respectively. Crossover from capillary to viscous fingering was observed for logCa = -5.91 to -5.21, resulting in a large decrease in scCO(2) saturation. The discontinuous-rate experimental results confirmed the decrease in nonwetting fluid saturation during crossover from capillary to viscous fingering predicted by numerical simulations by Lenormand et al. (J. Fluid Mech.1988, 189, 165-187). Capillary fingering was the dominant mechanism for all injection rates in the continuous-rate experiment, resulting in monotonic increase in scCO(2) saturation.

The use of air-water, θ(wa), or air-liquid contact angles is customary in surface science, while oil-water contact angles, θ(ow), are of paramount importance in subsurface multiphase flow phenomena including petroleum recovery, nonaqueous phase liquid fate and transport, and geological carbon sequestration. In this paper we determine both the air-water and oil-water contact angles of silica surfaces modified with a diverse selection of silanes, using hexadecane as the oil. The silanes included alkylsilanes, alkylarylsilanes, and silanes with alkyl or aryl groups that are functionalized with heteroatoms such as N, O, and S. These silanes yielded surfaces with wettabilities from water wet to oil wet, including specific silanized surfaces functionalized with heteroatoms that yield intermediate wet surfaces. The oil-water contact angles for clean and silanized surfaces, excluding one partially fluorinated surface, correlate linearly with air-water contact angles with a slope of 1.41 (R = 0.981, n = 13). These data were used to examine a previously untested theoretical treatment relating air-water and oil-water contact angles in terms of fluid interfacial energies. Plotting the cosines of these contact angles against one another, we obtain the relationship cos θ(wa) = 0.667 cos θ(ow) + 0.384 (R = 0.981, n = 13), intercepting cos θ(ow) = -1 at -0.284, which is in excellent agreement with the linear assumption of the theory. The theoretical slope, based on the fluid interfacial tensions σ(wa), σ(ow), and σ(oa), is 0.67. We also demonstrate how silanes can be used to alter the wettability of the interior of a pore network micromodel device constructed in silicon/silica with a glass cover plate. Such micromodels are used to study multiphase flow phenomena. The contact angle of the resulting interior was determined in situ. An intermediate wet micromodel gave a contact angle in excellent agreement with that obtained on an open planar silica surface using the same silane.

Soil vapor extraction (SVE) is typically effective for removal of volatile contaminants from higher-permeability portions of the vadose zone. However, contamination in lower-permeability zones can persist due to mass transfer processes that limit the removal effectiveness. After SVE has been operated for a period of time and the remaining contamination is primarily located in lower-permeability zones, the remedy performance needs to be evaluated to determine whether the SVE system should be optimized, terminated, or transitioned to another technology to replace or augment SVE. Numerical modeling of vapor-phase contaminant transport was used to investigate the correlation between measured vapor-phase mass discharge, MF(r), from a persistent, vadose-zone contaminant source and the resulting groundwater contaminant concentrations. This relationship was shown to be linear, and was used to directly assess SVE remediation progress over time and to determine the level of remediation in the vadose zone necessary to protect groundwater. Although site properties and source characteristics must be specified to establish a unique relation between MF(r) and the groundwater contaminant concentration, this correlation provides insight into SVE performance and support for decisions to optimize or terminate the SVE operation or to transition to another type of treatment., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Permeability contrasts exist in multilayer geological formations under consideration for carbon sequestration. To improve our understanding of heterogeneous pore-scale displacements, liquid CO(2) (LCO(2))-water displacement was evaluated in a pore network micromodel with two distinct permeability zones. Due to the low viscosity ratio (logM = -1.1), unstable displacement occurred at all injection rates over 2 orders of magnitude. LCO(2) displaced water only in the high permeability zone at low injection rates with the mechanism shifting from capillary fingering to viscous fingering with increasing flow rate. At high injection rates, LCO(2) displaced water in the low permeability zone with capillary fingering as the dominant mechanism. LCO(2) saturation (S(LCO2)) as a function of injection rate was quantified using fluorescent microscopy. In all experiments, more than 50% of LCO(2) resided in the active flowpaths, and this fraction increased as displacement transitioned from capillary to viscous fingering. A continuum-scale two-phase flow model with independently determined fluid and hydraulic parameters was used to predict S(LCO2) in the dual-permeability field. Agreement with the micromodel experiments was obtained for low injection rates. However, the numerical model does not account for the unstable viscous fingering processes observed experimentally at higher rates and hence overestimated S(LCO2).

A major issue with in situ subsurface remediation is the ability to achieve an even spatial distribution of remedial amendments to the contamination zones in an aquifer or vadose zone. Amendment delivery to the aquifer using shear thinning fluid and to the vadose zone using aqueous foam has the potential to enhance the distribution. 2-D saturated flow cell experiments were conducted to evaluate the enhanced fluid sweeping over heterogeneous system, improved contaminant removal, and extended amendment presence in low-permeability zones achieved by shear thinning fluid delivery. Unsaturated column and flow cell experiments were conducted to investigate the improvement on contaminant mobilization mitigation, amendment distribution, and lateral delivery implemented by foam delivery. It was demonstrated that the shear thinning fluid injection enhanced the fluid sweeping and increased the delivery of remedial amendment into low-perm zones. The presence of amendment distributed by the shear thinning fluid in the low-permeability zones was increased. Foam delivery was shown to mitigate the mobilization of highly mobile contaminant from sediments. It also achieved more uniform amendment distribution in a heterogeneous unsaturated system, and demonstrated remarkable increasing in lateral distribution of the injected liquid compared to direct liquid injection., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A microfluidic pore structure etched into a silicon wafer was used as a two-dimensional model subsurface sedimentary system (i.e., micromodel) to study mineral precipitation and permeability reduction relevant to groundwater remediation and geological carbon sequestration. Solutions containing CaCl(2) and Na(2)CO(3) at four different saturation states (Ω = [Ca(2+)][CO(3)(2-)]/K(spCaCO(3))) were introduced through two separate inlets, and they mixed by diffusion transverse to the main flow direction along the center of the micromodel resulting in CaCO(3) precipitation. Precipitation rates increased and the total amount of precipitates decreased with increasing saturation state, and only vaterite and calcite crystals were formed (no aragonite). The relative amount of vaterite increased from 80% at the lowest saturation state (Ω(v) = 2.8 for vaterite) to 95% at the highest saturation state (Ω(v) = 4.5). Fluorescent tracer tests conducted before and after CaCO(3) precipitation indicate that pore spaces were occluded by CaCO(3) precipitates along the transverse mixing zone, thus substantially reducing porosity and permeability, and potentially limiting transformation from vaterite to the more stable calcite. The results suggest that mineral precipitation along plume margins can decrease both reactant mixing during groundwater remediation, and injection and storage efficiency during CO(2) sequestration.

Contaminant hydrogeological processes occurring in porous media are typically not amenable to direct observation. As a result, indirect measurements (e.g., contaminant breakthrough at a fixed location) are often used to infer processes occurring at different scales, locations, or times. To overcome this limitation, non-invasive imaging methods are increasingly being used in contaminant hydrogeology research. Four of the most common methods, and the subjects of this review, are optical imaging using UV or visible light, dual-energy gamma radiation, X-ray microtomography, and magnetic resonance imaging (MRI). Non-invasive imaging techniques have provided valuable insights into a variety of complex systems and processes, including porous media characterization, multiphase fluid distribution, fluid flow, solute transport and mixing, colloidal transport and deposition, and reactions. In this paper we review the theory underlying these methods, applications of these methods to contaminant hydrogeology research, and methods' advantages and disadvantages. As expected, there is no perfect method or tool for non-invasive imaging. However, optical methods generally present the least expensive and easiest options for imaging fluid distribution, solute and fluid flow, colloid transport, and reactions in artificial two-dimensional (2D) porous media. Gamma radiation methods present the best opportunity for characterization of fluid distributions in 2D at the Darcy scale. X-ray methods present the highest resolution and flexibility for three-dimensional (3D) natural porous media characterization, and 3D characterization of fluid distributions in natural porous media. And MRI presents the best option for 3D characterization of fluid distribution, fluid flow, colloid transport, and reaction in artificial porous media. Obvious deficiencies ripe for method development are the ability to image transient processes such as fluid flow and colloid transport in natural porous media in three dimensions, the ability to image many reactions of environmental interest in artificial and natural porous media, and the ability to image selected processes over a range of scales in artificial and natural porous media., (2010. Published by Elsevier B.V.)

Knowledge of IFT values for chemical mixtures helps guide the design and analysis of various processes, including NAPL remediation with surfactants or alcohol flushing, enhanced oil recovery, and chemical separation technologies, yet available literature values are sparse. A comprehensive comparison of thermodynamic and empirical models for estimating interfacial tension (IFT) of organic chemical mixtures with water is conducted, mainly focusing on chlorinated organic compounds for 14 ternary, three quaternary, and one quinary systems. Emphasis is placed on novel results for systems with three and four organic chemical compounds, and for systems with composite organic compounds like lard oil and mineral oil. Seven models are evaluated: the ideal and nonideal monolayer models (MLID and MLNID), the ideal and nonideal mutual solubility models (MSID and MSNID), an empirical model for ternary systems (EM), a linear mixing model based on mole fractions (LMMM), and a newly developed linear mixing model based on volume fractions of organic mixtures (LMMV) for higher order systems. The two ideal models (MLID and MSID) fit ternary systems of chlorinated organic compounds without surface active compounds relatively well. However, both ideal models did not perform well for the mixtures containing a surface active compound. However, for these systems, both the MLNID and MSNID models matched the IFT data well. It is shown that the MLNID model with a surface coverage value (0.00341 mmol/m2) obtained in this study can practically be used for chlorinated organic compounds. The LMMM results in poorer estimates of the IFT as the difference in IFT values of individual organic compounds in a mixture increases. The EM, with two fitting parameters, provided accurate results for all 14 ternarysystems including composite organic compounds. The new LMMV method for quaternary and higher component systems was successfully tested. This study shows that the LMMV may be able to be used for higher component systems and it can be easily incorporated into compositional multiphase flow models using only parameters from ternary systems.

The purpose of this work is to identify the mechanisms that govern the removal of carbon tetrachloride (CT) during soil vapor extraction (SVE) by comparing numerical and analytical model simulations with a detailed data set from a well-defined intermediate-scale flow cell experiment. The flow cell was packed with a fine-grained sand layer embedded in a coarse-grained sand matrix. A total of 499 mL CT was injected at the top of the flow cell and allowed to redistribute in the variably saturated system. A dual-energy gamma radiation system was used to determine the initial NAPL saturation profile in the fine-grained sand layer. Gas concentrations at the outlet of the flow cell and 15 sampling ports inside the flow cell were measured during subsequent CT removal using SVE. Results show that CT mass was removed quickly in coarse-grained sand, followed by a slow removal from the fine-grained sand layer. Consequently, effluent gas concentrations decreased quickly at first, and then started to decrease gradually, resulting in long-term tailing. The long-term tailing was mainly due to diffusion from the fine-grained sand layer to the coarse-grained sand zone. An analytical solution for a one-dimensional advection and a first-order mass transfer model matched the tailing well with two fitting parameters. Given detailed knowledge of the permeability field and initial CT distribution, we were also able to predict the effluent concentration tailing and gas concentration profiles at sampling ports using a numerical simulator assuming equilibrium CT evaporation. The numerical model predictions were accurate within the uncertainty of independently measured or literature derived parameters. This study demonstrates that proper numerical modeling of CT removal through SVE can be achieved using equilibrium evaporation of NAPL if detailed fine-scale knowledge of the CT distribution and physical heterogeneity is incorporated into the model. However, CT removal could also be fit by a first-order mass transfer analytical model, potentially leading to an erroneous conclusion that the long-term tailing in the experiment was kinetically controlled due to rate-limited NAPL evaporation.

An existing multiphase flow simulator was modified in order to determine the effects of four mechanisms on NAPL mass removal in a strongly layered heterogeneous vadose zone during soil vapor extraction (SVE): a) NAPL flow, b) diffusion and dispersion from low permeability zones, c) slow desorption from sediment grains, and d) rate-limited dissolution of trapped NAPL. The impacts of water and NAPL saturation distribution, NAPL-type (i.e., free, residual, or trapped) distribution, and spatial heterogeneity of the permeability field on these mechanisms were evaluated. Two different initial source zone architectures (one with and one without trapped NAPL) were considered and these architectures were used to evaluate seven different SVE scenarios. For all runs, slow diffusion from low permeability zones that gas flow bypassed was a dominant factor for diminished SVE effectiveness at later times. This effect was more significant at high water saturation due to the decrease of gas-phase relative permeability. Transverse dispersion contributed to fast NAPL mass removal from the low permeability layer in both source zone architectures, but longitudinal dispersion did not affect overall mass removal time. Both slow desorption from sediment grains and rate-limited mass transfer from trapped NAPL only marginally affected removal times. However, mass transfer from trapped NAPL did affect mass removal at later time, as well as the NAPL distribution. NAPL flow from low to high permeability zones contributed to faster mass removal from the low permeability layer, and this effect increased when water infiltration was eliminated. These simulations indicate that if trapped NAPL exists in heterogeneous porous media, mass transfer can be improved by delivering gas directly to zones with trapped NAPL and by lowering the water content, which increases the gas relative permeability and changes trapped NAPL to free NAPL.

The nonaqueous-phase liquid (NAPL)-water interfacial area is an important parameter which influences the rate of NAPL dissolution in porous media. The aim of this study was to generate a set of baseline data for specific interfacial area for a two-phase-entrapped NAPL-water system in well-characterized porous media and subsequently use these data to evaluate two current theoretical models. The first model tested distributes entrapped NAPL over the pore classes based on Land's algorithm and assumes the resulting blobs to be spherical. The other model is thermodynamically based, assuming that reversible work done on the system results in an increase in interfacial area, such that the area between drainage and imbibition retention curves can be related to the interfacial area. Interfacial tracer tests (IFTT) were used to measure specific entrapped NAPL (hexadecane)-water interfacial areas in columns packed with four grades (12/20, 20/30, 30/40, 40/50) of silica sand. By use of the anionic surfactant dihexylsulfosuccinate (Aerosol MA80), IFTT gave specific interfacial areas between 58 cm(-1) for the finest sand and 16 cm(-1) for the coarsest, compared to values of between 33 and 7 cm(-1) for the first model and between 19 and 5 cm(-1) for the thermodynamic model. Results from the literature suggest that nonspherical blobs shapes occur relatively frequently; hence it is reasonable to suggest that the assumption of spherical NAPL blobs may explain the underprediction by the first model. The thermodynamic model underestimates the interfacial area because it assumes that entrapment occurs only within the largest pores. A modified version of the latter model, allowing entrapment across all pore classes, yielded values between 58 and 13 cm(-1). Of the models tested the modified thermodynamic model best predicts the interfacial area.

The purpose of this work is to examine the effect of nonuniform distributions of immiscible organic liquid on dissolution behavior, with a specific focus on the condition dependency of dissolution (i.e., mass transfer) rate coefficients associated with applying mathematical models of differing complexities to measured data. Dissolution experiments were conducted using intermediate-scale flow cells packed with sand in which well-characterized zones of residual trichloroethene (TCE) and 1,2-dichloroethane (DCA) saturation were emplaced. A dual-energy gamma radiation system was used for in-situ measurement of NAPL saturation. Aqueous concentrations of TCE and DCA measured in the flow-cell effluent were significantly less than solubility, due primarily to dilution associated with the nonuniform immiscible-liquid distribution and bypass flow effects associated with physical heterogeneity. A quantitative analysis of flow and transport was conducted using a three-dimensional mathematical model wherein immiscible-liquid distribution, permeability variability, and sampling effects were explicitly considered. Independent values for the initial dissolution rate coefficients were obtained from dissolution experiments conducted using homogeneously packed columns. The independent predictions obtained from the model provided good representations of NAPL dissolution behavior and of total TCE/DCA mass removed, signifying model robustness. This indicates that for the complex three-dimensional model, explicit consideration of the larger scale factors that influenced immiscible-liquid dissolution in the flow cells allowed the use of a dissolution rate coefficient that represents only local-scale mass transfer processes. Conversely, the use of simpler models that did not explicitly consider the nonuniform immiscible-liquid distribution required the use of dissolution rate coefficients that are approximately 3 orders of magnitude smaller than the values obtained from the column experiments. The rate coefficients associated with the simpler models represent composite or lumped coefficients that incorporate the effects of the larger scale dissolution processes associated with the nonuniform immiscible-liquid distribution, which are not explicitly represented in the simpler models, as well as local-scale mass transfer. These results demonstrate that local-scale dissolution rate coefficients, such as those obtained from column experiments, can be used in models to successfully predict dissolution and transport of immiscible-liquid constituents at larger scales when the larger scale factors influencing dissolution behavior are explicitly accounted for in the model.

In a randomized trial at the Leiden University Hospital, comparing (modified) radical mastectomy with tumorectomy followed by radiotherapy, all patients have been studied with respect to the quality of their lives 11 months and 18 months after surgery. The body image of women was more severely impaired after mastectomy than it was after breast conserving treatment (P less than 0.01). This was true for both younger and older women. Fear of recurrence of cancer was not related to the type of treatment. Thus, from a psychological point of view, breast conserving treatment is to be preferred in women of all ages. The overall quality of life improved and the suffering from psychological and physical complaints decreased with time in both groups of patients. This change may, therefore, have to be attributed to getting over the experience of having had cancer, and not to the treatment schedule.