A Universal Model of Unsaturated Hydraulic Conductivity with Complementary Adsorptive and Diffusive Process Components

Accurate estimation of unsaturated hydraulic conductivity (HC) is one of the most challenging problems in soil science. Here, we propose a novel approach to model HC using percolation theory. Transient behavior of water transport phenomena at low moisture contents requires additional physical process representation, beside capillary conductivity, to ensure accurate prediction of unsaturated HC. We augment the capillary model from percolation theory with two additional components, namely, (1) film flow, which is the product of volumetric flow rate per perimeter by specific perimeter of solid particles, and (2) isothermal vapor HC, derived from the Fick\u27s law of vapor diffusion and relative humidity. The fractal characteristics of last fractal regime are used to model tortuosity and ultimately HC of vapor flow. Since the typical pressure head range of universal scaling from percolation theory is analogous to the range of vapor flow, we demonstrate that the universal scaling presented in previous studies is not sufficient to model HC for water contents below a crossover point. We also, by analyzing the scaled water retention properties, demonstrate that most studied soils exhibit three fractal regimes. Therefore, a piecewise HC function of capillary flow is developed to account for three fractal regimes, providing more flexibility for soils with multimodal characteristics. The proposed joint HC function is more accurate compared to the model of Peters‐Durner‐Iden and predecessor percolation theory models

Comparison of Bioimpedance Analysis and Dual Energy X-Ray Absorptiometry in Division III Football Athletes

Body composition is an integral component of physiology and pathology, as well as an indication of how the musculoskeletal system changes over time in response to training and/or nutritional modifications. Two common methods of estimating body composition include bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA). There is a debate regarding the agreement between these two methods, and it is thought that the population being tested may influence the similarity of estimates obtained by these technologies. Limited data comparing these two methodologies in athletic populations are available. PURPOSE: The purpose of this study was to take examine the agreement between BIA and DXA for estimates of body mass (BM) and body fat percentage (BF%). METHODS: Forty-three division III football players (mean ± SD; age: 19.9 ± 1.7 y; height: 179.7 ± 7.4 cm; BM: 100.3 ± 21.9 kg; DXA BF%: 21.8 ± 7.1%) reported to the Human Performance Lab after abstaining from exercise for the previous 24 hours and fasting from food/beverages (except water) for 12 hours. After an initial height assessment, BM and BF% were assessed using both BIA (Inbody 770) and DXA (Hologic Horizon W). BIA was performed in the standing position using an 8-point electrode arrangement. The electrode panels were placed at the hands and feet. DXA was performed with the participants in a supine position and hips internally rotated. Differences in BM and BF% from DXA and BIA were compared using paired-samples t-tests, Bland-Altman analysis, and validity metrics. RESULTS: BM detected by DXA was significantly lower than BM obtained from the BIA scale (DXA: 98.2 ± 20.8 kg, BIA: 100.3 ± 21.9 kg; p \u3c 0.001). Additionally, Bland-Altman analysis indicated significantly greater underestimation of BM by DXA in individuals with higher BM values (slope: 0.053; p \u3c 0.001). BF% did not significantly differ between DXA and BIA (DXA: 21.8 ± 7.1%, BIA: 21.8 ± 8.4%; p = 0.86). However, Bland-Altman analysis indicated significant proportional bias, with underestimations of BF% by BIA in leaner individuals but overestimations of BF% in those with higher BF% (slope: 0.176; p = 0.005). The total error and 95% limits of agreement for BF% were 3.2% and ± 6.4%, respectively. CONCLUSION: This study demonstrates that although DXA and BIA exhibit good group-level agreement for BF%, several inconsistencies between these methodologies are present. Estimates of BM differed between technologies. Additionally, proportional bias for BF% was observed indicating different levels of agreement between DXA and BIA depending on the body fat of the individuals being tested. Based on these findings, caution should be employed when interpreting data from DXA and BIA assessments in athletic populations

Use of groundwater lifetime expectancy for the performance assessment of a deep geologic waste repository: 1. Theory, illustrations, and implications

Long-term solutions for the disposal of toxic wastes usually involve isolation of the wastes in a deep subsurface geologic environment. In the case of spent nuclear fuel, if radionuclide leakage occurs from the engineered barrier, the geological medium represents the ultimate barrier that is relied upon to ensure safety. Consequently, an evaluation of radionuclide travel times from a repository to the biosphere is critically important in a performance assessment analysis. In this study, we develop a travel time framework based on the concept of groundwater lifetime expectancy as a safety indicator. Lifetime expectancy characterizes the time that radionuclides will spend in the subsurface after their release from the repository and prior to discharging into the biosphere. The probability density function of lifetime expectancy is computed throughout the host rock by solving the backward-in-time solute transport adjoint equation subject to a properly posed set of boundary conditions. It can then be used to define optimal repository locations. The risk associated with selected sites can be evaluated by simulating an appropriate contaminant release history. The utility of the method is illustrated by means of analytical and numerical examples, which focus on the effect of fracture networks on the uncertainty of evaluated lifetime expectancy.Comment: 11 pages, 8 figures; Water Resources Research, Vol. 44, 200

Hot dry rock fracture propagation and reservoir characterization

North America's largest hydraulic fracturing opeations have been conducted at Fenton hill, New mexico to creae hot dry rock geothermal reservoirs. Microearthquakes induced by these fracturing operations were measured with geophones. The large volume of rock over which the microearthquakes were distributed indicates a mechanism of hydraulic stimulation which is at odds with conventional fracturing theory, which predicts failure along a plane which is perpendicular to the least compressive earth stress. Shear slippage along pre-existing joints in the rock is more easily induced than conventional tensile failure, particularly when the difference between minimum and maximum earth stresses is large and the pre-existing joints are oriented at angles between 30 and 60)degree) to the principal earth stresses, and a low viscosity fluid like water is injected. Shear slippage results in local redistribution of stresses, which allows a branching, or dendritic, stimulation pattern to evolve, in agreement with the patterns of microearthquake locations. Field testing of HDR reservoirs at the Fenton Hill site shows that significant reservoir growth occurred as energy was extracted. Tracer, microseismic, and geochemical measurements provided the primary quantitative evidence for the increases in accessible reservoir volume and fractured rock surface area. These temporal increases indicate that augmentation of reservoir heat production capacity in hot dry rock system occurred. For future reservoir testing, Los Alamos is developing tracer techniques using reactive chemicals to track thermal fronts. Recent studies have focused on the kinetics of hydrolysis of derivatives of bromobenzene, which can be used in reservoirs as hot as 275)degree)C

Francisella tularensis subsp. novicida isolated from a human in Arizona

<p>Abstract</p> <p>Background</p> <p><it>Francisella tularensis </it>is the etiologic agent of tularemia and is classified as a select agent by the Centers for Disease Control and Prevention. Currently four known subspecies of <it>F. tularensis </it>that differ in virulence and geographical distribution are recognized:<it>tularensis </it>(type A), <it>holarctica </it>(type B), <it>mediasiatica</it>, and <it>novicida</it>. Because of the Select Agent status and differences in virulence and geographical location, the molecular analysis of any clinical case of tularemia is of particular interest. We analyzed an unusual <it>Francisella </it>clinical isolate from a human infection in Arizona using multiple DNA-based approaches.</p> <p>Findings</p> <p>We report that the isolate is <it>F. tularensis </it>subsp. <it>novicida</it>, a subspecies that is rarely isolated.</p> <p>Conclusion</p> <p>The rarity of this <it>novicida </it>subspecies in clinical settings makes each case study important for our understanding of its role in disease and its genetic relationship with other <it>F. tularensis </it>subspecies.</p

Temporal phylogeography of Yersinia pestis in Madagascar : Insights into the long-term maintenance of plague

Data Availability: All relevant data are within the paper and its Supporting Information files except for the sequence read archives for 31 newly sequenced strains that are available at NCBI under the accession numbers: SRR4175414-SRR4175444. The direct link to this data is: https://www.ncbi.nlm.nih.gov/sra/?term=SRP086709. Funding: Funding for this study was provided by the US Department of Homeland Security’s Science and Technology Directorate award number HSHQDC-10-C-00139 to PK; the Cowden Endowment at Northern Arizona University; and Wellcome fellowships 081705 and 095171 to ST. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD