193 research outputs found
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Probabilistic Approach to Site Characterization: MIU site, Tono Region, Japan
Geostatistical simulation is used to extrapolate data derived from site characterization activities at the MIU site into information describing the three-dimensional distribution of hydraulic conductivity at the site and the uncertainty in the estimates of hydraulic conductivity. This process is demonstrated for six different data sets representing incrementally increasing amounts of characterization data. Short horizontal ranges characterize the spatial variability of both the rock types (facies) and the hydraulic conductivity measurements. For each of the six data sets, 50 geostatistical realizations of the facies and 50 realizations of the hydraulic conductivity are combined to produce 50 final realizations of the hydraulic conductivity distribution. Analysis of these final realizations indicates that the mean hydraulic conductivity value increases with the addition of site characterization data. The average hydraulic conductivity as a function of elevation changes from a uniform profile to a profile showing relatively high hydraulic conductivity values near the top and bottom of the simulation domain. Three-dimensional uncertainty maps show the highest amount of uncertainty in the hydraulic conductivity distribution near the top and bottom of the model. These upper and lower areas of high uncertainty are interpreted to be due to the unconformity at the top of the granitic rocks and the Tsukyoshi fault respectively
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Tracer tests in a fractured dolomite: 2. Analysis of mass transfer in single-well injection-withdrawal tests
We investigated multiple-rate diffusion as a possible explanation for observed behavior in a suite of single-well injection-withdrawal (SWIW) tests conducted in a fractured dolomite. We first investigated the ability of a conventional double-porosity model and a multirate diffusion model to explain the data. This revealed that the multirate diffusion hypothesis/model is consistent with available data and is capable of matching all of the recovery curves. Second, we studied the sensitivity of the SWIW recovery curves to the distribution of diffusion rate coefficients and other parameters. We concluded that the SWIW test is very sensitive to the distribution of rate coefficients but is relatively insensitive to other flow and transport parameters such as advective porosity and dispersivity. Third, we examined the significance of the constant double-log late time slopes (ā2.1 to ā2.8), which are present in several data sets. The observed late time slopes are significantly different than would be predicted by either conventional double-porosity or single-porosity models and are believed to be a distinctive feature of multirate diffusion. Fourth, we found that the estimated distributions of diffusion rate coefficients are very broad, with the distributions spanning a range of up to 3.6 orders of magnitude. Fifth, when both heterogeneity and solute drift are present, late time behavior similar to multirate mass transfer can occur. Although it is clear that multirate diffusion occurs in the Culebra, the number of orders of magnitude of variability may be overestimated because of the combined effects of drift and heterogeneity.Keywords: Hydrology, Groundwater transportKeywords: Hydrology, Groundwater transpor
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Tracer tests in a fractured dolomite: 3. Double-porosity, multiple-rate mass transfer processes in convergent flow tracer tests
Convergent flow tracer tests conducted in the Culebra dolomite (Rustler Formation, New Mexico) are analyzed with both single- and multiple-rate, double-porosity models. Parameter estimation is used to determine the mean and standard deviation of a lognormal distribution of diffusion rate coefficients as well as the advective porosity and longitudinal dispersivity. At two different test sites both multirate and single-rate models are capable of accurately modeling the observed data. The single-well injection-withdrawal test provides more precise estimates of the mass transfer parameters than the convergent flow tracer tests. Estimation of the multirate distribution parameters is consistent across locations for the two types of tests. Limits of resolution are calculated for the multirate distribution, and these limits explain the precision with which the standard deviation of the multirate distribution can be estimated. These limits also explain the necessary increase in the advective porosity for the single-rate model at one location and not the other. Implications of the multirate mass transfer model at time and length scales greater than those of the tracer tests include the instantaneous equilibrium of a significant fraction of the matrix and the possibility of a fraction of the diffusive porosity not reaching an equilibrium solute concentration at long times.Keywords: Hydrology, Groundwater transpor
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On the late-time behavior of tracer test breakthrough curves
We investigated the late-time (asymptotic) behavior of tracer test breakthrough
curves (BTCs) with rate-limited mass transfer( e.g., in dual-porosity or multiporosity
systems) and found that the late-time concentration c is given by the simple expression
C = tā{Cāg-- [mā(āg/āt)]}, for t >> tā and tĪ± >> tā, where tad is the advection
time, Cā is the initial concentration in the medium, mā is the zeroth moment of the
injection pulse, and tĪ± is the mean residence time in the immobile domain (i.e., the
characteristic mass transfer time). The function g is proportional to the residence time
distribution in the immobile domain; we tabulate g for many geometries, including several
distributed (multirate) models of mass transfer. Using this expression, we examine the
behavior of late-time concentration for a number of mass transfer models. One key result
is that if rate-limited mass transfer causes the BTC to behave as a power law at late time
(i.e.,c ~ tā»įµ), then the underlying density function of rate coefficients must also be a
power law with the form Ī±įµā»Ā³ as Ī± ā 0. This is true for both density functions of first order
and diffusion rate coefficients. BTCs with k < 3 persisting to the end of the
experiment indicate a mean residence time longer than the experiment, and possibly an
infinite residence time, and also suggest an effective rate coefficient that is either
undefined or changes as a function of observation time. We apply our analysis to
breakthrough curves from single-well injection-withdrawal tests at the Waste Isolation Pilot Plant, New Mexico
Feed-Forward Inhibition of Androgen Receptor Activity by Glucocorticoid Action in Human Adipocytes
SummaryWe compared transcriptomes of terminally differentiated mouse 3T3-L1 and human adipocytes to identify cell-specific differences. Gene expression and high content analysis (HCA) data identified the androgen receptor (AR) as both expressed and functional, exclusively during early human adipocyte differentiation. The AR agonist dihydrotestosterone (DHT) inhibited human adipocyte maturation by downregulation of adipocyte marker genes, but not in 3T3-L1. It is interesting that AR induction corresponded with dexamethasone activation of the glucocorticoid receptor (GR); however, when exposed to the differentiation cocktail required for adipocyte maturation, AR adopted an antagonist conformation and was transcriptionally repressed. To further explore effectors within the cocktail, we applied an image-based support vector machine (SVM) classification scheme to show that adipocyte differentiation components inhibit AR action. The results demonstrate human adipocyte differentiation, via GR activation, upregulates AR but also inhibits AR transcriptional activity
Septic Arthritis of the Temporomandibular Joint: Case Reports andĀ Review of the Literature
Septic arthritis of the temporomandibular (TM) joint is rare, but it is associated with high risk for significant morbidity
Authorsā response to comments on āFlame retardants in UK furniture increase smoke toxicity more than they reduce fire growth rate"
Burning behaviour of rainscreen faƧades
Four reduced-height (5 m) BS 8414-1 faƧade flammability tests were conducted, three having mineral-filled aluminium composite material (ACM-A2) with polyisocyanurate (PIR) and phenolic (PF) foam and stone wool (SW) insulation, the fourth having polyethylene-filled ACM (ACM-PE) with PIR insulation. Each faƧade was constructed from a commercial faƧade engineerās design, and built by practising faƧade installers. The ACM-PE/PIR faƧade burnt so ferociously it was extinguished after 13.5 min, for safety. The three ACM-A2 cladding panels lost their structural integrity, and melted away from the test wall, whereupon around 40% of both the combustible PIR and PF insulation burnt and contributed to the fire spread. This demonstrates why all faƧade products must be non-combustible, not just the outer panels. For the three ACM-A2 tests, while the temperature in front of the cavity was independent of the insulation, the temperatures within it varied greatly, depending on the insulation. The system using PF/A2 allowed fire to break through to the cavity first, as seen by a sharp increase in temperature after 17 min. For PIR/A2, the temperature increased sharply at 22 minutes, as the panel started to fall away from the wall. For SW/A2, no rapid temperature rise was observed
Flame retardants in UK furniture increase smoke toxicity more than they reduce fire growth rate
This paper uses fire statistics to show the importance of fire toxicity on fire deaths and injuries, and the importance of upholstered furniture and bedding on fatalities from unwanted fires. The aim was to compare the fire hazards (fire growth and smoke toxicity) using different upholstery materials. Four compositions of sofa-bed were compared: three meeting UK Furniture Flammability Regulations (FFR), and one using materials without flame retardants intended for the mainland European market. Two of the UK sofa-beds relied on chemical flame retardants to meet the FFR, the third used natural materials and a technical weave in order to pass the test. Each composition was tested in the bench-scale cone calorimeter (ISO 5660) and burnt as a whole sofa-bed in a sofa configuration in a 3.4āÆĆāÆ2.25āÆĆāÆ2.4āÆm3 test room. All of the sofas were ignited with a No. 7 wood crib; the temperatures and yields of toxic products are reported. The sofa-beds containing flame retardants burnt somewhat more slowly than the non-flame retarded EU sofa-bed, but in doing so produced significantly greater quantities of the main fire toxicants, carbon monoxide and hydrogen cyanide. Assessment of the effluents' potential to incapacitate and kill is provided showing the two UK flame retardant sofa-beds to be the most dangerous, followed by the sofa-bed made with European materials. The UK sofa-bed made only from natural materials (CottonsafeĀ®) burnt very slowly and produced very low concentrations of toxic gases. Including fire toxicity in the FFR would reduce the chemical flame retardants and improve fire safety. [Abstract copyright: Crown Copyright Ā© 2017. Published by Elsevier Ltd. All rights reserved.
Fire behaviour of modern faƧade materials ā Understanding the Grenfell Tower fire
The 2017 Grenfell Tower fire spread rapidly around the combustible faƧade system on the outside of the building, killing 72 people. We used a range of micro- and bench-scale methods to understand the fire behaviour of different types of faƧade product, including those used on the Tower, in order to explain the speed, ferocity and lethality of the fire. Compared to the least flammable panels, polyethylene-aluminium composites showed 55x greater peak heat release rates (pHRR) and 70x greater total heat release (THR), while widely-used high-pressure laminate panels showed 25x greater pHRR and 115x greater THR. Compared to the least combustible insulation products, polyisocyanurate foam showed 16x greater pHRR and 35x greater THR, while phenolic foam showed 9x greater pHRR and 48x greater THR. A few burning drips of polyethylene from the panelling are enough to ignite the foam insulation, providing a novel explanation for rapid flame-spread within the facade. Smoke from polyisocyanurates was 15x, and phenolics 5x more toxic than from mineral wool insulation. 1kg of burning polyisocyanurate insulation is sufficient to fill a 50m3 room with an incapacitating and ultimately lethal effluent. Simple, additive models are proposed, which provide the same rank order as BS8414 large-scale regulatory tests
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