141 research outputs found

    In-Drift Natural Convection and Condensation

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    The Yucca Mountain repository configuration consists of waste packages stored inside of underground tunnels, or drifts. The waste packages generate heat due to radioactive decay, and moisture flows into and out of the drifts in liquid and vapor form. Heat and mass transfer within the drifts, including interaction with the surrounding rock, are potentially important processes for the performance of the repository. The present report documents models for in-drift heat and mass transfer during the post-closure period. Pre-closure, or ventilated, conditions are documented in a separate report (BSC 2004 [DIRS 169862])

    Czech version of the Outcome Rating Scale : Selected psychometric properties

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    Objectives. The Outcome Rating Scale (ORS) is an ultra-brief self-report scale designed to measure change during psychotherapy. The goal of this study was to test (a) the factor structure of the ORS, (b) the measurement invariance between a clinical and a non-clinical sample, between pre-therapy and post-therapy assessment (within the clinical sample), and between online and paper-and-pencil forms of administration (within the non-clinical sample), (c) concurrent validity with other outcome measures, and (d) sensitivity to therapeutic change. Sample and settings. N = 256 patients, N = 210 non-clinical respondents, and N = 89 students participated in the study. Patients responded to the ORS before and after psychotherapy. Statistical analysis. The factor structure and measurement invariance were tested using confirmatory factor analysis. Concurrent validity and test-retest reliability were assessed using correlational analysis. Sensitivity to change was assessed using the Reliable Change Index and pre-post effect size. Results. The unidimensional structure was supported. The best-fitting model was a partially tau-equivalent model with the first and the fourth items’ loadings fixed to the same value. While only metric invariance was demonstrated between the clinical and non-clinical samples, the ORS demonstrated scalar invariance between pre- and post-therapy assessment and strict invariance between the paper-and-pencil and online forms of administration. Internal consistency, as well as concurrent validity, were satisfactory. The sensitivity to the therapeutic change was adequate. Furthermore, internal consistency and sensitivity to change were increased if the score was computed as a weighted sum of items. Study limitation. The samples were not representative

    Deliquescence of NaCl–NaNO(3), KNO(3)–NaNO(3), and NaCl–KNO(3 )salt mixtures from 90 to 120°C

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    We conducted reversed deliquescence experiments in saturated NaCl–NaNO(3)–H(2)O, KNO(3)–NaNO(3)–H(2)O, and NaCl–KNO(3)–H(2)O systems from 90 to 120°C as a function of relative humidity and solution composition. NaCl, NaNO(3), and KNO(3 )represent members of dust salt assemblages that are likely to deliquesce and form concentrated brines on high-level radioactive waste package surfaces in a repository environment at Yucca Mountain, NV. Discrepancy between model prediction and experiment can be as high as 8% for relative humidity and 50% for dissolved ion concentration. The discrepancy is attributed primarily to the use of 25°C models for Cl–NO(3 )and K–NO(3 )ion interactions in the current Yucca Mountain Project high-temperature Pitzer model to describe the nonideal behavior of these highly concentrated solutions

    Evaporative evolution of a Na–Cl–NO(3)–K–Ca–SO(4)–Mg–Si brine at 95°C: Experiments and modeling relevant to Yucca Mountain, Nevada

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    A synthetic Topopah Spring Tuff water representative of one type of pore water at Yucca Mountain, NV was evaporated at 95°C in a series of experiments to determine the geochemical controls for brines that may form on, and possibly impact upon the long-term integrity of waste containers and drip shields at the designated high-level, nuclear-waste repository. Solution chemistry, condensed vapor chemistry, and precipitate mineralogy were used to identify important chemical divides and to validate geochemical calculations of evaporating water chemistry using a high temperature Pitzer thermodynamic database. The water evolved toward a complex "sulfate type" brine that contained about 45 mol % Na, 40 mol % Cl, 9 mol % NO(3), 5 mol % K, and less than 1 mol % each of SO(4), Ca, Mg, ∑CO(2)(aq), F, and Si. All measured ions in the condensed vapor phase were below detection limits. The mineral precipitates identified were halite, anhydrite, bassanite, niter, and nitratine. Trends in the solution composition and identification of CaSO(4 )solids suggest that fluorite, carbonate, sulfate, and magnesium-silicate precipitation control the aqueous solution composition of sulfate type waters by removing fluoride, calcium, and magnesium during the early stages of evaporation. In most cases, the high temperature Pitzer database, used by EQ3/6 geochemical code, sufficiently predicts water composition and mineral precipitation during evaporation. Predicted solution compositions are generally within a factor of 2 of the experimental values. The model predicts that sepiolite, bassanite, amorphous silica, calcite, halite, and brucite are the solubility controlling mineral phases

    Climate Extremes Promote Fatal Co-Infections during Canine Distemper Epidemics in African Lions

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    Extreme climatic conditions may alter historic host-pathogen relationships and synchronize the temporal and spatial convergence of multiple infectious agents, triggering epidemics with far greater mortality than those due to single pathogens. Here we present the first data to clearly illustrate how climate extremes can promote a complex interplay between epidemic and endemic pathogens that are normally tolerated in isolation, but with co-infection, result in catastrophic mortality. A 1994 canine distemper virus (CDV) epidemic in Serengeti lions (Panthera leo) coincided with the death of a third of the population, and a second high-mortality CDV epidemic struck the nearby Ngorongoro Crater lion population in 2001. The extent of adult mortalities was unusual for CDV and prompted an investigation into contributing factors. Serological analyses indicated that at least five “silent” CDV epidemics swept through the same two lion populations between 1976 and 2006 without clinical signs or measurable mortality, indicating that CDV was not necessarily fatal. Clinical and pathology findings suggested that hemoparsitism was a major contributing factor during fatal epidemics. Using quantitative real-time PCR, we measured the magnitude of hemoparasite infections in these populations over 22 years and demonstrated significantly higher levels of Babesia during the 1994 and 2001 epidemics. Babesia levels correlated with mortalities and extent of CDV exposure within prides. The common event preceding the two high mortality CDV outbreaks was extreme drought conditions with wide-spread herbivore die-offs, most notably of Cape buffalo (Syncerus caffer). As a consequence of high tick numbers after the resumption of rains and heavy tick infestations of starving buffalo, the lions were infected by unusually high numbers of Babesia, infections that were magnified by the immunosuppressive effects of coincident CDV, leading to unprecedented mortality. Such mass mortality events may become increasingly common if climate extremes disrupt historic stable relationships between co-existing pathogens and their susceptible hosts
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