99 research outputs found

    Cosmic muon flux at shallow depths underground

    Full text link
    We consider the cosmic muon background for the installations located at shallow depths. We suggest a relatively simple formula for the sea-level muon spectrum, which allows calculate dependencies of the vertical muon intensity and integral muon flux density on overburden. Muon flux dependency on the zenith angle at overburden of 10 to 100 meters of standard rock shows that muon angular distribution practically does not change in this interval. We present muon angular distributions for three typical apparatus locations in measurements on the surface and at shallow depths. It is shown that for such installations the active shielding "umbrella" should overlap a zenith angle of \theta ~ 80^o to remove the cosmic muon background.Comment: 9 pages, 6 figures, submitted to Phys.Atom.Nuc

    Global sensitivity analysis of stochastic computer models with joint metamodels

    Get PDF
    The global sensitivity analysis method used to quantify the influence of uncertain input variables on the variability in numerical model responses has already been applied to deterministic computer codes; deterministic means here that the same set of input variables gives always the same output value. This paper proposes a global sensitivity analysis methodology for stochastic computer codes, for which the result of each code run is itself random. The framework of the joint modeling of the mean and dispersion of heteroscedastic data is used. To deal with the complexity of computer experiment outputs, nonparametric joint models are discussed and a new Gaussian process-based joint model is proposed. The relevance of these models is analyzed based upon two case studies. Results show that the joint modeling approach yields accurate sensitivity index estimatiors even when heteroscedasticity is strong

    Tracing the effects of high-pressure metasomatic fluids and seawater alteration in blueschist-facies overprinted eclogites: Implications for subduction channel processes

    Get PDF
    Eclogites from the Tian Shan high-pressure/low-temperature (HP/LT) metamorphic belt show evidence for successively increasing metasomatic alteration with increasing retrograde, blueschist-facies overprint. To constrain the source(s) of the metasomatizing fluid and to evaluate elemental and isotopic changes during this overprint, two sequences of eclogite-blueschist transitions were investigated: A layered transition from eclogite to blueschist (FTS 9–1 sequence) and blueschist-facies overprinted pillow metabasalts (FTS 4 samples). Geochemical trends based on the relationships of K, Ba, Rb and Th are consistent with HP metasomatism, but distinct from typical seafloor alteration trends. In contrast, oxygen isotope ratios in garnet (δ18OV-SMOW = 7.3–8.7‰) and omphacite (δ18OV-SMOW = 8.2–9.7‰) are similar to δ18OV-SMOW in bulk low-temperature altered oceanic crust (AOC), suggesting O isotopic preservation of a seafloor alteration signature. Carbonate crystallization related to the metasomatic overprint demonstrate CO2 mobility during subduction and potential C storage in HP metamorphic rocks. Carbon isotope ratios in the two sequences differ markedly: Disseminated calcite in the layered FTS 9–1 sequence has δ13CV-PDB = − 9.14 ± 0.19‰, whereas vein-forming ankerite in the pillow metabasalts has δ13CV-PDB = − 2.08 ± 0.12‰. The ankerite reflects an inorganic marine/hydrothermal signature, as observed in ophiolites, whereas the low δ13CV-PDB values from the calcite point to a contribution of organic carbon. The time when the metasomatic overprint occurred is estimated to be ~ 320 ± 11 Ma based on a Rb-Sr isochron age of six blueschist samples from the pillow metabasalts, which is in agreement with active subduction in this region. Initial (T = 320 Ma) 87Sr/86Sr ratios for all HP/LT rocks range from 0.7059 – 0.7085, and εNd320Ma varies from − 0.4 to + 10.9. Both eclogite-blueschist sequences have initial Sr isotope compositions (87Sr/86Sr ~ 0.707) that are significantly higher than those of typical oceanic mantle-derived basalts. They are thought to derive from a fluid that preserved the Sr isotopic signature of seawater by fluid-rock interaction with seawater-altered oceanic lithosphere in a subduction channel. Mixing models between eclogite and various fluids suggest that the contribution of a sediment-derived fluid was likely less than 20%. A fluid predominantly derived from seawater-altered oceanic lithosphere is also supported by the calculated O isotope composition of the fluids (10.2 – 11.2‰). It is thus evident that subduction channel fluids carry complex, mixed elemental and isotopic signatures, which reflect the composition of their source rocks modified by interaction with various other lithologies. Highlights ► Eclogites from the Tian Shan show blueschist-facies metasomatic overprint ► Fluid-induced metasomatism occurred at 320 ± 11 Ma ► Fluid predominantly derived from seawater-altered oceanic lithosphere ► Carbonates reflect C sequestration of mixture of organic and inorganic component

    Genetics of Host Response to Leishmania tropica in Mice – Different Control of Skin Pathology, Chemokine Reaction, and Invasion into Spleen and Liver

    Get PDF
    Several hundred million people are exposed to the risk of leishmaniasis, a disease caused by intracellular protozoan parasites of several Leishmania species and transmitted by phlebotomine sand flies. In humans, L. tropica causes cutaneous form of leishmaniasis with painful and long-persisting lesions in the site of the insect bite, but the parasites can also penetrate to internal organs. The relationship between the host genes and development of the disease was demonstrated for numerous infectious diseases. However, the search for susceptibility genes in the human population could be a difficult task. In such cases, animal models may help to discover the role of different genes in interactions between the parasite and the host. Unfortunately, the literature contains only a few publications about the use of animals for L. tropica studies. Here, we report an animal model suitable for genetic, pathological and drug studies in L. tropica infection. We show how the host genotype influences different disease symptoms: skin lesions, parasite dissemination to the lymph nodes, spleen and liver, and increase of levels of chemokines CCL2, CCL3 and CCL5 in serum

    Suboptimal herd performance amplifies the spread of infectious disease in the cattle industry

    Get PDF
    Farms that purchase replacement breeding cattle are at increased risk of introducing many economically important diseases. The objectives of this analysis were to determine whether the total number of replacement breeding cattle purchased by individual farms could be reduced by improving herd performance and to quantify the effects of such reductions on the industry-level transmission dynamics of infectious cattle diseases. Detailed information on the performance and contact patterns of British cattle herds was extracted from the national cattle movement database as a case example. Approximately 69% of beef herds and 59% of dairy herds with an average of at least 20 recorded calvings per year purchased at least one replacement breeding animal. Results from zero-inflated negative binomial regression models revealed that herds with high average ages at first calving, prolonged calving intervals, abnormally high or low culling rates, and high calf mortality rates were generally more likely to be open herds and to purchase greater numbers of replacement breeding cattle. If all herds achieved the same level of performance as the top 20% of herds, the total number of replacement beef and dairy cattle purchased could be reduced by an estimated 34% and 51%, respectively. Although these purchases accounted for only 13% of between-herd contacts in the industry trade network, they were found to have a disproportionately strong influence on disease transmission dynamics. These findings suggest that targeting extension services at herds with suboptimal performance may be an effective strategy for controlling endemic cattle diseases while simultaneously improving industry productivity
    corecore