434 research outputs found

    Analysis Of Dynamic Tensile Deformation Characteristics Of Deep Coal Rock

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    In order to study the dynamic tensile deformation failure characteristics of deep coal rock, the impact loading system of Split Hopkinson Pressure Bar (SHPB) was used to carry out the Brazilian disc splitting test under the impact for the deep coal rock samples, and the influences of impact speed and bedding angle in the coal samples on the dynamic tensile strength, failure strain and strain rate of coal samples were discussed. The results show that the larger the impact speed is, the larger the dynamic tensile strength is, but its increase gradually decreases with the impact speed increasing. The failure strain of coal samples is the maximal as the impact speed is 3.3 m/s. With the same impact speedwhen the bedding is vertical to the loading direction, the failure strain of coal rock is relatively larger, however, the strain rate is the smallest. Simultaneously, when the bedding is parallel or vertical to the loading direction, the tensile failure appears in the coal samples, but if the bedding is not parallel or vertical to the loading direction, there would appear the matrix tension and the shear failure of bedding together

    Pharmacogenetic aspects of the use of tacrolimus in renal transplantation: Recent developments and ethnic considerations

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    Introduction: Tacrolimus (Tac) is effective in preventing acute rejection but has considerable toxicity and inter-individual variability in pharmacokinetics and pharmacodynamics. Part of this is explained by polymorphisms in genes encoding Tac-metabolizing enzymes and transporters. A better understanding of Tac pharmacokinetics and pharmacodynamics may help to minimize different outcomes amongst transplant recipients by personalizing immunosuppression.Areas covered: The pharmacogenetic contribution of Tac metabolism will be examined, with a focus on recent discoveries, new developments and ethnic considerations.Expert opinion: The strongest and most consistent association in pharmacogenetics is between the CYP3A5 genotype and Tac dose requirement, with CYP3A5 expressers having a ∌ 40-50% higher dose requirement compared to non-expressers. Two recent randomized-controlled clinical trials using CYP3A5 genotype, however, did not show a decrease in acute rejections nor reduced toxicity. CYP3A4∗22, CYP3A4∗26, and POR∗28 are also associated with Tac dose requirements and may be included to provide the expected improvement of Tac therapy. Studies focusing on the intracellular drug concentrations and on calcineurin inhibitor-induced nephrotoxicity also seem promising. For all studies, however, the ethnic prevalence of genotypes should be taken into account, as this may significantly impact the effect of pre-emptive genotyping

    Exact eigenstate analysis of finite-frequency conductivity in graphene

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    We employ the exact eigenstate basis formalism to study electrical conductivity in graphene, in the presence of short-range diagonal disorder and inter-valley scattering. We find that for disorder strength, W≄W \ge 5, the density of states is flat. We, then, make connection, using the MRG approach, with the work of Abrahams \textit{et al.} and find a very good agreement for disorder strength, WW = 5. For low disorder strength, WW = 2, we plot the energy-resolved current matrix elements squared for different locations of the Fermi energy from the band centre. We find that the states close to the band centre are more extended and falls of nearly as 1/El21/E_l^{2} as we move away from the band centre. Further studies of current matrix elements versus disorder strength suggests a cross-over from weakly localized to a very weakly localized system. We calculate conductivity using Kubo Greenwood formula and show that, for low disorder strength, conductivity is in a good qualitative agreement with the experiments, even for the on-site disorder. The intensity plots of the eigenstates also reveal clear signatures of puddle formation for very small carrier concentration. We also make comparison with square lattice and find that graphene is more easily localized when subject to disorder.Comment: 11 pages,15 figure

    Quantifying atmospheric nitrogen deposition through a nationwide monitoring network across China

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    A Nationwide Nitrogen Deposition Monitoring Network (NNDMN) containing 43 monitoring sites was established in China to measure gaseous NH3, NO2, and HNO3 and particulate NH4+ and NO3− in air and/or precipitation from 2010 to 2014. Wet/bulk deposition fluxes of Nr species were collected by precipitation gauge method and measured by continuous-flow analyzer; dry deposition fluxes were estimated using airborne concentration measurements and inferential models. Our observations reveal large spatial variations of atmospheric Nr concentrations and dry and wet/bulk Nr deposition. On a national basis, the annual average concentrations (1.3–47.0 ÎŒg N m−3) and dry plus wet/bulk deposition fluxes (2.9–83.3 kg N ha−1 yr−1) of inorganic Nr species are ranked by land use as urban > rural > background sites and by regions as north China > southeast China > southwest China > northeast China > northwest China > Tibetan Plateau, reflecting the impact of anthropogenic Nr emission. Average dry and wet/bulk N deposition fluxes were 20.6 ± 11.2 (mean ± standard deviation) and 19.3 ± 9.2 kg N ha−1 yr−1 across China, with reduced N deposition dominating both dry and wet/bulk deposition. Our results suggest atmospheric dry N deposition is equally important to wet/bulk N deposition at the national scale. Therefore, both deposition forms should be included when considering the impacts of N deposition on environment and ecosystem health

    Partial Wave Analysis of J/Ïˆâ†’Îł(K+K−π+π−)J/\psi \to \gamma (K^+K^-\pi^+\pi^-)

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    BES data on J/Ïˆâ†’Îł(K+K−π+π−)J/\psi \to \gamma (K^+K^-\pi^+\pi^-) are presented. The K∗Kˉ∗K^*\bar K^* contribution peaks strongly near threshold. It is fitted with a broad 0−+0^{-+} resonance with mass M=1800±100M = 1800 \pm 100 MeV, width Γ=500±200\Gamma = 500 \pm 200 MeV. A broad 2++2^{++} resonance peaking at 2020 MeV is also required with width ∌500\sim 500 MeV. There is further evidence for a 2−+2^{-+} component peaking at 2.55 GeV. The non-K∗Kˉ∗K^*\bar K^* contribution is close to phase space; it peaks at 2.6 GeV and is very different from K∗K∗ˉK^{*}\bar{K^{*}}.Comment: 15 pages, 6 figures, 1 table, Submitted to PL

    Inhibition of T Helper Cell Differentiation by Tacrolimus or Sirolimus Results in Reduced B-Cell Activation: Effects on T Follicular Helper Cells

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    The effect of immunosuppressive drugs on the generation of T follicular helper (Tfh) cells, specialized in supporting B-cell differentiation, is largely unknown. We examined whether the calcineurin inhibitor tacrolimus (TAC) and the mammalian target of rapamycin (mtor) inhibitor sirolimus (SRL) inhibit Tfh cell differentiation, and affect subsequent B-cell functions. Isolated naive T cells were polarized into Tfh-like cells in the presence of TAC or SRL. To demonstrate their functionality, we co-cultured these cells with isolated B cells in the presence of alloantigen and studied the activation and differentiation of these B cells. Tfh-like cells were defined as CD4+CXCR5+ T cells, expressing immunoinhibitory programmed death protein 1 (pd1) and inducible T-cell costimulator (icos). We found that TAC and SRL significantly inhibited Tfh-like cell differentiation. Therapeutic concentrations of TAC and SRL reduced the percentage of pd1+ and icos+ Tfh cells compared to controls. In addition, T cells grown in the presence of TAC or SRL expressed less IL-21 and provided less B-cell help. TAC and SRL both inhibited Tfh-dependent alloantigen-activated B-cell proliferation and differentiation into plasma cells and transitional B cells. In conclusion, TAC and SRL inhibited the differentiation of naive T cells into functional Tfh-like cells, a finding that can be extrapolated to immunosuppressive regimens in transplant patients

    BESII Detector Simulation

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    A Monte Carlo program based on Geant3 has been developed for BESII detector simulation. The organization of the program is outlined, and the digitization procedure for simulating the response of various sub-detectors is described. Comparisons with data show that the performance of the program is generally satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM

    A Measurement of Psi(2S) Resonance Parameters

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    Cross sections for e+e- to hadons, pi+pi- J/Psi, and mu+mu- have been measured in the vicinity of the Psi(2S) resonance using the BESII detector operated at the BEPC. The Psi(2S) total width; partial widths to hadrons, pi+pi- J/Psi, muons; and corresponding branching fractions have been determined to be Gamma(total)= (264+-27) keV; Gamma(hadron)= (258+-26) keV, Gamma(mu)= (2.44+-0.21) keV, and Gamma(pi+pi- J/Psi)= (85+-8.7) keV; and Br(hadron)= (97.79+-0.15)%, Br(pi+pi- J/Psi)= (32+-1.4)%, Br(mu)= (0.93+-0.08)%, respectively.Comment: 8 pages, 6 figure

    Direct Measurements of the Branching Fractions for D0→K−e+ÎœeD^0 \to K^-e^+\nu_e and D0→π−e+ÎœeD^0 \to \pi^-e^+\nu_e and Determinations of the Form Factors f+K(0)f_{+}^{K}(0) and f+π(0)f^{\pi}_{+}(0)

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    The absolute branching fractions for the decays D0→K−e+ÎœeD^0 \to K^-e ^+\nu_e and D0→π−e+ÎœeD^0 \to \pi^-e^+\nu_e are determined using 7584±198±3417584\pm 198 \pm 341 singly tagged Dˉ0\bar D^0 sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC. In the system recoiling against the singly tagged Dˉ0\bar D^0 meson, 104.0±10.9104.0\pm 10.9 events for D0→K−e+ÎœeD^0 \to K^-e ^+\nu_e and 9.0±3.69.0 \pm 3.6 events for D0→π−e+ÎœeD^0 \to \pi^-e^+\nu_e decays are observed. Those yield the absolute branching fractions to be BF(D0→K−e+Îœe)=(3.82±0.40±0.27)BF(D^0 \to K^-e^+\nu_e)=(3.82 \pm 0.40\pm 0.27)% and BF(D0→π−e+Îœe)=(0.33±0.13±0.03)BF(D^0 \to \pi^-e^+\nu_e)=(0.33 \pm 0.13\pm 0.03)%. The vector form factors are determined to be ∣f+K(0)∣=0.78±0.04±0.03|f^K_+(0)| = 0.78 \pm 0.04 \pm 0.03 and ∣f+π(0)∣=0.73±0.14±0.06|f^{\pi}_+(0)| = 0.73 \pm 0.14 \pm 0.06. The ratio of the two form factors is measured to be ∣f+π(0)/f+K(0)∣=0.93±0.19±0.07|f^{\pi}_+(0)/f^K_+(0)|= 0.93 \pm 0.19 \pm 0.07.Comment: 6 pages, 5 figure

    Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta

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    Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector, the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and (7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
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