44 research outputs found

    Spatio-Temporal Patterns of Water Table and Vegetation Status of a Deserted Area

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    Understanding groundwater-vegetation interactions is crucial for sustaining fragile environments of desert areas such as the Horqin Sandy Land (HSL) in northern China. This study examined spatio-temporal variations in the water table and the associated vegetation status of a 9.71 km2 area that contains meadowland, sandy dunes, and intermediate transitional zones. The depth of the water table and hydrometeorologic parameters were monitored and Landsat Thematic Mapper (TM) and Moderate Resolution Imaging Spectroradiometer (MODIS) data were utilized to assess the vegetation cover. Spatio-temporal variations over the six-year study period were examined and descriptive groundwater-vegetation associations developed by overlaying a water table depth map onto a vegetation index map derived from MODIS. The results indicate that the water table depends on the local topography, localized geological settings, and human activities such as reclamation, with fluctuations occurring at annual and monthly scales as a function of precipitation and potential evapotranspiration. Locations where the water table is closer to the surface tend to have more dense and productive vegetation. The water table depth is more closely associated with vegetative density in meadowlands than in transitional zones, and only poorly associated with vegetation in sandy dunes

    Cosmic test of sTGC detector prototype made in China for ATLAS experiment upgrade

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    Following the Higgs particle discovery, the Large Hadron Collider complex will be upgraded in several phases allowing the luminosity to increase to 7×1034cm2s17 \times 10^{34}cm^{-2}s^{-1}. In order to adapt the ATLAS detector to the higher luminosity environment after the upgrade, part of the ATLAS muon end-cap system, the Small Wheel, will be replaced by the New Small Wheel. The New Small Wheel includes two kinds of detectors: small-strip Thin Gap Chambers and Micromegas. Shandong University, part of the ATLAS collaboration, participates in the construction of the ATLAS New Small Wheel by developing, producing and testing the performance of part of the small-strip Thin Gap Chambers. This paper describes the construction and cosmic-ray testing of small-strip Thin Gap Chambers in Shandong University

    Agonist Anti-GITR Monoclonal Antibody Induces Melanoma Tumor Immunity in Mice by Altering Regulatory T Cell Stability and Intra-Tumor Accumulation

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    In vivo GITR ligation has previously been shown to augment T-cell-mediated anti-tumor immunity, yet the underlying mechanisms of this activity, particularly its in vivo effects on CD4+ foxp3+ regulatory T cells (Tregs), have not been fully elucidated. In order to translate this immunotherapeutic approach to the clinic it is important gain better understanding of its mechanism(s) of action. Utilizing the agonist anti-GITR monoclonal antibody DTA-1, we found that in vivo GITR ligation modulates regulatory T cells (Tregs) directly during induction of melanoma tumor immunity. As a monotherapy, DTA-1 induced regression of small established B16 melanoma tumors. Although DTA-1 did not alter systemic Treg frequencies nor abrogate the intrinsic suppressive activity of Tregs within the tumor-draining lymph node, intra-tumor Treg accumulation was significantly impaired. This resulted in a greater Teff:Treg ratio and enhanced tumor-specific CD8+ T-cell activity. The decreased intra-tumor Treg accumulation was due both to impaired infiltration, coupled with DTA-1-induced loss of foxp3 expression in intra-tumor Tregs. Histological analysis of B16 tumors grown in Foxp3-GFP mice showed that the majority of GFP+ cells had lost Foxp3 expression. These “unstable” Tregs were absent in IgG-treated tumors and in DTA-1 treated TDLN, demonstrating a tumor-specific effect. Impairment of Treg infiltration was lost if Tregs were GITR−/−, and the protective effects of DTA-1 were reduced in reconstituted RAG1−/− mice if either the Treg or Teff subset were GITR-negative and absent if both were negative. Our results demonstrate that DTA-1 modulates both Teffs and Tregs during effective tumor treatment. The data suggest that DTA-1 prevents intra-tumor Treg accumulation by altering their stability, and as a result of the loss of foxp3 expression, may modify their intra-tumor suppressive capacity. These findings provide further support for the continued development of agonist anti-GITR mAbs as an immunotherapeutic strategy for cancer

    A CsI hodoscope on CSHINE for Bremsstrahlung {\gamma}-rays in Heavy Ion Reactions

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    Bremsstrahlung γ\gamma production in heavy ion reactions at Fermi energies carries important physical information including the nuclear symmetry energy at supra-saturation densities. In order to detect the high energy Bremsstrahlung γ\gamma rays, a hodoscope consisting of 15 CsI(Tl) crystal read out by photo multiplier tubes has been built, tested and operated in experiment. The resolution, efficiency and linear response of the units to γ\gamma rays have been studied using radioactive source and (p,γ)({\rm p},\gamma) reactions. The inherent energy resolution of 1.6%+2%/Eγ1/21.6\%+2\%/E_{\gamma}^{1/2} is obtained. Reconstruction method has been established through Geant 4 simulations, reproducing the experimental results where comparison can be made. Using the reconstruction method developed, the whole efficiency of the hodoscope is about 2.6×1042.6\times 10^{-4} against the 4π4\pi emissions at the target position, exhibiting insignificant dependence on the energy of incident γ\gamma rays above 20 MeV. The hodoscope is operated in the experiment of 86^{86}Kr + 124^{124}Sn at 25 MeV/u, and a full γ\gamma energy spectrum up to 80 MeV has been obtained.Comment: 9 pages, 19 figure

    Probing high-momentum component in nucleon momentum distribution by neutron-proton bremsstrahlung {\gamma}-rays in heavy ion reactions

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    The high momentum tail (HMT) of nucleons, as a signature of the short-range correlations in nuclei, has been investigated by the high-energy bremsstrahlung γ\gamma rays produced in 86^{86}Kr + 124^{124}Sn at 25 MeV/u. The energetic photons are measured by a CsI(Tl) hodoscope mounted on the spectrometer CSHINE. The energy spectrum above 30 MeV can be reproduced by the IBUU model calculations incorporating the photon production channel from npnp process in which the HMTs of nucleons is considered. A non-zero HMT ratio of about 15%15\% is favored by the data. The effect of the capture channel npdγnp \to d\gamma is demonstrated

    Revisit to the yield ratio of triton and 3^3He as an indicator of neutron-rich neck emission

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    The neutron rich neck zone created in heavy ion reaction is experimentally probed by the production of the A=3A=3 isobars. The energy spectra and angular distributions of triton and 3^3He are measured with the CSHINE detector in 86^{86}Kr +208^{208}Pb reactions at 25 MeV/u. While the energy spectrum of 3^{3}He is harder than that of triton, known as "3^{3}He-puzzle", the yield ratio R(t/3He)R({\rm t/^3He}) presents a robust rising trend with the polar angle in laboratory. Using the fission fragments to reconstruct the fission plane, the enhancement of out-plane R(t/3He)R({\rm t/^3He}) is confirmed in comparison to the in-plane ratios. Transport model simulations reproduce qualitatively the experimental trends, but the quantitative agreement is not achieved. The results demonstrate that a neutron rich neck zone is formed in the reactions. Further studies are called for to understand the clustering and the isospin dynamics related to neck formation

    Aspect of Clusters Correlation at Light Nuclei Excited State

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    The correlation of αα\alpha\alpha was probed via measuring the transverse momentum pTp_{T} and width δpT\delta p_{T} of one α\alpha, for the first time, which represents the spatial and dynamical essentialities of the initial coupling state in 8^{8}Be nucleus. The weighted interaction vertex of 3α\alpha reflected by the magnitudes of their relative momentums and relative emission angles proves the isosceles triangle configuration for 3α\alpha at the high excited energy analogous Hoyle states.Comment: 8 pages, 9 figure

    Variation of Tensor Force due to Nuclear Medium Effect

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    The enhancement of Jπ(T)J^{\pi}(T)=3+^{+}(0) state with isospin T=0T=0 excited by the tensor force in the free 6^{6}Li nucleus has been observed, for the first time, relative to a shrinkable excitation in the 6^{6}Li cluster component inside its host nucleus. Comparatively, the excitation of Jπ(T)J^{\pi}(T)=0+^{+}(1) state with isospin T=1T=1 for these two 6^{6}Li formations take on an approximately equal excitation strength. The mechanism of such tensor force effect was proposed due to the intensive nuclear medium role on isospin TT=0 state.Comment: 6 pages, 4 figure

    Multi-alpha Boson Gas state in Fusion Evaporation Reaction and Three-body Force

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    The experimental evidence for the α\alpha Boson gas state in the 11^{11}C+12^{12}C\rightarrow23^{23}Mg^{\ast} fusion evaporation reaction is presented. By measuring the α\alpha emission spectrum with multiplicity 2 and 3, we provide insight into the existence of a three-body force among α\alpha particles. The observed spectrum exhibited distinct tails corresponding to α\alpha particles emitted in pairs and triplets consistent well with the model-calculations of AV18-UX and chiral effective field theory of NV2-3-la*, indicating the formation of α\alpha clusters with three-body force in the Boson gas state.Comment: 7 pages, 6 figure
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