575 research outputs found

    Climate and soil moisture content during development ofthe frst palaeosol in the southern Loess Plateau

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    The scientific problems concerning Quaternary soil water content and the water cycle have not been researched. This study examined the soil water content and depth of distribution of gravitational water in the south Loess Plateau during development of the first palaeosol layer (S1) by methods such as field investigation, electron microscopy, energy spectrum analysis, chemical analysis, and so on. The purpose was to reveal the climate, water balance and vegetation type at the time when S1 developed. The depth of migration of CaCO3 and Sr were 4.2 m below the upper boundary of the S1 palaeosol, and the depth of weathered loess beneath the argillic horizon was 4.0 m. Ferri‐argillans developed well in the argillic horizon and their depth of migration was 1 m below the argillic horizon. These findings suggest that the climate during the last interglacial was subtropical and humid, and the soil‐water balance was positive. Gravitational water was present to a depth of least 4.2 m from the top of S1, and the water content was adequate for tree growth. The chemical weathering index showed that this palaeosol has been moderately weathered

    Effect of Lactobacillus acidophilus, Oenococcus oeni, and Lactobacillus brevis on Composition of Bog Bilberry Juice

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    This study investigated the impact of Lactobacillus acidophilus NCFM, Oenococcus oeni Viniflora((R)) Oenos and Lactobacillus brevis CICC 6239 on bog bilberry juice with a considerably low pH and rich in anthocyanins content. Moreover, the effects of the strains on the composition of phenolic compounds, amino acids, ammonium ion, biogenic amines, reduced sugars, organic acids, and color parameters of the juice were studied. All three bacteria consumed sugars and amino acids but exhibited different growth patterns. Lactic acid was detected only in L. acidophilus inoculated juice. The content of the phenolic compounds, especially anthocyanins, decreased in juice after inoculation. The CIELa*b* analysis indicated that the juice inoculated with L. acidophilus and O. oeni showed a decrease on a* and b* (less red and yellow) but an increase on L (more lightness), whereas the color attributes of L. brevis inoculated juice did not significantly change. Based on this study, L. brevis showed the most optimal performance in the juice due to its better adaptability and fewer effects on the appearance of juice. This study provided a useful reference on the metabolism of lactic acid bacteria in low pH juice and the evolution of primary and secondary nutrients in juice after inoculated with lactic acid bacteria

    Observation of a ppb mass threshoud enhancement in \psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) decay

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    The decay channel ψπ+πJ/ψ(J/ψγppˉ)\psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) is studied using a sample of 1.06×1081.06\times 10^8 ψ\psi^\prime events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the ppˉp\bar{p} invariant mass spectrum. The enhancement can be fit with an SS-wave Breit-Wigner resonance function with a resulting peak mass of M=186113+6(stat)26+7(syst)MeV/c2M=1861^{+6}_{-13} {\rm (stat)}^{+7}_{-26} {\rm (syst)} {\rm MeV/}c^2 and a narrow width that is Γ<38MeV/c2\Gamma<38 {\rm MeV/}c^2 at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with those of any known meson resonance.Comment: 5 pages, 3 figures, submitted to Chinese Physics

    Effect of Aspect Ratio on Field Emission Properties of ZnO Nanorod Arrays

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    ZnO nanorod arrays are prepared on a silicon wafer through a multi-step hydrothermal process. The aspect ratios and densities of the ZnO nanorod arrays are controlled by adjusting the reaction times and concentrations of solution. The investigation of field emission properties of ZnO nanorod arrays revealed a strong dependency on the aspect ratio and their density. The aspect ratio and spacing of ZnO nanorod arrays are 39 and 167 nm (sample C), respectively, to exhibit the best field emission properties. The turn-on field and threshold field of the nanorod arrays are 3.83 V/μm and 5.65 V/μm, respectively. Importantly, the sample C shows a highest enhancement of factorβ, which is 2612. The result shows that an optimum density and aspect ratio of ZnO nanorod arrays have high efficiency of field emission

    Resuscitation of Newborn Piglets. Short-Term Influence of FiO2 on Matrix Metalloproteinases, Caspase-3 and BDNF

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    Perinatal hypoxia-ischemia is a major cause of mortality and cerebral morbidity, and using oxygen during newborn resuscitation may further harm the brain. The aim was to examine how supplementary oxygen used for newborn resuscitation would influence early brain tissue injury, cell death and repair processes and the regulation of genes related to apoptosis, neurodegeneration and neuroprotection.Anesthetized newborn piglets were subjected to global hypoxia and then randomly assigned to resuscitation with 21%, 40% or 100% O(2) for 30 min and followed for 9 h. An additional group received 100% O(2) for 30 min without preceding hypoxia. The left hemisphere was used for histopathology and immunohistochemistry and the right hemisphere was used for in situ zymography in the corpus striatum; gene expression and the activity of various relevant biofactors were measured in the frontal cortex. There was an increase in the net matrix metalloproteinase gelatinolytic activity in the corpus striatum from piglets resuscitated with 100% oxygen vs. 21%. Hematoxylin-eosin (HE) staining revealed no significant changes. Nine hours after oxygen-assisted resuscitation, caspase-3 expression and activity was increased by 30-40% in the 100% O(2) group (n = 9/10) vs. the 21% O(2) group (n = 10; p<0.04), whereas brain-derived neurotrophic factor (BDNF) activity was decreased by 65% p<0.03.The use of 100% oxygen for resuscitation resulted in increased potentially harmful proteolytic activities and attenuated BDNF activity when compared with 21%. Although there were no significant changes in short term cell loss, hyperoxia seems to cause an early imbalance between neuroprotective and neurotoxic mechanisms that might compromise the final pathological outcome

    CdSe Ring- and Tribulus-Shaped Nanocrystals: Controlled Synthesis, Growth Mechanism, and Photoluminescence Properties

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    With air-stable and generic reagents, CdSe nanocrystals with tunable morphologies were prepared by controlling the temperature in the solution reaction route. Thereinto, the lower reaction temperature facilitates the anisotropic growth of crystals to obtain high-yield CdSe ring- and tribulus-shaped nanocrystals with many branches on their surfaces. The photoluminescence properties are sensitive to the nature of particle and its surface. The products synthesized at room temperature, whose surfaces have many branches, show higher blue shift and narrower emission linewidths (FWHM) of photoluminescence than that of samples prepared at higher temperature, whose surfaces have no branches. Microstructural studies revealed that the products formed through self-assembly of primary crystallites. Nanorings formed through the nonlinear attachment of primary crystallites, and the branches on the surfaces grew by linear attachment at room temperature. And the structure of tribulus-shaped nanoparticle was realized via two steps of aggregation, i.e., random and linear oriented aggregation. Along with the elevation of temperature, the branches on nanocrystal surfaces shortened gradually because of the weakened linear attachment

    Variants of the Matrix Metalloproteinase-2 but not the Matrix Metalloproteinase-9 genes significantly influence functional outcome after stroke

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    <p>Abstract</p> <p>Background</p> <p>Multiple lines of evidence suggest that genetic factors contribute to stroke recovery. The matrix metalloproteinases -2 (MMP-2) and -9 (MMP-9) are modulators of extracellular matrix components, with important regulatory functions in the Central Nervous System (CNS). Shortly after stroke, MMP-2 and MMP-9 have mainly damaging effects for brain tissue. However, MMPs also have a beneficial activity in angiogenesis and neurovascular remodelling during the delayed neuroinflammatory response phase, thus possibly contributing to stroke functional recovery.</p> <p>Methods</p> <p>In the present study, the role of <it>MMP-2 </it>and <it>MMP-9 </it>genetic variants in stroke recovery was investigated in 546 stroke patients. Functional outcome was assessed three months after a stroke episode using the modified Rankin Scale (mRS), and patients were classified in two groups: good recovery (mRS ≤ 1) or poor recovery (mRS>1). Haplotype tagging single nucleotide polymorphisms (SNPs) in the <it>MMP-2 </it>(N = 21) and <it>MMP-9 </it>(N = 4) genes were genotyped and tested for association with stroke outcome, adjusting for significant non-genetic clinical variables.</p> <p>Results</p> <p>Six SNPs in the <it>MMP-2 </it>gene were significantly associated with stroke outcome (0.0018<<it>P </it>< 0.0415), two of which survived the Bonferroni correction for multiple testing. In the subset of ischemic stroke patients, association of five of these SNPs remained positive (0.0042<<it>P </it>< 0.0306). No significant associations were found for the <it>MMP-9 </it>gene.</p> <p>Conclusions</p> <p>The results presented strongly indicate that <it>MMP-2 </it>genetic variants are an important mediator of functional outcome after stroke.</p

    Semimetallic carbon allotrope with topological nodal line in mixed sp2sp^2-sp3sp^3 bonding networks

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    Graphene is known as a two-dimensional Dirac semimetal, in which electron states are described by the Dirac equation of relativistic quantum mechanics. Three-dimensional analogues of graphene are characterized by Dirac points or lines in momentum space, which are protected by symmetry. Here, we report a novel 3D carbon allotrope belonging to a class of topological nodal line semimetals, discovered by using an evolutionary structure search method. The new carbon phase in monoclinic CC2/m/m space group, termed mm-C8C_8, consists of five-membered rings with sp3sp^3 bonding interconnected by sp2sp^2-bonded carbon networks. Enthalpy calculations reveal that mm-C8C_8 is more favorable over recently reported topological semimetallic carbon allotropes, and the dynamical stability of mm-C8C_8 is verified by phonon spectra and molecular dynamics simulations. Simulated x-ray diffraction spectra propose that mm-C8C_8 would be one of the unidentified carbon phases observed in detonation shoot. The analysis of electronic properties indicates that mm-C8C_8 exhibits the nodal line protected by both inversion and time-reversal symmetries in the absence of spin-orbit coupling and the surface band connecting the projected nodal points. Our results may help design new carbon allotropes with exotic electronic properties.Comment: 18 pages, 5 figure
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