54 research outputs found
A Comprehensive Analysis of Fermi Gamma-ray Burst Data: III. Energy-Dependent T90 Distributions of GBM GRBs and Instrumental Selection Effect on Duration Classification
The durations (T90) of 315 GRBs detected with Fermi/GBM (8-1000 keV) by 2011
September are calculated using the Bayesian Block method. We compare the T90
distributions between this sample and those derived from previous/current GRB
missions. We show that the T90 distribution of this GRB sample is bimodal, with
a statistical significance level being comparable to those derived from the
BeppoSAX/GRBM sample and the Swift/BAT sample, but lower than that derived from
the CGRO/BATSE sample. The short-to-long GRB number ratio is also much lower
than that derived from the BATSE sample, i.e., 1:6.5 vs 1:3. We measure T90 in
several bands, i.e., 8-15, 15-25, 25-50, 50-100, 100-350, and 350-1000 keV, to
investigate the energy-dependence effect of the bimodal T90 distribution. It is
found that the bimodal feature is well observed in the 50-100 and 100-350 keV
bands, but is only marginally acceptable in the 25-50 keV and 350-1000 keV
bands. The hypothesis of the bimodality is confidently rejected in the 8-15 and
15-25 keV bands. The T90 distributions in these bands are roughly consistent
with those observed by missions with similar energy bands. The parameter T90 as
a function of energy follows \bar T90 \propto E^{-0.20\pm 0.02} for long GRBs.
Considering the erratic X-ray and optical flares, the duration of a burst would
be even much longer for most GRBs. Our results, together with the observed
extended emission of some short GRBs, indicate that the central engine activity
time scale would be much longer than T90} for both long and short GRBs and the
observed bimodal T90 distribution may be due to an instrumental selection
effect.Comment: 29 pages, 2 tables, 9 figures, accepted for publication in Ap
Subcutaneous Administration of PDGF-AA Improves the Functional Recovery After Spinal Cord Injury
Previous studies by our group have demonstrated that the transplantation of exogenous platelet-derived growth factor (PDGF)-AA-overexpressing oligodendrocyte progenitor cells (OPCs) promotes tissue repair and recovery of neurological function in a rat model of spinal cord injury (SCI). However, it remains unclear whether treatment with PDGF-AA also affects endogenous oligodendrocytes (OLs) or even neurons, thus promoting further functional recovery after SCI. In the present study, we evaluated the therapeutic potential of PDGF-AA treatment by direct subcutaneous injection of PDGF-AA immediately after SCI. We demonstrated that PDGF-AA injection resulted in increased tissue sparing, myelination and functional recovery in rats following SCI. Further experimentation confirmed that PDGF-AA increased the survival of endogenous OPCs and OLs, and promoted the proliferation of OPCs and their differentiation into OLs. Moreover, PDGF-AA also protected motor neurons from death in the injured spinal cord. These results indicated that PDGF-AA administration may be an effective treatment for SCI
Synthesis and applications of porous non-silica metal oxide submicrospheres
© 2016 Royal Society of Chemistry. Nowadays the development of submicroscale products of specific size and morphology that feature a high surface area to volume ratio, well-developed and accessible porosity for adsorbates and reactants, and are non-toxic, biocompatible, thermally stable and suitable as synergetic supports for precious metal catalysts is of great importance for many advanced applications. Complex porous non-silica metal oxide submicrospheres constitute an important class of materials that fulfill all these qualities and in addition, they are relatively easy to synthesize. This review presents a comprehensive appraisal of the methods used for the synthesis of a wide range of porous non-silica metal oxide particles of spherical morphology such as porous solid spheres, core-shell and yolk-shell particles as well as single-shell and multi-shell particles. In particular, hydrothermal and low temperature solution precipitation methods, which both include various structure developing strategies such as hard templating, soft templating, hydrolysis, or those taking advantage of Ostwald ripening and the Kirkendall effect, are reviewed. In addition, a critical assessment of the effects of different experimental parameters such as reaction time, reaction temperature, calcination, pH and the type of reactants and solvents on the structure of the final products is presented. Finally, the practical usefulness of complex porous non-silica metal oxide submicrospheres in sensing, catalysis, biomedical, environmental and energy-related applications is presented
X-ray-Induced Changes in the Expression of Inflammation-Related Genes in Human Peripheral Blood
Using quantitative real-time polymerase chain reaction (PCR) array, we explored and compared the expression changes of inflammation-related genes in human peripheral blood irradiated with 0.5, 3, and 10 Gy doses of X-rays 24 h after exposure. Results indicated that the expression of 62 out of 84 genes was significantly altered after X-ray radiation. Among these 62 genes, 35 (such as TNFSF4) are known to be associated with radiation response, but others are novel. At a low radiation dose (0.5 Gy), 9 genes were up-regulated and 19 were down-regulated. With further increased dose to 3 Gy, 8 unique genes were up-regulated and 19 genes were down-regulated. We also identified 48 different genes that were differentially expressed significantly after 10 Gy of irradiation, and among these transcripts, up-regulated genes accounted for only one-third (16 genes) of the total. Of the 62 genes, 31 were significantly altered only at a specific dose, and a total of 10 genes were significantly expressed at all 3 doses. The dose- and time-dependent expression of CCL2 was confirmed by quantitative real-time reverse-transcription PCR. A number of candidate genes reported herein may be useful molecular biomarkers of radiation exposure in human peripheral blood
Epidemiological survey of a captive Chinese rhesus macaque breeding colony in Yunnan for SRV, STLV and BV
Nonhuman primates are critical resources for biomedical research.
Rhesus macaque is a popularly used laboratory nonhuman primate that
share many characteristics with humans. However, rhesus macaques are
the natural host of two exogenous retroviruses, SRV (simian type D
retrovirus) and STLV (simian T lymphotropic virus). SRV and STLV may
introduce potentially significant confounding factors into the study of
AIDS model. Moreover, B virus (ceropithecine herpesvirus 1) is likely
to harm not only rhesus macaque but also humans in experiments
involving rhesus macaque. Yunnan province has large-scale breeding
colonies of Chinese rhesus macaque. Therefore there is an urgent need
for SPF Chinese rhesus macaque colonies. Here we investigated SRV, STLV
and BV infections in 411 Chinese rhesus macaque by PCR technique. The
results showed that the prevalence of SRV, STLV and BV among Chinese
rhesus macaque breeding colony was 19.71% (81/411), 13.38% (55/411) and
23.11% (95/411), respectively. Comparison of viruses infection in
different age-groups and male/female of Chinese rhesus macaque was also
analyzed. This study will contribute to establishment of SPF Chinese
rhesus macaque breeding colony
Genomic epidemiology reveals early transmission of SARS-CoV-2 and mutational dynamics in Nanning, China
Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants are a fatal pathogen resulting in substantial morbidity and mortality, and posing a great threat to human health with epidemics and pandemics. Methods: Next-generation sequencing (NGS) was performed to investigate the SARS-CoV-2 genomic characterization. Phylogenetic analysis of SARS-CoV-2 genomes was used to probe the evolutionary. Homology protein structure modelling was done to explore potential effect of the mutations. Results: The eighty genome sequences of SARS-CoV-2 obtained from the thirty-nine patients with COVID-19. A novel variant with mutation H625R concomitant with S50L in spike glycoprotein had been identified. Phylogenetic analysis revealed that SARS-CoV-2 variants belong to several distinct lineages. Homology modelling indicated that variant with mutation H625R and S50L increases flexibility of S1 subunit. Conclusions: SARS-CoV-2 genomes are constantly evolving by accumulation of point mutations. The amino acid H625R in combination with S50L may have a significant impact on the interaction between spike glycoprotein and ACE2
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