363 research outputs found
Observation of orbital ordering and origin of the nematic order in FeSe
To elucidate the origin of nematic order in FeSe, we performed
field-dependent 77Se-NMR measurements on single crystals of FeSe. We observed
orbital ordering from the splitting of the NMR spectra and Knight shift and a
suppression of it with magnetic field B0 up to 16 T applied parallel to the
Fe-planes. There is a significant change in the distribution and magnitude of
the internal magnetic field across the orbital ordering temperature Torb while
stripe-type antiferromagnetism is absent. Giant antiferromagnetic (AFM) spin
fluctuations measured by the NMR spin-lattice relaxation are gradually
developed starting at ~ 40 K, which is far below the nematic ordering
temperature Tnem. These results demonstrate that orbital ordering is the origin
of the nematic order, and the AFM spin fluctuation is the driving mechanism of
superconductivity in FeSe under the presence of the nematic order.Comment: 6 pages, 4 figure
An annular gap acceleration model for -ray emission of pulsars
If the binding energy of the pulsar's surface is not so high (the case of a
neutron star), both the negative and positive charges will flow out freely from
the surface of the star. The annular free flow model for -ray emission
of pulsars is suggested in this paper. It is emphasized that: (1). Two kinds of
acceleration regions (annular and core) need to be taken into account. The
annular acceleration region is defined by the magnetic field lines that cross
the null charge surface within the light cylinder. (2). If the potential drop
in the annular region of a pulsar is high enough (normally the cases of young
pulsars), charges in both the annular and the core regions could be accelerated
and produce primary gamma-rays. Secondary pairs are generated in both regions
and stream outwards to power the broadband radiations. (3). The potential drop
in the annular region grows more rapidly than that in the core region. The
annular acceleration process is a key point to produce wide emission beams as
observed. (4). The advantages of both the polar cap and outer gap models are
retained in this model. The geometric properties of the -ray emission
from the annular flow is analogous to that presented in a previous work by Qiao
et al., which match the observations well. (5). Since charges with different
signs leave the pulsar through the annular and the core regions, respectively,
the current closure problem can be partially solved.Comment: 11 pages 2 figures, accepted by Chinese Journal of Astronomy and
Astrophysic
Rapidity dependence of hadron production in central Au+Au collisions at GeV
The rapidity and transverse momentum spectra for identified hadrons in
central Au+Au collisions at GeV are computed in a quark
combination model. The data of rapidity distributions for ,
, and net protons are well described. We
also predict rapidity distributions for , ,
() and
. The multiplicity ratios of
charged antihadrons to hadrons as a function of rapidity are reproduced. The
results for spectra of , , and for
the ratios in a broader range agree well with the data.
Finally the rapidity dependence of transverse momentum distributions for
hadrons are given.Comment: 10 pages,11figures,3 table
Modeling realistic Earth matter density for CP violation in neutrino oscillation
We examine the effect of a more realistic Earth matter density model which
takes into account of the local density variations along the baseline of a
possi ble 2100 km very long baseline neutrino oscillation experiment. Its
influence to the measurement of CP violation is investigated and a comparison
with the commonly used global density models made. Significant differences are
found in the comparison of the results of the different density models.Comment: 16 pages, 8 figure
Epidemiologic Features and Environmental Risk Factors of Severe Fever with Thrombocytopenia Syndrome, Xinyang, China
Background:Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease discovered in rural areas of Central China in 2009, caused by a novel bunyavirus, SFT
Investigating the Role of P311 in the Hypertrophic Scar
The mechanisms of hypertrophic scar formation are not fully understood. We previously screened the differentially expressed genes of human hypertrophic scar tissue and identified P311 gene as upregulated. As the activities of P311 in human fibroblast function are unknown, we examined the distribution of it and the effects of forced expression or silencing of expression of P311. P311 expression was detected in fibroblast-like cells from the hypertrophic scar of burn injury patients but not in peripheral blood mononuclear cells, bone marrow mesenchymal stem cells, epidermal cells or normal skin dermal cells. Transfection of fibroblasts with P311 gene stimulated the expression of alpha-smooth muscle actin (α-SMA), TGF-β1 and α1(I) collagen (COL1A1), and enhanced the contraction of fibroblast populated collagen lattices (FPCL). In contrast, interference of fibroblast P311 gene expression decreased the TGF-β1 mRNA expression and reduced the contraction of fibroblasts in FPCL. These results suggest that P311 may be involved in the pathogenesis of hypertrophic scar via induction of a myofibroblastic phenotype and of functions such as TGF-β1 expression. P311 could be a novel target for the control of hypertrophic scar development
Transcriptome and Network Changes in Climbers at Extreme Altitudes
Extreme altitude can induce a range of cellular and systemic responses. Although it is known that hypoxia underlies the major changes and that the physiological responses include hemodynamic changes and erythropoiesis, the molecular mechanisms and signaling pathways mediating such changes are largely unknown. To obtain a more complete picture of the transcriptional regulatory landscape and networks involved in extreme altitude response, we followed four climbers on an expedition up Mount Xixiabangma (8,012 m), and collected blood samples at four stages during the climb for mRNA and miRNA expression assays. By analyzing dynamic changes of gene networks in response to extreme altitudes, we uncovered a highly modular network with 7 modules of various functions that changed in response to extreme altitudes. The erythrocyte differentiation module is the most prominently up-regulated, reflecting increased erythrocyte differentiation from hematopoietic stem cells, probably at the expense of differentiation into other cell lineages. These changes are accompanied by coordinated down-regulation of general translation. Network topology and flow analyses also uncovered regulators known to modulate hypoxia responses and erythrocyte development, as well as unknown regulators, such as the OCT4 gene, an important regulator in stem cells and assumed to only function in stem cells. We predicted computationally and validated experimentally that increased OCT4 expression at extreme altitude can directly elevate the expression of hemoglobin genes. Our approach established a new framework for analyzing the transcriptional regulatory network from a very limited number of samples
Environmental Adaptation: Genomic Analysis of the Piezotolerant and Psychrotolerant Deep-Sea Iron Reducing Bacterium Shewanella piezotolerans WP3
Shewanella species are widespread in various environments. Here, the genome sequence of Shewanella piezotolerans WP3, a piezotolerant and psychrotolerant iron reducing bacterium from deep-sea sediment was determined with related functional analysis to study its environmental adaptation mechanisms. The genome of WP3 consists of 5,396,476 base pairs (bp) with 4,944 open reading frames (ORFs). It possesses numerous genes or gene clusters which help it to cope with extreme living conditions such as genes for two sets of flagellum systems, structural RNA modification, eicosapentaenoic acid (EPA) biosynthesis and osmolyte transport and synthesis. And WP3 contains 55 open reading frames encoding putative c-type cytochromes which are substantial to its wide environmental adaptation ability. The mtr-omc gene cluster involved in the insoluble metal reduction in the Shewanella genus was identified and compared. The two sets of flagellum systems were found to be differentially regulated under low temperature and high pressure; the lateral flagellum system was found essential for its motility and living at low temperature
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