6,208 research outputs found
transitions in the light cone sum rules with the chiral current
semi-leptonic decays to the light scalar meson, , are investigated in the QCD
light-cone sum rules (LCSR) with chiral current correlator. Having little
knowledge of ingredients of the scalar mesons, we confine ourself to the two
quark picture for them and work with the two possible Scenarios. The resulting
sum rules for the form factors receive no contributions from the twist-3
distribution amplitudes (DA's), in comparison with the calculation of the
conventional LCSR approach where the twist-3 parts play usually an important
role. We specify the range of the squared momentum transfer , in which the
operator product expansion (OPE) for the correlators remains valid
approximately. It is found that the form factors satisfy a relation consistent
with the prediction of soft collinear effective theory (SCET). In the effective
range we investigate behaviors of the form factors and differential decay
widthes and compare our calculations with the observations from other
approaches. The present findings can be beneficial to experimentally identify
physical properties of the scalar mesons.Comment: 22 pages,16 figure
Expression and significance of HIF-1 α and VEGF in rats with diabetic retinopathy
AbstractObjectiveTo investigate the expression of hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) in diabetic retinopathy (DR) rats and its effect on the DR occurrence and development.MethodsA total of 120 SD rats were randomly divided into trial group and control group with 60 in each. STZ i.p. was used in the trial group to establish the DM model, citrate buffer salt of same amount was used i.p. to the control group. 1, 3 and 6 months after injection, respective 20 rats were sacrificed in each group to observe expression of HIF-1α and VEGF in the rat retina tissue at different time points.ResultsExpression of HIF-1α and VEGF were negative in the control group; expression of HIF-1α and VEGF protein in retinal tissue were weak after 1 month of DR mold formation. It showed progressive enhancement along with the progression in different organizations, differences between groups were significant (P<0.05).ConclusionsExpressions of HIF-1α and VEGF were correlated with disease progression in early diabetic retinopathy. Retinal oxygen can induce over-expression of HIF-1α and VEGF. It shows that HIF-1α and VEGF play an important role in the pathogenesis of DR
Exact solution of gyration radius of individual's trajectory for a simplified human mobility model
Gyration radius of individual's trajectory plays a key role in quantifying
human mobility patterns. Of particular interests, empirical analyses suggest
that the growth of gyration radius is slow versus time except the very early
stage and may eventually arrive to a steady value. However, up to now, the
underlying mechanism leading to such a possibly steady value has not been well
understood. In this Letter, we propose a simplified human mobility model to
simulate individual's daily travel with three sequential activities: commuting
to workplace, going to do leisure activities and returning home. With the
assumption that individual has constant travel speed and inferior limit of time
at home and work, we prove that the daily moving area of an individual is an
ellipse, and finally get an exact solution of the gyration radius. The
analytical solution well captures the empirical observation reported in [M. C.
Gonz`alez et al., Nature, 453 (2008) 779]. We also find that, in spite of the
heterogeneous displacement distribution in the population level, individuals in
our model have characteristic displacements, indicating a completely different
mechanism to the one proposed by Song et al. [Nat. Phys. 6 (2010) 818].Comment: 4 pages, 4 figure
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