195 research outputs found
Dyonic Reissner-Nordstrom Black Holes and Superradiant Stability
Black holes immersed in magnetic fields are believed to be important systems
in astrophysics. One interesting topic on these systems is their superradiant
stability property. In the present paper, we analytically obtain the
superradiantly stable regime for the asymptotically flat dyonic
Reissner-Nordstrom black holes with charged massive scalar perturbation. The
effective potential experienced by the scalar perturbation in the dyonic black
hole background is obtained and analyzed. It is found that the dyonic black
hole is superradiantly stable in the regime , where
are the event horizons of the dyonic black hole. Compared with the purely
electrically charged Reissner-Nordstrom black hole case, our result indicates
that the additional coupling of the charged scalar perturbation with the
magnetic field makes the black hole and scalar perturbation system more
superradiantly unstable, which provides further evidence on the instability
induced by magnetic field in black hole superradiance process
Analytic study of superradiant stability of Kerr-Newman black holes under charged massive scalar perturbation
The superradiant stability of a Kerr-Newman black hole and charged massive
scalar perturbation is investigated. We treat the black hole as a background
geometry and study the equation of motion of the scalar perturbation. From the
radial equation of motion, we derive the effective potential experienced by the
scalar perturbation. By a careful analysis of this effective potential, it is
found that when the inner and outer horizons of Kerr-Newman black hole satisfy
and the charge-to-mass ratios of scalar
perturbation and black hole satisfy , the
Kerr-Newman black hole and scalar perturbation system is superradiantly stable.Comment: 7 pages, references adde
The heavy quarkonium inclusive decays using the principle of maximum conformality
The next-to-next-to-leading order (NNLO) pQCD correction to the inclusive
decays of the heavy quarkonium ( being or ) has been done in
the literature within the framework of nonrelativistic QCD. One may observe
that the NNLO decay width still has large conventional renormalization scale
dependence due to its weaker pQCD convergence, e.g. about
for and for , by varying the scale within
the range of . The principle of maximum conformality (PMC)
provides a systematic way to fix the -running behavior of the
process, which satisfies the requirements of renormalization group invariance
and eliminates the conventional renormalization scheme and scale ambiguities.
Using the PMC single-scale method, we show that the resultant PMC conformal
series is renormalization scale independent, and the precision of the
inclusive decay width can be greatly improved. Taking the relativistic
correction into consideration, the ratios of the
decays to light hadrons or are: and , respectively.
Here the errors are for . As a step forward,
by applying the Pad approximation approach (PAA) over the PMC
conformal series, we obtain approximate NNNLO predictions for those two ratios,
e.g.
and .
The ratio agrees with the latest PDG
value , indicating the
necessity of a strict calculation of NNNLO terms.Comment: 10 pages, 4 figure
Strangelets at finite temperature: nucleon emission rates, interface and shell effects
We investigate the properties of strangelets at finite temperature , where
an equivparticle model is adopted with both the linear confinement and
leading-order perturbative interactions accounted for using density-dependent
quark masses. The shell effects are examined by solving the Dirac equations for
quarks in the mean-field approximation, which diminish with temperature as the
occupation probability of each single-particle levels fixed by the Fermi-Dirac
statistics, i.e., shell dampening. Consequently, instead of decreasing with
temperature, the surface tension extracted from a liquid-drop formula increases
with until reaching its peak at -40 MeV with vanishing shell
corrections, where the formula roughly reproduces the free energy per baryon of
all strangelets. The curvature term, nevertheless, decreases with despite
the presence of shell effects. The neutron and proton emission rates are fixed
microscopically according to the external nucleon gas densities that are in
equilibrium with strangelets, which generally increase with (
MeV) for stable strangelets but decrease for those that are unstable against
nucleon emission at . The energy, free energy, entropy, charge-to-mass
ratio, strangeness per baryon, and root-mean-square radius of -stable
strangelets obtained with various parameter sets are presented as well. The
results indicated in this work are useful for understanding the products of
binary compact star mergers and heavy-ion collisions
Genome-wide identification and expression analysis of serine proteases and homologs in the silkworm Bombyx mori
<p>Abstract</p> <p>Background</p> <p>Serine proteases (SPs) and serine proteases homologs (SPHs) are a large group of proteolytic enzymes, with important roles in a variety of physiological processes, such as cell signalling, defense and development. Genome-wide identification and expression analysis of serine proteases and their homologs in the silkworm might provide valuable information about their biological functions.</p> <p>Results</p> <p>In this study, 51 SP genes and 92 SPH genes were systematically identified in the genome of the silkworm <it>Bombyx mori</it>. Phylogenetic analysis indicated that six gene families have been amplified species-specifically in the silkworm, and the members of them showed chromosomal distribution of tandem repeats. Microarray analysis suggests that many silkworm-specific genes, such as members of SP_fam12, 13, 14 and 15, show expression patterns that are specific to tissues or developmental stages. The roles of SPs and SPHs in resisting pathogens were investigated in silkworms when they were infected by <it>Escherichia coli</it>, <it>Bacillus bombysepticus</it>, <it>Batrytis bassiana </it>and <it>B. mori </it><it>nucleopolyhedrovirus</it>, respectively. Microarray experiment and real-time quantitative RT-PCR showed that 18 SP or SPH genes were significantly up-regulated after pathogen induction, suggesting that SP and SPH genes might participate in pathogenic microorganism resistance in <it>B. mori</it>.</p> <p>Conclusion</p> <p>Silkworm SP and SPH genes were identified. Comparative genomics showed that SP and SPH genes belong to a large family, whose members are generated mainly by tandem repeat evolution. We found that silkworm has species-specific SP and SPH genes. Phylogenetic and microarray analyses provide an overview of the silkworm SP and SPHs, and facilitate future functional studies on these enzymes.</p
The First Human Infection with Severe Fever with Thrombocytopenia Syndrome Virus in Shaanxi Province, China
Background: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease discovered in China in 2009. In July 2013, the first human infection with SFTS virus (SFTSV) was detected in Shaanxi Province, Western China. Methods: A seroprevalence study among humans was carried out in an SFTS endemic village; specifically, serum samples were collected from 363 farmers in an SFTS endemic village in Shaanxi Province. The presence of SFTSV antibodies in serum was determined using an ELISA. Results: SFTSV antibodies were found in a total of 20 people (5.51%), with no significant difference between males and females (6.93% and 4.42%, respectively; Chi-square = 1.29, p = 0.25). Moreover, the SFTSV antibody positive rate was not significantly different across different age groups (Chisquare = 2.23, p = 0.69). Conclusions: SFTSV readily infects humans with outdoor exposure. The results of the serological study indicate that the virus circulates widely in Shaanxi Province. SFTSV represents a public health threat in China
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