176 research outputs found
Strong gravitational lensing in a squashed Kaluza-Klein black hole spacetime
We investigate the strong gravitational lensing in a Kaluza-Klein black hole
with squashed horizons. We find the size of the extra dimension imprints in the
radius of the photon sphere, the deflection angle, the angular position and
magnification of the relativistic images. Supposing that the gravitational
field of the supermassive central object of the Galaxy can be described by this
metric, we estimated the numerical values of the coefficients and observables
for gravitational lensing in the strong field limit.Comment: 13pages, 5 figures, Final version appeared in PR
Strong gravitational lensing in a squashed Kaluza-Klein G\"{o}del black hole
We investigate the strong gravitational lensing in a squashed Kaluza-Klein
black hole immersed in the G\"{o}del universe with global rotation. Our result
show that the strong gravitational lensing in the squashed Kaluza-Klein
G\"{o}del black hole spacetime has some distinct behaviors from that in the
Kerr case. In the squashed Kaluza-Klein G\"{o}del black hole spacetime, the
photon sphere radius, the minimum impact parameter, the coefficient ,
and the deflection angle in the direction are
independent of whether the photon goes with or against the global rotation of
the G\"{o}del Universe. While in the Kerr black hole, the values of these
quantities for the prograde photons are different from those for the retrograde
photons. Moreover, the coefficient of increases with in the
squashed Kaluza-Klein G\"{o}del black hole, but decreases with in the Kerr
case. We also probe the influence of the squashed effect on the strong
gravitational lensing in this black hole and find that in the extremely
squashed case , the coefficient is a constant 1 and is
independent of the global rotation of the G\"{o}del Universe. Furthermore, we
assume that the gravitational field of the supermassive central object of the
Galaxy can be described by this metric and estimate the numerical values of the
coefficients and the main observables in the strong gravitational lensing.Comment: 16 pages, 7 figures, accepted for publication in Phys. Rev.
Rotating non-Kerr black hole and energy extraction
The properties of the ergosphere and energy extraction by Penrose process in
a rotating non-Kerr black hole are investigated. It is shown that the
ergosphere is sensitive to the deformation parameter and the shape
of the ergosphere becomes thick with increase of the parameter . It
is of interest to note that, comparing with the Kerr black hole, the
deformation parameter can enhance the maximum efficiency of the
energy extraction process greatly. Especially, for the case of , the
non-Kerr metric describes a superspinning compact object and the maximum
efficiency can exceed 60%, while it is only 20.7% for the extremal Kerr black
hole.Comment: 16 pages, 5 figures, and 2 table
Cloning and Characterization of a Pyrethroid Pesticide Decomposing Esterase Gene, \u3cem\u3eEst3385\u3c/em\u3e, from \u3cem\u3eRhodopseudomonas palustris\u3c/em\u3e PSB-S
Full length open reading frame of pyrethroid detoxification gene, Est3385, contains 963 nucleotides. This gene was identified and cloned based on the genome sequence of Rhodopseudomonas palustris PSB-S available at the GneBank. The predicted amino acid sequence of Est3385 shared moderate identities (30–46%) with the known homologous esterases. Phylogenetic analysis revealed that Est3385 was a member in the esterase family I. Recombinant Est3385 was heterologous expressed in E. coli, purified and characterized for its substrate specificity, kinetics and stability under various conditions. The optimal temperature and pH for Est3385 were 35 °C and 6.0, respectively. This enzyme could detoxify various pyrethroid pesticides and degrade the optimal substrate fenpropathrin with a Km and Vmax value of 0.734 ± 0.013 mmol·l−1 and 0.918 ± 0.025 U·µg−1, respectively. No cofactor was found to affect Est3385 activity but substantial reduction of enzymatic activity was observed when metal ions were applied. Taken together, a new pyrethroid degradation esterase was identified and characterized. Modification of Est3385 with protein engineering toolsets should enhance its potential for field application to reduce the pesticide residue from agroecosystems
Soliton generation in CaF crystalline whispering gallery mode resonators with negative thermal-optical effects
Calcium fluoride (CaF) crystalline whispering gallery mode resonators
(WGMRs) exhibit ultrahigh intrinsic quality factors and a low power anomalous
dispersion in the communication and mid-infrared bands, making them attractive
platforms for microresonator-based comb generation. However, their unique
negative thermo-optic effects pose challenges when achieving thermal
equilibrium. To our knowledge, our experiments serve as the first demonstration
of soliton microcombs in Q > 109 CaF WGMRs. We observed soliton
mode-locking and bidirectional switching of soliton numbers caused by the
negative thermo-optic effects. Additionally, various soliton formation dynamics
are shown, including breathing and vibrational solitons, which can be
attributed to thermo-photomechanical oscillations. Thus, our results enrich the
soliton generation platform and provide a reference for generating solitons
from WGMRs that comprise other materials with negative thermo-optic effects. In
the future, the ultrahigh quality factor of CaF crystal cavities may enable
the generation of sub-milliwatt-level broad-spectrum soliton combs.Comment: 4 pages,5 pictures,description of soliton generation in a calcium
fluoride whisper gallery mode microresonators with negative thermo-optical
effect,ready for publication in optics lette
Analysis of the current status of tuberculosis transmission in China based on a heterogeneity model
Tuberculosis (TB) is an infectious disease transmitted through the
respiratory system. China is one of the countries with a high burden of TB.
Since 2004, an average of more than 800,000 cases of active TB have been
reported each year in China. Analyzing the case data from 2004-2018, we find
significant differences in TB incidence by age group. Therefore, the effect of
age heterogeneous structure on TB transmission needs further study. We develop
a model of TB to explore the role of age heterogeneity as a factor in TB
transmission. The model is fitted numerically using the nonlinear least squares
method to obtain the key parameters in the model, and the basic reproduction
number Rv 0.8017 is calculated and the sensitivity anal-ysis of Rv to the
parameters is given. The simulation results show that reducing the number of
new infections in the elderly population and increasing the recovery rate of
elderly patients with the disease could significantly reduce the transmission
of tuberculosis. Furthermore the feasibility of achieving the goals of the WHO
End TB Strategy in China is assessed, and we obtain that with existing TB
control measures it will take another 30 years for China to reach the WHO goal
to reduce 90% of the number of new cases by year 2049. However, in theoretical
it is feasible to reach the WHO strategic goal of ending tuberculosis by 2035
if the group contact rate in the elderly population can be reduced though it is
difficulty to reduce the contact rate.Comment: We think this is a very interesting work that gives a good
understanding of the current TB transmission in China and assesses the
possibility of China achieving the 2035 TB control target and also explores
possible ways for how to prevent and control the TB in Chin
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