5,813 research outputs found
Generalized Log-Normal Chain-Ladder
We propose an asymptotic theory for distribution forecasting from the log
normal chain-ladder model. The theory overcomes the difficulty of convoluting
log normal variables and takes estimation error into account. The results
differ from that of the over-dispersed Poisson model and from the chain-ladder
based bootstrap. We embed the log normal chain-ladder model in a class of
infinitely divisible distributions called the generalized log normal
chain-ladder model. The asymptotic theory uses small asymptotics where
the dimension of the reserving triangle is kept fixed while the standard
deviation is assumed to decrease. The resulting asymptotic forecast
distributions follow t distributions. The theory is supported by simulations
and an empirical application
NF-{kappa}B-dependent induction of microRNA miR-146, an inhibitor targeted to signaling proteins of innate immune responses
Activation of mammalian innate and acquired immune responses must be tightly regulated by elaborate mechanisms to control their onset and termination. MicroRNAs have been implicated as negative regulators controlling diverse biological processes at the level of posttranscriptional repression. Expression profiling of 200 microRNAs in human monocytes revealed that several of them (miR-146a/b, miR-132, and miR-155) are endotoxin-responsive genes. Analysis of miR-146a and miR-146b gene expression unveiled a pattern of induction in response to a variety of microbial components and proinflammatory cytokines. By means of promoter analysis, miR-146a was found to be a NF-{kappa}B-dependent gene. Importantly, miR-146a/b were predicted to base-pair with sequences in the 3' UTRs of the TNF receptor-associated factor 6 and IL-1 receptor-associated kinase 1 genes, and we found that these UTRs inhibit expression of a linked reporter gene. These genes encode two key adapter molecules downstream of Toll-like and cytokine receptors. Thus, we propose a role for miR-146 in control of Toll-like receptor and cytokine signaling through a negative feedback regulation loop involving down-regulation of IL-1 receptor-associated kinase 1 and TNF receptor-associated factor 6 protein levels
Prevention and control of Zika fever as a mosquito-borne and sexually transmitted disease
The ongoing Zika virus (ZIKV) epidemic poses a major global public health
emergency. It is known that ZIKV is spread by \textit{Aedes} mosquitoes, recent
studies show that ZIKV can also be transmitted via sexual contact and cases of
sexually transmitted ZIKV have been confirmed in the U.S., France, and Italy.
How sexual transmission affects the spread and control of ZIKV infection is not
well-understood. We presented a mathematical model to investigate the impact of
mosquito-borne and sexual transmission on spread and control of ZIKV and used
the model to fit the ZIKV data in Brazil, Colombia, and El Salvador. Based on
the estimated parameter values, we calculated the median and confidence
interval of the basic reproduction number R0=2.055 (95% CI: 0.523-6.300), in
which the distribution of the percentage of contribution by sexual transmission
is 3.044 (95% CI: 0.123-45.73). Our study indicates that R0 is most sensitive
to the biting rate and mortality rate of mosquitoes while sexual transmission
increases the risk of infection and epidemic size and prolongs the outbreak. In
order to prevent and control the transmission of ZIKV, it must be treated as
not only a mosquito-borne disease but also a sexually transmitted disease
Dynamic Magneto-Conductance Fluctuations and Oscillations in Mesoscopic Wires and Rings
Using a finite-frequency recursive Green's function technique, we calculate
the dynamic magneto-conductance fluctuations and oscillations in disordered
mesoscopic normal metal systems, incorporating inter-particle Coulomb
interactions within a self-consistent potential method. In a disordered metal
wire, we observe ergodic behavior in the dynamic conductance fluctuations. At
low , the real part of the conductance fluctuations is essentially
given by the dc universal conductance fluctuations while the imaginary part
increases linearly from zero, but for greater than the Thouless energy
and temperature, the fluctuations decrease as . Similar
frequency-dependent behavior is found for the Aharonov-Bohm oscillations in a
metal ring. However, the Al'tshuler-Aronov-Spivak oscillations, which
predominate at high temperatures or in rings with many channels, are strongly
suppressed at high frequencies, leading to interesting crossover effects in the
-dependence of the magneto-conductance oscillations.Comment: 4 pages, REVTeX 3.0, 5 figures(ps file available upon request),
#phd0
Magneto-Optical Stern-Gerlach Effect in Atomic Ensemble
We study the birefringence of the quantized polarized light in a
magneto-optically manipulated atomic ensemble as a generalized Stern-Gerlach
Effect of light. To explain this engineered birefringence microscopically, we
derive an effective Shr\"odinger equation for the spatial motion of two
orthogonally polarized components, which behave as a spin with an effective
magnetic moment leading to a Stern-Gerlach split in an nonuniform magnetic
field. We show that electromagnetic induced transparency (EIT) mechanism can
enhance the magneto-optical Stern-Gerlach effect of light in the presence of a
control field with a transverse spatial profile and a inhomogeneous magnetic
field.Comment: 7 pages, 5 figure
QCD Multipole Expansion and Hadronic Transitions in Heavy Quarkonium Systems
We review the developments of QCD multipole expansion and its applications to
hadronic transitions and some radiative decays of heavy quarkonia. Theoretical
predictions are compsred with updated experimental results.Comment: 23 pages, 7 figures. Some typos corrected, and 3 references adde
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