1,536 research outputs found
Nonlinear optomechanical resonance entering a self-organized energy transfer pattern
The energy transfer between different subsystems or different vibration modes
is always one of the most interested problems in the study of the resonance
phenomena in coupled nonlinear dynamical systems. With an optomechanical system
operating in the regime of unresolved sideband, where its mechanical frequency
is lower than the cavity field damping rate, we illustrate the existence of a
special nonlinear resonance phenomenon. This type of previously unknown
resonance manifests an organized pattern of the coupled cavity field and
mechanical oscillation, so that the cavity field precisely pushes the
mechanical oscillator within an appropriate small time window in each
mechanical oscillation period and the mechanical energy will increase by a jump
of almost fixed amount after each oscillation cycle. The scenario is realized
at a resonance point where the frequency difference of two driving fields
matches the mechanical frequency of the system, and this condition of
drive-frequency match is found to trigger a mechanism to lock the two
subsystems of an unresolved-sideband optomechanical system into a highly
ordered energy transfer as the above mentioned. Due to a significantly enhanced
nonlinearity in the vicinity of the resonance point, optical frequency combs
can be generated under pump powers of thousand times lower, as compared to the
use of a single-tone driving field for the purpose. An unresolved sideband
system under the drives without satisfying the resonance condition also
demonstrates other interesting dynamical behaviors. Most of all, by providing a
realistic picture for the nonlinear optomechanical dynamics in unresolved
sideband regime, our study points to a direction to observe novel dynamical
phenomena and realize other applications with the systems of less technical
restrictions.Comment: 13 pages, 13 figures. To be published on Chaos, Solitons & Fractal
Fish species-specific TRIM gene FTRCA1 negatively regulates interferon response through attenuating IRF7 transcription
In mammals and fish, emerging evidence highlights that TRIM family members play important roles in the interferon (IFN) antiviral immune response. Fish TRIM family has undergone an unprecedented expansion leading to generation of finTRIM subfamily, which is exclusively specific to fish. Our recent results have shown that FTRCA1 (finTRIM C. auratus 1) is likely a fish species-specific finTRIM member in crucian carp C. auratus and acts as a negative modulator to downregulate fish IFN response by autophage-lysosomal degradation of protein kinase TBK1. In the present study, we found that FTRCA1 also impedes the activation of crucian carp IFN promoter by IRF7 but not by IRF3. Mechanistically, FTRCA1 attenuates IRF7 transcription levels likely due to enhanced decay of IRF7 mRNA, leading to reduced IRF7 protein levels and subsequently reduced fish IFN expression. E3 ligase activity is required for FTRCA1 to negatively regulate IRF7-mediated IFN response, because ligase-inactive mutants and the RING-deleted mutant of FTRCA1 lose the ability to block the activation of crucian carp IFN promoter by IRF7. These results together indicate that FTRCA1 is a multifaceted modulator to target different signaling factors for shaping fish IFN response in crucian carp.</p
Blind Image Restoration via the Integration of Stochastic and Deterministic Methods
This paper addresses the image restoration problem which remains a significant field of image processing.
The fields of experts- (FoE-) based image restoration has been discussed and some open issues including noise estimation and parameter selection have been approached. The stochastic method FoE performs fairly well; meanwhile it might also produce unsatisfactory outcome especially when the noise is grave. To improve the final performance, we introduce the integration with deterministic method K-SVD. The FoE-treated image has been used to obtain the dictionary, and with the help of sparse and redundant
representation over trained dictionary, the K-SVD algorithm can dramatically solve the problem, even though the pretreated result is of poor quality under severe noise condition. The experimental results via our proposed method are demonstrated and compared in detail. Meanwhile the test results from both qualitative and quantitative aspects are given, which present the better performance over current
state-of-art related restoration algorithms
A supra-massive magnetar central engine for short GRB 130603B
We show that the peculiar early optical and in particular X-ray afterglow
emission of the short duration burst GRB 130603B can be explained by continuous
energy injection into the blastwave from a supra-massive magnetar central
engine. The observed energetics and temporal/spectral properties of the late
infrared bump (i.e., the "kilonova") are also found consistent with emission
from the ejecta launched during an NS-NS merger and powered by a magnetar
central engine. The isotropic-equivalent kinetic energies of both the GRB
blastwave and the kilonova are about erg, consistent
with being powered by a near-isotropic magnetar wind. However, this relatively
small value demands that most of the initial rotational energy of the magnetar
is carried away by gravitational wave
radiation. Our results suggest that (i) the progenitor of GRB 130603B would be
a NS-NS binary system, whose merger product would be a supra-massive neutron
star that lasted for about seconds; (ii) the equation-of-state of
nuclear matter would be stiff enough to allow survival of a long-lived
supra-massive neutron star, so that it is promising to detect bright
electromagnetic counterparts of gravitational wave triggers without short GRB
associations in the upcoming Advanced LIGO/Virgo era.Comment: Five pages including 1 Figure, to appear in ApJ
Spectroscopy of broad absorption line quasars at -- I: evidence for quasar winds shaping broad/narrow emission line regions
We present an observational study of 22 broad absorption line quasars (BAL
QSOs) at based on optical/near-IR spectroscopy, aiming
to investigate quasar winds and their effects. The near-IR spectroscopy covers
the \hb\ and/or \mgii\ broad emission lines (BELs) for these quasars, allowing
us to estimate their central black hole (BH) masses in a robust way. We found
that our BAL QSOs on average do not have a higher Eddington ratio than that
from non-BAL QSOs matched in redshift and/or luminosity. In a subset consisting
of seven strong BAL QSOs possessing sub-relativistic BAL outflows, we see the
prevalence of large \civ-BEL blueshift (3100 km s) and weak \oiii\
emission (particularly the narrow \oiii5007 component), indicative of
nuclear outflows affecting the narrow emission-line (NEL) regions. In another
subset consisting of thirteen BAL QSOs having simultaneous observations of
\mgii\ and \hb, we found a strong correlation between 3000~\AA\ and 5000~\AA\
monochromatic luminosity, consistent with that from non-BAL QSOs matched in
redshift and luminosity; however, there is no correlation between \mgii\ and
\hb\ in FWHM, likely due to nuclear outflows influencing the BEL regions. Our
spectroscopic investigations offer strong evidence that the presence of nuclear
outflows plays an important role in shaping the BEL/NEL regions of these
quasars and possibly, regulating the growth of central supermassive black holes
(SMBHs). We propose that BEL blueshift and BAL could be different
manifestations of the same outflow system viewed at different sightlines and/or
phases.Comment: 13 pages, 10 figures. Accepted for publication in Ap
helicity form factors and the decays
In this paper, we calculate the helicity form factors (HFFs)
up to twist-4 accuracy by using the light-cone sum rules (LCSR) approach. After
extrapolating those HFFs to the physically allowable region, we
investigate the -meson two-body decays and semi-leptonic decays with stands for light
pseudoscalar/vector meson, respectively. The branching fractions can be derived
by using the CKM matrix element and the lifetime from the Particle Data
Group, and we obtain , , , , and . We then obtain and , which agree with the LHCb measured value within
-error. We also obtain ,
which like other theoretical predictions, is consistent with the LHCb measured
value within -error. Those imply that the HFFs under the LCSR approach
are also applicable to the meson two-body decays and semi-leptonic
decays , and the HFFs obtained by
using LCSR in a new way implies that there may be new physics in the semi-leptonic decays.Comment: 10 pages, 4 figures, published versio
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