Determining the luminosity function of Swift long gamma-ray bursts with pseudo-redshifts

The determination of luminosity function (LF) of gamma-ray bursts (GRBs) is of an important role for the cosmological applications of the GRBs, which is however hindered seriously by some selection effects due to redshift measurements. In order to avoid these selection effects, we suggest to calculate pseudo-redshifts for Swift GRBs according to the empirical L-E_p relationship. Here, such a $L-E_p$ relationship is determined by reconciling the distributions of pseudo- and real redshifts of redshift-known GRBs. The values of E_p taken from Butler's GRB catalog are estimated with Bayesian statistics rather than observed. Using the GRB sample with pseudo-redshifts of a relatively large number, we fit the redshift-resolved luminosity distributions of the GRBs with a broken-power-law LF. The fitting results suggest that the LF could evolve with redshift by a redshift-dependent break luminosity, e.g., L_b=1.2\times10^{51}(1+z)^2\rm erg s^{-1}. The low- and high-luminosity indices are constrained to 0.8 and 2.0, respectively. It is found that the proportional coefficient between GRB event rate and star formation rate should correspondingly decrease with increasing redshifts.Comment: 5 pages, 5 figures, accepted for publication in ApJ

Dynamic dissipative cooling of a mechanical oscillator in strong-coupling optomechanics

Cooling of mesoscopic mechanical resonators represents a primary concern in cavity optomechanics. Here in the strong optomechanical coupling regime, we propose to dynamically control the cavity dissipation, which is able to significantly accelerate the cooling process while strongly suppressing the heating noise. Furthermore, the dynamic control is capable of overcoming quantum backaction and reducing the cooling limit by several orders of magnitude. The dynamic dissipation control provides new insights for tailoring the optomechanical interaction and offers the prospect of exploring macroscopic quantum physics.Comment: accepetd in Physical Review Letter

Statistics of Chaotic Resonances in an Optical Microcavity

Distributions of eigenmodes are widely concerned in both bounded and open systems. In the realm of chaos, counting resonances can characterize the underlying dynamics (regular vs. chaotic), and is often instrumental to identify classical-to-quantum correspondence. Here, we study, both theoretically and experimentally, the statistics of chaotic resonances in an optical microcavity with a mixed phase space of both regular and chaotic dynamics. Information on the number of chaotic modes is extracted by counting regular modes, which couple to the former via dynamical tunneling. The experimental data are in agreement with a known semiclassical prediction for the dependence of the number of chaotic resonances on the number of open channels, while they deviate significantly from a purely random-matrix-theory-based treatment, in general. We ascribe this result to the ballistic decay of the rays, which occurs within Ehrenfest time, and importantly, within the timescale of transient chaos. The present approach may provide a general tool for the statistical analysis of chaotic resonances in open systems.Comment: 5 pages, 5 figures, and a supplemental informatio

2-(Carboxy­methyl­sulfan­yl)pyridine-3-carboxylic acid monohydrate

The title compound, C8H7NO4S·H2O, was obtained by reaction of 2-mercaptopyridine-3-carboxylic acid with chloro­acetic acid. In the mol­ecular structure, the dihedral angle between the two least-squares planes defined by the pyridine ring and the carb­oxy group is 8.32 (9)°. The carboxy­methyl­sulfanyl group makes a torsion angle of 82.64 (12)° with the pyridine ring. An intra­molecular O—H⋯N hydrogen bond between the acidic function of the carboxy­methyl­sulfanyl group and the pyridine N atom stabilizes the conformation, whereas inter­molecular O—H⋯O hydrogen bonding with the uncoordinated water mol­ecules is responsible for packing of the structure, leading to chains propagating in [001]

Summarization and Analysis on Commercial Bank Risk Management

Risk management of commercial banks is an important part of their operation activity. The risk management development of commercial banks in the world is a process from single risk management to integrated risk management, while the risk management technology has been developed from qualitative analysis to comprehensive measurement and analysis with various quantitative methods. Currently, the world advance commercial banks already have more mature ways and results in concepts, organization settings and risk management technologies. For the late development of risk management in our country, a scientific and complete risk management system has not been established. At present stage, we are making efforts in introducing and establishing a scientific risk management system step by step. Key words: Commercial bank; risk management; risk management technology Résumé: La gestion des risques est une partie importante des activités d’opération des banques commerciales. Le développement de la gestion des risques des banques commerciales dans le monde est un processus qui va de la gestion simple à la gestion intégrée, quand la technologie de la gestion des risques a développé de l’analyse qualitative à la mesure globale et l’analyse avec des méthodes quantitatives diverses. Aujourd’hui, les banques commerciales avancées du monde ont déjà plus de méthodes et résultats mûrs en concept, organisation et technologie de la gestion des risques. A cause du développement retardé de la gestion des risques dans notre pays, un système scientifique et complet n’a pas encore été établi. Actuellement, nous sommes en train de faire des efforts pour introduire et établir pas à pas un système scientifique de la gestion des risques. Mots-Clés: banque commerciale, gestion des risques, technologie de la gestion des risque

Broadband enhancement of light harvesting in luminescent solar concentrator

Luminescent solar concentrator (LSC) can absorb large-area incident sunlight, then emit luminescence with high quantum efficiency, which finally be collected by a small photovoltaic (PV) system. The light-harvesting area of the PV system is much smaller than that of the LSC system, potentially improving the efficiency and reducing the cost of solar cells. Here, based on Fermi-golden rule, we present a theoretical description of the luminescent process in nanoscale LSCs where the conventional ray-optics model is no longer applicable. As an example calculated with this new model, we demonstrate that a slot waveguide consisting of a nanometer-sized low-index slot region sandwiched by two high-index regions provides a broadband enhancement of light harvesting by the luminescent centers in the slot region. This is because the slot waveguide can (1) greatly enhance the spontaneous emission due to the Purcell effect, (2) dramatically increase the effective absorption cross-section of luminescent centers, and (3) strongly improve the quantum efficiency of luminescent centers. It is found that about 80% solar photons can be ultimately converted to waveguide-coupled luminescent photons even for a low luminescent quantum efficiency of 0.5. This LSC is potential to construct a tandem structure which can absorb nearly full-spectrum solar photons, and also may be of special interest for building integrated nano-PV applications