Tunable Fano resonances in the ballistic transmission and tunneling lifetime in a biased bilayer graphene nanostructure

Dynamics of the Dirac fermions, in particular the transmission coefficient and the resonant tunneling lifetime are studied across a bilayer graphene electrostatic double barrier structure modulated by an in plane homogeneous electric field. Asymmetric Fano type resonances are noted for the first time in the transmission spectrum of the bilayer graphene nanostructures and are found to be highly sensitive to the direction of incidence of the charge carriers and the applied homogeneous electric field. The effect of the external field on the extended and the evanescent modes is also analysed. Resonant tunneling lifetime is found to be highly anisotropic in nature. The chiral carriers are either accelerated or decelerated by the electric field depending on the energy of the quasi-bound states, the angle of incidence and the magnitude of the applied field. Effects of the external field on the localization of the chiral carriers are also discussed.     

The nucleon wave function at the origin

We calculate the next-to-leading order perturbative corrections to the SVZ sum rules for the coupling fN$f_N$, the nucleon leading twist wave function at the origin. The results are compared to the established Ioffe sum rules and also to lattice QCD simulations.     

First observation of trapped high-field seeking ultracold neutron spin states

Ultracold neutrons were stored in a volume, using a magnetic dipole field shutter. Radial confinement was provided by material walls. Low-field seeking neutrons were axially confined above the magnetic field. High-field seeking neutrons are trapped inside the magnetic field. They can systematically shift the measured neutron lifetime to lower values in experiments with magnetic confinement.     

质子衰变实验进展

按照粒子物理标准模型理论,重子数是绝对守恒的.而大统一理论(GUTs)明确地否定了重子数的对称性,预言质子会衰变成更轻的次粒子.文章论述了质子衰变的物理概念、基本探测条件和主要实验现状,并在探测方法的探讨和探测技术的改进方面融入了一些想法.目前一般认为质子的寿命为τp>1032年左右.质子衰变的探测,对于新理论模型的验证、宇宙学和粒子物理学的发展具有重要意义.     

光参量荧光寿命分布

 根据荧光寿命定义和放大过程获得的增益方程,研究了新型非线性晶体BaAlBO₃F₂中三种不同的相位匹配模式下中心波长532 nm泵浦的参量荧光光子寿命的分布特性。结果表明,当注入单色信号光时,参量荧光寿命随泵浦光相位匹配角的增加由椭圆体分布变化为圆环体分布。采用宽带信号光时,则由分散分布改变为集中在近200 nm波长范围内分布,并随泵浦光相位匹配角的增加而逐步减小。考虑宽带泵浦光注入情况时,参量荧光寿命的分布范围由于相位匹配范围增加而随之扩展。     

A note on “Seller’s optimal credit period and cycle time in a supply chain for deteriorating items with maximum lifetime”

In 2014, Wang et al. (2014) extended the model of Lou and Wang (2012) to incorporate the credit period dependent demand and default risk for deteriorating items with maximum lifetime. However, the rates of demand, default risk and deterioration in the model of Wang et al. (2014) are assumed to be specific functions of credit period which limits the contributions. In this note, we first generalize the theoretical results of Wang et al. (2014) under some certain conditions. Furthermore, we also present some structural results instead of a numerical analysis on variation of optimal replenishment and trade credit strategies with respect to key parameters.     

Fluorescene Difference Decay Curves: Resolution Of Complex Decays

Abstract

The use of fluorescence difference decay curves was explored as a way to isolate the decays of components in a complex system. Time-correlated single photon methodology allows one to subtract a “reference” curve from a “sample” curve from a “sample” curve to yield a difference decay curve. To test the feasibility of this method, a model 3-component system (6-carboxyfluorescein, pyranine, and 1-dimethyl-aminoaphtalene-5-sulfonate) was examined. From its complex fluorescence decay curve, the individual decays were obtained by subtracting the appropriate binary solution decay curves. These difference curves coincided with those of the single component systems. Stringent requirements included: use of the same instrumental settings for all solutions, low counting efficiency, avoidance of inner filter effects, absence of energy transfer, and lack of chemical interaction between components. The difference decay method was applied to: 1. Sequential dansylation of serum albumin. Lifetimes of the first two dyes bound are longer than those of the third. 2. Dynamic quenching of quinine fluorescence by chloride ion. When the reference differs from the sample only by having a shorter lifetime, the difference decay curve has a characteristic shape. 3. Quenching of intrinsic protein fluorescence by acrylamide. Bovine serum albumin and liver alchol dehydrogenase were examined. Of the two tryptophans in each protein, one was preferentially quenched and its decay curve was obtained by difference.     

Combining the independent pixel and point-spread function approaches to simulate the actinic radiation field in moderately inhomogeneous 3D cloudy media

A fast method is presented for gaining 3D actinic flux density fields, F_act, in clouds employing the Independent Pixel Approximation (IPA) with a parameterized horizontal photon transport to imitate radiative smoothing effects. For 3D clouds the IPA is an efficient method to simulate radiative transfer, but it suffers from the neglect of horizontal photon fluxes leading to significant errors (up to locally 30% in the present study). Consequently, the resulting actinic flux density fields exhibit an unrealistically rough and rugged structure. In this study, the radiative smoothing is approximated by applying a physically based smoothing algorithm to the calculated IPA actinic flux field.     

Study of Spectroscopic Properties of Yb-doped Calcium Fluorapatite

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Voltage-Gated Metal-Enhanced Fluorescence

We demonstrate the influence of electrical current on the ability of surface plasmons to amplify fluorescence signatures. An applied direct current across Silver Island Films (SIFs) of low electrical resistance perturbs the fluorescence enhancement. For a given applied current, surface plasmons in just-continuous films are sparsely available for fluorophore dipole-coupling and hence the enhanced fluorescence is gated as a function of the applied current. For thicker, low resistance films, sufficient charge carriers are now present in the metal that metal-enhanced fluorescence (MEF) is perturbed to a lesser extent, induced surface plasmons readily formed on the surface by the close-proximity dipole.