Analysis of the spatial distribution between successive earthquakes

Spatial distances between subsequent earthquakes in southern California exhibit scale-free statistics, with a critical exponent delta approximately 0.6, as well as finite size scaling. The statistics are independent of the threshold magnitude as long as the catalog is complete, but depend strongly on the temporal ordering of events, rather than the geometry of the spatial epicenter distribution. Nevertheless, the spatial distance and waiting time between subsequent earthquakes are uncorrelated with each other. These observations contradict the theory of aftershock zone scaling with main shock magnitude.     

The relation between the radii and the densities of magnetic skyrmions

Compared with the traditional magnetic bubble, a skyrmion has a smaller size, and better stability and therefore is considered as a very promising candidate for future memory devices. When skyrmions are manipulated, erased and created, the density of skyrmions can be varied, however the relationship between the radii and the densities of skyrmions needs more exploration. In this paper, we study this problem both theoretically and by using the lattice simulation. The average radius of skyrmions as a function of material parameters, the strength of the external magnetic field and the density of skyrmions is obtained and verified. With this explicit function, the skyrmion radius can be easily predicted, which is helpful for the future study of skyrmion memory devices.     

氟苯-水体系界面不稳定现象

以乙醇、正丁醇和聚乙烯醇为水相表面活性剂,采用悬滴法测定了氟苯-水溶液体系的界面张力,观测了氟苯-水溶液体系的界面。实验结果表明:氟苯和去离子水相互饱和,氟苯-水体系界面清晰,氟苯液滴的形态和大小不发生变化;体系中界面张力与溶液中表面活性剂浓度间的关系遵守Langmuir-Szyszkowski方程;Sternling和Scriven的界面稳定性判据适用于实验中的氟苯-水体系的界面稳定性判定。     

Cyclotron drift along the boundary between regions of differing gyroradii

The cyclotron drift of charged particles along the boundary between regions of differing gyroradii is considered. Expressions for the drift velocity and drift current along a straight boundary, as well as for the drift velocity along a curvilinear boundary, are derived. The proportion between the parts into which the drift current divides along a branched boundary is estimated using a T-shaped boundary as an example.     

Connection between the 2-body energy of the Kaxiras-Pandey and the Biswas-Hamann potentials

Relationship among interatomic potential functions can be useful in shedding insight on the extent of similarity, and in obtaining a potential function from parameters of another potential function. The 2-body portion of the Biswas-Hamann (BH) and the Kaxiras-Pandey (KP) potential functions are related by equating both functions, as well as their corresponding derivatives up to the third order at the equilibrium bond length. Validity of the parametric relationship is verified by plotting the loose form of the 2-body BH potential in terms of KP parameters and comparing it with the KP potential function. The parametric relationships developed herein are then compared with those that concern other potential functions, with particular emphasis on the scaling factors.     

On the relation between resonances andK-matrix poles

The relation between resonances andK-matrix poles for the potential scattering problem is investigated. The analysis is carried out in two stages. We first discuss the analytic properties of aK-matrix related to a model phase-shift which embodies the relevant features of a potential scattering resonance; we then consider the specific case of a square-well potential. The result emerging from the analysis is that to each resonance two poles of theK-matrix are associated; they appear either as a real resonance-echo pair or as a complex conjugate doublet, according to the value of a suitable background parameter. The relevance of this result in connection with the Huby theory is briefly discussed.     

On the relation between FDTD and Fibonacci polynomials

In this paper we show that the Finite-Difference Time-Domain method (FDTD method) follows the recurrence relation for Fibonacci polynomials. More precisely, we show that FDTD approximates the electromagnetic field by Fibonacci polynomials in ΔtA, where Δt is the time step and A is the first-order Maxwell system matrix. By exploiting the connection between Fibonacci polynomials and Chebyshev polynomials of the second kind, we easily obtain the Courant-Friedrichs-Lewy (CFL) stability condition and we show that to match the spectral width of the system matrix, the time step should be chosen as large as possible, that is, as close to the CFL upper bound as possible.     

Interactions between coadsorbed species on the Rh(111) surface as a function of the separation distance between them

The interaction energies as a function of the separation distance between two molecules of CO and between CO and H or O coadsorbed on the Rh(111) surface have been calculated by the Extended Hückel Method. Weak interactions of the order of a few hundredths of eV occur between the adsorbates via the metal lattice. The interaction energy is found to change its signs as the distance between the adsorbates increases. For first neighbor occupation sites the interaction energies are positive. Second and third neighbor interaction energies between CO and CO are, however, negative, the latter being stronger than the former. The interaction energies between CO and H or O are positive for first and second order neighbors and, in general, negative for third order neighbors. The computed interaction energies allow one to explain the observed LEED patterns of adsorbed CO at low temperatures. The compression of the p(2 × 2) LEED structure of CO to the (√3 × √3)R30° structure, induced by the subsequent exposure to hydrogen or oxygen, is explained on the basis of the more favorable interaction energies when CO and H, or CO and 0 are segregated.     

最优速度模型与元胞自动机模型的比较研究

用解析分析与数值仿真的手段研究了一种典型的车辆跟驰模型(OV模型)与元胞自动机模型(NS模型)之间的区别与联系.首先通过对模型规则的分析,证明了确定NS模型是OV模型的一种离散形式.随后针对两模型更复杂的具体形式,通过数值仿真的手段进行了模型的密度-流量关系与模型在开放边界下的动态特性的研究.实验结果表明,从现象来看,OV模型与NS模型具有非常近似的性质,但两种模型的机制不相同,并且各自具有不能相互替代的优势.为交通流模型的使用和改进提供了参考.     

Geometric study of the connection between the Lagrangian and Hamiltonian constraints

The second order differential equation character of the solutions of the dynamical equation i(Γ)ω_L = dE_L for a singular Lagrangian L, as well as the conditions for the existence of such a solution, are studied. We also introduce a couple of maps R (L)_v : T _FL(v)(T¹Q) → T_v(TQ) and T(L)_v : T_FL(v)(T¹Q) → T_FL(v)(T¹Q), with v ϵ TQ, which are shown to be very useful for establishing the connection between the constraints arising in the Lagrangian and Hamiltonian formulations.     

Transition between the tent map and the Bernoulli shift

We introduce a one-dimensional map which can be considered as a transition from the tent map to the Bernoulli shift map. This map is a simple example of a system with two different attractors, for certain values of the parameter, with well defined basins of attraction.     

A comparison between the local-energy method and the variation principle

In order to compare the local-energy method with the variation principle as an optimization technique, numerical results are given for the ground states of the hydrogen molecule ion and the helium atom. Although the optimum wave functions obtained from the two methods are very similar, expectation values of various operators are given more accurately by the variation-principle functions. Conditions are discussed under which the local-energy method could be superior to the variation principle as an optimization technique.     

Upon the magnitude of the recombination volume between vacancies and self-interstitials in metals

Previously obtained results of measurements of the radiation damage rate in metals as a function of the irradiation temperature are analysed. It is found that the effective migration energy of self-interstitials is linearly decreasing with decreasing irradiation temperature i.e. with increasing concentration of defects. It results from the analysis that i) the recombination volume must be as large as 10⁵ atomic volumes and that ii) the migration energy of defects is slightly decreased during an irradiation with high energy particles.     

Reversible transitions between synchronization states of the cardiorespiratory system

Phase synchronization between cardiac and respiratory oscillations is investigated during anesthesia in rats. Synchrograms and time evolution of synchronization indices are used to show that the system passes reversibly through a sequence of different phase-synchronized states as the anesthesia level changes, indicating that it can undergo phase transitionlike phenomena. It appears that the synchronization state may be used to characterize the depth of anesthesia.     

Modeling the interactions between noise exposure and other variables

The interaction of noise exposure with other variables is reviewed. For the case of the interaction of noise with other variables that produce behavioral threshold shifts, the application of a newly developed model is described and demonstrated. This model, referred to as the modified power-law model, provides an accurate prediction of the combined effects of two threshold-elevating factors. The model accounts for the interaction of post-exposure a pre-existing pre-existing permanent loss or a pre-existing temporary loss. The model's application is demonstrated for multiple exposures to steady-state noise in which each exposure lasts as short as 12 min or as long as 6 h. Finally, implications of the model's application to the interaction long as 6 h. Finally, implications of the model's application to the interaction of noise with other ototraumatic agents are reviewed.     

On the connection between the gamma and radio spectra of pulsars

We suggest a model of pulsar radio emission in which a coherent radio emission is excited in a vacuum gap above the polar cap of a neutron star. The pulsar X-ray and gamma radiation is considered as the result of inverse Compton scattering of radio emission by ultrarelativistic electrons accelerated in the gap. The influence of the pulsar magnetic field on the inverse Compton scattering is taken into account. The relationship between the radio and gamma spectra has been found in this model.     

Correlation between the Efficiency of Singlet Oxygen Generation and the Luminescence Parameters of Photosensitizers

Optics and Spectroscopy - The quantum yield of interconversion to triplet states for free-base 2,3,7,8,12,13,17,18-octaethylporphyrin and 5,10,15,20-tetraphenylporphyrin, as well as of...     

黄芩素与黄芩苷抗氧化活性差异的结构原因

黄芩素是黄芩苷的初级代谢产物,二者的分子结构差别仅在于7-位取代基,前者为酚羟基而后者为糖苷.本文通过稳态吸收光谱和循环伏安实验,以及量化计算等方法考察了黄芩素和黄芩苷的酸离解常数(pKa)、脂水分配系数、氧化-还原电位、分子偶极矩等基本物理化学性质,以及清除ABTS.+自由基活性(TEAC)的差异.结果表明,黄芩素酚羟基7-OH的酸性较强(pKa=5.4);在生理pH下黄芩素的氧化还原电位(0.32 Vvs.NHE)略低于黄芩苷,且TEAC值约为黄芩苷的1.8倍.量化计算结果表明,7-取代基对黄酮分子骨架的构型、物理化学性质以及自由基清除活性有显著影响.文中探讨了黄芩素和黄芩苷的微观和宏观分子属性与抗氧化活性之间的关系,得出酚羟基数量及其pKa值、黄酮分子骨架构型以及电子结构是影响类黄酮化合物抗氧化活性主要因素的结论.研究结果可为深入研究类黄酮化合物的抗氧化结构-活性关系提供依据.     

On the nature of the correlation between cosmic-ray intensity and cloud cover

Various aspects of the connection between low cloud cover (LCC) and cosmic rays (CRs) are considered. Most features of this connection point to the absence of substantial causal relationship between LCC and CRs. Even on the assumption that some LCC fraction is related to CR intensity and varies with it, its most likely value is about 2% (although, within two standard deviations it can be as high as 20%). The most serious argument against the causal relationship between CRs and LCC is the existence of negative correlation between low and medium cloud cover (MCC). The scenario of simultaneous influence of solar activity on CRs and cloud cover is discussed, which might lead to the observed correlations.     

Effect of the electric current on the Casimir force between graphene sheets

The dependence of the thermal component of the Casimir force and Casimir friction between graphene sheets on the drift velocity of charge carriers in one of the sheets has been analyzed. It has been shown that the drift motion results in the measurable change in the thermal Casimir force owing to the Doppler effect. The thermal Casimir force, as well as Casimir friction, increases strongly in the case of resonant photon tunneling, when the energy of an emitted photon coincides with the excitation energy of an electron-hole pair. In the case of resonant photon tunneling, the dominant contribution to the Casimir friction even at temperatures above room temperature comes from quantum friction caused by quantum fluctuations. Quantum friction can be detected in an experiment on the friction drag between graphene sheets in a high electric field.