On some Einstein-Maxwell fields of high symmetry

The literature on Einstein-Maxwell fields with high symmetry (including some work by the present author) abounds in errors and unwitting rediscoveries. In the present paper certain static axisymmetric, stationary cylindrically symmetric and nonstatic spatially homogeneous space-times which were previously investigated in a series of papers by Raychaudhuri, Datta, Bera, and De [1–11] are considered. In most cases the general solution of the problems tackled is now known, and is repeated here. The earlier papers are analyzed; while errors (some already pointed out by Carminati and McIntosh [12]) and duplications are found, it is believed that the papers discussed contain the first occurrences of three of the solutions. The calculations in this paper have been verified using the computer algebra system SHEEP.     

复相系平衡条件及平衡稳定性条件的分析

复相系平衡条件及平衡稳定性条件的分析曾丹苓（重庆大学热力工程系重庆６３００４４）关键词复相系，平衡条件，平衡稳定性条件１引言汽液相变是工程上常见的现象，它是一个复杂的物理过程，涉及到传热传质、相转变、表面现象、流体流动及工质热物性等领域，但从热力学的...     

Observation of atomic-number-dependent hot electrons due to the resonance absorption in laser plasmas

Various hot electron temperatures depending on atomic number were measured in laser plasmas produced by a YAG laser with energy 100 mJ and pulseduration 30 ps, as was reported in our previous paper. In the present work the absorbed laser energy was evaluated as a function of the angle of incidence for both p-polarized and s-polarized beams. For carbon plasmas, it was found that the absorbed energy depends on the angle of incidence and this effect was attributed to resonance absorption. For aluminum plasmas, the resonance absorption did not occur. These results confirmed that hot electrons shown in the X-ray continuum spectrum described in the previous paper were generated by resonance absorption.     

A computational and experimental study of resonators in three dimensions

In a previous work by the present authors, a computational and experimental investigation of the acoustic properties of two-dimensional slit resonators was carried out. The present paper reports the results of a study extending the previous work to three dimensions. This investigation has two basic objectives. The first is to validate the computed results from direct numerical simulations of the flow and acoustic fields of slit resonators in three dimensions by comparing with experimental measurements in a normal incidence impedance tube. The second objective is to study the flow physics of resonant liners responsible for sound wave dissipation. Extensive comparisons are provided between computed and measured acoustic liner properties with both discrete frequency and broadband sound sources. Good agreements are found over a wide range of frequencies and sound pressure levels. Direct numerical simulation confirms the previous finding in two dimensions that vortex shedding is the dominant dissipation mechanism at high sound pressure intensity. However, it is observed that the behavior of the shed vortices in three dimensions is quite different from those of two dimensions. In three dimensions, the shed vortices tend to evolve into ring (circular in plan form) vortices, even though the slit resonator opening from which the vortices are shed has an aspect ratio of 2.5. Under the excitation of discrete frequency sound, the shed vortices align themselves into two regularly spaced vortex trains moving away from the resonator opening in opposite directions. This is different from the chaotic shedding of vortices found in two-dimensional simulations. The effect of slit aspect ratio at a fixed porosity is briefly studied. For the range of liners considered in this investigation, it is found that the absorption coefficient of a liner increases when the open area of the single slit is subdivided into multiple, smaller slits.     

On the verification of the applicability of the orthotropic plate wave theory to paper

In the literature one basic work can be found that describes an attempt to verify the applicability of the orthotropic plate wave theory to paper. In the present study we have repeated the key experiment and also modified the original experimental set-up to be able to make new complementary measurements. The performed verification attempt is based on a key experiment in which an ultrasonic resonance method is used. When it is applied to paper, a second resonance can be observed in addition to the one that originates from the asymmetric A0 mode. The result of the verification experiment is conclusive only if the source of this second resonance is the symmetric S0 mode. Our results show that the second resonance is not generated by the S0 mode. Instead, they indicate that the source is a longitudinal wave propagating in the thickness direction of the paper. We therefore conclude that the applicability of the orthotropic plate wave theory to paper cannot be verified by performing the key experiment that is described in the literature.     

Experimental and theoretical investigations of optical properties of GaN/AlGaN MQW nanostructures. Impact of built-in polarization fields

We report the results from detailed optical spectroscopy from MOCVD grown GaN/AlGaN multiple quantum wells (MQWs), as opposed to most previous studies where MBE was employed by means of photoluminescence (PL) technique. In this paper we will present theoretical and experimental results demonstrating how polarization induced electric fields and bound interface charges in GaN/AlGaN MQWs affect the emission peak energy, PL line shape, as well as the emission line width. Theoretically estimated fields in this work are consistent with experimental data. Transition energy of the heavy hole and electron ground state Ee-hh in GaN/AlGaN MQWs were calculated and it is found that it stays in good agreement with the experimental data.     

超晶格材料内部热流传递的分子动力学分析

本文用非平衡分子动力学方法计算了超晶格材料内部热流的组成和分布,发现在固体中,热能主要是通过分子间作用力做功的方式传递,此方式在固体中的热流传递中占的比率比液体或气体情况下要大,因此可以忽略动能和势能传递项的贡献。超晶格材料的分于动力学模拟显示,它的界面对切向热流有阻碍作用,热流分布比普通的复合材料不均匀。由此导致超晶格材料平面热导率的降低。本文对于探讨和解释超晶格材料的热特性具有指导意义。     

Nonlinear dose dependence of TL and LM-OSL within the one trap-one center model

In a recent paper, it has been shown that strong sub-linearity of the occupancy n₀ of trapping states far from saturation can be explained by the simplest model of one trap-one recombination center (OTOR). In the present work we report on results of numerical simulation of dose dependence of the TL maximum under similar conditions. In some cases, the TL maximum is found to be strictly proportional to the filling of the traps, but this is not always the case. Different sublinear dose-dependence functions of the trap occupancy and the maximum TL are demonstrated. With the same sets of parameters, curves of LM-OSL have also been simulated; superlinear as well as sublinear dependencies on the excitation dose have been found.     

What’s Wrong with this Criticism

One of the endearing traits of Asher Peres is that when somebody publishes something he knows to be wrong, he does not bother to refute it, even if the paper criticizes his own work. Life is too brief for such frivolity. As a small 70th birthday present I would like to answer one such recent attack. It’s not much of a present, since Asher will not read my paper. Why should he? He already knows this criticism is nonsense. But somebody has to set the written record straight for future historians, so I will do it as part of this celebration. Fortunately this particular issue is so easily settled that this can be a very short paper. Since Asher is a master of the very short paper, my Peresian brevity is an important part of my act of homage. The criticism I address can be found in a new formulation by Karl Hess and Walter Philipp(1) of their view that all versions of Bell’s theorem are fundamentally flawed. I focus here only on their criticism of the version in Asher’s book.(2) This essay was completed and submitted before the sad and unexpected death of Asher Peres on January 1, 2005. I have left it in its original form because I sent Asher a preprint, and he told me that his wife Aviva had enjoyed it. I like to think that perhaps he had a quick look and enjoyed it a bit himself. Life in the field of quantum foundations will not be as much fun without his opinions, his wit, and his warmth I point out that in spite of recent claims to the contrary, the proof of Bell’s theorem in Asher Peres’s book works even in the presence of time-correlated hidden variables in the detectors.     

A kinetic approach to the calculation of surface tension of a spherical drop

In literature, surface tension has been investigated mainly from a Thermodynamics standpoint, more rarely with kinetic methods. In the present work, surface tension of drops is studied in the framework of kinetic theory, starting from the Sutherland approximation to Van Der Waals interaction between molecules. Surface tension is calculated as a function of drop radius: it is found that it approaches swiftly an asymptotic value, for radii of several times the distance of minimum approach D of the Sutherland potential. This theoretical asymptotic value is compared to experimental values of surface tension in plane surfaces of a few liquids, and is found in reasonable agreement.     

MULTI-MODE TRIMMING OF IMPERFECT THIN RINGS USING MASSES AT PRE-SELECTED LOCATIONS

This paper presents a practical method for trimming the natural frequencies of an initially imperfect ring to simultaneously eliminate certain of the frequency splits present. Compared with previous work, the novel feature of this method is that the trimming masses are positioned at pre-selected locations on the ring. The basis for the proposed method is the concept of equivalent imperfection mass, which allows any imperfect ring to be considered as a perfect ring with equivalent imperfection masses attached. By considering this trimming problem it is deduced that it is possible to trim N pairs of modes simultaneously by removing (a minimum of) 2 N trimming masses at particular locations around the ring. By positioning the trimming masses at pre-selected locations, it is shown that a simple set of trimming masses can be calculated easily, and from this set an infinite number of solution sets can be found. Methods for generating these sets are outlined for the trimming of both a single and a dual pair of modes. In practice, it is likely that the trimming masses will be spaced regularly. For this special case, it is found that it is not possible to trim all single- and dual-mode pairs with any arrangement of masses. Validation of the derived simple solution set and the proposed procedure to generate further sets is achieved by studying a number of theoretical examples.     

超氧化物歧化酶在L-半胱氨酸修饰金电极上电化学行为的现场拉曼光谱研究

在以电化学方法确认L半胱氨酸对铜锌超氧化物歧化酶(copper,zincsuperoxidedismutase,SOD)在金丝电极上的电子迁移过程起促进作用的基础上,本文论述了将拉曼光谱电化学方法应用于猪红细胞SOD在经L半胱氨酸修饰的金丝电极上的电化学行为的现场拉曼光谱研究。研究结果从分子水平上提供了有关L半胱氨酸修饰在金电极上的电化学过程中,以及SOD在L半胱氨酸修饰的金电极上发生电子迁移过程中,存在于SOD、L半胱氨酸与金电极之间的相互成键作用情况随电化学过程进行而发生变化的微观结构信息,并进行了必要的分析和探讨。     

The laws of electromagnetism and an electrostatic analogue

Starting from the idea of a current-carrying coil as a magnetic ‘dipotential’, i.e. a dipole of constant potential difference, the relationships between the electromagnetic laws of Ampere, Biot-Savart, Grassmann and Faraday are discussed.

Different text-books on electricity and magnetism have used various methods of relating the laws of electromagnetism, but there remain difficulties whichever method is adopted. The present work is an attempt to put elementary work on a more logical basis without elaborate mathematics, by a greater use of the concept of magnetic potential. While it is not claimed that anything fundamentally new will be found here, it is hoped that the ideas will be useful for teaching.     

Nonequilibrium Measurements of Free Energy Differences for Microscopically Reversible Markovian Systems

An equality has recently been shown relating the free energy difference between two equilibrium ensembles of a system and an ensemble average of the work required to switch between these two configurations. In the present paper it is shown that this result can be derived under the assumption that the system's dynamics is Markovian and microscopically reversible.     

Fluorescence Anisotropy Studies on Bodipy (Pyrromethene 546) Dye as a Novel Thermal Probe

Journal of Fluorescence - In the present work, fluorescence anisotropy studies of BODIPY (pyrromethene 546 or C14H17BF2N2) dye have been performed and found that it has a potential to be used as a...     

Ultrasound and deep eutectic solvent (DES): A novel blend of techniques for rapid and energy efficient synthesis of oxazoles

The present work deals with the synthesis of novel oxazole compounds by using effective combination of ultrasound (US) and deep eutectic solvent (DES). The reaction was also conducted by thermal method (NUS) and the comparative studies are provided. It was observed that applying ultrasound not only improved yields and reduced reaction times but also saved more than 85% energy as shown by energy consumption calculations. The advantages of using DES as reaction medium is highlighted from the fact that it is bio-degradable, non-toxic, recyclable and could be easily prepared using inexpensive raw materials. The recyclability for DES was studied wherein it was found that ultrasound has no negative effects on DES even up to four runs. In addition, the present work is the first report on the combinative use of DES and US in organic synthesis.     

Effect of Bohm potential on a charged gas

Bohm’s interpretation of Quantum Mechanics leads to the derivation of a Quantum Kinetic Equation (QKE): in the present work, propagation of waves in charged quantum gases is investigated starting from this QKE. Dispersion relations are derived for fully and weakly degenerate fermions and bosons (for the latter above critical temperature) and the differences discussed. Use of a kinetic equation permits investigation of “Landau-type” damping: it is found that the presence of damping in fermion gases is dependent upon the degree of degeneracy, whereas it is always present in boson gases. In fully degenerate fermions a phenomenon appears that is akin to the “zero sound” propagation.     

Structural and electronic properties of BN M?bius stripes

In the present contribution it is applied first-principles calculations to investigate the electronic structure of boron nitride M?bius stripes, with armchair and zigzag configurations, obtained from boron nitride nanoribbons using a ??cut?? and ??glue?? process. The results show that the structural stability strongly depends on the length and width of the stripe. It is also found that the energy gap and work function depends on the structure chirality. Due to the formation of an antiphase boundary, zigzag stripes present tunable electronic properties, with significant potential for technological applications.     

Size Measurement of Very Small Spherical Particles by Mie Scattering Imaging (MSI)

The Mie Scattering Imaging method (MSI) gathers out‐of‐focus images of dispersed spherical particles present in a laser light sheet and extracts the individual particle diameter from these images. The general idea of the method has been around for more than a decade and a number of papers has dealt with it over recent years. Our work focuses on small particle sizes from 20 μm down to 2 μm, a range which has not been tackled so far although it is of great importance in particle systems. We present an optical set‐up with a special arrangement of camera lenses that allows to work in this range. An evaluation algorithm based on correlation of the experimental optical information with theoretical Mie scattering was found to give the most accurate results for particle sizing. Besides accuracy measurements on solid spheres the versatility of the method is demonstrated by an example of transient droplet growth between 2–7 μm.     

Numerical solution of fractional differential equations by using fractional B-spline

In this paper, we present fractional B-spline collocation method for the numerical solution of fractional differential equations. We consider this method for solving linear fractional differential equations which involve Caputo-type fractional derivatives. The numerical results demonstrate that the method is efficient and quite accurate and it requires relatively less computational work. For this reason one can conclude that this method has advantage on other methods and hence demonstrates the importance of this work.