Statistical description of a paired nucleus with the inclusion of angular momentum

The effect of angular momentum on an excited paired nucleus has been studied. The BCS Hamiltonian, modified to include the z-projection of angular momentum has been diagonalized and expressed in terms of the quasiparticle occupation numbers. The grand partition function and all the relevant thermodynamical functions as well as the level-density expression have been derived for the general case of an arbitrary set of single-particle levels. Furthermore, the formalism has been applied to the uniform model and, whenever possible, analytical expressions have been derived. In particular the zero-temperature angular momentum dependence of the gap parameter, the critical angular momentum as well as the yrast line have been calculated. The critical temperature as a function of angular momentum, which defines the phase transition between paired and unpaired systems, has been calculated. A new effect called the thermally assisted pairing correlation, involving an increase of pairing with increasing temperature has been predicted. The completeness of the formalism as applied to spherical or deformed nuclei has been discussed.     

Theoretical analysis of wave dispersion in the slow-wave structure such as a coaxial ribbed line

The wave dispersion in the slow-wave structure such as a coaxial ribbed line has been analyzed. For the case of the excitation of an axially symmetric wave in this structure, the generalized dispersion equation has been obtained using the method of sewing the conductivities. The particular cases of a solution of the dispersion equation have been analyzed, as well as its solutions for relatively high and low frequencies, since these cases are of practical interest. The parameters of a coaxial ribbed line have been simulated and the dependences of the slowing coefficient and the wave impedance of the structure on its geometrical dimensions have been obtained.     

Some Exact Solutions of String Cosmological Models in?Bianchi Type-II Space-Time

The Bianchi type-II cosmological solutions of massive strings have been investigated in the presence as well as absence of the magnetic field. The energy conditions for a cloud of strings coupled to the Einstein equations have been examined. The physical features of the models have also been discussed.     

Surface wave scattering by a nano-object situated on a surface

The scattering of the surface electromagnetic waves by a nano-defect (object) on a surface was calculated. The scattered field has been considered as a field caused by the current generated by the self-consistent local field inside the defect. In turn, the self-consistent local field has been determined as a result of solution of the integral Lippmann-Schwinger equation. The effective susceptibility of the object has been calculated using a self-consistent procedure. The corrections of self-energy part due to direct and indirect electromagnetic interactions, as well as due to interaction with surface wave field are taken into account. The self-energy part is calculated analytically within the framework of the near-field approximation. The scattering indicatrisses in reciprocal space have been computed for different shapes of the scatterer. Strong dependence of the scattered field on geometry of the scatterer has been found and explained.     

MASS ATTENUATION COEFFICIENTS FOR ELEMENTS MEASURED WITH CHARACTERISTIC X-RAYS FROM TARGETS EXCITED BY ENERGETIC PROTON

The characteristic X-rays from elemental or compound targets excited by energetic proton are quasi-monochromatic X-ray sources. The advantages of high line/ background ratio, controllable intensity as well as many available energies, make them suitable for applications in many important fields. The total mass attenuation cross sections of yttrium have been systematically measured by using this kind of X-ray source. The accuracy of experimental data has been improved to ±1%, which is much better than that of earlier results. The contributions of the coherent and incoherent scattering crees sections have been calcu-lated in accordance with the present experimental condition. And the total photoelectric cross sections have been obtained by subtracting the scattering cross section from the measured total cross sections. The com-parisons of our experimental results with the available data of earlier investigations as well as with the theo-retical calculations have been presented and discussed.     

Investigation of relativistic bosons in the presence of two-dimensional time-dependent harmonic interaction

The Duffin–Kemmer–Petiau (DKP) equation has been exactly solved for the spin-one particle in the presence of time-dependent harmonic potential in a two dimensional space using the Lewis–Riesenfeld dynamical invariant and unitary transform methods. The dynamical invariant has been constructed and its eigen functions have been obtained. The total wave function as well as the evolution operator have been derived.     

X射线截面形貌术中衍衬干涉条纹的消衰现象

用X射线衍射截面形貌术研究了金刚石晶体中Pendellosung条纹的消衰(fading)现象。实验表明,在尖劈形晶体和平板状晶体以及包含一片层错的晶体中都观察到动力学衍衬干涉条纹的消衰现象。用动力学理论和实验结果进行定量的比较,结果是一致的。 关键词：     

Temperature tunable optical gratings in nematic elastomer

We have investigated the behaviour of temperature dependent periodic-index gratings fabricated in a nematic elastomer. The gratings have been obtained by photopolymerisation under a microscopy apparatus. Contraction properties, as well as diffraction properties, have been studied as a function of temperature. Unidirectional contraction has been demonstrated by means of circular figure deformation and the polarisation dependency of the diffraction by the gratings has been determined.     

Novel Silica Fillers — Preparation and Physicochemical Evaluation

Precipitation of silicas in the emulsion medium from sodium silicate with hexane as the organic phase and hydrochloric or sulphuric(VI) acids as the precipitation agent, has been studied. The effect of the conditions of the reaction of precipitation on the physical and chemical properties of the products has been analysed and the optimum conditions have been established. Synthetic silicas made of spherical particles have been obtained, showing high uniformity for certain contents of the emulsifiers used. By adjusting the amount of the emulsifiers and with hydrochloric acid as the precipitating agent, uniform silicas have been obtained showing a low tendency towards aggregate and agglomerate formation. The physical and chemical properties of the precipitation products obtained have been observed to deteriorate with sulphuric(VI) acid as the precipitating agent, as indicated by particle size distribution curves and SEM images. Agglomeration of the silicas enhances their sedimentation in water, as follows from the sedimentation profiles taken.     

Fractional Fourier plane image encryption technique using radial hilbert-, and Jigsaw transform

A new method for image encryption using integral order radial Hilbert transform (RHT) filter in the fractional Fourier transform (FRT) domain has been proposed. The technique is implemented using the popular double random phase encoding method in the fractional Fourier domain. The random phase masks (RPMs), integral orders of the RHT, fractional orders of FRT, and indices of the Jigsaw transform (JT) have been used as keys for encryption and decryption. Simulation results have been presented and the schematic representation for optical implementation has been proposed. The mean-square-error and signal-to-noise ratio between the decrypted image and the input image have been calculated for the correct as well as incorrect orders of the RHT. Effect of occlusion and noise on the performance of the proposed scheme has also been studied. The robustness of the technique has been verified against attack using partial windows of the correct random phase masks. Similar investigations have also been carried out for the chosen-, and the known-plain-text attacks.     

Vibrational Spectra of Thiazole-2-Carboxylic Acid and Thiazole-2-Carboxylate Ion

The i-r. spectra of thiazole-2-carboxylic acid and thiazole-2-carboxylate ion as CsI pellets and Nujol mull as well as Raman spectrum of an aqueous solution of the salt have been investigated. Most vibrations have been assigned on the basis of group frequencies and by correlation between the spectra of both molecules. The -COOH characteristic vibrations have been assigned as vibrations of the intermolecularly associated species.     

The effective absorption cross-section of thermal neutrons in a medium containing strongly or weakly absorbing centres

The structure of a heterogeneous system influences diffusion of thermal neutrons. The thermal-neutron absorption in grained media is considered in the paper. A simple theory is presented for a two-component medium treated as grains embedded in the matrix or as a system built of two types of grains (of strongly differing absorption cross-sections). A grain parameter is defined as the ratio of the effective macroscopic absorption cross-section of the heterogeneous medium to the absorption cross-section of the corresponding homogeneous medium (consisting of the same components in the same proportions). The grain parameter depends on the ratio of the absorption cross-sections and contributions of the components and on the size of grains. The theoretical approach has been verified in experiments on prepared dedicated models which have kept required geometrical and physical conditions (silver grains distributed regularly in Plexiglas). The effective absorption cross-sections have been measured and compared with the results of calculations. A very good agreement has been observed. In certain cases the differences between the absorption in the heterogeneous and homogeneous media are very significant. A validity of an extension of the theoretical model on natural, two-component, heterogeneous mixtures has been tested experimentally. Aqueous solutions of boric acid have been used as the strongly absorbing component. Fine- and coarse-grained pure silicon has been used as the second component with well-defined thermal-neutron parameters. Small and large grains of diabase have been used as the second natural component. The theoretical predictions have been confirmed in these experiments.     

Elastic properties and heat capacity of opal matrices and related 3D-nanocomposite materials

The elastic properties of opal matrices and related 3D-nanocomposites, as well as their heat capacity, have been investigated. The velocities and attenuation coefficients of longitudinal and transverse waves have been measured at room temperature. The Debye temperature has been calculated from the velocities of ultrasound. The temperature dependence of the heat capacity of the opal matrix has been studied. It has been shown that the low-temperature part of this dependence contains contributions proportional to the first and third powers of the temperature. It has been found that the Debye temperatures determined from the velocities of ultrasound and those obtained from the heat capacity differ significantly.     

Synthesis,growth and characterization of 4-dimethylaminobenzaldehyde-4-nitrophenylhydrazone single crystals

4-Dimethylaminobenzaldehyde-4-nitrophenylhydrazone (DANPH) single crystals exhibit polymorphism such as DANPH-G form (greenish red) and DANPH-R form (red). The different polymorphic phases of the grown crystals have been identified by X-ray diffraction studies. The functional groups of the crystals have been identified by FT-IR study. Crystallographically independent environment of polymorphs has been confirmed by NMR study. The thermal properties such as melting and decomposition temperatures of the compound have been analyzed. Optical constants of DANPH polymorph crystals have been calculated.     

Particle tunneling and scattering in a three-dimensional potential with a barrier

The particle tunneling through a 3-D rectangular potential barrier has been studied. The simplest model for multiple internal reflections has been assumed. The explicit expression for all the transmission and reflection probability amplitudes have been derived, as well as the tunneling and reflection phase times.      

Cinchona alkaloid-based polymer-bound phase-transfer catalysts: Efficient enantioselective alkylation of benzophenone imine of glycine esters

Summary Cross-linked polystyrene-bound and poly(ethylene glycol)-bound phase-transfer catalysts as well as homopolymers of cinchona alkaloid derivatives have been synthesised. Both soluble and insoluble polymers have been investigated. The enantioselective alkylation of N-diphenyl methylene glycine t-butyl ester has been successfully carried out in heterogeneous and homogeneous systems. High enantioselectivities (up to 96%) have been obtained. The polymer-bound catalysts have been easily recovered and conditions for efficient recycling have been studied.     

Beam-size measurement with optical diffraction radiation at KEK accelerator test facility

An experiment on the investigation of optical diffraction radiation (ODR) from a slit target as a possible tool for noninvasive electron beam-size diagnostics has been performed at the KEK accelerator test facility. The experimental setup has been installed at the diagnostics section of the extraction line. We have performed the first incoherent ODR observation from a slit target. The measured angular distributions are in reasonable agreement with the theoretical expectation. The beam-size effect onto the ODR angular pattern has been observed. Moreover, the sensitivity to the beam size as small as 14 microm has been achieved.     

参外联合激励复合非线性振子的分岔分析

讨论了参外联合激励复合非线性振子的动力学行为.对其定常解在一阶近似下的方程进行了局部分岔分析,给出了简单分岔和Hopf分岔发生的条件,并通过对近似方程和原系统的数值模拟加以验证.分析了多种参数对该振子动力学行为演化过程的影响.根据全局分岔理论探讨了该振子在不同条件下发生同宿、异宿分岔的必要条件,其结论与数值计算的结果大致符合. 关键词： 复合非线性振子 局部分岔 全局分岔 混沌     

Effects of the randomly distributed magnetic field on the phase diagrams of the Ising Nanowire II: Continuous distributions

The effect of the random magnetic field distribution on the phase diagrams and ground state magnetizations of the Ising nanowire has been investigated with effective field theory with correlations. Gaussian distribution has been chosen as a random magnetic field distribution. The variation of the phase diagrams with that distribution parameters has been obtained and some interesting results have been found such as disappearance of the reentrant behavior and first order transitions which appear in the case of discrete distributions. Also for single and double Gaussian distributions, ground state magnetizations for different distribution parameters have been determined which can be regarded as separate partially ordered phases of the system.     

All electron ab initio investigations of the electronic states of the FeC molecule

The low-lying electronic states of the molecule FeC have been investigated by performing all electron ab initio multi-configuration self-consistent-field (CASSCF) and multi reference configuration interaction (MRCI) calculations. The relativistic corrections for the one-electron Darwin contact term and the relativistic mass-velocity correction have been determined in perturbation calculations. The electronic structure of the FeC molecule is interpreted as antiferromagnetic couplings of the localized angular momenta of the ions and resulting in a triple bond in the valence bond sense. The electronic ground state is confirmed as being . The spectroscopic constants for the ground state and eleven excited states have been derived from the results of the MRCI calculations. The spectroscopic constants for the ground state have been determined as and ,and for the low-lying state as and . The values for the ground state agree well with the available experimental data. The FeC molecule is polar with charge transfer from Fe to C. The dipole moment has been determined as in the ground state and as 1.51 D in the state. From the results of the MRCI calculations the dissociation energy, , is determined as 2.79 eV, and D₀ as 2.74 eV. Received: 2 October 1998 / Received in final form: 30 March 1999