Modifying a graphene layer by a thymine or a uracil nucleobase: DFT studies

The hybridizations of a graphene layer by a thymine and a uracil nucleobase have been investigated by performing density functional theory (DFT) calculations. The isolated and hybrid structures have been firstly stabilized to reach the minimum energy and the electronic properties have been subsequently evaluated for the optimized structures. The structural and atomic scale parameters indicated that the tip of graphene is important in determining the properties of new hybrids. Moreover, different effects of thymine and uracil nucleobases have been identified in the hybrid structures. Quadrupole coupling constants have been evaluated to characterize the atomic scale properties, in which the most notable effects of hybridizations have been observed for the atoms close to the linking regions whereas negligible effects have been seen for other atoms.     

Investigation of the radial compression of carbon nanotubes with a scanning probe microscope

Efforts have been made to characterize the mechanical properties of carbon nanotubes. Previous work has concentrated on the tubes' longitudinal properties, and studies of their radial properties have lagged behind. We have used a scanning probe microscope with an indentation/scratch function to investigate the radial compression of multiwalled carbon nanotubes under an asymmetric stress. In particular, we have determined the radial compressive elastic modulus at different compression levels and have estimated the compressive strength to be well beyond 5.3 GPa.     

RLC暂态电路的理论分析和数值模拟

利用Maple符号计算软件做RLC电路方程的拉普拉斯变换,得到电路的精确解,绘制解的图像,并且理论分析了这些解的特点,得到了一些有助于教学应用的结论.     

Quantum glassiness in strongly correlated clean systems: an example of topological overprotection

This Letter presents solvable examples of quantum many-body Hamiltonians of systems that are unable to reach their ground states as the environment temperature is lowered to absolute zero. These examples, three-dimensional generalizations of quantum Hamiltonians proposed for topological quantum computing, (1) have no quenched disorder, (2) have solely local interactions, (3) have an exactly solvable spectrum, (4) have topologically ordered ground states, and (5) have slow dynamical relaxation rates akin to those of strong structural glasses.     

插入生长AlGaAs薄膜对InAs量子点探测器性能的影响

利用分子束外延生长获得的两个InAs量子点样品制备了n型的量子点红外探测器.对于其中一个器件,在InAs量子点有源区的底部和顶部分别插入生长了AlGaAs势垒层.利用透射电阻显微技术研究了两个样品的结构特性;利用光致发光光谱和光电流谱研究了两个器件的光电性质.实验结果表明,AlGaAs层的插入对器件的探测性质有显著的影响.利用有三维效质量近似模型的计算结果,指认了带内光电流谱中峰结构的起源. 关键词： InAs 量子点 AlGaAs薄膜 光致发光光谱 有效质量近似模型     

插入生长AlGaAs薄膜对InAs量子点探测器性能的影响

利用分子束外延生长获得的两个InAs量子点样品制备了n型的量子点红外探测器.对于其中一个器件，在InAs量子点有源区的底部和顶部分别插入生长了AlGaAs势垒层.利用透射电阻显微技术研究了两个样品的结构特性；利用光致发光光谱和光电流谱研究了两个器件的光电性质.实验结果表明，AlGaAs层的插入对器件的探测性质有显著的影响.利用有三维效质量近似模型的计算结果，指认了带内光电流谱中峰结构的起源.     

On wave propagation in a random micropolar thermoelastic medium,second moments,and associated Green’s tensor

The couple stress theory developed by Eringen comprises granular materials as also composite fibrous materials. As such, micropolar materials present an inclusive model of composite materials. This article endeavors to study aspects of wave propagation in a random weakly thermal micropolar elastic medium. The smooth perturbation technique has been employed. The classical thermoelasticity has been used. Six different types of waves have been observed to propagate in the random interacting medium. Dispersion equations have been derived. The effects due to random variations of micropolar elastic and thermal parameters have been observed. Change of phase speed occurs on account of randomness. Attenuation coefficients for high-frequency waves have been computed. Second moment properties have been discussed with application to wave propagation in the random micropolar elastic medium. 36 + 1 components of the associated Green’s tensor have been computed. Integrals involving correlation functions have been transformed to radial forms. A special type of correlation function has been used to approximately measure effects of random variations of parameters.     

Electromagnetic cavity to explore disordered systems

In the course of characterizing an electromagnetic cavity we have come to understand details of transmission and reflection traces, some of which may be useful as tools to investigate local modes in random media. We have demonstrated quantitative agreement of frequency shift observations with theory, have demonstrated that the spatial distribution of electric and magnetic fields can be measured using insulating and conducting spheres, and have used perturbation due to wires and disks to demonstrate the local direction of electric and magnetic fields. We have observed that not only frequency shifts but also spatial shifts of modes can be used to observe the intensity of interaction of modes with extended objects in the cavity.     

分形用于材料断裂韧性研究的不定性问题

 本文基于物理、断裂力学与分形三者必须自洽的原则，提出了消除码尺的量纲与量值选择的不确定性的几何与物理准则，克服了分形用于断裂韧性研究中的不确定性困难。本文的某些观点用于分形在其它学科中的应用，也颇有益处。     

Raman Scattering by Crystals of Rare-Earth Hexaborides with Different Isotopes of Boron

Monocrystals of lanthanum hexaboride LaB₆ containing both natural boron and its isotopes ¹⁰B and ¹¹B have been produced using the solution-melt method. Polyelement hexaboride rare-earths have been grown and the corresponding ceramics have been synthesized for the first time. All these crystals have been studied by means of various techniques, generally using Raman scattering. The Raman spectra attributed to various spectral lines corresponding to nonanalyzable representations have been obtained and interpreted. Frequencies and half-widths of spectral lines have been obtained, the removal of degeneracy and the development of respective splitting of degenerate oscillations induced by defects, mainly by boron isotope inclusions, have been identified. The influence of defects on the Raman spectra has been determined.     

Pion interferometry in jet events at the CERN Intersecting Storage Rings

We have revised the additive quark model for inelastic hadronic cross sections with its implications to the average charged multiplicities. The correction to the additive quark model is on the level of 2 mb only if we take into account all possible quark-quark cross sections with respect to flavour. The quark-quark constitutent cross sections have been evaluated. We have attributed average charged multiplicities to the constituent quark cross sections and have found some regularities according to the flavour of the quarks.     

The Coulomb explosion of charged drops

In the framework of the density functional theory using a simple variational model we have calculated the first-order size corrections to electro-physical characteristics of small metal particles. We have discovered that the curvature correction to the surface energy is of positive sign. We have shown that it is possible to use macroscopic electrodynamics in calculations of the ionization potential and the electron affinity. We have determined the maximum charge which can be retained by a particle of a given size.     

19F NMR in the S=12 antiferromagnets CuF2 and AgaF2

¹⁹F NMR has been observed in the antiferromagnetic phases of CuF₂ and AgF₂. These compounds, which are known to have very similar magnetic structures, have been shown to have similar magnetization curves and to have saturation sublattice magnetizations that scale approximately as their Neel temperatures.     

Some physical properties of In doped copper oxide films produced by ultrasonic spray pyrolysis

In this work, we have reported the effect of In doping on structural, optical and surface properties of copper oxide films obtained by a low-cost ultrasonic spray pyrolysis technique. Thicknesses, refractive indices and extinction coefficients of the films have been determined by Spectroscopic ellipsometry technique using Cauchy-Urbach model for fitting. A very good agreement was found between experimental and theoretical parameters with low MSE values. Transmission and reflectance spectra have been taken by UV Spectrophotometer, and band gap values have been determined by optical method. Structural properties of the films were investigated with X-ray diffraction patterns. In doping caused the films to growth through some certain directions. Atomic force microscope images have been taken to see the effect of In doping on surface topography and roughness of copper oxide films. Surface properties of undoped films have been improved by In doping. Lowest roughness values have been obtained for In doping at 1%. As a result, we have concluded that properties of copper oxide films which are commonly used in solar cells may have improved by In doping (especially In doped at 1%).     

第一过渡族金属离子光谱参数的线性拟合

本文研究了第一过渡族金属离子光谱参数与有效核电荷的关系，通过对实验值的拟合，得到了较好的线性关系，并对结果作了初步讨论。     

Characteristic of microstructured optical fibers: an analytical approach

We have recently developed a simple analytical model to study propagation characteristics of microstructured optical fibers (MOFs). We have used this model to study splice losses between two MOFs and also between an MOF and a conventional fiber. We have also presented here the results on evolution of fundamental mode from near-field to far-field, the effective mode area and the beam divergence using this model. Comparisons with available experimental and modeling results have also been included.     

Lattice static properties of vacancy clusters and interstitials in hcp magnesium: Computer simulation studies

Computer simulation studies have been made to investigate the static properties of mono-, di- and tri-vacancy clusters and of self-interstitials in hcp magnesium in different configurations. Three interatomic potentials have been chosen for which the results have been compared. A crystallite containing about 1500 atoms and a model with the interatomic interaction extending upto the fourth neighbour distance have been used. Relaxation field, defect relaxation and formation energies, strength dipole tensors and relative changes in volume in the above defects have been computed and our final results compared with those of earlier workers. The formation energies of the defects are highly sensitive to the choice of the potential whose detailed structure guides the nature of relaxation and the dipole tensors. Calculations have been done for octahedral, tetrahedral and dumb-bell interstitials of which the last is found to be the most stable.     

Apparent molar volumes and transport behavior of glycine and l-valine in aqueous solutions of tripotassium citrate at T = (308.15 and 318.15) K

Densities and viscosities of glycine and l-valine have been measured at 308.15 and 318.15 K in aqueous tripotassium citrate solutions ranging from 0.2 to 0.8 mol kg^− 1 of tripotassium citrate. The viscosity data have been analyzed by Jones-Dole equation. The activation parameters of viscous flow have been obtained to throw light on the mechanism of viscous flow. The values of apparent molar volume, partial molar volume at infinite dilution and relative viscosities of each amino acid in various aqueous tripotassium citrate solutions have been evaluated from the density and viscosity data. The partial molar volumes of transfer from water to aqueous tripotassium citrate solution at infinite dilution have also been calculated. Transfer volume data have been used to calculate the pair and triplet interactions. The results have been discussed in terms of solute-solute and solute-solvent interactions and the structural changes of the solutes in solutions.     

Surface tensions and stress tensors of liquid and solid clusters by molecular dynamics

Surface tension and pressure (stress) tensors of Lennard-Jones clusters, in the size range 200 ~ 2700 atoms/cluster, formed from evaporating liquid droplets were calculated in a Molecular Dynamics simulation. Icosahedral clusters have a much larger surface tension than decahedral, fcc, and hcp ones, meanwhile asymmetric icosahedral clusters have a lower surface tension. Fcc and hcp clusters have a very small surface tension. Decahedral clusters have a surface tension closer to that of fcc and hcp ones than to that of icosahedral ones, though both icosahedral and decahedral structures have five fold symmetry axis. Binary component clusters have a higher surface tension than single component ones.     

Conformational Analysis of 1,2-Dichlorobutane

Vibrational spectra have been published and normal coordinate calculations have been made for 1,2-dichlorobutane.^1,2 Those calculations were limited to the three conformers that had all four carbon atoms coplanar. Molecular mechanics calculations have now shown a conformer that was omitted to be the second most abundant conformer. Therefore, normal coordinate calculations have been made for this conformer and molecular mechanics calculations have been made for all possible conformers.