Electron impact single and double ionization of halogens

The binary encounter approximation has been used for calculations of electron impact single ionization cross-sections for F, Cl, Br and I and double ionization cross-sections for Br and I. Contributions of ionization from inner shells have also been included in the calculations. Hartree-Fock momentum distribution has been used for the bound electron as far as possible. The results have been found to be in satisfactory agreement with experimental observations.     

Data acquisition and instrument control system for neutron spectrometers

A personal computer (PC)-based data acquisition and instrument control system has been developed for neutron spectrometers in Dhruva reactor hall and Guide Tube laboratory. Efforts have been made to make the system versatile so that it can be used for controlling various neutron spectrometers using single end-on detector in step scan mode. Commercially available PC add-on cards have been used for input-output and timer-counter operations. An interface card and DC motor driver card have been developed indigenously. Software for the system has been written in Visual C++ language using MS Windows operating system. This data acquisition and instrument control system is successfully controlling four spectrometers at Dhruva reactor.     

Holography in partially coherent light

A Michelson interferometer has been used to obtain good holographic carrierfringes of the order of 200 to 300 fringes/ mm over an area of 1 cm × 1.5 cm with a Hg-are source and extended aperture with and without filter. The fringes have been used to record holograms. The image reconstruction has been done with light from the Hg-arc without the use of any filter. Experimental results for a continuous-tone object have been presented. The advantages and disadvantages and some of the potential applications of this technique have been mentioned.     

KLOE results on scalar and pseudoscalar mesons

The data collected by the KLOE Collaboration at the Frascati φ-factory DAΦNE from 2001 to 2006 have been used for extensive studies in meson spectroscopy.The decays of the scalar mesons a0(980) and f0(980) into two pseudoscalar mesons have been exploited to measure the relevant parameters of those resonances.The radiative decays φ→ηγ and ηγ have been used for the determination of the pseudoscalar mixing angle and to search for a possible gluonium content in the η.The dynamics of the η→ 3π decay has been studied and the Dalitz Plot parameters have been measured.The large amount of η mesons produced allowed also to study interesting rare η decays.     

Chaos based multiple image encryption using multiple canonical transforms

We propose a new method for multiple image encryption using linear canonical transforms and chaotic maps. Three linear canonical transforms and three chaotic maps are used in the proposed technique. The three linear canonical transforms that have been used are the fractional Fourier transform, the extended fractional Fourier transform and the Fresnel transform. The three chaotic maps that have been used are the tent map, the Kaplan-Yorke map and the Ikeda map. These chaotic maps are used to generate the random phase masks and these random phase masks are known as chaotic random phase masks. The mean square error and the signal to noise ratio have been calculated. Robustness of the proposed technique to blind decryption has been evaluated. Optical implementation of the technique has been proposed. Experimental and simulations results are presented to verify the validity of the proposed technique.     

稀土和锕系化合物中重费密子行为

本文采用周期Anderson哈密顿量研究了稀土和锕系化合物中的重费密子行为。对f电子间库仑关联项做了平均场近似并引入自能项反映多体作用的效应。对自能项采用了单格位近似,在准粒子表象中讨论了系统的性质,通过对f电子平均占据数的自洽计算,得到了准粒子有效质量,讨论了形成重费密子的条件,以及相应的磁性的变化,并做了数值计算。所得结果与最近的实验进行了比较。 关键词：     

Simple approach to approximate predictions of the vapor–liquid equilibrium curve near the critical point and its application to Lennard-Jones fluids

We propose a simple analytical form of the vapor–liquid equilibrium curve near the critical point for Lennard-Jones fluids. Coexistence densities curves and vapor pressure have been determined using the Van der Waals and Dieterici equation of state. In described method the Bernoulli differential equations, critical exponent theory and some type of Maxwell?s criterion have been used. Presented approach has not yet been used to determine analytical form of phase curves as done in this Letter. Lennard-Jones fluids have been considered for analysis. Comparison with experimental data is done. The accuracy of the method is described.     

Calculation of the rotation-vibration spectrum of NH+

Ab initio molecular orbital calculations have been used to compute potential energy and dipole moment functions for the X²II and a⁴Σ^? states of NH⁺. These functions have been used to compute rotational-vibrational energy levels, including the interaction between the two states. Transition moments have been calculated for transitions between these levels, using either the results of numerical diagonalization of the Hamiltonian, or more approximately by fitting analytic functions. Good agreement with experimental data is found, and our results have also been used to interpret previously unassigned spectral lines.     

Calibration of electron spectra

Energy calibration procedures, which have been used in ESCA, are reviewed. Binding energies of calibration lines suitable for solid and for gaseous samples have been determined. Charging effects of nonconducting samples have been investigated for different X-radiation, sample thickness and material. A calibration relative to lines from some insulating standard compound mixed into the sample was shown to be unreliable, while experiments indicated that in calibrating relative to a surface layer, the carbon line from the hydrocarbon contamination layer can be used as well as a line from a thick layer of a noble metal on a part of the sample.     

Monte Carlo calculation of CR-39 efficiency for fast neutron detection using a combination of MCNP and SRIM codes,and comparison with experimental results

The elastic scattering of light nuclei, especially hydrogen, is widely used for detection of fast neutrons. Fast neutrons have a few interactions in solid state nuclear track detectors (SSNTDs), such as CR-39. It has been shown that to increase the efficiency of detector, a radiator layer, e.g. polyethylene may be used. In this work, the optimum thickness of the radiator layer has been determined. Some different thicknesses of aluminium layers have been used as discriminators for which the efficiency of detector to Am–Be neutron source has been calculated. A program FTRAC has been developed for the calculation of the detection efficiency. This software determines the specifications of recoil protons (using PTRAC card of MCNP code) and also the kinematics of interactions. Transport of recoil protons has been carried out using SRIM Monte Carlo code. A good agreement have been shown between measurement and simulation results.     

Molecular dynamics simulation of liquid tetrahydrofuran: on the uniqueness of force fields

Molecular dynamics simulations of liquid tetrahydrofuran have been performed with different force fields to illustrate that there is no unique way to model a given system of molecules. Parameters for the force fields have been taken from existing force fields and have been used as starting guesses for a simplex optimization. In spite of the very different final parameter values, all optimized force fields reproduce properly the physical properties for which they have been optimized, but not necessarily other ones.     

Technological study of ancient ceramics produced in Casteldurante (central Italy) during the Renaissance

In order to recover the ancient tradition concerning the materials used for the decoration, majolica shards produced during the Renaissance period in Casteldurante, a famous centre for ceramic production in Italy (Marche), have been examined. In the present study, pigments used for the decorations have been investigated by means of inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDX) and diffuse-reflectance UV-Vis spectroscopy. Ochre, lead antimonate yellow, copper-based pigment and smalt have been used as colourants to obtain respectively yellow-orange, yellow, green and blue decorations in accordance with what is reported by the ancient recipes. PACS 81.05.Mh; 82.80.-d; 61.66.Fn; 61.66.Hq     

Absorption properties of the near infrared CO2 bands

The equivalent widths of the near i.r. CO₂ bands at 1.4, 1.6, 2.0, 2.7, 4.8 and 5.2 μm have been measured for various sample parameters. By comparing the data obtained for pure CO₂ samples with theoretical values resulting from line0by-line calculations, band intensities have been determined for these six bands. The data obtained for the mixtures of CO₂ with N₂ have been used to check the validity of the band intensities thus determined. These data have also been used to check the applicability of the empirical formulae proposed by Howard, Burch and Williams.     

Ion-ion interactions in a polarized electron gas

Formally exact expressions have been derived for the response to a spin-dependent non-local pseudopotential and for the ion-ion interaction in a spin-polarized electron gas. These expressions have been compared to previously used expressions for these quantities and have been found to differ in several important ways. The improved expressions will make possible a quantitative investigation of the influence of a magnetic field on lattice properties of simple metals.     

Etude du chromatisme d'un systeme optique par photographie “speckle”

Speckle photography experiments have been used for studying optical systems and more recently we have used image speckle photography to measure displacements and deformations of a partial diffuser. The same method is now used for studying chromatic aberrations of a lens system. Experimental results are given for three optical lenses.     

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.     

Novel highly sensitive Cu‐based SERS platforms for biosensing applications

Novel surface enhanced Raman spectroscopy (SERS) platforms have been prepared and used for the bacteria detection. Unlike typical, expensive SERS platforms prepared from gold or silver, the presented platforms are prepared using copper. A new, simple, cost‐efficient and fast high pressure method is used for platform fabrication, through the decomposition of copper hydride. The platform enhancement factors are verified using the malachite green isothiocyanate as a standard. The platforms exhibit extremely high SERS enhancement factors depending on pressure used for their preparation. The calculated enhancement factors have been found in the range between 1.5 × 10⁶ and 4.6 × 10⁷. The SERS spectra reproducibility is established both across a single platform and among different platforms. The average spectral correlation coefficient (Γ) has been calculated to be 0.82. Fully characterized SERS platforms have then been used for detecting Staphylococcus aureus bacteria. These novel platforms have great potential to become excellent tools for biological or medical diagnostics as an alternative to more common silver or gold SERS platforms. Copyright © 2015 John Wiley & Sons, Ltd.     

Direct determination of free energies of colloidal dispersions

Helmholtz free energies of electrostatically-stabilized colloidal dispersions of monodispersed spherical particles have been obtained using computer experiments. Boltzmann sampling has been shown to be sufficient for determining free energy differences between two dispersions whose pair-potentials are close to each other. Non-Boltzmann sampling has been used when the pair-potentials differ substantially. These results have been compared with the results based on perturbation theory. The techniques used, thus, offer a direct method to test the latter.     

Acoustic sounder monitoring of windshear within the atmospheric boundary layer over Ile-Ife, Nigeria

Summary A tri-axial acoustic sounder with Doppler wind measuring capability has been used to measure boundary layer winds from which windshear fields have been evaluated over Ile-Ife (7.29° N, 4.34° E) Nigeria between April and June, 1988. The correlation between SODAR-derived windshear profile and a radiosonde-derived temperature profile is examined. Associated Richardson numbers have been used to categorize atmospheric layers into various stability types. A case study of wind fields and derived windshear zones associated with a rain event has been made. The authors of this paper have agreed to not receive the proofs for correction.     

丝蛋白分子的红外光谱研究

本文记录并研究了桑蚕丝、柞蚕丝、天蚕丝和天柞杂交蚕丝等几类共42种蚕丝样品的红外光谱,确定了柞丝类和桑丝类两大类蚕丝样品在红外光谱方面的差别。从而为鉴别蚕丝样品的种类建立起一种简便易行的方法。通过对各类样品的红外光谱数据处理,计算了某些谱带的相对强度比,获得了一些半定量的规律性结果。