Calculation of CWKB envelope in boson and fermion productions

We present the calculation of envelope of boson and of both low-and high-mass fermion production at the end of inflation when the coherently oscillating inflatons decay into bosons and fermions. We consider three different models of inflation and use CWKB technique to calculate the envelope to understand the structure of resonance band formation. We observe that though low-mass fermion production is not effective in preheating because of Pauli blocking, it is quite probable for high-mass fermion to take part in pre-heating.      

Thin film stress measurement by instrumented optical fibre displacement sensor

Residual stress can adversely affect the mechanical, electronic, optical and magnetic properties of thin films. This work describes a simple stress measurement instrument based on the bending beam method together with a sensitive non-contact fibre optical displacement sensor. The fibre optical displacement sensor is interfaced to a computer and a Labview programme enables film stress to be determined from changes in the radius of curvature of the film-substrate system. The stress measurement instrument was tested for two different kinds of thin film, hard amorphous carbon nitride (CN) and soft copper (Cu) films on silicon substrates deposited by RF magnetron sputtering. Residual stress developed in 500 nm thick CN thin films deposited at substrate temperatures in the range 50-550 °C was examined and it was found that stress in CN films decreased from 0.83 to 0.44 GPa compressive with increase of substrate temperature. Residual stress was found to be tensile (121 MPa) for Cu films of thickness 1500 nm deposited at room temperature.     

Study of photophysical properties of capped CdS nanocrystals

Here, we have examined the role of capping agent on the optical properties of CdS nanoparticles by steady-state and time-resolved photoluminescence (PL) spectroscopy. The estimated particles sizes are 3.45, 2.5 and 2.39 nm for uncapped, capped with silica (SiO₂) and thiosalicylic acid (TSA), respectively. The absorption and emission spectra show a clear blue shift to shorter wavelengths in presence of TSA- and SiO₂-capped nanoparticles. It is found that the average decay time 〈τ〉 are 6.24, 4.54 and 2.84 ns for uncapped, capped with SiO₂ and TSA nanoparticles, respectively. Our analysis suggests that the hole or the electron is trapped on thiol molecule of TSA or hydroxyl group of SiO₂, then radiative recombination of the electron and hole is delayed, resulting in strong quenching of PL efficiency.     

Oxidation of Dimethyl Sulfide in Air Using Electron-Beam Irradiation,and Enhancement of its Oxidation Via an MnO<Subscript>2</Subscript> Catalyst

The decomposition of dimethyl sulfide (DMS) at initial concentrations of 4.5–18.0 ppmv in air was studied under electron-beam (EB) irradiation. Doses to decompose 90% of input DMS were 2.5 kGy for 4.5 ppmv, 3.4 kGy for 10.6 ppmv, and 3.9 kGy for 18.0 ppmv. HCOOH, (CH₃)₂SO, and trace CH₃OH and (CH₃)₂SO₂ were produced as irradiation products in addition to CO₂ and CO. Application of an O₃ decomposition catalyst to an irradiated sample gas led to an enhancement in the oxidation of DMS and its products into CO₂ and the decomposition of O₃. For 10.6 ppmv DMS/air, the mineralization ratio increased from 41% via only EB irradiation to 100% via the combination treatment at 6.3 kGy. The yield of CO₂ to CO_x increased from 5.3 to 87.6% by combination with catalytic oxidation. This combination treatment enables the irradiation energy used to deodorize gas streams containing DMS to be reduced.     

Assessment of the Nature of Depolarization Current in Thermally Treated Kapton Polyimide

Pyrolysis of normally insulating aromatic polyimide is known to impart electrical conductivity to the polymer due to the formation of carbonized regions in an insulating matrix with a concomitant change in the polymer’s structural arrangement. The wholly pyrolyzed polyimide is potentially useful for specific applications in certain types of semiconductor devices because of the polyimide’s insulator/conductor transition which creates a barrier type conduction. Pyrolysis, however, degrades the required mechanical integrity of the polyimide for construction of such devices. In order to evaluate the fundamental aspects of barrier conduction by high voltage electron transfer from metal contact that can still produce measurable current in thermally treated non-pyrolyzed polyimide, the nature of depolarization in Kapton was assessed by the thermally stimulated depolarization current (TSDC) technique. The results show that thermal treatment of polyimide without pyrolysis and therefore without loss of mechanical integrity offers a viable means of steady electron conduction for semiconductor operation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Radial variation of pump and signal intensities in EDFA; accurate prediction by a novel approximation of the fundamental modal field

The doped fiber amplifier has already emerged as the indispensable potential candidate for repeaterless transmission of information processed through single mode. Therefore the fundamental modal field in the doped single-mode fiber needs to be accurately prescribed both in the pump as well as the signal to facilitate further study of their variation with distance. Based on the novel approximation of the fundamental modal field in graded-index fiber, we formulate analytical expression as regards the variation of modal intensity with radial distance from the axis of the fiber both for the pump and the signal fields and estimate such variation for step-index fiber of some typical V values as example. We find that our estimation matches excellently with the available exact results in case of both the pump and the signal and is shown to be much superior to one-parameter Gaussian approximation. In addition, our methodology involves less computation compared to the exact analysis involving cumbersome computation.     

On the Stability of Davey-Stewartson System - A Dressing Operator Approach

The problem of stability associated with perturbations around solitonic excitations of Davey-Stewartson equation in three dimension is discussed within the framework of dressing operator approach of Zakharov. The system is stable so far as long time behaviour is concerned and unstable for large transverse directions depending upon the sign of the eigenvalue of the linearized problem.     

Exploring anionic emission of 2-benzoyl benzimidazole in micellar environments

In this paper, an interesting transformation of the emission of anionic conformer of 2-benzoyl bezimidazole in ionic and non-ionic micelles is reported. Deprotonation is hindered in cationic and non-ionic micelles owing to probe molecule's passage deep inside positive ion-rich Stern-layer in contrast with anionic micelle. The orientation of probe molecule in the two ionic micelles, as determined from the spectral properties is opposite in nature. Micellar environment shields the formation of mono- and di-cationic species at very low pH. Three decay times of the probe in different time domains were attributed to three possible anionic species and they are modified differently in ionic and neutral micelles. Quantum chemical calculations also predict the existence of three different possible anionic species.     

Monte Carlo simulation of three-dimensional dilute Ising model

A multispin coding program for site-diluted Ising models on large simple cubic lattices is described in detail. The spontaneous magnetization is computed as a function of temperature, and the critical temperature as a function of concentration is found to agree well with the data of Marro et al.⁽⁴⁾ and Landau⁽³⁾ for smaller systems.The first successful epsilon expansion seems to be by D. E. Khmelnitskii,ZhETF 68:1960 (1975), English translationSov. Phys. JETP 41:981 (1975); for numerical estimates see K. E. Newman and E. K. Riedel,Phys. Rev. H25:264 (1982), for experiments see R. J. Birgenau, R. A. Cowley, G. Shirane and H. Yoshizawa,J. Stat. Phys. 34:817 (1984).