Propagation of Gaussian beams through parabolic index optical waveguides with random dielectric constant gradient

Abstract

The propagation of gaussian beams through parabolic index optical waveguides having random irregularities in the dielectric constant gradient has been studied. For fundamental mode propagation, the perturbation approach has been employed and an analytic expression for the loss of power from the fundamental mode has been obtained. For an incident gaussian beam with arbitrary width, geometrical optics approximation has been used and an exact analytical expression for the average value of the beamwidth has been derived for a particular random process, namely, the dichotomic Markov process. The fluctuations in the beamwidth have also been calculated.     

A novel di-triazole based peptide as a highly sensitive and selective fluorescent chemosensor for Zn2+ ions

A di-triazole based peptide has been synthesised by copper catalyzed Huisgen cycloaddition. Fluorescence intensity is enhanced selectively in the presence of Zn(2+), which is ascribed to reversal of photoelectron transfer. Compound 7 was found to self-assemble in the presence of Zn(ClO(4))(2) in an exclusive 2:1 ratio, which is supported by (1)H NMR titration and mass spectral data. The fluorescence intensity of 7 shows a subsequent ON-OFF phenomenon upon repetitive and alternate addition of Zn(ClO(4))(2) and HClO(4).     

New exact solutions of the Einstein-Maxwell equations for magnetostatic fields

The symmetry reduction method based on the Fr′echet derivative of differential operators is applied to investigate symmetries of the Einstein-Maxwell field equations for magnetostatic fields, which is a coupled system of nonlinear partial differential equations of the second order. The technique yields invariant transformations that reduce the given system of partial differential equations to a system of nonlinear ordinary differential equations. Some of the reduced systems are further studied to obtain the exact solutions.     

Single tone and multi tone microwave over fiber communication system using direct detection method

In this paper, an analog microwave over fiber link for long haul distance based upon Rate Equation Laser is demonstrated. This system uses the advantage of high potential bandwidth of fiber in transmission of microwave signal. The interface of the two systems needs an up-conversion of microwave band into baseband (at which fiber operates). An Intensity Modulation Direct Detection (IMDD) technique is used to achieve this purpose. The Rate Equation laser is operated in a dynamic state, where its intensity oscillates at a microwave frequency that varies with the input signal fed by wave generator. This system can also use for two modulating tones. The frequency of the first tone is varied from 1 to 20 GHz and second is set at 5 GHz. A data signal of 10 Gbps is transmitted over long haul single mode fiber by single tone system. A very good bit error rate (BER) 10^?40 performances for 100 km and 25 km fiber link is achieved for both single tone and two tones respectively in proposed microwave over fiber communication system.     

Effect of correlation on energy of solids

In the present paper we make an attempt to model the lattice energy with the lattice constants through the first-principles calculations. This formalism is designed particularly for application with the self-consistent pseudopotential (PP) method within the density functional (DF) framework and includes exchange and correlation effects. Applying the above formalism we have calculated the lattice energy and correlation energy for a number of solids belonging to groups I–VII and II–VI of the periodic table. The convergence of our results is in the favour of used PP. These results will be helpful in determining various structural and elastic properties of these solids and in the generation of equation of state.     

In situ Synthesis of Metal Nanoparticle Embedded Free Standing Multifunctional PDMS Films

We demonstrate a simple one‐step method for synthesizing noble metal nanoparticle embedded free standing polydimethylsiloxane (PDMS) composite films. The process involves preparing a homogenous mixture of metal salt (silver, gold and platinum), silicone elastomer and the curing agent (hardener) followed by curing. During the curing process, the hardener crosslinks the elastomer and simultaneously reduces the metal salt to form nanoparticles. This in situ method avoids the use of any external reducing agent/stabilizing agent and leads to a uniform distribution of nanoparticles in the PDMS matrix. The films were characterized using UV‐Vis spectroscopy, transmission electron microscopy and X‐ray photoemission spectroscopy. The nanoparticle‐PDMS films have a higher Young's modulus than pure PDMS films and also show enhanced antibacterial properties. The metal nanoparticle‐PDMS films could be used for a number of applications such as for catalysis, optical and biomedical devices and gas separation membranes.

     

An application of Genetic Algorithm in solving an inventory model with advance payment and interval valued inventory costs

The purpose of this research is to solve the mixed integer constrained optimization problem with interval coefficient by a real-coded genetic algorithm (RCGA) with ranking selection, whole arithmetical crossover and non-uniform mutation for non-integer decision variables. In the ranking selection, as well as in finding the best solution in each generation of RCGA, recently developed modified definitions of order relations between interval numbers with respect to decision-making are used. Also, for integer decision variables, new types of crossover and mutation are introduced. This methodology is applied to solve a finite time horizon inventory model with constant lead-time, uniform demand rate and a discount by paying an amount of money in advance. Moreover, different inventory costs are considered to be interval valued. According to the consumption of items during lead-time and reorder level, two cases may arise. For each case, the mathematical model becomes a constrained nonlinear mixed integer problem with interval objective. Our objective is to determine the optimal number of cycles in the finite time horizon, lot-size in each cycle and optimal profit. The model is illustrated with some numerical examples and sensitivity analysis has been done graphically with the variation of different inventory parameters.     

Extreme ultraviolet and soft x-ray spectral lines in Rb XXIX

An extensive theoretical set of atomic data for Rb XXIX in a wide range with L-shell electron excitations to the M-shell has been reported. We have computed energy levels for the lowest 113 fine structure levels of Rb XXIX. The fully relativistic multiconfigurational Dirac-Fock method (MCDF) within the framework of Dirac-Coulomb Hamiltonian taking quantum electrodynamics (QED) and Breit corrections into account has been adopted for calculations. Radiative data are reported for electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions from the ground level, although calculations have been performed for a much larger number of levels. To assess the accuracy of results, we performed analogous calculations using flexible atomic code (FAC). Comparisons are made with existing available results and a good agreement has been achieved. Most of the wavelengths calculated lie in the soft x-ray (SXR) region. Lifetimes for all 113 levels have also been provided for the first time. Additionally, we have provided the spectra for allowed transitions from n=2 to n= 3 within the x-ray region and also compared our SXR photon wavelengths with experimentally recognized wavelengths. We hope that our results will be beneficial in fusion plasma research and astrophysical applications.     

Shape and size dependent thermophysical properties of nanocrystals

A theoretical model based on thermodynamic variables is employed in the present work to study the thermophysical properties of nanomaterials of different shapes and sizes. The model proposed by Qi and Wang [19] is applied to determine the cohesive energy of nanomaterial. The number of atoms on the surface to the total number of atoms in nanosolid is considered in terms of shape factor (α) and size of nanocrystal. The variation of cohesive energy?(E_cn?), melting temperature?(T_mN), Debye temperature (θ_DN), Specific heat capacity (C_pN), and Energy band gap (E_gN?) is studied for spherical, regular tetrahedral, regular hexahedral and regular octahedral nanocrystals. The cohesive energy, melting temperature and Debye temperature are found to decrease as the grain size is reduced. However, the energy band gap and specific heat capacity are found to increase with decrease of grain size of nanomaterial. The results achieved in the present study are compared with the available experimental and also with those calculated from other theoretical models. The consistency between the present calculated results and the results reported earlier confirms the validity of the present model theory to explain the shape and size dependence of thermophysical properties of nanomaterials.     

Applicability of equation of state in extreme compression region and study of diatomic solids under pressure

In the present study, the expression of first pressure derivative of bulk modulus B′?earlier derived by Goyal and Gupta EoS [7] is corrected and the validity of the EoS is then verified in extreme compression region. The expressions of second and third order pressure derivative $(B^{{}^{″}},B^{″\prime })$of bulk modulus are obtained. The values of B′, B²B? to BB″,?Grunesien parameters?λ_∞,?γ_∞,?q_∞ at infinite pressure (P?→?∞)?are calculated using the identities [11–13] to check the validity of the equation in extreme compression region. The Goyal and Gupta EoS is then used to study the volume compression in diatomic solids, LiH and MgO. The values of pressure, bulk modulus and its first order pressure derivative at different compressions are calculated and compared with the results obtained from Hama–Suito EoS. The results justify the validity of the present EoS in high pressure region and the results for diatomic solids are also found in good consistency with the compared results.