Ram Chandra Singh

Structure and freezing of fluids interacting via the Gay-Berne (n-6) potentials.

We have calculated the pair-correlation functions of a fluid interacting via the Gay-Berne (n-6) pair potentials using the Percus-Yevick integral equation theory and have shown how these correlations depend on the value of n that measures the sharpness of the repulsive core of the pair potential. These results have been used in the density-functional theory to locate the freezing transitions of these fluids. We have used two different versions of the theory known as the second order and the modified weighted-density-functional theory and examined the freezing of these fluids for 8< or =n< or =30 and in the reduced temperature range lying between 0.65 and 1.25 into the nematic and the smectic A phases. For none of these cases smectic A phase was found to be stabilized though in some range of temperature for a given n it appeared as a metastable state. We have examined the variation of freezing parameters for the isotropic-nematic transition with temperature and n. We have also compared our results with simulation results wherever they are available. While we find that the density-functional theory is good to study the freezing transitions in such fluids the structural parameters found from the Percus-Yevick theory need to be improved particularly at high temperatures and lower values of n.

Effects of molecular elongation on liquid crystalline phase behaviour: isotropic–nematic transition

We present the density-functional approach to study the isotropic–nematic transitions and calculate the values of freezing parameters of the Gay–Berne liquid crystal model, concentrating on the effects of varying the molecular elongation, x0. For this, we have solved the Percus–Yevick integral equation theory to calculate the pair-correlation functions of a fluid the molecules of which interact via a Gay–Berne pair potential. These results have been used in the density-functional theory as an input to locate the isotropic–nematic transition and calculate freezing parameters for a range of length-to-width parameters 3.0⩽x0⩽4.0 at reduced temperatures 0.95 and 1.25. We observed that as x0 is increased, the isotropic–nematic transition is seen to move to lower density at a given temperature. We find that the density-functional theory is good to study the freezing transitions in such fluids. We have also compared our results with computer simulation results wherever they are available.

Integral equation theory for molecular fluids: effect of quadrupolar interactions

The Percus–Yevick (PY) and the hypernetted chain (HNC) integral equations have been solved for fluids of hard ellipsoids of a revolution represented by a hard Gaussian overlap model and for fluids of quadrupolar hard Gaussian overlap model. The structural and thermodynamic properties of the isotropic phase are discussed in detail. Ellipsoids with length-to-width ratios of 1.792, 3.0, 4.0 and 5.0 are considered and results are reported for different densities and quadrupole moments. It is shown that both the HNC and PY theories are in reasonable agreement with the computer simulation results.

Temperature-dependent study of isotropic?nematic transition for a Gay?Berne fluid using density-functional theory

We have used the density-functional theory to study the effect of varying temperature on the isotropic–nematic transition of a fluid of molecules interacting via the Gay–Berne intermolecular potential. The nematic phase is found to be stable with respect to isotropic phase in the temperature range 0.80≤T*≤1.25. Pair correlation functions needed as input information in density-functional theory is calculated using the Percus–Yevick integral equation theory. We find that the density-functional theory is good for studying the isotropic–nematic transition in molecular fluids if the values of the pair-correlation functions in the isotropic phase are known accurately. We have also compared our results with computer simulation results wherever they are available.

Orientational Phase Transition of Long Elongated Gay–Berne Molecules

We have performed a detailed study of the temperature dependence and of the isotropic–nematic phase transition in a fluid of moderately long elongated molecules interacting via a Gay–Berne potential with anisotropy parameters x 0 = 4.4, k′ = 20.0, μ = 1, andν = 1. The nematic phase is found to be stable with respect to the isotropic phase for reduced temperatures T* ≤ 1.60. In the temperature range 1.60 ≤ T* ≤ 3.0, the phase boundaries of the isotropic–nematic transition are obtained by using the density-functional theory. The pair-correlation functions of the isotropic phase that enter in the density-functional theory as input informations are found from the Percus–Yevick integral equation theory. The accuracy of the Percus–Yevick integral equation theory has been tested by comparing the pair-correlation functions of the Gay–Berne fluids with computer simulation results. The density-functional theory is good enough to study the freezing parameters of complex fluids if the values of the pair-correlation functions of the isotropic phase are known accurately.

Mental stress: Neurophysiology and its regulation by Sudarshan Kriya Yoga

Aim: The present study focuses on analyzing the effects of Sudarshan Kriya yoga (SKY) on EEG as well as ECG signals for stress regulation. To envision the regulation of stress Determination Test (DT) has been used. We have chosen a control group for contriving a cogent comparison that could be corroborated using statistical tests. Subjects and Methods: A total of 20 subjects were taken in the study, of which 10 were allotted to a control group. Electroencephalograph was taken during a DT task, before and after SKY the sky session with 30 days of SKY session given to the experimental group. No SKY was given to the control group. Results: We quantified mental stress using EEG, ECG and DT synergistically and used SKY to regulate it. We observed that alpha band power decreases in the frontal lobe of the brain with increasing mental stress while frontal brain asymmetry decreases with increasing stress tolerance. Conclusions: These EEG, ECG and DT shows a significant decrement in mental stress and improvement in cognitive performance after SKY, indicating SKY as a good alternative of medication for stress management.

The Percus-Yevick approximation for quadrupolar molecular fluids

The Percus-Yevick integral equation theory has been solved to study the equilibrium and structural properties of quadrupolar Gay-Berne fluids. The method used involves an expansion of angle-dependent functions appearing in the integral equations in terms of spherical harmonics and the harmonic coefficients are obtained by an iterative algorithm. All the terms of harmonic coefficients which involve l indices up to less than or equal to 6 have been considered. Molecules with length-to-breadth ratios 3.0 and 4.0 have been considered and results are reported for different densities, temperatures, and quadrupole moments. The values of pair correlation functions have been compared with the available computer simulation results.

Wavelets in meteorology

This paper deals with the meteorological applications of wavelets and fuzzy logics and a hybrid of wavelets and fuzzy logics. The wavelet transform has emerged over recent years as a powerful time-frequency analysis and signal coding tool favoured for the interrogation of complex non-stationary signals. It has been shown that the wavelet transform is a flexible time-frequency decomposition tool which can form the basis of useful time series analysis. It is expected to see an increased amount of research and technology development work in the coming years employing wavelets for various scientific and engineering applications.

A study of isotropic-nematic transition of quadrupolar Gay-Berne fluid using density-functional theory approach

The effects of quadrupole moments on the isotropic–nematic (IN) phase transitions are studied using the density-functional theory (DFT) for a Gay–Berne (GB) fluid for a range of length-to-breadth parameters in the reduced temperature range . The pair-correlation functions of the isotropic phase, which enter into the DFT as input parameters are found by solving the Percus–Yevick integral equation theory. The method used involves an expansion of angle-dependent functions appearing in the integral equations in terms of spherical harmonics and the harmonic coefficients are obtained by an iterative algorithm. All the terms of harmonic coefficients which involve l indices up to less than or equal to 6 are considered. The numerical accuracy of the results depends on the number of spherical harmonic coefficients considered for each orientation-dependent function. As the length-to-breadth ratio of quadrupolar GB molecules is increased, the IN transition is seen to move to lower density (and pressure) at a given temperature. It has been observed that the DFT is good to study the IN transitions in such fluids. The theoretical results have also been compared with the computer simulation results wherever they are available.

Footprint-Based Personal Recognition Using Dactyloscopy Technique

The uniqueness of human footprint has drawn attention of academia and industry in recent years and is emerging as a latest biometric trait for biometric authentication. A robust technique to be used for identification and recognition of an individual using footprint as a biometric trait has been proposed in this work. Most of the footprint recognition methods require segmentation or connected component analysis. The determinant values that produce the features of the human footprint are generally utilized in the recognition processes. Static footprint images of 94 individuals (57 males and 37 females) of different regions of North India between age group 15–25 years have been acquired using Dactyloscopy technique. Biometric performance parameters such as false accept rate, false reject rate, genuine accept rate, half total error rate, and accuracy have been computed. The experimental results show that the performance parameters computed for Dactyloscopy technique could be used for biometric authentication. This study could be of potential use for forensic and non-forensic purposes and researchers working in foot biometrics.