006615   Das S;Gangopadhyay S;Ghosh C;Bhar G C (Laser Lab Phys Dep, Burdwan Univ, Burdwan-715 104, Email: dgp_buphygcb@sancharnet.in) : Singly-resonant optical parametric oscillator based on KTA crystal. Pramana J Phys 2005, 64(1), 67-74.

Tunable mid-infra-red radiation by singly resonant optical parametric oscillation based on KTA crystal pumped by multi-axial Gaussian shape beam from Q-switched Nd:YAG laser has been demonstrated. Threshold energy of oscillation at different idler wavelengths for different cavity length has been demonstrated. Single pass conversion efficiency of incident pump energy to infra-red wavelength has also been measured.

3 illus, 25 ref

006614   Cornu F (Laboratoire de Physique Theorique Laboratoire associe au CNRS UMR 8627, Universite Paris-Sud, 91405 Orsay Cedex, France, Email: francoise.cornu@th.u-psud.fr ) : Classical charged fluids at equilibrium near an interface: Exact analytical density profiles and surface tension. Pramana J Phys 2005, 64(5), 785-801.

The structure of equilibrium density profiles in an electrolyte in the vicinity of an interfacewith an insulating or conductive medium is of crucial importance in chemical physics and colloidal science. The Coulomb interaction is responsible for screening effects, and in dilute solutions the latter effects give rise to universal leading corrections to nonideality, which distinguish electrolyte from nonelectrolyte solutions. An example is provided by the excess surface tension for an air-water interface, which is determined by the excess particle density, and whichwas first calculated by Onsager and Samaras. Because of the discrepancy between the dielectric constants on both sides of the interface, every charge in the electrolyte interacts with an electrostatic image, and the Boltzmann factor associated with the corresponding self-energy has an essential singularity over the length scale l from the wall. Besides Coulomb interactions, short-range repulsions must be taken into account in order to prevent the collapse between charges with opposite signs or between each charge and its image when the solvent dielectric constant is lower than that of the continuous medium on the other side of the interface. For a dilute and weakly-coupled electrolyte, l is negligible with respect to the bulk Debye screening length εD. In the framework of the grand-canonical ensemble, systematic partial resummations in Mayer diagrammatics allow one to exhibit that, in the regime, the exact density profilesat leading order are the same as if they were calculated in a partially-linearized mean-field theory, where the screened pair interaction obeys an inhomogeneous Debye equation. In the latter equation the effective screening length depends on the distance x from the interface: it varies very fast over the length l and tends to its bulk value over a few εDs. The equation can be solved iteratively at any distance x, and the exact density profiles are calculated analytically up to first order in the coupling parameter l/ε D. They show the interplay between three effects: (1) the geometric repulsion from the interface associated with the deformation of screening clouds, (2) the polarization effects described by the images on the other side of the interface, (3) the interaction between each charge and the potential drop created by the electric layer which appears as soon as the fluid has not a charge-symmetric composition. Moreover, the expressions allow us to go beyond Onsager-Samaras theory: the surface tension is calculated for charge-asymmetric electrolytes and for any value of the ratio between the dielectric constants on both sides of the interface. Similar diagrammatic techniques also allow one to investigate the charge renormalization in the dipolar effective pair interaction along the interface with an insulating medium.

21 ref

006613   Cohen E G D (NO, The Rockefeller Univ, 1230 York Avenue, New York, NY 10021, USA, Email: egdc@rockefeller.edu) : Boltzmann and Einstein: statistics and dynamics an unsolved problem. Pramana J Phys 2005, 64(5), 635-43.

The struggle of Boltzmann with the proper description of the behavior of classical macroscopic bodies in equilibrium in terms of the properties of the particles out of which they consist will be sketched. He used both a dynamical and a statistical method. However, Einstein strongly disagreed with Boltzmann's statistical method, arguing that a statistical description of a system should be based on the dynamics of the system. This opened the way, especially for complex systems, for other than Boltzmann statistics. The first non-Boltzmann statistics, not based on dynamics though, was proposed by Tsallis. A generalization of Tsallis; statistic as a special case of a new class of superstatistics, based on Einstein's criticism of Boltzmann, is discussed. It seems that perhaps a com-bination of dynamics and statistics is necessary to describe systems with complicated dynamics.

2 illus, 31 ref

006612   Clisby N;McCoy B M (ARC Cent Excellence Math Statist Complex Systems 139 Barry Street, The Univ of Melbourne, Victoria 3010, Australia, Email: N.Clisby@ms.unimelb.edu.au) : New results for virial coefficients of hard spheres in D dimensions. Pramana J Phys 2005, 64(5), 775-83.

New results for the virial coeficients B_k for k <131> 10 for hard sphers in dimensions D = 2,....,8 have been discussed.

5 illus, 5 tables, 22 ref

006611   Chowdhury A;Gupta G P;Naik P A;Gupta P D (Laser Plasma Div, Cent for Advd Technol, Indore-452 013, Email: avijit@cat.ernet.in) : Effect of dielectronic recombination on the charge state distribution and soft X-ray line intensity of laser-produced carbon plasma. Pramana J Phys 2005, 64(1), 141-6.

The effect of dielectronic recombination in determining charge-state distribution and radiative emission from a laser-produced carbon plasma has been investigated in the collisional radiative ionization equilibrium. It is observed that the relative abundances of different ions in the plasma, and soft X-ray emission intensity get significantly altered when dielectronic recombination is included. Theoretical estimates of the relative population of CVI to CV ions and ratio of line intensity emitted from them for two representative formulations of dielectronic recombination are presented.

3 illus

006610   Benjamin C;Jayannavar A M (NO, Inst of Phys, Sachivalaya Marg, Bhubaneswar-751 005) : Trends in mesoscopic transport. Natn Acad Sci Lett 2004, 27(5-6), 177-86.

Mesoscopic physics is the area of solid state physics that covers the transition regime between macroscopic objects and the microscopic atomic world. In this regime electron retains its phase coherence throughout the entire sample. At low temperatures mesoscopic systems exhibit a wonderful new range of unexpected quantum phenomena. In the article a brief sketch of this field is presented.

s, 27 ref

006609   Balibar S;IShiguro R (Labortoire de Physique Statistique de 1, Ecole Normale Superierure associe au CNRS et aux Universites, Paris 6 et 7, 24 rue Lhomond, 75231 Paris Cedix 05, France) : Critical Casimir forces and anomalous wetting. Pramana J Phys 2005, 64(5), 743-55.

Authors present a review of critical Casimir forces in connection with successive experiments on wetting near the critical point of helium mixtures.

9 illus, 31 ref

006608   Balaram V (NO, Natn Geophys Res Inst, Hyderabad-500 007, Email: balaramv1951@yahoo.co.in) : Recent developments in analytical techniques for characterization of ultra pure materials. Bull Mater Sci 2005, 28(4), 345-8.

With continual decrease of geometries used in modern IC devices, the trace metal impurities of process materials and chemicals used in their manufacture are moving to increasingly lower levels, i.e. ng/g and pg/g levels. An attempt is made to give a brief overview of the use of different analytical techniques in the analysis of trace metal impurities in ultrapure materials, such as, high purity tellurium (7N), high purity quartz, high purity copper (6N), and high purity water and mineral acids. In recent times mass spectrometric techniques such as ICP-MS, GD-MS and HR-ICP-MS with their characteristic high sensitivity and less interference effects were proved to be extremely useful in this field. A few examples of such application studies using these techniques are outlined. The usefulness of other analytical techniques such as F-AAS, GF-AAS, XRF, ICP-AES and INAA was also described. Specific advantages of ICP-MS and HR-ICP-MS such as high sensitivity, limited interference effects, element coverage and speed would make them powerful analytical tools for the characterization of ultrapure materials in future.

3 tables, 12 ref

006607   Bakshi H V;Ghan S D;Kasture M W;Bhoskar B T (Dept Phys, ACS Coll, Shankarnagar, Dist Nanded M S) : Thermal behaviour of natural stilbite. Int J chem Sci 2005, 3(2), 347-52.

Crystals collected from the Ajantha, Aurangabad, Maharashtra, India, have been characterized as stilbite by X-ray diffraction, IR spectroscopy and chemical analyses. The thermal behaviour was studied using thermogravimetric/differential thermal analysis (TG/DTG/DTA). The sample was exchanged at reflux temperature with NH₄Cl and NaCl. The sample exchanged with NH₄Cl was further transformed to the H-form of stilbite by heating at 823 K for 2 h. Investigations suggest that thermal stability of zeolite framework can be varied due to ion exchange.

2 illus, 12 ref

006606   Asolkar V G;Mande C (NO, L.A.D. Coll for Women, Nagpur-440 010) : Internuclear distance in some diatomic molecules, viz. SrCl, CaBr, MgI, BiF, AsCl, SbCl, LiRb and SbS. Natn Acad Sci Lett 2004, 27(5-6), 221-5.

Values of internuclear distance r_e in some diatomic molecules, viz. SrCl, CaBr, MgI, BiF, AsCI, SbCl, LiRb and SbS which are not reported in literature have been estimated from the consideration of rotational constant following the method given by authors earlier.

s, 1 table, 13 ref

006605   Agrawal A K (Natn Phys Lab, , Dr K S Krishnan Marg, New Delhi-110 012) : Certified refrence materials of trace elements in water. Bull Mater Sci 2005, 28(4), 373-8.

Measurement of trace elements is playing a vital role in industries and various sectors of science and technology including semiconductors, food, health and environmental sectors. In most of the cases a small error in measurement can vitiate all the measures taken for quality control and management. Many decisions regarding the suitability of material/products are based on the analysis. To reduce or eliminate the rejection rate of the products, accurate and reliable measurements are needed which can be achieved by the use of certified reference materials (CRMs). Their use in calibration of analytical equipments and validation of test methods ensures high quality in measurements and it provides traceability to the measurement data with national/international measurement systems (SI unit) also. In the present scenario of globalization of economy, use of certified reference materials (CRMs) in measurements is essential for global acceptance of products and test reports. Their use fulfil a mandatory requirement of international quality systems (ISO 9000, ISO/IEC standard 17025) including our national accreditation body, National Accreditation Board for Testing and Calibration Laboratories (NABL), World Trade Organization (WTO) etc. International manufacturers of CRMs are meeting most of the requirement of CRMs of the country. To meet the demand of CRMs indigenously, the National Physical Laboratory, India initiated a national programme on preparation and dissemination of certified reference materials.

3 illus, 3 tables, 16 ref

005555   Vyawahare S K;Shamkuwar N R;Sable M C (Dep of Phys, Deogiri Coll, Aurangabad-431 005) : Structural and magnetic properties, of Mn_1+xSi_xFe_1-xCr_1-xO₄ system. Indian J pure appl Phys 2005, 43(7), 545-9.

The structural and magnetic properties of mixed spinel system Mn_1+x Si_xFe_1-xCr_1-xO₄ (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) have been investigated by X-ray diffraction and magnetization studies. X-ray intensity calculations indicate that Si⁴⁺ ions occupy only tetrahedral (A) sites replacing Fe³⁺ ions and Mn³⁺ ions replace Fe³⁺ ions from (B) site. The variation of saturation magnetic moment per formula unit measured at 300 K with the Si⁴⁺ content is explained on the basis of Neel's collinear spin ordering model.

5 illus, 3 tables, 18 ref

005554   Vyas R K;Joshi S K;Shrivastava B D;Shah M C; Prasad J (Phys Dep, Government Post Grad Arts and Sci Coll, Ratlam-457 001) : X-ray K-absorption fine structure studies on some copper(II) complexes. Indian J pure appl Phys 2005, 43(7), 509-16.

The X-ray K-absorption spectra of copper and arsenic in complexes [Cu (φ₃AsO)₂X₂] and [Cu(φ₃PO)₂ X₂], where X = Cl or Br and φ = C₆H₅, have been studied using a 40 cm bent crystal spectrograph. Various X-ray absorption parameters such as edge shift, phase parameters and bond-distances have been estimated. The studies reveal that triphenylarsine oxide is a better σ-donor than triphenylphosphine oxide. The splitting of the main edge K into K₁ and K₂ components have been explained. The existence of the white line have been attributed to the transition of K-electrons into a high density of normally unoccupied states with p symmetry in the neighbourhood of the copper or arsenic atom. Further, the studies on phase shift determination indicate that variation in the first or second coordination environment around the central absorbing atom has a dominant effect on the values of backscattering phase shifts.

4 illus, 5 tables, 31 ref

005553   Vishwakarma J P (Dep of Math, Pachhunga Univ Coll, Aizawal-796 001) : Implosion of a cylindrical shock wave in a non-homogeneous gas under the action of an azimuthal magnetic field. Indian J Theor Phys 2004, 52(2), 161-77.

The problem of cylindrical magnetogasdynamic shock wave, convergent axis of symmetry through a gas with varying intial density, is studied by using Whitham's rule. The shock velocity and other flow variables just behind the shock are determined in the cases, when (i) the gas is weakly ionized before and behind the shock front, (B) the gas is strongly ionized before and behind the shock front and (iii) non-ionized gas undergoes intense ionization as a result of of the shock. It is found that the inhomogeneity of the undisturbed medium and the azimuthal magnetic field affect the shock propagation signficantly.

5 illus, 20 ref

005552   Vijaya Kumar K;Dasaradhudu Y;Reddy V R (Dep of Phys, Chitanya Bharathi Inst of Technol, Hyderabad-500 075) : Dielectric studies on polybutylene terephthalate polymer thin films. Acta Cienc Indica-Phys 2005, 31(2), 195-200.

The dielectric capacitance and loss tangent (tan δ) of solution grown polybutylene terephthalate (PBT) films over a wide range of frequency 100 Hz - 10 MHz and temperature 143 K - 420 K have been measured. In PBT films, the capacitance decreases with increasing frequency at constant temperature and increases with temperature at constant frequency. The temperature variation of dielectric loss exhibited two loss peaks with increasing temperature, one (peak I) at - 78°C and the other (peak II) at 57°C in the vicinity of the glass transition temperature, T_g. The high temperature peak (α) at 57°C may be due to micro-Brownian motion of the segments of the main chain. The low temperature peak (β) at - 78°C may be due to rotation of polar side groups. The ac conductivity has been evaluated and plotted as a function of temperature and frequency. The ac conductivity data has been interpreted in terms of Pike's theory, suggesting the charge carrier hopping between the localized states.

3 illus, 8 ref

005551   Verma A K;Saxena S (Dep of Phys, Bareilly Coll, Bareilly-243 001) : Recent interest in atomic collision physics. Acta Cienc Indica-Phys 2005, 31(2), 215-18.

The study of atomic physics provides the most powerful means available to physicists for understanding a number of phenomena related to other branches of science and technology, e.g., condensed matter physics, plasma physics, space science etc. Authors has dicussed applications of atomic physics to these fields with staring from its origin. Some basic facts about the collision processes are also discussed in detail.

11 ref

005550   Tyagi S K;Chen J;Lin G;Kaushik S C (Dep of Phys, Xiamen Univ, Xiamen 361005, People's Republic of China) : Effect of several irreversibilities on the thermo-economic performance of a realistic Brayton heat engine cycle. Indian J pure appl Phys 2005, 43(8), 612-19.

The thermo-economic study of a more realistic regenerative Brayton cycle heat engine with finite heat capacity of external reservoirs is presented. The external irreversibility is due to finite temperature differences between the external reservoirs and the heat engine while the internal irreversibilities are due to the non-isentropic processes in the compressor and turbine and the regenerative heat loss. The thermo-economic function is defined as the power output divided by the total cost plus the running and maintenance costs of the system. The objective function is optimized with respect to the cycle temperatures and the optimum performance parameters are calculated for a typical set of operating conditions. It is found that the effect of the turbine efficiency is more than that of the compressor efficiency on all the performance parameters. It is also found that the effects of the sink-side heat capacitance rate are more than those of the heat capacitance rates on the source-side and working fluid on all the performance parameters of the cycle for the same set of operating condition.

5 illus, 57 ref

005549   Tiwari S N;Pandey R;Dubey K K;Singh L K; Shukla S (Dep of Phys and Electron, Dr Ram Manohar Lohia Avadh Univ, Faizabad-224 001) : Charactertistic studies and circuit implimentation of the series and parallel combinations of like diodes. Acta Cienc Indica-Phys 2005, 31(2), 257-63.

PN-diodes have been proved very useful due to its wide range of applications. Authors has studied the forward characteristics of network of pn-diodes (lN4002) connected in series and parallel. Series connected like diodes were found suitable for high voltage applications while parallel connected diodes for high current applications. Philosophy of series and parallel connected diodes are also implemented to study the behaviour of AND and OR gates and improvement in fan -out, noise immunity and fan-in is noticed. All the studies are made by PSpice circuit s imulation software (PSpice 9.1 student version) and the experimental verification of the simulation results are carried out in laboratory.

4 illus, 4 tables, 12 ref

005548   Thapa S R B (Birenda Multiple Campus, , Bharatpur, Chitwan, Nepal) : Axially symmetric forces and crystal dynamics of noble metals. Acta Cienc Indica-Phys 2005, 31(2), 179-86.

Phenomenological model for the crystal dynamics of noble metals has been developed. The model considers the potential energy of lattice due to (i) ion-ion interaction and (ii) ion-electron interaction. The potential energy due to ion-ion intraction has been calculated applying axially symmetric model which assumes that the restoring force between the ions have the character of bond-stretching and bond-bending. The secular equation obtained on the basis of present model is solved to calculate the frequencies of the normal modes of vibration of lattice. The frequencies calculated have been employed to obtain the phonon dispersion curves, specific heats and Debye characteristic temperatures of the monovalent noble metals Cu, Ag and Au. The theoretical results for dispersion curves, specific heats and Debye characteristic temperatures of above mentioned metals have been compared with experimentally observed values. The agreement between calculated and experimental results is found to be satisfactory.

9 illus, 4 tables, 20 ref

005547   Thakur M L;Jha A K (Dep of Phys, T M Bhagalpur Univ, Bhagalpur-812 007) : Cause of discrepancies between theory and experiments of thermal conductivity of metals at low temperature. Acta Cienc Indica-Phys 2005, 31(2), 209-14.

Results of analysis of thermal conductivity of metals at low temperatures reveal a significant contribution of phonons to thermal conductivity of metals. Due consideration of it leads to a rational formula of thermal conductivity of metals and minimizes the discrepancies between theory and experiments of thermal conductivity of metals, at low temperature.

2 tables, 15 ref

005546   Thakur A K;Singh S N (Dep of Phys, C M Sci Coll L N Mithila Univ, Darbhanga, Bihar) : Design of SC active delay equalizers with tuning characteristics. Acta Cienc Indica-Phys 2005, 31(2), 247-55.

A design technique of the realization of switched capacitor (sc) delay equalizer is presented. The basic limitation of sc delay equalizers are discussed. The techniques have been evolved to control the centre frequency, bandwidth and gain of equalizer. The proposed structure uses only two non-overlapping clock phases and it is fully programmable through the uses of three independent capacitor arrays. Effect of finite gain of the operational amplifiers are investigated simulation results are presented, verifying the models involved in the analysis. A comparison of the preformance of the proposed equalizer with that of others reported in the literature is made.

7 illus, 8 ref

005545   Srinivasan S;Gunasekaran S;Ponnambalam U; Savarianandam A;Natarajan S (Dep of Phys, Presidency Coll, Chennai) : Spectroscopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactone. Indian J pure appl Phys 2005, 43(6), 459-62.

A qualitative analysis of the enolic form of 3-oxo-L-gulofuranolactone (ascorbic acid) has been made by a satisfactory vibrational band assignment using FTIR and FT Raman spectra. The calculated theoretical vibrational frequencies are compared with the experimental frequencies by employing the molecular mechanics method using MM3 force field. The observed frequencies are used to compute the thermodynamic functions, namely, the entropy, heat capacity and heats of formation using standard expressions, at one atmospheric pressure in the 298-398 K temperature range.

4 illus, 2 tables, 10 ref

005544   Sreekumar K (Laboratory of Photothermal Sci Dep of Phys, Univ of Kerala, Thiruvananthapuram-695 581) : Simple diffusion wave analyzer. Indian J pure appl Phys 2005, 43(8), 596-601.

A simple, cost-effective, compact and efficient photothermal diffusion wave analyzer for 1 Hz-150 kHz frequency band has been developed and analyzed. The sensitivity is 12 nV and the total error is about 1.5% at 60 dB dynamic reserve, excluding the laser intensity variation that may be corrected. The input voltage and current noises are 15nV/√Hz and 2fA/√Hz, respectively. The low power consumption of about 4 W is advantageous for long time off-line applications. The instrument has been used for the metrology of silicon wafers by radiometric simulations. Results regarding the studies on transport parameters and contamination control are presented.

4 illus, 1 table, 17 ref

005543   Sinha R;Avantika (Dep of Phys, B N Mandal Univ, Laloo Nagar, Madhepura, Bihar) : Radiation characteristics circular microstrip antenna in weakly ionised plasma. Acta Cienc Indica-Phys 2005, 31(2), 265-71.

Theoretical investigation has been carried out to evaluate the effect of weakly ionized plasma on the radiation characteristics of circular microstrip antenna. For this purpose, the concept of vector magnetic potential and vector electric potential has been utilized. Consequently the components of electric and magnetic fields in spherical polar coordinate system have been obtained. It has been found that the presence of weakly ionized plasma enhances the radiation characteristics and directivity of the antenna to a great extent. The collision frequency has also significant effect on the directivity and radiation characteristics of the antenna.

2 illus, 7 ref

005542   Sinha A K;Chaudhary N N (Dep of Phys, M L S M Coll, Darbhanga-846 004) : Study of elliptical microstrip antenna on method of moment. Acta Cienc Indica-Phys 2005, 31(2), 229-32.

Analysis of an elliptical microstrip antenna by the method of moment for circular polarization has been presented. Attachment mode was used to ensure the continuity and the singularity of the currents in the patch-probe conjunction point. Results showed that an elliptical patch can be used to generate circular polarization with one probe-feed and attachment mode should be used to obtain the exact impedance when excited by a probe.

3 illus, 9 ref

005541   Singh S N;Jha P; (Dep of Phys, CMSC Coll, Darbhanga-846 004) : Miniaturization of loop antenna at resonance using fractals. Acta Cienc Indica-Phys 2005, 31(2), 189-92.

Fractal shaped wire antennas have been found to exhibit a lower resonant frequency than a some sited Euclidean antenna. It exhibits resonance compression and multiband behaviour. The fractal shaped antenna can be made smaller than its counter part Euclidian that is resonant at the same frequency. Miniaturization of loop antennas at resonance using fractals has been presented. The physical variables miniaturizing loop anten-L at resonance have also been presented in tabular form. Input resistance of fractal loop antenna has also been discussed.

2 illus, 1 table, 6 ref

005540   Singh P;Gupta C B (NO, B S A Coll of Enggg & Tech, Mathura) : The permeability and hydromagnetic effects on the three-dimensional flow past an accelerated porous plate. Indian J Theor Phys 2004, 52(3), 251-60.

An analytic study of three-dimensional flow past a porous plate in the presence of magnetic field and porous medium has been presented. The expression for velocity distribution has been obtained by assuming (u=u_o + εu₁) in the neighbourhood of the plate. The effect of permeability parameter of the medium on the velocity and skin-friction has been investigated and discussed graphically with the help of the table.

2 illus, 2 tables, 8 ref

005539   Singh H C;Chaudhary V K (NO, Coll of Commerce, Patna, Bihar) : Mixed spin relaxation of Fe<. Indian J Theor Phys 2004, 52(2), 119-24.

In the mixed spin relaxation process, the relaxation path is such that it requires a 'change in spin state as well as phonon state' at the two sites coupled through dipolar or weak exchange interaction besides each site being coupled to lattice vibrations also. Such a situation may arise for a close pair (dimer) of Fe²⁺ ions in a lattice. The aim of the present work is to calculate the 'mixed spin relaxation rates' for low concentration Fe²⁺ ions in FeCo₃ and compare them with the observed Mossbauer data as a function of temperature. This will involve setting up the Hamiltonian matrix for Fe²⁺ in lattice of trigonal symmetry by taking the appropriate crystal field interaction, spin orbit coupling and the lattice vibrational interaction and then solving it for eigenvalues and eigenfunctions. From the resulting scheme of quantum states the relaxation paths has been considered. It is seen that the calculated 'mixed relaxation rates' and the observed rates are agreeable within the order of magnitude. It appears that at low temperature mixed relaxation process also provides a competing mode for exchange of energy between electronic spins and phonons in the context of Mossbauer study of Fe²⁺ in anti-ferromagnetic FeCo₃ at low temperatures, which becomes paramagnetic at 20K.

1 table, 11 ref

005538   Singh A K (Dep of Math, V S S D Coll, Kanpur-208 002) : Convective flow of two immiscible viscous fluids using Brinkman model. Indian J pure appl Phys 2005, 43(6), 415-21.

Generalised Couette flow of two viscous, incompressible, immiscible fluids with heat transfer through two straight parallel horizontal walls is studied. A naturally permeable material of high porosity bound below the lower wall and the flow inside the porous medium is assumed to be of moderate permeability, modeled by Brinkman equation. Analytical solutions of the momentum and energy equations have been obtained for the flow domain by dividing it into three zones. Appropriate matching conditions of velocity and temperature have been used to link various flow regimes. The effects of inverse permeability parameter, Reynolds number and viscous parameter on velocity fields and temperature fields in various zones along with mass flow rate, skin-friction at the walls and rates of heat transfer have been presented.

3 illus, 4 tables, 20 ref

005537   Shrimali M D;Ramaswamy R (Dep of Phys, Dayanand Coll, Ajmer-305 001) : Partial and complete synchronization in quasiperiodically forced coupled maps. Proc Indian Natn Sci Acad-Pt A 2005, 71(1-2), 85-96.

Studies different coupling schemes in a system of three coupled nonlinear maps in which the parameters are subject to quasiperiodic modulation. This gives rise to phase diagram that has coexisting regimes of synchronized and desynchronized dynamics on torus and chaotic attractors, as well as on strange nonchaotic attractors (SNAs). Discusses the influence of coupling topology on the extent of partial synchronization; this suggests strategies for controlling the dynamics of assemblies of driven coupled map lattices.

8 illus, 36 ref

005536   Sharma A;Kargupta K (Dep of Chem Engng, Indian Inst of Technol, Kanpur-208 016) : Self assembly and pattern formation in thin liquid film. Proc Indian Natn Sci Acad-Pt A 2005, 71(1-2), 17-45.

A review of recent theoretical and experimental work on spontaneous evolution of morphological patterns in thin (<60> 100 nm) liquid film on homogeneous and heterogeneous solid substrate is presented. Theoretically, the film stability, dynamics, morphology and the sequences of dewetting are resolved based on numerical solutions of the nonlinear 3-D equations of motion, in which the excess short and long-range interactions are incorporated as body forces. The thin film experiments as well as simulations show two distinct pathways for the evolution of instability leading to dewetting on a homogeneous substrate. Initially a small amplitude bi-continuous structure emerges, which either grows and fragments into collection of micro-droplets (for relatively thinner films), or leads directly to isolated circular holes (relatively thicker films) that dewet the surface. The characteristics of a pattern, is dependent on the form of intermolecular potential in an extended neighbourhood of the initial thickness. Instability and pattern formation in thin film are greatly influenced by the presence of heterogeneity of the substrate. The presence of chemical heterogeneities on very small length scales, substantially smaller than the spinodal length scales can destabilize and rupture a thin film by engendering a gradient of chemical potential along the solid-liquid interface. Heterogeneities can even destabilize spinodally stable films, reduce the time of ruptures substantially, and produce novel complex and locally ordered morphological features (e.g. "castle-moat" structures, "ripples", lack of undulations before rupture) that are not predicted by spinodal mechanism. For a system displaying both primary and secondary minimum in free energy, presence of heterogeneity can lead to surmount the energy barrier and produce rupture at the primary minimum. Under the right set of conditions, spontaneous dewetting of thin films on chemically patterned heterogeneous substrates can be modulated to produce a variety of ordered and desired microstructures; for example arrays of liquid cylinders, 2D arrays of closely spaced liquid columns, 2D arrays of holes in a flat liquid sheet. A general set of conditions, have been simulated for the ideal templating of substrate pattern by the thin film meso-structures. This makes it possible to use surface directed dewetting as an alternative route of optical lithography for the formation of meso-patterns in soft materials. Based on the matching of experimental and simulated patterns a novel thin film microscopy concept was proposed, that can determine the unknown intermolecular interactions based on facile observation of thin film pattern.

33 illus, 87 ref

005535   Shajahan T K;Sinha S;Pandit R (Cent for Condensed Matter Theory Dep of Phys, Indian Inst of Sci, Bangalore-560 012) : Spatiotemporal chaos and spiral turbulence in models of cardiac arrhythmials. Proc Indian Natn Sci Acad-Pt A 2005, 71(1-2), 47-57.

Ventricular fibrillation (VF), the major reason behind sudden cardiac death, is turbulent cardiac electrical activity in which rapid, irregular disturbances in the spatiotemporal electrical activation of the heart make it incapable of any concerted pumping action. Partial-difFerential-equation models of excitable media, based on reaction-diffusion equations, have proved to be very useful in the study of cardiac arrhythmias such as VF. Gives an overview of such models, with special emphasis on the control and characterization of the spiral turbulence and spafiotemporal chaos that occur in them. Such spiral turbulence is associated with VF, so its control has implications for defibrillation schemes.

5 illus, 41 ref

005534   Shah N A;Rather M F;Iqbal S Z (Dep of Electron and Instrumentation Technol, The Univ of Kashmir, Srinagar-190 006, Email: farsgr@yahoo.co.in) : High output impedance current-mode universal filter. Indian J pure appl Phys 2005, 43(7), 556-8.

A new current-mode universal filter with single input and three outputs employing two second-generation current conveyors (CCIIs), one current follower (CF) and four grounded/virtually grounded passive elements is presented. The proposed circuit enjoys the following features: simultaneous realization of lowpass(LP), bandpass(BP), and highpass(HP) filtering responses, no need of matching conditions, employment of grounded resistors which are ideal for IC implementation, employment of grounded/virtually grounded capacitors, orthogonal control of ω₀ and ω₀/Q, high output impedance suiting cascadibility for higher order filters, and low passive sensitivity. PSPICE simulation results are included, confirming the workability of the proposed circuit.

4 illus, 12 ref

005533   Sewak Singh R;Suresh Singh R;Anzer A;Singh N P;Sinha A K;Verma P K;Mishra L K (Dep of Phys, Magadh Univ, Bodh-Gaya-824 234) : An evaluation of thermodynamic quantities like excitation energy, molar specific heat, chemical potential and osmotic pressure of <. Acta Cienc Indica-Phys 2005, 31(2), 149-56.

Using L-P theory (Landau and Pomeranchuk) authors has evaluated the excitation energy as a function of k, ³He contribution to the molar heat capacity of three liquid mixtures as a Function of temperature, ³He chemical potential as a function of concentration X and osmotic pressure Π(X) as a function of X for ⁴He-³He liquid mixtures. The theoretical results are in good agreement with those of the others workers and with, the experimental data.

1 illus, 4 tables, 35 ref

005532   Saxena S K (Dep of Phys, Upadhi P.G. Mahavidhyalaya, Pilibhit-262 001) : Theoretical study of dynamics of electron and positron scattering by lithium atoms. Acta Cienc Indica-Phys 2005, 31(2), 201-8.

Author has obtained results for the angular variation of component of polarization (P₁, P₂ & P₃) of the radiation emitted normal to scattering Plane. From these results the linear Polarization (P_l), Coherence of excitation P and the alignment angle (γ) of charge clouds are investigated at energy 20 eV.

2 illus, 4 tables, 15 ref

005531   Sarkar N G;Chakrabarty I (Dep of Math, Maulana Azad Coll, 8 Rafi Ahmed Kidwai Road, Kolkata-700 013) : Fisher information: thermodynamic stability and uncertainty relation. Acta Cienc Indica-Phys 2005, 31(2), 283-7.

Studies the role of Fisher information in the statistical characterization of thermal equilibrium, stability and phenomenological uncertainty relation for a closed system the point of view of thermodynamic theory of measurement.

20 ref

005530   Sarangi K C;Jose C B (Dep of Math, Univ of Rajasthan, Jaipur-302 004) : Three-dimensional MHD free convective flow and heat transfer through a porous medium with periodic permeability. Indian J Theor Phys 2004, 52(2), 109-18.

The analysis of periodic permeability on the free convective MHD flow of a viscous incompressible fluid through a highly porous medium is discussed. The porous medium is bounded by infinite vertical porous plate. Assuming the free stream velocity to be uniform, approximate solutions are obtained for the flow field, the temperature field and are shown graphically. Also effects of various physical parameters are considered on the skin-friction and on the rate of heat transfer.

1 illus, 1 table, 9 ref

005529   Sanjeev Kumar;Bhattacharya B (Dep of Phys, C C S Univ, Meerut-250 004) : Variation of band gap in CdPbS with composition prepared by a precipitation technique. Indian J pure appl Phys 2005, 43(8), 609-11.

Cadmium sulphide (CdS) is highly sensitive of light and has high absorption coefficient. Only disadvantage with CdS is its wide band gap (2.4eV). The band gap of CdS has been tailored by mixing it with lead sulphide (PbS)(low band gap material). The material of configuration (Cd_1-xPb_xS) for this study has been prepared by precipitate technique in the methanol with x = 0.2, 0.4, 0.6, 0.8. The films of the material were deposited by the vacuum deposition method. Spectroscopic technique has been used for the band gap determination. The variation of band gap with their composition has been reported. It has been found that the band gap decreases with increase in Pb concentration. The nature of the band gap has also been determined.

7 illus, 1 table, 12 ref

005528   Sambasiva Rao P;Reddy R R;Potukuchi D M (NO, Jawaharlal Nehru Technological Univ, Kukatpalli, Hyderabad-500 072) : On the dissociation energies of silver halide molecules. Acta Cienc Indica-Phys 2005, 31(2), 225-8.

The experimental potential energy curves for the ground states of Silver Halide molecules have been constructed by applying the Rydberg-Klein-Rees method as modified by Vanderslice, et al. The dissociation energies of the molecules have been estimated by fitting the five parameter Hulburt-Hirsh lifelder function. The estimated values of the dissociation energies are low when compared with the recommended values-which indicates the strong ionic binding in the ground state of each silver halide molecule.

5 tables, 25 ref

005527   Raychaudhuri P (Dep of applied Math, Calcutta Univ, Calcutta-700 009) : Cyclic variation of the solar energy source and the global magnetic field. Indian J Theor Phys 2004, 52(3), 261-70.

It is known that the solar activity cycle is in many respects related to the formation and development of solar magnetic fields. It is suggested that recurrent and non-recurrent geomagnetic disturbances which are related to the release of solar magnetic energy in the form of unipolar and bipolar magnetic regions, respectively are connected with the variations in the solar energy source. It is also suggested that the true beginning of the solar activity cycle takes place several years (2-3 years) before the epoch of the relative sunspot number minimum (phase 1). Relative sunspot number minimum can be taken as phase 2. Sunspot number maximum can be taken as phase 4 whereas before and after 2-3 years from sunspot number maximum can be taken as phase 3 and phase 5 respectively. These phases are the characteristics of solar energy source and the formation and development of solar magnetic fields are connected with the cyclic variations of the solar energy source through dynamo action. In fact, the magnetic field generation in five phases almost coincides with the reference point introduced by Vitinsky, Kuklin and Obridko for variation of solar activity features and Obridko and Shelling for global magnetic fields.

4 illus, 27 ref

005526   Raychaudhuri P (Dep of Appl Math, Calcutta Univ, Calcutta-700 009) : Neutrinos in pion and muon decays at neutrino factories, LAMPF, accelerators and LSND excess. Indian J Theor Phys 2004, 52(2), 125-36.

The proper and precise determination of neutrino properties in neutrino beams produced in pion and muon decays may lead to the new physics i.e., either neutrino oscillation mechanism or neutrino is a mixture of electron neutrinos moun neutrinos and tau neutrinos. The neutrino factory, LAMPF and accelerators facilities may be the ideal place to look for the lepton flavour violating decays of the kind π⁺→μ⁺<110>_e, μ⁺ν and μ⁺→e⁺+ν ^-_e+ν_μ and μ⁺→e⁺+ν ^-_e+ν^-_μ. The detector must be made in such a way so that the detector can be capable of electron, muon and tauon identification with charge discrimination. An alternative solution of LSND excess has been suggested by the above mentioned decays apart from neutrino oscillation mechanism.

19 ref

005525   Ramesh K;Arumugam V;Senthil Kumar G R (Dep of Phys, Annamalai Univ, Annamalai Nagar-608 001) : Study of attenuation and compressive strength investigation in some selected rock specimens. Acta Cienc Indica-Phys 2005, 31(2), 187-8.

The absorption coefficient measurement have been carried out in some selected rock specimens collected from different parts of Tamil Nadu (INDIA) using the pulse echo overlapping technique and the stress measurements were carried out by compression test machine. Some cases have been tested and the results are also given.

1 table, 4 ref

005524   Rama Rao G V;Viswanatha Sarma A;Ramachandran D;Rambabu C (Dep of Phys, Dharma Appa Rao Coll, Nuzvid 521 201) : Evaluation of excess free volumes and excess internal pressures of binary solutions of O-chlorophenol at different temperatures. Indian J pure appl Phys 2005, 43(8), 602-8.

Ultrasonic velocity, density and viscosity have been measured experimentally and free volume as well as internal pressure and enthalpy were calculated for the binary mixtures of o-chlorophenol with ethyl benzoate, anisic aldehyde and acetonitrile at 303.15, 308.15, 313.15 and 318.15 K over the entire range of composition. Excess values of free volume, internal pressure, enthalpy and Gibb's free energy of activation have been calculated for these systems. The results were discussed in the light of existing theories of molecular interactions involved and chemical constitution of the liquid components.

5 illus, 3 tables, 35 ref

005523   Rahimi F;Iraji zad A (Dep of Phys, Sharif Univ of Technol, Tehran, Iron P O Box 11365-9161, Email: rahimi@mehr.sharif.edu) : Ethanol-sensing properties of porous poly-silicon. Asian J Phys 2005, 14(1-2), 183-8.

Porous poly-silicon (PPS) has a large surface area and ability to adsorb gas molecules from the environment. This phenomenon changes the surface electrical conductance of porous layers. In the research authour has studied gas sensing properties of porous poly-silicon on the basis of poly-silicon wafer. The topography of the surface was investigated by Scanning Electron Microscopy (SEM) and Scanning Tunneling Microscopy (STM) which showed the existence of macroporous structure. The red photoluminescence of sample proved the existence of nanopores in addition to micron size islands. Gas-sensing properties of samples showed good response to ethanol and Scanning Tunneling Spectroscopy (STS) revealed that the electrical surface properties of porous layer changes in presence of ethanol.

8 illus, 4 ref

005522   Raghupathi P S;George J;Menon C S (Sch of Pure & Appl Phys, Mahatma Gandhi Univ, Kottayam-686 560) : Effect of substrate temperature on the electrical and optical properties of reactively evaporated tin oxide thin films. Indian J pure appl Phys 2005, 43(8), 620-3.

Transparent conducting thin films of tin oxide have been prepared by reactively evaporating pure tin in oxygen atmosphere under controlled conditions. Variation in parameters such as sheet resistance, activation energy, optical band gap with variation in substrate temperature (100 to 275°C) and annealing temperature (200 to 275°C) were studied. The electrical, optical and structural properties of these films were measured to characterize the films. It is found that the activation energy of the film is decreased with increase in substrate temperature. The lowest activation energy of 0.268 eV was obtained for a film, deposited at a substrate temperature of 275°C. The direct optical band gaps of the films at various substrate temperatures were determined and found to vary from 3.76 to 3.97eV. A conductivity of 1.8x10^-3 Ωm and a transmittance of more than 85% in visible region was obtained in the optimized conditions. It is observed from the XRD results that the films are polycrystalline. From SEM photograph, the grain size of tin oxide thin film annealed for 30 min at 275°C is found to be 19.5 nm.

4 illus, 2 tables, 9 ref

005521   Prasad R;Anju;Gupta R N;Gupta G K (Dep of Phys, DDU Gorakhpur Univ, Gorakhapur-273 001) : Electrical properties of multilayer thin films. Acta Cienc Indica-Phys 2005, 31(2), 279-81.

Gallium arsenide and germanium multilayer thin films of different thicknesses between 5 nm to 25 nm were deposited on clean glass substrate at room temperature in a high vacuum of 5 x 10^-6 torr. In the paper, authors has reported the preparation of GaAs/Ge multilayer thin films using electron beam (e-beam) evaporation technique. The conductivity of the film was determined by measuring the developed current and its temperature variation with applied voltage between two probe points of four-probe system. It is found that the conductivity decreases with reciprocal temperature and also with film thickness. From the slope of the plot, which is nearly linear throughout the temperature region studied, the activation energy was evaluated to be about 400 MeV. It has been concluded that at lower temperatures the conduction is due to hopping of carriers whereas at higher temperatures and for thick films band model is prevailing.

1 illus, 22 ref

005520   Patel J B;Parmar M N;Deshpande M P;Solanki G K;Agarwal M K (Dep of Phys, Sardar Patel Univ, Vallabh Vidyanagar-388 120) : Thermoelectric power of mixed tungsten sulphoselenide single crystals grown by vapour phase technique. Indian J pure appl Phys 2005, 43(7), 527-31.

The growth of mixed tungsten sulphoselenide single crystals i.e. WS_xSe_2-x (0≤x≤2) grown by vapour phase technique and their characterization by Hall effect and thermoelectric power measurements have been reported. The Hall effect measurement indicates that these crystals are p-type in nature, which is very well supported by thermoelectric power measurements. From the temperature dependence of thermoelectric power, the Fermi energy (E_F) and the constant (A) indicating the nature of scattering process have been obtained for all the samples. The density of states (NA) and effective mass of holes (m^*_h), have also been calculated for WS_xSe_2-x samples.

3 illus, 3 tables, 16 ref

005519   Pandey S N;Tewari V N (Dep of Phys, Sant Longowal Inst of Engng and Technol, Longowal, Sangrur-148 106) : Analytical solutions of one-dimensional schrodinger equation for the non-polynomial potential. Indian J Theor Phys 2004, 52(4), 305-10.

Author has presented an infinite set of exact solutions of the non-relativistic Schrodinger equation for the non-polynomial potential V(x)=x⁴+x²(1+g)/(x²+1). apart from the instrinsic interest of solving an eigenvalue problem exactly, these solutions provide a bench mark to check numerical results.

25 ref

005518   Mohan D;Mishra S K;Saha S K (Instruments Res & Dev Establishment, , Dehra Dun) : Adaptive optics and its applications. Indian J pure appl Phys 2005, 43(6), 399-414.

The adaptive optics (AO) system combines technologies that enable corrections in real time for the deleterious effects of the atmosphere allowing terrestrial telescopes to achieve their near diffraction-limit. Such a system introduces controllable counter wavefront distortions, which both spatially and temporally follow that of the atmosphere. AO system has advantages over post-detection image restoration techniques that are limited by noise and recovers near diffraction-limited images and improves the point source sensitivity. This system may become standard tool for the new generation large optical imaging systems. Development of such a technique was made possible due to the significant improvements in technological innovation over the past few decades. After a brief introduction on the deleterious effects of the atmosphere on the image, required components have been discussed in detail in order to develop the AO system and its applications in various fields, particularly in observational astronomy.

16 illus, 47 ref

005517   Misra A;Pankaj Kumar;Dhawan S K;Kamalasanan M N;Subhas Chandra (Polymetric & Soft Material Sect, Natn Phys Laboratory, Dr K S Krishnan Road, New Delhi-110 012, Email: mnkamal@mail.nplindia.ernet.in) : Bright-blue organic electroluminescent device based on bis (2-methyl 8-quinolinolato) (triphenyl siloxy) aluminium. Indian J pure appl Phys 2005, 43(7), 522-6.

An organic luminescent material bis (2-methyl 8-quinolinolato) (triphenyl siloxy) aluminium (III) (SAlq) was synthesized and its electrical and optical properties were studied. The material exhibited high photoluminescence (PL) and electroluminescence (EL). Photoluminescence (PL) spectra recorded at room temperature revealed a broad blue emission peak at 490 nm along with a shoulder at 448 nm. The material was characterized by UV-visible, photoluminescence, electroluminescence and IR spectroscopic methods. The thermal stability of the material was determined using Thermo Gravimetric Analysis (TGA), which suggests that the material is thermally stable up to 300°C. Using the Tauc relation and the absorbance cut-off wavelength at 410 nm, the optical band gap of the material was evaluated to be 3.1 eV. OLEDs were fabricated in the configuration ITO/TPD/SAlq/LiF/Al. The CIE chromaticity was also studied and the coordinates were found to be independent of operating voltage. The devices show typical non-linear diode I-V characteristics under forward bias with the threshold voltage of 5 V.

7 illus, 25 ref