007268   Vijayalakshmi M;Saroja S;Mythili R (Physical Metallurgy Sect, Mater Characterisation Group, Indira Gandhi Centre for Atomic Res, Kalpakkam 603 102) : Convergent beam electron diffraction - A novel technique for materials characterisation at sub-microscopic levels. Sadhana 2003, 28(131-132), 763-82.

A review of the developments is Convergent Beam Electron Diffraction (CBED), a technique widely used for determination of structure, symmetry details and atom positions in a crystal as small as 20Å in size has been presented. The understanding of this technique in related to the rapid advancements in the field of transmission electron microscopy with respect to development of choherent, finer probes and electron optics for higher spatial resolution. Energy filtering devices enable imaging of several finer features in the CBED pattern from which useful information about a crystal can be obtained. These include (i) three-dimensional information about the reciprocal lattice, (ii) point and space group symmetry details, (iii) lattice parameter from regions as fine as 2nm, (iv) atom positions within a unit cell and (v) defects in crystals and (vi) thickness. Due to abundant data obtained from microscopic regions, this technique is unique and finds wide application in materials characterization. It has been used for studying problems like identification of the presence of lattice strain, identification of point defects etc. in a material used often in the nuclear industry, namely 9Cr-1Mo steel. The current status of CBED starting from its historical development, the information that can be obtained and its used in a variety of applications have been provided.

16 illus, 1 table, 80 ref

007267   Vijay Kumar (Dr Vijay Kumar Foundation, , 45, Bazaar St., K K Nagar (West), Chennai 600 078) : Computational materials science: the emergence of predictive capabilities of material behaviour. Sadhana 2003, 28(131-132), 815-31.

The availability of high performance computers and development of efficient algorithms has led to the emergence of computational materials science as the third branch of materials research complementing the traditional theoretical and experimental approaches. It has created new virtual realities in materials design that are either experimentally not realizable easily or are prohibitively expensive. The possibilities of doing calculations from first principles have led to predictive capabilities that open up new avenues of discovering novel materials with desired properties, understanding material behaviour on the nano-to the macroscopic scale and helping research in new frontiers that could interface between nano-materials and drug design, as well as in understanding biological systems. Some significant recent development related to alloy and steel design as well as the study of matter on the nano-scale-an area that has gained much prominence in current materials research have been described.

6 illus, 64 ref

007266   Torres-Silva H;Zamorano Lucero M (Departamento de Electronica, Facultad de Ingenieria, Universided de Tarapaca, Casilla 6 D, Av. 18 de Septiembre 2222, Arica-Chile) : Non-linear polarization and chiral effects in birefringent solitons. Pramana J Phys 2004, 62(1), 37-52.

Novel effects resulting from joint action of chirality and non-linearity are discussed using a basic equation describing the temporal evolution of fields in a chiral medium with Kerr non-linearity. The spatial chirality effect is characterized through the Born-Fedorov formalism. Our simulations are based on the split-step Fourier method and the solution of the Stokes parameters. The numerical results show the chiral effect on solitons with circular polarization and mixed polarization spatial solitons.

7 illus, 21 ref

007265   Tewari S P;Silotia P;Saxena A (Physics and Astrophysics Dep, University of Delhi, Delhi 110 007) : Ground state properties of BECs of <. Indian J pure appl Phys 2003, 41(12), 905-13.

Ginzburg-Pitaevskii Gross (GPG) non-linear equation for the Bose Einstein Condensate (BEC) having different number of ⁸⁷Rb atoms (in the range 10² to 5x10⁶) in an isotropic magnetic trap, has been numerically solved to obtain its eigenvalue, the chemical potential, and the corresponding wave function, to study its various observable physical properties, such as, the correlation length, healing length, inter-particle separation in the core and the speed of sound in the condensate. These have been compared with the corresponding results computed by using the approximate expression obtained in the limiting case when the number of atoms in the condensate tends to a large value, that is, in the Thomas-Fermi approximation. Significance and inter-relationships of various physical quantities have also been discussed in the light of recent experimental results.

9 illus, 15 ref

007264   Suresh Swapna S;Chandramouli V (Physics Dep, Osmania University, Hyderabad 500 007) : ESR, optical absorption and transport studies of Cu<. Indian J pure appl Phys 2003, 41(12), 954-60.

The preparation and studies on the spectroscopic and transport properties of lithium boro bismuthate glasses are reported. From IR results, it is observed that at low concentrations, Bi₂O₃ (less than 30 mol %) in the glass acts as glass modifier thereby, increasing non-bridging oxygen ions. At higher concentrations, it enters into the network. The structure of the resulting glass consists of(BiO₃+BO₃) units. The hyperfine splitting in the parallel feature of ESR spectra of Cu²⁺ in the glass is detectable at low concentration of Bi₂O₃, which, however, diminishes at higher concentration of Bi₂O₃. The ionic conductivity results indicate that, the conductivity is due to the mobile lithium ions and log (electrical conductivity) found to increase with the concentration of bismuth oxide and passes through a maximum at 30 mol % of Bi₂O₃ indicating a mixed glass former effect.

5 illus, 4 tables, 21 ref

007263   Singh M P;Bhandari C M (Physics Dep, University of Allahabad, Allahabad 211 002) : Electronic transport in one-dimensional systems. Indian J pure appl Phys 2003, 41(12), 950-3.

Electronic thermal transport and electrical transport in quasi one-dimensional structures is the subject matter of present communication. Expressions have been obtained for electronic thermal conductivity, electrical conductivity and Lorenz factor. Results of calculation for polycrystalline bismuth telluride have been presented at 300 K for different carrier densities and wire diameters. It is concluded that, cross-sectional size of the wire influences the Lorenz factor in carrier density range 10²³-10²⁶m^-3. Effect of cross-sectional size on electrical conductivity and electronic thermal conductivity is appreciable at carrier densities above 10²³m^-3.

3 illus, 1 table, 18 ref

007262   Singh A K (Mathematics Dep, VSSD College, Kanpur 208 002) : Numerical solution of free convection flow of a micro-polar fluid past a porous vertical plate. Indian J pure appl Phys 2003, 41(12), 936-40.

An implicit finite difference method is applied to obtain the numerical solution of free convection flow of an incompressible micro-polar fluid past an infinite vertical porous plate taking into account transpiration effect. The effects of material constants, transpiration parameter and Prandtl number are observed on velocity field and skin-friction. In addition, the effects of material constants and Prandtl number are observed on micro-rotation of the micro-polar fluid.

3 illus, 19 ref

007261   Shokri B;Khorashadi S M (Physics and Laser Center Dep, Shahid Beheshti University, Evin 19839, Tehran, Iran) : Anti-screening in magnetically quantized plasmas. Pramana J Phys 2004, 62(1), 69-76.

It is shown that in magnetically quantized plasmas, static Debye screening is changed. Furthermore, it is shown that under special circumstances, two electrons in such media may attract each other.

2 illus, 16 ref

007260   Shah N A;Malik M A (Postgraduate Electronics and Instrumentation Technology Dep, University of Kashmir, Srinagar 191 006) : High input impedance HP, BP and LP filters using FTFNs. Indian J pure appl Phys 2003, 41(12), 967-9.

Presents a new multifunction filter based on and employing four terminal floating nullors (FTFNs) which simultaneously realizes bandpass (BP) and lowpass (LP) filtering functions. The circuit can be made to realize highpass (HP) and bandpass (BP) filtering signals as well by changing one admittance and exhibits high input impedance thus, facilitating cascading of such circuits to realize higher order filters. The circuit employs grounded capacitors which suits contemporary IC design techniques and has the distinct feature of providing controllable gain of all the filtering functions through grounded passive components. Besides enjoying low passive sensitivity figures, the resonnace frequeancy ω₀ and bandwidth ω₀/Q are independently tunable in a sequential manner. PSPICE simulation results are also included.

3 illus, 12 ref

007259   Setlur G S (NO, Institute of Mathematical Sciences, Taramani, Chennai-600 113) : U(1) gauge theory as quantum hydrodynamics. Pramana J Phys 2004, 62(1), 1011-14.

It is shown that gauge theories are most naturally studied via a polar decomposition of the field variable. Gauge transformations may be viewed as those that leave the density invariant but change the phase variable by additive amounts. The path integral approach is used to compute the partition function. When gauge fields are included, the constraint brought about by gauge invariance simply means an appropriate linear combination of the gradients of the phase variable and the gauge field is invariant. No gauge fixing is needed in this approach that is closest to the spirit of the gauge principle. Derived an exact formula for the condensate fraction and in case it is zero, an exact formula for the anomalous exponent. Formula for the vortex strength which involves computing radiation corrections has also been derived.

13 ref

007258   Saikia D;Kumar A (Physics Dep, Tezpur University, Napaam, Tezpur, Assam 784 028) : Fast ion transport in P(VDF-HFP)-PMMA-PC-LiCIO₄-TiO₂ composite gel polymer electrolytes. Indian J pure appl Phys 2003, 41(12), 961-6.

The films of poly (vinylidene flurodie-co-hexafluoropropylene) P(VDF-HFP) and poly (methylmethacrylate) PMMA polymer blend electrolytes plasticized with propylene carbonate (PC) and LiCIO₄ as salt and TiO₂ as inorganic filler have been prepared by solution casting technique. Films of thickness in the range of 30 μm - 1 mm prepared by varying the plasticizer-filler and salt-filler ratio were characterized by ac impedance measurements in the temperature range 293-373 K. Addition of ceramic filler to the polymer electrolyte was found to result in an enhancement of the ionic conductivity. A maximum electrical conductivity of <126>2.81x10^-2 S/cm at 293 K and <126>4.5x10^-2 S/cm at 373 K has been achieved with the dispersion of the TiO₂. Transport number measured by Wagner's polarization method, using silver blocking electrodes, was found to be 0.985. FTIR spectral studies confirmed the formation of polymer-salt complex. XRD patterns exhibit the increased amorphicity in the blended composite gel polymer electrolytes.

4 illus, 1 table, 30 ref

007257   Purohit G;Joshi G C (Physics Dep, HNB Garhwal University, Srinagar (Garhwal), Uttaranchal 246 174) : Second-order polarizabilities of some quinolines. Indian J pure appl Phys 2003, 41(12), 922-7.

Second order polarizabilities (β) of some quinolines viz. 8-hydroxyquinoline (8-HQ), 8-aminoquinoline (8-AQ) and 8-hydroxyquinolidine (8-HQD) have been experimentally determined by solvatochromic technique using two-level quantum mechanical model. Comparison has been made with other useful organic molecules and the role of hydrogen bonding has been discussed.

5 illus, 4 tables, 22 ref

007256   Kapoor K;Dass N;Rajendra Kumar (Physics Department, College of Engineering Roorkee, Roorkee-247 667) : Melting temperature of H₂, D₂, N₂ and CH₄ under high pressure. Pramana J Phys 2004, 62(1), 95-100.

The melting temperatures of H₂, D₂, N₂ and Ch₄ are analysed. The computed results are in very good agreement with the experimental data in each solid. Further, the analysis indicates the presence of the melting maximum in these solids.

5 illus, 3 tables, 7 ref

007255   Giri D K;Gupta P S (Applied Physics Dep, Indian School of Mines, Dhanbad 826 004) : Higher-order squeezing in Raman scattering. Indian J pure appl Phys 2003, 41(12), 946-9.

The occurrence of fourth and fifth-order squeezing in the fundamental mode of the electromagnetic field in spontaneous Raman process under the short-time approximation is investigated based on a fully quantum mechanical approach. The coupled Heisenberg equations of motion involving real and imaginary parts of the quadrature operators are established. The dependence of the higher-order squeezing on the number of photons is investigated. It is shown that higher-order squeezing allows a much larger fractional noise reduction.

2 illus, 18 ref

007254   Emami M;Babazadeh A;Rasouli H (Plasma Physics Laboatory, NFRC, AEOI, P.O. Box 14155-1339, Tehran, Iran) : Optimization and performance of a high-speed plasma position digital control system. Pramana J Phys 2004, 62(1), 53-60.

Addesses optimization of a high-speed digital feedback controller for a plasma position in Damavand tokamak. Damavand tokamak discharges have plasma currents up to 40 kA with discharge duration gerater than 15 ms and toroidal magnetic fields up to 1.2 T. The plasma position is measured using saddle-lopps and Rogowski coil and is controlled by electromagnetic forces generated by passing currents through control colis placed around the plasma. A desired control objective is maintaining the plasma in the center of vacuum vessel and to stabilize the plasma in the presence of distrubances in a time domain of the order of few milliseconds. In order to achieve maximum performance it is essential to optimize the control system. In this paper plasma position measurement and the details of implementing high-speed PID controllers based on a TMS 320c25 digital signal processor along with the system optimization are presented.

7 illus, 1 table, 11 ref

007253   Das S K (Physics Dep, Maulana Azad College, 8 Rafi Ahmed Kidwai Road, Calcutta 700 013) : Extensivity of entropy. Indian J pure appl Phys 2003, 41(12), 941-5.

In the conventional framework of thermodynamics it is an established fact that, in absence of surface effects, infinitesimal change in entropy is extensive. But this does not automatically guarantee the extensivity of entropy. Discusses the problems, strictly within the framework of thermodynamics, using a principle of linear superposition in conjunction with a simple postulate, which contains a feature consistent with quantum mechanical concept of indistinguishability of atoms and molecules. Some important consequences of the extensivity of entropy are also discussed. Extensivity of entropy is essential to calculate the change in entropy in an adiabatic irreversile process where the number of atoms of a system is not fixed as well as to make thermodynamics free from the well-known Gibbs paradox.

3 illus, 9 ref

007252   Das N (Mathematics Dep, University of North Bengal, P.O. North Bengal University, Dist. Darjeelin-734 430) : Note on the surface wave due to the prescribed elevation. Pramana J Phys 2004, 62(1), 135-42.

A study of the deep-sea water wave caused by an oscilatory wind stress due to the atmospheric depression, resulting in spiral cyclonic wind pressure on the surface of the sea is made. It has been observed that the motion of the water wave in the case of wind stress exhibits a greater elevation on the sea surface as g the acceleration due to gravity decreases and maintains the oscillatory nature with the increase of time. For the case of spiral cyclonic motion for which the sea surface experiences the elliptical pressure on the surface, the motion diminishes as g diminishes and oscillates with the variation of time. The motion also diminishes asymptotically as the radius vector of the elliptical pressure approaches unity.

6 illus, 10 ref

007251   Choi J R (New Material Science Dep, Natural Sciences Div, Sunmoon University, Asan 336-708, Republic of Korea) : Coherent states of general time-dependent harmonic oscillator. Pramana J Phys 2004, 62(1), 13-29.

By introducing an invariant operator, Exact wave functions are obtained for a general time-dependent quadratic barmonic oscillator. The coberent states, both in χ- and p- spaces, are calculated. Confirms that the uncertainty product in coherent state is always larger than h/2 and is equal to the minimum of the uncertainty product of the number states. The displaced wave packet for Caldirola-Kanai oscillator in coherent state oscillates back and forth with time about the center as for a classical oscillator. The amplitude of oscillation with no driving force decreases due to the dissipation in the system. However, the oscillation with resonant frequency oscillates with a large amplitude, even after a sufficient time elasps.

2 illus, 36 ref

007250   Batra K;Kundliya R;Man Mohan (Physics and Astrophysics Dep, Delhi University, Delhi-110 007) : Atom in a femtosecond bichromatic laser field. Pramana J Phys 2004, 62(1), 31-6.

The ionization of real hydrogen atom is studied under the action of a two color pulsed laser field of duration 2.12 fs consisting of a fundamental frequency ω and one of its harmonics. Effect of phase difference φ between ω and its harmonic on the ionization probabilityn has been studied. It is found that ionization can be switched on and off by varying the relative phase φ between ω and its harmonic.

5 illus, 12 ref

007249   Banerjee S (Mater Sci Div, Bhabha Atomic Res Centre, Mumbai) : In-situ studies on phase transformations under electron irradiation in a high voltage electron microscope. Sadhana 2003, 28(131-132), 799-814.

High voltage electron microscopy (HVEM), using electron energies adequate for causing displacements of atoms from lattice sites, is a very effective technique for studying mechanisms of solid state phase transformations and for charting the path of phase evolution in real time. This has been demonstrated in studies on chemical ordering in nickel-molybdenum alloys and on the β→ω displacement ordering in zirconium-niobium alloys. The enhanced diffusivity due to electron irradiation makes it possible to explore a sequence of phase evoluation at low enough temperatures where even some first-order transformations are driven by free energy (G) instabilities with respect to the relevant order parameter (η). Specific issues addressed in these studies are reviewed.

7 illus, 1 table, 24 ref

007248   Banerjee P K;Sengupta A (Radio and Atmospheric Sciences Div, National Physical Laboratory, New Delhi 110 012) : Doppler technique for detection of victims buried under earthquake rubble. Indian J pure appl Phys 2003, 41(12), 970-4.

Design and development of an electronic remote victim locator^* is described. It has been designed for locating remotely, any animate subject buried under rubble behind a barrier. It works on the principle of Doppler effect at microwave frequencies. Electromagnetic signal travels down the debris from a transmit/receive antenna, illuminates the animate subjet under the rubble and returns to the top of the debris having phase modulated with body movements. The antenna picks up the phase-modulated signal, which is proocessed by a microwave phase synchronous receiver. The detected signal is displayed on an oscilloscope or any other suitable display device. The display is either a regular breathing cycle or any sudden shift in its steady level, resulting from even a slight movement of any part of the body. An important part of the system is the clutter (unwanted reflections) canceller. Presently, the system can penetrate a dry concrete debris depth of about 2 m. Detection depth may be greater if there are more air voids in the debris. Efforts are on to improve the depth of penetration in the rubble. The same system can detect presence of any person behind a barrier, which has security applications.

3 illus, 6 ref

007247   Ali A;Nain A K;Dinesh Chand;Bhajan Lal (Chemistry Dep, Jamia Millia Islamia (Central University), Jamia Nagar, New Delhi 110 025) : Volumetric and viscometric studies on N,N-dimethylacatamide + 1-hexanol/1-heptanol binary liquid mixtures at different temperatures. Indian J pure appl Phys 2003, 41(12), 928-35.

Densities ρ, and viscosities η, have been measured for pure N,N-dimethylacetamide (DMA), 1-hexanol, 1-heptanol and for their 18 binary mixtures with DMA as common component, covering the entire composition range, at 25, 30, 35, 40 and 45 °C. Using the experimental values of ρ and <104><255>, the excess molar volume V^E, excess viscosity η^E, excess rheochore [R^E], excess partial molar volume V₂<144><255>^E, of alkanols in DMA at infinite dilution and excess free energy of activation of viscous flow ΔG^*E, have been calculated. The dependence of these excess functions on composition and temperature has been dicussed from the point of view of inter-molecular interactions in these mixtures. Furthermore, from the temperature dependence of viscosity, the enthalpy ΔH^*, and entropy ΔS^*, of activation of viscous flow have also been calculated and their dependence on composition have been discussed.

5 illus, 3 tables, 29 ref

007246   Ajay Kumar;Singh S (Physics Dep, Guru Nanak Dev University, Amritsar-143 005) : Radon exhalation studies in building materials using solid-state nuclear track detectors. Pramana J Phys 2004, 62(1), 143-6.

Indoor radon has been recognized as one of the health hazards for mankind. Building materials constitute the second most important source of radon in dwellings. The common building materials used in the construction of dwellings are studied for radon exhalation rate. The `Can' technique using LR-115 type-II solid-state nuclear track detector has been used for these measurements. The radon exhalation rate in these samples varies from 4.75 m Bq m^-2 h^-1 (0.14 m Bq kg^-1 h^-1) for limestone to 506.76 m Bq m^-2 h^-1 (15.24 m Bq kg^-1 h^-1) for soil.

1 table, 13 red