009416   Deka N K;Saikia B J;Goswami K S (Physics Dep, Cotton College, Guwahati-781 001, Email: goswamiks@rediffmail.com) : Generation of whistler mode in a relativistic plasma. Pramana J Phys 2008, 70(3), 517-25.

The plasma maser interaction between high frequency nonresonant whistler R-mode and low frequency resonant ion acoustic mode in a relativis-tic plasma. It shows that the whistler R-mode grows through the plasma maser interaction between the relativistic electrons and the ion acoustic fluctuation.

21 ref

009415   Dar P A;Verma S;Devi R;Khosa S K (Physics and Electronics Dep, Jammu Univ, Jammu-180 006, Email: rani_rakwal@yahoo.co.in) : Microscopic insight in the study of yrast bands in selenium isotopes. Pramana J Phys 2008, 70(5), 817-33.

The yrast bands of even-even selenium isotopes with A = 68-78 are studied in the framework of projected shell model, by employing quadrupole plus monopole and quadrupole pairing force in the Hamiltonian. The oblate and prolate structures of the bands have been investigated. The yrast energies, backbending plots and reduced E2 transition probabilities and g-factors are calculated and compared with the experimental data. The calculated results are in reasonably good agreement with the experiments.

4 illus, 3 tables, 46 ref

009414   Clausen K N (Paul Scherrer Institut, WBBA/122, CH--5232 Villigen PSI, Switzerland, Email: kurt.clausen@psi.ch) : Fission, spallation or fusion-based neutron sources. Pramana J Phys 2008, 71(4), 623-8.

The most promising technology for high power neutron sources is briefly discussed. The conclusion is that the route to high power neutron sources in the foreseeable future is spallation - short or long pulse or even CW - all of these sources will have areas in which they excel.

3 illus, 1 table, 3 ref

009413   Chowdhury B D (Physics Dep, Ohio State Univ, Columbus, OH 43210, USA, Email: borundev@padific.mps.ohio-state.edu) : Problems with tunneling of thin shells from black holes. Pramana J Phys 2008, 70(1), 3-26.

It is shown that exp(-2 Im(∫p dr)) is not invariant under canonical transformations in general. Specifically for shells tunneling out of black holes, this quantity is not invariant under canonical transformations. It can be interpreted as the transmission coefficient only in the cases in which it is invariant under canonical transformations. Although such cases include alpha decay, they do not include the tunneling of shells from black holes. The simplest extension to this formula which is invariant under canonical transformations is proposed. However, it is shown that this gives half the correct temperature for black holes.

3 illus, 23 ref

009412   Choudhury N;Chaplot S L (Solid State Physics Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: dynamics@barc.gov.in) : Inelastic neutron scattering and lattice dynamics of minerals. Pramana J Phys 2008, 71(4), 819-28.

Review current research on minerals using inelastic neutron scattering and lattice dynamics calculations. Inelastic neutron scattering studies in combination with first principles and atomistic calculations provide a detailed understanding of the phonon dispersion relations, density of states and their manifestations in various thermodynamic properties. The role of theoretical lattice dynamics calculations in the planning, interpretation and analysis of neutron experiments are discussed. These studies provide important insights in understanding various anomalous behaviour including pressure-induced amorphization, phonon and elastic instabilities, prediction of novel high pressure phase transitions, high pressure-temperature melting, etc.

3 illus, 1 table, 43 ref

009411   Choudhury J;Karumuri S R;Sarkar N K; Bhattacharjee R (Physics Dep, Assam Univ, Silchar-788 011, Email: chodhuryjoy@rediffmail.com) : Vibrational spectroscopy of SnBr₄ and CCl₄ using lie algebraic approach. Pramana J Phys 2008, 71(3), 439-45.

The stretching and bending vibrational energies of SnBr₄ and CCl₄ are calculated in the one-dimensional framework. The dynamical symmetry group of tetrahedral molecule was taken into consideration to construct the model Hamiltonian in this framework. Casimir and Majorana invariant operators were also determined accordingly. Using the model Hamiltonian so constructed, we reported the vibrational energy levels of SnBr4 and CCl₄ molecules accurately.

4 tables, 22 ref

009410   Choudhuri A;Ghosh S;Talukdar B (Physics Dep, Visva-Bharati University, Santiniketan-731 235, Email: binoy123@bsnl.in ) : Symmetries and conservation laws of the damped harmonic oscillator. Pramana J Phys 2008, 70(4), 657-67.

Work with a formulation of Noether-symmetry analysis which uses the properties of infinitesimal point transformations in the space-time variables to establish the association between symmetries and conservation laws of a dynamical system. Here symmetries are expressed in the form of generators. Studied the variational or Noether symmetries of the damped harmonic oscillator representing it by an explicitly time-dependent Lagrangian and found that a five-parameter group of transformations leaves the action integral invariant. Amongst the associated conserved quantities only two are found to be functionally independent. These two conserved quantities determine the solution of the problem and correspond to a two-parameter Abelian subgroup.

1 table, 15 ref

009409   Chang J J;Mesot J (Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland, Email: joel.mesot@psi.ch) : Microscopic neutron investigation of the Abrikosov State of high-temperature superconductors. Pramana J Phys 2008, 71(4), 679-85.

Using small angle neutron scattering we have been able to observe for the first time a well-defined vortex lattice (VL) structure both in the hole-doped LSCO and electron-doped NCCO superconductors. Measurements on optimally doped LSCO reveal the existence of a magnetic field-induced phase transition from a hexagonal to a square coordination of the VL. Various scenarios to explain such phase transition are presented. In NCCO also a clear square VL could be detected, which is unexpectedly kept down to the lowest measurable magnetic fields.

7 illus, 14 ref

009408   Chakrabarti B (Physics Dep, Lady Braboune College, P1/2 Surawardty Avenue, Kokata-700 017, Email: chakb@rediffmail.com) : Spectral properties of supersymmetric shape invariant potentials. Pramana J Phys 2008, 70(1), 41-50.

Presents the spectral properties of supersymmetric shape invariant potentials (SIPs). Although the folded spectrum is completely random, unfolded spectrum shows that energy levels are highly correlated and absolutely rigid. All the SIPs exhibit harmonic oscillator-type spectral statistics in the unfolded spectrum. Concludes that this is the reflection of shape invariant symmetry.

1 illus, 1 table, 18 ref

009407   Brown C M;Liu Y;Neumann D A (National Institute of Standards and Technology, Center for Neutron Research, 100 Bureau Drive, MS 6102, Maryland 20899, USA, Email: craig.brown@nist.gov ) : Neutron powder diffraction of metal-organic frameworks for hydrogen storage. Pramana J Phys 2008, 71(4), 755-60.

Reviews recent structural studies that have undertaken aimed at, elucidating the fundamental properties of metal-organic framework materials and their interactions with hydrogen. Showns that exposing coordinatively unsaturated metal centers can greatly enhance the hydrogen binding energy and that they result in a significant increase of the surface packing density of adsorbed hydrogen molecules on materials' surface. Reviews some of the structural aspects of these materials, especially the adsorbed hydrogen molecule surface packing density in one type of metal-organic framework, MOF-74, which can be packed even denser than that in solid hydrogen.

3 illus, 22 ref

009406   Blackburn E;Goodkind J;Sinha S K;Broholm C; Copley J;Erwin R (University of California San Diego, La Jolla, CA 92093-0319, USA, Email: ssinha@physics.used.edu) : Neutron scattering study of the excitation spectrum of solid helium at ultra-low temperatures. Pramana J Phys 2008, 71(4), 673-8.

There has been a resurgence of interest in the properties of solid helium due to the recent discovery of non-classical rotational inertia (NCRI) in solid ^{4He by Chan and coworkers below 200 mK which they have interpreted as a transition to a 'supersolid' phase. We have carried out a series of elastic and inelastic neutron scattering measurements on single crystals of hep 4He at temperatures down to 60 mK. While we have found no direct evidence of any change in the excitation spectrum at low temperatures, we have found that the excitation spectrum of solid 4He shows several interesting features, including extra branches in addition to the phonon branches. We interpret these extra branches as single particle excitations due to propagating vacancy waves, which map on to the famous 'roton minimum' long known in the excitation spectrum of superfluid liquid 4He. The results show that in fact solid 4He shares several features in common with the superfluid.}

2 illus, 25 ref

009405   Biju R K;Sahadevan S;Santhosh K P;Joseph A (P.G. Dep of Physics and Research Centre, Payyanur College, Payyanur-670 327, Email: kpsanthosh@eth.net) : Cold valleys in the radioactive decay of <. Pramana J Phys 2008, 70(4), 617-32.

Based on the concept of cold valley in cold fission and fusion, we have investigated the cluster decay process in ^{248-254Cf isotopes. In addition to alpha particle minima, other deep minima occur for S, Ar and Ca clusters. It is found that inclusion of proximity potential does not change the position of minima but minima become deeper. Taking Coulomb and proximity potential as interacting barrier for post-scission region, we computed half-lives and other characteristics for various clusters from these parents. Our study reveals that these parents are stable against light clusters and unstable against heavy clusters. Computed half-lives for alpha decay agree with experimental values within two orders of magnitude. The most probable clusters from these parents are predicted to be 46Ar, 48,50Ca which indicate the role of doubly or near doubly magic clusters in cluster radioactivity. Odd A clusters are found to be favorable for emission from odd A parents. Cluster decay model is extended to symmetric region and it is found that symmetric fission is also probable which stresses the role of doubly or near doubly magic 132Sn nuclei. Geiger-Nuttal plots were studied for various clusters and are found to be linear with varying slopes and intercepts.}

17 illus, 4 tables, 35 ref

009404   Bianconi G (NO, The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34014 Trieste, Italy, Email: gbiancon@ictp.it) : Most probable degree distribution at fixed structural entropy. Pramana J Phys 2008, 70(6), 1135-42.

The structural entropy is the entropy of the ensemble of uncorrelated networks with given degree sequence. Here we derive the most probable degree distribution emerging when we distribute stubs (or half-edges) randomly through the nodes of the network by keeping fixed the structural entropy. This degree distribution is found to decay as a Poisson distribution when the entropy is maximized and to have a power-law tail with an exponent γ → 2 when the entropy is minimized.

18 ref

009403   Bhavyashri;Sarangi S;Saldanha G;Vijaya Kumar K B (Physics Dep, Mangalore Univ, Mangalagangotri, Mangalore-574 199, Email: kbvijayakumar@yahoo.com) : Effect of instanton-induced interaction on P-wave meson spectra in constituent quark model. Pramana J Phys 2008, 70(1), 75-85.

The mass spectrum of the -P-wave mesons is considered in a non-relativistic constituent quark model. The full Hamiltonian used in the investigation includes the kinetic energy, the confinement potential, the one-gluon-exchange potential (OGEP) and the instanton-induced quark-antiquark interaction (III). A good description of the mass spectrum is obtained. The respective role of III and OGEP in the P-wave meson spectrum is discussed.

6 tables, 33 ref

009402   Bhattacharya R;Saha S (Physics and Technophysics Dep, Vidyasagar Univ, West Bengal-721 102, Email: sahaphys.vu@gmail.com) : Growth of CdS nanoparticles by chemical method and its characterization. Pramana J Phys 2008, 71(1), 187-92.

In the work a simple chemical reduction method is followed to grow CdS nanoparticles at room temperature. The grown sample is ultrasonicated in acetone. The dispersed sample is characterized using electron diffraction technique. Simultaneously optical absorption of this sample is studied in the range of 400-700 nm. The photolumines-cence spectrum of the sample is also studied. Results show the formation of nanoparticles. Hence an increase in band gap compared to bulk CdS and the as-prepared CdS nanoparticles have surface sulphur vacancies.

5 illus, 26 ref

009401   Bhatnagar P (Chemical and Excimer laser Section, Laser Programme, Raja Ramanna Center for Advanced Technology, Indore-452 013, Email: bpankaj@cat.ernet.in) : Magnified seld filtering unstable resonator (MSFUR). J Optics 2008, 37(1), 25-8.

A new self-filtering unstable resonator configuration, incorporating a beam expander as one of its cavity mirrors, is discussed. The novelty of this scheme is that the overall magnification of the resonator can be independently controlled with the beam expander. This scheme can also greatly improve the mode filling quality of the resonator by providing magnified collimated beams to oscillate in the cavity.

5 llus, 17 ref

009400   Belushkin A V (Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia, Email: belushk@nf.jinr.ru) : Modern trends in the development of position sensiitive neutron detectors for condensed matter research. Pramana J Phys 2008, 71(4), 639-651.

Different types of neutron scattering experiment for the study of condensed matter properties pose specific and often contradictory requirements for detector characteristics. There is no single type of detector which satisfies all the criteria. Therefore, compromise is inevitable and some of the characteristics are trade off in favour of others. Gives an overview of detector systems presently operating at the leading neutron scattering facilities as well as some development work around the globe.

10 illus, 29 ref

009399   Basu S (Soild State Physics Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: sbasu@garc.gov.in) : Specular neutron reflectivity and beyond. Pramana J Phys 2008, 71(4), 777-84.

A polarized neutron reflectometer for vertical samples is available at Dhruva reactor guide hall, Trombay. The reflectometer has been designed for horizontal scattering vector. It uses a position-sensitive detector for obtaining the reflectivity pattern. This arrangement allows one to obtain diffuse or off-specular intensity around any specular peak at one go. We have used this instrument for studying the structure of various metal-metal and metal-semiconductor multilayers by specular reflectometry. We have also been successful in understanding interface morphology of several films through diffuse neutron reflectometry (DNR) on this reflectometer. Some of the recent results are presented to demonstrate the strength of these two techniques.

4 illus, 18 ref

009398   Bandyopadhyay M;Dattagupta S (NO, S.N. Bose National Centre for Basic Sciences, JD Block, Sector III, Slat Lake, Kolkata-700 098, Email: malay@bose.res.in) : Quantum mechanics of rapidly and periodically driven systems. Pramana J Phys 2008, 70(3), 381-98.

Deals with the dynamics of quantum systems that are subject to high frequency external perturbations. Though the problem may look hopelessly time-dependent, and poised on the extreme opposite side of adiabaticity, there exists a 'Kapitza Window' over which the dynamics can be treated in terms of effective time-independent Hamiltonians. The consequent results are important in the context of atomic traps as well as quantum optic properties of atoms in intense and high-frequency electromagnetic fields.

4 illus, 34 ref

009397   Balakrishnan G (Physics Dep, Warwick Univ, Goventry CV4 7AL, UK, Email: galakrishnan@warwick.ac.uk) : High-quality single crystals for neutron experiments. Pramana J Phys 2008, 71(4), 721-7.

To make headway on any problem in physics, high-quality single crystals are required. In this talk, special emphasis will be placed on the crystal growth of various oxides (superconductors and magnetic materials), borides and carbides using the image furnaces at Warwick. The floating zone method of crystal growth used in these furnaces produces crystals of superior quality, circumventing many of the problems associated with, for example, flux growth from the melt. This method enables the growth of large volumes of crystal, a prerequisite especially for experiments using neutron beams. Some examples of experimental results from crystals grown at Warwick, selected from numerous in-house studies and our collaborative research projects with other UK and international groups will be discussed.

6 illus, 6 ref

009396   Arvind (NO, Indian Institute of Science Education and Research, Mohali, Transit Campus, MGSIPAP Compex, Sector 26, Chandigarh, Email: arvind@iisermohali.ac.in) : Continuous variable systems: entanglement, decoherence and quantum cryptography. J Indian Inst Sci 2009, 89(3), 283-94.

Review some aspects of quantum information processing (QIP) using continuous variable systems for one and two-modes. The objective of the article is to convey a flavor of the kind of developments which has taken place in this subfield of QIP in the past decade and not to write a comprehensive review of the field. We hence focus on Gaussian states, their entanglement and their utilization in various quantum cryptographic protocols that have been proposed and recently implemented.

^iia60 ref

009395   Arneodo E M;Alonso L M;Alliende J A;Mindlin G B (Departamento de Fisica, FCEyN, Universidad de Buenos Aires, Argentina, Buenos Aires, cp 1428, Email: gabo.mindlin@gmail.com) : Dynamical origin of physiological instructions used in birdsong production. Pramana J Phys 2008, 70(6), 1077-85.

Reports experimental measurements of pressure patterns used in canary song. We find that these patterns are qualitatively similar to the subharmonic solutions of a simple dynamical system. This is built to account for the activities of subpopulations of neurons arranged in a simple architecture compatible with anatomical observations. The consequences of Hebbian plasticity in the coupling between the driving and the driven systems are outlined.

4 illus, 23 ref

009394   Arakeri J H (Mechanical Engng Dep, Indian Institute of Sci, Bangalore-560 012, Email: jaywant@mecheng.lisc.ernet.in ) : Fluid mechanics of fish swimming. Resonance 2009, 14(1), 32-45.

Fish swim by coordinated motion of their body and fins. Discusses the lift-based propulsion adopted by fast swimmers like dol-phins.

15 illus, 5 ref

009393   Arai M (J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan, Email: masatoshi.arai@j-parc.jp) : J-PARC and the prospective neutron sciences. Pramana J Phys 2008, 71(4), 629-38.

Overview of the neutron target system, instrument suite and perspective neutron sciences of J-PARC are described. The neutron facility of J-PARC, JSNS, will be operated from May 2008. JSNS will be a 1 MW pulsed spallation neutron source. About 10 high performance instruments are under construction to be ready by the Day-One.

8 illus, 14 ref

009392   Arafah M R (Physics Dep, Faculty of Sciences, King Abdulaziz University, Jeddah, Saudi Arabia, Email: marafah@kau.edu.sa) : ζ<. Pramana J Phys 2008, 70(1), 113-20.

Phenomenological analysis of the π^{- -12C elastic scattering differential cross-section at 400, 486, 500, 584, 663, 672 and 766 MeV is presented. The analysis is made in the diffraction model framework using the recently proposed parametrization of the phase-shift function. Good description of the experimental data is achieved at all energies. Microscopic interpretation of the parameters of the phase-shift function is provided in terms of Helm's model density parameters.}

1 illus, 1 table, 16 ref

009391   Anita Kanwar;Sureshchandra G;Patil S;Vakil G B (Physics Dep, VES College of Arts, Science & Com. Sindhi Society, Chembur, Mumbai-400 071, Email: anita_s_kanwar@yahoo.com) : PDLC and PDCLC mixtures using various techniques. J Optics 2008, 37(1), 9-15.

Polymer Dispersed Liquid Crystal (PDLC) and Polymer Dispersed Cholesteric Liquid Crystal (PDCLC) films were prepared by thermal-induced phase separation method. PDLC and PDCLC films are analyzed using Fabry Parot Scattering Studies (FPSS), Differential Thermal Analysis (DTA) and Fourier Transform Infra-red (FTIR) Spectroscopy. Changes in the structure, phase transition temperatures (PTTs) and clearing temperatures i.e. the temperature at which the material becomes isotropic are listed. FTIR spectrometer is used to find the structural changes due to the addition of cholesteric material to PDLC. DTA technique is used to corroborate the results obtained using the FPSS technique. Studies reveals that the PDCLC samples are a homogeneous mixture at the room temperature. Transmission intensity and hence the homogeneity of the samples is seen to be maximum for the PDCLC sample containing 80% (80% TL205+20% Cholesteryl Pelargonate) + 20%PN393. Approximate range of percentage transmission decreases as the concentration of the cholesteric material increases.

6 illus, 2 tables, 14 ref

009390   Ando H;Sinha S;Aihara K (Aihara Complexity Modelling Project, ERATO, JST, 4-18, Honcho, Kawaguchi, Saitama, Japan, Email: andoh@sat.t.u-tokyo.ac.jp) : Emergent organiztion of oscillator clusters in coupled self-regulatory chaotic maps. Pramana J Phys 2008, 70(6), 1153-64.

Introduces a model of parametrically coupled chaotic maps on a one-dimensional lattice. In this model, each element has its internal self-regulatory dynamics, whereby at fixed intervals of time the nonlinearity parameter at each site is adjusted by feedback from its past evolution. Additionally, the maps are coupled sequentially and unidirectionally, to their nearest neighbor, through the difference of their parametric variations. Interestingly we find that this model asymptotically yields clusters of superstable oscillators with different periods. We observe that the sizes of these oscillator clusters have a power-law distribution. Moreover, we find that the transient dynamics gives rise to a 1/f power spectrum. All these characteristics indicate self-organization and emergent scaling behavior in this system. We also interpret the power-law characteristics of the proposed system from an ecological point of view.

9 illus, 11 ref

009389   Alone S T;Jadhav K M (NO, Shiv Chhatrapati College, Aurangabad-431 004, Email: drstalone@yahoo.co.in) : Structural and magnetic properties of zinc- and aluminum-substituted cobalt ferrite prepared by co- preciptiation method. Pramana J Phys 2008, 70(1), 173-87.

Spinal ferrites having the general formula Co_1-xZn_xFe_2-xAl_xO₄ (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) were prepared using the wet chemical co-operation technique. The samples were annealed at 800° C for 12 h and were studied by means of X-ray diffraction, magnetization and low field AC susceptibility measurements. The X-ray analysis showed that all the samples had single-phase cubic spinel structure. The variation of lattice constant with Zn and Al concentration deviates from Vegard's law. The saturation magnetization σ_s and magneton number n_B measured at 300 K using high field hysteresis loop technique decreases with increasing x, suggesting decrease in ferrirnagnetic behaviour. Curie temperature TC deduced from AC susceptibility data decreases with x, suggesting a decrease in ferrirnagnetic behaviour.

5 illus, 12 tables, 23 ref

009388   Ahmed M;Lafi A E (Physics Dep, Faculty of Science, Minia Univ, 61519 El-Minia, Egypt, Email: moustafafarghal@yahoo.com) : Analysis of small-signal intensity modulation of semiconductor lasers taking account of gain suppression. Pramana J Phys 2008, 71(1), 99-15.

Demonstrates theoretical characterization of intensity modulation of semiconductor lasers (SL's). The study is based on a small-signal model to solve the laser rate equations taking into account suppression of optical gain. Analytical forms of the small-signal modulation response and modulation bandwidth are derived. Influences of the bias current, modulation index and modulation frequency as well as gain suppression on modulation characteristics are examined. Computer simulation of the model is applied to 1.55-μm. In GaAsP lasers. The results show that when the SL is biased far-above threshold, the increase of gain suppression increases both the modulation response and its peak frequency. The modulation bandwidth also increases but the laser damping rate decreases. Quantitative description of the relationships of both modulation bandwidth vs. relaxation frequency and maximum modulation bandwidth vs. nonlinear gain coefficient are presented.

8 illus, 26 ref

009387   Ahalpara D P;Verma A;Parikh J C;Panigrahi P K (NO, Institute for Plasma Research, Near Indira Bridge, Bhat, Gandhinagar-382 428, Email: prasanta@prl.res.in) : Characterizing and modelling cyclic behaviour in non-stationary time series through multi-resolution analysis. Pramana J Phys 2008, 71(3), 459-85.

A method based on wavelet transform is developed to characterize variations at multiple scales in non-stationary time series. We consider two different financial time series, S&P CNX Nifty closing index of the National Stock Exchange (India) and Dow Jones industrial average closing values. These time series are chosen since they are known to comprise of stochastic fluctuations as well as cyclic variations at different scales. The wavelet transform isolates cyclic variations at higher scales when random fluctuations are averaged out; this corroborates correlated behaviour observed earlier in financial time series through random matrix studies. Analysis is carried out through Haar, Daubechies-4 and continuous Morlet wavelets for studying the character of fluctuations at different scales and show that cyclic variations emerge at intermediate time scales. It is found that Daubechies family of wavelets can be effectively used to capture cyclic variations since these are local in nature. To get an insight into the occurrence of cyclic variations, we then proceed to model these wavelet coefficients using genetic programming (GP) approach and using the standard embedding technique in the reconstructed phase space. It is found that the standard methods (GP as well as artificial neural networks) fail to model these variations because of poor convergence. A novel interpolation approach is developed that overcomes this difficulty. The dynamical model equations have, primarily, linear terms with additive Pade-type terms. It is seen that the emergence of cyclic variations is due to an interplay of a few important terms in the model. Very interestingly GP model captures smooth variations as well as bursty behaviour quite nicely.

35 illus, 1 table, 26 ref

009386   Adegoke J A;Olowofela J A (Physics Dep, Ibadan Univ, Ibadan, Oyo State, Nigeria, Email: adegokeja@yahoo.com) : Variability of permeability with diameter of conduit. Pramana J Phys 2008, 70(5), 901-9.

An entry length is always observed before laminar flow is achieved in fluid flowing in a conduit. This depends on the Reynolds number of the flow and the degree of smoothness of the conduit. This work examined this region and the point where laminar flow commences in the context of flow through conduit packed with porous material like beads, of known porosity. Using some theoretical assumptions, it is demonstrated that permeability varies from zero at wall-fluid boundary to maximum at mid-stream, creating a permeability profile similar to the velocity profile. An equation was obtained to establish this. We also found that peak values of permeability increase with increasing porosity, and therefore entry length increases with increasing porosity with all other parameters kept constant. A plot of peak permeability versus porosity revealed that they are linearly related.

7 illus, 1 table, 10 ref

009385   Abramson G;Gusman S R (Statistical and Interdisciplinary Physics Group, Centro Atomico Bariloche, Conicet, Email: g.abrambon@gmail.com) : Assessing the quality of stochastic oscillations. Pramana J Phys 2008, 70(6), 1047-53.

Analyzes the relationship between the macroscopic and microscopic descriptions of two-state systems, in particular the regime in which the microscopic one shows sustained 'stochastic oscillations' while the macroscopic tends to a fixed point. We propose a quantification of the oscillatory appearance of the fluctuating populations, and show that good stochastic oscillations are present if a parameter of the macroscopic model is small, and that no microscopic model will show oscillations if that parameter is large. The transition between these two regimes is smooth. In other words, given a macroscopic deterministic model, one can know whether any microscopic stochastic model that has it as a limit, will display good sustained stochastic oscillations.

3 illus, 12 ref

009384   Abdullah K K;Ramachandran N;Nair K K;Babu B R S;Joseph A;Thomas R;Varier K M (Physics Dep, Farook College, Calicut-673 632, Email: kmvarier@gmail.com) : Attenuation studies near K-absorption edges using compton scatered <. Pramana J Phys 2008, 70(4), 633-41.

Carried out photon attenuation measurements at several energies in the range from 49.38 keV to 57.96 keV around the K-absorption edges of the rare earth elements Sm, Eu, Gd, Tb, Dy and Er using 59.54 keV gamma rays from ^{241 Am source after Compton scattering from an aluminium target. Pellets of oxides of the rare earth elements were chosen as mixture absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. The scattered gamma rays were detected by an HPGe detector. The results are consistent with theoretical values derived from the XCOM package.}

9 illus, 10 ref

008398   Umesh Kumar (Isotope Applications Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Planar and volume tomography imaging for NDE applications. BARC Newsl 2009, 309(Oct; spl), 34-48.

Electronic imaging devices for gamma and x-ray based Radiography Testing (RT) have shown a remarkable presence during the last decade, due to their technical adaptability to existing inspection systems and easy availability of different configurations to suit a variety of applications. The process of NonDestructive Testing or Examination (NDT or NDE) determines the existence of flaws, discontinuities, leaks, contamination, thermal anomalies or imperfections in materials, components or assemblies, without impairing the integrity or function of the inspected component. NDE is also utilized for real - time monitoring during manufacturing, inspection of assemblies for tolerances, alignment and periodic in-service monitoring of flaw/damage growth, in order to determine the maintenance requirements and to assure the reliability and continued safe operation of a particular part. Today, one can find both analog and digital imaging systems like tube-type fluoroscopy devices, solid-state Linear Detector Arrays (LDA) and two-dimensional detector arrays like Flat Panel Detectors (FPD). These devices can be adapted to suit a variety of imaging requirements like Digital Radiography (DR) operating in online and/or real-time mode and the fast emerging Industrial Computed Tomography (ICT) imaging for non-medical applications. A typical DR and ICT system may be very compact and modular for low-energy applications. However, dedicated DR/ICT systems designed and developed for specific requirements and making use of high-energy X-rays, may be a fixed installation. The Isotope Applications Division (IAD) at BARC, Mumbai has been active in the research and development activities, in the field of advanced radiation-based imaging, for industrial applications for almost a decade. IAD has demonstrated long-back, indigenous efforts in x-ray and gamma ray-based tomographic imaging systems, for various applications. It has continued its effort to modify and develop a facility for Digital Industrial Radiography (DIR) and Volume Computed Tomography (VCT) imaging systems primarily for industrial and other non-medical applications. The present paper briefly discusses research and "development efforts in the planar and volume tomography imaging for NDE applications, it may be sfressed here, that the work carried out so far, was primarily aimed at indigenous technology and know-how development for various applications.

19 illus, 23 ref

008397   Topkar A;Praveen Kumar S;Aggarwal B; Mukhopadhyay P K;Srivastava G P (Electronics and Instrumentation Group, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Technology development of silicon sensors for the compact muon solenoid experiment at the large hadron collider, Cern, for physics experiments and for radiation monitoting. BARC Newsl 2009, 309(Oct; spl), 49-61.

Demanding technology and capability for large scaleproduction of silicon sensors with good uniformity, low leakage currents and high breakdown voltage have been developed by BARC, for the CMS Experiment at LHC, CERN. The individual strip leakage is of the order of few nA/cm^{2 and the strip and total leakage currents are quite well below the specified limits. Irradiation tests carried out have shown, that the sensors meet the stringent specifications for reliable operation in the high radiation environment of LHC. Eleven hundred sensors supplied by us in the form of micromodules, have been installed in CMS preshower at LHC, CERN. The R&D carried out in the past few years has given us the technological capability for large scale production of large area sensors. Though the R&D was targeted for the development of sensors for the international experiment at CERN, this R&D triggered the indigenous development of a wide variety of high performance sensors, for nuclear physics experiments and radiation monitoring instrumentation applications at BARC. Development of new types of sensors such as silicon photomultiplier and integrated ΔE-E silicon detector telescope are underway [17].}

18 illus, 17 ref

008396   Tiwari S N;Dwivedi A K;Shukla S (Physics and Electronics Dep, Dr. R.M.L. Avadh Univ, Faizabad-224 001, Email: sachida_shukla@yahoo.co.in) : Darlington pair amplifiers in cascade. Ultra Scient phys Sci 2009, 21(2), 253-8.

Qualitative analysis of two-stage Darlington pair amplifier is carried out. Enhancement in voltage and current gain is observed with distinct behaviour of bandwidth. This two-stage amplifier may be quite useful for amplification of small signals of mili-volts range and suitable for various analog electronics and communication applications.

8 illus, 12 ref

008395   Tiwari R K;Shukla H P (Physics and Electronics Dep, Dr. R.M.L. Awadh Univ, Faizabad) : Energy efficient portable electronic devices using reversible logic gates. Ultra Scient phys Sci 2009, 21(2), 443-50.

The new generations of Portable Electronic devices are intended to provide a wide range of information, services and receiving a large volume of information, data, image and video so on. Further, portable electronic devices have integrated and advanced function like multimedia portable communication, monitoring and control facilities including high resolution video transmission, selection of services and application by customer i.e. monitoring and control of industrial applications, weather forecasting, location services and connection with other transmission media as well as achieving higher level of security and authentication. Wide coverage of future Portable electronic device services being provided through portable devices are on the rise and new technologies put more computing power in these small devices. However, the slow up gradation of battery technology forms an ultimate constraint on running heavier application on these devices. To prolong battery life, many power saving techniques are being used at all levels of system design. In this paper, we have described the concept of the reversible logic gates which may be used for replacement of conventional logic gate in the design of digital integrated circuit for portable devices to reduce power dissipation resulting prolonged battery life.

2 illus, 13 ref

008394   Tewari R;Dey G K;Banerjee S;Kutty T R G (Materials Science Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Study on microstructural evolution, phase transformations and high temperature properties of ZR₃ AL and its ternary derivatives for future applications in Indian pressurized heavy water reactors. BARC Newsl 2009, 309(Oct; spl), 90-9.

Due to the limitation imposed by existing materials on the performance of Indian nuclear reactors, Zr₃Al base intermetallics have been considered as candidate materials, for structural components in pressurized heavy water nu clear reactors, due to their attractive properties. However, these alloys could not be used for structural applications in the reactors, because of poor room temperature ductility and irradiation-induced amorphization. Our recent studies of ternary addition of niobium in Zr₃AI, have shown some promising results. The present paper reports microstructural evolution and high temperature properties of these alloys, upon long time annealing treatment. The formation of various phases, temperature regime of their stability, chemical composition and volume fraction of these phases during prolonged annealing, have also been studied. A pseudo-binary phase diagram with varying niobium concentrations has also been developed. The morphology and distribution of the Zr₃Al phase have been explained on the basis of long range diffusion, as the rate controlling step. High temperature properties are determined and suitable range of deformation as well as for applications, have been established.

7 illus, 5 tables, 13 ref

008393   Singh V A;Harbola M K;Pathak P (NO, Homi Bhabha Centre for Science Education (TIFR), V.N. Purav Marg, Mankhurd, Mumbai-400 088, Email: vsingh@hbcse.tifr.res.in) : Defects in semiconductor nanostructures. Pramana J Phys 2008, 70(2), 255-61.

Impurities play a pivotal role in semiconductors. One part in a million of phosphorous in silicon alters the conductivity of the latter by several orders of magnitude. Indeed, the information age is possible only because of the unique role of shallow impurities in semiconductors. Although work in semiconductor nanostructures (SN) has been in progress for the past two decades, the role of impurities in them has been only sketchily studied. We outline theoretical approaches to the electronic structure of shallow impurities in SN and discuss their limitations. Find that shallow levels undergo a SHADES (SHAllow-DEep-Shallow) transition as the SN size is decreased. This occurs because of the combined effect of quantum confinement and reduced dielectric constant in SN. Level splitting is pronounced and this can perhaps be probed by ESR and ENDOR techniques. Finally, we suggest that a perusal of literature on (semiconductor) cluster calculations carried out 30 years ago would be useful.

4 illus, 22 ref

008392   Singh M (Physics Dep, Govt. P.G. College, Bageshwar-263 642, Email: dmpsc@rediffmail.com) : Anisotropy in supercurrent density in layered cuprate superconductors. Ultra Scient phys Sci 2009, 21(2), 245-52.

Due to layered structure, the electronic conduction in high-T_c cuprate superconductors is highly anisotropic. Therefore, in the present work, we have made an attempt to study the anisotropy in supercurrent density in layered cuprate superconductors like YBa₂Cu₃O_6+x. Considered tight binding bilayered Hubbard Hamiltonian. The situation considered here for the bilayered cuprates is similar to a SIS junction. Using Green function technique, we have got the expressions for superconducting order parameters, carrier density and supercurrent densities. The numerical analysis shows that the anisotropy in supercurrent density depends on the temperature and various other microscopic parameters of the model Hamiltonian. The anisotropy in supercurrent density increases with temperature and diverges as system reaches towards the superconducting transition temperature. On increasing the carrier density within the plane, the anisotropy in supercurrent density decreases because around optimal doping region, bilayer system(YBaCuO) behaves like almost isotropic three dimensional superconductors. On increasing the interlayer attractive interaction, the anisotropy in supercurrent density decreases. It is also shown that when interlayer attractive interaction (W) is just equal to the intralayer pairing interaction (U), the anisotropy in supercurrent density vanishes i.e. the bilayer Quasi-2D system becomes almost isotropic(three dimensional) in supercurrent flow in the superconducting state. We have shown, using tight binding bilayer Hubbard model within BCS meanfield formalism, that the anisotropy in supercurrent density depend on various microscopic intra and interlayer interactions as well as on the thermodynamics of superconducting order parameter in an essential way. Finally we have compared our theoretical results of anisotropy in supercurrent density with the existing experimental findings in bilayered cuprate superconductors.

3 illus, 26 ref

008391   Singh K B;Mukesh Kumar (NO, Govt. Polytechnic, Darbhanga, Bihar, Email: kbsphysics@yahoo.co.in) : Optical binding between dielectric particles through millimeter wave propagation. Ultra Scient phys Sci 2009, 21(2), 269-74.

Shows that the optical binding between dielectric particles through millimeter wave propagation at 30-50 GHz having bulk mixture of two dielectric bodies at different sizes. We suppose the dielectric particles having dimensionless than the wavelength of the interacting light under millimeter wave propagation. An optimum increase in binding energy was noted for all cases. This study further indicates the suitability of this technique for construction of two or three-dimensional arrangement of objects. The observed dependence of the separation of optically bond particles on millimeter wave propagation is in good agreement with earliest theoretical predictions.

2 illus, 7 ref

008390   Singh A (Teachnical Physics and Prototype Engineering Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Technology development for thermoelectric devices. BARC Newsl 2009, 309(Oct; spl), 108-14.

Diffusion bonded very low resistance electrical contacts (specific contact resistance <60> 10 (μΩcm²) have been developed on n-type Pb Te and p-type TAGS-85 ((AgSbTe₂)_0.15 (GeTe) thermoelements. Thermoelectric devices having two p-n couples in series (each of four elements having 7.5 mm dia) generated an output power of 1.2 W (at operating current of <126> 17 Amp) at hot side temperature T_h = 500 °C and a temperature difference I ∪ T = 410 °C. Internal resistance of the devices was found to increase linearly with increase in the number of thermoelements. The efficiency of developed thermoelectric devices was found to be 6%. The devices have been continuously operated for more than 8 months in air without any degradation of the output power.

8 illus, 4 ref

008389   Sharma Y C;Vyas V;Purvia V;Joshi K B;Sharma B K (Physics Dep, Swami Keshvanand Institute of Technology, Jaipur-302 025, Email: yogeshchandra.sharma@gmail.com) : Compton profile study of V₃Ge and Cr₃Ge. Pramana J Phys 2008, 70(2), 323-37.

Results of a Compton profile study of two polycrystalline A15 compounds, namely, V₃Ge and Cr₃Ge, have been reported. The measurements have been performed using 59.54 keV γ-rays from an ²⁴¹Am source. The theoretical Compton profiles have been computed for both the compounds using ab-initio linear combination of atomic orbitals (LCAO) method employing CRYSTAL98. For both the A15 compounds, the isotropic experimental profiles are found to be in good overall agreement with the calculations. The comparison points out residual differences in V₃Ge whereas for Cr₃Ge the differences are within experimental error. The behaviour of valence electron in the two iso-structural compounds has been examined on the scale of Fermi momentum. The valence electron distribution seems to be dominated by the metallic constituents rather than Ge and two compounds show covalent nature of bonding which is larger in V₃Ge compared to Cr₃Ge.

7 illus, 2 tables, 33 ref

008388   Sharma V K;Rao M N;Gautam S;Mitra S;Chaplot S L;Mukhopadhyay R;Tripathi A K;Kamble V S (Solid State Physics Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Rotational diffusion of propylene in Na-ZSM5 zeolite : a molecular dynamics simulation and quasi - elastic neutron scattering study. BARC Newsl 2009, 309(Oct; spl), 380-9.

Rotational dynamics of propylene adsorbed in ZSM5 zeolite, as studied by using Molecular Dynamics (MD) simulation and QuasiElastic Neutron Scattering (QENS) techniques are reported here. MD simulation studies indicated that the rotational motion is almost an order of magnitude faster than translational motion. While the slower-translational motion was studied by QENS spectrometer, the rotational motion was studied using triple axis spectrometer, which has a wider energy window. The variation of the elastic incoherent structure factor showed, that the rotational motion is isotropic in nature. Intermediate scattering function, corresponding to rotational motion obtained from MD simulation, also indicated an isotropic rotation of propylene in Na-ZSM5. However, the trajectory of a CH₃ site of propyiene molecules, in the centre of mass frame shows a restricted behaviour for short periods. Migration of the molecule across different channels for longer per covers the entire orientational space, thereby giving rise to isotropic rotation.

7 illus, 28 ref

008387   Sen S (Technical Physics and Prototype Engineering Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Room temperature toxic gas sensors based on tellurium. BARC Newsl 2009, 309(Oct; spl), 135-8.

Various morphologies of Tellurium, such as thin films and films made from Te nanostructures, have been explored as toxic gas sensors, operating at room temperature, The resistance of these films was found to increase reversibly, on exposure to reducing gases, while the opposite effect was observed on exposure to oxidizing gases. The sensitivity as well as the selectivity of these sensors, with respect to different gases has been studied, Response to different gases was found to be a function of various parameters like: deposition temperature, substrate crystallinity, grain size and effect of intra-grain and grain boundary regions. Techniques like Raman spectroscopy, X-ray photoelectron spectroscopy and impedance spectroscopy has been employed, for investigating the gas-tellurium interaction.

7 ref

008386   Selvam T Palani;Sahoo S;Vishwakarma R S (Radiological Physics & Advisory Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Monte carlo dosimetry of CSA1 and CSA2 <. BARC Newsl 2009, 309(Oct; spl), 163-72.

1 illus, 5 tables, 21 ref

008385   Samal M K (Reactor Safety Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : New damage mechanics - based approach for integrity assessment of plant components. BARC Newsl 2009, 309(Oct; spl), 128-34.

It is now widely recognized in literature, that the results of the local damage model are mesh-dependent. The growth of damage tends to localize in the smallest band that can be captured by spatial discretization. Upon mesh refinement, the solution converges to a localization zone of zero width (in the limit), which results in zero energy dissipation and hence the results become physically meaningless. In this work, the Rousselier's damage model has been extended to a nonlocal form, using the nonlocal damage parameter as an additional degree of freedom of the finite element (FE) model. The rnesh independent nature of the model has been demonstrated through the simulation of fracture behaviour of a standard fracture mechanics specimen, using different mesh sizes. The model has also been applied for simulation of ductile to brittle transition behaviour of ferritic steels. It demonstrated that the temperature dependency of the Weibull parameters is observed due to the inability of the elasto-plastic and conventional damage models to predict the pre-cleavage ductile crack growth of the order of few microns. With the use of the new model it has been possible to predict the fracture toughness master curve of a ferritic pressure vessel steel in the ductile to brittle transition regime.

5 illus, 1 table, 13 ref

008384   Reddy G R (Reactor Safety Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Seismic safety of nuclear facilities. BARC Newsl 2009, 309(Oct; spl), 25-33.

Nuclear facilities need to be safe during postulated earthquakes. The subject of seismic design of nuclear facilities has gained importance and substantial research was conductd apart from regular design and analysis work. The goal of achieving absolute seismic safety at optimized cost, is still being pursued. The work related to seismic safety of nuclear facilities was grouped under: Analysis and design of AHWR containment building, fuelling machine and down comers, Analysis of 32 m DSN antenna of the Chandrayan project of I5RO, Experimental programme pursued for better understanding of the structural behaviour of beam-column joints and piping components under earthquake loading, development of seismic response control devices, requalification of older facilities and retrofitting of systems such as CIRUS ball, tank, retrofitting scheme proposed for APSARA reactor building and developing Advanced Seismic Testing and Research Laboratory (ASTaR) at SERC, Chennai.

11 illus

008383   Rao R M;Parab A R;Sasibhushan K;Aggarwal S K (Fuel Chemistry Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Determination of isotopic composition of boron AS Rb₂ BO₂<. BARC Newsl 2009, 309(Oct; spl), 199-203.

The work focuses on the experimental methods for generating Rb₂BO₂⁺ions and explores the possibility of a correlation between the K-factor(mass discrimination factor) for boron isotope ratios and the observed isotopic composition of rubidium. NIST-SRM-951 which is in the form of boric acid with ¹⁰B/¹¹B isotopic ratio of 0.2473 ± 0.0002 and Rubidium carbonate with natural isotope abundance of rubidium was used.

4 illus, 2 tables, 9 ref

008382   Rajput P (Physics Dep, Allahabad Agricultural Institute-Deemed University, Allahabad-211 007, Email: paru10606@yahoo.com) : Enhancement of ion-induced nucleation for convex substrate. Natn Acad Sci Lett 2008, 31(9-10), 289-91.

For ion-induced nucleation for a convex substrate at a given super saturation, the energy of formation of critical water nucleus and its radius is comparatively less than those in a classical case are presented.

^ssc2 tables, 8 ref