009466   Nandi A;Ramaswamy R (School of Physical Sciences, Jawaharlal Nehru Univ, New Delhi-110 067, Email: writeamitabha@gmail.com) : Synchronization of coupled stochastic oscillators: the effect of topology. Pramana J Phys 2008, 70(6), 1165-74.

Studies sets of genetic networks having stochastic oscillatory dynamics. Depending on the coupling topology we find regimes of phase synchronization of the dynamical variables. We consider the effect of time-delay in the interaction and show that for suitable choices of delay parameter, either in-phase or anti-phase synchronization can

7 illus, 25 ref

009465   Muruganandam P;Ferreira F F;EL-Nashar H F; Cerdeira H A (School of Physics, Bharathidasan Univ, Palkalaiperur, Tiruchirappalli-620 024, Email: cerdeira@ictp.it) : Analytical calculation of the transition to complete phase synchronization in coupled oscillators. Pramana J Phys 2008, 70(6), 1143-51.

Presents a system of coupled phase oscillators with nearest neighbors coupling, which we study for different boundary conditions. We concentrate at the transition to the total synchronization. We are able to develop exact solutions for the value of the coupling parameter when the system becomes completely synchronized, for the case of periodic boundary conditions as well as for a chain with fixed ends. We compare the results with those calculated numerically.

3 illus, 2 tables, 30 ref

009464   Murti M V R;Raju S S;Seetharami Reddy B; Koteswara Rao V;Mombaswala L S;Seshi Reddy T;Lakshminarayana S; Premachand K (Center of Studies in Resources Engineering, Indian Institute of Technology, Powai, Mumbai-400 076, Email: bsr_au@yahoo.com) : Kα X-ray satellite spectra of Ti, V, Cr and Mn induced by photons. Pramana J Phys 2008, 70(4), 747-52.

K X-ray emission spectra of Ti, V, Cr and Mn generated by photon excitation have been studied with a crystal spectrometer. The measured energy shifts of K_α satellite relative to the diagram line are compared with values obtained by electron excitation and with different theoretical estimates. The present experimental values of K_αL¹/K_αL⁰ relative intensities are compared with values obtained by electron excitation.

4 illus, 2 tables, 12 ref

009463   Murani A P (Institut Max von Laue Paul Langevin, 6 Rue Jules Horowitz, 38042 Grenoble, France, Email: murani@ill.fr) : Neutron scattering from α-Ce at epithermal neutron energies. Pramana J Phys 2008, 71(4), 859-67.

Neutron scattering data, using neutrons of incident energies as high as 2 eV, on α-Ce and α-Ce-like systems such as CeRh₂, CeNi₂, CeFe₂, CeRu₂, and many others that point clearly to the substantially localized 4f electronic state in these systems are reviewed. The present interpretation is contrary to the widely held view that the 4f electrons in these systems form a narrow itinerant electron 4f band.

5 illus, 19 ref

009462   Mukherjee S;Gupte N (Physics Dep, Indian Institute of Technology Madras, Chennai-600 036, Email: mukherjee@physics.iitm.ac.in) : Message transfer in a communication network. Pramana J Phys 2008, 70(6), 1109-16.

Study message transfer in a 2-d communication network of regular nodes and randomly distributed hubs. Both single message transfer and multiple message transfer on the lattice were studied. The average travel time for single messages travelling between source and target pairs of fixed separations shows g-exponential behaviour as a function of hub density with a characteristic power-law tail, indicating a rapid drop in the average travel time as a function of hub density. This power-law tail arises as a consequence of the log-normal distribution of travel times seen at high hub densities. When many messages travel on the lattice, a congestion-decongestion transition can be seen. The waiting times of messages in the congested phase show a Gaussian distribution, whereas the decongested phase shows a log-normal distribution. Thus the waiting time distributions carry the signature of congested or decongested behaviour.

5 illus, 13 ref

009461   Moukam Kakmeni F M;Baptista M S (NO, Max-Planck-Institut fur Physik Komplexer Systeme, Nothnitzerstr, 38, D-01187 Dresden, Deutschland, Email: murilo.baptista@fc.up.pt) : Synchronization and information transmission in spatio-temporal networks of deformable units. Pramana J Phys 2008, 70(6), 1063-76.

Study the relationship between synchronization and the rate with which information is exchanged between nodes in a spatio-temporal network that describes the dynamics of classical particles under a substrate Remoissenet-Peyrard potential. We also show how phase and complete synchronization can be detected in this network. The difficulty in detecting phase synchronization in such a network appears due. to the highly non-coherent character of the particle dynamics which unables a proper definition of the phase dynamics. The difficulty in detecting complete synchronization appears due to the spatio character of the potential which results in an asymptotic state highly dependent on the initial state.

6 illus, 17 ref

009460   Mittal R (Forschungszentrum Julich GmbH, Julich Centre for Neutron Science, C/O TU Munchen, Lichtenbergstr 1, 85747 Garching, Germany, Email: rmitttal70@yahoo.co.in) : Negative thermal expansion in framework compounds. Pramana J Phys 2008, 71(4), 829-35.

Studied negative thermal expansion (NTE) compounds with chemical compositions of NX₂O₈ and NX₂O₇ (N = Zr, Hf and X = W, Mo, V) and M₂O (M = Cu, Ag) using the techniques of inelastic neutron scattering and lattice dynamics. There is a large variation in the negative thermal expansion coefficients of these compounds. The inelastic neutron scattering experiments have been carried out using polycrystalline and single crystal samples at ambient pressure as well as at high pressures. Experimental data are useful to confirm the predictions made from our lattice dynamical calculations as well as to check the quality of the interatomic potentials developed by us. We have been able to successfully model the NTE behaviour of these compounds. Our studies show that unusual phonon softening of low energy modes is able to account for NTE in these compounds.

6 illus, 27 ref

009459   Mitra A;Kumar A (NMR Quantum Computation and Quanum Information, Group, Physics and NMR, Indian Institute of Science, Bangalore-560 012, Email: anilnmr@physics.iisc.ernet.in) : Experimental implementation of quantum ulams's problem in a nuclear magnetic resonance quantum information processor. J Indian Inst Sci 2009, 89(3), 309-16.

The Ulam's problem is a two person game in which one of the player tries to search, in minimum queries, a number thought by the other player. Classically the problem scales polynomially with the size of the number. The quantum version of the Ulam's problem has a query complexity that is independent of the dimension of the search space. The experimental implementation of the quantum Ulam's problem in a Nuclear Magnetic Resonance Information Processor with 3 quantum bits is reported here.

6 illus, 1 table, 24 ref

009458   Mishra D R (NO, Government Post Graduate College, Berinag, Pithoragarh, Uttaranchal, Email: dr_devraj_mishra@yahoo.co.in) : Gd-substituted Bi-2223 superconductor. Pramana J Phys 2008, 70(3), 535-41.

The effects of gadolinium doping at calcium site on the normal and superconducting properties of Bi-2223 system were studied. The Gd-doped (BiPb)-2223 series of specimens, namely Batch I, II and III were sintered at three different sintering temperatures 830, 850 and 895°C respectively. The properties investigated are (1) the normal state resistivity with a view to study metal-to-insulator transition, (2) the XKD patterns of the specimens with a view to study the relative composition of (BiPb)-2212 and (BiPb)-2223 phases and (3) the superconducting fluctuation behaviour (SFB) with a view to determine the effect of doping, if any, on the dimensionality of the fluctuation conductivity of the system. The normal state resistivity of Gd-substituted Bi-2223 specimens shows metallic, semiconducting and insulating behaviour. The T_c(R = 0) values indicate that (BiPb)-2223 phase is responsible for the observed superconducting transitions in Batch I and Batch II specimens with Gd concentrations x < 0.7. This observation is further confirmed in the analysis of XRD patterns of these specimens. Gadolinium, being a magnetic impurity, has pair breaking effect near the Fermi level and decreases T_c(R = 0). The analysis of the superconducting fluctuation behaviour (SFB) shows a 2D dimensionality without any cross-over.

15 ref

009457   Mignot J M;Robert J;Sera M;Iga F (Laboratoire Leon Brillouin, CEA-CNRS, CEA/Saclay, F-91191 Gif sur Yvette, France, Email: jean-michel.mignot@cea.fr) : Neutron diffraction study of multipole order in light rare-earth hexaborides. Pramana J Phys 2008, 71(4), 831-45.

Multipole interactions are known to play a central role in the unconventional properties of light rare-earth hexaborides and especially of CeB₆. Substituting Pr at the Ce sites has the effect of enhancing exchange interactions and changing the symmetry of the local 4f charge distribution, while suppressing the octupole moment. The (T, H) magnetic phase diagrams of the Ce_xPr_1-xB₆ compounds display a large variety of ordered phases involving magnetic and/or charge degrees of freedom. Here we focus on the compound Ce_0.7Pr_0.3B₆, which is located slightly beyond the Pr concentration where the antiferroquadrupolar phase of pure CeBe is suppressed in zero field. The different magnetic structures have been characterized by neutron diffraction and their origin is discussed in connection with recent non-resonant X-ray results by Tanaka et al.

4 illus, 21 ref

009456   Mehrotra I;Prakash S (Physics Dep, Allahabad Univ, Allahabad-211 002, Email: i8ndum81@gmail.com) : Proton radioactivity with analytically solvable potential. Pramana J Phys 2008, 70(1), 101-11.

The phenomenon of proton emission is treated as a process of asymmetric fission through a one-dimensional potential barrier developed due to combined effects of the Coulomb potential, centrifugal potential and various renormalization processes. The barrier is simulated to an asymmetric, smooth and analytically solvable potential with adjustable depth, shape and range. The half-lives of proton emitters in the mass range A = 105-171 have been calculated using exact expression for the transmission coefficients. Good agreement with the experimental data is obtained by the adjustment of just one parameter in all the cases.

2 illus, 4 tables, 23 ref

009455   Manpreet Singh;Bhajan Singh;Sandhu B S (Physics Dep, Punjabi Univ, Patiala-147 002, Email: balvir99@indiatmes.com ) : Energy and intensity distributions of 279 keV multiply scattered photons in bronze-an inverse response matrix approach. Pramana J Phys 2008, 70(1), 61-73.

An inverse response matrix converts the observed pulse-height distribution of a NaI(Tl) scintillation detector to a true photon spectrum. This also results in extraction of intensity and energy distributions of multiply scattered events originating from interactions of 279 keV photons with thick targets of bronze. The observed pulse-height distributions are a composite of singly and multiply scattered events in addition to bremm-strahlung originating from slowing down of Compton and photo-electrons in thick targets. To evaluate the contribution of multiply scattered events, the spectrum of singly scattered events contributing to inelastic Compton peak is reconstructed analytically. The optimum thickness (saturation depth), at which the number of multiply scattered events saturate, has been evaluated in different energy bin meshes chosen for scintillation detec-liir response unfolding. Monte Carlo calculations based upon the package developed by Bauer and Pattison (Compton scattering experiments at the HMI (1981), HMI-B 364, pp. 1-106) supports the present experimental results.

6 illus, 3 tables, 16 ref

009454   Manneville P (Hydrodynamics Laboratory, Ecole Polytechnique, Palaiseau, F-91128, France, Email: paul.manneville@ladhyx.polytechnique.fr) : Understanding the sub-critical transition to turbulence in wall flows. Pramana J Phys 2008, 70(6), 1009-21.

In contrast with free shear flows presenting velocity profiles with inflection points which cascade to turbulence in a relatively mild way, wall bounded flows are deprived of (inertial) instability modes at low Reynolds numbers and become turbulent in a much wilder way, most often marked by the coexistence of laminar and turbulent domains at intermediate Reynolds numbers, well below the range where (viscous) instabilities can show up. There can even be no unstable mode at all, as for plane Couette flow (pCf) or for Poiseuille pipe flow (Ppf) that are currently the subject of intense research. Though the mechanisms involved in the transition to turbulence in wall flows are now better understood, statistical properties of the transition itself are yet unsatisfactorily assessed. A widely accepted interpretation rests on non-trivial solutions of the Navier-Stokes equations in the form of unstable travelling waves and on transient chaotic states associated to chaotic repellors. Whether these concepts typical of the theory of temporal chaos are really appropriate is yet unclear owing to the fact that, strictly speaking, they apply when confinement in physical space is effective while the physical systems considered are rather extended in at least one space direction, so that spatiotemporal behaviour cannot be ruled out in the transitional regime. The case of pCf will be examined in this perspective through numerical simulations of a model with reduced cross-stream (y) dependence, focusing on the in-plane (x, z) space dependence of a few velocity amplitudes. In the large aspect-ratio limit, the transition to turbulence takes place via spatiotemporal intermittency and we shall attempt to make a connection with the theory of first-order (thermodynamic) phase transitions, as suggested long ago by Pomeau.

7 illus, 42 ref

009453   Mallik D C V (NO, Indian Institute of Astrophysics, Sarjapur Road, Bangalore-560 034, Email: dcvmlk@iap.res.in) : Solar physics observatory at kodaikanal and john evershed. Resonance 2009, 14(11), 1032-39.

Kodaikanal Observatory was established during the closing years of the 19th century to carry out scientific observations of the Sun. John Evershed, an established amateur solar observer, came to Kodaikanal in 1907 as the Chief Assistant to the Director and became the director of the observatory 4 years later. In 1909, he discovered the phenomenon of radial motion of gases in sun spots, the earliest successful observation of velocity fields due to a complex magnetohydrodynamical process in action in a celestial setting. Through Evershed's work Kodaikanal became known as one of the premier solar observatories in the world.

5 illus, 5 ref

009452   Majumdar R N (Physics Dep, Vivekananda College, 269, Diamond Harvour Road, Kolkata-700 063, Email: ramendranath.majumdar@saha.ac.in) : Dissociation of deuteron, <. Pramana J Phys 2008, 70(5), 949-53.

The fragmentation of deuteron, ^{6He and 11Be have been studied during interaction with the 208Pb nucleus at various projectile energies. The Coulomb dissociation cross-sections and the momentum distribution of the break-up fragments have been analysed within the framework of the direct fragmentation model. The post-acceleration effect of deuteron during break-up and the halo structures of both the 6He and 11Be have been investigated.}

2 illus, 1 table, 18 ref

009451   Majumdar D (NO, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata-700 064, Email: debasish.majumdar@saha.ac.in) : Probing pseudo-Dirac neutrino through detection of neutrino-induced muons from gamma ray burst neutrinos. Pramana J Phys 2008, 70(1), 51-60.

The possibility to verify the pseudo-Dirac nature of neutrinos is investigated here via the detection of ultra-high energy neutrinos from distant cosmological objects like γ-ray bursts (GRBs). The very long baseline and the energy range from ~TeV to ~EeV for such neutrinos invoke the likelihood to probe very small pseudo-Dirac splittings. The expected secondary muons from such neutrinos that can be detected by a kilometer scale detector such as ICECUBE is calculated and compared with the same in the case of mass-flavour oscillations and for no oscillation cases. The calculated muon yields indicate thiil to probe such small pseudo-Dirac splittings one needs to look for a nearby GRB (red shift z ~ 0.03 or less) whereas for a distant GRB (z ~ 1) the flux will be much depleted and such phenomenon cannot be distinguished. Also calculated are the muon-to-shower ratios.

2 illus, 1 table, 15 ref

009450   Lunazzi J J;Rivera N I R (Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin, Caixa Postal 6165, 13083-970 Campinas, SP, Brazil) : White-light imaging in a two gratings diffraction process. J Optics 2008, 37(2), 56-62.

A diffractive arrangement that allows imaging of an object without any intei-mediate or complementary element is presented. This optical system with only two diffraction gratings forms color images with white light.

5 illus, 18 ref

009449   Lohani J;Saho P;Kumar U;Balakrishnan V R;Basu P K (Solid State Physics Laboratory, , Lucknow Road, Timarpur, Delhi-110 054, Email: jaya_mishri@yahoo.co.in) : Electrical characteristics of top contact pentacene organic thin film transistors wih SiO₂ and poly(methyl methacrylate) as gate dielectrics. Pramana J Phys 2008, 71(3), 579-89.

Organic thin film transistors (OTFTs) were fabricated using pentacene as the active layer with two different gate dielectrics, namely SiO2 and poly(methyl methacrylate) (PMMA), in top contact geometry for comparative studies. OTFTs with SiO2 as dielectric and gold deposited on the rough side of highly doped silicon (n^{+-Si) as gate electrode exhibited reasonable field effect mobilities. To deal with poor stability and large leakage currents between source/drain and gate electrodes in these devices, isolated OTFTs with reduced source/drain contact area were fabricated by selective deposition of pentacene on S1O2/PMMA through shadow mask. This led to almost negligible leakage currents and no degradation in electrical performance even after 14 days of storage under ambient conditions. But, the field effect mobilities obtained were lower than 10-3 cm2 V-1 s-1, whereas by using PMMA as gate dielectric with chromium deposited on the polished side of n+-Si as gate electrode, improved field effect mobilities (>0.02 cm2 V-1 s-1) were obtained. PMMA-based OTFTs also exhibited lower leakage currents and reproducible output characteristics even after 30 days of storage under ambient conditions.}

7 illus, 13 ref

009448   Lin B;Zhao Y;Chen J (Physics and Institute of Theoretical Physics and Astrophysics Dep, Xiamen Univ, Xiamen 361005, People's Republic of China, Email: linbh@xmu.edu.cn) : Parametric optimum analysis of an irreversible ericsson cryogenic refrigeration cycle working with an ideal fermi gas. Pramana J Phys 2008, 70(5), 779-95.

An irreversible model of an Ericsson cryogenic refrigeration cycle working with an ideal Fermi gas is established, which is composed of two isothermal and two iso-baric processes. The influence of both the quantum degeneracy and the finite-rate heat transfer between the working fluid and the heat reservoirs on the performance of the cycle is investigated, based on the theory of statistical mechanics and thermodynamic properties of an ideal Fermi gas. The inherent regeneration losses of the cycle are analyzed. Expressions for several important performance parameters such as the coefficient of performance, cooling rate and power input are derived. By using numerical solutions, the cooling rate of the cycle is optimized for a given power input. The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal regions of the coefficient of performance and power input are determined. Especially, the optimal performance of the cycle in the strong and weak gas degeneracy cases and the high temperature limit is discussed in detail. The analytic expressions of some optimized parameters are derived. Some optimum criteria are given. The distinctions and connections between the Ericsson refrigeration cycles working with the Fermi and classical gases are revealed.

8 illus, 27 ref

009447   Liang M L;Xu Z C;Yuan B (Physics Dep, School of Science, Tianjin Univ, Tianjin 300072, Email: mailinliang@yahoo.com) : Berry phases in the three-level atoms driven by quantized light fields. Pramana J Phys 2008, 70(3), 399-407.

A theoretical analysis of Berry's phases is given for the three-level atoms interacting with external one-mode and two-mode quantized light fields. Three main results are obtained: (i) There is a Berry phase which vanishes in the classical limit or this Berry phase is completely induced by the field quantization; (ii) Berry's phases for the one-mode field and the two-mode field can be equal so long as the photon numbers of the two-mode field are properly chosen; (iii) In the two-mode case, Berry phases of the atom interacting with one mode is affected by the other mode even if the photon number of the other mode is zero.

25 ref

009446   Kuila P;Sinha A;Mukhopadhyay S (Physics Dep, V.S. Mahavidyalaya, Manikpara, Midnapore-721 513) : Theoretical approach for generation of optical soliton pulse inside an optical fiber using electoptic modulator. J Optics 2008, 37(1), 16-24.

One of the most interesting phenomena in the Physics of non-linear optics is the formation of a stable wave packet propagating over a long long distance with unattenuated, unchirped and undistorted in character, the so called soliton. The success of the ensuing photonic revolution depends upon the use of optical soliton pulse in fiber optic communication systems. Here we propose a completely new technique for generation of optical soliton pulse by controlling the power of a gaussion pulse properly. For this purpose, we use the amplitude modulation scheme of an electro-optic modulator in transverse mode of operation due to some special advantages. Some new important characteristics of the output pulse are pointed out in this approach.

1 illus, 17 ref

009445   Kuang S;Wang J;Zeng T;Cao A (Physical Science and Technology Dep, Wuhan Technology Univ, Wuhan, 430070, China, Email: whutjoey@hotmail.com) : Thermal impact on spiking properties in hodgmin-huxley neuron with synaptic stimulus. Pramana J Phys 2008, 70(1), 183-90.

The effect of environmental temperature on neuronal spiking behaviors is investigated by numerically simulating the temperature dependence of spiking threshold of the Hodgkin-Huxley neuron subject to synaptic stimulus. We find that the spiking threshold exhibits a global minimum in a specific temperature range where spike initiation needs weakest synaptic strength, which form the engineering perspective indicates the occurrence of optimal use of synaptic transmission in the nervous system. We further explore the biophysical origin of this phenomenon associated with ion channel gating kinetics and also discuss its possible biological relevance in information processing in neuronal systems.

6 illus, 32 ref

009444   Krishnamurthy K S;Pramoda Kumar;Tadapatri P (NO, , ) : Flexoelectrically driven instabilities in liquid crystals. J Indian Inst Sci 2009, 89(2), 255.

Flexoelectricity is an important mechanoelectric property of liquid crystals that provides a reciprocal, linear relation between curvature distortions and electric polarization. We review here a few of the less known electric field generated flexoelectric effects observed in recent years and relating to (a) dc field excited flexo-response at defect sites in nematic inversion walls, (b) gradient flexoelectric switching at polarity reversals in nematics, (c) flexoelectrically driven phase propagation in the undulatory structure of the smectic C phase and (d) asymmetric distortion in sheared annular walls in free-standing nematic films.

18 illus, 44 ref

009443   Krishan K (Physics and Astronomy Dep, California-Irvine Univ, Irvine, California 92697-4575, USA, Email: kkrishan@uci.edu) : Importance of packing in spiral defect chaos. Pramana J Phys 2008, 70(4), 669-78.

Develops two measures to characterize the geometry of patterns exhibited by the state of spiral defect chaos, a weakly turbulent regime of Rayleigh-Benard convection. These describe the packing of contiguous stripes within the pattern by quantifying their length and nearest-neighbor distributions. The distributions evolve towards a unique distribution with increasing Rayleigh number that suggests power-law scaling for the dynamics in the limit of infinite system size. The techniques are generally applicable to patterns that are reducible to a binary representation.

6 illus, 29 ref

009442   Kouacou M A;Koua A A;Zoueu J T;Konan K;Pierre J (Genie Electrique et Electronique Dep, Institut National Polytechnique, Houphouet-Boigny (INP-HB), BP 1093 Yamoussoukro, Cote d'Ivoire, Email: abakaci@yahoo.fr) : Onset of itinerant ferromagnetism associated with semiconductor-metal transition in Ti_xNb_1-xCoSn half heusler solid solution compounds. Pramana J Phys 2008, 71(1), 157-66.

The magnetic and transport properties of the Ti_xNb_1-x CoSn solid solution compounds with half Heusler cubic MgAgAs-type structure have been studied. This work shows the onset of ferromagnetism associated with a semiconductor to metal transition. The transition occurs directly from ferromagnetic metal to semiconducting state as it is the case in the TiCo_xNi_1-xSn series studied previously. A weak quantity of Ti in NbCoSn is sufficient to allow the appearance of ferromagnetic order and metallic state. The variations of the Curie temperature as a function of saturation and effective paramagnetic moments are related to the itinerant ferromagnetism model. A comparison is made with the TiCoSn_xSb_1-x series (also studied previously), where the transition from TiCoSn ferromagnetic metal to non-magnetic semiconductor TiCoSb occurs through an intermediate metallic Pauli-like state.

7 illus, 2 tables, 25 ref

009441   Keshri S;Dayal V (Applied Physics Dep, Birla Institute of Technology, Mesra, Ranchi-835 215, Email: s_keshri@bitmesra.ac.in) : Structural and electrical transport properties of nanosized La_0.67Ca_0.33MnO₃ sample synthesized by a simple low-cost novel route. Pramana J Phys 2008, 70(4), 697-704.

Synthesized nanosized La_0.67Ca_0.33MnO₃ by a simple low-cost novel synthesis route without calcination at high temperature. The study of these nanoparti-cles indicates excellent properties similar to colossal magnetoresistance (CMR) materials sintered at ~ 1600°C for 20 h. The resulting particle size is in the range of 50-160 nm as determined by scanning electron microscopy. Resistivity measurement has been carried out down to 12 K. The sample shows metal-to-insulator (M-I) transition at 205 K.

3 illus, 2 tables, 19 ref

009440   Kalra Y;Sinha R K (TIFAC-Center of Relevance & Excllence in Fiber Optics & Optical Commun, Delhi College of Engineering, Faculty of Technology, (Delhi Univ), Bawana Road, Delhi-110 042, Email: yogita25@rediffmail.com) : Modelling and design of complete photonic band gaps in two-dimensional photonic crystasl. Pramana J Phys 2008, 70(1), 153-61.

Investigate the existence and variation of complete photonic band gap size with the introduction of asymmetry in the constituent dielectric rods with honeycomb lattices in two-dimensional photonic crystals (PhC) using the plane-wave expansion (PWE) method. Two examples, one consisting of elliptical rods and the other comprising of rectangular rods in honeycomb lattices are considered with a view to estimate the design parameters for maximizing the complete photonic band gap. Further, it has been shown that complete photonic band gap size changes with the variation in the orientation angle of the constituent dielectric rods.

6 illuts, 1 table, 4 rer

009439   Jones J A (Centre for Quantum, Computation, Clarendon Laboratory, Oxford Univ, Parks Road, OX1, 3PU, United Kingdom, Email: jonathan.jones@qubit.org) : Composite pulses in NMR quantum computation. J Indian Inst Sci 2009, 89(3), 303-8.

Describe the use of techniques based on composite rotations to combat systematic errors in quantum logic gates. Although developed and described within the context of Nuclear Magnetic Resonance (NMR) quantum computing these sequences should be applicable to other implementations of quantum computation.

^iia60 ref

009438   Janyani V (Electronics and Communication Engineering Dep, Malaviya National Institute of Technology, Jaipur-302 017) : Formation and propagation-dynamics of primary and secondary soliton-like pulses in bulk nonlinear media. J Optics 2008, 37(1), 1-8.

Time-domain numerical modelling of soliton propagation in dispersive nonlinear bulk media is considered. An accurate transmission line modelling (TLM) tool based on the direct discretisation of the Maxwell's equations is developed. The dispersive nonlinearity of the material is considered using the Duffing model. The TLM tool provides useful insidht into the spatio-temporal dynamics of soliton formation and propagation in media with dispersive nonlinearity, including the formation of secondary solitons.

4 illus, 15 ref

009437   Jamil U;Sarma J K (Physics Dep, Tezpur Univ, Napam, Tezpur-784 028, Email: jks@tezu.ernet.in) : Regge behaviour of distribution function and evolution of gluon distribution function in next-to-leading order at low-x. Pramana J Phys 2008, 71(3), 509-19.

Evolution of gluon distribution function from Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equation in next-to-leading order (NLO) at low-x is presented assuming the Regge behaviour of quark and gluon at this limit. We compare our results of gluon distribution function with MRST2004, GRV98LO and GRV98NLO parametrizations and show the compatibility of Regge behaviour of quark and gluon distribution functions with perturbative quantum chromodynamics (PQCD) at low-x.

4 illus, 17 ref

009436   Jafarizadeh M A;Behnia S;Faizi E;Ahadpour S (Theoretical Physics and Astrophysics Dep, Tabriz Univ, Tabriz 51664, Iran, Email: jafarizadeh@tabrizu.ac.ir) : Generalized N-coupled maps with invariant measure in Bose-Mesner algebra perspective. Pramana J Phys 2008, 70(3), 417-38.

Choosing a dynamical system with d different couplings, one can rearrange a system based on the graph with a given vertex dependent on the dynamical system elements. The relation between the dynamical elements (coupling) is replaced by a relation between the vertexes. Based on the E0 transverse projection operator, synchronization problem of an array of the linearly coupled map lattices of identical discrete time systems has been addressed. The synchronization rate is determined by the second largest eigenvalue of the transition probability matrix. Algebraic properties of the Bose-Mesner algebra with an associated scheme with definite spectrum has been used in order to study the stability of the coupled map lattice. Associated schemes play a key role and may lead to analytical methods in studying the stability of the dynamical systems. The relation between the coupling parameters and the chaotic region is presented. It is shown that the feasible region is analytically determined by the number of couplings (i.e. by increasing the number of coupled maps, the feasible region is restricted). It is very easy to apply our criteria to the system being studied and they encompass a wide range of coupling schemes including most of the popularly used ones in the literature.

34 ref

009435   Hegab N A;El-Mallah H M (Physics Dep, Faculty of Education, Ain Shams Univ, Roxy-Cairo, Egypt) : Optical properties of As₄₅Te₃₃Ge₁₀Si₁₂ thin films. J Optics 2008, 37(1), 29-40.

Several amorphous As₄₅Te₃₃Ge₁₀Si₁₂ thin films obtained by thermal evaporation onto glass substrates held at about 300K during the deposition process. Optical transmittance and reflectance spectra, at normal incidence were obtained in the wavelength range 500 - 2500 nm. The optical constants (the refractive index n, the absorption index k and the absorption coefficient a) have been calculated. The refractive index has anomalous behavior in the region of the fundamental absorption edge. Analysis of the refractive index has yielded optical dielectric constant œ,. The allowed optical transitions responsible for optical absorption were found to be nondirect transitions, with an optical energy gap of 1.00 eV for samples under test. The band tail, obeys Urbach's empirical relation. The effect of annealing on the optical energy gap is interpreted in terms of the density of states proposed by Mott and Davis.

8 illus, 1 table, 21 ref

009434   Hamed A M (Physics Dep, Sur College of Applied Science, P.O. Box 484, Postal Code 411, Sultanate of Oman, Email: amhamed73@hotmail.com) : Modeling of the fringe shift in multiple beam interference for glass fibers. Pramana J Phys 2008, 70(4), 643-48.

A quadratic model is suggested to describe the fringe shift occurred due to the phase variations of uncladded glass fiber introduced between the two plates of the liquid wedge interferometer. The fringe shift of the phase object is represented in the harmonic term which appears in the denominator of the Airy distribution formula of Fabry-Perot's interferometer. A computer program is written to plot the computed fringe shifts of the described model. An experiment is conducted using liquid wedge interferometer where the fiber of a nearly quadratic thickness variation is introduced between the two plates of the interferometer. The obtained fringe shift shows a good agreement with the proposed quadratic model. Also, it is compared with the previous theoretical shift based on ray optics of semi-circular shape.

4 illus, 13 ref

009433   Haffner H (Physics Dep, California Univ, Barkeley, CA 94720, USA, Email: hhaeffner@berkeley.edu) : Quantum computing with trapped ions. J Indian Inst Sci 2009, 89(3), 317-31.

Quantum information encoded in single trapped ions provides a promising avenue towards a scalable quantum computer. This contribution describes most of the necessary building blocks for such a device. Particular emphasis is given to the implementation of single-qubit and multi-qubit gate operations.

^iia9 illus, 140 ref

009432   Gupta A;Rao P M (Spectroscopy Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: pushpam@magnum.barc.ernet.in) : Numerical calculations of potential distribution in non-ideal quadrupole trap and simulations of anharmonic oscillations. Pramana J Phys 2008, 70(3), 457-70.

A quadrupole ion trap consisting of electrode structures symmetric about z-axis is an important tool for conducting several precision experiments. In practice the field inside the trap does not remain purely quadrupolar, and can be calculated using numerical methods. We have used boundary element method to calculate the potential inside the truncated as well as symmetrically misaligned quadrupolar ion trap. The calculated potential values are fitted to multipole expansion and the weights of multipole moments have been evaluated by minimizing the least square deviation. The higher-order multi-pole contribution in the fabricated hyperbolic electrodes due to truncation and machining imperfections is discussed. Non-linear effects arising due to the superposition of octupole moment manifest as anharmonic oscillations of trapped ions in the non-ideal Paul trap. Theoretical simulations of non-linear effects have been carried out.

10 illus, 2 tables, 28 ref

009431   Gruska J (Faculty of informatics, Masaryk Univ, Botanicka 68a, 60200, Brno, Czek Rapublik, Email: gruska@fi.muni.cz ) : From classical cryptography to quantum physics through quantum cryptography. J Indian Inst Sci 2009, 89(3), 271-82.

Goa of the paper is point out and to demonstrate large importance security issues (in a very broad sense) have for modern science, technology and society and to discuss briefly the main areas, problems and challenges of classical cryptography. Second goal is to survey some of the main problems, directions and challenges of quantum cryptography. The last goal is to review some of the main impacts the outcomes of quantum cryptography have for our understanding of quantum physics.

^iia 35 ref

009430   Gour A;Singh S;Singh R K;Singh M (Physics Dep, Barkatullah Univ, Hoshangabad Road, Bhopal-462 026, Email: atul_gour@rediffmail.com) : Pressure-induced phase transition and stability of EuO and EuS with NaCl structure. Pramana J Phys 2008, 71(1), 181-6.

Predicted the phase transition pressures and corresponding relative volume changes of EuO and EuS having NaCl-type structure under high pressure using three-body interaction potential (TBIP) approach. In addition, the conditions for relative stability in terms of modified Born criterion has been checked. Our calculated results of phase transitions, volume collapses and elastic behaviour of these compounds are found to be close to the experimental results. This shows that the inclusion of three-body interaction effects makes the present model suitable for high pressure studies.

i illus, 2 tables, 11 ref

009429   Gohain Barua A;Hazarika S;Saikia N M;Baruah G D (Physics Dep, Gauhati Univ, Guwahati-781 014, Email: agohainbarua@yahoo.com) : Biluminescence emissions of the firefly Luciola praeusta Kiesenwetter 1874 (Coleoptera : Lampyridae : Luciolinae). J Biosci, Bangalore 2009, 34(2), 287-92.

Recorded the in vivo emission and time-resolved spectra of the firefly Luciola praeusta Kiesenwetter 1874 (Coleoptera : Lampyridae : Luciolinae). The emission spectrum shows that the full width at half maximum (FWHM) value for this particular species is 55 mn, which is significantly narrower than the in vivo half-widths reported till now. The time-resolved spectrum reveals that a flash of about 100 ms duration is, in fact, composed of a number of microsecond pulses. This suggests that the speed of the enzyme-catalysed chemiluminescence reaction in the firefly for the emission of light is much faster than was previously believed.

5 illus, 18 ref

009428   Ghosh S;Avinash Singh (Physics Dep, Indian Institute of Technology, Kanpur-208 016, Email: gsap@iitk.ac.in) : Anisotropic Hubbhard model on a triangular lattice-spin dynamics in HoMnO₃. Pramana J Phys 2008, 70(1), 163-71.

The recent neutron scattering data for spin-wave dispersion in HoMnO₃ are well-described by an anisotropic Hubbard model on a triangular lattice with a planar (XY) spin anisotropy. Best fit indicates that magnetic excitations in HoMnOs correspond to the strong-coupling limit U/t >~ 15, with planar exchange energy J = 4t²/U ≈ 2.5 meV and planar anisotropy ΔU ≈ 0.35 meV.

3 illus, 25 ref

009427   Ghosh D;Roy S;Pal M;Pal A;Bhadra S K (Fiber Optics Laboratory, Central Glass and Ceramic Research Institute, CSIR, 196, Raja S.C. Mullick Road, Kolkata-700 032, Email: skbhadra@cgcri.res.in) : Index-guided photonic crystal fibers: study of fiber drawing parameters. J Optics 2008, 37(2), 72-7.

Reports the effect of drawing parameters in fabricating Microstructured Optical Fiber (MOF) or Photonic Crystal Fiber (PCF). PCFs have been fabricated by 'stack and draw' technique, both in double and single stage and hole diameter of 3-13 μm have been obtained. The salient parameters of PCF drawing, like the furnace temperature, preform feed rate, fiber draw speed and the differential pressure within the preform stack, are precisely studied and optimized to obtain the desired microstructure of the fiber. Furnace temperature and differential pressure play a critical role in controlling the shape and size of holes of the ultimate fiber. The spectral attenuation curve of a double-stage drawn PCF is obtained using a special measurement technique.

4 illus, 3 tables, 7 ref

009426   Gavai R V;Gupta S;Mukherjee S (Theoretical Physics Dep, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005, Email: smukher@physik.uni-bielefeld.de) : Lattice quantum chromodynamics equation of state: a better differential method. Pramana J Phys 2008, 71(3), 487-508.

Proposes a better differential method for the computation of the equation of state of QCD from lattice simulations, fn contrast to the earlier differential method, our technique yields positive pressure for all temperatures including the temperatures in the transition region. Employing it on temporal lattices of 8, 10 and 12 sites and by extrapolating to zero lattice spacing we obtained the pressure, energy density, entropy density, specific heat and speed of sound in quenched QCD for 0.9 ≤ T/T_c ≤ 3. At lemperatures comparisons of our results are made with those from the dimensional letion approach and also with those from a conformal symmetric theory.

7 illus, 2 tables, 44 ref

009425   Gautam S;Mitra S;Mukhopadhyay R (Solid State Physics Div, Bhabha Atomic Research Cintre, Mumabi-400 085, Email: mukho@barc.gov.in) : Molecular motion in restricted geometries. Pramana J Phys 2008, 71(4), 809-18.

Molecular dynamics in restricted geometries is known to exhibit anomalous behaviour. Diffusion, translational or rotational, of molecules is altered significantly on confinement in restricted geometries. Quasielastic neutron scattering (QENS) offers a unique possibility of studying molecular motion in such systems. Both time scales involved in the motion and the geometry of motion can be studied using QENS. Molecular dynamics (MD) simulation not only provides insight into the details of the different types of motion possible but also does not suffer limitations of the experimental set-up. Here we report the effect of confinement on molecular dynamics in various restricted geometries as studied by QENS and MD simulations. An example where the QENS technique provided direct evidence of phase transition associated with change in the dynamical behaviour of the molecules is also discussed.

6 illus, 25 ref

009424   Fujii Y (Quantum Beam Science Directorate & J-PARC Center, Japan Atomic Energy Agency (JAEA), tOKAI, Ibaraki 319-1195, Japan) : Basic to industrial research on neutron platform in Japan. Pramana J Phys 2008, 71(4), 617-22.

The co-location of reactor- and accelerator-based neutron sources offers a great opportunity for complementary use of steady and pulsed neutron beams in a wide variety of neutron science and technology areas ranging from basic research to industrial applications. In Japan, such a balance of two kinds of neutron sources has a long tradition and now we are entering into a new era with the commissioning of the world's most intense pulsed neutron beams at JSNS/J-PARC plus the existing JRR-3 reactor both co-located within 1 km of each other in Tokai. The joint operation of these neutron facilities in close proximity under a program called 'neutron platform', will allow neutron beam access not only to professional users, familiar with both pulsed and steady state techniques but also to first-time academics and industrial researchers to neutron scattering.

4 illus

009423   Feng W L;Zheng W C (Material Science Dep, Sichuan Univ, Chengdu-610 064) : Defect structure from the calculations of optical and electron paramagnetic resonance spectra for N_i<. Pramana J Phys 2008, 71(3), 573-8.

By calculating the optical spectrum band positions and EPR parameters (g factors, g||, g⊥ and zero-field splitting D) by diagonalizing the complete energy matrix of 3d⁸ ions in trigonal symmetry, the defect structure of Ni²⁺ centre in α-LiIO₃ crystal is studied. It is found that to reach the good fits of optical and EPR data between calculation and experiment, the Ni^{2+ ion should shift by Δz ≈ 0.298 Angustrum along C₃-axis and the O2- ions between the Ni2+ ion and Li+ vacancy (V_Li) should be displaced away from the V_Li by Δx ≈ 0.097 Angustrum because of the electrostatic interaction. The results are discussed.}

2 illus, 2 tables, 27 ref

009422   Feng W L (Applied Physics Dep, Chongqing Institute of Technology, Chongqing 400050, People Republic of China, Email: wenlinfeng@126.com) : Theoretical studies of the spin-hamiltonian parameters for the orthorhombic Pr<. Pramana J Phys 2008, 70(4), 705-9.

Theoretical studies of spin-Hamiltonian (SH) parameters associated with Pr⁴⁺ in Sr₂CeO₄ single crystals have been made by using the complete diagonalizing energy matrix method (CDM) for the 4f¹ electronic configuration. The calculated results are in excellent agreement with the experimental data. The negative signs of the anisotropic g_i-factors and hyperfine structure constants A_i (where i = || or ₉₄) for the orthorhombic Pr⁴⁺ ion in Sr₂CeO₄ are suggested from the calculations. By comparing the results obtained by the CDM with the experimental data, one finds it is valid to interpret the SH parameters for 4f¹ ions in crystals. The results are discussed.

1 table, 22 ref

009421   Erram V C;Gupta G (NO, Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai-410 218, Email: vinit_erram@yahoo.co.in) : Tectonic structure of the Guhagar-Chiplun region based on ground magnetic data. J Geophys 2009, 30(1-4), 93-8.

Morphometric data of the Konkan coast region of Maharashtra unfolds the presence of a number of NNW-SSE trending fractures. One of the prominent fractures, as clearly observed from satellite imagery is seen to be developed from the Vashishti in the North to the Shastri river in the South. In order to delineate the fractures and fault zones and to ascertain their depth, ground magnetic studies have been carried out in the Guhagar and Chiplun region. The ground magnetic data revealed the presence of some fractures parallel to the Arabian coast; prominent amongst them are at Rampur and Shringar Tali, having depths of 2.5 and 2.8 km respectively. It has been inferred that these fractures penetrate through the basaltic and the Dharwar rocks and form a part of the fracture system-paralleling fault.

4 illus, 17 ref

009420   Elahi P;Taghavi A;Gharaati A (Physics Dep, Payame Noor Univ, Shiraz, Iran, Email: pelahi@spnu.ac.ir) : Analytical investigation of temperature distribution in off-central diode-pumped lasers. Pramana J Phys 2008, 70(4), 649-56.

The influence of displacement of the pump source with respect to the crystal center on the thermal behavior of the laser crystal is studied analytically. Pump energy to be deposited into the pump region which has been slightly displaced with respect to the crystal center has been considered. An analytical expression for temperature distribution for such off-central diode-pumped laser is investigated. The results are then applied to the Nd : YAG and Nd : YVO₄ laser crystals and compared with the conventional diode-pumped lasers. We showed that in this special case, the temperature distribution equation in the off-central pumping convert to the conventional central pump scheme.

7 illus, 13 ref

009419   Dutta S;Pati S K (Theoretical Sci Unit and DST Unit on Nanosci, Jawaharlal Nehru Centre for Advanced Scientific Res Jakkur Campus, Bangalore-560 064, Email: swapan.jnc@gmail.com) : Electrical rectification. Resonance 2009, 14(1), 80-9.

The long-standing history and interesting properties of two isomeric organic molecules, their electrical conductance property and posible electronic device applications that exploit the unique characteristics associated with their structural aspects. Single molecule of azulene shows higher conductivity than naphthalene. The charge transfer from the seven-membered ring to the five-membered ring in azulene gives the system aromatic stability, making it dipolar. As a consequence, the conductance becomes asymmetric for forward and reverse bias, opening an efficient application of azulene as molecular rectifier in electronic device fabrication.

7 illus, 19 ref

009418   Dongare M L;Awatade M N;Shaligram A D (Elecronic Science Dep, S.M. Joshi College, Hadapsar, Pune-28) : Development of low cost instrument for measuring suspended solids in fermented wash. J Optics 2008, 37(2), 51-5.

An attempt has been made to develop a low cost system based on nephelometric principle for measurement of suspended particles in the effluent from Sugar factories and distilleries. The instrument uses a potential arrangement of two LDRs of 20mm in diameter, for compensating for inherent non-linearity of LDRs and providing a low cost alternative. The paperdescribes mathematical model and the experimental results.

4 illus, 5 ref

009417   Dey C C (Nuclear and Atomic Physics Div, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata-700 064, Email: chandicharan.dey@saha.ac.in) : Perturbed angular correlation spectrometer for material science studies. Pramana J Phys 2008, 70(5), 835-46.

A four-detector perturbed angular correlation (PAC) spectrometer has been developed with ultra-fast BaF2 detectors to acquire four coincidence spectra simultaneously, two at 180° and two at 90°. This spectrometer has double efficiency compared to that of a three-detector set-up. Higher efficiency is desirable for PAC studies in solid state physics where large number of coincidences are required to obtain the PAC spectra with good statistics and is particularly useful when the half-lives of the parent probe nuclei used for PAC measurements are ~2-3 days or less as in ¹¹¹In (2.8 d), ⁹⁹Mo (2.7 d) and ¹⁴⁰La (1.7 d). The performance of the spectrometer has been tested for the HfO₂ monoclinic crystal in the temperature range from 77 to 873 K and for the HfF_4.33H₂O crystal at room temperature. The polycrystalline HfO₂ has been synthesized from Hf metal by heating in air. The hydrated hafnium fluoride has been crystallized by dissolving Hf metal in 40% HF and drying slowly at room temperature.

5 illus, 16 ref