017817   Blochl P E;Forst C J;Schimpl J (NO, Clausthal University of Technology, Institute for Physics, Leibnizstr.10, D-38678 Clausthal-Zellerfeld, Germany) : Projector augmented wave method: ab initio molecular dynamics with full wave functions. Bull Mater Sci 2003, 26(1), 33-41.

A brief introduction to the projector augmented wave method is given and recent developments are reviewed. The projector augmented is an all-electron method for efficient ab initio molecular dynamics simulations with full wave functions. It extends and combines the traditions of existing augmented wave methods and the pseudopotential approach. Without sacrificing efficiency, the PAW method avoids transferability problems of the pseudopotential approach and it has been valuable to predict properties that depend on the full wave functions

2 illus, 37 ref

017816   Bhide M K;Kadam R M;Sastry M D;Singh A;Sen S; Manmeet Kaur;Aswal D K;Gupta S K (Radiochemistry Div, BARC, New Delhi-400 085) : Microwave absorption studies of MgB2 superconductor. Pramana J Phys 2002, 58(5-6), 799-802.

Microwave absorption studies have been carried out on MgB₂ superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ~ 10μm) samples suggested the absence of weak-link character. The filed dependent direct microwave absorption has been found to obey a √H dependence with two different slopes, which indicated a transition from strongly pinned lattice to flux flow regime.

017815   Bhattacharjee A;Ahmed M;Mookerjee A;Halder A (Physics Mathematics Dep, University of Dhaka, Dhaka 100, Bangladesh) : Effect of alloying on the electronic structure and magnetic properties of Fe, Co and Ni with Au and Ag. Bull Mater Sci 2003, 26(1), 199-205.

Self-consistent, augmented space reursion technique has been used to study the electronic structure and magnetic properties of alloys of the transition metals, Fe, Co and Ni with noble metals, Ag and Au. Effect of local environment and the hybridization between the constituent bands on the electronic and magnetic properties have been analysed.

9 illus, 1 tables, 13 ref

017814   Bhatia S N;Yassin O A (Dep of Phys, Indian Institute of Tech, Powai, Mumbai-400 076) : Effect of doping Ca on polaron hopping in LaSr 2 Mn 2 O 7. Pramana J Phys 2002, 58(5-6), 1061-3.

From the transport studies in teh bilayer manganites LaSr_2-xCa_xMn₂O₇, Founds the variable-range hopping model proposed by Viret et al to be inadequate to describe the transport of charge in these materials. The polarons appear to hop to their nearest neighbors with an activation energy, which in part is dependent on the magnetic interactions in the lattice.

1 illus, 7 ref

017813   Bhatia S N (Dep of Phys, Indian Institute of Tech, Mumbai-400 076) : Fluctuation conductivity in cuprate superconductors. Pramana J Phys 2002, 58(5-6), 817-25.

Measures the in-plane resistivity of Bi₂Sr_{2CaCu2O8+=δ and Tl2Ba2CaCu2O8+δ single crystals in the temperature range 70-300 K. The thermodynamic fluctuations in the conductivity of both the samples start around ~ 125 K. Finds the Lawrence and Doniach [1] model to be inadequate to describe the fluctuation conductivity in these materials. The modification suggested by Ramallo et al [4] where by the conductivity is enhanced due to the presence of two superconducting layers in each unit cell is also not adequate. Suggests the fluctuation conductivity to be reduced due to the reduction in the density of states (DOS) of the quasiparticles which results due to the formation of Cooper pairs at the onset of the fluctutation. The data agrees with the theory proposed by Dorin et al [5] which takes into account this reduction in DOS.}

5 illus, 10 ref

017812   Bhangale A R;Banerjee T;Raychaudhuri P; Bhagwat S S;Pai S P;John J;Bagwe V C;Shirodkar V S;Pinto R (Electronics Dep, K C College, Mumbai-400 020) : Peak effect in surface resistance at microwave frequencies in Dy-123 thin films. Pramana J Phys 2002, 58(5-6), 955-8.

A pronounced peak in the microwave (at frequency 9.55 GHz) surface resistance, R_s vs. T plot (where T is the temperature) has been observed in epitaxial DyBa₂Cu₃O_7-y superconducting thin films in magnetic fields (parallel to c-axis) in the range 2 to 8 KOe, and temperatures close to the superconducting transition temperature T_c(H). Data suggest that the nature of peaks observed in the two films is different, thereby indicating different defect structures in the films.

3 illus, 7 ref

017811   Basa D K;Raj S;Padhi H C;Polasik M;Pawlowski F (Dep of Physics, Utkal Univ, Bhubaneswar-751 004) : Studies on the valence electronic structure of Fe and Ni in Fe x Ni 1-x alloys. Pramana J Phys 2002, 58(5-6), 783-6.

K_β-to-K_<97> X-ray intensity ratios of Fe and Ni in pure metals and in Fe_xNi alloys (x=0.20, 0.50, 0.58) exhibiting similar crystalline structure have been measured following excitation by 59.54 kg V γ-rays from a ²⁴¹ Am point source, to understand as to why the properties of permalloy Fe_0.2 Ni_0.8 is distinct from other alloy compositions. It is observed that the valence electronic structure of Fe_0.2Ni_0.8 alloy is totally different from other alloys which may be attributed to its special magnetic properties.

3 tables, 10 ref

017810   Barat P;Sen P;Sinha B (NO, Variable Energy Cyclotron Center, 1/AF, Bidhan Nagar, Kolkata-700 064) : Enrichment of helium from hydrothermal gases. Curr Sci 2003, 84(12), 1519-24.

Extraction of gaseous helium from natural sources is potentially important for its use in frontier technologies and as an essential ingredient for advanced research. In India, an attempt is being made to harness helium from hot spring gases, since India lacks helium-bearing natural gases or petrolium reserves. In this effort, a helium-enrichment plant based on the principle of cryo-condensation have been described and fabricated. The plant has been commissioned successfully and is now in operation. Although the plant has been designed analytically, it is unique in the sense that it can enrich helium from 0.75 vol% to ″ 90.0 vol%. The basic principle, approach and philosophy of the plant have been discussed. The plant process has been computer-modelled to optimize and understand the relevance of the various process parameters. This model is capable of predicting the yield of enrichment efficiently for a pre-assigned setting of the process parameters.

^iia7 illus, 1 table,11 ref

017809   Banerjee T;Bhangale A;Kanjilal D;Pai S P; Pinto R (Tata Institute of Fundamental Res, , Homi Bhabha Road, Mumbai-400 005) : Peak effect at microwave frequencies in swift heavy ion irradiated YBa2Cu3O7- thin films. Pramana J Phys 2002, 58(5-6), 949-54.

The vortex dynamics at microwave frequencies in YBa₂Cu₃O₇-δ (YBCO) films have been studied. Observes a peak in the microwave (4.88 and 9.55 GHz) surface resistance in some films in magnetic fields up to 0.8 T. This is associated with the `peak-effect' phenomenon and reffects the order-disorder transformation of the flux line lattice near the transition temperature. Introduction of artificial pinning centers like columnar defects created as a result of irradiation with 200 MeV Ag ion (at a fluence of 4 x 10<sup>10</sup> ions/cm<sup>2</sup>) leads to the suppression of the peak in films previously exhibiting `peak effect'.

3 illlus, 12 ref

017808   Bancroft N J;Paul D M K;Intyre G M;Dewhurst C D;Cubitt R (Dep of Phys, Univ of Warwick, Convntry CV4 7AL, UK) : Magnetism and superconductivity in ErHi2B2C. Pramana J Phys 2002, 58(5-6), 907-11.

Performs a series of neutron diffraction experiments from the magnetic order and the vortex lattice in single crystal ErNi₂B₂C. The incommensurate magnetic structure develops additional even harmonics below the `ferromagnetic' ordering temperature, T_F of 2.3 K. This feature and the existence of rods of diffuse scattering suggest the development of ferromagnetic microdomain walls. The magnetic structure is very sensitive to the application of a magnetic field with changes in modulation vector and harmonic content. Studies of the vortex lattice show the presence of a 45° reorientation transition and a distorted hexagonal to square transition as a function of applied field. Further distortions of the vortex lattice occur and T_N, but no changes are seen at T_F.

3 illus 14 ref

017807   Balamurugan S;Gopalakrishnan I K;Yakhmi J V; Selvam P (Dep of Chem, IIT, Mumbai-400 076) : Magnetization study of mercurocuprate (Hg,Re)Sr2CuO4+. Pramana J Phys 2002, 58(5-6), 839-41.

The nominal (Hg_1-xRe_x)Sr₂CuO₄₊δ (x = 0.10 and 0.20) samples were synthesized at ~ 920°C in partial vacuum. the compound with x = 10 exhibits supercondictivity at ~ 54 K while the composition x = 0.20 is non-superconducting down to 5 K. On cooling below 10 K in an applied field of 4 kOe, the former causes a noticeable upturn in the field cooled (FC) magnetization signal. Such a change in magnetic response is also reflected in the magnetic hysteresis loop generated at 9 K. Attributes this effect to a paramagnetic contribution arising from Re in (hg, Re)-1201 phase.

3 illus, 9 ref

017806   Balamurugan D;Prasad R (Physics Dep, Indian Institute of Technology, Kanpur-208 016) : Ground state structures and properties of Si₃H_n (n=1-6) clusters. Bull Mater Sci 2003, 26(1), 123-5.

The ground state strucutres and properties of Si₃H_n (1≤n≤6) clusters have been calculated using Car-Parrinello molecular dynamics with simulated annealing and steepest descent optimization methods. Studies Cohesive energy per particle and ifrst excited electronic level gap of the clusters as a function of hydrogenation. Hydrogenation is done till all dangling bonds of silicon are saturated. The results show that over coordination of hydrogen is favoured in Si₃H_n clusters and the geometry of Si₃ cluster does not change due to hydrogenation. Cohesive energy per particle and first excited electronic level gap study of the clusters show that Si₃H₆ cluster is most stable and Si₃H₃ cluster is most unstable among the clusters considered.

3 illus, 17 ref

017805   Awana V P S;Karppinen M;Yamauchi H (Material and Structures Lab, Tokyo Institute of Tech, Yokohama 226-8503, Japan) : Comment on magnetism and superconductivity in rutheno cuprates: RuSr2GdCu2O8 and RuSr2Gd1.5Ce0.5Cu2O10. Pramana J Phys 2002, 58(5-6), 809-15.

4 illus, 14 ref

017804   Anwar Ali;Yasmin Akhtar;Hyder Soghra (Chemistry Dep, Jamia Millia Islamia (Central University), New Delhi-110 025) : Ultrasonic and volumetric studies of glycine in aqueous electrolytic solutions. J pure appl Ultrasonics 2003, 25(1), 13-18.

Densities, (p) and ultrasonic speeds, (u) of glycine (0.1-0.9M) in aqueous NaCl and MgCl₂ (0.02, 0.06 and 0.10 M) solutions have been measured at 303 K. From these experimental data isentropic compressibility (K_s), acoustic impedance (Z), hydration number (H_n), apparent molar volume (∅_v), apparent molar compressibility (∅_Ks), partial molar volume (∅⁰_v) and partial molar compressibility (∅⁰_Ks) at infinite dilution were calculated for the ternary systems. The data have been interpreted in terms of solute-cosolute and solute-solvent interactions. These results show that dipole-dipole and ion-solvent interactions are strong in glycine-aqueous NaCl and MgCl₂ solutions.

3 tables, 12 ref

017803   Angappane S;Sethupathi K;Rangarajan G (Phys Dep, Low Temperature Lab, Indian Institute of Tech, Chennai-600 036) : Electrical transport in La 1-x Ca x MnO3 thin films at low temperatures. Pramana J Phys 2002, 58(5-6), 1079-83.

Reports the low-temperature resistivity of the chemical solution deposited La_1-xCa_xMnO_{3 (x=0.2, 0.3 and 0.33) thin films on LaAlO3 substrates. The films were post annealed in atmosphere at 850°C. The low-temperature resistivity data has been studied in order to understand the nature of low-temperature conduction processes. The data showed T² dependence from 60 K to 120 K consistent with the single magnon scattering proess. The deviation from this quadratic temperature dependence at low temperatures is attributed to the collapse of the minority spin band. The two-magnon and electron-phonon processes contribute to scattering of carriers in the temperatute range above 120 K.}

3 illus, 1 table, 11 ref

017802   Andersen O K;Saha-Dasgupta T;Ezhov S (NO, Max-Planck Institute fur Festkorperforschung, D-70569, Stuttgart, Ger, ) : Third-generation muffin-tin orbitals. Bull Mater Sci 2003, 26(1), 19-26.

By the example of sp³ bonded semiconductors, 3rd-generation muffin-tin orbitals (MTOs) are illustrated. That they can be downfolded to smaller and smaller basis sets: sp³d¹⁰, sp³, and bond orbitals. For isolated bands, it is possible to generate Wannier functions a priori. Also for bands, which overlap other bands, Wannier-like MTOs can be generated a priori. Hence, MTOs have a unique capability for providing chemical understanding.

8 illus, 20 ref

017801   Ananda Kumari R;Chandramani R (Physics Dep, Bangalore University, Bangalore-560 0056) : Second harmonic generation efficiency in KDP crystal containing alkali halide. Indian J Phys-Pt A 2003, 77(4), 315-18.

Pure KDP and KDP crystals containing alkali halides with and without Au⁺ ions were grown from aqueous solution by slow evaporation. Second harmonic generation (SHG) efficiency measurements were carried out by Kurtz mehtod. The study justifies that the KDP crystals containing alkali halides have appreciable increase in SHG efficiency compared to pure KDP crystals.

1 illus, 1 tables, 8 ref

017800   Anand Kumar R;Chandramani R (Physics Dep, Bangalore University, Bangalore-560 056) : Ion transport in Au<. Bull Mater Sci 2003, 26(2), 255-9.

Undoped KDP and KDP crystals containing KI/NaI with/without gold doping were grown by slow evaporation technique. All the grown crystals were y-irradiated using ⁶⁰Co source. Electrical conductivity measurements were carried out on all these crystals perpendicular to teh unique direction before adn after y-irradiation. Results show that the conductivity of KDP crystals increase with teh addition of KI/NaI and with gold doping as well as upon rise in temperature. Computed values of activation energies from the conductivity measurements are given. For all the grown crystals, dielectirc constant is measured as a function of frequency.

9 illus, 2 tables, 11 ref

017799   Almulhem A A (Physics Dep, King Faisal University, P.O. Box 9149, Al-Ahssa, 31982, Saudi Arabia) : Theory of auger neutralization of positron at metal surface. Indian J Phys-Pt A 2003, 77(4), 341-5.

The transition rate in the process of positron neutralization via Auger mechanism during scattering from metal surfaces is studied. In this mechanism, a positron is neutralized by picking up an electron while another electron picks up enough energy to escape the potential barrier at the surface. A unitary transformation is introduced to the second quantized Hamiltonian. The bound state is described by a state orthogonal to all conduction band states of the metal. The theory is applied to the case of a positron, capturing an electron from aluminum surface while an Auger electorn is released. The neutralization rate is calculated as a function of distance from the surface. The transition rate for neutralization decays exponentially with distance from the surface. The general behaviour is similar to the ion neutralization at metal surfaces.

1 illus, 35 ref

017798   Ali K;Ahmed M G;Moussa M R;Rushdy M (NO, National Institute for Standards, Giza, Egypt) : Realization of gallium and indium fixed points on ITS-90 at national institute for standards (NIS) in Egypt. MAPAN 2003, 18(2), 51-6.

Melting point of Gallium and freezing point of Indium have been realized at the National Insitute for Standards (NIS) in order to fulfill the requirements of the International Temperature Scale of 1990. The gallium cell with its bath and the indium cell with its furnace were imported from NPL, UK. This work presents decriptions and measurements made to realize the two fixed points at NIS.

4 illus, 4 tables,5 ref

017797   Akerman J J;Rao K V (Dep of Materials Science-Tmfy-MSE, Royal Institute of Technology, S-100 44 stockholm, Sweden) : Low-field vortex dynamics in various high-T c thin films. Pramana J Phys 2002, 58(5-6), 985-93.

Presents a novel ac susceptibility technique for the study fo vortex creep in supercon ducting thin films. With this technique we study the dynamics of dilute vortices in c-axis oriented Y-123, Hg-1212, and Tl-1212 thin films, as well as a-axis oriented Hg-1212 thin films. Results on the Hg-1212 and Tl-1212 thin films indicated that dislocation-mediated plastic flux creep of single vortices dominates at low temperatures and fields. As the temperature (or the field) is increased, the increasing vortex-vortex interactions promote a collective behavior, which can be characterized by elastic creep with a non-zero μ exponent. Also, in some of these samples effects of thermally assisted quantum creep are visible up to 45 K in some of these samples. In Y-123 thin films, creep is found to be collective down to the lowest temperatures and fields investigated, while the quantum creep persists only to 10-11 K.

5 illus, 34 ref

017796   Ail U;Banerjee T;Bhangale A R;Kanjilal D; Pinto R (Dep of Materials Sci, Mangalore Univ, Mangalagangothri-574 199) : Effect of swift heavy ion irradiation on surface resistance of DyBa2Cu3O 7- thin films at microwave frequences. Pramana J Phys 2002, 58(5-6), 959-63.

Reports the observation of a pronounced peak in surface resistance at microwave frequencies of 4.88 GHz and 9.55 GHz and its disappearance after irradiation with swift ions in laser ablated DyBa₂Cu₃O_7-δ (DBCO) thin films. The measurements were carried out in zero field as well as in the presence of magnetic fields (us to 0.8 T). The films were irradiated using 90 MeV oxygen ions at Nuclear Science Centre, New Delhi at a fluence of 3 x 10¹³ ions/cm². Introduction of point defects and extended defects after irradiation suppresses the peak at 9.55 GHz whereas no supperession is observed at 4.88 GHz. These results and the vortex dynamics in the films at microwave frequencies before and after irradiation are discussed.

2 illus, 8 ref

017795   Abdellatif G (Physics Dep, Faculty of Science, Cairo University, Giza, Egypt) : Effect of Zn dilution on the electrical properties of Co_1-xZn_xLa_yFe_2-yO₄ (0.1≤x≤0.9 and y = 0.25). Indian J Phys-Pt A 2003, 77(4), 359-64.

The AC conductivity, dielectric constant ε' and dielectirc loss factor ε" were measured for the ferrite samples Co_1-xZn_xLa_yFe_2-yO₂ (0.1 ε x ε 0.9 and y = 0.25), prepared by standard ceramic technique. Z-ray and IR analysis were carried out to assure the formation of the spinel samples. The measurements were performed at different temperatures from 300 K upto =800 K. The conductivity results were discused on the basis of hopping mechanism of electrons and holes where the activation energy values are in the semiconducting region. The electron exchange between the different cations in the same equivalent lattice sites or in different sites, plays a role in the conductivity behaviour. The measurements of the dielectric constant ε' reveals a decrease with the increase of both frequency and Zn-content. The optimum condition of the critical concentration was x = 0.7. The decrease in viscosity and lattice vibration as well as the phonon generation help in increasing energy dissipation and in turn ε".

4 illus, 2 tables, 18 ref

016815   Wolschin G (NO, Universitat Heidelberg, D-69120 Heidelberg, Germany) : Strong coupling diffusion in relativistic systems. Pramana J Phys 2003, 60(5), 1035-8.

Different from the early universe, heavy-ion collisions at very high energies do not reach statistical equilibrium, although thermal model explain many of their features. To account for nonequilibrium strong coupling effects, a Fokker-Planck equation with time-dependent diffusion coefficient is proposed. A schematic model for rapidity distributions of participant baryons is set up and solved analyticaly. The evolution from SIS via AGS and SPS to RHIC energies is discussed. Strong-coupling diffusion produces double-peaked spectra in central collisions at the higher SPS momentum of 158 A GeV/c and beyond

1 illus

016814   Velkovska J (NO, Brookhaven National Laboratory, Bldg. 510C, Upton, NY 11973, USA) : Identified hadron production in √s = 130 GeV Au-Au collisions at relativistic heavy-ion collider. Pramana J Phys 2003, 60(5), 1011-15.

Identified π^+/-,K^+/-, p and p' transverse momentum spectra at mid-rapidity in √S_NN = 130 GeV Au-Au collisions were measured by PHENIX experiment at RHIC as a function of collision centrality. Average transverse moments increase with the number of participating nucleons (N_part)similarly for all particle species. The multiplicity densiites scale faster than N_part. The K^+/- and p^+/- yields per participant increase faster than the π^+/- yields. Combines the PHENIX neutral and charged pion measurement and find that in central collisions for p_T ≥ 2 GeV/c, p' and p yields are comparable to or even exceed the pion yields.

3 illus, 11 ref

016813   Vaidya R; (Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388 120) : Effect of pressure on electrical resistance of WSe₂ single crystal. Pramana J Phys 2003, 61(1), 183-6.

The results of electrical resistance measurements under pressure on single crystals of WSe₂ are reported. Measurements up to 8.5 GPa are carried out using Bridgman anvil set up and beyond it using diamond anvil cell (DAc) up to a pressure of 27 GPa. There is no clear indication of any phase transition till the highest pressure is reached in these measurements.

2 illus, 9 ref

016812   Talukdar B;Shamanna J;Ghosh S (Department of Physics, Visva-Bharati University, Santiniketan-731 235) : Canonical structure of evolution equations with non-linear dispersive terms. Pramana J Phys 2003, 61(1), 99-107.

The inverse problem of the variational calculus for evolution equations characterized by non-linear dispersive terms is analysed with a view to clarify why such a system does not folow from Lagrangians. Conditions are derived under which one could construct similar equations which admit a Lagrangian representation. It is shown that the system of equations thus obtained can be Hamiltonized by making use of the Dirac's theory of constraints. The specific results presented refer to the third-and fifth-order equations of the so-called distinguished subclass.

19 ref

016811   Sullivan J (NO, , P-25 MS-H846, Los Alamos National Laboratory, Los Almos, NM 87545, USA) : Global variables and identified hadrons in the PHENIX experiment. Pramana J Phys 2003, 60(5), 953-63.

PHENIX measurements related to global variables and identified hadrons are discussed. These include two-pion correlation, elliptic flow, and dN/dη. Measurements of event-by-event fluctuations in mean transverse momentum, mean transverse energy, and net charge are presented for particles within the PHINIX acceptance. The centrality dependence of these measurements is also discussed.

6 illus, 2 tables, 32 ref

016810   Sivermyr D (Department of Physics, Lund University, Box-118, 22100 Lund, Swedan) : Charged-particle multiplicity at mid-rapidity in Au-Au collisions at relativistic heavy-ion collider. Pramana J Phys 2003, 60(5), 983-6.

The particle density at mid-rapidity is an essential global variable for the characterization of nuclear collisions at ultra-relativistic energies. It provides information about the initial conditions and energy density reached in these collisions. The pseudorapidity densities of charged particle at mid-rapidity in Au-Au collisions at √S_NN = 130 and 200 GeV at RHIC (realtivistic heavy ion collider) have been measured with the PHENIX detector. The measurements were performed using sets of wire-chambers with pad readout in two central PHENIX tracking arms. Each arm covers one quarter of the azimuth in the pseudorapidity interval |η| <60> 0.35. Data is presented and compared with results from proton-proton collisions and nucleus-nucleus collisions at lower energies. Extrapolations to LHC energies are discussed.

3 illus, 9 ref

016809   Shukla P;Mohanty A K (Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085) : Spinodal decomposition : An alternate mechanism of phase conversion. Pramana J Phys 2003, 60(5), 1117-20.

The scenario of homogeneous nucleation is investigated for a first-order-quark-hadron phase transition in a rapidly expanding background of quark gluon plasma. It is found that significant supercooling is possible before hadronization begins. This study also suggests that spinodal decomposition competes with nucleation and may provide an alternative mechanism for phase conversion.

2 illus, 52 ref

016808   Sharma A (EP Division, CERN, 1211 Geneva 23, Switzerland) : Gaseous tracking at linear hadron collider : pushing the limits. Pramana J Phys 2003, 60(5), 865-75.

Gaseous detectors have been pushed to the limits when required to operate in the ferocious and aggressive rate environment of the new generation of HEP experiments. A great effort has resulted in the optimization and construction of large systems of gas detectors, some operational and some due for installation. Some examples are presented along with the impedients that have been overcome some open issues will be highlighted.

16 illus, 20 ref

016807   Seuring C;Scheidt E W;Bauer E (Lehrstuhl fur Experimentalphysik III, Universitat Augsburg, D-86159 Augsburg, Germany) : Field and pressure response of YB compounds close to a quantum critical point. Pramana J Phys 2002, 58(5-6), 731-6.

YbCu_5-xAl_x provides the possibility to tune ground state properties by a change of the valence due to the Cu/Al substitution, by pressure as well as by the application of a magnetic field. Near to the critical concentrating x_cr ~~ 1.5 non-Fermi-liquid properties (NFL) are obvious, obeying hyperscaling. If magnetic order sets in for x <62> 1.5, the application of moderate magnetic fields quenches order and again NFL features become evident. Hyperscaling in this case indicates strongly interacting spin fluctuation.

3 illus, 13 ref

016806   Sarkar S;Jan-E Alam;Hatsuda T (NO, Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata-700 064) : Low mass dileptons from Pb + Au collisions at 158 A GeV. Pramana J Phys 2003, 60(5), 1073-7.

The medium modification of vector meson properties in hot/dense hadronic matter and its role in explaining the CERES/NA45 dilepton data at different centralities are discussed.

2 illus, 11 ref

016805   Santosh Kumar;Yadav M P (Dep of P.G. Studies and Research in Physics and Electronics, R.D. University, Jabalpur-482 001) : Study of solar features causing GMSs with 250γ<60>H<60>400<103>. Pramana J Phys 2003, 61(1), 21-31.

The effect of solar features on geospheric conditions leading to geomagnetic storms (GMSs) with planetary index, A_p≥20 and the range of horizontal component of the Earth's magnetic field such that 250γ<60>H<60>400<103> has been investigated using interplanetary magnetic field (IMF), solar wind plasma (SWP) and solar geophysical data (SGD) during the period 1978-99. Statistically, it is observed that the maximum number of GMSs have occurred during the maximum solar activity years of 21st and 22nd solar cycles. A peculiar result has been observed during the years 1982, 1994 when sunspot numbers (SSNs) decrease very rapidly while numbers of GMSs increase. No distinct association between yearly occurrence of distributed days and SSNs is observed. Maximum numbers of distributed days have occurred during spring and rainy seasons showing a seasonal variation of distributed days. No significant correlation between magnitude (intensity) of GMSs and importance of H_α, X-ray solar flares has been observed. Maximum number of GMSs is associated with solar flares of lower importance, i.e. SF during the period 1978-93. H_α, X-ray solar flares occurred within lower helio-latitudes, i.e., (0-30)°N to (0-30)°S are associated with GMSs. No H_α, X-ray solar flares have occurred beyond 40°N or 40°S in association with GMSs. In helio-latitude range (10-40)°N to (10-40)°S, the 89.5% concentration of active prominences and disappearing filaments (APDFs) are associated with GMSs. Maximum number of GMSs are associated with solar flares. Coronal mass ejections (CMEs) are related with eruptive prominences, solar flares, type IV radio burst and they occur at low helio-latitude. It is observed that CMEs related GMS events are not always associated with high speed solar wind streams (HSSWSs). In many individual events, the travel time between the explosion on the Sun and maximum activity lies between 58 and 118 h causing GMSs at the Earth.

8 illus, 47 ref

016804   Sahu P K;Otuka N;Ohnishi A;Baldo M (Istitito Nazionale di Fisica Nucleare, Sezione di Catania, 57, Corsa Italia, I-95129 Catania, Italy) : Systematics of elliptic flow in heavy-ion collisions. Pramana J Phys 2003, 60(5), 1107-11.

Analyzes elliptic flow from SIS to RHIC energies systematically in a realistic dynamical casacade model. Compares results with the recent data from STAR and PHOBOS collaborations on elliptic flow of charged particles at midrapidity in Au + Au collisions at RHIC. In the analysis of elliptic flow at RHIC energy, finds a good fitting with data at 1.5 times a scaling from the subsequent parton scattering after the initial minijet production. In energy dependence of elliptic flow, notices re-hardening nature at RHIC energies. Both these two observations would probably imply the possible formation of quark-gluon plasma.

2 illus, 10 ref

016803   Sahu B;Agarwalla S K;Shastry C S (Dep of Physics, Khallikote College, Berhampur-760 001) : Fusion, resonances and scattering in <. Pramana J Phys 2003, 61(1), 51-66.

The variation of fusion cross-section (σ_fus) with energy in the ¹²C+¹²C collision is linked to the underlying resonance phenomenon through the behaviour of reaction cross-section (σ_r) of which σ_fus is taken as a part. The calculation of σ_fus is done through an energy-dependent imaginary potential in the optical model potential (OMP). Through dispersion relation, such an imaginary potential gives rise to energy-dependent real potential which is incorporated in the OMP. In the calculation, a form of potential for the nuclear part which has a soft repulsive in-built core is introduced based on similar works done earlier. The calculated results of σ_fus are used to explain the oscillatory structure, astrophysical S-factor and the decreasing trend at higher energies of the experimental σ_fus data in the case of ¹²C+¹²C system with remarkable success. The potential used for fusion calculation is tested for fitting elastic scattering data at some energies and is found good in forward angles. Further improvement of the fitting of these data is obtained by incorporating a coupling potential in the surface region. About twenty resonance are observed in the calculation in the specific partial waves and some of them are found close to the experimentlly identified resonances in ¹²C+¹²C reaction. Thus, an integrated and comprehensive analysis of fusion, resonance and scattering data in the best studied case of ¹²C+¹²C reaction within the framework of optical potential model has been provided.

8 illus, 2 tables, 21 ref

016802   Rindani S D (Theory group, Physical Research Laboratory, Navrangpura, Ahmedabad-380 009) : Single decay-lepton angular distributions in polarized e<. Pramana J Phys 2003, 61(1), 33-50.

In the presence of an electric dipole coupling of tt to a photon, and an analogous `weak' dipole coupling to the Z, CP violation in the process e⁺e^- → tt results in modified polarization of the top and the anti-top. This polarization can be analyzed by studying the angular distributions of decay charged leptons when the top or anti-top decays leptonically. Analytic expressions are presented for these distributions when either t or t decays leptonically, including O(α_s) QCD corrections in the soft-gluon approximation. The angular distributions are insensitive to anomalous interactions in top decay. Two types of simple CP-violating polar-angle asymmetries and two azimuthal asymmetries, which do not need the full reconstruction of the t ot t, are studied. Independent 90% CL limits that may be obtained on the real and imaginary parts of the electric and weak dipole couplings at a linear collider operating at √s=500 GeV with integrated luminosity 500 fb^-1 and also at √s=1000 GeV with integrated luminosity 1000 fb^-1 have been evaluated. The effect of longitudinal electron and/or positron beam polarizations has been included.

5 illus, 5 tables, 27 ref

016801   Ray R (NO, Institute of Physics, Sachivalaya Marg, Bhubaneswar-751 005) : Observing B-violation in relativistic heavy-ion collisions. Pramana J Phys 2003, 60(5), 1005-9.

Under certain situations, partons formed in heavy-ion collision experiments may expand out forming a shell-like structure. The partons in the outer shell subsequently hadronize, leaving a bubble of pure deconfined vaccum for a first-order quark-hadron phase transition. The bubble collapses and may eventually decay into particles which may thermalize to temperatures exceeding the electroweak transition temperature (~100 GeV) at LHC. This will lead to the possibility of unsuppressed electroweak baryon violating processes.

2 illus, 4 ref

016800   Ranbeer Singh; (Department of Physics, Panjab University, Chandigarh-160 014) : Dynamics of hydrogen in hydrogenated amorphous silicon. Pramana J Phys 2003, 61(1), 121-9.

The problem of hydrogen diffusion in hydrogenated amorphous silicon (a-Si:H) is studied semiclassically. It is found that the local hydrogen concentration fluctuations-induced extra potential wells, if intense enough, lead to the localized electronic states in a-Si:H. These localised states are metastable. The trapping of electrons and holes in these states leads to the electrical degradation of the material. These states also act as recombination centers for photo-generated carriers (electrons and holes) which in turn may excite a hydrogen atom from a nearby Si-H bond and breaks the weak (strained) Si-Si bond thereby apparently enhancing the hydrogen diffusion and increasing the light-induced dangling bonds.

3 illus, 15 ref

016799   Rami F (Institut de Recherches Subatomiques, IN2P3-CNRS, Universite Louis Pasteur, Strasbourg, France) : Charged particle density distributions in Au + Au collisions at relativistic heavy-ion collider energies. Pramana J Phys 2003, 60(5), 1095-8.

Charged particle pseudorapidity distribution have been measured in Au + Au collisions using the BRAHMS detector at RHIC. The results are presented as a function of the collision centrality and the center of mass energy. They are compared to the predictions of different parton scattering models and the important role of hard scattering processes at RHIC energies is discussed.

3 illus, 13 ref

016798   Rahaman F;Das S;Begum N;Hossain M (Department of Mathematics, JAdavpur University, Kolkata-700 032) : Higher-dimensional homogeneous cosmology in Lyra geometry. Pramana J Phys 2003, 61(1), 153-9.

Assuming a homogeneous perfect fluid with ρ = ρ(t) and p = p(t), exact solutions for cosmological models in higher-dimension based on Lyra geometry have been obtained. Depending on the form of metric chosen, the model is similar to FRW type. The explicit solutions of the scale factor are found via the assumption of an equation of state p = mρ, where m is a constant. Some astrophysical parameters are also calculated.

26 ref

016797   Pierog T;Drescher H J;Ostapchenko S;Werner K (NO, SUBATECH, 4 rue Alfred Kastler, BP 20 722, 44307 Nantes Cedex 3, France) : Simulating ultra-relativistic nuclear collisions: Screening corrections. Pramana J Phys 2003, 60(5), 1121-5.

A new approach was presented to treat hadronic interactions or the initial stage of nuclear collisions [1, 2]. It is an effective theory based on the Gribov-Regge formalism, where the internal structure of the Pomersons at high energies is governed by perturbative parton evolution, therefore the name parton-based Gribov-Regge theory. The main improvement compared to models used so far is the appropriate treatment of the energy sharing between the different elementary interactions in case of multiple scattering. It is clear that the above formalism is not yet complete. At high energies (RHIC, LHC), the multiple elementary interactions (Pomersons) cannot be purely parallel, they interact. So introduces multiple Pomerson vertices into the theory.

3 illus, 7 ref

016796   Patra B K;Srivastava D K (NO, Variable Energy Cyclotron Centre, 1.AF Bidhan Nagar, Kolkata-700 064) : Quarkonium suppression : Gluonic dissociation vs. colour screening. Pramana J Phys 2003, 60(5), 1089-93.

Evaluates the suppression of J/ψ production in an equilibrating quark gluon plasma for two competing mechanisms: Debye screening of colour interaction and dissociation due to energetic gluons. Results are obtained for S + S and Au + Au collisions at RHIC and LHC energies. At RHIC energies the gluonic dissociation of the charmonium is found to be equally important for both the systems while the screening of the interaction plays a significant role only for the larger systems. At LHC energies the Debye mechanism is found to dominate both the systems. While considering the suppression of directly produced ϒ at LHC energies, finds that only the gluonic dissociation mechanism comes into play for the initial conditions taken from the self screened parton cascade model in these studies.

3 illus, 16 ref

016795   Pandey B P;Van Der Holst B;Vranjes J;Poedts S (NO, Computational Plasma Dynamics Laboratory, Kettering University, Flint, MI-48504, USA) : Jeans instability of an inhomogeneous streaming dusty plasma. Pramana J Phys 2003, 61(1), 109-20.

The dynamics of a self-gravitating unmagnetized, inhomogeneous, streaming dusty plasma is studied. The presence of the shear flow causes the coupling between gravitational and electrostatic forces. In the absence of self-gravity, the fluctuations in the plasma may grow at the expense of the density inhomogeneity and for certain wavelengths, such an unstable mode may dominate the usual streaming instability. However, in the presence of self-gravity, the plasma inhomogeneity causes an overlap between Jeans and streaming modes and collapse of the grain will continue at all wavelengths.

2 illus, 18 ref

016794   Panda S;Panda B K;Fung S (NO, Institute of Physics, Sachivalaya Marg, Bhubaneswar-751 005) : Comparison of resonant tunneling in AIGaAs/GaAs parabolic and diffusion modified quantum wells. Pramana J Phys 2003, 61(1), 131-9.

Double barrier resonant tunneling diode using annealing induced diffusion modiified quantum well is proposed as a viable alternative to that using parabolic quantum well which requires complex techniques to fabricate it. The transmission coefficients are calculated using the hybrid incremental airy function plane wave approach. The room temperature current-voltage characteristics have been calculated using transmission coefficients. The current-voltage characteristics are found to be similar in both diodes.

4 illus, 29 ref

016793   Pal D;Sen A;Mustafa M G;Srivastava D K (Dep of PArticle Physics, Weizmann Institute of Science, Rehovot-76100, Israel) : The extent of strangeness equilibration in quark gluon plasma. Pramana J Phys 2003, 60(5), 1083-7.

The evolution and production of strangeness from chemically equilibrating and transversely expanding quark gluon plasma which may be formed in the wake of relativistic heavy-ion collisions is studied with initial conditions obtained from the self screened parton cascade (SSPC) model. The extent of partonic equilibration increases almost linearly with the square of the initial energy density, which can then be scaled with the number of participants.

3 illus, 10 ref

016792   Pal A;Pal T;Stokes D L;Vo-Dinh T (Dep of Civil Engineering, Indian Institute of Technology, Kharagpur-721-302) : Photochemically prepared gold nanoparticles: A substrate for surface enhanced Raman scattering. Curr Sci 2003, 84(10), 1342-6.

Gold nanoparticles have been prepared in aqueous Trinton X-100 medium using a new photochemical procedure. The characterization of the particle is made using transmission electron microscopy studies. The effects of analyte molecules such as pyridine and salt such as sodium chloride on the sol are studied. The photochemically prepared gold nanoparticles has been used successfully for surface enhanced Raman scattering studies with various types of compounds.

4 illus, 28 ref

016791   Padhakrishna V;Rajanna K;Desai S S;Shaikh A M (Dep of Instrumentation, Indian Institute of Science, Banglore-560 012) : Development and studies on microstrip detector. Curr Sci 2003, 84(10), 1327-36.

Development of gas microstrip detectors using thin film and lithography techniques have been reported. The detectors were tested for their performance for X-rays (5.9 keV) and a maximum gas gain of ″ 13,000 and best resolution of ″ 12 % was obtained. Factors affecting gain and resolution were investigated. The detectors were tested for their one-dimensional position sensitivity. Meandering resistive strips were used for charge division method. A position resolution of 0.48 mm was obtained.

17 illus, 1 table, 30 ref

016790   Oeschler H;Cleymans J;Redlich K (NO, Institut fur Kernphysik, Darmstadt University of Technology, D-64289,Germany) : Strange particle production from SIS to LHC. Pramana J Phys 2003, 60(5), 1039-44.

A review of meson emission in heavy-ion collisions at incident energies from SIS up to collider energies is presented. A statistical model assuming chemical equilibrium and local strangeness conservation (i.e. strangeness conservation per collision) explains most of the observed features, e.g. the different centrality dependences of pions and kaons. Furthermore, the independence of the K⁺ to K^- ratio on the number of participating nucleons observed between SIS and relativistic heavy-ion collider (RHIC) is consistent with this model. The observed maximum is the K⁺/π⁺ excitation function is also seen in the ratio of strange to non-strange particle production. The appearance of this maximum around 30 A GeV is due to the energy dependence of the chemical freeze-out parameters T and λ_B.

3 illus, 12 ref

016789   Navarra F S;Nielsen M (Instituto de Fisica, Universidade de Sao Paulo, C.P. 66318, 05389-970 Sao Paulo, Brazil) : Quark condensate effects on charmonium-pion scattering. Pramana J Phys 2003, 60(5), 1113-16.

The J/ψπ→ D^-D^*, D^-D, D^-*D^* and D^- D^* cross-section as a function of √s are evaluated in a QCD sum rule calculation. We study the Borel sum rule for the four point function involving pseudoscalar and vector meson currents, up to dimension four in the operator product expansion. We find that our results are close to those obtained with qaurk exchange models. Also finds that the quark condensate gives the main nonperturbative contribution to the cross-section.

1 illus, 11 ref