002218   Ghosh D;Deb A;Ghosh J;Bhattacharyya S;Patra K K (High Energy Physics Division, Jadavpur University, Calcutta-700 032) : Maximum fluctuations of pion density in relativistic heavy-ion interactions. Indian J Phys-Pt A 2001, 75(2), 197-200.

Maximum density fluctuation of charged pions in narrow pseudo-rapidity intervals in a Monte-carlo background has been studied using ¹⁶O-AgBr interactions data at 2.1 AGeV. The study indicates correlated pion emission in pseudo-rapidity intervals δη = 0.1 to 1. Further analysis suggests that a maximum charged particle density in a given pseudo-rapidity interval rises linearly with pion multiplicity.

^ssc2 illus, 9 ref

002217   Gambhir Y K (Department of Physics, Indian Institute of Technology, Powai, Mumbai-400 076) : Success and limits of the relativistic mean field description of nuclear properties. Pramana J Phys 2001, 57(2-3), 545-56.

Presents the current status and the perspectives of the relativistic mean field (RMF) description of various nuclear reperties. Some remarkable successful applications of RMF to several different class of nuclear properties are first sketched in a short list. Three selective applications of RMF to the : Loosely bound nuclei; Anti-proton (p) annihilation and spin observables (asymmetry parameter) in the parity-violating experiments with different motivations, are discussed in detail.

3 illus, 24 ref

002216   Feller J;Dasgupta D;Hinks D G;Ketterson J B; Sarma B K (Department of Physics, University of Wisconsin-Milwaukee, Milwaukee WI-53201, USA) : Velocity measurements at the metamagnetic transition in UPt₃. Indian J Phys-Pt A 2001, 75(4), 293-6.

The longitudinal ultrasonic attenuation and velocity were measured on a single crystal of UPt₃ in high magnetic fields up to field of 33 Tesla. Earlier measurements had reported a metamagnetic behaviour in the vicinity of 20 Tesla, where a pronounced dip in velocity (softening of the lattice) is seen. Simultaneous measurements at three frequencies during the same run were possible. A xmall dispersion in the velocity is seen at the metamagnetic transition. An additional structure is seen at a slightly higher magnetic field at lower temperatures. Also at temperatures below 100mK, quantum acoustic oscillations are seen in the ultrasonic velocity.

4 illus, 8 ref

002215   Facco A (NO, INFN Lab. Nazionali di Legnaro, Via Romea 4, 35020 Legnaro (PD), Italy) : Project SPES and LNL: accelerator challenges. Pramana J Phys 2001, 57(2-3), 623-37.

Project SPES (study and production of exotic nuclei) aims at the full design of a facility based on a 100 MeV, 1-30 mA CW proton Linac used for production of fission fragments from a uranium like-target by means of a neutron converter. Neutron rich ion species are extracted, selected, further ionized at high charge state, isotopically purified and then accelerated through a superconducting Linac at energies up to 20 MeV/A. SPES represents INFN's effort in view of the construction of the European next generation ISOL-type facility, which is expected to be operative by 2010. A conceptual design report of such a European facility is being prepared with the support of the European Commission, R and D activities, covering the most critical parts of the facility, have been partially started in the last two years, triggered by the French-Italian feasibility study of an accelerator driven system for waste transmutation.

9 illus, 29 ref

002214   El-Mashad M (Department of Physics, Faculty of Education, Ain Shams University, Roxi, Cairo, Egypt) : Pseudo-rapidity distribution for C<. Indian J Phys-Pt A 2001, 75(2), 169-73.

Pseudo-rapidity distribution of the shower particles in heavy ion collisions have been studied in the framework of the parton two - fireball model. The predicted distributions are compared to its corresponding experimentally measured distributions.

3 illus, 1 table, 11 ref

002213   El-Akkad F A (Department of Physics, Faculty of Science, Alexandria University, Alexandria, Egypt) : Polarization analysis of elastically scattered neutron by <. Indian J Phys-Pt A 2001, 75(2), 193-5.

Angular distribution of the polarized and elastically scattered neutrons from ⁹Be, has been studied using a modified form of Simon's theory. The differential cross section has also been analyzed using Blatt and Beidenharn's theory. The experimental data for neutrons in the energy range from 0.77 to 0.90 MeV have been fitted to the theoretical formulae. A reasonable agreement between the theoretical calculation and experimental data was found in both shape and magnitude of polarization and cross section.

^ssc1 illus, 14 ref

002212   Ejiri H (RCNP, Osaka University, Ibaraki, Osaka 567-0047, Japan) : Nuclear responses for neutrinos and neutrino studies by double beta decays and inverse beta decays. Pramana J Phys 2001, 57(2-3), 371-7.

Studies of nuclear responses for neutrinos (ν) by charge exchange reactions, ν masses by double beta (ββ) decays and of solar and supernova ν's by inverse β decays. Subjects discussed include : ν studies in nuclear micro-laboratories, ν masses studied by ββ decays of ¹⁰⁰Mo and nuclear responses for ββ - ν, solar and supernova ν's by inverse β decays and ν responses for ⁷¹Ga and ¹⁰⁰Mo, and MOON (molybdenum observatory of neutrinos) for spectroscopic studies of Majorana ν masses with sensitivity of mν <126> 0.03 eV by ββ decays of ¹⁰⁰Mo and real-time studies of low energy solar and supernova ν's by inverse β decays of ¹⁰⁰Mo.

1 table, 12 ref

002211   Dole B N;Kothawale R R;Shah S S (Department of Physics, Dr B A Marathwada University, Aurangabad-431 004) : The role of praseodymium in Y₁Ba₂Cu₃o₇ high temperature superconducting compounds. Indian J Phys-Pt A 2001, 75(4), 343-5.

Praseodymium is playing very interesting role in Y₁Ba₂Cu₃O₇ high T_c superconducting compounds when yttrium is partly replaced by praseodymium. Superconductivity is suppressed as Pr content is increased, there is no unique agreement in experimental results about the role of Pr in these compounds. XRD and Neutron Diffraction work is done on these compounds when yttrium is replaced upto 50% by Pr. Samples were prepared by solid state reaction method and chemical route. THe XRD and ND results on lattice parameters, orthorhomoboicity are reported in those samples and the observed differences in these results are discussed. The possible existence of Pr in 3+ and 4+ valence states is discussed on the basis of XRD, lattice parameter variations and orthorhombocity. The results indicate that the presence of praseodymium is in 3+ state. Decreasing in puckering and increase in Cu(1) - O(4) bonds is responsible for suppression of T_c.

6 illus, 2 table, 9 ref

002210   Detmold W;Leinweber D B;Melnitchouk W;Thomas A W;Wright S V (Department of Physics, Mathematical Physics and Special Research Centr, Adelaide University, Adelaide S A 5005, Australia) : New slant on hadron structure. Pramana J Phys 2001, 57(2-3), 251-61.

Rather than regarding the restriction of current lattice QCD simulations to quark masses that are 5-10 times larger than those observed as a problem, presents a wonderful opportunity to deepen the understanding of QCD. Just as it has been possible to learn a great deal about QCD by treating Nc as a variable, so the study of hadron properties as a function of quark mass is leading to a deeper appreciation of hadron structure. As examples cities progress in using the chiral properties of QCD to connect hadron masses, magnetic moments, charge radii and structure functions calculated at large quark masses within lattice QCD with the values observed physically.

5 illus, 29 ref

002209   Dattagupta S;Jayannavar A M;Narendra Kumar (S N Bose National Centre for Basic Sciences, , Block JD, Sector III, Salt Lake, Kolkata-700 098) : Landau diamagnetism revisited. Curr Sci 2001, 80(7), 861-3.

Problem of diamagnetism, solved by Landau, continues to pose fascinating issues which have relevance even today. These issues relate to inherent quantum nature of the problem, the role of boundary and dissipation, the meaning of thermodynamic limits, and above all, the quantum-classical crossover occasioned by environment-omdiced decoherence. The Landau diamagnetism provides a unique paradigm for discussing these issues, the significance of which is farreaching. Our central result connects the mean orbital magnetic moment, a thermodynamic property, with the electrical resistivity, which characterizes transport properties of material.

1 illus, 8 ref

002208   Datta U et al (NO, Gesellschaft fur Schwerionenforschung, Planckstr. 1, D-64291 Darmstadt, Germany) : Structure of light neutron-rich nuclei through Coulomb dissociation. Pramana J Phys 2001, 57(2-3), 535-44.

Coulomb breakup of neutron-rich nuclei around mass A <126> 20 has been studied experimentally using secondary beams (<126> 500-600 MeV/u) of unstable nuclei produced at GSI. The spectroscopic factor deduced for the neutron occupying s1/2 level in ¹⁵C ground state is consistent with the earlier reported value. The data analysis for Coulomb breakup of ¹⁷C ground state is consistent with the earlier reported value. The data analysis for Coulomb breakup of ¹⁷C shows that most of the cross section yields the ¹⁶C core in its excited state. For ^17-22O, the low-lying E1 strength amounts up to about 12% of the energy weighted dipole sum rule strength depending on neutron excess. The cluster sum rule limit with ¹⁶O as a core is almost exhausted for ^17,18O, while for more neutron rich isotopes the strength with respect to that limit decreases.

5 illus, 34 ref

002207   Datta S;Pal A K;Banerjee D (Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Calcutta-700 032) : Single crystal EPR studies on low dimensional ferromagnet cyclohexylammonium copper bromide. Indian J Phys-Pt A 2001, 75(4), 461-5.

The title compound (CHAB, in brief) is one of the best realisations of 1D, S = 1/2 Heisenberg like ferromagnet as evidenced by the specific heat studies and the existence of a 3D ordering temperature at 1.50 K. EPR linewidths in several crystallographic planes are measured at X-band, at room temperature and LNT temperature and analysed on the basis of the anisotropic exchange theories of McGregor and Soos and Ritter et al. to shed light on the spin dynamics in CHAB. The principal findings are Anisotropic antisymmetric exchange (1.47 cm^-1) i sof the same order of magnitude as that of the anisotropic symmetric exchange (1.21 cm^-10. This indicates that the well known Moriya relations regarding anisotropic exchange interaction requires revision. The z-direction of the anisotropic antisymmetric exchange is along the b-axis of the orthorhombic crystal i.e. at right angles to the chain axis (c-axis). Pronounced orthorhombicity in the anisotropic symmetric exchange tensor is indicated. Principal ionic g-factors are evaluated from crystalline g-factors and the nature of the ligand field in this ionic compound has been discussed.

7 illus, 2 table, 19 ref

002206   Datta S;Pal A K (Department of Solid State Physics, Indian Association for the Cultivation of Science, Kolkata-700 032) : Anisotropic heisenberg exchange in a 3-D copper compound. Indian J Phys-Pt A 2001, 75(4), 467-9.

X-band EPR investigations on copper malonate dihydrate are carried out in the temperature range 300K-77K. Although two types of Cu(II) ions having square bipyramidal and square pyramidal coordinations are present in the crystal only a single-line spectrum having Lorentizian lineshape is observed in all directions of the crystal in the magnetic field range, 0-8000Oe employed in the experiment. The linewidth varies in the range 85-117Oe, having maximum value along crystallographic c-axis. To evaluate the various interactions responsible for anisotropic linewidth in the principal crystallographic planes, the fitting of linewidth is done, following well known linewidth experession of Anderson and Weiss applicable for 3D magnetic solids. Additional contribution from hyperfine interaction is also considered but the fitting is not at all satisfactory. However, It has been shown that introduction of anistropic Heisenberg exchange (J) in the linewidth expression of the form J = J_a cos² α+J_c sin² α (where J_a and J_c are the exchange parameters along a- and c-directions respectively and α is the angle between the applied magnetic field and a-direction) has provided excellent fitting of linewidth in (010) plane. Similar agreement in fitting linewidth anisotropy in (100) plane has been obtained using a similar expression of the anisotropic Heisenberg exchange.

2 illus, 3 table, 12 ref

002205   Dasgupta D;Feller J R;Sarma B K (Department of Physics, University of Wisconsin-Milwaukee, 1900 E Kenwood Blvd, Milwaukee, Wisconsin-532 11, USA) : Ultrasonic attenuation changes near the superconducting and melting transition temperatures in a twinned YBa₂ Cu₃O_{7-δ single crystal.} Indian J Phys-Pt A 2001, 75(4), 323-6.

Using Sampled Continuous Wave technique and an unique bonding of the sample to the transducer to achieve optimal coupling, quasi free oscillations are set up in a transducer + sample oscillator system using low frequency RF sigbaks Under optimal coupling conditions, the acoustic energy dissipation is primarily in the crystal and is monitored through the changing Q of the composite oscillator. Ultrasonic experiments performed on a twinned single crystal of YBa₂Cu₃O7-δ was able to reveal the superconducting transition in the bulk of the material and also the melting transitions in the flux lattice system in presence of an external magnetic field. The results obtained with this techniquem using low frequency and low excitation amplitude, points towards sampled CW technique to be a very sensitive and an alternative experimental probe for small HTS single crystals.

3 illus, 8 ref

002204   Das D;Mukhopadhyay P K;Mukherjee G D; Chintalapudi S N;Mookerjee A (Inter University Consortium for DAE Facilities, , LB 8, Setor III, Bidhannagar, Calcutta-700 098) : <. Indian J Phys-Pt A 2001, 75(4), 471-3.

Disordered magnetic system NiMo is investigated in the critical region (Mo concentration 10 and 11 wt %) using Mossbauer spectroscopy as a local probe. ⁵⁷Co activity has been diffused in the alloy and is used at the source while stainless steel is used as standard absorber. Mossbauer spectrum of the alloy showed a sharp singlet at room temperature which indicates that Co-57 atoms have gone to the substitutional site. Below 200K, Mossbauer spectra indicate complicated hyperfine interactions and more than one magnetic phase in the samples. Mossbauer results are corroborated by ac susceptibility, resistivity and positron annihilation Doppler broadening measurements.

5 illus, 4 ref

002203   Das C;Chaudhuri P;Sood A K;Krishnamurthy H R (Department of Physics, Indian Institute of Science, Bangalore-560 012) : Laser-induced freezing in 2-d colloids. Curr Sci 2001, 80(8), 959-71.

Dielectric colloid particles prefer occupying the intensity maxima of an applied stationary interference pattern of laser beams. A 2-d system of colloidal liquid freezes to form a triangular lattice structure when the external laser modulation is in 1-d and the period of the intensity maxima is commensurate to that of the triangular lattice. In this article we review our recent simulation results on this phenomenon of laser-induced freezng.

12 illus, 1 table, 36 ref

002202   Dang N D;Kim Au V;Suzuki T;Arima A (RI-Beam Factory Project Office, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan) : E1 resonances in neutron-rich nuclei within the phonon damping model. Pramana J Phys 2001, 57(2-3), 505-18.

Quasiparticle representation of the phonon damping model (PDM) is developed to include the superfluid pairing correlations microscopically. The formalism is applied to calculate the photoabsorption and the electromagnetic (EM) differential cross sections of E1 excitations in neutron-rich oxygen and calcium isotopes. The calculated photoabsorption cross sections agree reasonably well with the available data for ^16,18O and ^40,48Ca. The results of calculations show that the change of the fraction of the E1 integrated strength in the region of pygmy dipole resonance (PDR) as a function of mass number A with increasing neutron number N is in agreement with the recent experimental data, and does not follow the prediction by the simple cluster model. The EM differential cross sections obtained within PDM in this work show prominent PDR peaks below 15 MeV for ^20,22O in agreement with the recent experimental observation. It is also shown that, using low-energy RI beams at around 50-60 MeV/nucleon, one can observe clean and even enhanced PDR low-energy without the admixture with the GDR in the EM differential cross sections of neutron-rich nuclei.

10 illus, 31 ref

002201   Choudhury R K (Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085) : Recent studies in heavy ion induced fission reactions. Pramana J Phys 2001, 57(2-3), 585-600.

From the various investigations carried out in the past years, it is now well recognized that there is large scale damping of collective modes in heavy ion induced fission reactions, which in other words implies that nuclear motion is highly viscous. In recent years, there have been many experimental observations in heavy ion induced fission reactions at medium hombarding energies, which suggest possible occurrence of various non-equilibrium modes of fission such as quasi-fission, fast fission and pre-equilibrium fission, where some of the internal degrees of freedom of the nucleus is not fully equilibrated. Carried out extensive investigations on the fission fragment angular distributions at near barrier bombarding energies using heavy fissile targets. The measured fragment anisotropies when compared with the standard saddle point model (SSPM) calculations show that for projectile-target systems having zero or low ground state spins, the angular anisotropy exhibits a peak-like behaviour at the sub barrier energies, which cannot be explained by the SSPM calculations. For projectiles or targets with large ground state spins, the anomalous peaking gets washed out due to smearing of the K-distribution by the intrinsic entrance channel spins. Recently studies have been carried out on the spin distributions of fission fragments through the gamma ray multiplicity measurement....

5 illus, 46 ref

002200   Choudhury D K;Deshamukhya A (Department of Physics, Gauhati University, Guwahati-781 014) : Non-singlet structure function at high x and neutrino scattering. Indian J Phys-Pt A 2001, 75(2), 175-80.

Reports an approximate solution of DGLAP equation appromixated at high x for non-singlet structure function and comment on uniqueness problem. Apply the formalism to the CCFR neutrino structure function data of xF3(x, Q²) and suggest a phenomenological form of it using Gross Llewellyn Smith Sum Rule. Higher twist effects are also incorporated in the analysis.

4 illus, 34 ref

002199   Chandra B P;Pandey R K;Jain R (Department of Post Graduate Studies and Research in Physics and Electr, Rani Durgavati University, Jabalpur-482 001) : Photoplastic effect in coloured alkali halide crystals. Indian J Phys-Pt A 2001, 75(4), 443-7.

The proposed theory is able to explain temporal, deformation, strain-rate, spectral, light intensity, coloration, dimension and thermal characteristics of PPE, PPE can be used to determine the life time of the dislocation captured F¹-centres in crystals and the pinning time of dislocations. It is shown that the lifetime of dislocation-captured F¹-centres is longer as compared to the lifetime of normal F¹-centres, i.e. the dislocation non-captured F¹-centres present in the bulk.

5 illus, 15 ref

002198   Chakrabarti S;Sarkar R L (Department of Physics, University of Kalyani, Kalyani-741 235) : Possible co-existence of superconductivity and magnetism in heavy fermion systems. Indian J Phys-Pt A 2001, 75(4), 389-91.

The Periodic Anderson Model with an exchange induced non-phononic pairing interaction is considered to study the possible co-existence of superconductivity and magnetism in a heavy fermion system. Various two-site states with spin are used as basis. Entropy is calculated and it is found to be lowered giving a signature of possible ordering. It is found that there is a critical hopping below which ordering starts and the ordering temperature has a dependance on the exchange parameter J.d-d and f-f pair densities and intersite spin correlations are obtained and their variations with the correlation U and the exchange parameter J are studied. Co-existance of two phases are observed with a certain range of values of J. It is found that the nature of co-existence is sensitivity to the strength of hybridization and is fairly independent of the strength of the strength of correlation. Results are compared with the current status of the concept.

5 illus, 16 ref

002197   Chakrabarti S;Goswami K;Chakravorty J N (Condensed matter Physics Research Centre, Department of Physics, , Jadavpur, Calcutta-700 032) : Microwave reflection antennas - a comparative study. Phys Teacher 1997, 39(2), 35-9.

The theory and descriptions of different types of reflection antenna in the microwave region are presented. A typical microwave reflection antenna based on diffraction principle has also been suggested. Some results which give best performance in different microwave propagation window frequencies have been discussed in this context.

14 ref

002196   Chaddah P;Roy S B (Low Temperature Physics Laboratory, Centre for Advanced Technology, Indore-452 013) : Vortex matter and its phase transitions. Curr Sci 2001, 80(8), 1036-42.

Mixed state of type II superconductors has magnetic flux penetrating the sample in the form of vortices, with each vortex carrying an identical quantum of flux. These vortices generally form a triangular lattice under weak mutually repulsive forces; the lattice spacing can be easily varied over many orders of magnitude by varying the external magnetic field. The elastic moduli of this lattice are small and this soft vortex matter can undergo phase transitions like normal matter, but with thermal functions and underlying defects playing an important role. Discusses experimental studies on vortex matter phase transitions, with some emphasis on DC magnetization measurements investigating the nature of the phase transition.

5 illus, 65 ref

002195   Burghate D K;Deogaonkar V S (P G Department of Physics, Shri Shivaji Science College, Amravati-444 603) : AC-conductivity of lead-bismuth-titanate glasses. Indian J Phys-Pt A 2001, 75(4), 423-7.

The ac-conductivity of five samples of lead-bismuth-titanate glasses have been measured at various temperatures and frequencies. It is observed that, the activation energy for dc-conductivity increases with decrease in PbO concentration at temperature 533K. The ac-conductivity follow the relation σ (ω)=Aω^s (where A is constant and S is exponent). The values of the exponent (S) has been evaluated from the plot of log σ(ω) versus log ω. It is found that the values of S decreases with decrease in PbO composition except for the glass BX1. Existing theories of ac-conduction have been analysed for interpretation of the results. Values of the density of state at the Fermi level for different composition of glasses has the order of 10²⁰ eV^-1 cm^-3 (considering α-electron wave function decay constant equal to 0.9 A^-1 evaluated from the log σdc versus hopping distance R) which suggest that the conduction is in localized states near the Fermi level. It is observed that the ac-conductivity increases with frequency. THe value of exponent (S) has been calculated and was found to be less than 1. The results of ac-conductivity are discussed on the basis of QMT model for the preset glass system.

5 illus, 2 table, 18 ref

002194   Blumenfeld Y;Khan E;Marechal F;Suomijarvi T (NO, Institut de Physique Nucleaire, IN2P3-CNRS, 91406 Orsay, France) : Proton scattering from unstable nuclei. Pramana J Phys 2001, 57(2-3), 493-504.

Recent improvements in the intensities and optical qualities of radioactive beams have made possible the study of elastic and inelastic proton scattering on unstable nuclei. The design and performances of an innovative silicon strip detector array devoted to such experiments are described. The quality of the data obtained are illustrated with recent results obtained at the GANIL facility for unstable oxygen, sulfur and argon isotopes. Methods to analyse the data using phenomenological and microscopic optical model potentials are discussed.

8 illus, 20 ref

002193   Bhattacharjee A;Miyazaki Y;Feyerherm R; Steiner M;Sorai M (Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka-560 043) : Magnetic and heat capacity studies of a molecule-based material NBu₄[Fe<. Indian J Phys-Pt A 2001, 75(4), 399-404.

The magnetisation and heat capacity studies of ferrimagnetic molecule-based material NBu₄[Fe^IIFe^III(ox)₃] (Bu = n-butyl, ox = oxalate) were made. The magnetization studies demonstrated the negative magnetization phenomenon in the field cooled mode below 30 K under magnetic fields lower than 5 kOe. A magnetic field dependence of the compensation temperature was observed. The absolute value of saturation magnetization, estimated from the field dependence of the field cooled magnetization at 5 K was observed to be 0.07 μ_B / mole, which was only the 7% of the theoretically expected value at 0 K. The adiabatic heat capacity calorimetry detected two phase transitions at 43.3 K was due to the ferrimagnetic transition, whereas that at 217 K was assigned to an order-disorder phase transition due to increasing conformational change of the organic cation. The sum of the gain in entropies (= 3.31 R) corresponding to the heat capacity anomalies at 43.3 K and 16.3 K is very close to the expected magnetic entropy R In 30 (= 3.4 R) considering the spin multiplicity of high spin Fe^III and Fe^II ions. The small heat capacity anomaly at 16.3 K seems to arise from a spin glass like disordered state at low temperatures.

6 illus, 20 ref

002192   Bhattacharjee A;Feyerherm R;Steiner M (Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan) : Spin glass like behaviour of mixed-metal molecule-based magnetic material : NBu4Co<. Indian J Phys-Pt A 2001, 75(2), 127-30.

Temperature variation of magnetisation of oxalate-bridged molecule based magnetic material NBu4Co^II[Fe^III0.5Cr^III0.5(ox)3< D>], (N Bu4 = n-(C4H9)4⁺ = tetra-n-butyl ammonium ion, ox^2- = oxalate ion) was studied in 5-3000 K range under different magnetic field conditions. This material was found to be ferrimagnetic with TN = 20 K and exhibited some spin glass like behaviour below the magnetic transition temperature. A hump was apparent in the field dependence of isothermal remnant magnetisation and thermal remnant magnetisation studies. Possible reason for the spin glass like behaviour has been explored. The results have been compared with those of some analogous materials.

3 illus, 17 ref

002191   Bhatt R M;Gairola R P (Birla Campus, HNB Garhwal University, , Srinagar Garhwal-246 174) : Simulation analysis for the lattice thermal conductivity of YBCO superconductors. Curr Sci 2001, 80(7), 864-7.

Theory of Callaway for the lattice thermal conductivity, is extended to include the interference scattering between point defect and 3-phonon Umklapp-scattering (U-scattering). The experimental measurements of Ravindran and co-workers, in which radiation loss effects are minimized have been fitted by varying the parameters for boundary, sheet-like fault, point defect, 3-phonon scattering and the new scattering (interference scattering) terms. Since a large amount of disorder is present in YBCO samples, as emphasized by Kaiser, the interference scattering plays an important role in describing the phonon conductivity of these materials, particularly near the low temperature maximum. In the high temperature region (T<62>150 K), where radiation losses become significant, the 3-phonon U-scattering term with exponential temperature dependence, leads to a good agreement with experimental data for the three different samples of YBCO superconductors.

3 illus, 2 table, 18 ref

002190   Banerjee A;Chaudhuri B K;Rozenberg E (Department of Solid State Physics, Indian Association for the Cultivation of Science, Calcutta-700 032) : Effect of Cr doping on the transport properties of La_0.5Pb_0.5Mn_1-xCr_xO₃. Indian J Phys-Pt A 2001, 75(4), 475-7.

The influence of chromium doping on the magneto-transport properties of La_0.5Pb_0.5Mn_1-xCr_xO₃ is studied for a wide range of doping concentration (x). Cr is doped at the Mn site of La_0.5Pb_0.5MnO₃. A systematic change of different physical parameters such as metal-insulator transition temperature (T_mi), resistivity (ρ) and the value of magnetoresistance (MR) have been observed with increase of doping content in the base material. Both ,114> (T_mi) and ρ _{room temp} show greater values in the doped samples but the effect of Cr doping suppresses the resisivity peak to a lower temperature. Fox = 0.3, we obtain a peak in the ρ-T curve which is in sharp contrast to the result reported by Cabeza et al. This difference in our result it considered to be due to the presence of Pb in our samples. One may also conclude that T_mi and the overall conductivity of this system depend strongly on Cr doping. This is also verified from the observed change of several model parameters obtained from the fitting of the high temperature (above T_mi) conductivity data with polaron hopping model.

4 illus, 2 table, 17 ref

002189   Bandyopadhyay S;Sen S K (Department of Materials Science, Indian Association for the Cultivation of Science, Calcutta-700 032) : Effect of series resistance and standard deviation on the nonlinear behavior of I-V characteristics in metal-conducting polymer schottky diode. Indian J Phys-Pt A 2001, 75(4), 385-8.

The current voltage characteristics of metal/conducting polymer Schottky diode are simulated using a Gaussian distribution of barrier height (BH), with a linear bias dependence. The calculated data are analyzed in order to get the effect of standard deviation (SD) on BH, activation energy and the ideality factor over the temperature range 100-300K. The analysis has been carried out-using appropriate values of average of zero bias BH (φ_bo), and the two constant terms (γ and ξ are selected from our earlier work on I-V measurements of metal/conducting polymer (Sn/PAN-PC) film. While the abnormal decrease of BH is due to SD, bias dependence of SD adn BH account for the higher ideality factors at low temperatures. Also, the role played by diode series resistance for the nonlinearity of the In(I)-V plots is discussed.

7 illus, 5 ref

002188   Babita Devi;Jain I P (Material Science Laboratory, Centre for Non Conventional energy Resources, University of Rajasthan, Jaipur-302 004) : Resistance change during cyclic hydrogen charging and discharging in LaNi₅ thin films. Indian J Phys-Pt A 2001, 75(4), 393-7.

Hydrogen storage alloys are very important due to their variety of technological applications. Bulk alloys have been studied extensively and research field of thin film hydride is relatively new. In present work thin film of LaNi₅ of thickness 1300 Angstrom were obliquely deposited at Θ =0°, 30°, 45°, 60° and 75° by flash evaporation technique onto glass substrate at a pressure 2 x 10^-5 Torr and at room temperature. It was found that the activation of LaNi₅ thin films for hydrogen absorption is fairly easy compared to the bulk material. The effect of number of hydrogen absorption/desorption cycles on the resistance of LaNi₅ increases during hydrogen absorption and decrease during desorption. The resistance change in subsequent cycles was found to decrease and finally reaches equilibrium state denoting the saturation stage of thin films due to hydrogen absorption.

7 illus, 31 ref

002187   Auslender M I;Rozenberg E;Gorodetsky G (Department of Electrical Engineering and Computer, Ben Gurion University of the Negev POB 653, 84105, Beer-Sheva, Israel, ) : Low-temperature minimum of resistivity and magnetoresistance in ceramic manganites : an integrain tunneling model versus experiment. Indian J Phys-Pt A 2001, 75(4), 317-21.

Measurements of magnetoresistivity and magnetization were carried out on a ceramic sample of La_0.5Pb_0.5MnO₃ and a sample of La_0.5Pb_0.5MnO₃ containing 10 at. % of Ag in a dispersed form. The resistivity (ρ) at zero applied magnetic field exhibits a shallow minimum at the temperature T<126>25-30 K. This minimum shifts towards lower T upon applying a magnetic field (H) and disappears at a certai field H_cr), while residual resistivity decreases notably with increasing of H. It is found that a model of enhanced Coulomb interaction in disordered metals is not adequate for decribing of such behavior of ρ in the presence of H. It seems that the proposed model of charge-carrier tunneling between antiferromagnetically coupled grains accounts for the results obtained.

4 illus, 23 ref

002186   Ansari A (NO, Institute of Physics, Bhubaneswar-751 005) : Nuclear structure at high excitation energies. Pramana J Phys 2001, 57(2-3), 459-67.

Deals with the investigation of hot GDR and quadrupole shapes of ^{106, 120}Sn isotopes as a function of temperature and spin utilizing cranked quadrupole-quadrupole model interaction hamiltonian in the linear response theory and static path approximation to the grand canonical partition function.

3 illus, 30 ref

002185   Ahmad I;Madani J H (Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia) : On determination of phase function from phase shift. Indian J Phys-Pt A 2001, 75(2), 201-04.

Accuracy of the phase function χ^(b) as determined from the phase shift δl using the relation χ^(B)=2χl<124> l=kb-1/2 has been studied taking the example of ¹²C-¹²C system in which case the phase function so obtained has been used recently to determine the optical model potential by inversion in the energy range of about 0.14 - 1.0 GeV. The phase function as determined from the above prescription has been found and differs significantly from the realistic one at lower side of the energy range.

^ssc5 illus, 14 ref

001262   Zakaria A K M;Sikder S S;Asgar M A;Amanullah Choudhury M (NO, Institute of Nuclear Science and Technology, Atomic Energy Research Es, G.P.O. Box-3787, Dhaka 1000, Bangladesh) : Effect of aluminum substitution on the magnetic properties of iron-boron-silicon amorphous alloy. Indian J Phys-Pt A 2001, 75(3), 219-23.

Specific magnetization of as-quenched amorphous ribbon of compositions Fe₈₂Si₈B₁₀ and Fe₈₂Al₃Si₅B₁₀ have been measured at room temperature using Vibrating Sample Magnetometer (VSM). The latter composition was formed by replacing three out of the eight silicon atoms by Al atom per formula unit. Initial permeability (°_i), frequency dependence of the complex permeability μ_i(f) and relative quality factor (μ_i / tan δ) have been measured in the frequency range 1 KHz to 13 MHz. The measurements have been carried out for the as-quenched and annealed conditions using a LCR bridge. It is observed that due to aluminum substitution magnetization increases while initial permeability and relative quality factor decreases in the low field region. Initial permeability increases with increasing annealing temperature of the ribbons upto a certain value and then decreases for both the compositions.

8 illus, table, 13 ref

001261   Wagh D K;Avashia A (Department of Applied Mathematics, Shri G.S. Institute of Technology and Science, Indore-452 003) : Investigation of the flow of non-Newtonian magnetic fluid in a pipe of circular cross-section and experimental method for determining the rheogram of the magnetic fluid based on this investigation. Indian J Theor Phys 1999, 47(3), 253-7.

An attempt has been made to investigate the problem of the follow of non-Newtonian magnetic fluid in a rigid circular pipe. The analysis is based on the basic laws of fluid mechanics. Based on these investigations, an experimental method to obtain the rheogram of the magnetic fluid subject to magnetic field gradient is proposed.

8 ref

001260   Vyas P R;Pandya C V;Pandya T C;Gohel V B (Department of Physics, School of Sciences, Gujarat University, Ahmedabad-380 009) : Tempertature variation of Debye-Waller factor and mean square displacement for some transition metals. Indian J Phys-Pt A 2001, 75(3), 271-2.

Debye-Waller factors and mean square displacement at different temperatures for ten fcc transition metals (Cu, Ni, Fe, Co, Ag, Pd, Rh, Au, Pt and Ir) have been computed on the basis of a lattice mechanical model proposed recently by Antonov et al. The theoretical values are compared with those recently obtained from experimental density of states by Peng et al. A satisfactory agreement between theory and experiment has been found. For Ir and Rh the theoretical values have predictive meaning.

^ssc2 illus, 1 table, 10 ref

001259   Vishwakarma R R;Kannan R;Yadav R K;Sivaraman G;Bhatt B C (Bhabha Atom Res Ctr, Radiol Phys and Advisory Div, , Bombay-400 095) : Performance of industrial gamma radiography exposure devices in India. Mater Evaluation 2001, 59(8), 977-979.

001258   Vishwakarma R L;Nayak G (Department of Mathematics, S.G.R.P.G. College, Dobhi, Jaunpur) : Radiation-driven spherical shock wave in non-ideal gas. Indian J Theor Phys 1999, 47(4), 285-91.

Similarity solutions have been studied in non-ideal gas for a radiation driven shock wave. Radiation, propagation radially inwards, is completely absorbed in the shock layer of a spherical expanding shock wave. The shock wave propagates as an over-driven detonation. The results are obtained for adiabatic flows behind the shock front and illustrated through figures.

4 illus, 6 ref

001257   Verma Y K;Agarwal A;Sarkar B K (NO, SAMEER, IIT Campus, Powai, Mumbai-400 076) : Design of a mm-wave 1 : 3 waveguide power divider using E-plane bifurcated waveguide. Indian J Phys-Pt B 2001, 75(3), 217-19.

New design of mm-wave waveguide power divider is presented here. The waveguide used is WR28 rectangular waveguide. The concept of bifurcated waveguide is used to divide the input waveguide into three standard height waveguide outputs. In general, an E-plane bifurcated waveguide consists of a rectangular waveguide and a thin metal plate that effectively converts the guide into two reduced height waveguides. Since the plate is perpendicular to the TE10 electric field, the field and current patterns are unchanged and hence no reflections are created. This assumes that the metal plate is negligibly thin compared to the guide height. The electric field is same in all the guides and the voltage in the output guide is proportional to the height of the guide. The currents in all the waveguides remain same, which means that the E-plate bifurcation represents a series connection. On the same concept of the bifurcated waveguide, the waveguide is divided into three reduced height guides of equal height by putting two thin metal plates. Since the voltage in the guide is proportional to the height of the guide, E-field bifurcated is same in all the three branches resulting into equal power division in all the three outputs. Chebyshev waveguide impedance transformers are designed to step up the reduced height guide impedance to the standard WR28 waveguide impedance....

2 illus, 5 ref

001256   Verma K L (Department of Mathematics, Government Post Graduate College, Hamirpur-177 005) : Thermoelastic wave propagation problems in linear thermoelasticity without energy dissipation. Indian J Theor Phys 2000, 48(3), 207-24.

Analysis is based on the decoupled field equations of linear thermoelasticity without energy dissipation. These equations have been solved with the help of integral transforms. The dynamic behaviour of an elastic half-space due to a thermal shock and a mechanical load, on the boundary is also discussed. The displacement is continuous in both the cases and temperature, strain as well stress are discontinuous at the elastic and thermal wave fronts. The characteristic fratures of the underlying theory are analyzed in light of these solutions and their counterparts in earlier works. The results obtained theoretically have been verified numerically and are represented graphically.

4illus, 1 table, 18 ref

001255   Venkatesh Gopal;Anantha Ramakrishna S;Sood A K;Kumar N (Department of Physics, Indian Institute of Science, Bangalore-560 012) : Photon transport in thin disordered slabs. Pramana J Phys 2001, 56(6), 767-78.

Examines using Monte Carlo simulations, photon transport in optically 'thin' slabs whose thicknes L is only a few times the transport mean free path l^*, with particles of different scattering anisotropies. The confined geometry causes an auto-selection of only photons with looping paths to remain within the slab. The results of the Monte Carlo simulations are borne out by analytical treatment that incorporates directional persistence by the use of the Ornstein-Uhlenbeck process, which interpolates between the short time ballistic and long time diffusive regimes.

4 illus, 22 ref

001254   Upadhyay C S (NO, M. R. Engineering College, Jaipur-302 017) : Some views on spin relativity and its impact on science. Indian J Theor Phys 2000, 48(2), 149-60.

It is felt that the phenomenon of `Spin Relativity' plays important role in science, technology an astro-physics and its also leads to the phenomenon of `cold nuclear fusion' or `cold fusion' as observed recently by the author. It is attempted to logically establish similarities in relativistic mechanics of translation and relativistic mechanics of rotation. An analogus formula for relativisitc inertia of a body rotating/ spinning about fixed axis has been derived by simple analogus method. It is discussed that the highest spin or the highest angular velocity is w<sub>b</sub> = 10<sup>16</sup> red./secs. This is as observed in hydrogen spectrum. A simple experiment, with circulating currents in water in electrostatic fields show the existence of w<sub>b</sub> = 10<sup>16</sup> rad./secs. by measurement of magnetic flux density. An astrophysical data study in `Red Shift', `Jupiter Perihelion' and `Sun Mercury Orbit' also give the evidence of existence of `Highest Angular Velocity' supporting the concept of `Inertial Relativity'.

2 illus, 13 ref

001253   Tyagi P;Vedeshwar A G (Department of Physics and Astrophysics, University of Delhi, Delhi-110 007) : Grain size dependent optical band gap of CdI2 films. Bull Mater Sci 2001, 24(3), 297-300.

The thermally evaporated stoichiometric CDI2 films show good c-axis alignment normal to substrate plane for film thickness up to 200 nm. The optical absorption data indicate an allowed direct interband transition across a gap of 3.6 eV in confirmation with earlier band structure calculations. However, part of the absorption data near band edge can be fitted to an indirect band gap of 3 eV. The dependence of band gap on film thickness (<62> 200 nm) can be explained qualitatively in terms of decreasing grain boundary barrier height with grain size.

5 illus, 20 ref

001252   Tripathy S;Soni R K;Ghoshal S K;Jain K P (Department of Physics, Indian Institute of Technology, New Delhi-110 016) : Optical properties of nano-silicon. Bull Mater Sci 2001, 24(3), 285-9.

Investigates the optical properties of silicon clusters and Si nanocrystallites using photoluminescence (PL) and Raman scattering techniques. Broad luminescence band in the red region was observed from Si-doped SiO2 thin films deposited by co-sputtering of Si and SiO2 on p-type Si (100) substrates, annealed in Ar and O2 atmosphere. Nanocrystalline Si particles fabricated by pulsed plasma processing technique showed infrared luminescence from as grown film at room temperature. Raman spectra from these films consisted of broad band superimposed on a sharp line near 516 cm^-1 whose intensity, frequency, and width depend on the particle sizes arising from the phonon confinement in the nanocrystalline silicon. Also performed PL, Raman and resonantly excited PL measurements on porous silicon film to compared the optical properties of Si nanostructures grown by different techniques. An extensive computer simulation using empirical pseudopotential method was carried out for 5-18 atoms Si clusters and the calculated gap energies were close to our PL data.

5 illus, 1 table, 12 ref

001251   Tadepalli S;Sarkar S;Bhattacharya R;Poddar D R;Chowdhury S K (Department of ETCE, Jadavpur University, Kolkata-700 032) : Linearly polarized wide-band microstrip antenna. Indian J Phys-Pt B 2001, 75(3), 209-10.

New patch geometry, originally proposed for compact microstrip patch antenna, has been investigated experimentally and through computer simulation for broadband operation. It has been found that for a given feed position the antenna offers a 2 : 1 VSWR bandwidth of 6.76%, which is greater than three times the bandwidth of a conventional rectangular microstrip patch antenna. The antenna is linearly polarized with 3 dB beamwidth š.

5 illus, 2 ref

001250   Swaminadham V;Santhamma C;Rama Sastry C V; Murthy Y L N;Pradeep Kumar (NO, Andhra University, Visakhapatnam) : Second derivative synchronous excitation fluorescence spectroscopy (SDSEFS) to identify isomers in a mixture - a new technique. Indian J pure appl Phys 2000, 38(3), 158-65.

Identification of individual dimethyl naphthalenes which have very closely electronic transitions could be well distinguished by using a new technique second derivative synchronous excitation fluorescence spectroscopy (SDSEFS). It can be treated as a general analytical method for the identification of any two molecules, which have very closely lying electronic transitions. A commercially obtained dimethyl mixture is analyzed and its significant component molecules could be identified.

4 illus, 2 tabl

001249   Srivastava P K;Rai D K;Rai S B (Laser and Spectroscopy Laboratory, Department of Physics, Banaras Hindu University, Varanasi-221 005) : Overtone spectroscopy of some benzaldehyde derivatives. Pramana J Phys 2001, 56(6), 823-30.

Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000-12000 cm^-1 region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined. Also determined internuclear distances for the aryl CH bond in the different molecules. The small variation observed in these distances is an indication of the substitution effect. It is observed that in the case of p-disubstituted benzenes, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the case of o-disubstituted it is only 80% of the para-substituted shift.

3 illus, 5 tables, 12 ref

001248   Sridhar V N;Ghosh R;Mahtab A (Space Applicat Ctr, ISRO, Remote Sensing Applicat Area, Ahmedabad-380 015) : Atmospheric and angular effects on NDVI temporal profiles derived from ADEOS-POLDER data over India. IEEE Trans Geosci Remote Sen 2001, 39(5), 1099-1102.

Variations of NDVI for crop, semi-evergreen forest, dry deciduous forest, and sand have been analyzed as a function of date of acquisition at 670 and 865 nm using ADEOS-polarization and directionality of Earth resources (POLDER) data acquired over India. After correcting the data for atmospheric effects, a semi-empirical bidirectional reflectence distribution function (BRDF) model has been fitted to the data to extract angularly normalized target reflectances. It is shown that atmospheric corrections and angular normalization are important in the quantitative analysis of NDVI and its temporal variations.

9 ref

001247   Singh R V;Singh N P;Singh A K (Department of Mathematics, C. L. Jain (PG) College, Firozabad-283 203) : Flow of a visco-elastic fluid through a porous medium near an oscillating pate in slip flow regime in the presence of electromagnetic field. Indian J Theor Phys 1999, 47(3), 203-09.

MHD flow of an electrically conducting incompressible visco-elastic fluid (Oldroyd B-liquid) through a porous medium near an oscillating plate in slip flow regime has been studied. The expressions for liquid velocity and skin-friction have been obtained following Das and Sengupta. The effect of magnetic field, visco-elastic parameter and rarefaction parameter on the velocity of the liquid and skin-friction have been studied for different values of z and t.

6 tables, 9 ref