010989   Debnath B;Talukdar R;Bhattacharjee B (Physics dep, Gauhati Univ, Guwahati-781 014, Email: bb_22@rediffmail.com ) : Emission characteristics of intermediate mass fragments on the residual part of the projectile nucleus. Indian J Phys 2008, 82(5), 633-8.

In the study of projectile multifragmentation, a number of properties such as multiplicities, energy of fragments etc. of the emitted intermediate mass fragments (IMFs) are found to vary significantly with Z_b, where Z_b is a measure of the mass of the fragmenting system. In this work we report the variation of <N_IMF > with Z_bfor 950 MeV/A ⁸⁴Kr interactions with different targets of photonuclear emulsion. The maximum value of <N_IMF> has been found to vary systematically with the target mass. Further, from this study it has been observed that <Z_b> is linearly correlated with the number of emitted projectile protons (N_p) for the studied interactions.

3 illus, 1 table, 11 ref

010988   De B;Sarkar B C (Physics Dep, Presidency College, Kolkata-700 073, Email: bcsarkar_phy@yahoo.co.in) : Performance of non-linear amplifier based phase locked loop systems in presence of channel perturbations. Indian J pure appl Phys 2009, 47(4), 310-6.

The tracking performance of non-linear amplifier based conventional second order phase locked loop (PLL) and charge pump phase locked loop have been examined numerically by solving the system equations in the presence of lognormal type of fading signal. Some analytical results for non-linear amplifier based conventional phase locked loop and charge pump phase locked loop are also incorporated to confirm the simulation results and for the choice of optimum design system parameter.

010987   Das K;Mamaruzzaman S M;Middya T R;Datta S (Physics Dep, Jadavpur University, Kolkata-700 032, Email: middya@phys.jdvu.ac.in) : Thermal diffusivity of advanced composite materials of e-glass fiber reinforced plastic in the temperature range 5-120K. Indian J pure appl Phys 2009, 47(4), 273-6.

Thermal diffusivity of plain-woven fabric composite in a closed cycle cryo-refrigerator (CCR) based setup in the temperature range 5-120K has been studied. The modified temperature wave method (Angstrom) is applied to measure the thermal diffusivity of glass fiber reinforced plastic (GFRP). The set up is a plug in type which can be used anywhere because of its portability and also works without use of any cryogenic fluid. The results show that there exists an inverse relation between the thermal diffusivity of e-glass fiber composite and temperature in very low temperature domain but decreases very slowly after 100K.

010986   Das D;Ahmed G A;Choudhury A (Physics Dep, North Gauhati College, Guwahati-781 031, Email: dasdilip_3@sify.com) : Water vapour droplets using a laser based air quality monitoring system. Indian J Phys 2008, 82(5), 539-44.

Deals with the design and fabrication of a laser based air quality monitoring system combining the design principle of the nepheiometer, transmissiometer and a point visibility meter. The system is tested by investigations on water droplet formation in air having different concentration of different gases. As such the work involves the theory of extinction and scattering, especially Mie scattering. Essentially in the system light from a laser source passes through a simulation chamber and the extinction and angular scattering of the light is monitored by photo detector arrangement. The signals are digitized and interfaced with pc for data recording and processing. Finally a correlation is drawn between the experimental results and the theoretical work.

4 illus, 8 ref

010985   Choudhury J;Sarkar N K;Bhattacharjee R (Physics Dep, Assam Univ, Silchar-788 011, Email: chodhuryjoy@rediffmail.com) : Algebraic approach to analyze the vibrational spectra of tetrahedral molecules. Indian J Phys 2008, 82(5), 561-5.

Molecular spectroscopy is undergoing a considerable attention in last few decades. There is a considerable current research interest in the study of vibrational ground and excited states of polyatomic molecules using Lie algebraic method. Both the stretch and bend fundamental vibrational modes of tetrahedral molecules are calculated by using U(2) algebraic model. Its application to four molecules are presented. The result obtained by this model are the best fit with the observed data. This study will give a general approach for solving tetrahedral molecules with good accuracy.

1 illus, 1 table, 20 ref

010984   Choudhury D K;Gogoi R (Physics Dep, Gauhati Univ, Guwahati-781 014, Email: rupjyotigogoi@gmail.com) : Analysis of self-similarity in quark and gluon densities at small x. Indian J Phys 2008, 82(5), 621-5.

Sometimes back, the concept of self-similarity in the structure of the proton at small x has been introduced. Comment on the limitations of the models based on self-similarity. We then extend the formalism and phenomenology to unintegrated and integrated gluon densities.

1 illus, 27 ref

010983   Chaliha S;Borah M N;Sarmah P C;Rahman A (Physics Dep, Bahona College, Jorhat-785 101, Email: sumbite@gmail.com) : Current -voltage characteristics of ITO/(p)Si heterojunctions. Indian J Phys 2008, 82(5), 595-601.

A ITO/(p)Si heterojunction was fabricated by depositing Indium Tin Oxide (ITO) thin films onto well cleaned p-type silicon wafer by thermal evaporation method from pure ITO powder at substrate temperature 523K. The different diode parameters were calculated from the current-voltage characteristics of the junctions. The diode ideality factor was found to be greater than 1 and the diode had high series resistance. The I-V characteristics under illumination showed poor photovoltaic effect of the junction. Large series resistance, high defect density and presence of interfacial layer are thought to be the main causes for higher value diode ideality factor and poor photovoltaic conversion efficiency.

5 illus, 1 table, 13 ref

010982   Borah R R;Bhuyan K;Bhuyan P K (Physics Dep, Dibrugarh Univ, Dibrugarh-786 004, Email: rashmirekha_b@rediffmail.com) : Correlation distance of ionospheric total electron content in the Indian low latitude region. Indian J Phys 2008, 82(5), 545-50.

The Global Positioning System Satellite (GPS) provides an opportunity for studying Ionospheric total electron content (TEC). Used GPS TEC data collected at 16 stations across India since 2003 to obtain correlation distance of ionospheric total electron content in the Indian low latitude ionosphere. The correlation coefficients at each local time for 118 pairs of stations are calculated for every month. It has been found that the r= 0.7 correlation distance in longitude is approximately 1500 km in winter months, 1100 km for summer months and 1200 km for equinoxes. The r= 0.7 correlation distance in latitude is approximately 900 km in winter months and 700 km in summer and equinox months. The nighttime correlation distance is found to be greater than the daytime distance.

4 illus, 11 ref

010981   Baruah R;Duorah K;Duorah H L (Physics Dep, HRH The Prince of Wales Institute of Engineering and Technology, Jorhat-785 001, Email: ruleebaruah@yahoo.co.in) : Rapid neutron capture process in an explosive astrophysical environment. Indian J Phys 2008, 82(5), 523-9.

The rapid neutron capture process (r-process) is one of the major nucleosynthesis processes responsible for the production of heavy elements beyond iron. Recent models of r-process nucleosynthesis rely on a neutrino-heated bubble developing at late times, which provides both the necessary conditions and the requisite amount of ejected mass for the r-process. Meyer et al. [1 ] showed that the hot bubble that forms outside the protoneutron star during a supernovae (SN) explosion may be a viable site for the r-process as long as the entropy per baryon can be made sufficiently high. But in a very neutron rich environment such as a neutron star, the r-process could occur even at low entropy. The high entropy wind is not the correct r-process site, owing to the inherent deficiencies in the abundance pattern below A=110 as well as the problems in obtaining the high entropies in SN II explosions required for producing the massive r-process nuclei up to A ≈ 195 and beyond. Tries to associate the explosion entropies with the site-independent classical approach (n_n and T₉) and thereby compare the results of the two approaches from the abundances at different entropy conditions. We find that an entropy of = 300 with V_e ≈ 0.45 can lead to a successful r-process. This is in agreement with the r-process abundance peaks at n_n ≈ 10³² cm^-3 and T₉ ≈ 1.5.

2 illus, 10 ref

010980   Baruah K K (Mathematics Dep, North Guwahati College, Guwahati-781 031, Email: kkbng-1@sify.com) : Bianchi type-1 string cosmology with a scalar field. Indian J Phys 2008, 82(5), 513-17.

The Bianchi type-1 anisotropic cosmological model containing a self - interacting scalar field with an exponential potential of the form V(Φ) = e^kΦ in the context of cosmic strings have been studied. Physical features of this model are briefly discussed.

ref

010979   Babu J C;Mouli V C (Glassy Materials Research Lab, Physics Dep, Osmania University, Hyderabad-500 007, Email: vorucm90@yahoo.com) : Spectroscopic and dc conductivity studies of Cu<. Indian J pure appl Phys 2009, 47(4), 241-7.

DSC, ESR, IR, Raman, optical absorption and dc conductivity studies on 10Liv>2O- xNb₂O₅-(89-x) TeO₂ glasses containing Cu²⁺ spin probe have been carried out. Glass transition temperature (T_g) and thermal stability of glass samples are estimated from the DSC measurements and it has been found that both increase with increasing the Nb₂O₅ content. From IR and Raman spectra, it is clear that, the glass system consists of structural units of TeO₃ (tp), TeO₄ (tbp) and NbO₆ octahedra. TeO4 units are found to be converted into TeO₃ units with increase in Nb₂O₅ content. From ESR spectra, it is found that the Cu²⁺ ion is in tetragonal distorted octahedral site with as ground state. The observed optical absorption peak of Cu²⁺ is found to be maximum at 800 nm for 10 mol% of Nb₂O₅ content. Bonding parameters and per cent bonding symmetry are calculated from both optical and ESR data and are found to change with increase in Nb₂O₅ content. The observed dc conductivity is found to be increasing with temperature and decreasing with increase in Nb₂O₅ content.

010978   Ashrafi A R;Mirzargar M (NO, Institute of Nanoscience and Nanotechnology, University of Kashan, Kas, , Email: ashrafi@kashanu.ac.ir) : PI, Szeged and edge szeged indices of an infinite family of nanostar dendrimers. Indian J Chem-Sect A 2008, 47(4), 538-41.

A topological index of a graph G is a numeric quantity related to G which describes the molecular graph G. A dendrimer is an artificially manufactured or synthesized molecule built up from branched units called monomers. The PI and Szeged indices of a class of nanostar dendrimer are computed.

^ssc3 illus, 34 ref

010977   Ashok Kumar;Kukreti A;Naithani U C (Physics Dep, Garhwal University, Pauri, Campus, Pauri (Garhwal), Uttarakhand 246 001, Email: ashishkukreti07@gmail .com) : Field dependent soft mode frequency in Ba_xSr_1-xTiO₃ ferroelectric perovskites. Indian J pure appl Phys 2009, 47(4), 300-5.

An expression has been obtained for the soft mode frequency in Ba_xSr_1-xTiO₃ ferroelectric perovskites in the presence of external electric field, by using double time temperature dependent Green's function technique. The mass and force constant change due to impurity atoms which are taken into account in the presence of higher order anharmonic and electric moment terms in the Silverman Joseph Hamiltonian. The soft mode frequency is obtained in the presence of both the electric field and impurity of Ba in an anharmonic SrTiO₃ ferroelectric perovskites. The soft mode frequency decreases with increase of impurity concentration of Ba in pure SrTiO₃. The soft mode frequency also increases with increase of external electric field in Ba_xSr_1-xTiO₃ ferroelectric perovskites.

010077   Yurtseven H;Tilki O (Physics Dep, Middle East Technical Univ 06531, Ankara-Turkey, Email: hamit@metu.edu.tr) : Critical behaviour of the thermodynamic quantities near the melting point in the solid phase of hexadecane. Indian J Phys 2008, 82(1), 105-15.

Studies here critical behaviour of the thermodynamic quantities such as thermal expansivity α_p, isothermal compressibility K_Tand the specific heat C_P close to the melting point in solid hexadecane. By analyzing experimental data for the thermal expansivity measured at various pressures for constant temperatures of 302 and 325 K, we calculate the pressure dependence of the isothermal compressibility K_T and specific heat C_p near the melting point in solid hexadecane. Then establish the Pippard relations (C_P vs. α_p and α_p vs. K_T ) for this molecular organic compound close to its melting point. Values of the slope dP_m/dT which we deduce from the linear plots of the Pippard relations, are in good agreement with the experimentally measured value for solid hexadecane near the melting point.

^ssc4 illus, 1 table, 47 ref

010076   Yadav M K;Surbhi (Molecular Spectroscopy and Biophysics Laboratory, D N (PG) College, Meerut-250 002, Email: sap_am@rediffmail.com) : Electronic spectral studies of 4-bromo-2-fluoro phenol in various solvents. Indian J Phys 2008, 82(1), 117-21.

Electronic spectra of 4-bromo-2-fluoro phenol in polar solvents (ethanol, methanol and chloroform) have been recorded in liquid state in the region 200 to 400 nm. The effect of halogen atom on the π-π*, N-π* and n-≈* transitions have been studied. The π-π*, N-π* and n-σ* transitions have been shown the usual behavior towards the substitution and polarity of solvent. The effect of pH variation on electronic transitions of this compound in ethanol solvent has also been studied.

^ssc3 illus, 2 tables, 17 ref

010075   Sreenivasulu A;Prasad T N V K V;Buddhudu S (Physics Dep, Sri Venkateswara Univ, Tirupati-517 502, Email: profsb_svuniv@hotmail.com) : Optical analysis of RE<. Proc Indian Natn Sci Acad 2008, 74(1), 1-4.

Ferroelectric materials Ba_0.95 RE_0.05TiO₃ (RE=Eu³⁺, Sm³⁺ & Dy³⁺) containing certain rare-earth ions as the luminescent ion's were prepared by a conventional solid state method. Structural analysis of these materials has been carried out by using both XRD and FTIR spectral measurements. By measuring the excitation, emission spectra and lifetimes of the prominent emission bands, luminescence performance of these optical materials has been investigated.

8 illus, 1 table, 22 ref

010074   Sreenivasulu A;Prasad T N V K V;Buddhudu S (Physics Dep, Sri Venkateswara Univ, Tirupati-517 502, Email: drsb99@hotmail.com) : Luminescence properties of RE<. Indian J Phys 2008, 82(1), 51-8.

Reports on the optical analysis of LiNb_0.95RE_0.05O₃ ceramic powders with certain rare earth ions as the dopant ions. These materials have been prepared by using a solid state reaction method. Emission spectrum of Eu³⁺: LiNbO₃ ceramic has shown strong a red emission at 613 nm (⁵D₀ → ⁷F₂) with λ_exci = 393 nm (⁷F₀ → ⁵L₆). An orange red emission has been observed at 609 nm (⁴G_5/2 → ⁶H_7/2) for Sm³⁺ : LiNbO₃ with λ_exci = 409 nm (⁶H_5/2 → ⁴L_13/2) and similarly for Dy³⁺: LiNbO₃ ceramic powder, an yellow emission has been measured at 577 nm (⁴F_9/2 → ⁶H_13/2) with λ_exci = 355 nm (⁴H_15/2 → ⁶P_7/2). Besides, X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) have also been carried out to analyze the structural properties of those ceramic powders.

7 illus, 1 table, 21 ref

010073   Singh B B (Mathematics Dep, Babasaheb Ambedkar Technological Univ, Lonere-402 103, Email: brijbhansingh@yahoo.com) : Asymptotic behaviour of free convective boundary layer flows of newtonian fluids. Indian J Theor Phys 2007, 55(2), 155-62.

Deals with the asymptotic behaviours of the solutions of Falkner-Skan equations governing the free convective boundary layer flows of Newtonian fluids past a vertical flat plate with suction/injection as the independent variable 'η' tends to infinity ; the discussion being based on the asymptotic integrations of second order linear differential equations. It has been found that the principal solutions exhibit asymptotic nature as η → ∞, whereas corresponding linearly independent solutions don't.

17 ref

010072   Sharma P R;Agarwal B (Mathematics Dep, Rajasthan Univ, Jaipur-302 004) : Steady laminar flow and heat transfer through parallel porous discs of different permeabillities with heat source. Indian J Theor Phys 2007, 55(2), 163-84.

Investigates steady laminar flow and heat transfer through two parallel porous discs of different permeabilities in the presence of heat source when the flow is entirely due to injection at the rate V₁* through lower disc and suction at the rate V₂* through upper disc. The governing equations of motion and energy are solved by power series method for small values of V₁* and V₂. The velocity, temperature and pressure distributions are derived, discussed numerically and shown through graphs. The skin-friction co-efficient and rate of heat transfer in terms of the Nusselt number at both the discs are derived, discussed numerically and their numerical values for various values of physical parameters are presented through tables.

2 tables, 16 ref

010071   Selvanayagam S;Velmurugan D;Yamane T;Suzuki A (Biomater Sci Dep, , Nagoya-464-8603, Japan, Email: d_velu@yahoo.com) : High throughput structure determination for single-wavelength laboratory X-ray source anomalous diffraction data sets using iodinated tyrosines. Indian J Phys 2008, 82(1), 27-37.

The availability of high-intensity synchrotron facilities, technological advances in data-collection techniques in synchrotron as well as laboratory source and improved user friendly crystallographic software have ushered in a new era in high-throughput macromolecular crystallography. Single-wavelength anomalous diffraction (SAD) phasing has become a useful tool for high-throughput structure determination. Attempts have been made to use SAD method using laboratory X-ray source in determining the three dimensional structure of an enzyme glucose isomerase (nearly 44 kDa molecular weight) using Cu Kα and Cr Kα anomalous scattering data sets corresponding to 1.8 and 2.4 Angstrum resolutions, respectively. The tyrosine residues in this enzyme were iodinated with N-iodo-succinimide in crystallization. PHENIX program was used to locate the iodine atom positions and also for phasing and model building. The model-building program ARP/wARP with REFMAC5 using SAD likelihood function can be used of to proceed further with the incomplete model built by PHENIX. In both the data sets, nine iodine positions initially located by PHENIX are sufficient enough to build the entire structure.

3 illus, 3 tables, 19 ref

010070   Sarangi K C;Sharma V K (Mathematics Dep, Rajasthan Univ, Jaipur-302 004) : Unsteady free convective MHD flow past and heat absorbing sink. Indian J Theor Phys 2007, 55(2), 113-22.

The porous medium can be considered homogeneous medium by assuming its dynamical properties to be equal to local averages of the original non-homogenous continuum. Various scholars discussed flow of fluid through porous media due to its wide use in science and technology. The channel flow through porous medium also have numerous application in the field of engineering and geophysics as, in chemical engineering for the filtration and purification processes, in the fields of agriculture engineering to study the underground water resources, in the petroleum technology to study the movement of natural gas oil and water through the oil channels/reservoirs. Gupta analyzed the effect of magnetic field on free convective flow of electrically conducting fluids past a semi-infinite flat plate. The exact solution for the unsteadv MHD problem has been obtained by Singh and Cowing, Nanda and Monanty, Sancheu, Chandran.

2 illus, 2 tables, 7 ref

010069   Santra S B;Deb D (Physics Dep, Indian Institute of Technology Guwahati, Guwahati-781 039, Email: santra@iitg.ernet.in) : Sandpile under rotational constraint. Indian J Phys 2008, 82(3), 295-302.

Sandpile model is studied here imposing rotational constraint on the flow of sand grains. The rotational constraint is constituted by certain deterministic rules. The rotational dynamics evolves the system into a non-equilibrium steady state characterized by power law correlations and exhibits self organized criticality. The exponents characterizing the power law distributions of avalanche properties are found different from other models. Consequently the present model belongs to a new universality class.

4 illus, 15 ref

010068   Sahu P P (Electronics Dep, Tezpur Univ, Nappam, Tezpur-784 028, Email: pps@tezu.ernet.in) : Silicon oxinitride: a material for compact waveguide device. Indian J Phys 2008, 82(3), 265-72.

Growing attention has been paid to silicon oxynitride (SiO_xN_yor SiON in short) as a potential material for Compact integrated optical waveguide devices due to its excellent optical properties such as wide range of refractive index between 1.45 (SiO₂) - 2.0 (Si₃N₄). The reduction of coupling length of directional coupler with small gap using high index contrast waveguide with SiON Core and SiO₂ cladding has been studied. The experimental results of the coupler power versus coupling length of the directional couplers are shown and the corresponding beat legnth is 65 μm. Finally, the wavelength multiplexing/demultiplexing using compact directional couplers is discussed.

6 illus, 10 ref

010067   Sable M C;Vyawhare S K;Labde B K;Shamkuwar N R (Physics Dep, Dr. Baba Saheb Ambedkar Univ, Aurangabad-431 003) : Structural and magnetic properties of Pb<. Indian J Phys 2008, 82(1), 39-43.

X-Ray diffraction was used to study the formation and structure of mixed ferrites Li_0.5+0.5xPb_xFe_2.5-1.5xO₄ (where x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 ). X- ray diffraction pattern proved that the prepared samples were formed in the spinel structure. The lattice parameter is found to increase with increase is Pb⁴⁺ content(x) which is attributed to ionic size differences of the cation involved. From X-ray diffraction pattern, X-ray density and particle size were determined. The values of magnetic moment n_B for all the samples were determined. X-Ray intensity calculations, magnetization and site preference energies were taken into consideration to determine the cation distribution. n_B is found to increase with increase in (x) form 0.0 to 0.2 and further increase in Pb⁴⁺ concentration showed decrease in n_B value.

3 illus, 2 tables, 13 ref

010066   Pharhad Hussain A M;Kumar A (Physics Dep, Tezpur Univ, Napaam, Assam-784 928, Email: abu@tezu.ernet.in) : Electrochemcal synthesis and characterization of co-polymers of aniline and pyrrole. Indian J Phys 2008, 82(3), 349-56.

Conducting polymer (CP) films of polyaniline (PAni), polypyrrole (Ppy) and copolymers of aniline and pyrrole are synthesized electrochemically in sulfuric acid (H₂SO₄) aqueous electrolyte on indium doped tin oxide (ITO) coated glass substrate. Cyclic voltammetry (CV) studies are carried out for electrochemical characterization and the polymer films showed high electroactivity in acidic media. X-ray diffraction study revealed polyaniline as completely amorphous and polypyrrole and co-polymer as polycrystalline. Electrical (dc) conductivity of the co-polymer films was measured by four probe method and found to lie between those of polyaniline and polypyrrole. UV-VIS spectra of the co-poiymer show a peak at 370 nm which is in between the characteristic π-π transition peak of polyaniline polypyrrole suggesting formation of copolymer. FTIR spectra also suggest formation of copolymer poly (aniline-co-pyrrole).

2 illus, 34 ref

010065   Narendra Kumar;Sanyal G S (NO, Raman Research Institute, Bangalore-560 080, Email: nkumar@rri.res.in) : Characterization of radiation as an electromagnetic wave or a particle-a criterion. Proc Indian Natn Sci Acad 2008, 74(1), 19-20.

The wave-particle duality of radiation from a source in the electromagnetic spectrum is well-known. A criterion is proposed to determine when the radiation will predominantly exhibit the properties of a particle and when will it behave as a wave. An experiment is suggested to validate the criterion.

1 illus, 5 ref

010064   Mishra N;Jha L (University Department of Physics, L.N. Muthila Univ, Darbhanga-846 004) : Analysis of radiation quality factor of microstrip antenna. Indian J Theor Phys 2007, 55(2), 97-103.

Analysis of antenna quality factor has been an interesting and controversial topic for years. Analysed radiation quality factor of microstrip patch antenna by introducing a complex power balance relation for an antenna system with special reference to microstrip antenna using the complex poynting theorem showing the antenna as a one port lossy network. Foster reactance theorem has been used for the calculation of radiation quality factor of microstrip antenna.

2 illus, 10 ref

010063   Mirafzali S Y;Sarbishaei M (Physics Dep, Faculty of Sciences, Ferdowsi Univ of Mashhad, Iran, Email: al_as82@stu-mail.um.ac.ir) : Effect of anisotropy and external magnetic field on the thermal entanglement in two spin-one system. Indian J Phys 0000, 82(1), 59-67.

Study the thermal entanglement in a two-spin-one system with anisotropy in the exchange coupling between two spins. Uses the realignment criterion to distinguish the entangled states, and the negativity for measuring the entanglement in this system. The anisotropy can provide an additional parameter for enhancing the entanglement.

3 illus, 19 ref

010062   Medhi A;Basu S;Kadolkar C Y (Physics Dep, Indian Institute of Technology, Guwahati, Guwahati-781 039, Email: amedhi@iitg.ernet.in) : Variational Monte Carlo study of magnetic correlations in bilayert-J model. Indian J Phys 2008, 82(3), 251-7.

Study the magnetic correlations in a t-J bilayer using Variational Monte Carlo (VMC) method, the variational wavefunction being the solution of the Hartree-Fock (HF) t-J Hamiltonian with antiferromagnetic (AF) order. We calculate the spin-spin correlation functions and spin structure factors at half filling and slightly away from half filling. The results show that, at half filling perfect antiferromagnetic long range order (AFLRO) exists, which starts to diminish as soon as holes are introduced. It is observed that the holes drastically reduce the interplanar spin correlations, whereas the effect on the planar correlations is rather small. This is to be contrasted with the Experimental results on the cuprates, which show that the AFLRO in the copper oxide planes gets completely destroyed even at a small hole concentration. This is possibly due to the competition of AFLRO with the superconducting order, which has not been incorporated in the calculations. We also examine the effect of the pterplanar parameters, e.g. the hopping integral, t and exchange constant, J, on the magnetic correlations. Finds that t₁ reduces planar correlations while the effect of J is small.

4 tables, 11 ref

010061   Maiti S K (Theoretical Condensed Matter Physics Div, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata-700 064, Email: maiti@saha.ac.in) : Persistent current and low-field magnetic susceptibility in n-fold twisted moebius strips. Indian J Phys 2008, 82(3), 281-7.

Study persistent currents and sign of these currents in the limit φ → 0 for n-fold twisted Moebius strips threaded by a slowly varying magnetic flux φ concerning the dependence of the total number of electrons N_e, chemical potential μ, number of twist n and randomness. In odd-fold twisted Moebius strips current gets φ₀/2 flux-quantum periodicity only when v_L=Q (transverse hopping stregth), while, it shows φ₀ flux-quantum periodicity as long as the electrons are allowed to hop along the transverse direction (v_L ≠ 0). On the other hand, current always exhibits φ₀ flux-quantum periodicity for even-fold twisted Moebius strips, irrespective of the transverse hopping strength (v_L). The sign of the low-field currents also strongly depends on the number of twist n. For v_L = 0 the sign of the low-field currents can be mentioned exactly in old-fold twisted Moebius strips those are characterized by fixed N_e only. In absence of any impurity current shows always the diamagnetic nature irrespective of N_e i.e., whether N_e is odd or even, while, in presence of impurity it exhibits respectively the diamagnetic and the paramagnetic behavior for the systems with odd and even N_e. The sign of these low-field currents cannot be predicted exactly when the electrons are allowed to hop along the transverse direction. Since then it strongly depends on the N_e, μ and specific realization of randomness.

3 illus, 15 ref

010060   Kumar A;Hussain A M P;Avasthi D K (Electronics Dep, Tezpur Univ, Nappam, Tezpur-784 028, Email: ask@tezu.ernet.in) : Swift Ni<. Indian J Phys 2008, 82(3), 273-80.

All -polymer solid state supercapacitors with LiCF₃SO₃ doped polypyrrole electrodes and P(VDF-HFP)-PMMA based polymer gel electrolyte have been fabricated. The polypyrrole electrodes are irradiated with 160 MeV Ni¹²⁺ ions at three different fluences of 5 x 10¹⁰, 5x10¹¹ and 5 x 10¹² ions/cm². A comparative study has been made between unirradiated and irradiated polypyrrole electrode based supercapacitors. An average capacitance value of about 200 F/gm is obtained for the supercapacitors. Upon successive charging and discharging, the capacitance is found to decrease for supercapacitors with unirradiated electrodes whereas the supercapacitors with SHI irradiated polypyrrole electrodes exhibit almost stable capacitance, though the capacitance value is slightly decreased as compared to that for the supercapacitors with unirradiated electrodes. The charge-discharge studies show a decrease in total charge-discharge time for the supercapacitors with irradiated electrodes. Coulombic efficiency of the order of 90% is obtained for all the supercapacitors.

4 illus, 1 table, 23 ref

010059   Kharab R;Pardeep Singh;Ravinder Kumar (Physics Dep, Kurukshetra Univ, Kurukshetra-136 119) : Effects of E2 transitions in the coulomb dissociation of <. Indian J Theor Phys 2007, 55(2), 123-44.

Presents main steps involved in the derivation of transition amplitude for the coulomb break up process in the first order Eikonal approximation. Aplies this theory to the coulomb break up of ¹¹Be and ¹⁹C under the electromagnetic field of Pb target. The effects of E2-transitions on the cross-section and the relative energy spectrum are evaluated. The calculations indicate that the E1-transitions are dominating in, the coulomb break up process but the E2-contribution is non-negligible. Hopes that this will be helpful for the researchers engaged in this field.

4 illus, 1 table, 18 ref

010058   Khan A;Atre R;Panigrahi P K (Physical Research Laboratory, , Navrangpura, Ahmedabad-380 009, Email: akhan@prl.res.in) : Complex envelope soliton in Bose-Einstin condensate with time depndent scattering length. Indian J Phys 2008, 82(2), 185-8.

Elaborates on a general method to find complex envelope solitons in a cigar shaped Bose-Einstein condensate in a trap. The procedure incorporates time dependent scattering length, oscillator frequency and loss/gain. A variety of time dependencies of the above parameters, akin to the ones occurring in the experiments can be tackled.

1 illus, 10 ref

010057   Karanjai S;Islam Z (Mathematics Dep, North Bengal Univ, West Bengal-734 430) : Exact solution of the equation of radiative transfer with a constant source and rayleigh's phase function in a semi-infinite atmosphere by the method of laplace transform and Wiener-Hope technique. Indian J Theor Phys 2007, 55(2), 145-54.

The equation of radiative transfer with a constant source and Rayleigh's phase function in a semi-infinite atmosphere has been solved by the method of Laplace transform and Wiener-Hope technique. The emergent intensity has been derived in terms of Chandrasekhar's H-function. The intensity I(t, μ) is derived by inversion.

1 illus, 10 ref

010056   Gogoi P;Ansari T A;Agarwal P (Physics Dep, Indian Institute of Technology, Guwahati-781 039, Email: purabig@iitgernet.in) : Steady state photo carrier grating technique for measurement of charge carrier diffusion length. Indian J Phys 2008, 82(2), 179-84.

Steady State Photo carrier Grating technique (SSPG) is fabricated to measure the charge carrier diffusion length in semi conducting thin films. The experiment is carried out in some hydrogenated amorphous silicon and silicon germanium alloys, the values of diffusion length are found to be in good agreement with literature.

4 illus, 1 table, 5 ref

010055   Gogoi A;Bhattacharyya N S (Microwave Engineering Laboratory, Physics Dep, Tezpur Univ, Napaam-784 028, Email: nidhi@tezu.ernet.in) : Development of LDPE/TiO₂ composite as substrate material in microwave integrated circuits. Indian J Phys 2008, 82(3), 341-7.

Polymer composite films of LDPE/TiO₂ were prepared using a simple chemical route. The morphological, thermal and microwave properties of the composite with various concentrations of TiO₂ till the percolation limit were measured. An increase in complex permittivity to 11.79% of this novel composite material is observed when compared with the pure polymer, as the filler concentration changes to 6% volume fraction (VF). A 7.45 times enhancement of thermal conductivity of the composites is seen as compared to pure LDPE. The morphological studies show that the distribution of the filler particles are homogeneous and size is less than the probing wavelength which makes the LDPBTiO₂ composite system continuous of microwave propagation. FTIR and XRD revealed that TiO₂ does not change its crystalline properties in the composite.

5 illus, 11 ref

010054   Ghosh D N;Ghosh K (mathematics Dep, B.C. Roy Engineering College, Durgapur-713 206) : Search for periodicity in given time-dependent data obtained from any dynamical system by miximum likelihood method and rayleigh power spectrum analysis. Indian J Theor Phys 2007, 55(2), 105-12.

The method of maximum likelihood estimation is a well-known and powerful method of estimation in statistics. Here, in this persent work, this method is employed to verify whether a given series of time-dependent data obtained from any dynamical system is periodic in nature or not. Also developes and employes Rayleigh power spectrum analysis to serve the practical purpose. Analytical stray is made on the application of these methods in this field.

3 illus, 6 ref

010053   Dutta T;Tarafdar S (Condensed Matter Physics Research Centre, Physics Dep, Jadavpur Univ, Kolkata-700 032, Email: sujata_tarafdar@rediffmail.com) : Chaotic behaviour of population on a square lattice. Indian J Phys 2008, 82(2), 201-7.

Coverage of occupied sites on a square lattice is allowed to evolve according to a set of rules. The rules imply an attractive interaction for growth of new members, the original members 'die', and the new 'population' multiplies and redistributes randomly over the lattice. Shows that this scenario leads to a steady coverage, cycles with a finite number of points and ultimately chaos as model parameters vary. The calculated results are verified by computer simulation. An immobile situation, where migration or redistribution over the lattice is restricted is also simulated.

3 illus, 13 ref

010052   Dutta N;Mohanta D;Choudhury A (Physics Dep, Tezpur Univ, P.O. Napaam, Sonitpur, Assam-784 028, Email: nabanita@tezu.ernet.in) : Synthesis and characterization of quality PbS quantum dots in SBR matrix. Indian J Phys 2008, 82(3), 327-32.

Successfully grown PbS quantum dots in styrene butadiene rubber (SBR) matrix following solution chemistry. The formation of monodisperse isolated PbS quantum dots with size distribution 5-10 nm was confirmed by transmission electron micrographs. Structural and optical properties have been characterized by X-ray diffractometer and photoluminescence spectroscopy. Since, there is significant enhancement in the band gap of quantum dots by (7-8 times 2.15 eV) compared to bulk PbS (0.29 eV at 300 K), PbS quantum dots can be promising candidates for application in optoelectronic sensors/devices, operated over broad spectrum of light.

4 illus, 20 ref

010051   Dev P;Basu S (Physics Dep, Indian Institute of Technology Guwahati, Guwahati-781 039, Email: poulumi@iitg.ernet.in) : D-wave correlations for anisotropic superconductors. Indian J Phys 2008, 82(3), 289-94.

The experimental scenario supporting a stripe-like arrangement for the added charge carriers to the copper oxide planes of cuprate superconductors is fairly robust. Inhomogeneities, e.g. the stripes, can be incorporated in a simple manner by introducing a hopping anisotropy in the planes, i.e. the hopping frequency of the charge carriers in the x-direction (t_x) is much greater than that in the y-direction (t_y). Such anisotropies lead to a reduction of symmetry of the system compared to the isotropic case and hence the superconducting gap function may be assumed to have a mixing of s and d-wave correlations. In this work, we made an ansatz of mixed symmetry for the gap function and studied pairing correlations in both s and d-wave channels as a function of the anisotropy parameter, r (r = t_y/t_x) by solving the finite temperature BCS gap equations at low electronic density for a t - J model. The results point towards a significant increase in the pairing correlations. mainly in the d-wave channel, corresponding to the extreme anisotropy limit (r → 0). Thus a system with anisotropic kinetic energy of the charge carriers but interacting via an isotropic exchange (J) results in stabilisation of the superconducting state.

2 illus, 9 ref

010050   De U;Venkatesh M;Shaikh M S;Venkataraman B (NO, , Variable Energy Cyclotron Centre, DAE, I/AF Bidhannagar, Kolkata-700 064, Email: ude@veccal.ernet.in) : Study of elemental composition in some II-VI oxides by atomic absorption spectroscopy. Indian J Phys 2008, 82(3), 259-63.

There has been an increasing number of measurements in various oxides, of significant physical property changes ascribed to non-stoichiometry. But there has hardly been any direct measurement of the exact composition to find the degree of non-stoichiometry. For the well-studied cadmium oxide problem, for example, DSC (differential scanning calorimetry) showed an unexplained exothermic peak at 270°C. Metal content has been estimated here by Atomic Absorption Spectroscopy (AAS) for cadmium oxide, magnesium oxide and zinc oxide. Some of these II-VI compounds have electronic and other applications. In this work, metal at% has thus been determined (at room temperature) from AAS for as-supplied metal oxide and after 36 hour firing at different temperatures. With increase of the firing temperature, we observe a sudden fall in AAS-determined Cd at% at 270°C, and then a steady increase of much larger magnitude. Findings are new, matching the new DSC and RBS data, and of significant importance in view of the incompleteness of the Cd-O phase diagram available in the literature.

1 illus, 1 table, 14 ref

010049   Das U;Mohanta D;Bordoloi A K;Singh F;Tripathi A;Avasthi D K;Choudhury A (Physics Dep, Tezpur Univ, P.O. Napaam, Assam-784 028, Email: upam@tezu.ernet.in) : Structural and optical properties of 150 Me V Ti<. Indian J Phys 2008, 82(2), 163-8.

Reports transition metal (Mn, Cu) impurity doped ZnS nanoparticles fabricated by a simple solution growth technique and their response to 150-MeV Ti⁺¹¹ ion irradiation. The size of the nanostructures increases with ion fluence due to melting led grain growth. The increased size as a results of grain growth has been observed in the optical absorption spectra in terms of red shift. The dopant related and fluence dependent luminescence properties are studied by Photoluminescene spectroscopy and the results are discussed.

8 illus, 1 table, 21 ref

010048   Chowdhury S;Choudhury A (Physics Dep, Tezpur Univ, Napaam, Tezpur-784 028, Email: sky@tez.ernet.in) : Optical and structural studies of SHI irradiated SiO₂ coated IV-VI semiconductor quantum dots. Indian J Phys 2008, 82(3), 311-16.

Among narrow band gap (IV-VI) semiconductor quantum dots, PbS has been widely used due to their unique physical properties arising from their large strong confinement regime. Silica (SiO₂) coated PbS quantum dots have been synthesized and their structural and optical properties have been investigated through X-ray diffraction (XRD), UV-Vis optical absorption spectroscopy, Transmission Electron Microscopy (TEM) and Photoluminescence (PL) spectroscopy. Swift Heavy Ion (SHI) irradiation was carried out with 160 MeV Ni¹²⁺ ion beam at different fluences. The samples exhibit structural stability. Further increase in PL intensity has been observed in these samples after SHI irradiation.

8 illus, 21 ref

010047   Chowdhury P;Ray P C;Ray S (Physics Dep, Barasat Government College, North 24 Parganas, Kolkata-700 124, Email: saibal@iucaa.ernet.in) : Periodicity of ~ 155 days in solar electron fluence. Indian J Phys 2008, 82(1), 95-104.

Investigated the occurrence rate of high energetic (E > 10 MeV) solar electron flares measured by IMP-8 spacecraft of NASA for solar cycle 21 (June 1976 to August 1986) first time by three different methods to detect periodicities accurately. Power-spectrum analysis confirms a periodicity ~155 days which is consistent with the earlier result of Chowdhury and Ray [1], that "Rieger periodicity" was operated throughout the cycle 21 and it is independent on the energy of the electron fluxes.

^ssc5 illus, 1 table, 47 ref

010046   Chaliha S;Borah M N;Sarmah P C;Rahman A (Physics Dep, Bahona College, P.O. Bahona, Jorhat-785 101, Email: sumbite@gmail.com) : Optical and electrical properties of thermally eveporated ZnSe thin films. Indian J Phys 2008, 82(3), 303-10.

Zinc Selenide (Znbe) thin films were deposited onto glass substrates by thermal evaporation technique. From optical studies, different optical constants were calculated and the transition of the deposited films were found to be direct allowed transition. The optical band gap of the films were found to be in the range from 2.6eV to 2.7 eV. The films deposited at elevated substrate temperature followed by heat treatment in vacuum have showed stable electrical nature. The electrical conductivity of the ZnSe films were found to be about 10^-7 ohm^-1 cm^-1 and found to increase to about 10^-5 ohm^-1 cm^-1 when films were doped with Al or Cu. From the conductivity measured at different temperatures, the activation energy of the films were calculated and found to be between 0.1 eV to 0.2 eV for low temperature regions and between 0.5 eV to 0.6 eV for high temperature region.

5 illus, 3 tables, 13 ref

010045   Biswal R;John J;Behera D;Mallick P;Kumar S; Kanjilal D;Mishra N C (Physics Dep, Utkal Univ, Bhubaneswar-751 004, Email: rajib@iopb.res.in) : Ion velocity dependent secondary electron induced point defects in SHI irradiated solids. Indian J Phys 2008, 82(2), 147-54.

Swift Heavy Ion (SHI) mostly dissipates its energy in electron excitations rather than nuclear collisions inside a target material. It is known that about half of the energy deposited into the electron excitation contributes to track formation; the remaining energy is transported far away by the energetic secondary electrons. A certain fraction of the secondary electrons are finally ejected from the surface. Reports the effect of the remaining fraction left behind in the target in modifying the target properties. Show that the energy of these secondary electrons is too low to induce defects by elastic scattering process. Therefore considers the inelastic interaction of the low energy electrons in YBa₂Cu₃O_7-y (YBCO). As a consequence, the secondary electrons induce dissociative recombination in YBCO by breaking some of the Cu-O bonds. We Estimates the maximum energy of the emanated secondary electrons from the ion tracks and their corresponding ranges in YBCO for different initial ion energies. In contrast to the velocity effect that leads to smaller diameter tracks for ions with higher energies, Shows that the diameter of the defected zone due to ion induced secondary electrons increases with increasing energy of the ion.

3 illus, 17 ref

010044   Bishoyi K C;Rout G C (P. G. Dep of Physics, F.M. College (Autonomous), Balasore-756 001, Email: bishoyi@iopb.res.in) : Antiferromagnetism in cuprates through Raman active phonon peaks. Indian J Phys 2008, 82(2), 215-22.

Study the antiferromagnetism in couprates in normal state through Raman active phonon peaks observed in the system. Calculates phonon spectral density function (SDF) from S(q, ω) = -2Im D_qq(ω). The self energy reflects the properties of the ground state of the cuprates in normal state. It is observed that the staggered field (h1) is stronger at lower temperatures and decreases as the temperature becomes higher and ultimately vanishes at the Neel temperature (t_N). The value of h1 at the corresponding temperatures are taken from the (h1 ~ t) plot and are used in the plot of SDF ~ reduced frequency. The observed shift of the Raman active phonon peaks in this plot helps one to infer about the nature of antiferromagnetism in the system.

3 illus, 8 ref

010043   Bhattacharjee B;Baishya B (Physics Dep, Dibrugarh Univ, Dibrugarh-786 004, Email: suparna_bhattacharjee2000@yahoo.com) : Study of superconducting order parameter fluctuation effects in Dy₂O₃, Eu₂O₃ and Pr₆O₁₁ substituted compounds. Indian J Phys 2008, 82(1), 45-9.

Rare earth oxide substituted compounds have been prepared by reacting the powders of rare earth oxides (RE)₂O₃ where (RE = Dy, Eu, Pr), barium carbonate (BaCO₃), and Cupric Oxide, CuO at 950°C for 16 hours by solid-solid reaction method. The thin films have been deposited by high vacuum (≈10^{-6 torr) evaporation technique. Variation of electrical resistivity (ρ) with temperature (T) from liquid nitrogen temperature (77 K) to room temperature have been studied. The transition temperatures have been observed at 89 K, 86 K and 88 K for Dy₂O₃, Eu₂O₃ and Pr₆O₁₁ substituted compounds respectively. The excess conductivity, Aa, and the reduced temperature, ∈, at the respective temperatures have been determined. Compared the effects of superconducting order parameter fluctuations in the three compounds in the light of Aslamasov-Larkin(AL) theory using InΔσ vs In ∈ plots.}

3 illus, 10 ref

010042   Bharat Singh (NO, Prince Institute of Innovative Technology, D-16, Sector-9, New Vijay Nagar, Ghaziabad-201 009, Email: baratprince@hotmail.com) : Forgotten variational principle. Indian J Phys 2008, 82(1), 11-26.

An old variational principle (Maugertuis principle), forgotten as unconvenient quirk of History has been reformulated into the modified variational principle (MP) along with its reciprocal principle (RMP) and both these principles have been derived classically as well as quauntum mechanically. In order to demonstrate the scope of very wide applicability of these new principles, the RMP has been applied to simple problems of Linear Oscillator, Anharmonic Oscillator, Anistropic 2D-Quartic Oscillator (chaotic system) and Central force problem.

^iia12 ref

010041   Bezares-Roder N M;Hemwati Nandan (Centre for Theoretical Studies, Indian Institute of Technology Kharagpur, Kharagpur-721 302, Email: hnandan@cts.iitkgp.ernet.in) : Spontaneous symmetry breakdown and critical perspectives of higgs mechanism. Indian J Phys 2008, 82(1), 69-93.

The foundations of the mass generation mechanism of particles are reviewed. The spontaneous symmetry breaking (SBB) process within the standard model (SM) and minimal supersymmetric standard model (MSSM) is used to explore the present status of the Higgs Mechanism along with the constraints in detecting the Higgs particles in experiments. The possible explanations and generalizations for the case that the Higgs particles should not appear or to couple the Higgs Mechanism (because of their gravitational nature of interaction) are also discussed in detail in view of the Higgs field gravity.

65 ref