003288   Ubale S K;Adgaonkar C S;Nafde R A (NO, Dharampeth, M P Deo Memorial Science College, Nagpur-440 010) : Effect of ferroelectric (lead titanate) doping on dielectric properties of zinc-borate glasses. Indian J pure appl Phys 2001, 39(9), 582-5.

Semi-conducting glasses of the composition (1-x) [50 ZnO-10 V2O5-40 B2O3] + x PbTiO3, where x = 0, 0.1, and 0.2 were prepared in the laboratory by usual quenching method. The dielectric measurements were carried out within frequency range 10-100 kHz and Cole-Cole plots were drawn from which relaxation time for all the three samples was determined. The dielectric properties are found to be influenced by ferroelectric dopant.

3 illus, 1 table, 13 ref

003287   Tiwari V;Bhattacharya T K (NO, S A T I, Vidisha) : Study of stability of flow past a rotating ciruclar plate in porous medium in the presence of a variable magnetic field. Jl MACT 1998, (31), 59-64.

Investigation of flow of a dusty viscous fluid generated by a rotating circular plate in the presence of a variable magnetic field has been studied. Condition of stability for the fluid particles is obtained.

5 ref

003286   Srivastava K S;Sinha K;Rastogi V K;Srivastava S;Saxena K K (Physics Department, Lucknow University, Lucknow-226 007) : Relative intensities of high energy plasmon satellites in Kα X-ray emission spectra of various fluorine compounds. Indian J pure appl Phys 2001, 39(9), 591-4.

The K¹L¹ satellites of Kα1.2 X-ray emission line of various fluorine compounds may be identified as plasmon satellites. An explanation for their origin is suggested using the Bohm and Pines theory of plasma oscillations in solids. Present calculated values for the relative intensities of the K¹L¹ satellites with respect to the main Kα1.2 X-ray line agree well with the experimentally observed values of Endo et al.

2 tables, 25 ref

003285   Singh N P;Singh R V;Singh A K (Department of Mathematics, C L Jain (PG) College, Firozabad-283 203) : Flow of a dusty viscoelastic fluid through a porous medium near an oscillating porous plate in slip flow regime in presence of magnetic field. Jl MACT 1998, (31), 99-108.

MHD flow of an electrically conducting dusty incompressible viscoelastic liquid (Oldroyd B-liquid model) through a porous medium near an oscillating porous plate in slip flow regime has been investigated. Exact solutions for the liquid velocity and particle velocity have been obtained.

7 illus, 9 ref

003284   Singh N P;Singh A K (Department of Mathematics, C L Jain (PG) College, Firozabad-283 203) : MHD effects of heat and mass transfer in flow of a dusty viscous fluid with volume fraction. Indian J pure appl Phys 2001, 39(8), 496-509.

Laminar flow of an electrically conducting, incompressible, viscous fluid embedded with solid, identical, spherical, non-conducting dust particles through a channel consisting of two parallel infinite plates under the influence of a uniform transverse magnetic field has been studied. The solutions for velocity field, temperature distribution and concentration field have been obtained taking into account the volume fraction dust particles. The expressions for shear stress, rate of heat and mass transfer are also obtained. The effects of various parameters for externally cooled channel walls (G_r <62> 0) and externally heated channel walls (G_r <60> 0) are discussed.

6 tables, 22 ref

003283   Roy S K (Department of Physics, Government Polytechnic, Darbhanga-846 004) : Study of the gain of circularly or elliptically polarized antennae. Indian J pure appl Phys 2001, 39(9), 603-6.

Simple and accurate method for determining the gain of an elliptically or circularly polarized antenna has been presented. The gain procedure uses ordinary polarized standard gain antennae in conjunction with the rotating source antenna, direct comparison method of gain measurement. Attempts are made to determine theoretically, the approximate accounts on the antenna under several simplifying assumptions. The gain procedure is valid for right and left hand, circularly or elliptically polarized antenna. A good agreement with experimental results for an elliptically or circularly antennae is obtained.

2 illus, 1 table, 9 ref

003282   Rastogi R G;Subbarao K S V (Department of Physics, Gujarat University, Ahmedabad-380 009) : Ionospheric E-region irregularities during equatorial counter electrojet. Indian J Radio Space Phys 2001, 30(3), 130-7.

Describes a coordinated study of the geomagnetic fields at Trivandrum and Alibag, digital vertical incidence ionograms and oblique VHF backscatter radar echoes at Thumba on a day with a large counter electrojet (CEJ) event in the afternoon hours. It is shown that the cusp type of sporadic-E (E_sc), above the normal E-layer continues to descend with time after the start of CEJ up to about 110 km, indicating downward Hall electric field. When the E_sc layer descends to around 110 km, the downward Hall polarization field due to CEJ, acting on the downward gradient of plasma density in the top side of the layer, generates irregularities by the cross-field instability mechanism. These irregularities give the signature of the q-type of sporadic-E (E_sqeq disappears and no VHF echoes are recorded. With intensification of CEJ, the eastward streaming velocity of the electrons exceed the ion acoustic velocity and strong type-1 echoes are observed on VHF backscatter radar. With the decrease of CEJ even type-2 echoes disappear and no scatter echoes are observed by HF ionosonde or on VHF radar.

8 illus, 27 ref

003281   Ram Prakash;Agrawal B M;Singh A P (Department of Physics, Bipin Bihari PG College, Jhansi-284 001) : Theoretical explanation of intensities of storm-time VLF hiss emissions observed at low latitudes. Indian J Radio Space Phys 2001, 30(3), 121-6.

For known plasma parameters and considering quasi-linear electron cyclotron resonance instability and incoherent Cerenkov radiation process, the intensities of intense storm-time VLF hiss emissions, observed in the low latitude ground stations of Japan, are explained. Based on the intensity calculations in low latitude equatorial plane, which are inconsistent with the observed intensities, the local generations by either of the above two mechanisms are ruled out. It is suggested that the emissions are due to mechanism of quasi-linear electron cyclotron resonance instability in the equatorial plane at L ≈3.6 by <126> 5 keV electrons which drift eastward from higher latitudes and enter the ionosphere at a latitude higher than that of Moshiri (L ≈ 1.6). These then propagate towards the observer in earth-ionsphere wave-guide mode.

2 illus, 2 tables, 28 ref

003280   Rahman M M (Solar Energy Development Laboratory, Department of Physics, University of Rajshahi, Rajshahi-6205, Bangladesh) : Better method for computing H_o appearing in the correlations of solar radiation estimates. Indian J Radio Space Phys 2001, 30(3), 127-9.

Extra-terrestrial solar radiation H_o mainly depends on different parameters (δ, ω_s, φ, E_o), where the solar declination angle δ and the eccentricity correction factor E_o are only the variable quantities in a particular site. Compares the different forms of δ and E_o and recommends one that is most appropriate to assess the value of H_o as well as the solar radiations.

2 table, 19 ref

003279   Quamara J K;Singh N;Singh A (Department of Applied Physics, Regional Engineering College, Kurukshetra-136 119) : Field-induced thermally stimulated currents in poly (p-phenylene sulphide. Indian J pure appl Phys 2001, 39(9), 595-602.

Thermally stimulated polarization currents (TSPC) have been investigated in poly p-phenylene sulphide (PPS) in temperature region 30-250°C under various polarization fields, ranging from 3 to 18 kV/cm and with different heating rates. The effect of high temperature annealing on TSPC behaviour has also been investigated. The TSPC spectra show the presence of a single peak (P1) around 110°C. This peak has been attributed to a weak polar nature of C-S linkage. A phenomenal rise of several order of magnitudes in the current dominated by conduction current is observed above 170°C. During the successive cooling the current retains its positive polarity and in the 2nd TSPC cycle the peak P1 disappears due to temperature dependence of saturation polarization confirming the polar nature of this peak. The kinks observed in the TSPC spectra of annealed samples and with slow heating rates around 170°C are due to the dipolar relaxation process associated with ether linkage, a cross-linked structure formed due to high temperature annealing. The thermal variation in dielectric constant, deduced from TSPC spectra is in good agreement at low temperature, with the result obtained by other method.

5 illus, 2 tables, 21 ref

003278   Pandey R S;Misra K D;Tripathi A K (Department of Applied Physics, Institute of Technology, Banaras Hindu University, Varanasi-221 005) : Kelvin-Helmholtz instability in an anisotropic magneto-plasma in the presence of inhomogeneous perpendicular electric field and parallel flow velocity shear. Indian J Radio Space Phys 2001, 30(3), 113-20.

Electrostatic Kelvin-Helmholtz (K-H) instability by parallel flow velocity shear in the presence of perpendicular inhomogeneous d.c. electric field and density gradient has been investigated by characteristic method using details of particle trajectories. The dispersion relation and growth rate are obtained. The growth rate has been evaluated in the long wavelength region for plasma parameters suited to magnetopause. The velocity shear is found to be the main driving force of this instability in addition to the temperature anisotropy and temperature ratios of electron and ion. The electric field inhomogeneity has destabilizing effect on K-H instability.

8 illus, 26 ref

003277   Mahapatra B P;Santi N;Pradhan N B (Department of Physics, Sambalpur University, Burla-768 019) : Vacuum structure, stability and non-triviality of λφ<. Indian J pure appl Phys 2001, 39(9), 545-52.

Through an explicit construct of the vacuum state in λφ⁴ theory by Bogoliubov transformation the authors show variationally that the theory can be rendered stable and non-trivial. The structure of the vacuum so constructed is characterised by a condensate of off-shell particle pairs. The effective potential based on the vacuum emerges identical to that obtained in the Gaussian approximation. In contrast, the effective potential based upon the perturbative vacuum is shown to lead either to an unstable theory or to a trivial one. The two-point correlation-function and the momentum distribution function for the particle-condensate in the vacuum (vacuum structure function) are calculated.

25 ref

003276   Kor S K;Pandey G;Devraj Singh (Department of Physics, University of Allahabad, Allahabad-211 002) : Ultrasonic attenuation in semi-metallic GdX single crystals (X=P, As, Sb and Bi) in the temperature range 10 to 300 K. Indian J pure appl Phys 2001, 39(8), 510-13.

Ultrasonic attenuation studies have been made in semi-metallic GdX single crystals (X=P, As, Sb and Bi) in the temperature range 10-300 K. Attenuation due to e-p interaction has been studied from 10 to 80K and due to p-p interaction between 100-300 K. Morse potential has been used to evaluate second and third order elastic constants at 0<248> K and then at higher temperatures. Mason's approach has been used to evaluate ultrasonic attenuation. Results have been discussed, at Neel-temperature slight kink in ultrasonic attenuation is observed in all the cases.

5 tables, 15 ref

003275   Khan R;Varshney N K;Varshney G G (NO, Sri Varshney College, Aligarh) : MHD free convective boundary layer flow through porous media. Jl MACT 1998, (31), 135-43.

Purpose of the work is to study the effect of Porosity (K) and Groshoff parameter (G), on the boundary layer of hydromagnetic flow. The velocity of the fluid increases with the increase in porosity parameter and Grashoff parameter but it decreases with the decrease in the Hartmann number.

1 illus, 10 ref

003274   Hegab N A (Physics Department, Faculty of Education, Ain Shams University, Cairo, Egypt) : Electrical properties of amorphous Te38+yAs40-y Ge10Si12. Indian J pure appl Phys 2001, 39(9), 586-90.

The ac conductivity and the dielectric constant have been studied for the chalcogenide glasses Te28+Y As40-y Ge10Si12(y=0,3,6 and 7 at %) as a function of temperature (290-383k) and frequency (10²10⁵Hz). The experimental results indicate that the ac conductivity and the dielectric constant depend on the temperature and frequency and the Te content. The ac conductivity is found to obey the ω⁸ law, in accordance with the hopping model and s is found to be temperature dependent and its value goes down as the temperature is increased. The temperature dependence of the ac conductivity can be reasonably interpreted in terms of the correlated barrier-hopping model (CBH).

5 illus, 20 ref

003273   Gupta A;Pourush P K S (Department of Physics, Institute of Basic Sciences, Dr B R Ambedkar University, Khandari, Agra-282 002) : Microstrip array antenna with and without airgap in plasma environment. Indian J Radio Space Phys 2001, 30(3), 143-7.

Explores the important characteristics of an array of 4x4-element planar array of circular patch microstrip antenna (CPMA) designed on RT-duroid substrate (ε_r = 2.32) at 1.155 GHz (L-band) for on-board applications in mobile communication through satellite. An airgap is introduced in between the dielectric and the ground plane which improves the bandwidth and maintain the gain of the antenna geometry. This antenna geometry is studied in presence of plasma environment and the effect of generation of electroacoustic waves on the radiation characteristics of the given geometry is determined. For this, a well established linearized hydrodynamic theory and vector wave function technique is used to derive the expression for the field pattern and radiated power by the antenna. The important antenna parameters like radiation conductance, efficiency, directive gain and bandwidth along with radiation patterns are computed and plotted for both plasma as well as for the free space.

11 illus, 2 tables, 13 ref

003272   Ghosh B;Chakrabarty S (Department of Physics, , Visva-Bharati, Santiniketan-731 235) : Bounds on the lightest Higg's boson mass in the minimal supersymmetric standard model. Indian J pure appl Phys 2001, 39(8), 481-6.

Implications of the lower bound on the standard-model like Higgs boson mass of the order of that reported by LEP 2 collaborations for the parameters of the Minimal Supersymmetric extension of the Standard Model (MSSM) have been studied. The lower bound on tan α, on the basis of this presently allowed value of Higgs boson mass has been obtained. The possibility of higher value of lower bound allowed in MSSM and their implications for lower bounds on tanα is discussed.

4 illus, 6 ref

003271   El Batal H A;Khalifa F A;Azooz M A (Glass Research Department, National Research Centre, , Dokki, Cairo, Egypt) : Gamma ray interaction, crystallization and infrared absorption spectra of some glasses and glass-ceramics from the system Li2O.B2O3Al2O3. Indian J pure appl Phys 2001, 39(9), 565-73.

Infrared absorption spectra of some selected ternary glasses and their glass-ceramic derivatives from the system Li2O-B2O3-Al2O3 have been measured in the spectral range 200-4000 cm^-1 before and after successive gamma rays irradiation. Vibrational and crystallization techniques are employed to investigate the structure and phases which are found in this system by controlled crystallization. The role of Al2O3 in the structure and the crystallization behaviour of the system has been discussed. The effect of gamma rays on the surface of the glasses and glass-ceramics as revealed from infrared spectroscopy is discussed.

6 illus, 36 ref

003270   Dube G S;Kumar N (Department of Mathematics, Vikramajit Singh Sanatan Dharma College, Kanpur University, Kanpur) : Infinitely long journal bearings under simultaneous effects of inertia and small rotation. Jl MACT 1998, (31), 35-58.

Effects of inertia and small rotation about an axis that lies across the fluid film is being considered for Infinitely long journal bearing. Results concerning the pressure, load capacity, shear stress, frictional force and frictional coefficient for Infinitely long journal bearing have been obtained and the existence of certain fundamental solutions is shown in this extended frame work which are not allowed in any of the three theories of Hydrodynamic lubrication : the classical; the inertia free rotatory and the rotation free inertial. While the load capacity increases with increasing values of the coefficient of fluid viscosity for Infinitely long journal bearing in the classical theory, it is independent of the fluid viscosity in the rotatory frame of reference for the first order of the effect of rotation and is increased by a quantity which is directly proportional to the product of the cube of fluid density, square of the fluid velocity along the span of the bearing and inverse square of the coefficient of fluid viscosity in the inertio-rotatory frame of reference of the first order. This indicates that low viscous fluids could also be successfully utilized as lubricants.

1 illus, 7 ref

003269   Chauhan R P;Kant K;Mahesh K;Chakarvarti S K (Department of Physics, I G N College, Ladwa, Kurukshetrta-136 132) : Radium concentration and radon exhalation measurements in the water around thermal power plants of North India. Indian J pure appl Phys 2001, 39(8), 491-5.

Samples of water from different thermal power plants in northern India have been collected and analysed for radium and radon concentration. For the measurements, α-sensitive LR-115 type II plastic track detectors are used. The radium and radon levels measured in some samples are high and thus unsafe from health point of view. Based upon the available data, the radon exhalation rates have been calculted. The radium concentration varies from 1.11 to 3.11 Bq 1^-1 and the radon concentration varies from 10.64 to 29.78 pCi l^-1. The radon mass exhalation rates vary from 8.95 to 25.08 mBq kg^-1 hr^-1 and surface exhalation rates vary from 245.21 to 690.24 mBq m^-2 hr^-1 in different water samples.

3 illus, 1 table, 15 ref

003268   Bhosale P N;Deshmukh L P;Patil A R (Department of Chemistry, Shivaji University, Kolhapur-416 004) : Bi2(S1-x, Sex)3 thin film composites : synthesis and properties. Indian J pure appl Phys 2001, 39(9), 574-81.

Chemical synthesis of the bismuch sulphoselenide (Bi2(S1-x,Sex)3) composite thin films is presented for the first time. The composites were obtained onto the plane microscopic amorphous glasses by a simple electroless solution growth process. The different preparation conditions and parameters (temperature, time, solution composition and pH etc) were finalized in the initial stages of the work and the reaction kinetics and growth mechanism have been discussed. The content of Bi and Se in the bath and in the film were determined by the spectrophotometric and atomic absorption spectrophotometric techniques. The X-ray diffraction analysis showed that the composites are microcrystalline in nature and are mixed ternary chalcogens of the general formula Bi2(S1-x,Sex)3. The optical studies revealed that the films are highly absorptive with a band to band type transitions and the energy gap decreased, typically, from 1.9 eV for Bi<>2S3 to 0.97eV for Bi2Se3. The electrical conductivity and thermoelectric power measurements showed increased in the conductivity with increased Se-content (x) in the film and n-type conduction of the samples, respectively. The thermo power is of the order of μV/K.

5 illus, 2 tables, 25 ref

003267   Bhatnagar N;Kushwaha M S (Department of Physics, Govt. Model Science College, Gwalior-474 002) : Light front quantization of bilinear quark operators. Jl MACT 1998, (31), 13-21.

Rigorous relation has been established between the matrix elements of Ψ-Ψ and the quark distributions by the light cone approach where the quark field operators are quantized on a light front. This allows a separation of the physical quark degrees of freedom, by means of decomposition of the fermion field operators into unconstrained and constrained components. This quantization automatically eliminates the spurious contributions to Ψ-Ψ which vanish upon time averaging and also corresponding to pair creation, in that the physical quark degrees of freedom are selected by the projection of the good components of Dirac field.

8 ref

003266   Bansal A K;Singh P J;Sharma K S (Department of Physics, MSJ College, Bharatpur-321 001) : Dielectric properties of different varieties of rapeseed-mustard oil at different temperatures. Indian J pure appl Phys 2001, 39(8), 532-40.

Dielectric properties of five rapeseed-mustard oil samples having different percentage of erucic acid have been studied at 100 kHz, 8.93 GHz and optical frequency of sodium light. The dielectric constant at optical frequency (ε_∞) is almost the same for all the five samples, while the dielectric constant at 100 kHz (ε₀), the dielectric constant at 8.93 GHz (ε^') and the loss factor (ε^") show dependence on erucic acid content, but no systematic variation with change in erucic acid is obtained which may be attributed to the presence of other fatty acids in these samples. Temperature variation of dielectric properties has also been investigated in the range 303 to 333 K. ε₀ and ε_∞ decrease regularly with increase in temperature, while ε^' and ε^" do not show a regular variation with temperature, except for Hyola-401, which contains zero level of erucic acid. In other samples ε^' and ε^" show a maximum or minimum type of behaviour at about 313 K, which may be attributed to the presence of some type of molecular resonance/antiresonance at this temperature. The molar free energy of activation, (ΔF_ε) and the macroscopic relaxation time (τ_m) have also been worked out whose.....

7 illus, 4 tables, 11 ref

003265   Balagi V;Prasad K R;Jakati R K;Kataria S K (Electronics Division, Bhabha Atomic Research Centre, , Mumbai-400 085) : Use of nitrogen - filled ion chamber for wide-range gamma monitoring. Indian J pure appl Phys 2001, 39(9), 607-10.

Gamma-sensitive ion chamber has been developed for area gamma monitoring. It has 800 cc sensitive volume filled with nitrogen at 120 psig pressure. With a current sensitivity of 0.6 nA/R/h the chamber needs 250 V for 90% saturation at 10R/h. Authors have developed an instrument to derive exposure rates as high as 80,000 R/h with the help of a single current reading at an applied voltage of 300 V. The instrument can be used to measure unknown exposure rate with accuracy within ±3.5%.

3 illus, 2 tables, 3 ref

003264   Arul G;Palaniappan L (Department of Physics (DDE), Annamalai University, Annamalainagar-608 002) : Molecular interaction studies in the ternary mixture of cyclohexane + toluene + 2 - propanol. Indian J pure appl Phys 2001, 39(9), 561-4.

Ultrasonic velocities, densities and viscosities have been measured for the ternary system of cyclohexane + toluene + 2-propanol at 303, 308 and 313 K. From these data, acoustical parameters such as adiabatic compressibility, free length, free volume and internal pressure have been estimated using the standard relations. The results have been analysed on the basis of variations in ultrasonic velocities and free lengths. Cyclohexane-toluene complexes are observed to be broken by 2-propanol. The presence of weak interactions are noticed in the ternary system.

4 illus, 2 tables, 22 ref

003263   Ahmed N K;Abbady A;El-Kamel A H;Steinhausler F;El Arabi A M (Physics Department, Faculty of Science Qena, South Valley University, ) : Natural radioactivity of some Egyptian rock phosphates. Indian J pure appl Phys 2001, 39(9), 553-60.

²²⁶Ra, ²³⁵U, ²³²Th and ⁴⁰K activity concentration (Bq/kg) in some Egyptian phosphate samples have been measured using HPGe gamma spectrometer. Also their radium equivalent activities were calculated and discussed.

6 illus, 1 table, 12 ref

002292   Yusuf S M;Sahana M (Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085) : Magnetic ordering in La_0.67 Ca0.33 Mn_0.9 Fe_0.1 O₃. Indian J Phys-Pt A 2001, 75(4), 357-61.

The nature of magnetic ordering in La_0.67 Ca_0.33 Mn_0.9 Fe_0.1 O₃ perovskite has been studied by DC magnetization, neutron diffraction and neutron depolarization measurements. A randomly canted ferromagnetic phase has been observed at temperatures below <126> 108 K. Neutron depolarization measurements indicate that the size of magnetic domains is <126> 2 μM in this magnetically ordered phase.

4 illus, 38 ref

002291   Yashwant Singh (Department of Physics, Banaras Hindu University, Varanasi-221 005) : Elasticity of thermotropic liquid crystals. Curr Sci 2001, 80(8), 1026-35.

Describes the elastivity associated with liquid crystalline structures. The deviations from a spatially constant ground state of configurations of liquid crystals often arise due to imposition of boundary conditions, from external fields, or from thermal fluctuations. Since the characteristic distances involved in these phenomena are large compared to molecular dimentsions, liquid crystals are assumed to be continuum with a set of elastic constants. I also descuss a microscopic theory involving the molecular parameters for the elastic constants. This theory which is based on the density-functional formalism, leads to expressions for the elastic constants of any system with continuous broken symmetry and are expressed in terms of the order parameters characterizing the degree and type of ordering and the pair correlation functions of an effective isotropic phase.

21 ref

002290   Yadav K L;Narula A K;Sinha R D P;Ramadhar SIngh;Chandra S (Polymeric and Soft Materials Division, National Physical Laboratory, New Delhi-110 012) : Dielectric and piezoelectric properties of PbTiO₃/PVDF and BaTiO₃/PVDF composites. Indian J Phys-Pt A 2001, 75(4), 479-81.

Synthesis of lead titanate (PbTiO₃) and barium titanate (BaTiO₃) based composites dispersed in a piezoelectric polymer (PVDF) have been undertaken. The composites were formed using sintered PbTiO₃ and BaTiO₃ powder dispersed in PVDF granules using dimethylformamide (DMF) as the solvent. Smooth (thick<126> 1 MM) films of PbTio₃/PVDF and BaTiO₃/PVDF were made The poled films were used for carrying out piezoelectric and dielectric measurements. The results indicate that the measured values of dielectric constant (ε') and piezoelectric charge constant (d₃₃) were strongly influenced by the relative proportions of the two constituents and the poling conditions.

4 illus, 9 ref

002289   Vijayaraghavan R (Sameer, IIT Campus, Mumbai-400 076) : Nuclear magnetic resonance and bulk magnetism. Indian J Phys-Pt A 2001, 75(4), 289-91.

Reviews the power of nuclear magnetic resonance (NMR) technique by giving few examples of studies in solids and their correlation with bulk magnetism. As illustration, the investigation in some transition metal and rare earth alloys are discussed. NMR shift of specific nuclei from that of a diamagnetic solid are correlated to the nature of magnetism in the solids. In the ordered or paramagnetic state, the local field at the nucleus is proportional to the magnetic moment of the magnetic ion either directly or through the polarization of the conduction electrons at different nuclear sites. Examples in spin glass, and superconductors are presented.

7 ref

002288   Viesti G et al (Dipartimento di Fisica dell, Universita di Padova and I N F N, I-35131 Padova, Italy) : Open problems in formation and decay of composite systems in heavy ion reactions. Pramana J Phys 2001, 57(2-3), 469-79.

New highly exclusive experiments in the field of formation and decay of composite systems in heavy ion reactions are presented. Dynamical effects are reviewed in the light of recent works on the role of the N/Z asymmetry between projectile and target. The possibility of extracting directly from the experimental data the emission barrier of alpha particles emitted from highly excited nuclei is discussed. Finally, the first experimental evidence of double giant resonance excitation in fusion-evaporation reaction is presented.

7 illus, 26 ref

002287   Venkatesh J;Subramanian V;Murthy V R K (Microwave Laboratory, Department of Physics, Indian Institute of Technology, Madras-600 036) : Microwave dielectric properties of Pb (Mg_1/3Nb_2/3)O₃ relaxor ferroelectrics. Indian J Phys-Pt A 2001, 75(4), 339-42.

The dielectric properties of lead magnesium niobate relaxor (PMN) has been done at microwave frequencies from 140 MHz to 1 GHz. The measurements was done by reflection technique using co-axial transmission line. Possible uncertainties in the measurement of various parameters are also discussed. The relaxation spectrum of lead magnesium niobate is discussed in terms of Vogel-Fulcher relationship.

6 illus, 16 ref

002286   Upadhyay C;Rai D K;Verma H C;Jitendra Kumar (Department of Physics, Indian Institute of Technology, Kanpur-208 016) : Site preferences for cobalt and cobalt-titanium in substituted barium ferrites. Indian J Phys-Pt A 2001, 75(4), 405-7.

Cobalt and cobalt-titanium substituted barium hexaferrite samples having composition BaFe_12-x Co_xO_{19-x/²(0<60>x<60>1.6) and BaFe12-2x CoxTixO19 (0<60>x<60>1.0) were prepared using an autoignition method and characterized by Mossbauer spectroscopy and magnetization measurements. It is shown that the cobalt ions prefer to occupy 1 k and 2b crystallographic sites of BaFe12-x CoxO19-x/2. Mossbauer spectra of BaFe12-2x CoxTixO19 reveal that the magnetic cobalt and nonmagnetic titanium ions assume 12k, 2b and 4fiv crystallographic sites preferentially with no significant involvement of other sites. The coercivity (Hc) decreases considerably with increasing substitution amount. In BaFe12-x CoxO19-x/2` Hc decreases from 4223 Oe to 2072 Oe as x varies from 0 to 1.6, while in BaFe12-2x CoxTixO19, it decreases much faster and becomes 407 Oe for x = 1. It is suggested that the site preferences of substituted elements weaken the uniaxial anisotropy of the material which, in turn, leads to significant decrease in the coercivity value.}

3 illus, 1 table, 10 ref

002285   Tserruya I (NO, Weizmann Institute of Science, Rehovot 76100, Israel) : Searching for quark matter with dileptons and photons: from SPS to relativistic heavy-ion collider. Pramana J Phys 2001, 57(2-3), 271-83.

Heavy-ion programme at the CERN SPS, which started back in '86, has produced a wealth of very interesting and intriguing results in the quest for the quark-gluon plasma. The high-lights of the programme on dilepton and direct photon measurements are reviewed emphasizing the most recent results obtained in Pb-Pb collisions at 158 A GeV. Prospects from RHIC are discussed.

7 illus, 2 table, 49 ref

002284   Tendolkar N P;Madare M A;Salvi S V (Department of Physics, Institute of Science, 15, Madame Cama Road, Mumbai-400 032) : Electrical behaviour of molybdenum substituted Ba(Fe_0.5Nb_0.5)O₃ perovskite. Indian J Phys-Pt A 2001, 75(4), 367-70.

Diffuse Phase Transition through relaxation is observed in perovskites of A (B`B")O₃. Hence, perovskites viz. Bz(Fe_0.5Nb_0.5)O₃ and Ba(Fe_{0.5Nb0.4Mo0.1)O3 type have been synthesized by high temperature (1100°C) solid state reaction technique. The structural information has been obtained using XRD and FTIR techniques. Investigation of XRD indicates the formation of single phase disordered cubic (a ≅ 4.06 Angstrom) perovskite for both the samples. The particles size decreases slightly on substitution with molybdenum. The IR spectra correspond to a cubic perovskite. The d.c. resistivity at room temperature is considerably larger for the latter sample. The investigation of resistivity with temperature reveals larger band gap for the latter sample. The measurement of dielectric constant as a function of temperature has a broad maximum implying a diffuse phase transition. The relaxation spectra of Ba(Fe0.5Nb0.5)O3 measured at room temperature between 20 Hz and 1 MHz fit into the Maxwell-Wagner model for interfacial polarization. The relaxation time is 5.6 μs and the latter sample has larger relaxation time (5.6 ms). A dielectric relaxation process is attributed to mobile charge relaxation. The longer relaxaton time indicates that the mobile charge motion is slower in the molybdenum substituted perovskite.}

7 illus, 3 table14 ref

002283   Tata B V R (Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102) : Colloidal dispersions and phase transitions in charged colloids. Curr Sci 2001, 80(8), 948-58.

Reviews the structural ordering and phase transitions brought about by parameters such as particle volume fraction, surface charge density, salt concentration and polydisperity. The recent investigations of a two-dimensional system of charged large size metal balls, which has commaness with the charged colloidal system, are also discussed.

10 illus, 70 ref

002282   Srivastava D K (Physics Group, Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata-700 064) : Single photons, dileptons and hadrons from relativistic heavy ion collisions and quark-hadron phase transition. Pramana J Phys 2001, 57(2-3), 235-49.

Production of single photons in Pb+Pb collisions at the CERN SPS as measured by the WA98 experiment is analysed. A quark gluon plasma is assumed to be formed initially, which expands, cools, hadronizes, and undergoes freeze-out. A rich hadronic equation of state is used and the transverse expansion of the interacting system is taken into account. The recent estimates of photon production in quark-matter (at two loop level) along with the dominant reactions in the hadronic matter leading to photons are used. About half of the radiated photons are seen to have a thermal origin. The same treatment and the initial conditions provide a very good description to hadronic spectra measured by several groups and the intermediate mass dileptons measured by the NA50 experiment, lending a strong support to the conclusion that quark gluon plasma has been formed in these collisions. Predictions for RHIC and LHC energies are also given.

10 illus, 1 table, 37 ref

002281   Srivastava B K (Department of Physics and Chemistry, Purdue University, West Lafayette, Indiana, USA) : Multifragmentation and the phase transition: a systematic study of the multifragmentation of 1A GeV Au, La and Kr. Pramana J Phys 2001, 57(2-3), 301-13.

Systematic analysis of the multifragmentation (MF) in fully reconstructred events from 1A GeV Au, La and Kr collisions with C has been performed. Detailed comparisons of the various fragment properties are presented as a function of excitation energy, E^*th <126> 8 MeV/nucleon for Kr. The universal behavior of intermediate mass fragment yields and of the size of the largest is observed only for Au and La when scaled with size of the system. The Kr data are found to lack this property. Moments of the fragment size distribution show that the Kr MF is different than the MF of Au and La. A power law behavior is observed for Au and La with exponent τ <62> 2, while for Kr τ <60> 2. The results are compared with the statistical multifragmentation model (SMM). A single value of all the parameters of the model fits the data for all the three systems. The breakup of Au and La is consistent with a continuous phase transition. The data indicate that both E^*th and the isotope ratio temperature THe-DT decrease with increase in system size at the critical point. The breakup temperature obtained from SMM also shows the same trend as seen in data. This trend is attributed primarily to the increasing Coulomb energy with finite size effects playing a smaller role. The percolation and Ising model studies for finite size neutral matter show behavior which is opposite to the one sen in the present work

8 illus, 29 ref

002280   Srinivasan B;Singh S K;Pillay R G;Kurup M B; Pandey M K (Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085) : Superconducting LINAC booster for the Mumbai pelletron. Pramana J Phys 2001, 57(2-3), 651-8.

Superconducting linear accelerator (LINAC), to boost the energy of heavy ion beams from the 14UD Pelletron accelerator, is under process of construction at Tata Institute of Fundamental Research, Mumbai. The accelerating structures in the LINAC are quarter wave resonators (QWR) coated with lead which is superconducting at liquid helium temperature. With feasibility studies having been completed during the course of the 4th and 5th five-year plan periods, culminating with the demonstration of beam acceleration using one accelerating module, the construction of the LINAC is now under way.

4 illus

002279   Srinivasa Rao K;Madhuri K V;Uthanna S;Naidu B S;Hussain O M (Thin Film Laboratory, Department of Physics, S V University, Tirupati-517 502) : Electrical properties of MoO3 films. Indian J Engng Mater Sci 2001, 8(3), 177-81.

DC conductivity of thin films of MoO3, prepared by activated reactive evaporation technique, revealed electron hopping conduction at lower temperature and the intrinsic thermally activated process at higher temperature. The dielectric properties of Al/MoO3/Al thin film sandwich structures were studied in the frequency range 0.050-100 kHz and in the temperature range 80-400 K. The frequency and temperature dependences of capacitance and dielectric loss were also studied.

6 illus, 13 ref

002278   Singh S K (Department of Physics, Aligarh Muslim University, Aligarh-202 002) : Neutrino anomaly and ν-nucleus interactions. Pramana J Phys 2001, 57(2-3), 315-24.

Review of various calculations of the inclusive quasi-elastic reactions and pion production processes in neutrino reactions for various nuclei at intermediate energies relevant to solar, atmospheric and accelerator neutrinos is presented.

5 illus, 2 table, 20 ref

002277   Singh P (Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085) : Folded tandem ion accelerator facility at Trombay. Pramana J Phys 2001, 57(2-3), 639-50.

Folded tandem ion accelerator (FOTIA) project at BARC has been commissioned. The analysed carbon beams of 40 nA(3⁺) and 25 nA(4⁺), at terminal voltage of 2.5 MV with N2 + CO2 as insulating gas, were obtained. The beams were characterized by performing the Rutherford back scattering (RBS) on gold, tin and iron targets. The beam energy of 12.5 MeV for ¹²C⁴⁺ was consistent with the terminal voltage of 2.5 MV. The N2 + CO2 mixture is being replaced by SF6 gas in order to achieve 6 MV on the terminal. Some of the salient features of the FOTIA and its present status are discussed.

6 illus, 20 ref

002276   Shlomo S (NO, Cyclotron Institute, Texas A and M University, College Station, Texas 77843, USA) : Compression modes and the nuclear matter incompressibility coefficient. Pramana J Phys 2001, 57(2-3), 557-70.

Reviews the current status of the nuclear matter (N = Z and no Coulomb interaction) incompressibility coefficient, Kn,m, and describe the theoretical and the experimental methods used to determine Knm from properties of compression modes in nuclei. In particular consides the long standing problem of the conflicting results obtained for Knm deduced from experimental data on excitation cross sections for the isoscalar giant monopole resonance (ISGMR) and data for the isoscalar giant dipole resonance (ISGDR).

6 illus, 30 ref

002275   Shames A I;Rozenberg E;Gorodetsky G;McCarroll W H;Greenblatt M (Department of Physics, Ben-Gurion University of the Negev POB 653, 84105, ) : Electron magnetic resonance in doped colossal magnetoresistive manganites. Indian J Phys-Pt A 2001, 75(4), 313-6.

The experimental results of electron magnetic resonance study on powdered ceramics samples of LaMn-perovskites doped by divalent Pb, Sn and Zn ions, as well as those for powdered single crystals doped by Na are presented. The main and common features observed for the resonant spectra of all the samples could be noted : a) gradual change of the broad asymmetric line of ferromagnetic resonance (FMR) to narrow line of electron paramagnetic resonance (EPR) with temperature T; b) coexistence within certain temperature intervals of FMR and EPR signals, as well as the signals of FMR and ferromagnetic antiresonance ; c) minimum of the linewidth in the vicinity of 1.1 T_c and its linear broadening above this temperature; d) double integrated intensity of the signal obeys Arrhenius law above 1.1 T_c ; e) specific effect of the non-resonant surface microwave absorption. The results obtained for poly- and single-crystaline samples are compared. The disputable problems in this field are noted.

4 illus, 16 ref

002274   Schukraft J (NO, Email : schukraft@cern.ch, ) : Heavy ions at the LHC: physics perspectives and experimental program. Pramana J Phys 2001, 57(2-3), 345-54.

Ultrarelativistic heavy ion physics is entering the new era of collider experiments with the start-up of RHIC at BNL and construction for detectors at LHC well under way. Gives a summer of the experimental program and current view of heavy ion physics at the LHC, concentrating in particular on physics topics that are different or unique compared to current facilities.

3 illus, 14 ref

002273   Sartale S D;Lokhande C D (Thin Film Physics Laboratory, Department of Physics, Shivaji University, Kolhapur-416 004) : Effect of annealing on the structural and optical properties of SILAR grown Cu_xs thin films. Indian J Phys-Pt A 2001, 75(4), 375-8.

Thin films of copper sulphide (Cu_xS) with thickness up to 0.5 μm were deposited on glass substrates using simple successive ionic layer adsorption and reaction (SILAR) method. Copper (II) sulphate complexed with triethaneloamine (TEA) and thiourea were used as (cuprous ions) cation and (sulphide ions) anion precursors, respectively. The deposition was carried out at room temperature with optimized conditions. The as deposited samples were annealed in air at 100, 200, 300, 400 and 500°C for one hour. These films were characterized by means of X-ray diffraction and optical absorption techniques.

4 illus, 2 table, 20 ref

002272   Sarkar S;Ghorai A K;Middya T R (NO, Sripat Singh College, Murshidabad) : Multiple scattering : a theoretic approach to nonlinear mechanical property of composites. Indian J Phys-Pt A 2001, 75(2), 117-22.

Multiple scattering theory has been used to determine the effective third order elastic constants (TOEC) of polycrystals with constituent crystallites having noncubic symmetry. The same theoretical approach has been utilised here to determine the effective nonlinear elastic constants of isotropic composites. The results obtained have been applied to investigate the elastic percolation behaviour of a two-phase composite, one phase of which is void. The behaviours of both second order and third order elastic constants and cross-over strain field near the percolation threshold have been studied.

24 ref

002271   Santra A B (Nucelar Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085) : Chiral symmetry and nuclear matter equation of state. Pramana J Phys 2001, 57(2-3), 337-44.

Investigates the effect on the nuclear matter equation of state (EOS) due to modification of meson and nucleon parameters in nuclear medium as a consequence of partial restoration of chiral symmetry. To get the EOS, used Brueckner-Bethe-Golstone formalism with Bonn-B potential as two-body interaction and QCD sum rule and Brown-Rho scaling prescriptions for modification of hadron parameters. Finds that EOS is very much sensitive to the meson parameters. It can be fit, with two body interaction alone, both the saturation density and the binding energy per nucleon.

2 illus, 36 ref

002270   Sankapal B R;Lokhande C D (Thin Film Physics Laboratory, Department of Physics, Shivaji University, Kolhapur-416 004) : Room temperature chemical bath deposition of Sb2Se3 thin films from alkaline medium. Indian J Phys-Pt A 2001, 75(2), 143-7.

Room temperature (300 K) deposition of antimony triselenide thin films has been carried out onto glass substrates using simple and less expensive chemical bath deposition (CBD) method. These films are characterized by means of structural, optical and electrical properties. X-ray diffractogram shows that Sb2Se3 films consist of fine grains or nanoparticles. These films are smooth and homogeneous from optical microphotographs and nanocrystalline as seen from SEM images. The bandgap estimated from optical absorption is found to be 1.8 eV. The room temperature dark electrical resistivity is of the order of 10⁶ Ω-cm with n-type electrical conductivity.

9 illus, 16 ref

002269   Samantaray C B;Dhar A;Ray S K;Mukherjee M L (Department of Physics and Meteorology, IIT Kharagpur, West Bengal-721 302) : Optical and infrared studies of Ba_x Sr_1-x TiO₃ thin film. Indian J Phys-Pt A 2001, 75(4), 347-50.

BST thin films have been deposited using rf magnetron sputtering on different substrates like corning glass, MgO single crystal at various deposition conditions. Optical properties of the films were correlated with deposition parameters to optimize the film properties. Optical spectra of all films show a high transmission coefficient (T = 0.9) in the visible and near infrared region. Post deposition annealing strongly affects both optical and structural properties of the films. Optical band gap was found to decrease with Ba content in the BST films, with a typical value of 3.35 eV for BST film. Refractive index and absorption coefficient as a function of wavelength were derived from both transmission and reflection data. IR transmission spectrum of BST (80/20) films on corning glass substrate shows absorption band at 594 cm^-1 which can be attributed to stretching mode of vibration.

6 illus, 1 table, 13 ref