009676   Bandyopadhyay S;Venkatesh R;Gopala Rao R V (Department of Chemistry, Banaras Hindu University, Varanasi-221 005) : Evaluation of partial and total structure factors, bhatia-thornton correlation functions, compressibility and diffusion coefficient of Pb-Pd alloy at different compositions ad temperatures. Indian J pure appl Phys 2002, 40(1), 32-41.

Partial and total structure factors of Pd-Pb alloy have been computed using Lebowitz solution of hard spheres with a square well attractive tail. The calculated values of the total structure factors and also that of the reduced radial distribution function are in excellent agreement with experiment. It is found that the partial structure factors show peculiarities due to the formation of a compound Pb₂-Pd as reported by Christian et al/[J Noncryst Solids, 156(1993)38]. Bhatia-Thornton correlation functions are also calculated, namely, S_NN(k), which show strong correlation in k-space while S_CC(k) and S_NC(k) do not show such correlation. The partial and total radial distribution functions (RDF) are also calculated from which first coordination numbers are obtained. The RDFs show for all compositions the first peaks at 3.35 Angstrom. Exactly the same value has been obtained by Christian et al. This value is in no way nearer to the first nearest neighbour distances in pure Pb or Pd. Thus, the small value of 3.35 Angstrom, which corresponds to the first peak position, has been attributed to the formation of a compound Pb₂Pd, which in crystalline form shows exactly the same distance between unlike neighbouring atoms. The values of compressibility have also been calculated, which show a bigger value of 41.6 x 10^-12 cm²/dyne at 60 atomic percent of Pb. This also indicates the formation of a compound.

8 illus, 21 ref

009675   Asundi A;Eng O K;Huimin X;Boay C G (Nanyang Technological University, School of Mechanical and Production Engineering, Nanyang Avenue, Singapore-639 798) : Advanced moire methods. Asian J Phys 2001, 10(1), 95-104.

Describes two effective methods for the deformation measurement-Moire interferometry method and atomic force microscope (AFM) moire method, which are new ways for the deformation measurement in the micro- and nano-range. The measurement principle, specimen grating preparation techniques, measurement accuracy as well as some applications of these methods are introduced. The micro-moire interferometer was applied to measure the thermal deformation of quad flat pack (QFP) and flip chip (FC) package. The AFM moire method was used to measure the residual strain of mica after being damaged by a Nd:YAG laser.

13 illus, 8 ref

009674   Araslanov S F;Safioulline R K (NO, Kazan State University, Institute of Mathematics and Mechanics, 42008, University Street, 17, Kazan Tatarstan, Russia) : Numerical simulation of flowing gas discharge and electronized CO lasers. Asian J Spectrosc 2001, 5(1), 25-33.

Mathematical model for gas discharge CO lasers includes vibrational kinetics of CO and N2 molecular species as well as the equation for electron energy distribution function and relative gas dynamic equations. The effective method for numerical simulation of powerful CO lasers has been developed. The method allows to calculate laser efficiency, spectrum of CO laser, intensities of separate lines and other important laser characteristics. The results of computation are in satisfactory agreement with the experimental ones.

8 illus

009673   Acharya S;Parichha T K;Talapatra G B (Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700 032) : Spectroscopic study of pentacene assembled in Langmuir-Blogett film mixed with stearic acid. Indian J pure appl Phys 2002, 40(1), 12-16.

Langmuir Blodgett (LB) films of non-amphiphilic pentacene mixed with stearic acid have been prepared and its photophysical properties are reported. Surface pressure versus area-per-molecule isotherms (π-A) at different compositions are measured. Spectroscopic properties (UV-Visible absorption, emission and Scanning Electron Micrograph) of pentacene in LB film have been reported. The blue-shifted absorption and red shifted emission suggest the formation of H-type of aggregates.

5 illus, 16 ref

008660   Mohan M;Srivastava K K (Radio and Atmospheric Science Division, National Physical Laboratory, , New Delhi-110 012) : Computing energy budget within a crop canopy from Penmann's formulae. Proc Indian Acad Sci-Earth Planet Sci 2001, 110(2), 179-84.

The Lhomme's model (1988a), that extended Penmann's formulae to a multi-layer model, is redefined as a function of micrometeorological and physiological profiles of crop canopy. The sources and sinks of sensible and latent heat fluxes are assumed to lie on a fictitious plane called zero displacement plane. Algorithms are given to compute sensible and latent heat flux densities. Performance of the algorithms is compared with that of earlier algorithms.

1 table, 16 ref

008659   Manchanda R K (NO, Tata Institute of Fundamental Research, Colaba, Mumbai-400 005) : Observation of ultra low hard X-ray flux from Cyg X-1 : a possible partial occultation of the X-ray source. J Astrophys Astr 2001, 22(1), 9-20.

Black hole candidate Cyg X-1 was observed in ultra low state on March 30, 1997 using Large Area Scintillation counter Experiment (LASE) in the hard X-ray energy region of 20-180 keV. During the 30 minute exposure a combined signal of 68 sigma was obtained, however, the measured flux at 50 keV was lower by a factor of 2 than the minimum flux reported so far. Using the recent orbital ephemeris of the source, our snap-shot observations were made at φ_5.6 = 0.915, which corresponds to the binary minimum revealed by the ASM light curves. The daily average data from the BATSE detectors give the source intensity level to be higher by a factor of 5. Very low flux values measured in the experiment suggests that the hard X-ray source may have been partially occulted by the primary companion during its transit near the X-ray minimum.

6 illus, 27 ref

008658   Bharadwaj S;Nath B B;Sethi S K (Department of Physics and Meteorology and Center for Theoretical Studi, I.I.T. Kharagpur-721 302, ) : Using HI to probe large scale structures at z <126> 3. J Astrophys Astr 2001, 22(1), 21-34.

Redshifted 1420 MHz emission from the HI in unresolved damped Lyman-α clouds at high z will appear as a background radiation in low frequency radio observations. This holds the possibility of a new tool for studying the universe at high-z, using the mean brightness temperature to probe the HI content and its fluctuations to probe the power spectrum. Existing estimates of the HI density at z <126> 3 imply a mean brightness temperature of 1 mK at 320 MHz. The cross-correlation between the temperature fluctuations across different frequencies and sight lines is predicted to vary from 10^-7 K² to 10^-8K² over intervals corresponding to spatial scales from 10 Mpc to 40 Mpc for some of the currently favoured cosmologica models.

4 illus, 31 ref

007649   Umashankar D C (Application Laboratory, Waters (India) Pvt. Ltd., 36A, 2nd Phase, Peenya Industrial Area, Bangalore-560 058) : Quantitative and qualitative analysis of (-)- epigallocatechin gallate from green tea by LC-MS. J nat Remedies 2001, 1(2), 151-4.

Studies the rapid analysis of the natural product using parallel procesing of High performance Liquid Chromatography (HPLC) with on-line mass detection. The parallel processing of HPLC with mass detection (LC-MS) was used to decrease the cycle time between the analysis, such as (-)-epigallocatechin gallate (EGCG) from green tea. The parallel processing LC-MS method provided a rapid procedure for qualitative and quantitative analysis of EGCG from green tea sample.

^ssc2 illus, 1 table, 8 ref

007648   Suri K;Annapoorni S;Tandon R P (Department of Physics and Astrophysics, Delhi University, Delhi-110 007) : Novel nanocomposite sensor for detection of humidity. J scient ind Res 2001, 60(9), 724-7.

Nanocomposite of iron oxide and polypyrrole were prepared by sol-gel process. The X-ray diffraction study of the nanocomposite has shown the presence of single cubic phase of iron oxide. The composite in the pellet form was used for humidity sensing investigations. The sensitivity of this sensor to humidity was found to increase even at high relative humidities. The device possesses highly stable and reproducible characteristics and has applications in pharmaceutical, medical and environmental industry along with the possibility of their application in detecting gases usch as, CO₂, CH₄, and N₂.

6 illus, 16 ref

007647   Singh A K (Department of mathematics, V S S D College, Kanpur-208 002) : Effect of mass transfer on MHD free convective flow of a viscous fluid through a vertical channel. J Energy Heat Mass Transfer 2000, 22(2), 41-6.

Unsteady free convection and mass transfer flow of an incompressible, homogeneous, electrically conducting viscous fluid through a porous medium in a vertical channel consisting of semi-infinte parallel plates are studied under the influence of uniform magnetic field applied normal to the flow. The solution for velocity, temperature, concentration field and the expressions for skin-friction, Nusselt number and Sherwood number have been obtained using Laplace transform technique. As the solutions and the expressions obtained are in series from, the numerical values have been obtained by truncating the series when the absolute value of the last term is less than 10^-6. The effects of Schmidt number, magnetic parameter, permeability parameter and time parameter on velocity field and skin-friction have been discussed for Grashof number G_r <62> 0 which coresponds to symmetrical cooling and G_r <60> 0 which corresponds to symmetrical heating of channel walls. In addition heat and mass transfer characteristics have also been discussed.

2 illus, 2 tables, 14 ref

007646   Senior T B A;Legault S R (Radiation Laboratory, Department of Electrical Engineering and Compute, University of Michigan, Ann Arbor, MI 48109-21 22 (USA)) : Diffraction by impedance wedges. Proc Indian Natn Sci Acad-Pt A 2001, 67(6), 575-95.

For the classical problem of a plane electromagnetic wave incident at an oblique angle on an impedance wedge having open angle 2Φ, the angular spectra for the total fields in the complex α plane satisfy coupled first order difference equations. These can be expressed alternatively as second order difference equations of period 4Φ for two linear combinations of the spectra, whose solution is then required subject to certain constraints. In many special cases, each equation can be reduced to a pair of first order equations, and when their coefficients are rational functions of sinα and cosα, the determination of the required solutions is easily accomplished. These cases are examined and include that of a wedge of arbitrary angle whose impedances are polarization independent. In other instances such as a half plane with anisotropic impedances and a right-angled wedge with isotropic impedances, the first order equations involve branched functions, and these are are the focus of the study.

7 illus, 12 ref

007645   Sengupta P R;Arup Kumar (Department of Mathematics, University of Kalyani, Kalyani-741 235) : Visco-elastic fluids : and approach to generalized model. Proc Indian Natn Sci Acad-Pt A 2001, 67(6), 687-95.

Attempt has been made to study the behaviour of an extensive class of real fluids-first for purely viscous fluids and then for visco-elastic fluids through the formation of their empirical rheological equations. An attempt has also been made to form a possible generalized empirical equation, which may be an useful representation of the properties of visco-elastic fluids.

22 ref

007644   Sattar M A;Maleque M A (Department of Mathematics, University of Dhaka, Dhaka 1000, Bangladesh, ) : Unsteady MHD Natural convection flow along an accelerated porous plate with Hall current and mass transfer in a rotating porous medium. J Energy Heat Mass Transfer 2000, 22(2), 67-72.

Unsteady MHD free convection flow with Hall current and mass transfer of an electrically conducting incompressible fluid past an accelerated vertical porous plate in a rotating porous medium have been analyzed. In this analysis a constant heat source and a variable suction are also introduced. The plate temperature and cocentration are assumed to be functions of time. With a goal to attain similarity solutions of the problem posed, similarity equations are derived by introducing a time dependent length scale. These equations are then solved numercially. The resulting locally similar solutions are presented in the form of primary and secondary velocities showing the effect of various parameters entering into the problem. Finally, the corresponding skin-friction coefficients and the Nusselt number, which are of physical interest, are tabulated.

7 illus, 1 table, 21 ref

007643   Porsezian K (Centre for Laser Technology, Department of Physics, Anna University, Chennai-600 025) : Optical solitons in resonant and nonresonant nonlinear fibre optics. Proc Indian Natn Sci Acad-Pt A 2001, 67(6), 609-49.

Discusses the concept of optical solitons by considering important linear and nonlinear optical effects like group velocity dispersion, higher order dispersion, Kerr nonlinearity, nonlinear dispersion, simulated inelastic scattering, birefringence, self -induced transparency and various inhomogeneous effects in fibres. After discussing some of these effects, discusses the derivation of pulse envelope equation and the different exact optical soliton possessing models and the effect of gain (loss) is investigated through numerical methods. Finally, discusses the different soliton models in nonlinear couplers.

13 illus, 182 ref

007642   Kumar S;Kishor B (Physics Department, Agra College, Agra-282 002) : Effects of overtaking disturbances on the motion of plane and cylindrical hydromagnetic shock waves. Ultra Scient phys Sci 2001, 13(2), 259-66.

Effects of overtaking disturbances behind the flow, on the motion of diverging plane and cylindrical shock waves in an ideal gas in presence of a magnetic field having only constant axial and azimuthal (Hz₀=constant=H_θ0) components; have been included. Assuming an initial density distribution p₀=p'r^-w where p' is the density at the plane/axis of symmetry and W is a constant, the analytical expressions for flow variables have been deduced. Their numerical estimates, only at permissible shock front locations, have been computed and compared with earlier results.

7 illus, 16 ref

007641   Chattoraj D K (Department of Food Technology & Biochemical Engineering, Jadavpur University, Calcutta-700 032) : Thermodynamics of adsorption at interfaces and the Gibbs surface excess. Proc Indian Natn Sci Acad-Pt A 2001, 67(6), 663-85.

Fundamental principle of thermodynamics of adsorption of solute and solvent at air-water, oil-water and solid-water interfaces in contact with multi-component bulk liquid phase has been discussed. The solute component in the bulk aqueous phase may be non-ionic or ionic surfactant in th absence or presence of a neutral salt. For the fluid interface, the interfacial tension γ decreases with increase in bulk surfactant concentration C₂ so that the value of Gibbs positive surface excesses <71>1₂ or surfactant or negative surface excesses -<71²₁ can be calculated using thermodynamically derived Gibbs adsorption equation. The concept of the Gibbs surface excesses has been clarified and its relation with absolute composition of the interface has been discussed. For electrolyte solution γ increases with increase of C2 so that the negative surface excess -Γ ²₁ for such systems can be calculated using suitable forms of the Gibbs adsorption equations. In case of solid liquid interfaces, positive value of adsorption of surfactants and its negative value for electrolytes can be directly obtained from experiments and their relations with their Gibbs surface excess quantities have been discussed. Using integrated forms of the Gibbs adsorption equations in all cases, standard free energy changes ΔG° for change of the bulk solute activities.

11 illus, 8 tables, 186 ref

007640   Bansod V J;Singh P;Rathishkumar B V (Department of mathematics, Indian Institute of Technology, Kanpur-208 016) : Heat and mass transfer by natural convection from horizontal surface in a Darcian fluid. J Energy Heat Mass Transfer 2000, 22(2), 89-95.

Reports the study of the phenomenon of natural convection heat and mass transfer near a horizontal surface embedded in a fluid saturated porous medium. Similarity solutions for buoyancy induced heat and mass transfer from a horizontal plate are obtained where the wall temperature and concentration are a power function of distance from the origin. Governing parameters for the problem are the buoyancy ratio, B. and Lewis number, Le. Results for Nusselt and Sherwood numbers are presented for wide range of these parameters and the velocity, temperature and concentration profiles are constructed.

6 illus, i tabl, 12 ref

007639   Anila A K;Renuka G;Venugopal C (Department of Physics, S N G College, Chelannur, Calicut) : Loss cone instability and flute instability in mirror devices. Ultra Scient phys Sci 2001, 13(2), 160-63.

The analytical work of lesscone instability (LCI) arising in mirror devices is carried out. The instability equation was derived. Computational work on the growth rate of flute instability in mirror configuration was carried out. The variation of growth rate of FI with wave number was established. The tendency to increase the growth rate as the fraction of the hot ions increases was also verified.

2 illus, 9 ref

007638   Alam M M;Sattar A (NO, Mathematics Discipline,Khulna University, Khulna-9208, Bangaldesh) : Unsteady MHD free convection and mass transfer flow in a rotating system with Hall current, viscous dissipation and Joule heating. J Energy Heat Mass Transfer 2000, 22(2), 31-9.

Unsteady MHD free convection and mass transfer flow with Hall current of an electrically conducting incompressible viscous fluid past an accelerated vartical porous plate is studied by taking the effects of viscous dissipation and joule heating. A similarly parameter, taken as function of time, is introduced in the analysis in order to make the governing equations similar. The suction velocity is then taken to be inversely proprtional to the above parameter. Similarity equations are then derived and solved numerically by the method of superposition. The numerical results are then displayed graphically which shows the effects of various parameters entering into the problem. A qualitative comparison with recent know solutions are also presented. Finally, the local values of the corresponding x and z components of the skin friction and the Nusselt number are shown in tabular form.

10 illus, 3 tables, 12 ref

007637   Aghlara H (Faculty of Physics, University of Tabriz, Iran) : An apparatus for dead-time losses correction in gamma-ray spectrometry. Ultra Scient phys Sci 2001, 13(2), 135-44.

An apparatus with different fixed dead-times has been designed for dead-time losses correction in gamma-ray spectrometry. This unit includes an integrated Schmitt trigger circuit which its main function is to produce a square-wave from the incoming pulses. It counts incoming pulses in random sequence and displays the number of counted pulses, total imposed dead-time and also real time on a display panel. Counting rates have been tested up to 10 kcps, but the unit is designed to operate up to 6x10⁵ cps for uniformally spaced pulses. The design, construction and response of the instrument are discussed in details.

5 illus, 3 tables, 8 ref

006688   Walia U S;Naveen Kumar;Brar L S;Brar H S (Department of Agronamy, Punjab Agricultural University, Ludhiana-141 004) : Influence of rice straw management techniques on the bio-efficacy of isoproturon for the control of phalaris minor in wheat. Indian J Weed Sci 2000, 32(1-2), 63-6.

Bio-efficacy of isoproturon applied at 0.94, 1.41 and 1.88 kg/ha to control Phalaris minor from wheat sown after complete burning, partial burning, incorporation and removal of rice straw was studied from 1995-96 to 1997-98. Population and dry matter of P. minor was found to be significantly less in rice straw removal plots as compared to all other rice straw management system particularly during 1995-96 and 1996-97. Incorporation of rice straw at 8 t/ha significantly decreased grain yield of wheat as compared to removal or complete burning treatment during all the three years. Among the herbicide treatment, application of isoproturon at 1.41 and 1.88 kg/ha as well as diclofop-methyl .90 kg/ha significantly improved grain yield over the recommended level i.e. 0.94 kg/ha of isoproturon. On an average, isoproturon at 0.94 and 1.88 kg/ha increased grain yield by 37.2 and 50.337> over unweeded control.

2 tables, 4 ref

006687   Vyas A D;Rana V A (Department of Physics, University School of Sciences, Gujarat University, Ahmedabad-380 009) : Dielectric dispersion and relaxation mechanism of some polar molecules and their binary mixtures in benzene solutions at microwave frequencies. Indian J Phys-Pt A 2001, 75(6), 643-6.

Dielectric Permitivity (ε') and dielectric loss (ε") of pyridine, chlorobenzene, benzophenone, p-fluoroaniline and mixtures of pyridine + p-fluoroaniline, chlorobenzene + p-fluoroaniline and benzophenone + p-fluoroaniline have been measured at three different microwave frequencies 7.22, 9.1, 19.61 GHz at 30°C in benzene solution. The static permittivity at 455 KHz and refractive index were also measured. The most probable relaxation time (τ0)) and distribution parameter (α) have been determined from measured data using Cole-Cole method of analysis. The presence of intermolecular association through hudrogen bonding (N-H-N_ was observed in the mixtue of pyridine + p-fluroaniline. The dielectric data for p-fluoroaniline and mixtures were analysed in terms of two relaxation times τ1 and τ2.

2 illus, 2 tables, 30 ref

006686   Vani V C (Department of Instrumentation, Indian Institute of Science, Bangalore-560 012) : Interference from multiple reflections of light in a wedge : possible application in profilometry. Indian J Phys-Pt B 2001, 75(5), 433-7.

Interference of light as caused by a wedge is investigated, for an arbitrary angle of incidence, when the wedge is illuminated by a Gaussian beam of narrow width. The width of the beam sets the diffraction properties while the characteristics of the wedge determine the path differences for the rays under multiple reflections. Interference patterns are calculated from simplified expressions. Practical usefulness of this result in determining the profile of a surface is presented, an advantage of this technique being its simplicity i.e. fringe counting and also simplicity in computations.

8 illus, 8 ref

006685   Ullah N (Department of Physics, University of Mumbai, Vidyanagari, Santa Cruz (E), Mumbai-400 098) : Transition from chaotic to regular behaviour in superposed matrix ensemble. Indian J Phys-Pt B 2001, 75(4), 369-71.

Expression has been derived for the probability density function of the nearest level spacing using superposed matrix ensemble. In one limit, it gives Poisson and in the other, Wigner distribution. The explicit form of the spacing distribution is Brody distribution which was given earlier by Brody empirically.

4 ref

006684   Srivastava A K;Virk H S (Department of Physics, Guru Nanak Dev University, Amritsar-143 005) : Modification of optical response of polyvinyl acetate induced by 250keV D<. J Polym Mater 2000, 17(3), 325-8.

Optical response of polyvnyl acetate (PVAc) polymer irradiated by 250 eV D^* ion beam is studied by spectrophotometer technique in the UV-Visible range of 200-500 nm. It is observed that optical absorption varies with time of irradiation. The development of a new peak due to irradiation and its shifting towards the higher wavelength, with time of irradiation has been observed. Due to irradiation the change in the band shape and decrease in the band gap has also been observed.

3 illus, 14 ref

006683   Sreemany M;Ghosh T B (Central Glass and Ceramic Research Institute, , Jadavpur, Kolkata-700 032) : Near surface composition of some alloys by x-ray photoelectron spectroscopy. Pramana J Phys 2001, 57(4), 809-20.

Chemical compositions of the alloys of CuNi(Cu_0.10Ni_0.90, Cu_0.30Ni_0.70, Cu_0.70Ni_0.30) and BiSb (Bi_{0.80Sb0.20, Bi0.64Sb0.34, Bi0.55Sb0.45) are determined by X-ray photoelectron spectroscopy. The stoichiometries are determined and are compared with the bulk compositions. Possible sources of systematic errors contributing to the results are discussed. Errors arising out of preferential etching in these alloys have been investigated. It has been inferred from such studies that the preferential etching does not enrich the surface composition with a particular component for the two systems reported here. Quantitative results of CuNi system indicate that the surface regions of the Cu0.70Ni0.30 alloy is Cu-rich, although no such evidence is observed in case of BiSb system.}

4 illus, 6 tables, 21 ref

006682   Soni S N;Shahlot S (Department of Physics, J.N.V. University, Jodhpur-342 003) : Sommerfeld screening parameters for K-state of the atoms. Indian J Phys-Pt B 2001, 75(5), 469-71.

Acceptable range of values of thh Sommerfeld screening constant σ2, applicable for K-state useful in X-ray spectra, has been estimated by using the first ionisation potential of helium, the measured energies of K α hypersatellites and the available values of α2 valid for other singly ionised states of atoms. Using this range of values of α2, the constant α1 has been calculated for singly ionised K-state of the atoms with Z = 10 to 100. The acceptability of these calculated values has been indicated by their variation with Z.

^ssc1 illus, 1 table, 12 ref

006681   Singh S K;Rai S B (Department of Physics, Banaras Hindu University, Varanasi-221 005) : Study of plasma parameters of a discharge. Indian J Phys-Pt B 2001, 75(4), 363-7.

Plasma parameters viz. electron temperature, electron-, ion-saturation current density, electron density etc. have been measured for the discharge of N2,O2 and Ar under various excitation conditions of discharge using a triple probe method. It is found that electron temperature for monoatomic gas argon is much larger compared to diatomic gases oxygen and nitrogen in the same experimental conditions. A reverse thing is observed for electron density. The electron temperature increases whereas density decreases with the increase of discharge voltage (discharge current).

5 illus, 9 ref

006680   Singh N P;Yadav R A (Department of Physics, Udai Pratap (Autonomous) College, Varanasi-221 002) : Vibrational studies of trifluoromethyl benzene derivatives I : 2-amino, 5-chloro and 2-amino, 5-bromo benzotrifluorides. Indian J Phys-Pt B 2001, 75(4), 347-55.

Polarized Raman spectra of 2-amino, 5-chloro and 2-amino, 5-bromo benzotrifluorides have been recorded in the liquid phase on a Yobin Yvon Raman HG 2S spectrometer and a 1403 Spex monochromator in the region 100-4000 cm^-1. Infrared spectra have been recorded on a Perkin-Elmer-783 and an FTIR-200 spectrometers in the region 200-4000 cm^-1. Vibrational assignments for the observed Raman and infrared bands have been made assuming Cs point group symmetry. It could be possible to assign 43 normal modes for the two molecules on the basis of the observed bands directly. The remaining two modes that the below 120 cm^-1 could be assigned using combination and overtone bands.

5 illus, 3 tables, 23 ref

006679   Singh B;Singh R P (Department of Physics, Jaglal Choudhary College, Chapra-841 301) : Vibrational spectra of 2,4- and 3,4-dimethyl phenol. Indian J Phys-Pt B 2001, 75(4), 373-5.

Infrared and laser Raman spectra of 2,4- and 3,4-dimethyl phenols have been recorded. The vibrational spectra have been analysed assuming CS point group. Assignments for fundamental vibrations, internal modes of vibration of CH3 and OH groups and combination and overtone frequencies have been proposed.

2 tables, 11 ref

006678   Singh A K;Singh D K;Singh R P (Department of Physics, Maharaja College, V.K.S. University, Arrah-802 301) : Estimation of ionospheric parameters by propagation of electromagnetic waves at low latitude. Indian J Phys-Pt B 2001, 75(4), 315-20.

Some results related with the propagation characteristics of electromagnetic waves in very high frequency (VHF), very low frequency (VLF) and extremely low frequency (ELF) ranges through the ionospheric plasma have been reported. Amplitude of scattered VHF signal is recorded and morphological features of ionospheric plasma irregularities are studied. Auto-correlation and power spectrum analysis are carried out to estimate scale length which varies between 200 m to 500 m and drift velocity of plasma irregularities which varies betwen 75 m/sec to 20 m/sec. VLF waves propagate in guided and ducted mode. The VLF whistler wave spectrum is analysed to estimate electron density of ionospheric plasma and the total electron content in a flux tube of unit cross section. Dispersion analysis of ELF proton whistlers is carried out to estimate ionospheric proton density and proton temperature. The results are found in good agreement with the other reported works.

8 illus, 27 ref

006677   Sharma S B;Upadhyaya S C;Sharma B S (NO, Dau Dayal Institute of Vocational Education, Dr. B.R. Ambedkar Univer, Khandari Campus, Agra-282 002) : Molar volume dependence of ultrasonic velocity in some organic liquids. Indian J Phys-Pt B 2001, 75(5), 473-6.

Investigates a simple relationship for the molar volume dependence of ultrasonic velocity in some organic liquids viz. methyl alcohol, ethyl alcohol, n-propyl alcohol, n-butyl alcohol, carbon tetrachloride, n-hexane and toluene. The relationship has been found to hold good for the liquids under the effect of pressure as well as temperature. The values of isothermal and isobaric thermoacoustic parameters have been obtained and reported for the liquids under study.

^ssc3 illus, 2 tables, 10 ref

006676   Sharma R C;Kumar P;Sharma S (Department of Mathematics, Himachal Pradesh University, Summer-Hill, Shimla-171 005) : Rayleigh-Taylor instability of Rivlin-Ericksen elastico-viscous fluid through porous medium. Indian J Phys-Pt B 2001, 75(4), 337-40.

Rayleigh-Taylor instability of Rivlin-Ericksen elastico-viscous fluid through porous medium is considered. Studies the stability aspects of the system. The effects of a uniform horizontal magnetic field and a uniform rotation on the problem are also considered separately. The uniform magnetic field is found to stabilize certain wave-number band whereas the system is unstable for all wave numbers in the absence of magnetic field.

10 ref

006675   Sandhu B S;Saddi M B;SIngh B;Ghumman B S (Physics Department, Punjabi University, Patiala-147 002) : Scattering and absorption differential cross sections for double photon compton scattering. Pramana J Phys 2001, 57(4), 733-41.

Scattering and absorption differential cross sections for nonlinear QED process such as souble photon Comption scattering have been measured as a function of independent final photon energy. The incident gamma photons are of 0.662 MeV in energy as produced by an 8 Ci ¹³⁷ Cs radioactive source and thin aluminum foils are used as scatter. The two simultaneously emitted photons in this process are detected in coincidence using two NaI(E1) scintillation detectors and a slow-fast coincidence set-up of 30 nsec resolving time. The measured values of scattering and absorption differential cross sections agree with theory within experimental estimated error.

5 illus, 1 table, 11 ref

006674   Rostami A;Moayedi S K (Electrical Engineering Department, Faculty of Engineering, Tabriz Univ, , No. 8 Bld, Tabriz 51664, Iran) : Exact solution for light propagation through inhomogeneous media. Indian J Phys-Pt B 2001, 75(4), 357-61.

Inhomogeneous media, the index of refraction is a coordinate-dependent parameter. In this domain, the exact analytical solutions for the electric and magnetic fields can not in general, be found and numerical methods must be used. A suitable algorithm, using the supersymmetric quanturm mechanical approach has been given for the transmission of light through some special case of these media which have spatial one-dimensional coordinate-dependent index of refractions (shape-invariant index of refractions). Exact solutions for electromagnetic fields in these media are expressed in terms of well known special functions.

5 illus, 10 ref

006673   Rajwant Kaur;Beri S B;Kohli J M (Punjab University, , Chandigarh-160 014) : Measuring the top quark mass in the eμ channel. Pramana J Phys 2001, 57(4), 689-700.

Describes a simple method to measure the top quark mass in the tt→ WbWb → eμ channel that may be useful in Run II of DO detector. The method is validated by applying it to the Run Ib eμ data.

9 illus, 3 tables, 12 ref

006672   Phukan A N;Bhuyan P J (Theoretical Physics Laboratory, Department of Physics, Dibrugarh University, Dibrugarh-786 004) : Radial distribution function for superfluid <. Indian J Phys-Pt A 2001, 75(6), 623-8.

Radial distribution function (rdf) for a system of interacting Bosons, with the particles interacting via. stanard two body potentials, has been studied using expression for structure factor derived for such potentials. The dependence of the rdf on the form of potential has been studied. Calculations indicate that potential with soft core does not appear to be realistic, so far as low temperature properties of liquid ⁴He are considered. However, potentials with short-ranged hard core followed by long-ranged repulsive and attractive components yield results comparable to predictions obtainable from experimental studies on liquid ⁴He.

4 illus, 20 ref

006671   Patnaik R C;Das R K;Hota R L;Tripathi G S (Department of Physics, S K C G College, Parlakhemundi-761 200) : Theory of anisotropic diamagnetism, local moment magnetization and carrier spin-polarization in Pb_1-xEu_X Te. Pramana J Phys 2001, 57(4), 795-808.

Presents theoretical analyses of anisotropic lattice diamagnetism, magnetization due to magnetic ions and carrier spin-polarization in the dilluted magnetic semiconductor, Pb_1-xEu_xTe. The lattice diamagnetism results from orbital susceptibility due to inter band effects and spin-orbit contributions. The spin-orbit contribution is found to be dominant. However, both the contributions show pronounced anisotropy. With increase in x, the diamagnetism decreases. Considers contributions from randomly distributed isolated magnetic ions and clusters of pairs and triads for the local moment magnetization. The isolated magnetic-ion contribution is the dominant one. Calculates the magnetization for two typical magnetic ion concentrations: x=0.03 and x=0.06. Temperature dependence of the magnetization is also considered. Apart from lattice and localized magnetic ions, the carrier contribution to the spin-density is also calculated for a carrier density of p=10¹⁸¹ cm^-3. The relative spin-density of carriers increases with increase in the magnetic field strength and magnetic ion concentration. The agreement with experiment where available is reasonably good.

4 illus, 2 tables, 26 ref

006670   Patil P E;Keller J M;Dubey R K;Datt S C (Department of Postgraduate Studies & Research in Physics, Rani Durgavati University, Jabalpur-482 001) : Polarization in poly (Vinyl chloride) (PVC) and poly (methyl methacrylate) PMMA) blends films investigated by thermally stimulated depolarization current technique. Indian J Phys-Pt A 2001, 75(6), 661-4.

Thermally stimulated depolarization current (TSDC) characteristics in short circuit configuration have been studied in the laboratory grown PVC and PVC : PMMA blends of different wt % composition ratio as a function of polarizing field and polarizing temperature. Films of thickness 100μm were thermally polarized with fields of 25,50,60 and 75 kV/cm at temperatures 50, 70, 90 and 110°C. The TSDC thermograms obtained, exhibit a broad hump between 50 - 90°C and well-defined peak between 128 - 148°C. The high temperature peak is considered to be associated with interfacial polarization due to space charge accumulated at the crystalline amorphous boundaries. The hump which is observed between 50-90°C is attributed to the relaxation of dipoles connected to the main chain of PVC having a continuous spectrum of activation energy and relaxations times. The results also indicate that PVC dipoles in the polyblend are so entangled that their contribution to the total polarization of the polyblend samples become insignificant.

5 illus, 18 ref

006669   Pandya J N;Vinodkumar P C (Department of Physics, Sardar Patel University, Vallabh vidyanagar-388 120) : Masses of S and P wave mesons and pseudoscalar decay constants using a confinement scheme. Pramana J Phys 2001, 57(4), 821-7.

In the framework of relativistic harmonic confinement model for quarks and antiquarks, the masses of S- and P-wave mesons and pseudoscalar decay constants from light flavour to heavy flavour sectors are computed. The residual two-body Coulomb interaction and the spin-dependent interaction of the confined one fluon exchange effects (COGEP) such as spin-spin and spin-orbit interactions are perturbatively incorporated with the confinement energy to get the respective vector-pseudoscalar meson mass differences. Employs the same parametrization and model parameters as used in recent study of low-lying hadron masses and leptonic decay widths. The results are being compared with the values obtained from other theoretical models and the experimental values.

3 tables, 27 ref

006668   Natarajan S (Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore-560 064) : Open architectures-is there a rationale in their formation. J Indian Inst Sci 2001, 81(1), 25-36.

Efforts made to understand the formation of potentially important solids with extended architectures are presented. Studies clearly demonstrate the importance of zero-dimensional 4-membered ring monomer and the one-dimensional edge-shared ladder structures in the building-up process of complex structures of higher dimensionalities. The transformation reactions, carried out on zero- and one-dimensional structures, provide insight into the possible pathways involved in the formation of two-and three-dimensional structures. All the studies described herein have been carried out on single crystals using X-ray crystallography and in order to have better understanding, it is important to carry out in-situ experiments under real-time conditions.

9 illus, 25 ref

006667   Narasimhan S (Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore-560 064) : Surprises in the physics of metal surfaces. J Indian Inst Sci 2001, 81(1), 15-23.

Metal surfaces sometimes exhibit surpisingly complex properties, such as complicated surface structures, vibrational anisotropies, and a strongly enhanced surface anharmonicity, which result in drastic changes in properties as a function of temperature. Some examples are discussed in detail: the strong temperature dependence of interlayer spacings for Ag(111), the complicated herringbone reconstruction of Au(111), and reversed vibrational anisotropies and thermal contraction on unreconstructed FCC(10) surfaces. It is shown that ab initio density functional theory calculations can shed useful insight on these puzzling phenomena.

4 illus, 1 table, 22 ref

006666   Munish Kumar (Department of Physics, SRMS College of Engineering and Technology, Bareilly-243 202) : Isothermal compression and thermal expansion of rhenium. Indian J Phys-Pt A 2001, 75(6), 665-7.

Simple theoretical method based on the theory of equation of state is proposed to investigate the isothermal compression of rhenium upto V/V° = 0.734. Thermal expansion is reported from room temperature upto the melting temperature (Tm = 3543K) by varying the pressures from 0 to 200 GPa. The results are compared with the available experimental and theoretical data. The good agreement obtained with the results based on the first principle calculations, support the validity of the work.

2 illus, 23 ref

006665   Mukhopadhyay T K;Kundu K K;Das N C (Krishnarampur High School, , Rondia, Burdwan-713 420) : Problem of piezoelectric bar under electrical and thermal excitation. Indian J Phys-Pt A 2001, 75(6), 639-41.

Attempt has been made to investigate analytically the mechanical behaviour of an open-circuited piezoelectric quartz bar, one end of which is subjected to some prescribed electrical and thermal excitations while the other end is kept fixed. The method of operational calculus has been used and the numerical results are illustrated graphically. For time-scale ranging from 0 to 1s variations of mechanical exhibit parabolic in nature and it is found to be of the order of 10^-13 m.

1 illus, 1 table, 12 ref

006664   Mishra A P;Balasubramanian T K (Spectroscopy Division, Modular Laboratories, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Rovibrational matrix elements of the multipole moments and of the polarizability of the H₂ molecule in the solid phase: effect of intermolecular potential. Pramana J Phys 2001, 57(4), 727-32.

Rovibrational matrix elements of the multipole moments Q_l up to rank 10 and of the linear polarizability of the H₂ molecule in the condensed phase have been computed taking into account the effect of the intermolecular potential. Comparison with gas phase matrix elements shows that the effect of solid state interactions in marginal.

3 tables, 20 ref

006663   Manam J;Rao A N C V (Department of Applied Physics, Indian School of Mines, Dhanbad-826 004) : Evaluation of trapping parameters of thermally stimulated glow curves in KC1:Pb:Mn single crystals. Indian J Phys-Pt A 2001, 75(6), 657-9.

Amongst the various experimental techniques to study the trapping parameters associated with thermally stimulated luminescence glow curves, isothermal luminescence decay method (ILDM) is more effective for estimating order of kinetics (b) and activation energy (E). The results of trapping parameters for the most prominent glow peak (Peaking at 140°C) of RT (Room temperature), γ-irradiated KCl:Pb:Mn are reported. It is established that 140°C glow peak of KCl:Pb:Mn is associated with first order kinetics and the activation energy is found to be 0.54eV. This method is applicable not only for first order and second order kinetics but also for T S L (Thermally stimulated luminescence) process involving intermediate order of kinetics.

3 illus, 6 ref

006662   Maiti M;Misra T;Bhattacharya T;Sinha S; Ganguly T (Department of Spectroscopy, Indian Association for the Cultivation of, , Jadavpur, Calcutta-700 032) : Non-radiative transitions of 2-methylindole and 2-methylindoline in presence of the electroc acceptor 2-nitrofluorene at the ambient as well as at liquid N2 temperatures. Indian J Phys-Pt A 2001, 75(6), 615-22.

The results of detailed investigations have been reported, both at the ambient temperature and at 77 K, on the fluorescence and phosphorescence quenching of the two electron donors, 2-methylindole (2MI) and 2-methylindoline (2MN), in presence of the acceptor 2-nitrofluorene (2NF). Both steady state and time-resolved spectroscopic techniques have been used. At the ambient temperature and at very dilute solutions of the donor (<126> 10^-4 mol dm^-3) and acceptor molecules (<126> 10^-6 mol dm^-3 to <126>10^-5 mol dm^-3), static quenching process appears to be primarily responsible for the observed fluorescence quenching. However, at higher concentrations of the donor and acceptors (<126> x 10^-3 mol dm^-3), dynamic process, specially photoinduced electron transfer (PET) reactions has been confirmed by the direct observations of the radical ions (both cation and anion) in the transient absorption spectra. PET reaction turns out to be highly exothermic type (-Δ GSET⁰ ≥ 2.0 e V) in highly and moderately polar environments eg., acetonitrile (ACN) and tetrahydrofuran (THF) while in low polarity medium n-heptane (NH), the exothermicity reduces considerably (-Δ GSET⁰ ≥ 0.7 to 0.9 eV). Spectral argument in favour of occurrence of another dynamic process "energy transfer" at the room temperature.

8 illus, 2 tables, 40 ref

006661   Mahapatra S;Nag J;Sural D P;Mukherjee S N (Department of Physics, Jadavpur University, Kolkata-700 032) : Simple coordinate space approach to three-body problems-examples; Halo nucleus and double-λ hypernucleus. Pramana J Phys 2001, 57(4), 717-26.

Shows how to treat the dynamics of an asymmetric three-hody system consisting of one heavy and two identical light particles in a simple coordinate space variational approach. The method is constructive and gives and efficient way of resolving a three-body system to an effective two-body system. It is illustrated by explaining the structural properties of some nuclei of current interest, namely halo nuclei and double-λ hypernuclei. The ansatz used may be of value in a number of three particle problems of similar nature.

2 illus, 2 tables, 19 ref

006660   Khan M A;Das T K (Department of Physics, University of Calcutta, 92 APC Road, Kolkata-700 009) : Investigation of halo structure of <. Pramana J Phys 2001, 57(4), 701-16.

Hyperspherical harmonics expansion method is applied to a three-body model of two neutron halo nuclei. Convergence of the expansion has been ensured. A repulsive part is introduced in the interaction between the core and the extra-core neutron, to simulate Pauli principle. Two neutron separation energy, r.m.s. radii, correlation factor and probability density distributions have been calculated for ⁶He. It is found that the convergence of the two neutron separation energy is relatively slow, while other quantities reach convergence quickly.

1 illus, 5 tables, 66 ref

006659   Kanchana G;Arivuoli D;Kazimierz L;Fornari R (Crystal Growth Centre, Anna University, Chennai-600 025) : Growth and characterization of bismuth thiourea chloride (BTC). Indian J Phys-Pt A 2001, 75(6), 647-50.

Bismuth thiourea chloride (BTC) single crystals (red and yellow) were grown in sodium meta silica gel at ambient temperature. The conditions for the growth of large size BTC single crystals were investigated. The crystal structure of red crystal redetermined using single crystal X-ray diffraction studies and found to be rhombohedral with space group P 3 and that of the yellow crystal to be triclinic with space group P 1. Thermal analyses such as TGA and DSC indicate that the compound is thermally stable upto 140°C. The presence of sulphur-bismuth bonds in the complex has been revealed by Fourier transform infrared analysis. The hardness test was carried out using vicker's microhardness tester.

10 illus, 1 table, 12 ref