002068   Gaur N K;Singh P;Rini E G;Galgle J;Singh R K (Phys Dep, Barkatullah Univ, Bhopal-462 026, Email: surela@sancharnet.in) : Phonon dispersion curves of CsCN. Pramana J Phys 2004, 63(2), 419-23.

Recent publication on phonon dispersion curves (PDCs) of CsCN from the neutron scattering technique has motivated the ited work. The extended three-body force shell model (ETSM) has been applied by incorporating the effect of coupling between the translation modes and the orientation of cyanide molecules for the description of phonon dispersion curves of CsCN between the temperatures 195 and 295 K. the results on PDCs in symmetric direction are in good agreement with the experimental data measured with inelastic neutron scattering technique.

2 illus, 1 table, 33 ref

002067   Ganguly R;Aswal V K;Hassan P A;Gopalakrishnan I K;Yakhmi J V (Novel Mater and Structural Chem Div, Solid State Phys Div, TP&PED, Bhabha Atomic Res Centre, Mumbai-400 085) : Sphere-to-rod transition of triblock copolymer micelles at room temperature. Pramana J Phys 2004, 63(2), 277-83.

A room temperature sphere-to-rod transition of the polyethylene oxidepolypropylene oxide-polythylene oxide-based triblock copolymer (PEO)₂₀ (PPO)₇₀ (PEO)₂₀ micelles have been observed in aqueous medium under the influence of ethanol and sodium chloride. Addition of 5-10% ethanol induced as high temperature sphere-to-rod transition of the micelles, which is brought to room temperature upon addition of NaCl. The inference about the change in the shape of the miceles has been drawn from small-angle neutron scattering (SANS) and viscosity studies.

3 illus, 2 tables, 13 ref

002066   Galgale J;Kaur N;Singh P;Manake M;Gaur N K; Singh R K (Phys Dep, Barkatullah Univ, Bhopal-462 026) : Static and dynamic properties of KCN_xCl_1-x. Pramana J Phys 2004, 63(2), 413-7.

An extended three-body force shell model (ETSM) has been applied to investigate the static and dynamic properties of KCN_xCl_1-x for the composition x = 0.56 and 1.0 at 300 K. The phonon dispersion curves computed are compared with the single crystal neutron diffraction data. The unusual features of these curves are the upward curvature seen in some of the acoustic branches. This is a result of K-dependent softening of the phonon due to translation-rotation coupling. The transverse acoustic branch is more soft near the zone centre.

2 illus, 3 tables, 27 ref

002065   Efrem D'Sa J B C;Bhobe P A;Priolkar K R;Das A;Krishna P S R;Sarode P R;Prabhu R B (Phys Dep, Goa Univ, Taleigao Plateau, Goa 403 206) : Low temperature magnetic structure of MnSe. Pramana J Phys 2004, 63(2), 227-32.

Low temperature neutron diffraction studies have been reported on MnSe in order to understand the anomalous behaviour of their magnetic and transport properties. The study indicates that at low temperatures MnSe has two coexisting crystal structures, high temperature NaCl and hexagonal NiAs. NiAs phase appears below 266 K and is antiferromagnetically ordered at all temperatures while the NaCl phase orders antiferromagnetically at 130 K.

5 illus, 14 ref

002064   Dixit M;Bhattacharya S;Mohan R;Singh K; Krishna P S R;Shelke V;Gaur N K;Singh R K (Phys Dep, Barkatullah Univ, Bhopal-462 026) : HgO-added YBa₂Cu₃O₇-δ superconductors. Pramana J Phys 2004, 63(2), 233-7.

The HgO-added YBa₂Cu₃O₇-δ (YBCO) superconductor has been studied for its structural and superconducting properties. Polycrystalline YBCO samples were synthesized through solid-state reaction method by adding HgO in different concentrations without using oxygen annealing. All the samples showed a sharp superconducting transition temperature around 90 K. The X-ray diffraction patterns of all the samples revealed monophasic Y-123 nature. The structural studies were carried out by neutron scattering and Rietveld analysis. The neutron scattering revealed that Hg is not incorporated in the Y-123 system and has shown optimum oxygen concentration. The significant role played by the HgO is to provide oxygen ambient through its decomposition, thus changing the oxygen balance in favour of high Cu-valence state.

3 illus, 1 table, 19 ref

002063   Desai S S;Shaikh A M;Radhakrishna V;Rajanna K (Solid State Phys Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Development of a microstrip-based neutron detector. Pramana J Phys 2004, 63(2), 471-5.

A gas-filled microstrip detector for thermal neutrons has been built and successfully tested in the laboratory. The detector has an active area of 20 mm x 15 mm and consists of alternate anodes and cathodes of widths 12 μm and 300 μm respectively. The anode to cathode gap is 150 μm and the pitch is 612 μm. A high resistance, meandering type horizontal strip connects the anodes at one end and aids in position sensing by charge division method. The detector is tested with gas mixture ³He+Kr (1:2) and ^He+CF₄ (2:1) at pressure of 3 atmospheres and using a Pu-Be neutron source. The pulse height spectrum shows energy resolution of ~ 8% (FWHM) for the 764 keV peak at anode voltage of 525 V for ³He+Kr and ~15% at anode voltage of 800 V or ³He+CF₄. Gas gains up to 6.3 x 10³ and 3.6 x 10³ are obtained respectively with these gas mixtures. The overall efficiency of the detector along the sensitive length is tested by exposing the active area to neutrons and recording the position spectrum. The detector shows fairly uniform efficiency (~45%) over the active length.

4 illus, 1 table, 8 ref

002062   Das N C;Raja Sekhar B N;Padmanabhan S;Shastri A;Jha S N;Bhattacharya S S;Bhat S;Sinha A K;Sahani V C (Spectroscopy Division, Centre for Design and Manufacture, Physics Group Bhabha Atomic Research Centre, Mumbai-400 085) : Development of photophysics beamline at indus-1 synchrotron radiation source. J Optics 2003, 32(4), 169-76.

A beamline to carry out photoabsorption and fluorescence experiments using INDUS1 synchrortron radiation source has been recently commissoned at the Centre for Advanced Technology,Indore India. The optical system for the beamline consists of a pre-focusing toroidal mirror, an indigenously developed one meter Seya-Namioka monochromator and a post-facusing toroidal mirror to cover the wavelength range of 500 Angstrom-2000 Angstrom. An experimental chamber for performing VUV excited fluorescence on solid samples is coupled to the beamline. A quarter meter gas cell has also been fitted with the experimental station. Presents the salient features of the beamline and the recorded photoabsorption spectra of benzene and benzene d₆.

6 illus, 1 table, 10 ref

002061   Das N C et al (Spectroscopy Division, Centre for Design and Manufacture, Bhabha Atomic Research Centre, Mumbai-400 085) : Design development and performance evaluation of a high resolution VUV spectrometer at Indus-I synchrotron source. J Optics 2003, 32(4), 177-92.

An indigenous design, fabrication and performance evaluation of a vacuum ultraviolet (VUV) spectrometer are described for carrying out spectroscopic research of atomic and molecular gases and vapours using Indus-I synchrotron source of raditiation commissioned at Center for Advanced Technology, Indore India. The spectrometer is based on an off-axis Eagle type of compact mounting suitable for the VUV region of the spectrum. The spectrometer consists of a concave grating of radius of curvature 6.65 m as a dispersing element and a photomultiplier tube (PMT) as a radiation detection element. The reciprocal linear dispersion of the instrument is about 1.24 Angstrom/mm with a grating of 1200 grooves/mm. The wavelength resolution achieved is 0.08 Angstrom. The wavelength resolution can be obtained as 0,005 Angstrom by replacing the present grating of 1200 grooves/m with a grating of 4800 grooves/mm useful in the wavelength region from 400 Angstrom to 2000 Angstrom. The present wavelength range of the spectrometer is from 400 Angstrom to 5800 Angstrom with the grating of 1200 groovesum. For one wavelength setting of the grating, a spectral band of 200 Angstrom can be recorded by moving the PMTalong the Rowland circle of diameter 6.65 m. For changing the wavelength region, the grating is first rotated and then translated by two stepper motors controlled by a personal computer. The accuracy achieved in the angular rotation of the grating is I arc-sec whereas the accuracy achieved in the linear displacement of the grating is 22 microns. The precision optical alignment for obtaining a well focused spectrum and subsequent performance evaluation of the spectrometer-have been done in the wavelength region from 2900 Angstrom to 5800 Angstrom because of the availability of spectral lamps such as mercurydischarge lamp and He-Ne laser and due to the convenience of aligning the optical spectrometer in air rather than in vacuum. Various spectral lines of mercuryhave been recorded in the photographic mode as well as in the photoelectric mode. The recorded spectral lines of wavelengths 5790.66 Angstrom, 5769.6 Angstrom, 5460.74 Angstrom, 4358.33 Angstrom, 4077.83 Angstrom, 4046.56 Angstrom, 3663.28 Angstrom, 3654.84 Angstrom, 3650.15 Angstrom, 3131.84 Angstrom, 3131.55 Angstrom, 3125.67 Angstrom, 3021.5 Angstrom, 2967.28 Angstrom are found to be sharp. The spectrometer will be coupled to the high resolution VUV beam line at Indus-I, Centre for Advance Technology, Indore, The expected resolution will be 0.005 Angstrom in the wavelength range of 700 Angstrom to 2000 Angstrom by using the grating of 4800 grooves/mm as a dispersing element.

6 illus, 1 table, 14 ref

002060   Chitra R;Das A;Choudhury R R;Ramanadham M; Chidambaram R (Solid State Phys Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Hydrogen bonding in oxalic acid and its complexes: a database study of neutron structures. Pramana J Phys 2004, 63(2), 263-9.

The basic result of carboxylic group that the oxygen atom of the -OH never seems to be a hydrogen bond acceptor is violated in the cases, namely urea oxalic acid and bis urea oxalic acid complexes, where the hydroxyl oxygen atom is an acceptor of a weak N-H...O hydrogen bond. The parameters of this hydrogen bond, respectively in these structures are: hydrogen acceptor distance 2.110 Angstrom and 2.127 Angstrom and the bending angle at hydrogen, 165.6° and 165.8°. The bond strength around the hydroxyl oxygen is close to 1.91 valence units, indicating that it has hardly any strength left to form hydrogen bonds. These two structures being highly planar, force the formation of this hydrogen bond. As oxalic acid is the common moiety, the structures of the two polymorphs, α-oxalic acid and β-oxalic acid, also were looked into in terms of hydrogen bonding and packing.

8 illus, 2 tables, 11 ref

002059   Chandra P;Nanda B K;Dimri G P (Instruments research and Development and Establishment, , Raipur, Dehradun 248 008) : Test set-up for the measurement of higher dioptric powers. J Optics 2003, 32(4), 193-6.

Magnifiers are used as low vision aids by partially visually handicapped persons. Such magnifiers were developed by Instruments Research and Development Establishment (DRDO) and are being mass-produced in the country. Those are distributed by the National Institute of Visually Handicapped to the low vision persons. Before using the particular type of magnifier one must know the power of his eye so that suitable magnifier can be used. Such instruments are available in the market and are generally known as dioptrometer. Existing dioptrometers can not measure the powers beyond ±22 Dioptres. Therefore it was felt necessity to rig up a test set up to measure the powers beyond ±22 Dioptres. The proposed set-up is capable of measuring dioptric power between ±005 to F±40 D. Measurement of powers of standard dioptric sets are carried out using the proposed set-up and are compared with the existing dioptrometre measurements. Results are within reasonable accuracy. Measurement of higher dioptric powers (+ 16 D, + 24D, +24D, +28D) of magnifiers developed by IRDE are also carried out using the proposed set-up.

^ssc3 illus, 1 table

002058   Chander S;Krishnamurthy a;Srivastava B;Gupta A;Nigam a K (Phys Dep, Univ of Rajasthan, Jaipur-302 004) : Verwey type transition in nano-particle spinel ferrite Fe₂CO_0.8O₄. Indian J Engng Mater Sci 2004, 11(4), 343-8.

8 illus, 1 table, 11 ref

002057   Chakraborty K R;Yusuf S M;Krishna P S R; Ramanadham M;Tyagi A K (Solid State Phys Div, Applied Chem Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Low-temperature neutron diffraction study of La_0.95Nd_0.05CrO₃. Pramana J Phys 2004, 63(2), 251-5.

It has been synthesized polycrystalline La_0.95Nd_0.05CrO₃ sample by doping the La-site of LaCrO₃ with Nd and its magnetic properties have been studied using DC magnetization and neutron diffraction techniques. DC magnetization study shows a paramagnetic to a weak ferromagnetic-like transition at ~ 295 K followed by signatures of a spin re-orientation phenomenon at 233 and 166 K and finally a transition to an antiferromagnetic like phase at ~ 21 K. Low-temperature neutron diffraction measurements confirm a weak ferrimagnetic ordering of Cr³⁺ moments at all temperatures below 295 K.

3 illus, 1 table, 6 ref

002056   Chakraborty K R;Krishna P S R;Hegde M S (Solid State Physics Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Neutron scattering study of combustion-synthesized Ce_1-xCu_xO_2-x. Pramana J Phys 2004, 63(2), 245-9.

Powder neutron diffraction and Hi-Q neutron diffraction data have been recorded and analysed in order to obtain the local and long range order of Cu in Cu- doped CeO₂ with three doping levels of Cu. Rietveld method and MCGR techniques of data analysis for the two types of data reveal that the Cu ion is in the 2+ oxidation state and has a vacancy in its first coordination shell. These deductions from the data analysis fit well with the mechanism of catalysis propose.

2 illus, 1 table, 7 ref

002055   Bozhko A A;Putin G F (General Phys Dep, Perm State Univ, 15 Bukirev St., 614600, Perm, Russia) : Magnetic action on convection and heat transfer in ferrofluid. Indian J Engng Mater Sci 2004, 11(4), 309-14.

The interplay of buoyance and thermo-magnetic convection mechanisms are investigated in a horizontal ferrofluid layer heated from one wide side and cooled from another in the presence of external uniform transversal magnetic field. The influence of gravitational settling of magnetic particles and their aggregates on heat transfer and convection instability is also condidered. The ferro-colloids with different concentrations of magnetic phase are employed for the control of driving magnetic forces. It is shown that in concentrated colloid the driving forces prevail over suppress ones, but in weak concentrated colloid the gradients of density due to gravity sedimentation of particles overwhelm convection stirring. It is important that thermo-magnetic convection mechanism allows strengthening of heat transfer in ferrofluid three times.

11 illus, 13 ref

002054   Balachary M;Ram Pal;Kumar A;Bhramaramba K (Defence Electronics Res Lab, , Hyderabad-500 005) : Broadband MMW reflector antenna with fine breading auto track horms for ECM applications. IETE Tech Rev 2003, 20(6), 577-82.

A broadband millimeter wave (MMW) Reflector with fine bearing auto track horns for Electronic Counter Measure (ECM) application is described. The antenna generates high Effective Radiated Power (ERP) of the order of 100 kW and more. Two pairs of fine bearing auto track horns, one each for Azimuth and Elevation plane, working on amplitude comparison monopulse technique steer the narrow beam parabolic reflector antenna accurately on to the enemy radar for effective jamming. Design, development, fabrication, electrical evaluation and results achieved for this antenna system are presented.

9 illus, 7 ref

002053   Aswal V K;Joshi J V;Goyal P S;Patel R; Upadhyay R V;Mehta R V (Solid State Phys Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Temperature dependent small-angle neutron scattering of CTABr-magnetic fluid emulsion. Pramana J Phys 2004, 63(2), 285-90.

Small-angle neutron scattering studies have been carried out to check the structural integrity of citryltrimethylammonium bromide (CTABr) micelles in a magnetic fluid for different magnetic fluid concentrations at two different temperatures 303 and 333 K. It is found that the CTABr micelles grow with increasing magnetic fluid concentration and there is a decrease in the micellar size with increase in temperature.

4 illus, 1 table, 16 ref

002052   Aswal V K;Goyal P S;Amenitsch H;Bernstorff S (Solid State Phys div, IUC-DAEF, Mumbai Centre, Bhabha Atomic Res centre, Mumbai-400 085) : Counterion condensation in ionic micelles as studied by a combined use of SANS and SAXS. Pramana J Phys 2004, 63(2), 333-8.

A combined use of small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) to the study of counterion condensation in ionic micelles has been reported. Small-angle neutron and X-ray scattering measurements have been carried out on two surfactants cetyltrimethylammonium bromide (CTABr) and cetyltrimethylammonium chloride (CTACl), which are similar but having different counterions. SANS measurements show that CTABr surfactant forms much larger micelles than CTACl. This is explained in terms of higher condensation of Br^- counterions than Cl^- counterions. SAXS data on these systems suggest that the Br^- counterions are condensed around the micelles over smaller thickness than those of Cl^- counterions.

2 illus, 9 ref

002051   Acharya N K;Yadav P K;Wate S;Vijay Y K;Singh F;Avasthi D K (Physics Dep, University of Rajasthan, Jaipur-302 004) : Irradiation of large area Mylar membrane and characterization of nuclear track filter. Bull Mater Sci 2004, 27(5), 417-20.

Ion irradiation of Si⁸⁺ ion beam of 100 MeV was scattered by a gold foil on a Mylar membrane of 25 μm thickness in the form of film roll (width, 12.5 cm and length, 400 cm) at the Nuclear Science Centre, New Delhi. The characterization of etched nuclear tracks was carried out by gas permeation measurements. The samples cut from the film roll of required size for permeability measurements were etched in a controlled manner in a constant temperature bath of 6N NaOH solution. The opening of the conical etched tracks was characterized by hydrogen gas permeation.

4 illus, 2 tables, 14 ref

002050   Abbas S;Wagh A G (Solid State Phys Div, Bhabha Atomic Res Centre, Mumbai-400 085) : On measuring the neutron coherent scattering length with ultrahigh precision. Pramana J Phys 2004, 63(2), 375-9.

An order of magnitude improvement in the present five parts in 10⁵ precision of a nondispersive interperometric measurement of the neutron coherent scattering length b_c has been proposed. For this purpose a judicious selection of the Bragg angle for the interferometer and the sample thickness has been made. the precision is further improved by an optimal choice of the Bragg reflection (and a consequent neutron wavelength). By performing the experiment in vacuum, errors arising from possible variations in the pressure, composition or humidity of the ambient air can be eliminated. On attaining such precision, one is ought of account for the neutron beam refraction at the sample-ambient interfaces, to infer the correct b_c from the observed phase. The formula for the phase used hitherto is approximate and would significantly overestimate b_c. The refractive index for neutrons can thus be determined to a phenomenal precision of a few parts in 10¹².

3 illus, 1 tables, 4 ref

000049   Tiwari V K;Bhardwaj V;Saini J S;Bhatnagar D (Microwave Laboratory, Dep of Physics, Univ of Rajasthan, Jaipur 302 004) : Theoretical analysis of right isosceles triangular microstrip antenna on ferrite substrate. Indian J Phys-Pt B 2003, 77(6), 639-43.

Radiation characteristics of a right isosceles triangular microstrip antenna (RITMA) structure on a biased ferrite substrate are investigate theoretically in this paper by applying Green's function and vector potential technique. The analysis is carried out in TM₁₁ mode of excitation that predicts a larger bandwidth than similar antenna on a non-magnetic dielectric substrate. Far field radiation patterns, impedance characteristics, quality factor and directivity of antenna are computed theoretically as a function of bias field strength. Out comes of present investigations may be applied in designing switchable and frequency agile ferrite RITMA structures.

5 illus, 3 tables, 14 ref

000048   Tewari S P;Sood J (Dep of Physics and Astrophysics, Univ of Delhi, Delhi 110 007) : Variation of temperature and density dependent screened potential between two charges and static pair correlation function of electrons. Indian J Phys-Pt B 2004, 78(2), 211-16.

Screened poential between two charges and the static pair correlation function of electrons around a positron in two dimensional one component classical and quantum weakly coupled plasmas at different temperatures 0.1 K≤T≤ 5 K, have been studied using the recently suggested were vector and frequency dependent complex dielectric functions of the plasmas.

3 illus, 19 ref

000047   Srivastava S K;Jain A (Dep of Physics, Govt P G College, Ambikapur - 497 001 Chattisgarh) : Microwave emissivity characterstics of soil of 10.45 GHz for remote sensor data. Indian J Phys-Pt B 2004, 78(2), 177-81.

An attempt has been made to measure the complex dielectric constant of soil under laboratory condition at 10.45 GHz using the infinite sample method. Emissivity, both for vertical and horizontal polarization, have been calculated using measured dielectric data and emissvity model. It is found that dielectric constant and emissivity depend upon moisture contents. The measured values of dielectric constant and emissvity are compared with calculated values using Wang-Schmuggee empirical model and Dobson et al empirical model. It is found that both calculated and experimental values are in close agreement. The brightness temperature (Ta) of soils are also calculted with moisture contents using emissivity data.

6 illus, 8 ref

000046   Singh V B;Rai A K;Mishra S K;Pandey V K (Dep of Physics, Udai Pratap Autonomous College, Varanasi 221 002) : Vibratoinal spectra of 2-phenyl-4H-3, 1-benzoxazin-4-one studied by IR spectroscopy and AMI semiempirical molecular orbital calculations. Indian J Phys-Pt B 2004, 78(2), 205-9.

FTIR and Raman spectra of a leading bleach activator 2-phenyl-4H-3,1-benzoxazin-4-one have been recorded in the region 200-4000 cm^-1 and 400-3200 cm^-1 respectively. Vibrational frequencies for the fundamental modes of this polycyclic heteratomic molecule have been calculated using Austin method1 (AM1) semiempirical molecular orbital method. Vibrational assignments have been made for the fundamnetal modes and the observed combination and overtone band are also assigned. The carboyl frequency (C=O) is observed at <126> 1766 cm^-1 whereas the C=N stretching vibration is observed at 1611 cm^-1 in the FTIR spectrum. The net atomic changes for each atom as well as the heat of formation of this molecule are also calculated.

1 illus, 2 tables, 15 ref

000045   Singh S K;Gwal A K (Space Physics Research Institute, School of Pure & Applied Physics, Univ of Natal, King George V Avenue, Durban 4001 South Africa) : Whistlers observed at low latitude stations Bhopal and Jammu. Indian J Phys-Pt B 2003, 77(6), 625-9.

The whistler data presented has been observed duirng nightime of February-March 1998-99 though the occurrence is very small. The characteristics whistlers are presented and the discussion indicates that whistlers recordes are strongly indicative of non-ducted propagation for low latitude nighttime whistlers observed at Bhopal (geomag lat.,13° 47/N) and Jammu (geomag. lat. 19°26/N). To explain these results, it is proposed that whistlers recorded are the VLF waves radiated from the return stroke of the lighting discharge launched at the ionosphere with different initial wave normal angles. Such type of whistlers has never been reported from any of the low latitude ground stations so far.

4 illus, 42 ref

000044   Sharma R C;Sharma M (Dep of Mathematics, Himachal Pradesh Univ, Shimla 171 005, Himachal Pradesh) : On couple-stress fluid permeated with suspended particles, heated and soluted from below in porous medium. Indian J Phys-Pt B 2004, 78(2), 189-94.

A layer of couple-stress fluid, permeated with suspended particles, heated and soluted from below in porous medium is considered. The couple-stress and stable solute gradient postpone the onset of convection whereas the medium permeability and suspended particles hasten the onset of convection. The principle of exchange of stabilities is valid for the couple-stress fluid permeated with suspended particles heated from below is porous medium. The oscillatory modes are introduced due to the presence of stable solute gradient.

12 ref

000043   Sharma R C;Mehta C B (Dep of Mathematics, Himachal Pradesh Univ, Shimla 171 005) : Double-diffusive convection in compressible walters `B/ elastico-viscous fluid in hydromagnetics. Indian J Phys-Pt B 2003, 77(6), 657-61.

A layer of compressible, electrically conducting Walters' B<47> elastico-viscous fluid heated and soluted from below, in presence of magnetic field is considered. The presence of viscoelasticity, magnetic field and stable solute gradient introduce oscillatory models in the system which were non-existent in their absence. The sufficient conditions for non-existence of overstability are obtained. For the case of stationary convection, the Walters' elastico-viscous fluid behaves like a Newtonian fluid and compressiblity magnetic field and stable solute gradient have stabilizing effects on the system.

14 ref

000042   Sengwa R J;Abhilasha (Microwave Research Laboratory, Dep of Physics, J.N.V. Univ, Jodhpur 342 005) : Microwave dielectric relaxation and molecular dynamics in ternary mixtures of poly (vinylpyrrolidone)- poly (propylene glycol) - poly (ethylene glycol)s of varying molecular weights in non polar solvent. Indian J Phys-Pt B 2003, 77(6), 645-50.

Molecular dynamics of ternary mixtures of poly (vinyl pyrrolidone) (PVP) (Mw = 40000 g mol^-1), poly (propylene glycol) (PPG) (Mw = 2000 g mol^-1) and poly (ethylene glycol)s (PEGs) (Mw = 200, 400 and 600 g mol^-1) with PVP concentration variation has been explored in dilute solutions of benzene using microwave dielectric relxation times at 10.1 GHz and 35°C. The average relaxation time τ₀, distribution parameter α, relaxation time corresponding to segmental motion τ₁ and group rotation τ₂ has been determined for the PVC-PEGs-PPG mixtures in benzen solvent. The large value of α≈0.3 to 0.63 of these polymers and their mixtures confirms that besides the overall rotation there is large contribution of the segmental motion, and group rotations in dielectric relaxation processes. The dynamics of PEGs molecules has been explored by considering the chain coiling and intra - and intermolecular hydrogen bonding in the complex heterogenous species with the help of observed values of relaxation times. It is found that the value of τ_O and τ₁ are independent of the mixture viscosity. The observed of τ₂ are attributed to the rotation of chain ends hydroxyl groups/ methyl side-groups of these polymer molecules. The free energy of activation ΔF_τ of these systems has also been evaluated. These values are found in the range of ≈ 2-4 kcal mol^-1.

1 illus, 2 tables, 40 ref

000041   Salimullah M;Salahuddin M;Rizwan A M (Dep of Physics, Jahangirnagar Univ, Savar, Dhaka-1342, Bangladesh) : Wake field in a magnetized dusty plasma with streaming ions. Indian J Phys-Pt B 2004, 78(2), 245-8.

Three-dimensional wake potential for a stationary test dust particulate in uniformly magnetized dusty plasma with a continuous flow of ions, has been studied thoretically. Two standard directions of the external static magnetic field with respect to the direction of the flow of ions, have been considered. For magnetic field along the ion-flow direction, the lattice sapcing along this direction is affected significantly for stronger magnetic field and unaffected for weaker magnetic field, while the spacing in the perpendicular plane in unaffected for both high- and low-density plasma. However, for magnetic field perpendicular to the ion-flow direction, the wake potential becomes weaker with large (constant) spacing along (perpendicular) the direction of the flow of ions in a high-density plasma.

26 ref

000040   Rangra V S;Sharma D R (Dep of Physics, H.P. Univ, Shimla 171 005) : Dielectric relaxation studies of binary mixtures of acetone and N-methylformamide in the benzene solutions using microwave absorption data. Indian J Phys-Pt B 2004, 78(1), 111-14.

Dielectric relaxation times (τ) and the dipole moments (μ) of the binary mixtures of different molar concentrations of acetone (CH₃COCH₃) in the binary mixtures of acetone and N-methylformamide (NMF) in benene solutions have been calculated by using standard standing wave microwave techniques and Gopala Krishna's single frequency (9.88 GHz) concentration variational method at different temperatures (25°C, 30°C, 35°C, 40°C). The dielectric relaxation process have been found to be an activated process. The energy parameters (ΔH_E,ΔF_E,ΔSE) for the dielectric relaxation process of binary mixtures containing 50% mole-fraction of acetone have been calculated at the respective given temperatures and the comparison has been made with the corresponding energy parameters (ΔH_η,(ΔF_{< 104>,}(ΔS_η) for the viscous flow. On the basis of the observations, it is found that the dielectric relaxation process can be treated as the rate process like the viscous flow process. Solute-solute and solute-solvent molecular association have been presented.

3 illus, 2 tables, 15 ref

000039   Ramasamy V;Ponnusamy V;Helmalatha J; Anandalakshmi K (Dep of Physics, Annamalai Univ, Annamalainagar 608 002, Cuddalore) : Quality assessment through the determination of clay index in limestones of South Tamil Nadu with the adsorption of methylene blue using UV-VIS spectroscopy. Indian J Phys-Pt B 2004, 78(2), 195-9.

The clay index values of 20 different limestone samples collected from South Tamilnadu were determined using UV-VIS spectrophotmetric method with the help of the absorbance value at 663 nm of a known concentration of methlene blue. The type of clay was-determined as kaolinite through the FTIR technique. The results are correlated in accordance with FTIR analysis. The applicability of this approach and advantages over the current methods in cement and chemical industries are demonstrated. According to the clay index values, the quality of the samples obtained from Tuticorin marine area is higher than the other samples.

5 illus, 2 tables, 10 ref

000038   Rajarajan G;Revathy P;Nambinarayanan T K (Raman School of Physics, Pondicherry Univ, Pondicherry 605 014) : Ultrasonic velocity studies in aqueous lithium salts. Indian J Phys-Pt B 2003, 77(6), 677-80.

The effect of electrolyts viz lithium acetate and lithium chloride, on the temperature of sound velocity maximum of water, has been studied by ultrsonic velocity method. Ultrasonic velocity measurements are carried out in aqueous lithium acetate and lithium chloride in the concentration range 0.1-0.5 molar between 303K and 353K and 10K increment in the temperature. The results are discussed in terms of structure breaking effect of accetate and chloride ions, which changes the temperature velocity maxiumum of water and on the basis of flickering cluster model of liquid water.

2 illus, 1 table, 16 ref

000037   Rai V K;Rai S B (Laser and Spectroscopy Lab, Dep of Physics, Banaras Hindu Univ, Varanasi 221 005) : Spectroscopic studies of some aliphatic alcohols. Indian J Phys-Pt B 2004, 78(1), 81-6.

Spectra of a number of aliphatic alcohols (pure as well as diluted with hexane and CCI₄) have been studied in the 500-14000 cm^-1 region. In addition to the fundamental and overtone bands and CH and OH stretch vibrations, a large number of combination bands involving different frequencies have been observed. Vibrational constants for the CH and for free as well as associated OH stretch vibration have been determined. It is found that where as the peaks due to CH stretch remain almost unchanged in magnitude on dilution, the peaks due to OH vibration show a blue shift. The blue shift decreases in the higher overtones in the case of CCI₄ diluted sample but remains nearly constant in the case of hexane diluted sample. This has been explained as due to the formation of OH...Cl bond. The combination band were explained in terms of local-normal and normal-normal combinations.

3 illus, 8 tables, 27 ref

000036   Prasad R S;Kumar S (Dep of Physics, Magadh Univ, Bodh Gaya - 824 234) : Electronic spectra of tetraazatetrahedrane (N₄) isomers. Indian J Phys-Pt B 2004, 78(2), 201-4.

MRINDO/S calculations augmented by singly excited configuration interaction were performed on the isomers of tetraazatetrahedrane (N₄). This work considered two isomers of N₄ which belong to D_zh and C_zv symmetry. These isomers are metastable and hence the interpretation of their spectra seems to be important. Reports ionization potentials, allowed siglet excitation, the corresponding triplet excitation, and the singlet splittings in each isomer. Rydberg excitations are also interpreted.

3 tables, 11 ref

000035   Paul S K;Duha S S;Banerjee A K;Mamun A A (Dep of Physics, Jahangirnagar Univ, Savar, Dhaka, Bangladesh) : Electromagnetic waves in partially ionized dusty plasma. Indian J Phys-Pt B 2004, 78(1), 87-92.

The propagation of low-frequency electromagnetic waves in partially ionized, self-gravitating magnetized dusty plasma has been theoretically studied. The elctromagnetic waves having the wavelength of the order of few AU and the frequency of the order of 10^-15s^-1 are found to be unstable due to the effect of the self-gravitational force acting on the dust gains. On the other hand, the electromagnetic waves having relatively high-frequency (<126>10^-5s^-1) are found to be damped due to the effect of the collisions of the plasma particles (namely, the electron, the ions and the dust gains) with the background neutrals. The effects of the obliquenees of the wave propagation, the background neutral number density etc. are also observed to significantly modify the dispersion properties of such obliquely propagating electromagnetic waves. The present investigation may be of relevance to the formation of stars in glaxies via the fragmentation of partially ionized dusty plasma systems.

3 illus, 32 ref

000034   Pandey R K;Jokhan Ram (Synod Higher Secondary School, Mission Vegthlang, Aizawl - 796 005) : Pair correlation function for the hard ellipsoids under decoupling approximation. Indian J Phys-Pt B 2004, 78(2), 171-5.

Pair correlation functions have been calculated using decouping apporximation under Percus Yevick approximation by employing spherical harmonics coefficients and a potential model suggested by Singh and Singh [Phys. Rev. B33 2725 (1986)] for the hard ellipsoids. It has been reported that the decoupling approximation compared well with Monte Carlo results of Nezbeda only at lower values of packing fraction and parametric ratio of length-to-breadth.

3 illus, 16 ref

000033   Nihor R;Misra S;Saxena S K (Dep of Physics, D.B.S. (P.G.) College, Kanpur 208 027 Uttar Pradesh) : Viscous losses of non-polar solvent in microwave frequency 9.8 GHz. Indian J Phys-Pt B 2003, 77(6), 681-5.

The dielectric relaxation time and viscosity of two polar molecules viz. ethyl accetate and n-butyl acetate in the mixture of paraffin oil (P.O.) and benzene at different concentrations, have been used to measure the viscous losses at microwave frequencies 9.8 GHz. The visco-elestic relaxation of solute molecule has been used to calculate the real part of the viscosity (η'). viscous loss (Δ"), and corresponding storage modulus (G'), and loss modulus (G") at microwave frequencies for both the molecules have been investigated. The viscoisity lost has also been calculated. The great difference of total viscosity loss for diploar relaxation process, is interpreted in terms of damped oscillatory motion of polar molecules in viscous medium and losses due to restoring force acting on polar molecules by surrounding flexible viscous solvent molecules. A hypothetical equation has been proposed to imterpret the difference in the total viscosity loss for dipolar rotation. It has been observed that the log τ vs log η' and log τ vs log η" plots deviates from linearity for higher concentration of P.O. and benzene but the plots of τ' and τ" were found to be linear.

3 illus, 2 tables, 30 ref

000032   Nandi R N;Bhattacharya A K;Jaman A I (Saha Institute of Nuclear Physics, , Sector-1, Block-AF, Bidhnnagar, Kolkata 700 064) : Infrared radiofrequency double resonance spectrometer : an unique machine to probe excited vibrational states. Indian J Phys-Pt B 2004, 78(1), 75-80.

The construction of an Infrared-Radiofrequency Double Resonance (IR-RE-DR) spectrometer to study `pure' nuclear quadrupole hyperfine spectra in the ground and the excited vibrational state of a molecul in the gas phase is presented. An indigenously built CO<sub>2</sub> laser was used as the Infrared radiation source. The spectrometer has been used to observe `pure' nuclear quadrupole hyperfine spectro of methyl lodide (CH₃I), a symmetric top molecular with a single quadrupole nucleus.

6 illus, 1 table, 5 ref

000031   Nagarajan R;Gupta D;Varma S P (Infrared Radiation Standards Section, National Physical Laboratory,, Dr. K.S. Krishna Road, New Delhi 110 012) : Theoretical determination of reflectance of materials. Indian J Phys-Pt B 2004, 78(1), 107-10.

The spectral emittance of material at ambient temperature can be derived from its spectral reflectance and spectral transmittance. In order to compute easily both the spectral specular reflectance and spectral diffuse reflectance of the material from its optical constants, a computer code is developed. The details of the code are discussed here.

2 illus, 7 ref

000030   Mandal S;Chakrabarti S K (Centre for Space Physics, , Chalantika, 43, Gariar Station Road, Kolkata - 700 084) : Emitted radiation from a two temperature advective flow around black holes. Indian J Phys-Pt B 2004, 78(2), 145-9.

Low angular momentum accretion flows very often have centrifugal pressure supported standing shock waves which can accelerate flow particles. The accelerated particles in turn, emit synchrotron radiation of presence of magnetic fields. Efficient cooling of the electron reduces its temperature in comparison to the protons. Assumes two temperature flows to explore this property of shocks and present an example of the emitted radiation spectrum.

2 illus, 13 ref

000029   Khah S K (Dep of Physics, Jaypee Univ of Information Technology, Waknaghat Solan 173 215) : Experimental study of eight element circular array of circular patch antenna. Indian J Phys-Pt B 2004, 78(1), 71-3.

Experimental analysis of eight element circular array of circular patch antenna is proposed for X-band of microwave frequency range. Radiation characteristics are measured and plotted. The far-zone field expressions for the array geometry are derived using vector wave function technique and pattern multiplication approach. The total field patterns are compared with the computed plots. Other important antenna parameters like Voltage Standing wave ratio and gain are also measured and plotted. The results are useful for phased array antenna systems in mobile communications.

7 illus, 7 ref

000028   Karmakar P K;Chattopadhyay (Institue of Radiophysics & Electronics, Univ of Calcutta, 92, A P C Road, Kolkata 700 009) : Radiosonde studies of microwave attenuation and water vapour. Indian J Phys-Pt B 2004, 78(1), 13-29.

Microwave absorption due to water vapour has been studied. This paper deals with the modelling of meterological parameters as well as the attenuation coefficient due to water vapour at the weak water vapour resonance line. The corresponding microwave brightness temperatures has been related with water vapour content in Kolkata. The result has been compared to those obtained at New Delhi. Response in finding water vapour distribution with frequency in terms of water vapour weighting function have been discussed along with those obtained at Antarctica. A special efforts has been extended in finding the effect of water vapour in oxygen absorption band which appears to be major factor to the communication engineers.

22 illus, 4 tables, 47 ref

000027   Gupta K K;Singh P J (Dep of Physics, M.S.J. College, Bharatpur 321 001) : Dielectric relaxation in para-methyl acetophenone, pyridine and their binary mixtures in benzene solutions. Indian J Phys-Pt B 2003, 77(6), 673-6.

The dielctric behaviour of para-methyl acetophenone (PMA), pyridine and their binary mixture as liquid dielectric samples have been studied at microwave frequency 8.93 GHz. in dilute solutions of benzene at temperature 303, 313, 323 and 333K. The various dielectric paramters have been evaluated by the observed data for the system and the results have been interpreted on the basis of H-bonding and inductive effect due to the presence of methyl group and compared with the results of acetophenone. The thermodynamical parameters indicate that the cooperative orientation of the pure molecules changes into non-cooperative orientation in 1:1 mixture composition. Comparative study of free energy of activation for the dielectric relaxation and viscous flow suggests the presence of solute-solvent interactions.

2 illus, 3 tables, 7 ref

000026   Gupta K K;Sharma M K;Singh P J (Dep of Physics, M.S.J. College, Bharatpur 321 001) : Dielectric relaxation study of intrmolecular hydrogen bonded o-hydroxy acetophenone in non-polar solvents. Indian J Phys-Pt B 2003, 77(6), 651-5.

The static permittivity of o-hydroxy acetopheone (OHA) in three non-polar solvents namely benzene, 1,4-dioxane and cyclothexane have been measured at 303K and frequency 100 KHz. The data were used to evalute Kirkwood correlation factor g, excess molar polarization (Δp), excess correlation factor (δg) and excess free energy (ΔG). It is observed that in dilute solutions β-multimers with antiparallel dipolar orientation predominate for benzene and cyclohexane but 1,4-dioxane α-multimers with parallel orientation dominate in the entire concentration range. OHA behaves as a rigid molecule because of the intramolecular hydrogen bond between hydrogen and acetyl groups.

4 illus, 19 ref

000025   Ghanshyam;Tripath V K (Dep of Physics, B I T, Sindri, Dhanbad 828 123, Bihar) : Magnetic field generation by ion acoustic waves in an inhomogeneous plasma with temperature gradient. Indian J Phys-Pt B 2004, 78(1), 121-3.

The ion acoustic wave propagating perpendicular to the temperature gradient in plasma produces and oscillatory magnetic field via the Vn x VT mechanism. For a 1 Kev plasma of density <126>10^-21 cm^-3, having temperature scale length L_T<126>35 μm, ion acoustic density petrurbation <126>% and wave frequency 10¹¹ red sec^-1. One obtains oscillatory magnetic field B<126>30 KG. This magnetic filed is large to influence plasma pheomena.

19 ref

000024   Devadoss D;Thairiyaraja M;Palaniappan L (Dep of Physics, TBML College, Porayer 609 307 Tamil Nadu) : Molecular intraction studies in the ternary mixture of 1-hexanol + acetonitrile + cyclohexane. Indian J Phys-Pt B 2003, 77(6), 669-72.

The ultrasonic velocities, densities and viscosities have been measured in the ternary sytem of 1-hexanol + acetonitrile + cycloherxane at 303, 308 and 313 K. From these data acoustical parameters suchas adiabatic compressiblity, 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 length. It is observed that the addition of 1-ol leads to a compact strucutre. The presence of strong interactions are noticed in the ternary system. The presence of strong interactions are noticed in the ternary system. The peculiar behaviour of cyclohexane drastically influences the temperature variations.

4 illus, 2 tables, 33 ref

000023   De S S;Dubey S K;De M (Centre for Advanced Study in Radio Physics & Electronics, Univ of Calcutta, 1, Girish Vidyaratna Lane, Kolkata- 700 009) : Cerenkov radiation within the ionospheric anisotropic plasma. Indian J Phys-Pt B 2004, 78(2), 217-22.

Cerenkov radiation for a point charge moving with uniform within the ionospheric plasma has been investigated in presence of geomagnetic field, time-varying irrgularities and motion of heavy ions. The expression for frequency spectrum of radicated energy is derived. From numerical analysis, the direction of Cerenkov radiation has been graphically along with the results of an earlier work.

1 illus, 30 ref

000022   Chaudhuri S;Bhattacharyya D (Dep of Physics, Gushkara Mahavidyalaya, Gushkara 713 128, Burdwan) : Magnetovac solutions of the static Einstein-Maxwell equations. Indian J Phys-Pt B 2004, 78(1), 93-6.

Magnetostatic solutions of Einstein-Maxwell field equations for a mass magnetic dipole moment are constructed by the method developed by Gutsunaev [Gen. Rel. Grav 20 327 (1988), Phy. Lett A132 (1988)]. The generated solutions are well behaved at spatial infinity. However, in absence of magnetic field, the solutions do not reduce to the Schwarzschild metric.

6 ref

000021   Chatterjee P;Das B (Dep of Mathematics, Siksha Bhavana, Visva Bharati, Santiniketan 731 235) : Speed and shape and solitary waves in nonisothermal plasma with warm ions. Indian J Phys-Pt B 2004, 78(2), 223-7.

Large amplitude solitary waves are investigated in a collisionless plasma with nonisothermal electrons and finite ion-temperature. The Sagdeev's pseudopotential is determined in terms of `u' the ion speed and depends of v, the velocity of the wave. It is found that there exists a critical value of u_o(≠0) the value of u at which (u)² = 0, beyond which the solitary waves cease to exit. The critical value also depends on β, the ratio of the free and the trapped electron respectively.

4 illus, 25 ref

000020   Bhattacharya J;Moulick R G;Choudhri U; Bhattacharya P K;Lahiri P;Chakrabarti B;Dasgupta A K (Dep of Biochemistry, Calcutta Univ, 35, Ballygunge Circular Road, Kolkata-700 019) : Lazy dynamics of unfolding and ligand interaction-signatures in hemoglobin and its glycated form. Indian J Phys-Pt B 2004, 78(1), 55-63.

The dynamics of unfolding of hemoglobin (Hb) and its glycated form (GHb) have been studied. The temporal profile of the wavelength maxima in the Q band of Soret region (408-420 nm) showed a characteristic periodic dynamics. Typically, an irregular periodic behaviour, a staircase like profile or a combination of the two was observed. The time scale associated with unfolding was of the order of seconds. Multiple possible liganded states of heme and heme dependent incremental alterations in the quaternary structure are proposed to cause such sluggish periodic behaviour. The mechanism of protein unfolding, unlike the folding process is an important cellular even in protein transport, but has got lesser attention in literature. Further exploration in the dynamical features of unfolding, as described in the present work, can lead to deeper understanding of the regulation of unfolding and it can also provide an indirect insight of the reversible steps in the folding process.

9 illus, 19 ref

000019   Arun Kumar;Chakravarty T;Basu A K (SAMEER Kolkata Centre, , Plot-L-2, Block-GP, Sector-5, Salt Lake, Kolkata 700 091) : A simple design implementation of a tracking local oscillator system. Indian J Phys-Pt B 2004, 78(2), 183-7.

A simple to implement, design schematic of VHF traking local oscillator (LO) is presented. The tracking LO is required in a high power transmitter system with an inbuilt automatic phase controller, where it is required to track the variable frequency RF input to produce a fixed IF. The design approach of the tracking LO sub-system has been discussed and key circuit features are described in detail. Results indicate successful implementation of the design approach.

4 illus, 1 table, 5 ref