012156   Kumar V;Srivastava K;Kumar N;Sikka H (Mathematics Dep, J V Jain Coll, Saharanpur 247 001) : Kelvin-Helmholtz instability in a rotating ideally conducting inhomogeneous plasma. Pramana J Phys 2004, 62(4), 899-909.

The Kelvin-Helmholtz instability in sheared magnetohydrodynamic flow of an ideally conducting rotating inhomogeneous compressible plasma is investigated. The asymptotic behaviour in x of the Kelvin-Helmholtz eigenfunctions for the case of finite compressibility in the presence of rotation is discussed and instability condition is derived. In the incompressible limit, a dispersion relation is derived which has been solved numerically discussed in detail. It is found that the inhomogeneous system is unstable in incompressible plasma.

2 illus, 13 ref

012155   Krishna Prasad S;Nair G G;Sandhya K L;Shankar Rao D S (Cen for Liquid Crystal Res, , Jalahali, Bangalore-560 013) : Photoinduced phase transitions in liquid crystalline systems. Curr Sci 2004, 86(6), 815-23.

In recent years, a field of research that is growing steadily is the photoinduced phenomenon in which the incident light itself brings about molecular ordering/disordering of the liquid crystalline system. This particular aspect of photonics, in which light can be controlled by light as a stimulus, is being proposed as the technology for high-speed information processing and photochromic materials. The azo compounds in particular, have been found to be promising candidates for optical data storage. An illustration of nature utilizing photoinduced effects is that of the biological photochrome bacteriorhodopsin found in the eye. Apart from their biological and technological importance, these systems exhibit photo-driven phase transitions, thus providing a new tool to study phase transitions and the associated critical phenomena. Some of the recent contributions to this field of photoinduced isothermal phase transitions in various liquid crystalline systems have been reviewed. The application of the random-field Ising model to describe the photoinduced nematic-isotropic transition, the influence of nanophase segregation to bring about a unique photo-driven disorder to order transition, local racemization phenomenon in bentcore banana B₂ phase and the effect of high pressure have been discussed.

11 illus, 34 ref

012154   Khanikar L;Baruah G D (Laboratory of Laser and Non-linear Optics, Department of Physics, Dilbrugarh University, Dilbrugarh-786 004 (Assam)) : Effect of short pulses on soft X-ray laser gain. Asian J Phys 2002, 11(1), 78-80.

The rate of growth and fall of electron temperature in a highly ionized plasma depends on the width of the heating laser pulse. Shorter the laser pulse, the electron temperature falls more quickly. The fall of electron temperature creats an environment suitable for soft X-ray lasing. Theoretical investigation indicated that the gain in the soft X-ray laser pumped with short pulse increases with the decreases of the width of laser pulses.

1 illus, 1 table, 7 ref

012153   Kashyap Y;Sarkar P S;Sinha A;Godwal B K (High Pressure Phys Div, Bhabha Atomic Res Cen, Mumbai-400 085) : Simulation studies of atomic resolution X-ray holography. Bull Mater Sci 2004, 27(1), 79-84.

X-ray holography is a new method of structure determination based on measurement of interference of a known reference wave with an unknown object wave (containing information on atomic sites scattering the reference wave) so that phase information is preserved. Unlike X-ray diffraction, it does not demand for translational periodicity in the material. It is based on the idea simlar to that of optical holography and has been tested on crystals, quasicrystals, thin films and doped semiconductors for their structure determination. In order to analyse potentials and limitation of this technique. Theoretical simulation studies on simple structures have been carried out. The basic algorithm of hologram generation and reconstruction of atomic positions from generated data has been described. This technique has been illustrated using Fe (bcc) single crystal as sample case to demonstrate its capabilities and limitations. Simulations were carried out on the Cu (fcc) structure and on complex structure such as the Al-Pd-Mn quasicrystal. Technical isssues such as low signal to noise ratio, twin image problem etc have been discussed briefly to emphasize the need for high intensity X-ray source such as synchrotron for experiments and proper reconstruction algorithm. Finally the scope and potential of this technique have been discussed.

11 illus, 15 ref

012152   Kapoor K;Lahiri D;Rao S V R;Sanyal T;Kashyap B P (Advanced Mater Characterization Lab, , Nuclear Fuel Complex, Hyderabad-500 062) : X-ray diffraction line profile analysis for defect study in Zr-2.5% Nb material. Bull Mater Sci 2004, 27(1), 59-67.

The microstructure characterization by X-ray line profile analysis is possible for determination of dislocation density, micro-strain within grains due to dislocation and average coherent domain size (sub grain) within the grain. This study presents the X-ray diffraction peaks shape analysis and their broadening with different thermal treatments in Zr-2.5% Nb pressure tube material. The peak shape is analysed using Fourier transformation and information about coherent domain size, micro-strain and dislocation density could be obtained from the Fourier coefficients of the peak. Analysis of broadening of the peaks by integral breadth method also gives the coherent domain size, dislocation density and micro-strain present in the material. The results from the X-ray techniques are comparable to those obtained from direct observation of transmission electron microscopy. The measured yield strength increases with dislocation density. An empirical relationship is obtained for the yield strength from the dislocation density of the material. The measured strength is in agreement with the one calculated from dislocation density.

9 illus, 7 tables, 18 ref

012151   Kalai Arasi C;John Bosco Balaguru R;Alfred Cecil Raj S;Lawrence N (Unit of Phonon Physics, Department of Physics, St Joseph's College, Trichirappali-620 002) : Localised defect modes of zinc-blende structed systems. Asian J Phys 2002, 11(1), 61-5.

The calculated values of localised vibrational mode (LVM) frequencies of compound semiconductors of Zinc-Blende structure with substitutional impurities using the effective charge model are reported. The calculated values are compared with the experimental values and as well the values obtained by using other theoretical models.

1 table, 13 ref

012150   Jain K; (Electronic Materials Division, National Physical Laboratory, Dr. Krishnan Marg, Hill side road, New Delhi-110 012) : Investigation on porous silicon/CdTe system. Indian J Phys-Pt A 2004, 87(2), 261-4.

CdTe layer was electro-chemically deposited over porous silicon layer formed by standard anodization process. The Pl spectrum shows no change in peak position (630nm) or the line shape (FWHM = 140nm) but the intesity is increased by a factor of two. FTIR studies of the porous silicon surface before and after CdTe deposition shows that the Si-H bonds formed during anodization are replaced to a large extent by S-O and Si-OH bridges. Pore filling by CdTe revealed no major changes in the I-V and C-V characteristics except a small decrease in barrier catacitance.

4 illus, 11 ref

012149   Hota P K;Vijayan V;Senapati S;Singh L P (Medical Physics Unit, Department of Radiation Oncology, Acharya Harihar Regional Cancer Centre, Cuttak-753 007) : PIXE analysis of blood and tissue in malignancy. Asian J Phys 2002, 11(1), 57-60.

Particle Induced X-ray Emission (PIXE) spectroscopic technique is used to analyse elements like K, Ca, Fe, Br, Zn, Cu, Mn, Se and Pb in human blood and tissue samples collected from different cancer patients as well as some healthy persons. Significant variations of some elements were observed in cancer patients compared to that of the healthy persons, which could suggest that changes in trace profile in human body possibly can be used as a diagnostic tool as well as a prognostic index in cancer.

1 table, 11 ref

012148   Harun S W;Ahmad H (Photonics Lab, Physics Dep, UNiv of Malaya, 50603 Kuala Lumpur, Malaysia) : Gain clamping in double-pass L-band EDFA using a broadband FBG. Pramana J Phys 2004, 62(4), 893-7.

A highly efficient gain-clamped L-band EDFA with improved noise figure characteristic is demonstrated by simply adding a broadband C-band FBG in double-pass system. The combination of the FBG and optical circulator has created laser in the cavity for gain clamping. By adjusting the power combination of pumps 1 and 2, the clamped gain level can be controlled. The amplifier gain is clamped at 28.1 dB from - 40 to -25 dBm with a gain variation of less than 0.5 dB by setting the pumps 1 and 2 at 59.5 and 50.6 m W, respectively. The gain is also flat from 1574 nm to 1604 nm with a gain variation on less than 3 dB. The corresponding noise figure varies from 5.6 to 7.6 dB, which is 0.8 to 2.6 dB less than those of unclamped amplifier.

4 illus, 6 ref

012147   Gupta V P;Virdi A;Sharma A (Department of Physics, University of Jammu, Jammu Tawi-180 006) : Molecular structure, conformation and electronic spectra of methyl acetate. Asian J Phys 2002, 11(1), 36-41.

A complete quantum mechanical study of the possible conformations and their relative satatilities, electronic transitions and thermodynamic parameters of methyl acetate has been reported for the electronic ground and first excited states. Semi-empirical (AMI and CNDO/2) and ab initio calculations using 6-311 G extented basis sets have been used for the purpose. Potential energy curves for the rotation of the milecule about C2-O3 bond and O3-C4 bonds have been plotted. In both the electronic states the trans conformer is found to be more stable than the cis. Fully relaxed geometries of the possible conformers have been obtained. Theoretical and experimental findings have been compared. A complete interpretation of the ultraviolet spectra of the conformers in terms of nature, frequency and intensity of electronic transitions has been provided.

3 illus, 2 tables, 15 ref

012146   Gupta V P;Sharma A;Virdi A (Department of Physics, University of Jammu, Jammu-180 006) : Theoretical study of rotational isomerism and electronic spectra of ethyl methyl ketone. Asian J Phys 2002, 11(1), 31-5.

Results of ab initio quantum mechanical calculations using extended basis sets, with and without polarization functions and semi-empirical calculations in MNDO(AM1) and CNDO/2 approximations have been reported for the ground (S₀) and first electronically excited (S₁) states of ethyl methyl ketone. Relative total energies have been obtained for asymmetric rotation of the molecule about C-C bond and for the methyl rotation in the two states. It is inferred that while the molecule can exist in two rotameric forms, trans and gauche in the ground state, trans being more stable than gauche by 1.02 kcal/mol, it has only the gauche conformation in the nα excited state (S₁). Significant changes in geometrical and steric conformations and thermodynamic properties are observed in the two states. The methyl group maintains its C_3v symmetry in both the electronic states. Optimized geometries in the two states have been calculated. A complete assignment for the electronic spectra of the trans and gauche conformers in terms of position and intensity of bans is provided.

4 tables, 17 ref

012145   Gopalakrishna G S;Doreswamy B H;Mahesh M J; Mahendra M;Sridhar M A;Shashidhara Prasad J;Ashamanjari K G (Studies in Geo Dep, Univ of Mysore, Manasagangotri, Mysore-570 006) : Synthesis and structural characterization of CsNiP crystal. Bull Mater Sci 2004, 27(1), 27-30.

CsNiP crystals were synthesized by hydrothermal technique and characterized by the X-ray diffraction method. This alkaline transition metal phosphide crystallizes in the hexagonal system with space group P6₃/mmc and cell parameters, a = 7.173(2) Angstrom, c = 5.944(9) Angstrom, V = 264.87(7) Angstrom³ and Z = 2. The final residual factor is R1 = 0.0362 for 206 reflections with I <62> 2 σ(I).

6 illus, 4 tables, 27 ref

012144   Ghosh R; (Department of Solid State Physics, Indian Association for the cultivation of Science, Jadavpur, Kolkata-700 032) : Growth of nanostructured ZnO by simple calcination method. Indian J Phys-Pt A 2004, 87(2), 253-5.

Nanostructured ZnO were fabricated through a simple calcination method by heating a semisolid sol-gel of zinc acetate in a horizontal furnace at 90°. The resultant powdered products were characterized by means of X-ray powder diffraction (XRD), transmission electron microscope (TEM), transmittance and photoluminescence measurements. XRD results showed a single phase hexagonal structure. TEM image showed that nanorod of average diameter 33 nm was formed whtn the sol-gel was calcined. The zinc accetate powder was also calcined directly which resulted in small hexagonal crystallites of size 46 nm. 95 transparency in the visible region was found in nano crystalline Zno film on sapphire substrate. Photoluminescence measurements showed a blue shift in the band-edge emission due to the size effect.

4 illus, 1 tables, 25 ref

012143   Garg V;Tripathi V K;Sharma R K (Department of Physics, M M College, Modinagar-201 004) : Resonant excitation of millimeter waves by beating two lasers in a plasma embedded with a magnetic wiggler. Asian J Phys 2002, 11(1), 137-43.

Two high power lasers of frequencies ω¹ and ω₂, co-progagating in a plasma or a semiconductor embedded with a magnetic wiggler, produce electromagnietic radiation at the difference frequency (ω₁-ω₂). The lasers exert a pondermotive force on the electrons at the difference frequency, giving them longitudinal oscillator velocity. This velocity beats with the magnetic wiggler to produce a transverse current, driving a millimeter wave at frequencyω₁-ω₂ and wavenumber k₁ - k₂ + k^ω, where k₁ and k₂ are the wavenumbers of the lasers and k^ω is the wavenumber of the wiggler. For a suitable value of wigger wavenumber the process a resonant one, giving high efficiency of millimeter wave generation.

2 illus, 21 ref

012142   Garg A K (Department of Physics, N A S College, Meerut-250 001) : Optical phonon in IV-VI semiconducting mixed crystals SnS_xSe_2-x. Asian J Phys 2002, 11(1), 126-9.

Long wavelength optical phonons have been studies experimentally for IV-VI semiconducting mixed crystals SnS_xSe_2-x (x = 0, 0.2, 0.5, 0.8, 1.0, 1.2, 1.5, 1.8 and 2.0) by laser Raman scattering at four different temperatures 290, 205, 150 and 80K. The effect of change in temperature on frequency, peak height and FWHM of Raman bands is reported. The analysis of the profile using Lorentzian fitting is done.

3 illus, 1 table, 5 ref

012141   Gadhvi M;Upadhyay R V;Parekh K;Mehta R V (Phys Dep, Bhavnagar Univ, Bhavnagar 364 002) : Magnetically textured ferrofluid in a non-magnetic matrix: magnetic properties. Bull Mater Sci 2004, 27(2), 163-8.

Texturing of two different magnetic fluids were carried out in paraffin wax under the influence of an external magnetic field. The textured samples were characterized using magnetization measurement and a.c. susceptibility techniques. The results are discussed in the light of ratio of anisotropic energy to magnetic and thermal energies.

6 illus, 1 tables, 7 ref

012140   Ferencz C (MTA-ELTE Res Group for Geoinformatics and Space Sci, Eotvos Univ, H-1518 Budapest, P O Box 32, Hungary) : Real solution of monochromatic wave propagation in inhomogeneous media. Pramana J Phys 2004, 62(4), 943-55.

The earlier phenomenological descriptions of the propagation of signals in inhomogeneous media - except the mirror-type, scattering-type descriptions - have an inherent misunderstanding and therefore these methods are wrong except the non-coupled WKB approximation. The cause of the problem is the wrong physical concept about the structure of the signals propagating in inhomogeneous media. Using a better physical concept of the signal structure propagting in inhomogeneous media and the method of inhomogeneous basic modes (MIBM) it was possible to derive correct full-wave solutions for propagating signals. The investigated example is a monochromatic plane wave propagating in an isotropic, inhomogeneous, linear media parallel to the gradient of the onedimensional inhomogeneity. However, a generalization of the process for more complex inhomogeneities is possible.

1 illus, 12 ref

012139   El-Sersy A;Mansy M;Hussein A (National Institute for Standards, , Tersa St., El-Haram, Giza Egypt]) : Effect of environmental conditions on radon concentration-track density calibration factor of solid-state nuclear track detectors. Pramana J Phys 2004, 62(4), 861-7.

The effect of environmental conditions viz., temperature (T) and relative humidity (RH) on the track density-radon concentrations calibration factor (K) has been studied for CR-39 and LR-115 track detectors. The factor K was determined using a reference radon chamber in the National Institute for Standards (NIS) in Egypt. Track detectors were etched at the recommended optimum etching conditions. It is found that, the calibration factor K varies with both T and RH, so they should be considered for the sake of uncertainty reduction. Good agreement is found between the calculated and measured values of K and the compatibility between them is in the range of experimental uncertainty.

5 illus, 2 tables, 17 ref

012138   Ekhelikar S;Bichile G K (Phys Dep, Dr Babasaheb Ambedkar Marathwada Univ, Aurangabad-431 004) : Synthesis and structural characterization of (Bi₂O₃)_1-x (Y₂O₃)_x and (Bi₂O₃)_1-x (Gd₂O₃)_x solid solutions. Bull Mater Sci 2004, 27(1), 19-22.

Solid solution series, (Bi₂O₃)_1-x (Y₂O₃)_x and (Bi₂O₃)_1-x (Gd₂O₃)_x, for x = 0.10, 0.20, 0.30 and 00.40 were synthesized by standard ceramic technique. The structural phase characterization was carried out using X-ray powder diffraction technique. It was found that the solid solution containing 20-40 mole % of Y₂O₃ had face-centred cubic structure. All samples of the solid solution series, (Bi₂O₃)_1-x (Gd₂O₃)_x, had rhombohedral single phase in the concentration range 0-10 ≤ x ≤ 0.40. Lattice parameters of fcc phase of Y₂O₃ doped samples were calculated from the X-ray diffraction data. The lattice constant `a' gradually decreases with increasing content of dopant concentration (x) for the Y₂O₃ doped system and obeys Vegard's rule. The unit cell parameters for the (Bi₂O₃)_1-x (Gd₂O₃)_x doped samples showing rhombohedral phase were obtained on hexagonal setting.

3 illus, 2 tables, 8 ref

012137   Dutta S; (M C K V Institute of Engineering, Liluah, Howrah-711 204) : Influence of polymer matrix and magnetic field on the optical and electrical properties of fine particles of nickel ferrite. Indian J Phys-Pt A 2004, 87(2), 243-6.

Polymer magnetic composite film based on fine nickel ferrite particles and poly vinyl alcohol has been prepared in the presence and absence of magnetic field. Various properties of the films such as morphology, electrical properties, and optical sbsorption reveal a clear effect of the presence of magnetic field of very low field strength (20 Oe) during gelation of polymer.

7 illus, 1 tables, 2 ref

012136   Dutta J;Sarmah N C;Baruah G D (Department of Physics, Dibrugarh University, Dibrugarh-786 004) : Gain and dispersion relations in the semiclassical theory of lasers. Asian J Phys 2002, 11(1), 108-11.

Gain and dispersion relations in the semiclassical theory of laser have been worked out using the complex conjugate terms. It has been shown that the use of the complex conjugate terms in the expression for electric field and polarization give rise to additional terms for dispersion relations having physical significance.

4 ref

012135   Durai S;Ramadoss P (P G & Res Dep of Phys, A M Jain Coll, Chennai 600 114) : Dynamic properties and phonon frequencies of some liquid metals. Bull pure appl Sci-Sect D 2003, 22(2), 145-50.

Bhatia and Singh (1985) have derived expressions for the elastic constants and the bhonoon dispersion relations [frequency ω versus wave number k in liquids. The method is adopted with some modifications for the calculation of phonon frequencies of eight liquid metals. The potential function φ selected for the evaluation takes into account the Coulomb interaction between ions and indirect interaction through conduction electrons which bring the attaraction between the ions. The long range Coulomb force in liquids results into a strong polarization field. In all these case disperision cure in the longitudinal mode show oscillatory behaviour while in the transverse mode in reaches a maximum nd oscillation is insignificant. Further the maximum ω is correlated to the Debye temperature of liquids. The results can generate new ideas.

8 illus, 3 tables, 11 ref

012134   Durai S;Ramadoss P (P.G. and Res Dep of Phys, A.M. Jain Coll, Chennai-600 114) : Fresh study of optical and thermal properties of polystyrene solutions. Bull Mater Sci 2004, 27(1), 57-8.

Polymers have immense practical applications and one such polymer is polystyrene. It is a linear polymer and useful for plastic optical components. The optical and thermal properties of polystyrene solutions are investigated making use of the ultrasonic velocity and fluid parameters. The results reveal a number of significant informations.

3 tables, 6 ref

012133   Durai S;Babu P (P G & Res Dep of Phys, A M Jain Coll, Chennai 600 114) : Role of anharmonicity factor and spin fluctuations in A15 compounds. Bull pure appl Sci-Sect D 2003, 22(2), 129-36.

Using mass and the force constant change parameter, effective Debye temperature of some A₃B type compounds of β-tungsten structure is calculated. McMillan equation has been used to calculate the T_c values. Other properties like specific heat and Pauli's susceptibility have also been calculated. The T_c values of some other A₃B compounds have been calculaed using the modified McMillan equation incorporating the spin fluctuations which has been shown to be related to mass change parameter which is a measure of anharmonicity.

15 ref, 9 ref

012132   Dave M;Vaidya R;Patel S G;Jain A R (Phys Dep, Sardar Patel Univ, Vallabh Vidyanagar 388 120) : High pressure effect on MoS₂ and MoSe₂ single crystals grown by CVT method. Bull Mater Sci 2004, 27(2), 213-16.

Single crystals of MoS₂ and MoSe₂ were grown by chemical vapour transport method using iodine as a transporting agent and characterized by optical microscopy, energy dispersive analysis (EDAX), X-ray powder diffraction (XRD) and Hall mobility at room temperature. The variation of electrical resistance under pressure was monitored in a Bridgman anvil set-up up to 6.5 GPa to identify occurrence of any structural transition. MoS_{2 and MoSe2 do not undergo any structural transitions under pressure.}

3 illus, 4 tables, 15 ref

012131   Datta M S; (Department of Metallurgy, Jadavpur University, Kolkata-700 032) : Preparation of nanoα-silicon carbide crystalline particles by attrition grinding. Indian J Phys-Pt A 2004, 87(2), 257-60.

Nano crystalline α-silicon carbide crystalline particles have been prepared from sub-micron sized particles by attrition grinding in the medium of water with surfactants in 12 hours with a ratio of weight of iron balls to the weight of α-silicon carbide of 12; 1.

10 illus, 13 ref

012130   Dass S; (Department of Chemistry,Faculty of Science, Dayalbagh Educational Institute,, Dayalbagh, Agra-228 005.) : Nanostructured Mn-doped and undoped CuO thin films-PEC studies. Indian J Phys-Pt A 2004, 87(2), 229-31.

The photoelectrochemical properties of copper oxide thin film (p-type) on the SnO2 : F coated glass (conducting glass) prepared by spray pyrolysis has been investigated as a function dopant and pH of electrolyte. X-ray diffractogram pattern of thin films confirm the cupric oxide (CuO) phase. Mn-doped samples exhibited decreased photoelectrochemical response as compared to undoped CuO. the onset of photocurrent in undoped CuO is at ~120mV, while in Mn doped CuO films it is ~375 mV. The observed reverse effect of the Mn-doping on the photoelectrochemical response of the films, can be attributed to the possible neutralization of naturally occurring majority charge carriers (holes) present in undoped copper oxide with the extra electrons furnished by the dopant Mn atoms, particularly, from their d orbitals. Beter photoresponse has been observed at pH 13.

4 illus, 1 tables, 10 ref

012129   Dash P C;Panigrahi M (Physics Dep, College of Engng and Technol, Biju Patnaik Univ of Technol, Bhubaneswar 751 003) : Soliton dynamics in a modified Yakushevich model. Pramana J Phys 2004, 62(4), 815-26.

Studies a modified Yakushevich model with different disc diameters representing different bases and finds two new in-phase solitonic solutions. Also discusses the effect of helical structure which acts a perturbation on soliton centre of mass.

15 ref

012128   Choi Y;Kim J (NO, Korea Advanced Insitute of Science and Technology, Taejon 305 701, Korea) : Relaxation dynamics and analysis of a very broad dielectric spectrum. Asian J Phys 2002, 11(1), 9-15.

In an attempt to understand relaxation dynamics associated with glass freezing transition in a dipole glass DRADP-x examine various experimental data of low frequency dielectric constant spectra as a function of temperature. Very weak and broad dielectric spectra observed at each temperature as a function of frequency was analyzed by the Tikhonov regularization method to derive the relaxation time distribution at the corresponding temperature.

7 illus, 15 ref

012127   Chelvane J A;Kasiviswanathan S;Rao M V; Markandeyulu G (Phys Dep, Indian Inst of Technol, Madras, Chennai 600 036) : Magnetic properties of ball-milled TbFe₂ and TbFe₂B. Bull Mater Sci 2004, 27(2), 169-73.

The magnetic properties of ball-milled TbFe₂ and TbFe₂B were studied by magnetization measurements. X-ray diffraction studies on TbFe₂B showed that boron occupied interstitial position in the crystal structure, just as hydrogen did. The value of the saturation magnetization of TbFe₂B was found to be smaller than that of TbFe₂. This is explained on the basis of a charge transfer between the boron atoms and the 3d band of Fe. the anisotropy of TbFe₂B was found to be large compared to that of TbFe₂. X-ray diffractograms for the ball milled samples showed that after 80 h of milling, a predominantly amorphous phase was obtained. TbFe₂B was found to undergo easy amorphization compared to TbFe₂. Magnetization of TbFe₂ was found to decrease rapidly with initial milling hours and was found to be constant with further hours of milling. TbFe₂B exhibited an anomalous behaviour with an increase in moment with milling hours and this may be due to the segregation of α-Fe.

5 illus, 18 ref

012126   Chandra S;Shinde S A (School of Physical Sci, SRTM Univ, Nanded 431 606) : Einstein a-coefficients for rotational transitions in the ring-chain isomer of C5H2. Pramana J Phys 2004, 62(4), 967-71.

Laboratory formation of four isomers of C₅H₂ molecule is reported and detection of the ring-chain isomer (isomer 1) of C₅H₂ in sosmic objects has been suggested. For identification of a molecule in cosmic objects, one of the required input data is Einstein A-coefficients (radiative transition probabilities) for the molecule. Reports Einstein A-coefficients for electric dipole transitions in the ring-chain isomer of C₅H₂ among the rotational levels of the gound electronic and ground vibrational states up to 21 cm^-1 the rotational levels of the ground electronic and ground vibrational states up to 21 cm^-1.

012125   Chakrabarti S; (Department of Materials Science, Indian Association for the Cultivation Science, Kolkata-700 032) : Structural and magnetic properties γ-Fe2O3 nanoparticles coated on silica spheres. Indian J Phys-Pt A 2004, 87(2), 247-51.

The structural and magnetic properties of γ-Fe<2O3 nanoparticles dispersed on sol-gel silica spheres were investigated through XRD, TEM, Mossbauer (20, 80 and 300K) and EPR (80, 300K) measurements. The XRD spectra clearly indicated the formation of pure γ-Fe<2O3 nanoparticles and the absence of any other form of iron oxide. TEM images showed a uniform distribution of the nanoparticles of size ~6nm on the surfaces of silica spheres (diameter ~35-60nm). The low temperature (20 K) Mossbauer spectra consisted of a partially split sextet superimposed on a doublet. The partial magnetic splitting of the sextet at 20 K revealed the effect of surface magnetization and surface modifications of the γ-Fe<2O3 nanoparticles coated on silica spheres.The surface magenitization arising out of mil-aligned spins at the surface as evidenced by Mossbauer spectra was further confirmed by electron paramagnetic resonance (EPR) studies.

5 illus, 1 tables, 23 ref

012124   Boyo A O;Boyo H O;Akomolafe T (Phy Dep, Lagos State Univ, Ojo Badagry, Lagos, Nigeria) : Thermal ageing and noise index of iron-clay composite resistores. Bull pure appl Sci-Sect D 2003, 22(2), 121-7.

Results of the effects of thermal ageing and noise index on iron-clay composite resistors at different percentage weights of iron i.e. 60 wt%Fe, 70 wt%Fe. 80 wt%Fe and 90 wt%Fe and temperature range of 300°C and 600°C have been reported. One notices, that the resistance variation with length at firing temperatures of 300°C and 600°C is non-linear for almost all the resistors. The non-linearity might be due to the control mode of the amount and distribution of impurties and defects still present in the resistors. Also it is noticed that the resistance drifts after 300oh. increasing with increase in resistor length. Thus the stability of the resistors improves with decrease in resistor length. The poor stability exhibited by these resistors may be attributed to envrironmental problems such as humidity and vapor. It is evident from the result that the noise index increase with increase in length, this shows that the increase in excess noise in thick film resistors is dependent on the size of the resistor and then a proper selection on material and geometry is very useful.

12 illus, 12 ref

012123   Boyo A O;Boyo H O (Phy Dep, Lagos State Univ, Lagos, Nigeria) : Using self association model to compute the thermodynamics and surface properties of liquid Cs-K alloys. Bull pure appl Sci-Sect D 2003, 22(2), 151-7.

The calculation results of the thermodynamic properties of system with unlimited solubility Cs-K, was done by using the Self Association Model. The Self Association model was used to explain the excess free energy of mixing. Heat of mixing, excess entropy, activity, concentration-concentration fluctuation in the long wavelength limit, chemical shot-range order parameter and surface phenomena for Cs-K molten alloys. The calculation results of the thermodynamics properties indicate that Cs-K is a compound forming system with chemical ordering throughout the whole concentration range with a peak concentration of 0.50.

8 illus, 14 ref

012122   Borah G;Bora T (Chemistry Department, Dibrugarh University, Dilbrugarh-786 004) : Spectroscopic Study of some ruthenium (III) complexes with N-donor ligands. Asian J Phys 2002, 11(1), 86-90.

Ruthenium (III) chloride is found to form six coordinated complexs of the types (LH)₂[RuCl₅L].2H₂O, (LH)₂ [RuCl₅L] and (L'H) [RuCl₄L₂'], where L = 2-methyl imidazole (2-Melm), 2-ethyl imidazole (2-Etlm), 1,2-dimethyl 5-nitroimidazole (1,2-Me₂-5-NO₂lm), α-picoline (α-pic), β-picoline (β-pic), χ-picoline (χ-pic); L' - 1,2-dimethylimidazole (1,2-Me₂lm). The compounds have been characterized by elemental analysis, molar conductance measurements, IR and UV visible spectral analysis and thermal studies. ESR spectral analysis indicates paramagnetic nature of these compounds. Proton NMR spectral studies indicate that resonance positions of protons on carbon attached to coordinated nitrogen shift down compared to protons on other carbon atoms. ¹H-NMR spectra also confirms the involvement of pyridine nitrogen of imidazoles and picolines as donor site.

2 illus, 3 tables, 11 ref

012121   Bhatt N;Vaidya R;Patel S G;Jani A R (Phys Dep, Sardar Patel Univ, Vallabh Vidyanagar-388 120) : X-ray diffraction studies of NbTe₂ single crystal. Bull Mater Sci 2004, 27(1), 23-5.

NbTe₂ is a member of transition metal dichalcogenide (TMDC) group. Single crystals of niobium ditelluride (NbTe₂) have been grown by a chemical vapour transport technique using iodine as transporting agent. The composition of the grown crystals was confirmed on the basis of energy dispersive analysis by X-ray (EDAX) and remaining structural characterization was also accomplished by X-ray diffraction (XRD) studies. Lattice parameters, volume and X-ray density have been carried out for the grown crystals. The particle size for a number of reflections has been calculated using Scherrer's formula.

2 illus, 4 tables, 19 ref

012120   Bhargava P;Kumar M;Kumar H;Pandit P;Pandey R; Nath A K (Industrial CO2 Laser Section, Centre for Advanced Technol, Indore-452 013) : Impulse coupling in laser-driven microtargets. Pramana J Phys 2004, 62(4), 923-32.

Studies about the thrust imparted to targets of different materials by pulsed TEA CO₂ laser and chopped CW CO₂ laser in air and its dependence on different parameters such as laser intensity and pulse duration. Estimates the impulse-coupling coefficient and compares it with the published results. The mechanism of generation of thrust by laser incident on targets in air is, in effect, combination of those involved in laser ablation in vacuum and laser-induced air detonation.

5 illus, 1 table, 16 ref

012119   Arora S K;Patel V;Amin B;Kothari A (Phys Dep, Sardar Patel Univ, Vallabh Vidyanagar 388 120) : Dielectric behaviour of strontium tartrate single crystals. Bull Mater Sci 2004, 27(2), 141-7.

Strontium tartrate trihydrate (STT) crystals have been grown in silica hydrogel. Various polarization mechanisms such as atomic polarization of lattice, orientational polarization of dipoles and space charge polarization in the grown crystals have been understood using results of the measurements of dielectric constant (ε') and dielectric loss (tanδ) as functions of frequency and temperature. Ion core type polarization is seen in the temperature range 75-180°C, and above 180°C, there is interfacial polarization for relatively lower frequency range. One observes dielectric dispersion at lower frequency presumably due to domain wall relaxation.

7 illus 23 ref

012118   Ali S A;Ali A S;Nasir Ali S;Jain R (Zoology Dep, Saifia Coll of Sci and Edu, Bhopal 462 001) : Effects of ultraviolet-C radiation on isolated fish scale melanophores. Indian J Radio Space Phys 2004, 33(2), 58-60.

The effects of ultraviolet-C radiation on isolated fish scale melanophores are studied. The responses of melanophores were measured by mean melanophores size index (MMSI). At a temperature range of 27-29°C, the melanophores were exposed for varying durations ranging from one min to 60 min, to a direct source of ultraviolet-C radiation of wavelength 254 nm. It was found that the exposure of 30 min of UV-C radiation produced the highest effects on the melanophores of C. punctatus, where the MMSI reached a peak value of 8.351±0.3798. The melanophores had become highly dispersed, with their cellular process extending maximally.

1 illus, 13 ref

012117   Aldwayyan A S;Masilamani V (Laser Group, Department of Physics, College of Science, King Saud University, Riyadh-11451) : A Simple photoacoustic instrumentation for simultaneous measurement of radiative and non-radiative processes. Asian J Phys 2002, 11(1), 130-6.

Describes a novel optical instrumentation based on photoacoustic detection (PAD), to have a self-consistent, simultaneous measurement of fluorescent and non-ratiative process in dye solutions. The instrumentation is so simple that it could be easily adopted in any molecular photophysics laboratory.

6 illus, 1 table, 8 ref

012116   Akode C G;Kanse K S;Lokhande M P;Kumbharkhane A C;Mehrotra S C (Physics Dep, Vasantrao Naik College, Nanded) : Dielectric relaxation studies of aqueous sucrose in ethanol mixtures using time domain reflectometry. Pramana J Phys 2004, 62(4), 973-81.

Time domain reflectometry method has been used in the frequency range of 10 MHz to 10 GHz to determine dielectric properties of aqueous sucrose in ethanol. The dielectric parameters, i.e., static dielectric constant and relaxation time were obtained from the complex permittivity spectra using the non-linear least squares fit method. The Luzar theory is applied to compute the cross-correlation terms for the mixtures. It adequately reproduces the experimental values of static dielectric constants. The Bruggeman model for the non-linear case has been fitted to the dielectric data for mixtures.

2 illus, 3 tables, 28 ref

012115   Ahlawat D S;Sharma A K;Mohan D;Singh R D (Phy Dep, M D Univ, Rohtak 124 001) : Photobleaching of nile blue dye by photoacoustic. Bull pure appl Sci-Sect D 2003, 22(2), 137-40.

Photoacoustic investigation of photobleaching effect in Nile Blue dye doped in Polymethyl Metha Acrylate (PMMA) has been studied by using an indigencously developed photoacoustic spectrometer. Experimental results indicate that the photobleaching rate is directly proportional to the incident laser power while it decreases with the increase in the concentration of dye molecules.

2 illus, 7 ref

012114   Abraham V S;Swapna S;Rajesh S;Sajeev U S; Anantharaman M R (Phys Dep, International Sch of Photonics, Cochin Univ of Sci and Technol, Cochin 682 022) : Magnetic field induced assembling of nanoparticles in ferrofluidic liquid thin films based on Ni_xFe_1-xFe₂O₄. Bull Mater Sci 2004, 27(2), 155-61.

Ultra fine precursors for ferrofluid synthesis, belonging to the series Ni_xFe_1-xFe₂O₄ (where `x' varies from `0' to `0.6' in steps of 0.1) were synthesized. Ferrofluids based on these fine particles were prepared with oleic acid as surfactant and kerosene as carrier. Ferrofluidic thin films were made on glass substrates and magnetic field induced laser transmission was studied. The pattern exhibited by the films under the influence of a magnetic field was observed with the help of a CCD camera. The analysis of results confirms the chain formation of particles in the presence of an applied magnetic field and their saturation at higher applied fields.

10 illus, 1 tables, 23 ref

011165   Yadav T P;Mukhopadhyay;Srivastava O N (Dep of Physics, Banaras Hindu University, Varanasi-221 005) : Synthesis of nano-quasicrystalline decagonal phase. Indian J Phys-Pt A 2004, 87(2), 189-91.

AI-Co-Ni system exhibits the existence of a stable decagonal phase with various degrees of order in periodic and quasiperiodic planes. Now it is a routine technique to grow micron to cm size rods of the decagonal phase by slow cooling technique. There are attempts to develop nano scale microstructure by various non-equilibrium processing techniques. Employ mechanical milling (MM) technique for the synthesis of the nano decagonals phases. The alloy ingots have been prepared by melting the consituent pure metals in the iduction furnace, and then crushed to around 200 mesh size, as a starting meterial in the attritor. The milling was performed at 400 rpm under hexane medium with a ball : charge ratioas 20 : 1. During the course of milling, the disordering has been noticed from the broadening of the peaks and lowering of the peak height in the X-ray diffraction patterns. Milled powder after 40 h showed thd diffraction peaks confirming the evolution of nano-D phase. The size aspects and the phase constituents has further been confirmed by the transmission electron microscopic investigation. The composition of the as-castingot and the milled powder has been analyzed by EDX.

4illus, 17 ref

011164   Yadav S N;Mishra P K (Dep of Phys, L.N. Mithila Univ, Darbhanga- 846 004) : Prediction of rain attenuation of microwave in the 10-40 GHz band. Acta Cienc Indica-Phys 2003, 29(4), 451-3.

The measurements of microwave rain attenuation over a period of (1988-1998) have been presented. The rain attenuation of vertically and horizontally polarised microwaves at 15, 21 and 38 GHz propagating over a path length of approximately 1.1 km were calculated. A negative exponential raindrop size distribution model is then developed by fitting of the experimental data with the total extinction cross-section of oblate spheroidal raindrops computed from the T-matrix approach. The attenuation versus rain rate at selected frequencies and attenuation versus frequency at selected rain rates are in good agreement with the experimental as well as other theoretical results.

2 illus, 7 ref

011163   Wary G;Rahman A (Physics Dep, Cotton College, Guwahati-781 001) : Electrical and optical properties of Ag-(p)CdTe-ITO structure. Indian J pure appl Phys 2003, 41(6), 474-8.

Ag-(p)CdTe-ITO heterojunctions were prepared by thermal evaporation under pressure 10^-5 torr. The p-type CdTe films, with acceptor concentration (3.85-5.20) 10¹⁷/Cm³, were obtained by mixing 4.9 Sb with CdTe powder. The junctions exhibited rectifying I-V characteristics. Saturation current density was calculated for dark and illuminated junctions and found to be (5.5-9.12) x 10^-5 A/cm² and (1.37-7.50) x 10^-6A/cm², respectively. The ideality factor of a typical junction was found to be 4.75 in dark and 2.18 under illumination, at room temperature (296K). Also ideality factor was found to decrease with increase in temperature. The value of A^*, the effective Richardson constant of a typical junction was found to be 81 Acm^-2K^-2 and the value of barrier height was found to be 0.65 eV in dark which increased to 0.74 under illumination. The barrier height did not show significant change with the variation of temperature in the range 299-338K. The structure exhibited photovoltaic effect characterized by high series resistance. The maximum power outpur under 759 lux of illumination was found to be 2 x 10^-4mW.

8 illus, 1 table, 2 ref

011162   Upadhyay P.N (Phys Dep, Nalanda Mahila Coll, Bhiharsharif- 803 116) : Separation of scintillation and cerenkov radiation. Acta Cienc Indica-Phys 2003, 29(4), 413-28.

Some methods for separating scintillation and Cerenkov radiation produced in a scintillation counter has been presented. With the passage of a particle through the scintillator of a scintillation counter, and output pulse is obtained. Alternatively, an undersired, time-correlated or time-uncorrelated particle with a very high velocity may pass through the perspex light guide of a counter and gives to Cerenkov radiation in it. Corresponding to it, an output pulse is obtained from it. This is undersired and it creates many problems in the identification of a particle. So on determining these two types of output pulses, events with Cerenkov radiation is rejected. Different properties of scintillation and Cerenkov radiation have been exploited to separate these cosmic rays and accelator experiments, electronic methods, analytical and graphical methods. Possibility for using a clip on the output of the PMT of the counter has also been examined. It would reflect and invert the output pulses by introducing a delay between the reflected and original output pulses of the PMT. For separating these two types of radiation a delay of 1 to 1.5 nsec was found. However, it has been found the best to employ a air-light-guide in place of a perspex light guide.

11 illus, 3 tables, 38 ref

011161   Upadhyay P N;Sushma Kumari (Phys Dep, Nalanda Mahila Coll, Biharsharif- 803 101) : Theoretical aspects of the φ (1020) meson. Acta Cienc Indica-Phys 2003, 29(4), 401-12.

Some theoretical aspects on the properties of the φ (1020) meson. Theoretical predictions have been compared with the experimental results. A good agreement has been found.

3 illus, 30 ref

011160   Umarajan K M;Vivekanandan O S;Karunakaran S; Gunasekaran S (Dep of Botany, Pachaiyappa's College, Chennai-600 030) : The effect of electromagnetic radiation on the blood of Swiss albino mice. Asian J Phys 2002, 11(2), 262-4.

Blood mainly consist of plasma and several types of cells e.g. red blood cell. In pathogenic condition, the red blood cells are affected due to physical and biochemical changes in the blood. These changes are detected by characteristic absorption in the UV-visible region. A study has been carried out to analyse the response of blood to electromagnetic radiation at 100Hz, 300Hz, 135Hz and 400MHz in albino mice.

4 tables, 13 ref

011159   Ullas G;Venkatakrishna K;Joseph R M;Krishna C M;Kartha V B (NO, Manipal Academy of Higher Education (Deemed University), Manipal-576 119) : Early detection of cancer: laser spectroscopy methods. Asian J Phys 2002, 11(2), 204-12.

Generally histopathological methods are used for detection of carcinogenic diseases. These methods are not able to diagnose these diseases in time, so treatment is likely to be delayed. New spectroscopical technique for early detection of these diseases are discussed.

6 illus, 1 table, 18 ref