017472   Chandra S;Musrif P G;Prasad L (Sch of Phys Sci, S.R.T.M. Univ, Nanded-431 606, Email: suresh492000@yahoo.co.in) : Coronal heating efficiency for resonant (A.C.) and non-resonant (D.C.) mechanism. Bull Astr Soc India 2005, 33(3), 275-82.

Ionson (1985a) extended his unified theory of coronal resonance heating having non-resonant (D.C.) and resonant (A.C.) components. Narain and Kumar (1995) calculated heating efficiency for resonant and non-resonant components for coronal heating. Since, some inconsistencies are noticed in these calculations, it has been decided to reinvestigate the work of Narain and Kumar (1995). The results are found to vary remarkably. Reasons for these variations has been discussed.

8 illus, 6 ref

017471   Balakrishna K M;Varghese T (Stud in Phys Dep, Mangalore Univ, Mangalore-574 199, Email: surajthomas@sancharnet.in) : Physical properties of carbon nanotubes. Sci Soc 2005, 3(2), 11-14.

Carbon nanotubes are long and thin cylinders of carbon having tubular structures. Carbon nanotubes are extremely thin (their diameter is about 10,000 times smaller than a human hair), hollow cylinders made of carbon atoms. Nanotubes, depending on their structure, can be metals or semiconductors. Carbon nanotubes exhibit many interesting electronic, mechanical and thermal properties.

2 illus, 1 table, 10 ref

016461   Wu A;Xu J;Qian G;Lu B;Ge Z;Tang L;Wu X (Shanghai Inst of Ceramics, Chin Acad of Sci, 1295 Dingxi Road, Shanghai 200050, People's Republic of China, Email: crystalxu@mail.sic.ac.cn) : Bridgman growth of bismuth tellurite crystals. Bull Mater Sci 2005, 28(6), 561-4.

Photorefractive crystal, Bi₂TeO₅, was grown by the modified Bridgman method for the first time. High purity Bi₂O₃ and TeO₂ were used as starting materials and were mixed thoroughly with molar ratio of Bi₂O₃/TeO₂ = 1:1. Platinum crucible was fabricated with a seed well of 10 mm in diameter and several folds were pressed so that the spontaneous nuclei could be eliminated through competition. The crucible was sealed during the growth so that the evaporation of TeO₂ was controlled effectively. By optimizing growth parameters, transparent and crack-free Bi₂TeO₅ crystal up to 25 mm in diameter and 40 mm in length was grown successfully.

5 illus, 9 ref

016460   Vishwakarma P N;Prasad V;Subramanyam S V; Ganesan V (Dep of Phys, Indian Inst of Sci, Bangalore-560 012, Email: svs@physics.iisc.ernet.in) : Structural morphology of amorphous conducting carbon film. Bull Mater Sci 2005, 28(6), 609-15.

Amorphous conducting carbon films deposited over quartz substrates were analysed using X-ray diffraction and AFM technique. X-ray diffraction data reveal disorder and roughness in the plane of graphene sheet as compared to that of graphite. This roughness increases with decrease in preparation temperature. The AFM data shows surface roughness of carbon films depending on preparation temperatures. The surface roughness increases with decrease in preparation temperature. Also some nucleating islands were seen on the samples prepared at 900°C, which are not present on the films prepared at 700°C. Detailed analysis of these islands reveals distorted graphitic lattice arrangement. So author believe these islands to be nucleating graphitic. Power spectrum density (PSD) analysis of the carbon surface indicates a transition from the nonlinear growth mode to linear surface-diffusion dominated growth mode resulting in a relatively smoother surface as one moves from low preparation temperature to high preparation temperature. The amorphous carbon films deposited over a rough quartz substrate reveal nucleating diamond like structures. The density of these nucleating diamond like structures was found to be independent of substrate temperature (700-900°C).

5 illus, 1 table, 27 ref

016459   Verma K C;De U (NO, Variable Energy Cuyclotron Cent, 1/AF Bidhannagar, Kolkata-700 064, Email: ude@veccal.ernet.in) : Electrical resistivity and XRD of differently annealed CdO from different manufacturers. Indian J Phys 2005, 79(9), 1075-8.

Room temperature (RT) electrical resistivity, ρ = 1/σ, has been measured accurately in van der Pauw geometry for identical cadmium oxide pellets, before as well as after heat treatments (mostly for 36 h) at different temperatures. These pellets have been made from cadmium oxide powder procured from different suppliers and two sets of measurements taken for each of two of the suppliers, for a rigid confirmation of the new findings. For each type of cadmium oxide, room temperature resistivity of fired cadmium oxide decreases as firing temperature increases. All products, however, reach same ρ of the order of 1 mW cm on firing at 800°C. Such a low resistivity for pellets of cadmium oxide is a remarkable result. Non-stoichiometry in these differently fired samples has been experimentally confirmed. This increase of conductivity is discussed in terms of earlier reported hand gap values and Hall measurement of carrier concentration and mobility. Such higher electrical conductivity in cadmium oxides should be favourable for use as transparent conducting oxides (TCO) and some other applications.

2 illus, 1 table, 11 ref

016458   Upadhyay P N;Verma A K (Phys Dep, Nalanda Mahila Coll, Biharsharif-803 101) : Production of the η(548) meson in the π<. Indian J Theor Phys 2005, 53(2), 145-50.

Just near the production threshold pion beam momentum in the π^<126>p → ηn interaction, the η meson has been produced copiously. Its mass is near 548 MeV and it has a narrow width. The result is in agreement with those of others.

4 illus, 8 ref

016457   Sinha S;Mandal K (C K Majumdar Lab, S N Bose Natn Cent for Basic Sci, JD Block, Sector III, Salt Lake, Kolkata-700 098, Email: suman@boson.bose.res.in) : Effect of tensile stress on the magnetic Barkhausen noise in amorphous Fe₇₀Ni₈Si₁₀B₁₂ ribbon. Indian J Phys 2005, 79(9), 991-3.

Magnetic Barkhausen noise (MBN) measurements were performed on a sample of amorphous Fe₇₀Ni₈Si₁₀B₁₂ ribbon. Studied the MBN by varying the magnetic field from 0.7 Oe to 29 Oe under different tensile stresses starting from 0 MPa to 38 MPa. The results suggest that MBN increases with magnetic field and gets saturated at higher fields. It is also observed that MBN increases with tensile stress applied along the length of the sample. The external stress changes the magnetoelastic anisotropy energy which is the main source of anisotropy in amorphous magnetic materials. As a result of it magnetisation dynamics and hence the MBN also changes.

4 illus, 5 ref

016456   Singh T N;Singh S D (Phys Dep, C.I. Coll, Bishnupur-795 126, Email: tnando1@yahoo.com) : Computerised glow curve deconvultion of TL curves of impurity phases in high-temperature superconductors. Indian J Phys 2005, 79(9), 1003-07.

Thermoluminescence glow curve can be observed in insulators and semi-conductors having a band gap. Metals and superconductors do not exhibit thermoluminescence. Impurity phases present in high T_c superconductors are insulators or semiconductors and these trace of impurity phases can be considered as the thermoluminescent materials. TL glow curves of BaCO₃ contain three peaks at 132, 186 and 322°C. Y₂O₃ shows two peaks at 130 and 190°C with a shoulder peak at 237°C. Computerised glow curve deconvultion (CGCD) method is used to extract the kinetic parameters of the impurity phases in superconductors and that of BaCO₃.

7 illus, 1 table, 15 ref

016455   Singh N P;Singh A K;Yadav M K (Math Dep, C.L. Jain Coll, Firozabad-283 203) : MHD free convection transient flow through a porous medium in a vertical channel. Indian J Theor Phys 2005, 53(2), 137-44.

Deals with the effect of uniform transverse magnetic field on free convection transient flow of an incompressible, electrically conducting, viscous liquid through a porous medium confined in a vertical channel when a wall of the channel suddenly starts to move along the flow of fluid with uniform velocity in its own plane while the other is at rest. The velocity field, temperature field, skin-friction and rate of heat transfer have been obtained following Laplace transform technique. The effects of magnetic parameter, porosity parameter and time parameter on velocity and skin-friction are discussed. The problem of Jha has been deduced as a particular case of present study.

1 illus, 1 table, 13 ref

016454   Singh N L;Shah N;Singh K P (Phys Dep, M.S. Univ of Baroda, Vadodara-390 002, Email: singhn1_msu@yahoo.com) : Proton induced modification in makrofol-DE. Bull Mater Sci 2005, 28(6), 599-602.

Irradiation effects of a 3 MeV proton beam on polycarbonate (makrofol-DE (MFD) have been studied with respect to its electrical, thermal and structural behaviour by using an LCR meter, DSC/TGA and FTIR spectroscopy. The dielectric loss/constant was observed to change with the fluence. Thermal analysis revealed that chain scission is the dominant phenomena in irradiated samples based on the reduction of its thermal stability by about 19% at a fluence of 10¹⁵ ions/cm², which is also corroborated by FTIR spectra. No significant change in intensity of the absorbance bands of the irradiated sample was observed up to a fluence of 10¹⁴ ions/cm² while on increasing fluence (10¹⁵ ions/cm²) the polymer structure was modified. It appears from DSC thermograms that Te is observed to change with fluence.

6 illus, 13 ref

016453   Singh K (Photonics Grp Phys Dep, Indian Inst of Technol, New Delhi) : Optoelectronic techniques for information security. Ann Indian Natn Acad Engng 2005, 2(Dec), 111-16.

Optical techniques offer many advantages for information security applications. Being inherently 2-D, optical systems can process and relay 2-D data in parallel, resulting in higher throughput rate compared to electronic systems. Optics offers several dimensions such as phase, polarisation and wavelength, etc. to encode data securely. These advantages offered by optical information processing systems, coupled with advancements in enabling technologies like photorefractive crystals, spatial light modulators, and charge coupled device cameras have led to an increasing use of optoelectronic data processing techniques for security applications. Reviews the optical encryption techniques developed by us at the Photonics Group, IIT Delhi.

^iia10 illus, 30 ref

016452   Singh J;Gupta C B;Varshney N K (NO, B.S.A. Coll of Engg & Tech, Mathura) : MHD flow of a dusty visco-elastic (Rivlin-Ericksen type) liquid past an inclined plane. Indian J Theor Phys 2005, 53(3), 257-63.

The present problem is concerned with the MHD laminar flow of an unsteady visco-elastic (Rivlin-Ericksen type) liquid with uniform distribution of dust particles past an inclined plane under the influence of exponential pressure gradient. The liquid is bounded by a paralled upper surface at a distance h from the plane. Analytical expressions for velocities of liquid and dust particles are obtained which is in elegant forms. The important characteristics of the problem such as Hartmann number (M₀) and elastic parameter (α are discussed graphically with the help of the tables.

2 illus, 2 tables, 12 ref

016451   Singh A K;Ashish Kumar;Singh N P;Vinod Kumar (Math Dep, V.S.S.D. Coll, Kanpur-208 002) : Effects of mass transfer and rotation on flow past a porous plate in a non-homogenous porous medium. Indian J Theor Phys 2005, 53(3), 231-45.

The effects of heat and mass transfer, rotation, constant suction and time dependent porous medium on flow of a incompressible, electrically conducting, viscous fluid past an infinite porous vertical plate under the influence of uniform magnetic field applied perpendicular to the flow region is discussed.

4 illus, 4 tables, 11 ref

016450   Sengupta P R;Banerjee S (Math Dep, Univ of Kalyani, Kalyani-741 235) : Unsteady MHD flow of visco-elastic Rivlin-Ericksen and Walters fluid through a straight tube. Indian J Theor Phys 2005, 53(2), 121-35.

The flow of an electrically conducting visco-elastic fluid of Rivlin-Ericksen type through a straight tube of rectangular cross-section has been studied. Further to this the same problem has been investigated when the visco-elastic fluid exhibits the properties of Walters model. The flow has been considered in presence of transverse magnetic field which is uniform and under the influence of time varying pressure gradient. Using integral transform technique, the exact solution for velocity has been obtained. A few particular cases of pressure gradient have been discussed for both Rivlin-Ericksen fluid and Walters fluid. Besides, the corresponding viscous flow problem has been derived as a limiting case when the relaxation time parameter tends to become zero.

14 ref

016449   Roy S;Bhattacharjee K;Rundhe M;Dev B N (NO, Instiutute of Phys, Sachivalaya Marg, Bhubaneswar-751 005, Email: sumalay@iopb.res.in) : High resolution X-ray diffraction studies of some aspects governing epitaxial growth. Indian J Phys 2005, 79(9), 1023-6.

Silver thin films (<126> 10 nm) were deposited on Si(111) surface at room temperature using the molecular beam epitaxy (MBE) technique under ultrahigh vacuum (UHV) (<126> 10^-10 mbar) condition. Such films were annealed at 700°C for 30 min and cooled down to room temperature. High resolution X-ray diffraction (HRXRD) experiments on the annealed films show the improvement of epitaxial quality of the film. HRXRD measurement on this sample also reveal the effect of lattice parameter mismatch and thermal expansion coefficient mismatch on epitaxy. Ag (111) planar spacing and the strain in the Ag layer in the direction normal to the substrate have been determined for this annealed film. Fullerine (C₆₀) layers were deposited on hydrogen-passivated Si(111) substrates under UHV conditions. HRXRD experiments on this system reveal the lack of epitaxial growth. These experiments have also shown that the Si(111) substrate is vicinal. The angle of miscut of the vicinal Si(III) substrate has been determined. The lack of epitaxial growth of fullerene has been attributed to the vicinality of the substrate surface.

5 illus, 17 ref

016448   Rewatkar K G;Patil N M;Gawali S R (Dep of Phys, Dr Ambedkar Coll, Nagpur-440 010, Email: kishor_rewatkar@rediffmail.com) : Synthesis and magnetic study of Co-Al substituted calcium hexaferrite. Bull Mater Sci 2005, 28(6), 585-7.

Series of calcium substituted polycrystalline ferrite ceramics with magnetoplumbite structures were synthesized using perfect stoichiometric mixtures of oxides with chemical composition, CaAl_xCo_xFe_12-2xO₁₉ (x = 2-5), by standard ceramic technique. The variation in the values of H_c and M_s, which depends on the additive content and the temperature, was studied by means of a vibration magnetometer. The strong variation observed in coercivity, saturation magnetization and Curie temperature with chemical composition give rise to the possibility of controlling these properties and hence applying these compounds in the millimeter-microwave range.

3 tables, 14 ref

016447   Raychaudhuri A (Math Dep, Sikkim Manipal Inst of Technol, Majhitar, Sikkim-737 132) : Solution of a radiative transfer problem in finite atmosphere with planetary phase function. Indian J Theor Phys 2005, 53(2), 161-8.

A new modification of the form of the intensity in the double interval spherical harmonic method has been introduced to solve the integro-differential equation of radiative transfer. The method was used to solve problems in case of semi-infinite atmosphere. Here it is extended to the problem in plane geometry in case of finite atmosphere where the form of the function φ(r) present in the expression of the intensity has been taken to be φ(r) = Ae^r + Be^-r, where A and B are constants which are to be determined, and assume r to be small. The phase function used in this case is the planetary phase function given by p(μ, μ') = 1 aφφ', where a is some constant.

15 ref

016446   Raishma Krishnan;Mahato M C;Jayannavar A M (NO, Inst of Phys, Bhubaneswar-751 005) : Noise induced transport and energetics in adiabatically rocked time asymmetric ratchets. Indian J Phys 2005, 79(9), 947-51.

Efficiecy of energy transduction, the nature of currents, input energy and entropy production in a temporally asymmetric adiabatically rocked ratchets by the method of stochastic energetics. The temporal asymmetry is found to favour current in one direction and suppress it in the opposite direction leading to a very high efficiency in comparison with earlier studied various classes of ratchets. From analysis of energy loss in the medium, entropy production and currents, concludes that there is no underlying resonance or synchronisation phenomena in the dynamics of the particle and also that the maxima seen in the current and the total entropy production are not directly correlated. Fine tuning of system parameters leads to current reversals even in the adiabatic regime.

5 illus, 28 ref

016445   Prahalad Singh;Gupta C B (NO, B.S.A. Coll of Engg & Tech, Mathura, U P) : MHD free convective flow of viscous fluid through a porous medium bounded by an oscillating porous plate in slip flow regime with mass transfer. Indian J Theor Phys 2005, 53(2), 111-20.

The study is concerned with MHD free convective flow of viscous fluid through a porous medium bounded by an oscillating porous plate in slip flow regime with mass transfer. The expression for velocity, temperature distribution, mass distribution, skin friction and rate of heat and mass transfer of the flow of a viscous incompressible fluid of small electrical conductivity in a porous medium near an oscillating infinite porous flat plate in slip flow regime under influence of a transverse magnetic field of uniform strength has been obtained and discussed graphically.

3 illus, 3 tables, 8 ref

016444   Pohlong S S;Ram P N (Phys Dep, North East Hill Univ, Shillong-793 022, Email: sspohlong@yahoo.com) : Vibrational density of states of self-interstitial atoms (SAIs) in metals. Indian J Phys 2005, 79(9), 973-7.

The vibrational properties of self-interstitial atoms (SIAs) in metals are discussed by using the Green function method. The vibrational behaviour of the <60>100<62>-dumbbell in fcc metals and the <60>110<62>-dumbbell in bcc metals has been treated. In the case of fcc metals with Cu as a typical example, an embedded atom method (EAM) potential, based on approximation in density functional theory has been used to discuss the local density of state of the <60>100<62>-dumbbell atoms. In bee metals with Mo as a typical example, the local density of states of the <60>110<62>-dumbbell atoms are discussed by using short-range pair potentials. In both fcc and bee metals, the local frequency spectrum consists of a number of low-frequency resonance modes and high-frequency localised modes. The observed resonance modes provide consistent explanation to long range migration of the SIAs as well as the observed change in shear moduli.

2 illus, 2 tables, 30 ref

016443   Omolo J A (Phys Dep, Maseno Univ, P.O. Private Bag, Maseno, Kenya, Email: dean-science@swiftkisumu.com) : Quantised oscillator: an alternative solution procedure and general commutation brackets. Indian J Theor Phys 2005, 53(3), 177-98.

Presents an alternative approach to the solution of the eigenvalue equation for a quantised one-dimensional linear harmonic oscillator through a factorisation procedure. The general solution is expressed in the form of a recursion relation for generating the excited state wave functions. An appropriate number eigenfunction is introduction and used to develop general commutation brackets equations providing the basis for operator algebra. The expectation values of operators are calculated without evaluating integrals.

2 ref

016442   Om Prakash;Mohan Lal (NO, Natn Phys Lab, Dr K.S. Krishnan Road, New Delhi-110 012) : Reflectance and optical rotation techniques to study the nature of surfaces. J Instrum Soc India 2005, 35(4), 392-9.

In some of the cases to study the new materials, being exploited for development of newer devices, the materials are prepared in the form of thin films or wafers. In order to study thin films or wafers of the materials one of the powerful techniques is reflectance measurement. Another method may be the study of optical rotation of plane of polarisation due to interaction of the incident light with the surface under study. Presently, the angle of rotation θ of plane of polarisation of incidence light beam on reflection from the sample surface at nearly 45°C was measured. Also, the reflectance, R of the surfaces under study were measured at normal incidence. In order to establish a relation between R, and e of the surfaces, a graph was plotted in between R and θ. If the value of θ is measured for the test sample surface, its value of R can be estimated and vice-versa with the help of the graph. The distinguished feature of the method is that the samples of diffused nature whose reflectance cannot be measured on reflectometer can be studied with the help of this technique.

4 illus, 2 tables, 6 ref

016441   Murugendrappa M V;Khasim S;Ambika Prasad M V N (Dep of Mater Sci and Phys, Gulbarga Univ, Gulbarga-585 106, Email: Prasad1_Amb@rediffmail.com) : Synthesis, characterization and conductivity studies of polypyrrole-fly ash composites. Bull Mater Sci 2005, 28(6), 565-9.

In situ polymerization of pyrrole was carried out in the presence of fly ash (FA) to synthesize polypyrrole-fly ash composites (PPy/FA) by chemical oxidation method. The PPy/FA composites have been synthesized with various compositions (10, 20, 30, 40 and 50 wt%) of fly ash in pyrrole. The surface morphology of these composites was studied with scanning electron micrograph (SEM). The polypyrrole-fly ash composites were also characterized by employing X-ray diffractometry (XRD) and infrared spectroscopy (IR). The a.c. conductivity behaviour has been investigated in the frequency range 10²-10⁶ Hz. The d.c. conductivity was studied in the temperature range from 40-200°C. The dimensions of fly ash in the matrix have a greater influence on the observed conductivity values. The results obtained for these composites are of greater scientific and technological interest.

5 illus, 15 ref

016440   Mohapatra U K;Behera D;Mishra N C (Phys Dep, Utkal Univ, Bhubaneswar-751 004, Email: ncm@iopb.res.in) : Superconducting order parameter fluctuation effects in cuprate superconductors. Indian J Phys 2005, 79(9), 995-1001.

Analysis of the experimental results on superconducting order parameters fluctuations (SCOPF) in high T_c superconductors becomes extremely complicated due to the presence of different types of inhomogeneities like grain boundary, voids, micro-cracks, twin boundaries etc. In addition to these mesoscopic structural inhomogeneities, there also occur microscopic inhomogeneities due to local oxygen content/ordering variation, local strains, stacking faults etc. The latter types of inhomogeneities contribute to the local variation of T_c. Focuses on the interplay of the different types of inhomogeneities and the SCOPF in a set of YBCO/Ag composite superconductors. In the mean field region, crossover in the dimensionality of the fluctuations from 2D to 3D and the interlayer coupling strength J has been analysed in YBCO/Ag composites with varying Ag wt. %. The variation of these intra-granular parameters with Ag content, which is believed to accupy the inter-granular region, is explained by considering the incorporation of some amount of Ag into the grains and modifying the overall electronic structure of grains.

4 illus, 1 table, 32 ref

016439   Mohanta D;Saikia P;Choudhury A (Phys Dep, Tezpur Univ, Napaam-784 028, Email: best@tezu.ernet.in) : Synthesis and some novel aspects of ZnS:Mn nanoaggregates. Indian J Phys 2005, 79(9), 1015-18.

Manganese doped zinc sulphide nanoparticles were fabricated by adopting a chemical route. The ZnS-Mn films have been casted with the help of a spin-coating machine. Formation of nanoparticles are confirmed by transmission electron microscopy (TEM) studies. UV-VIS optical absorption spectra show excitonic absorption band at <126>323 nm and absorption related to impurity state at <126>334 nm. The magnetooptic studies revealed that with varying Mn concentration, optical rotation as large as <126>24° can be achieved.

5 illus, 1 table, 19 ref

016438   Mehta N;Dwivedi A;Arora R;Kumar S;Kumar A (Dep of Phys, Harcourt Butler Technol Inst, Kanpur-208 002, Email: dr_ashok_kumar@yahoo.com) : Electrical properties of glassy Se_100-xTe_x alloys. Bull Mater Sci 2005, 28(6), 579-83.

Temperature and frequency dependence of a.c. conductivity have been studied in glassy Se_100-xTe_x (x = 10, 20 and 30) over different range of temperatures and frequencies. An agreement between experimental and theoretical results suggests that the a.c. conductivity behaviour of selenium-tellurium system (Se_100-xTe_x) can be successfully explained by correlated barrier hopping (GBH) model. The density of defect states has been determined using this model for all the glassy alloys. The results show that bipolaron hopping dominates over single-polaron hopping in this glassy system. This is explained in terms of lower values of the maximum barrier height for single-polaron hopping. The values of density of charged defect states increase with increase in Te concentration. This is in agreement with previous results obtained from SCLC measurements.

4 illus, 2 tables, 11 ref

016437   Mallick B;Behera R C;Patel T (NO, Inst of Phys, Sachivalay Marg, Bhubaneswar-751 005, Email: bmallick@iopb.res.in) : Analysis of microstress in neutron irradiated polyester fibre by X-ray diffraction technique. Bull Mater Sci 2005, 28(6), 593-8.

Microstresses developed in the crystallites of polymeric material due to irradiation of high-energy particle causes peak broadening and shifting of X-ray diffraction lines to lower angle. Neutron irradiation significantly changes the material properties by displacement of lattice atoms and the generation of helium and hydrogen by nuclear transmutation. Another important aspect of neutron irradiation is that the fast neutron can produce dense ionization at deep levels in the materials. The polyethylene terephthalate (PET) fibre of raw denier value, 78.2, were irradiated by fast neutron of energy, 4.44 MeV, at different fluences ranging from 1 x 10⁹ n/cm² to 1 x 10¹² n/cm². In the work, the radiation heating microstresses developed in PET micro-crystallites was investigated applying X'Pert-MPD Philips Analytical X-ray diffractometer and the effects of microstresses in tensile strength of fibre measured by Instron have also been reported. The shift of 0.45 cm^-1 in the Raman peak position of 1614.65 cm^-1 to a higher value confirmed the development of micro-stresses due to neutron irradiation using micro-Raman technique. The defects due to irradiation were observed by SEM micrographs of single fibre for virgin and all irradiated samples.

3 illus, 2 tables, 29 ref

016436   Maisnam M;Phanjoubam S;Sarma H N K;Radhapiyar Devi L;Thakur O P;Chandra Prakash (Phys Dep, Manipur Univ, Canchipur, Imphal-795 003, Email: mam_ata@yahoo.co.in) : B-H loop properties of V<. Indian J Phys 2005, 79(9), 981-3.

Reports the influence of V⁵⁺ substitution on the B-H loop properties of Li-Zn-Ti ferrite. Six samples with compositional formula Li_0.5+t Zn_0.2Ti_0.2V_tFe_{2.1-2t04 where 0 ≤ t ≤ 0.25 in steps of 0.05 were prepared by the ceramic technique. The samples were sintered at 950°C for 2 hours. X-ray diffraction technique confirmed the single-phase spinel structure of the samples. The lattice constant was determined. The theoretical density was calculated and the experimental density was measured using the Archimedes principle. Curie temperature, saturation magnetisation were measured. The B-H loop for all the samples was traced and from the loops, the hysteresis parameters such as remanance, coercivity and remanance ratio were determined and studied as a function of composition. The possible mechanisms involved are discussed.}

2 illus, 2 tables, 13 ref

016435   Mahanta R;Siam C;Konwar M;Baruah G D (Laser & Spectroscopy Lab Phys Dep, Dibrugarh Univ, Dibrugarh-786 004, Email: gdbaruah@rediffmail.com) : Role of diffusion on the chromatic pattern associated with the Christiansen effect. Indian J Phys 2005, 79(9), 1065-9.

Concerned with the some salient features of the Christiansen phenomenon observed with transparent particles immersed in suitable liquids. Also studied colloidal substances in different liquids and observed features of Christiansen phenomenon. The effect of temperature and diffusion on the chromatic effect has been studied. It is observed that the diffusion plays a major role in the Christiansen effect.

5 illus, 2 tables, 17 ref

016434   Kaviraj B;Ghatak S K (Phys and Meteorology Dep, Indian Inst of Technol, Kharagpur-721 302, Email: bhaskar@phy.ittkgp.ernet.in) : Excitation amplitude dependence of low freqnency magneto-impedance of amorphous Fe_73.5Nb₃Cu₁Si_13.5B₉ ribbon. Indian J Phys 2005, 79(9), 979-80.

Magneto-impedance (MI) of soft ferromagnetic materials is a sensitive function of the amplitude and frequency of exciting a.c. magnetic field. MI (Z) of amorphous ferromagnetic ribbon of nominal composition Fe_73.5Nb₃Cu₁Si_13.5B₉ is measured at different excitation currents with frequency ranging from 30 kHz to 120 kHz. The excitation (ac) and biasing (dc) magnetic fields H_dc are parallel to ribbon axis. At zero dc fields, Z exhibits nonlinear dependence on excitation amplitude whereas at higher dc fields (9Oe), Z is nearly independent of excitation amplitude. The impedance is maximum at zero bias field and sharply decreases as H_dc increased and almost zero hysteresis has been observed as H_ad is scanned. The maximum relative change of impedance (Z(H) - Z(H = 0))/Z(H = 0) is found to increase from nearly 45 to 60 percent when the excitation fields goes up from 14 A/m to 140A/m. The large MI is associated with screening of electromagnetic field by magnetisation induced by exciting ac field.

3 illus, 6 ref

016433   Jain Y S (NO, North-Easterh Hill Univ, Shillong-793 022, Email: ysjain@nehu.ac.in) : Unification of the physics of bosonic and fermionic systems. Indian J Phys 2005, 79(9), 1009-14.

Introduces new approach of macro-orbital representation of a particle in a many-body quantum system as a means to unify the physics of widely different bosonic and fermionic systems. Application of the approach in revealing the ground state of N hard core particles in a 1-D box and the basic mechanism of superconductivity has been briefly discussed. As a novels aspect it reveals that superfluidity (including superconductivity as superfluidity of electron fluid) is an interplay of zero-point repulsion and inter-particle attraction (inherent or induced). Finds that the superfluid state of each system assumes a kind of mechanical strain the relative configuration of its particles and in the case of superconductor, a strain in the lattice. The strain plays a primary role in developing a kind of Cooper pair. Concludes that BCS moel of superconductivity clubbed with mechanical strain can explain superfluidity of widely different many-body systems including high temperature superconductors, atomic nucleus, trapped dilute gases, etc.

20 ref

016432   Islam Z;Mukherjee A;Karanjai S (Mahematics Dep, Malda Coll, Malda, West Bengal-732 101) : Exact solution of the equation of radiative transfer with Pomraning phase function together with a constant source. Indian J Theor Phys 2005, 53(3), 199-214.

The equation of transfer with Pomraning phase function and an additional constant source function in a plane-parallel semi-infinite axial symmetric atmosphere has been solved by the method of Laplace transform and Weiner Hopf technique. The emergent intensity has been derived in terms of Chandrasekhar's H-function and the intensity at any optical depth has been determined by inversion.

16 ref

016431   Hussain A M P;Kumar A (Phys Dep, Tezpur Univ, Napaam-784 028) : Electrochemically synthesised polyaniline films with different dopant. Indian J Phys 2005, 79(9), 1033-9.

Polyaniline is studied extensively in different acidic media like sulphuric acid [1, 2], hydrochloric acid [3, 4], perchloric acid [1], different sulphonic acids [5] and maleic acid [6]. Thin films of polyaniline are synthesised electrochemically (potentiostatically and potentiodynamically) in sulphuric acid (H₂SO₄), hydrochloric acid (HCl), phosphoric acid (H₃PO₄), perchloric acid (HClO₄) electrolytic (aqueous) and in organic media with LiClO₄ salt as dopant. Indium tin oxide (ITO) coated glass plates are used as substrate for the polymer films. Cyclic voltammetry studies are carried out of the films for electrochemical characterisation. Polyaniline films doped with different protonic acid and salt exhibit similar electronic transition absorption as observed in UV-VIS spectra study. FTIR spectra study confirms the electropolymerisation of polyaniline in all the media dc conductivity of LiClO₄, HClO4 and HCl-doped polyaniline films are found higher in four probe measurements at room temperature than the other two polyaniline films doped with H₂SO₄ and H₃PO₄ acid HCl-doped polyaniline films are of smooth surface with nanowire type surface morphology and other polymer films with rough and porous surface morphology were found in scanning electron micrograph study.

9 illus, 18 ref

016430   Himanshu A K;Ray D K;Sinha T P (Sch of Stud in Phys, Jiwaji Univ, Gwalior-474 011, Email: sinha_tp@yahoo.com) : Ac conductivity of conducting polymer prepared with the use of water soluble support polymer. Indian J Phys 2005, 79(9), 1049-52.

The intrinsically conducting polymer, polyaniline (PANI) is synthesised by chemical oxidative polymerisation process with the help of water soluble support polymer poly-vinyl alcohol (PVA). The field dependence of the dielectric response is measured in a frequency range of 42 Hz to 2 MHz and in a temperature range of 133 K to room temperature. An analysis of real and imaginary parts of dielectric permitivity with frequency and temperature are performed, showing the polydispersive nature of the material as confirmed by cole-cole plots of complex permitivity. The frequency-dependent electrical data are analysed in the framework of the conductivity. The results are discussed in the context of models for the dc and ac transports in polymers, with results supporting hopping of charge among positively charged polaron and bipolaron states in the PANI-PVA.

3 illus, 19 ref

016429   Goswami J N Et Al (Phys Res Lab, , Ahmedabad-380 009, Email: goswami@prl.ernet.in) : High energy X-γ ray spectrometer on the Chandrayaan-1 mission to the Moon. J Earth Syst Sci 2005, 114(6), 733-8.

The Chandrayaan-1 mission to the Moon scheduled for launch in late 2007 will include a high energy X-ray spectrometer (HEX) for detection of naturally occurring emissions from the lunar surface due to radioactive decay of the ²³⁸U and ²³²Th series nuclides in the energy region 20-250 keV. The primary science objective is to study the transport of volatiles on the lunar surface by detection of the 46.5 keV line from radioactive ²¹⁰Pb, a decay product of the gaseous ²²²Rn, both of which are members of the ²³⁸U decay series. Mapping of U and Th concentration over the lunar surface, particularly in the polar and U-Th rich regions will also be attempted through detection of prominent lines from the U and Th decay series in the above energy range. The low signal strengths of these emissions require a detector with high sensitivity and good energy resolution. Pixelated Cadmium-Zinc-Telluride (CZT) array detectors having these characteristics will be used in this experiment. The science considerations that led to this experiment, anticipated flux and back-ground (lunar continuum), the choice of detectors, the proposed payload configuration and plans for its realization have been described.

2 illus, 1 table, 16 ref

016428   Goswami A S;Ahmed G A;Choudhury A (Phys Dep, Tezpur Univ, Na Pam, Sonitpur-784 028, Email: anjalisgl@rediffmail.com ) : Measurement of second order nonlinear susceptibility of matter with the help of SHSOM. Indian J Phys 2005, 79(9), 1059-62.

On the basis of the fact that the intensity of second harmonic generation (SHG) from a nonlinear substance depends on the effective second order nonlinear coefficient (d_eff) of the substance, an attempt has been made to measure the value of d_eff. For this purpose, second harmonic images obtained from a second harmonic scanning optical microscope (SHSOM) designed by author was studied. The intensity profile of these images give the position of highest second harmonic with its intensity value, generated in the specimen. Using these data for SH intensity, the second order nonlinear coefficient of the nonlinear optical substance KDP is calculated. The other factors such as symmetry property, phase matching condition, etc. which affect the second order onlinear coefficient are also discussed. Comparison of the experimental value of nonlinear coefficient with the listed value shows a close agreement which in turn, establishes an easy and reliable technique for the measurement of the second order nonlinear coefficient. The second order onlinear coefficient is again related to the second order nonlinear susceptibility of the matter.

3 illus, 19 ref

016427   Gajjar P N;Manjul Kumar;Joshi M;Thakore B Y; Jani A R (Phys Dep, Sardar Patel Univ, Vallabh Vidyanagar-388 120, Email: pngajjar@rediffmail.com) : Structural study of some non-simple elements of group II-VI: a charged hard sphere approach. Indian J Phys 2005, 79(9), 967-72.

Charged Hard Sphere (CHS) approach is employed to study the temperature dependence of the structure factor S(q) and electronic transport properties of some non-simple elements of group II-VI. Based on CHS model, pair-correlation function g(r), interatomic distance r₁ and coordination numner n₁ are also reported which provide fine feature about the less simple elemts viz., Zn, Al, Ga, In, Tl, Sn, Sb, Se and Te of group II-VI. The electron-ion interaction is involved through a newly proposed local model potential. The overall aggrement with experimental data for S(q) and g(r) of Zn, Al, Ga, In, Tl, Sn, Sb, and Te is good. In the background of pseudopotential concept and CHS reference system, the results generated for temperature dependence of electrical resistivity and thermoelectric power show semiconducting behaviour of Se. Thus, newly proposed model potential together with CHS is capable of explaining the structural information of non-simple elements of filled 3d-, 4d- and 5d- series.

9 illus, 3 tables, 17 ref

016426   Dey T K;Singh H D;Karki S S;Sinha S K (Phys Dep, L.S. Coll B.B.A. Bihar Univ, Muzaffarpur-842 001, Email: sk_sinha_phy@yahoo.co.in) : Equilibrium theory for equation of state of two-dimensional hard-body fluid and fluid mixture. Indian J Phys 2005, 79(9), 959-65.

The problem of calculating the thermodynamic properties of two-dimensional (2D) hard-body fluid and fluid mixture is studied. Explicit expressions are given for the equation of state and free energy. The results for hard discorectangles and planar hard dumbbells are compared with the `modified' SPT and simulation data. Moderately good agreement is obtained. The theory is further applied to calculate the equation of state and excess free energy for the 2D fluid mixture of (i) planar hard dumbbells and (ii) hard discs and hard discorectangles under the conditions of (i) σ⁰₁₁ = σ⁰₂₂ and (ii) v₁ = v₂. These properties depend on the conditions, shape parameter L^*₁₁, L^*₂₂ and concentration x₁, x₂ in general, and increase with the packing fraction η in particular.

2 illus, 5 tables, 14 ref

016425   Dehingia N;Changmai R;Konwar M;Baruah G D (Phys Dep, Dibrugarh Univ, Dibrugarh-786 004, Email: gdbaruah@rediffmail.com) : Correlation between the quality of tea in liquid phase and scattered radiation. Indian J Phys 2005, 79(9), 1063-4.

Scattered radiation at wavelength 6328 Angstrom from nine samples of blended tea solutions of different qualities have been investigated. Intensity measurements of the radiations indicate a possible correlation with the quality of the sample.

1 illus, 2 ref

016424   Deb S;Biswas S;Hussain S A;Bhattacharjee D (Phys Dep, Tripura Univ, Suryamaninagar-799 130, Email: tuphysic@sancharnet.in) : Ageing effect of mixed Langmuir-Blodgett film of 9-phenyl anthracene in PMMA and SA matrices. Indian J Phys 2005, 79(9), 1027-31.

Reports the time-dependent changes of molecular arrangement in the mixed LB films of nonamphiphilic 9-phenyl anthracene (PA) in stearic acid (SA) and polymethyl methacrylate (PMMA) in the light of absorption and fluorescence spectroscopic study. Molecular movements have been observed in the recently lifted LB films and about 200 hours is required to get the films in stable condition. Dimer and higher order n-mers exist in the LB films lifted at higher surface pressure of 30 mN/m.

3 illus, 9 ref

016423   Datta B K;Sabbata V D (Dipartimento Di Fisica, Universita Di Bologna, Via Irnerio 46, 40126-Bologna, Italy) : History of the development of Einstein's general theory of relativity (1907-1916). Indian J Theor Phys 2005, 53(2), 89-109.

Almost immediately after the publication of this work on the theory of special relativity, Einstein moved on with untiring efforts to develop the theory of gravitation in a consistent theoretical framework. For the sake of comprehensive discussion, it would be worth while to consider three distinct stages of the early development of general relativity. During the first period, from 1907 to 1914, Einstein attempted to formulate and develop the principle of equivalence. During this period, Max Abraham, a brilliant disciple of Max Planck and Gunnar Nordatrom of Helsingfors entered into serious and stimulating discussion with Einstein. The second period from 1912 to 1914 that overlapped with the first one saw Einstein and his mathematical friend Maroel Grossmann struggling hard for finding the way of translating the physical postulates into the language of the absolute differential calculus. During the third period, 1915-1916, Einstein formulated the field equations of gravitation, which were also independently derived by David Hilbert, one of the greatest mathematicians of the twentieth century.

25 ref

016422   Das P S (NO, Kolaghat Thermal Pwr Pl Township, B-55/6, Purba Medinipur-721 171) : Stdady flow of a micropolar fluid through co-axial circular cylinders under the action of a constant pressure gradient. Indian J Theor Phys 2005, 53(2), 169-75.

The aim of the research is to investigate the steady flow of a micropolar fluid through co-axial cylinders under the action of a constant pressure gradient. Accordingly, it is assumed that the annular flow takes place due to the action of a constant pressure gradient. The velocity, microrotation components, the rate of discharge of the fluid through the annulus and the time of efflux have been presented in a closed and neat forms. The final results of the titled problem show that the effect of micropolar is very significant on the velocity of the fluid as well as on the rate of discharge of the fluid through the annulus.

16 ref

016421   Chowdhury S;Dolui S K;Avasthi D K;Choudhury A (Phys Dep, Tezpur Univ, Napaam-784 028, Email: sky@tezu.ernet.in) : Irradiation induced grain growth and PL study of PbS quantum dots. Indian J Phys 2005, 79(9), 1019-22.

PbS quantum dots of average size 10 nm are encapsulated in a matrix (PVA) following chemical route. They are irradiated with 160 MeV Ni¹²⁺ ion beam with fluences 10¹²-10¹³ ions/cm². Red shift in the absorption response in the optical absorption spectra reveal size enhancement of the quantum dots after irradiation and was confirmed by transmission electron microscopy (TEM). Photoluminescence (PL) study was carried out with excitation wavelength 325 nm on both unirradiated and irradiated samples at different fluence and fluence-dependent surface state emission is observed in the PL study.

5 illus, 2 tables, 23 ref

016420   Chen H;Ge C;Li R;Wang J;Wu C;Zeng X (Municipal Key Lab of Inorganic Mater, Inst of Solid St Chem Ningbo Univ, Ningbo-315 211 P.R. China, Email: chenhongbing@nbu.edu.cn) : Growth of lead molybdate crystal by vertical Bridgman method. Bull Mater Sci 2005, 28(6), 555-60.

Growth of PbMoO₄ crystals by the modified Bridgman method has been reported. The feed material with strict stoichiometric composition is desirable for the Bridgman growth of the crystals. The continuous composition change of the melts during growth can be avoided because the volatilization of melts is limited by sealed platinum crucibles. By means of the optimum growth parameters such as the growth rate of <60> 1.2 mm/h and the temperature gradient of 20 <126> 40°C/cm across the solid-liquid interface under the furnace temperature of 1140 <126> 1200°C, large size crystals with high optical uniformity were grown successfully. The distribution of Pb and Mo concentration along the growth axis was measured by X-ray fluorescence analysis. The single crystallinity of the grown sample was evaluated by the double-crystal X-ray rocking curve. The transmission spectra were measured in the range of 300-800 nm at room temperature.

9 illus, 10 ref

016419   Chauhan D S;Sahal S (NO, , ) : Flow and heat transfer over a naturally permeable bed of very small permeability with a variable suction. Indian J Theor Phys 2005, 53(2), 151-9.

Heat transfer in the flow of a viscous incompressible fluid past a naturally permeable bed subjected to a variable suction, is investigated with the exponentially increasing free stream velocity. The response of the skin-friction and temperature to the accelerating stream is investigated for different values of the permeability parameter K and the accelerating parameter λ. It is found that the effect of K is to decrease both the skin-friction and the temperatures, where as λ increases the skin-friction but decreases temperatures.

4 illus, 1 table, 5 ref

016418   Chaudhuri D;Sengupta S (NO, Satyendra Nath Bose Natn Cent for Basic Sci, Block-JD, Sector-III, Salt Lake, Kolkata-700 098, Email: debc@bose.res.in) : Mechanical failure of a small and confined solid. Indian J Phys 2005, 79(9), 941-5.

Starting from a commensurate triangular thin solid strip, confined within two hard structureless walls, a stretch along its length introduces a rectangular distortion. Beyond a critical strain, the solid fails through nucleation of `smectic' - like bands. Shows using computer simulations and simple density functional based arguments, how a solid-smectic transition mediates the failure. Shows that the critical strain introducing failure is inversely proportional to the channel width i.e. thinner strips are stronger.

7 illus, 21 ref

016417   Chaudhary U S (Phys Dep, Nirmali Coll, Nirmali-847 452) : Study of corner-fed microstrip patch antenna for dual-polarisation operation. Indian J Theor Phys 2005, 53(3), 225-30.

a systematical study on the dual-polarised corner-fed microstrip patch antenna with thin single-layer structure is presented. The impedance matrices and S-parameters of the element are investigated by the proposed extended multiport network method. The co-and cross-polarisation patterns are also analysed. It is shown that this kind of antenna element has the isolation about 10 dB higher than that of a conventional edge-fed square patch.

2 illus, 6 ref

016416   Changmai R;Mahanta R;Tamuly T;Baruah G D (Phys Dep, Dibrugarh Univ, Dibrugarh-786 004, Email: ranjan_changmai@rediffmail.com) : Experimental proof of modification and quenching of fluorescence in polymer films. Indian J Phys 2005, 79(9), 1045-8.

The development of synthetic dyes in great variety on the one hand and of new polymer materials by chemical process on the other hand has enlarged the range of such activities very much. In fact these polymers act as host materials where dyes of suitable amount are doped. In the experiment used Ar⁺ laser (500 mW) for exciting the fluorescence of the sample. The exciting radiation were 4880 Angstrom (blue) and 5145 Angstrom (green). The salient feature of the experiment is that the laser radiation is allowed to fall on the sample and fluorescence is observed in the same direction. In the experiment obtained evidence of quenching of fluorescence when excited with the help of Ar⁺ laser. In one specific example of polymer of polyvinyl type the 1st positive bond system of N₂ is dramatically narrowed down. This quenching is of particular importance because modification of spontaneous emission via quantum interference has also been considered as a research topic in quantum optics.

1 illus, 2 tables, 28 ref

016415   Boruah B K;Baishya B (Phys Dep, Dibru Coll, Dibrugarh-786 003) : Microwave absorption and dielectric relaxation of some benzene derivatives and their binary mixtures. Indian J Phys 2005, 79(9), 1041-3.

The dielectric absorption of some benzene derivatives and their binary mixtures has been studied at 3-cm wave length microwave region in the range of temperature from 25°C to 45°C. The relaxation time, dipole moment, and the thermodynamics parameters for the dielectric relaxation as well as for viscous process have been measured. The results have been discussed on the basis of molecular size, molecular polarity, molecular environment, molecular interaction, effect of localisation of charge density and contribution arising from the formation of H-bond structure.

2 illus, 8 ref

016414   Bordoloi R;Bordoloi R B;Singh S N;Baruah G D (Phys Dep, Tinsukia Coll, Tinsukia-786 125, Email: rajib_assam01@yahoo.com) : On the nature of laser induced transient change in electrical conductivity of polymer extract from "Chali" (conocephalus suaveolens). Indian J Phys 2005, 79(9), 1071-4.

Every molecular medium reacts to an externally applied monochromatic optical field in a manner similar to a two-level molecular system under the influence of a monochromatic resonant field. In a two-level system, the dipoles undergo nutation about the applied field vector, which in turn cause the transition probability of the dipoles to vary periodically. This periodic variation in transition probability can induce many transient changes in the behaviour of the material, electrical conductivity being one of them. In this work, the conductivity of a polymer extracted from a toxic sample Chali, is observed in presence of a 2mW diode laser source. The sample shows dip its conductivity on being exposed to laser. Ths dkp in the electrical conductivity finds its explanation nutation of the molecular dipoles of the sample.

1 illus, 1 table, 9 ref