003115   Krishnagopal S;Maiti S;Prabhu S S;Sarkar S K (Centre for Advanced Technol, , Indore-452 013) : Free-electron laser. Curr Sci 2004, 87(8), 1066-78.

Free-electron laser (FELs) are lasers that use an electron beam from an accelerator to produce widely tunable, high power, ultrafast pulses of coherent radiation. FELs are today important sources of infrared radiation around the world. Quasi-CW high-power FELs are also operational FELs that operate on the self-amplified spontaneous emission principle are leadind candidates for X-ray lasers and fourth-generation light sources. We discuss the physics, technology, advantages and application of FELs, the orontiers of X-ray and high-power FELs are discussed.

7 illus, 1 table, 29 ref

003114   Khare A;Sukhatme U (Inst of Phys, , Sachivalaya Marg, Bhubaneswar-751 005) : Connecting Jacobi elliptic functions with different modulus parameters. Pramana J Phys 2004, 63(5), 921-36.

The simplest formulas connecting Jacobi elliptic functions with different modulus parameters were first obtained over two hundred years ago by John Landen. His approach was to change integration variables in elliptic integrals. Landen's formulas and their subsequent generalizations can also be obtained from a different approach, using which several new Landen transformations wer obtained. New method is based on recently obtained periodic solutions of physically interesting non-linear differential equations and remarkable new cyclic identities involving Jacobi elliptic functions.

12 ref

003113   Kant K;Chauhan R P;Sharma G S;Chakarvarti S K (Phys Dep, G G D S D Coll, Palwal (Faridabad)-121 102) : Radium concentration measurements in coal flyash and cement samples using LR-115 plastic track detectors. Indian J envir Prot 2003, 23(10), 1146-50.

The increased interest in measureing radium (²²⁶Ra) concentration in coal, flyash and cement is due to its health hazards and environmental pollution. Samples of coal and flyash from different thermal power stations in northern India were collected and analysed for radium concentration. Cement samples were collected from National Council for Cement and Building Materials (NCB), Ballabgarh (Haryana). The radium concentration is estimated through track etch technique using LR-115 CN detectors.

3 tables, 20 ref

003112   Jalori H;Singh S K;Gwal A K (Phys and Electronics Dep, space Sci Lab, Barkatullah Univ, Bhopal-462 026) : Upconversion of whistler waves by gyrating ion beams in a plasma. Pramana J Phys 2004, 63(3), 595-610.

A gyrating ion beam, with a ring-shaped distribution in velocity, supports negative energy beam modes near the harmonics of beam gyro-frequency. An investigation of the non-linear interaction of high-frequency whistler waves with the negative energy beam cyclotron mode is made. A non-linear dispersion relation is dervied for the coupled modes. It is shown that a gyrating ion-beam frequency upconverts the whistler waves separated by harmonics of beam gyro-frequency. The expression for the growth rate of whistler mode waves has been derived. In Case 1, a high-amplitude whister wave decays into two lower frequency waves, called a low-frequency mode and a side band of frequency lower than that of pump wave. In Case 2 a high-amplitude whistler wave decays into two lower frequency daughter waves, called the low-frequency mode and whistler waves. Generation mechanism of these waves has application in space and laboratory plasmas.

2 illus, 13 ref

003111   Iyer D S;Raje D V;Purohit H J;Gupta A;Singh R N (Natnl Environ Engng Res Inst, , Nehru Marg, Nagpur-440 020) : CAGCAG - the most consistent repeating pattern in evolution of small subunit of rRNA gene sequences. Curr Sci 2004, 87(4), 494-500.

Conserved patterns in nucleotide sequences are often suspected for their possible structural or functional implications. In this exercise, repeating patterns of nucleotides of size six or more that are conserved in rRNA sequences of three evolutionary domains, hve been targeted. The pattern CAGCAG was gound to be the most consistent repeating pattern in 16S rRNA of Proteobacteria and 18S rRNA of Eucarya, but the repetitivenes was not observed in Archaea. This pattern or the residues within have not been reported for their biological relevance; but still the information contained between the repeats of the pattern was found to be of much relevance in classification using similarity and multiple discriminant analysis.

5 illus, 1 table, 13 ref

003110   Gowda S;Krishnaveni S;Yashoda T;Umesh T K; Gowda R (Studies in Phys Dep, Univ of Mysore, Mysore-570 006) : Photon mass attenuation coefficients, effective atomic numbers and electron densities of some thermoluminescent dosimetric compounds. Pramana J Phys 2004, 63(3), 529-41.

Photon mass attenuation coefficients of some thermoluminescent dosimetric (TLD) compounds, such as LiF, CaCO₃, CaSO₄ 2H₂O, SrSO₄, CdSO₄, BaSO₄, C₄H₆BaO₄ and 3CdSO₄ 8H₂O were determined at 279.2, 320.07, 514.0, 661.6, 1115.5, 1173.2 and 1332.5 keV in a well-collimated narrow beam good geometry set-up using a high resolution, hyper pure germanium detector. The attenuation coefficient data were then used to compute the effective atomic number and the electron density of TLD compounds. The interpolation of total attenuation cross-sections of photons of energy E in elements of atomic number Z was performed using the logarithmic regression analysis of the data measured by the authors and reported earlier. The best-fit coefficients so obtained in the photon energy range of 279.2 to 320.07 keV, 514.0 to 661.6 keV and 1115.5 to 1332.5 keV by a piece-wise interpolation method were then used to find the effective atomic number and electron density of the compounds. these values are found to be in agreement with other available published values.

6 illus, 5 tables, 28 ref

003109   Giri M;Jaggi N;Singh N;Jaiswal R M P (Phys Dep, Kurukshetra Univ, Kurukshetra-136 119, Haryana) : Absorption, excitation and fluorescence spectra of Congo red in aqueous solutions. Indian J Phys 2004, 87(10), 1137-40.

The absorption, excitation and fluorescence spectra of Congo red [C₃₂H₂₂H₆Na₂O₆S₂] have been recorded in aqueous solution at concentrations between 10^-3 and 10^-6 Ml^-1. This has led to the determination of optimum concentrations, for the absorption and fluorescence spectra of the compound. The absorption spectrum has been recorded only in the spectral region of 350-600 nm showing at peak at 497 nm. The excitation spectrum has been recorded with λ_em = 600 nm. The fluorescence spectra are recorded with <108>ex = 450-550 nm showing a peak at 602 nm. The absorption and fluorescence transitions have been shown to correspond to each other. The absorption band has been assigned to (<112>* ←n) ¹W←¹A transition of the azo-biphenyl moiety of the compound.

6 illus, 14 ref

003108   Ghoshal A;Kar S;Mandal P (Math Dep, Visva-Bharati Univ, Santiniketan-731 235) : Physical properties of normal two-electron systems considering correlation. Indian J Phys 2004, 87(10), 1099-1105.

9 tables, 19 ref

003107   Ghosh T K;Sharma S K;Chopra A K;Srivastava V; Joshi S N (Microwave Tubes Area, Central Electronics Engng Res Inst, Pilani (Raj) - 333 031) : Development of collector electrodes for high efficiency space twts. Bull Indian Vacuum Soc 2004, 7(2), 25-7.

A 4-stage depressed collector has been designed for a Ku-band 140 W space travelling wave tube to enhance its efficiency more than 60% with minimum back streaming caused by secondary electrons. It is planned to fabricate the electrodes with graphite material to reduce the secondary electron emission. Efficiencies between the collectors of copper and graphite electrodes have been compared through simulation. The engineering drawings of the parts and the complete assembly have been made. A sequence of assembly has also been finalized.

3 illus, 2 tables, 4 ref

003106   Ghosh D;Deb A;Mallick S K;Sarkar S;Purkait K; Sengupta R (High Energy Physics Div, Phys dep, Jadavpur Univ, Kolkata-700 032) : Strong pionic intermittency in `cold' events in <. Pramana J Phys 2004, 63(5), 963-8.

Intermittent behaviour of the poins from `cold' and `hot' classes of events of ¹²C-AgBr interactions at 4.5 GeV has been studied, separately. The results reveal strong intermittent pattern in case of `cold' class of events.

2 illus, 3 tables, 24 ref

003105   Fahmy T;Ahmed M T (Polymer Laboratory, Polymer Research Group, Pshys Dep, Faculty of Scie, Msansoura University, 35516 Mansoura, Egypt) : Alternating-current conductivity and dielectric relaxation of poly (Acrylonitrile-Butadiene-Styrene) terpolymer doped with tetrabutylammonium tetrafluoroborate. J Polym Mater 2003, 20(4), 367-76.

Different polmeric composite samples from Poly(acrylonitrile-butadiene-styrene) ABS) Terpolymer and Tetrabutylammonium Tetrafluoroborate were prepared and their dielectric spectra were measured in the frequency range from 0.2 Hz to 100 kHz and in temperature interval from room temperature to 463 K. AC conductivity of these composites is found to be frequency and temperature dependent, and it generally follows the exponential law, σ_ac ∝ ωⁿ. The values of n were calculated at all temperatures for all samples. Dielectric relaxation has been investigated and it was found that all samples are characterized by high dielectric constant values at very low frequency and high temperature. The results are discussed in terms of interfacial Maxwell-Wagner-Sillars (MWS) polarization ad space-charge polarization.

6 illus, 1 table, 42 ref

003104   Duha S S;Paul S K;Banerjee A K;Mamun A A (Phys Dep, Jahangirnagar Univ, Savar, Dhaka, Bangladesh) : Low-frequency electrostatic dust-modes in a non-uniform magnetized dusty plasma. Pramana J Phys 2004, 63(5), 1011-19.

A self-consistent and general description of obliquely propagating low-frequency electrostatic dust-modes in a non-uniform magnetized dusty plasma system has been presented. A number of different situations, which correspond to different low-frequency electrostatic dust-modes, namely, dust-acoustic mode, dust-drift mode, dust-cyclotron mode, dust-lower-hybrid mode, and other associated modes (such as, accelerated and retarded dust-acoustic modes, accelerated and retarded dust-lower-hybrid modes, etc.), have also been investigated. It has been shown that the effects of obliqueness and inhomogeneities in plasma particle number densities introduce new electrostatic dust modes as well as significantly modify the dispersion properties of the other low-frequency electrostatic dust associated modes. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring-systems and cometary tails, are briefly mentioned.

30 ref

003103   Datta P K;Basu C;Mukhopadhyay S;Das S K; Samanta G K;Agnesi A (Phys and Meteorology Dep, Indian Inst of Technol, Kharagpur-721 302) : Diode array pumped, non-linear mirror Q-switched and mode-locked Nd:YVO_{4 laser a good tool for powder SHG measurement.} Pramana J Phys 2004, 63(5), 1003-10.

a non-linear mirror consisting of a lithium triborate crystal and a dichroic output coupler are used to mode-lock (passively) an Nd:YVO₄ laser, pumped by a diode laser array. The laser can operate both in cw mode-locked and simultaneously Q-switched and mode-locked (QML) regime. The peak power of the laser while operating QML regime is much higher but pulses suffers from poor amplitude stability. The incorporation of an acousto-optic modulator as an active Q-switch enhances the stability of the QML pulse envelope. The second-order non-linerarity of powdered crystalline urea is conclusively measured with respect to KDP while the laser is operating in passively Q-switched and passively mode-locked regime as well as in actively Q-switched and passively mode-locked regime.

3 illus, 17 ref

003102   Choudhary V;Singh A;Vhandra V K;Gupta R K; Chandra B P (Sch of Studies in Phys, Pt. Ravishankar Shukla Univ, Raipur-492 010) : Theoretical approach to the tunneling mechanoluminescence produced during cleavage of II-VI semiconductors. Indian J Engng Mater Sci 2004, 11(5), 421-8.

8 illus, 7 ref

003101   Chauhan R K;Srivastava M K;Srivastava R (Phys Dep, Indian Inst of Technol, Roorkee-247 667) : Triple differential cross sections of coplanar (e,2e) process on helium-like ions. Indian J Phys 2004, 87(10), 1073-7.

Triple differential cross sections (TDCS) for electron impact ionization of Li⁺, Be², B³ and C⁴⁺ are obtained using distorted-wave approximation in (i) equal energy sharing and ξ_ab = 180° kinematics close to ionization threshold and (ii) coplanar doubly symmetric kinematics and excess energy E_ex = 30-60 e V. The changes in the angular distribution of TDCS with E_ex and increase in the target nuclear charge are analyzed.

3 illus, 35 ref

003100   Chandra S (Sch Phys Sci, SRTM Univ, Nanded-431 606) : Search for an interstellar Si₂C molecule: a theoretical prediction. Pramana J Phys 2004, 63(3), 627-31.

It was suggest that Si₂C molecule may be identified in astronomical objects through its transitions 4₁₄→ 5₀₅, 5₁₅→6₀₆, 2₁₂→3₀₃, 3₁₃→4₀₄, and 1₁₁→2₀₂ at 15.9, 5.1, 33.6, 24.9, and 42.3 GHz in absorption even against the cosmic 2.7 K background, in a region having low temperature. The absorption phenomenon is found rather large in the first two transitions. Dependence of results on the set of molecular parameters is discussed.

2 illus, 1 table, 14 ref

003099   Chaman M;Verma P K;Khan E H;Shafi S; Shafiullah (Phys Dep, Aligarh Muslim Univ, aligarh-202 002) : Vibrational spectra of cholesterol derivative and its assignment. Indian J Phys 2004, 87(10), 1129-35.

The FT-laser Raman spectrum of Tosyl Cholesterol molecule was recorded using Nd-YAG laser operating at 1064 nm as a source of excitation in the region of 50-3500 cm^-1. The FTIR spectra of above molecule have also been recorded in the solid phase as well as in the liquid phase in the regions of 400-4000 cm^-1. The molecule has been assumed to belong to CS-point group. Symmetric and asymmetric vibration have been explained to a" and a" respectively. These molecular vibrations have been correlated with the vibrations observed in the FTIR spectrum of the said molecule.

3 illus, 3 tables, 31 ref

003098   Bhore P V;Shah a P;Gokhale M R;Ghosh S; Bhattacharya A;Arora B M (Satumull Inst of Electronic Engng and Computer Technol, , Worli, Mumbai-400 018) : Effect of facet coatings on laser diode characteristics. Indian J Engng Mater Sci 2004, 11(5), 438-40.

The cleaved facets of semiconductor diode laser act like mirror. Mirror coatings are applied to change the reflectivity and passivate the surfaces. Design of antireflection coating is optimized for single layer of Al₂O₃ and high reflection coating is optimized for stacks of Al₂O₃ and Si Bragg reflector. Electron beam evaporation has been used to deposit uniform Al₂O₃/Si film under high vacuum with pressure 10^-6 mbar and temperature 150-160,144>C. The optimization of experimental parameters for the dummy GaAs substrate has been discussed. Using these parameters laser facets were coated and changes in the L-I characteristics have been measured and investigated step by step. the output light power versus current characteristics of coated laser diode is compared with that of uncoated one for its characterization under pulsed conditions and have shown that the facet reflectivity has played a major role in determining threshold current density of semiconductor laser.

2 illus, 8 ref

003097   Bhattacharya S;Rao P M;Nakhate S G;Joshi G (Spectroscopy Div, Electronics Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Trapping of positive europium ions in a Paul trap. Indian J Phys 2004, 87(10), 1051-4.

Reports the trapping of positively charged Europium ions in a rf trap. The effect of collisional cooling due to buffer gas on the storage time of the trapped ions is studied. The storage time of trapped ions in vacuum is observed to be only a few tens of seconds. Cooling the ions using nitrogen and helium as buffer gas, improved the storage time by orders of magnitude. Collisional cooling was more effective using helium as buffer gas.

4 illus, 6 ref

003096   Bhattacharya S;Choudhury K B;Deb N C;Roy K (Phys Dep, surendranath Coll, Kolkata-700 009) : Angular distribution for the proton impact ionizations of 3p-electrons in Ar. Indian J Phys 2004, 87(10), 1079-83.

Using recently published theoretical model for proton impact ionization of Ar [Phys. Rev. A68 052702 (2003)] has been calculated the double differential cross sections for the same system at various ejected electron energies and angle of ejection. Results are compared with available measurements and other calculated results. It is found that well results agree reasonably with the measurement in the binary encounter region but slightly overestimate the measurement around the recoil peak, At 350 ke V impact energy calculated double differential cross section for outgoing electron energies at (a) 46 eV, (b) 100 eV and (c) 308 eV. all three cases exhibit similar behaviour.

1 illus, 15 ref

003095   Bhatia P K;Mathur R P (Math Statistics Dep, Jai Narain Vyas Univ, Jodhpur-342 001, Raj) : Kelvin-helmholtz discontinuity in partially ionized plasmas. Indian J Phys 2004, 87(10), 1147-50.

Treats the linear Kelvin-Helmholts discontinuity in partially ionized plasmas in a uniform vertical magnetic field. The dispersion relation has been derived by using the normal mode technique. Both the streaming velocity and the frequency collision are found to have a destabilizing influence on the instability of system.

1 illus, 14 ref

003094   Basu C (Saha Inst of Nuclear Physics, , 1/AF Bidhan Nagar, Kolkata-700 064) : Spectroscopic factors for two-proton radioactive nuclei. Pramana J Phys 2004, 63(5), 1047-52.

Spectroscopic factors for two-proton emitting nuclei are discussed in the framework of the BCS (Bardeen-Cooper-Schriefer) model. Calculations carried out for the two-proton unstable ⁴⁵Fe, ⁴⁸Ni and ⁵⁴Zn nuclei are presented.

2 tables, 28 ref

003093   Bali R;Anjali (Math Dep, Univ Rajasthan, Jaipur-302 004) : Bianchi type-I bulk viscous flud string dust magnetized cosmological model in general relativity. Pramana J Phys 2004, 63(3), 481-90.

Bianchi type-I magnetized bulk viscous fluid string dust cosmological model is investigated. To get a determinate model, Conditions σ x θ and ζθ = constant where σ is the shear, θ the expansion in the model and ζ the coefficient of bulk viscosity. The behaviour of the model in the presence and absence of magnetic field together with physical and geometrical aspects of the model are also discussed.

9 ref

003092   Aggarwal A K;Kaura S K;Chhachhia D P;Sharma A K (Coherent Optics Div, Central Scientific Instruments Organ, Sector 30, Chhandigarh-160 030) : Realization of an optical interferometer based on holographic optics for real-time testing of phase objects. Pramana J Phys 2004, 63(5), 993-1001.

Describes a simple and cost effective method for the realization of an optical interferometer based on holographic optics, which use minimal bulk optical components. The optical arrangement in the proposed method involves a very simple alignment procedure and inexpensive holgraphic recording material is used in the formation of holographic optical elements. The proposed interferometer set-up is quite suitable for performing optical test studies on phase (transparent) objects in real-time. Recording schemes for the formation of holographic optical elements and the related technique for the realization of the interferometer set-up along with the experimental results have been presented.

8 illus, 17 ref

003091   Abou El-Ela F M (Phys Dep, Faculty of Girls, Ain Shams Univ, Heliopolis, Cairo, Egypt, Email: fadlaeg@yahoo.com) : Electron lucky-drift impact ionization coefficients of ZnS:Mn. Pramana J Phys 2004, 63(5), 1089-97.

Fit of the experimental data of ZnS : Mn by a modified lucky-drift formula has been performed using the least square algorithm. The fit agrees well with the experimental data only at high field. The best fitting parameters at high field are the mean free path of order 102.74 Å and Keldysh factor, Po = 0.0138. a generalized Keldysh formula has been used, due to introduction of a soft threshold factor. The soft lucky-drift theory can also be used to calculate the impact ionization coefficients of high electron energy of ZuS:Mn without losing its physical significance compared to full band-structure Monte Carlo calculation with a remarkably reduced amount of computer resources. The curvature on semi-log plot of experimental impact ionization coefficient against the inverse of electric field is different from what is observed for other materials at low electric fields due to impact ionization of deep level impurities.

5 illus, 24 ref

002143   Xinghua F;Lianwei S;Biyan D;Wenping H;Zhou F; Zhengyi F (The State Key Laboratory of Material Composite and Advanced Technology, Wuhan University of Technology, Wuhan 430070, PR China) : Progress of (Sr, Ba) TiO₃ ferroelectric thin film and tunability. Bull Mater Sci 2004, 27(5), 433-9.

The fabrication method, technology route and structure performances of (Sr, Ba) TiO₃ (SBT) ferroelectric thin film have been summarized. The tunability of dielectric constant, dielectric loss and leakage current are the basic parameters of tunable microwave devices. The thin films of SBT with high properties could be fabricated by means of RF magnetron sputtering and sol-gel processing. The electrical performances of thin film material can be improved largely by dopants. Some problems are put forward to pay attention to this material research process.

2 illus, 26 ref

002142   Walia R S;Shan H S;Kumar P (Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee 247 667) : Improving EDM process efficiency by ultrasonic vibrations. J pure appl Ultrasonics 2004, 26(2-3), 84-9.

Among the newly developed non-conventional machining process, Electrical Discharge Machining (EDM) is the most popular because of its large industrial applications. EDM is a thermal machining process, which is capable of machining any electrical conductive material irrespective of its hardness and strength. In the last decade many attempts have been made to improve the performance of EDM. Deals with the improvement of EDM process by applying ultrasonic vibrations to the tool electrode. Studies have indicated that EDM operation with vibrating tool electrode allows deeper penetration and higher feed rates. This is especially useful during finishing operation, where machining time is reduced with the surface quality of workpiece unaffected. The modified EDM process is well adapted to the production of very intricately shape electrodes. Other major advantages of this process include the reduced recast layer, highr machining rate, low thermal residual stresses, and better metallurgical properties of workpiece. Analysis shows that improved dielectric fluid flushing is responsible for most of the advantage achieved. In ultrasonic assisted EDM process, what seems to be more important is the ability of working without instability, particularly when the gap is narrow.

4 illus, 6 ref

002141   Wagh A G;Rakhecha V C;Strobl M;Treimer W (Solid State Phys Div, Bhabha Atomic Res Centre, Mumbai-400 085) : A polarised SUSANS facility to study magnetic systems. Pramana J Phys 2004, 63(2), 369-73.

Using a right-angled magnetic air prism, achieves a separation of ~ 10 arcsec between ~ 2 arcsec wide up-an down-spin peaks of 5.4 a neutrons. the polarised neutron option has thus been intoduced into the SUSANS instrument. Strongly spin dependent SUSANS spectra have been observed over ±1.3 x 10^-4 A^-1 range for several magnetic alloy samples. Spatial pair-distribution functions for the up and down-spins as well as the nuclear and magnetic scattering length density distributions in the micrometer domain, have been deduced from these spectra.

7 illus, 9 ref

002140   Wagh A G;Rakhecha V C (Solid State Phys Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Geometric formula for prism deflection. Pramana J Phys 2004, 63(2), 381-5.

While studying neutron deflections produced by a magnetic prism, we have stumbled upon a simple `geometric' formula. For a prism of refractive index n close to unity, the deflection simply equals the product of the refractive power n - 1 and the base-t-height ratio of the prism, regardless of the apex angle. The base and height of the prism are measured respectively along the perpendicular to the direction of beam propagation within the prism. The geometric formula greatly simplifies the optimisation of prism parameters to suit any specific experiment.

5 illus, 7 ref

002139   Venkatramani N (Beam Technol Development Group, Bhabha Atomic Res Centre, Mumbai-400 085) : History of vacuum: the Indian ethos. Bull Indian Vacuum Soc 2004, 7(3), 13-20.

This report traces the history of Vacuum Science and Technology in the Indian context. It is a homage to the illustrious individuals and the distinguished institution that played a leading role during the last century. It is also tribute to the Indian Vacuum Society that brought them under one umbrella.

^iia2 tables

002138   Vaidyanathan G;Arulmurugan R;Likhite S D; Anantharaman M R;Vaidya M;Sendhilnathan S;Senthilram N D (Phys Dep, Pondicherry Engng Coll, Pondicherry-605 014) : Effect of preparation on magnetic properties of Mn-Zn ferrite. Indian J Engng Mater Sci 2004, 11(4), 289-94.

Mixed ferrites belonging to the type Mn_0.9Zn_0.1Fe₂O₄ have been prepared by the double sintering method and by the chemical co-precipitation for comparing their magnetic properties. Sintered and precipitated ferrites exhibit different characteristics, especially in their magnetic properties like magnetization (M_s), coercive field (H_c) and Curie temperature (T_c). The sintered particles were size reduced in order to compare with the nanosized co-precipitated particles. The effected of grinding has also been studied. Particles have been collected at regular intervals of grinding and their properties have been studied. The increase in the coercive field has been recorded by a hysteresis curve tracer confirming size reduction. X-ray diffraction studies confirmed the structure and consequent size reduction.

4 illus, 3 tables, 5 ref

002137   Tynjala T;Ritvanen J (Energy and Envir Technol Dep, Lappeenranta Univ of Technol, P.O.Box 20, FIN 53851, Lappeenranta, Finland) : Simulations of thermo-magnetic convection in an annulus between two concentric. Indian J Engng Mater Sci 2004, 11(4), 283-8.

In this paper the thermo-magnetic convection of a magnetic fluid held between two vertical concentric cylinders is studied. Three-dimensional computer simulations of thermo-magnetic convection have been conducted under an azimuthal magnetic field, when the inner cylinder is kept at a higher temperature than the peripheral one. simulations have been carried out both in the absence and in the presence of gravity. In the absence of gravity, the problem will be analogous to the classical Rayleigh-Bernard instability in a radial gravitation field. The objective of theis study is to investigate the combined effects of magnetic and buoyancy driven convection. In the absence of gravity the simulations revealed the expected flow pattern consisting of counter rotating convection cells with diameter equal to the thickness of the fluid layer. When the gravity is introduced, the case may become unsteady consisting of cells drifting upward. For small gravitational Rayleigh numbers introduction of magnetic field gradient may stabilize the flow. The onset of instability depends on the magnetic and the gravitational Rayleigh numbers and their ratio, radius and aspect ratios of the cylinders as well as on the fluid properties.

5 illus, 9 ref

002136   Timko M;Koneracka M;Kopcansky P;Tomori Z; Vekas L;Jozefczak A;Skumiel A;Radenovic A;Dietler G;Bystrenova E et al (Inst of Experimental Phys of Slovak Academy of Sci, , Kosice, Slovakia) : Complex characterization of physiology solution based magnetic fluid. Indian J Engng Mater Sci 2004, 11(4), 276-82.

Atomic force microscopy (AFM), transmission electron microscopy (TEM) and magnetization measurements by vibrating sample magnetometer (VSM) were used for estimation and comparison of size of magnetite particles in physiology soluation based magnetic fluid (MF). The mean particle diameter values were 7.6 nm, 9.3 nm and 10.6 obtained by AFM, VSM and TeM, respectively. For the analysis of AFM pictures the more precise method was developed where the particle size was calculated as the geometrical mean of sizes in all three dimensions. The structural stability of prepared MF was affirmed by the ultrasonic measurements.

8 illus, 12 ref

002135   Taneja R;Jain N C (Univ of Rajasthan, , Jaipur-302 004) : MHD flow with slip effects and temperature-dependent heat source in a viscous incompressible fluid confined between a long vertical wavy wall and a parrallel flat wall. Def Sci J 2004, 54(1), 21-9.

This study examines the problem of an MHD free convenction flow in the presence of a temperature dependent heat source in a viscous incompressible fluid between a long vertical wavy wall and a prarallel flat wall with constant heat flux and slip flow boundary condition. A uniform magnetic field is assumed to be applied prependicular to the walls. It is assumed that the flow consists of two parts' a mean part and a perturbed part. Expressions for the zeroth-order and first-order velocity, temperature, skin friction, and Nusselt number at the walls are obtained. The effects of different parameters entering into the problem, viz., free convenction parameter, magnetic parameter, and heat source parameter on the zeroth-order and first-order velocity fields, temperature field, skin friction, and Nusselt number at the walls are shown graphically and discussed numerically.

3 illus, 7 ref

002134   Talapatra A;Bandyopadhyay S K;Sen P;Sarkar A; Barat P (Variable Energy Cyclotron Centre, , 1/AF, Bidhan Nagar, Kolkata-700 064) : Phase formation of superconducting MgB₂ at ambient pressure. Bull Mater Sci 2004, 27(5), 429-32.

MgB₂ superconductor has been synthesized using a simple technique at ambient pressure. The synthesis was carried out in helium atmosphere over a wide range of temperatures. Magnesium was employed in excess to the stoichiometry to prevent the decomposition of MgB₂. Samples of MgB₂ thus prepared have been almost free from MgO as compared to other methods. Resistivities of the samples are quite low with residual resistivity ratio (RRR) of around 3. T_c(R=0) is 38.2-38.5 K with ΔT_c of 0.6-1.0 K. Comparative studies of various methods of low pressure synthesis have been presented.

3 illus, 2 tables, 6 ref

002133   Surkiran J S;Shinde A B;Krishna P S R (Solid State Physics Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Structure and magnetic properties of colossal magnetoresistance compound Tb_0.5Sr_0.5CoO₃. Pramana J Phys 2004, 63(2), 221-6.

The structure and the magnetic properties of the doped rare earth cobaltite systems are of recent interest owing to the CMR phenomenon that occur in them. In this paper, we investigate the structure and magnetic properties of Tb_0.5Sr_0.5CoO₃ solid solution, for the first time, using neutron powder diffraction technique. The sample Tb_0.5Sr_0.5CoO₃ is found to crystallize in orthorhombic (Pbnm) symmetry. The unit cell volume and Co-O bound length reduce with temperature. The calculated e_g bandwidth obtained from structural parameters turns out to be 0.989 eV. Low temperature neutron diffraction profiles exhibit a magnetic contribution to the fundamental Bragg peaks in dicating a ferromagnetic ordering below T_c. The results are compared with Co-O-Co bond angles and Co-O bond length of La_0.5Sr_0.5CoO₃, highlighting the ionic size effects on substitution of Tb ion for La in the compound.

1 illus, 1 table, 9 ref

002132   Subramaniam S;Ravindra B Y;Rabindranath B; Basheerullah B G;Viswanath P V;Bajpai O P (National Remote Sensing Agency, , Hyderabad-500 037) : Sationary spatially modulated fourier transform spectro-radiometer. J Indian Soc Remote Sens 2003, 31(3), 187-96.

A stationary, compact, spatially modulated Fourier Transform spectro-radiometer based on triangular, common path Sagnac interferometer has been developed using linear CCD array detector for sampling the interferogram fringe pattern. The optics and system configuration are described and the preliminary results are given. The system modification of making a push-broom Imaging hyper spectral system suitable for airbourne/specebourne measurements has been discussed.

6 illus, 1 table, 5 ref

002131   Subhash Chander;Lakhanpal S;Krishnamurthy A; Srivastava B K;Aswal V K (Phys Dep, Univ of Rajasthan, Jaipur-302 004) : Magnetic behaviour of nano-particles of Fe_2.8Zn_0.2O₄. Pramana J Phys 2004, 63(2), 345-50.

Magnetization measurements are reported on a nano-particle sample of Zn-substituted spinel ferrite Fe_2.8Zn_0.2O₄ in the temperature range 20-300 K. Analysis of small-angle neutron scattering data shows the sample to have a log-normal particle size distribution of median diameter 64.4 A and standard deviation 0.38. Magnetization evolves over a long period of time t going nearly linearly with log t. Magnetic anisotropy, estimated by fitting M-log t curve, shows many fold increase over that of bulk particle sample. Major enhancement owes to discordered moments in surface layer. In the nano-particle state as well increasing amount of Zn causes anisotropy to decrease.

6 illus, 7 ref

002130   Sirivasava A K;Kishore R;Swati;Agnihotry S A (Materials Characterization Div, Electronic Materials, National Phys Lab, Dr K S Krishnan Road, New Delhi-110 012) : Electron microscopy and diffraction analysis of nano-structured prussian blue thin films. Indian J Engng Mater Sci 2004, 11(4), 315-8.

Prussian blud (PB) thin films have been deposited galvanostatically on transparent conducting coated glass plates with a current density of 20 μA/cm² using equivolume mixture of 10 mM FeCl₃ and 10 mM K₃Fe(CN)6 in 0.01 N NCL. During deposition the process conditions have been suitably varied to obtain electron beam transparent thin films. A transmission electron microscope has been extensively used to understand the microstructural features at nano-scale, evolved during deposition and the respective selected area electron diffraction patterns have also been studied to reveal amorphous and crystalline behaviour of nano-grains in the microstructure. A detailed charactrization of these films illustrated that the films in general constituted of amorphous nano-grains (20-100 nm) with some regions consisting of crystalline phase in the microstructure. The fine details associated with structure and microstructure of PB thin films have been discussed and correlated with their electro-chromic properties.

3 illus, 8 ref

002129   Singh S;Thakur O P;Chandra Prakash;Raina K K (Electroceramics Group, Solid State Physics Laboratory, Lucknow Road, Delhi 110 054) : Electrical properties of tantalum modified PCT ceramics. J pure appl Ultrasonics 2004, 26(2-3), 35-9.

Tantalum substituted lead calcium titanate ceramics with composition Pb_0.76Ca_0.24Mn_0.02Ti_0.98-5x/4Ta_xO₃ ; where x = O-0.05 in steps of 0.01 were prepared by coventional mixed-oxide method. Structural behaviour has been studied using XRD and SEM. Single phase with perovskite type tetragonal structure was observed. SEM results show the decrease in grain size and increase in porosity with increase in Ta⁵⁺. Dielectric behaviour as a function of temperature at different frequencies was examined. Room temperature value of ε decreases with Ta⁵⁺ content. The position of TC also shifts to lower temperature. It has been found that the d_h of PbTiO₃ ceramics is about twice that of PZT ceramics making it suitable for acoustic aplications. It has also been observed that the d₃₃ decreases with the increase in the amount of Ta⁵⁺.

4 illus, 1 table, 10 ref

002128   Singh S;Basu S (Solid State Phys Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Polarized neutron reflectometry at Dhruva reactor. Pramana J Phys 2004, 63(2), 387-91.

Polarized neutron reflectometry (PNR) is an ideal non-destructive tool for chemical and magnetic characterization of thin films and multilayers. We have installed a position sensitive detector-based polarized neutron reflectometer at Dhruva reactor, Trombay. In this paper we will discuss the results obtained from this instrument for two multilayer samples. The first sample is a (Ni-Mo alloy)/Ti multilayer sample. We have determined the chemical structure of this multilayer by unpolarized neutron reflectometry (NR). The other sample is a Fe/Ge multilayer sample for which we obtained the chemical structure by NR and magnetic moment per Fe atom by PNR.

4 illus, 1 table, 13 ref

002127   Shukla A;Kiselev M A;Hoell A;Neubert R H H (Phys Dep, Optics Group, Martin-Luther Univ, D-06099 Halle/Saale, Germany) : Characterization of nanoparticles of lidocaine in w/o microemulsions using small-angle neutron scattering and dynamic light scattering. Pramana J Phys 2004, 63(2), 291-5.

Microemulsions (MEs) are of special interest because a variety of reactants can be introduced into the nanometer-sized aqueous domains, leading to materials with controlled size and shape. In the past few years, significant research has been conducted in the reverse ME-mediated synthesis of organic nanoparticles. In this study, a w/o ME medium was employed for the synthesis of lidocaine by direct precipitation in w/o microemulsion systems: water/isopropylpalmitat/Tween80/Span80. The particle size as well as the location of nanoparticles in the ME droplet were characterized by means on dynamic light scattering (DLS) and small angle neutron scattering (SANS). It is observed that lidocain precipitated in the aqueous cores because of its insolubility in water. Hydrodynamic radius and gyration radius of microemulsion droplets were estimated as ~15 nm and ~4.50 nm from DLS and SANS respectively. Furthermore, different size parameters obtained by DLS and SANS experiments were compared.

2 illus, 1 table, 5 ref

002126   Shinde S;Talati M;Jha P K;Sanyal S P (Phys Dep, Faculty of Sci, M S Univ of Baroda, Vadodara-390 002) : Theoretical study of the transverse acoustic phonons of GaSb at high pressure. Pramana J Phys 2004, 63(2), 425-9.

It has been investigated the phonon dispersion curves and one-phonon density of states up to the pressure of 8 GPa using a theoretical model, namely the rigid ion model. The transverse acoustic phonons as a function of pressure have been compared with the recently measured inelastic neutron scattering data which show a strong softening near the zone boundaries. The calculated one-phonon density of states show pronounced shift in the peak positions with the increase in pressure.

3 illus, 1 table, 14 ref

002125   Sharma S;Joshi J V;Aswal V K;Goyal P S; Rakshit A K (Chem Dep, Faculty of Sci, The Maharaja Sayajirao Univ of Baroda, Vadodara-390 002) : Small-angle neutron scattering studies of nonionic surfactant: effect of sugars. Pramana J Phys 2004, 63(2), 297-302.

Micellar solution of nonionic surfactant n-dodecyloligo ethyleneoxide surfactant, decaoxyethylene monododecyl ether [CH₃(CH₂)₁₁(OCH₂CH₂)₁₀OH], C₁₂E₁₀ in D₂O solution have been analysed by small-angle neutron scattering (SANS) at different temperatures (30, 45 and 60°C) both in the presence and absence of sugars. The structural parameters like micelle shape and size, aggregation number and micellar density have been determined. It is found that the micellar structure significantly depends on the temperature and concentration of sugars. The micelles are found to be prolate ellipsoids at 30°C and the axial ratio of the micelle increases with the increase in temperature. The presence of lower concentration of sugar reduces the size of micelles and its grows at higher concentration of sugar. The structure of micelles is almost independent of the different types of sugars used.

2 illus, 1 table, 11 ref

002124   Shanmugavelayutham G;Selvarajan V (Physcis Dep, Bharathiar University, Coimbatore-641 046) : Plasma spheroidization of nickel powders in a plasma reactor. Bull Mater Sci 2004, 27(5), 453-7.

Thermal spray coatings of surfaces with metal, alloy and ceramic materials for protection against corrosion, erosion and wear is an intense field of research. The technique involves injection of the powder into a plasma flame, melting, acceleration of the powder particles, impact and bonding with the substrate. Feedstock powders of metals, alloys and ceramics for thermal spray applications have to meet several requirements. Particle shape, size and its distribution, powder flow characteristics and density are the important factors to be considered in order to ensure high spray efficiency and better coating properties. For smooth and uniform feeding of powders into plasma jet, the powder particles have to be spherical in shape. High temperatures and steep temperatures present in thermal plasma is exploited to spheroidize particles in the investigation. Nickel powder particles in the size range from 40-100 μm were spheroidized using plasma processing. SEM and optical micrographs showed sphericl shape of processed particles.

8 illus, 2 tables, 14 ref

002123   Shaikh a M;Desai S S;Patra A K (Solid State Physics Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Two-dimensional position sensitive neutron detector. Pramana J Phys 2004, 63(2), 465-70.

A two-dimensional position sensitive neutron detector has been developed. The detector is a ³He+Kr filled multiwire proportional counter with charge division position readout and has a sensitive area of 345 mm x 345 mm, pixel size 5 mm x 5 mm, active depth 25 mm and is designed for efficiency of 70% for 4 Angstrom neutrons. The detector is tested with 0.5 bar ³He + 1.5 bar krypton gas mixture in active chamber and 2 bar ⁴He in compensating chamber. The pulse height spectrum recorded at an anode potential of 2000 V shows energy resolution of ~25% for the 764 keV peak. A spatial resolution of 8 mm x 6 mm is achieved. The detector is suitable for SANS studies in the Q range of 0.02-0.25 Angstrom^-1.

4 illus, 1 table, 8 ref

002122   Senadeera G K R;Pathirathne W M T C (Institute of Fundamental Studies, , Hantana Road, Kandy, Sri Lanka) : Utilization of conducting polymer as a sensitizer in solid-state photocells. Curr Sci 2004, 87(3), 339-42.

Solvent-free, solid-state solar cells were fabricated with mesoporous TiO₂ sensitized by electronically conducting polymer; poly(3-thiophenyleneacetic acid) (P3TAA) and reasonably high photocurrent were observed for the first time in polymer sensitized solid state photovoltaic devices. When CuI was employed as the hole transporting material together with an ionic liquid 1-ethyl-3-methylimidazolium bis(trifluromethylsulfonyl) amide (EMImTf₂N) and LiTf₂N as additives for charge transport promotion, the cell TiO₂/P3TAA/ CuI delivered a respectable short circuit photocurrent of ~ 1.2 mA cm^-2 with an open circuit voltage of ~ 275 mV under the irradiance of 100 mW cm^-2 (1.5 Air Mass).

3 illus, 16 ref

002121   Sen Gupta A;Hanjura A K;Mathur B S;Koul R; Kaul S K;Kaul I K;Kothari M;Goel H C;Bhat C L;Das (Time and Frequency Secrtion, Nut Phys Lub, , Dr K.S. Krishnan Mg, New Delhi-110 012) : Results of differential mode of operation of the standard time and frequency signal (STFS) broadcast via INSAT. IETE Tech Rev 2003, 20(6), 493-505.

We describe the operation of the Standard Time & Frequency Signal (STFS) broadcast via INSAT satellite in the so-called online differential mode. The transmission setup at the Delhi Earth station and the recent version of the STFS decoder are briefly described. Regular data recording carried out at NPL, New Delhi, NRL, Trombay, field station at Mt Abu and ERTL(E), Calcutta have been used to draw conclusions regarding improvement in time transfer accuracy.

13 illus, 10 ref

002120   Sen D;Sengupta S (Barasat Govn Coll, , Barasat-700 124) : Classical limit for quantum mechanical energy eigenfunctions. Curr Sci 2004, 87(5), 620-7.

The classical limit problem is discussed for the quantum mechanical energy eigenfunctions using the Wentzel-Kramers-Brillouin approximation, free from the problem at the classical turning points. A proper perspective of the whole issue is sought to appreciate the significance of the discussion. It is observed that for bound states in arbitrary potential, appropriate limiting condition is definable in terms of a dimensionless classical limit parameter leading smoothly to all observable classical results. Most important results are the emergence of classical phase space, keeping the observable distribution functions non-zero only within the so-called classical region at the limit point and resolution of some well-known paradoxes.

40 ref

002119   Sen D;Patra A K;Mazumder S;Mittra J;Dey G K; De P K (Solid State Physics Div, Materials Sci Div, Bhabha Atomic Res Centre, Mumbai-400 085) : Carbide precipitates in solution-quenched PH13-8 Mo stainless steel: a small-angle neutron scattering investigation. Pramana J Phys 2004, 63(2), 321-6.

This paper deals with the small-angle neutron scattering (SANS) investigation on solution-quenched PH13-8 Mo stainless steel. From the nature of the variation of the functionality of the profiles for varying specimen thickness and also from the transmission electron microscopy (TEM), it has been established that the small-angle scattering signal predominantly originates from the block-like metallic carbide precipitates in the specimen. The contribution due to double Bragg reflection is not significant in the present case. The single scattering profile has been extracted from the experimental profiles cor-responding to different values of specimen thickness. In order to avoid complexity and non-uniqueness of the multi-parameter minimization for randomly oridented polydisperse block-like precipitate model, the data have been analyzed assuming randomly oriented polydisperse cylindrical particle model with a locked aspect ratio.

4 illus, 1 table, 10 ref