011108   Dube D C (Physics Dep, Indian Institute of Technology, New Delhi-110016) : Microwave processing of electronic ceramics - State of art and emerging trends. Indian J pure appl Phys 2003, 41(6), 423-7.

Microwave processing is emerging as a noble technique for the processing of advanced cermics. A large variety of materials have been successfully microwave processed. The materials thus processed demonstrate greater phase homogeneity, higher density and better microstructure as compared to conventionally prepared materials. The process is fast and energy efficient. Recent advancements and achievements in the microwave processing are discussed along with the future challenges and opportunities.

2 illus, 1 table, 14 ref

011107   Dhawan A;Sharma S K (Physics Dep, Malaviya National Institute of Technology, Jaipur 302 017) : Role of alloying elements during high temperature oxidation of bulk amorphous alloy Zr₆₅Cu_17.5Ni₁₀Al_7.5 in air. Indian J pure appl Phys 2003, 41(6), 453-6.

Oxidation of the bulk amorphous alloy Zr₆₅Cu_17.5Ni₁₀Al_7.5 (also known as Inoue alloy) in air has been studied at 573 and 603 K using X-ray photoelectron spectroscopy (XPS). The oxide film at these temperatures mainly consists of the oxides of Zr (as ZrO₂) and Al (as Al₂O₃) in addition to small amounts of Cu (as CuO) while no significant signal due to Ni on the top surface could be detected. The results of high temperature oxidation are in contrast with those at room temperature oxidation (native oxidation) as neither Cu nor Ni is present in the oxide film formed at room temperature. The role of the various alloying elements during oxidaiton at high temperatures (573 and 603 K) and at room temperature in air has been discussed.

5 illus, 14 ref

011106   Dey T K (Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur-721 302) : Nature of heat conduction in manganese perovskites at cryogenic temperatures. Indian J pure appl Phys 2003, 41(6), 417-22.

While electronic transport has received considerable attention, very few studies are reported in the literature on thermal conductivity of manganites. Heat conduction in these systems is dominated by phonons over that of the charge carriers. However, presence of double exchange interaction, Jahn-Teller effect, the strong electron-phonon interaction and local lattice distortions makes the interpretation of thermal conductivity of manganites complicated and interesting. In the present report, recent data of the authors on the electrical resistivity and thermal conductivity on La_0.67Ca_0.33MnO₃La_0.67Sr_0.33MnO₃ and La_0.67Ca_0.16Sr_0.16MnO₃between 300 and 10K. Electrical conductivity data for T<62>T_MIconfirms small polaronic transport, while analysis of the thermal conductivity data indicates a small (<126>5-18%) contribution from phonon-spin wave near T_MI Strengths of the various phonon scattering mechainsms at low temperatures (<60>100K) are evaluated and discussed.

3 illus, 3 tables, 36 ref

011105   Datta A;Chattopadhyay S (Surface Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata-700 064) : Novel aspects of confined organic systems. Indian J Phys-Pt A 2004, 87(2), 211-14.

Confined organic systems such as ultra-thin polymer films exhibit structures and properties that are distinct from bulk organic materials. Au nanoparticles grown by sputter deposition in polystyrene films spin-coated on quartz and glass substrates have been studied using grazing incidence X-ray reflectivity and UV-visible spectroscopy. The nanoparticles are seen to form on top of the polymer film and they exhibit a transition in shape from spherical to ellipsoidal when the film thickness is decreased below 10 R, R being the radius of gyration of the polymer. This result correlate with formation of layers and partial dewetting of substrates previously observed in strongly confined polymers.

3 illus, 18 ref

011104   Dashora P;Parnami U;Karnawat P (Physics Dep, University of Rajasthan, Jaipur-302 004) : A theoretical study of heat capacity of inert liquids. Indian J pure appl Phys 2003, 41(6), 438-42.

A statistical theory for heat capacity of atomic liquids is presented. Both the characteristic features of the liquid phase viz. the short-range spatial order and significant temporal disorder have been incorporated in the development of the theory. A relation has been deduced for specific heat at constant volume C_v in terms of topological-short-range-order parameter, x. Calculates values of C_v for neon, argon, krypton and xenon over temperature region T_m-0.9T_c are in good agreement with the experimental values. The maximum deviation is less than 5 . Interestingly, it is found that for these inert liquids, some of the equilibrium and transport properties, viz. average coordination number, surface tension, self-diffusion, viscosity and thermal conductivity, studied by the authors earlier, trends of C_vr=C_v/C_vm versus T_r=T/T_m also correspond quite closely.

1 illus, 1 table, 8 ref

011103   Dashora P;Karnawat P;Parnami U (Physics Dep, Rajasthan University, Jaipur-302 004) : Theoretical study of self-diffusion of liquid alkali elements. Indian J pure appl Phys 2003, 41(6), 479-83.

A new approach to study the variation of the self-diffusion coefficient through the temperature dependence of the topological-short-range-order(TSRO) existing in the liquid phase has been presented. A relation has been obtained for the temperature dependence of the coefficient of self-diffusion (D). Present study indicates that, both the decrease in TSRO as well as the increase in thermal energy govern the trend of self-diffusion coefficient with temperature. Calculated values of the self-diffusion coefficient for alkali elements (Li, Na, K, Rb) are in good agreement with available experimental data, over a wide range of temperatures (T_m-T_b)i.e. from melting to normal boiling temperature, the maximum deviation is 6.9%. It is found that, the trends of reduced self-diffusion coefficient D_r=D/D_m versus reduced temperature T_r=T/T_m correspond quite closely, for all alkali elements except lithium, the maximum deviaiton from common trend being <126>6%.

1 illus, 1 table, 10 ref

011102   Das R P;Anand S (NO, Regional Research Laboratory, Bhubaneswar-751 013, Orissa) : Preparation of fine particles through aqueous processing route. Indian J Phys-Pt A 2004, 87(2), 165-74.

Aqueous processing routes for preparation of oxides in micron, sub micron and nano size have gained enormous importance due to their ability to alter shapes and sizes of the end product by varying preparation parameters. The most studied oxides are the ones used as magnetic and ceramic materials. Briefly reviews the preparation of ferrites, aluminum oxides/hydroxides, aluminates and iron oxides following aqueous routes as one of the process steps. The aqueous processing routes include precipitation by sol-gel method, co-precipitation at ambient temperature and hydrothermal precipitation. The work done by the authors and their co-workers for preparing the above mentioned oxides has been briefly discussed. Fine particles of zinc oxide, barium aluminates and Mn-doped barium aluminates were prepared following precipitation-calcination route.

2 illus, 2 tables, 184 ref

011101   Das G P (TEchnical Physics & Prototype Engineering Div, Bhabha Atomic Research Centre, Mumbai-400 085) : Nanoscale magnetic multilayers : density functional calculations. Indian J Phys-Pt A 2004, 87(2), 151-7.

In nanostructured materials and devices, the basic principle lies in geometric confinement and proximity effects, which are size-related quantum effects. The former can be realized in two-dimensional, one-dimensional or zero-dimensional confinements as can be respectively seen in epitaxial interfaces/quantum wells, quantum wires and quantum dots. While the later can be found in atomically engineered array of quantum dots on some substrate, or multilayers (superlattices) of alternate metallic (semi-conducting) A/B planes. Discusses how first-principles density functional calculations can be used to probe such nanostructures. Focuses on magnetic multilayers where confinement of electrons in a quantum well formed in the nonmagnetic layer by the spin-dependent potentials of the magnetic layers give rise to the GMR effect which is exploited in the magnetoelectronic devices. Two of the most widely studied magnetic multilayer systems viz. Ni/Cu and Fe/Cr will be taken up as case studies.

5 tables, 40 ref

011100   Das G C;Kalita P (Mathematical Sciences Division, Institute of Advanced Study in Sciences and Technology, Khanapara, Guwahati-781 022) : Effect of trapped charges in sheath formation in non-isothermal plasma. Indian J pure appl Phys 2003, 41(8), 612-620.

The salient features of sheath formation in plasma with the effect of trapped electrons have been studied. The trapping process of electrons causes the generation of multi-temperature electrons in plasma medium, which modifies the plasma sheath formation. The study has been augmented through the derivation of a non-linear wave equation known as Sagdeev potential equation with the consideration of multi-temperature electrons. The numerical studies show that, the presence of high temperature electrons enhances the plasma sheath. Further, the levitation of dust dynamics along with its characteristic behaviours within the sheath have been studied, which in turn finds the formation of dust cloud atmosphere in plasma sheath. The study enables to calculate the sizes of the dust suspended in the sheath and thus, the forces acted on the dust grains.

4 illus, 2 tables, 25 ref

011099   Das D (NO, Inter University Consortium for Department of Atomic Energy Facilities, LB 8, Sector III, Bidhannagar, Kolkata-700 098) : Mossbauer spectroscopy : an excellent technique to characterize magnetic materials of nanometer dimension. Indian J Phys-Pt A 2004, 87(2), 185-8.

Effectiveness of Mossbauer spectroscopy in characterizing nanometric mangetic materials are highlighted with the spectra recorded at different temperatures for nanocrystalline cabalt ferrite, α- Fe₂O₃ and nanocomposites of Fe-SiO₂ and Fe-Fe₃O₄. It is shown that in superparamagnetic state when the effective internal magnetic field at the probe nucleus is zero resulting in the collapse of the sexted pattern, the quadrupolar interaction can be used to identify the nanoparticles.

5 illus, 8 ref

011098   Chowdhury D;Paul A;Chattopadhyay A (Dep of Chemistry, Indian Institute of Technology, Guwahati-781 039, Assam) : Patterning sub-micron scale channel structures on glass by chemical etching. Indian J Phys-Pt A 2004, 87(2), 193-6.

Reports a soft lithography based approach in generating predetermined channel structures, in the form of parallel lines and cross patterns at the sub-micron scale, by chemical etching of glass slides. Uses the polycarbonate part of a commercially available compact disc as the mold to generate suitable imprinting patterns generated a negative replica of crests and troughs on glass slides. Cross patterns with submicron scale channel structures could also be obtained if the slide was etched twice with the inked mold.

6 illus, 16 ref

011097   Chatterjee P;Deb A K;Sen Gupta S P (Physics Dep, Vivekananda Mahavidyalaya, Haripal, Hooghly-712 405, West Bengal) : A novel method for the determination of grain size distribution and microstrain in nanocrystalline materials from single X-ray diffraction peak. Indian J Phys-Pt A 2004, 87(2), 205-9.

A new method for determining simultaneous grain-size distribution and microstrain from single X-ray diffraction peak is presented. The method combines both the single peak real-space method of Langford and single peak Fourier-space method of Nandi et al to determine two apparent size parameters. If the morphology of the grains is known from a separate experiment (viz. TEM) the apparent size value may be used to determine the grain size distribution. In the present work log-normal distribution of spherical grains was assumed and the median and variance of the distribution was determined for ball-milled vanadium-pentoxide samples. It is proposed that the present method gives reliable information regarding grain size distribution and microstrain compared to any other single peak methods. The method may be widely applicable to most nanocrystalline materials with only limitation in case of materials exhibiting grain size disparity (viz. bi-modal or multi-modal size distribution and does not require extensive TEM analysis.

2 illus, 11 ref

011096   Chakraverty S;Mandal K;Chatterjee S;Kumar S (C K Majumdar Laboratory, S N Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata-700 098) : The magnetic properties of NiFe₂O₄ - SiO₂nanocomposite. Indian J Phys-Pt A 2004, 87(2), 177-83.

Weakly interacting inverse spinel Nife₂O₄ ferrite nanoparticles in SiO₂ matrix were prepared by sol-gel method. The samples were prepared with well separated ferrite particles to reduce the interaction between them. The ferrite particle size was varied from 2.5 nm to 25 nm by changing the temperature and duration of heat-treatment during the preparation on the samples. X-Ray diffraction method was used to identify the phase and average particle diameter of the samples. The particle size distribution was studied from the micrographs taken by a transmission electron microscope. The size dependent magnetic properties were investigated using a vibrating sample magnetometer. Superparamagnetic behaviour was observed at room temperature when the average particle size is less than 5 nm. Mossbauer measurements also show similar results, which change from double peak structure to sextet with the increase of particle size. Two sets of sextets in Mossbauer spectra indicate the presence of Fe ion in tetrahedral as well as octahedral sites. The average particle size in the superparamagnetic state was estimated from the magnetization measurement by considering the samples as consisting of noninteracting single domain particles.

8 illus, 1 table, 25 ref

011095   Bhushan K G;Jagannath;Korgaonkar A V (Technical physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : A low-energy, high current pulsed electron gun for cluster physics experiments. Bull Indian Vacuum Soc 2003, 6(3), 3-9.

Describes the design, construction and performance of a low energy, high curent pulsed electron gun spercifically intended for studying mass distributions of agglomerated clusters. The design of the electron gun is basically a pierce-type cathode that delivers a current of about 1mA at a distance of 50 mm from the anode into a circular cross-section. The gun could be pulsed upto 100 Hz in microsecond pulses. A unique feature of this gun is that it allows itself to be floated electrically upto 5 kV, which is essential for cluster-ionization experiments.

6 illus, 9 ref

011094   Bhattacharya S;Barua R;Baruah G D (Department of Physics, Dibrugarh University, Dibrugarh-786 004) : Optical studies of few kidney and bladder stones. Asian J Phys 2002, 11(2), 244-9.

Few kidney and bladder stones have been analysed using XRD. Major crystalline components have been identified. Concentric ring patterns have been observed in three bladder stones belonging to children in the age group 5-10 years. Intensity measurement of the rings shows the nature of the crystalline layer formation in the sample.

5 illus, 13 ref

011093   Bhardwaj D M;Jain D C;Rao K V;Ravi Kumar; Asokan K (Physics Dep, Rajasthan University, Jaipur) : Photoluminescence studies on pre- and post- irradiated ruby. Indian J pure appl Phys 2003, 41(6), 498-500.

Results of photoluminescence (PL) measurements on the Fe³⁺ion irradiated ruby samples at different fluence have been presented. Absence of R₁ and R₂ lines in spectra at 4.2 K compared to that at room temperature in pristine ruby and appearance of a band centered around 1.6 eV have been discussed in terms of coexistence of Cr³⁺ and Cr⁴⁺. The variation in intensity of this band at 4.2 K with fluence rate is discussed in terms of depopulation of ²E state and lattice deformation. Appearance of a band at 0.95eV at fluence rate 10¹²ions/cm² is also reported. This band has been found absent in all other cases.

4 illus, 1 table, 7 ref

011092   Battabyal M;Ray A;Dey T K (Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur, 721 302) : Magneto-transport studies in yttrium doped lanthanum manganites between 10-300K. Indian J pure appl Phys 2003, 41(6), 443-7.

The hole doped manganite systems A_1-xA_xMnO₃ (where A represents lanthanides and A's are divalent cations) with x ≤0.45 exhibit the electronic transport behavior that result from the complex interplay among charge carriers, spin and lattice. The system shows a metal-insulator transition and the transition temperature (T_MI) is strongly dependent on various factors, viz, dopant, thermal history, oxygen content grain size etc. Large magneto-resistance observed near T_MI in these perovskites is another interesting feature that has enormous implications in device and sensor technology. Results on the temperature dependence of the electrical resistivity on a set of samples of the type La_0.6Y_0.07Ca_0.33MnO₃, prepared by a new pyrophoric technique have bee presented. Analysis confirms adiabatic small polaron hopping for T<62>T_MI while, in the metallic region (T<60>T_MI), electron-elecron and electron-magnon scattering play the dominant role in defining the influence of annealing time on the electrical resistivity of fine grained polycrystalline La_0.6Y_0.07Ca_0.33MnO₃ pellets.

1 illus, 3 tables, 24 ref

011091   Arya B C;Jain S L;Arun Kumar (Radio and Atmospheric Science Division, National Physical Laboratory, New Delhi-110 012) : Measurements of various minor constituents using a differential absorption LIDAR. Asian J Phys 2002, 11(2), 163-70.

The measurement of various minor constituents in the atmosphere is of great significance to understand physics, chemistry and dynamics of the atmosphere. A Differential Absorption LIDAR (DIAL) using a tunable CO₂ laser has been designed and developed at National Physical Laboratory, New Delhi, to monitor various minor constituents in the atmosphere. The system is being used to monitor water vapour, surface ozone, ammonia and ethylene concentration. Sometimes ethylene and surface ozone was found to be more than 20 ppb and 100 ppb respectively which is a health hazard, The high value of ethylene surface ozone observed may be attributed to anthropogenic activities. The variation of water vapour and ethylene as well as that of ammonia and relative humidity was found to be anti-correlated. Salient features of experimental set up and results obtained have been presented in detail.

8 illus, 2 tables, 23 ref

011090   Arun Murthy T V S;Wakde S D;Murthy V R (Dep of Physics, S.S.G.M. College of Engineering, Shegaon-444 203 (M.S.)) : Anisotropic properties of a few nematic compounds. Asian J Phys 2002, 11(2), 256-7.

The mean molecular diamagnetic susceptibility of a few nematic compounds, p-azoxyanisole, p-azoxyphenetole and anisaldazine are presented by a molecular vibration approach using molecular parameters. These results are compared with those calculated from a semi empirical relation of Rao et al from polarizabilities and from Pascal's method.

2 tables, 8 ref

011089   Amresh Kumar;Yadav S (Univ Dep of Phys, L.N.Mithila Univ, Darbhanga, Bihar) : Electrostatic sheath at the boundary of a collisional dusty plasma. Acta Cienc Indica-Phys 2003, 29(4), 385-8.

Applying the Boltzmann response of the ions and electrons of plasma dynamics and inertial dynamics of the dust charged grains in a highly collisional dusty plasma, the nature of the electronic potential near a boundary is investigated. Based on the fluid apporoximation, the formation as well as the characteristic behaviour of the sheath has been studied. It is expected that the presence of dust charged grains will lead to a very different behaviour of the sheath as compared to that of electron-ion plasma.

2 illus, 9 ref

011088   Ahmed A M (Physics Nucleus Department, Faculty of Science, South Valley University, Sohag, Egypt) : Superconducting properties of K0.2Ba0.5Y0.3CuOx powder compacts. Indian J pure appl Phys 2003, 41(8), 646-50.

Measurements of the electrical resistivity and thermoelectric power for sintered samples of K0.2Ba0.5Y0.3CuOx system were carried out. Two sets of the samples were prepared, the first set was sintered in air and the second set was sintered during flowing oxygen. The temperature dependence of the resistivity was found to be similar to that of metals. Further, the zero resistance was attained at 91-95 K depending on the sintering time. The author belives, the prolonged sintering time caused oxygen vacancies (which may reside either along central-cage Cu-O chains) to become positively charged on trapping the hole, and thus enhance the superconductivity. The thermoelectric power of all samples was found to possess plus sign and decreases slightly with decreasing temperature, and then it falls down to zero, at the critical temperature (Tc).

3 illus, 1 table, 25 ref

011087   Ahmad Z (Dep of Phys, Faculty of Sci, Univ of Maiduguri, P.M.B 1069, Borno State (Nigeria)) : Cluster size dependence on relativistic charged particle multiplicity in nucleus-nucleus collisions. Acta Cienc Indica-Phys 2003, 29(4), 389-96.

Dependence of culster size on relativistic charged particle multiplicity is examined by analyzing experimental data involving 530 and 283 interactions with n_h ≥ 0 caused by 4.5 A and 14.5 Ge V/c ²⁸Si-beam in nuclear emulsion. The results reveal that the maximum number of charged of particles constituting a cluster is four for the collisions having n_s ≥ 10, where n_s is the number of relativistic charged particle produced in an interaction with relative velocity β≥0.7. However, this number is found to be three for the interactions having n_s≤ 9. Results also show that the cluster size is essentially insensitive to the projectile energy.

4 illus, 1 tables, 13 ref

011086   Agarwal R;Saxena N S;Sharma K B;Thomas S; Pothan L A (Physics Dep, Gov Coll, Dausa-303 303) : Thermal conduction and diffusion through glass-banana fiber polyester composites. Indian J pure appl Phys 2003, 41(6), 448-52.

The analysis of variation in thermal conductivity and thermal diffusivity of Banana fiber reinforced polyester composites caused by the addition of glass fiber have been presented. The composite shows an increase in thermal conductivity in comparison to matrix. However, the thermal conductivity of the composites with increased percentage of glass fiber, decreases in comparison to composite of pure banana fiber. It is minimum when glass fiber fraction is 11% in the composite. The decrease in thermal conductivity values with increasing percentage of glass fiber from 3% to 11% in the composite is due to fiber/matrix de-bonding, fiber pull out and matrix fracture. Increase in thermal conductivity at 15% of glass fiber can be attributed to a change in the energy dissipation mechanism. Y. Agari model is used to evaluate the thermal conductivities of the fibers in the hybrid composite.

5 illus, 4 tables, 17 ref

011085   Agarwal R K;Goel N;Sharma A K (Dep of Chemistry, LR College, Sahibabad-201 005) : Synthetic and magneto spectral studies of some six-coordinated complexes of lanthanide (III) perchlorates derived from 4-[N-(4-methoxy-benzylidene)amino]antipyrine thiosemicarbazone. Asian J Phys 2002, 11(2), 171-3.

Describes the synthesis and characterization of some six coordinated lanthanide(III) perchlorato complexes of 4-[N-(4-methoxy-benzylidene) amino] antipyrine thiosemicarbazone (MBAAPTS) with the general composition Ln(CIO₄)₃.2(MBAAPTS)(Ln=La, Pr, Nd, Sm, Gd, Tb, Dy or Ho). The conductivity measurement suggest the complexes are 1:3 electrolytes. The infrared spectra reveal that the CIO₄^- groups are present outside the coordination sphere and MBAAPTS is neutral tridentate (N,N,S) ligand. Magnetic, electronic spectral and thermal properties of these complexes are also investigated.

1 table, 14 ref

011084   Abullias;Ashok Kumar (Dep of Physics, M.L.S.M. College, Darbhanga-846 004, Bihar) : Study of electromagnetically coupled rectangular microstrip antenna. Acta Cienc Indica-Phys 2003, 29(4), 363-8.

A simplified theory is developed to analyse electromagnetically coupled rectangular microstrip antenna using improved transmission line method. An equivalent circuit has been investigated to represent an electromagnetically coupled microstrip antenna. The theoretical results were compared with the experimental results available in literature.

5 illus, 7 ref

010101   Pimpale A V (Inter-University Consortium for Dep of atomic Energy Facilities, University Campus, Khandwa Road, Indore (MP) 452 017) : Basic concepts of Quantum mechanics. Phys Educ 2003, 19(4), 319-33.

Presents basic concepts of nonrelativistic quantum mechanics emphasizing the vector space approach. The subject is developed systematically starting with mathematical idealization of a physical system, the state of a quantum mechanical system as a vector or rather ray in a vector space, the role of operators as linear transformations on the vector space and the geometry of the vector space described by the eigenspectrum of a commuting set of hermitian operators. The dynamics of the system is governed by the Schrodinger equation. Dirac bra and ket notation is introduced and operator vector space spanned by the ket-bra combination using the eigenvectors of the commuting set of operators is used to obtain general operators on the vector space. The connection between classical variables and quantum operators is described and some simple examples are given to illustrate the abstract concepts.

6 ref

010100   Paranjape V V (Dep of Physics, Lakehead University, Thunder Bay, Canada) : Demonstration based on angular momentum conservation. Phys Educ 2003, 19(4), 335-6.

1 illus

010099   Nityananda R (National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University Campus, Pune- 411 007) : Phase space and the Optics mechanics analogy. Phys Educ 2003, 19(4), 299-306.

The notion of phase space is explained in the context of both mechanics and paraxial optics. The conservation of volume in this space is a very useful and powerful result. The analogy between optics and mechanics is shown to solve the mirage problem.

6 illus

010098   Modi K B;Shah H J;Trivedi U N;Vara R P; Chhantbar M C;Joshi H H (Dep of Physics, Saurashtra University, Rajkot-360 005) : Effect of Fe<. Indian J Engng Mater Sci 2003, 10(6), 502-6.

The structural and bulk magnetic properties of Fe³⁺ substituted yttrium iron garnet with general formula Y_3-xFe_5+xO₁₂ (x=0.0, 0.05, 0.15, 0.30 and 0.50) have been investigated by means of X-ray diffraction, EDAX, high field magnetization and low field a.c. susceptibility measurements. It is found that substituted Fe³⁺ ions occupy c-sites and increase in lattice constant for x <62> 0.30 is due to presence of Fe²⁺ ions, determined through EDAX, on a-sites. Variation of magneton number with x can be explained satisfactorily assuming the collinear spin ordering model and Neel temperature values deduced experimentally from a.c. susceptibility measurements are in good agreement to those calculated theoretically.

2 illus, 1 table, 17 ref

010097   Kembhavi A K (NO, Inter-University Centre for Astronomy and Astrophysics, Pune- 411 007) : Some physics of stars. Phys Educ 2003, 19(4), 275-80.

1 illus, 5 ref

010096   Jog C J (Dep of Physics, Indian Institute of science, Bangalore- 560 012) : Rotation curves of galaxies: evidence for dark matter. Phys Educ 2003, 19(4), 281-4.

The rotation curve of the disk in a spiral galaxy gives a direct dynamical estimate of the mass distribution with radius. It has been observed that in most galaxies, the rotation speed remains constant as far from the galactic centre as it can be measured. This implies that nearly half of the total mass within the optical region of the galaxy is in a dark or invisible halo. Despite various attempts over the last twenty-five years to understand it, the physical nature of this dark matter remains elusive.

6 ref

010095   Bhasin V S (Dep of Physics and Astrophysics, University of Delhi, Delhi- 110 007) : Bose-Einstein condensates and the three body Efimov effect. Phys Educ 2003, 19(4), 313-17.

With the experimental observation of realizing Bose-Einstein condensates in dilute vapours of alkali atoms, the research activities in this field sprang up considerably during the past few years. some recent theoretical investigations highlighting the role of three body dynamics which can affect, under certain conditions, the achievable density in Bose-Einstein condensates of trapped atoms, are briefly reviewed.

24 ref

010094   Balaya P;Shrikhande V K;Kothiyal G P;Goyal P S (Technical Physics and Prototype Engineering Div, Bhabha Atomic Research Centre, Mumbai-400 085) : Dielectric and conductivity studies on lead silicate glasses having mixed alkali and alkaline earth metal oxides. Curr Sci 2004, 86(4), 553-6.

Lead silicate glasses containing different amounts of Na₂O and K₂O along with BaO were prepared by conventional melt and quench method. Dielectric constant and its dispersion were investigated as a function of frequency over the range 10 kHz to 5 MHz at room temperature. Ionic conductivity was studied on three selected mixed alkali glasses (Na₂O)_0.069 - (₂O)_0.036 - (BaO)_0.026 - (PbO)_0.11 - (SiO₂)_0.736 (LS31), (Na₂O)_0.066 - (K₂O)_0.07 - (BaO)_0.021 - (PbO)_0.106 - (SiO₂)_0.736 (LS1) and (Na₂O)_0.062 - K₂O)_0.013 - (BaO)_0.02 - (PbO)_0.099 - (SiO₂)_0.689 (LS33) as a function of frequency over the range 100 Hz to 500 kHz in the temperature interval 25-380°C in vacuum of 10^-2 mbar. Both DC conductivity and the hopping frequency, inferred from the analysis of AC conductivity data, exhibit Arrhenius behaviour with temperature. Unlike the conventional mixed alkali system, in the present glass system, it is found that the activation energies associated with DC conduction (E_σ) and that of hopping process (E_h) for LS1, having nearly equal amounts of Na⁺ and K⁺ ions, are found to be less compared to those for glasses LS31 and LS33. E_σ (1.14 eV) calculated for LS1 using Anderson-Stuart model agrees well with that obtained experimentally (1.18 eV). The above behaviour observed in E_σ and E_h for the present glass system may be attributed to the complex effect due to both mixed alkali effect and the structural changes introduced by the change in SiO₂ content.

4 illus, 3 tables, 9 ref

010093   Arora A K;Sharma S R (Dep of Physics, University of Rajasthan, Jaipur) : Fall of magnet through a thick conducting cylinder. Phys Educ 2003, 19(4), 307-12.

Presents a theory for the evaluation of a drag force on a magnet falling through a thick conducting cylinder. The results of two earlier analyses for a thin cylinder and very short magnets are recovered as a special case of theory. The results of the experiment conducted agree fairly well with the theoretical value of the drag force. This experiment can be an educative quantitative experiment for the students laboratory at the undergraduate level.

2 illus, 1 table, 9 ref

020178   Znojil M;Jakubsky V (NO, Nuclear Physics Institute ASCR, 250 68 Rez, Czech Republic, Email: znojil@ujf.cas.cz) : Supersymmetric quantum mechanics living on topologically non-trivial Riemann surfaces. Pramana J Phys 2009, 73(2), 397-404.

Supersymmetric quantum mechanics is constructed in a new non-Hermitian representation. Firstly, the map between the partner operators H^(±) is chosen antilinear. Secondly, both these components of a super-Hamiltonian H, are defined along certain topologically non-trivial complex curves r^(±) (x) which spread over several Riemann sheets of the wave function. The non-uniqueness of our choice of the map T between 'tobogganic' partner curves r⁺(x) and r^-'(x) is emphasized.

2 illus, 16 ref

020177   Znojil M;Geyer H B (NO, Nuclear Physics Institute, ASCR, 250 68 Rez, Czech Republic, Email: znojil@ujf.cas.cz) : Strum-Schridinger eqations: formula for metric. Pramana J Phys 2009, 73(2), 299-306.

Sturm-Schrodinger equations Hψ = EWtψ with H ≠ H and W≠ W ≠ I are considered, with a weak point of the theory lying in the purely numerical matrix-inversion form of the double-series definition of the necessary metric operator Θ in the physical Hilbert space of states. This shortcoming is removed here via an amended, single-series definition of 6.

14 ref

020176   Zhang X;Zhao Q (Mathematics School, Central South Univ, Changsha 410075, China, Email: zxshuxue@yahoo.com.cn) : Degree distribution of a new model for evolving networks. Pramana J Phys 2010, 74(3), 469-74.

Proposes and study an evolving network model with both preferential and random attachments of new links, incorporating the addition of new nodes, new links, and the removal of links. We first show that the degree evolution of a node follows a nonhomogeneous Markov chain. Based on the concept of Markov chain, we provide the exact solution of the degree distribution of this model and show that the model can generate scale-free evolving network.

2 illus, 15 ref

020175   Zhang S;Dong L;Ba J M;Sun Y N (Mathematics Dep, Bohai Univ, Jinzhou 121013, People's Republic of China, Email: zhshaeng@yahoo.com.cn) : The (G'/G)-expansion method for a discrete nonlinear schrodinger equation. Pramana J Phys 2010, 74(2), 207-18.

An improved algorithm is devised for using the (G¹/G)-expansion method to solve nonlinear differential-difference equations. With the aid of symbolic computation, we choose a discrete nonlinear Schrodinger equation to illustrate the validity and advantages of the improved algorithm. As a result, hyperbolic function solutions, trigonometric function solutions and rational solutions with parameters are obtained, from which some special solutions including the known solitary wave solution are derived by setting the parameters as appropriate values. It is shown that the improved algorithm is effective and can be used for many other nonlinear differential-difference equations in mathematical physics.

2 illus, 26 ref

020174   Zhang J M;Lin Z L;Zhang Y;Ji V (College of Physics and Information Technology, Shaanxi Normal Univ, Xian 710062, Shaanxi, People's Republic of China) : Structural stability and theoretical strength of Cu crystal under equal biaxial loading. Pramana J Phys 2010, 74(2), 261-70.

Cu has been used extensively to replace Al as interconnects in ULSI and MEMS devices. However, because of the difference in the thermal expansion coefficients between the Cu film and the Si substrate, large biaxial stresses will be generated in the Cu film. Thus, the Cu film becomes unstable and even changes its morphologies which affects the device manufacturing yield and ultimate reliability. The structural stability and theoretical strength of Cu crystal under equal biaxial loading have been investigated by combining the MAEAM with Milstein-modified Born stability criteria. The results indicate that, under sufficient tension, there exists a stress-free BCC phase which is unstable and slips spontaneously to a stress-free metastable BCT phase by consuming internal energy. The stable region ranges from -15.131 GPa to 2.803 GPa in the theoretical strength or from -5.801% to 4.972% in the strain respectively.

5 illus, 2 tables, 20 ref

020173   Zaki N G (Plasma and Nuclear Fusion Dep, Nuclear Research Centre, AEA, Cairo, Egypt, Email: easternone15us@yahoo.com) : Absolute parametric instability of low-frequency waves in a 2D nonuniform anisotropic warm plasma. Pramana J Phys 2010, 74(5), 755-63.

Using the separation method, absolute parametric instability (API) of electrostatic waves in a magnetized pumped warm plasma is investigated. In this case the effect of static strong magnetic field is considered. The problem of strong magnetic field is solved in two-dimensional (2D) nonuniform plane plasma. Equations which describe the spatial part of the electric potential are obtained. Also, the growth rates and conditions of the parametric instability for periodic and aperiodic cases are obtained. It is found that the spatial nonuniformity of the plasma exerts a stabilizing effect on the API. It is shown that the growth rates of periodic and aperiodic API in warm plasma are less when compared to that in cold plasma.

23 ref

020172   Yuehong B;Chen L;Sun F (Institute of Civil & Architectural Engineering, Beijing Univ of Technology, Beijing 100124,people's Republic of China, Email: lgchenna@yahoo.com) : Exergetic efficiency optimization for an irreversible heat pump working on reversed brayton cycle. Pramana J Phys 2010, 74(3), 351-63.

Deals with the performance analysis and optimization for irreversible heat pumps working on reversed Brayton cycle with constant-temperature heat reservoirs by taking exergetic efficiency as the optimization objective combining exergy concept with finite-time thermodynamics (FTT). Exergetic efficiency is defined as the ratio of rate of exergy output to rate of exergy input of the system. The irreversibili-ties considered in the system include heat resistance losses in the hot- and cold-side heat exchangers and non-isentropic losses in the compression and expansion processes. The analytical formulas of the heating load, coefficient of performance (COP) and exergetic efficiency for the heat pumps are derived. The results are compared with those obtained for the traditional heating load and coefficient of performance objectives. The influences of the pressure ratio of the compressor, the allocation of heat exchanger inventory, the temperature ratio of two reservoirs, the effectiveness of the hot- and cold-side heat exchangers and regenerator, the efficiencies of the compressor and expander, the ratio of hot-side heat reservoir temperature to ambient temperature, the total heat exchanger inventory, and the heat capacity rate of the working fluid on the exergetic efficiency of the heat pumps are analysed by numerical calculations. The results show that the exergetic efficiency optimization is an important and effective criterion for the evaluation of an irreversible heat pump working on reversed Brayton cycle.

18 illus, 39 ref

020171   Yakut H;Kuliev A A;Guliyev E;Yildirim Z (Physics Dep, Sakarya Univ, Sakarya, Turkey, Email: hyakut@sakarya.edu.tr ) : Intrinsic gk factors of odd-mass <. Pramana J Phys 2009, 73(5), 829-37.

In this paper, QK-factors of the intrinsic magnetic moments and effective spin gyromagnetic factors (g^eff_s) of the ^167-179Lu isotopes have been studied within the Tamm-Dancofrapproximation (TDA) (Kuliev et al, Son. J. Nucl. Phys. 9, 185 (1969)) by using a realistic potential such as Woods-Saxon potential for the first time. The effects of the spin-spin and spin-isospin interactions on magnetic moments were investigated. The results of the theoretical calculations are compared with the experimental data for related nuclei. The experimental values of gK and g^eff_s were computed from the observed magnetic moments (Georg et al, Eur. Phys. J. A3, 225 (1998)) using the spin matrix elements. The theoretical predictions for the gK factors exhibit good agreement with the experimental gk factors with increasing mass number A of the lutetium isotopes. The strongest influence of the neutron-proton spin interaction occurs at q = - 1. Sufficient agreement between the calculated and the experimental values of gK is obtained for κ = (45/A) MeV and q = -1.

2 illus, 2 tables, 24 ref

020170   Yadugiri V T (NO, , 1184, 5th Main, Sector-7, H.S.R. Layout, Bangalore-560 102, Email: vtyadugiri@gmail.com) : Milking diatom-a new route to sustainable energy. Curr Sci 2009, 97(6), 748-50.

2 illus, 7 ref

020169   Xu J;Wu X;Ma D Z (Physics Dep, Nanchang Univ, Nanchang 330031, China, Email: xwu@2ncu.edu.cn) : Chaotic motion of dust particles in planetary magnetospheres. Pramana J Phys 2010, 74(6), 907-17.

Numerically investigate the motion of a charged particle in a planetary magnetosphere using several kinds of equatorial plane phase portraits determined by two dynamical parameters: the charge-to-mass ratio and the z-component of the angular momentum. The dependence of chaos on any of the three factors including the two parameters and the energy is mainly discussed. It is found that increasing the energy or the absolute value of the ratio always causes the extent of chaos. However, chaos is weaker for larger angular momentum. Qualitative interpretations to the results obtained are also given.

5 illus, 2 tables, 27 ref

020168   Wibig T (Physics Dep, Univ of Lodz, Cosmic Ray Laboratory, Soltan Institute for Nuclear Stud, Uniwersytecka 5, 90-950 Lodz, Poland, Email: wibig@zpk.u.lodz.pl) : On the discovery of the greisen-zatzepin-kuzmin cut-off. Pramana J Phys 2009, 73(5), 807-20.

The recent claim of the '5 sigma' observation of the Greisen-Zatzepin-Kuzmin cut-off by the HiRes group based on their nine years data is a significant step towards the eventual solution of one of the most intriguing questions in physics for more than 40 years. Recent results from Pierre Auger Observatory seem to confirm the statement. However, the word 'significance' is used in the mentioned paper in a sense which is not quite obvious. In the present paper we argue that this claim is a little premature.

11 illus, 31 ref

020167   Wellingation Fernando G;Alfred Cecil Raj S (Physics Dep, St. Joseph's College, Tiruchirappalli (Tamil Nadu)) : Preparation and characterisation of lithium doped and nickel - doped Co3O4 films. Bull pure appl Sci-Sect D 2009, 28(1), 29-41.

A Novel material of Lithium - doped and Nickel - doped CO3O4 thin films has been successfully prepared and The deposited films were annealed as mentioned in the case of lithium - doped films and made ready for characterisation. The Li - doped and Ni - doped Co₃O₄ have been characterized by different instrumentation techniques like XRD pattern, thickness measurement, SEM, Optical behaviour, Electrical resistivity. The Absorption for 0.0025M Li doped Co₃O₄ is higher than the pure Co₃O₄ while for other concentrations absorption decreases with the increases in molarity in concentration of the dopant. Same trend is observed for Ni doped also.

17 illus, 2 table, 17 ref

020166   Wel Q;Zhang P X;Zhang D Y;Zhou J H (Physics Dep, Baoji Univ of Arts and Science, Baoji-721 007, Email: weiaqum@tom.com) : Investigations of the electron paramagnetic resonance spectra of Vo<. Pramana J Phys 2009, 73(6), 1087-94.

The EPR spectra for Vo²⁺ in CaO-Al₂O₃-SiO₂ system are calculated using complete diagonalization method (CDM) and perturbation theory method (PTM). The calculated results are in good agreement with the observed values. By comparing the calculated results by CDM and PTM in a wide range of crystal field parameters, the validity of the PTM formulas has been studied. It is shown that, the PTM formulas are reasonable and relPiable in a wide range of CF parameters.

8 illus, 1 table, 12 ref

020165   Wei Q;Xu Q M;Yang Z Y;Zhang D Y;Zhang J G (College of Material Science & Engineering, Xi'an Univ of Architecture & Technology, Xian 710055, China, Email: weiaqun@tom.com) : Zero-field splitting and local structure for V<. Pramana J Phys 2009, 73(5), 939-44.

The zero-field splitting and local structure for V²⁺ ions in CsMgX₃ (X = Cl, Br, I) crystals are theoretically investigated using complete diagonalization method (CDM) for a 3d³ ion in trigonal symmetry. Spin-spin (SS) and spin-other-orbit (SOO) interactions are taken into account in addition to the general spin-orbit (SO) interaction. On this basis, using ligand ion displacement model, we find that the ligand ions move away from C₃-axis, and therefore the local angles in the V²⁺ centres are larger than the angles in the hosts. The results show good agreement with the observed values.

1 illus, 1 table, 36 ref

020164   Wang Q H (Physics Dep, National Univ Singapore, Singapore-117 542, Email: phywq@nus.edu.sg) : Level crossings in complex two-dimensional potentials. Pramana J Phys 2009, 73(2), 315-22.

Two-dimensional 'PT-symmetric quantum-mechanical systems with the complex cubic potential V₁₂ = x² + y² + igxy² and the complex Henon-Heiles potential V_HH = x² + y² + ig(xy² - x³/3) are investigated. Using numerical and perturbative methods, energy spectra are obtained to high levels. Although both potentials respect the "PT symmetry, the complex energy eigenvalues appear when level crossing happens between same parity eigenstates.

4 illus, 9 ref

020163   Vyas M;Kota V K (NO, Physical Research Laboratory, Navrangpura, Ahmedabad-380 009, Email: vkbkota@prl.res.in) : Random matrix ensembles with random interactions: results for EGUE(2)-SU (4). Pramana J Phys 2009, 73(3), 521-31.

Introduced in this paper embedded Gaussian unitary ensemble of random res, for m fermions in Ω number of single particle orbits, generated by random two-body interactions that are SU(4) scalar, called EGUE(2)-ST/(4). Here the SU(4) algebra corresponds to Wigner's supermultiplet SU(4) symmetry in nuclei. Formulation based on Wigner-Racah algebra of the embedding algebra U(4Ω1)⊃U(<84><164> SU(4) allows for analytical treatment of this ensemble and using this analytical formulas are derived for the covariances in energy centroids and spectral variances. It is found that these covariances increase in magnitude as we go from EGUE(2) to EGUE(2)-s to EGUE(2)-ST/(4) implying that symmetries may be responsible for chaos in finite interacting quantum systems.

2 illus, 2 tables, 22 ref