006228   Rao R M V G K (NO, National Aerospace Laboratories, Bangalore-560 017) : Push pull mechanics of glass transition phenomenon in thermoset polymer matrices. Proc Indian Sci Congr Ass - Pt IV, Sect-I 2000, (NULL), 218-19.

abstr

006227   Raghavendra S C;Raibagkar R L;Kulkarni A B (Applied Electronics Dep, Gulbarga Univ, Gulbarga-585 106) : Dielectric properties of fly ash. Bull Mater Sci 2002, 25(1), 37-9.

Reports the dielectric properties of fly ash. The dielectric measurements were performed as a function of frequency and temperature. The sample of fly ash shows almost similar behaviour in the frequency and temperature range studied. The large value of dielectric constant in the typical frequency range is because of orientation polarization and tight binding force between the ions or atoms in the fly ash. The sample of fly ash is of great scientific and technological interest because of its high value of dielectric constant (10⁴)

1 illus, 17 ref

006226   Paulose P I;Jose G;Thomas V;Jose G; Unnikrishnan N V;Warrier M K R (Sch of Pure and App Phys, Mathatma Gandhi Univ, Kottayam-686 560) : Spectroscopic studies of Cu<. Bull Mater Sci 2002, 25(1), 69-74.

The Cu²⁺ ion doped silica gel matrices in monolithic shape were prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS). The absorption, transmittance and fluorescence spectra of the gel matrices heat treated at different temperatures were monitored. The loss of water and hydroxyl group from silica network changes the optical properties of the Cu²⁺ ions in the host, noted by the change in colour of monolith and spectral characteristics. The pronounced blue shift observed (700-900 nm to 600-850 nm) for the broad band of the absorption spectra of the smaples heated up to 700°C is attributed to the ligand field splitting and partial removal of hydroxyl group from the silica matrices. The results indicate broadband filtering effects of the smaples in the wavelength region 400-600 nm. Absorption and fluorescence spectra of the glass matterices heated to 1000°C confirms the conversion of Cu²⁺ ion to Cu⁺ion.

8 illus, 15 ref

006225   Pandya C V;Vyas P R;Pandya T C;Gohel V B (Dep Phy, Univ Sch of Sci, Gujarat Univ, Ahmedabad-380 009) : Volume variation of Gruneisen parameters of fcc transition metals. Bull Mater Sci 2002, 25(1), 63-7.

The volume variation of the Gruneisen parameters of ten fcc transition metals, up to 40% compression, has been studied on the basis of a model approach proposed by Antonov et al. The results are reasonably good for six metals except for Rh, Ag, Au and Ni when comared with available experimental and other theoretical values. The model requires an appropriate modification for Rh, Ag, Au and Ni.

1 illus, 1 table, 41 ref

006224   Motke S G;Yawle S P;Yawale S S (Dep Phys Government Vidarbha Mahavidyalaya, , Amravati-444 604) : Infrared spectra of zinc deped lead borate glasses. Bull Mater Sci 2002, 25(1), 75-8.

The infrared spectra of zinc-doped lead borate glases (10-30 mol% ZnO) were measured over a continuous spectral range (400-4000 cm^-1) in an attempt to study their structure systematically. No boroxol ring formation was observed in the structure of these glasses. THe formation of Zn in tetrahedral coordination was not observed. The conversion of three-fold to four-fold coordinated boron took place.

1 illus, 1 table, 30 ref

006223   Joag D S (Physics Dep, Centre for Advanced studies in Material Science and Solid State Physic, Pune-411 007) : Field emitter displays: displays of the future. Proc Indian Sci Congr Ass - Pt IV, Sect-I 2000, (NULL), 219.

abstr

006222   Bojarski P;Kulak L;Kaminska A (Institute of Experimental Physics, Univ of Gdansk, Wita Stwosza 57,80-952 Gdansk, Poland) : Nonradiative excitation energy transport and its analysis in concentrated systems. Asian J Spectrosc 2001, 5(4), 145-63.

Nonradiative excitation energy transport is analyzed in different concentrated systems : donor - acceptor systems, systems adopting different ionic forms and monomer - dimer systems. It is shown that the results of spectroscopic measurements performed for all systems discussed can be described by uniform modern theories of forward and reverse energy transport and by Monte - Carlo simulations of luminescence characteristics.

14 illus, 112 ref

005356   Vaidya N;Shah B S (Solid State Physics and Materials Science Laboratories, Department of Physics, Saurashtra University, P O Rajkot-360 005) : Absolute hardness of phenanthrene doped anthracene single crystals by Knoop indentation technique. Indian J Phys-Pt A 2003, 77(1), 59-61.

The absolute hardness value of anthracene doped with phenanthrene using Knoop hardness technique has been obtained. The absolute hardness is defined as the hardness which is not load dependent. The results obtained by graphical analysis compare well with the calculated results, within experimental error. Reports the results obtained, using the method utilizing the extrapolation function. The higher absolute hardness of the phenanthrene doped anthracene is due to the molecular hindrance to slip

2 illus, 8 ref

005355   Vaidya N;Shah B S (Solid State Physics and Materials Science Laboratories, Department of Physics, Saurashtra University, P O Rajkot-360 005) : Study of absolute hardness of some organic molecular solids. Indian J Phys-Pt A 2003, 77(1), 55-8.

The absolute hardness is defined as the hardness number independent of the applied load. An evaluation has been made of the absolute or true hardness values for the organic solids anthracene, phenanthrene and carbazole using both the Knoop and Vickers microhardness versus load data. The results obtained by graphical analysis agree very well with the calculated results, within experimental error. Reports the results obtained, using the method utilizing the extrapolation function

3 illus, 1 table, 20 ref

005354   Tripathy S K;Rao S A (Department of Physics, Jagannath Institute for Technology and Management, Parlakhemundi-761 200) : Expressions for third-order aberration theory for holographic images. Pramana J Phys 2003, 60(1), 151-7.

Expressions for third-order aberration in reconstructed wave front of point objects are established by Meier. But Smith, Neil Mohon, Sweatt independently reported that their results differ from that of Meier. It has been found that coefficients for spherical aberration, astigmatism, tally with Meier's while coefficients for distortion and coma differ.

1 illus, 1 table, 5 ref

005353   Sureshkumar M B;Shah N R;Jaituni A (Physics Department, Faculty of Science, The M S University of Baroda, Vadodara-390 002) : Estimation of rotational temperature of <. Pramana J Phys 2003, 60(1), 95-8.

The (0,1), (0,0), (1,0) and (2,0) bands of B→X system of antimony monoxide have been excited in rf discharge tube source and photographed in the 9th order of a two metre plane grating spectrograph (PGS-2). Intensity records of the rotational lines have been obtained. The intensity measurements of Q and P branch lines of the above four bands nad J numberings are used to estimate the effective rotational temperature of the source emitting the spectrum of ¹²¹Sb¹⁶O molecule. It is concluded that ¹²¹Sb¹⁶O may be present in K type stars.

1 table, 12 ref

005352   Srivastava S K (Inter University Centre for Astronomy and Asrophysics, , Post Bag 4, Ganeshkhind) : Riccion from higher-dimensional space time with D-dimensional sphere as a compact manifold and one-loop renormalization. Pramana J Phys 2003, 60(1), 29-45.

Lagrangian density of riccions is obtained with the quartic self-interacting potential using higher-derivative gravitational action in (4 + D)-dimensional space-time with S^D as a compact manifold. It is found that the resulting four-dimensional theory for riccions is one-loop multiplicatively renormalizable. Renormalization group equations are solved and its solutions yield many interesting results such as dependence of extra dimensions on the energy mass scale showing that these dimensions increase with the increasing mass scale up to D = 6, phase transition at 3.05 x 10¹⁶ GeV and dependence of gravitational and other coupling constants on energy scale. Results also suggest that space-time above 3.05 x 10¹⁶ GeV should be fractal. Moreover, dimension of the compact manifold decreases with the decreasing energy mass scale such that D = 1 at the scale of the phase transition. Results imply invisibility of S¹ at this scale (which is 3.05 x 10 ¹⁶ GeV).

1 table, 18 ref

005351   Soliman L I (National Research Centre, Department of Solid State Physics, Dokki, Cairo, Egypt) : Threshold switching effects in amorphous CuInSeS thin films. Indian J Phys-Pt A 2003, 77(1), 27-30.

The switching effects in amorphous CulnSeS thin films have been investigated. The amorphous CuInSeS thin films were obtained by thermal evaporation of the polycrystalline materials under vacuum of about 10-6 Torr and with evaporation rate about 80 Angstrom/sec. The annealing of the films at different annealing temperature improves the switching characteristics and decreases the threshold voltage V_th. The threshold switching voltage and threshold activation energy E_s were found to decrease linearly with increasing annealing temperature and decreases with thickness. Moreover, the threshold switching voltage increased exponentially with temperature.

8 illus, 20 ref

005350   Singh K;Singh C;Sidhu G S;Singh J (Department of Physics, Punjab University, Patiala-147 002) : Flyash : A radiation shielding material. Indian J Phys-Pt A 2003, 77(1), 41-5.

To support the use of flyash material as a radiation shielding material for gamma or X-rays, the radiation interaction parameters (attenuation coefficients and buildup factors) have been studied as a function of incident photon energy. The attenuation coefficients are found to have large values in low and high energy region whereas the buildup factor values have a maxima in the medium energy region. These variations in attenuation coefficient as well as in the buildup factor in different energy regions, have been interpreted in terms of Z-dependence of partial photon interaction processes and have been presented in the form of graphs.

3 illus, 3 tables, 13 ref

005349   Sharma H;Prakash S (Department of Physics, Panjab University, Chandigarh-160 014) : Strain field due to self-interstitial impurity in Ni. Pramana J Phys 2003, 60(1), 159-66.

The embeded-atom method have been applied to study the strain field produced by the self-interstitial impurity at the octahedral site in Ni. The calculation have been carried out consistently on the basis of discrete lattice theory, using Kanzaki method. The atomic force constants are evaluated using Wills and Harrison interatomic potential. The dynamical matrix and external force are evaluated considering the interaction up to first nearest neighbors. The atomic displacements are tabulated up to 20NN's. These displacements are of oscillatory nature and of decreasing magnitude with NN's distance. The physical properties such as self-interstitial formation energy and volume change calculated using atomic displacements are in accordance with the earlier studies.

2 illus, 3 tables, 12 ref

005348   Sharma H;Prakash S (Department of Phys, Panjab University, Chandigarh-160 014) : Strain field due to transition metal impurities in Ni and Pd. Pramana J Phys 2003, 60(1), 123-41.

The strain field due to body centered substitutional tansition metal impurities in Ni and Pd metals are investigated. The calculations are carried out in the discrete lattice model of the metal using Kanzaki lattice static method. The effective ion-ion interaction potential due to Wills and Harrison is used to evaluate dynamical matrix and the impurity-induced forces. The results for atomic displacements due to 3d, 4d and 5d impurities (Fe, Co, Cu, Nb, Mo, Pd, Pt and Au) in Ni and (Fe, Co, Cu, Ni, Nb, Mo, Pt and Au) impurities in Pd are given up to 25 NN's of impurity and these are compared with the available experimental data. The maximum displacements of 4.6% and 3.8% of 1NN distance are found for NiNb and PdNb alloys respectively, while the minimum displacements of 0.63% and 0.23% of 1NN distance are found for NiFe and PdFe alloys respectively. Except for Cu, the atomic displacements are found to be proportional to the core radii and d state radius. The relaxation energies for 3d impurities are found less than those for 4d and 5d impurities in Ni and Pd metals. Therefore, 3d impurities may easily be solvable in these metals.

7 illus, 10 tables, 12 ref

005347   Sen Gupta N D (Tata Institute of Fundamental Research, , Mumbai-400 005) : Invariance properties of the Dirac equation with external electro-magnetic field. Pramana J Phys 2003, 60(1), 11-9.

An attempt has been made to obtain the nature of the external field such that the Dirac equation with external electro-magnetic field is invariant. The Poincare group, which is the maximal symmetry group for field free case, is constrained by the presence of the external field. Introducing infinitesimal transformation of x and ψ. Lie's extended group method is applied to obtain the class of external field which admit of the invariance of the equation. It is important to note that the constraints for the existence of invariance are explicitly on the electric and magnetic field, though only potentials explicitly appears in the equation.

6 ref

005346   Sarkar S K (Department of electronics and Telecommunication Engineering, Jadavpur University, Kolkata-700 032) : GA based parameter optimizations for better millimeter and sub-millimeter wave response characteristics of GaAs quantum wells. Indian J Phys-Pt A 2003, 77(1), 23-6.

Predicts the optimum values of the system parameters of GaAs quantum wells incorporating the relevant scattering mechanisms for getting better millimeter and sub-millimeter wave response characteristics and to explore the possibilities of new applications of such nanostructures. Optimized parameters have been computed by employing the Genetic Algorithms to get the desired response as an aid to the device related work. The optimized parameters like phase angle, ac mobility, channel width, carrier concentration, lattice temperature and electron temperature will obviously save the search time for the technologists involved in the fabrication of devices.

2 tables, 18 ref

005345   Rajasekaran T R;Selvaraj S;Santhosh Kumar S (Department of Physics, Manonmaniam Sundaranar University, Tirunelveli-627 012) : The phenomenonon of nucleon emission at high angular momentum states of fused compound systems. Pramana J Phys 2003, 60(1), 75-93.

Nucleon emission from high spin fused compound systems is analyzed in the framework of the statistical theory of hot rotating (STHR) nuclei. THis is an elaborate verison of earlier work and results for ¹⁵⁶Er, ^/166Er ¹⁶⁸Yb and ¹⁸⁸Hg have been presented. An increase in neutron emission for ¹⁶⁶Er due to the abrupt decrease in neutron separation energy around I≈55h is predicted. Since the drop in the separation energy is closely associated with the structural changes in the rotating nuclei, relative increase in neutron emission probability around certain values of angular momentum may be construed as evidence for the shape transition. A similar effect is predicted for ¹⁶⁸Yb around I≈55h. Extended the microscopic cranked Nilsson method (CNM) to hot nuclear systems and comapre the results with that of the STHR method. The two methods yield different results for triaxially deformed nuclei although for biaxial deformations the results are identical. This is illustrated for ¹⁸⁶Hg

12 illus, 29 ref

005344   Pradyumnan P P;Ittyachen M A (Department of Physics, University of Calicut, Calicut University, P O-673 635) : Growth of praseodymium samarium hydrogen selenite mixed crystals and their characterisation. Indian J Phys-Pt A 2003, 77(1), 31-5.

Following chemical reaction method, mixed crystals of praseodymium samarium hydrogen selenite were grown in silica gel by single diffusion method. The difference in growth features by varying different growth parameters was studied in detail. Optimum growth conditions yielded good quality crystals of praseodymium samarium hydrogen selenite (PSHS). These crystals were characterised by X-ray, Uv-Visible and infrared spectroscopic methods. The energy dispersive analysis by X-rays was utilised to find the percentage of praseodymium and samarium ions in the grown crystals. The unit cell parameters of the crystals were obtained from single crystal and powder X-ray diffraction techniques. The molecular formula of the crystals was clarified with TG in complement with infrared study. The micro-indentation studies were carried out to study the hardness of well faceted PSHS crystals.

8 illus, 13 ref

005343   Paul I;Joseph C;Ittyachen M A;Varghese P A; GEorge J;Varghese G (School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam-686 560) : Micro hardness studies of pure and doped brushite crystals. Indian J Phys-Pt A 2003, 77(1), 37-40.

Vicker's micro hardness studies on pure and doped brushite (CaHPO₄.2H₂O) crystals are reported. The micro hardness value (H_v), work hardening coefficient (n), and first order elastic stiffness coefficient (C₁₁) are reported for brushite crystals doped with Ni, Cd Mg and Pb. It has been observed that the micro hardness has a load dependent part and a load independent part.

3 illus, 3 tables, 22 ref

005342   Pati S P;Satapathy S;Dash S K (Physics Dep, Sambalpur University, Jyoti Vihar, Burla-768 019) : Microwave properties of Si impatt diodes at different temperatures. Proc Indian Sci Congr Ass - Pt III(YS abstr), Sect-III 2000, (NULL), 4.

005341   Narendra Singh (Harish Chandra Research Institute, , Chhatang Road, Jhusi, Allahabad-211 019) : Hermitian quark matrices. Pramana J Phys 2003, 60(1), 53-8.

Assuming a relation between the quark mass matrices of the two sectors, a unique solution can be obtained for the CKM flavor mixing matrix. A numerical example is worked out which is in excellent agreement with experimental data.

8 ref

005340   Mollah S;Yang H D;Chaudhuri B K (Department of Physics, National Sun Yat Sen University, Kaohsiung, Taiwan-804, R.O.C) : MgB₂ superconductor. Indian J Phys-Pt A 2003, 77(1), 9-22.

Synthesis, structure and properties of the most intensively studied newly discovered intermetallic binary superconductor MgB₂ have been reviewed up to October, 2002. Deals with experimental results obtained by different research groups working on this new superconductor. Since more new and interesting results are expected in near future, critical theoretical analysis of the existing experimented data has not been made.

17 illus, 92 ref

005339   Misra T;De A K;Bhattacharya T;Ganguly T (Spectroscopy Dep, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700 032) : Photophysical properties of 5-hydroxyindole (5HI): laser flash photolysis study. Proc Indian Acad Sci-Chem Sci 2002, 114(6), 547-56.

Steady state fluorescence emission and transient absorption spectra of 9-fluorenone (9FL) were measured in the presence of 5-hydroxyindole (5HI) in highly polar acetonitrile (ACN) environment at ambient temperature. Cyclic voltammetry measurements demonstrate that ground state 6HI as a donor could take part in highly exothermic electron transfer (ET) reactions with excited 9FL, which should serve as electron acceptor. From the transient absorption measurements it is inferred that in geminate ion-pair (GIP) (or contact ion pair), formed initially due to photoinduced ET, the decay of this contact ion-pair occurs not only through ion recombination (back electron transfer to ground state of reactant), but through the other processes also such as proton-transfer (hydrogen abstraction) from radical cation to anion and separation of ion-pair producing the free ions. From the computed reorganisation energy parameter (λ) and experimentally observed -ΔG^°_ET values it is hinted that there is a possibility that highly exothermic forward electron transfer reactions in the singlet state S₁ occur, within present reacting systems, in Marcus inverted region. Back transfer seems to follow the same path. Investigations with similar other reacting systems are underway.

30 ref

005338   Manoj Kumar;Deshpande A;Gupta C;Biswas A K; Nath A K (Centre for Advanced Technology, , Indore-452 013) : Maximization of yield of C-13 isotope by multiphoton dissociation of freon-22 using high average power TEA CO₂ laser. Proc Indian Acad Sci-Chem Sci 2002, 114(6), 659-73.

Selective multi-photon dissociation (MPD) of Freon-22 (CF₂HCl) molecules has been carried out using a TEA CO₂ laser at various CO₂ laser lines (9P(20)-9P(26)) in order to maximize the yield of C-13 isotope in the product (C<2>F₄) at an enrichment factor of 100. The effects of laser pulse tail due to the presence of N₂ in the laser mixture on the enrichment factor and yield of C-13 are investigated. It is found that the addition of a small amount of ₂ is possible in the laser mixture without a significant drop in the yield at desired enrichment factor. Addition of a small amount of N₂ improves the laser efficiency considerably. At a given pulse energy, a slight change in the near field intensity distribution of a laser severely affects the selectivity of C-13 isotope. The computed far-field intensity distributions of the measured near-field intensities show marked spatial variation in the focal spots that leads to a drop in selectivity. For macroscopic production of C-13 isotope a simple and novel multi-pass cavity has been designed and tested to focus the energy repeatedly keeping the optimum fluence constant at each focal spot.

6 illus, 1 table, 23 ref

005337   Maiti M;Nandy M;Roy S N;Sarkar P K (Physics Department, Visva Bharati, Santiniketan-731 235) : An empirical fit to estimated neutron emission cross sections from proton induced reactions. Pramana J Phys 2003, 60(1), 143-50.

Neutron emission cross section for various elements from ⁹Be to ²⁰⁹Bi have been calculated using the hybrid model code (ALICE-91 proton induced reactions in the energy range 25 MeV to 105 MeV. An empirical expression relating neutron emission cross section to target mass number and incident proton energy has been obtained. The simple expression reduces the computation time significantly. The trend in the variation of neutron emission cross sections with respect to the target mass number and incident proton energy has been discussed within the framework of the model used.

4 illus, 2 tables, 5 ref

005336   Kundu T;Pradhan B;Singh B (Phys Dep, Indian Institute of Technology, Bombay, Powai, Mumbai-400 076) : Origin of methyl torsional potential barrier. Proc Indian Acad Sci-Chem Sci 2002, 114(6), 623-38.

Presents the evolution of views on methyl internal rotation potential barrier. Various mechanisms proposed for the origin of torsional barrier in ethane have been reviewed. Inadequacy of one dimensional description of internal rotation has been highlighted in small methyl conjugated molecules in the light of its multidimensional nature. The effect of skeletal flexing on the picture of barrier formation by dissecting the barrier energy into potential type, virial type and symmetry type is described. The role of π and σ electrons at different stages of molecular flexing is discussed. The analysis identifies the dominant contributions to barrier origin as π-bonding changes during rigid rotation and σ-bonding changes resulting from bond lengthening during methyl group rotation. The contribution of lone pair electrons in determining the preferred structure of the methyl group in imine compounds such as 1-methyl 2-(III)-pyridinimine is presented.

8 illus, 5 tables, 55 ref

005335   Kota V K B (Physical Research Laboratory, , Ahmedabad-380 009) : O (12) limit and complete classification of symmetry schemes in proton-neutron interacting boson model. Pramana J Phys 2003, 60(1), 59-74.

It is shown that the proton-neutron interacting boson model (pnIBM) admits new symmetry limits with O(12) algebra which break F spin but preserves the F_z quantum number M_F. The generators of O(12) are derived and the quantum number v of O(12) for a given boson number N is determined by identifying the corresponding quasi-spin algebra. The O(12) algebra generates two symmetry schemes and for both of them, complete classification of the basis states and typical spectra are given. With the O(12) algebra identified, complete classification of pnIBM symmetry limits with good M_F is established.

1 illus, 1 table, 24 ref

005334   Kher S;Srikant G;Chaube S;Chakraborty A L; Nathan T P S;Bhawalkar D D (Fibre Optics Lab, Solid State Laser Division, Centre for Advanced Technology, Indore-452 013) : Design, development and studies on Raman-based fibre-optic distributed temperature sensor. Curr Sci 2002, 83(11), 1365-8.

Reports the development of an optical fibre-based multi-point temperature measurement system. Such sensors permit the measurement of temperature as a function of length along a single fibre with no taps or branches. This feature greatly increases the information from a single instrument and hence decreases the cost-benefit ratio. With the present setting, it is possible to measure temperature at 16 points simultaneously with a resolution of ±5°C using a 200-m long silica fibre.

5 illus, 4 ref

005333   Khare Jai;Sreedhar R;Paul C P;Reghu T;Nath A K (Industrial CO2 Laser Section, Centre for Advanced Technology, Indore-452 013) : Operational characteristics and power scaling of a transverse flow transversely excited CW CO₂ laser. Pramana J Phys 2003, 60(1), 99-107.

Transverse flow transversely excited (TFTE) CO₂ lasers are easily scalable to multi kilowatt level. The laser power can be scaled up by increasing the volumetric gas flow and discharge volume. It was observed in a TFTE CW CO₂ laser having single row of pins as an anode and tubular cathode that the laser power was not increasing when the discharge volume and the gas volumetric flow were increased by increasing the electrode separation keeping the gas flow velocity constant. The discharge voltage too remained almost constant with the change of electrode separation at the same gas flow velocity. This necessitated revision of the scaling laws for designing this type of high power CO₂ laser. Experimental results of laser performance for different electrode separations are discussed and the modifications in the scaling laws are presented.

5 illus, 2 tables, 12 ref

005332   Gohain Barua A;Boruah B R;Bhattacharyya S; Baruah G D (Department of Physics, Gauhati University, Guwahati-781 014) : Spectroscopic investigation of the Dergaon meteorite with reference to 10 μm and 20 μm bands. Pramana J Phys 2003, 60(1), 47-52.

3 illus, 1 table, 7 ref

005331   Ghosh D;Deb A;Haldar P K;Sahoo S R (High Energy Physics Division, Department of Physics, Jadavpur University, Kolkata-700 032) : Fragmentation in S<. Indian J Phys-Pt A 2003, 77(1), 63-5.

Presents new data target fragment model in S³²-AgBr interaction at 200 GeV/n. The data do not favour evaporation model instead a preferential backward emission of black track is indicated by the data.

1 illus, 15 ref

005330   Chandra B P;Patel N L;Rahangdale S S;Patel R P;Patle V K (Department of Postgraduate Studies and Research in Physics and Electro, , Rai Durgavati Vishwavidyalaya, Jabalpur-482 001) : Characteristics of the fast electron emission produced during the cleavage of crystals. Pramana J Phys 2003, 60(1), 109-22.

Reports the fast electron emission produced during the cleavage of alkali halide crystals and models the dynamics of the process. The mechano-emission arises as a result of the ionization of surface traps at the expense of the energy which is released in the annihilation of the defects which are formed during cleavage. The slow electrons which appear upon the ionization of surface traps are subsequently accelerated in the field of negatively charged segment of the freshly cleaved surface. Considering the basic mechanism of fast electron emission, expressions are derived which are able to explain satisfactorily the temporal, thermal, charge, surface, coloration, water adsorption and other characteristics of the fast electron emission produced during the cleavage of crystals. The decay time of the charges on the newly created surfaces, and the velocity of cracks can be determined from the measurements of fast electron emission produced during the cleavage of crystals. It is shown that two types of diffusing centres are responsible for the charge relaxation and thereby for the emission of fast electrons produced during the cleavage of alkali halide crystals.

5 illus, 1 table, 39 ref

005329   Bose M;Basa D K (Physics Dep, Utkal University, Bhubaneswar-751 004) : Effect of ammonia plasma pretreatment on the electrical properties of plasma deposited silicon nitride films. Proc Indian Sci Congr Ass - Pt III(YS abstr), Sect-III 2000, (NULL), 5.

005328   Azharul Islam S M;Al Sewaidan H (Department of Physics, Jahangirnagar University, Savar, Dhaka, Bangladesh) : Application of MCNP code to shielding analysis for single and multilayers of polyethylene and lead. Indian J Phys-Pt A 2003, 77(1), 51-4.

Calculations were made using MCNP-4B code to study the neutron shielding effectiveness of polyethylene (PE) and lead (Pb) as a single and multilayer arrangements against U²³⁵ fission neutron source. Shielding slabs of 5 cm thickness were employed successively. Transmission factors for the above-mentioned shielding setups were determined upto 100 cm thickness. Dose spectra hae been calculated for different thicknesses of the shielding arrangements. The results revealed that using slabs successively of 15 cm PE plus 15 cm Pb is as efficient in shielding fission neutrons as using of 30 cm PE shield alone. It was also found that after 40 cm shield thickness, the removal cross section values of the multilayers and single PE shield are not very much different, and are approaching each other with increasing shield thickness.

3 illus 16 ref

005327   Azad A K;Islam J N (Research Centre for Mathematical and Physical Sciences, Chittagong University, Bangladesh) : Cosmological constant in the Bianchi type-I-modified Brans-Dicke cosmology. Pramana J Phys 2003, 60(1), 21-7.

In 1961, Brans and Dicke provided an interesting alternative to general relativity based on Mach's principle. To understand the reasons leading to their field equations, homogeneous and isotropic cosmological models in the Brans-Dicke theory are considered. Accordingly, the Robertson-Walker line element and the energy tensor of a perfect fluid are started with. The scalar field ϕ is now a function of the cosmic time only. Then Λ spatially homogeneous and anisotropic Bianchi type-I-cosmological solutions of modified Brans-Dicke theory containing barotroic fluid are considered. These have been obtained by imposing a condition on the cosmological parameter Λ (ϕ). Again, the meaning of this cosmological term is focussed upon and an attempt is made to relate it to the time coordinate which gives collapse singularity or initial singularity. On the other hand, the solution is a generalization of the solution found by Singh and Singh.

20 ref

005326   Alam MS (Department of Physics, Shahjalal University of Science and Technology, Sylhet, Bangladesh) : Comparative study of mixed product and quaternion product. Indian J Phys-Pt A 2003, 77(1), 47-9.

Mixed number is the sum of a scalar and a vector. The quaternion can also be written as the sum of a scalar and a vector but the product of mixed numbers and the product of quaternions are different. Studies the mixed product which is derived from the product of mixed numbers and the quaternion product which is derived from the product of quaternions. It is observed that mixed product is more consistent with Physics than that of quaternion product.

1 table, 8 ref

004197   Yadav M (Physics Dep, Govt. P G College, Kotdwara-246 149) : Hydromagnetic cylindrical shock through rotatings gas. Indian J Theor Phys 2002, (NULL), 23-35.

Propagation of diverging cylinderical hydromagnetic shock in a rtotating gas has been studied by Chisnell-Chester-Whitham method, simultaneously for both strong and weak cases for an initial density distribution _po=_p'e^{λ r}, where _p' is the density at the axis of symmetry and λ is non-dimensionalizing constant. The magnetic field has been assumed to have only constant axial (H_zo) and variable azimuthal (H²_θ=rH^2_zo) components. Analytical expressions for flow variables have been derived. Their numerical estimates have been computed only at distances permissible by initial entropy distribution condition i.e. _{poαp^γo, where po is the pressure in unperturbed medium and γ is the adiabatic index of the gas, with the initial strength of the shock at some instant as the initial condition.}

3 illus, 1 table, 18 ref

004196   Sindhu S;Anantharaman M R;Thampi B P;Malini K A;Kurian P (Department of Physics, Cochin University of Science and Technology, Cochin-682 022) : Evaluaiton of a.c. conductivity of rubber ferrite composites from dielectric measurements. Bull Mater Sci 2002, 25(7), 599-607.

THe effectof frequency, composition and temperature on the a.c. electrical conductivity were studied for the ceramic, Ni_1-xZn_xFe₂O₄, as well as the filler (Ni_1-xZn_xFe₂O₄) incorporated rubber ferrite composites (RFCs). Ni_1-xZn_xFe₂O₄ (where x varies from 0 to 1 in steps of 0.2) were prepared by usual ceramic techniques. They were then incorporated into a butyl rubber matrix according to a specific recipe. The a.c. electrical conductivity (σ_{1.c.) calculations were carried out by using the data available from dielectric measurements and by employing a simple relationship. The a.c. conductivity values were found to be of the order of 10^-3 S/m. Analysis of the results shows that σa.c. increases with increase of frequency and the change is same for both ceramic Ni1-xZnxFe2O4 anf RFCs. σ<>a.c. increases initially with the increase of zinc content and then decreases with increase of zinc. Same behaviour is observed for RFCs too. The dependence of σ a.c. on the volume fraction of the magnetic filler was also studied and it was found that the a.c. conductivity of RFCs increases with increase of volume fraction of the magnetic filler. Temperature dependence of conductivity was studied for both ceramic and rubber ferrite composites. Conductivity shows a linear dependence with temperature in the case of ceramic samples.}

9 illus, 28 ref

004195   Shukla A K;Kaman Singh (Chem Dep, Govt Autonomous College, Niwari-472 442) : Photoelectrochemical studies on thermally treated (ZnCd) Se films. Indian J Chem-Sect A 2002, 41(2), 308-311.

Photoresponsive mixed metal chalcogenide films of (ZnCd) Se of desired composition have been prepared by electrochemical codeposition and subjected to thermal treatment at 400°C in argon atmosphere under controlled conditions. Photoresponsiveness of thermally treated electrodes has been examined employed I₃/I₂ redox system and characterised by photoaction spectral (PAS) studies and impedance measurements. Thermal treatment of the electrodeposits is accompanied by inversion from p-to n-type semiconductivity and they exhibit somewhat lowered band gap perhaps due to recrystallisation. The thermally treated preparations have been endowed with increased stability and somewhat improved photoresponsiveness and they exhibit increased resistance towards impairment due to electrochemical corrosion.

^ssc5 illus, 1 table, 16 ref

004194   Parikh P;Bhardwaj D M;Gupta R P;Saini N L; Fernandes S;Singhal R K;Jain D C;Garg K B (Department of Physics, University of Rajasthan, Jaipur-302 004) : Comparative study of the electronic structure of natural and synthetic rubies using XAFS and EDAX analyses. Bull Mater Sci 2002, 25(7), 653-6.

Studies the Cr-K-edge XANES and EXAFS in natural Indian Rubies from two sources and a synthetic ruby at ESRF. Weight % of various constituents in them is determined using EDAX measurements. Taking the results from the three techniques together demonstrate their feasibility in quantitative study of precious stones.

4 illus, 2 tables, 12 ref

004193   Padma Survarna R;Raghavendra Rao K; Subbarangaiah K (Department of Physics and Electronics, Sri Krishnadevaraya University, Anantapur-515 003) : Simple technique for a.c. conductivity measurements. Bull Mater Sci 2002, 25(7), 647-51.

An inexpensive, indigenous and a simple electronic instrument based on voltage follower, current-to-voltage converter, zero crossing detector and a phase detector has been developed for measurement of a.c. conductivity. Real and imaginary parts of complex impedance are determined for a given sample as a function of frequency and the given sample is represented by a pure electronic model.

7 illus, 2 tables, 11 ref

004192   Meenakshi;Garg V K;Yadava K;Gupta R;Malik M (Centre for Rural Development and Technology, Indian Institute of Technology, Hauz Khas, New Delhi) : Water quality monitoring of western Yamuna canal from Tajewala to Haiderpur treatment plant, Delhi. Res J Chem Envir 2002, 6(3), 21-4.

Water quality of Western Yamuna Canal (WYC) was assessed from Tajewala barrage (Haryana) to Haiderpur treatment plant (Delhi). 20 samples were collected from different locations along the course of canal. The physico-chemical parameters analyzed were temperature, pH, electrical conductivity, total dissolved salts, dissolved oxygen, turbidity, total hardness, total alkalinity, sodium, potassium, calcium, magnesium, carbonate, bicarbonate, chloride, sulfate, nitrate and phosphate content in collected samples. It was observed that the water quality of WYC gets degrade to with respect to some of analyzed parameters as it proceeds towards Delhi. A systematic study of correlation among various water quality parameters has been done, which conlcuded that electrical conductivity and total dissolved salts are positively and significantly correlated with most of the analyzed parameters. No disposal of industrial and domestic sewage has been found all along the route of WYC except at one location in Yamunanagar.

3 tables

004191   Kumar A;Naithani U C;Semwal B S (Physics Dep, Garhwal University, Pauri Campus, Pauri (Garhwal), U.C.-246 001) : Dynamics of soft mode in Ba_x Sr_1-x TiO₃ perovskites. Indian J Theor Phys 2002, 50(1), 55-61.

An expression for the soft mode frequency in Ba_x Sr_1-x TiO₃ perovskites is obtained, by using double time temperature dependent Green's function technique. The mass and force constant changes due to impurity atoms are taken into account in the presence of higher order anharmonic terms in the Silverman Joseph Hamiltonian. The soft mode frequency is stabilized in the presence of impurity of Ba in an anharmonic Sr TiO₃ ferro-electric perovskites. The soft mode frequency decreases with addition of impurity of Ba atoms.

23 ref

004190   Kalidoss M;Srinivasamoorthy R (Physics Dep, St. Joseph's College, Tiruchirapalli-620 002) : Khasare's equation of state applied to mixtures. J pure appl Ultrasonics 2000, 22(3), 78-81.

It was shown earlier that the equation of state proposed by Khasare could be applied to binary and ternary liquid mixtures with ample success. Khasare's equation has now been applied to a series of (Ten) mixtures of bromoform with hydrocarbons. The analysis reveals a gradual variation in the parameters (molecular radius and intermolecular potential) of the hydrocarbons as their chain length varies.

3 tables, 8 ref

004189   Justin R R;Bisht P B (Physics Dep, Indian Institute of Technology Madras, Chennai-600 036) : Measurment of ultrafast relaxation times by femtosecond optical delay line. J Optics 2002, 31(2), 47-51.

Ultrafast relaxation time profiles of the order of femtoseconds(fs) can be recorded by using an optical delay line. Fabrication details of this economical and indigenous PC-controlled optical delay line along with the requirements of improving signal-to-noise ratio are given here.

2 illus, 5 ref

004188   Joshi S S;Temgire M K (Chemistry Dep, University of Pune, Pune-411 007) : Radiation induced studies of capped silver nanoparticles. Res J Chem Envir 2002, 6(3), 7-11.

Gamma radiolysis method was used to prepare PVA and Brij'97 capped Silver nanoparticles by optimizing various conditions like metal ion concentration, polymer/surfactant concentration and the amount of dose absorbed. The role of different scavengers was also studied. The decrease in particle size was observed with increase in the molecular weight of capping agent. ϒ-radiolytic method provides silver nanoparticles in fully reduced and highly pure state. X-ray diffraction technique confirmed the zero valent state of silver. Optical studies were done using UV-visible spectrophotometer to see the variation of electronic structure of metal. Transmission Electron Microscopic studies reveal the fcc geometry. The TEM shows clearly split Debye Scherrer rings. The d values calculated from the diffraction ring pattern are in perfect agreement with the ASTM data. Ag particles less than 10nm are spherical in shape, whereas the particles above 30nm have structure of pentagonal biprisms or decahedra, referred to as multiply twinned particles.

4 illus, 2 tables, 24 ref

004187   Dubey V;Singh S (Department of Physics, G B Pant University of Agriculture and Technology, Pantnagar-263 145) : Formation of oxygen related donors in step-annealed CZ-silicon. Bull Mater Sci 2002, 25(7), 589-92.

The effect of step-annealing necessitated by the difficulties being faced in the long duration annealing treatments to be given to CZ-silicon has been studied. One pre-anneal of 10 h followed by annealing of 10 h causes a decrease in the absorption coefficient for carbon (α_c). Oxygen and carbon both accelerate thermal donor (TD) formation process but oxygen plays a dominating role. Three anneals of 10 h each followed by one anneal of 10 h support the view that carbon suppresses the donor formation. The absorption coefficient for carbon decreases after a few number of step-anneals resulting in the transformation of TD to new donor (ND) as brought about by annealing at temperature, <62> 500°C. It is quite logical to conclude that step-annealing may bring about the same results as obtained on continuous annealing fora longer duration. The results have been fully supported by proper interpretation in the light of existing theories.

4 illus, 2 tables, 20 ref

004186   Caltenco J H;Lo'pez-Bonilla J L;Pena-Rivero R (Escuela Superior de Ingenieri'a Meca'nica y Electrica, Instituto Politecnico Nacional, Edif. Z. Acc. 3-3er Piso, Col. Lindavista C.P. 07708, Mexico, D. F.) : Electromagnetic Weyl tensor for the Lienard-Wiechert field. Indian J Theor Phys 2002, 50(1), 1-3.

Newman showed analogies between the Lienard-Wiechert field and the Robinson-Trautman (RT) solutions of the Einstein gravitational euations. Presents one more analogy : The Maxwell field produced by a point charge in arbitary motion has been same algebraic type as the RT metrics. This result is possible because the Weert superpotential permits to construct an 'electromagnetic Weyl tensor" which admits the Petrov classification as in general relativity.

24 ref