015746   Kalaivani T;Kumar S;Krishnan S (Dep of Physics, Annamalai University, Annamalainagar-608 002) : Dielectric relaxation study of some binary liquid mixtures using frequency domain technique. Indian J pure appl Phys 2003, 41(5), 398-401.

Dielectric relaxation studies have been carried out in three binary liquid systems namely hexanol, heptanol and octanol with benzene solution. The oscillating frequency of X-band microwave bench is at 9.36 GHz. The orientation of molecular dipoles have been identified by the Kirkwood linear correlation factor (g′). The relaxation time (τ) is obtained by both Higasi's and Cole-Cole method. The dipole moments of the systems are determined by Higasi's and Gopalakrishna's method. The activation energies due to the relaxation process (ΔF_τ) and the viscous flow (ΔF_η) are calculated.

1 illus, 1 table, 15 ref

015745   Gupta N K;Godwal B K (High Pressure Physics Division Dep, Bhabha Atomic Research Centre, Mumbai-400 085) : Effects of non-local thermodynamic equilibrium conditions on numerical simulation of inertial confinement fusion plasms. Pramana J Phys 2002, 59(1), 33-51.

Effects of non-local thermodynamic equilibirium (non-LTE) condition on emission and hydrodynamics of typical intertial confinement fusion (ICF) plasmas are studied. The average degree of ionization at high temeratures is seen to be much lower compared to the values obtained from Thomas-Fermi scaling or Saha equation for high-Z element like gold. LTE and non-LTE predictions for emitted radiation from laser-driven gold foil are compared with the experiment results and it is seen that non-LTE simulations show a marked improvement over LTE results. The effects of one group and multigroup, LTE and non-LTE approximations of radiation transport on hydrodynamic parameters are studies for laser-driven aluminium and gold foils. It is further seen that non-LTE and multigroup effects play an important role in predicting conversion efficienct of laser light to X-rays.

14 illus, 44 ref

015744   Ghorui S;Sahasrabudhe S N;Murthy P S S;Das A K;Venkatramani N (Laser and Plasma Technology Division Dep, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085) : Estimation of dynamic properties of attractor observed in hollow copper electrode atmospheric pressure are plasma system. Pramana J Phys 2002, 59(1), 143-50.

Understanding of the basic nature of arc root fluctuation is still one of the unsolved problems in thermal are plasma physics. It has direct impact on myriads of thermal plasma applications being implemented at present. Recently, chaotic nature of arc root behaviour has been reported through the analysis of voltage, acoustic and optical signals which are generated from a hollow copper electorde are plasma torch. Presents details of compurtaions involved in the estimation process of various dynamic properties and show how they reflect chaotic behaviour of arc root in the system.

6 illus, 8 ref

015743   Gagnanai M A;Shukla R S;Hari S K;Misra S N (NO, Central Salt & Marine Chemicals Research Institute, Bhavnagar, Gujarat-364 002) : Comparative absorption spectroscopy involving 4f-4f transitions to explore kinetics of complexation of Zn(II) with Er(III)-glutathione complex & compositional dependence of intensity parameters. Indian J pure appl Phys 2003, 41(5), 374-83.

The kinetic and spectroscopic investigations on complexation of Zn(II) with Er₂(GSH)₂(H₂O)₄ 1 (GSH = reduced glutathione) to form Er₂(GSH)₂Zn(H₂O)₆ complex 2 have been performed at 30°C by following five, 4f-4f sensitive transitions of lanthanide Er(III), ⁴I_15/2 → ⁴G_11/2, ⁴I_15/2 → ⁴F_7/2, ⁴I_15/2 → ²H_11/2, ⁴I_15/2 → ⁴F_9/2 and ⁴I_15/2 → ⁴I_11/2 in water as well as in equimolar mixture of DMF and water. Performances of all the five bands were found to be competently sensitive, on the basis of kinetic studies done by following the changes in the intensity (absorbance, molar absorptivity) and intensity parameters (oscillator strength P and Judd-Ofelt T_λ intensity). Kinetics showed first order dependence in terms of concentrations of Zn(II) and complex 1 on the rate of formation of complex 2. In order to support the kinetic and spectroscopic observations, complex 1 and 2 were synthesized also, and were characterized by C, H, N, S and elemental analysis, UV/VIS, NMR and IR techniques. Kinetics, mechanistic and spectroscopic aspects of the complexation reaction are presented and discussed.

2 illus, 3 tables, 33 ref

015742   Das A K;Dev B N;Sundaravel B;Luo E Z;Xu J B; Wilson I H (NO, Institute of Physics, Sachivalya Marg, Bhabaneswar-751 005) : Self-assembled growth of nanostructural Ge islands on bromine-passivated Si(111) surface at room temperature. Pramana J Phys 2002, 59(1), 133-42.

Reports deposision of relatively thick (~60 nm) Ge layers on Br-passivated Si(111) substrates by thermal evaporation under high vacuum conditions at room temperature. Ge has grown in a layer-plus-island mode although it is different from the Stranski-Krastanove growth mode observed in epitaxial growth. Both the islands and the layer are nanocrystalline. This appears to be a consequence of reduction of surface free energy of the Si(111) substrate by Br-passivation. The size distribution of the Ge nanoislands has been determined. The Br-Si(111) substrates were prepared by a liquid treatment, which may not produce exactly reproducible surfaces. Nevertheless, some basic features of the nanostructural island growth are reasonably reproducible, while there are variations in the details of the island size distribution.

4 illus, 34 ref

015741   Choudhury M G M;Kao J S;Lai G R;Ali G M R (Dep of Physics, University of Rajshahi, Rajshahi-6205, Bangladesh) : Characterization of zirconium dioxide thin films prepared by cw CO₂ laser-assisted evaporation. Indian J pure appl Phys 2003, 41(5), 362-8.

Zirconium dioxide thin films have been deposited by cw CO₂ laser-assisted evaporation on Si(100), quartz and optically polished glass substrates at different substrate temperature. Films were grown in oxygen, under partial pressure. The surface morphology of the films has been observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the structure has been studied by X-ray diffraction (XRD). The optical bandgap has been calculated from transmission spectra, taken in the UV range. The dc dark conductivity has been investigated in the temperature range 30-130 °C. The SEM micrographs show that, the film surfaces are smooth and polycrystalline and grows in a well-alligned columnar structure. XRD observations revealed that, the structure of the films deposited at 250 °C substrate temperature is tetragonal having lattice constants a = 0.5074 nm and c = 0.572 nm. The bandgap evaluated from optical spectra is = 5.25 eV. The dc conductivity shows linear variation with temperature with the experimental temperature range, suggesting an activated process, having single activation energy.

5 illus, 1 table, 16 ref

015740   Bhar G C;Kumbhakar P;Chatterjee U;Chaudhary A K;Kokh A (Physics Dep, Laser Laboratory, Burdwan University, Burdwan-713 104) : Highly efficient deep ultraviolet generation by sum-frequency mixing in a BBO crystal pair. Pramana J Phys 2002, 59(1), 69-74.

Generation of deep ultraviolet radiation at 210 nm by Type-I third harmonic generation is achieved in a pair of BBO crystals with conversion efficiency as high as 36%. The fundamental source is the dye laser radiation pumped by the second harmonic of a Q-switched Nd: YAG laser. A walk-of compensated configuration with the BBO crystal pair has enabled us to realize such as high conversion efficiency in the interaction.

3 illus, 1 tables, 11 ref

015739   Bali R;Jain V C (Mathematics Dep, University of Rajasthan, Jaipur-302 004) : Bianchi type I inflantionary universe in general relativity. Pramana J Phys 2002, 59(1), 1-7.

Investigate Bianchi type I inflationary universe in the presence of massless scalar field with a flat potential. To get an inflationary solution, consideres a flat region in which potential V is constant. The inflationary scenario of the model is discussed in detail.

10 ref

015738   Balasubramanian G;Olinger D J;Demetriou M A (Mechnical Enigneering Dep, Worcester Polytechnic Institute, Worcester, MA-01609-2280, USA) : Control of a coupled map lattice model for vortex shedding in the wake of a cylindeer. Pramana J Phys 2002, 59(1), 91-111.

Studies the addition of control terms into the highly efficient CML models and explored the resulting dynamics. Proportional, adaptive proportional and discontinuous non-linear (DNL) control methods were used to derive the control laws. The first method employed occasional proportional feedback. The adaptive method used spatio-temporal feedback control. The DNL method used a discontinuous feedback linearization procedure, and the controller was designed for the resulting linearized system using eigenvalue assignment. These techniques were applied to a modeled vortex dislocation structure in the wake of a vibrating cable in uniform freestream flow. Parallel shedding patterns were achieved for a range of forcing frequency-forcing amplitude combinations studied to validate the control theory. The adaptive proportional and DNL mehtods were found to be more effective than the proportional control method due to the incorporation of a spatially varying feedback gain across the cylinder span. The DNL method was found to be the most efficient controller of the low-order. CML model. The required control lever across the cable span was correlated to the 1/1 lock-on behavior of the temporal circle map.

11 illus, 31 ref

015737   Ambika G;Sujatha N V (Physics Dep, Maharaja's College, Cochin-682 01) : Critical exponent in the transition to chaos in one-dimensional discrete system. Pramana J Phys 2002, 59(1), 9-18.

Reports the numerically evaluated critical exponents associated with the scaling of generalized fractal dimensions during the transition from order to chaos. The analysis is carried out in details in the context of unimodal and bimodal maps representing typical one-dimesional discrete dynamical systems. The behaviour of Lyapunov exponents (LE) in the cross over regio is also studied for a complete characterization.

6 illus, 2 tables, 21 ref

015736   Ambika G;Menon K (Physics Dep, Maharaja's College, Cochin-682 011) : Fractal pattern on the onset of coherent structure in a coupled map lattice. Pramana J Phys 2002, 59(1), 155-61.

Reports the formation of Cantor set-like fractals during the development of coherent structures in a coupled map lattice (CML). The dependence of these structures of the size of the lattice as well as the first three dimensions of the associated fractal patterns are analyzed numerically.

5 illus, 29 ref

000039   Uniyal M;Singh K;Bhatt S;Bhatt S C;ant R P; Suri D K;Semwal B S (Dielectric and Ultrasonic Laboratory Physics Dep, HNB Garwal University, Srinagar, Garhwal-246 174) : Preparation, characterization and dielectric studies of K<. Indian J pure appl Phys 2003, 41(4), 305-9.

Ceramic pellets of K<^>1-xNa<^>xNbO<^>3 system (for x <61><255> 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.7) have been prepared by solid-state reaction method and sintering process. The prepared sampled were characterized by XRD technique. All prepared samples show orthorhombic structure at room temperature. Frequency varriations of dielectric constant, loss tangent, and electircal conductivity have been investigated, at room temperature, in the frequency range 1-40 MHz. It is observed that, dielectric constant decrease as sodium is mixed by a step of 10% in postassium niobate.