015094   Muralidhar K R;Pangam S;Srinivas P;Ali M A; Sujana Priya V;Komanduri K (Radiation Physics Dep, American Oncology Institute, CTSH, Hyderabad, Telangana, Email: krmuralidhar@rediffamail.com) : Phantom study on the behavior of Acuros XB algorithm in flattening filter free photon beams. J med Phys 2015, 40(3), 144-9.

To study the behavior of Acuros XB algorithm for flattening filter free (FFF) photon beams in comparison with the anisotropic analytical algorithm (AAA) when applied to homogeneous and heterogeneous phantoms in conventional and RapidArc techniques. Acuros XB (Eclipse version 10.0, Varian Medical Systems, CA, USA) and AAA algorithms were used to calculate dose distributions for both 6X FFF and 10X FFF energies. RapidArc plans were created on Catphan phantom 504 and conventional plans on virtual homogeneous water phantom 30 x 30 x 30 cm^{3, virtual heterogeneous phantom with various inserts and on solid water phantom with air cavity. Dose at various inserts with different densities were measured in both AAA and Acuros algorithms. The maximum % variation in dose was observed in (-944 HU) air insert and minimum in (85 HU) acrylic insert in both 6X FFF and 10X FFF photons. Less than 1% variation observed between -149 HU and 282 HU for both energies. At -40 HU and 765 HU Acuros behaved quite contrarily with 10X FFF. Maximum % variation in dose was observed in less HU values and minimum variation in higher HU values for both FFF energies. Global maximum dose observed at higher depths for Acuros for both energies compared with AAA. Increase in dose was observed with Acuros algorithm in almost all densities and decrease at few densities ranging from 282 to 643 HU values. Field size, depth, beam energy, and material density influenced the dose difference between two algorithms.}

12 illus, 24 ref

015093   Maheshwari R K;Pandey L;Shah A P;Tiwari S P (Pharmacy Dep, Shri G S Institute of Technology and Science, Indore-452 003) : Solid as solvent- novel spectrophotometric quantitative analysis of ornidazole tablets using solids (eutetic liquid of phenol and lignocaine hydrochloride) as solubilizing agents (mixed solvency concept). Pharma Innovation 2016, 5(3), 26-7.

Pollution and toxicity caused by most of the organic solvents is a big challenge. The researchers are doing much work to give eco-friendly solutions for this challenge. The present investigation is an attempt to show that solids can also be wisely used to act as solvent precluding the use of organic solvents. The main objective of the present study is to demonstrate the solvent action of solids. In the present study, a eutectic liquid (PL-41) obtained by triturating phenol crystals and lignocaine hydrochloride in 4:1 ratio on weight basis was employed to extract (dissolve) ornidazole drug from fine powder of its tablets. Distilled water was used for dilution to carry out spectrophotometric estimation at 319 nm without the help of organic solvent. The solubility of ornidazole in distilled water at room temperature was found to be 8.03mg/ml. The solubility of the same drug in PL-41was more than 150 mg per ml (of PL-41). Proposed spectrophotometric analytical method is novel, rapid, free from toxicity of organic solvent, accurate and reproducible. Recovery studies and statistical data proved the accuracy, reproducibility and precision of the proposed method. The presence of tablet excipients, phenol and lignocaine hydrochloride did not interfere in the spectrophotometric estimation at 319 nm. Phenol does not interfere above 300 nm and lignocaine hydrochloride does not interfere above 310 nm.

2 tables, 6 ref

015092   Liu J M;Liang H W;Zhang M;Su H (College of Electronic Science and Technology, Shenzhen Univ, Shenzhen 518060, China, Email: hwliang@szu.edu.cn) : Coupling of sommerfeld waves using odd TM mode of double-dielectric-slab waveguide. J Optics 2015, 44(1), 53-8.

Authors report the coupling of cylindrical metal wire THz surface plasmon-polaritons using odd TM mode of double-dielectric-slab waveguide. We analyze the mode matching issue. We calculate the coupling efficiency of the double-dielectric-slab waveguide to copper wire of 1 mm diameter with respect to waveguide structure, beam structure and the THz frequency, theoretically. It is concluded that at 4.2 THz the highest coupling efficiency achieved to be is 43.5%. We further show the coupling experimental system.

10 illus, 29 ref

015091   Li Y;Zhu L;Chen T (School of Transportation, Wuhan Univ of Technology, Wuhan-430 070, People's Republic of China, Email: liyinggang@whut.edu.in) : Large band gaps in two-dimensional phononic crystal with jerusalem cross slot structures. Indian J pure appl Phys 2015, 53(12), 813-18.

Band gap properties in a novel two-dimensional phononic crystal with Jerusalem cross slot structures have been investigated theoretically in the present paper. The dispersion relations, the power transmission spectra and the displacement fields of the eigenmodes are calculated by using the finite element method. Numerical results show that the proposed structures with periodic Jerusalem cross slots can yield large band gaps in the low-frequency range as compared to the typical phononic crystals composed of periodic square rods embedded in a homogenous matrix. The formation mechanisms of the large low-frequency band gaps as well as the effects of the geometrical parameters on the band gaps are further explored numerically. Results show that the openings of the low-frequency band gaps are mainly attributed to the interaction between the local resonances of the square scatterers with Jerusalem cross slot structures and the traveling wave modes in the matrix. The band gaps can be significantly modulated by changing the geometrical parameters of Jerusalem cross slot structures.

7 illus, 25 ref

015090   Johnson D;Chen Y;Ahmad S (Radiation Onconlogy Dep, Peggy and Charles Stephenson Cancer Centre, The Univ of Oklahoma Healt, Oklahoma-73104, USA, Email: salahuddin-ahmad@ouhsc.edu) : Dose and linear energy transfer distributions of primary and secondary particles in carbon ion radiation therapy: A monte carlo simulation study in water. J med Phys 2015, 40(4), 214-19.

The factors influencing carbon ion therapy can be predicted from accurate knowledge about the production of secondary particles from the interaction of carbon ions in water/tissue-like materials, and subsequently the interaction of the secondary particles in the same materials. The secondary particles may have linear energy transfer (LET) values that potentially increase the relative biological effectiveness of the beam. Our primary objective in this study was to classify and quantify the secondary particles produced, their dose averaged LETs, and their dose contributions in the absorbing material. A 1 mm diameter carbon ion pencil beam with energies per nucleon of 155, 262, and 369 MeV was used in a geometry and tracking 4 Monte Carlo simulation to interact in a 27 L water phantom containing 3000 rectangular detector voxels. The dose-averaged LET and the dose contributions of primary and secondary particles were calculated from the simulation. The results of the simulations show that the secondary particles that contributed a major dose component had LETs <60>100 keV/μm. The secondary particles with LETs <62>600 keV/μm contributed only <60>0.3% of the dose.

4 illus, 4 tables, 16 ref

015089   Jananakumar D;Mani P (Physics Dep, Velalar College of Engineering and Technology, Erode-638 012, Email: deepaavanthikaa@yahoo.co.in) : Some amino acid based non-linear optical materials. Indian J pure appl Phys 2015, 53(12), 819-26.

Non-linear optical (NLO) single crystals of L-valine l-valinium orthophosphate (LVP) and L-valine l-valinium nitrate (LVN) were grown by slow evaporation solution growth method using water as the solvent at room temperature. Purity of the crystals was increased by the method of recrystallization. The cell parameters of LVP and LVN were determined using single crystal X-ray diffraction technique. The grown crystals were characterized by measuring their thermal, optical and mechanical properties by Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TGA), Powder Second Harmonic Generation (SHG) efficiency, FTIR, UV-VIS NIR, damage threshold and microhardness measurements. The dielectric constant and dielectric loss of the crystals have been studied as a function of frequency at room temperature. Our studies showed that L-valine inorganic acids emerged as most promising NLO materials having SHG efficiency, mechanical and thermal stability greater than other semi-organic NLO materials.

10 illus, 3 tables, 23 ref

015088   Jain V;Soni K K;Maheshwari K P;Malav H;Jaiman N K (Pure & Applied Physics Dep, Kota Univ, Kota-324 010, Email: k_p_maheshwari@rediffamil.com) : Effect of laser-pulse-shape on the transference of laser energy into the energy of fast ions in radiation pressure dominant regime. Indian J pure appl Phys 2015, 53(12), 785-9.

Effect of laser-pulse temporal-profile on the transference of laser energy into the energy of fast ions when the radiation pressure is dominant, has been studied. The laser temporal profiles considered are Lorentzian, hyperbolic secant, and Gaussian. The numerical results are compared for different temporal profile of the laser pulse. It is found that the Lorenztian pulse is more effective to impart kinetic energy to the ions in comparison to Gaussian or hyperbolic secant laser pulse.

5 illus, 15 ref

015087   Hoshoudy G A (Applied Mathematics and Computer Science Dep, Faculty of Science, South valley Univ, Kena-83523, Egypt, Email: g_hoshoudy@yahoo.com) : Parabola instability fo Rayleigh-Taylor instability in quantum magnetized plasmas. Indian J pure appl Phys 2015, 53(11), 740-7.

Quantum effects on the Rayleigh-Taylor instability in an inhomogeneous stratified incompressible plasma layer have been investigated. The combined effect of horizontal and vertical magnetic field has been taken into account. The solution of the linearized equations of the system together with the boundary conditions leads to derive the dispersion relation. The behaviour of growth rates with respect to the quantum effects beside the combined effect of magnetic field components has been analyzed. The results show that the growth rate depends on the λ*=λL (λ and L_D are constants). The square normalized growth rate as a function λ* describes in a parabola equation formula, where the maximum instability happens at λ*=-0.5.

3 illus, 21 ref

015086   Habubi N F;Ismail R A;Abd A N;Hamoudi W K (Physics Dep, Faculty of Education, Univ of Al-Mustansiriyah, Baghdad, Iraq, Email: raidismail@yahoo.com) : Improved photoresponse of porous silicon photodetectors by embedding CdSe nanoparticles. Indian J pure appl Phys 2015, 53(11), 718-24.

Paper presents the effect of incorporating colloidal cadmium selenide nanoparticles on the characteristics of porous silicon Al/porous Si/p-Si photodetectors prepared with 7 mA/cm^{2 electrochemical etching for 15 min. The spherical cadmium selenide nanoparticles of size 35-60 nm, synthesized by laser ablation in methanol, had covered the pore walls of porous silicon matrix. Structural, morphological and optical properties of porous silicon and cadmium selenide nanoparticles were characterized by X-ray diffraction, photo-luminescence, Fourier transformation infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy and UV-Vis spectrophotometer. Electrical and photosensitivity of porous silicon photodetectors have been investigated before and after the embedding of cadmium selenide nanoparticles. The ideality factor of porous silicon has decreased after the incorporation of cadmium selenide nanoparticles in porous silicon. Photodetector sensitivity has increased from 0.5 to 0.8 A/W at 800 nm after embedding CdSe NPs in silicon pores.}

18 illus, 31 ref

015085   Didi S;Moussa A;Yahya T;Mustafa Z (Physics Dep, Laboratory of Physics of Radiation and Matter, Faculty of Sciences, Un, Morocco, Email: tayalati@cern.ch) : Simulation of the 6 MV elekta synergy platform linac photon beam using geant4 application for tomographic emission. J med Phys 2015, 40(3), 136-43.

Present work validates the Geant4 Application for Tomographic Emission Monte Carlo software for the simulation of a 6 MV photon beam given by Elekta Synergy Platform medical linear accelerator treatment head. The simulation includes the major components of the linear accelerator (LINAC) with multi-leaf collimator and a homogeneous water phantom. Calculations were performed for the photon beam with several treatment field sizes ranging from 5 cm x 5 cm to 30 cm x 30 cm at 100 cm distance from the source. The simulation was successfully validated by comparison with experimental distributions. Good agreement between simulations and measurements was observed, with dose differences of about 0.02% and 2.5% for depth doses and lateral dose profiles, respectively. This agreement was also emphasized by the Kolmogorov-Smirnov goodness-of-fit test and by the gamma-index comparisons where more than 99% of the points for all simulations fulfill the quality assurance criteria of 2 mm/2%.

4 illus, 6 tables, 44 ref

015084   Chattopadhyay S (NO, Variable Energy Cyclotron Centre, 1/AF Bidhannagar, Kolkata-700 064) : Facility for antiproton and ion research (Fair): India's participation. Sci Cult 2015, 81(9-10), 265-8.

India is having a significant participation in building and use of the upcoming accelerator facility known as FAIR in Darmstadt, Germany. FAIR will have provision to perform experiments in atomic physics, plasma physics, hadron structure physics and high-energy nuclear physics. India is contributing in building major accelerator items like power converter, vacuum chambers and is taking part in major experiments like NUSTAR and CBM. Key features of Indian contribution in the FAIR project have been discussed.

4 illus, 2 ref

015083   Bhatt K;Tripathi C C (Electronics and Communication Engineering Dep, Univ Institute of Engineering and Technology, Kurukshetra Univ, Kurukshetra, Email: rai1kapil@gmail.com) : Comparative analysis of efficient diode design for terahertz wireless power transmission system. Indian J pure appl Phys 2015, 53(12), 827-36.

Wireless power transmission (WPT) technology is an extension of wireless communication. The physics of WPT and wireless communication are related, but WPT is distinct from wireless transmission for transferring information (such as radio and mobile phones etc.), where the percentage of the power that is received is only important if it becomes too low to successfully recover the signal. With WPT, the efficiency is a more critical parameter and this creates important differences in these technologies. This paper presents the wireless power transmission (WPT), from past work to most recent accomplishments including recent developments, potential approaches and factors responsible for designing most critical rectifying diodes operating at terahertz/petahertz frequencies.

14 illus, 37 ref

014098   Zhang S;Wang Di (School Of Mathematics and Physics, Bohai Univ, Jinzhou-121 013) : Variable-coefficient nonisospectral Toda lattice hierarchy and its exact solutions. Pramana J Phys 2015, 85(6), 1143-56.

In this paper, a hierarchy of nonisospectral equations with variable coefficients is derived from the compatibility condition of Toda spectral problem and its time evolution. In order to solve the derived Toda lattice hierarchy, the inverse scattering transformation is utilized. As a result, new and more general exact solutions are obtained. It is shown that the inverse scattering transformation can be generalized to solve some other nonisospectral lattice hierarchies with variable coefficients.

33 ref

014097   Vishwakarma R G (Unidad Academica de Matematicas, Universidad Autonoma de Zacatecas, C.P. 98068, Zacatecas, ZAC, Mexico, Email: vishwa@uaz.edu.mx) : A new solution of Einstein's vacuum field equations. Pramana J Phys 2015, 85(6), 1101-10.

A new solution of Einstein's vacuum field equations is discovered which appears as a generalization of the well-known Ozsvath-Schucking solution and explains its source of curvature which has otherwise remained hidden. Curiously, the new solution has a vanishing Kretschmann scalar and is singularity-free despite being curved. The discovery of the new solution is facilitated by a new insight which reveals that it is always possible to define the source of curvature in a vacuum solution in terms of some dimensional parameters. As the parameters vanish, so does the curvature. The new insight also helps to make the vacuum solutions the Machian solutions.

11 ref

014096   Shayesteh S F;Saie M (Physics Dep, Guilan Univ, Rasht, Guilan 4193833697, Iran, Email: saber@guilan.ac.ir) : Effect of surface plasmon resonance on optical response in dielectric (core)-metal (shell) nanoparticles. Pramana J Phys 2015, 85(6), 1245-55.

In this work, we present the effect of refractive index of an embedding medium, core and shell having various sizes of metallic nanoshells on the surface plasmon resonance (SPR) properties in the spherical dielectric-metal core-shell nanoparticles based on the quasistatic approaches and Mie theory. For the metallic nanoshell with dimensions comparable to the wavelength of light, the quasistatic approximation shows good agreement with the Mie theory results. However, for large nanoparticles the quasistatic approximation is not appropriate and Mie theory illustrates SPR due to dipole and quadrupole in extinction cross-section. The typical cross-section calculations show two peaks that related to inner and outer surfaces. The dimensional dependence of optical constant in the Drude model leads to a decrease in plasma absorption in metal core-shell. By increasing the shell radius and therefore increasing the metal content the SPR at the outer surface shifts to higher energy and the weaker peak (at inner surface) shifts to lower energy. Also, depending on the metal shell materials SPR occurs in different energy regions and therefore can be tuned the SP frequency at higher energy by changing the shell materials. In addition, SPR frequency is sensitive to variation in refractive index of the environment of core-shell.

6 illus, 1 table,33 ref

014095   Sharma P P D;Sarkar D (Physics Dep, Gauhati Univ, Guwahati-781 028, Email: sarkardeepali@gmail.com) : Bile salt incorporated polypyrrole thin film for ethanol sensing. Indian J Biochem Biophys 2015, 52(2), 203-8.

Polypyrrole (PPy)-bile salt composite was used for sensing ethanol vapour. PPy was synthesized by interface polymerization for subsequent fabrication of thin film of its composite with bile salt, by in-situ co-dispersion method and then exposed to ethanol vapour. Sensing was visualized through changes in morphological, structural and optical characterizations. The ethanol exposed film showed larger agglomeration as revealed in its surface morphology on scanning electron microscope (SEM) and greater crystallinity as seen through X-Ray diffraction (XRD). Fourier transform infra red (FTIR) and nuclear magnetic resonance spectroscopy (NMR) of the ethanol incorporated film also gave signature of the presence of bile salt and alcohol. Alcohol incorporation pattern resulted in increase in electrical conductance from 7.08539 x 10^{-5 mA/V to 8.0356 x 10-5 mA/V, as determined from current voltage characterizations. Average molecular weight (M_n) obtained from gel permeation chromatography changed from 6160 to 10300 on ethanol intake. Photoluminescence (PL) intensity was quenched and the PL peak shifted from 430 to 409 on ethanol exposure. Changes in morphological, structural, optical and electrical properties of the composite on ethanol exposure showed its prospective application for sensing ethanol.}

6 illus, 32 ref

014094   Rajeev Kumar;Gupta R K;Bhatia S S (Mathematics Dep, Maharishi Markandeshwar Univ, Mullana, Ambala-133 001, Email: rajeevkumarbudhiraja@gmail.com) : Painleve analysis and some solutions of variable coefficient Benny equation. Pramana J Phys 2015, 85(6), 1111-22.

In this paper, variable coefficient Benny equation (also called the KdV Burgers-Kuramoto equation) has been considered. By using the Painleve analysis and Lie group analysis methods, the Painleve properties and symmetries have been studied. Some solutions of the reduced ODEs are obtained.

2 illus, 31 ref

014093   Mukherjee J K (Electronics and Instrumentation Services Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: jkmukh@yahoo.co.uk) : Physics-based vicinity emulation for enhanced perception in teleoperation. Pramana J Phys 2015, 85(6), 1157-80.

A workspace modelling technique, that achieves real-time detection of closeness of robot to workspace object, has been developed by additional physics attribute attachment to workspace. Physics phenomena suiting the realistic work conditions have been identified and a computational model for emulating the phenomenon has been developed. Need for building sensitivity to dynamics in the model has also been addressed. Model building and algorithms for embedding the model in workspace comprising complex object shapes have been studied in detail. Applications like fast execution in real-time scenarios, design of data structure for realistic implementation and the problem of attaining functionality without new sensor addition to telerobots working in radioactive environment are addressed.

34 illus, 2 tables, 36 ref

014092   Liu C;Li Y Y;Gao M;Wang Z;Dai Z;Wang C (School of Mathematics, Wenshan Univ, Wenshan, 663000, People's Republic of China, Email: chfuliu@163.com) : Rogue wave solutions of the nonlinear Schrodinger equation with variable coefficients. Pramana J Phys 2015, 85(6), 1063-72.

In this paper, a unified formula of a series of rogue wave solutions for the standard (1+1)-dimensional nonlinear Schrodinger equation is obtained through exp-function method. Further, by means of an appropriate transformation and previously obtained solutions, rogue wave solutions of the variable coefficient Schrodinger equation are also obtained. Two free functions of time t and several arbitrary parameters are involved to generate a large number of wave structures.

5 illus, 38 ref

014091   Lin Q;Wu X;Chen Y (College of Electronic Engineering, Naval Univ of Engineering, Wuhan-430 033, People's Republic of China, Email: linqian19825@gmail.com) : Frequency-domain criterion for the chaos synchronization of time-delay power systems under linear feedback control. Pramana J Phys 2015, 85(6), 1131-42.

This paper studies the global synchronization of non-autonomous, time-delay, chaotic power systems via linear state-error feedback control. The frequency domain criterion and the LMI criterion are proposed and applied to design the coupling matrix. Some algebraic criteria via a single-variable linear coupling are derived and formulated in simple algebraic inequalities. The effectiveness of the new criteria is illustrated with numerical examples.

2 illus, 14 ref

014090   Khan M Z;Lim L K;Yap S L;Wong C S (Physics Dep, Plasma Technology Research Centre, Faculty of Science, Malaya Univ, 50603 Kuala Lumpur, Malaysia, Email: mzubairkhan_um76@yahoo.com) : Imperative functions of electron beams in low-energy plasma focus device. Pramana J Phys 2015, 85(6), 1207-19.

A 2.2 kJ plasma focus device was analysed as an electron beam and an X-ray source that operates with argon gas refilled at a specific pressure. Time-resolved X-ray signals were observed using an array of PIN diode detectors, and the electron beam energy was detected using a scintillator-assisted photomultiplier tube. The resultant X-rays were investigated by plasma focus discharge for pressures ranging from 1.5 mbar to 2.0 mbar. This range corresponded to the significant values of X-ray yields and electron beam energies from the argon plasma. The electron temperature of argon plasma at an optimum pressure range was achieved by an indirect method using five-channel BPX65 PIN diodes of aluminum foils with different thicknesses. X-ray yield, electron beam energy, and electron temperature of argon plasma were achieved at 1.5-2.0 mbar because of the strong bombardment of the energetic electron beam.

14 illus, 2 tables, 32 ref

014089   Jena S;Ghodke A D (Indus Operations and Accelerator Physics Design Div, Raja Ramanna Centre For Advanced Technology, Indore-452 013) : Observation and mitigation of ion trapping in Indus-2. Pramana J Phys 2015, 85(6), 1193-1205.

The presence of trapped ions in electron storage rings causes considerable degradation in the performances of the beam, such as increase in beam size, reduction in beam lifetime, shifting of betatron tune, beam instabilities etc. This paper discusses the effects of ion trapping and its mitigation in Indus-2 electron storage ring. Ion-induced instability generating partial beam loss is one of the main barriers in higher beam current accumulation in any electron storage ring. Though there are several techniques to clear the ions from the electron beam path, in Indus-2, it is addressed mainly by filling the storage ring in partial bunch filling pattern. In order to improve the electron beam performance and to mitigate the ion-related problem, a suitable bunch filling pattern has been determined. The theoretical prediction and the result of optimal bunch filling pattern are presented in this paper.

8 illus, 2 tables, 15 ref

014088   Jena K;Swain R;Lenka T R (Electronics and Communication Engineering Dep, National Institute of Technology, Silchar-788 010, Email: trlenka@gmail.com) : Impact of oxide thickness on gate capacitance-Modelling and comparative analysis of GaN-based MOSHEMTs. Pramana J Phys 2015, 85(6), 1221-32.

In this paper, we have developed a mathematical model to predict the behaviour of gate capacitance and threshold voltage with nanoscale variation of oxide thickness in AlInN/GaN and AlGaN/GaN metal oxide semiconductor high electron mobility transistor (MOSHEMT). The results obtained from the model are compared with the TCAD simulation results to validate the model. It is observed that AlInN/GaN MOSHEMT has an advantage of significant decrease in gate capacitance up to 0.0079 pF/μm^{2 with increase in oxide thickness up to 5 nm as compared to conventional AlGaN/GaN MOSHEMT. This decrease in gate capacitance in AlInN/GaN MOSHEMT reduces the propagation delay and hence improves the RF performance of the device.}

10 illus, 2 tables, 15 ref

014087   Eslamizadeh H (Physics Dep, Persian Gulf Univ, 75069 Bushehr, Iran, Email: m_eslamizadeh@yahoo.com) : Fission anisotropy of <. Pramana J Phys 2015, 85(6), 1181-91.

The anisotropy of fission fragment angular distribution, evaporation residue crosssection and the fission cross-section were calculated for ^{197Tl formed in 16O+181Ta reactions in the framework of the modified statistical model and the results were compared with the experimental data. The effects of temperature and projection of spin about the symmetry axis K have been considered for calculating potential energy surfaces and fission widths. It was shown that in the framework of the modified statistical model, by choosing appropriate values for the temperature coefficient of the effective potential, α, and scaling factor of the fission-barrier height, r_s, one can satisfactorily reproduce the above-mentioned experimental data. It was also shown that the appropriate values of these parameters for 197Tl are α = 0.0185 ± 0.0050 MeV-2 and r_s = 1.0006 ± 0.0020.}

6 illus, 48 ref

014086   Campos D (NO, , Academia Colombiana De Ciencias Exactas, Fisicas Y Naturales, ACCEFYN, Bogota, Colombia, Email: dcamposr@cable.net.co) : On the discretization of probability density functions and the continuous Renyi entropy. Pramana J Phys 2015, 85(6), 1073-87.

On the basis of second mean-value theorem (SMVT) for integrals, a discretization method is proposed with the aim of representing the expectation value of a function with respect to a probability density function in terms of the discrete probability theory. This approach is applied to the continuous Renyi entropy, and it is established that a discrete probability distribution can be associated to it in a very natural way. The probability density functions for the linear superposition of two coherent states is used for developing a representative example.

5 illus, 2 tables, 20 ref

014085   Banerjee N;Sen S (Physical Science Dep, Indian Institute of Science Education and Research- Kolkata, Mohanpur Campus-741 252, Email: narayan@iiserkol.ac.in) : Towards a characterization of fields leading to black hole hair. Pramana J Phys 2015, 85(6), 1123-9.

In the present work, it is shown that an asymptotically flat spherical black hole can have a nontrivial signature of any field, for an exterior observer, if the energy-momentum tensor of the corresponding field is either trace-free or if the trace falls off at least as rapidly as the inverse cube of the radial distance. In the absence of a general `No Hair Theorem', this result can provide a characterization of the fields leading to a black hole hair.

20 ref

014084   Asomba G C;Abah O;Ogbuu O A;Okoye C M I (Physics and Astronomy Dep, Nigeria Univ, Nsukka, Nigeria, Email: abahobinna@gmail.com) : Analysis of the superconductivity in Perovskite oxides using three-square-well BCS formalism. Pramana J Phys 2015, 85(6), 1233-44.

Superconductivity in perovskite, BaKBiO, is studied in the Bardeen-Cooper-Schrieffer (BCS) model, with three-square-well potentials. Components of the new coupling are: the attractive acoustic phonon-electron, optical phonon-electron and repulsive Coulomb interactions. With these in the BCS pairing Hamiltonian, expressions for the superconducting transition temperature and isotope effect exponent are obtained. Results of our analysis are consistent with experiments. Contributions of interactions to system properties are exhibited and analysed. Acoustic phonon-electron and optical phonon-electron interactions have near-identical elevation of transition temperature, holding out possible explanations for high-T_c. Contrastingly, optical phonon-electron and Coulomb couplings cause debilitation of isotope exponent, a possible explanation for low isotope exponent in the cuprates and other high-T_c systems. It is found that BCS electron-phonon coupling appears synonymous with acoustic phonon-electron coupling.

4 illus, 66 ref

014083   Abdel Khalek S;Halawani S H A (Mathematics Dep, Faculty of Science, Taif Univ, Taif, Saudi Arabi, Email: sayedquantum@yahoo.co.uk) : Dynamical properties of moving atom-atom entanglement and entanglement between two atoms with optical field. Pramana J Phys 2015, 85(6), 1089-99.

Quantum information technology largely relies on a sophisticated and fragile resource, called quantum entanglement, which exhibits a highly nontrivial manifestation of the coherent superposition of the states of composite quantum systems. In this paper, we study the interaction between the general and even coherent fields with moving and stationary two two-level atoms. In this regard, this paper investigates the von Neumann entropy and the atoms-field tangle as a measure of entanglement between the general and even coherent fields with the two atoms. Also, the entanglement between the two atoms using concurrence and negativity during time evolution is discussed. This paper examines the effects of multiphoton transitions and initial state setting on the entanglement for the system under consideration. Finally, the results demonstrate an important phenomenon such as the sudden death and birth of entanglement when the two atoms are initially in entangled states.

4 illus, 30 ref

013082   Wang R F (Physics Dep, Beijing Jiotong Univ, 100044, Beijing, China) : Experimental scheme to precisely measure the magnetic penetration depth of a superconducting film. Indian J pure appl Phys 2015, 53(10), 681-5.

Penetration depth is an important parameter of superconductors, but its absolute value is difficult to measure without a special device. By introducing the modern microfabrication technology, this paper proposes a new experimental scheme to measure the susceptibility of a superconducting film. By this new method, the absolute value of the penetration depth can be determined with satisfactory accuracy. The accuracy was estimated from the measurement error of the experimental scheme. This method should be useful for investigating the pairing mechanisms of superconductors by measuring the temperature dependence of the penetration depth.

2 illus, 1 table, 11 ref

013081   Vijayan P K;Basak A;Dulera I V;Vaze K K;Basu S;Sinha R K (Reactor Engineering Div, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085, Email: vijayanp@barc.gov.in) : Conceptual design of Indian Molten Salt Breeder Reactor. Pramana J Phys 2015, 85(3), 539-54.

The third stage of Indian nuclear power programme envisages the use of thorium as the fertile material with ^{233U, which would be obtained from the operation of Pu/Th based fast reactors in the later part of the second stage. Thorium-based reactors have been designed in many configurations, from light water-cooled designs to high-temperature liquid metal-cooled options. Another option, which holds promise, is the molten salt-fuelled reactor, which can be configured to give significant breeding ratios. A crucial part for achieving reasonable breeding in such reactors is the need to reprocess the salt continuously, either online or in batch mode. India has recently started carrying out fundamental studies so as to arrive at a conceptual design of Indian molten salt breeder reactor (IMSBR). Presently, various design options and possibilities are being studied from the point of view of reactor physics and thermal hydraulic design. In parallel, fundamental studies on natural circulation and corrosion behaviour of various molten salts have also been initiated.}

10 illus, 3 tables, 21 ref

013080   Thoennessen M (National Superconducting Cyclotron Laboratory and Dep of Physics and A, Michigan State Univ, East Lansing, MI 48824, USA, Email: thoennessen@nscl.msu.edu) : Discoveries of isotopes by fission. Pramana J Phys 2015, 85(3), 457-66.

Of the about 3000 isotopes presently known, about 20% have been discovered in fission. The history of fission as it relates to the discovery of isotopes as well as the various reaction mechanisms leading to isotope discoveries involving fission are presented.

3 illus, 1 table, 60 ref

013079   Tandel S K (NO, UM-DAE Centre for Excellence in Basic Sciences, Mumbai-40 098, Email: sujit.tandel@cbs.ac.in ) : Spectroscopy of heavy fissionable nuclei. Pramana J Phys 2015, 85(3), 385-94.

Structural studies of heavy nuclei are quite challenging due to increased competition from fission, particularly at high spins. Nuclei in the actinide region exhibit a variety of interesting phenomena. Recent advances in instrumentation and analysis techniques have made feasible sensitive measurements of nuclei populated with quite low cross-sections. These include K isomers and rotational band structures in isotopes of Pu (Z = 94) to Rf (Z = 104), and octupole correlations in the Th (Z = 90) region. The obtained experimental data have provided insights on various aspects like moments of inertia and nucleon alignments at high spins, quasiparticle energies and evolution of quadrupole and octupole collectivity, among others. An overview of some of these results is presented.

6 illus, 26 ref

013078   Su X (School of Mathematics and Physics, North China Electric Power Univ, Baoding-071 003, China, Email: suxh2005@163.com) : Analytical computation of unsteady MHD mixed convective heat transfer over a vertical stretching plate wih partial slip conditions. Indian J pure appl Phys 2015, 53(10), 643-51.

Analysis of the unsteady MHD mixed convective flow and heat transfer over an impulsively stretched permeable vertical surface in a moving fluid with partial velocity slip and thermal slip conditions in the presence of thermal radiation, internal heat absorption or generation, and injection or suction, has been studied in the present paper. The governing boundary layer equations are converted into a system of nonlinear coupled ordinary differential equations by suitable similarity transformations. The appropriate analytical solutions for the velocity and temperature fields are gotten by the DTM-BF which is an analytical method based on the differential transformation method (DTM) and basis functions. The results obtained by the DTM-BF are in good agreement with those presented by the numerical method. The effects of the various parameters which determine the velocity and temperature fields are shown by plotting graphs and discussed in detail.

12 illus, 31 ref

013077   Sonawane M S;Shinde M S;Patil R S (Physics Dep, P S G V P M'S Arts, Science & Commerce College, Shahada, Nandurbar-425 409, Email: rspatil-shahada@yahoo.co.in) : Chracterization of nickel sulphide thin films prepared by modified chemical method. Indian J pure appl Phys 2015, 53(10), 686-90.

Semiconducting nickel sulphide (NiS) thin films were deposited onto glass substrates using a new modified chemical bath method (MCBD). The MCBD is the solutions grow technique in which substrates are immersed in cations and anions alternatively and film growth takes place on the substrates. The preparative conditions such as concentration, pH, temperature, immersion time, immersion cycles, etc are optimized to get nanocrystalline NiS films. The characterization of the films was carried out by using X-ray diffraction, scanning electron microscopy, optical absorption and electrical resistivity. The XRD analysis of the as-grown NiS films showed hexagonal structure. The average grain size is found to be 14 nm. Electrical resistivity measurements showed semiconducting nature with at room temperature resistivity which is found to be of the order of 10 Ωcm for as-deposited NiS films. Scanning electron micrographs (SEM) reveal a very dense surface structure with the presence of irregular shaped grain particles of size <126>200 nm. The optical absorption studies show that the absorption coefficient of the NiS thin film is high and a direct band gap of <126>2.4 eV has been observed.

5 illus, 15 ref

013076   Singh O P;Muhunthan N;Singh V N (NO, Acadamy of Scientific and Innovative Research (AcSIR), New Delhi-110 012, Email: singhvn@nplindi.org) : Investigation of Cu₂ZnSnS₄ thin film by scanning Kelvin force microscopy. Indian J pure appl Phys 2015, 53(10), 691-5.

CZTS thin film has been grown on Mo-coated soda lime glass by co-sputtering the metal targets and post sulfurization in H₂S ambient. The structural, microstructural, compositional and optical properties have been studied using glancing incidence XRD, Raman spectroscopy, SEM, EDS, XRF and UV-Vis spectrophotometry. Local electrical transport measurements using conducting AFM show that for small bias voltage (-0.5 V), the dark negative currents flow mainly through grain boundaries (GBs) rather than grain interior. Kelvin probe force microscopic measurements (local surface potential) indicated positive surface potential in the vicinity of GBs in a Cu-deficient CZTS thin film. All measurements indicated that grain interior to GBs have a smaller effective band gap than the bulk, due to the composition change (Cu-vacancies or Cu_Zn anti site defects) at GBs. Electrical measurement revealed the presence of defects in the CZTS thin film.

4 illus, 28 ref

013075   Sharma M;Gurvinder K (School of Physics and Materials Science, Thapar Univ, Patiala-147 004) : Cluster decay analysis and related structure effects of fissionable heavy and superheavy nuclei. Pramana J Phys 2015, 85(3), 431-7.

Collective clusterization approach of dynamical cluster decay model (DCM) has been applied to study the attributes of hot (T ≠ 0) and rotating (l ≠ 0) nuclei lying in heavy and superheavy mass regimes. We present here an overview of the characteristic fission decay properties such as shell effect, role of entrance channel, quadrupole (β₂) deformations and impact of hot (equatorial) compact orientation degree of freedom in comparison to cold (polar) elongated configuration. The presence of non-compound nucleus process, i.e., quasifission, is also investigated. Apart from studying the decay of excited state nuclei, the dynamics of heavy particle cluster emission is also addressed using the preformed cluster model (PCM).

3 illus, 3 tables, 12 ref

013074   Sarkar M S;Sarkar S (NO, Saha Institute of Nuclear Physics, Didhan Nagar, Kolkata-700 064, Email: maitrayee.sahasarkar@saha.sc.in) : <. Pramana J Phys 2015, 85(3), 403-13.

New experimental data on 2^{+ energies of 136,138Sn confirm the trend of lower 2+ excitation energies of even-even tin isotopes with N<62>82 compared to those with N<60>82. However, none of the theoretical predictions using both realistic and empirical interactions can reproduce experimental data on excitation energies as well as the transition probabilities (B(E2;6+ → 4+) of these nuclei, simultaneously, apart from the ones whose matrix elements have been changed empirically to produce mixed seniority states by weakening the pairing. We have shown that the experimental result also shows good agreement with the theory in which three-body forces have been included in a realistic interaction. The new theoretical results on transition probabilities are discussed to identify the experimental quantities which will clearly distinguish between different views.}

6 illus, 1 table, 22 ref

013073   Santhosh K P (School of Pure and Applied Physics, Kannur Univ, Swami Anandatheertha Campus, Payyanur-670 927, Email: drkpsanthosh@gmail.com) : Superheavy elements and decay properties. Pramana J Phys 2015, 85(3), 447-55.

α decay properties of the isotopes of Z = 115, 117, 118 and 119 have been extensively investigated, focussing on the newly synthesized isotopes within the Coulomb and proximity potential model for deformed nuclei (CPPMDN). The α half-lives have also been evaluated using the Viola-Seaborg systematic (VSS) and the analytical formulae of Royer and it can be seen that our calculated values match well with these theoretical values. The mode of decay of these isotopes has also been studied by calculating the spontaneous fission half-lives. Thus, we have predicted 4α chains from ^{287115, 3α chains from 288115, 3α chains from 293117, 4 α chains from 294117 and 3α chains from 294118 and, it can be seen that our predictions on the a decay chains also match well with the experimental observations. The study on Z = 119 has predicted six consistent α chains from 292-295119, 5 α chains from 296119, 4 α chains from 297119 and 3α chains from 298,299119. Thus, through our study on isotopes of Z = 115, 117, 118 and 119 superheavy nuclei, we could predict the range of isotopes that may be detectable using α decay and we hope that the findings on the isotopes of Z = 119 will provide a new guide for future experiments.}

1 illus, 1 tables, 47 ref

013072   Sane M;Barro F I (Semiconductors and Solar Energy Laboratory, Faculty of Science and Technique, Cheikh Anta Diop Univ, BP5005, Dakar, Senegal, Email: moustaphasane2003@yahoo.fr) : Effect of both magnetic field and doping density on series and shunt resistanses under frequency modulation. Indian J pure appl Phys 2015, 53(9), 590-5.

Solar cells are aggregated in series and parallel combination into an array to produce desired voltage and power levels. In the present study, a new method has been investigated to study the electrical parameters of solar cell. Both the photocurrent density and photovoltage have been derived from continuity equation. The effects of both applied magnetic field and doping density on these electrical parameters have been studied.

7 illus, 1 table, 18 ref

013071   Salem A;Ahmed S S;Alamri S N (Physics Dep, Faculty of Science, South Valley Univ, Qena, Egypt, Email: salembouewafa@yahoo.co.uk) : Structural and optical properties of nanocrystalline tin sulphide thin films deposited by thermal evaporation. Indian J pure appl Phys 2015, 53(10), 696-700.

Thermal evaporation technique was used to fabricate the nanocrystalline tin sulphide (SbS) thin films of thicknesses 200 and 377 nm on good quality glass substrate. The various physical properties of deposited thin films have been investigated using X-ray diffraction (XRD), Atomic force microscopy (AFM), and ultraviolet-visible-near infrared spectroscopy at room temperature. X-ray diffraction analysis confirmed the orthorhombic phase of SnS films and the calculated lattice parameters have been calculated. The grain size, dislocation density and micro strain have been calculated using X-ray data. The result from AFM analysis shows that the surface of films was compact, dense and smooth. The optical band gap and types of transitions involved in the absorption process have been investigated. For allowed direct and indirect transition, the band gap values varied in the range 1.96-1.72 eV and 1.58-0.92 eV, respectively. The deduced values of the band gap suggest that the deposited thin films can be used in the fabrication of solar cell devices.

6 illus, 1 table, 22 ref

013070   Razak N F;Ahmad H;Zulkifli M Z;Muhammad F D; Munajat Y;Harun S W (Physics Dep, Advanced Photonics Sciences Institute, Faculty of Science, Univ Techno, 81310 Skudai, Johor, Malaysia, Email: nfarhah89@gmail.com) : Single mode EDF fiber laser using an ultra-narow bandwidth tunable optical filter. Indian J pure appl Phys 2015, 53(9), 579-84.

Single longitudinal mode (SLM) erbium-doped fiber (EDF) laser operation using a commercialized ultra-narrow bandwidth optical filter has been studied. A two-meter long EDF with an absorption coefficient of 24 dBm^{-1 at the pump wavelength is used as gain medium. The ultra-narrow tunable filter is used for selection of a single longitudinal mode from the available spectrum of multiple modes, which originally exists in the FBG's reflection spectrum. Our approach provides a relatively simple and direct method for the realization of SLM operation. A high-resolution optical spectral analyzer with a resolution of 0.16 pm, is used to observe the output spectrum. To verify the SLM operation, the delayed self-heterodyne method is used, giving a measured laser linewidth of 61.5 kHz.}

9 illus, 19 ref

013069   Poenaru D N;Gherghescu R A (NO, Horia Hulubei National Institute for Physics and Nuclear Engineering(I, P.O.Box MG-6, 077-125 Magurele-Bucharest, Romania, Email: poenaru@nipne.ro) : Fission approach to cluster radioactivity. Pramana J Phys 2015, 85(3), 415-21.

Fission theory is used to explain α decay. Also, the analytical superasymmetric fission (ASAF) model is successfully employed to make a systematic search and to predict, with other models, cluster radioactivity. The macroscopic-microscopic method is illustrated for the superheavy nucleus ^{286Fl. Then a few results of the theoretical approach of α decay (ASAF, UNIV and semFIS models), cluster decay (ASAF and UNIV) and spontaneous fission dynamics are described with Werner-Wheeler and cranking inertia. UNIV denotes universal curve and semFIS the fission-based semiempirical formula.}

2 illus, 2 tables, 47 ref

013068   Poddar G C;Asha Kumar;Das S;Srivastava D; Singh G S (NO, , CSIR-Central Scientific Instruments Organisation, Sector-30-C, Chandigarh-160 030, Email: gopal287@rediffmail.com) : Fiber optic extrinsic Fabry-perot interferometric sensor for high blast pressure measurement. Indian J pure appl Phys 2015, 53(9), 573-8.

Optical fiber based Extrinsic Fabry-Perot Interferometric (EFPI) sensor significantly emerged as an advanced optical sensor for the health monitoring of civil, mechanical and aeronautical structures. This sensor responds its well capability also towards the measurement of acoustic/shock wave pressure. This paper presents an approach for high blast (acoustic/shock wave) pressure measurement using low cost indigenous rugged type optical fiber EFPI sensor. Optical fiber EFPI sensor works on the two fundamental principles; Fresnel reflection and Fabry-Perot Interferometry by interconnecting single mode optical fiber within the silica capillary which represents Fabry-Perot cavity (or air cavity) as sensing elements. This sensor consists of dielectric materials and is immune to Electromagnetic Interference (EMI), Radio Frequency Interference (RFI) and less sensitive to noise. This paper highlights the fabrication as well as packaging techniques of EFPI sensor which are experimentally more reliable in blast pressure.

5 illus, 1 table, 12 ref

013067   Palit R;Biswas S (Nuclear and Atomic Physics Dep, Tata Institute of Fundamental Research, Mumbai-400 005, Email: palit@tifr.res.in) : Spectroscopy of fission fragments using prompt-delayed coincidence technique. Pramana J Phys 2015, 85(3), 395-402.

The time-stamp structure of the digital data acquisition system of the Indian National Gamma Array (INGA) has been utilized to carry out prompt-delayed coincidence technique for the spectroscopic study of fission fragments. This technique was found to be useful to determine the states above the long-lived isomer (with half-life up to <126>5 μs), present in the fission fragments. The angular correlation of γ-rays, emitted by the fission fragments, has also been used in the present INGA geometry to determine the spins of the de-exciting states.

7 illus, 22 ref

013066   Nemade K R;Waghuley S A (Physics Dep, Sant Gadge Baba Amravati Univ, Amravati-444 602, Email: sandeepwaghuley@sgbau.ac.in) : Molecular interactions in CdCl₂/H₂C₂O₄ nanofluid using acoustical studies at room temperature. Indian J pure appl Phys 2015, 53(10), 670-4.

Nanofluids have been prepared by dispersing nanometer size particles in base fluid. The very essence of nanofluids research and development has to enhance the fluid macroscopic and mega scale properties such as thermal conductivity through manipulating microscopic physics. The acoustical properties of rhombohedral symmetry CdCl₂/H₂C₂O₄ nanofluids have been studied using ultrasonic technique at room temperature (303 K). The ultrasonic velocity, density and viscosity of nanofluids have been measured to manipulate the acoustical parameters such as specific acoustic impedance, adiabatic compressibility, internal pressure, viscous relaxation time, relative association, Gibbs free energy, intermolecular free length to know the molecular interaction. The particle size of CdCl₂/H₂C₂O₄ fluid was estimated by using UV-Vis analysis. The results were discussed and compared with experimental and theoretical facts.

8 illus, 15 ref

013065   Mustafa M K;Abdullah M M;MohammedNoori Z T; Jumaa M A (College of Science, Baghdad Univ, Iraq, Email: mkm_49@yahoo.com) : Effect of annealing temprature on the optical properties of spin coated Cds/PVA thin films. Indian J pure appl Phys 2015, 53(9), 617-24.

CdS thin films have been prepared using cadmium nitrate (mw=308.47 and 0.6 M) as cadmium source and thiourea (M.Wt=76.12 and 1 M) as sulfur source and polyvinyl alcohol (PVA) as a matrix. Thin films are deposited on glass substrate using spin coating technique. The measured sample thickness was 67.7 μm. The effect of annealing temperatures (100°, 150° and 200°C)on the structural and optical properties of CdS thin films has been investigated. The surface morphology has been studied by AFM and also by X-ray technique. The results show that the grain size of the sample increases with increase in annealing temperature. The absorption coefficient, refractive index, extinction coefficient and dielectric constant increase with increasing of annealing temperature while the transmission and energy gap decrease with increase of annealing temperature.

14 illus, 3 tables, 17 ref

013064   Mondal T;Tripahi A;Tiwari A (Physics Dep, School of Physics Sciences, Sikkim Univ, Gangtok, Sikkim-737 102, Email: archana.tiwari.ox@gmail.com) : Magnetization reversal of transition metal doped ZnO nanosystems. Indian J pure appl Phys 2015, 53(10), 701-4.

Magnetization reversal of magnetic moments in transition metal ions doped ZnO nanosystems has been studied in the present paper. Stoner-Wohlfarth model is used to illustrate the energy surfaces, magnetic hysteresis and the coherent switching behaviour of magnetic moments. Low magnetic anisotropy in Zn_1-xM_xO (M=Fe, Co, Ni) nanosystems is observed for various concentrations (x) of the doped ions. The anisotropies of Zn_1-xM_xO when synthesized by three different techniques viz. chemical precipitation, pulsed laser deposition and sol-gel, have been compared. The temporal reversal paths of Zn_1-xM_xO magnetic moments are elucidated and their switching times are reported.

2 illus, 2 tables, 38 ref

013063   Lee C N (Computer and Communication Engineering Dep, Taipei Chengshih Univ of Science and Technology, Taipei 112, Taiwan, R O C, Email: cnlee@tpcu.edu.tw) : Independently tunable high-input impedance voltage-mode universal biquadratic filter using grounded passive components. Indian J pure appl Phys 2015, 53(9), 625-34.

This paper presents an independently tunable high-input impedance voltage-mode universal biquadratic filter using one plus-type second-generation current conveyor (CCII+), one full differential current conveyor (FDCCII), two grounded capacitors and three grounded resistors which can realize voltage-mode universal filtering responses (lowpass, highpass, bandpass, notch and allpass) from the same topology. The proposed circuit not only permits orthogonal tunability of ω₀ and ω₀/Q but also achieves independent tunability of ω₀ and ω₀/Q by using only grounded resistors without any matching conditions. Moreover, the proposed circuit still offers the following advantages: (i) high-input impedance, (ii) the employment of all grounded passive components, (iii) the employment of only two current conveyors, (iv) no need of component matching conditions for realizing any filter responses, (v) no need of extra inverting or non-inverting amplifiers for special input signals, and (vi) low active and passive sensitivities. H-spice simulations with TSMC 0.18 μm 1P6M CMOS process technology validate theoretical predictions.

12 illus, 2 tables, 50 ref

013062   Kushwaha A K (Physics Dep, K N Govt P G College, Gyanpur, Bhadohi-221 304, Email: akkphys_bu@yahoo.com) : Latice dynamical, elastic properties and sound velocity of γ-Si₃N₄. Indian J pure appl Phys 2015, 53(9), 585-9.

Lattice dynamical, elastic properties and sound velocities of γ-Si₃N₄ have been calculated by using a proposed six parameter bond-bending force constant model. In this model, the potential energy of the compound γ-Si₃N₄ is expanded by using the Taylor's expansion in the harmonic approximation. The proposed theoretical model is used to calculate the zone-centre phonon frequencies, elastic properties, sound velocities and Debye characteristic temperature for γ-Si₃N₄ and compared our results with experimental and previously calculated results available in the literature. It is found to be in good agreement with the experimental results. The significant outcome of the present work is that the octahedral bonding is stronger than that of the tetrahedral bonding.

1 illus, 2 tables, 44 ref

013061   Khemiri F;Trabelsi M;Saidi S;Coulomb J P; Larher Y (Physique Dep, Faculte des Sciences de Bizerte, 7021 Jarzouna Bizerte, Tunisie, CINaM/UPR CNRS 3118, Compus de Luminy, 13288 Marseille Cedex 9, France, Email: mohansen.trabelsi@fsb.rnu.tn) : Thermodynamic study of C₂H₂ thin films adsorbed on graphite (0001). Indian J pure appl Phys 2015, 53(9), 612-16.

Thermodynamic properties of C₂H₂ thin films adsorbed on (0001) surfaces of an exfoliated graphite substrate have been investigated by means of volumetric adsorption isotherms technique. A complete isotherm of C₂H₂ adsorbed on graphite shows five steps with different height. Such steps represent a transition from a (2D) dilute phase to a (2D) dense one. For each step, a set of adsorption isotherms is measured. Clapeyron equations P:f(1/T) are then determined and thermodynamic quantities are calculated and compared to the literature available ones. The second step is divided into two sharp steps at a given range of temperature which means that the condensed matter undergoes two phase transitions. The nature of such phases is discussed in light of thermodynamic quantities. The molecules orientation in the suggested structures seems to be governed by quadrupole-quadrupole interaction. Recent neutron diffraction measurements support thermodynamic conclusions.

4 illus, 3 tables, 10 ref