011274   Singh K B (University Physics Dep, B R A Bihar University, Muzaffarpur-842 001) : Photonics. Bhartiya Vaigyanik Evam Audyogik Anusandhan Patrika 2004, 12(2), 341.

Willium Shaukley and his associates John Wardin and Walter Bretain discovered transistor. Due to this invention works are being carried out controlling the microelectrons. In place of electrons quanta of light that is the use of photons has become possible. This new techniques are called photonics. Important role of photonic crystal, photonic band gap, photonic fiber etc. in communication and information field is discussed in the paper.

011273   Singh A K;Mehrotra N K (Physics Dep, Lucknow University, Lucknow-226 007) : NMR spin-lattice relaxation time and activation energy of some substituted phenols. Indian J pure appl Phys 2005, 43(1), 39-43.

The experimental values of NMR spin-lattice relaxation time (T₁) of m-aminophenol, p-aminophenol, o-nitrophenol, resorcinol and p-chlorophenol have been reported. The values of activation energy (ΔE_A) obtained using dielectric relaxation time, have been correlated with calculated values of ΔE_A obtained using Arrhenius equation of NMR spin-lattice relaxation time (T₁) for these compounds. A correlation between the experimental values of T₁ and its calculated values obtained using different equations of dielectric relaxation time (τ) has been established.

4 tables, 14 ref

011272   Shrivastava P K;Singh G N (Physics Dep, Govt New Science College, Rewa-486 001) : Effect of coronal mass ejections on cosmic ray intensity variation. Bhartiya Vaigyanik Evam Audyogik Anusandhan Patrika 2004, 12(2), 340.

Coronal Mass Ejections (CMEs) carry large amount of energy and mass into the interplanetary space. Recently CMEs are known as a main source of geomagnetic disturbances and changes in cosmic ray intensity. In this work, 55 halo CME events are selected for the period of 1996 to 2000 to derive their effects on cosmic ray intensity. It has been investigated that CMEs in association with sudden storm commencement (SSC) are found to be more effective in producing short-term transient decreases in cosmic ray intensity.

011271   Shiva Prasad K;Prasad P S R;Sharma S R (NO, National Geophysical Research Institute, Hyderabad-500 007, Email: psrprasad@ngri.res.in) : Infrared spectroscopic study of phase transitions in natural scolecite. Indian J pure appl Phys 2005, 43(2), 79-82.

In-situ infrared spectroscopic (FTIR) studies are carried out on a naturally occurring scolecite, from Deccan traps, in the temperature range 300-850 K. Five bands are observed at 3589, 3507, 3409, 3327, and 3232 cm^-1 in the (OH) stretching mode region, and three bands at 1665, 1649 and 1591 cm^-1 in the bending mode region indicating a more complex molecular interaction between H₂O and network cations in scolecite. At around 500 K, stretching mode region is replaced with three band structure, and the bending mode region with a band around 1658 cm^-1, indicating partial dehydration in scolecite. At around 720 K complete disappearance of infrared modes due to water molecules indicates total dehydration. X-ray diffraction (XRD) of the sample corroborates the transformation to amorphous phase at higher temperatures.

4 illus, 1 table, 12 ref

011270   Sharma S K;Ojha V N (National Physical Laboratory, , Dr. K S Krishnan Road) : Calibration and dissemination of industrial volt through newly established bank of zener reference standard. Bhartiya Vaigyanik Evam Audyogik Anusandhan Patrika 2004, 12(2), 347.

The conventional 'National Standard' of DC voltage is maintained as a bank of saturated standard cells. Presently it is maintained by newly established automated bank of Zener reference standard. Establishment, properties and traceability have been discussed. Furthermore, dissemination of unit of volt through traceable calibration of Zener reference standard (secondary standard/working standard) their sources of uncertainty in measurements, uncertainty budget and their evaluation based on the ISO 17025 guidelines (Type A and Type B evaluation) have been discussed.

011269   Sharma S;Bajpai R;Chandra B P (Dep of Postgraduate Studies and Research in Physics, Rani Durgavati University, Jabalpur-482 001) : Temperature dependence of the photo-plastic effect in polycarbonate. Indian J pure appl Phys 2005, 43(1), 34-8.

The transparent polycarbonate specimens were illuminated with light of suitable wavelength. The magnitude of the photoplastic effect has been detected and found to be strongly temperature dependent in the range 25-100°C. At low temperature, it shows negative photoplastic effect whereas as high temperature it shows positive photoplastic effect. This observation suggests a way to distinguish among several theories of photoplasticity.

3 illus, 10 ref

011268   Sen V;Panwar N;Singhal S K;Singh B P;Agarwal S K (Superconductivity Div, National Physical Laboratory, New Delhi-110 012) : Effect of external and internal pressures on the insulator-metal transition temperature of the colossal magneto-resistive materials. Bhartiya Vaigyanik Evam Audyogik Anusandhan Patrika 2004, 12(2), 338.

The effect of external pressure (10-40Kbar) and internal pressure was studied on the conduction mechanism of Pr_2/3Ca_1/3MnO₃ colossal magneto-resistive materials. Pr_2/3Ca_1/3MnO₃ is an insulator at low temperatures and on applying external pressure above 10Kbar there is a plateau in resistivity at 115K temperature, giving indications of an insulator-metal transition. Similar indications are also seen at 113K on replacing Mn⁺³ by Fe⁺³ in Pr_2/3Ca_1/3MnO₃. Such a behaviour of Pr_2/3Ca_1/3MnO₃ and Pr_2/3Ca_1/3FeO₃ has been explained on the basis of competition between double exchange and super-exchange mechanisms.

011267   Rostami A;Tajalli H;Sahrai M (Faculty of Electrical Engineering, Tabriz University, Tabriz-51664, Iran, Email: rostami@tabrizu.ac.ir ) : Photon tunneling and light transmission in transparent media. Indian J Phys 2004, 78(6), 479-84.

It is shown that the light transmission in transparent media can be described using photon tunneling phenomenon. Photon tunneling time for the index of refraction barrier can be investigated using Helmholtz wave equation. An analytical expression for the tunneling time of a photon from the index of refraction barrier as well as the transmission coefficient have been reported. It is predicted that the tunneling time depends on the refractive index, the thickness of barrier, and also on the incident wave frequency.

6 illus, 20 ref

011266   Roshan Lal;Sharma N D;Taneja S P;Kailash Chandra (Physics Dep, Kurukshetra University, Kurukshetra-136 119) : Mossbauer, X-ray and magnetization studies of basic volcanic and hyperbasal rocks. Indian J pure appl Phys 2005, 43(2), 119-22.

The ⁵⁷Fe Mossbauer, X-ray diffraction and magnetic susceptibility studies were carried on two samples, basic volcanic (basalt) and hyperbasal (dolerite) rocks, collected from Kundal area of Rajasthan, India to identify iron-bearing minerals. Room temperature Mossbauer parameters of basalt sample show the presence of hematite (Fe₂O₃), aluminium substituted magnesioferrite [Mg(Fe_2-xAl_x)O₄] and illite. Iron is present as both Fe³⁺ and Fe²⁺ in illite. Temperature dependence of magnetic susceptibility measurements shows no transition around 120 K (Verway transition) for both the samples, indicating existence of (Mg, Al) substituted spinel ferrites. These results have been corroborated by X-diffraction and chemical analysis of the samples.

3 illus, 2 tables, 13 ref

011265   Ramamurthy N;Subashini J;Thillaivelavan K (Phys Dep, Annamalai Univ, Annamalai Nagar-608 002) : Fourier transform infrared study of some cess pool environment soils. Indian J envir Prot 2004, 24(4), 251-7.

Infrared spectra of soil samples at different depths from septic tank drainfield leachate were recorded. The observed frequencies in the region 4000-400 cm^-1 have been given in the table along with vibrational assignments and intensities. Probable assignments of the bands were made with respect to the components present in the samples.

4 illus, 1 table, 25 ref

011264   Panwar N;Sen V;Ajay Kumar;Agarwal S K;Pandya D K (Superconductivity Division, National Physical Laboratory, New Delhi-110 012) : Effect of substitution on the metal-insulator transition temperature in colossal magneto-resistive materials. Bhartiya Vaigyanik Evam Audyogik Anusandhan Patrika 2004, 12(2), 337.

The insulator-metal transition temperature T_MI of the colossal magneto-resistive materials with the perovskite structure (ABO₃) depends upon the tolerance factor t and the lattice distortion associated with it. The effect of lattice distortion on T_MI has been reported by tuning the tolerance factor t through substitution of different trivalent and divalent ions at A and B sites of La_2/3Ca_1/3MnO₃ type colossal magneto-resistive materials. The results have been analyzed in terms of a competition between double exchange and super-exchange mechanisms.

011263   Misra U D;Kumar N (Physics Dep, Lucknow University, Lucknow-226 007, Email: udmisra@rediffmail.com) : Systematization of L X-ray satellites II: Lβ₂ and Lγ satellites. Indian J pure appl Phys 2005, 43(2), 83-8.

By the use of the method of iteration, based on Hagstrom's doubly modified Moseley plot, the wavelengths of a large number Lβ₂ and Lγ satellite lines in the atomic number range Z=39 to 80 have been calculated. This has resulted in the removal of anomalies in the measurement of the wavelengths of some of these satellites. A number of experimentally measured satellites have been identified for the first time as a result of our calculations, while in other cases, erroneous identifications by earlier researchers have been corrected.

6 tables, 21 ref

011262   Mishra R;Tiwari M S (Physics & Electronics Dep, Dr. H S Gour Viswavidyalaya, Sagar-470 003, Email: tiwarims@yahoo.co.in) : Particle aspect analysis of the electrostatic ion-cyclotron instability : effects of ion and electron beam and general distribution function. Indian J Phys 2004, 78(6), 495-504.

Dispersion relation, resonant energy transferred, growth rate and marginal stability of the electrostatic ion cyclotron wave (with general loss-cone distribution function in low ft homogeneous plasma) in the presence of upgoing ion beam and downcoming electron beam are discussed by investigating the trajectories of the charged particles. The wave is assumed to propagate obliquely to the static magnetic field. The whole plasma is considered to consist of resonant and non-resonant particles. It is assumed that resonant particles participate in energy exchange with the wave whereas non-resonant particles support the oscillatory motion of the wave. Effects of the steepness of the loss-cone distribution and ion and electron beam velocities on resonant energy transferred and growth rate of the instability are discussed. It is found that the effect of upgoing ion beam is to stabilize the wave and enhance the transverse acceleration of ions whereas the downcoming electron beam acts as a source of free energy for the electrostatic ion-cyclotron wave and enhances the growth rate. Effect of steepness of loss cone is also to enhance the growth rate and decrease the transverse acceleration of ions. The results are interpreted for the space plasma parameters appropriate to the auroral acceleration region.

6 illus, 25 ref

011261   Mandal G;Pradeep Kumar P (Physics Dep, University of Pune, Pune-411 007, Email: ppk@phystcs.unipune.ernet.in) : A laboratory study on the effect of sulfuric acid on charge transfer during ice-graupel collision. Indian J Phys 2004, 78(6), 439-44.

Charge transfer experiments were carried out inside a walk-in cold room to investigate the sign and magnitude of charge that is transferred to the graupel (soft-hail) during collision between ice crystal and graupel. Different concentrations (0%, 25%, and 50%) of aqueous solution of sulfuric acid were used to produce cloud during the experiments. A cloud of supercooled droplets is formed inside the cloud chamber by heating the aqueous solution of sulfuric acid, and the ice crystal formation in the cloud is initiated by momentarily introducing a metal rod dipped in liquid nitrogen into the cloud. It is observed that the magnitude of charge transfer increases with concentration of sulfuric acid in the aqueous solution. If the aqueous solution contains 25% and 50% of sulfuric acid by weight, a coat of dark film is seen on the crystal surface. Due to this film, the crystal boundaries are no longer sharp and well defined like that observed in the crystals produced in pure water cloud. It is suggested that during collision between ice crystal and graupel, this film could be transferred to the graupel resulting in higher values of charge transfer.

6 illus, 37 ref

011260   Lokendra Kumar;Koireng R R;Misra A;Pankaj Kumar;Dhawan S K;Kamalasanan M N;Subhas Chandra (Physics Dep, University of Allahabad, Allahabad, Email: mnkamal@mail.nplindia.ernet.in ) : Blue organic light emitting diode based on lithium tetra-(8-hydroxy-quinolinato) boron complex. Indian J pure appl Phys 2005, 43(1), 56-9.

Blue electro-luminescent materials are essential for the development of full colour display. The synthesis and characterization of blue emitter lithium tetra-(8-hydroxy-quinolinato) boron complex for organic light emitting diode (OLED) applications have been reported. The boron complex was synthesized by the reaction of lithium borohydride with 8-hydroxyquinoline at room temperature and shows absorption cut-off wavelength at 410 nm and bright blue photoluminescence (PL) with a peak wavelength at 485 nm. The electro-luminescence (EL) and I-V characteristics of bilayer OLED are also reported. The results show that boron complexes have a great potential for the blue emitters for OLED applications.

5 illus, 13 ref

011259   Joshi B C;Dhondiyal C C (Physics Dep, Kumaun University, Almora Campus, Almora) : Sensitizing Eu<. Indian J pure appl Phys 2005, 43(1), 21-3.

Enhancement of Eu³⁺ emission by non-radiative energy transfer from Dy³⁺ in zinc phosphate glass has been observed at room temperature. The variation of Dy³⁺ (donor) emission with varying Eu³⁺ concentration (acceptor) and the emission of Eu³⁺ emission in steady-state excitation have been studied. Various parameters necessary for the quantitative study e.g. energy transfer efficiencies, transfer probabilities, critical transfer distances have been computed.

4 illus, 1 table, 11 ref

011258   Harish Chander;Ghosh P K;Shanker V;Haranath D;Sharma P (Luminescent Materials and Devices Group, Electronic Materials Division, National Physical Laboratory, Dr. K S Krishnan Road, New Delhi-110 012) : Research and development of luminescent materials. Bhartiya Vaigyanik Evam Audyogik Anusandhan Patrika 2004, 12(2), 336.

To compete with global market in the field of display devices the development of high quality luminescent materials or phosphors is quite essential. In view of this, Luminescent Materials and Devices Group, NPL has been actively involved in synthesis of inorganic phosphors and fabrication of display devices for more than three decades. The main inorganic fluorescent materials are ZnS and rare-earth oxysulfide based phosphors. While alkaline earth aluminate and titanate are important amongst long decay phosphors. To increase the luminescence efficiency of the phosphors the synthesis of nanoparticles has also been initiated. The R & D activities include modification of various synthesis techniques - Sol-gel process, Combustion process, Chemical synthesis route etc.- to achieve the high efficiency nanoparticle phosphors. The paper describes in brief the synthesis and applications of fluorescent and long decay phosphors.

011257   Gunasekaran S;Abraham L (PG Dep Physics, Pachaiyappa's College, Chennai-600 030, Email: guna_pachai@hotmail.com) : Spectroscopic investigation and vibrational analysis of paraldehyde by FTIR and laser Raman techniques. Indian J Phys 2004, 78(6), 485-8.

Paraldehyde is a trimer of acetaldehyde formed from this under acid catalysis. It falls under the broad classification of the sedative hypnotics used as anti-convulsant in eplepticus and tetanus. The work presents vibrational band analysis on the molecular structure of the compound paraldehyde through infrared and Raman spectral measurements. Normal coordinate analysis has been carried out with a new set of symmetry coordinates to obtain the molecular force field of the system based on C₃V point group symmetry. Potential energy distribution evaluated for all the normal modes of vibration, confirm that the chosen set of vibrational frequencies contribute maximum to the potential energy associated with the normal coordinates of the molecule.

3 illus, 2 tables, 15 ref

011256   Getinet T (Physics Dep, Debub University, Dilla College, P.O. Box 419, Dilla, Ethiopia) : Hall coefficient and coefficient of transverse magneto-resistance of intermediately doped n-type silicon with mixed scattering. Indian J pure appl Phys 2005, 43(2), 104-8.

The explicit expressions for Hall coefficient and coefficient of transverse magneto-resistance in an intermediately doped n-type silicon with mixed scattering of electrons by both ionized impurities as well as acoustic phonons by using the modified density of states function have been derived. These explicit expressions are used to numerically calculate the dimensionless Hall coefficient and coefficient of transverse magneto resistance for different doping concentrations at room temperature. By using the modified density of states function changes the coefficients by as much as 62% and 11% for the normalized Hall coefficient and coefficient of transverse magneto resistance, respectively at room temperature when compared with the corresponding calculations obtained by using the parabolic density of states function.

3 illus, 8 ref

011255   Dutta T;Kabiraj S K;Tarafdar S (Physics Dep, St Xavier's College, Kolkata-700 016) : Three-dimensional viscous fingering patterns in a lifting Hele-Shaw cell: a simulation study. Indian J Phys 2004, 78(6), 455-61.

A hierarchical pattern is formed by viscous fingers in a lifting Hele-Shaw cell. If the defending fluid is visco-plastic, a permanent three-dimensional pattern is formed which is usually approximated as quasi-two-dimensional. The viscous fingers show a hierarchical pattern due to competition between growing fingers in a converging geometry. Using a simple algorithm, a Monte-Carlo simulation is presented which attempts to reproduce the real three-dimensional pattern in rectangular geometry. The finger-length distribution, rate of increase of coverage of the invading fluid, the height profile of the final pattern is calculated and their variation studied with changes in the characteristics of the fluid.

5 illus, 19 ref

011254   Dubey R K;Menon V J;Tripathi D N (Physics Dep, Banaras Hindu University, Varanasi-221 005, Email: jayaram_bhu@yahoo.co.in) : Time dependence of Lippmann-Schwinger states. Indian J pure appl Phys 2005, 43(1), 63-6.

Due to the presence of an infinitesimal parameter ε in the resolvent, the Lippmann-Schwinger states cannot be strict eigenstates of the Hamiltonian, and their time evolution is very non-trivial (in agreement with Fermi's golden rule). In sharp contrast, strict Schrodinger eigenstates cannot make transitions into free channels. Artefacts such as adiabatic switching, wave packets, or infinite time span are not needed in the analysis.

6 ref

011253   Chaturvedi A;Singh M P (Computer Science Dep, Institute of Basic Science, Khandari, Dr. B R A University, Agra-282 002, Email: manu_p_singh@hotmail.com) : Study of bound states in Schrodinger equation of a particle using the Hopfield model of artificial neural network. Indian J Phys 2004, 78(6), 463-9.

In the solution of Schrodinger equation for a particle, confined within one-dimensional infinitely hard boundaries, there are discrete energy states in which the particle can exist. The particle has finite probability of finding itself inside the boundaries for ground, first, second... n-th excited states (i.e. for quantum numbers n = 1, 2, 3,..n). To explore the optimized possibility of finding a particle inside the boundaries for any quantum number, the Stochastic Hopfield Neural Network Model with Mean field Approximation of Simulated Annealing has been used. In this process, the network activation dynamics at a given temperature, reaches the thermal equilibrium position. This equilibrium position is the steady state position of the network that is achieved only if the probability of visiting the global minimum energy states becomes maximum and it refers to the optimized probability of finding the particle inside the boundaries.

1 illus, 13 ref

011252   Chatterjee P (Mathematics Dep, , ) : Large amplitude ion-acoustic solitary waves in a relativistic multi-component plasma. Indian J Phys 2004, 78(6), 505-9.

Exact Sagdeev potential for a multidimensional relativistic multi-component plasma consisting of both positive and negative ions is derived without neglecting electron inertia. It is shown how the negative ion concentration, solitary L.v_λ0/c all play significant role in determining the nature of solitary waves.

3 illus, 20 ref

011251   Chakrabarti S;Chatterjee S;Chattopadhyay U L; Chakravorty J N (NO, Centre for Space Physics, 43, Chalantika, Garia Station Main Road, Kolkata-700 084, Email: space_phys@vsnl.com) : Theoretical study of waves diffracted from asymmetrical profile lamellar gratings. Indian J Phys 2004, 78(6), 471-7.

Diffraction from a microwave asymmetrical lamellar grating (ALG) has been thoroughly investigated. Expressions for intensity, dispersive and resolving power for such a grating have been derived. It is anticipated that such gratings with asymmetrical structure may be used with significant advantage for taking observations in both optical and quasi-optical region. By a suitable choice of geometrical parameters, its applicability may as well be extended to the millimeter and microwave bands which will have significant applications in instruments for astronomical observations and microwave space-communication.

6 illus, 16 ref

011250   Chakrabarti S;Chatterjee S;Chattopadhyay U; Chakravorty J N (Centre for Space Physics, , 43, Chalantika, Garia Station Main Road, Kolkata-700 084, Email: space_phys@vsnl.com) : Studies on microwave lamellar reflection gratings. Indian J Phys 2004, 78(6), 431-7.

The expression was derived for the intensity of the diffracted waves from a lamellar reflection grating. The effects of the elevations and that of the depressions were examined separately and finally derive the resultant intensity was derived. If suitably designed, the applicability of such a grating may be extended to the microwave regions apart from the normal optical and near infra-red region in which it is mostly used- Such a microwave reflection lamellar grating can have significant applications in astronomy and astrophysics. By proper choice of geometrical parameters and modifying its construction with suitable materials, a lamellar grating may be used as a microwave antenna in space communications as well.

7 illus, 18 ref

011249   Aynyas M;Jha P K;Sanyal S P (Physics Dep, S V P G College, Bairagarh, Bhopal-462 030, Email: spsanyal@sancharnet.in) : Lattice dynamics of thorium pnictides and chalcogenides. Indian J pure appl Phys 2005, 43(2), 109-14.

The phonon spectra of thorium pnictides and chalcogenides (ThX) have been analysed using rigid ion and breathing shell models, in view of their structural properties at high pressure. The significance of these two approaches in predicting the dynamical properties of ThX compounds has been discussed and the role of f-electron has been examined. The dominant ionic nature of bonding has been predicted for ThX compound from the large LO-TO phonon splitting at zone centre. The low temperature specific heat for these compounds has been reported.

3 illus, 4 tables, 25 ref

011248   Ananda Kumari R;Chandramani R (Physics Dep, Sree Siddaganga College for Women, Tumkur-572 101, Email: smshashidhara@yahoo.com) : Electrical conductivity and dielectric measurements in Au<. Indian J pure appl Phys 2005, 43(2), 123-8.

Pure potassium dihydrogen orthophosphate (KDP) containing KC1 or NaCl with and without gold doping were grown by slow evaporation technique. All the grown crystals were γ-irradiated using ⁶⁰Co source. Electrical conductivity measurements were carried out perpendicular to the unique direction before and after γ-irradiation. The conductivity of KDP crystals increases with the addition of KCl and NaCl and with gold doping as well as temperature. Computed values of activation energies from the conductivity measurements are given. The dielectric constant and dielectric loss have been measured as a function of frequency. The study confirms the contribution of space charge polarization.

11 illus, 2 tables, 13 ref

011247   Ahsan M R;Uddin M A;Mortuza M G (Physics Dep, University of Rajshahi, Rajshahi 6205, Bangladesh, Email: ranzuphy@yahoo.com) : Infrared study of the effect of P₂O₅ in the structure of lead silicate glasses. Indian J pure appl Phys 2005, 43(2), 89-99.

The infrared spectra of xPbO (1-x-z)SiO₂zP₂O₅ glasses with a PbO:SiO₂ molar ratio of 3:2 and z=0,1,2,5,30,40 and 50 mol% have been examined in the region 4000-400 cm^-1, together with XRD. The structure of PbO-SiO₂ binary glass is significantly different from that of P₂O₅ substituted glasses. The low amount of P₂O₅ containing PbO-SiO₂ glasses results in infrared spectra of the same pattern as 3:2 binary lead silica glass but the maximum peak intensities and positions are different. The spectra of high P₂O5 (30-50 mol%) containing glasses show an increased number of distinct peaks in the low frequency region with a convolution of several broad Gaussians in the high frequency region. All the spectra are base line corrected and deconvoluted to appropriate number of Gaussians. The peaks and peak positions of the Gaussians are assigned to Si-O-Si, Si-O-Pb, Si-O-P, P-O-P, O-P-O, P=O, P-O^- etc. bonds. A variation in the band positions and the relative amounts of bonds with P₂O₅ is also shown. The result indicates that ortho- and pyro-phosphate are formed around 1-5 mol% P₂O₅ containing glasses and meta-phosphate species from the high P₂O5 containing glasses. The ionic character of the phosphate groups P-O^-, PO₄^3- is well revealed by the formation of new band within 1250-900 cm^-1. The incorporation of high contents of P₂O₅ in the materials suggests that P⁵⁺ occupies the network position and forms the linkage Si-O-P in the glasses. This Si-O-P bond may lead to the formation of five and six coordinated silicon in the glass matrix. X-ray diffraction pattern of the base samples, within the detection limit shows that all are homogeneous glasses and these have not shown any evidence of phase separation on optical inspection.

4 illus, 5 tables, 40 ref

009181   Venkateswarlu K;Rao J A (Mathematics Dep, A.V. College, Gagan Mahal, Hyderabad-500 029) : Numerical solution of free convection of a dusty conducting fluid. J Energy Heat Mass Transfer 2002, 24(4), 361-8.

The present paper deals with unsteady laminar free convection flow of an incompressible, viscous, electrically conducting dustry fluid through some porous medium, which is bounded by an infinite vertical plate surface of constant temperature, in the presence of a uniform magnetic field, acting perpendicular to the surface. The effects of Grashof number, Prandtl number, Permeability parameter and mass concentration on the velocity ad temperature of thefluid are discussed graphically.

2 illus, 14 ref

009180   Tiwari S;Tiwari S;Chandra B P (S.O.S. in Electronics, Pt Ravishankar Shukla University, Raipur, Chhattisgarh-492 010) : Effects of temperature on the mechano luminescence of gold-doped ZnS phosphors. Indian J Phys 2004, 78(7), 575-8.

Reports the effects of temperature on the mechanoluminescence (ML) intensity of gold-doped ZnS phosphors. The ML intensity decreases with temperature and follows the relation I_{T = IT^{0(1-T/Tc)n the value of n lies between 0.90 and 1.10 for ZnS phosphors. Generally, ML of ZnS phosphors ceases much below their melting point. The process of thermal quenching in the ML can be understood by electro and photoluminescence (PL) studies. The faster rate of decrease of ML intensity than the PL intensity suggests that in addition to increase in the non-radiative transition probability, the temperature also affects some other parameters such as piezoelectric constant or surface charge density responsible for the ML excitation.}}

6 illus, 1 table, 15 ref

009179   Singh V;Tiwari M;Awasthi O N;Dhoble S J;Dubey R N;Qureshi M S (Dep of Physics, Regional Institute of Education, Bhopal, Madhya Pradesh-462 013) : Thermally stimulated conductivity of CaS phosphors activated by Ce. Indian J Phys 2004, 78(7), 579-82.

Thermally Stimulated Conductivity (TSC) study has been made on CaS:Ce phosphors, prepared with different activator concentrations. Energies of trap levels corresponding to peaks were calculated using three different methods. Trap depths/activation energy, relaxation time and attempts to escape frequency are evaluated. The variation in the values of trap depths is studied for the observation of TSC of γ-irradiated phosphors.

2 illus, 3 tables, 18 ref

009178   Singh R;Anand P P;Agarwal V K;Arora V P;Raina K K (Dep of Physics, Meerut College, Meerut-250 001, Uttar Pradesh) : Thermo-optical studies of nematic liquid crystal mixtures. Indian J Phys 2004, 78(7), 583-5.

Integrated optical transmittance (IOT) and differential scanning calorimeter (DSC) studies of two nematic liquid crystal mixtures (ZLI- 3497-100 and ZLI-3741) were made for phase transition measurements, during both heating and cooling cycles. Transition temperatures, transition enthalpies (ΔH) and entropies (ΔS) have been determined using DSC technique. The IOT and DSC studies indicated good agreement for the transition temperatures for the both mesogens, which exhibited broad nematic - isotropic phase transition. The different peaks observed in IOT studies during phase transitions seems to correspond to different constituents of the mesogens.

2 illus, 1 table, 14 ref

009177   Sen P;Akhtar J (School Physical Sciences, Jawaharlal Nehru University, New Delhi-110 067) : Nonequilibrium processes for generating silicon nanostructures in single crystalline silicon. Curr Sci 2003, 85(12), 1723-9.

The possibility to modify existing materials through technology has become the recipe for preparation of advanced materials. Nonequilibrium processing of silicon through MeV ion irradiation will be shown here to yield interesting properties. It propose localization of vibrational energy following an ion irradiation process and their transport (nonlinear transport of energy) through linear chains of a single crystalline lattice. The localization of energy can involve, distinguishable from the remaining periodic lattice by their unique interatomic distances. The energy required to produce these structures is supplied by a single high energy heavy ion, incident normal to a suitable crystal face so as to lose energy by the electronic energy loss mechanism. These entities can be trapped at a desired location which lead to silicon nanostructures with modified band-gaps.

9 illus, 19 ref

009176   Sarkar S K (Dep of Electronics and Telecommunication Engineering, Jadavpur University, Jadavpur, Kolkata-700 032) : Effects of wave function modulation on high-frequency carrier transport in quantum wells under high biasing field. Indian J Phys 2004, 78(7), 535-8.

The effects of wave function modulation on the high frequency response of GaAs/AlAs quantum wells with several thin barrier layers being inserted inside the wells are studied. Carrier scattering by longitudinal optic phonons, deformation potential acoustic phonons and background-ionized impurities are considered. The wave function modulation induced inside the quantum well is found to reduce the scattering strength and reduces the ac mobility normalized by the dc mobility because the enhancement rate of dc mobility is much higher than the ac values. The variation of ac mobility normalized by dc mobility with the frequency of the applied field is found to be fairly constant upto a certain frequency beyond which it drops down.

28 illus, 20 ref

009175   Rajput N;Tiwari S;Chandra B P (Dep of Post Graduate Studies and Research in Physics and Electronics, Rani Durgavati University, Jabalpur-482 001) : Mechanoluminescence produced during impulsive deformation of coloured alkali halide crystals. Indian J Phys 2004, 78(7), 569-73.

Mechanoluminescence (ML) in coloured alkali halide crystals is reported. During impulsive excitation of γ-irradiated alkali halide crystals two peaks are observed in the ML intensity versus time curves. The first peak lies in the deformation region and the second peak in the post-deformation region. The ML in the deformation region is due to the recombination of dislocation-trapped electrons with the holes in defect centres. The ML in the post-deformation region is due to the transient thermostimulated luminescence from shallow traps which get populated due to the Auger process occurring during transfer of dislocation-trapped electrons to deep traps. In the frame work of the mechanism proposed, an equation is derived which is able to explain the ML in the deformation and post-deformation region of the crystal. Several other facts related to the ML produced during impulsive excitation of coloured alkali halide crystals, are also discussed.

6 illus, 12 ref

009174   Rajnikant;Dinesh (Condensed Matter Physics Group, Department of Physics, University of Jammu, Jammu Tawi-180 006) : Intramolecular C-H...N and intermolecular N-H...N interactions in 2-amino-4-phenyl-l,3-thiazole. Indian J Phys 2004, 78(7), 587-9.

The crystal structure of 2-amino-4-phenyl-1, 3-thiazole derivative has been determined by X-ray diffraction methods with an aim of describing intra- and intermolecular interactions in thiazoles. The title compound crystallizes in tetragonal space group P4_{1 and its structure has been refined upto the reliability index of 5%. There occurs N-H...N bond at a distance of 2, 19 and 3.01Å, respectivley and it appears to be formed by symmetry-related amino atom and nitrogen atom of the parental thiazole ring. The crystal cohesion is pronounced, may be due to an intramolecular phenyl-thiazole C-H...N interaction.}

2 illus, 4 tables, 27 ref

009173   Oza A T;Solanki G K;Patel R G;Prajapati S M (Dep of Physics, Sardar Patel University, Vallabh Vidyanagar-388 120, Gujarat) : Electron-phonon resonance in some new charge transfer complexes. Indian J Phys 2004, 78(7), 591-8.

Some new charge transfer complexes of organic donors and acceptors were prepared and the infrared spectra in the range 400-4000 cm^{-1 were obtained. The analysis of featureless absorption between the two envelopes at 1400 cm-1 and 3400 cm-1 were carried out for the transitions across the band gap. Six complexes show spectral characteristic of the presence of charge density waves. Electron-phonon resonance is found. Bands are ascribed to various intramolecular bond vibrations of donor and acceptors. Systematic distortion of the Gaussian band as the occurrence of electron - phonon resonance is discussed. Other four complexes show variation of the band gap.}

10 illus, 4 tables, 48 ref

009172   Narasimha Murthy V N;Kokila M K;Puttaraja (Dep of Physics, Jnanabharathi Campus, Bangalore University, BangaIore-560 056, Karnataka) : Structure of 1-cyano, l-carbethoxy-2-(3' methoxy-4'-hydroxy) phenyl ethylene. Indian J Phys 2004, 78(7), 639-42.

The title compound [C_{13H13O4N] has been taken up for study as it shows non-linear optical (NLO) properties with an electron withdrawing group at one end and an electron donating group at the other, with an extended conjugation in between. The crystal structure has been determined at room temperature. Needle like crystals of the compound crystallizes in monoclinic system, space group P21/n with cell dimensions a = 10.646(3) Å, b = 9.351(4) Å, c = 12.647(5)Å, β = 97.13(3)° and Z = 4. The structure was solved by direct method and refined by full-matrix least-squares method to a final R = 0.046 for 1993 observed reflections. The molecule on the whole is almost planar, the methoxy group makes a dihedral angle of 0.7° with planar phenyl ring. The carbethoxy moiety forms an extended planar zigzag chain with the neighboring atoms. The molecules are held by strong 0-H....O, C-H....O and C-H....N inter- and intra- molecular hydrogen bonds.}

3 illus, 5 tables, 7 ref