008179   Banerjee S;Pal A K;Pal R S;Saha S;Banerjee N; Banerjee A;De M (Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032) : Crystal and molecular structure of bis(2,4-diaminopyrimidinium) phosphate monohydrate, 2C₄H₇N₄+.PO₄<. Indian J Phys 2004, 78(7), 635-7.

The crystal and molecular structure of bis (2,4-diaminopyrimidinium) phosphate monohydrate 2C₄H7N₄ + PO₄³. H₃O⁺ has been determined by X-ray crystallographic method. The crystal belongs to the monoclinic space group P2₁/a with cell dimensions a = 20.992<2>, b = 6.948(1), c = 10.083(1) A and β = 102.15 (1)°. The asymmetric unit of the structure consists of one phosphate ion, one water molecule and two 2,4-diminopyrimidine (DAP) molecules stacked parallel to the b direction with average perpendicular separations of 3.311 (4) and 3.344(4) A, respectively. The tilt angle between the least squares planes of the two DAP molecules in the asymmetric unit is 2.0 (1)°. The structure is stabilized by stacking forces,N-H-N and N-H-O hydrogen bonds.

2 tables, 10 ref

008178   Bambah B;Mukku C (School of Phys, Univ of Hyderabad, Hyderabad-500 046) : Isospin squeezed states, disoriented chiral condensates and pion production: a dynamic group theoretical approach. Ann Phys 2004, 314(1), 54-74.

008177   Aggarwal A K;Kaura S K;Sharma A K;Raj Kumar; Chhachhia D p (Coherent Optics Division, Central Scientific Instruments Organisation, Sector 30, Chandigarh-160 030) : Interferometry based security hologram readable with an encoded key hologram. Indian J pure appl Phys 2004, 42(11), 816-19.

A simple and cost-effective method for making security holograms has been presented, which incorporates holographic interferometry as verification feature in addition to spatially separated sharp focus spots. When the security hologram is illuminated with decoding reconstructing beam generated from an encoded key hologram, two spatially separated sharp focus spots emerge at the predefined positions and can be read through a photoelectric detector array. In addition, these focused spots upon divergence in longitudinal direction further generate specific kind of interferometric fringe patterns of random profile contained in them, which are suitable for further visual inspection. These machine-readable and visual verifiable features can be used for better counterfeit-resistant security codes in embossed holograms. Recording schemes for the formation of such security holograms and typical experimental results have been presented.

5 illus, 14 ref

007260   Yadav R;Pathak P;Anzer A;Singh S K;Mishra L K (Department of Physics, Magadh University, Bodh-Gaya-824 234) : Determination of real and imaginary part of refractive index (n and k) for metals like Pd, Pt, Cu, Ag and Au. Acta Cienc Indica-Phys 2004, 30(2), 155-62.

Using Kramers-Kroning relation the real and imaginary part of the refractive index (n and k) of metals like Pd, Pt, Cu, Au and Ag as a function of Photon Energy have been . The theoretical results are in a good agreement with the experimental data and also with other workers.

6 tables, 30 ref

007259   Yadav M (Department of Physics, Govt P G College, Kotdwara 246 149) : Strong hydromagnetic cylindrical shock waves in a rotating gas. Acta Cienc Indica-Phys 2004, 30(2), 137-42.

The propagation of strong diverging cylindrical shock waves through an ideal and rotating gas in presence of a magnetic field having all the three components of the form, H²_ro=ηrH²_zo (η is a constant), H²_θo=rH²_zo and H_zo as constant, taking an initial density distribution of the form ρo=ρ'r^w. Expressions for flow variables have been derived and their numerical estimates have been computed at permissible shock front locations.

2 illus, 1 table, 20 ref

007258   Yadav A K;Jha R C;Yadav A K (University Dept of Physics, L N Mithila University, Darbhanga, Bihar 846 004) : Phonon-drag contribution to the thermopower of Rl at low temperatures. Acta Cienc Indica-Phys 2004, 30(2), 227-9.

There is discrepancy between the theoretical and the experimental values of thermopower of Rb. According to the present view, the phonon-drag, which is very influencive at low temperatures, is responsible for this anomaly, theoretically the thermopower, S of Rb due to electron diffusion, S_e and phonon-drag contribution, S_g at very low temperatures have been measured. These differ seriously in magnitude. Theoretically the thermopower of Rb have been compared with a modified formula based on electron diffusion with thermolectric parameter. The electronic contribution of thermopower of Rb has been separated These two sets of theoretical values of thermopower has been the experimental values at low temperatures. The linear relation between S and T proves that electrons are the sole contributors to the thermopower.

1 illus, 2 tables, 7 ref

007257   Vaid R;Padha N;Anil Kumar;Gupta R S;Parikh C D (Phys and Electronics Dep, Univ of Jammu, Jammu-180 006) : Modeling power VDMOSFET transistors: device physics and equivalent circuit model with parameter extraction. Indian J pure appl Phys 2004, 42(10), 775-82.

A power VDMOSFET has been simulated using pisces-II, a 2-D numerical device simulator. The doping densities and device dimensions are chosen so as to sumulate a typical device structure with one micron channel length. These simulations are aimed at understanding the device physics through various internal electrical quantities like potential distribution, electric field distribution, and electron concentration etc. in different regions of the device both in on/off states. Simulated results have been used to extract circuit model parameters like V_T, K_P and λ etc. for a VDMOSFET equivalent circuit model comprising of a lateral MOSFET in series with a JFET. It advances the earlier models in terms of number of parameters extracted for its SPICE implementation. The characteristics obtained from the dc circuit model show good agreement with the simulated data, thus validating the device operation, the circuit model and its parameter extraction procedures.

13 illus,, 1 table, 13 ref

007256   Upadhyay P N (Department of Physics, Nalanda Mahila College, Biharsharif 803 101) : Study of the Π<. Acta Cienc Indica-Phys 2004, 30(2), 125-6.

An account of results on the data analysis of the Π^-_p→Π^- Π°p with Π° →YY has been presented. No enhancement appears for a meson near 950 MeV to 1 GeV region. An absence of a meson peak in this mass region is attributed to the presence of high background.

1 illus, 5 ref

007255   Thakor P B;Patel V N;Thakore B Y;Gajjaar P N; Jani A R (Phys Dep, Sardar Patel Univ, Vallabh Vidyanagar-388 120m Gujarat) : Thermodynamic properties of some simple metals in liquid phase by pseudopotential theory. Indian J pure appl Phys 2004, 42(9), 684-7.

The Gibbs-Bogoliubov (GB) variational method is applied to investigate the thermodynamic properties of some simple metals in liquid phase viz; Mg, Cd, Al, In, Tl and Pb using pseudopotential theory. For description of the structure, charged hard sphere (CHS) model is used as a reference system. Well established model potential is used to describe the electronion interaction. The local field correction function proposed by Sarkar et al. Mod Phys Lett B, 12 (1998) 639 is applied for the first time to introduce the exchange and correlation effects in the study of thermodynamics of these metals. The comparison with the experimental findings establishes the use of Sarkar et al. screening function in such study.

2 tables, 25 ref

007254   Talawar M B;Agrawal A P;Chhabra J S;Ghatak C K;Asthana S N;Rao K U B (High Energy Materials Res Lab, , Pune-411 021) : Studies on nickel hydrazinium nitrate (NHN) and bis-(5-nitro-2H tetrazolato N<. J scient ind Res 2004, 63(8), 677-81.

4 tables, 16 ref

007253   Suresh S S;Chandramouli V (Phys Dep, Osmania Univ, Hyderabad-500 007) : Spectroscopic and transport studies of Cu<. Indian J pure appl Phys 2004, 42(8), 560-4.

ESR, optical absorption, IR and dc electrical conductivity of (30-x)Na₂O-xNaF-50B₂O₃-20 Bi₂O₃ glass system have been investigated. From infrared results, it is observed that the glass is made up of [BO₃] and [BO₄] units and in fluorine rich glass B-F bonds are formed. ESR results show that Cu²⁺ has tetragonal distorted octahedral coordination and its ground state is d²_x-y². The observed changes in spin-Hamiltonian parameters with increasing concentration of NaF can be attributed to the decrease in the field strength at Cu²⁺ ion site. The decrease in α value can be attributed to decreasing ionic character of the glass. The existence of maxima of optical absorption at x=18 mole % of NaF is attributed to the formation of BO₂F₂ structural units. The dc electrical conductivity studies whow that mobile ions are Na⁺ and the activation energy is attaining a maximum value at x=18 mole% of NaF characterizing a mixed anion effect.

3 illus, 3 tables, 20 ref

007252   Sundaraganesan N;Ilakiamani S;Saleem H;Mohan S (Phys Dep (Engg), Annamalai Univ, Annamalai Nagar-608 002) : FT-Raman, FTIR spectra and normal coordinate analysis of 5-bromo-2-nitropyridine. Indian J pure appl Phys 2004, 42(8), 585-90.

The Fourier Transform-Raman and Fourier Transform-Infrared spectra of 5-bromo-2-nitropyridine have been recorded. The observed frequencies were assigned to various modes of vibrations on the basis of normal coordinate calculations assuming C_s point group symmetry. The potential energy distribution associated with normal modes is also reported here. The assignment of fundamental vibrations agrees well with the calculated frequencies.

2 illus, 2 tables, 19 ref

007251   Srivastava K K P;Sinha K K (Phys Dep, T M Bhagalpur Univ, Bhagalpur-812 007) : Thermal and XRD studies of polycrystalline (Fe, Sr) TiO3 ceramics. Indian J pure appl Phys 2004, 42(10), 745-8.

Ferroelectrics of ABO₃ type perovskite structure like PbTiO₃ and BaTiO₃, and those synthesized with a varied concentration of other divalent, tetravalent and pentavalent atoms are important because of their application as dielectric materials and the study of phase change in such materials in interesting. In the same series SrTiO₃ is cubic at room temperature with no ferroelectric property and it can serve as a reference lattice. Mossbauer, EPR and IR studies of Fe_xSr_1-xTiO₃(x≤0.3) ceramics have indicated phonons occupying two energy states and a phase change. The specific heat of 7.5 R deg^-1 mole^-1 at 500°C is much greater than 3R for simple elemental systems (metals), which indicates that other internal modes of vibrations are excited or anharmonic movements of atoms are present. The XRD intensity peaks are quite sharp that indicates that samples are made of well-grown crystallites mostly in single phase. The samples have orthorhombic structure though there are significant changes in unit cell volumes. For example, the sample with x = 0.3 has a = 6.3853, b=4.7769 Å, c = 3.9039 Å.

4 illus, 10 ref

007250   Singh V K;Khanna K N (Phys Dep, V S S D Coll, Kanpur) : Statistical associating fluid theory-dimer of the solid phase of the pearl-necklace model. Indian J pure appl Phys 2004, 42(9), 688-92.

Statistical associating fluid theory-Dimer (SAFT-D) of chain molecules for liquid phase is extended to model the solid phase of chains. The model of freely jointed chains of tangent hard spheres requires the equation of state of hard sphere monomers in solid phase and contact values of the radial distribution function of the dimer molecules for solid phase. The theoretical results for the equation of state and free energies for the chains up to 8 mers are compared with simulation results. The agreement between theory and simulation is imporved over the recent results of Vega and Mac Dowell (Vega C and MacDowell L G, J Chem Phys, 114(2001) 10411) employing thermodynamics perturbation theory of first order (TPT-1).

2 illus, 1 table, 28 ref

007249   Singh S P;Kumar S (Phys Dep, Christ Church Coll, Kanpur-208 001) : Space charge limited conduction in Se_80-xTe₂₀Ag_x thin films. Indian J pure appl Phys 2004, 42(8), 615-20.

The dc conductivity measurements at high electric fields in vacuum evaporated thin films of amorphous Se_80-xTe₂₀Ag_x (x=0,5,10,15) have been reported. The current-voltage (I-V) characteristics have been measured at various fixed temperatures. In all the samples ohmic behaviour is observed at low electric fields. However, at high electric fields (E~10⁴ V/cm), non-ohmic behaviour is observed. An analysis of the experimental data confirms the presence of space charge limited conduction (SCLC) in all the glassy materials studied in present case. From the fitting of the data in the theory of SCLC, the density of defect states near the Fermi level is calculated. It is concluded from the results obtained that the density of defect states do not changes significantly with increasing concentration of Ag in the pure binary Se₈₀Te₂₀ system.

5 illus, 2 tables, 18 ref

007248   Singh R P;Birbal Singh;Kushwah V K;Chauhan R V S (Department of Physics, R B S College, Bichpuri, Agra 283 105) : Attenuation of ULF-VLF seismo-electromagnetic signals and their propagation to long distances. Indian J Radio Space Phys 2004, 33(3), 189-95.

Using a two-layer crust model between the source region and earth surface, the attenuation of seismo-electromagnetic signals is calculated. Results show that attenuation of Ultra Low Frequency (ULF) signals is very low and they can penetrate the crustal region to enter the atmosphere and ionosphere over the epicentral area of the earthquakes. However, the attenuation increases steeply in the crust for the ELF and VLF ranges of signals. These results are utilized to discuss the propagation mechanism of VLF signals (f=3 kHz), which are recorded at Agra by employing a borehole antenna during the periods of Chamoli earthquakes in India and large magnitude earthquakes in Afghanistan. It is suggested that these VLF signals propagate upward and find windows of very low conductivity in the skin layer through which they get transmitted to teh atmosphere. They then propagate to the observing station at Agra through earth-ionosphere waveguide.

189 illus, 29 ref

007247   Singh M;Vijay Y K (Phys Dep, Univ of Rajasthan, Jaipur-302 004) : Electrical, optical and structural properties of indium-antimonide (In-Sb) bilayer film structure. Indian J pure appl Phys 2004, 42(8), 610-14.

The indium-antimonide having small band gap is an important material for IR detectors and sources. The In-Sb thin film was deposited on glass substrate in the high vacumm chamber at pressure 10^-5 torr. The samples were annealed for three hours on two different temperatures. The electrical resistivity decreases with increasing temperature, shows the semiconducting behaviour. The optical band gap varies from 0.22 to 0.23 eV with annealing temperature. The observed positive thermoelectric power indicates that In-Sb thin films were p-type in nature. The Rutherford back scattering analysis shows that the inter-diffusion concentration varies with temperature and X-ray diffraction pattern shows the imporvement of crystallinity with annealing temperature.

4 illus, 1 table, 26 ref

007246   Singh C P;Tiwari D P;NIgam S K (Department of Physics, V S S D College, Kanpur) : Radiative decays of vector mesons with confined quarks. Acta Cienc Indica-Phys 2004, 30(2), 205-8.

Summing that quark inside a meson behaves as a confined/bound quark and not as a free Diracarticle, then using it's effective mass the radiative decays of vector mesons <60>V →PY<62> are restigated in an additive quark model. A remarkable improvement over naive quark model is observed.

1 table, 15 ref

007245   Shettigar V;Bhat S G;Dharmaprakash S M (Phys Dep, Mangalore Univ, Mangalagangotri-574 199) : Crystal amd molecular structure of antimony thiourea bromide. Indian J pure appl Phys 2004, 42(8), 581-4.

The structure of antimony thiourea bromide hydrate (ATB) with molecular formulat Sb[SC(NH₂)₂]₂Br₃H₂O has been determined by X-ray single crystal diffraction. ATB crystallizes in the orthorhombic system with the lattice parameters a=12.272(3)Å; b=11.675(4)Å; c=18.617(5)Å; the space group is Cmc2₁, Z=8, and D_c=2.648Mg/m³. The final R=0.0366 (wR=0.0914) for 1273 reflections. The asymmetric unit consists of two symmetrically independent halves of a complex Sb[SC(NH₂)₂]₂Br₃] and one crystal water molecule which are completed to a complex dimer by the mirror plane of the space group. The whole crystal is found packed in mm2 point group, which is non-centrosymmetric arrangement of atoms.

2 illus, 4 tables, 9 ref

007244   Sharma S L;Anil Kumar G;Acharya H N (Phys & Meteorology Dep, Indian Inst of Technol, Kharagpur-721 302) : Optoelectronic properties of mercuric iodide crystals for radiation detection. Indian J pure appl Phys 2004, 42(9), 653-65.

Optoelectronic properties of some red mercuric iodide (α-HgI₂) crystals have been studied for wavelengths 450-70 nm at temperatures 80-300 K. These crystals were grown by solvent evaporation from alpha-HgI₂-tetrahydrofurane saturated solution, by hydration of α-HgI₂-tetrahydrofurane saturated solution by polymer controlled growth (PCG) in vapour phase. Important aspects of optical generation of the charge carriers have been discussed. The measurements of thermally stimulated currents were also carried out in order to understand the temperature dependence of photocurrents in different wavelength regions. With the computer simulation of the photocurrent versus wavelength spectrum, the room temperature transport properties (the mobility-lifetime products and surface recombination velocities of the two charges carriers) for the crystals of three types have been estimated. For a typical electrical field strength of about 2x10³ V/cm, the electron drift lengths for the crystals of three types were found to be 1150, 1350 and 6500 μm, respectively, whereas the hole drift lengths were found to be 50, 50 and 150 μm, respectively. As the typical thickness of α-HgI₂ crystals present high potential for their use as photodetectors in conjunction with most of the scintillators.

11 illus, 1 table, 27 ref

007243   Shah N A;Rather M F;Iqbal S Z (Postgraduate Dep of Electronics and Instrumentation Technology, Univ of Kashmir, Srinagar-190 006) : Current-mode lowpass, bandpass and highpass biquads using a single current feedback amplifier. Indian J pure appl Phys 2004, 42(9), 697-9.

A novel current-mode second-order filtering configuration employing an inverting current feedback amplifier (CFA) and four passive elements is presented. The circuit can realize simultaneously lowpass (LP) and bandpass (BP) functions. The circuit supports realisation of highpass (HP) and bandpass (BP) filtering responses as well through RC : CR transformation. All passive sensitivities are low. The circuit has been simulated using Personal Computer-Simulation Programme with Integrated Circuit Emphasis (PSPICE) and simulation results and found to be in close conformity with the theoretical values

^ssc3 illus, 20 ref

007242   Shah N A;Malik M A (Postgraduate Dep of Electronics & Instrumentation Technol, Univ of Kashmir, Srinagar-190 006) : High input impedance allpass networks using four terminal floating nullor. Indian J pure appl Phys 2004, 42(9), 700-02.

Two novel circuits to realize high input impedance voltage-mode allpass filter functions each using a single four terminal floating nullor (FTFN) and four passive components have been presented. The realizibility condition is simple and temperature invariant being in the form of resistor ratio. The phase besides being adjustable by the frequency of applied voltage signal can also be controlled by adjusting the values of passive components without disturbing the realizibility condition. Simulation results are also included.

^ssc3 illus, 14 ref

007241   Sekhon S S;Singh H P (Appl Phys Dep, Guru Nanak Dev Univ, Amritsar-143 005) : Proton conduction in polymer gel electrolytes containing chloroactic acids. Solid St Ionics 2004, 175(1-4), 545-8.

007240   Seetharaman V;Kalyanasundaram S;Gopalan A (Phys Dep, Industrial Chem Dep, Alagappa Univ, Karaikudi-630 003) : Ultrasonic studies of aqueous solutions of poly diallyl dimethyl ammonium chloride. Indian J pure appl Phys 2004, 42(10), 735-40.

Poly dialyl dimethyl ammonium chloride (DADMAC) was synthesized by solution polymerization technique using potassium peroxomono sulphate. The ultrasonic velocity and density for solutions of the synthesized poly (DADMAC) in the different concentration ranges are measured at three different temperatures 308, 313 and 318K. Parameters like apparent molal compressibility, apparent molal volume and molar solvated volume in terms of molar hydration number are computed on the basis of Podova model. The variation of apparent molal compressibility and molar solvation number indicates interaction between the polymer and the solvent.

5 illus, 4 tables, 15 ref

007239   Sarkar S K;Rajesh KUmar;Iqbal Ahmed;Gupta M M;Prasad M V S N (Radio and Atmospheric Sciences Division, National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110 012) : Rain attenuation and performance deterioration of a communication link at Ka band over Indian tropical eastern region. Indian J Radio Space Phys 2004, 33(3), 176-9.

Experimentally measured values of radiowave attenuation due to rains in Ka band are not available over the Indian subcontinent. An attempt has been made to present measured values of attenuation at 18 GHz taken during rainy conditions. Using rapid response rain gauge having integration time 10 s, simultaneous rain intensity measurements were carried out. The communication link operating at 18 GHz was monitored in eastern India and the signal intensity measured. The deterioration of the link in relation to measured signal level during rainy periods has also been discussed. Such types of measured values are useful to design future communication links in Ka band (17.3-31 GHz) over India.

7 illus, 7 ref

007238   Sainath M;Venkataramaniah K;Sood P C (Phys Dep, Sri Sathya Sai Inst of Higher Learning, Prasanthinilayam-515 134) : Spin-parity assignments to levels in the very-neutron-rich nucleus <. Indian J pure appl Phys 2004, 42(8), 553-559.

Spins and parities have been assigned to the low-lying energy levels in the very neutron-rich=45 nucleus ¹¹³Rh identified in beta decay of the exotic fission fragment ¹¹³Ru. The assignments are based on the experimental beta intensities and log ft values, gamma energies, intensities, branching and multi-polarities deduced from ¹¹³RU decacy, taken together with the trends for the analogous levels and their comparative feedings and decays in the lighter n-rich Rh isotopes with A=105-111, and the supporting model considerations. No abrupt pattern changes are noticed for this N=68 nucleus lying just beyond the N=66 mid sheel point. Whereas the low-lying positive parity level energies show very little variation or a slow decreasing trend, the negative parity level energies are seen to rise sharply with the addition of successive neutron pairs. The intruder band, having reached minimum energy in the N=64 isotope ¹⁰⁹Rh, appears to have a parabolic increase on either side.

5 illus, 1 table, 29 ref

007237   Sahu D K (Department of Physics, L N Mithila University, Darbhanga-846 004) : Analysis of isothermal compressibility of binary liquid mixtures. Acta Cienc Indica-Phys 2004, 30(2), 217-20.

The isothermal compressibility of binary liquid mixtures of cumene with methanol, n-propanol, and n-butanol at the temperatures 303.15, 308.15 and 313.15 K has been calculated theoretically using different models for the hard sphere equation of state. The computed values of the isothermal compressibility were also compared with experimental values and the relative merits of the various hand sphere models were tested.

4 tables, 22 ref

007236   Roy S K;Jha S K;Jha L (Department of Physics, L N Mithila University, Darbhanga) : Quality factor of an arbitrary antenna. Acta Cienc Indica-Phys 2004, 30(2), 199-204.

Rigorous study of antenna quality factor Q has been dealt with by introducing the complex power radiation of the antenna system. It also conforms whether the Fooster reactance theorem holds for the antennas. Finally this theorem has been applied to demonstrate the widely used Q ~1/B. Provided Q<62><62>1, where B stands for the fractional bandwidth of an arbitrary annenna.

1 illus, 7 ref

007235   Rout S K;Panigrahi S;Bera J (Phys Dep, Ceramic Engng Dep, National Inst of Technol, Rourkela-769 008) : Characterization of Ni-doped SrTiO₃ ceramics using impedance spectroscopy. Indian J pure appl Phys 2004, 42(10), 741-4.

The ceramic SrTiO₃ (ST) with 0.2 atom % Ni doped was prepared by solid state reaction route. Average grain size of doped samples was measured and found to be 2.8 micron. The relative permittivity and dielectric loss of ST ceramics were found to increase with Ni-doping. The capacitace was measured at temperatures ranging from 400° to 700°C in the frequency range 10 Hz-13MHz. The grain and grain boundaries relaxation frequencies were shifted to higher frequency with temperature. The impedance measurements were conducted at 500°C to separate grain and grain boundary contributions. The bulk and grain boundary resistance was evaluated from impedance complex plain plot and equivalent Resistance Capacitance (RC) circuits is proposed to model the experimental data.

5 illus, 11 ref

007234   Reddy A;Thipperudrappa J;Biradar D S;Lagare M T;Hanagodimath S M (Phys Dep, Gulbarga Univ, Gulbarga-585 106) : Fluorescence quenching of anthracene by aniline in different solvents. Indian J pure appl Phys 2004, 42(9), 648-52.

Fluorescence quenching of anthracene by aniline in five different solvents has been carried out at room temperature with a view to understand the quenching mechanisms. Experimental results show positive deviation in the Stern-Volmer plots in all the solvents studied. In order to interpret these results the ground state complex and sphere of action static quenching models have been invoked. Using these models various rate parameters have been dtermined. Ground state complex formation model is found not to be applicable. Using sphere of action static quenching model various rate parameters have been determined. The magnitudes of these parameters imply that sphere of action static quenching model agrees well with the experimental results. Hence, the positive deviation in the S-V plots is attributed to the static and dynamic quenching. Further, with the use of finite sink approximation model it has been observed that these bimolecular reactions are diffusion limited. The dependence of Stern-Volmer constant on dielectric constant of the solvents suggests the charges transfer character of the excited complex.

3 illus, 2 tables, 23 ref

007233   Ram Prakash;Singh A P;Gupta D D (Department of Physics, Bipin Bihari P G College, Jhansi 284 001) : Energetic electron precipitation by equatorial and off-equatorial wave-particle interactions at low latitudes. Acta Cienc Indica-Phys 2004, 30(2), 177-86.

Pitch angle diffusion and resulting precipitation of energetic electrons from their trapped regions have been studied at low latitudes by considering their equatorial and off-equatorial cyclotron and Landau resonance interactions with incoherent ELF-VLF whistler-mode waves. The results show that Landau resonance can act on resonant electrons of energy as low as ~2eV whereas first order cyclotron resonance can act on resonant electrons having energy as high as ~MeV range. The calculated fluxes of precipitating electrons for cyclotron resonance are found to be comparable with energy fluxes deposited in the lower ionosphere in the low latitude precipitation zone and those calculated for Landau resonance are found to be consistent with the observed spectrum of Precipitated electrons in the South Atlantic Magnetic Anomaly (SAMA) region. This result shows that higher energy electrons (a few hundred keV to MeV) are precipitated by cyclotron resonance and lower energy electrons (a few eV to ~210 keV) are precipitated by Landau resonance interaction involving ELF-VLF whistler-mode waves at low latitudes.

2 illus, 3 tables, 40 ref

007232   Raghavan A;Jha S S (Phys Dep, Indian Inst of Technol Bombay, Powai, Mumbai-400 076) : Photon detectors: Thermal background noise-equivalent power with frequency-dependent detector efficiency. Indian J pure appl Phys 2004, 42(10), 722-28.

Background thermal noise often becomes the limiting factor while detecting low signals of photon flux from a distant thermal source. This cannot be eliminated by simply cooling the photodetector. A general method is developed here to calculate the background thermal noise and the noise equivalent power (NEP) for background source temperature T, with any given frequency-dependent quantum efficiency function η(v) for the photodetector. Applications of our analysis to some specific model forms of η(v), with finite bandwidths, show that earlier calculations are highly inadequate for peak efficiency frequencies v_a <60> K_BT/h, where k_B is the Boltzmann constant and h is the Planck constant. The NEP, which determines the limit on the lowest signal power that can be detected by any given photodetector, is much higher in these frequency regions compared to earlier approximate estimates

8 illus, 8 ref

007231   Prasad M V S N;Bhaskara Rao S V;Rama Rao T; Sarkar S K;Sharma S (Radio & Atmospheric Sciences Division, National Physical Laboratory, Dr K S Krishan Road, New Delhi 110 012) : Double knife edge diffraction propagation studies over irregular terrain. Indian J Radio Space Phys 2004, 33(3), 180-4.

Mountain cliffs constituting knife edges influence radio wave propagating from VHF to microwave frequencies. The diffraction phenomena caused by these single or multiple knife edges are a dominant propagation mechanism that has to be taken into account in planning TV, FM networks, cellular radio, microwave network, etc., in mountainous regions. In order to investigate the above mechanism field strength measurements were conducted over five double knife edge paths and the measured signal levels are compared with several prediction techniques. The deviations of the prediction techniques and their suitability are presented. It is seen that out of all the prediction methods Giovanelli's method gives best agreement with the observed results.

5 illus, 1 table, 15 ref

007230   Prasad D S V V D;Brahmanandam P S; Venkateswarlu K;Nianjan K;Rama Rao P V S (Department of Physics, Andhra University, Visakhapatnam 530 003) : Characteristics of VHF scintillations in the Indian equatorial and low latitude stations. Indian J Radio Space Phys 2004, 33(3), 158-69.

The two anomaly crest region stations are considered for the study of some typical characteristic features and geophysical effects on the occurrence of VHF scintillations both on short and long term basis. The data pertaining to the period of increasing sunspot years of 1998 and 1999 from the three differetn locations are considered for these studies. The percentage occurrences of scintillations revealed that the occurrence is more at the equatorial station, Pondicherry, compared to those at the two off-equatorial stations, Waltair and Mumbai. The onset of scientillations, in most cases, is found to occur first at the equatorial station, and later at the two off-equatorial stations. However, there are some occasions when the occurrence of scintillations is first seen at Waltair and Mumbai without their prior occurrence at the equatorial station, Pondicherry. These cases are believed to be associated with the generation of regularities at the anomaly crest regions. Further, it is found that the scintillation occurrence increases as the sunspot number increases at all three stations with increasing latitude, suggesting the widening of the scintillation activity belt with the increase of solar activity. The suppression effects of magnetic activity on the occurrence of scintillations seem to be more evident during the pre-midnight hours than during post-midnight hours.

10 illus, 1 table, 26 ref

007229   Prakash J;Rai S K;Singh P K;Gupta H O (Phys Dep, D D U Gorakhpur Univ, Gorakhpur-273 009) : Mechanisms inherent in the thermoluminescence processes. Indian J pure appl Phys 2004, 42(8), 565-71.

Mechanisms inherent in the thermoluminescence (TL) processes are re-investigated with an aim to establish a generalized approach. It has been observed that the extents of recombination and simultaneous retrapping decide the order of kinetics involved. First order kinetics has been fount to be a recombination dominant process with negligible or no retrapping. Probabilities of recombination and retrapping are found to be equal in second order kinetics. With the increasing order of kinetics, the extent of recombination decreases alongwith a simultaneous increase in the retrapping. A generalized equation has been developed which is found to be capable of representing the intensities of TL glow curves of different orders of kinetics including that of the first order. It has been found that irrespective of the order of kinetics involved, TL intensity decays exponentially.

2 illus, 2 tables, 11 ref

007228   Prajapati J H;Patel S G;Oza A T (Phys Dep, Sardar Patel Univ, Vallabh Vidyanagar-388 120, Gujarat) : Infrared spectra of charge transfer complexes of bis(N-phenylsalicylaldiminato) Cu<. Indian J pure appl Phys 2004, 42(8), 572-80.

The charge transfer complexes of bis (N-phenylsalicylaldiminato) cu^II with organic acceptors like TCNQ, TCNE, TNF, DDQ, chloranil, and iodine are prepared and studied with Fourior transform infrared spectroscopy. The spectrum of the donor chelate shows systematic steps in transmission above 2500 cm^-1, which are analyzed by its first-derivative. Fine structure is also seen pronounced in the charge transfer complexes. Two or three electronic absorption envelopes are identified in all the complexes. The nature of transitions (whether direct or indirect), band tailing effects and free-carrier absorption are also analyzed. TNF complex shows free-carrier absorptions in a very wide range above 1800 cm^-1.

9 illus, 7 tables, 8 ref

007227   Pandey A N;Sharma S;Tripathi A K;Singh R (Department of Applied Science and Humanities, TMT College, Ganga Nagar, Meerut) : Application of an effective nuclear charge model to tetrahalides. Acta Cienc Indica-Phys 2004, 30(2), 169-72.

The valence force constants for tetrahalides are evaluated following effective nuclear charge model. The computed results are compared with the experimental force constants, which are determined by normal coordinate analysis. The agreement between the computed and experimental results is reasonably good. It is concluded that the effective nuclear charge model is successful in predicting the approximate valence force constants in more complicated polyatomic molecules.

2 tables, 17 ref

007226   Palaniappan L;Velusamy V (Phys Dep (DDE), Annamalai Univ, , Annamalainagar-608 002) : Ultrasonic study of human cerebrospinal fluid. Indian J pure appl Phys 2004, 42(8), 591-4.

Human cerebrospinal fluid (CSF) has been collected from various individuals of both sex including infants. Sound velocity and density have been measured in these samples and acoustical properties such as adiabatic compressibility and the acoustic impedance have been calculated. The observed variations have been used to interpret the possible interaction among the components of CSF. It has been found that age and sex play an important role in deciding the sound velocity in CSF. The restriction in wave propagation is observed due to the change of structure of protein molecules of CSF. A specific reduction in sound velocity is observed in aged female subjects, which has been attributed to the increase in specific protein AZ 68. Lack of estrogen is reflected in CSF analysis.

2 tables, 20 ref

007225   Okunade A A (Phys Dep, Obafemi Awolowo Univ, Ile-Ife, Nigeria) : Numerical evaluation of lead equivalence of patient and hardware materials in medical diagnostic X-ray shielding. Indian J pure appl Phys 2004, 42(9), 629-47.

Numerical comparison of attenuation and hardening properties of phantom (lucite, soft tissue, water) and hardware (aluminium and steel) materials with those of lead has been carried out. Results show that the shieldings that are affordable by lead attenuation equivalent thicknesses (LAE) and lead hardening equivalent thicknesses (LHE) are not strictly equivalent to those affordable by thickness of substitutes (phantom materials, aluminium and steel) when there are differences in attenuation and hardening properties. Even though beams through LAE that are not `exact' have equal exposure values, the half value layers are higher than those through thickness of lead substitutes. Example calculations show that the use of lead thickness (LAE) that are not `exact' to account for the the shielding afforded by the thickness of patient (water phantom) produce lesser reduction of primary radiation level in the area marked for shielding. The `exact' LAE that will reduce primary radiation level equally as the patient and radiographic table may be higher by close to 20 % or more of that which is not `exact'.

3 illus, 12 tables, 17 ref

007224   Mohapatra U S;Roy G S;Dash S K;Garabadu K; Moharana L (Department of Physics, K B D A V College, Nirakarpur, Orissa) : Evaluation of dipole moment of hydrogen bonded complexes of long-chain alcohols with acetic acid and chlorobenzene. Ultra Scient phys Sci 2003, 15(3), 421-8.

The formation of 1 : 1 complexes involving n-pentanol-acetic acid, n-hexanol-chlorobenzene and n-heptanol-chlorobenzene in a non-polar solvent tetrachlormethane have been studied at a radio frequency of 455 KHz and at temperature of 303.16K. The dipole moment of 1:1 complex μ_ab, molar polarization P_ab, and interaction dipole moment Δμ in all these ternary mixtures have been evaluated. The results indicated that complexation is due to polarization effect.

3 illus, 2 tables, 20 ref

007223   Mariappan C R;Govindaraj G (Raman Sch of Phys, Pondicherry Univ, R.V.Nagar, Kalapet, Pondicherry-605 014) : Conductivity dispersion and scaling studies in Na₃M₂P₃O₁₂ orthophosphate (M₂=Fe₂, TiCd, TiZn). Physica B 2004, 353(1-2), 65-74.

007222   Mallik H;Mukhopadhyay P;Sarkar A (Phys Dep, B.K.Girls' Voll, 5/3 M.G.Road, Howrah-711 101) : Ionic conduction in photosensitive biocomplex of acacia Arabica. Solid St Ionics 2004, 175(1-4), 769-72.

007221   Lochab J;Singh V R (Radiotherapy Dep, Safdarjung Hospital, New Delhi-110 016, ) : Acoustic behaviour of plastics for medical applications. Indian J pure appl Phys 2004, 42(8), 595-99.

The rectangular and square samples of bio-plastic materials namely, polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene plastic (PS material), polypropylene (PP), polyvinyl chloride (PVC), bakelite (G-10), nylon, Y-dent and teflon (PTFE) used for different applications in hospitals have been studied. These samples collected from different hospitals in Delhi (Safdarjang Hospital, Batra Hospital, AIIMS) have been studied for ultrasonic velocity, elasticity, acoustic impedance etc. at room temperature (24°C). The average values of ultrasonic velocity and elasticity are found to vary directly with the density. The ultrasonic parameters measured at 2.5 MHz are reported here.

3 illus, 3 tables, 18 ref

007220   Kumar D;Kumar S (Phys Dep, Christ Church Coll, Kanpur-208 001) : Steady state Photoconductivity in a Se_80-x Te₂₀Ge_x thin films. Indian J pure appl Phys 2004, 42(10), 771-4.

The steady state photoconductivity of vacuum evaporated thin films of amorphous Se_80-xTe₂₀Ge_x (x = 5, 10, 15 and 20) has been investigated. The measurements of temperature dependence of dark conductivity (σ_ph) show that the conduction is through a thermally activated process in both the cases. The activation energy decreases with the increase in light intensity. This indicates the shift of Fermi level with intensity. The measurements of intensity dependence of photoconductivity show that the photoconductivity increases with intensity as a power law where the power is found to be between 0.5 and 1.0. The photosensitivity (σ_ph/σ_d) increases with the increse of Ge concentration which indicates that the density of defect states decreases with the increase in Ge in a-Se_80-xTe₂₀Ge_x. This is consistent with the conclusions reported in the literature by dielectric loss measurements.

3 illus, 1 table, 18 ref

007219   Khare P K;Sahu D K;Verma A;Srivastava R K ({pstgraduate Studies & Res in Phys Dep, Rani Durgavati Univ, Jabalpur-482 002) : Depolarization studies of polyvinylidene fluoride foil electrets using thermally stimulated discharge. Indian J pure appl Phys 2004, 42(9), 693-6.

Thermally stimulated discharge current (TSDC) in foils of polyvinylidene fluoride (PVDF) was measured under various polarizing conditions. The TSDC thermograms were recorded by reheating the samples at a linear rate of 3°C/min. It was found that samples give rise to a peak around (100± 10°C). The peak position is not consistent with the polarization fields and temperatures. The activation energy associated with the peak is found to be ~ 0.62 eV. The dependence of TSD current and TSDC data on polarizing agents, i.e. field and temperature is explained on the basis of theoretical predictions. The space charge polarization contributes significantly to the polarization of the polymer.

2 illus, 1 table, 23 ref

007218   Khanna K M;Karap Kirui M S;Sakwa T W;Torongey P K;Ayodo K Y;Rotich S (Phys Dep, Moi Univ, P O Box 3900, Eldoret, Kenya) : Correlation amplitude for quasi-particles in high T_c superconductors. Indian J pure appl Phys 2004, 42(10), 758-63.

The correlation amplitude for the quasi-particles in high T_c superconductors has been deduced. From this amplitude, the maximum critical stransition temperature has been calculated. The assumption, which has been made is that, the superconductivity is due to condensation of electron pairs, which may be in a parallel spin-state, an antiparallel spin-state, or a mixture of the two states. It has been established that the maximum transition temperature in the optical phonon frequency is T_c = 262.6 K irrespective of the state of the electron pair.

1 illus, 12 ref

007217   Kane R P (Instituto Nacional de Pesquisas Espacias-INPE, Caixa Postal 515, 12201, Sao Jose dos Campus, SP, Brazil, ) : Distortion of a 27-day sequence of solar indices. Indian J Radio Space Phys 2004, 33(3), 149-57.

The interval 20 Feb.-4 July 1998 had strong~27-day oscillations, almost simultaneously, in various solar indices. Counting 20 Feb. 1998 as day number 1, the peaks ocured near day numbers 4, (27) 31, (18) 49, (27) 76, (8) 84, (24) 108, (27) 135, where the numbers in parantheses are the spacing in days. The first two peaks had a separation of 27 days, but the next peak was only 18 days away, heralding probably the commencement of a new, second sequence. The next peak was 27 days away which was the part of this second sequence, but the peak next to that was only 8 days away, indicating that the second sequence terminated. However, the next peaks were such that they fitted nicely as if the first sequence restarted (4, 31, 58 missed, 84, 108, 135), indicating that some sequences can remain dormant for a cycle or two and then reappear. The peaks at 4, 31, 49, 76, 84, 108, 135 were qualitatively the same for several solar indices, but their quantitative evolution was different for different indices.

3 illus, 1 table, 26 ref

007216   Jha V K;Singh S N;Roy T (Post Graduate, Department of Physics, C M Sc. College, Darbhanga) : Study of field pattern produced by leaky wave antenna operated with P-I-N diode switches. Acta Cienc Indica-Phys 2004, 30(2), 221-5.

One of the main characteristics of electronic switch wave antenna is that its main beam direction can be scanned by application of electronic circuit. In most of the cases the scanning is achieved on the cost of frequency variation, which restricts the application of such antenna. Technique has been presented for scanning, the main tube by using p-i-n diode to modulate the effective wave-guide size. This approach may be employed in the case of millimeter wave frequency by utilizing integrated circuit on semiconductor wave-guide.

4 illus, 12 ref

007215   Jha A K;Jha L;Jha A;Jha H K (Department of Physics, R M College, Saharsa (Bihar)) : Electromagnetic inverse scattering theory. Acta Cienc Indica-Phys 2004, 30(2), 213-16.

Inverse methods have become a fundamental tool in the physical sciences for remotely sensing unknown objects and reconstructing the physical properties. A qualitative introduction to electromagnetic inverse scattering has been given. Instead of surveying the many diverse applications of inverse methods, an example of analysis of remote sensing data from ocean surfaces which illustrates the fundamentals of inverse scattering has been taken. This is only tip of iceberg" of inverse scattering theory.

2 illus, 9 ref

007214   Jana P K;Nandi S C;Midya S K (Department of Chemistry, Institute of Education (PG) for Women, Chandernagore) : Percentage contribution of atmospheric minor constituents on marine lower tropospheric ozone. Indian J Radio Space Phys 2004, 33(3), 201-5.

A critical analysis has been made on contribution of atmospheric minor constituents on the formation of oceanic ozone at the lower troposphere. Altitudinal distributions of these constituents are also presented.

2 illus, 1 table, 32 ref