003028   Bishoyi K C;Rout G C;Behera S N (Physics Dep, F M College, Balasore-756 001, Email: bishoyi@iopb.res.in) : Magnetism and hybridization through ultrasonic attenuation in cuprate systems. Indian J Phys 2007, 81(1), 47-53.

Attempt is made to present a microscopic theoretical model for the cuprate systems in presence of antiferromagnetism (AFM), the position of impurity f-Ievel, hybridization between f-Ievel and copper d-electrons as well as phonon interaction to the hybridization in harmonic phonon vibration approximation. When the high frequency ultrasonic wave travels in the solid, it deforms the lattice. In theoretical model calculation, the phonon Green's function is evaluated by Zubarev's technique. The imaginary part of the phonon self-energy gives the ultrasonic attenuation of the system and displays the interplay of AFM and hybridization in it. The effect of model parameters like staggered magnetic field (h), position of f-Ievel (ε_t), hybridization (V), and electron-phonon coupling constant (g) on the temperature variation of ultrasonic attenuation is studied and the results are reported.

5 illus, 6 ref

003027   Bhaumik U (NO, Vidyasagar College, 39 Sankar Ghosh Lane, Kolkata-700 006, Email: umabhaumik@lycos.com) : DM interaction in triangular lattice. Indian J Phys 2007, 81(1), 75-81.

Studies the triangular lattice using linear spin-wave theory with Heisenberg antiferromagnets in addition to Dzyaloshinskii-Moriya interaction and weak magnetic field. The quantum corrections to the ground state energy and sub lattice magnetization has been calculated analytically as a function of DM interaction strength and also of the magnetic field. The gap in the excitation spectrum has also been calculated. Finally, it has come to the conclusion that the DM interaction stabilizes the LRO reducing the effect of the quantum fluctuation.

3 illus, 9 ref

003026   Bhattacharjee B;Kakati R K (Physics Dep, Gauhati University, Guwahati-781 014, Email: ranjan_kakati@rediffmail.com ) : Estimation of radon in various sources of water in various places of Karbi Anglong district of Assam. Chem envir Res 2006, 15(4), 228-31.

Alpha activity in water has been studied for various sources in Karbi Anglong district of Assam. The alpha track density are found to vary considerably from sample to sample. The concentrations are more in sources where fluoride concentration were reported to be also very high.

1 illus, 1 table, 5 ref

003025   Banarji B;Nayak P;Choudhary R N P (Physics Dep, Sambalpur University, Sambalpur-768 019, Email: banarji_behera@yahoo.co.in) : Dielectric and electrical properties of NaBa₂V₅O₁₅ ceramic. Indian J Phys 2007, 81(1), 63-7.

The dielectric and electrical properties of polycrystalline sample NaBa₂V₅O₁₅ (NBV) prepared through solid-state reaction technique is presented here. X-Ray diffraction study has confirmed the formation of single-phase compound with an orthorhombic structure at room temperature. The analysis of the dielectric constant (ε) and loss tangent (tanδ) as a function of frequency and temperature suggest the occurrence of phase transition above the room temperature and has a very low value of dielectric constant (ε) at the transition temperature. The electrical properties analysis (i.e., ac conductivity) shows that the compound exhibit negative temperature coefficient of resistance (NTCR) type of behavior like that of a semiconductor.

4 illus, 13 ref

003024   Ahirwar G;Varma P;Tiwari M S (Physics and Electronics Dep, Dr. H S. Gour University, Sagar-470 003,) : Electromagnetic ion-cyclotron wave with general loss-cone distribution function. Indian J Phys 2006, 80(12), 1179-87.

Electromagnetic ion-cyclotron (EMIC) waves have been studied by single particle approach with general loss-cone distribution function. The dispersion relation, growth rate, resonance energy and marginal stability of the electromagnetic ion-cyclotron wave with general loss-cone distribution function in a low β homogeneous plasma have been investigated. The effect of the steepness' of the loss-cone distribution has been studied with different plasma parameters. The wave is assumed to propagate parallel 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-esonant particles participate in the oscillatory motion of the wave. The effect of general loss-cone distribution function is to enhance the growth rate of EMIC waves. The results are interpreted for the space plasma parameters appropriate to the auroral acceleration region of the earth's magnetoplasma.

6 illus, 46 ref

003023   Abid I;Gargouri M;Smaali I;Limam F;Maugard T; Legoy M D;Marzouki N (INSAT, , BP 676, 1080 Tunis Cedex, Tunisia, Email: mohamed.gargouri@insat.rnu.tn) : Application of xylanolytic enzymes in alkyl-β-xyloside synthesis and purification of β-xylosidase from Sclerotinia sclerotiorum. Int J pure appl Chem 2006, 1(1), 83-90.

β-Xylosidase and endo-xylanase belong to an enzyme battery that phytopathogenic ffmgi use for the degradation of the cell walls. An enzyme preparation from Sclerotillia sclerotiorum was applied in synthesis of biosurfactants: hexyl-β-xyloside and hexyl-β-xylobioside from xylan and hexanol. Also, in order to characterize the enzyme activity, the β-xylosidase obtained in the culture filtrate was purified by the successive use of anion exchange chromatography DEAE-sepharose, anion exchange HPLC TSK-DEAE, gel filtration on TSK-200 SW HPLC followed by preparative native-PAGE. β-Xylosidase seems to be a monomeric protein with 70 kDa estimated by gel filtration and 72 kDa determined by SDS-PAGE. With pNPX as substrate. β-xylosidase has Michaelis-Menten kinetics: K_m = 1.61 mM and V_m = 0.14μmol min^-1 mg protein. The enzyme showed an optimal activity at 60°C and pH 4. It also showed stability over a wide pH range (from 2 to 9) and retained up to 50% of its activity at 50°C. The enzyme activity was further characterized by testing several divalent ions and reagents.

7 illus, 1 table, 24 ref

002117   Yadav B S;Tyagi S K;Saran R (Molecular Spectroscopy and Bio-Phys Lab, DN Coll, Meerut-250 002) : Effect of solvents and pH variation on electronic spectra of 2-hydroxy-4-methoxy benzaldehyde. Ultra Scient phys Sci 2006, 18(2), 123-6.

Electronic spectra in various polar solvents have been recorded in the region 1900-4000 Angstrom. The effect or change or solvent on electronic transition or 2-hydroxy -4 methoxy bonzaldehyde is explained. The effect of pH variation has also been studied.

4 illus, 2 tables, 12 ref

002116   Upadhyay A;Joshi S K;Chandel C (Snow & Avalanche Study Establishment, , Manali-175 103) : Tensile strength of snow using centrifugal technique. Def Sci J 2007, 57(6), 787-95.

Tensile strength of snow was determined using indigenously developed automated centrifugal machine. Processed snow (sintered at -20°C for 4 days) samples of dia: 65 mm and height: 130 mm were tested using this machine. The experiments were conducted on sieved snow at four temperature levels of 0°C, -3°C, -6°C and -9°C at density ranging from 200-460 kg/m³. Results of these experiments have been compared with the earlier suggested models. Probability distribution of snow strength on the basis of current experimental data has also been presented.

8 illus, 11 ref

002115   Pandey M K;Shrivastav P K;Tiwari R K (Phys Dep, Govt Model Sci Coll, Rewa) : Average characteristics of cosmic rays daily variation for solar cycle-23. Ultra Scient phys Sci 2006, 18(2), 199-202.

As we know that the solar modulated anisotropic variations in cosmic ray intensity can be detected by the ground based detectors. These anisotropies are generated due to the spin motion of the earth. Performs an average characteristics analysis to establish the amplitude and phase modulation for first two harmonics of the cosmic ray anisotropy. Pressure corrected hourly values of Kiel NM station have been used for the period 1996 to 2005. In the present study, derives the average characteristics of first two harmonics of cosmic ray daily variation for the period of 1996 to 2005, covering the almost whole solar cycle - 23.

2 illus, 1 table, 7 ref

002114   Khanna S;Sharma R;Rastogi V K (Phys Dep, Ch Charan Singh Univ, Meerut) : Studies on the piezoelectric and pyroelectric propeties of samarium modified lead zirconium titanate (PZT) electroceramic. Ultra Scient phys Sci 2006, 18(2), 133-6.

Modified PZT samples (pellets) of composition Pb_1-x Sm_x (Zr_0.53 Ti_0.47) O₃ where x = 0, 0.02, 0.04, 0.06 & 0.08 were prepared by conventional solid state reaction method using the oxide precursors. The samples were characterized for their pyroelectric and piezoelectric properties. PSZT samples have high piezoelectric and pyroelectric coefficients yielding them to have a variety of applications.

3 illus, 3 tables, 9 ref

002113   Ghosh K E (BESU, , Shibpur, Howrah) : Gas hydrate - the latest source of alternative energy. MGMI Trans 2005, 102(1-2), 63-8.

With gradual depletion in the reserve of the conventional sources of energy such as Coal and Petroleum, Man is frantically looking for alternative sources of energy. Clathrate or gashydrate in oceanic and lacustrine sediments is the latest source of alternative energy.. Clathrate is an ice like crystals of water where water molecules form a cage trapping methane and other gases. The generation of clathrate in sediments, its mode of occurrence global and Indian occurrences are discussed. The global and Indian reserve of clathrates, their methods and problems of exploitation are also mentioned.

5 illus, 11 ref

001135   Yadagiri Reddy P;Reddy K V K;Reddy C G;Reddy K R (Physics Dep, Osmania Univ, Hyderabad-500 007) : Indoor radiation levels in the proposed uranium mining areas of Andhra Pradesh, India. Envir Geochem 2005, 8(1-2), 104-7.

Lambapur and Peddagattu areas in the Nalgonda district of Andhra Pradesh, India are found to have significant uranium mineralization. Studies made by Atomic Minerals Directorate of Exploration and Research (AMDER), Hyderabad revealed that this mineralization could be a commercially viable source for extraction of uranium mineral. This paper reviews our studies taken up to establish base-line data of indoor radiation levels in the proposed uranium mining areas before the actual mining is taken up. The mean indoor radon and thoron levels in these areas are found to be 75.4 and 70.6 Bq.m^-3, respectively. Whereas the average effective dose due to indoor radon, thoron and their progenies is found to be 4.9 mSv.y^-1. A comparative study in these areas has shown that the radon and thoron levels are relatively higher in the mud type of dwellings. Since the mud is taken from the local soil, it can be concluded that the local soil contributes significantly to the indoor radiation levels. The average of the measured natural background gamma radiation levels in this area is found to be (2.51 ±0.42)x10³ μGy.y^-1.

4 illus, 11 ref

001134   Thakur N;Walia V;Sharma J N (Applied Sciences Dep, National Institute of Technology, Hamirpur-177 005, Email: jns@recham.ernet.in) : Propagation of thermo-elastodiffusive surface acoustic waves in semiconductors. Asian J Chem 2006, 18(5), 3329-34.

The propagation of thermoelastic diffusive surface waves in homogenous isotropic, thermally conducting semiconductor, half space materials has been investigated. The secular equations governing the phase velocity, attenuation coefficient and other characteristics of the thermoelastic (ET) and elastodiffusive (EN) waves have been obtained. The waves are found to be dispersive in character and attenuated in space. The secular equations have been solved numerically for silicon (Si) semiconductor to obtain the profile of phase velocity and attenuation coefficient. The numerically simulated results have also been presented graphically.

2 illus, 10 ref

001133   Thakkar R;Singh N;Allawadhi K L (Physics Dep, Nuclear Science Laboratories, Punjabi Univ, Patiala-147 002, Email: allawadhi@yahoo.co.in) : Variation of CK enhancement factors with energy for deuterons induced L subshell X-rays in Ag, Cd, In and Te. Asian J Chem 2006, 18(5), 3283-5.

The enhancement produced by the Coster Kronig transitions for deuterons induced L subshell X-rays and the variation of the enhancement factors (namely k₁ βbeta and kγlemda) with incident deuteron energy and the atomic number has been investigated in Ag, Cd, In and Te. The Coster-Kronig enhancement factors have been observed to be varying with incident proton energy as well as the atomic number. The maximum value of the enhancement factor among elements under investigation has been determined to be about .87 for k₁,a in Indium-49.

1 illus, 9 ref

001132   Tejbir Singh;Paramjeet Kaur;Singh P S (Physics Dep, Punjabi Univ, Patiala-147 002, Email: dr_parjit@hotmail.com ) : Parameters of dosimetric interest of some vanadium and nickel compounds. Asian J Chem 2006, 18(5), 3325-8.

Mass attenuation coefficients (μu_m), effective atomic numbers (Z_eff) and electron densities (N_el) of some vanadium compounds V₂0₃, VO₂, VF₃, VF₄, NH₄V0₃ and nickel compounds NiF₂, NiCl₂, NiCl₂.6H₂O, Ni(C10₄)₂.6H₂0, NiF₂.4H₂₀ have been computed over a wide energy region from 10 keV to 100 GeV. In all the parameters, a similar trend is observed. All the parameters initially possesses maximum values, which decreases very rapidly upto 100 keV, then becomes almost constant upto 3 MeV and with the further increase in the incident photon energy beyond 3 MeV, values of all the parameters also increase which may be due to dominance of different partial photon interaction process in different energy regions.

6 illus, 7 ref

001131   Tejbir Singh;Gurmel;Mudahar S;Singh P S (Physics Dep, Punjabi Univ, Patiala-147 002, Email: dr_parjit@hotmail.com ) : Effect of geometrical constraints on the intensity of multiple scattered gamma photons in soil medium. Asian J Chem 2006, 18(5), 3361-4.

Transverse thickness as well as the distance between source (¹³⁷Cs) and detector was varied in soil medium keeping fixed longitudinal thickness to investigate the variation of intensity of multiple scattered gamma rays with geometrical changes. The obtained results are in good agreement with previous findings in which source and detector were kept fixed and the dimensions of soil medium were varied. It is reported that the intensity of multiple scatter photons depends on the thickness of the interacting medium between the source and detector not on the geometrical constraints.

5 illus, 7 ref

001130   Tarsikka P S;Singh B (Mathematics Dep, Statistics and Physics, Punjab Agricultural Univ, Ludhiana-141 004) : AC conductivity of lead-tungsten phosphate glasses. Asian J Chem 2006, 18(5), 3376-80.

AC conductivity of six samples of lead-tungsten phosphate glasses having compositions x mol% PbO-(60-x) mol% W0_3-40 mol% P₂₀₅ has been studied at low frequencies in the temperature range 77 K to 300 K. Measured ac conductivity, σ_t(ϖ) at 1 kHz or at 10 kHz has been observed to decrease with the increase of tungsten ion concentration whereas for 60 mol% W0_3-40mol% P₂O₅ glass values of σ_t(ϖ) are larger than those for lead-tungsten phosphate glasses. The ac conductivity obeys σ_ac (ϖ) = A ϖ^S relation over a considerable range of low temperatures. At higher temperatures the ac conductivity starts deviating from linearity and the temperature at which the deviation from linearity starts, increases with increasing frequency. Values of s are slightly greater than unity for glass samples having lead ions concentration larger or equal to the tungsten ion concentration whereas for other samples the values of s are less than unity and the values decrease with the increase of tungsten ion concentration. Theoretical values of 's' are evaluated by applying the hopping over barrier model (HOB). Values of density of states at the Fermi level for different compositions of glasses have the order 10¹⁹ (assuming a to 0.5 A^-1), which suggest that the states are localized near the Fermi level.

4 illus, 1 table, 10 ref

001129   Sukhpal Singh;Ashok Kumar;Jarnail Singh;Thind K S;Mudahar G S (Physics Dep, Punjabi Univ, Patiala-147 002) : Mass attenuation coefficients studies in some flyash materials. Asian J Chem 2006, 18(5), 3314-16.

The linear and mass attenuation coefficients have been measured in some flyash materials for 662 keV gamma rays. The values of mass attenuation coefficient are found to be nearly constant for all the materials.

1 table, 7 ref

001128   Srinivasan R (NO, Raman Research Institute, C.V. Raman Avenue, Sadashivanagar, Bangalore-560 080, Email: rsv@rri.res.in) : Nonlinear magneto-optical rotation - a possible tool for sensitive magnetometry. Curr Sci 2007, 92(3), 298-307.

Optical pumping in an alkali metal vapour produces long-standing coherences of ground state Zeeman sub-levels. These coherences produce large nonlinear magneto-optic rotation (NMOR). Techniques using optical coherences for sensitive magnetometry have been in vogue for a long time. However, the sensitivity achieved has been three orders of magnitude lower than that of a SQUID magnetometer. The NMOR technique has yielded signals having a very narrow width of a few micro-Gauss. In principle, it has been demonstrated that with NMOR magnetometers one can obtain a sensitivity matching, or better than the sensitivity of a Squid magnetometer. There are still many problems to be resolved before these magnetometers can be put to use in geomagnetic and biological applications, where small magnetic fields need to be measured.

11 illus, 29 ref

001127   Sinha M M (Phys Dep, Sant Longowal Institute of Engineering and Technology, Longowal-148 106) : Phonons in the novel antiperovskite ZnCNi₃. Asian J Chem 2006, 18(5), 3412-17.

The discovery of superconductivity in MgCNi₃ has generated a new puzzle in the recent series of found superconductors. Despite its relatively low T_c ca. 8K, the presence of Ni signals the possible importance of correlation effects which makes the physics of the pairing mechanism relevant to the famous high T_c cuprates and brings the discussion of unconventional non-electron phonon mechanism. ZnCNi₃ is very similar to MgCNi₃ structurally and having Tc ca. 2K. The lack of superconductivity transition down to 2K is quite unexpected. Understanding why superconductivity is seen in one compound but not the other could be important in resolving the unusual behavior of MgCNi₃. It is, therefore, in the present work, the phonons in ZnCNi₃ is investigated by applying a de Launey angular force constant model. In this model, the relative displacement of the reference atom and one of its neighbors is considered. The calculated zone center phonons and phonon dispersion curves of ZnCNi₃ in the symmetric directions are compared with recently calculated values of MgCNi₃ in order to find the mechanism of superconductivity in these compounds.

1 illus, 2 tables, 25 ref

001126   Singh R J (Physics Dep, Aligarh Muslim University, Aligarh-202 002, Email: ranajsingh@yahoo.com) : Heating of manganites by magnetic component of microwave. Indian J pure appl Phys 2007, 45(5), 454-8.

When the dependence of EPR spectra of La_0.67 Pb_0.33 MnO₃ , La_0.6Pb_0.4 MnO₃ , La_0.7 Ba₃ MnO₃ and La_0.67 Sr0₃₃ MnO₃ on microwave power (1-200mW) applied in the EPR instrument was investigated, it was observed that the samples became unusually hot on high microwave power levels. The cause of heat generation has been explained as interaction of the spin of e_g electron of Mn³⁺ with the magnetic component of microwave field which ultimately leads to Debye type of relaxation of a physical ensemble ,i.e., spin-orbital-lattice polaron . The polaron so created is found to be of 11 Å size and consists of Mn³⁺ ion, its nearest neighbours Mn⁴⁺ and La³⁺ ions and the alkaline earth ions along with oxygen octahedra surrounding Mn-ion sites.

001125   Singh M P;Sandhu B S;Bhajan Singh (Physics Dep, Punjabi Univ, Patiala-147 002) : Determination of effective atomic number using Rayleigh to Compton scattering of gamma rays. Asian J Chem 2006, 18(5), 3275-8.

Rayleigh to Compton scattering intensity ratio method is used to determine the effective atomic number of binary alloys. The experiment is performed with various elements (13 ≤ Z ≤ 79) using HPGe solid-state detector placed at 50° relative to incident beam of 279 keV gamma photons. The intensity ratio under Rayleigh to Compton scattered peaks is plotted as a function of atomic number and fitted with a curve. From this calibration curve, the effective atomic number of the brass is determined.

2 illus, 4 ref

001124   Singh J (Mathematics Dep, Statistics and Physics PAU, Ludhiana-141 004, Email: jsgalsin@yahoo.com) : Spin density and magnetic moments on impurities in Ni and Pd metals. Asian J Chem 2006, 18(5), 3286-91.

Formalism is developed, using the partial wave method in the mixed band scheme, for evaluating magnetic moments on magnetic d-band impurities in metals. The magnetic moments are calculated on d-band impurities in Ni and Pd metals and the values show reasonable agreement with the experimental results and explains the existence of giant magnetic moments in Pd alloys.

2 tables, 10 ref

001123   Singh J (Mathematics Dep, Statistics and Physics PAU, Ludhiana-141 004) : Nanomaterials and nanotechnology. Asian J Chem 2006, 18(5), 3271-4.

The concept of nanoparticles and nanomaterials has been introduced. An attempt has been made to review the different types of nanomaterials (fullerenes, quantum dots and nanotubes) along with their applications in different fields.

3 illus, 4 ref

001122   Shukla D K;Mollah S (Physics Dep, AMU, Aligarh-202 002, Email: smollah@rediffmail.com) : DC conductivity of copper-bismuth glasses doped with TiO₂ and ZnO. Asian J Chem 2006, 18(5), 3321-4.

The dc electrical conductivity of glasses with composition 40CuO-40Bi₂O₃-20Ti0₂ and 40CuO-40Bi₂0₃-20ZnO prepared by rapid quenching method has been investigated over the temperature range 300-600 K. The glassy phase is confirmed from X-ray diffraction (XRD) pattern which shows a broad hump around 20 = 30°. The dc conductivity of ZnO doped glass at all the temperatures is higher than that of the corresponding composition doped with TiO₂ but the eneral trend of the increase or decrease of conductivity and activation energy are similar in both the glasses. Holstein's relation suggests that hopping conduction is in non-adiabatic region for both the glasses.

1 illus, 8 ref

001121   Sharma P;Mittal R (Physics Dep, Nuclear Science Laboratories, Punjabi Univ, Patiala-147 002, Email: punm_90@yahoo.co.in) : Quadrupole moments of super deformed bands in different isotopes of elements in the range 30 ≤Z ≤82. Asian J Chem 2006, 18(5), 3352-6.

Quadrupole moments for super deformed (SD) bands in different isotopes of elements 30≤ Z ≤82 have been found to vary regularly with mass number. An attempt has been made to find an empirical relation between quadrupole moments and mass numbers for different bands.

2 illus, 1 table, 10 ref

001120   Sharma A;Tiwari M K;Mittal R (Physics Dep, Nuclear Science Laboratory, Punjabi Univ, Patiala-147 002, Email: rmsingla@yahoo.com) : Anisotrophy of L sub-shell x-rays in tungsten at photon energies, below and above the L2-edge. Asian J Chem 2006, 18(5), 3335-9.

Angular distribution of relative intensities of L X-rays from Tungsten (W) following ionization by photons has been studied at incident photon energies, 10.676 keV (lying between L3 and L2 edges of W) and 17.781 keV. The relative Le, Lα and Lβ intensities has been observed at both the photon energies that have been found to be comparable. Furthermore, the Lλ X-rays were found to show anisotropy more in comparison to other L X-ray groups at both the energies.

3 illus, 8 ref

001119   Sabharwal A D;Sandhu B S;Singh B (Physics Dep, Punjabi Univ, Patiala-147 002) : Compton backscattering from broad beam of gamma rays in Al and Zn. Asian J Chem 2006, 18(5), 3390-4.

The intensity distribution of Compton backscattered photons for a broad beam of gamma rays has been measured as a function of scatterer thickness for aluminium and zinc at incident photon energies of 279. 356 and 511 keV.

3 illus, 4 ref

001118   Rajesh Kumar;Ali S A;De U;Rajendra Prasad (Applied Physics Dep, Z.H. College of Engineering and Technology AMU, Aligarh-202 002) : Characterization of optical modification in polyethersulfone due to irradiation with Si and Ne ions. Asian J Chem 2006, 18(5), 3365-70.

Irradiation of the polymeric materials with radiation results into the modification of their physico-chemical properties due to the transfer of high value of energy by the heavy ions causing unusual density of electron hole pairs close to the ion path. Films of 250 μm thickness of the polymer, polyethersulphone (PES) were irradiated to Si⁸⁺ ions of energy 100 MeV to the fluences of 1 x 10¹⁰, 1 x 10¹¹, 1 x 10¹² and 5 x 10¹² ions/cm² and Ne⁶⁺ ions of energy 145 MeV to the fluences of 1 x 10¹² and 1 x 10¹³ ions/cm². Optical modifications were characterized by UV-Vis. Spectroscopy is found to decrease with transferred energy density of the ion beams. The energy band gap (E_g) values were computed from the absorption edge in the 200-800 nm region. E_g varied from 2.68 to 1.63 eV in Si⁸⁺ irradiated PES samples and from 2.68 to 1.61 eV Ne⁶⁺ irradiated PES samples. The cluster size varied in a range of 6 to 11 carbon atoms per cluster.

2 illus, 2 tables, 18 ref

001117   Raj Kumar;Aggarwal K (Coherent Optics Div, Central Scientific Instruments Organisation, Sector 30, Chandigarh-160 030, Email: aka1945@rediffmail.com) : Schlieren interferometric concealed coded security holograms. Indian J pure appl Phys 2007, 45(5), 429-33.

Method has been described to create concealed codes in security holograms. The codes are in the form of pure phase patterns and require an interferometric scheme to convert these invisible phase variations into detectable amplitude/intensity variations. An interferometrically encoded reference beam from the key hologram captures a phase modulated object beam to form the security hologram. In the final reading process, a moir‚-like fringe pattern gets generated in the observation plane when the same reference beam illuminates security hologram. This moir‚ pattern is helpful in verifying the genuineness of the hologram and also facilitates in repositioning of security hologram. In the null mode moir‚ position, true object wavefront gets reconstructed but the information of concealed codes still remains invisible. Use of Schlieren technique is proposed as a simple way to reveal the concealed codes for security hologram authentication. These concealed codes can be used as an anti-counterfeiting feature in embossed security holograms.

001116   Raina K K;Pankaj Kumar;Sumana G (Materials Research Laboratory, School of Physics and Materials Science Thapar Institute of Engineerin, Patiala-147 004, Email: kkraina@tiet.ac.in) : Ferroelectric liquid crystal-polymer composites: a novel display material. Asian J Chem 2006, 18(5), 3384-9.

Liquid crystals constitute an important class of display materials used in liquid crystal display (LCD) devices. Although, these materials were discovered over a century back (1988), but they gained importance about mid 1970's when used in seven segment display devices like digital watches, calculators etc. Since then, the X subject became a household name considering the market potential and varied use in consumer electronics. At present, LCD's constitute about 68% market share in display industry starting from small seven segments to high definition projection displays. Behind this technological development, liquid crystalline materials play a very important role. Discusses the work being carried out in the research group at TIET in this subject. Also deliberate on the development of ferroelectric liquid crystal-composite materials and physics behind the LCD technology.

2 illus, 18 ref

001115   Prasher S;Mukesh Kumar;Surinder Singh (Physics Dep, RIMT Institute of Engineering and Technology, Mandi Gobindgarh-147 301, Email: moka_esh9@yahoo.com) : IR induced modifications in some solid state track recorders. Asian J Chem 2006, 18(5), 3357-60.

The environmental conditions may affect the characteristics of solid state nuclear track detectors during their exposure in space. Hence, it is essential to study the environmental effect on these detectors. The effect of infrared radiations on the etching characteristics of CR-39 and glass has been reported. CR-39 plastic track detector has been found to be more sensitive to these radiations than glass.

1 table, 6 ref

001114   Paramjeet Kaur;Tejbir Singh;Singh P S (IAS and Allied Services Training Centre, Punjabi Univ, Patiala-147 002, Email: dr_parjit@hotmail.com) : Effective atomic numbers and electron densities of some HCO materials as a function of weight fraction of constituent elements. Asian J Chem 2006, 18(5), 3340-3.

Effective atomic numbers and electron densities of some HCO materials (here HCO materials means organic compounds containing H, C and O only) such as benzyl alcohol, benzaldehyde, ethanol, methanol and glycerol have been computed using computer program over a wide energy range from 1 keV to 100 GeV and the effect of fractional abundance of constituent elements have been investigated and presented in the graphical form.

6 illus, 7 ref

001113   Pagare G;Sanyal S P;Jha P K (NO, Government M L B Girls P G College, Bhopal-462 011, Email: spsanyal@sanchanet.in) : High-pressure behaviour of rare earth mono bismuthides. Indian J pure appl Phys 2007, 45(5), 459-64.

Pressure induced structural phase transition of mono-bismuthides of cerium, praseodymium, uranium and plutonium (REBi, RE= Ce, Pr, U and Pu) has been studied theoretically by using suitable two body inter-ionic potential which parametrically includes the effect of Coulomb screening by the delocalized f electrons of rare earth (RE) ion. The anomalous structural properties of these bismuthides, where Bi ion has the largest ionic radius, have been studied to investigate the role of f electrons on the structural phase transition. Except UBi, all the three compounds transform to body -centered tetragonal (BCT) structure at high pressure. UBi prefers to transform to cubic CsCl phase at high pressure. A static simulation technique has been used to calculate the equation of state, change in anion-anion and anion-cation distances with increasing pressure, for these compounds. The important finding is that, from the total energy point of view except UBi, all the compounds prefer to transform to BCT structure than CsCl structure at high pressure.

001112   Narayana Y;Rajashekara K M;Siddappa K (Studies in Physics Dep, Mangalore Univ, Mangalagangothri-574 199, Email: narayanay@yahoo.com) : Natural radioactivity in a major river of coastal Karnataka. Envir Geochem 2005, 8(1-2), 186-9.

Discusses the results of systematic measurement of activity concentrations of the ²²⁶Ra, ²³²Th and ⁴⁰K in reverine samples of river Netravathi, one of the major river of coastal Karnataka. This study was initiated to throw light on the transportation of radionuclides in the riverine environs of the coastal Karnataka. The ²²⁶Ra activity in soil varies from 38.0 Bq kg^-1 to 73.2 Bq kg^-1 with mean values 56.6 Bq/ kg^-1, for sediment the activity varies from 45.4 to 196.6 with mean values 82.0 Bq kg^-1 and 36.8 to 60.2 Bq/ Kg with mean values 44.0 Bq/kg for rock. ²³²Th activity was found to be 82.9Bq kg^-1 to 222.3 Bq kg^-1 with mean values of 121.5 Bq kg^-1 for soil, 25.1 Bq kg^-1 to 394.5 Bq kg^-1 with mean value of 185.8 Bq kg^-1 and 15.2 Bq kg^-1 to 179.4 Bq kg^-1 with mean values of 65.15 Bq kg^-1 for sediment and rock samples respectively. The activity of ⁴⁰K was found to vary from 430.2 Bq kg^-1 to 720.9 Bq kg^-1 with mean 570.3 Bq kg^-1, 377.7 Bq kg^-1 to 879.1 Bq kg^-1 with mean value 581.9 Bq kg^-1 and 342.9 Bq kg^-1 to 1322.1 Bq kg^-1 with mean values of 709.0 Bq kg^-1 for soil, sediment and rock samples respectively. The contributions of natural radionuclides to the total gamma absorbed dose have been calculated. ²³²Th was found to be the highest contributor to the external gamma dose rates in air.

1 illus, 3 tables, 13 ref

001111   Nandi T (NO, Accelerator Centre Inter Univ, JNU Campus, New Delhi-110 067) : Effect of foil thickness on excited states in the beam-foil interactions. Asian J Chem 2006, 18(5), 3260-4.

Reports experimental studies on the interaction mechanism of excited states produced by fast heavy ions passing through carbon foil with a thin carbon foil. Oscillatory structure of the lifetime spectrum of the combined peak of Ml and M2 decays in He-like Ti-ions gives a direct evidence of the transitions between Is2p ³P₂ and Is2s ³S₁ states on every collision.

4 illus, 7 ref

001110   Mollah S (Physics Dep, AMU, Aligarh-202 002, Email: smollah@rediffmail.com) : Properties of MgCNi₃ superconductor. Asian J Chem 2006, 18(5), 3265-70.

Describes the properties of superconducting MgCNi₃ with T_C (ca. 8 K) having a simple cubic perovskite structure with space group Pm-3m and lattice parameter a ca. 3.812 A. Its conduction electrons are derived from the partially filled Ni d-states that typically lead to the ferromagnetism in metallic Ni and many Ni-based binary alloys. It has electron type carriers in the normal state. The T_C increases with the increase of x in MgC_XNi₃ but generally decreases due to the Ni site doping by Co, Fe, Mn, Cu etc. Again, the T_C is found to increase with the increase of external pressure. The electronic contribution is slightly higher than the lattice one in its normal state thermal conductivity. The specific heat and tunneling spectroscopic studies indicate that this is an s-wave BCS-type weak/moderate coupling type-II superconductor.

2 illus, 10 ref

001109   Mohan S;Murugesan P (Faculty of Applied Sciences, PR Institute of Science and Technology, 33, Natarajapuram South, M.C. Road, Thanjavur-613 007, Email: smoh14@rediffmail.com) : New materials for diode pumped solid state lasers and its applications to medical photonics. Asian J Chem 2006, 18(5), 3253-9.

In the history of lasers, 1980 is a remarkable year. In this year an efficient, powerful room temperature AlGaAs semiconductor laser revolutionized the field of solid-state laser. Replacement of conventional flash lamps paved a path for diode pumped solid-state lasers. Many Nd³⁺ ions doped laser crystals such as Nd:LiYF₄ and Nd:YVO₄ has emerged. As you know, erbium doped fiber amplifier (EDFA) needed 980 nm laser to make a revolution in amplifying optical signals. Luckily, InGaAs laser diode with 980 nm was developed. This laser was used as diode pumped laser for Yb: YAG laser, which was discarded as inefficient laser during 1960s. Hence, Ytterbium (Yb³⁺) doped solid-state laser (Yb:YAG) pumped with InGaAs laser diodes has been intensively and successfully developed. A search is in progress for novel Yb doped crystals possessing properties superior to known Yb laser with new capabilities. Several such materials have been identified and characterised recently. This talk concerns with such new laser materials for diode pumped solid-state lasers and its potential use in cosmetic, medical and veterinary photonics.

ref

001108   Mishra R K;Vishweswara Rao K;Vamshi Krishna V;Pillai A M G (NO, Aeronautical Development Establishment, CV Raman Nagar, Bangalore-560 075) : Estimation of electro-optical payload performance. Indian J pure appl Phys 2007, 45(5), 437-40.

Evaluation of the performance of electro-optical payload within the laboratory is discussed. This method is valid for the system, which has output in the form of electrical signal though the input is optical in nature. The methodology enables the evaluation of entire configuration of electro-optical payload comprising of lens system, photo detecting device (one or two dimension array) and processing electronics. The data collected can also be utilized to compute different parameters to estimate National image interpretability rating scale of payload.

001107   Manpreet Singh;Gurvinderjit Singh;Sandhu B S; Bhajan Singh (Physics Dep, Punjabi Univ, Patiala-147 002, Email: balvir@pbi.ac.in) : Measurement of saturation depth of 279 ke V gamma rays in bronze. Asian J Chem 2006, 18(5), 3292-4.

The optimum thickness, known as saturation thickness, at which the number of multiply scattered events saturates, is measured for 279 keV gamma photons in bronze. An inverse matrix approach converts the pulse-height distribution of Nal(Tl) scintillation detector to a photon spectrum.

3 illus, 3 ref

001106   Mali C S;Chavan S D;Kanse K S;Kumbharkhane A C;Mehrotra S C (School of Physical Sciences, Swami Ramanand Teerth Marathwada, University, Vishnupuri, Nanded-431 606) : Dielectric relaxation of poly ethylene glycol-water mixtures using time domain technique. Indian J pure appl Phys 2007, 45(5), 476-81.

Complex dielectric measurements in the frequency range 10 MHz-20 GHz have been carried out in poly ethylene glycol- water mixtures with various concentrations using Time Domain Reflectometry (TDR) method at 25°C. The dielectric dispersion spectra could be fitted with a single relaxation time with Davidson-Cole behaviour at low volume fraction of water. However, at higher volume fraction of water in poly ethylene glycol dielectric dispersion spectra can be fitted with the Debye behaviour. The values of static dielectric constant, relaxation time, distribution parameter, Bruggeman factor and Kirkwood correlation factor have been determined for the poly ethylene glycol-water system. The study confirms that the intermolecular homogeneous and heterogeneous hydrogen bonding vary significantly with the increase in concentration of poly ethylene glycols in aqueous solutions.

001105   Main K S;Kahlon K S;Singh N;Allawadhi K L (Phys Dep, Sant Longowal Institute of Engineering and Technology, Longowal-148 106, Email: ksmann_2000@yahoo.com) : Measurement of relative K-shell photoionization cross-sections of 6-25 ke V photons in S, Ca ad V. Asian J Chem 2006, 18(5), 3428-31.

Relative K-shell photoionization cross-sections of 6-25 keV photons in S, Ca and V are measured. Experimental results are found to agree with calculated theoretical values within the experimental uncertainties.

1 table, 8 ref

001104   Mahur A K;Rajesh Kumar;Rajendra Prasad (Applied Physics Dep, Z.H. College of Engineering and Technology Aligarh Muslim Univ, Aligarh-202 002, Email: ajaymahur345@rediffmail.com) : Radon exhalation rate from different types of building construction materials through SSNTD's. Envir Geochem 2005, 8(1-2), 300-3.

Building materials are the main source of radon inside the dwellings. Because of low level of radon emanation from these materials, long term measurements are essential. Can technique using Solid state nuclear track detector can be employed conveniently and successfully for these measurements. Radon activity and exhalation rate are measured in a number of building materials commonly used for building construction in our region by Can technique using LR-115 type II nuclear track detector. Radon activity is found to vary from 288.8 to 6885.7 Bqm^-3 with an average value 1992.6 Bqm^-3 and radon exhalation rate varies from 174.6 to 4162.8 mBqm^-2h^-1 for different building materials. Radon emanation from unfired bricks is found to be maximum while marble and ceramic tiles give minimum radon emanation. In unfired bricks it appears that radon emanation is produced not only from the surface layers but also from inside the brick. Effective dose equivalent for radon decay products is estimated to vary from 20.5 to 490.8 μSv y^-1.

1 illus, 1 table, 12 ref

001103   Mahur A K;Rajesh Kumar;Jojo P J;Ashavani Kumar;Singh A K;Varshney A K;Rajendra Prasad (Physics Dep, Z.H. College of Engineering and Technology AMU, Aligarh-202 002, Email: ajaymahur345@rediffmail.com) : Radon levels in dwellings of some Indian cities. Asian J Chem 2006, 18(5), 3371-5.

Radiological importance of radon among other naturally occurring radionuclides is due to the fact that it is a noble gas in the uranium decay series with a fairly long half-life of 3.7 days. Being an inert gas it can easily disperse into the atmosphere as soon as it is released. The solid alpha active decay products of radon (²¹⁸Po, ²¹⁴Po) become airborne and attach themselves to the dust particles, aerosols and water droplets in the atmosphere. When inhaled, these solid decay products along with air may get deposited in the trachea-bronchial and pulmonary region of lungs resulting in the continuous irradiation of the cells, which may cause lung cancer. Measurement of time integrated concentration of indoor radon and its progeny are important as these are responsible for a major part of natural radiation dose to human beings and may be responsible for lung cancer. LR-115 Type II solid state nuclear track detectors have been used to estimate the radon concentration in dwellings in various cities from different states of India. Annual effective dose has been calculated from the radon concentration to carry out the assessment of the variability of expected radon exposure of the population due to radon and its progeny. The radon levels in the dwellings vary from 64.8 to 222.1 Bq m^-3 whereas annual effective dose vary from 2.5 to 7.5 m Sv. Radon concentration in Panmana (Kerala), the so called high back ground area is about two times more than the normal back ground area.

2 tables, 15 ref