022838   Ojha V N;Sharma S K (JVS & DC Stand, Natn Phys Laboratory, Dr K S Krishnan Road, New Delhi-110 012) : Precision calibration of reference standard of volt by primary standard. Bhartiya Vaigyanik Evam Audyogik Anusandhan Patrika 2005, 13(1), 78-80.

Josephson Voltage Standard is the primary standard of voltage that is used to calibrate the secondary/reference standard of voltage to maintain the traceability. In the paper, authors has discus in brief about the Josephson series array voltage standard and its use in the calibration of reference standard of voltage. Furthermore, authors has discus their sources of uncertainty in measurements, uncertainty budget and their evaluation based on the ISO/TEC 17025 guidelines.

2 illus, 1 table, 1 ref

022837   Mazumdar C;Nagarajan R (ECMP Div, Saha Inst of Nuclear Phys, Kolkata-700 064, Email: chandan@cmp.saha.emet.in) : Quaternary boraocarbides - a new class of superconductors and materials. Curr Sci 2005, 88(1), 83-93.

Quaternary rare earth transition metal borocarbides are a new class of interesting superconducting and magnetic materials which have their origin in the discovery of superconductivity a decade ago at TIFR, Mumbai, inyttrium-nickel-boron-carbon (Y-Ni-B-C) system - the first quaternary system to exhibit superconductivity (T_c <126> 13 K). The single phase material, YNi₂B₂C (T_c = 15.5 K) has a tetragonal structure. A family of materials have attracted from this structure - the quaternary borocarbides. The discovery and the materials have attracted worldwide attention for a variety of reasons. Many members have high T_c (<126><60> 10 K) for intermetallics, with a phase in Y-Pd-B-C having a T_c as high as 23 K which equalled highest T_c then known for intermetallics. In the RNi2B₂C (R=rare earth) series, a range of other phenomena also occur, such as, valence fluctuation (CaNi₂B₂C), heavy fermion behaviour (YbNi₂B₂C) and the not-so-common phenomenon of coexistence of superconductivity and magnetism in RNi₂B₂C (R = Dy, Ho, Er, Tm). The high (<62>5 K) T_c and T_N of superconductivity and magnetism and their different combinations (T_c<62> T_N, T_c <126> T_N and T_c <60> T_N) in these magnetic superconductors,...

129 ref

022836   Malhotra M;Gautam M;Radhakrishnan J K;Kapoor V;Verma S;Upendra Kumar;Anand Kumar;Gupta G;Goyal A;Sitharaman S (Solid St Phys Laboratory, , Lucknow Road, New Delhi-110 054) : Growth and characterization of Hg_1-xCd_x Te epitaxial films by isothermal vapour phase epitaxy (ISOVPE). Bull Mater Sci 2005, 28(2), 97-102.

Growth of Hg_1-x Cd_x Te epitaxial films by a new technique called asymmetric vapour phase epitaxy (ASVPE) has been carried out on CdTe and CZT substrates. The critical problems faced in normal vapour phase epitaxy technique like poor surface morphology, composition gradient and dislocation multiplication have been successfully solved. The epitaxial films have been electrically characterized by using the Hall effect and capacitance-voltage (C-V) measurements.

10 illus, 3 tables, 18 ref

022835   Kumar N (NO, Raman Res Inst, Bangalore-560 080, Email: nkumar@rri.res.in) : Viscosity of suspensions and glass: Turning power-law divergence into essential singularity. Curr Sci 2005, 88(1), 143-5.

Starting with an expression, due originally to Einstein, for the shear viscosity η(δφ) of a liquid having a small fraction δφ by volume of solid particulate matter suspended in it at random, an effective-medium viscosity η(φ) for arbitrary φ is derived, which is precisely of the Vogel-Fulcher form. An essential point of the derivation is the incorporation of the excluded-volume effect at each turn of the iteration φ_n+1 = φ_n + χδ. The model is frankly mechanical, but applicable directly to soft matter like a dense suspension of microspheres in a liquid as a function of the number density. Extension to a glass-forming supercooled liquid is plausible inasmuch as the latter may be modelled statistically as a mixture of rigid, solid-like regions (φ) and floppy, liquid-like regions (1-φ), for φ increasing monotonically with supercooling.

^ssc1 illus, 17 tables

022834   Kaul S N (Sch of Phys, Univ of Hyderabad, Hyderabad-500 046) : Magnetic inhomogeneities inherent to spin systems with quenched random-exchange disorder. Curr Sci 2005, 88(1), 78-82.

A critical assessment of theoretical models proposed in the literature for the spin structure in amorphous Fe_100-xZr_x alloys (a three-dimensional ferromagnet with quenched random-exchange disorder which exhibits a re-entrant behaviour at low temperatures), based on a detailed comparison between theoretical predications and available experimental results, is presented. The infinite ferromagnetic matrix plus finite ferromagnetic spin clusters model, originally proposed by the author, is shown to provide a coherent basis for understanding the nature and origin of magnetic inhomogeneities in this system.

5 illus, 35 ref

022833   Godbole R M;Mukhi S (Cent for High Energy Phys, IISc, Banglore-560 012, Email: rohini@cts.lisc.ernet.in) : Nobel for a minus sign. Resonance 2005, 10(2), 33-51.

Article survey the research work for which the Nobel Prize in Physics was awarded in 2004, and discuss the three scientists - David Gross, H David Politzer and Frank Wilczek, who received the honour.

3 illus, 2 table

022832   Eid M A;Moustafa H R;Al-Ashkar E A;Ali S S (Spectroscopy Dep, Natn Res Cent, Dokki, Cairo, Egypt, Email: mohaeid38@hotmail.com) : Spectral lines of some volatile hydride forming elements of determination of excitation temperature in analytical plasmas. Indian J pure appl Phys 2005, 43(4), 246-52.

The spectra of some volatile hydride forming elements have been investigated to select thermometric species for determination of excitation temperature in analytical plasmas woking in argon under atmospheric pressure. Groups of lines of As I, Sb I and Sn I in addition to Ar I were found appropriate for the determination of excitation temperature in inductively coupled plasma (ICP) and wall-stabilized arc (WSA). The Boltzmann plots were straight lines, which determined temperature in ICP and WSA using different groups of spectral lines that agree well with each other as well with the most familiarly used thermometric species. These lines are recommended for determination of temperature when gaseous hydrides are introduced into the plasma and no other thermometric species excepts the atoms of working gas are present.

6 illus, 6 tables, 20 ref

022831   Dole B N;Shah S S (J E S Res Cent Dep of Phys, J E S Coll, Jalna-431 203) : Study of Pr_xY_1-xBa₂Cu₃O₇-<10 0> high T_c superconductors. Indian J pure appl Phys 2005, 43(4), 279-86.

The substitution of Pr in high T_c superconducting compound plays very interesting role such as annihilation of superconductivity with increase of Pr concentration, which is not adequately explained yet. The samples of the system Y_1-x Pr_x Ba₂ Cu₃ O_7-δ with compositions (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared by well known conventional ceramic route and chemical route. The results of resistivity, X-ray diffraction, orthorhombicity, X-ray density, bulk density, volume cell and oxygen content of both the routes are reported. The samples prepared by chemical route give better results than conventional ceramic route. Bond distances obtained from neutron diffraction show that the electron phonon interaction becomes weaker and results in loss of superconductivity.

9 illus, 2 tables, 12 ref

022830   Dash S K;Mishra K C;Mishra S N;Swain B B (Natn Coun of Educ Res and Training, , New Delhi-110 016) : Dielectric study of surface modification of linear low density polyethylene treated with chromic acid and sodium carbonate. Indian J pure appl Phys 2005, 43(4), 287-90.

The relative permittivity (ε) and dielectric loss (ε") of linear low density polyethylene (LLDPE) sample of 60 μm thickness treated successively with a highly oxidizing environment like chromic acid of normality N/5 to N/30 for time duration of 0.5 to 12 hr and sodium carbonate for 24 hr are measured using GRA 650A impedance bridge over 100 Hz to 10 kHz range at 303.16±1K. The N/10 chromic acid treated sample exhibited increase in values of ε'(from 3.2 to 4.3) and ε" (from 0.48 to 0.75) relative to the virgin sample at 300 Hz while the rest of the samples recorded reduction. But these chromic acid treated LLDPE samples being further treated with N/10 sodium carbonate (Na₂CO₃), exhibit change in ε and ε values in as much as those for N/10 chromic acid treated sample drops while that of N/15 chromic acid treated sample increases significantly. This indicates intense polarization penetrating to reasonable depth of the surface of the material. The higher value of ε and ε in N/10 chromic acid treated sample may be due to intra-molecular three-dimensional network of H-bonding between PE-COOH species. Attempt is made to explain these features.

6 illus, 18 ref

022829   Chaplot S L (Solid Ssatate Phys Div Bhabha Astomic Res Cent, , Mumbai-400 085, Email: Chaplot@magnum.barc.ernet.in) : Negative thermal expansion in ZrW₂O₈ - do we give up the concept of normal mode. Curr Sci 2005, 88(3), 347-9.

3 illus, 16 ref

022828   Bose I (Phys Dep, Bose Inst, 93/1, A.P.C. Road, Kolkata-700 009) : Spin gap antiferromagnets: materials and phenomena. Curr Sci 2005, 88(1), 62-70.

There are several interacting spin systems which have a gap in their spin excitation spectra. The gap doses not occur due to anisotropies present in the system but is quantum mechanical in origin. A brief over view is given on different types of spin gap (SG) antiferromagnets, the models proposed to describe their physical properties and experimental realizations of such systems. Special focus is on exactly-solvable models and rigorous theories which provide the correct physical picture for the novel phenomena exhibited by SG systems.

3 illus, 60 ref

022827   Bera S C;Chattopadhyay S;Chakraborty B (Instrumentation Engng Sect Appl Phys, Univ of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata-700 009) : Study of the effect of excitation frequency on electrode polarisation impedance of a bio-electrode. J Instrum Soc India 2005, 35(2), 197-204.

The polarisation impedance of a bio-electrode is non-linearly related with dc and ac current density and ac excitation frequency etc. In the paper the effect of excitation frequency on the polarisation impedance have been studied experimentally by a modified bridge technique on a number of subjects. The experimental results are presented in the paper. From these results an empirical relation between the impedance and excitation frequency has been obtained.

5 illus, 10 ref

022826   Barman S R (Surf Phys Laboratory, UGC-DAE Consortium for Scientific Res, University Campus, Khandwa Road, Indore-452 017, Email: barman@udc.ernet.in) : Electronic excitations on metal surfaces and nano-structures. Curr Sci 2005, 88(1), 54-61.

Collective electron excitations on a free-electron-like metal surface like Al have been studied by X-ray photoemission spectroscopy. Photoemission studies on quantization of electron states due to confinement in nano-structure like epitaxial Na films on Al(111) have been discussed. The electronic structure of Ar nano-bubbles embedded in the sub-surface region of Al has been discussed. For Al, an asymmetric line-shape is observed for both monopole surface and bulk plasmon in good agreement with theory. The relative contributions of the intrinsic, extrinsic and the interference processes to the surface plasmon intensity are determined from theoretical plasmon line-shape calculations and angle-dependent photoemission. The characteristics of the multipole plasmon mode are also discussed. Using angle resolved phtoemission, Na thin filems on Al(111) have been studied for different thicknesses. Autho find features in the valence band spectra that behave like quantum well resonances in a narrow photon energy range where the overlayer collective excitations are observed. These resonances are observed because for quantum confinement due to a potential step at the Na/Al interface and the dynamical enhancement of the electric field in the overlayer. In case of argon nano-bubbles in Al, we find that the Ar 2p binding energy and the Doniach-Sunjic asymmetry of the core level line shape vary systematically as functions of Ar⁺ implantation energy and number of ions bombarded (fluence).

8 illus, 65 ref

022825   Arora M;Gupta S K (Mater Characterization Div, Natn Phys Laboratory, Dr K S Krishnan Road, New Delhi-110 012) : Characterization of hydrogenated amorphous silicon thin films by infrared and EPR spectroscopy. Bhartiya Vaigyanik Evam Audyogik Anusandhan Patrika 2005, 13(1), 86-90.

Hydrogenated amorphous silicon thin films grown by glow - discharge process were characterized by high resolution, non - destructive infrared (IR) and electron paramagnetic resonance (EPR) spectroscopic techniques to investigate different local arrangements formed in the film network like SiH, SiH₂ and (SiH₂)_n bonding groups, defects and microcrystalline silicon during growth. These groups and defects effect the conductivity and recombination process which plays important role in device fabrication. In this work, the vibrational bands pertaining to silicon and hydrogen bonded groups were tentatively assigned to reveal structural details of local bonding arrangements in amorphous and microcrstalline state. Infrared absorptance spectra were measured in the region 4000 - 400 cm^-1 at ambient and different low temperatures. In these spectra, absorption bands of SiH, SiH₂, (SiH₂)₂, (SiH₂)_n groups of amorphous hydrogenated silicon coexisted with microcrystalline silicon (mc-Si:H) stretching, bending, breathing, wagging and silicon transverse optic phonon vibrations. The appearance of microcrystalline silicon bands in these film spectra confirms its formation which starts growing due to the reaction of hydrogen radicals with unstable SiH₂ group present at the grain boundery. This chemical etching reaction is exothermic which breaks weak Si-Si and Si-H bonds and form strong Si-Si microcrystalline bonds and silicon particles through reorientational ordering of silicon hydrogen bonded groups in amorphous film network. Recently microcrystalline silicon find wide usage in optoelectronic devices and these investigations are very important in this context also. Electron paramagnetic resonance studies showed an isotropic single line spectrum due to formation of dangling bonds in amorphous hydrogenated silicon film.

3 illus, 24 ref

022824   Andavan P M;Elango P;Venkatachalam K; Rajasekaran P (PG and Res Dep of Phys, Government Arts Coll, Coimbatore-18) : PEC behaviour of slurry-coated cadmium selenide thin films. Bull Electrochem 2005, 21(1), 33-6.

CdSe films were slurry-coated and heat treated at different temperatures and characterized. The photoelectrodes exhibit efficiencies that are comparable to reported values. The films exhibit n-type behaviour with a flat band potential value of -1.10 V (SCE) and a carrier density of 1017 cm^-3.

6 illus, 8 ref

022823   Ananthakrishnan R;Guck J;Wottawah F; Schinkinger S;Lincoln B;Romeyke M;Kas J (NO, Inst for Soft Matter Phys Univ of Leipzi, 04103 Leipzig, Germany) : Modelling the structural response of an eukaryotic cell in the optical stretcher. Curr Sci 2005, 88(9), 1434-40.

The cytoskeleton of an eukaryotic cell is a composite polymer material with unique structural (mechanical) properties. To investigate the role of individual cytoskeletal polymers in the deformation response of a cell to an external force (stress), creates two structural models-a thick shell model for the actin coretex, and a three-layered model for the whole cell. These structural models for a cell are based on data obtained by deforming suspended cells, where each cell is stretched between two counter-propagating laser beams using an optical stretcher. The models, with the data, suggest that the outer actin cortex is the main determinant of the structural response of the cell.

7 illus, 16 ref

021772   Verma M K (Physics Dep, Indian Institute of Technology, Kanpur-208 016) : Incompressible turbulence as non-local field theory. Pramana J Phys 2005, 64(3), 333-41.

It is well-known that incompressible turbulence is non-local in real space because sound speed is infinite in incompressible fluids. The equation in fourier space indicates that it is non-local in Fourier space as well. However, the shell-to-shell energy transfer is local. Contrast this with Burgers equation which is local in real space. Note that the sound speed in Burgers equation is zero. In the presentation these two equations using non-local field theory are contrasted. Energy spectrum and renormalized parameters are discussed.

5 illus, 13 ref

021771   Subramaniam T K (Department of Physics, Rajalakshmi Engineering College, Thandalam-602 105, Email: subra_t_2000@yahoo.com) : Optogalvanic transitions in lutetium in the 570-630 nm region. Indian J Phys 2005, 79(4), 381-4.

Laser optogalvanic (LOG) technique is now a well-established spectroscopic tool to study the spectra of atoms and molecules. Rare earth atoms have high melting point and normally their excitation is difficult using ordinary methods. The emission spectrum of the lutetium/neon hollow cathode lamp was recorded in the 500-750 nm region using a 0.5 m monochromator, a cooled photomultiplier coupled to a picoammeter and a chart recorder. The LOG spectrum of Lu/Ne lamp was recorded using an argon ion (Ar+) laser and a tunable linear dye laser with rhodamine 6G in the 570-630 nm region. The dye laser output power at its maximum was <126> 200 mW with nearly 40 GHz bandwidth. The lutetium lines wavelengths are expected to be accurate to within 1 nm. In the LOG spectrum, only 47 lines could be observed and some of these lines have already been observed by earlier workers. Three new lines have been identified here, whereas in the emission spectrum, in the same region, only 16 lines of neutral and singly-ionized lutetium besides neon lines were recorded. Three new lines are at 600.15 nm, 611.527 nm, 614.73 nm which are assigned to different transitions.

2 illus, 1 table, 11 ref

021770   Sreenivasan K R;Bershadskii A (The Abdus Salam International Center for Theoretical Physics, , Strada Costiera 11, 34100 Trieste, Italy) : Logarithmic scaling in the near-dissipation range of turbulence. Pramana J Phys 2005, 64(3), 315-21.

A logarithmic scaling for structure functions, in the form S_p <126> [In(r/η)]^ζ_p, where η is the Kolmogorov dissipation scale and ζ_p are the scaling exponents, is suggested for the statistical description of the near-dissipation range for which classical power-law scaling does not apply. From experimental data at moderate Reynolds numbers, it is shown that the logarithmic scaling, deduced from general considerations for the near-dissipation range, covers almost the entire range of scales (about two decades) of structure functions, for both velocity and passive scalar fields. This new scaling requires two empirical constants, just as the classical scaling does, and can be considered the basis for extended self-similarity.

9 illus, 13 ref

021769   Sivaram C (NO, Indian Institute of Astrophysics, Bangalore-560 034) : Black hole entropy: some skin deep subtleties sans strings. Asian J Phys 2004, 13(3-4), 293-6.

The entropy increase by a huge factor when a star collapses into a black hole remains an enigma. In the recent past in attempt to understand the physics involved in the large number of microstates involved as well as other aspects like Hawking radiation it has become fashionable to invoke exotic objects like superstrings, D-branes, etc. The black holes axe assumed stuffed and stacked with these objects. Here an attempt has been made to understand several of these subtle features of black hole entropy and decay, linking them to 'skin deep' horizon properties. We have also made connection with several remarkable recent experiments on coherent optical information storage. Our braneless approach is mostly in the framework of familiar physical and astrophysical phenomena associated with general relativity.

13 ref

021768   Sharma A;Verma M P;Sodha M S (Institute of Advanced Studies in Education, University of Lucknow, Lucknow-226 007) : Self focussing of a laser beam, inciden normally on a plasma-free space interface. Indian J Phys 2005, 79(4), 401-7.

Authors have analyzed the propagation of the transmitted part of a laser beam with transverse Gaussian intensity profile incident normally from free space onto a plane plasma surface. The modification of irradiance profile of the beam, caused by the nonlinear dielectric constant of the plasma has been taken into account. It has been shown that in this case also there exist three regimes of propagation in the beam width-beam power plane; the regions are characterized by steady divergence, oscillatory divergence and self-focussing. The dependence of beam width on distance of propagation has been investigated for typical points in the three regions. It is seen that the transverse irradiance profile, the three regions in the beam power-beam width plane and the dependence of beam width parameter on distance of propagation get considerably modified by considering incidence on plasma-free space interface.

4 illus, 1 table, 23 ref

021767   Sharma A;Varma M P;Sodha M S (Institute of Advanced Studies in Education, University of Lucknow, Lucknow-226 007) : Self-focussing of TEM₁₀ mode laser beams in plasmas. Indian J Phys 2005, 79(4), 393-9.

The nonlinear propagation of a laser beam in the TEM₁₀ mode, through a plasma, has been studied by expanding the eikonal around the axis and an intensity maximum. Three kinds of nonlinearities viz. ponderomotive, collisional and relativistic, have been considered. It has been observed that uneven refraction of the beam in x and y directions, rules out the possibility of a uniform waveguide mode propagation (i.e. without convergence or divergence). The beam width parameters characterizing convergence/divergence in x and y directions respectively, have been obtained by numerically integrating the corresponding differential equations. In the axial region, the beam suffers steady divergence, enhanced by nonlinearity. For regions close to irradiance maxima, two coupled differential equations for beam widths in x and y directions have been obtained. These have been solved for a set of typical parameters and a discussion of the results is presented.

6 illus, 13 ref

021766   Sharat Singh N K;Nandakumar Sarma H (Phys Dep, Manipur Univ, Canchipur, Imphal-795 003, Email: hnksarma@rediffmail.com) : X-ray - A boon for elemental analysis. Resonance 2005, 10(6), 60-9.

The characteristic X-rays coming out from an unknown sample due to the irradiation of gamma rays or X-ray photons or due to the bombardment of high velocity protons are used for elemental analysis in a sample. We describe here two techniques viz., Energy Dispersive X-ray Fluorescence (EDXRF) and Proton Induced X-ray Emission (PIXE) which have the capability of nondestructive and multi-elemental analysis of the sample.

7 illus

021765   Shamala K S;Murthy L C S;Rao K N (Department of Physics, Bangalore University, Jnanabharathi, Bangalore-560 056) : Electrical and optical properties of Al₂O₃ thin films prepared by electron beam evaporation and spray pyrolysis method. J Instrum Soc India 2005, 35(1), 166-71.

Al₂O₃ thin films find a number of applications in optoelectronics sensors and tribology. Reports the preparation and characterization of alumina films prepared by both electron beam evaporation and spray pyrolysis methods. The electrical properties of alumina films were determined by measuring C-V and I-V characteristics in Metal Oxide Semiconductor (MOS) structure. A relative dielectric constant (e_r) of 9.6 for spray pyrolysed films and 8.3 for evaporated films was found. The breakdown electric field was found to be 5MV / cm and IMV / cm respectively for spray pyrolysed and evaporated films. The refractive index of alumina films by evaporation was found to be 1.71 and 1.61 at 300nm and 500nm respectively. The optical band gap of spray pyrolysed films deposited at 300°C was found to be in the range of 5.4eV to 5.55eV.

4 illus, 16 ref

021764   Sengar Chaturvedi S;Dhoble S J;Chandra B P (Department of Physics, Indian Institute of Technology, Powai, Bombay, Mumbai-400 076, Email: sjdhoble@rediffmail.com) : Anti stokes luminescence in Pr<. Indian J Phys 2005, 79(4), 355-60.

Infrared-to-visible up-conversion in Pr³⁺ activated ZBLAN fluoride crystalline phosphors has been investigated at room temperature for different activator concentrations. In the excitation spectra as well as in the emission spectra, initially the intensity increases with activator concentration, attains an optimum value and then it decreases with further increase in the activator concentration. It seems that blue excitation of the phosphor is due to Excited State Absorption (ESA) mechanism. The 2nd power dependence of the blue fluorescence from the ³P₀ state under IR pumping of ¹G₄ state indicates a dominant two photon ESA mechanism. The mechanism of anti-Stokes luminescence in an unique optical activator Pr³⁺ in the ZBLAN fluoride host material, is discussed.

5 illus, 19 ref

021763   Saxsena A K;Chinnappan V;Ismail Jabilullah R (NO, Indian Institute of Astrophysics, Koramangala, Bangalore-560 034) : Characterization of adaptive optics morrors using long trace profilometer. Asian J Phys 2004, 13(3-4), 205-14.

A Long Trace Profilometer (LTP) was designed and fabricated in-house primarily to measure the profile of long, non-circularly symmetric grazing incidence optics. The system was used to calibrate the tip-tilt and deformable mirrors that were used for our adaptive optics research program. Gives optical layout and details of the LTP and the test results of tip-tilt mirror based on piezo-electric actuators and a deformable mirror based on Micro Electro mechanical system (MEMS) technology.

9 illus, 1 table, 7 ref

021762   Samuel J (Harish Chandra Res Inst, , Jhusi, Allahabad-211 019, Email: sam@mri-ernet.in) : Of connections and fields - I. Resonance 2005, 10(4), 10-21.

Author describe some instances of the appearance of Chern's mathematical ideas in physics. By means of simple examples, it bring out the geometric and topological ideas which have found application in describing the physical world. These applications range from magnetic monopoles in electrodynamics to instantons in quantum chromodynamics to the geometric phase of quantum mechanics.

2 illus

021761   Samuel J (Harish Chandra Res Inst, , Jhusi Allahabad-211 019, Email: sam@rri.res.in) : Of connections and fields - II. Resonance 2005, 10(5), 54-61.

The article describe advanced applications of Chern's ideas.

021760   Saksena M D;sunanda K (Spectroscopy Division, Modular Laboratories, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085, Email: sunanda@magnum.barc.ernet.in) : Franck condon factors and r-centroids of the A-X and B-X band systems of GaCl and GaI molecules. Indian J Phys 2005, 79(4), 409-15.

High resolution studies of the electronic spectra of GaCl and Gal carried out in the laboratory, have led to accurate rotational and vibrational constants of the excited states. Using these constants, the Franck Condon factors and r-centroids were computed for the bands of the A³∏₀-X¹ ∑⁺ and B³∏₁-X¹ ∑⁺ transitions in these molecules. Comparisons of the visually estimated intensities of the observed bands recorded on a 3.4 m Ebert grating spectrograph showed reasonable agreement with the computed Franck Condon factors. These results indirectly ascertained the vibrational numbering of the vibrational band heads after head of heads formation in GaCl and reversal of the degradation in Gal.

3 tables, 7 ref

021759   Sahoo S;Mandal M K (Physics Dep, National Institute of Technology, Durgapur-9, Email: sukadevsahoo@yahoo.com) : Supersymmetric oscillator. Phys Educ 2004, 21(2), 113-21.

The aim of theoretical physics is to describe the natural phenomena and experiment observations by a simple and well-appreciated theory. Theoretical physicists introduce symmetries with the aim of solving difficult problems. Presents the salient features of symmetry with emphasis on supersymmetry. Supersymmetry introduces a fermionic (bosonic) partner for every boson (fermion) differing by half a spin quantum number. This partner is known as superpartner (sparticle) of the original particle. Then bosonic and fermionic quantum harmonic oscillator, are combined to show the natural emergence of a supersymmetric oscillator.

2 tables, 8 ref

021758   Sahaya Shajan X;Mahadevan C K (Department of Physics, Sivathi Aditanar College, Pillayarpuram-629 501, Email: mahad@sancharnet.in) : Electrical conductivity measurements on pure and impurity-added calcium tartrate tetrahydrate single crystals. Indian J Phys 2005, 79(4), 425-7.

Electrical conductivity measurements were carried out on polycrystalline samples of pure and impurity-added calcium tartrate tetrahydrate (CTT) crystals grown by the gel method. The conductivities (both a.c.and d.c.) were measured from room temperature to 75°C in the frequency range 10² to 10⁴ Hz. The study shows that the conductivity in pure and impurity-added CTT, increase in temperature.

4 illus, 1 table, 13 ref

021757   Rajendran A;Neelamegam P (Research & P G Department of Applied Physics, Nehru Memorial College, Puthanampatti, Tiruchirappalli-621 007) : Design of AT89C52 microcontroller based system for the measurement of temperature and control. J Instrum Soc India 2005, 35(1), 99-105.

An AT89C52 microcontroller based system is developed to measure and to control temperature for conductivity studies of liquids. The system improve the accuracy of recorded data, eliminates varying degrees of human participation, and saves operator time. Software programs developed in this system are simple to use and provide versatility in programming temperature ranges and timing processes.

6 illus, 3 ref

021756   Raja V;rajamanickam N (Physics Research Centre, VHNSN College, Virudhunagar-263 001) : On the dissociation energy of bil molecule. Asian J Spectrosc 2004, 8(2), 83-6.

The experimental potential energy curve for the electronic ground state of Bil molecule is constructed by Rydberg-Klein-Rees method. By fitting the empirical potential function to the experimental potential energy curve, the dissociation energy D^o_o of Bil is found to be 1.89±0.06eV using correlation coefficient.

2 tables, 14 ref

021755   Raghunathan V A (Raman Res Inst, , Bangalore-560 080, Email: vraghu@rri.res.in) : Zmall angle X-ray scattering: going beyond the bragg peaks. Resonance 2005, 10(6), 24-34.

The article gives an introduction to the principles of small angle scattering. Some applications of this technique are also briefly discussed.

5 illus

021754   Praveen Kumar L;Arulmozhivarman P;Ganesan A R (Photonics Laboratory, Department of Physics, Regional Engineering College, Tiruchirappalli-620 015) : Wavelet based measurement of moments in Shack Hartmann wavefront sensor. J Instrum Soc India 2005, 35(1), 172-8.

Presents a method for the exact computation of the centroid determination or the moments of a region bounded by a scaling function of wavelet basis. The squares φ²(x) and ψ²(x) of orthonormal scaling functions and wavelets are interesting probability densities. Their moments can be computed in terms of the filter coefficients h_n and g_n in the dilation equation and wavelet equation. The multidimensional filter coefficients are precomputed exactly as the solution of a two-scale function. To demonstrate the performance improvement of this centroiding method, this technique has been applied to a wavefront sensor sub-aperture samples and compared it with existing methods such as Statistical Averaging, finding moments using FFT and Least Square fittings.

1 illus, 1 table, 10 ref

021753   Prakash S;Natarajan S;Alagar M (Physics Dep, Virdhunagar Hindu Nadars Senthikumara Nadar College, Virudhunagar-626 001, Email: alagaranjac@yahoo.co.in) : Infrared spectra of bis (DS-Serinium) oxalate dihydrate. Asian J Spectrosc 2004, 8(2), 87-90.

The infrared absorption spectra of bis(DL-serinium)oxalate dihydrate was recorded at room temperature. Tentative assignments of the observed wavenumbers were made by comparison with the known assignments of wavenumbers of the parents of the complex. The intermolecular hydrogen bonding in the crystal leads to a shift of bands due to the stretchign and bending modes of various functional groups. Also the existence of the ionized carboxylic group in the anion and the presence of water molecule were confirmed.

2 illus, 2 tables, 8 ref

021752   Pradeep Kumar;Chandrasekaran N;Sharma A K; Joseph C S (Faculty of Applied Physics, Institute of Armament Technology, Girinagar, Pune-411 025) : A fiber optic microbend pressure transducer for air speed measuremtnt. J Instrum Soc India 2005, 35(1), 142-8.

A fiber optic microbend air pressure sensor is designed and fabricated for airspeed measurement. The differential pressure experienced in a pitot-static tube is the direct indication of the airspeed. A multimode step index optical fiber undergoing periodic bending between a pair of corrugated tooth blocks served as the transducer. One tooth block is positioned at the center of a diaphragm that deflects in propertion to the pressure difference due to air velocily. The deftection causes a change in the amplitude of the periodic distortion of the fiber, which reduce its transitivity and subsequently the detector output. This provides a signal proportional to the air pressure and is calibrated for the air speed. The developed transducer is a simple low cost device and is tested for air pressure up to 1.354 Kgf/cm² corresponding to air speed up to 1450 km/hr.

7 illus, 10 ref

021751   Prabha S;Sharma K C (Edcucation in Science and Mathematics Dep, Regional Institute of Education (NCERT), Ajmer-305 004, Email: prabhashashi105@yahoo.com) : Values through physics practicals. Phys Educ 2004, 21(2), 93-7.

The potential of the experimental work in physics for the inculcation of values has hardly been exploited. The performance of experiments has more or less become a ritual, for from fulfilling its objectives. Examined responses of questionnaire submitted to students and teachers of senior secondary level. Lack of awareness of the power of physics practicals work in transacting values in action is notable. Suggestions are made to incorporate values in physics practicals work to make it a process and value oriented activity.

021750   Patel K;Prajapati J;Vaidya R;Patel S G (Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388 120, Email: shantibhaip@yahoo.com) : Study of optical and electrical properties of ZrS₃ single crystals. Indian J Phys 2005, 79(4), 373-6.

Single crystals of the lamellar compound ZrS₃ has been grown by chemical vapour transport technique using iodine as a transporting agent. The growh crystals were characterized with the help of Energy dispersive analysis by X-rays (EDAX), which gives confirmation about the stoichiometry. Structural analysis has been carried out by X-ray diffraction (XRD). The optical band gap of as grown crystals has been obtained with the help of absorption spectra taken in the range of 300-1500 nm. An electrical resistivity measurement has been performed for this crystal in the temperature range of 303-550 K. The crystals were found to exhibit semiconducting nature in this range. The effect of pressure on electrical resistance of as grown crystals have been studied using Bridgman opposed anvil upto 8 GPa, which shows resistive behaviour of ZrS₃ single crystals. The results obtained are discussed in detail.

5 illus, 2 tables, 17 ref

021749   Parvate A;Gangal A D (Physics Dep, Pune Univ, Pune-411 007) : Fractal differential equations and fractal-time dynamical systems. Pramana J Phys 2005, 64(3), 389-409.

Differential equations and maps are the most frequently studied examples of dynamical systems and may be considered as continuous and discrete time-evolution processes respectively. The processes in which time evolution takes place on Cantorlike fractal subsets of the real line may be termed as fractal-time dynamical systems. Formulation of these systems requires an appropriate framework. A new calculus called F^α-calculus, is a natural calculus on subsets F ⊂ R of dimension α, 0 <60> α ≤ 1. It involves integral and derivative of order α, called F^α-integral and F^α-derivative respectively. The F^α-integral is suitable for integrating functions with fractal support of dimension α, while the F^α-derivative enables us to differentiate functions like the Canto staircase. The functions like the Cantor staircase function occur naturally as solutions of F^α-differential equations. Hence the latter can be used to model fractal-time processes or sublinear dynamical systems.

4 illus, 35 ref

021748   Natarajan V;Sen D (Phys Dep, Indian Inst of Sci, Bangalore-560 012, Email: vasant@physics.iisc.ernet.in) : The special theory of relativity. Resonance 2005, 10(4), 32-50.

3 illus

021747   Muruganandam P;Francisco G (Physics Dep, Centre for Nonlinear Dynamics, Bharathidasan Univ, Tiruchirapalli-620 024) : Local dimension and finite time prediction in coupled map lattices. Pramana J Phys 2005, 64(3), 381-7.

Forecasting, for obvious reasons, often become the most important goal to be achieved. For spatially extended systems (e.g. atmospheric system) where the local nonlinearities lead to the most unpredictable chaotic evolution, it is highly desirable to have a simple, diagnostic tool to identify regions of predictable behaviour. Discusses the use of the bred vector (BV) dimension, a recently introduced statistics, to identify the regimes where a finite time forecast is feasible. Using the tools from dynamical systems theory and Bayesian modelling, it has been shown the finite time predictability in two-dimensional coupled map lattices in the regions of low BV dimension.

4 illus, 10 ref

021746   Murali K;Sinha S;Ditto W L (Physics Dep, Anna Univ, Chennai-600 025) : Construction of a reconfigurable dynamic logic cell. Pramana J Phys 2005, 64(3), 433-41.

Reports the first experimental realization of all the fundamental logic gates, flexibly, using a chaotic circuit. In the scheme a simple threshold mechanism allows the chaotic unit to switch easily between behaviours emulating the different gates. Also demonstrates the combination of gates through a half-adder implementation.

6 illus, 2 tables, 9 ref

021745   Mitra T;Keller J M;Bajpai R (Department of Postgraduate Studies and Research in Physics, Rani Durgvati Vishwavidyalaya, Jabalpur-482 001, Email: jhoom_mitra@yahoo.com) : A thermally stimulated depolarization current investigation of poly (phenylene oxide) : poly(styrene) polymer blends. Indian J Phys 2005, 79(4), 361-6.

A thermally stimulated depolarization current (TSDC) investigation in short circuit configuration has been carried out on physical blends of an amorphous polymer poly(phenylene oxide) (PPO) and semicrystalline polymer poly(styrene) (PS). Blends of composition PPO: PS :: 95 : 05; 90 : 10; 85 : 15 and 80 : 20 were polarized at various temperatures ranging from 308 to 383 K with fields 100, 150, 160 and 190 kV/cm. The depolarization currents recorded as a function of temperature and field were characterized by two well defined peaks. The low temperature peak observed in the temperature range 323-338 K has been identified as the manifestation of the dipolar processes associated with the orientation of molecular dipoles attached to the phenyl groups. The high temperature peak appearing in the temperature range 343-363 K is a complex relaxation process associated with the motion of excess charges together with dipolar reorientation. The anomalous character of the TSDC under certain condition of field and temperature is considered due to detrapping of excess charge carriers in large number resulting in partial blocking of polymermetal interface.

4 illus, 21 ref

021744   Mangalam A (Indian Institute of Astrophysics, , Koramangala, Bangalore-560 034, Email: mangalam@iiap.res.in) : A unified description of anti-dynamo conditions for incompressible flows. Asian J Phys 2004, 13(3-4), 251-8.

A general type of mathematical argument is described, which applies to all the cases in which dynamo maintenance of a steady magnetic field by motion in a uniform density is known to be impossible. Previous work has demonstrated that magnetic field decay is unavoidable under conditions of axisymmetry and in spherical or planar incompressible flows. These known results are encompassed by a calculation for flows described in terms of a generalized poloidal-toroidal representation of the magnetic field with respect to an arbitrary two dimensional surface. Show that when the velocity field is two dimensional, the dynamo growth, if any, that results, is linear in one of the projections of the field while the other projections remain constant. Also obtain criteria for the existence of and classification into two and three dimensional velocity results which are satisfied by a restricted set of geometries. In addition, discusses the forms of spatial variation of the density and the resistivity that are allowed so that field decay still occurs for this set of geometries.

15 ref

021743   Mahadevan C K;Vincent Jerin C;Maragatha Selvi S (Physics Research Centre, S T Hindu College, Nagercoil-629 002, Email: mahad@sancharnet.in) : Lattice variation and thermal parameters of KDP crystals added with NaCl and NaBr. Indian J Phys 2005, 79(4), 377-80.

Pure and impurity-added (with NaCI and NaBr) KDP (potassium dihydrogen orthophosphate) single crystals were grown by the slow evaporation method from aqueous solutions. X-Ray diffraction data were collected for powder samples and used for the estimation of lattice variation and thermal parameters like Debye-Waller factor, mean-square amplitude of vibration, Debye temperature and Debye frequency. The thermal parameters do not vary in a particular order with respect to impurity concentration.The results obtained are reported.

2 tables, 37 ref

021742   Krishna Mohan T R;Sen S (NO, CSIR Centre for Mathematical Modelling and Computer Simulation (C-MMAC, Bangalore-560 037) : The quasi-equilibrium phase of nonlinear chains. Pramana J Phys 2005, 64(3), 423-31.

Shows that time evolution initiated via kinetic energy perturbations in conservative discrete, spring-mass chains with purely nonlinear, non-intcgrable, algebraic potentials of the form V(x_i-x_i+1) <126> (x_i - x_i+1)²ⁿ, n ≥ 2 and an integer, occurs via discrete solitary waves (DSWs) and discrete antisolitary waves (DASWs). Presence of reflecting and periodic boundaries in the system leads to collisions between the DSWs and DASWs. Such collisions lead to the breakage and subsequent reformation of (different) DSWs and DASWs. The calculations show that the system eventually reaches a stable 'quasi-equilibrium' phase that appears to be independent of initial conditions, possesses Gaussian velocity distribution, and has a higher mean kinetic energy and larger range of kinetic energy fluctuations as compared to the pure harmonic system with n = 1; the latter indicates possible violation of equipartition.

4 illus, 14 ref

021741   Keskin A U;Bayrakceken F (Dep of Electronics Engineering, Yeditepe Univ, 34755, Istanbul, Turkey) : A simple signal processing application in flash spectroscopy. Asian J Spectrosc 2004, 8(2), 63-71.

This study concentrates on UV-VIS molecular flash spectroscopy techniques in which registered analog data are transferred into PC medium in a simple manner, so that information can be processed using well known mathematics software tools, such as MATLAB. Considering the characteristics of this kind of spectrographic data, wave length scaling and some modified spectral smoothing methods, so called average of the moving average spectra and average of the moving median spectra (hereafter, AMAS and AMMS) are introduced and a method used for eliminating the effects of intense excitation source lines from the spectrogram are also described as two applications of the study.

8 illus, 18 ref

021740   Kawski A;Bojarski P;Kojro Z (Institute of Experimental Physics, Gdansk Univ, Wita Stwosza, 57, PL-80-952 Gdansk, Poland) : Effective volumes of DPS and POPOP in cyclohexane and ethanol determined from rotational fluorescence depolarization. Asian J Spectrosc 2004, 8(2), 49-53.

Based on the Perrin and Alicki et al. formulas the rotational diffusion coefficients D_R, rotational relaxation times τ_R and volumes including the solvent shell v_eff were determined for the unpolar molecule diphenylstilbene (DPS) and for the polar molecule 2,2' - p - phenylene - bis (5-phenyloxazole) (POPOP) in unpolar cyclohexane and polar ethanol using the fluorescence quenching method .i.e., for different mean lifetimes τ. It was found that the volume ratio for POPOP in ethanol (in which the association phenomenon occurs) to cyclohexane amounts to ≈ 1.25, whereas for DPS it is as low as 1.04.

2 illus, 1 table, 17 ref

021739   Kandpal D;Singh K Y;Gupta B R K (Department of Physics, G B Pant University of Agriculture and Technology, Pantnagar-263 145, Email: brkg@rediffmail.com) : Thermal properties of copper and aluminum at high temperatures. Indian J Phys 2005, 79(4), 367-71.

Authors investigated the thermo-elastic properties such as thermal expansion and expansivity of close packed phases of copper and aluminum upto their melting temperatures. The properties are calculated using the integral form of the equation of state (IFEOS) recently proposed by Singh and Gupta assuming the fact that the Anderson parameter (δ_T) strongly depends on temperature due to contribution from the thermal excitation of electrons. The values of thermal expansion (V/V₀), thermal expansivity (α_T) and bulk modulus (K_T) as determined in the study, agree closely with the data based on temperature-dependent experimental studies.

6 illus, 3 tables, 22 ref