011158   Suni Divya;Sharma V (Department of Applied Sciences, National Institute of Technology, Hamirpur,(HP)-177 005) : Compressible couple-stress fluid permeated with suspended particles heated and soluted from below in porous medium. Indian J pure appl Phys 2003, 41(8), 602-11.

A layer of compressible couple-stress fluid permeated with suspended particles, heated and soluted from below in a porous medium is considered. For the case of stationery convection, the stable solute gradient and couple-stress have stabilizing effects, whereas the suspended particles and medium permeability have destabilizing effects on the onset of convection in the couple-stress fluid permeated with suspended particles, heated and soluted from below in a porous medium. The effect of compressibility is to postpone the onset of thermosolutal instability. Results are illustrated, graphically, by giving numerical values to the parameters. The system is stable for (cp/g)β<62> 1; cp, β and g denote specific heat at constant pressure, uniform temperature gradient and acceleration due to gravity, respectively. The stable solute gradient is found to introduce oscillatory modes in the system for (cp/g)β<62> 1, which were non-existent in its absence. Sufficient conditions for the non-existence of over-stability are also obtained.

4 illus, 17 ref

011157   Sivagurunathan P;Dhinakaran B (Dep of Phys, Annamalai Univ, Annamalai Nagar-608 002) : FTIR analysis of human blood serum with special reference to cardiovascular disease incidence with diabetes. Acta Cienc Indica-Phys 2003, 29(4), 377-80.

An attempt has been made to study the variation of protein, lipid and glucose content in the cardiovascular disease with diabetes blood serum in comparison with that of healthy blood serum. Both healthy and cardiovascular disease with diabetes blood serum are collected from the patients age groups between 50 to 70 and analysed by FTIR. The intensity variations are observed for both healthy and cardiovascular disease with diabetes blood serum. The optical density was calculated for the prominent absorption bands at 3310, 2960, 2930, 1654, 1541 and 1404 cm^-1 in the IR. The higher optical density valuses for cardiovascular disease with diabetes blood serum than the healthy, may confirms the excess accumulation of protein lipid and glucose content in cordiovascular disease with the diabetes patients.

1 illus, 2 tables, 16 ref

011156   Singh K;Saxena N S (Physics Dep, Condensed Matter Physics Laboratory, Rajasthan University, Jaipur-302 004) : Pressure dependence of thermal conductivity and thermal diffusivity of Se-Te-In chalcogenide glasses. Indian J pure appl Phys 2003, 41(6), 466-9.

Measurements of effective thermal conductivity (λ_e) and effective thermal diffusivity (χ_e) of twin pellets of Se₈₀Te_20-xIn_x(x=2,4,6 and 10) chalcogenide glasses, prepared under pressure (load) of 5, 7, and 9 tons, have been made at room temperature, using transient plane source (TPS) technique. The results indicate that, both the values of λ_e and χ_e increase with the increase of In concentration. Besides, λ_e and χ_e also depends upon the load at which the pellets have been formed. The composition and pressure (load) dependent behaviour of λ_e and χ_e is explained in terms of the ion-covalent type of bond which In makes with Se as it is incorporated in the Se-Te glasses.

5 illus, 9 ref

011155   Singh D P;Singh A K;Srivastava O N (Dep of Physics, Banaras Hindu University, Varanasi-221 005) : Formation and alignment of silicon nanoparticles on DNA template. Indian J Phys-Pt A 2004, 87(2), 197-200.

One and two-dimensional alignments of silicon nanoparticles have been achieved by the assembly on DNA template of kilo base pairs. The silicon nanoparticles have a size of 15 nn and the alignment exends upto micrometer. It has been suggested that interaction between the phosphate groups of the DNA template network and silicon nanoparticles leads to aligned arrangements of Si nanoparticles.

4 illus, 16 ref

011154   Singh B P;Singh V;Lokendra Kumar;Sharma T P (Thin Films Laboratory, Dep of Physics, C C S University Meerut, Meerut-250 004) : Spectroscopic study of vacuum evaporated crystalline Zinc Selenide thin films. Asian J Phys 2002, 11(2), 199-203.

Vacuum evaporated crystalline films of Zinc selenide (ZnSe) have been characterized by using optical spectroscopy (especially absorption and transmission spectroscopy). Crystalline ZnSe films have been deposited by vacuum evaporation technique on highly clean glass substrates and their optical properties (energy band gap, refractive index and extinction coefficient) have been studied. The energy band gap (E_g) of the films has been calculated from absorption spectra by using Tauc relation. The transmission spectra in the spectral range 400-850 nm has been used to calculate the refractive index (n), extinction coefficient (k) and wave length dependence of n and k of the films have been studied. Optical spectroscopy of the films have been done with the help of the Hitachi spectrophotometer model U-3400.

5 illus, 11 ref

011153   Singh A K;Reddy N S (Institute of Armament Technology, , Girinagar, Pune-411 025, Maharashtra) : Field instrumentation for thermal conductivity measurement. Indian J pure appl Phys 2003, 41(6), 433-7.

Deals with the development of instrumentation for automated thermal conductivity measurement. Sensor used is transient thermal probe, which is based on line heat theory. The thermal probe is interfaced with PC by using a data acquisition module with, application software written in C/C++. The developed instrumentation has been tested by measuring thermal conductivity of standard materials like glycerol, distilled water, etc., for different sampling perods, number od samples and probe heater currents. The instrumentation has been used for measurement of thermal conductivity of propellants and other materials in laboratory, as well as, in field.

2 illus, 2 tables, 13 ref

011152   Shekhar I;Dhir S M;Vijayanand P;Dixit L (NO, Indian Institute of Petrolium, Dehradun-248 005) : Diffuse reflectance UV-VIS spectroscopic study on ZSM-5 surface chemically modified by tetraethyl ortho-silicate deposition. Asian J Phys 2002, 11(2), 221-4.

Diffuse reflectance UV-VIS spectroscopy has long been recognised as the diagnostic tool for the characterization of surface species of the solid samples. In case of zeolites such as ZSM-5, many times the surface is modified to alter its acidity depending upon the requirement of its use in a particular reaction. Two routes, viz., chemical liquid deposition (CLD) and chemical vapour deposition (CVD) are usually adopted to these modifications of the surface. Some preliminary results based on UV_VIS spectroscopy of ZSM-5 as well as modified ZSM-5 with tetraethyl ortho-silicate (TEOS) using chemical liquid deposition technique has been presented. This has been done with a view to know the conditions under which thin films of TEOS are deposited on ZSM-5 surface and see the resulting spectral changes as a function of drying and calcination. It has been found that in the spectra of surface modified ZSM-5, the intensity of additional band that appears at 230 nm due to TEOS disappears successively with rise in temperature and fully disappears at 500°C indicating the complete breaking of the TEOS. When such a catalyst is used for aromatization reactions, normally metals are introduced either in framework or cationic position. The diffuse reflectance UV-VIS spectra of metal loaded ZSM-5 catalyst are found to exhibit at 200 nm and 300 nm region whose intensities decrease as the catalyst is dried and calcined.

3 illus, 11 ref

011151   Sharma S K;Baveja J;Mehra R M (Electronic Science Dep, University of Delhi South Campus, New Delhi-110 021) : Dependence of electrical conductivity on selenium and sulphur doping in a-Si:H. Indian J pure appl Phys 2003, 41(6), 491-4.

Se-and S-doped a-Si:H films were prepared by the decomposition of H₂Se and H₂S with SiH4 gas mixtures by plasma enhanced chemical vapour deposition (PECVD) in a ratio of H₂Se/Si⁴=1.0x10^-4 to 1.0x10^-1 and H₂S/SiH₄=6.8x10^-7 to 1.0x10^-4. The dielectric constant of Se- and S-doped a-Si:Hfilms vary with doping concentration and can be tailored by changing the gas ratio. The dc dark and photoconductivity showed a maximum at H2Se/SiH₄=10^-3 and a-Si,S:H at H2S/SiH₄=1.0x10^-4 and the activation energy is lower at these doping levels. The room temperature dark and photoconductivity in Se and S-doped a-S:H films have been found to increase as the gas ratios increase for H₂SiH₄=10^-3 and H₂S/SiH₄=10^-4, after this range in Se-doped, the dark and photoconductivity decrease to the alloy range.

5 illus, 18 ref

011150   Sehrawat K;Mehra R M (Electronic Science Dep, University of Delhi, South Campus, New Delhi-110 021) : Photoconductivity spectrium of porous silicon as a function of preparation parameters. Indian J pure appl Phys 2003, 41(6), 495-7.

Photoconductivity (PC) which is controlled by non-radiative recombination could provide important information for the understanding of the transport and microscopic origin of photoluminescence (PL) and electro-luminescence (EL) or porous silicon (PS). With this, it may be possible to address the instability encountered in PS optoelectronic devices. An attempt has been made to investigate the transport properties of porous silicon by undertaking a systemsatic study of the influence of the anodisation parameters on photoconductivity spectra of PS, prepared by wet electrochemical anodisation of p-type c-Si. The PC peak was observed to blueshift with increasing current density/anodisation time and decreasing HF concentration, due to a decrease in crystallite size that was confirmed by SEM observations. The rsults have been explained as a consequence of bandgap widening, according to the quantum confinement mode.

4 illus, 12 ref

011149   Sathyanarayana J V (Dep of Physics, RVR & JC college of Engineering, Chowdavaram, Gutur-522 019) : Spectroscopic properties of Ho<. Asian J Phys 2002, 11(2), 191-8.

The spectral characteristics of Ho³⁺ : Lithium chloroborate glasses in the ternary system B₂O₃-Li₂O-LiCl has been carried out by changing the LiCl content. These Ho³⁺ : glasses display bluish colour when irradiated with suitable UV-radiation. Using the absorption parametrization, the measured emission spectra of these glasses have been analysed.

8 illus, 2 tables, 15 ref

011148   Sarkar M J A;Sarkar M A R (Department of Physics, University of Rajshahi, Rajshahi-6205, Bangladesh) : dc electrical properties of vacuum evaporated amorphous V2O5 thin films. Indian J pure appl Phys 2003, 41(8), 634-40.

Memory switching current versus voltage (I-V) characteristics of Al-V2O5-Al sandwich devices for different V2O5 film thickness (40-350 nm) and temperatures (300-420 K) were measured and from these measured data, OFF state I-V characteristics were selcted for the study of dc electrical properties to determine the type of conduction mechanism operating in the OFF state I-V characteristics. The OFF state log I-E^1/2 characteristics are found linear for the applied electric field E<62>2.25x10⁶Vm^-1. Valuation of activation energy ΔE obtained from the slope of log I-10³/T curves for 0.2, 0.4, 1.0 and 4.0V applied fixed voltages are found in the ranges 0.03-0.05 and 0.10-0.17 eV for the temperature intervals 300-350 K and 350-420 K, respectively. It was found from the dc data analyses that, the conduction mechanism operating in the OFF state I-V characteristics Al-V2O5-Al sandwhich devices appears to be predominated by the Poole-Frenkel emission.

6 illus, 4 tables, 22 ref

011147   Saikia D;Bora M N (Physics Dep, Duliajan College, Duliajan, Assam-786 602) : Study of hygroscopic properties of some plant fibres under thermal condition. Indian J pure appl Phys 2003, 41(6), 484-7.

The hygroscopic properties such as hygroscopicity, water yielding capacity, capillarity etc of cellulosic plant fibres such as sisal, bowstring hemp (dagger), pineapple, lady's finger and betel-nut annealed from 310 to 430 K have been investigated. The hygroscopicity of the plant fibres at constant relative humidity decreases with an increase in annealing temperature from 310 to 430 K. The bleached and mercerized samples are more hygroscopic than native samples. The rate of sorption of water content at constant relative humidity increase on pre-heating. The water-yielding capacity as well as capillary action at constant relative humidity decreases with increase in annealing temperature.

3 illus, 4 tables, 12 ref

011146   Ray S K;Rath J;Samal R N (P.G. Dep of Phys, Ravenshaw Coll, Cuttack-753 003) : Temperature variation of viscosity of a novel polymer "dextran" in distilled water. Acta Cienc Indica-Phys 2003, 29(4), 335-40.

Different viscosity parameters of a water soluble polymer "Dextran" at different concentration in distilled water at different temperatures are evaluated and the nature of variation of specific viscosity and reduced viscosity with respect to concentration at different temperatures are studied.

4 illus, 2 tables, 10 ref

011145   Ravi N;Sastikumar D;Subramanian N;Nath A K; Ramalingam A (Dep of Physics, St. Joseph's College (Autonomous), Tiruchirappalli-620 002) : Formation of intermetallic compounds on the surface of aluminium alloy with Fe-Ni using laser alloying. Asian J Phys 2002, 11(2), 225-31.

Al alloy was laser surface alloyed with Fe-Ni powders of various powers and scan speed. The effect of microhardness and microstructure on the alloyed samples were studied. The study shows that there is a large variation in microhardness with respect to the depth and appreciable increase in hardness. The formation of intermetallic compounds were identified using XRD. The presence of coating materials (Fe and Ni) were identified using XRF.

6 illus, 3 tables, 14 ref

011144   Rathore R S (Department of Physics, Indian Institute of Science, Bangalore 560012) : Molecular dynamics study of a tripeptide Z-Ala-Ala-Leu-pNA. J Indian Inst Sci 2002, 82(5-6), 227-33.

Conformations of a substrate of subtilisin enzyme,N-benzyloxycarbony1-L-alany1-L-alany1-L-leucy1-p-nitroanilide have been explored using molecular dynamics simulations. The dynamic structure is characterized by overall extended and folded conformations of the peptide.

5 illus, 1 table, 9 ref

011143   Rangra V S;Sharma D R (Department of Physics, HP University, Shimla-171 005) : Dielectric relaxation studies of binary mixtures of acetone and N, N-dimethylacetamide in the benzene solutions using microwave absorption data. Indian J pure appl Phys 2003, 41(8), 630-3.

Using standard standing wave microwave techniques and following Gopala Krishna's [Trans Faraday Soc, 33 (1957) 767] single frequency (9.88 GHz) concentration variational method, the dielectric relaxation times (τ) and the dipole moments (μ) of the binary mixtures of different molar concentrations of acetone (Ac) in binary mixtures of acetone and N,N-dimethylacetamide in benzene solutions have been calculated at different temperatures (25, 30, 35 and 40 °C. The energy parameters (ΔHε, ΔFε, ΔSε) for the dielectric relaxation process of binary mixtures containg 50% mole fractions of Ac have been calculated, at the respective given temperatures. Comparison has been made with the corresponding energy parameters for viscous flow. From the observations, it is found that the dielectric relaxation process like the viscous flow process can be treated as the rate process. On the basis of the above studies, solute-solvent type of the molecular association can be predicted.

1 illus, 1 table, 17 ref

011142   Rajesh Kumar;Mathur A K;Dwivedi K K;Das D; Prasad R (Department of Applied Physics, Z H College of Engineering and Technology, Aligarh Muslim University, Aligarh-202 002) : Au ion irradiated modification in CR-39 by positron annihilation. Indian J Phys-Pt A 2004, 87(2), 225-7.

CR-39 is a polycarbonate widely used as SSNTD for recording nuclear charged particles and in other applications. Latent ion tracks produced in the polymers due to damage produced by the passage of Swift Heavy Ions contain amorphous material with highest degree of disorder, changing the free volume properties which have strong correlation with the macroscopic propertoes of the material. Positron Annihilation Lifetime Spectroscopy (PALS) provides direct information about the dimension, content and hole size distribution of free volume in polymers. The effect of irradiation of ¹⁹⁷Au(13.5 MeV/n) ions on CR-39 polycarbonate by Positron Annihilation Lifetime Spectroscopy (PALS) is reported. PALS provides a non-destructive and non-interfering probe, having high detection efficiency for free volume hole properties. PAL measurement shows 8.9% increase in free volume size.

1 illus, 1 table, 9 ref

011141   Rai S;Baruah G D (Laboratory of Nonlinear Optics, Photonics and Laser Spectroscopy, Dep, Dibrugarh University, Dibrugarh-786 004) : Fluorescence and photoacoustic spectra of Eu + Ho in Ca-Li-Bo glass. Asian J Phys 2002, 11(2), 217-20.

The fluorescence and photoacoustic spectra of triply ionized Eu + Ho incorporated in Ca-Li-Bo glass have been studied with 1% of Eu³⁺ and different concentrations of Ho³⁺. The fluorescence and photoacoustic spectra show that the intensities of the Eu³⁺ transitions exhibit a linear function of Ho³⁺ concentrations.

2 illus, 2 tables, 11 ref

011140   Qaiyum A (Dep of Phys, A.M.U., Aligarh) : Far infrared line and continuum radiation from extragalactic photodissociation regions and photoelectric heating efficiency. Acta Cienc Indica-Phys 2003, 29(4), 341-8.

It is believed that the galactic and extragalactic photodissociation regions are primarily heated by photoelectrons ejected from the surface of interstellar dust grains by far-ultraviolet photons. These electrons carry excess kinetic energy, which is converted into gas thermal energy through successive collisions. But there is no mechanism for direct estimation of the heat deposited in the medium through photoelectrons. However, far-infrared line and continuum emissions from the regions may provide an indirect tool for the estimation of photoelectric heating. The FUV radiation field may be estimated from FIR continuum. The interpretation of line intensities of 158μm hyperfine transition of CII(²P_3/2→²P_3/2) and rotational transition of CO(1→0) provide an indirect method for the estimation of photoelectron heating efficiency of the medium. It is found that observed extragalactic line emissions from CII and CO are in good agreement with that of calculated values when a fraction of <126>0.025 of FUV radiation field incident on the medium is converted into heat. The indirect estimate of heating efficieny is slightly less with that of Juvela et al. (2003).

2 illus, 1 table, 13 ref

011139   Ponnusamy V;Ramasamy V;Dheenathayalu M (Dep of Physics, Annamalai University, Annamalainagar- 608 002) : Kinetics of thermoluminescent calcite. Indian J pure appl Phys 2003, 41(8), 621-6.

The thermo-stimulated luminescence (TSL) glow curve characteristics of five, blue coloured calcite samples of southern Tamilnadu are put to analysis. NTSL glow peaks are obtained for these samples. The glow curves of annealed (600°C) and un-annealed samples, irradiated with gamma dose of 500 Gy show three peaks at 145, 255 and 345°C, respectively, recorded with linear heating rate of 10°C/sec. The kinetic parameters such as activation energy (E), frequency factor (S) and order of kinetics (b) are evaluated, using partial heating, peak shape, isothermal and initial rise methods. The investigations show that, the trapping centres are not affected by the annealing procedure and it follows second-order kinetics. The activation energies have been determined.

5 illus, 15 ref

011138   Patel M H;Thakore B Y;Gajjar P N;Jani A R (Dep of Physics, Sardar Patel University, Vallabh Vidyanagar-388 120) : Temperature dependence of dynamical correlation in liquid lithium. Indian J pure appl Phys 2003, 41(6), 428-32.

The temperature dependence of dynamical variables, the velocity correlation function (VACF), the power spectrum (PS) and the mean square displacement (MSD) of liquid lithium at T=470K, 725K, 843 K and 1000 K are studied by static harmonic-well approximation. The effective interatomic potential for liquid lithium is computed using the recently proposed mode potential with the dielectric function of Sarkar et al. It is observed that for the higher temperature, the VACF furnishes very short memory than at melting temperature. The increase in the temperature decays the VACF slowly and also decreases the back scattering of atoms. The increase in the temperature increases the flatness of the shoulder of the power spectrum. The result of the MSD concludes that the presence of the vibrating component in the atomic motion decreases with increasing T.

3 illus, 1 table, 12 ref

011137   Nirala A K;Santosh Kumar (Postgrad Cen, Dep of Phys, Kisan Coll, Sohsarai, Nalanda-803 118) : Development of optical testing technique using N.O.P.C.I.which is least affected by exernal non-uniform perturbations and optical distortions. Acta Cienc Indica-Phys 2003, 29(4), 381-4.

4 illus, 11 ref

011136   Natarajan R K;Gunasekaran S;Santhosam K (Post Graduate and Research Department of Physics, Presidency College, Chennai) : Spectroscopic investigation on diethyl carbamazine citrate. Asian J Phys 2002, 11(2), 258-61.

Diethyl carbamazine citrate (DEC) is most effective antifilarial and anthelmintic drug. The FITR spectrum of the compound has been recorded to do the qualitative analysis of the vibrational bands. The light absorption characteristics of the drug in the UV-VIS region have also been studied. The light absorption activity of the drug under different storage conditions has also been analysed. Further the interaction of the drug with some of the trace elements like calcium, magnesium, sodium and potassium and vitamins E and B, present in human blood has been investigated by ultraviolet spectroscopial methods.

2 illus, 5 tables, 3 ref

011135   Manocha L M;Valandi L;Monacha S;Warrier A (Department of Materials Science, Sardar Patel University, Vallabh Vidyanagar-388 120) : Development of carbon nanomaterials through chemical routes. Indian J Phys-Pt A 2004, 87(2), 159-63.

With the attractive properties of carbon nanotubes and the potential applications in mind, there has been concerted efforts word-wide to produce these material in more economical way. Launched programs to synthesize aligned carbon nanomaterials through chemical methods. Aligned carbon nanomaterials have been synthesized through CVD method by cracking of hydrocarbon gases (benzene, xylene etc.) in presence of catalyst (Fe, Ni etc.) at temperature of 700-800°C. The substrate was prepared through sol-gel route in order to control the size and distribution of catalyst particles. Benzene leads to depelopment of more carbon nanofibers while higher concentration of nanotubes are observed with xylene as precursor. The relative amount of aligned and randomly oriented carbon nanotubes can be controlled through optimized processing conditions. Nanotubes have also been synthesized using ssolids (chars and cokes). The percrusors are impregneated with a suitable catalyst solution. On heating these precursors to a temperature of 650-900°C, carbon nanotubes have been observed embedded in amophous carbons. These carbon nanomaterials have been characterized using XRD, TEM, SEM and thermal analysis techniques.

7 illus, 8 ref

011134   Mangal R;Saxena N S;Joshi G P;Singh G P; Sreekal A M S;Thomas S (Physics Dep, Duger College, Bikaner-334 001) : Crystallization kinetics of pineapple leaf fiber reinforced phenol formaldhyde composites. Indian J pure appl Phys 2003, 41(6), 470-3.

Kinetics of crystallization in pineapple leaf fiber reinforced phenol formaldhyde (PF) composites has been studied employing Differential Scanning Calorimetry (DSC). Kinetic parameters such as activation energy in crystallization as well as in glass transition region have been investigated at different percentage of fiber (typically at 15,20,30,40 and 50 by weight) and at different heating rate (typically at 5,10,15,20 K/min). The obtained data has been analyzed in terms of modified Kissinger equation and also using other equation. It is found that, activation energy depends upon the fiber percentage whereas it shows a weak dependence on heating rate

3 illus, 2 tables, 13 ref

011133   Lokendra Kumar;Dhawan S K;Mahesh Kumar; Kamalasanan M N;Subhash Chandra (Polymeric and Soft Materials Section, National Physical Laboratory, Dr K S Krishnan Road, New Delhi-110 012) : Yellow-green organic light emitting diodes based on poly (p-phenylene vinylene)/CdS heterojunction thin films. Indian J pure appl Phys 2003, 41(8), 641-5.

Thin film electro-luminescent devices based on organic materials are very popular for organic light emitting diodes (OLEDs) fabrication. The authors have polymerized PPV precursor solution from p-Xylenebis ( tetrahydrothiophenium chloride) salt. Thin films of PPV were prepared by spin-coating, the precursor onto ITO substrates and curing it at 220 °C in the absence of oxygen. Organic light emitting diode structures were fabricated using ITO as the bottom electrode, PPV as an emitter layer as well as the hole transport layer, CdS as an electron transport layer and akluminium as the cathode. In this configuration, CdS provides the advantage of excellent charge-transporting properties of an inorganic semiconductor. Electro-luminescence spectrum obtained from this hetero-junction device was similar to the emission spectrum of PPV. The devices give bright greenish-yellow electro-luminescence on application of about 10V under forward biased condition.

7 illus, 20 ref

011132   Kumar R;Nath B K;Das D;Prasad R (Applied Dep, Z H College of Engineering & Technology, Aligarh Muslim University, Aligarh-202 002) : Positron annihilation lifetime measurements for C<. Indian J Phys-Pt A 2004, 87(2), 221-3.

Makrofol-N is the polycarbonate widely used in nuclear research, nuclear filters and in other applications. Latent ions tracks produced in the polymers due to the damage produced by the passage of Swift Heavy Ions contain amorphous material with highest degree of disorder, changing the free volume properties which have strong correlation with the macroscopic properties of the material. Positron Annihilatoin Lifetime Spectroscopy (PALS) provides direct information about the dimension, content and hole size distribution of free volume in polymers. The effect of irradiation of C⁵⁺ 70 MeV ions on Makrofol-N polycarbonate by Position Annihilation Lifetime Spectroscopy (PALS) is reported. PALS provides a non-destructive and non-interfering probe, having high detection efficiency for free volume hole properties. From the o-Ps lifetime, mean free volume, radius and average free volume have been obtained.

1 illus, 1 table, 9 ref

011131   Kumar H K T (Department of Physics, Siddaganga Institute of Technology, Tumkur-572 103) : Comparison of the detuning effects on the mode-locked pulse width in activily mode-locked broadband and narrow band lasers. Asian J Phys 2002, 11(2), 250-2.

Closed-form analysis of generation of mode-locked pulses in actively mode-locked broadband lasers in the presence of detuning effects is presented. A comparison study is made on the behaviour of mode-locked pulse width of an actively mode locked broadband laser to that of a narrow band laser in presence of detuning. The parametric study showed that the mode locked pulse width is insensitive to the detuning parameter. The results are presented in the graphical form.

1 illus, 1 table, 4 ref

011130   Krishnakumar V;John Xavier R (Postgraduate Department of Applied Physics, Nehru Memorial College, Puthanampatti-621 007) : Normal coordinate analysis of 2-mercapto and 4,6-dihydroxy -2-mercapto pyrimidines. Indian J pure appl Phys 2003, 41(8), 597-601.

The FTIR spectrum of 2-mercapto pyrimidine has been recorded in the region 4000-50 cm^-1 and normal coordinate analysis of 2-mercapto pyrimidine and 4,6-dihydroxy -2-mercapto pyrimidine has been carried out by assuming Cs point group symmetry. All the nodes of vibrations are assigned and calculations of potential energy distributions are also performed.

2 illus, 2 tables, 17 ref

011129   Khijwania S K;Gupta B D (Dep of Physics, Indian Institute of Technology, New Delhi-110 016) : Spiral probe for fiber optic evanescent field absorption spectroscopy. Asian J Phys 2002, 11(2), 187-90.

A highly sensitive probe for the fiber optic evanescent field absorption sensor is proposed. The high sensitivity is achieved by fabricating the probe in a spiral shape. The experimental results are compared with the straight and U-shaped probes. It has been found that the spiral probe with one and a half turn is about three times more sensitive than the U-shaped probe of same bending radius. The sensitivity can be increased to any desired value by adding more number of turns in the proposed probe. A good degree of reproducibility of results is obtained.

2 illus, 20 ref

011128   Khalil M M I; Elbatal F H A;Nada N;Desouky S A (Radiation Physics Department, National Centre for Radiation Research & Technology, Nasr City, Cairo, Egypt) : Optical and infrared absorption of gamma irradiated ternary silicate glasses containg NiO. Indian J pure appl Phys 2003, 41(8), 651-666.

The optical and infrared absorption spectra of ternary silicate glasses containg NiO were studied systematically, as function of glass composition. The same properties were measured after successive gama ray irradiation. The induced spectra and the rate of formation of the intrinsic defect of the base glass and the extrinsic defect due to the nickel ions were calculated. The experimental optical results were analysed and explained by assuming that nickel exists in glass as divalent Ni ions in two different states of coordination, namely, octahedral and tetrahedral. The infrared spectra of the doped glasses reveal the same spectra of the undoped glasses retaining the main vibrational bands which indicate that the dopant oxide has no effect on the main structural building groups. The rates of formation and annihilation of the color centers produced by gamma irradiation are belived to approach saturation or equilibrium with prolonged irradiaton.

20 illus, 3 tables, 31 ref

011127   Kalita D K;Boruah R K;Baruah G D;Sahu O P (NO, Regional Research Laboratory, Jorhat-785 006, Assam) : XRD study of Lekhapani coal. Asian J Phys 2002, 11(2), 213-16.

X-ray diffraction pattern of Lekhapani coal shows that it is amorphous in nature. X-ray radial distribution analysis of its XRD pattern indicates that this coal is lignite in type and there is no evidence of its graphite-like structure. The distribution curve shows 8 nearest neighbours at a distance of about 0.4 angstrong and 5 second neighbours at about 2.45 angstrong, 3.45 angstrong, 4.42 angstrong, 5.45 angstrong, 6.48 angstrong and 7.48 angstrong.

1 illus, 2 tables, 6 ref

011126   Joshi G P;Saxena N S;Sharma T P;Dixit V;Misra S C K (Physics Dep, Condensed Matter Physics Laboratory, University of Rajasthan, 5-6, Vigyan Bhawan, Jaipur-302 004) : Bandgap determination of chemically doped polyaniline materials from reflectance measurements. Indian J pure appl Phys 2003, 41(6), 462-5.

Spectroscopic techniques are very useful for characterizing semiconducting and conducting materials. The optical properties (specially reflection spectra) of polyaniline mix with metal Mn and Fe with different composition in bulk form were studied. The reflection spectra of these materials are recorded by a Hitachi spectro-photometer model (330), at room temperature, in the wavelength range 300-600 nm. From the analysis of reflection spectra, polyaniline mix with metal Mn and Fe have been found to have energy bandgap which decreases with increase of concentration of iron. An effort has also been made to study the structure formation using XRD techniques

5 illus, 1 table, 7 ref

011125   John Thruvadigal D;Sampath Krishnan S; Gnanasekaran S (Dep of Physics, S.R.M. Engineering College, Kattankulathur-603 203) : Extension of virial theorem approach of Redington to higher order vibrational problems. Asian J Phys 2002, 11(2), 238-40.

In the method of Redington, the n fundamental vibrational frequencies and n(n^-1)/2 additional angle parameters φ_ij serve to determine n(n+1)/2 independent force constants F_ij. The arbitary angle parameters are obtained from the maximum value of F_steep solutions which are calculated from the G-matrix elements, the vibrational frequencies and the T_k coefficients. To find the correct value of angle parameters, its valueis varied from -90° to +90° at a suitable interval and F_steep values are estimated. The particular angle at which F_steep value is maximum is taken as the value for the angle parameter. This method is applied to solve the inverse vibrational problem of dimethyl sulfoxide (DMSO). DMSO, which has a pyramidal structure contains ten atoms and the twenty four fundamentals are distributed among two symmetry species as 13A' + 11A'. The secular equation of A' and A'' vibrations are effectively solved by adopting Redington's method and are compared with literature values. From the observations made, it is found that the virial theorm approach of Redington can be successfully extended to solve the inverse vibrational problems of higher order.

1 table, 2 ref

011124   John Thiruvadigal D;Sampath Krishnan S; Gnanasekaran S (Dep of Physics, S.R.M. Engineering College, Kattankulathur-603 203) : Vibrational analysis of 2-fluoropropene. Asian J Phys 2002, 11(2), 241-3.

Reports the results of the force field studies of 2-fluoropropene and the validity of the application of method of kinetic constants and Isotani's method to higher order vibrational problems is discussed.

1 table, 3 ref

011123   Jha S R;Jha A (Post Grad Dep of Phys, C.M. Sci Coll, Darbhanga- 846 004) : Microwave scattering by a semi-infinite anisotropic thin dielectric layer. Acta Cienc Indica-Phys 2003, 29(4), 443-9.

Microwave scattering by a semi-infinite anisotropic thin dielectric layer is investigated which can be considered as an example for electromagnetic energy absorbing materials. A pair of second order boundary conditions is used to simulate an anisotropic thin dielectric layer as an infinitesimally thin sheet. Formulation is based on the Fourier Integral transform technique. Diffracted, reflected and transmitted field terms are evaluated by using the Wiener-Hopf solutions, that is obtained by the standard method. The uniqueness of the solution is satisfied by imposing an edge constraint in addition to the classical edge condition.

4 illus, 7 ref

011122   Jha M K;Jha L (Univ Dep of Phys, L.N. Mithila Univ, Darbhanga-846 004) : Analysis of electromagnetic scattering by a wedge with anisotropic impedance. Acta Cienc Indica-Phys 2003, 29(4), 371-6.

Electromagnetic sacttering from the edge of an anisotropic wedge, impedance, illuminated at oblique incidence is analysed. It intends to provide a brief review of existing solutions in diffraction theory. Both numerical and analytical techniques, suitable to properly account for the scattering properties of the Wedge's an isotropic impedance faces, are considered.

2 illus, 1 table, 13 ref

011121   Jain S K;Chander S;Dolia S N;Krishnamurthy A; Srivastava B K (Physics Dep, University of Rajasthan, Jaipur-302 004) : Magnetic behaviour of (Fe_0.90Mn_xCo_0.1-x)₂P. Indian J pure appl Phys 2003, 41(6), 488-90.

(Fe<>0.90Mn_xCo0.1-x)₂P with x=0.03, 0.05 and 0.07 (hereafter referred to as FMC37, FMC55 and FMC73, respectively) crystallize in Fe2 like hexagonal symmetry. DC magnetization measurements have been made on these alloy systems in external fields up to 8.5 KOe and in the temperature range 85-400K. The alloys are ferromagnetic with T_c <126> 325K for FMC37, <126> 250K for FMC55 and <126> 220K for FMC73. While FMC37 shows a clear paramagnetic to ferromagnetic transition, in FMC55 and FMC73, the transition anomaly is field-dependent and gets suppressed by rather low fields. In these two systems, FM order keeps evolving with cooling below these Curie points and at still lower temperatures negative exchange gains in strength, giving rise to disordered magnetic state, which shows long time magnetic relaxation. Below 85K, there could be another modification in magnetic states of the two systems with positive exchange interaction regaining in strength.

5 illus, 5 ref

011120   Jain R;Saxena N S;Bhandari D;Sharma S K (Physics Dep, Condensed Matter Physics Laboratory, University of Rajasthan, Jaipur-302 004) : Crystallization kinetics of Ni_xTi_100-x(x=35,40) glasses before and after high energy heavy ion irradiation. Indian J pure appl Phys 2003, 41(6), 457-61.

Non-isothermal crystallization process in amorphous alloys Ni₃₅Ti₆₅ and Ni₄₀Ti₆₀ before and after high-energy heavy ion irradiaiton with 150 MeVNi^+11>ions have been investigated using differential scanning calorimetry (DSC). The alloys have been irradiated with fluences varying between 1 x 10¹¹ and 1 x 10¹³ions/cm₂. DSC traces have been analyzed in terms of activation energy for crystallization, Avrami exponent dimensionality of growth by using four different models viz. Kissinger equation, Ozawa equation, Matusita equation and Gao and Wang equation. No effect of heavy ion irradiation of above mentioned energy, on the crystallization kinetics has been found.

8 illus, 3 tables, 7 ref

011119   Jain K;Kumar V;Rashmi;Sood K N;Lakshmikumar S T (Electronic Materials Division Characterization Division, National Physical Laboratory, New Delhi-110 012) : Preparation of Sb-doped SnO₂ transparent conducting oxide coating by dip coating technique. Indian J Phys-Pt A 2004, 87(2), 215-19.

Nanocrystalline SnO₂ powder, as well as thin thick film has been successfully prepared by means of polymeric citrate route, starting from in-expensive tin (IV) chloride for applications as TCO and gas sensor. Free flowing spherical granules (30-40 nm) were obtained which can be dispersed easily to prepared paste for screen printing. Transparent Conducting glass plates were prepared using dip coating process. An investigation was made of the influence of antimony as dopant, the concentration of Sb was varied between 0 to 10 . Preliminary investigations showed thick films prepared from these powders to be quite suitable for LPG gas sensors.

9 illus, 1 table, 13ref

011118   Islam M N;Ahasan M M;Alam M K;Uddin M S;Zaman M A (Institute of Nuclear Science and Technology, , AERE, GPO Box 3787, Dhaka 1000 Bangladash) : Measurements of D₂O-concentration in D₂O-H₂ mixture using neutron radiography technique. Indian J pure appl Phys 2003, 41(8), 593-6.

This study is based on the optical density results measured from neutron radiographs of different samples of light water (H₂O) and heavy water(D₂O), taken separately, and also in the D₂O-H₂O mixture. A calibration curve was drawn through the results, extracted from a series of standard mixtures of D₂O-H₂O, with the known D₂O concentration. The scale along the abscissa is to be explained as percentage of deuterium atoms present in the liquid compared with all atoms of hydrogen isotopes present. It may be concluded that, as D₂O concentration added to light water increases, the optical density also increases, i.e., optical density is a function of D₂O concentration. Neutron radiographs were then taken from two other samples of D₂O-H₂O mixture with different and unknown D₂O concentration. Concentration of D₂O was determined using the calibration curve via measurement of average optical density values.

1 illus, 2 tables, 13 ref

011117   Gupta B D (Physics Dep, Indian Institute of Technology, New Delhi-110 016) : Fiber-optic sensors based on evanescent field absorption spectroscopy. Asian J Phys 2002, 11(2), 145-62.

Several advances in designing fiber optic evanescent field absorption sensors for detecting various chemicals have been made during the last decade. The work includes the enhancement of the sensitivity, removal of non-linearity in the response curve, fabrication of porous cladding for the detection of gases, use of infrared fibers for the detection of chemicals which have absorption peak in infrared region and the detection of chemicals (such as pH) which do not absorb light directly. Presents a tutorial review of the advancement taken place in fiber optic sensors based on evanescent field absorption spectroscopy.

12 illus, 23 ref

011116   Gupta B D (Physics Dep, Indian Institute of Technology, New Delhi-110 016) : Fiber-optic sensors based on evanescent field absorption spectroscopy. Asian J Phys 2002, 11(2), 145-62.

Several advances in designing fiber optic evanescent field absorption sensors for detecting various chemicals have been made during the last decade. The work includes the enhancement of the sensitivity, removal of non-linearity in the response curve, fabrication of porous cladding for the detection of gases, use of infrared fibers for the detection of chemicals which have absorption peak in infrared region and the detection of chemicals (such as pH) which do not absorb light directly. Presents a tutorial review of the advancement taken place in fiber optic sensors based on evanescent field absorption spectroscopy.

12 illus, 23 ref

011115   Gunasekaran S;Krishnan B;Radhakrishnan N; Balaji J;Arumugam V;Sanjeevi R;Balakrishnan R (NO, D G Vaishnav College, Chennai-600 106) : Studies on miscibility behaviour of blend of cellulose acetate with polybutylacrylate. Asian J Phys 2002, 11(2), 253-5.

The viscosity behaviour of mixtures formed by two polymers-cellulose acetate (CA) and polybutylacrylate (PBA) in dilute solution has been studied at 30°C temperature. The intrinsic viscosity and visometric interaction parameters are measured using the Huggins plot. The Chee's more effective miscibility parameters α and μ are calculated. On analyzing by ultrasonic method, it is found that the two polymers are miscible. FTIR studies indicate that blending is only by mechanical process.

2 illus, 1 table, 5 ref

011114   Govinda Bhat S;Dharmaprakash S M (Dep of Physics, Mangalore University, Mangalagangotri- 574 199) : Linear and non-linear optical properties of antimony thiourea bromide crystals. Indian J pure appl Phys 2003, 41(8), 627-9.

Single crystals of antimony thiourea bromide with molecular formula Sb[CS(NH₂)₂]₂Br₃ (ATB) have been grown in gels at ambient temperature. Linear optical properties of this material such as, refractive indices, birefringence and absorption characteristics are measured in the wavelength range 200-1400 nm. No dispersion of the birefringence has been observed within the experimental accuracy. Optical second harmonic generation (SHG) of Nd:YAG laser (λ=1.064 μm) has been observed for ATB crystal.

3 illus, 2 tables, 6 ref

011113   Ghosh;D;Deb A;Bandyopadhyay P;Mondal M;Ghosh J;Bhattacharya S;Patra K;Maity D (Physics Dep, Jadavpur University, Kolkata-700 032) : Signature of void probability scaling in high energy hadronic intrenactions. Indian J pure appl Phys 2003, 41(8), 589-92.

The rapidity gap probability in the p-AgBr interactions at 200GeV/c and-AgBr interactions at 200 and 350 GeV/c have been studied in detail. The data indicate scaling behaviour of the void probability in the central rapidity domain, which hints the validity of the linked-pair approximation for the N-particle cumulant correlation function.

3 illus, 18 ref

011112   Ganotra D;Joseph J;Singh K (Photonic group, Physics Department, Indian Institute of Technology Delhi, new Delhi-110016) : Determination of optimal detector geometry for sampling of Fourier transform of fingerprints for classification using neural networks. Asian J Phys 2002, 11(2), 181-6.

Sampling of the Fourier transforms of fingerprints is studied with neural networks to detect regions useful for their detection. Ring-wedge detector is modified and simulated to sample such regions. The output of the detector is propagated through three-layer feedforward-backpropagation neural network for checking the classification performance. It has been found that fingerprints scanned at a specific resolution contain useful information for their classification in a specific band of pixels. This study has determined this specific combination (geometry) of detectors.

4 illus, 1 table, 10 ref

011111   Eappen S M;Rekha R;Shaji S;Rasheed T M A;Nair K P R (Laser & Spectroscopy Lab, Dep of Physics, Cochin University of Science & Technology, Cochin-682 022) : Application of Nakagaki and Hanazaki model on the aryl Ch overtone spectra of liquid phase o-chlorotolune and m-chlorotoluene. Asian J Phys 2002, 11(2), 232-7.

The effects of methylation and chlorination on the aryl CH local mode frequencies at various sites were analysed by Nakagaki and Hanazaki. The model suggested by them predicts A terms of any benzene derivatives containing chlorine atoms and methyl group assuming additivity of substiuent effect. The validity of their model is demonstrated by comparing the observed and predicted results in p-chlorotoluene. Applies this model to o-chlorotoluene and to m-chlorotoluene and account for the steric inhibition induced by the methyl group to its ortho substituent.

8 illus, 2 tables, 8 ref

011110   Dutta S;Manik S K;Pal M;Pradhan S K;Brahma P; Chakravorty D (Physics Dep, The University of Burdwan, Burdwan-713 104, West Bengal, India) : Phase transition of magnetite by mechanical alloying. Indian J Phys-Pt A 2004, 87(2), 201-4.

Nanocomposite of Fe₃O₄ (magnetite) and α-Fe₂O₃ have been prepared by mechanical grinding Fe₃O₄ powder at ambient with 20 : 1 ball to powder mass ration (BPMR for different durations. Crystalline phases and several microstructure parameters such as volume fraction of the individual phase, particle size, and strain have been determined by X-ray diffraction technique. A very interesting phase transformation kinetics has been noticed with progress of milling volume fraction of Fe₃O₄ reduces and that of α-Fe₂O₃ increases. After 10 hr of milling, content of Fe₃O₄ phase reduces to as low as 0.05 volume fraction. After 6 hr of milling particle size of phase reduces from 54 nm to 5nm. Then the size of the particles increases to 10 nm and remains almost unchanged upto 10 hr milling. The growth of α-Fe₂O₃ phase has been initiated from the Fe₃O₄ phase with very small particle size (4 nm) and in course of milling duration particle size grows upto 11 nm after 6 hrs of milling in an unusual manner. DC electrical conductivity measurements were carried out in the temperature range 110-500 K. Resistivity of the nanocomposites exhibits semiconducting nature comprised of three different activation energies in an unusual manner. Conduction mechanism can be explained on the basis of microstructure induced in composites during milling.

5 illus, 1 table, 18 ref

011109   Durai S ;Ramadoss P (P.G. and Res Dep of Physics, A.M. Jain Coll, Chennai- 600 114) : Debye temperature and refractive index of binary mixtures from ultrasonic velocity and related parameters. Acta Cienc Indica-Phys 2003, 29(4), 397-400.

The association of Debye temperature with the interaction of liquid mixtures has been studied by calculating Debye temperatures for two liquid mixtures of Tetrahydrofuran with Ter-butanal and 1-butanol. Also the refractive indices have been found using density rule and the mixing rules of refractive index have been verified.

2 tables, 11 ref