003397   Chatterjee P;Jana R K;Sen B (Department of Mathematics, Shiksha Bhavana, Visva Bharati Santiniketan-731 235, , Email: prasantachatterjee1@rediffmail.com) : Speed and shape of electron acoustic solitary waves in plasma. Indian J Phys 2005, 79(5), 523-7.

Large amplitude electron acoustic solitary waves are investigated in a two temperature plasma with finite ion-temperature. The Sagdeev's pseudopotential is derived in terms of cold electron speed (u_c). It is found that there exists a critical value of u_c (u_oc) at which u'_c = 0 beyond which the solitary waves cease to exist. This critical value also depends on T_c, the normalized cold electron temperature.

5 illus, 27 ref

003396   Bhowmick A;Gadkari S C;Yakhmi J V;Sahni V C (Technicl Physics & Prototype Engng Div, Bhabha Atomic Res Cent, Trombay, Mumbai-400 085) : The role of vacuum in the quality of TOF mass spectrometer. Bull Indian Vacuum Soc 2005, 8(1), 19-23.

The art in the designing of time-of-flight mass spectrometers has come across a long course of development. The present day state-of-the-art machines are essentially the outcome of knowledge from the advances in different other areas of technology. Discusses exclusively the role of UHV to enhance the quality of the TOF mass spectrometers and its application to the recently developed high resolution TOF mass spectrometer at TP&PED-BARC.

6 illus, 11 ref

003395   Ahmed S N;Reddy C V K;Reddy R R;Ahammed Y N; Gopal K R (Department of Physics, S.K.U.P.G. Centre, Kurnool-518 003) : Thermoacoustic parameters of ternary, antiflourite structure semiconductor compounds and elemental semiconductors. Acta Cienc Indica-Phys 2005, 31(1), 85-90.

Thermoacoustical parameters of Ternary Semiconductor with tetrahedral co-ordination, Antiflourite structure Semiconductor compounds and Elemental Semiconductors are evaluated from volume expansivity, data at 300 K. The various thermoacoustical parameters are evaluated by utilising Moelwym-Hughes parameter (C₁). A relationship between the isothermal, isochoric and isobaric Gruneisen parameters has also been studied. The results have been used to develop and understanding of the significance of microscopic factors such as molecular order and intermolecular forces upon macroscopic thermoacoustic properties. The parameter Y (compressibility) is found to be close to 0.111 from which one may infer that the normal modes of vibrations contributing to heat capacities are very small. The Sharma's acoustical parameter S₀ which is a characteristic of wide variety of substances and it has been found be approximately a constant value of 1.104. The correlation between these parameters nave been established and examined its validity in estimating various parameters like reduced volume is found to be equal to the ratio Moelwyn Hughes parameter (C₁) with Beyer's nonlinearly parameter (B/A)₀ in the case of semiconductors. The present treatment has the distinct advantage of calculating several thermoacoustical parameters through simple interrelationships from the knowledge of volume expansivity data alone.

2 illus, 1 table, 32 ref

003394   A Kumar;Sinha A K;Singh N P;Anzer A;Sinha A K;Verma P K;Mishra L K (Department of Physics, Magadh University, Bodh Gaya-824 234) : An evaluation of compression modulus of nuclear matter as a function of nucleon density. Acta Cienc Indica-Phys 2005, 31(1), 29-36.

Using Mishra and Tripathy Hamiltonian the values of compression modulus K of nuclear matter have been evaluated as a function of nucleon density. The theoretical results are in good agreement with that of the other workers and with the experimental data.

1 table, 15 ref

002274   Viji V R;Kumar K S;Mary Stella M;Vaidyan V K (Dep of Phys, Univ of Kerala, Thiruvananthapuram-695 581) : Studies on the properties of dip-coated indium tin oxide films considering substrate vibration. Indian J pure appl Phys 2005, 43(5), 368-71.

The indium tin oxide (ITO) thin films were deposited on glass substrates using an automated home made dip-coater, from a solution of indicum chloride. These films were characterized using X-ray diffraction, scanning electron microscopy, electrical resistivity measurement and optical transmission spectroscopy. The effect of substrate vibration on film properties was examined and observed that vibration of small amplitudes do not deteriorate the film qualities much. Films deposited at optimum conditions exhibited a resistivity of 2.1x10^-4 Ωm and a transmittance of 87% at 550 nm.

7 illus, 1 table, 16 ref

002273   Verma K C;Maitra M;Tarafdar S;Middya T R;De U (NO, Variable Energy Cyclotron Cent, 1/AF Bidhannagar, Kolkata-700 064, Email: minakshi_maitra@yahoo.com) : Effect of 160 MeV Ne-ion irradiation on polymer salt complex films containing laponite. Indian J Phys 2005, 79(7), 769-72.

The effect of heavy-ion irradiation on (PEO)_1-x-(NH₄ClO₄)_x, films containing 5% laponite as an additive and x varying in the range 16-22wt% have been studied. Impedance spectroscopy and differential scanning calorimetry (DSC) have been done before and after irradiation by 160 MeV Ne-ions. It has been found that irradiation reduces the ion-conductivity and increases the melting point of the polymer electrolyte. DSC results indicate that the reduction is due to cross-linking of polymer chains and increased crystallinity. The effect is more pronounced at the composition with 19 wt% NH₄ClO₄.

3 illus, 1 table, 12 ref

002272   Verma A;Shahi K (Solid St Ionics Laboratory Advd Cent for Mater Sci, Indian Inst of Technol, Kanpur-208 016, Email: verma.Ankur@alumni.iitk.ac.in) : Frequency response of the mechanochemically synthesized AgI-Ag₂O-B₂O₃ superionic glasses. Indian J Phys 2005, 79(7), 749-52.

The synthesis of xAgI(1-x)[Ag₂O.B₂O₃] amorphous superionic conductors is done via mechanochemical synthesis route (for x = 0.5 and 0.7). Ionic conductivities of 3xl0^-3Ω^-1 cm^-1 for x = 0.5 sample and 5xl0^-3Ω^-1 cm^-1 for x = 0.7 sample at room temperature, are observed, which are higher than those of the melt quenched glassy samples. Impedance plots (Nyquist plots) are found to be depressed semicircles with a tail at low frequency end. The corresponding equivalent circuit is postulated and each circuit element is related to a physical process. The ac conductivity σ(ω) is analyzed in view of the universal dynamic response(UDR), σ(ω,T) = σ_dc(T) + A₀(T)ωⁿ (Bode Plots). A unique feature of the mechnochemically synthesized glasses is that their (σ_dc vs 1/T behavior exhibits two distinct regions with different activation energies. The activation energy for dc conductivity (E_dc) and that for ac conductivity (E_ac) and the frequency exponent n are found to satisfy the UDR-relation, E_ac= (l-n)E_dc in the lower temperature regime. In the high temperature region, however, this correlation could not be established due to lack of σ_dc data over the available frequency domain.

6 illus, 7 ref

002271   Verma a;Bakhshi A K;Agnihotry S A (Natn Phys Laboratory, , Dr K S Krishnan Road, New Delhi-110 012, Email: agni@mail.nplindia.ernet.in) : Citric acid induced improved homogeneity of CeO₂ coatings for electrochromic device applications. Indian J Phys 2005, 79(7), 719-24.

An alcohol based sol-gel process involving cerium chloride heptahydrate and citric acid in different mole ratios has been employed for the deposition of CeO₂ coatings. The structural, electrochemical, and optical properties of the coatings have been investigated by a wide range of characterization techniques. The homogeneity induced in the films upon an addition of the stabilizer to the precursor sol, has been accompanied by a simultaneous reduction in the ion storage capacity (ISC) of the films. The emphasis is on the use of optimum content of the citric add such that the films are suitable in terms of transparency as well as uniformity characteristics and also exhibit good electrochemical response. A higher proportion of citric acid also resulted in a reduced crystallite size of the cerianite phase. The effect of the CeO₂ coatings on the switching kinetics of the tungsten oxide (WO₃) films revealed a rise in the colouration time with the diminished crystallite size of CeO₂ nanograins in consequence of the enhanced content of citric acid employed for the deposition of the CeO₂ films.

8 illus, 2 tables, 8 ref

002270   Trivedi P;Patel R G;Patel A;Patel V;Oza A T (Dep of Phys, Sardar Patel Univ, Vallabh Vidyanagar-388 120) : Spectroscopic study of charge transfer on photoconductivity of quinhydrone. Indian J pure appl Phys 2005, 43(5), 335-40.

Quinhydrone is a 1:1 charge transfer complex of hydroquinone and p-benzoquinone having intermolecular hydrogen bonding. The effects of charge transfer on the photonconductivity of quinhydrone have been studied. The charge transfer complexes (CTCs) of quinhydrone with organic donors like 2, 2'-bis(quinoline), benzidine, DPPD, 2,2'-bipyridyl, TMPD and pyrene were prepared and studied using infrared spectroscopy. Strong envelopes are formed in the spectrum below 1800 cm^-1. It interacts most with 2,2'-bis(quinoline) and least with pyrene. Other cases are intermediates. There is either free-carrier absorption or band-to-band transition above the gap region of the complexes and photoconducting gap is at lower frequency than Peierls gap.

8 illus, 3 tables, 11 ref

002269   Tiwari R U;Singh K;Bhoga S S (Dep of Phys, Nagpur Univ, Nagpur-440 033, Email: tiwariru@rknec.edu) : Proton conductors and their application. Indian J Phys 2005, 79(7), 703-6.

There has been a great deal of scientific and technological interest in developing improved battery systems for use in portable electronic devices, backup power systems to electric vehicles. Solid-state protonic conductors have also extensively been used in the following electrochemical devices (i) gas sensors, (ii) electro-chromic displays, and (iii) fuel cells. However, relatively less attention has been paid towards their application from solid state battery point of view. Compared to others like lithium and silver solid-state batteries, these are very simple to fabricate and economic. A solid proton conductor of crystalline/amorphous form allows the passage of electrical current through the bulk material exclusively by movement of protons, H⁺. The electrochemical transfer of H₂ from one electrode to the other has taken place due to applied potential difference to the electrodes when proton conductor is placed in between the two noble metals/hydrogen. The H⁺, H₃O⁺, OH^- or NH₄⁺ have been the known conducting species of this class. Some of the reported good proton conductors have been acidic and basic hydrates like, HUP, HUAS, PSA, PMA, etc. In general, the charge transfer in solid by motion of protons has been the major problem in the field of proton conduction. So, it has become all the more necessary to understand a clear-cut difference between electron, ion and proton conduction, and also to obtain convincing proof of charge transfer by proton species. A brief work on proton conductors and solid-state battery is presented.

7 illus, 1 table, 4 ref

002268   Tiwari R S;Mehta N;Shukla R K;Agarwal P;Kumar a (Dep of Phys, Harcourt Bulter Technological Inst, Kanpur-208 002) : Specific heat studies in glassy Se₇₈GE₂₂ and Se₆₈Ge₂₂M₁₀ (M=Cd, In, Pb) alloys. Indian J pure appl Phys 2005, 43(5), 363-7.

The specific heat of glassy Se₇₈Ge₂₂ and Se₆₈Ge₂₂M₁₀ (M = Cd, In, Pb) alloys using differential scanning calorimetry (DSC) technique have been measured. An extremely large increase in the specific heat values has been observed at the glass transition temperature. It has also been found that the values of C_p below glass transition temperature and the difference of C_p values before and after glass transition (ΔC_p) are highly composition dependent. This indicates that the additives used in the study influence the structure of the binary alloy. Specific heat of the additive element is found to be important for the observed changes in the specific heat of the ternary alloys as compared to binary alloy.

3 illus, 2 tables, 28 ref

002267   Suthanthiraraj S A;Sheeba D J (Dep of Energy, Univ of Madras, Guindy Campus, Chennai-600 025, Email: suthan98@yahoo.com) : Formation of polyethylene oxide-based composite polymer electrolytes blended with Al₂O₃ nanoparticles. Indian J Phys 2005, 79(7), 807-13.

Design and fabrication of a new class of solid polymer electrolytes based on polyethylene oxide (PEO) and silver triflate (AgCF₃SO₃) together with nanometer-sized Al₂O₃ dispersoid material in the form of thin films are reported. It has been found that an O/M (oxygen/ metal) value of 50 within the acetonitrile-based polymer/salt complex viz., PEO-AgCF₃SO₃ would yield more stable thin films than in the case of O/M = 30. For accurate thickness measurements, one of the best-known optical techniques involving an air-wedge arrangement has been successfully employed during the course of the investigation. The complex impedance analysis of such films has been made over the frequency domain 1 MHz - 20 Hz and in the temperature range 295 - 330 K. It has been revealed that the measured room-temperature electrical conductivity (a) of the typical nanocomposite polymer electrolyte P(EO)₅₀ AgCF₃SO₃-5wt% Al₂O₃ (n) is 1.33 x 10^-5 Scm^-1. This is four orders of magnitude higher than that of the polymer host, PEO thus suggesting the feasibility of enhancement in the electrical conduction as a result of incorporation of Al₂O₃ nanoparticles.

12 illus, 2 tables, 16 ref

002266   Suthanthiraraj S A;Mathew V (Dep of Energy, Univ of Madras, Guindy Campus, Chennai-600 025, Email: suthan98@yahoo.com ) : Structural and transport studies on rapidly quenched PbI₂-Ag₂O-WO₃ composites. Indian J Phys 2005, 79(7), 753-6.

Superionic transport in a series of compositions of the mixed system (PbI₂)_x- (Ag₂O - WO₃)_100-x (5 ≤ x ≤ 50) has been investigated by employing structural thermal and electrical characterization techniques. The structural characterization carried out by X-ray power diffraction method has indicated the formation of phases such as AgI, Ag₂WO₄ and PbWO₄ along with some new phases for relatively higher concentrations of PbI₂. Differential scanning calorimetric studies performed on the various samples have confirmed the presence of AgI in almost all the compositions of the mixed system. In addition, the detailed complex impedance measurements have suggested that the electrical conductivities are of the order of 10^-5-10^-3 Scm^-1 at 300K The transport number data for Ag⁺ ions determined by the emf method are found to be above 0.94 for all the compositions under investigation. The best conducting composition has been identified as the typical composition having 25 mol% PbI₂ which exhibited a silver ionic conductivity of 7.4 x 10^-3 Scm^-1 at room temperature.

4 illus, 21 ref

002265   Srinivasan S;Ponnambalam U;Gunasekaran S (Dep of Phys, Presidency Coll, Chennai-600 005, Email: srvs_srvs@yahoo.com ) : Thermodynamic functions of 2-chloroheptane from its vibrational frequencies. Indian J Phys 2005, 79(2), 201-5.

The complete assignments of the calculated vibrational frequencies of 2-chloroheptane are used to compute the thermodynamic functions, namely, the enthalpy (H_vib), heat capacity (C_vib) and entropy (S_vib) due to vibrational contribution. These functions have been calculated by using standard expressions, at one atmospheric pressure in the temperature range of 100-500 K, under the rigid rotator harmonic oscillator approximation.

3 illus, 2 tables, 7 ref

002264   Singh M;Vijay Y K (Dep of Phys, Univ of Rajasthan, Jaipur) : Magneto-resistance and I-V characteristic studies of AlSb and InSb thin film bilayer structure. Indian J pure appl Phys 2005, 43(5), 383-5.

The I-V characteristic and magneto-resistance of Al-Sb and In-Sb thin films were measured with Cu electrode as the electrical contact. It was found that I-V characteristics are non-linear in nature and magneto-resistance decreases in case of Al-Sb and increases in case of In-Sb thin film bilayer structure. The Rutherford backscattering measurements also indicate the inter-diffusion and the concentration varies with temperature.

4 illus, 10 ref

002263   Singh K;Bhoga S S;Bansod S M;Tiwari R U (Dep of Phys, Nagpur Univeristy, Nagpur-440 033, Email: msrll@hotmail.com) : Solid state proton conducting secondary battery at room temperature. Indian J Phys 2005, 79(7), 715-17.

Using P₂O₅, SiO₂, and Al₂O₃, a proton conducting electrolyte, zinc anode and with three different cathodes MnO₂, PbO₂, and V₂O₅, a few electrochemical cells were fabricated. The open circuit voltage (OCV) and short circuit current (SCC) of the cells are found to be 1.82, 2.23 and 1.91 V and 3, 2.1 and 0.8 mA, respectively. The performance of MnO₂ cathode is better than that of other two materials viz. PbO₂ and V₂O₅. The materials used in the cells are environment friendly and no special atmospheric conditions are required for cell fabrication as in case of lithium cells.

3 illus, 1 table, 7 ref

002262   Singh H P (Post Grad Dep of Phys, Lyallpur Khalsa Coll, Jalandhar-144 001, Email: harinder_palsingh@yahoo.co.uk) : Studies on proton conducting polymer electrolytes gelled with PVdF and PVdF-HFP. Indian J Phys 2005, 79(7), 789-92.

Non-aqueous proton conducting polymer gel electrolytes containing different weak carboxylic acids viz. ortho-, meta-, para-hydroxybenzoic acid (o-HBA, m-HBA, p-HBA) and succinic acid (SA) gelled with polyvinylidenefluoride (PVdF) and polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP) have been synthesized and characterized. The conductivity of these electrolytes has been found to be of the order of 10^-4 S/cm at room temperature and they show excellent stability over the operational temperature range. The conductivity of these electrolytes has been found to depend on dissociation constant of acid, nature of the solvent and the concentration of the polymer used. The addition of polymer to these electrolytes results in change in the electrical properties which has been explained to be due to the active role played by the polymer.

4 illus, 15 ref

002261   Singh H D;Gokhul S K;Sinha S K;Manoj Kumar (Dep of Phys, SNSRKS Coll B N Mandal Univ, Saharsa-852 201) : Semiclassical statistical mechanical theory for thermodynamics of hard body fluids. Indian J Phys 2005, 79(2), 123-30.

The simple theory is developed to derive the thermodynamic properties of the semiclassical fluid of hard convex body (HCB) molecules interacting via the hard Gaussian overlap potential. Analytic expressions are given and calculations are made for the thermodynamic properties and virial coefficients for the HCB fluids. The agreement with the Monte-Carlo data is good in all cases. The first order quantum corrections are also studied. The quantum effects increase with increase of packing fraction and depends on the shape parameter K.

3 illus, 6 tables, 14 ref

002260   Sharma R;Saxena T K;Agnihotry S A (Natn Phys Laboratory, , Dr K S Krishnan Marg, New Delhi-110 012, Email: agni@mail.nplindia.ernet.in) : Effect of Tio₂ addition on the durability of sol-gel derived WO₃ films. Indian J Phys 2005, 79(7), 733-6.

Tungsten oxide (WO₃) films are of practical importance for electrochromic device (ECD) technology. Amorphous WO₃ films show very good electrochromic properties and can be made by a variety of techniques. For large area application of ECDs like smart windows, sol-gel is the best processing technique for its many known advantages. Films (OX-APTA) deposited using ethanolic solution of acetylated peroxotungstic acid (APTA) with oxalic acid as a chemical additive, exhibit good optical modulation and fast kinetics, the most desired properties for their use as primary electrochromic electrodes in ECDs. However, the practical viability of ECDs demands extended durability. The paper presents preliminary results of attempt made towards enhancing durability of OX-APTA films by adding poly peroxotitanic acid (PPTA) in different proportions to the deposition solution so as to give Ti content varying between 5 to 25 mol %. Spin coated films with and without Ti, after appropriate thermal treatment, have been subjected to cyclic voltammetry over a large number of cycles. The studies revealed that for optimum amount of Ti, films have three times better durability without affecting the optical modulation and kinetics of the mixed films.

3 illus, 18 ref

002259   Sharma J P;Sekhon S S (Dep of Appl Phys, Guru Nanak Dev Univ, Amritsar-143 005) : Effect of different plasticizers on the conductivity behaviour of polymer electrolytes containing NH₄PF₆. Indian J Phys 2005, 79(7), 761-3.

Polymer electrolytes obtained by the complexation of ammonium hexafluorophosphate (NH₄PF₆) with polyethylene oxide (PEO) show conductivity of the order of 10^-7 S/cm at 25°C. The addition of propylene carbonate (PC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) as plasticizer results in an increase in conductivity which depends upon the concentration of plasticizer, dielectric constant (ε) of plasticizer and the concentration of salt in the polymer electrolytes. The conductivity increases by two order of magnitude and maximum conductivity of 1.4 x 10^-5 S/cm has been obtained for electrolytes containing PC. The increase in conductivity has been explained to be due to the dissociation of ion aggregates and an increase in amorphous content with the addition of plasticizers.

5 illus, 13 ref

002258   Selvasekarapandian S;Hirankumar G;Savitha T; Ramya C S (Solid St and Radiat Phys Laboratory Dep of Phys, Bharathiar Univ, Coimbatore-641 046, Email: sekarapandian@yahoo.com) : Ionic conductivity studies of PVA-PVP blends. Indian J Phys 2005, 79(7), 797-01.

PVA/PVP blended polymer electrolytes with ammonium thiocyanate as dopant have been prepared by solvent casting technique having different blend ratio. The blended polymer complexes have been characterized by AC impedance spectroscopy in the frequency range of 42 -1M HZ over the temperature range of 303 - 373 K. The bulk conductivity values are found to depend on the blend ratio of the polymers for constant salt ratio. The blended polymer complexes exhibit the Arrhenius behaviour in the temperature range studied. The high conductivity at ambient temperature has been observed for 75PVA-25PVP blend ratio and is found to be 2.5 x 10^-6 S Cm^-1. The activation energy for this system is found to be 0.49 eV, which is less than what is found in the other blended systems. The higher dielectric constant is observed for 75PVA-25PVP blend ratio and is due to the electrode polarization.

4 illus, 1 table, 10 ref

002257   Selvasekarapandian S;Bhuvaneswari M S (Solid St and Radiat Phys Laboratory Dep of Phys, Bharathiar Univ, Coimbatore-641 046, Email: sekarapandian@yahoo.com) : Structural analysis of lithium nickel vanadate Li_{xNiVO4(x = 0.8, 1.0, 1.2).} Indian J Phys 2005, 79(7), 695-8.

In recent years, inverse spinel vanadates such as LiNiVO₄ and LiCoVO₄ have been reported as new systems for cathode materials for secondary lithium batteries because of their high voltage up to 4.8 V. In the study the compounds Li_xNiVO₄ (x = 0.8, 1.0, 1.2} have been prepared by solid state reaction method. The XRD analysis of the three samples shows that there is no prominent structural change on addition of Li. The XRD patterns are found to be consistent with the JCPDS values. The vibrational analysis of the compounds have been studied using FTIR and Raman technique. A new peak at 1039 cm^-1 has been observed for Li_1.2 NiVO₄ in the FTIR analysis indicating the presence of Li⁺-O-V bond interactions. Raman analysis indicates the inverse spinel structure of the three samples.

3 illus, 14 ref

002256   Sarkar S K;Ahmed I;Gupta M M;Prasad M V S N; Das J;De A K;Rajesh Kumar (Radio and Atmospheric Sci Div, Natn Phys Laboratory, Dr. K S Krishnan Road, New Delhi-110 012) : Performance deterioration of a communication link at 13 GHz due to rain. Indian J Phys 2005, 79(2), 117-21.

Performance deterioration of a microwave communication link situated between Panihati and Cossipore located in Indian eastern sector and operating at 13.059 GHz during monsoon months, July-August 2002, has been tested. The link suffers substantial attenuation due to rain. The communication link belonging to an operational agency was monitored and rain rate measurements were carried out on twenty four-hour basis by a fast response rain gauge. It was seen that the radio signal is characterized with a steady signal level of-42 to 44 dBm with fade of 1 to 2 dB under non-precipitation situation. It has been seen that audio service of the link is affected when the signal level was ≤ -69 dBm. The link does not serve the purpose at all when the signal level is ≤-75 dBm. The cumulative distribution function (CDF) of the signal levels, attenuation values and rain rates have been derived. The results are discussed to indicate the performance of the communication link. Some techniques to provide extra gain in the radio system have also been suggested.

7 illus, 9 ref

002255   Salvi S V;Pimpale S S (Dep of Phys, The Inst of Sci, 15 Madame Cama Road, Mumbai-400 032) : Positive hysteresis of electrodeless discharge in hydrogen in a co-axial cylindrical configuration. Indian J pure appl Phys 2005, 43(5), 386-9.

If the voltage applied to the system increases from a low initial value to a maximum and then reduces progressively to the initial minimum, the variation in rising and falling fields presents three regions of I-V characteristic (i) rising positive approximately linear characteristic up to the breakdown potential of hydrogen gas (V_g), (ii) sharply inverting to a negative characteristic over the region V_g-V_v and (iii) a rising characteristic once again for the potential above valley voltage (V_v). The region of interest has been the potential range V_g-V_v for which the characteristic is negative. The segments (ii) and (iii) form roughly a parabola. Results show that for increasing and decreasing progress of the applied V, the values of unidirectional current are not identical. The values are comparatively less in the increasing progress of the voltage than those in the portion of the positive hysteresis (anti-hysteresis) corresponding to decreasing voltage. These results are discussed and a mechanism for the anti-hysteresis is proposed.

2 illus, 29 ref

002254   Saikia D;Hussain A M P;Kumar A;Singh F; Avasthi D K (Dep of Phys, Tezpur Univ, Tezpur-784 028, Email: digs@tezu.ernet.in) : Ionic conduction studies in C<. Indian J Phys 2005, 79(7), 803-6.

P(VDF-HFP)-(PC+DEC)-LiClO₄ gel polymer electrolyte system, irradiated with C⁵⁺ ions at nine different fluences, is studied. The maximum room temperature conductivity is found to be of the order of 10^-4 S/cm. Irradiation with swift heavy ion shows enhancement of conductivity at lower fluences and decrease in conductivity at higher fluences with respect to pristine polymer electrolyte films. For a particular ion beam with a given energy, higher fluence provides critical activation energy for crystallization to occur, which results in decreased ionic conductivity. XRD results show decreased crystallinity below and increased crystallinity above the critical fluence after irradiation, which supports this view. FTIR spectra show the polymer-salt interaction before and after irradiation.

3 illus, 15 ref

002253   Rath S K;Naik P C (Dep of Phys, Talcher Coll, Talcher-759 107, Email: sarojkarath@yahoo.co.in) : Fibonacci structure in conch shell. Curr Sci 2005, 88(4), 555-7.

2 illus, 3 tables, 1 ref