027571   PRADEEP T M, HEGDE V N, PUSHPA N, BHUSHAN K G, PRAKASH A P G (Studies in Physics Dep, Mysore Univ, Mysore-570 006, Email: gnanaprakash@physics.uni mysore.ac.in) : Comparison of 5 MeV proton and 1 MeV electron irradiation on silicon NPN rf power transistors. Indian J Pure Appl Phys 2018, 56(8), 646-9.

The total dose effects of 5 MeV protons and 1 MeV electrons on the dc electrical characteristics of silicon NPN transistors have been investigated in the dose range from 1 Mrad(Si) to 100 Mrad(Si). The different electrical characteristics such as Gummel characteristics, excess base current ($∆$IB), dc current gain (h_FE), transconductance (g_m) and output characteristics have been studied in situ as a function of total dose. A considerable increase in base current (I_B) and a decrease in h_FE, g_m and I_CSat have been observed after 5 MeV proton and 1 MeV electron irradiation. The results show that there is more degradation in the I-V characteristics of 5 MeV proton irradiated devices when compared to 1 MeV electron irradiation. The degradation in the observed electrical characteristics of the transistors is mainly due to generation- recombination (G-R) centers created in emitter–base (E-B) spacer oxide (SiO2) and displacement damage in the bulk of the transistor structure. In addition to G-R centers, high energy protons can also create various types of defects in the transistor structure.

7 illus, 12 ref

027575   RAJESHWARI T, HANUMANTAGOUDA (Physics Dep, Vijayanagara Sri Krishnadevaraya Univ, Ballari-583 105, Email: rajeshwari.phy@gmail.com) : Mass attenuation coefficient measurements in turmeric samples. Indian J Pure Appl Phys 2018, 56(8), 643-5.

Mass attenuation coefficient of turmeric has been measured at 662 keV gamma energy using NaI(Tl) scintillation detector coupled with Multichannel Analyzer (MCA). The elemental composition of turmeric was analyzed using SEM – EDS technique. Potassium and magnesium were found to be present in good amount. The study showed the dependency of mass attenuation coefficient on the energy of radiation and nature of the absorber. The results validated the gamma absorption law. The study performed would add knowledge and information towards interaction of gamma radiation with matter.

3 illus, 1 table, 10 ref

027546   KAMAT V A, SWAROOP K, KIRAN K U, SOMASHEKARAPPA H M (Mangalore Univ, Mangalore- 574 199, Email: carrtmu@gmail.com) : Studies on the effect of PbO-magnetite (Fe₃O₄) on shielding properties of EPDM composites for 662 keV gamma rays. Indian J Pure Appl Phys 2018, 56(8), 639-42.

In the present study different combinations of PbO and Fe₃O₄ in ethylene-propylene-diene monomer (EPDM) matrix have been synthesized and studied the ideal combination for gamma ray shielding. Attenuation parameters such as attenuation coefficient (µ), half value layer (HVL), tenth value layer (TVL), relaxation length (λ) and mass attenuation coefficient (µ_m) have been determined for all samples. It has been found that EPDM with 40 phr of lead oxide and 20 phr of magnetite (DCPM20) has good attenuation ability compared to other synthesized samples for 662 keV gamma rays. Also, DCPM20 has shown better mechanical and AC electrical conductivity properties compared to pure lead-based EPDM composites. Considering all the studied parameters DCPM20 sample has been found to be better radiation shielding material among the studied composites.

4 illus, 1 table, 9 ref

027561   NAGABHUSHANA K R, PRAKASH D, TATUMI S H, ROCCA R R, WATANABE S (Federal University of São Paulo, Brazil, Email: bhushankr@gmail.com) : Beta ray induced optically stimulated luminescence properties of calcium oxide phosphor. Indian J Pure Appl Phys 2018, 56(8), 635-8.

This work presents the results on optically stimulated luminescence of calcium oxide (CaO). Polycrystalline CaO phosphors are irradiated with beta rays in the dose range 10 – 100 Gy. The optically stimulated luminescence (OSL) from CaO sample is strong, the decay is fast and entire signal decays within 50 s. OSL intensity increases linearly with beta dose. The life time and photo ionization cross section (PICS) of decay are in the range ~0.045, 1.5 and 41.391 s and 1.32$\times$10^-16, 3.32$\times$10^-18 and 1.42$\times$10^-19 cm² for fast, medium and slow components, respectively. Further, the life time and PICS of fast, medium and slow LM-OSL components have been found to be 2.29, 6.0, 17.0 s and 2.56$\times$10^-18, 9.77$\times$10^-19, 3.45$\times$10^-19 cm², respectively. Both the OSL curves exhibits general order kinetics.

4 illus, 1 table, 13 ref

027588   SEENAPPAA L, MANJUNATHAA H C, CHANDRIKA B M, SRIDHARC K N, HANUMANTHARAYAPPA C (Physics Dep, Government College for Women, Kolar-563 101, Email: manjunathhc@rediffmail.com) : Study of gamma, X-ray and neutron shielding parameters of some alloys. Indian J Pure Appl Phys 2018, 56(8), 631-4.

The X-ray and gamma radiation shielding parameters such as mass attenuation coefficient, mean free path, half value layer, tenth value layer, effective atomic numbers, exposure buildup factors, dose rate and specific gamma ray constant have been studied in some alloys such as AL-6XN, nicrosil, nisil, terfenol-D, elektron and ferro-boron. The neutron shielding parameters such as coherent neutron scattering length, incoherent neutron scattering lengths, coherent neutron scattering cross section, incoherent neutron scattering cross sections, total neutron scattering cross section and neutron absorption cross sections have also been studied in the same alloys. It is observed that the alloy terfenol-D is good shielding material for X-ray/gamma radiation. The alloy Elektron is good shielding material for neutrons among the studied alloys. This study finds importance in the field of radiation shielding.

6 illus, 14 ref

027527   BHATTACHARYA T, NAGAIAH N, REDDY B R M, SHARMA P K (Atomic Energy Dep, Atomic Minerals Directorate for Exploration and Research, Bangalore-560 072, Email: tbhattacharya.amd@gov.in) : Monte Carlo calculation of the efficiency calibration curve for HPGe detectors. Indian J Pure Appl Phys 2018, 56(8), 628-30.

High purity germanium (HPGe) gamma ray spectrometer provides a good tool for measuring the concentrations of uranium, radium, thorium and potassium because of its high resolution. Accurate measurement of efficiency is crucial for their determination. The efficiency of a detection system varies significantly with geometry and matrix of the samples as well as energy of gamma rays. Thus, activity of samples has been determined by comparing the peak counts of samples and standards recorded under same configurations. But for geological samples, matrix varies from place to place giving samples of different densities. The activities of geological samples, especially in areas near to uranium deposits may also vary from ppm to percentage level. In such cases, computer simulations can help in calculating the efficiency of the system for different configurations and densities. Present work aims to create a computer model of HPGe detector being used at Physics Laboratory, Atomic Minerals Directorate for Exploration and Research (AMD), Bengaluru using the Monte Carlo N-Particle (MCNP) code. In this work, model obtained using the manufacturer’s parameter was modified to match the simulated efficiency curves with experimental efficiency curves. Efficiency curves were also calculated for 50, 90 and 150 g of 0.26 % equilibrium U₃O₈ sample. The calculated results compared well with those obtained experimentally.

6 illus, 1 table, 3 ref

027576   RAJU S P, HAREESH K, DHOLE S D, SANJEEV G (Physics Dep, Mangalore Univ, Mangalore-574 199, Email: ganeshsanjeev@rediffmail.com) : Gamma irradiation effects on optical properties of CdTe quantum dots. Indian J Pure Appl Phys 2018, 56(8), 624-7.

Gamma radiation assisted changes in stability and optical properties of CdTe colloidal quantum dots (QD) capped with 3-mercaptopropionic acid (MPA) molecules have been reported in this article. Synthesized QDs in water, using hydrothermal method, have been exposed to different gamma doses to see the changes in their light absorption and emission properties of QDs. Colour of light absorption and emissions are blue shifted for lower pH conditions followed by precipitation (after few days) of the whole dissolved materials as a response to irradiation due to photo-oxidation. Surprisingly, redshift has been observed for the same gamma doses when pH of QDs solution raised to higher number which also results in improved stability of QDs to with stand against irradiation (compared to acidic pH environment). Therefore, the solution of QDs with higher pH value is stable for future useful modifications of QD structures using radiation. These modifications may include the growth of single or multishells over core QDs by using this irradiation method to enhance their stability and optical properties.

4 illus, 1 table, 5 ref

027556   MAHANTESHA B K, RAVINDRACHARY V, PADMAKUMARI R, SAHANAKUMARI R, SANJEEV G, VERMA V P (Physics Dep, Mangalore Univ, Mangalagangotri- 574 199, Email: vravi2000@yahoo.com) : Microstructural, thermal and electrical properties of electron irradiated Li₂CO₃ doped PVA. Indian J Pure Appl Phys 2018, 56(8), 616-20.

Poly (vinyl alcohol) doped with Li₂CO₃ composite films have been prepared by solvent casting method and irradiated with energetic electrons. The FTIR study shows that the electron irradiation creates free radicals, chain scission and cross- linking within the polymer composite. The effect of these changes induces structural modifications and enhances the amorphosity of the composite, which has been studied using X-ray diffraction method. The thermal properties have been studied using thermogravimetric analysis and it has been found that the onset temperature (T_o) of decomposition increases  up to 150 kGy and then decreases for higher doses. Using this data activation energy of the thermal decomposition has been determined which is in good corroborated with T_o values. This indicates that the cross-linking of polymer chains takes place in lower dose and the cleavage occurs at higher doses. The DC conductivity results show that the conductivity increases up to 1.0103×10^-3 S/cm for 300 kGy doses.

5 illus, 2 tables, 9 ref

027599   TEERTHE S S, SHARANABASAPPA, KERUR B R (Physics Dep, Gulbarga Univ, Kalaburagi-585 106, Email: kerurbrk@yahoo.com) : Analysis of folk medicinal plant using atomic absorption spectrometer. Indian J Pure Appl Phys 2018, 56(8), 613-5.

Myrtaceae family’s folk medicinal plants are very essential for human health care in India and other countries of the world. The common people of Hyderabad -Karnataka region, viz., Bidar, Gulbarga and Yadgir districts, have been traditionally using medicinal plants for treatment of different types of disease. The collected medicinal plants have been dried in clean room without any ventilation and which is free from dust. Usual processes have been adopted to get a fine powder and ash sample, finally prepare 100 mL solution for analysis. A single beam iCE 3000 series atomic absorption spectrometer has been used for elemental analysis. The whole system is controlled via a data station running thermo scientific iCE SOLAAR software which runs under a windows operating system and changing different hollow cathode lamp sources and flames. The instrument was calibrated using different standards for analysis of trace/minor/major  elements. In the present study, authors have analysed the 12 useful nutrient elements namely Mg, Al, Si, S, Cl, K, Ca, Cr, Mn, Fe, Cu and Zn in Eucalyptus oblique and Gava medicinal plants. All estimated elemental concentrations have been found in acceptable quantity in studied medicinal plants (0.01-20.48 mg/L) and the variation of elemental concentration with respect to geographical changes of the regions and found their concentration within the permissible limits of WHO.

1 illus, 1 table, 9 ref

027533   DEVENDRAPPA M, SANNAKKI B (Physics Dep, Gulbarga Univ, Kalaburagi-585 106, Email: sannakki@rediffmail.com) : Energy loss and straggling of alpha particles. Indian J Pure Appl Phys 2018, 56(8), 609-12.

The energy loss (ΔE) in an atmospheric gas for light ions such as alpha particles (241 Am) of energy 5.48 MeV has been experimentally deliberated in a scattering chamber at different pressures of 4 to 7 mbar. The energy loss has also been obtained at variable distances from 4 mm to 32 mm. The energy loss of alpha particles has been exponentially decreased with increasing pressure. The measured energy loss of alpha particles at higher pressure that is at 7 mbar that is more but at lower pressure of 4 mbar is less. The energy loss of alpha particles increases as distance increases  from the source  to detector  in the scattering  chamber.  The transmitted energy  of alpha particles at lower pressure that is at 4 mbar is high but at higher pressure of 7 mbar is less. The transmitted energy increases as distance between sources to detector decreases. The nuclear and electronic energy loss in the energy range of 1 - 5.5 MeV for an alpha particle is given by SRIM 2008. The projected energy of the alpha particles increases the nuclear and electronic stopping powers decreases exponentially. Further the range of alpha particles is being increased by increasing ion energy. The electronic collision dominates in the higher energy region (MeV) and nuclear collision in lower projectile energies (keV). The energy loss straggling has been found to be increased by increasing pressure as well as increasing the distance between the source and detector in the scattering chamber.

5 illus, 16 ref

027523   AMBIKA M R, NAGAIAH N, SUMAN S K (Physics Dep, Bangalore Univ, Bangalore-560 056, Email: nagaiah@bub.ernet.in) : Evaluation of gamma shielding parameters of bismuth oxide filled polymer composites. Indian J Pure Appl Phys 2018, 56(8), 604-8.

The present work deals with the study of shielding ability of UP-Bi₂O₃ polymer composites for gamma rays of energy 0.662 MeV using a gamma ray spectrometer. The various shielding parameters such as linear and mass attenuation coefficients, half value and tenth value layer thickness, and mean free path have been evaluated for the composites. The attenuation coefficients of the composites have also been evaluated theoretically using the computer code XCOM and WinXCOM. The results show that, the shielding performance increases with increase in the filler concentration. The highest filled composite exhibits excellent shielding ability and is comparable to that of the conventional shielding materials. The theoretical and experimental values are in good agreement.

6 illus, 3 tables, 20 ref

027569   PATWARI D R, ERAIAH B (Physics Dep, Bangalore Univ, Bangalore-560 056, Email: beraiah@bub.ernet.in) : Investigation of gamma radiation effect on bismuth borate glasses doped with europium oxide and silver chloride. Indian J Pure Appl Phys 2018, 56(8), 600-3.

Europium doped bismuth borate glasses have been prepared by melt quenching technique, the structural and optical properties have been studied before and after the gamma radiation. The X-ray diffraction pattern confirms the amorphous nature of the prepared samples. Fourier transform infrared spectra show structurally it is not changed with few bands slightly red shifted. In the UV-Visible studies there are no extra peaks. The band gap energies determined are in the range 2.751-2.563 eV for direct and 2.303-1.911 eV for indirect transition before irradiation. The band gaps and Urbach energy have been changed a little in rare earth and silver doped samples. The base glass and with 0.3 mol % of Eu₂O₃ exhibit no significant change after the gamma radiation. The most absorbing bismuth borate glass catches importance as a radiation protection or shielding material.

5 illus, 2 tables, 13 ref

027568   PATTAJE R, YALAGOUD N, MENON R, SANJEEV G (Physics Dep, Mangalore Univ, Mangalore-574 199, Email: ganeshsanjeev@rediffmail.com) : Irradiation induced optical and electrical modification of Lexan films. Indian J Pure Appl Phys 2018, 56(8), 591-4.

Low energy Argon ions have been irradiated on to the surface of Lexan polycarbonate (PC) films using an electron cyclotron resonance ion source (ECRIS). Different energy of Argon ions have been used for the study by limiting the value of fluence to 1.04×1016 ions/cm². The ion irradiation has brought changes in electrical, optical and chemical properties of Lexan films. The results obtained from the study show an increase in the surface conductivity after irradiation, shift in optical absorption edge with decrease in optical energy gap and decrease in the intensity of peaks related to C=O, C-C, C-O groups. The irradiated films can find its application in antireflection materials, microelectronics devices and other surface coating applications.

6 illus, 1 table, 17 ref

027596   SUJATHA R, KHAN A R, RAVINDRA M, DAMLE R (Physics Dep, Bangalore Uni, Bengaluru-560 056, Email: sujathaksn@yahoo.co.in) : Study of the effect of gamma radiation on MOSFET for space applications. Indian J Pure Appl Phys 2018, 56(8), 587-90.

MOSFET is a basic component of VLSI and ULSI circuits and finds applications in many electronic systems used in satellite design. These devices are susceptible to degradation due to radiation in outer space. Conventional MOSFET can survive 3-10 krad (Si) of total dose without much parametric degradation. However, ionising radiation dose in excess of 35 krad (Si) may turn out to be detrimental to the functioning of the device. The space environment is hostile to the most integrated components such as those for navigation, communication, data processing function in satellites and various space missions. The radiation generally encountered in space includes α, β, γ, X-ray, energetic electrons, protons, neutrons and ions of various kinds. Gamma ray photons deposit energy in the components mainly by ionisation. In this paper, we report the gamma ray induced changes in the electrical characteristics of MOSFET 2N6796 (JANTXV) used in satellites. Pre- irradiation measurements of electrical parameters have been made using TESEC measurement system. Selected devices have been exposed to different gamma dose using a BRIT gamma irradiator. Post-irradiation measurements of electrical characteristics display significant degradation in threshold voltages and the leakage current increases as the gamma dose increases.

4 illus, 5 ref

027595   SUBRAMANIAN D V, HARIDAS A, KUMAR D S, ARUL A J, PUTHIYAVINAYAGAM P (Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102, Email: dvs@igcar.gov.in) : Neutron attenuation studies with borated polyethylene slabs containing 30% natural boron and its comparison with hydrogenous materials. Indian J Pure Appl Phys 2018, 56(8), 583-6.

Providing suitable shielding for neutrons is one of the challenging tasks in fast reactor fuel reprocessing facilities. The shield material should have good moderating and absorbing properties. In order to find cost effective prospective materials, a series of neutron attenuation measurements are performed with hydrogenous materials at the south beam end of Kalpakkam Mini (KAMINI) reactor to understand their attenuation characteristics. In the present experiment, the neutron attenuating properties of borated polyethylene (BPE) containing 30 % natural boron have been studied. The thermal and fast neutron flux attenuation characteristics of the material have been compared with 5 % and 10 % BPE and other hydrogenous materials. The thermal/epithermal neutron flux attenuation obtained with 30 % BPE for a thickness of 30 cm is 1.5 times more than 5 % and 10 % BPE and 10 times more than normal polyethylene. It is also observed that there is no significant difference in the fast flux attenuation of 30 %, 10 % and 5 % BPE. The outcome of the study indicates that if 30 % BPE is used instead of normal polyethylene in fuel reprocessing facilities, 50 % reduction in volume of shields can be achieved for thermal and epithermal neutron flux attenuation and 16 to 22 % reduction in volume shields for fast neutron flux attenuation.

4 illus, 1 table, 5 ref

027518   ABIRAM A, PRAVEENA G (Physics Dep, Karunya Univ, Coimbatore-641 114, Email: aabiram@gmail.com) : Exploring the structure and stability of β-dipeptide - A quantum chemical and molecular dynamics study. Indian J Pure Appl Phys 2018, 56(7), 561-9.

Density functional theory (DFT) calculations followed by molecular dynamics study has been performed to analyze the structure and stability of β-dipeptide structures in aqueous medium. From DFT study, three local minima with folded conformations and one local minimum with unfolded conformation have been identified. In gas phase, the most stable β-dipeptide has a folded conformation with a weak hydrogen bonding. The interaction of water molecules, approximated from the first solvation shell, also confirms the folded conformation to be the most stable structure. The DFT optimized β-dipeptide conformers have been simulated in explicit water to evaluate the tendency of folded and unfolded state formation. Simulations confirmed the transition of the structure from folded to unfolded and vice versa and further indicated the former to happen rapidly within a few pico second time scale.

6 illus, 4 tables, 39 ref

027550   KUMAR P, BHATT N K, P R VYAS P R, GOHEL V B (Science & Humanities Dep, Government Polytechnic, Gandhinagar-382 024, Email: priyank_kumar2007@yahoo.co.in) : Theoretical study of pressure dependence of superconducting state parameters of some metals using pseudopotential approach. Indian J Pure Appl Phys 2018, 56(7), 544-50.

In the present theoretical study, we have calculated superconducting state parameters (SSPs) viz; electron-phonon coupling strength ($\mathrm{\lambda }$), Coulomb pseudopotential (μ^∗), critical temperature (T_€), effective interaction strength (NOV) and isotopic effect parameter (α) of some polyvalent metals (Pb, Ga, In, Sn and Tl) using well-established structured local pseudopotential due to Fiolhais et al. (1995). The pseudopotential with its individual set of parameters has been found to be good in predicting transition temperature T_€ for all the metals. Looking to such success, we have extended the present model for the theoretical study of pressure dependence of transition temperature T_€ using Debye- Gruneisen model. Our predicted critical volumes using different approaches are well agreed with each other and also with other reported findings. Thus, the present model is consistent and better than nonlocal norm conserving pseudopotentials because it is found to be transferable without any kind of adjustment of its parameters along with its simplicity and predictivity.

4 illus, 3 tables, 46 ref

027529   BHOI J, MAJUMDER M, LAHA U (Physics Dep, National Institute of Technology, Jamshedpur-831 014, Email: ujjwal.laha@gmail.com) : Higher partial wave energy dependent and independent two-nucleon interactions via supersymmetry formalism. Indian J Pure Appl Phys 2018, 56(7), 538-43.

Within the formalism of supersymmetric quantum mechanics both energy-dependent and independent two-nucleon potentials for the D-wave are constructed from their respective ground state interactions. These potentials in turn are used to compute nucleon-nucleon scattering phase shifts to judge their merits. Energy-dependent potential is found to be more effective than its energy independent counterpart except in the very low energy range.

3 illus, 39 ref

027549   KUMAR M, PRASAD D, AKRAM M W (Electronics and Communication Engineering Dep, Jamia Millia Islamia, New Delhi-110 025, Email: dprasad@jmi.ac.in) : Current mode fractional order band pass and band reject filter using VDTAs. Indian J Pure Appl Phys 2018, 56(7), 533-7.

In this proposed work, current mode fractional order band pass and band reject filters using voltage differencing trans- conductance amplifier (VDTAs) as an active building block have been proposed. The approximated transfer function of the band stop and band pass filters on the basis of the integer order transfer function has been shown and the similar form of the approximate transfer function has been implemented for the band stop and band pass filters by using VDTAs as an active building block. In this work, fractional order band stop and band pass filters of the different orders have been realized. The operation of the design has been tested using simulation results on PSPICE with TSMC CMOS 180 nm technology parameters.

7 illus, 2 tables, 15 ref

027539   GAUR H M, SINGH A K, GHANEKAR U (Electronics & Communication Engineering Dep, N I T, Kurukshetra-136 119, Email: leoharimohan84@gmail.com) : Reversible circuits with testability using quantum controlled NOT and Swap gates. Indian J Pure Appl Phys 2018, 56(7), 529-32.

A new method of designing reversible circuits with inbuilt testability is presented by exploiting the properties of quantum controlled NOT and Swap gates. The design process is based on the methodology of placement of gates in such a manner that it produces parity preserving circuits. The testability of these circuits can be achieved by comparing the input and output parity under single bit fault detection. Experiments are conducted on a set of benchmark circuits which show an average reduction up to 51 % in operating costs, when compared to existing work.

3 illus, 2 tables, 15 ref

027578   RASAL Y B, SHIRSAT M D, HUSSAINI S S (Physics Dep, Science and Management Science College, Beed-431 122, Email: shuakionline@yahoo.co.in) : Investigation on thiourea crystal grown in presence of ammonium acetate. Indian J Pure Appl Phys 2018, 56(7), 522-8.

The optically good quality single crystals of thiourea crystal grown in presence of ammonium acetate have been grown by slow evaporation solution growth technique. The single crystal X-ray diffraction and FTIR have been studied for grown crystal. The UV-Vis transmittance spectrum has been recorded in the range of 200-900 nm. Theoretical calculations have been carried out to determine the linear optical constants such as extinction coefficient and refractive index. The analysis of third order non-linear optical properties like non-linear absorption coefficient (ß), non-linear refractive index (n₂) and susceptibility ($\chi$³) have been calculated using Z-scan technique. The dielectric and mechanical strength of doped crystals have been investigated and results are discussed.

11 illus, 3 tables, 36 ref

027574   RAJA B, BALACHANDRAN V, REVATHI B, ANITHA K (Physics Dep, A A Government Arts College, Musiri-621 211, Email: brsbala@rediffmail.com) : Structural study, NCA, FTIR, FT-Raman spectral investigations, NBO analysis and thermodynamic functions of N-benzyloxy carbonyl-L-alanine. Indian J Pure Appl Phys 2018, 56(7), 509-21.

The FTIR and FT-Raman spectra of N-benzyloxy carbonyl-L-alanine have been recorded and analyzed. Natural bond orbital analysis has been carried out for various intra-molecular interactions that are responsible for the stabilization of the molecule. HOMO-LUMO energy gap has been computed with the help of density functional theory. The statistical thermodynamic functions (heat capacity, entropy, vibrational partition function and Gibbs energy) have been obtained for the range of temperature 100-1000 K. The infrared and Raman spectra have been also predicted from the calculated intensities. Comparison of the experimental and theoretical spectra values provides important information about the ability of the computational method to describe the vibrational modes. In addition to these, Mulliken’s atomic charges associated with each atom have also been reported and mapped molecular electrostatic potential (MEP) surfaces have also been performed with the same level of DFT.

6 illus, 5 tables, 53 ref

027538   FATMA S, PARVEEN H, BISHNOI A, VERMA A K, SRIVASTAVA K (Chemistry Dep, Lucknow Univ, Lucknow-226 007, Email: abhabishnoi5@gmail.com) : Molecular orbital, spectroscopic, first order hyperpolarizability and NBO analysis of aryl-substituted 5-(benzylidine) thiazolidine-2,4-diones. Indian J Pure Appl Phys 2018, 56(7), 491-508.

In this study, the structure of three 5-(4-subs/3, 4- di substituted benzylidene) thiazolidine-2,4-diones has been studied by using density functional theory (DFT) at 6-31G(d,p) level basis set. Detailed interpretations of the vibrational spectra of these compounds have been made on the basis of the calculated potential energy distribution (PED). The ¹H and ¹³C NMR spectra have been recorded and the chemical shifts have been calculated using the gauge- independent atomic orbital method (GIAO). The values of frontier orbital energy gap (-3.64 eV) and dipole moment (4.7012 D) show that the compound 3b is less reactive and less polar, hence the most stable among the three molecules. The significantly higher value (131.96×10-30 esu) of total hyperpolarizability for compound 3c indicates the better use of this molecule as NLO material. The calculated local reactivity descriptors for 3(a-c) indicate that C2 is the most reactive site for nucleophilic attack whereas the oxygen attached to this C is more prone to electrophilic attack. Hyperconjugative interactions have been studied with the help of natural bond orbital analysis. The electronic properties and thermodynamic properties have also been performed.In this study, the structure of three 5-(4-subs/3, 4- di substituted benzylidene) thiazolidine-2,4-diones has been studied by using density functional theory (DFT) at 6-31G (d,p) level basis set. Detailed interpretations of the vibrational spectra of these compounds have been made on the basis of the calculated potential energy distribution (PED). The ¹H and ¹³C NMR spectra have been recorded and the chemical shifts have been calculated using the gauge- independent atomic orbital method (GIAO). The values of frontier orbital energy gap (-3.64 eV) and dipole moment (4.7012 D) show that the compound 3b is less reactive and less polar, hence the most stable among the three molecules. The significantly higher value (131.96×10^-30 esu) of total hyperpolarizability for compound 3c indicates the better use of this molecule as NLO material. The calculated local reactivity descriptors for 3(a-c) indicate that C2 is the most reactive site for nucleophilic attack whereas the oxygen attached to this C is more prone to electrophilic attack. Hyperconjugative interactions have been studied with the help of natural bond orbital analysis. The electronic properties and thermodynamic properties have also been performed.

9 illus, 12 tables, 71 ref

027600   VEERAPATHIRAN S, WOHLAND T (Biological Sciences Dep, National Univ of Singapore, Singapore-117 557, Email: twohland@nus.edu.sg) : Fluorescence techniques in developmental biology. J Biosci 2018, 43(3), 541–53.

Advanced fluorescence techniques, commonly known as the F-techniques, measure the kinetics and the interactions of biomolecules with high sensitivity and spatiotemporal resolution. Applications of the F-techniques, which were initially limited to cells, were further extended to study in vivo protein organization and dynamics in whole organisms. The integration of F-techniques with multi-photon microscopy and light-sheet microscopy widened their applications in the field of developmental biology. It became possible to penetrate the thick tissues of living organisms and obtain good signal-to-noise ratio with reduced photo-induced toxicity. In this review, we discuss the principle and the applications of the three most commonly used F-techniques in developmental biology: Fluorescence Recovery After Photo-bleaching (FRAP), Fo¨ rster Resonance Energy Transfer (FRET), and Fluorescence Correlation and Cross-Correlation Spectroscopy (FCS and FCCS).

3 illus, 118 ref

027582   ROOBALA C, ILANILA I P, BASU J K (Physics Dep, Indian Institute of Science, Bengaluru- 560 012, Email: basu@iisc.ac.in) : Applications of STED fluorescence nanoscopy in unravelling nanoscale structure and dynamics of biological systems. J Biosci 2018, 43(3), 471–84.

Fluorescence microscopy, especially confocal microscopy, has revolutionized the field of biological imaging. Breaking the optical diffraction barrier of conventional light microscopy, through the advent of super-resolution microscopy, has ushered in the potential for a second revolution through unprecedented insight into nanoscale structure and dynamics in biological systems. Stimulated emission depletion (STED) microscopy is one such super-resolution microscopy technique which provides real-time enhanced-resolution imaging capabilities. In addition, it can be easily integrated with well-established fluorescence-based techniques such as fluorescence correlation spectroscopy (FCS) in order to capture the structure of cellular membranes at the nanoscale with high temporal resolution. In this review, we discuss the theory of STED and different modalities of operation in order to achieve the best resolution. Various applications of this technique in cell imaging, especially that of neuronal cell imaging, are discussed as well as examples of application of STED imaging in unravelling structure formation on biological membranes. Finally, we have discussed examples from some of our recent studies on nanoscale structure and dynamics of lipids in model membranes, due to interaction with proteins, as revealed by combination of STED and FCS techniques.

10 illus, 2 tables, 85 ref

027531   CLAYTON A H A (Physics and Astronomy Dep, Swinburne Univ of Technology, Melbourne, Australia, Email: aclayton@swin.edu.au) : Fluorescence-based approaches for monitoring membrane receptor oligomerization. J Biosci 2018, 43(3), 463–9.

Membrane protein structures are highly under-represented relative to water-soluble protein structures in the protein databank. This is especially the case because membrane proteins represent more than 30% of proteins encoded in the human genome yet contribute to less than 10% of currently known structures (Torres et al. in Trends Biol Sci 28:137–144, 2003). Obtaining high-resolution structures of membrane proteins by traditional methods such as NMR and x-ray crystallography is challenging, because membrane proteins are difficult to solubilise, purify and crystallize. Consequently, development of methods to examine protein structure in situ is highly desirable. Fluorescence is highly sensitive to protein structure and dynamics (Lakowicz in Principles of fluorescence spectroscopy, Springer, New York, 2007). This is mainly because of the time a fluorescence probe molecule spends in the excited state. Judicious choice and placement of fluorescent molecule(s) within a protein(s) enables the experimentalist to obtain information at a specific site(s) in the protein (complex) of interest. Moreover, the inherent multi-dimensional nature of fluorescence signals across wavelength, orientation, space and time enables the design of experiments that give direct information on protein structure and dynamics in a biological setting. The purpose of this review is to introduce the reader to approaches to determine oligomeric state or quaternary structure at the cell membrane surface with the ultimate goal of linking the oligomeric state to the biological function. In the first section, we present a brief overview of available methods for determining oligomeric state and compare their advantages and disadvantages. In the second section, we highlight some of the methods developed in our laboratory to address contemporary questions in membrane protein oligomerization. In the third section, we outline our approach to determine the link between protein oligomerization and biological activity.

1 illus, 44 ref

027535   DEY S, MAITI S (Tata Institute of Fundamental Research, Mumbai- 400 005, Email: maiti@tifr.res.in) : Single-molecule photobleaching: Instrumentation and applications. J Biosci 2018, 43(3), 447–54.

Single-molecule photobleaching (smPB) technique is a powerful tool for characterizing molecular assemblies. It can provide a direct measure of the number of monomers constituting a given oligomeric particle and generate the oligomer size distribution in a specimen. A major current application of this technique is in understanding protein aggregation, which is linked to many incurable diseases. Quantitative measurement of the size distribution of an aggregating protein in a physiological solution remains a difficult task, since techniques such as dynamic light scattering or fluorescence correlation spectroscopy (FCS) can provide an average size, but cannot accurately resolve the underlying size distribution. Here we describe the smPB method as implemented on a home-built total internal reflection fluorescence microscope (TIRF). We first describe the construction of a TIRF microscope, and then demonstrate the power of smPB by characterizing a solution of Amylin (hIAPP) oligomers, a 37-residue peptide whose aggregation is associated with Type II diabetes. We compare our results with FCS data obtained from the same specimen, and discuss the advantages and disadvantages of the two techniques.

6 illus, 30 ref

027564   NI S, ZHOU T, ZHU Y, CAO Y, YANG P (Jinan Univ, Jinan-250 022, Email: mse_caoyq@ujn.edu.cn) : Sn⁴⁺-doped TiO₂ nanorod array film with enhanced visible light photocatalytic activity. Bull Mater Sci 2018, 41(4), 113.

Sn⁴⁺-doped TiO₂ nanorod array film (NAF) on the fluorine-doped tin oxide (FTO) conducting glass was successfully synthesized using the facile hydrothermal method. The NAF photocatalysts were characterized by the scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV–Vis diffuse reflectance spectra (DRS). The SEM images showed that both doped and pure TiO₂ NAFs exhibited a good nanorod array structure. Sn⁴⁺-doped TiO₂ NAF still maintains rutile crystal structure, which was identical to that of pure TiO₂ sample. By means of the DRS measurement, it was found that the Sn⁴⁺ doping in TiO₂ nanorod could induce an obvious enhancement of visible light absorption owing to the introduction of doping energy level in the band gap of TiO₂. The degradation of methyl orange (MO) demonstrated that the Sn⁴⁺-doped TiO₂ NAF exhibited an enhanced photocatalytic activity than pure TiO₂ NAF under the visible light (λ > 400 nm) irradiation, which should be attributed to the enhanced visible light response and improved separation efficiency of photogenerated carriers of Sn⁴⁺-doped TiO₂.

8 illus, 3 tables, 29 ref

027543   GÜLER E S (Baskent Univ, Ankara, Turkey, Email: esguler@baskent.edu.tr) : Rheological behaviours of silica/water, silica/PEG systems and mechanical properties of shear thickening fluid impregnated Kevlar composites. Bull Mater Sci 2018, 41(4), 112.

Evolution in armour materials is critical to improve the protection abilities together with the properties of flexibility and lightness. Silica colloidal suspensions are important candidates to improve strength of the armour materials. The dispersing medium of the silica particles acts as an important role in the formation of shear thickening fluids (STF). STF has the ability to have increased viscosity by increasing the shear rate. Rheological, impact, flexibility and yarn pull-out tests were performed during the study. This study demonstrated that STF did not occur in the case of dispersing silica in water, but increased the impact resistance when Kevlar treated by the silica dispersed in water as compared to neat Kevlar. Fumed silica distribution in polyethylene glycol (PEG) led to STF creation confirmed by the rheological tests. The impact resistance of STF-treated Kevlar was found to be improved when compared to silica-dispersed water-impregnated Kevlar. It was observed that the pull-out force values of STF-fertilized Kevlar were increased compared to neat Kevlar.

12 illus, 1 table, 44 ref

027536   ESTRADA I L V, NARRO-GARCÍA R, LÓPEZ-LUKE T, ROMERO V H, CHRISTEN J A, ROSA E D L (Guadalajara Univ, Jalisco, Mexico, Email: vicromare@gmail.com) : Synthesis and luminescence properties of TiO₂ :Yb-Er mesoporous nanoparticles. Bull Mater Sci 2018, 41(4), 110.

Mesoporous spherical Yb–Er-doped TiO₂ nanoparticles were prepared by sol–gel method. The structure and morphology of the nanoparticles were characterized using Raman, Fourier transform infrared spectroscopies, transmission electron microscopy and by low-temperature N₂ adsorption. It is shown that both anatase (tetragonal) and brookite (orthorhombical) phases are present in the titania nanoparticles. Their diameter size is between 12 and 15 nm and an average surface area of 136 m² g⁻¹. Under infrared irradiation, the nanoparticles show luminescence by an upconversion process of the ytterbium and erbium ions, the green emission corresponds to ²H_11/2 + ⁴S_3/2 → ⁴I_15/2 transition and for the red emission, the transition energy is: ⁴F_7/2–⁴I_15/2. The green and red photoluminescence intensities are highly dependent on the OH amount, which is produced during the hydrolysis and condensation processes and depends on the reaction time, nanoparticles wash and annealing temperature. The influence of synthesis parameters on the properties of porosity and luminescence was studied by the Plackett–Burman experimental design.

8 illus, 4 tables, 29 ref

027551   LIU Y, WANG X, HAN Y, CHEN H (Changchun Univ of Technology, Changchun- 130 012, China, Email: 1064864769@qq.com) : Effect of deposition times of Al₂O₃ buffer layer on the structural and optical properties of AZO film on the polyethylene terephthalate substrates. Bull Mater Sci 2018, 41(4), 106.

The aluminium-doped zinc oxide with Al₂O₃ buffer layer (AZO/Al₂O₃) films were deposited on the polyethylene terephthalate substrates by radio frequency magnetron sputtering. Compared with the AZO films without Al₂O₃ buffer layer, the crystallite size and (002) peak of the AZO/Al₂O₃ films changed with the deposition times; the full-width at halfmaximum (FWHM) of (002) peak decreases from 0 to 25 min. The effects of Al₂O₃ buffer layer on the surface morphology of AZO/Al₂O₃ and optical properties of films were investigated by SEM and UV–Vis–NIR spectrophotometer, respectively. The results reveal that the average transmittance of the AZO films in the visible wavelength region is ∼90 %, stronger deep level emissions centred on 550 nm is attributed to intrinsic defects in the AZO films on the organic polymer PET substrates.

6 illus, 22 ref

027583   SACHDEVA S, AGARWAL R, AGARWAL A (Thapar Univ, Patiala -147 001, Email: ssmiti27@gmail.com) : Effect of annealing on tungsten oxide thin films for acetone gas detection. Bull Mater Sci 2018, 41(4), 105.

The gas-sensing properties and topology of tungsten oxide thin films deposited by reactive-ion radiofrequency magnetron sputtering were investigated at room temperature. The abnormalities in sensing film behaviour were observed when acetone gas is flowed over surface. The reduction reaction of surface and oxidation reaction of acetone gas were studied. As the gas comes in contact with the surface, the molecules tend to reduce the surface, hence, decreasing the resistance. The sensing film was annealed at different temperatures, viz., 300, 400, 500, 600 and 700 °C for 1 h each for the purpose of finding the optimum annealing temperature to detect acetone gas. Various characterizations, viz., XRD, AFM, FESEM, thickness measurement through surface profiler, gas-sensing characterization for recording resistance changes were performed. The optimum annealing temperature at which the sensing film gives maximum response when it comes in contact with acetone gas was computed to be 500 °C. Also, operational optimum temperature for sensing film annealed at 500 °C was computed to be 260 °C. A grain size of 7.3 nm was computed through analysis of AFM image and a film thickness of 100 nm was calculated through surface profiler. The SEM image of the film demonstrates that the grains developed on the surface, which increase in size with increase in the annealing temperature. The XRD patterns reveal that the oxide showed up was WO₂. It was observed that the response percentage is ∼31% for acetone vapour concentration of 20 ppm, ∼19% for the concentration of 15 ppm and ∼15% for the concentration of 10 ppm. The response time of the sensor is ∼5 min and the recovery time is 4 min.

9 illus, 35 ref

027567   PARK Y W, PARK M, KIM H-Y, KIM H-C, LIM J-C, JIN F-L, PARK S-J (Chemistry Dep, Inha Univ, Incheon- 402 751, South Korea, Email: sjpark@inha.ac.kr) : Thermal and curl properties of PET/PP blend fibres compatibilized with EAG ternary copolymer. Bull Mater Sci 2018, 41(4), 104.

Blends of polyethylene terephthalate (PET)/polypropylene (PP) and the ternary copolymer ethylene–acrylic ester–glycidyl methacrylate (EAG) as the compatibilizer were prepared using a twin-screw extruder. The thermal properties, densities and morphologies of the blends were determined using various techniques. Next, PET/PP blend fibres were prepared using a melt–spinning system, and their curl properties were investigated. Scanning electron microscopy (SEM) results showed that the number of PP particles in the PET matrix and size of the PP phase decreased as the EAG content increased. The melting temperature (T_m) and cooling crystallization (T_cc) values of PP in the PET/PP blends decreased significantly after the addition of 1 % EAG. The density of the PET/PP blend fibres decreased significantly with increase in the EAG and PP contents. After curl formation, the curl length of PP in the fibres was shorter than that of PET.

8 illus, 1 table, 28 ref

027593   SINGH P, JHA R K, SINGH R K, SINGH B R (Electronics & Communication Dep, Indian Institute of Information Technology, Allahabad- 211 012, Email: psingh3688@gmail.com) : On the structural and electrical properties of metal-ferroelectric-high k dielectric-silicon structure for non-volatile memory applications. Bull Mater Sci 2018, 41(4), 101.

In this article, we report the structural and electrical properties of metal–ferroelectric–high k dielectric–silicon (MFeIS) gate stack for non-volatile memory applications. Thin film of sputtered SrBi₂Nb₂O₉ (SBN) was used as ferroelectric material on 5–15 nm thick high-k dielectric (Al₂O₃) buffer layer deposited using plasma-enhanced atomic layer deposition (PEALD). The effect of annealing on structural and electrical properties of SBN and Al₂O₃ films was investigated in the temperature range of 350–1000 °C. X-ray diffraction results of the SBN and Al₂O₃ show multiple phase changes with an increase in the annealing temperature. Multiple angle ellipsometry data show the change in the refractive index (n) of SBN film from 2.0941 to 2.1804 for non-annealed to samples annealed at 600 °C. For Al₂O₃ film, n < 1.7 in the case of PEALD and n > 1.7 for sputtered film was observed. The leakage current density in MFeIS structure was observed to two orders of magnitude lower than metal/ferroelectric/silicon (MFeS) structures. Capacitance–voltage (C–V) characteristics for the voltage sweep of −10 to 10 V in dual mode show the maximum memory window of 1.977 V in MFeS structure, 2.88 V with sputtered Al₂O₃ and 2.957 V with PEALD Al₂O₃ in the MFeIS structures at the annealing temperature of 500 °C.

8 illus, 3 tables, 37 ref

027584   SAIKIA D, SARMA R (Physics Dep, J.B. Coll, Jorhat- 785 001, Email: dhrubajun@gmail.com) : Fabrication of organic light-emitting diode using molybdenum trioxide interlayer between electrode and organic interface. Bull Mater Sci 2018, 41(4), 95.

In this study, high-performance of organic light-emitting diodes (OLEDs) with a buffer layer of MoO₃ is demonstrated. With an optimal thickness of MoO₃ (12 nm), the luminance efficiency is found to be increased compared to the single layer anode OLED. To study the influence of MoO₃ buffer layer on OLED performance, we deposited MoO₃ films with different thicknesses on the fluorine-doped tin oxide (FTO) surface and studied J–V and L–V characteristics of the OLED devices. Also, further analysis was carried out by measuring sheet resistance, optical transmittance and surface morphology with the FESEM images. Here, we found that MoO₃ (12 nm) buffer layer is a good choice to increase the efficiency of FTO-based OLED devices within the tunnelling region. Here, the maximum value of current efficiency is 6.15 cd A⁻¹.

5 illus, 1 table, 42 ref

027577   RANA D K, SINGH S K, KUNDU S K, CHOUDHARY R J, BASU S (Physics Dep, National Institute Technology, Durgapur- 713 209, Email: sou_menbasu@yahoo.com) : Electrical and magnetic properties of polyvinyl alcohol-cobalt ferrite nanocomposite films. Bull Mater Sci 2018, 41(4), 92.

Polyvinyl alcohol (PVA)–cobalt ferrite (CFO) nanocomposite films were synthesized by wet chemical method. The synthesized CFO nanomaterial was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), which confirm the formation of pure phase nanoparticles with cuboid shape. The variation in AC conductivity is measured as a function of frequency (within the range of 100 Hz–1 MHz) and temperature (from 303 to 403 K). It was observed that the frequency exponent, S, decreases with increasing temperature, which is explained by correlated barrier hopping (CBH) conduction mechanism. Frequency dependence of real and imaginary parts of the dielectric permittivity of PVA–CFO nanocomposite films for different temperatures is studied on the basis of the modified Cole–Cole model. The dielectric permittivity of the samples reveals an increasing tendency with the concentration of CFO filler in PVA matrix. A high value of 89 emu g⁻¹ saturation magnetization and 652 Oe coercivity are observed in CFO nanoparticle. The coercivity increased in PVA–CFO nanocomposite when compared to CFO nanoparticle, which is expected due to inverse magnetostrictive effect. The increasing tendency of dielectric constant and magnetization of the nanocomposites with the increasing CFO concentration enhances the potential of applications in miniaturization of the antenna system and electromagnetic shielding materials.

8 illus, 3 tables, 28 ref

027566   PANDA S K, CHAKRABORTI S, BASU R N (Electronics Dep, Bidhan Chandra Coll, Hooghly- 712 248, Email: sovan.panda@gmail.com) : Size and shape dependences of the colloidal silver nanoparticles on the light sources in photo-mediated citrate reduction technique. Bull Mater Sci 2018, 41(4), 90.

Colloidal silver nanoparticles (Ag NPs) with different sizes and shapes were synthesized by photo-mediated citrate reduction of aqueous AgNO₃ solution under UV, sun and visible–infrared (VIS–IR) light sources. Pale yellow colour colloid was obtained under VIS–IR light exposure, whereas reddish yellow colour colloid was yielded under UV light. The colloid prepared under natural sunlight initially appeared as yellow, which turns out to be deep green after 10 h exposure. The colloid prepared under UV light contains fine spherical NPs with diameter ranging from 5 to 10 nm. In addition to spherical NPs, some low-dimensional features like triangles, hexagonal platelets, nanorods were also formed under sunlight. Similar low-dimensional features including spherical particles, long chains of particles and large leaf-like platelets were grown under VIS–IR light. The colloid prepared under UV light exhibits single plasmonic absorption peak in the violet region of the visible spectra with absorption peak centred at ∼405 nm. However, the colloid prepared under sun and VIS–IR light demonstrates multiple plasmonic absorption peaks related to the multi-dimensional nanoparticles. All the NPs were made of pure silver and single crystalline. The colloid prepared under VIS–IR light exhibited significant ageing with time; whereas, the colloids prepared under UV and sunlight seem very stable against ageing even after long time.

6 illus, 1 table, 29 ref

027572   PRAVEENA R, SAMEERA V S, THIRUMALA N V P R, SUNANDANA C S, KRISHNA M G (Hyderabad Univ, Hyderabad-500 046, Email: mgksp@uohyd.ernet.in) : Effect of pre-annealing on the structural evolution and optical response of Ag films exposed to iodine vapours. Bull Mater Sci 2018, 41(4), 89.

Ag thin films of 5 nm thickness were deposited on glass substrates by thermal evaporation. The films were divided into two sets, out of which, one set was not annealed and the other set was subjected to pre-annealing at 300 °C for 2 h in air. The un-annealed and pre-annealed films were exposed to iodine vapours at room temperature for the durations from 5 min to 10 h. The un-annealed films were crystallized into the β phase of AgI after exposure for 5 h. In contrast, for the pre-annealed films, crystallization into the β phase occurred within the first 5 min. Both sets of films, however, exhibit a strong preferential c-axis orientation in the β-AgI phase. Optical absorption studies reveal that the un-annealed films exhibit a localized surface plasmon resonance (LSPR) with a peak at 545 nm and a long wavelength shoulder at 620 nm, which shifts to 516 nm after iodization for a few minutes. This peak position does not change with further iodization. The LSPR for the pre-annealed films has a single peak at 538 nm. After iodization for a few minutes, this peak shifts to 525 nm. Iodization for 3 h results in a further blue-shift of this resonance to 475 nm. The photoluminescence spectrum reveals two peaks, one at 368 nm and the other at 712 nm. The first one is assigned to the excitons of AgI, whereas the long wavelength peak is attributed to the presence of disorder in the films. The reasons for the difference in behaviour of the un-annealed and pre-annealed films are discussed.

6 illus, 27 ref

027565   PAL C (Physics Dep, Ramakrishna Mission Vidyamandira, Howrah- 711 202, Email: cmpmagra@gmail.com) : Singular spectrum analysis, harmonic regression and El-Nino effect on total ozone (1979-1993) over India and surrounding regions. J Earth Syst Sci 2018, 127(5), 74.

The Total Ozone Mapping Spectrometer (TOMS) is a satellite instrument that records Total Column Ozone (TCO) concentration (in DB) of the atmosphere in the form of different overpass files. We have selected 23 sites over India (15), Pakistan (4), Bangladesh (1) and adjoining China (3) to investigate the TCO scenario over this region. About 114,000 historical records (1979M1–1992M12) from 23 overpass files were processed to generate 23 monthly mean time series (TS) of TCO. Statistical analysis followed by singular spectrum analysis (SSA), harmonic regression (HR) and spatial interpolation have been used to accomplish the investigation. Four dominant signals; quasi-biennial signal (QBI, T = 30.12 months), quasi-annual signal (QAN, T = 19.69 months), annual signal (ANN, T = 12 months) and semi-annual signal (SAN, T = 6 months) were discerned to explain the variability. Direct latitudinal effect on the TCO distribution was observed. The variance was limited between 80.53 and 90.13 %; ANN contributes 65.93–93.22 % followed by SAN 0.58–5.69 %, QAN 0.33–5.48 %, and QBI 0.06–5.94 %. Peak values of the oscillations are estimated from phasor diagrams: QBI, March to May in the mid-latitude; QAN, April, and May; ANN, February to April; SAN, March to May. Incisive pictures of the average distribution and variability of four sinusoids were investigated from contour plots. Two ozone valley were discerned from Spatial interpolation; one over Deccan Plateau in low and other over Tibetan Plateau in high latitude. 179 outliers from 23 × 168 observations have been identified after harmonic regression. The appearance of the outliers is highly consistent with extreme phases of multivariate ENSO Index and Dipole Mode Index.

6 illus, 5 tables, 51 ref

027560   MURTI R, TRIPATHI S K, GOYAL N, PRAKASH S (Physics Dep, Punjab Univ, Chandigarh- 160 014, Email: rammurtisharma07@gmail.com) : Meyer-Neldel energy in Se-based binary and ternary chalcogenide glasses. Pramana- J Phys 2018, 91(2), 25.

The integral equations for DC conductivity and external conductance for the network of localised states in amorphous solids are solved by iteration method. The random free energy barriers and single polaron hopping model are used to obtain the DC conductivity σ_DC and Meyer–Neldel energy E_MN. The experimental estimates of optical band gap E_g, dielectric function , glass transition temperature Tg and σ_DC are used to calculate E_MN for Se-based binary and ternary chalcogenide glasses. The calculated values are found to be in agreement with the available experimental data. E_MN increases with increase of attempt frequency. The true pre-exponential factor σ₀₀ is related to E_MN as ln σ₀₀ = p − q E_MN, where p is nearly 7.3 and q is material-dependent. The calculated values of E_MN and σ₀₀ suggest that DC conduction in these chalcogenides is due to acoustic and optical phonon-assisted polaron hopping.

5 illus, 2 tables, 63 ref

027597   SUMA S P, SIRSI S (Physics Dep, Mysore Univ, Mysuru- 570 005, Email: sumarkr@gmail.com) : Trivariate analysis of two qubit symmetric separable state. Pramana- J Phys 2018, 91(2), 24.

One of the main problems of quantum information theory is developing the separability criterion which is both necessary and sufficient in nature. Positive partial transposition test (PPT) is one such criterion which is both necessary and sufficient for 2 × 2 and 2 × 3 systems but not otherwise. We express this strong PPT criterion for a system of 2-qubit symmetric states in terms of the well-known Fano statistical tensor parameters and prove that a large set of separable symmetric states are characterised by real statistical tensor parameters only. The physical importance of these states are brought out by employing trivariate representation of density matrix wherein the components of J, namely J_x , J_y , J_z are considered to be the three variates. We prove that this set of separable states is characterised by the vanishing average expectation value of J_y and its covariance with J_x and J_z. This allows us to identify a symmetric separable state easily. We illustrate our criterion using 2-qubit system as an example.

24 ref

027601   WEN X-Y, CHEN Y (Beijing Information Science and Technology Univ, Beijing- 100 192, China, Email: xiaoyongwen@163.com) : Dynamics of new higher-order rational soliton solutions of the modified Korteweg-de Vries equation. Pramana- J Phys 2018, 91(2), 23.

In this paper, we propose a generalised perturbation (n, N − n)-fold Darboux transformation (DT) of the modified Korteweg–de Vries (mKdV) equation using the Taylor expansion and a parameter limit procedure. We apply the generalised perturbation (1, N − 1)-fold DT to find the new explicit higher-order rational soliton (RS) solutions in terms of determinants of the mKdV equation. These higher-order RS solutions are different from those known soliton results in terms of hyperbolic functions which are obtained from the classical iterated DT. The dynamics behaviours of the first-, second-, third-, and fourth-order RS solutions are shown graphically. The wave propagation characteristics and stability are also discussed using numerical simulations. We find that the initial constant seed solution plays an important role on the wave propagation stability of RS. Through Miura transformation, we give some complex higher-order rational solutions of the Korteweg–de Vries (KdV) equation which are different from the known results. The relevant structures also are discussed using some figures. The method used can also be extended to seek explicit rational solutions of other nonlinear integrable equations.

12 illus, 32 ref

027524   ASER M S, ABDEL-KADER M E, SHAGAR A M, ELTAYEB H A, ALGAMAL H A, AL-HALIM M A A (Physics Dep, Benha Univ, Benha 13518, Egypt, Email: mohamed.abdalhalim@fsc.bu.edu.eg) : Characterisation of electric discharge in hollow electrode Z-pinch device by means of Rogowski coils. Pramana- J Phys 2018, 91(2), 22.

The hollow electrode Z-pinch (HEZP) is expressed as a new shape of Z-pinch devices in which one of the electrodes is ring-shaped. The periodic time of the discharge current is 35 μs with a total system inductance of 288 nH, total system resistance of 14 m, and 34 % deposited energy for a charging voltage of 8 kV. The pinch effect appears in the shape of a sharp spike in the signal of the discharge voltage and dip in the signal of discharge current, which leads to an increase in the plasma inductance at the pinch time. The plasma current density, which is measured using miniature Rogowski coil for 8 kV charging voltage and 1 torr pressure, has a maximum value of 12.1 kA/cm² near the axis of the discharge tube and decreases toward the wall. The helium gas pressure in the range of 1–2 torr expresses the situation of the maximum current density. The pinch time increases by increasing the gas pressure and also by decreasing the charging voltage leading to a decrement of the peak discharge current and hence the magnetic field is also decreased. A delay time of at least 4.1 μs is found to be required to form the pinch for the implemented set-up of anode–cathode dimensions and interdistance. The calculated sheath velocity is in the range of 1.2–6 cm/μs which is directly proportional to the charging voltage and inversely proportional to the gas pressure.

12 illus, 39 ref

027526   BAG A (Chemical Sciences Div, Indian Institute of Science Education and Research, Nadia- 741 246, Email: bagarijit@gmail.com) : Theoretical lower limit of mass of phonon and critical mass for matter-dark matter conversion. Pramana- J Phys 2018, 91(2), 21.

From Planck’s equation for black body radiation and de Broglie’s wave–particle duality relation, we can get a relation between the mass of a phonon and frequency of the emitted radiation. From this relation, we get the theoretical lower limit of the mass of a phonon and critical mass for matter–dark matter conversion. The maximum matter density and limit of the string length are also discussed in this respect. It is observed that there is a critical mass of the smallest particle, which is 7.367 × 10⁻⁵¹ kg, above which we get normal matter and below, the dark matter. It is also observed that if phonon obeys the de Broglie’s equation, generation of an electromagnetic radiation of frequency less than 56638721410 Hz is not possible by thermal heating.

3 illus, 2 tables, 28 ref

027602   XIE Q (Hainan Normal Univ, Haikou- 571 158, Email: qiongtaoxie@yahoo.com) : Analytical results for periodically-driven two-level models in relation to Heun functions. Pramana- J Phys 2018, 91(2), 19.

We introduce three different types of periodically-driven multiparametric two-level models whose analytical solutions are given in terms of Heun functions. These results are applied to obtain exact analytical results for certain types of periodic potentials and asymmetric double-well potentials. In particular, it is shown that under special parameter conditions, an experimentally realised periodic potential supports the exact in-gap solutions. In the asymmetric double-well potentials, some exact results of the bound-state wave functions and associated energies are found in explicit form.

2 illus, 50 ref

027548   KISOMI A F, MOUSAVI S J (Physics Dep, Islamic Azad Univ, Ardabil, Iran, Email: alif1364@yahoo.com) : Ab-initio calculations of structural, phonon and thermal properties of Al_xGa_1-xAs alloy. Pramana- J Phys 2018, 91(2), 18.

Structural, phonon and thermal properties of Al_xGa_1−xAs alloy for different values of x (x = 0.0, 0.25, 0.5, 0.75 and 1.0) have been investigated by quasiharmonic Debye–Einstein model and Quantum Espresso package. The correction of Vegard’s law for lattice constant has been examined and has a good agreement with other experimental and theoretical works. TO–LO splitting at gamma point, which is related to breaking of cubic symmetry, has been calculated by optical phonon mode calculation. It is found that by increasing the amount of Al in Al_xGa_1−xAs alloy, specific heat at constant pressure and Debye temperature will be increased.

6 illus, 1 table, 14 ref

027519   AEZAMI A (Physics Dep, Islamic Azad Univ, Ahvaz, Iran, Email: a.aezami@gmail.com) : Effect of tensile and compressive strain on the magnetic ordering of the (LaMnO₃)₁/(SrTiO₃)₁ superlattice. Pramana- J Phys 2018, 91(1), 15.

We study the effects of tensile and compressive strain on the (LaMnO₃)₁/(SrTiO₃)₁ superlattice from density functional theory using Quantum-Espresso open source code. In the unstrained superlattice, electron interactions in out-of-plane Mn–O–Ti chains are dominated by superexchange interactions, giving rise to ferromagnetic and half-metallic conducting characters. We found that the most stable magnetic configuration is G-type antiferromagnetic configuration for strong compressive strain and for strong tensile strain it is A-type antiferromagnetic configuration. The results are in accordance with the experimental observations which show that the superlattices can be grown on different substrates, and due to the difference in lattice parameters of the substrate and the main layer, there are also changes in the amount of strain applied to the superlattice.

6 illus, 1 table, 7 ref

027581   RIZWANA R, MOHAMED I R (Physics Dep, B.S. Abdur Rahman Crescent Institute of Science and Technology, Chennai- 600 048, Email: lirajamd.phy@gmail.com) : Applicability of strange nonchaotic Wien-bridge oscillators for secure communication. Pramana- J Phys 2018, 91(1), 10.

In this paper, experimental realisation of synchronisation of strange nonchaotic attractor in unidirectionally coupled Wien-bridge oscillator is presented. Preliminary work of chaotic and strange nonchaotic dynamics with diode as the nonlinear element is published in J. Nonlinear Dyn. 2015,1(2015). In this work, two Wien-bridge oscillators are coupled at the aperiodic dynamics for application in secure communication. The dynamics of the coupled system is explored by experimental and numerical studies. Employing the simple communication masking method with aperiodic dynamics offers some advantages rather than using chaotic attractors, i.e., the range of control parameter value is smaller than the range for which the system exhibits chaotic behaviour. The performance of the system is evaluated and it is found that experimental result agrees with numerical results.

7 illus, 2 tables, 21 ref

027534   DEVI K R, KUMAR S, PALIT R (Physics and Astrophysics Dep, Delhi Univ, Delhi- 110 007, Email: rojee29@gmail.com) : Geometry of magnetic rotational (MR) band-crossing phenomenon in MR bands. Pramana- J Phys 2018, 91(1), 8.

A semiclassical (SC) approach is proposed to calculate the B(M1) transition rates in the band-crossing region of two magnetic rotational (MR) bands. In the present work, a geometry is suggested for the shear blades to govern its behaviour during the band-crossing. In the crossing region, gradual alignment of two nucleons is responsible for the crossing behaviour and it must give a quantised resultant angular momentum. As an example, it is successfully implemented for the MR bands in the mass A = 110 and A = 200 regions. A good agreement of the present semiclassical calculations with the experimental values is presented and furthermore, it is seen that the present proposal is also helpful to see the core contribution in the MR phenomenon.

4 illus, 1 table, 25 ref

027540   GOVENDER G, MOOLLA S (KwaZulu-Natal Univ, Durban 4000, South Africa, Email: moollas@ukzn.ac.za) : The structure of ion-acoustic waves in a low-frequency three-component electron-ion space plasma with two-electron populations. Pramana- J Phys 2018, 91(1), 7.

Low-frequency ion-acoustic waves are analysed on the ion time-scale, in a three-component electron– ion space plasma. The solitary waves propagate in the positive x direction relative to an ambient magnetic field B₀ which forms static background for a configuration consisting of cool fluid ions and both warm and hot Boltzmanndistributed electrons with temperatures T_ic, T_ew and T_eh, respectively. We derive linear dispersion relation for the waves by introducing first-order density, pressure and velocity perturbations into the ion fluid equations. Additionally, the variation in the nonlinear structure of the waves are investigated by carrying out a full parametric analysis utilising our numerical code. Our results reveal that ion-acoustic waves exhibit well-defined nonlinear spikes at speeds of M ≥ 2.25 and an electric field amplitude of E₀ = 0.85. It is also shown that low wave speeds (M ≤ 2), higher densities of the hot electrons, antiparallel drifting of the cool fluid ions, and increased ion temperatures all lead to significant dispersive effects. The ion-acoustic plasma waves featured in this paper have forms that are consistent with those classified as the type-A and type-B broadband electrostatic noise (BEN) observed in the data obtained from earlier satellite missions.

9 illus, 25 ref