015791   Sharma V K;Rao M N;Gautam S;Tripathi A K; Kamble V S;Chaplot S L;Mukhopadhyay R (Solid State Physics Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: sharmavk@barc.gov.in ) : Rotational dynamics of propylene inside Na-Y zeolite cages. Pramana J Phys 2008, 71(5), 1165-9.

Reports the quasielastic neutron scattering (QENS) studies on the dynamics of propylene inside Na-Y zeolite using triple axis spectrometer (TAS) at Dhruva reactor, Trombay. Molecular dynamics (MD) simulations performed on the system had shown that the rotational motion involves energy larger than that involved in the trans-lational motion. Therefore, rotational motion was not observed in our earlier QENS studies on propylene adsorbed Na-Y zeolite using a higher resolution spectrometer at Dhruva. Analysis of the TAS spectra revealed that the quasielastic broadening observed in propylene-loaded zeolite spectra is due to the rotational motion of the propylene molecules. This is consistent with our simulation result. Further, the rotational motion is found to be isotropic. The rotational diffusion coefficient has been obtained.

5 illus, 1 table, 9 ref

015790   Shah K V;Goswami M;Manikandan S;Shrikhande V K;Kothiyal G P (Technical Physics and Prototype Engineering Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: gpkoth@barc.gov.in) : Surface degradation behaviour of sodium borophosphate glass in aqueous media. Bull Mater Sci 2009, 32(3), 329-36.

Degradation behaviour of phosphate glass with nominal composition, 40Na₂O-10BaO-xB₂O₃-(50-x)P₂O₅, where 0 ≤ x ≤ 20 mo%, was studied in water, HCl and NaOH solutions at room temperature to 60°C for different periods extending up to 300 h. These glasses were synthesized by conventional melt-quench technique. Dissolution rates were found to increase with B₂O₃ content in the glass. The dissolution rates for the glass having 10 mol% B₂O₃ were found to be 0.002 g/cm^{2 and 0.015 g/cm2 in distilled water and 5% NaOH solution, respectively, at room temperature after 225 h of total immersion period, whereas it increased considerably to 0.32 g/cm2 in 5% NaOH at 60°C after 225 h. However, glass samples with x = 15 and 20 mol% B₂O₃ were dissolved in 5% HCl solution after 5 h immersion. The degradation behaviour has been correlated with the structural features present in the glass. The optical microscopy of the corroded surface revealed that the corrosion mechanism were different in acid and alkali media.}

9 illus, 14 ref

015789   Sengupta J;Panda S K;Jacob C (Materials Science Centre, Indian Institute of Technology, Kharagpur-721 302, Email: cxj14_holiday@yahoo.com) : Carbon nanotube synthesis from propane decomposition on a pre-treated Ni overlayer. Bull Mater Sci 2009, 32(2), 135-40.

Growth of carbon nanotubes (CNTs) was performed by atmospheric pressure chemical vapour deposition (APCVD) of propane on Si(111) with a pre-treated Ni overlayer acting as a catalyst. Prior to the growth of CNTs, a thin film of Ni was deposited on Si(111) substrate by evaporation and heat treated at 900°C. The growth of nanotubes was carried out at 850°C using propane as a source of carbon. Distribution of the catalyst particles over the Si substrate was analysed before and after heat treatment by atomic force microscopy (AFM). The X-ray diffraction (XRD) pattern of the grown material revealed that they are graphitic in nature. Field emission scanning electron microscopy (FESEM) was used to investigate the growth process and it was found that a catalytic particle was always situated at the tip of the tube thus implying a tip growth mechanism. Evidence for the presence of radial breathing mode from multi-wall nanotubes (MWNTs) in the grown sample was obtained from micro-Raman analysis. Finally, high-resolution transmission electron microscopic (HRTEM) analysis confirmed that the graphene layers of the CNTs are well ordered with typical 0.34 nm spacing.

6 illus, 44 ref

015788   Sen D;Dasgupta K;Bahadur J;Mazumder S; Sathiyamoorthy D (Solid State Physics, Bhabha Atomic Research Centre, Mumbai-400 085, Email: debasis@barc.gov.in) : Morphology of carbon nanotubes prepared via chemical vapour deposition technique using acetylene: a small angle neutron scattering investigation. Pramana J Phys 2008, 71(5), 971-7.

Small angle neutron scattering (SANS) has been utilized to study the morªphology of the multi-walled carbon nanotubes prepared by chemical vapour deposition of acetylene. The effects of various synthesis parameters like temperature, catalyst concenªtration and catalyst support on the size distribution of the nanotubes are investigated. Distribution of nanotube radii in two length scales has been observed. The number density of the smaller diameter tubes was found more in number compared to the bigger one for all the cases studied. No prominent scaling of the structure factor was observed for the different synthesis conditions.

5 illus, 2 tables, 6 ref

015787   Sen D;Bahadur J;Mazumdr S;Mahata T;Syambabau M;Sinha P K (Solid State Physics Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: debasis@barc.gov.in) : Investigation on pore structure and small-scale agglomeration behaviour in liquid phase sintered SiC using small angle neutron scattering. Pramana J Phys 2008, 71(5), 979-84.

Mesoscopic density fluctuations in liquid phase sintered silicon carbide have been investigated using small angle neutron scattering (SANS). The increase in the addiªtives results in the modification in the pore size distribution and to some extent the total porosity. SANS revealed a mass fractal nature of the agglomerated matrix microstrucªture. The fractal dimension of the matrix does not change appreciably with the additives although the upper cut-off value of the fractal decreases significantly with the increase in the additives. The liquid phase sintering due to the presence of additives helps to achieve higher level of densification. However, the agglomeration hinders achievement of the fully dense pellets.

4 illus, 1 table, 9 ref

015786   Schober H et al (NO, Institut Laue-Langevin, BP 156 X, F-38042 Grenoble Cedex, France, Email: schober@ill.fr) : Dynamic instability at the origin of oxygen ion conduction in solid oxides at ambient temperature. Pramana J Phys 2008, 71(5), 898.

The conduction of ions in solids is of paramount importance for many technological devices like solid oxide fuel cells. It is inherent to solids that ions are trapped within potential wells. Their transport thus has to be activated at the price of elevated temperatures, a condition that is often incompatible with technological applications. While atomic vibrations have the potential of assisting the diffusion process, little is known about the exact conditions that have to be reunited to trigger such a process. Here we show that dynamic instability is responsible for the large ion conduction in SrFeO_2.5 with brownmillerite-type structure. Using ab-initio molecular dynamics calculations we observe the migration of oxygen ions away from the original lattice positions into the vacancy chanªnels of the brown millerite structure. The escape of the oxygen ion is rendered possible by the destabilization of a shallow potential well due to low-lying vibrational modes, the existence of which is confirmed by neutron spectroscopy. Analysing the lattice dynamics as a function of structural parameters it is possible to identify the structural subtleties responsible for the instability. It is found that in the isostructural compound CaFeO_2.5, fast oxygen ion diffusion is absent at low temperatures. The origin of this behaviour lies with the slightly different iron-oxygen distances rendering the potentials better defined and less amenable to dynamical destabilization. The here-introduced concept of dynamical instability is not restricted to the discussed class of materials but may be applied to any system that features ion conduction at low temperatures.

015785   Sastry P U;Krishna P S R;Panicker L;Shinde A B (Solid State Physics Div, Bhabha Atomic Research Centre, , Mumbai-400 085, Email: psastry@barc.gov.in) : Structural behaviour of AgNO₃ at low temperatures by neutron diffraction. Pramana J Phys 2008, 71(5), 929-33.

Structural behaviour of silver nitrate (AgNO₃) at low temperatures has been investigated by neutron powder diffraction and differential scanning calorimetry (DSC). Analysis showed abnormal changes in the rotations of nitrate (NO₃) anions and thermal displacement parameters of the atoms near 220 K and 125 K. However, the basic lattice is compatible with the orthorhombic symmetry (space group Pbca) till 12 K. The fine, small-scale structural anomalies probably originate from freezing of reorientation of NO₃ ions from high-temperature disordered phase.

3 illus, 1 table, 7 ref

015784   Sastry P U;Aswal V K;Wagh A G (Solid State Physics Div, Bhabha Atomic Research Centre, Mbumbai-400 085, Email: psastry@barc-gov.in) : Small angle neutron scattering and small angle X-ray scattering studies of platinum-loaded carbon foams. Pramana J Phys 2008, 71(5), 1075-8.

The morphology of carbon nanofoam samples comprising platinum nanoparªticles dispersed in the matrix was characterized by small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) techniques. Results show that the structure of pores of carbon matrix exhibits a mass (pore) fractal nature and the average radius of the platinum particles is about 2.5 nm. The fractal dimension as well as the size distribution parameters of platinum particles varies markedly with the platinum content and annealªing temperature. Transmission electron micrographs of the samples corroborate the SANS and SAXS results.

2 illus, 1 table, 7 ref

015783   Saranya D;Chaudhuri A R;Jayanta Parui; Krupanidhi S B (Materials Research Centre, Indian Institute of Science, Bangalore-560 012, Email: sbk@mrc.iisc.ernet.in) : Electrocaloric effect of PMN-PT thin films near morphotropic pahse boundary. Bull Mater Sci 2009, 32(3), 259-62.

Electrocaloric effect is calculated for PMN-PT relaxor ferroelectric thin film near morphotropic phase boundary composition. Thin film of thickness, ~240 nm, has been deposited using pulsed laser deposition technique on a highly (111) oriented platinized silicon substrate at 700°C and at 100 mtorr oxygen partial pressure. Prior to the deposition of PMN-PT, a template layer of LSCO of thickness, ~60 nm, is deposited on the platinized silicon substrate to hinder the pyrochlore phase formation. The temperature dependent P-E loops were measured at 200 Hz triangular wave operating at the virtual ground mode. Maximum reversible adiabatic temperature change, ΔT = 31 K, was calculated at 140°C for an external applied voltage of 18 V.

4 illus, 21 ref

015782   Santosh Kumar;Raizada A (P.G. Dep, Studies and Research in Physics and Electronics, Jabalpur-482 001, Email: a_kumar123@rediffmail.com) : Effect of solar features and interplanetary parameters on geomagnetosphere during solar cycle-23. Pramana J Phys 2008, 71(6), 1353-66.

The dependence of geomagnetic activity on solar features and interplanetary (IP) parameters is investigated. Sixty-seven intense (-200 nT ≤ Dst < -100 nT) and seventeen super intense (Dst < -200 nT) geomagnetic storms (GMSs) have been studied from January 1996 to April 2006. The number of intense and superintense GMSs show three distinct peaks during the ll-year period of 23rd solar cycle. The largest number of high strength GMSs are observed during maximum phase of solar cycle. Halo and partial halo CMEs are likely to be the major cause for these GMSs of high intensity. No relationship is observed between storm duration and the number of CMEs involved in its occurrence. The intensity of the GMS is also independent of the number of CMEs causing the occurrence of storm. These geoeffective CMEs show western and northern bias. Majority of the geoeffective CMEs are associated with X-ray solar flares (SFs). Solar and IP parameters, e.g., VCME, Vsw, B, B₂ (GSE and GSM coordinates) and their products, e.g., Vsw.B and Vsw.Bz are observed and correlated to predict the occurrence of intense GMSs. VCME does not seem to be the appropriate parameter with the correlation coefficient, r = -0.2 with Dst index, whereas the correlation coefficient, r = -0.57, -0.65, 0.75, -0.68 and 0.77 of the parameters Vsw, B, B₂, Vsw . Band Vsw . B₂ respectively, with Dst indicating that Vsw . Bz and Bz may be treated as the significant contributors in deteermining the strength of GMSs.

3 illus, 25 ref

015781   Robinson R A (NO, The Bragg Institute, ANSTO, Sydney, Australia, Email: rro@ansto.gov.an) : Progress with OPAL, the new Australian research reactor. Pramana J Phys 2008, 71(5), 894.

Australian science is entering a new 'golden age', with the start-up of bright new neutron and photon sources in Sydney and Melbourne, in 2006 and 2007 respectively. The OPAL reactor and the Australian Synchrotron can be considered as the greatest sinªgle investment in scientific infrastructure in Australia's history. They will essentially be 'sister' facilities, with a common open user ethos, and a vision to play a major role in international science. Fuel was loaded into the reactor in August 2006, and full power was (20 MW) achieved in November 2006. The first call for proposals was made in 2007, and commissioning experiments have taken place well before then. The first three instruªments in operation are high-resolution powder diffractometer (for materials discovery), high-intensity powder diffractometer (for kinetics experiments and small samples) and a strain scanner (for mechanical engineering and industrial applications). These are closely followed by four more instruments with broad application in nanoscience, condensed matªter physics and other scientific disciplines. Instrument performance will be competitive with the best research-reactor facilities anywhere. To date there is committed funding for nine instruments, with a capacity to install a total of ~18 beamlines. An update will be given on the status of OPAL, its thermal and cold neutron sources, its instruments and the first results.

015780   Renuga Devi T S;Gunasekaran S;Wesley Hudson J;Joybell S A (PG Physics Dep, Women's Christian College, Chennai, Email: dvi_renuga@yahoo.com) : Analysis on renal failure patients blood samples: characterization and efficacy study. Indian J Sci Technol 2009, 2(2), 46-50.

Study attempts to evaluate the spectral difference between healthy and renal failure blood sera and also to find the efficacy of peritoneal dialysis in renal failure patients using FTIR spectroscopic technique. Six chronic renal failure patients were enrolled in the study. FTIR blood spectra were recorded over the region 4000 - 400 cm -1 on a Perkin Elmer spectrum one FTIR spectrometer. The internal standard ratios among the absorption peaks were calculated and it is found to be an indicator to differentiate the diseased subjects from the healthy one. In order to find the efficacy of peritoneal dialysis the absorption values of the specific bands of both pre and post treatment spectra were noted and the internal ratio parameter were calculated. The comparison of these values showed that the spectra are not similar when compared down to finer details.

3 tables, 15 ref

015779   Razavi M;Rahimipour M R;Ebadzadeh T;Tousi S S R (NO, Materials and Energy Research Centre, P.O. Box 14155-4777, Tehran, Iran, Email: m_rahimi@merc.ac.ir) : Synthesis of Fe-TiC nanocomposite from ilmenite concentrate via microwave heating. Bull Mater Sci 2009, 32(2), 155-60.

Possibility of production of Fe-TiC nanocomposite as a useful ceramic, from ilmenite concentrate, aluminum powder and carbon black has been investigated. Different amounts of FeTiO₃, carbon black and Al powder were activated by a high-energy ball mill. Then the mixtures were synthesized by microwave heating at various times. The results of XRD investigation indicated that TiC has been synthesized within 5-10 min treatment microwave time. Moreover, it was found that by increasing the aluminum content, the Fe₂O₃ phase was replaced by SiC and Al₂O₃. In addition, from the broadening of the diffraction lines in the XRD patterns analysis, it was concluded that the TiC crystallites are nano-sized. Also, it was found that the existence of Al lead to increased grain size and decrease of the strain in the process.

7 illus, 4 tables, 13 ref

015778   Raveau B;Seikh M M;Pralong V;Caignaert V (NO, Laboratoire CRISMAT, UMR 6508, CNRS-ENSICAEN, Universite de Caen, 1405, , Email: bernard.raveau@ensicaen.fr ) : Ordered oxygen deficient `112' perovskites, LnBaCo₂O_5.50+δ: complex magnetism and transport properties. Bull Mater Sci 2009, 32(3), 305-12.

Ordered oxygen deficient `112' perovskites, LnBaCo₂O_5.50+δ (Ln = lanthanide or Y), exhibit a very flexible structure which can either uptake (δ > 0) or release oxygen (δ < 0) depending on the experimental conditions of synthesis and on the size of the lanthanide. These compounds exhibit remarkably complex magnetic transitions, metal-insulator transition and exceptionally high magnetoresistance. Authors shows herein that their physics is mainly dominated by three different ferromagnetic states, depending on the cobalt valency: FM1 for δ = 0 (Co³⁺), FM2 for δ < 0 (Co²⁺/Co³⁺) and FM3 for δ > 0 (Co³⁺/Co⁴⁺). The competition between ferromagnetism and antiferromagnetism in these phases and the various transitions are discussed taking into consideration the spin state of cobalt, the issue of phase separation and the effect of cobalt coordination and disproportionation.

12 illus, 47 ref

015777   Radhakrishnan S R (Physics Dep, Avinashilingam University for Women, Coimbatore-43) : Design, development and study of a demonstration model solar updraft tower-a novel approach for generating electricity from solar thermal convective acceleration. Ultra Scient phys Sci 2009, 21(2), 419-24.

The solar updraft tower is a renewable energy device which uses solar thermal energy to provide upward convective acceleration to the inflow air by greenhouse effect The hot air rising through the chimney stack drives the turbine and the rotational energy of the turbine is converted into electricity by a generator. The paper presents the design details and performance analysis of a self designed simple and compact demonstration model solar updraft tower made with locally available materials. The model is constructed with the prime aim of understanding chimney concept in experimental studies. Tests were conducted to evaluate the performance of the device by measuring the test parameters updraft velocity, temperature profiles of various junctions and power output. The results obtained indicate that the updraft velocity and power output depend on solar insolation and the height of the chimney stack with a constant collector area.

2 illus, 2 tables, 5 ref

015776   Qiu Z C;Zhou J P;Zhu G;Liu P;Bian X B (NO, School of Physics and Information Technology, Shaanxi Normal Universit, Xi'an 710062, Email: zhoujp@snnu.edu.cn) : Hydrothermal synthesis of Pb(Zr_0.52Ti_0.48)O₃ powders at low temperature and low alkaline concentration. Bull Mater Sci 2009, 32(2), 193-7.

Pb(Zr_0.52Ti_0.48)O₃ (PZT) powders were prepared by hydrothermal method. The effects of experimental parameters, including Pb/(Zr, Ti) ratio, alkaline concentration, reaction temperature and time on the product powders were studied in detail. Pure PZT powders were synthesized at suitable experimental conditions and Raman spectra confirmed the PZT with a perovskite-type structure. The homogeneous PZT powders with cubic-shaped morphology were formed at alkaline concentration of 1.2 M after reacting at 230°C for 2 h. The pure PZT powders obtained at low temperature and low alkaline concentration were attributed to precursors, TiCl₄, with high activity and mineralizer NaOH with small cation radius.

6 illus, 19 ref

015775   Putra E C R;Ikram A;Kohlbrecher J (Neutron Scattering Laboratory, National Nuclear Energy Agency of Indon, , Kawasan Puspiptek Serpong, Tangerang 15314, Indonesia, Email: giri@batan.go.id) : SMARTer for magnetic structure studies. Pramana J Phys 2008, 71(5), 1015-19.

SMARTer, a 36-meter small angle neutron scattering (SANS) spectrometer was installed at the Neutron Scattering Laboratory (NSL), National Nuclear Energy Agency of Indonesia - BATAN in Serpong, Indonesia and has performed the experiment for studying the magnetic structures of Cu(NiFe), CuCo and FeSiBNbCu metal alloys. The experiments were conducted at room temperature and up to 1 T (10 kOe) of external magnetic field. At zero fields, isotropic scattering identified as nuclear scattering is dominant. When a magnetic field is applied in a horizontal direction perpendicular to the neutron beam, the response of the magnetic scattering permits extraction of the field-induced re-arrangement of the magnetic moment. With increasing field the distortion is more pronounced and the magnetic scattering dominates the intensity and affects the peak position. Radial and angular averaging from experimental data are given to show the details of magnetic structures.

1 illus, 5 ref

015774   Prashant Kumar;Ghanshyam Krishna M; Bhattacharya A K (NO, School of Physics, University of Hyderabad, Hyderabad-500 046, Email: mgksp@uohyd.ernet.in) : Effect of microstructural evolution on magnetic properties of Ni thin films. Bull Mater Sci 2009, 32(3), 263-70.

Magnetic properties of Ni thin films, in the range 20-500 nm, at the crystalline-nanocrystalline interface are reported. The effect of thickness, substrate and substrate temperature has been studied. For the films deposited at ambient temperatures on borosilicate glass substrates, the crystallite size, coercive field and magnetization energy density first increase and achieve a maximum at a critical value of thickness and decrease thereafter. At a thickness of 50 nm, the films deposited at ambient temperature onto borosilicate glass, MgO and silicon do not exhibit long-range order but are magnetic as is evident from the non-zero coercive field and magnetization energy. Phase contrast microscopy revealed that the grain sizes increase from a value of 30-50 nm at ambient temperature to 120-150 nm at 503 K and remain approximately constant in this range up to 593 K. The existence of grain boundary walls of width 30-50 nm is demonstrated using phase contrast images. The grain boundary area also stagnates at higher substrate temperature. There is pronounced shape anisotropy as evidenced by the increased aspect ratio of the grains as a function of substrate temperature. Nickel thin films of 50 nm show the absence of long-range crystalline order at ambient temperature growth conditions and a preferred [111] orientation at higher substrate temperatures. Thin films are found to be thermally relaxed at elevated deposition temperature and having large compressive strain at ambient temperature. This transition from nanocrystalline to crystalline order causes a peak in the coercive field in the region of transition as a function of thickness and substrate temperature. The saturation magnetization on the other hand increases with increase in substrate temperature.

11 illus, 46 ref

015773   Patra A K;Sastry P U;Mukherjee S T;Bedekar V; Tyagi A K (Solid State Physics Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: apatra@barc.gov.in) : Small angle neutron scattering study of pore microstructure in ceria compacts. Pramana J Phys 2008, 71(5), 1057-61.

Ceria powders were prepared by gel combustion process using cerium nitrate and hitherto unexplored amino acids such as aspartic acid, arginine and valine as fuels. The powders have been characterized by X-ray and laser diffraction. Cold pressed compacts of these powders have been sintered at 1250°C for 2 h. Internal pore microstructure of the sintered compacts has been investigated by small angle neutron scattering (SANS) over a scattering wave vector q range of 0.003-0.17 nm^{-1. The SANS profiles indicate surface fractal morphology of the pore space with fractal dimensionality lying between 2.70 and 2.70.}

3 illus, 1 table, 10 ref

015772   Padalakshmi M;Shaikh A M (Solid State Physics Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: shaikham@barc.gov.in) : Effect of adding Ar gas on the pulse height distribution of BF₃-filled neutron deterctors. Pramana J Phys 2008, 71(5), 1177-81.

Boron trifluoride (BF₃) proportional counters are used as detectors for therªmal neutrons. They are characterized by high neutron sensitivity and good gamma disªcriminating properties. Most practical BF₃ counters are filled with pure boron trifluoride gas enriched up to 96% ^{10B. But BF₃ is not an ideal proportional counter gas. Worsening of plateau characteristics is observed with increasing radius due to impurities in gas. To overcome this problem, counters are filled with BF₃ with an admixture of a more suitªable gas such as argon. The dilution of BF₃ with argon causes a decrease in detection efficiency, but the pulse height spectrum shows sharper peaks and more stable plateau characteristics than counters filled with pure BF₃. The present investigations are underªtaken to study the pulse height distribution and other important factors in BF₃+Ar filled signal counters for neutron beam applications. Tests are performed with detectors with cylindrical geometry filled with BF₃ gas enriched in 10B to 90%, and high purity Ar in different proportions. By analysing pulse height spectra, a value of 6.1 ñ 0.2 has been obtained for the branching ratio of the 10B(n,a) reaction.}

3 illus, 4 ref

015771   Omolo J A (Physics Dep, Maseno University, P.O. Private Bag, Maseno, Kenya) : Revisiting non-degenerate parametric down-conversion. Pramana J Phys 2008, 71(6), 1311-20.

The quantum dynamics of a two-mode non-resonant parametric down-conversion process is studied by recasting the time evolution equations for the basic operators in an equivalent spin equation form with simpler exact solutions for a pump field with harmonic time dependence. Expectation values of suitable operators for studying important features such as squeezing and quantum revivals are presented in simple forms.

10 ref

015770   Nath G;Paikaray R (Engg Physics Dep, Dhaneswar Rath Institute of Engg and Management Studies (DRIEMS), Tangi, Cuttack-754-754 022, Email: ganesh_nath99@yahoo.co.in) : Frequency dependent studies of acoustic parameters in binary mixture of non-polar and polar liquid. Ultra Scient phys Sci 2009, 21(2), 333-8.

The binary mixture of di-isopropylether (DIPE) and toluene has been studied extensively from the view point of their acoustic behaviour at different frequencies (1 MHz, 3MHz and 5MHz) and constant temperature 303K. Experimental values of ultrasonic velocity and density are used to compute the derived parameters. Further, these values are used for the calculation of excess parameters, since excess parameters are a better measure of intermolecular interactions than the derived ones. The variations of these excess parameter with frequencies are useful in several industrial and technological processes.

7 illus, 13 ref

015769   Munirathnam B;Madhavan J (Physics Dep, Sir Theagaraja College, Chennai-600 021) : Investigations on the structural, mechanical and photoconductive studies of pure and lanthanum doped potassium pentaborate single crystals. Indian J Sci Technol 2009, 2(2), 44-5.

Single crystals of pure and lanthanum doped potassium pentaborate (KB5) have been successfully grown by slow solvent evaporation technique. The grown crystals are confirmed by powder X-ray diffraction (PXRD). The mechanical strengths of the pure and doped crystals were found out using Vicker's micro hardness tests. The Second Harmonic Generation (SHG) of the crystals are confirmed by Nd:YAG pulsed laser employing Kurtz powder technique. The photoconductive studies reveal the negative photoconductive nature of the grown crystals.

5 illus, 1 table, 4 ref

015768   Mukesh Kumar;Shahi D K;Nirmal Kumar;Pradhan K S (NO, , Diwakar Bhawan Mishratola, Email: mukbihar@rediffmail.com) : Millimeter wave propagation through vertical layer of dust particles. Ultra Scient phys Sci 2009, 21(2), 355-60.

Deals with the propagation of millimeter wave through the layers of dielectric bodies. In order to obtain the expression for power loss each layer has been assumed as a dielectric wave guide tied with dielectric particles. Using the concept of electromagnetic wave propagation through a wave guide the expression for dielectric loss has been obtained. It has been found that the dielectric loss increases with increasing frequency and decreases with increasing visibility. It has been also found that the dielectric loss of the incident energy dependence heavily on particle size for different frequencies and visibility. In the lower range of tile frequency the dielectric loss dominates over other losses, however at the higher range of the frequency the absorption loss has got its minimum value.

4 illus, 10 ref

015767   Mukesh kumar;Shahi D K;Manoj Kumar;Pradhan K S (NO, , Diwakar Bhawan Mishra Tola, Gannipur, Muzaffapur-842 001) : Millimeter wave propagation through the layers of dielectric bodies. Ultra Scient phys Sci 2009, 21(2), 327-32.

Deals with the propagation of millimeter wave through the layers of dielectric bodies. Theoretical investigation has been carried out to estimate the absorption loss (Pabs) in which the wave guide has been utilized. For simplicity of the problem each layers of the dielectric body has been considered as a wave guide and entire layers equated as a number of transmission lines in cascade. Consequently the equation for reflection coefficient and transmission coefficient has been developed. It will be further utilized for the evaluation of absorption loss as function of frequency and the particle density. The result has good agreement with theoretical value.

4 illus, 5 ref

015766   Mortensen K (Natural Sciences, University of Copenhagen, 1871 Frederiksberg, Denmark, Email: kell@life.ku.dk) : Stabilit of ordered phaes in block copolymer melts and solutiosn. Pramana J Phys 2008, 71(5), 903.

Block copolymer melts and solutions assemble into nanosized objects that order into a variety of phases, depending on molecular parameters and mutual interactions. Beyond the classical phases of lamella ordered sheets, hexagonally ordered cylinders and cubic ordered spheres, the complex bicontinuous gyroid phase and the modulated lamellar has been are observed near the phase boundaries. The stability of these phases has been discussed on the basis of theoretical calculations. Here, we will discuss new experimental results showing that the given ordered phase depends critically on both molecular purity and mechanical treatment of the sample. While a variety of block copolymer micellar systems have been shown to undergo the liquid-to-bcc-to-fcc phase sequence upon varying micellar parameters (or temperature), we find for a purified system a different sequence, namely liquid-to-fcc-to-bcc 1. The latter sequence is by the way the one predicted for pure block copolymer melts. External fields like shear or stress may also affect the ordered phase. Applying well-controlled large-amplitude oscillatory shear can be used to effectively control the texture of soft materials in the ordered states. As an example, we resent results on a body-cent red-cubic phase of a block copolymer system, showing how given texture can be controlled with the application of specific shear rate and shear amplitude 2,3. Shear may however also affect the thermodynamic ground state, causing ear-induced ordering and disordering (melting), and shear-induced order-order transitions. We will present data showing that the gyroid state of diblock copolymer melts is unstable when exposed to large amplitudefrequency shear, transforming into the hexagoal cylinder phase 4. The transformation is completely reversible. With the rather slow inetics in the transformation of copolymer systems, it is possible in detail to follow the complex transformation process, where we find transient ordered structures [5].

015765   Moon M;Lee C;Cheon J;Choi Y;Kim H;Desai S S (Korea Atomic Energy Research Institute, , 150 Duckjindong, Yusung, Daejeon, Bepublic of Korea-305 353, Email: moonmk@kaeri.re.kr) : Neutron detectors for scattering experiments at HANARO. Pramana J Phys 2008, 71(5), 1189-95.

Position sensitive detectors (PSD) measure the distribution of scattered neuªtrons and are essential tools for neutron scattering experiments. Various types of neutron detectors used at neutron diffractometers are conventional tube detectors, I-D and 2-D PSDs. Korea Atomic Energy Research Institute (KAERI) has been developing various kinds of PSDs to improve the instrument performance and to develop new scattering inªstruments. Our development work is initiated with I-D PSD for residual stress analysis spectrometer and finally the technology is extended to development of 2-D PSD with planar and curved geometry. All PSDs are based on multiwire grid assembly with delay line readout method for position encoding, as the response is faster than charge division method and enables higher count rate capability. Design details and operational characªteristics of some of the PSDs developed, for application at neutron scattering instruments are presented.

5 illus, 5 ref

015764   Mishra S K;Mittal R;Choudhury N;Chaplot S L; Pandey D (Solid State Physics Div, Bhabha Atomic Research Centre, Mumbai-400 085, Email: skmasspd@barc.gov.in) : Inelastic neutron scattering and lattice dynamics of NaNbO₃ and Sr_0.70Ca_0.30TiO₃. Pramana J Phys 2008, 71(5), 1129-34.

NaNbO₃ and (Sr,Ca)TiO₃ exhibit an unusual complex sequence of temperature- and pressure-driven structural phase transitions. We have carried out lattice dynamical studies to understand the phonon modes responsible for these phase transitions. Inelastic neutron scattering measurements using powder samples were carried out at the Dhruva reactor, which provide the phonon density of states. Lattice dynamical models have been developed for SrTiO₃ and CaTiO₃ which have been fruitfully employed to study the phonon spectra and vibrational properties of the solid solution (Sr,Ca)TiO₃.

5 illus, 12 ref

015763   Mazumder S (NO, Solid State Physics Division, Bombay-400 085, Email: smazn@barc.gov.in) : Dynamical scaling laws - a few unanswereed questions. Pramana J Phys 2008, 71(5), 892.

When a system with continuous symmetry is quenched instantly to a broken symmetry state, topological defects appear in an otherwise homogeneous medium of conªtinuous symmetry. Further growth of the topological defects are of continuous nature such that the time evolution of the system can be described by Ginzburg-Landau free energy functionals. The phenomenon of new phase formation is a representative example of first-order transition. The phenomenon is fundamental and of immense interest as an example of a highly nonlinear process far from equilibrium. The second phase grows with time and in later stages all domain sizes are much larger than all microscopic lengths. In the large time limit, the new phase-forming systems exhibit self-similar growth pattern with dilation symmetry, with time-dependent scale, and scaling phenomenon. The phenomenon is indicative of the emergence of a morphological pattern of the domains at earlier times looking statistically similar to a pattern at later times apart from the global change of scale implied by the growth of time-dependent characteristic length scale L(t) - a measure of the time-dependent domain size of the new phase. The scaling hypothesis assumes the existence of a single characteristic length scale L(t) such that the domain sizes and their spatial correlation are time invariant when the lengths are scaled by L(t). Quantitatively, for isotropic systems, the equal-time spatio-temporal composition modulation autocorrelation function g(r, t), which reflects the way in which the mean density of the medium varies as a function of distance from a given point, should exhibit the scaling form with time-dependent dilation symmetry g(r,t) = f(r/L(t)). The scaling function f(r/L(t)) is universal in the sense that it is independent of initial conditions and also interactions as long as they are short ranged. However, form of f(r/L(t)) depends non-trivially on n, the number of components in the vector order-parameter field exhibiting the scaling behaviour, and d, the dimensionality of the system. It is important to note that the scaling hypothesis has not been proved conclusively except for some model systems. The Fourier transform of g(r,t), the structure factor or scattering function B(q, t) for a d dimensional Euclidean system, obeys simple scaling ansatz at later times, S(q, t) = L(t^{)d F(qL(t)).}

015762   Mahto S B;Mahto J P;Pandit S R (Physics Dep, S.K.M. University, Dumka (Santhal Pragana), Jharkhand) : Evaluation of thermoelectric power oscillation in the vicinity of electronic topological transition (ETT). Ultra Scient phys Sci 2009, 21(2), 387-94.

Using the theoretical model developed by Va. M. Blanter et. at. (Nuovo Cemento 12, 1900 (1990) and taking into account the possibility of Fermi surface topology transformations in the presence of magnetic field, the expression in different regions of EIT vicinity has been obtained. On analysing in weak and strong magnetic field, Our analysis shows field dependence of the thermoelectric coefficient. The peaks weak linearly increases with increasing of the magnetic field.

21 ref

015761   Mahto S B;Mahto J P;Pandit S R (Physics Dep, S.K.M. University, Dumka (Santhal Pragana), Jharkhang) : Eelectron relaxation time in the vicinity of electronic topological transition (ETT) in the presence of magnetic field. Ultra Scient phys Sci 2009, 21(2), 301-6.

Kinetic phenomena in the vicinity of electronic topological transition predicted by Lifshitz have been widely studied both theoretically and experimentally. Using one electron Green's function in the framework of temperature diagrammatic technique developed by Ya. M. Blantr et. al. Nuovo Cimento vol. 12, 1900 (1990), we have studied the relaxation time τ(ωΔ) for EET transition. Our result shows that there is an influence of magnetic field of EETrelaxationtime τ(ω, Δ, Ω).

17 ref

015760   Mahto S B;Mahto J P;Pandit S R (Physics Dep, S.K.M. University, Dumka (Santhal Pragana), Jharkhand) : Giant oscillations of thermoelectric power of the normal metal in the presence of magnetic field using electronic topological transition (ETT). Ultra Scient phys Sci 2009, 21(2), 279-84.

Using the theoretical model developed by Ya. M. Blanter et. at. (Nuovo Cemento 12, 1900 (1900). We have studied the giant oscillations of thermoelectric power of the normal metal in the presence of magnetic field. This is achieved because of electronic topological transition (EET). Our theoretically evaluated result indicates the anharmonical behaviour of the thermoelectric power in the region 2π^{2/Ω ≤ ⊥}

1 illus, 18 ref

015759   Li Y F;Ouyang J H;Zhou Y;Liang X S;Zhong J Y (Materials Science Dep, Institute for Advanced Ceramics, Harbin Institute of Technology, PO Box 433, Harbin 150001, PR China) : Synthesis and characterization of nano-sized Ba_xSr_1-xSO₄ (0≤ X ≤ 1) solid solution by a simple surfactant-free aqueosus solution route. Bull Mater Sci 2009, 32(2), 149-53.

Facile aqueous solution route has been employed to synthesize Ba_x Sr_1-x SO₄ (0 ≤ x ≤ 1) solid solution nanocrystals at room temperature without using any surfactants or templates. The as-synthesized products were characterized by means of X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), scanning electron microscopy (SEM), and differential scanning calorimetry-thermogravimetry (DSC-TG). The Ba _x Sr_1-x SO₄ solid solution nanocrystals exhibit an orthorhombic structure and an ellipsoidal-shaped morphology with an average size of 80-100 nm. The lattice parameters of Ba _x Sr_1-x SO₄ solid solution crystals increase with increasing x value. However, they are not strictly coincident with the Vegard's law, which indicates that the as-obtained products are non-ideal solid solutions. The Ba _x Sr_1-x SO₄ solid solution nanocrystals have an excellent thermal stability from ambient temperature to 1300°C with a structural transition from orthorhombic to cubic phase at about 1111°C.

4 illus, 3 tables, 17 ref

015758   Lal J (Intense Pulsed Neutron Source, Argonne National Laboratory, , Argonne, Illinois 60439, USA, Email: jlal@anl.gov) : Structure of polymer chains under confinement. Pramana J Phys 2008, 71(5), 900.

Observe by SANS the structure of neutral polystyrene and charged polystyrene sulphonate chains in semi-dilute solutions confined in a model nanoporous glass, Vycor. The size of the free chains in solution is always larger than the pore diameter, 70. The use of a suitable mixture of hydrogenated and deuterated solvents and polymers enables us to measure directly the form factor of one single chain among the others. Single chain form factor was observed both for bulk and confined chains using the condition of zero average contrast. Our measurements on neutral polymer chains are in agreement with the theoretical predictions established by Daoud and de Gennes for chains confined in a cylindrical pore when the chains are entangled and laterally squeezed but remain ideal at large scale along the cylinder axis because of the screening of the exªcluded volume interactions (so-called regime of semi-dilute cigars). For confined charged polymers, a peak is observed whose intensity increases with molecular weight and the asymptotic l/q scattering region is extended compared to the bulk. We infer that the chains are sufficiently extended, under the influence of confinement, to highlight the large scale disordered structure of Vycor even under contrast matched conditions. The asymptotic behaviour of the observed interchain structure factor is (F128><155>1/q^{2 and (F128><155>l/q2 for free and confined chains respectively.}

015757   Kukreja L M;Das A K;Misra P (Laser Materials Processing Div, Raja Ramanna Centre for Advanced Technology, Indore-452 013, Email: kukreja@rrcat.gov.in) : Nonvolatile resistance memory switching in ZnO thin films. Bull Mater Sci 2009, 32(3), 247-52.

Six decades of research on ZnO has recently sprouted a new branch in the domain of resistive random access memories. Highly resistive and c-axis oriented ZnO thin films were grown by us using d.c. discharge assisted pulsed laser deposition on Pt/Ti/SiO₂/Si substrates at room temperature. The resistive switching characteristics of these films were studied in the top-bottom configuration using current-voltage measurements at room temperature. Reliable and repeated switching of the resistance of ZnO thin films was obtained between two well defined states of high and low resistance with a narrow dispersion and small switching voltages. Resistance ratios of the high resistance state to low resistance state were found to be in the range of 2-5 orders of magnitude up to 20 test cycles. The conduction mechanism was found to be dominated by the Ohmic behaviour in low resistance states, while Poole-Frenkel emission was found to dominate in high resistance state. The achieved characteristics of the resistive switching in ZnO thin films seem to be promising for nonvolatile memory applications.

6 illus, 18 ref

015756   Krishna B M;John M P;Nandakumaran V M (Sophisticated Test and Instrumentation Centre, Cochin University of Science and Technology, Cochin-682 022, Email: bindum@cusat.ac.in) : Performance characteristics of positive and negative delayed feedback on chaotic dynamics of directly modulated InGaAsP semiconductor lasers. Pramana J Phys 2008, 71(6), 1259-69.

The chaotic dynamics of directly modulated semiconductor lasers with deªlayed optoelectronic feedback is studied numerically. The effects of positive and negative delayed optoelectronic feedback in producing chaotic outputs from such lasers with nonlinªear gain reduction in its optimum value range is investigated using bifurcation diagrams. The results are confirmed by calculating the Lyapunov exponents. A negative delayed optoelectronic feedback configuration is found to be more effective in inducing chaotic dy-namics to such systems with nonlinear gain reduction factor in the practical value range.

7 illus, 1 table, 46 ref

015755   Koul D K (NO, Institute of Physics, Silesian University of Technology, Gliwice, Krzywoustego 2, 44-`00 Gliwice, Poland, Email: dkkoul@apsara.barc.ernet.in) : 110°C thermoluminescence glow peak of quartz. 0000, (NULL), (NULL).

The 110°C glow peak of quartz, though unstable at room temperature, has worked wonderfully in archaeology and retrospective dosimetry due to its pre-dose sensitization property. Various aspects of the peak, like its nature, defect centres involved, the impact of different stimuli and its application have been extensively studied. The main aims of this review are to (i) summarize briefly the work carried out on the various facets of this TL glow peak during the last four decades and (ii) identify the areas which need further attention in order to have a better understanding of the luminescence, characteristics of this TL peak.

13 illus, 1 table, 95 ref

015754   Kaushik S D;Braccini V;Patnaik S (School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110 067, Email: spatnaik@mail.jnu.ac.in) : Magnetic field dependence of vortex activation energy: a comparison between Mgb₂, NbSe₂ and Bi₂Ca₂Cu₃O₁₀ superconductors. Pramana J Phys 2008, 71(6), 1335-43.

The dissipative mechanism at low current density is compared in three differªent classes of superconductors. This is achieved by measuring the resistance as a function of temperature and magnetic field in clean polycrystalline samples of NbSe₂, MgB₂ and Bi₂Sr₂Ca₂Cu_{3Ol0 (BSCCO) superconductors. Thermally activated flux flow behaviour is seen in all the three systems and clearly identified in bulk MgB2. While the activation energy at low fields for MgB2 is comparable to Bi2Sr2Ca2Cu3O1O, its field dependence follows a parabolic behaviour unlike a power-law dependence seen in BbSr2Ca2Cu3OlO. We analyse our results based on Kramer's scaling for grain boundary pinning in MgB2 and NbSe2.}

4 illus, 23 ref

015753   Joshi J Y;Aswal V K;Goyal P S (UGC-DAE-CSR Mumbai Centre, Bhabha Atomic Research Centre, Mumbai-400 085, Email: jvjoshi@barc.gov.in) : Small angle neutron scattering study of mixed micelles of oppositely charged surfactants. Pramana J Phys 2008, 71(5), 1039-43.

Structures of mixed micelles of oppositely charged surfactants dodecyltriªmethylammonium bromide (DTAB) and sodium dodecyl sulphate (SDS) have been studied using small angle neutron scattering. The concentration of one of the components was kept fixed (0.3 M) and that of another varied in the range 0 to 0.1 M. The aggregation number and micellar size increase and fractional charge decreases dramatically with the addition of small amount of oppositely charged surfactant. The effect of addition of SDS on DTAB is significantly different from that of the addition of DTAB on SDS. The contrast variation SANS experiments using deuterated surfactant suggests the homogeneous mixing of two components in mixed micellar system.

2 illus, 1 table, 9 ref

015752   Johnson M (NO, Institut Laue Langevin, Grenoble, France, Email: Johnson@ill.fr) : Intermolecular hydrogen bonds: from temperature-driven proton transfer in molecular crystals to denaturation of DNA. Pramana J Phys 2008, 71(5), 899.

Combined neutron scattering and a range of numerical simulations to study hydrogen bonds in condensed matter. Two examples from a recent thesis will be presented. The first concerns proton transfer with increasing temperature in short intermolecular hydrogen bonds 1, 2. These bonds have unique physical and chemical properties and are thought to play a fundamental role in processes like enzymatic catalysis. By combining elastic and inelastic neutron scattering results with ab initio, lattice dynamics and molecular dynamics simulations, low frequency lattice modes are identified which modulate the potential energy surface of the hydrogen bond proton and drive proton transfer. The second example concerns base-pair opening in DNA which is the fundamental physªical process underlying biological processes like denaturation and transcription. We have used an emprical force field and a large scale, all-atom phonon calculation to gain insight into the base-pair opening modes and the apparent energy gap between the accepted frequencies for these modes (F128><126>100 cm^{-1 or (F128><126>140 K) and the temperature of the biological processes (room temperature to 100(F128><144>C) [3]. Inelastic neutron scattering spectra on aligned, highly crystalline DNA samples, produced at the ILL, provide the reference data for evaluating the precision of these simulation results.}

3 ref

015751   Jayarama A;Suresh Kumar M R;Dharmaprakash S M;Chitra R;Choudhury R R (Physics Dep, Mangalore univ, Mangalagangotri-574 199, Email: rchitra@barc.gov.in) : Thiourea-deped ammonium dihydrogen phosphate: a single crystal neutron diffraction investigation. Pramana J Phys 2008, 71(5), 905-10.

Thiourea-doped ammonium dihydrogen phosphate (TADP) exhibits nonlinªear optical property and the second harmonic generation efficiency of these crystals is three times that of pure ammonium dihydrogen phosphate (ADP) crystal. In this context, the study of structural distortion in the thiourea-doped ADP crystal is significant, hence single neutron diffraction investigations were undertaken. The final R-factors are RF^{2 2(F128><115>(F2) 0.11, Goodness of fit(S) 1.15. Though the dopant could not be located from the difference Fourier map, the cell parameters (a b 7.531(3) Angstrom, c 7.544(5) Angstrom) were found to be significantly greater than that of pure ADP at RT (a b 7.502(1) Angstrom, c 7.546(1) Angstrom). This indicates that the dopant concentration in the crystals is small but enough to bring changes in the overall average structure.}

3 illus, 4 tables, 7 ref

015750   Jain S R;Jain A R;Kailas S (Nuclear Physics Div, Bhabha Atomic Research, Centre, Mumbai-400 085, Email: arjain@barc.gov.in) : Electric dipolarizability of <. Pramana J Phys 2008, 71(6), 1271-7.

Calculates the electric dipolarizability of ^{7Li nucleus within the cluster model and estimate a value of about 0.0188 fm3. We also discuss the possibility of observing this in the scattering of 7Li from a 208Pb target at energies about 30 MeV.}

12 ref

015749   Jain A;Yusuf S M;Sher Singh (Solid State Physics Div, Bhabha Atomic Research Centre, Mumbai-100 085, Email: smyusuf@barc.gov.in) : Neutron diffraction study of quasi-one-dimensional spin-chain compounds Ca₃CO_2-xFe_xO₆. Pramana J Phys 2008, 71(5), 923-27.

Reports the results of the DC magnetization, neutron powder diffraction and neutron depolarization studies on the spin-chain compounds Ca₃Co_2-xFe_x06 (x = 0, 0.1, 0.2 and 0.4). Rietveld refinement of neutron powder diffraction patterns at room temperature confirms the single-phase formation for all the compounds in rhombohedral structure with space group R3c. Rietveld refinement also confirms that Fe was doped at the trigonal prism site, 6a (0, 0, 1/4) of Co. The high temperature magnetic susceptibility obeys the Curie-Weiss law; the value of the paramagnetic Curie temperature (θ_p) decreases as the concentration of iron increases and it becomes negative for x = 0.4. No extra Bragg peak as well as no observable enhancement in the intensity of the fundamental (nuclear) Bragg peaks has been observed in the neutron diffraction patterns down to 30 K. No depolarization of neutron beam has been observed down to 3 K confirming the absence of ferra- or ferrimagnetic-like correlation.

3 illus, 1 table, 4 ref

015748   Iyer R;Desai R;Upadhyay R V (Physics Dep, St. Xavier's College, Ahmedabad-380 009, Email: rajesh_iyer29@yahoo.com) : Low temperature synthesis of nanosized Mn_1-xZn_xFe₂O₄ ferrites and their characterizations. Bull Mater Sci 2009, 32(2), 141-7.

Nanosized Mn1-x Zn_x Fe₂O₄ (x = 0, 0.1, 0.3, 0.5, 0.6, 0.7, 0.9) mixed ferrite samples of particle size < 12 nm were prepared using the co-precipitation technique by doping the Zn^{2+ ion impurities. Autoclave was employed to maintain constant temperature of 80°C and a constant pressure. The X-ray nalysis and the IR spectrum analysis were carried out to confirm the spinel phase formation as well as to ascertain the cation distribution in the ferrite samples. This clearly points to the fact that the Zn2+ ion's presence is not restricted to A-site alone for some of the Mn-Zn ferrite series. The real part of a.c. susceptibility measurements clearly indicated the superparamagnetic behaviour of the ferrite samples. There is a systematic decrease in the particle size, Curie temperature and magnetization with the increase in the Zn2+ ion doping, measured using magneto thermal gravimetric analysis (MTGA) and vibrating sample magnetometer (VSM), respectively. The lattice constant is found to be constantly decreasing till x = 0.6 and beyond this an unusual slight increase in the lattice constant is found.}

6 illus, 2 tables, 35 ref

015747   Hodges J P (Neutron Scattering Sciences Div, Spallation Neutron Source, Oak Ridge National Laboratory, P.O. Box 2008, TN 37831-6474, USA, Email: hodgesj@ornl.gov) : Opportunities for in-situ diffraction studies of advanced materials under extreme conditions at the US spallation neutron source. Pramana J Phys 2008, 71(5), 897.

The spallation neutron source (SNS) is an accelerator-based neutron source in Oak Ridge, Tennessee. Currently ramping up to 1.4 MW operating power, SNS will provide the most intense pulsed neutron beams in the world for scientific research and industrial development. Built by a partnership of six DOE laboratories SNS is operated as a user facility, open to scientists and engineers from universities, industry, and government laboratories in the United States and abroad. Eighteen dedicated beamline instruments are currently funded four are completed and in operation, five are to be commissioned within a year and the others are at various stages of design and construction. AIl instruments at SNS have been designed to best in class and will provide unprecedented opportunities to explore the structure and dynamics of all materials. Amongst the funded instruments are a high-resolution very fast powder diffractometer (POWGEN3) optimized for parametric studies of materials under a wide range of conditions (T, P, H and flowing gases), an ultrahigh-pressure diffractometer (SNAP) for materials under extreme conditions of pressure (up to 100 GPa) and temperature, an engineering materials diffractometer (VULCAN) for mapping strain, texture and fundamental aspects of materials behaviour of high performance materials under strain forces, a high flux disordered materials diffractometer (NOMAD) for liquids, glasses and disorder in crystalline materials, and a small angle scattering diffractometer (EQSANS) for investigating precipitates, crystallization, domains and nanoparticles in composite materials. ORNLSNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.

015746   Hamilton W A;Porcar L;Warr G G;Butler P D (NO, Bragg Institute, Australian Nuclear Science and Technology Organisatio, Lucas Heights, NSW 2234, Australia, Email: william.hamilton@ansto.gov.au) : Constraint and flow: poiseuille shear response of a surfactant sponge phase. Pramana J Phys 2008, 71(5), 904.

To minimize their free energy in aqueous solution, surfactant molecules self-assemble to form some basic morphologies - globular micelles, highly extended the like micelles and membrane bilayers - which themselves order to display a rich variety of mesophase symmetries and properties. In membrane systems one of the more striking distinctions is that between the free flowing L₃ sponge phase and the adjacent highly birefringent viscous L_(F128><97> phase. Their different macroscopic properties reflect the mesophase membrane ordering - highly anisotropic stacking in the L_(F128><97> phase, and isotropic labyrinth of interconnecting passages in L₃ sponges spanning solution space, 1 without long range order. Our group has spent a number of years investigating the shear flow responses of L₃ phases as well as their accommodation to the constraint of a proximate surface - in both these situations over appropriate ranges the higher symmetry the stacked membrane phases is established. These phases exhibit a strong dynamical scaling due to their entropic stabilization by hydrodynamic fluctuations, and a narrow of this fluctuation spectrum in the proximity of a solid surface must also to some ext frustrate these membranes dynamically as well as geometrically. In recent experiments, we have begun measurements of the Poiseuille surface shear response of sponge phase situation in which one might expect effects from an interplay between these dynamic and geometric effects.

015745   Gupta R;Gupta M;Gutberlet T (VES College of Arts, Science and Commerce, , Sindhi Society, Chembur, Mumbai-400 071, Email: dr.rechana.gupta@gmail.com) : Magnetization in permalloy thin films. Pramana J Phys 2008, 71(5), 1123-7.

Thin films of permalloy (Ni₈₀Fe₂₀) were prepared using an Ar+N₂ mixture with magnetron sputtering technique at ambient temperature. The film prepared with only Ar gas shows reflections corresponding to the permalloy phase in X-ray diffraction (XRD) pattern. The addition of nitrogen during sputtering results in broadening of the peaks in XRD pattern, which finally leads to an amorphous phase. The M-H loop for the sample prepared with only Ar gas is matching well with the values obtained for the permalloy. For the samples prepared with increased nitrogen partial pressure the magnetic moment decreased rapidly and the values of coercivity increased. The polarized neutron reflectivity measurements (PNR) were performed in the sample prepared with only Ar gas and with nitrogen partial pressure of 5 and 10%. It was found that the spin-up and spin-down reflectivities show exactly similar reflectivity for the sample prepared with Ar gas alone, while PNR measurements on 5 and 10% sample show splitting in the spin-up and spin-down reflectivity.

3 illus, 12 ref

015744   Gupta M;Gupta A;Wildes A;Gutberlet T (UGC-DAE Consortium for Scientific Research, , -R-5 Shed, Bhabha Atomic Research Centre, Email: mgupta@car.ernet.in) : Fe and N difusion in nitrogen-rich FeN measured using neutron reflectometry. Pramana J Phys 2008, 71(5), 1085-9.

Grazing incidence neutron reflectometry provides an opportunity to measure the depth profile of a thin film sample with a resolution <1 nm, in a non-destructive way. In this way the diffusion across the interfaces can also be measured. In addition, neutrons have contrast among the isotopes, making it feasible to measure the self-diffusion. In the present work, the isotope multilayers of [FeN/⁵⁷FeN]₁₀ and [FeN/Fe¹⁵N]₁₀ were prepared using magnetron sputtering and self-diffusion of Fe and N was investigated. It was found that N diffusion is slower compared to Fe and does not follow the atomic size dependence.

3 illus, 15 ref

015743   Gunasekaran S;Kumaresan S;Arun Balaji R;Anand G;Seshadri S (Spectrophysics Research Laboratory, Pachaiyappa's College, Chennai-600 030, Email: yeskay72@gmail.com) : Vibrational spectra and normal corrdinate analysis on structure of chlorambucil and thioguanine. Pramana J Phys 2008, 71(6), 1291-1300.

A normal coordinate analysis on chlorambucil and thioguanine has been carried out with a set of symmetry coordinates following Wilsons F-G matrix method. The potential constants evaluated for these molecules are found to be in good agreement with literature values thereby confirming the vibrational assignments. To check whether the chosen set of vibrational frequencies contribute maximum to the potential energy associated with the normal coordinates of the molecule, the potential energy distribution has J been evaluated.

4 illus, 2 tables, 28 ref

015742   Goswami M;Sahoo S (Physics Dep, Regional Institute of Education (NCERT), Bhubaneswar-751 022) : Ultimate stable element Z = 137. Indian J Sci Technol 2009, 2(3), 16-19.

Analysed and highlighted an interesting prediction of Subrahmanyam Chandrasekhar that Z = 137 will be the ultimate element that can be artificially synthesised. The heaviest element found till today is of atomic number Z = 122 and atomic mass A = 292. The last possible stable element has, in fact, been a matter of disagreement.

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