Reduction of silver ions to silver with polyaniline/poly(vinyl alcohol) cryogels and aerogels

The macroporous conducting polymer cryogels were prepared by the oxidation of aniline hydrochloride in the frozen aqueous solutions of poly(vinyl alcohol) at ? 24 °C. Corresponding polyaniline aerogels supported with poly(vinyl alcohol) have been obtained after thawing of cryogels followed by freeze-drying. Silver was deposited on the composites using the ability of polyaniline to reduce silver ions after the immersion in silver nitrate solutions. Swollen cryogels were coated only on the surface with macroscopic silver particles due to the closed-pore structure in cryogels and limited penetration of silver ions into macropores. The diffusion of silver ions to freeze-dried aerogels was better and further improved by vacuum treatment. Silver microcubes were produced in the pores, the weight fraction of silver in dry composites being typically several per cent, a maximum 13 wt%. The conductivity of the aerogels compressed to pellets depended on the processing and the highest value was 0.27 S cm^?1. The aerogels containing silver were characterized in detail with Raman spectroscopy.     

A simple and sensitive particle induced gamma-ray emission method for non-destructive quantification of lithium in lithium doped Nd2Ti2O7 ceramic sample

A particle induced gamma-ray emission method using proton beam in conjunction with in situ current normalization approach was standardized for non-destructive determination of low Z element lithium and was applied for quantification of Li in lithium doped neodymium dititanate (Nd₂Ti₂O₇) ceramic sample. Thick pellets of heat treated samples, their precursors and Li standards were prepared separately by homogeneously mixing with cellulose and fixed amount of F used for in situ current normalization. For validation of the method, four synthetic samples were also analyzed. Samples and standards were irradiated with 4?MeV proton beam (~5?nA current) from folded tandem ion accelerator (FOTIA) BARC, Mumbai. Characteristic ??-rays of 478?keV from ⁷Li to 197?keV from ¹⁹F were measured by high resolution ??-ray spectrometry. The Li concentrations determined in the six samples were in the range of 0.29?C0.85?wt%. The Li contents in heat treated samples gave the idea about loss of Li compared to their precursors.     

Evaluation of the performance characteristics of a thermal transient anemometer

The Goertler instability of a hypersonic boundary layer and its influence on the wall heat transfer are experimentally analyzed. Measurements, made in a wind tunnel by means of a computerized infrared (IR) imaging system, refer to the flow over two-dimensional concave walls. Wall temperature maps (that are interpreted as surface flow visualizations) and spanwise heat transfer fluctuations are presented. Measured vortices wavelengths are correlated to non-dimensional parameters and compared with numerical predictions from the literature.List of symbols c _p Specific heat coefficient at constant pressure of the free stream - F Input (true) image - F ₀ Fourier number - Restored image - G Recorded (degraded) image - G Goertler number based on the boundary layer thickness, as defined by Eq. (3) - H System transfer function - M Mach number - Pr Prandtl number - p ₀ Stagnation pressure - Exchanged net heat flux - Convective heat flux - Radiative heat flux - r Recovery factor - Re _m Unit Reynolds number - Re _x Local Reynolds number based on the distance from the leading edge - Re Local Reynolds number based on the boundary layer thickness - Curvature radius - St Stanton number, as defined by Eq. (7) - T _aw Adiabatic wall temperature - T _w Wall temperature - T ₀ Stagnation temperature - t Time - V Free stream velocity - x Streamwise spatial coordinate - y Normal-to-wall spatial coordinate - z Spanwise spatial coordinate - Thermal diffusivity coefficient - Disturbance wavenumber - Non dimensional wavenumber - Boundary layer thickness - Goertler number based on the vortices wavelength - Vortices wavelength - Free stream density - Disturbance total amplification, as defined by Eq. (3) - Disturbance (spatial) growth rate - Non-dimensional growth rate - Perturbation amplitude of a generic quantity - Perturbation amount     

Tuning commercial diesel to microemulsified and blended form: phase behavior and implications

Abstract

Microemulsification and blending of commercial diesel is under constant research for possible fuel application. Microemulsions (ME) were prepared using diesel (D), kerosene (K), diesel and kerosene mixtures at various proportions (D?+?K) (oil phase: O), Triton X-100 surfactant (S), n-butanol, isobutanol (i-butanol), n-pentanol and n-octanol cosurfactants (C), and aqueous phase (W) containing water or brine for the study. Electrical conductance studies and temperature-induced separation of phase have been adopted for recognizing the o/w, w/o and bicontinuous zones. Dye probing has been done to explain the mass transfer among these phases. Percent of solubilization of oil in water has been enumerated in some of the ME. The possible fuel applications of the microemulsions are predicted from their density and flame brightness.     

Non-destructive compositional analysis of sol–gel synthesized lithium titanate (Li2TiO3) by particle induced gamma-ray emission and instrumental neutron activation analysis

Lithium titanate, one of the important tritium breeding materials in D–T based fusion reactor under ITER programme, was synthesized through sol–gel route. For chemical quality control of finished product, it was necessary to quantify the lithium and titanium contents. As this ceramic sample is difficult to dissolve, non-destructive analytical methods are preferred for compositional analysis. In the present work, two non-destructive nuclear analytical methods namely particle induced gamma-ray emission (PIGE) using proton beam and instrumental neutron activation analysis (INAA) using reactor neutrons were standardized for the determination of lithium and titanium concentrations, respectively and applied to eleven samples of lithium titanate. To the best of our knowledge, Li quantification in lithium titanate sample is being reported for the first time using PIGE. For quantifications of Li and Ti, 478 keV prompt gamma-ray from ⁷Li (p, p′γ) ⁷Li and 320 keV gamma-ray from ⁵⁰Ti (n,γ) ⁵¹Ti were measured, respectively, by high resolution gamma-ray spectrometry. The PIGE and INAA methods were validated using several synthetic samples containing lithium and titanium, respectively. Concentrations of lithium and titanium and Li/Ti mole ratios were evaluated and compared with the stoichiometric concentration of Li₂TiO₃.     

Analysis of SMELS by k 0-based IM-NAA method using PFTS position of KAMINI reactor for quality control exercise

As a part of QA/QC of k ₀-based internal monostandard neutron activation analysis (IM-NAA), three types of synthetic multielement standards (SMELS) were analyzed using pneumatic fast transfer system irradiation position of KAMINI reactor, IGCAR. Radioactive assay of activation products was carried out by high resolution gamma ray spectrometry. IM-NAA was used to determine relative concentration ratios of 22 elements with respect to gold internal monostandard. Absolute concentrations were calculated using assigned concentration of Au in all the types of SMELS. Z-score values within ±1 at 95.5 % confidence level and percentage deviations within ±5 % indicated good quality of the results by IM-NAA in most of the cases. Using this methodology, an ilmenite mineral sample was analyzed and concentrations of 14 elements were determined using Sc as monostandard.     

Evaluation of topographical variation in ocular surface temperature by functional infrared thermography

The objective of this work is to evaluate topographical variation in the ocular surface temperature (OST) among the young, elderly and the subjects wearing contact lens using thermographic methodology. We recorded thermographic sequence lasting of 25 s for each eye. The ocular region in each of the thermal images in the sequence was identified and warped into a standard form. Then, the warped sequence was divided into a number of sub-sequences. A differential image which is an image matrix was obtained from each of these sub-sequences, by subtracting thermal images within the sub-sequence. And the histogram of the differential image was modelled by Gaussian mixture model to discriminate eyelashes from the ocular surface for every thermal image in the sub-sequence. Later, thermal data of eyelashes were eliminated in every thermal image and statistical analysis was performed on the sequences. Finally, topographical profile of each subject group was approximated by equations and illustrated using various temperature profiles. The ocular surface of the young subject was observed to be the warmest, and tear film was determined to play a major role in the topographical and temporal variations in OST. Significant topographical variation was observed among subject groups. Based on our compiled average OST profile (AOSTP), the maximum predictability of the bioheat simulation on ocular model can reach up to 90%.     

Search for dilepton resonances in pp collisions at √s=7 TeV with the ATLAS detector

This Letter reports on a search for narrow high-mass resonances decaying into dilepton final states. The data were recorded by the ATLAS experiment in pp collisions at √s=7 TeV at the Large Hadron Collider and correspond to a total integrated luminosity of 1.08 (1.21) fb(-1) in the e(+)e(-) (μ(+)μ(-)) channel. No statistically significant excess above the standard model expectation is observed and upper limits are set at the 95% C.L. on the cross section times branching fraction of Z' resonances and Randall-Sundrum gravitons decaying into dileptons as a function of the resonance mass. A lower mass limit of 1.83 TeV on the sequential standard model Z' boson is set. A Randall-Sundrum graviton with coupling k/M(Pl)=0.1 is excluded at 95% C.L. for masses below 1.63 TeV.     

Search for a fermiophobic and standard model Higgs boson in diphoton final states

We present a search for the standard model Higgs boson and a fermiophobic Higgs boson in the diphoton final states based on 8.2 fb(-1) of pp collisions at sqrt[s]=1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No excess of data above background predictions is observed and upper limits at the 95% C.L. on the cross section multiplied by the branching fraction are set which are the most restrictive to date. A fermiophobic Higgs boson with a mass below 112.9 GeV is excluded at the 95% C.L.