Ultrafine powders of SrTiO3 from the hydrothermal preparation and their catalytic activity in the photolysis of water

Ultrafine powders of SrTiO3 are prepared at 100–150°C by the hydrothermal method, starting from TiO2·xH2O gel and Sr(OH)2 and H2O-isopropanol mixed solvent as the medium, The X-ray diffractograms of the powder show line broadening. The minimum crystallite size obtained ranges from 5 to 20nm with 20% H2O-80% C3H7OH as the reaction medium, as estimated from X-ray half-peak widths and TEM studies. The electron diffraction results indicate high concentration of lattice defects in these crystallites. The optical spectra of the particle suspensions in water show that the absorption around the band gap is considerably broadened, together with the appearance of maxima in the far ultraviolet. Aqueous suspensions of SrTiO3 powders, as such, do not produce H2 or O2 on UV irradiation. After coating with rhodium, H2 and O2 are evolved on illumination. However, the turn over number of O2 is lower than the stoichiometrically expected values from the corresponding values of H2. No correlation of the photocatalytic activity with surface area is observed. The activity of Rh-SrTiO3 slowly deteriorates with extended period of irradiation.

Heat-Transfer During Dropwise Condensation

A comprehensive model is developed for previous termheat transfernext term during previous termdropwise condensationnext term based on the assumption that previous termheat transfernext term takes place through the bare surface in between drops to form nuclei at nucleation sites during the waiting period required for nucleation. The dynamics of drop formation and surface renewal, and the presence of non-condensable gases in the vapour have been considered. The resulting equation expresses the dependence of the vapour-side previous termheat transfernext term coefficient on the previous termheatnext term flux, properties of the vapour, previous termcondensationnext term coefficient, mole fraction of non-condensable gases in the vapour, free area available for previous termcondensation,next term surface roughness and surface thermal properties. The equation is tested with the available data and the agreement is found to be satisfactory.

Salan: A microprocessor-based medium speed experimental local area network

In this paper the implementation and application of a microprocessor-based medium speed experimental local area network using a coaxial cable transmission medium are dealt with. A separate unidirectional control wire has been used in order to provide a collision-free and fair medium access arbitration. As an application of the network, the design of a packet voice communication system is discussed.

Film cooling at hypersonic Mach numbers using forward facing array of micro-jets

Experimental investigations are carried out in the IISc hypersonic shock tunnel on film cooling effectiveness of a single jet (diameter 2 mm and 0.9 mm), and an array forward facing of micro-jets (diameter 300 mu m each) of same effective area (corresponding to the respective single jet). The single jet and the corresponding micro-jets are injected from the stagnation zone of a blunt cone model (58, apex angle and nose radius of 35 mm). Nitrogen and Helium are injected as coolant gases. Experiments are performed at freestream Mach number 5.9, at 0 degrees angle of attack, with a stagnation enthalpy of 1.84 MJ/kg, with and without injections. The ratios of the jet stagnation pressure to the freestream pitot pressure used in the present study are 1.2 and 1.45. Up to 50% reduction in surface heat transfer rate was observed with the array of micro-jets, compared to that of the respective single jet with nitrogen as the coolant, while the corresponding eduction was up to 37% for helium injection, with the schlieren flow visualizations showing no major change in the shock standoff distance, and thus no major changes in other aerodynamic aspects such as drag.

Theory of the mixed valent state

After briefly discussing the question of a distinct mixed valent state and theoretical models for it, the area of greatest theoretical success, namely the mixed valent impurity, is reviewed. Applications to spectroscopy, energetics and Hall effect are then putlined. The independent impurity approximation is inadequate for many properties of the bulk system, which depend on lattice coherence. A recent auxiliary or slave boson approach with a simple mean field limit and fluctuation corrections is summarized. Finally the mixed valent semiconductor is discussed as an outstanding problem.

Design of high-order filters with restricted component values

The feasibility of realising a high-order LC filter with a small set of different capacitor values, without sacrificing the frequency response specifications, is indicated. This idea could be conveniently adopted in other filter structures also—for example the FDNR transformed filter realisations.

Nucleosome core protein: Asymmetric dissociation of the octamer

The octameric nucleosomal core-histone complex, (H2A)2-(H2B)2-(H3)2-(H4)2, isolated from rat liver, undergoes dissociation during gel exclusion chromatography as a result of dilution occurring in the columns. The elution pattern at pH 7.0 and 4°C showed a sharp leading peak containing all four histones but predominantly H3 and H4, and a trailing peak containing equal amounts of histones H2A and H2B. As column length was increased the area under the leading peak decreased and that under the trailing peak increased. In addition the relative positions of the two peaks varied with column length. From an analysis of the data on increase in elution volume of the leading peak in relation to column length an apparent molecular weight of 86 000 was calculated for the undissociated molecule. Its apparent molecular weight, histone composition and pattern of further dissociation in relation to column length suggest that this species is the hexamer, (H2A-H2B)-(H3)2-(H4)2. At pH 7.0 and 4°C the dissociation of the core complex appears to be as follows: (H2A)2-(H2B)2-(H3)2-(H4)2 → (H2A-H2B) + (H2A-H2B)-(H3)2-(H4)2 → 2(H2A-H2B) + (H3)2-(H4)2 This dissociation was accelerated by an increase in temperature or decrease in pH and was accompanied by marked conformational changes as judged by circular dichroism measurements.

A novel combustion process for the synthesis of fine particle α-alumina and related oxide materials

Synthesis of fine particle α-alumina and related oxide materials such as MgAl2O4, CaAl2O4, Y3Al5O12 (YAG), Image , β′-alumina, LaAlO3 and ruby powder (Image ) has been achieved at low temperatures (500°C) by the combustion of corresponding metal nitrate-urea mixtures. Solid combustion products have been identified by their characteristic X-ray diffraction patterns. The fine particle nature of α-alumina and related oxide materials has been investigated using SEM, TEM, particle size analysis and surface area measurements.

A hydro-wood net-energy approach to hydro project design

An integrated approach to energy planning, when applied to large hydroelectric projects, requires that the energy-opportunity cost of the land submerged under the reservoir be incorporated into the planning methodology. Biomass energy lost from the submerged land has to be compared to the electrical energy generated, for which we develop four alternative formulations of the net-energy function. The design problem is posed as an LP problem and is solved for two sites in India. Our results show that the proposed designs may not be viable in net-energy terms, whereas a marginal reduction in the generation capacity could lead to an optimal design that gives substantial savings in the submerged area. Allowing seasonal variations in the hydroelectric generation capacity also reduces the reservoir size. A mixed hydro-wood generation system is then examined and is found to be viable.

Handpumps: problems and search for remedies

This paper gives a brief survey of research and development work done on hand pumps in India as well as elsewhere and sets out the approach adopted by ASTRA Working Group. Ten ways in which a hand pump breakdown in practice have been identified. The physical reasons behind each type of breakdown analysed. Remedial measures have been developed from this analysis. Laboratory test rigs fabricated to evaluate these measures have been described and some experimental results presented. The course of further work has been charted.

Area Efficient Loop Filter Design for Charge Pump Phase Locked Loop

In this paper, two new dual-path based area efficient loop filtercircuits are proposed for Charge Pump Phase Locked Loop (CPPLL). The proposed circuits were designed in 0.25 CSM analog process with 1.8V supply. The proposed circuits achievedup to 85% savings in capacitor area. Simulations showed goodmatch of the new circuits with the conventional circuit. Theproposed circuits are particularly useful in applications thatdemand low die area.

Visualization of enantiomers using natural abundant 13C-filtered single and double quantum selective refocusing experiments: Application to small chiral molecules

The routine use of proton NMR for the visualization of enantiomers, aligned in the chiral liquid crystal solvent poly-γ-benzyl-l-glutamate (PBLG), is restricted due to severe loss of resolution arising from large number of pair wise interaction of nuclear spins. In the present study, we have designed two experimental techniques for their visualization utilizing the natural abundance 13C edited selective refocusing of single quantum (CH-SERF) and double quantum (CH-DQSERF) coherences. The methods achieve chiral discrimination and aid in the simultaneous determination of homonuclear couplings between active and passive spins and heteronuclear couplings between the excited protons and the participating 13C spin. The CH-SERF also overcomes the problem of overlap of central transitions of the methyl selective refocusing (SERF) experiment resulting in better chiral discrimination. Theoretical description of the evolution of magnetization in both the sequences has been discussed using polarization operator formalism.

Structure, energetics and diffusion properties of isomers of trimethyl benzene in beta zeolite: Uptake and Monte Carlo simulation study

A Monte Carlo study along with experimental uptake measurements of 1,2,3-trimethyl benzene, 1,2,4-trimethyl benzene and 1,3,5-trimethyl benzene (TMB) in beta zeolite is reported. The TraPPE potential has been employed for hydrocarbon interaction and harmonic potential of Demontis for modeling framework of the zeolite. Structure, energetics and dynamics of TMB in zeolite beta from Monte Carlo runs reveal interesting information about the diameter, properties of these isomers on confinement. Of the three isomers, 135TMB is supposed to have the largest diameter. It is seen TraPPE with Demontis potential predicts a restricted motion of 135TMB in the channels of zeolite beta.Experimentally, 135TMB has the highest transport diffusivity whereas MID results suggest this has the lowest self diffusivity. (C) 2009 Elsevier Inc. Ail rights reserved.

Mechanism of adsorption effects on electrode kinetics: Part I: Selection rules in the case of low coverage by molecular surfactants

It is shown that the effect of adsorption of inert molecules on electrode reaction rates is completely accounted for, by introducing into the rate equation, adsorption-induced changes in both the effective electrode area as well as in the electrostatic potential at the reaction site with an additional term for the noncoulombic interaction between the reactant and the adsorbate. The electrostatic potential at the reaction site due to the adsorbed layer is calculated using a model of discretely-distributed molecules in parallel orientation when adsorbed on the electrode with an allowance for thermal agitation. The resulting expression, which is valid for the limiting case of low coverages, is used to predict the types of molecular surfactants that are most likely to be useful for acceleration and inhibition of electrode reactions.

A Framework for Detecting Glaucomatous Progression in the Optic Nerve Head of an Eye Using Proper Orthogonal Decomposition

Glaucoma is the second leading cause of blindness worldwide. Often, the optic nerve head (ONH) glaucomatous damage and ONH changes occur prior to visual field loss and are observable in vivo. Thus, digital image analysis is a promising choice for detecting the onset and/or progression of glaucoma. In this paper, we present a new framework for detecting glaucomatous changes in the ONH of an eye using the method of proper orthogonal decomposition (POD). A baseline topograph subspace was constructed for each eye to describe the structure of the ONH of the eye at a reference/baseline condition using POD. Any glaucomatous changes in the ONH of the eye present during a follow-up exam were estimated by comparing the follow-up ONH topography with its baseline topograph subspace representation. Image correspondence measures of L-1-norm and L-2-norm, correlation, and image Euclidean distance (IMED) were used to quantify the ONH changes. An ONH topographic library built from the Louisiana State University Experimental Glaucoma study was used to evaluate the performance of the proposed method. The area under the receiver operating characteristic curves (AUCs) was used to compare the diagnostic performance of the POD-induced parameters with the parameters of the topographic change analysis (TCA) method. The IMED and L-2-norm parameters in the POD framework provided the highest AUC of 0.94 at 10 degrees. field of imaging and 0.91 at 15 degrees. field of imaging compared to the TCA parameters with an AUC of 0.86 and 0.88, respectively. The proposed POD framework captures the instrument measurement variability and inherent structure variability and shows promise for improving our ability to detect glaucomatous change over time in glaucoma management.