<Emphasis Type="Italic">T</Emphasis>-Coloring of Certain Networks

Given a graph G and a finite set T of non-negative integers containing zero, a T-coloring of G is a non-negative integer function f defined on V(G) such that \(|f(x)-f(y)|\not \in T\) whenever \((x,y)\in E(G)\). The span of T-coloring is the difference between the largest and smallest colors, and the T-span of G is the minimum span over all T-colorings f of G. The edge span of a T-coloring is the maximum value of \(|f(x)-f(y)|\) over all edges \((x,y)\in E(G)\), and the T-edge span of G is the minimum edge span over all T-colorings f of G. In this paper, we compute T-span and T-edge span of crown graph, circular ladder and mobius ladder, generalized theta graph, series-parallel graph and wrapped butterfly network.     

Electrochemical behaviour of zinc in alkaline solutions

As the whole passivation phenomenon in the case of zinc is very quick and sudden and as it cannot be fully studied and followed by galvanostatic techniques alone, the constant over-potential technique has, for the first time, been applied to zinc and results reported. A special apparatus consisting of suitable oscillator, modulator, demodulator and a stable D.C. amplifier with a gain of 100,000 was used for the purposes and is described. Potential curves for equilibrium current rates, achieved on 0·1 V. and 25 mV. steps after 1 minute each, have been obtained in 6N, N, 0·1 N KOH and zincate solutions for the complete range of ?1·3 to about ?2·0 volts with reference to Hg/HgO/KOH reference electrode. It has been found that in the first truly active region, the main electrode reaction is the formation of zinc ions while after the passivation it changes to gas evolution. Potentiostatic techniques reveal intermediary stages, undisclosed by constant current methods, of pseudo-passivation and current-plateau regions in which the anodic layer thickens, controlled by the high field cation transport. These observations and explanations are further supported by plotting rate-time transients obtained by suddenly dropping the potentials from higher to lower values, when the rates were found to cut off. Some anomalies and sudden reversal of currents with increasing over-voltages, have also been fully discussed. The influence of other factors,e.g., concentration, stirring, sudden changes in over-voltages, presence of zincate, sulphate, etc., has also been considered. Studies such as these are found to throw considerable light on the electrochemical behaviour of zinc.     

Crystal structure and physical characterization of neotame methanol solvate

The crystal structure of the methanol solvate (empirical formula: 2C₂₀H₃₀N₂O₅·3CH₃OH) of a new dipeptide sweetener, neotame (N-(3,3-dimethylbutyl)-L--aspartyl-L-phenylalanine 1-methyl ester), has been determined. Crystal data: a = 9.8989(1), b = 18.1331(1), c = 27.5725(1) Å, orthorhombic, space group P2₁2₁2₁, with Z = 4. Each unit cell includes 8 neotame and 12 methanol molecules. Disorder exists in one neotame molecule and one methanol molecule. The crystals were characterized by the following techniques: hot-stage microscopy (HSM), Karl-Fischer titrimetry (KFT), powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), thermogravimetry (TGA), ¹³C solid-state nuclear magnetic resonance (SSNMR) spectroscopy. Under HSM at a heating rate of 10°C/min in silicone oil, the sample melts at 64–84°C and liberates bubbles at 71–86°C. DSC in open pans shows two overlapping endotherms at 56 and 71°C, probably due to melting and desolvation, respectively. TGA in open pans shows 5.9% weight loss due to desolvation below 70°C. Under house vacuum (23 mm Hg) over phosphorus pentoxide at 23°C, the methanol solvate produces pure amorphous anhydrate, which converts to crystalline neotame monohydrate in the presence of moisture.     

Medium energy,heavy and inert ion irradiation of metallic thin films: studies of surface nano‐structuring and metal burrowing

In context to the ion induced surface nanostructuring of metals and their burrowing in the substrates, we report the influence of Xe and Kr ion‐irradiation on Pt:Si and Ag:Si thin films of ~5‐nm thickness. For the irradiation of thin films, several ion energies (275 and 350 keV of Kr; 450 and 700 keV of Xe) were chosen to maintain a constant ratio of the nuclear energy loss to the electronic energy loss (S_n/S_e) in Pt and Ag films (five in present studies). The ion‐fluence was varied from 1.0 × 10¹⁵ to 1.0 × 10¹⁷ ions/cm². The irradiated films were characterized using Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The AFM and SEM images show ion beam induced systematic surface nano‐structuring of thin films. The surface nano‐structures evolve with the ion fluence. The RBS spectra show fluence dependent burrowing of Pt and Ag in Si upon the irradiation of both ion beams. At highest fluence, the depth of metal burrowing in Si for all irradiation conditions remains almost constant confirming the synergistic effect of energy losses by the ion beams. The RBS analysis also shows quite large sputtering of thin films bombarded with ion beams. The sputtering yield varied from 54% to 62% by irradiating the thin films with Xe and Kr ions of chosen energies at highest ion fluence. In the paper, we present the experimental results and discuss the ion induced surface nano‐structuring of Pt and Ag and their burrowing in Si. Copyright © 2016 John Wiley & Sons, Ltd.     

Spectroscopic and microscopic study of aggregate formation in the nano-dimensional Langmuir-Blodgett films of perylene with a fatty acid/polymer

Perylene (PYL) mixed with Behenic acid (BA) and Polymethyl methacrylate (PMMA) separately have been incorporated in the Langmuir-Blodgett film. The surface pressure versus area per molecule area isotherms are measured at various molar ratios. Stability of the mixed monolayer of PYL and BA/PMMA and their collapse pressure are much higher than that of pure PYL. Negligible amount of hysteresis observed in the compression-decompression isotherms indicate the formation of stable monolayer. Miscibility of the mixed systems is found to vary with the film composition. The formation of PYL aggregates in the mixed films is investigated using UV-Vis absorption spectroscopy, emission spectroscopy and atomic force microscopy (AFM).     

Development of Carbon Materials for Energy and Environmental Applications

Methodologies for generating carbon materials from unusual natural sources like Limonea acidissima and Calotropis gigantea are reported. The carbon materials thus obtained have been characterized using a variety of tools. The possibility of modulating the textural properties of these materials has been examined. The carbon materials synthesized have been exploited for specific applications, such as support for noble metals for use in Direct Methanol Fuel Cells and as support for heteropoly acid for the production of gasoline additive. In addition, the utility of some of the activated carbon materials (from commercial sources) for the removal of sulphur from crude petroleum sources is also examined.     

Surface and interface engineering in transition metal–based catalysts for electrochemical water oxidation

A tremendous effort has been provided in last two decades to develop efficient transition metal–based heterogeneous catalysts for the electrochemical water oxidation. Several approaches such as composition modulation, heteroatom doping, morphological development, particle size tuning, surface area enhancement, and control over electronic structure have been explored for the designing of the materials with improved water oxidation activity. As the electrochemical process is a surface phenomenon, surface structure plays a crucial role in controlling the water oxidation activity. Rational engineering of the catalyst surface by composition modulation, crystal facet tuning, and generating functional overlayer has been reported to enhance the water oxidation activity. Heteroatom doping, cationic and anionic deficiencies, and ultrathin 2D morphology are also found to promote electrochemical performance. In addition, engineering in the interface provides intrinsic improvement of the catalytic activity and stability for the electrochemical water oxidation. Although, surface and interface engineering of the catalyst has come out as the major factors in the electrochemical water oxidation, no dedicated review is available in this field. In this review, we have described the strategies of improving water oxidation activity of the catalysts by surface and interface engineering. The progress in this field discussed in detail; the challenges have been identified and addressed to attain a clear understanding in this field.     

Zur quantitativen Scheidung von Sulfaten und Fluoriden

Ohne Zusammenfassung