Absolute stability of explicit Runge-Kutta-Nyström methods for y″=ƒ(x,y, y′)

We examine absolute stability of s-stage explicit Runge-Kutta-Nyström (R-K-N) methods of order s for $\text{s=2, 3, 4}\text{for}\text{y″=?(x, y, y′)}$ by applying these methods to the test equation: y″+2λy′+λ²y=0, λ>0. We show the existence of R-K-N methods of orders two, three and four possessing intervals of absolute stability as large as that of explicit Runge-Kutta (r-K) methods of respective orders.     

Extension to three dimensions of a holographic-moiré technique to separate patterns corresponding to components of displacement

The holographic-moiré technique to obtain separate patterns for the Cartesian components of the displacement vector is extended to curved surfaces. An initial pattern which is often required for the observation of the displacement fringes is analyzed for this case. Criteria are established for the localization of this initial pattern to follow close to the contour of the object surface. A PVC pipe subjected to torsion demonstrates the proposed technique and, when analytical arguments are checked experimentally, a close correlation is observed.     

Estimating errors of numerical approximation for analytic functions

Summary It is shown that very nearly the same estimates for the errors of numerical approximation for analytic functions can be obtained more simply through Cauchy's integral formula that otherwise result from Davis' method using Hilbert space techniques.Research supported in part by the Atomic Energy Commission under contract U.S. AEC AT (11-1) 1469, and in part by the National Science Foundation under grant NSF-GJ-812.     

Structural phase diagram for ZnS nanocrystalline thin films under swift heavy ion irradiation

The synthesis of nanocrystalline ZnS thin films by pulsed laser deposition and their modification by swift heavy ions are presented. The irradiations with 150 MeV Ni ions at fluences of 1×10¹¹, 1×10¹² and 1×10¹³ ions/cm² have been used for these studies. Irradiation results in structural phase transformation and bandgap modification of these films are investigated by using X-ray diffraction and UV-visible absorption measurements, respectively. Since stoichiometry changes induced by irradiation can contribute to the modification of these properties, elastic recoil detection analysis has been performed on pristine and 150 MeV Ni ions irradiated ZnS thin films using a 120 MeV Ag ion beam. The stoichiometry of the films has been found to be similar for pristine and ion irradiated samples. A structural phase diagram based on thermal and pressure spikes has been constructed to explain the structural phase transformation.     

Polymeric stabilization of hybrid nanocomposites: a comparison between in situ and ex situ-grown CuInS2 in poly(3-hexylthiophene) polymer

CuInS₂ (CIS) particles were directly synthesized in P3HT matrix with different concentrations ratio of P3HT and CIS (1:2, 1:4, and 1:8) by decomposition of copper indium xanthate (CIX). Here, copper indium xanthate and P3HT were mixed homogeneously in o-dichlorobenzene (DCB), which induced the formation of the CIS nanoparticles by the thermal decomposition of the precursor compound in situ at temperatures as low as 110 °C. The effects of the precursor concentration on the size of the CIS nanoparticles was studied by microstructure investigations (TEM, AFM, XRD) and UV–vis measurements show that these CIS composites possess a direct bandgap energy higher than 1.45 eV depending on the concentration of P3HT. PL quenching of P3HT polymer (i.e., higher accessible fraction of fluorophores) was found to be more for in situ rather than ex situ conditions for comparable CIX concentrations or particle size. This can be attributed to the fact that in in situ synthesis, P3HT act as surface directing template for CIS nanoparticles which is not so in the case of ex situ synthesis. Due to this, the polymeric stabilization of the CIS nanocomposites is better realized for in situ synthesis as compared to ex situ synthesis.     

Cloud Point Studies of Tween and Glycol in the Presence of Salts

This article deals with the cloud point studies of ethoxylated sorbitan ester, Tween in the presence of glycols, and salts. Cloud point temperature of Tween 20 (5 mol dm^?3) and Tween 80 (1 mol dm^?3) has been determined in the presence of various salts in addition to glycols. The glycols chosen for these studies were triethylene glycol (TEG), and ethylene glycol mono butylether (EGMBE). At concentration below 0.02 M these salts have no significant effect on cloud point temperature in all cases. The cloud point temperature of Tween+TEG and Tween+EGMBE found to decrease in the presence of sodium chloride (NaCl) and potassium chloride (KCl). The cloud point temperature of Tween 20 + TEG and Tween 20 + EGMBE found to increase in the presence of urea and nicotinamide. The change in cloud point was found to be more in case of nicotinamide as compare to urea. The influence of an additive on the cloud point depends on how it affects the intermicellar interactions. An effort has been made to understand the interaction between solvent and additives leading to a change in solubility of Tween.     

A Facile Synthesis of Tetracycles of the γ-Lycorane Type

When an attempted application of the general scheme of alkaloid synthesis, based on the partial hydrogenation of 1 -alkyl-3-acylpyridinium salts and acid-induced cyclization of the resultant 2-piperideines,² to the construction of an Amaryllidaceae alkaloid system failed in the cyclization step, i.e. the transformation of dihydroisoquinoline 4a (prepared by the treatment of ester 2a ³ with 5-bromo-2 -pentanone ethylene ketal, followed by hydrogenation of the salt over palladium-charcoal) into a tricyclic ketal ester,⁴ an alternate, route of synthesis still utilizing a previously prepared isoquinoline precursor (3b) was investigated. The initial observation of the easy conversion of 3b into N-methyl (1a) and O-ethyl products (2b) was helpful in this connection.     

Highly regioselective ring-opening of aziridines with arenesulfinates on water: a facile access to β-amino/vinyl sulfones

We have developed a LiBr catalyzed efficient synthesis of β-amino sulfones from readily available aziridines and sodium sulfinates in good to excellent yields. The synthetic potential of β-amino sulfones has also been demonstrated by their facile conversion to the corresponding vinyl sulfones. The use of water as reaction media, atom-economy and isolation of products by simple filtration in the case of solid β-amino sulfones are certain green virtues of the synthetic protocol.     

TL and EPR studies of CaSO4:Dy phosphor to investigate its efficacy in measurement of food irradiation dose at sub-ambient temperatures

The effects of sub-ambient temperatures of irradiation and dose response of CaSO₄:Dy phosphor was investigated. The irradiation dose in the range 0.5–7.0 kGy was chosen to meet the requirement of commercial food irradiation at low temperature. Commercially available phosphor showed no significant change in glow curve structure with low temperature of irradiation. In order to enhance the sensitivity of the low temperature glow peak (142 °C), the phosphor was subjected to different post-preparation thermal treatments at 700–900 °C. The change in glows and improvement in dose response characteristics were explained by Electron Paramagnetic Resonance (EPR) spectroscopy. At sub-ambient temperature of irradiation, the behavior of thermally treated CaSO₄:Dy phosphor with increasing dose revealed improved linear response of the low temperature glow peak and could be an efficient dosimetry system for the food commodities irradiated at low temperatures.