Anomalous scattering factors of some rare earth elements evaluated using photon interaction cross-sections

The real and imaginary parts,f’(E) and”(E) of the dispersion corrections to the forward Rayleigh scattering amplitude (also called anomalous scattering factors) for the elements La, Ce, Pr, Nd, Sm, Gd, Dy, Ho and Er, have been determined by a numerical evaluation of the dispersion integral that relates them through the optical theorem to the photoeffect cross-sections. The photoeffect cross-sections are derived from the total attenuation cross-section data set experimentally determined using high resolution high purity germanium detector in a narrow beam good geometry set-up for these elements in the photon energy range 5 to 1332 keV and reported earlier by the authors. Below 5 keV, Scofield’s photoeffect cross-sections compiled in XCOM program have been interpolated and used. Simple formulae forf” in terms of atomic number and energy have also been obtained. The data cover the energy region from 6 to 85 keV and atomic numberZ from 57–68. The results obtained are found to agree fairly well with the other available data.     

Zero-sum stochastic games with stopping and control

We study a zero-sum stochastic game where each player uses both control and stopping times. Under certain conditions we establish the existence of a saddle point equilibrium, and show that the value function of the game is the unique solution of certain dynamic programming inequalities with bilateral constraints.     

Environmentally benign one-pot multicomponent synthesis of 1,4-dihydropyridine derivatives applying montmorillonite K10 as reusable catalyst

Chemistry of Heterocyclic Compounds - Environmentally benign one-pot multicomponent synthesis of different 1,4-dihydropyridine derivatives using montmorillonite K10 has been achieved. The...     

Comparative study of in-cylinder tumble flows in an internal combustion engine using different piston shapes—an insight using particle image velocimetry

This paper deals with the experimental investigations of the in-cylinder tumble flows in a single-cylinder engine with five different piston crown shapes at an engine speed of 1,000 rev/min., during suction and compression strokes under motoring conditions using particle image velocimetry. Two-dimensional in-cylinder tumble flow measurements and analysis are carried out in combustion space on a vertical plane passing through cylinder axis. Ensemble average velocity vectors are used to analyze the tumble flow structure. Tumble ratio and average turbulent kinetic energy are evaluated and used to characterize the tumble flows. From results, it is found that at end of compression, pentroof-offset-bowl piston shows about 41 and 103% improvement in tumble ratio and average turbulent kinetic energy respectively, compared to that of flat piston. The present study will be useful in understanding effect of piston crown shapes on nature of the in-cylinder fluid tumble flows under real engine conditions.     

Noble Metal Decoration and Alignment of Carbon Nanotubes in Carboxymethyl Cellulose

A facile microwave method (MW) is described that accomplishes alignment and decoration of noble metals on carbon nanotubes (CNT) wrapped with carboxymethyl cellulose (CMC). Carbon nanotubes such as single‐ and multi‐walled, and Buckminsterfullerene (C‐60) are well dispersed using the sodium salt of CMC under sonication. Addition of respective noble metal salts then generates noble metal‐decorated CNT composites at room temperature. However, aligned nanocomposites of CNTs could only be generated by exposing the above nanocomposites to MW irradiation. The CNT composites are characterized using scanning electron microscopy, energy dispersive X‐ray analysis, X‐ray mapping, transmission electron microscopy, and UV‐visible spectroscopy. The general preparative procedure is versatile and provides a simple route to manufacturing useful metal‐coated CNT nanocomposites.

     

Transient dynamics of composite sandwich plates using 4-, 8-, 9-noded isoparametric quadrilateral elements

A finite element method based on Mindlin's theory is employed in the prediction of the dynamic transient response of multilayered composite sandwich plates. Numerical convergence and stability of 4-noded linear, 8-noded serendipity, and 9-noded Lagrangian elements are established using an explicit time integration technique. A special mass matrix diagonalization scheme is adopted which conserves the total mass of the element and includes the effects due to rotary inertia terms. The parametric effects of the time step, finite element mesh, lamination scheme, and orthotropy on the transient response are investigated. Numerical results for deflections and stresses are presented under various boundary conditions and loadings. The results presented herein should be of interest to composite-structure designers, experimentalists, and numerical analysists in verifying their results.     

Combustion Derived Ultrafine γ-Fe2O3 Structure,morphology and thermal studies

A novel combustion method of employing poly(ethylene glycol) with the precursor in a fixed ratio for the synthesis of ultrafine γ-Fe₂O₃ through a self-propagating combustion synthesis is reported. Four different precursors viz. ferrous hydroxide, ferrous oxalate dihydrate, ferric 8-hydroxyquinoline and ferric acetylacetonate are employed in this study for the conversion of these precursors to ultrafine g-Fe₂O₃ particles. The as synthesized γ-Fe₂O₃ samples are characterized by XRD, SEM and thermal techniques. A case study for the synthesis of γ-Fe₂O₃ employing ferric acetyl acetonate as precursor is reported. The importance of employing thermal analysis techniques in understanding the combustion synthesis is envisaged. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dapsone a new diazotizing reagent for the spectrophotometric determination of nitrite in waste and natural water samples

A new diazotizing reagent for the spectrophotometric determination of nitrite is described. The method is based on diazotization-coupling reaction between dapsone and phloroglucinol in hydrochloric acid medium. The reactions were conducted at room temperature, the molor absorptivity at 425 nm is 4.28 x 10(4) l mol-1cm-1 and was stable for 50 h. Beer's law was obeyed in the nitrite range of 0.008-1.0 microgram ml-1. Tolerance limits were tested for 33 species. The method has been found to be applicable for the determination of nitrite in natural and wastewater.     

Highly functionalized pyranopyrazoles: synthesis,antimicrobial activity,simulation studies and their structure activity relationships (SARs)

Research on Chemical Intermediates - Development of potent antibacterial and antifungal agents is a permanently new and unremitting investigation in the therapeutic field. Still, medicinal research...