Photo-transformations of 6-chloro-3-propargyloxy-2-aryl-4-oxo-4H-1-benzopyran: 1,4-hydrogen abstraction in propargylethers

1,4-Biradicals generated in the Norrish type-II reactions of 3-propargyloxy-2-arylchromones lead to cyclic products involving the 2-aryl group. The formation and distribution of products varied with the nature of 2-aryl group.     

Diode laser spectrum and analysis of the 882-cm−1 band of s-tetrazine

A high-resolution diode laser spectrum of the 882-cm^?1 band of s-tetrazine has been obtained. A complete rotational analysis of this band, incorporating quartic and sextic centrifugal distortion coefficients, has been carried out. The rotational constants A, B, and C have been determined with an accuracy better than 10^?5 cm^?1. The analysis has shown the band to be A-type and, on this basis, the vibrational assignment of this band has been revised from ν₁₂ to ν₁₄.     

An oxidimetric method for the determination of thiophanatemethyl in commercial formulations

A simple, accurate and reliable titrimetric method is described for the determination of thiophanate-methyl, an important commercial fungicide. The method is based on its direct titration at room temperature with ammonium hexanitratocerate(IV) in sulphuric acid medium in the presence of potassium iodate as catalyst. The method permits detection of the end-point visually, potentiometrically or spectrophotometrically. The proposed method is recommended for routine determination of the fungicide in its commercial formulations.     

Error analysis for convex separable programs: Bounds on optimal and dual optimal solutions

Computable lower and upper bounds on the optimal and dual optimal solutions of a nonlinear, convex separable program are obtained from its piecewise linear approximation. They provide traditional error and sensitivity measures and are shown to be attainable for some problems. In addition, the bounds on the solution can be used to develop an efficient solution approach for such programs, and the dual bounds enable us to determine a subdivision interval which insures the objective function accuracy of a prespecified level. A generalization of the bounds to certain separable, but nonconvex, programs is given and some numerical examples are included.     

Structure and stereochemistry of paristerone,a novel phytoecdysone from the tubers of paris polyphylla

Paristerone, a novel phytoecdysone has been isolated from the tubers of P. polyphylla and its structure and stereochemistry has been established as 2α, 3β, 14α, 20(R), 22(r), 25-hexahydroxy-5β-chloest-7-en-6-one (2-epiecdysterone) on the basis of chemical and physical evidence.     

Determination of microgram quantities of gadolinium by cathode-ray polarography

A cathode-ray polarographic method has been developed for the determination of microgram quantities of gadolinium with the use of an azo-dye, Solochrome Violet RS. Disadvantages in the use of 0sd1M potassium chloride, commonly recommended as electrolyte for the polarographic determination of rare earths, have been demonstrated. The influence of pH, temperature, ligand concentration and purity, and the stability of the complex, have been investigated for the optimum performance of the method. The linear range is 0.5-12 mug/ml of gadolinium. Interferences by some lanthanides and other cations have been examined.     

Asymptotic behavior of the pion electromagnetic form factors in Bethe-Salpeter model

Asymptotic behavior of the pion form factors has been discussed treating pion as a bound state of the elementary nucleon and antinucleon system. The matrix-element of the electromagnetic current is written in terms of the Bethe-Salpeter amplitude for the nucleon-antinucleon bound system. Using suitable approximations the Bethe-Salpeter equation for nucleon-antinucleon bound state with nucleons as Dirac spinors has been solved and the corresponding off-shell pion form factors are determined. The form factors are strongly interaction dependent. For coupling $\text{g}{}^2\text{16π}{}^2\text{=}\text{15}\text{4}$ the form factors vanish asymptotically like t^?1 and for $\text{14}\text{4}\text{<}\text{g}{}^2\text{16π}{}^2\text{<}\text{15}\text{4}$ the form factors still vanish but less rapidly than t^?1.