The convenient route to cd fragment for the synthesis of vitamin D3 relatives

The efficient degradation of $\text{1}$ to the α-methylene ketone $\text{4}$ is described. Compound $\text{4}$ was then converted to the allylic alcohol $\text{8a}$ - the precursor of vitamin D³ relatives.     

Electrochromism of indolinobenzospirans dissolved in rigid amorphous polymer matrices

The effect of a static electric field on the position of absorption bands of colored stereoisomers of two photochromic compounds of the indolinobenzospiropiran group dissolved in matrices of poly(methyl methacrylate), poly(n-butyl methacrylate), polystyrene, and polycarbonate at room temperature was studied. In the case of matrices with the polymethacrylates the effects observed show that applied electric field produces a shift of thermal equilibrium towards stablization of stereoisomers of larger dipole moment. On the basis of kinetic measurements of attainment of thermal equilibrium on switching the electric field off, the rate constants of their interconversion have been determined. In the case of matrices with polystyrene and polycarbonate, a small red shift only was observed.     

Effect of solvent upon competitive liquid-liquid extraction of alkali metal cations by isomeric dibenzo-16-crown-5-oxyacetic acids

The selectivity and efficiency of competitive liquid-liquid extraction of alkali metal cations into organic solvents containingsym-(octyl)dibenzo-16-crown-5-oxyacetic acid (2) andsym-bis[4(5)-tert-butylbenzo]-16-crown-5-oxyacetic acid (3) have been determined. Solvents examined include: dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, benzene, toluene,p-xylene, chlorobenzene, 1,2-dichlorobenzene, and 1,2,3,4-tetrahydronaphthalene. The Na⁺/K⁺ and Na⁺/Li⁺ extraction ratios are highest in chloroform. The extraction selectivity is found to correlate with the diluent parameter (DP) of the organic solvent.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Dynamic investigations of loads on gear teeth in single gear transmission

Summary In the paper a discrete-continuous model for the analysis of dynamic loads on gear teeth of a single gear transmission is proposed. In this model a constant equivalent mesh stiffness and ponderable shafts deformed by torsion are taken into account. In the discussion a wave method is applied which utilizes the wave solution of the equations of motion. Numerical calculations are concentrated on the determination of amplitudes for dynamic loads on gear teeth with respect to frequencies of external excitation in the first and second resonant regions.

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Untersuchung der dynanischen Zahnbelastung in einstufigen Getrieben

Übersicht Zur Untersuchung der dynamischen Zahnbeanspruchung in einstufigen Getrieben wird ein Modell aus diskreten und kontinuierlichen Massen mit einer konstanten, äquivalenten Zahneingriffssteifigkeit und massebehafteten, tordierbaren Wellen vorgeschlagen. Die Bewegungsgleichungen werden durch einen Wellenfunktionsansatz gelöst. Numerische Berechnungen werden vorwiegend für die Amplituden der Zahnbelastung bei einer äußeren Erregung im Bereich der ersten und zweiten Resonanz durchgeführt.

     

THE STUDY OF 2-CHLORO-5,5-DIMETHYL-2-OXO-1,3,2-DIOXAPHOSPHORINANE IN SOLUTIONS BY MOLECULAR DYNAMICS METHODS USING IR AND RAMAN SPECTROSCOPY

Abstract

2-Chloro-5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinane has been studied in CCl₄, CHCl₃ and CD₃CN solutions by IR and Raman line shape analysis. Equilibrium process of dimerization and ring conversion in CCl₄ solutions have been considered. On the contrary to the commonly expected dominance of the conformer with the equatorial oriented P[dbnd]O bond for 2-halo-2-oxo-1,3,2-dioxaphosphorinanes, it was found that for the 2-chloro derivative both conformers are nearly equally distributed. It has been shown that the interactions induced absorption is an important mechanism of relaxation in the studied compound and this mechanism gives significant contribution to the total IR band broadening, while the interaction induced light scattering is negligible. The obtained results show that the molecular dynamics method can be useful in studying cyclic compounds in solutions.     

From micro-to nanosized particles:Selected characterization methods and measurable parameters

Airborne microand nanoparticles-aerosols-play an important role in many natural phenomena and in a variety of industrial processes,as well as the public health issue. They may be of natural or anthropogenic origin;their presence in an environment might be intentional or due to undesirable release. In any case,merely the particle detection and characterization,ideally in real-time,provide an insight into the potential burden allowing also controlling and abatement measures. Due to the broad size range it is ...     

Anisochronism of large geminal groups in the 1H and 13C nuclear magnetic resonance spectra

The role of steric factors in magnetic non-equivalence anisochronism of complex geminal groups and of their fragments in compounds of the general formula RCH(Ph)CH(COOR′)₂ has been investigated. CMR anisochronism is more sensitive to conformational and other steric changes than is PMR.     

Application of wave method in investigations of single gear transmission

Summary Dynamic investigations for the discrete-continuous model of a single gear transmission are performed using the wave solution of the equations of motion. Transient as well as steady states are considered. Damping is taken into account by means of an equivalent external damping of the viscous type and an equivalent damping of the Voigt type. Angular displacements in arbitrary shaft cross-sections and dynamic reactions on teeth of the gear transmission in resonance conditions are determined. Results for the wave method and the multibody system approach are compared in the case of amplitude-frequency curves.

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Anwendung der Wellengleichungen bei Untersuchungen einstufiger Getriebe

Übersicht Mit Hilfe der Wellengleichungen werden dynamische Untersuchungen für das Modell eines einstufigen Getriebes aus Starrkörpern und verformbaren, kontinuierlichen Teilen durchgeführt. Sowohl Übergangs- als auch stationäre Zustände werden betrachtet. Dämpfung wird mit Hilfe einer äquivalenten äußeren viskosen Dämpfung und einer äquivalenten Dämpfung vom Voigt-Typ berücksichtigt. Bestimmt werden die Winkeländerungen in beliebigen Wellenquerschnitten und die dynamischen Reaktionen der Getriebezähne unter Resonanzbedingungen. Die Ergebnisse dieser Methode werden anhand der Amplituden-Frequenz-Kurven mit denen nach der Mehrkörper-Dynamik verglichen.

     

Longitudinal waves in a damped layered system

Summary In the paper a layered system with a finite length connected to discrete elements is considered. It is assumed that the layers of the system as well as the discrete elements undergo longitudinal deformations only. In the considerations a wave method taking into account all wave reflections is utilized. Exemplary numerical calculations are carried out for a two-layered system. These concern the determination of the ranges and locations of resonant regions for selected cross-sections and for various mechanical properties of the layers.

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Longitudinalwellen in einem geschichteten system mit dämpfung

Übersicht Betrachtet wird ein geschichtetes Kontinuum endlicher Abmessung, das mit diskreten Feder/Dämpfer/Masse-Elementen verbunden ist. Es wird angenommen, daß sowohl der Schichtwerkstoff als auch die diskreten Elemente nur longitudinale Verformungen erleiden. Bei den Betrachtungen wird eine auf den Wellenlösungen aufbauende Methode benutzt, die alle Wellenreflektionen berücksichtigt. Exemplarische numerische Rechnungen werden für ein Zweischichten-System mit ausgewählten Querschnitten und verschiedenen Stoffeigenschaften durchgeführt.

     

Direct mass spectrometric analysis of the 18O/16O ratio in sulfur-containing organophosphorus compounds

High precision measurements of the ¹⁸O/¹⁶O ratio in bis-(5,5-dimethyl-2-oxo-1,3,2-P-dioxaphosphorinanyl)-sulfide and P¹-oxo-P²-thiono(5,5-dimethl-1,3,2-dioxaphosphorinanyl)oxidee have been carrid out using a Finnigan 4000 mass spectrometer.