A Self-Similar Dynamics in Viscous Spheres

We study the evolution of radiating and viscous fluid spheres assuming an additional homothetic symmetry on the spherically symmetric space-time. We match a very simple solution to the symmetry equations with the exterior one (Vaidya). We then obtain a system of two ordinary differential equations which rule the dynamics, and find a self-similar collapse which is shear-free and with a barotropic equation of state. Considering a huge set of initial self-similar dynamics states, we work out a model with an acceptable physical behavior.     

H2 CARS thermometry in a fuel-rich,premixed, laminar CH4/air flame in the pressure range between 5 and 40 bar

To establish H₂ CARS thermometry at high pressure, accumulated H₂ Q-branch CARS spectra were recorded in the exhaust of a fuel-rich CH₄/air flame at pressures between 5 and 40 bar. Temperatures were deduced by fitting theoretical spectra to experimental data points. The Energy-Corrected Sudden (ECS) scaling law was employed to set up an empirical model for the calculation of H₂ linewidths in high-pressure hydrocarbon flames with H₂ as a minority species. Experimental H₂ CARS spectra could be simulated very accurately with this model. The evaluated temperatures agreed well with reference temperatures obtained by spontaneous rotational Raman scattering of N₂.     

Effect of p-toluensulfonic acid on oxidation of polyethylene and polyethylene-poly-p-methylstyrene blends

p-Toluensulfonic acid retards oxidation of polyethylene and, to a greater extent, of polyethylene-poly-p-methylstyrene blends. The real antioxidant is p-cresol, formed by p-toluensulfonic acid transformation in oxidizing polyethylene and, in blends, through peroxidation and subsequent acid-catalyzed decomposition of hydroperoxides of poly-p-methylstyrene.     

Bestmögliche innere Schalengleichungen für schubweiche Werkstoffe unter Berücksichtigung von Dickenänderungen

Übersicht Konsistente Schalentheorien lassen sich in einer besonders anschaulichen Weise durch lineare Approximation der Erhaltungssätze eines als Multi-Direktor-Körper beschriebenen, dreidimensionalen Kontinuums herleiten. Im vorliegenden Beitrag entstchen auf diesem Wege bestmögliche, in Geschwindigkeiten formulierte innere Schalengleichungen für beliebig große Deformationen und willkürliche, in eine Leistungsaussage einpaßbare Materialgesetze. Dabei finden Schub- und Querdeformationen Berücksichtigung. Der optimale Charakter der Schalentheorie mit gleichen Unschärfen in allen Einzelbeziehungen wird durch den Herleitungsgang sichergestellt und durch Einschrankungen mittels lokaler Tensornormen bewiesen.

---

Best interior shell equations including transverse shear deformations and thickness changes

Summary Consistent shell theories can be derived in a particular correct manner by linear approximation of conservation laws of a three-dimensional continuum, described as a multi-director-body. In the present paper best interior shell equations-formulated in velocities—are developed, valid for arbitrarily large deformations and rather optional material laws, incorporating shear distorsions and thickness changes. The optimal character of the theory is guaranteed by the derivation process and proven by bounding techniques using tensor norms.

     

Quantitative vibration amplitude measurement with time-averaged digital speckle pattern interferometry

A new method of using time-averaged digital speckle pattern interferometry for the quantitative measurement of vibration amplitude was developed. Signal processing techniques especially the Hilbert transformation for quantitative evaluation of the Bessel fringes obtained in time-averaged digital speckle pattern interferometry were explored. The quadrature signal after Hilbert transformation is equivalent to a 90° phase-shifted interferogram for a monotonically increasing or decreasing phase function. An algorithm was developed for Bessel fringe contrast enhancement and phase extraction. The techniques were tested numerically and experimentally. Sub-fringe quantification of the time-averaged vibration fringes is realised with the proposed method. Compared with the commonly used phase shift method which requires a minimum of two images for image processing, this method requires only one fringe pattern for data extraction.     

Time-resolved fluorescence study of the single tryptophan in thiocyanate and azide derivatives of horseradish peroxidase: Implication for a p H-induced conformational change in the heme cavity

Detailed pH-dependent steady state and picosecond time-resolved tryptophan fluorescence studies on thiocyanate and azide complexes of horseradish peroxidase have been carried out. The fluorescence decay of the single tryptophan in these species was fitted to a discrete three exponential model. Maximum entropy method analysis also gave three distinct regions of lifetime distributions. The fast subnanosecond lifetime component was found to have > 97% amplitude contribution while other two longer lifetime components have small contributions. Small contributions from the nanosecond lifetime components possibly arise from apoprotein impurity or some small amount of disordered heme conformer of the protein. pH dependence of the fast picosecond lifetime components was found to show a systematic behavior which has been interpreted in the light of obligatory conformation change associated with activation of the enzyme at low pH.     

Intramolecular heterocyclization with accompanying exoiminization in the reaction of ammonia with 2-chloroperfluoro-1-cyclohexene-1-thiocyanate

The reaction of ammonia with 2-chloroperfluoro-1-cyclohexene-1-thiocyanate leads to 2-amino-7-iminoperfluoro-4,5,6-trihydrobenzo-1,3-thiazole (II) due to intramolecular heterocyclization in the Thorpe reaction with the concurrent exoiminization. Analysis of the IR spectra of (II) in CCl₄ and in the solid phase indicated that molecules of (II) in the crystal form hydrogen-bonded centrosymmetric dimers (D), which are in equilibrium with free molecules of (II) in solution.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2366–2370, October, 1991.The authors express their gratitude to D. I. Zagorevskii for taking the mass spectrum of (II) and to L. S. German for a useful discussion of this work.