Lignans and Alkaloids from Haplophyllum suaveolens

Summary.  A new lignan of the dibenzylbutyrolactone type, haplotonin, was isolated from the aerial parts of Haplophyllum suaveolens together with five known compounds-the alkaloids flindersine, 6-methoxyflindersine, N-acetoxymethylflindersine, and evoxine and the lignan 4-acetyldiphyllin. This is the first report on the occurrence of N-acetoxymethylflindersine in the genus Haplophyllum and on 6-methoxyflindersine and 4-acetyldiphyllin as constituents of the investigated species. Received August 10, 1999. Accepted (revised) October 12, 1999     

Stochastic response determination of structural systems modeled via dependent coordinates: a frequency domain treatment based on generalized modal analysis

Generalized independent coordinates are typically utilized within an analytical dynamics framework to model the motion of structural and mechanical engineering systems. Nevertheless, for complex systems, such as multi-body structures, an explicit formulation of the equations of motion by utilizing generalized, independent, coordinates can be a daunting task. In this regard, employing a set of redundant coordinates can facilitate the formulation of the governing dynamics equations. In this setting, however, standard response analysis techniques cannot be applied in a straightforward manner. For instance, defining and determining a transfer function within a frequency domain response analysis framework is challenging due to the presence of singular matrices, and thus, the machinery of generalized matrix inverses needs to be employed. An efficient frequency domain response analysis methodology for structural dynamical systems modeled via dependent coordinates is developed herein. This is done by resorting to the Moore–Penrose generalized matrix inverse in conjunction with a recently proposed extended modal analysis treatment. It is shown that not only the formulation is efficient in drastically reducing the computational cost when compared to a straightforward numerical evaluation of the involved generalized inverses, but also facilitates the derivation and implementation of the celebrated random vibration input–output frequency domain relationship between the excitation and the response power spectrum matrices. The validity of the methodology is demonstrated by considering a multi-degree-of-freedom shear type structure and a multi-body structural system as numerical examples.

     

Lyotropic mesomorphism in some thermotropic,polycatenar complexes of silver(I)

A wide range of mesophases are induced on treating polycatenar complexes of silver(I) with a wide range of organic solvents.     

Comparative Effect of Low-intensity Laser Radiation in Green and Red Spectral Regions on Functional Characteristics of Sturgeon Sperm

A comparative study of the effect of low-intensity laser radiation in green (λ = 532 nm) and red (λ = 632.8 nm) spectral regions at equal average irradiance (3 mW cm⁻²) on functional characteristics of Siberian sturgeon spermatozoa is carried out. Confirmation of the photobiomodulation effect of the radiation is obtained by analyzing spermatozoa motility, percentage of motile spermatozoa and fertilization rate. It is shown that, depending on the energy dose, the laser radiation in red and green spectral regions can have both stimulatory and inhibitory effects on spermatozoa motility. Contrary to popular belief that the short-wavelength radiation has great prospects in reproductive biotechnologies (due to more efficient absorption of radiation by cellular chromophores and increased generation of ROS), convincing evidence of a more pronounced stimulatory effect of radiation in the red spectral region was obtained. For the first time, metal-free porphyrins capable of acting as endogenous photosensitizers generating ROS were detected and identified in animal sperm. Using luminol-dependent chemiluminescence, it is shown that the increased production of ROS capable of exerting an inhibitory effect on biological systems at high concentrations is among the possible reasons for reduction in the stimulatory effect of radiation when moving from red to green spectral region.     

Quantitative Analysis of Chemical and Phase Composition of Zn−Ni Alloy Coating by Potentiodynamic Stripping

We propose quantitative analysis of chemical and phase composition of Zn−Ni alloy depending on the film thickness, using potentiodynamic stripping in an alkaline ammonia-glycinate electrolyte. The mechanism of dissolution of zinc-enriched Zn−Ni alloy films in this electrolyte comprises sequential stages of dissolution of zinc-phase and zinc from a γ-phase of various structures, followed by dissolution of the nickel-enriched residue, formed by dezincification, and matrix nickel.