Ansamycine, 5. Mitt., Chemie der Metacycloprodigiosine

In order to obtain a better partition of a prodigiosin derivative in biological media, two hydroxy groups were introduced into theansa-part of the molecule. The synthesis of the title compound is described in detail.     

Norrish Type I Cleavage of Aliphatic Carboxylic Acids and Esters in Solution. A CIDNP.-study

UV.-irradiation of pivalic and isobutyric acid and their methyl esters as well as of α-hydroxy isobutyric and malonic acid in solution lead to chemically induced dynamic nuclear polarization (CIDNP.) of parent compounds and of various reaction products. CIDNP.-effects and product distributions confirm α-cleavage of the C(α), CO bond to be the major mode of photodecomposition. Scavenger experiments indicate that decomposition of the molecules from a triplet excited state is roughly equally or more probable than from a singlet excited state. Quantum yields of educt disappearance are also given for the methyl esters of pivalic and isobutyric acid.     

Über die optimale Beleuchtung einer geraden Straße

The following problem is due toL. Fejes Tóth: For a given sort of lamps letf(x) be the intensity of brightness in each point having distancex from the foot of the lamp. How must infinitely many lamps of this kind be arranged on a both-side infinite rectilinear road, such that the infimum of the intensities of brightness, extended over the whole street, is maximal, subject to the condition that the average number of lamps per kilometer is bounded by a fixed number (“Best distributions”)? The main result of this paper is: Iff is strictly convex, the equidistant distribution is best.     

Transport Coefficients and Structural Principles of PbO?Ga2O3 Melt

More Precise knowledge of the growth mechanism of garnets in form of epitaxial layers or single crystals in high temperature solutions on the base of trivalent oxides Me₂O₃ in PbO B₂O₃ solvent is desirable. Data of physicochemical properties of the melts especially density, shear viscosity, and electrical conductivity and their dependence on the temperature are useful in endeavour to recognize the structural principles of oxidie melts. Therefore as a first step the binary system PbO Ga₂O₃ was investigated to understand the influence of the Ga component on a complete mixed garnet solution, for instance (Y, Sm)₃ (Fe, Ga)₅O₁₂ in PbO B₂O₃ solvent.     

Untersuchungen zum Kristallwachstum in der Hochtemperaturlösung mit Hilfe der differentiellen Thermoanalyse

A DTA-apparatus is described which is suitable for solubility measurements of garnets in flux melts. It is important that the temperature will be measured as near as possible to the crystallization region. Solubility temperatures are measured with an uncertainty ≦ 10 deg. A mixture of PbO, PbF₂ and B₂O₃ was used as solvent. The following garnet systems were investigated: Y₃Fe_5−xM_xO₁₂ (M = Ga, Al, In, Cr; x = 0 …︁ 5) and Gd₃Ga₅O₁₂. If results of other authors are available they are in good agreement with our data. Habit and chemical analysis of crystallites give informations about the grown phases and their composition. In connexion with the solubility thus it is possible to select appropriate solvents.     

Chemoenzymatic synthesis of discotic liquid crystals

Abstract

Acylations at the 6-position of alkyl glycosides were obtained using the esterification potential of lipases. Thus, sugars with two alkyl chains result showing columnar discotic phases. The correlation between the configuration of the sugar moieties and the different clearing points can be understood on the basis of simple stereochemical assumptions.     

Influence of processing and clay type on nanostructure and stability of polypropylene–clay nanocomposites

Melt processing is a critical step in the manufacture of polymer articles and is even more critical when dealing with inhomogeneous polymer–clay nanocomposites systems. The chemical composition, and in particular the clay type and its organic modification, also plays a major contribution in determining the final properties and in particular the thermal and long-term oxidative stability of the resulting polymer nanocomposites. Proper selection and tuning of the process variable should, in principle, lead to improved characteristics of the fabricated product. With multiphase systems containing inorganic nanoclays, however, this is not straightforward and it is often the case that the process conditions are chosen initially to improve one or more desired properties at the expense of others.     

Evolution of radiocaesium contamination in mushrooms and influence of treatment after collection

In literature quite a lot of data is available on uptake of radioactive caesium in mushrooms. There is less available on the evolution of concentration in fruitbodies after several years and on “outbound” transfer of radiocaesium from fruitbodies to their direct environment, i.e. dilution according to cooking techniques. The recent event at Fukushima has put the question of radionuclides in food, and the following exposure of consumers, high on the agenda. The purpose of this paper is twofold: (1) in order to investigate the variation in time of caesium uptake by fungi, analyses of the same species having grown on the same spot at different intervals during the last 25 years have been performed and (2) in terms of radiation protection the most important thing is the activity taken in by the consumer and not the contamination of raw products. Preparation can have a great impact on activity concentration. Various species of mushrooms frequently eaten have been sampled in Europe and contaminated areas in Japan. Different preparation techniques that can break the walls of the hyphae (drying, deepfreezing etc.) have been applied as well as different treatments: boiling or macerating in water with salt, in acid and basic media. The pH of different media was adjusted and measured. The samples and the medium were analysed separately in gamma spectrometry.