Buchbesprechungen

Ohne Zusammenfassung     

Buchbesprechungen

Ohne Zusammenfassung     

Republication of: The redshift of extragalactic nebulae

This English translation of the paper by F. Zwicky, “Die Rotverschiebung von extragalaktischenNebeln”, Helv. Phys. Acta 6, 110–127 (1933), in which he concludedfrom the results of observations that the amount of non-luminous matter in the Universe must be greaterthan that of luminous matter—thus becoming an early precursor of the dark matter idea, has beenselected for publication in the Golden Oldies series of General Relativity and Gravitation. The paper is accompanied by an editorialnote written by Jürgen Ehlers and by Zwicky’s brief biography compiled by Andrzej Krasiński.     

Stereocontrol in organic synthesis using silicon-containing compounds. Studies directed towards the synthesis of ebelactone A

Several approaches to the synthesis of ebelactone A 2 are described, culminating in the synthesis of the benzenesulfonate of 2-epi-ebelactone A 161. All the approaches were based on three fragments A, B and C, originally defined in general terms in, but eventually used as the aldehyde 72, the allenylsilane 3 and the aldehyde 139, respectively. They were joined, first B with C, and then B+C with A. In the main routes to fragments A and C, the relative stereochemistry was controlled by highly stereoselective enolate methylations 67-->67, 68-->69, and 135-->136, in each case anti to an adjacent silyl group, and by a highly stereoselective hydroboration of an allylsilane 137-->138, also anti to the silyl group. The hydroxyl groups destined to be on C-3 and C-11 were unmasked by silyl-to-hydroxy conversions 69-->70 and 138-->139 with retention of configuration. The stereochemistry created in the coupling of fragment B to C was controlled by the stereospecifically anti S(E)2' reaction between the enantiomerically enriched allenylsilane 3 and the aldehyde 139. The double bond geometry was controlled by syn stereospecific silylcupration 148-->151, and preserved by iododesilylation 151-->152 of the vinylsilane with retention of configuration, and Nozaki-Hiyama-Kishi coupling with the aldehyde 72 gave the whole carbon skeleton 153 of ebelactone A with the correct relative configuration, all of which had been controlled by organosilicon chemistry. In the steps to remove the superfluous allylic hydroxyl, an intermediate allyllithium species 156 abstracted the proton on C-2, and its reprotonation inverted the configuration at that atom. Other routes to the fragments A and C were also explored, both successful and unsuccessful, both silicon-based and conventional, and a number of unexpected side reactions were investigated.     

Radiological dose assessment of naturally occurring radioactive materials in concrete building materials

Previous studies have shown that the natural radioactivity contained in building materials have significantly influenced the dose rates in dwelling. Exposure to natural radiation in building has been of concerned since almost 80 % of our daily live are spend indoor. Thus, the aim of the study is to assess the radiological risk associated by natural radioactivity in soil based building materials to dwellers. A total of 13 Portland cement, 46 sand and 43 gravel samples obtained from manufacturers or bought directly from local hardware stores in Peninsular of Malaysia were analysed for their radioactivity concentrations. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied building materials samples were found to be in the range of 3.7–359.3, 2.0–370.8 and 10.3–1,949.5 Bq kg^?1 respectively. The annual radiation dose rates (μSv year^?1) received by dwellers were evaluated for 1 to 50 years of exposure using Resrad-Build Computer Code based on the activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K found in the studied building material samples. The rooms modelling were based on the changing parameters of concrete wall thickness and the room dimensions. The annual radiation dose rates to dwellers were found to increase annually over a period of 50 years. The concrete thicknesses were found to have significantly influenced the dose rates in building. The self-absorption occurred when the concrete thickness was thicker than 0.4 m. Results of this study shows that the dose rates received by the dwellers of the building are proportional to the size of the room. In general the study concludes that concrete building materials; Portland cements, sands, and gravels in Peninsular of Malaysia does not pose radiological hazard to the building dwellers.     

Zeaxanthin Production by Novel Marine Isolates from Coastal sand of India and its Antioxidant Properties

Zeaxanthin carotenoids are class of commercially important natural products and diverse biomolecules produced by plants and many microorganisms. Bacteria often produce a cocktail of polar and nonpolar carotenoids limiting their industrial applications. Marine members of the family Flavobacteriaceae are known to produce potential carotenoids such as astaxanthin and zeaxanthin. A few bacterial species have been reported for the predominant production zeaxanthin. Here, we report the molecular identification of the zeaxanthin as a major carotenoid produced by two novel bacteria (YUAB-SO-11 and YUAB-SO-45) isolated from sandy beaches of South West Coast of India and the effect of carbon sources on the production of zeaxanthin. The strains were identified based on the 16S rRNA gene sequencing as a member of genus Muricauda. The closest relatives of YUAB-SO-11 and YUAB-SO-45 were Muricauda aquimarina (JCM 11811^T) (98.9 %) and Muricauda olearia (JCM 15563^T) (99.2 %), respectively, indicating that both of these strains might represent a novel species. The highest level of zeaxanthin production was achieved (YUAB-SO-11, 1.20?±?0.11 mg g^?1) and (YUAB-SO-45, 1.02?±?0.13 mg g^?1) when cultivated in marine broth supplemented with 2 % NaCl (pH 7) and incubated at 30 °C. Addition of 0.1 M glutamic acid, an intermediate of citric acid cycle, enhanced the zeaxanthin production as 18 and 14 % by the strains YUAB-SO-11 and YUAB-SO-45 respectively. The zeaxanthin showed in vitro nitric oxide scavenging, inhibition of lipid peroxidation, and 2,2-diphenyl-1-picryl hydrazyl scavenging activities higher than the commercial zeaxanthin. The results of this study suggest that two novel strains YUAB-SO-11 and YUAB-SO-45 belonging to genus Muricauda produce zeaxanthin as a predominant carotenoid, and higher production of zeaxanthin was achieved on glutamic acid supplementation. The pigment showed good in vitro antioxidant activity, which can be exploited further for commercial applications.     

X-ray fluorescence spectrometry for high throughput analysis of atmospheric aerosol samples: The benefits of synchrotron X-rays

The determination of trace element mass concentrations in ambient air with a time resolution higher than one day represents an urgent need in atmospheric research. It involves the application of a specific technique both for the aerosol sampling and the subsequent analysis of the collected particles. Beside the intrinsic sensitivity of the analytical method, the sampling interval and thus the quantity of collected material that is available for subsequent analysis is a major factor driving the overall trace element detection power. This is demonstrated for synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) of aerosol samples collected with a rotating drum impactor (RDI) in hourly intervals and three particle size ranges. The total aerosol mass on the 1-h samples is in the range of 10 µg. An experimental detection of the nanogram amounts of trace elements with the help of synchrotron X-rays was only achievable by the design of a fit-for-purpose sample holder system, which considered the boundary conditions both from particle sampling and analysis. A 6-µm polypropylene substrate film has evolved as substrate of choice, due to its practical applicability during sampling and its suitable spectroscopic behavior. In contrast to monochromatic excitation conditions, the application of a ‘white’ beam led to a better spectral signal-to-background ratio. Despite the low sample mass, a counting time of less than 30 s per 1-h aerosol sample led to sufficient counting statistics. Therefore the RDI-SR-XRF method represents a high-throughput analysis procedure without the need for any sample preparation. The analysis of a multielemental mass standard film by SR-XRF, laboratory-based wavelength-dispersive XRF spectrometry and laboratory-based micro XRF spectrometry showed that the laboratory-based methods were no alternatives to the SR-XRF method with respect to sensitivity and efficiency of analysis.