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81.
Adult long-tailed ducks (Clangula hyemalis) were collected from nine locations across their breeding grounds in northern Canada and measurements of stable isotopes of carbon (delta(13)C), nitrogen (delta(15)N) and sulfur (delta(34)S) in bone collagen were used to investigate if relative use of freshwater habitats such as the Great Lakes (with expected depleted stable isotope profiles) compared with coastal marine environments (with expected enriched stable isotope foodweb profiles) could explain tissue trace element profiles. Contrary to expectation, all three stable isotopes did not covary in our sample, suggesting that mechanisms other than simple freshwater vs. marine isotopic gradients were involved among populations. All three stable isotopes varied significantly with collection location and both delta(15)N and delta(13)C values varied significantly between sexes suggesting that males exploit either a different food base or occur in different geographic areas than females for at least part of the year. The delta(34)S data, in particular, suggested that many of the birds breeding in the western Canadian Arctic probably overwinter in the Great Lakes along with many of the birds breeding in Hudson Bay. Males at the majority of collection locations had higher concentrations of hepatic Hg (1.1-8 microg/g dw), Cu (25-40 mug/g dw), Se (7.3-27 mug/g dw) and renal Cd (33-129 microg/g dw) than females. Concentrations of Hg, Cu and Cd were well below toxicological threshold levels found in the literature. However, hepatic Se concentrations in 64% of the females exceeded 10 mug/g dw and concentrations in 8% of the birds measured exceeded 33 microg/g dw suggesting levels of potential concern. 相似文献
82.
Birgit A.-L.
stman 《火与材料》1981,5(4):153-162
Ignitability, one of the new fire test methods for building materials developing within the International Standards Organization is compared with the national fire test methods in Austria, Britain, France, Germany and Scandinavia. Different commercial wood-based panels have been tested, including fire retardant treated panels. The International Standards Organization ignitability test measures the time to ignition at radiation intensities from 1 to 5 Wm ?2; it seems to be able to distinguish between different materials in an intelligible way. An evaluation of the results of this ignitability test is discussed. One possibility which is proposed here is to calculate the mean time to ignition at different fixed radiation intensities; such a mean value simplifies the evaluation and takes into account all the test data. Agreement with the national fire test methods is rather low, since they partly measure other fire parameters; agreement with the Austrian Schlyter method, which also evaluated ignitability, is somewhat better and agreement between the national fire test methods is relatively good for wood-based panels. This is consistent with earlier experience, which has shown that mainly new types of materials behave differently according to different national test methods. 相似文献
83.
84.
Here we present a modular process for the flexible production of magnetic beads with variable magnetic properties and anion or cation exchanger functionalities. Magnetic beads are used in bio‐separations and downstream processing to remove a valuable substance from e.g., a fermentation broth (Magnetic Fishing). The magnetic beads we are presenting here consist of a composite material, containing nanoscale magnetite and ion exchanger particles which are embedded into a polymer matrix. With this composite concept, anion and cation exchanger properties are available in magnetic beads with different matrix polymers (PVB, PVA, PMMA, and PVAc). The content of magnetite was varied in a range between 0 and 40 wt %, ion exchanger particles between 0 and 60 wt % and the matrix polymer between 20 and 60 wt %. The magnetic bead characteristics, which determine the application properties, are shown. Thermo gravimetrical analyses, FTIR spectra and measurements of the ion exchange capacity prove the different properties in respect to the magnetic beads composition. In an adsorption experiment, it was possible to achieve a maximum capacity of 270 mg/g for β‐galactosidase with PVB‐beads. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
85.
182Hf (T(1/2) = 9 x 10(6) y) is believed to be formed by pure r-process during a supernova explosion, and therefore, the search for minute traces of 182Hf in the earth's crust is of great interest. Only accelerator mass spectrometry (AMS) is well suited for detecting such low levels of 182Hf. But any attempt to measure 182Hf by AMS must ensure that the sample is free from its naturally occurring stable isobar 182W. A simple method for separation of tungsten and hafnium has been developed using radiometric simulation followed by checking the decontamination of tungsten from Hf in a synthetic sample by AMS. The separation studies were performed by a liquid-liquid extraction technique using tri-n-octylamine (TOA) as the organic reagent. It has been found that a very high separation factor (1.6 x 10(6)) can be achieved when 0.3 M TOA diluted in cyclohexane is used as the organic phase and 6 M HCl (in the presence of small amount of H2O2) is used as the aqueous phase. 相似文献
86.
Tanja Brockmann Patrick Fontana Birgit Meng Urs Müller 《Beton- und Stahlbetonbau》2008,103(7):446-454
Nanotechnology in Construction Engineering In general, nanotechnology comprises the development, production and application of materials yielding novel functionalities and performances. In the construction industry and materials research nanotechnology can be utilized for a variety of areas of application, such as the optimisation of material properties, the prevention of damages and the implementation of new functionalities. This article gives an overview of areas in the construction sector where nanotechnology gains prominently of significance, such as cementitious binders, façades, windows and glazing, fire protection, interior decoration and infrastructure buildings. Furthermore, actual scientific research activities in the field of building materials on a nano‐scale performed by the Federal Institute for Materials Research and Testing (BAM) in Berlin are being presented. The research activities relate to the modification of hydrate phases in ultra high performance concrete (UHPC) and to the enhancement of performance of anti‐graffiti‐systems. 相似文献
87.
Fourier-transformed infrared spectroscopy has been established for analysing most of the physical–chemical parameters of honey.
Additionally this technique can be used for determination of the botanical origin of a honey sample by comparison of the mid-infrared
spectra. In this study calibrations for authentification of the main regional honey types should be developed to be able to
measure simultaneously physical–chemical properties and the botanical origin at a minimum of time and at low costs. Honey
samples from local beekeepers were collected and characterized by standard methods. The most common honey types were used
for calibration. We recorded the mid infrared spectrum from each honey sample. Classification models were achieved by PCA-calibration
and validated with samples from various botanical origins. Honey of Brassica spp., Robinia pseudoacacia, Calluna vulgaris, Trifolium spp., Tilia spp., Helianthus annuus, Centaurea cyanus and honeydew honey was used for calibration. Afterwards the calibration models were improved during routine analysis. Most
of the honey samples from rape, false acacia, heather and honeydew can be classified correctly by the FTIR in consideration
of the physical–chemical and sensorial properties. 相似文献
88.
Vikström AC Eriksson S Paulsson B Karlsson P Athanassiadis I Törnqvist M 《Molecular nutrition & food research》2008,52(8):974-980
The formation of acrylamide during heating of certain foodstuffs constitutes a potential health hazard. The health risk assessment should be based on knowledge about the relation between dietary exposure to acrylamide and internal doses of acrylamide and its genotoxic metabolite glycidamide. The primary aim of this study in mice was to measure these relationships at low levels of acrylamide intake through the diet. A secondary aim was to clarify which extraction method should be used when analyzing acrylamide in food in order to obtain a correct measure of the acrylamide that is available for absorption. In the analysis procedure, alkaline extraction has earlier shown much higher measured acrylamide levels in certain foods compared to water extraction. In this subcronic study the administered diets were composed to give five levels of acrylamide intakes between 3 and 50 mug/kg body weight per day (calculated on figures obtained after water extraction). Internal doses of acrylamide and glycidamide were measured through hemoglobin (Hb)-adducts. The results showed linear relationships between the exposure of acrylamide and Hb-adduct levels from both acrylamide and glycidamide at these low exposure levels. The study also showed that the "extra" acrylamide measured with alkaline extraction does not correspond to bioavailable acrylamide. 相似文献
89.
Birgit Köhn Prof. Dr. Michael Kovermann 《Chembiochem : a European journal of chemical biology》2019,20(6):759-763
In all intracellular processes, protein structure and dynamics are subject to the influence of macromolecular crowding (MC). Here, the impact of MC agents of different types and sizes on the model protein Bacillus subtilis Cold shock protein B (BsCspB) during both thermal and chemical denaturation have been comprehensively investigated. We consistently reveal a distinct stabilization of BsCspB in a manner dependent on the MC concentration but not on viscosity, polarity, or size of the MC agent used. This general stabilization has been decoded by use of NMR spectroscopy, through monitoring of chemical shift (CS) perturbations and the intramolecular hydrogen-bonding networks, as well as local protection of amide protons against exchange with solvent protons. Whereas CSs and hydrogen-bonding networks are not systematically affected in the presence of MC, we detected a pronounced reduction in exchange in loop regions of BsCspB. We conclude that this reduced accessibility of solvent protons is a key parameter for the increases in protein stability seen under MC. 相似文献
90.
Rasool Shumaila Cárdenas Pablo D. Pattison David I. Jensen Birgit Meyling Nicolai V. 《Journal of chemical ecology》2021,47(4-5):476-488
Journal of Chemical Ecology - Entomopathogenic fungi (EPF) can be experimentally established in several plant species as endophytes. Ecological effects of EPF inoculations on plant growth and... 相似文献