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Organisationseinheit der BAM
Introducing fluorine into molecules has a wide range of effects on their physicochemical properties, often desirable but in most cases unpredictable. The fluorine atom imparts the C–F bond with low polarizability and high polarity, and significantly affects the behavior of neighboring functional groups, in a covalent or noncovalent manner. Here, we report that fluorine, present in the form of a single fluoroalkyl amino acid side chain in the P1 position of the well-characterized serine-protease inhibitor BPTI, can fully restore inhibitor activity to a mutant that contains the corresponding hydrocarbon side chain at the same site. High resolution crystal structures were obtained for four BPTI variants in complex with bovine b-trypsin, revealing changes in the stoichiometry and dynamics of water molecules in the S1 subsite. These results demonstrate that the introduction of fluorine into a protein environment can result in “chemical complementation” that has a significantly favorable impact on protein–protein interactions.
This paper discusses a method for determining the kinetics of biomass pyrolysis based on comparing isoconversional methods, such as the Kissinger and KAS methods, and least squares fitting in a parallel reaction scheme with three pseudo-components roughly representing cellulose, hemicellulose and lignin. The activation energies of the different pseudo-components reported in the literature vary widely. This variation could be reduced if care were taken to determine the kinetics of biomass pyrolysis: First, the reference experiments with pure cellulose are reproduced to validate the thermogravimetric analysis. Then, experiments are performed and analyzed with different heating rates and isoconversional methods are employed to verify the reliability of the experiments and to avoid selecting inappropriate reaction models in a fitting routine.
Polycapillary halflenses are widely used to focus X-ray radiation onto a small spot. Additionally they can reduce the field of view of a semiconductor detector when placed in front of one. In 3D micro X-ray fluorescence spectroscopy (3D Micro-XRF) with synchrotron radiation, two polycapillary halflenses are used in a confocal geometry. Up until now, characterization measurements in the focal plane have only been performed in the case of the lens focusing parallel radiation. Assumptions have been made, that in the other case, when isotropic radiation from a spot source is transported to a detector, the acceptance distribution in the focal plane is also Gaussian. We performed measurements with an electron beam as well as a proton beam which confirm this assumption. In addition, a comparison between measurements in collecting and focusing mode show differences in spot size and transmission. These differences exemplify the fact that there is not one global spot size or transmission function of a polycapillary halflens. Illumination and divergence effects can alter both characteristic lens parameters.
The Federal Institute for materials research and testing (BAM)in cooperation with the Fachhochschule Münster has developed a new certified polymeric reference material, BAM-H010. The reference material consists of acrylonitrile–butadiene–styrene terpolymer (ABS) and has been doped with different contents of the elements Br, Cd, Cr, Hg and Pb. The monitoring of these elements is demanded in the EU directive 2002/95/EG, commonly referred to as RoHS. We have shown that the uncertainty contribution of the thermal long-term stability (ustability) is negligible compared to the contribution to the uncertainty caused by the method used for the characterization of the elemental content and the batch inhomogeneity (uhomogeneity). The stability of theABS material during exposure of the samples with hard X-radiation leads to a degradation of the ABS matrix with either long- or short-chain products.
Das Forschungsprojekt "RC-Leichtgranulate" umfasst die Optimierung des Herstellungsprozesses von Leichtgranulaten aus heterogenen und teilweise feinkörnigen Bau- und Abbruchabfällen und Applikationsuntersuchungen dieser Granulate. Aufgrund der großen Verwertungsdefizite von Mauerwerkbruch im Vergleich zu Betonbruch, wird das Hauptaugenmerk auf den Einsatz von Mauerwerkbruch als Ausgangsmaterial für die Leichtgranulate gelegt. Dabei wird das Rohstoffpotential des Mauerwerkbruchs genutzt, das heißt die chemisch-mineralogische Zusammensetzung des Ausgangsmaterials ist von entscheidender Bedeutung. Die Produktion der Leichtgranulate erfolgt durch einen mehrstufigen Herstellungsprozess mit abschließender thermischer Erhärtung.
Die Leichtgranulate sollen sowohl im Beton als auch in Spezialmörteln in der Denkmalpflege Anwendung finden. Der vorliegende Beitrag beschäftigt sich mit dem Einsatz von RC-Leichtgranulaten mit Korngrößen kleiner als 2 mm in Restauriermörteln und Steinersatzmassen. In einem ersten Schritt wird eine für Restauriermörtel entwickelte Basismischung mit Natursand im Hinblick auf den Einsatz leichter Gesteinskörnungen modifiziert. Ziel ist es, einen gut verarbeitbaren Leichtmörtel herzustellen, der aber Ähnliche Festigkeiten wie die Basismischung erreicht. Die Anforderungen an die Mörtel, die Mischungszusammensetzungen und die Ergebnisse aus den Frisch- und Festmörtelprüfungen werden vorgestellt.
We performed spatially resolved synchrotron-induced x-ray fluorescence analyses (SY-XRF) of five silverpoint drawings from the famous `Karlsruhe sketchbook´ and a silverpoint, which is assumed to be an original one used by the Renaissance artist Hans Baldung Grien (1484-1545) himself. The silverpoint, one out of a very small number of ancient styli conserved nowadays, is fixed on the so-called `Karlsruhe sketchbook´. Measurements were executed at the FLUO-TOPO beamline at the electron storage ring ANKA. It has been shown, that SY-XRF at this beamline is nondestructive and sensitive enough for the analysis of minor and major elements in the silver strokes. This study provides new insights into this graphical technique and ancient drawing instruments: results are that three drawings have been created with a common type of silverpoint containing about (10.4 ± 0.7) wt% of Cu. In all the cases, Hg at a 10% level by weight was identified in the strokes. Presence of Hg is not due to the original silver alloy, but is a result of a general alteration phenomenon of silverpoint drawings. This fact is confirmed by the analysis of the original silverpoint, which contains only small traces of Hg. The result for the copper content of the silverpoint (10.4 ± 1.7) wt% is in good agreement with that of these three drawings. It is supposable that the silverpoint found attached today served for the creation of the corresponding drawings. Moreover, the graphical technique of Baldung is found to be continual over three decades. Only one very late drawing dated to 1543 was probably realized with another silverpoint, containing about 3 wt% of Cu. This difference in the chemical composition of drawings from the late period might be used as a more precise dating indicator of Baldung drawings that are not clearly attributed to a certain period.