An approach to monitor the real-time deformation during heat treatment of 3D-printed glass

This study suggests a tool for a better control on the sintering/crystallization of 3D-printed bioactive glass-ceramics bodies. A small cantilever in form of a bar with square cross section attached to a base and inclined 34° with the horizon, was used to monitor the viscous flow and sintering/crystallization headway of a glass-ceramic systems. 3D printing and sintering of bioactive glass-ceramics is of great interest for medical care applications. Viscous flow ensures sufficient densification of the typically low density printed green bodies, while crystallization prevents the structure from collapsing under the gravitational load. As a model system, a bioactive glass called BP1 (48.4 SiO₂, 1 B₂O₃, 2 P₂O₅, 36.6 CaO, 6.6 K₂O, 5.6 Na₂O (mol%)), which has a chemical composition based on that of ICIE16, was employed in this work. In addition, ICIE16 was used as a reference glass. The results show that the suggested design is a very promising tool to track the real-time deformation of 3D printed glass-ceramic specimens and gives a good indication for the onset of crystallization as well.     

Cross-Recognition of Promoters by the Nine SigB Homologues Present in Streptomyces coelicolor A3(2)

In contrast to Bacillus subtilis, Streptomyces coelicolor A3(2) contains nine homologues of stress response sigma factor SigB with a major role in differentiation and osmotic stress response. The aim of this study was to further characterize these SigB homologues. We previously established a two-plasmid system to identify promoters recognized by sigma factors and used it to identify promoters recognized by the three SigB homologues, SigF, SigG, and SigH from S. coelicolor A3(2). Here, we used this system to identify 14 promoters recognized by SigB. The promoters were verified in vivo in S. coelicolor A3(2) under osmotic stress conditions in sigB and sigH operon mutants, indicating some cross-recognition of these promoters by these two SigB homologues. This two-plasmid system was used to examine the recognition of all identified SigB-, SigF-, SigG-, and SigH-dependent promoters with all nine SigB homologues. The results confirmed this cross-recognition. Almost all 24 investigated promoters were recognized by two or more SigB homologues and data suggested some distinguishing groups of promoters recognized by these sigma factors. However, analysis of the promoters did not reveal any specific sequence characteristics for these recognition groups. All promoters showed high similarity in the -35 and -10 regions. Immunoblot analysis revealed the presence of SigB under osmotic stress conditions and SigH during morphological differentiation. Together with the phenotypic analysis of sigB and sigH operon mutants in S. coelicolor A3(2), the results suggest a dominant role for SigB in the osmotic stress response and a dual role for SigH in the osmotic stress response and morphological differentiation. These data suggest a complex regulation of the osmotic stress response in relation to morphological differentiation in S. coelicolor A3(2).     

Genetische Analysen an Arbeitnehmern

Die Zulässigkeit genetischer Untersuchungen an Arbeitnehmern wird in Deutschland neu diskutiert, nachdem einer hessischen Lehrerin die Verbeamtung auf Probe zunächst verweigert wurde, weil ihr Vater an der Huntington-Krankheit leidet. Es soll untersucht werden, ob eine gesetzliche Regelung genetischer Untersuchungen in der Arbeitsmedizin wünschenswert ist und welche ethischen Maßstäbe dabei zu berücksichtigen wären. Gendiagnostische Untersuchungsverfahren im engeren Sinn finden noch keine breite Anwendung in der Arbeits- und Betriebsmedizin. Die Nutzung genetischer Informationen gehört aber auch hier zum Standard. Damit sind verschiedene ethische Konflikte verbunden, die insbesondere die Bereiche Autonomie und Diskriminierung betreffen. Gesetzliche Regelungen sollten sich daher nicht an der jeweiligen gendiagnostischen Technologie orientieren, sondern an der prognostisch-prädiktiven Qualität genetischen Wissens. Das Machtungleichgewicht am Arbeitsplatz und die immanenten Interessenkonflikte machen gesetzliche Regelungen erforderlich, die angesichts der zunehmenden Verfügbarkeit prädiktiver medizinischer Informationen Personenrechte schützen und einen fairen Interessenausgleich fördern.     

Determination of oxygen permeability/transmissibility and storage of contact lenses using HPLC with reductive electrochemical detection in combination with a specifically designed sampling unit

A new analytical technique for the determination of oxygen permeability/transmissibility of contact lenses is presented in this paper. The method is based on high performance liquid chromatography (HPLC) with reductive electrochemical detection at -750 mV (vs Ag/AgCl) in combination with a patented sampling chamber that was designed especially for the purpose to determine oxygen at nanomolar levels. Compared to conventional method, the new technique exhibits higher sensitivity, selectivity, and versatility. The method permits the selective determination of oxygen permeability (Dk/L)/transmissibility (Dk) of soft as well as rigid contact lenses with good agreement with the Dk/L (Dk) values reported in the literature. Precision was determined by repeated measurements and yielded relative standard deviations of 3-8% for hydrophile lenses and 5-13% for rigid contact lenses. Because of the extraordinarily high sensitivity of the chromatographic oxygen sensor for the first time, the capability of hydrogel lenses to store oxygen could also be directly monitored.     

Methods,architecture, evaluation and usability of a case-based antibiotics advisor

In this paper, we discuss the usability of an antibiotics therapy adviser, with a broad, complex spectrum of functions which we have developed within the ICONS project. We present the architecture of the system, case-based reasoning methods used, steps and results of medical evaluations, which are concerning the quality of the recommended therapies, the user friendliness of the system and the interpretation of laboratory results. Furthermore, we discuss problems of transferability of such a system from one site to another as well as problems of local susceptibility patterns and individual dose regimens.     

Separation of the bulk and grain boundary contributions to the total conductivity of solid lithium-ion conducting electrolytes

The transport properties of lithium-ion conducting Li_3xLa_2/3-xTiO₃ are studied for bulk and grain-boundary effects. This paper introduces a procedure for investigating bulk and grain-boundary polarization contributions using electrochemical impedance spectroscopy (EIS) and subsequent analysis via the distribution function of relaxation times (DRT) [1]. The frequency range of impedance spectroscopy is extended up to 120 MHz to resolve all conductivity contributions occurring in a polycrystalline solid electrolyte. Intra grain (bulk) and inter grain (grain boundary) conductivity contributions are separated using (i) a systematic variation of solid electrolyte contacting, (ii) two different solid electrolyte microstructures and activation energies were determined using adequate equivalent circuit models. Finally, these results are supported by SEM analysis, revealing different grain size distributions and different contents of inhomogeneities in Li_3xLa_2/3-xTiO₃ solid electrolytes sintered at 1400°C and at 1450°C.     

The role of residues outside the active site: structural basis for function of C191 mutants of Escherichia coli aspartate aminotransferase

In previous kinetic studies of Escherichia coli aspartate aminotransferase,it was determined that some substitutions of conserved cysteine191, which is located outside of the active site, altered thekinetic parameters of the enzyme (Gloss,L.M., Spencer,D.E. andKirsch,J.F., 1996, Protein Struct. Funct. Genet., 24, 195–208).The mutations resulted in an alkaline shift of 0.6–0.8pH units for the pK_a of the internal aldimine between the PLPcofactor and Lys258. The change in the pK_a affected the pH dependenceof the k_cat/K_m (aspartate) values for the mutant enzymes. Tohelp to understand these observations, crystal structures offive mutant forms of E.coli aspartate aminotransferase (themaleate complexes of C191S, C191F, C191Y and C191W, and C191Swithout maleate) were determined at about 2 Å resolutionin the presence of the pyridoxal phosphate cofactor. The overallthree-dimensional fold of each mutant enzyme is the same asthat of the wild-type protein, but there is a rotation of themutated side chain around its C