Charge Transfer Variability in Misfit Layer Compounds: Comparison of SnS-SnS2 and LaS-TaS2

The present paper compares and discusses two selected misfit (layer) compounds exemplarily, namely SnS-SnS₂ and LaS-TaS₂. We have employed a density-functional theory-based approach to calculate structural, energetic, and electronic properties of these structures. We have put emphasis on the difference between single layers, combined double-layer systems and periodically stacked bulk structures. Especially the varying magnitudes of charge transfer between the sublayers were studied. We demonstrate how the chemical constitution of the sublayers affects the interlayer interactions: these may be a weak non-bonding van-der-Waals dominated interlayer interaction as in SnS-SnS₂ and many other layered structures or a strong interaction related to a remarkable charge transfer between the layers as in LaS-TaS₂.     

System-guided view integration for object-oriented databases

Some of the shortcomings of current view integration methodologies, namely, a low emphasis on full-scale automated systems, a lack of algorithmic specifications of the integration activities, inattention to the design of databases with new properties such as databases for computer-aided design, and insufficient experience with data models with a rich set of type and abstraction mechanisms, are attacked simultaneously. The focus is on design databases for software engineering applications. The approach relies on a semantic model based on structural object-orientation with various features tailored to these applications. The expressiveness of the model is used to take the first steps toward algorithmic solutions, and it is demonstrated how corresponding tools could be embedded methodically within the view integration process and technically within a database design environment. The central ideal is to compute so-called assumption predicates that express suggested similarities between structures in two schemas to be integrated, and then have a human integrator confirm or reject them. The basic method is exemplified for the CERM data model that includes molecular aggregation, generalization, and versioning     

Characterization and expression analysis of a gene cluster for nitrate assimilation from the yeast Arxula adeninivorans

In Arxula adeninivorans nitrate assimilation is mediated by the combined actions of a nitrate transporter, a nitrate reductase and a nitrite reductase. Single‐copy genes for these activities (AYNT1, AYNR1, AYNI1, respectively) form a 9103 bp gene cluster localized on chromosome 2. The 3210 bp AYNI1 ORF codes for a protein of 1070 amino acids, which exhibits a high degree of identity to nitrite reductases from the yeasts Pichia anomala (58%), Hansenula polymorpha (58%) and Dekkera bruxellensis (54%). The second ORF (AYNR1, 2535 bp) encodes a nitrate reductase of 845 residues that shows significant (51%) identity to nitrate reductases of P. anomala and H. polymorpha. The third ORF in the cluster (AYNT1, 1518 bp) specifies a nitrate transporter with 506 amino acids, which is 46% identical to that of H. polymorpha. The three genes are independently expressed upon induction with NaNO₃. We quantitatively analysed the promoter activities by qRT–PCR and after fusing individual promoter fragments to the phytase (phyK) gene from Klebsiella sp. ASR1. The AYNI1 promoter was found to exhibit the highest activity, followed by the AYNT1 and AYNR1 elements. Direct measurements of nitrate and nitrite reductase activities performed after induction with NaNO₃ are compatible with these results. Both enzymes show optimal activity at around 42°C and near‐neutral pH, and require FAD as a co‐factor and NADPH as electron donor. Copyright © 2009 John Wiley & Sons, Ltd.     

Atan1p—an extracellular tannase from the dimorphic yeast Arxula adeninivorans: molecular cloning of the ATAN1 gene and characterization of the recombinant enzyme

The tannase‐encoding Arxula adeninivorans gene ATAN1 was isolated from genomic DNA by PCR, using as primers oligonucleotide sequences derived from peptides obtained after tryptic digestion of the purified tannase protein. The gene harbours an ORF of 1764 bp, encoding a 587‐amino acid protein, preceded by an N‐terminal secretion sequence comprising 28 residues. The deduced amino acid sequence was similar to those of tannases from Aspergillus oryzae (50% identity), A. niger (48%) and putative tannases from A. fumigatus (52%) and A. nidulans (50%). The sequence contains the consensus pentapeptide motif (–Gly–X–Ser–X–Gly–) which forms part of the catalytic centre of serine hydrolases. Expression of ATAN1 is regulated by the carbon source. Supplementation with tannic acid or gallic acid leads to induction of ATAN1, and accumulation of the native tannase enzyme in the medium. The enzymes recovered from both wild‐type and recombinant strains were essentially indistinguishable. A molecular mass of ～320 kDa was determined, indicating that the native, glycosylated tannase consists of four identical subunits. The enzyme has a temperature optimum at 35–40 °C and a pH optimum at ～6.0. The enzyme is able to remove gallic acid from both condensed and hydrolysable tannins. The wild‐type strain LS3 secreted amounts of tannase equivalent to 100 U/l under inducing conditions, while the transformant strain, which overexpresses the ATAN1 gene from the strong, constitutively active A. adeninivorans TEF1 promoter, produced levels of up to 400 U/l when grown in glucose medium in shake flasks. Copyright © 2009 John Wiley & Sons, Ltd.     

On the trueness of total boron contents of some certified reference steel samples

In order to obtain true values for the boron content of steel samples, the need for complete dissolution of all boron phases present in the steels is stressed and the importance of an appropriate calibration procedure is also emphasised. The results of international research by ECISS/TC20 using direct spectrophotometry with curcumin (pr EN 10 200) have been compared with those of the curcumin method after separation by 2-ethyl-1.3-hexanediol-chloroform extraction and those of the 1.1'-dianthrimide method after distillation of the boron methylester by means of an all-quartz apparatus. The results obtained were independent of the method of determination.     

Erfahrungen bei der Bestimmung der Bindungsverhältnisse des Stickstoffs in Stählen durch Heißextraktion mit Wasserstoff

Untersuchung über die Nitridausscheidung in Stählen durch Bestimmung eines Stickstoffanteils, der durch Heißextraktion mit Wasserstoff ermittelt wird (N_H). Ergebnisse eines Ringversuches. Beschreibung des Verfahrens und Beurteilung von Fehlermöglichkeiten. Anwendungen.     

Bestimmung von Stickstoffanteilen im Stahl durch Reduktion mit Wasserstoff

Möglichkeiten zur Ermittlung der Art der Stickstoffbindung. Untersuchung der Stickstoffabbindung in aluminiumberuhigten Stählen bei verschiedenen Ausscheidungszuständen. Anwendung des Wasserstoffreduktionsverfahrens zur Bestimmung des nicht an Aluminium gebundenen Stickstoffs. Isolierung des Aluminiumnitrids durch Lösen von Stahlspänen in Brom-Ester-Gemisch. Elektronenmikroskopische Beobachtung der Aluminiumnitridausscheidung. Einfluß der Teilchengröße auf die Untersuchungsergebnisse.