Säurekatalysierte Umsetzungen von Aromaten mit Alkanen und Cycloalkanen. IX. Alkylierungen mit 2,2,4-Trimethylpentan (Isooctan)

Acid-catalyzed Reactions of Aromatic Hydrocarbons with Alkanes and Cycloalkanes. IX. Alkylations with 2,2,4-Trimethylpentane (Isooctane) The non-conventional alkylation of benzene, toluene, ethyl- and isopropylbenzene, fluoro- and chlorobenzene with 2,2,4-trimethylpentane in the presence of acid catalysts is described. The composition of the rather complex reaction mixtures is determined by gas-liquid chromatography and mass spectrometry, tert. butylarenes being the main products beside alkylsubstituted indanes and tetralines. Their formation is interpreted as a competition between fragmentation and isomerization of the alkylating agent. By use of trifluoromethanesulfonic acid or combinations of catalysts from HF or HSO₃F with variant metallic fluorides at lower temperatures the selectivity of the reaction may be partially raised.     

Bekämpfung der Computerkriminalität

Die Autoren setzen sich mit dem Gesetzentwurf zur Bek?mpfung der Computerkriminalit?t auseinander, insbesondere mit der Strafbarkeit des Einsatzes von Analysetools.     

Confinement-Induced Phonon Softening and Hardening in Sb2Te3 Thin Films

Scaling effects in Sesqui-chalcogenides are of major interest to understand and optimize their performance in heavily scaled applications, including topological insulators and phase-change devices. A combined experimental and theoretical study is presented for molecular beam epitaxy-grown films of antimony-telluride  (Sb₂Te₃). Structural,vibrational, optical, and bonding properties upon varying confinement are studied for thicknesses ranging from 1.3 to 56 nm. In ultrathin films, the low-frequency coherent phonons of A_1g¹ symmetry are softened compared to the bulk (64.5 cm⁻¹ at 1.3 nm compared to 68 cm⁻¹ at 55.8 nm). A concomitant increase of the high-frequency A_1g² Raman mode is seen. X-ray diffraction analyses unravel an accompanying out of plane stretch by 5%, mainly stemming from an increase in the Te-Te gap. This conclusion is supported by density functional theory slab models, which reveal a significant dependency of chemical bonding on film thickness. Changes in atomic arrangement, vibrational frequencies, and bonding extend over a thickness range much larger than observed for other material classes. The finding of these unexpectedly pronounced thickness-dependent effects in quasi-2D material Sb₂Te₃ allows tuning of the film properties with thickness. The results are discussed in the context of a novel bond-type, characterized by a competition between electron localization and delocalization.     

Dimensional stability and irreversible thickness swell of thermally treated oriented strandboards (OSB)

This paper discusses thickness swell and irreversible thickness swell properties after immersion in water for 24, 48, 96 and 168 h, changes in equilibrium moisture content (EMC) and determination of dimensional changes associated with changes in relative humidity of laboratory-made methylene diphenyl diisocyanate (MDI)-bonded oriented strandboards (OSB). It was observed that thermal post-treatment of said OSB had a positive effect on the above mentioned properties. As far as thickness swell and irreversible thickness swell are concerned, it could be shown that the thermally modified variants generally performed better, i.e. lower values than the respective untreated ones for all four immersion periods and MDI dosages of 3.0, 4.0 und 5.0 %. It was furthermore noticeable that the swelling potential was not exhausted after immersion for 24 h and a prolonged immersion period led to significant increases in respective thickness swelling values. The EMC was decreased and the determination of dimensional changes associated with changes in relative humidity showed that thermally post-treated OSB displayed lower thickness changes when “drying“(from 65 to 30 % relative humidity; RH) as well as when “moistening“(from 65 to 85 % RH) than the untreated controls. For all of the above mentioned properties it can be concluded that the influence of the post-treatment temperature proved to be greater than the reduction of the hydrophobing agent from 1.0 to 0 %.     

Säurekatalysierte Umsetzungen von Aromaten mit Alkanen und Cycloalkanen. VI. Alkylierungen mit niederen Alkanen (C3?C5)

Acid-catalyzed Reactions of Aromatic Hydrocarbons with Alkanes and Cycloalkanes. VI. Alkylations with Lower Alkanes (C₃ C₅) Benzene and toluene are alkylated in the presence of HF/SbF₅, CF₃SO₃H/SbF₅, HBr/AlBr₃ or CF₃SO₃H/AlBr₃ by propane, n- and isobutane or n- and isopentane to products of complex composition, using a special apparature where the gases are circulated. The results of these experiments are compared with corresponding results in an autoclave. The reaction products of benzene with isobutane were analyzed, qualitatively and quantitatively, by gas-liquid chromatography and mass spectrometry.     

Biological Activity of Different Forms of Oxidized Parathyroid Hormone

Preclinical studies have shown that parathyroid hormone (PTH) loses its biological effects through oxidation. PTH can be oxidized at methionines 8 and 18. Three possible variations of oxidized PTH (oxPTH) exist: Met8(ox)PTH, Met18(ox)PTH, and Met8, Met18(di-ox)PTH. A recent study showed that Met18(ox)PTH retained biological activity and was able to upregulate Fgf23 gene expression, whereas Met8(ox)PTH and Met8, Met18(di-ox)PTH showed less or no biological activity. An earlier study likewise showed that the oxidation of Met18 has minor effects on the secondary structure of PTH, whereas the oxidation of Met8 causes substantial structural changes, consistent with another study showing that oxidization just at Met8 blocks the generation of the second messenger cAMP, whereas the effect of the oxidation of Met18 is much less potent in inhibiting cAMP formation. A considerable percentage of circulating PTH in chronic kidney disease (CKD) patients is oxidized. However, we do not know the relative amounts of the different forms of oxPTH with agonistic, partial agonistic, or even antagonistic biological actions in different CKD populations. This might explain different clinical findings in the different CKD populations analyzed so far. The currently available method that was used in these clinical studies just distinguishes between oxPTH and noxPTH without being able to differentiate between different forms of oxPTH. Only methods of PTH measurement that are able to differentiate between PTH forms (noxPTH, Met8(ox)PTH, Met18(ox)PTH, and Met8, Met18(di-ox)PTH) have the potential to improve patient care, because only these methods will definitively separate bioactive from non-bioactive PTH forms. Such methods need to be developed, validated, and used in prospective randomized clinical trials to define the potential value of bioactive PTH forms as a predictor of cardiovascular events, mortality, and bone turnover.     

Tool life increase of coated carbide tools by micro blasting

In today’s production engineering nearly every cutting tool is coated. Since using the technology of coating different process chains for reconditioning have been developed. The last innovation is micro blasted coatings, which is the main topic of this paper. Concerning this topic influences on tool life have been investigated. Investigations on the tool life especially of hobbing tools were made thereby and coherences between coating bond, roughness and other attributes were discovered. The investigations were made with an aluminum oxide and a zirconium oxide as blasting abrasives and a variation of the blasting parameters pressure and period. The final result is an optimization of tool wear behavior by micro blasting of the coating.