Braunschweig University of Technology

About: Braunschweig University of Technology is a education organization based out in Braunschweig, Germany. It is known for research contribution in the topics: Population & Computer science. The organization has 13268 authors who have published 26707 publications receiving 611590 citations.

An Investigation into Fixed Energy Consumption of Machine Tools

Abstract: Improving energy efficiency of manufacturing processes requires knowledge about the energy consumption as a function of the machine tool and cutting process itself. Both theoretical and empirical models of unit process energy consumption have emphasized the relevance of fixed energy consumption which ensures the machine readiness. However, the machine tool behavior during the stand-by mode is lack of thorough study. This paper presented the investigation of fixed energy consumption from definition and description to improvement strategies. Six machine tools covering different manufacturing processes are selected for this investigation in order to evaluate the future savings.

Natural microbial diversity in superficial sediments of Milazzo Harbor (Sicily) and community successions during microcosm enrichment with various hydrocarbons.

Abstract: Summary Hydrocarbon-contaminated superficial sediments collected from the Harbor of Milazzo (Tirrenean Sea, northern Sicily), a zone strongly affected by anthropogenic activities, were examined for in situ biodegradative capacities. A culture-independent molecular phylogenetic approach was used to study the influence of hydrocarbon and nutrient addition on the activity and diversity of the indigenous microbiota during a microcosm evaluation. The autochthonous microbial community in non-polluted sediments was represented by eubacterial phylotypes grouped within Proteobacteria, CFB and Firmicutes. The archaeal domain was represented by members of Marine Group I of Crenarchaeota. The majority of recovered sequences was affiliated with heterotrophic genera Clostridium and Vibrio, typical members of eutrophic coastal environments. Amendments of hydrocarbons and mineral nutrients to microcosms dramatically changed the initial diversity of the microbial community. Only bacterial phylotypes affiliated with Proteobacteria and CFB division were detected. The decrease in diversity observed in several microcosms could be explained by the strong selection for microorganisms belonging to group of marine hydrocarbonoclastic γ-Proteobacteria, namely Alcanivorax, Cycloclasticus, Marinobacter, Marinobacterium/Neptunomonas and Thalassolituus. This study demonstrated that nutrient amendment to hydrocarbon-contaminated superficial sediments enhanced the indigenous microbial biodegradation activity and that highly specialized marine hydrocarbonoclastic bacteria, representing a minor fraction in the natural microbial community, play an important role in the biodegradation of petroleum hydrocarbons accidentally entering the coastal environment.

Prokaryotic Heme Biosynthesis: Multiple Pathways to a Common Essential Product.

Abstract: The advent of heme during evolution allowed organisms possessing this compound to safely and efficiently carry out a variety of chemical reactions that otherwise were difficult or impossible. While it was long assumed that a single heme biosynthetic pathway existed in nature, over the past decade, it has become clear that there are three distinct pathways among prokaryotes, although all three pathways utilize a common initial core of three enzymes to produce the intermediate uroporphyrinogen III. The most ancient pathway and the only one found in the Archaea converts siroheme to protoheme via an oxygen-independent four-enzyme-step process. Bacteria utilize the initial core pathway but then add one additional common step to produce coproporphyrinogen III. Following this step, Gram-positive organisms oxidize coproporphyrinogen III to coproporphyrin III, insert iron to make coproheme, and finally decarboxylate coproheme to protoheme, whereas Gram-negative bacteria first decarboxylate coproporphyrinogen III to protoporphyrinogen IX and then oxidize this to protoporphyrin IX prior to metal insertion to make protoheme. In order to adapt to oxygen-deficient conditions, two steps in the bacterial pathways have multiple forms to accommodate oxidative reactions in an anaerobic environment. The regulation of these pathways reflects the diversity of bacterial metabolism. This diversity, along with the late recognition that three pathways exist, has significantly slowed advances in this field such that no single organism's heme synthesis pathway regulation is currently completely characterized.

Bell inequalities and Entanglement

Abstract: We discuss general Bell inequalities for bipartite and multipartite systems, emphasizing the connection with convex geometry on the mathematical side, and the communication aspects on the physical side. Known results on families of generalized Bell inequalities are summarized. We investigate maximal violations of Bell inequalities as well as states not violating (certain) Bell inequalities. Finally, we discuss the relation between Bell inequality violations and entanglement properties currently discussed in quantum information theory.