Identification of Suitable Ligands for a Transition Metal‐Catalyzed Reaction: Screening of a Modular Ligand Library in the Enantioselective Hydroboration of Styrene

Based on a general modular synthetic scheme, a variety of chiral bidentate P/P‐, P/S‐, P/N‐, and P/Se‐ligands is accessible in an efficient divergent manner starting from phenol or naphthol derived backbone systems. A library of 20 selected ligands was tested in the Rh‐catalyzed asymmetric hydroboration of styrene to give 1‐phenylethanol in up to 91% ee after oxidative work‐up. It was demonstrated that small variations of the ligand structures lead to pronounced, unpredictable differences in the performance of the in situ generated rhodium complexes. The modular approach should be applicable for the identification and optimization of suitable ligands for other transition metal‐catalyzed transformations with comparably low effort.     

In situ characterization of alloy catalysts for low-temperature graphene growth

Low-temperature (～450 °C), scalable chemical vapor deposition of predominantly monolayer (74%) graphene films with an average D/G peak ratio of 0.24 and domain sizes in excess of 220 μm(2) is demonstrated via the design of alloy catalysts. The admixture of Au to polycrystalline Ni allows a controlled decrease in graphene nucleation density, highlighting the role of step edges. In situ, time-, and depth-resolved X-ray photoelectron spectroscopy and X-ray diffraction reveal the role of subsurface C species and allow a coherent model for graphene formation to be devised.     

Das Aufspritzen des Kraftstoffes im Dieselmotor

Ohne Zusammenfassung VDI Die ausführliche Arbeit erscheint demn?chst als Heft 53 der Reihe “Deutsche Kraftfahrtforschung”, Berlin 1940.     

Early warning in the light of theories of technological change

The crystal structure of the molybdenum enzyme dimethylsulphoxide reductase (DMSOR) has been determined at 1.9 A resolution with substrate bound at the active site. DMSOR is an oxotransferase which catalyses the reduction of dimethylsulphoxide (DMSO) to dimethylsulphide (DMS) in a two stage reaction which is linked to oxygen atom transfer and electron transfer. In the first step, DMSO binds to reduced (Mo(IV)) enzyme, the enzyme is oxidised to Mo(VI) with an extra oxygen ligand and DMS is released. Regeneration of reduced enzyme is achieved by transfer of two electrons, successively from a specific cytochrome, and release of the oxygen as water. The enzyme, purified under aerobic conditions, is in the oxidised (Mo(VI)) state. Addition of a large excess of DMS to the oxidised enzyme in solution causes a change in the absorption spectrum of the enzyme. The same reaction occurs within crystals of the enzyme and the crystal structure reveals a complex with DMSO bound to the molybdenum via its oxygen atom. X-ray edge data indicate that the metal is in the Mo(IV) state. The DMSO ligand replaces one of the two oxo groups which ligate the oxidised form of the enzyme, suggesting very strongly that this is the oxygen which is transferred during catalysis. Residues 384 to 390, disordered in the oxidised enzyme, are now clearly seen in the cleft leading to the active site. The side-chain of Trp388 forms a lid trapping the substrate/product.     

3D T 1-mapping for the characterization of deep vein thrombosis

Purpose  

The aim of this work was to investigate fast T ₁-mapping for the characterization of deep vein thrombosis (DVT).     

Parallel programming with Polaris

Parallel programming tools are limited, making effective parallel programming difficult and cumbersome. Compilers that translate conventional sequential programs into parallel form would liberate programmers from the complexities of explicit, machine oriented parallel programming. The paper discusses parallel programming with Polaris, an experimental translator of conventional Fortran programs that target machines such as the Cray T3D     

Hardware-accelerated design space exploration framework for communication systems

The efficient hardware implementation of signal processing algorithms requires a rigid characterization of the interdependencies between system parameters and hardware costs. Pure software simulation of bit-true implementations of algorithms with high computational complexity is prohibitive because of the excessive runtime. Therefore, we present a field-programmable gate array (FPGA) based hybrid hardware-in-the-loop design space exploration (DSE) framework combining high-level tools (e.g. MATLAB, C++) with a System-on-Chip (SoC) template mapped on FPGA-based emulation systems. This combination significantly accelerates the design process and characterization of highly optimized hardware modules. Furthermore, the approach helps to quantify the interdependencies between system parameters and hardware costs. The achievable emulation speedup using bit-true hardware modules is a key enabling the optimization of complex signal processing systems using Monte Carlo approaches which are infeasible for pure software simulation due to the large required stimuli sets. The framework supports a divide-and-conquer approach through a flexible partitioning of complex algorithms across the system resources on different layers of abstraction. This facilitates to efficiently split the design process among different teams. The presented framework comprises a generic state of the art SoC infrastructure template, a transparent communication layer including MATLAB and hardware interfaces, module wrappers and DSE facilities. The hardware template is synthesizable for a variety of FPGA-based platforms. Implementation and DSE results for two case studies from the different application fields of synthetic aperture radar image processing and interference alignment in communication systems are presented.     

Improving chlorine disinfection of wastewater by ultrasound application .

The presence of soluble organic material as well as high concentrations of suspended matter in waters and wastewaters affect the efficiency when chlorine is used as disinfection agent. The objective of our work is to explore to which extend ultrasonic treatment can facilitate wastewater disinfection with chlorine in order to bring down doses of ecologically questionable chlorine and to shorten contact times. Sewage treatment plant (STP) effluents with different concentrations of suspended solids are exposed to sonication in combination with chlorine dosage. We observed that enhancement of chlorine efficiency is better for samples with higher concentrations of suspended matter. For samples with a TSS concentration of 50 mg/L chlorination efficiency (2 mg/L) can be doubled from 0.7 to 1.4 log when treated simultaneously with 20 kHz ultrasound for 5 minutes, i.e. levels of indicator organisms can be brought down to numbers that conventionally require far higher doses of chemical disinfectants. As subsequent sonication/chlorination does not have the same significant effect as simultaneous application of these two means, ultrasound does not just have a declumping effect; it seems that ultrasound application provokes a better chlorine dispersion in the aqueous media which improves the fast chemical and bactericidal reaction.