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排序方式: 共有668条查询结果,搜索用时 31 毫秒
1.
Sebastian Roth Peter Stockinger Jakob Steff Simon Steimle Dr. Viktor Sautner Prof. Dr. Kai Tittmann Prof. Dr. Jürgen Pleiss Prof. Dr. Michael Müller 《Chembiochem : a European journal of chemical biology》2020,21(18):2615-2619
The family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs) comprises numerous biocatalysts capable of C=O or C=C reduction. The highly homologous noroxomaritidine reductase (NR) from Narcissus sp. aff. pseudonarcissus and Zt_SDR from Zephyranthes treatiae, however, are SDRs with an extended imine substrate scope. Comparison with a similar SDR from Asparagus officinalis (Ao_SDR) exhibiting keto-reducing activity, yet negligible imine-reducing capability, and mining the Short-Chain Dehydrogenase/Reductase Engineering Database indicated that NR and Zt_SDR possess a unique active-site composition among SDRs. Adapting the active site of Ao_SDR accordingly improved its imine-reducing capability. By applying the same strategy, an unrelated SDR from Methylobacterium sp. 77 (M77_SDR) with distinct keto-reducing activity was engineered into a promiscuous enzyme with imine-reducing activity, thereby confirming that the ability to reduce imines can be rationally introduced into members of the “classical” SDR enzyme family. Thus, members of the SDR family could be a promising starting point for protein approaches to generate new imine-reducing enzymes. 相似文献
2.
Viktor G. Khizhnyak Vitalii I. Korol' Alexei D. Kostenko 《Powder Metallurgy and Metal Ceramics》2003,42(11-12):644-648
Wear resistance measurements have been made with U8A steel bearing protective coatings based on the carbides of titanium, vanadium, and chromium or iron borides, for various forms of wear. The carbide and boride coatings raise the wear resistance considerably (by factors of 6-30 in accordance with the type of wear). Measurements have been made on the microhardness, microbrittleness, and adhesion of the coating to the substrate, which are effective characteristics that quite fully reflect the effects of the microhardness and state of stress, structure, and defectiveness on the wear resistance. 相似文献
3.
Lavrenko Vladimir A. Shvets Vera A. Talash Viktor N. 《Powder Metallurgy and Metal Ceramics》2004,43(1-2):62-66
The corrosion properties of TiCN, TiCN – AlN, and (TiCN – AlN) – (Fe – Cr) ceramics as well as those of the individual components TiN and TiC in a 3% NaCl solution have been investigated. The kinetics and the mechanism of anode dissolution of metals and oxidation of specimens have been studied by using polarization curves, chemical and x-ray phase analyses, Auger electron spectroscopy, and scanning electron microscopy (SEM). TiCN and TiCN – AlN composites have been found to be the most corrosion-resistant. The presence of a metallic binder in the titanium carbon nitride somewhat decreases the corrosion resistance of the ceramics. On the whole, however, the ceramics developed boast a significantly higher corrosion resistance than that of structural steel. 相似文献
4.
5.
A GaAs microwave power MESFET structure is described that achieves a significant improvement of the gate mode attenuation by incorporating a suitably terminated transmission line parallel to the gate. The reduced attenuation allows a much wider single gate (a factor of 4 is possible) and a corresponding improvement of the total output power. It is shown that this approach leads to higher gain and cutoff frequency. An additional advantage of this MESFET structure is its higher input resistance relative to a device with equal total gate width but more gates in parallel. This results in simpler matching circuits of greater bandwidth. The single-gate structure can be connected in parallel to further increase the total output power. The results of an electrical characterization of the devices are presented, and its advantages and potential application are discussed 相似文献
6.
Mikhail Yu. Sinev Yurii P. Tulenin Olga V. Kalashnikova Viktor Yu. Bychkov Vladimir N. Korchak 《Catalysis Today》1996,32(1-4):157-162
The analysis of methane oxidation in a wide range of pressures (0.05–10 atm) demonstrates that the efficiency of CH3 radicals recombination is of great importance for high selectivity of C2 hydrocarbons formation. The relative efficiency of different “colliders” assisting the stabilization of exited C2H*6 molecules increases in the series: solid surface> Ar> He. The increase of the overall reaction rate upon increasing pressure of the inert gases in the case of catalysts having a higher surface area and more developed pore structure is likely due to the contribution of the surface-induced chain reaction in the volume of pores. 相似文献
7.
Yury G. Gogotsi Franz Porz Viktor P. Yaroshenko 《Journal of the American Ceramic Society》1992,75(8):2251-2259
The study examines the effect which the composition of hot-pressed electroconductive ceramics has on their structure, mechanical properties, and oxidation behavior, for ceramics of the type AIN–Al2 O3 –42 wt% TiN, differing in the AIN/Al2 O3 ratio. The results are physico-mechanical property data, including density, hardness, strength, fracture toughness, and wear resistance. A correlation was found between the wear resistance and fracture toughness. The analysis of oxidation products revealed the formation of α-Al2 O3 and rutile in the temperature range from 600° to 1100°C and aluminum titanate above 1200°C. The spallation of the oxide layer caused low oxidation resistance of Al2 O3 -rich composites above 1250°C. The oxidation of composites was compared with the oxidation of pure TiN. The relationship is discussed between material properties, composition, phases, and processing parameters. 相似文献
8.
We have designed Particle-in-Cell algorithms for emerging architectures. These algorithms share a common approach, using fine-grained tiles, but different implementations depending on the architecture. On the GPU, there were two different implementations, one with atomic operations and one with no data collisions, using CUDA C and Fortran. Speedups up to about 50 compared to a single core of the Intel i7 processor have been achieved. There was also an implementation for traditional multi-core processors using OpenMP which achieved high parallel efficiency. We believe that this approach should work for other emerging designs such as Intel Phi coprocessor from the Intel MIC architecture. 相似文献
9.
Nam Ma Yinglong Xia Viktor K. Prasanna 《International journal of parallel programming》2014,42(1):219-237
We investigate data parallel techniques for belief propagation in acyclic factor graphs on multi-core systems. Belief propagation is a key inference algorithm in factor graph, a probabilistic graphical model that has found applications in many domains. In this paper, we explore data parallelism for basic operations over the potential tables in belief propagation. Data parallel techniques for these table operations are developed for shared memory platforms. We then propose a complete belief propagation algorithm using these table operations to perform exact inference in factor graphs. The proposed algorithms are implemented on state-of-the-art multi-socket multi-core systems with additional NUMA-aware optimizations. Our proposed algorithms exhibit good scalability using a representative set of factor graphs. On a four-socket Intel Westmere-EX system with 40 cores, we achieve 39.5 $\times $ speedup for the table operations and 39 $\times $ speedup for the complete algorithm using factor graphs with large potential tables. 相似文献
10.
In the literature on optimal regular volume sampling, the Body‐Centered Cubic (BCC) lattice has been proven to be optimal for sampling spherically band‐limited signals above the Nyquist limit. On the other hand, if the sampling frequency is below the Nyquist limit, the Face‐Centered Cubic (FCC) lattice was demonstrated to be optimal in reducing the prealiasing effect. In this paper, we confirm that the FCC lattice is indeed optimal in this sense in a certain interval of the sampling frequency. By theoretically estimating the prealiasing error in a realistic range of the sampling frequency, we show that in other frequency intervals, the BCC lattice and even the traditional Cartesian Cubic (CC) lattice are expected to minimize the prealiasing. The BCC lattice is superior over the FCC lattice if the sampling frequency is not significantly below the Nyquist limit. Interestingly, if the original signal is drastically undersampled, the CC lattice is expected to provide the lowest prealiasing error. Additionally, we give a comprehensible clarification that the sampling efficiency of the FCC lattice is lower than that of the BCC lattice. Although this is a well‐known fact, the exact percentage has been erroneously reported in the literature. Furthermore, for the sake of an unbiased comparison, we propose to rotate the Marschner‐Lobb test signal such that an undue advantage is not given to either lattice. 相似文献