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排序方式: 共有208条查询结果,搜索用时 31 毫秒
51.
Mikhail Gorlov Nikolay Bredov Andrey Esin Igor Sirotin Mikhail Soldatov Volodymyr Oberemok Vyacheslav V. Kireev 《International journal of molecular sciences》2021,22(11)
Despite a significant number of investigations in the field of phosphazene chemistry, the formation mechanism of this class of cyclic compounds is still poorly studied. At the same time, a thorough understanding of this process is necessary, both for the direct production of phosphazene rings of a given size and for the controlled cyclization reaction when it is secondary and undesirable. We synthesized a series of short linear phosphazene oligomers with the general formula Cl[PCl2=N]n–PCl3+PCl6– and studied their tendency to form cyclic structures under the influence of elevated temperatures or in the presence of nitrogen-containing agents, such as hexamethyldisilazane (HMDS) or ammonium chloride. It was established that linear oligophosphazenes are inert when heated in the absence of the mentioned cyclization agents, and the formation of cyclic products occurs only when these agents are involved in the process. The ability to obtain the desired size phosphazene cycle from corresponding linear chains is shown for the first time. Known obstacles, such as side interaction with the PCl6– counterion and a tendency of longer chains to undergo crosslinking elongation instead of cyclization are still relevant, and ways to overcome them are being discussed. 相似文献
52.
Mykola V Sopinskyy Viktoriya S Khomchenko Viktor V Strelchuk Andrii S Nikolenko Genadiy P Olchovyk Volodymyr V Vishnyak Viktor V Stonis 《Nanoscale research letters》2014,9(1):182
Carbon films on the Si/SiO2 substrate are fabricated using modified method of close space sublimation at atmospheric pressure. The film properties have been characterized by micro-Raman and X-ray photoelectron spectroscopy and monochromatic ellipsometry methods. Ellipsometrical measurements demonstrated an increase of the silicon oxide film thickness in the course of manufacturing process. The XPS survey spectra of the as-prepared samples indicate that the main elements in the near-surface region are carbon, silicon, and oxygen. The narrow-scan spectra of C1s, Si2p, O1s regions indicate that silicon and oxygen are mainly in the SiO
x
(x ≈ 2) oxide form, whereas the main component of C1s spectrum at 284.4 eV comes from the sp2-hybridized carbon phase. Micro-Raman spectra confirmed the formation of graphene films with the number of layers that depended on the distance between the graphite source and substrate. 相似文献
53.
Volodymyr Bushlya Filip Lenrick Axel Bjerke Hisham Aboulfadl Mattias Thuvander Jan-Eric Ståhl Rachid M'Saoubi 《CIRP Annals》2021,70(1):73-78
Recently, PcBN tooling have been successfully introduced in machining Ni-based superalloys, yet our knowledge of involved wear mechanisms remains limited. In this study, an in-depth investigation of PcBN tool degradation and related wear mechanisms when machining Inconel 718 was performed. Diffusional dissolution of cBN is an active wear mechanism. At high cutting speed oxidation of cBN becomes equally important. Apart from degradation, tool protection phenomena were also discovered. Oxidation of Inconel 718 resulted in formation of γ-Al2O3 and (Al,Cr,Ti)3O4 spinel that were deposited on the tool rake. Also on the rake, formation of (Ti,Nb,Cr)N takes place due to cBN-workpiece interaction. This creates a sandwich tool protection layer forming continuously as tool wear progresses. Such in operando protection enabled counterbalancing tool wear mechanisms and achieved high performance of PcBN in machining. 相似文献
54.
Andrey A. Poletaev Roman V. Denys Jan Petter Maehlen Jan Ketil Solberg Boris P. Tarasov Volodymyr A. Yartys 《International Journal of Hydrogen Energy》2012
In our earlier publication (Poletaev et al., J Alloys Compd., 509S (2011) S633) we reported a drastic variation of the structural and hydrogenation properties of LaMg∼12 intermetallic alloy caused by Rapid Solidification (RS). In present work we have probed the effect of nickel during the chemical modification of LaMg12, in combination with RS, on the structure, microstructure and hydrogen absorption–desorption properties of the alloys. 相似文献
55.
56.
Olena Stabnikova Suay‐Siong Ang Xue‐Yan Liu Volodymyr Ivanov Joo‐Hwa Tay Jing‐Yuan Wang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(4):455-461
The hybrid anaerobic solid–liquid (HASL) system was a modified two‐phase anaerobic digester developed for bioconversion of food waste. The aim of this study was to estimate the feasibility of the HASL system for the treatment of food waste with a high content of lipids. The presence of lipids in food waste increased the energy value of nutrients but could inhibit growth of methanogens. The positive effect of lipids on the performance of anaerobic digestion dominated when the contents of lipids were in the range from 20 to 30% of total solids of food waste. Lipid contents of 40% diminished the production of volatile fatty acids in the acidogenic reactor as well as biogas production and the concentration of total bacteria and methanogens in the methanogenic reactor. Therefore, the HASL system can be used for the treatment of lipid‐containing food wastes if the lipid content is below 40% of total solids. Copyright © 2005 Society of Chemical Industry 相似文献
57.
Guochun Shi Volodymyr Kindratenko Steven Gottlieb 《International journal of parallel programming》2009,37(5):488-507
We report the results of the bottom-up implementation of one MILC lattice quantum chromodynamics (QCD) application on the
Cell Broadband Engine™ processor. In our implementation, we preserve MILC’s framework for scaling the application to run on
a large number of compute nodes and accelerate computationally intensive kernels on the Cell’s synergistic processor elements.
Speedups of 3.4 × for the 8 × 8 × 16 × 16 lattice and 5.7 × for the 16 × 16 × 16 × 16 lattice are obtained when comparing
our implementation of the MILC application executed on a 3.2 GHz Cell processor to the standard MILC code executed on a quad-core
2.33 GHz Intel Xeon processor. We provide an empirical model to predict application performance for a given lattice size.
We also show that performance of the compute-intensive part of the application on the Cell processor is limited by the bandwidth
between main memory and the Cell’s synergistic processor elements, whereas performance of the application’s parallel execution
framework is limited by the bandwidth between main memory and the Cell’s power processor element. 相似文献
58.
Sunghan Kim Volodymyr F. Korolovych Rachel L. Muhlbauer Vladimir V. Tsukruk 《应用聚合物科学杂志》2020,137(44):49381
Three-dimensional (3D) printing is an attractive approach to fabricate highly porous extremely lightweight structures for architecture antivibrational packaging. We report 3D printing processing of model packaging structures using biodegradable poly(lactic acid) (PLA) as a source material, with acrylonitrile butadiene styrene (ABS) utilized as a common 3D printing source material as a traditional benchmarked material. The effects of printing temperature, speed, and layer morphology on the layer-by-layer 3D-printed structures and their mechanical properties were considered. Three different characteristic morphologies were identified based on printing temperature; the microscopic surface roughness was dependent on the printing speed and layer height. We demonstrate that the mechanical performances and surface properties of 3D-printed PLA structures could be improved by optimization of printing conditions. Specifically, we evaluate that these PLA-based 3D structures printed exhibited better surface qualities and enhanced mechanical performance than traditional ABS-based structures. Results showed that the PLA-based 3D structures possessed the favorable mechanical performance with 34% higher Young's modulus and 23% higher tensile strength in comparison to the ABS-based 3D structures. This study provides guidelines for achieving high-quality 3D-printed lightweight structures, including smooth surfaces and durable mechanical properties, and serves as a framework to create biodegradable 3D-printed parts for human use. 相似文献
59.
Min Seong Kwon Seung Kyoon Woo David B. Kurland Sung Hwan Yoon Andre F. Palmer Uddyalok Banerjee Sana Iqbal Svetlana Ivanova Volodymyr Gerzanich J. Marc Simard 《International journal of molecular sciences》2015,16(3):5028-5046
Neuroinflammation is a well-recognized consequence of subarachnoid hemorrhage (SAH), and may be responsible for important complications of SAH. Signaling by Toll-like receptor 4 (TLR4)-mediated nuclear factor κB (NFκB) in microglia plays a critical role in neuronal damage after SAH. Three molecules derived from erythrocyte breakdown have been postulated to be endogenous TLR4 ligands: methemoglobin (metHgb), heme and hemin. However, poor water solubility of heme and hemin, and lipopolysaccharide (LPS) contamination have confounded our understanding of these molecules as endogenous TLR4 ligands. We used a 5-step process to obtain highly purified LPS-free metHgb, as confirmed by Fourier Transform Ion Cyclotron Resonance mass spectrometry and by the Limulus amebocyte lysate assay. Using this preparation, we show that metHgb is a TLR4 ligand at physiologically relevant concentrations. metHgb caused time- and dose-dependent secretion of the proinflammatory cytokine, tumor necrosis factor α (TNFα), from microglial and macrophage cell lines, with secretion inhibited by siRNA directed against TLR4, by the TLR4-specific inhibitors, Rs-LPS and TAK-242, and by anti-CD14 antibodies. Injection of purified LPS-free metHgb into the rat subarachnoid space induced microglial activation and TNFα upregulation. Together, our findings support the hypothesis that, following SAH, metHgb in the subarachnoid space can promote widespread TLR4-mediated neuroinflammation. 相似文献
60.
Lin Li Minghui Hong Michael Schmidt Minlin Zhong Ajay Malshe Bert Huis in’tVeld Volodymyr Kovalenko 《CIRP Annals》2011,(2):735-755
This paper provides an overview of advances in laser based nano-manufacturing technologies including surface nano-structure manufacturing, production of nano materials (nanoparticles, nanotubes and nanowires) and 3D nano-structures manufacture through multiple layer additive techniques and nano-joining/forming. Examples of practical applications of laser manufactured nano-structures, materials and components are given. A discussion on the challenges and outlooks in laser nano-manufacturing is presented. 相似文献