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排序方式: 共有350条查询结果,搜索用时 31 毫秒
81.
Dr. Christoph Borek Valentin F. Reichle Dr. Stefanie Kellner 《Chembiochem : a European journal of chemical biology》2020,21(19):2768-2771
Ribonucleic acid (RNA) is central to many life processes and, to fulfill its function, it has a substantial chemical variety in its building blocks. Enzymatic thiolation of uridine introduces 4-thiouridine (s4U) into many bacterial transfer RNAs (tRNAs), which is used as a sensor for UV radiation. A similar modified nucleoside, 2-thiocytidine, was recently found to be sulfur-methylated especially in bacteria exposed to antibiotics and simple methylating reagents. Herein, we report the synthesis of 4-methylthiouridine (ms4U) and confirm its presence and additional formation under stress in Escherichia coli. We used the synthetic ms4U for isotope dilution mass spectrometry and compared its abundance to other reported tRNA damage products. In addition, we applied sophisticated stable-isotope pulse chase studies (NAIL-MS) and showed its AlkB-independent removal in vivo. Our findings reveal the complex nature of bacterial RNA damage repair. 相似文献
82.
83.
Development of an expert system for preliminary risk assessment of existing concrete dams 总被引:1,自引:1,他引:0
The paper presents an expert system to assist in the field inspection of existing concrete dams within the context of a preliminary risk assessment. The paper describes the engineering knowledge and reasoning required to conduct a deterministic field evaluation of the structural stability of the dam. The symptoms and failure modes identified by the expert system along with the required knowledge and procedures are organized in a structured knowledge tree. The instantiation of the frames and firing of the rules for each consultation traces part of the inference tree contained in the structured knowledge tree. Interaction between nearly decomposable problems are executed with metaknowledge procedures, shared rule groups, and active values. Examples are provided. 相似文献
84.
The emulsion copolymerization of styrene with acrylonitrile, seeded on a polybutadiene support and initiated either potassium persulfate or γ-rays has been studied. The original technique of support activation consists of two steps: the start of the copolymerization in the presence of a small fraction of monomers, followed by the addition of the rest of monomers, which leads to a great increase in the reaction rate. The experimental data provide evidence for a new mechanism that takes into account the desorption–reentry of the free oligoradicals into another particle, their transfer to the polybutadiene support, which results in the accumulation of trapped free radicals. As a consequence of free radicals' accumulation, the overall copolymerization rate increases. The accumulation as well as the desorption processes place this type of copolymerization far from Smith–Ewart theory case II. 相似文献
85.
U. Nagel A. Nowak E. Kellner H. -J. Gebauer P. Colling S. Cooper D. Dummer P. Ferger M. Frank P. Freund G. Forster J. Igalson A. Nucciotti F. Pröbst A. Rulofs W. Seidel L. Stodolsky 《Journal of Low Temperature Physics》1993,93(3-4):543-548
We have studied the proximity effect in bilayers of thin films of iridium covered by gold. These structures were evaporated onto sapphire single crystals for use as phase transition thermometers in cryogenic particle detectors. By varying the thicknesses of the iridium and gold layers, we achieved critical temperatures as low as 33 mK. The critical temperature of the bilayers is lower than predicted by the theory of de Gennes-Werthamer, but adding a free parameter to the theory allows good agreement. The transitions of the bilayers typically had widths of a few mK, with the narrowest reaching 0.2 mK, and were always sharper than those of pure iridium films evaporated simultaneously. 相似文献
86.
S Kohl M Christ-Adler E Apfelstedt-Sylla U Kellner A Eckstein E Zrenner B Wissinger 《Canadian Metallurgical Quarterly》1997,34(8):620-626
Patients from 76 independent families with various forms of mostly central retinal dystrophies were screened for mutations in the RDS/peripherin gene by means of SSCP analysis and direct DNA sequencing. Two nonsense mutations (Gln239ter, Tyr285ter), five missense mutations (Arg172Trp, Lys197Glu, Gly208Asp, Trp246Arg, Ser289Leu), and one single base insertion (Gly208insG), heterozygous in all cases, were detected. Only one of these mutations, Arg172Trp, has been reported previously. Cosegregation of the mutation with the disease phenotype could be established in selected families. Other missense mutations were excluded from a panel of 55-75 control subjects. The patients showed remarkable variation in phenotype and disease expression not only between cases with different mutations but also between affected members of the same family. This study indicates that RDS/peripherin mutations are a frequent cause of various types of central retinal dystrophies and that the RDS/peripherin gene exhibits a broad spectrum of allelic mutations. Comparative analysis of known mutations allowed us to hypothesise that the deleterious effect of RDS/peripherin gene mutations is the result of different molecular mechanisms. 相似文献
87.
Ohheum Bak Theodor S. Holstad Yueze Tan Haidong Lu Donald M. Evans Kasper A. Hunnestad Bo Wang James P. V. McConville Petra Becker Ladislav Bohatý Igor Lukyanchuk Valerii M. Vinokur Antonius T. J. van Helvoort J. Marty Gregg Long‐Qing Chen Dennis Meier Alexei Gruverman 《Advanced functional materials》2020,30(21)
Application of scanning probe microscopy techniques such as piezoresponse force microscopy (PFM) opens the possibility to re‐visit the ferroelectrics previously studied by the macroscopic electrical testing methods and establish a link between their local nanoscale characteristics and integral response. The nanoscale PFM studies and phase field modeling of the static and dynamic behavior of the domain structure in the well‐known ferroelectric material lead germanate, Pb5Ge3O11, are reported. Several unusual phenomena are revealed: 1) domain formation during the paraelectric‐to‐ferroelectric phase transition, which exhibits an atypical cooling rate dependence; 2) unexpected electrically induced formation of the oblate domains due to the preferential domain walls motion in the directions perpendicular to the polar axis, contrary to the typical domain growth behavior observed so far; 3) absence of the bound charges at the 180° head‐to‐head (H–H) and tail‐totail (T–T) domain walls, which typically exhibit a significant charge density in other ferroelectrics due to the polarization discontinuity. This strikingly different behavior is rationalized by the phase field modeling of the dynamics of uncharged H–H and T–T domain walls. The results provide a new insight into the emergent physics of the ferroelectric domain boundaries, revealing unusual properties not exhibited by conventional Ising‐type walls. 相似文献
88.
89.
Octavian Morariu Cristina Morariu Theodor Borangiu 《Journal of Intelligent Manufacturing》2016,27(2):447-462
Large scale emergence of mature cloud solutions, ranging from software-as-a-service based solutions for business management, to very sophisticate private cloud solutions; offer the building blocks for constructing extremely flexible enterprise systems that can respond to environmental changes with great agility. Manufacturing enterprises need to adopt these new technologies to advance in a new era of mass customization where flexibility, scalability and agility are the differentiating factors. In this context, this paper introduces the virtualized MES and shop floor architecture as an intermediate layer in the manufacturing stack and discusses the advantages offered by this approach for manufacturing enterprises. A classification of MES and shop floor devices is presented focusing on the virtualization techniques suitable for each device type, considering the level of distributed intelligence and the virtualization overhead. Shop floor virtualization through shop floor profiles is presented and discussed underlying the flexibility of the solution. A pilot multi-agent implementation for virtual shop floor configuration based on the CoBASA reference architecture is presented and discussed. The shop floor profiles which define the virtual layout and mappings of the robotized manufacturing system are also provided in this context. The pilot implementation using six Adapt robots and a IBM CloudBurst 2.1 private cloud, is described and virtualization overhead in terms of event propagation delays is measured and presented in several scenarios of resource workload collocation on physical cloud blades 相似文献
90.
Elias Kellner Irina Mader Marco Reisert Horst Urbach Valerij Gennadevic Kiselev 《Magma (New York, N.Y.)》2018,31(3):439-448