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排序方式: 共有4040条查询结果,搜索用时 968 毫秒
961.
962.
Johannes G. Rebelein Prof. Yilin Hu Prof. Markus W. Ribbe 《Chembiochem : a European journal of chemical biology》2015,16(14):1993-1996
Two reaction systems based on vanadium nitrogenase were previously shown to reduce CO2 to hydrocarbons: 1) an enzyme‐based system that used both components of V nitrogenase for ATP‐dependent reduction of CO2 to ≤C2 hydrocarbons; and 2) a cofactor‐based system that employed SmI2 to supply electrons to the isolated V cluster for an ATP‐independent reduction of CO2 to ≤C3 hydrocarbons. Here, we report ATP‐independent reduction of CO2 to hydrocarbons by a reaction system comprising EuII DTPA and the VFe protein of V nitrogenase. Combining features of both enzyme‐ and cofactor‐based systems, this system exhibits improved C?C coupling and a broader product profile of ≤C4 hydrocarbons. The C?C coupling does not employ CO2‐derived CO, and it is significantly enhanced in D2O. These observations afford initial insights into the characteristics of this unique reaction and provide a potential template for future design of catalysts to recycle the greenhouse gas CO2 into useful products. 相似文献
963.
Raffaella Paparcone Markus J. Buehler 《JOM Journal of the Minerals, Metals and Materials Society》2010,62(4):64-68
Amyloids are associated with severe degenerative diseases and show exceptional mechanical properties, in particular great
stiffhess. Amyloid fibrils, forming protein nanotube structures, are elongated fibers with a diameter of ≈8 nm with a characteristic
dense hydrogen-bond (H-bond)patterning in the form of beta-sheets (β-sheets). Here we report a series of molecular dynamics
simulations to study mechanical failure properties of a twofold symmetric Aβ(l–40) amyloid fibril, a pathogen associated with
Alzheimer’s disease. We carry out computational experiments to study the response of the amyloid fibril to compressive loading.
Our investigations reveal atomistic details of the failure process, and confirm that the breakdown of H-bonds plays a critical
role during the failure process of amyloid fibrils. We obtain a Young’s modulus of ≈12.43 GPa, in dose agreement with earlier
experimental results. Our simulations show that failure by buck-ling and subsequent shearing in one of the layers initiates
at ≈1% compressive strain, suggesting that amyloid fibrils can be rather brittle mechanical elements. 相似文献
964.
Markus Weiss Thorsten Staake Friedemann Mattern Elgar Fleisch 《Personal and Ubiquitous Computing》2012,16(6):655-664
When it comes to conserving electricity, it is crucial for users to know how much energy is consumed by individual appliances. However, the technical feedback provided by existing energy consumption feedback systems in the form of dry numbers and intangible units is not appropriate for most users. To address this shortcoming, we developed PowerPedia, a system that provides behavior-influencing feedback over and above pure consumption values. By integrating a community platform—a Wikipedia for electrical appliances—PowerPedia enables users to identify and compare the consumption of their domestic appliances with that of others. It thus helps users to better understand their electricity consumption and take effective action to save electricity. 相似文献
965.
Sören Zimmermann Alexander van Duellen Markus Wieghaus Sergio Alfredo Garnica Barragán Sergej Fatikow 《International Journal of Optomechatronics》2016,10(3-4):97-109
Resist based lithographical techniques are widely applied for graphene processing. These resists can leave residues leading to parasitic effects that deteriorate the desired properties of graphene. This paper presents an experimental setup tailored for resist-free robotic processing of graphene with in-situ vision based control. A robust graphene detection and classification approach is presented applying multiple image processing operations of the visual feedback provided by a high-resolution light microscope. Detected graphene flakes can be modified using scanning probe based lithographical processes, such as mechanical and bias-assisted approaches, that are directly linked to the in-situ optical images. The results of this process are discussed with respect to further application scenarios. 相似文献
966.
967.
Thomas D. Weddell Yury M. Yarin Markus Drexl Ian J. Russell Stephen J. Elliott Andrei N. Lukashkin 《Journal of the Royal Society Interface》2014,11(93)
The round window (RW) membrane provides pressure relief when the cochlea is excited by sound. Here, we report measurements of cochlear function from guinea pigs when the cochlea was stimulated at acoustic frequencies by movements of a miniature magnet which partially occluded the RW. Maximum cochlear sensitivity, corresponding to subnanometre magnet displacements at neural thresholds, was observed for frequencies around 20 kHz, which is similar to that for acoustic stimulation. Neural response latencies to acoustic and RW stimulation were similar and taken to indicate that both means of stimulation resulted in the generation of conventional travelling waves along the cochlear partition. It was concluded that the relatively high impedance of the ossicles, as seen from the cochlea, enabled the region of the RW not occluded by the magnet, to act as a pressure shunt during RW stimulation. We propose that travelling waves, similar to those owing to acoustic far-field pressure changes, are driven by a jet-like, near-field component of a complex pressure field, which is generated by the magnetically vibrated RW. Outcomes of research described here are theoretical and practical design principles for the development of new types of hearing aids, which use near-field, RW excitation of the cochlea. 相似文献
968.
Antonio Tricoli Markus Graf Sotiris E. Pratsinis 《Advanced functional materials》2008,18(13):1969-1976
Tin oxide nanocrystals (5–10 nm) doped with silica (0–15 wt %) were made by flame‐spray‐pyrolysis direct deposition onto the sensing electrodes and in situ stabilization by rapid flame annealing. Although increased SiO2‐doping reduced the SnO2 crystal and grain size, its sensing performance to ethanol vapor (0.1–50 ppm) exhibited an optimum with respect to SiO2 content. The thermal stability and morphology of SiO2‐doped SnO2 nanoparticles were evaluated by sintering at 200–900 °C for 4–24 h in air. At low SiO2 content, sintering of SnO2 was prevented only partially resulting in small sinter necks (bottlenecks) between SnO2 primary particles (smaller than twice the Debye length). This morphology drastically enhanced the sensitivity toward the analyte by maintaining a thermally stable high surface area and fully depleted connections at the primary particle necks. This enhancement is attributed mostly to the decreasing neck size of the SnO2 SiO2 heterojunctions rather than the decreasing SnO2 crystallite and grain sizes with increasing SiO2 doping. At high SiO2 contents, SnO2 sintering was inhibited as its grains were separated effectively by dielectric SiO2; this resulted in isolated SnO2 nanocrystals with drastically reduced sensitivity, thereby effectively being insulators. 相似文献
969.
Nawel S. Khelfallah Maxim Peretolchin Markus Klapper Klaus Müllen 《Polymer Bulletin》2005,53(5-6):295-304
Summary The role of the triazolinyl radical as additive for controlled radical polymerisation is investigated for N,N-dimethylaminoethyl methacrylate (DMAEMA) as polar monomer. A linear increase of the molecular weight with conversion and first-order kinetics are observed proving the controlled behaviour of the polymerization. The end-functionalisation of the obtained polymers was proven by both GPC und UV-spectroscopy. Furthermore, various amphiphilic block copolymers were obtained by chain extension with styrene, methyl methacrylate and ethyl methacrylate. In all cases monomodal GPC curves were obtained indicating an almost quantitative reinitiation. 相似文献
970.
Markus Hofmann Leland R. Beaumont 《Internet Computing, IEEE》2007,11(1):67-73
The IETF's open pluggable edge services (OPES) working group focuses on rule-based, in-line transformation services of data flows between two Internet endpoints, such as Web servers and Web clients. The group has developed an architectural framework to authorize, invoke, and trace such application-level services. The framework follows a one-party consent model, which requires that at least one of the application-layer endpoints explicitly authorize each service. OPES services must also be reversible by request of the application endpoints 相似文献