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Designing nanoscale objects with the potential to perform externally controlled motion in biological environments is one of the most sought-after objectives in nanotechnology. Different types of chemically and physically powered motors have been prepared at the macro- and microscale. However, the preparation of nanoscale objects with a complex morphology, and the potential for light-driven motion has remained elusive to date. Here, we go a step forward by designing a nanoscale hybrid with a propeller-resembling shape, which can be controlled by focused light under biological conditions. Our hybrid, hereafter "Au@DNA-origami", consists of a spherical gold nanoparticle with self-assembled, biocompatible, two-dimensional (2D) DNA sheets on its surface. As a first step toward the potential utilization of these nanoscale objects as light-driven assemblies in biological environments, we show that they can be optically trapped, and hence translated and deposited on-demand, and that under realistic trapping conditions the thermally induced dehybridization of the DNA sheets can be avoided.  相似文献   
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Blue emitting CaWO4 and greenish blue emitting ZnWO4 nanoparticles are synthesized via microemulsion techniques applying a cationic (CTAB) as well as a non-ionic surfactant (TritonX-100). The influence of the surfactant on particle size and shape is studied. Scanning electron microscopy and dynamic light scattering confirm the presence of uniform and non-agglomerated nanoparticles, 60–80 nm in diameter. Photoluminescence confirms [WO4]2−-related broad-band emission with its maximum at 440 nm (CaWO4) and 420 nm (ZnWO4). The highest quantum yield (QY) is observed for nanoscaled CaWO4 with a value of 23–25%. Doping of CaWO4 and ZnWO4 with Tb3+ and Eu3+ was performed and in the case of CaWO4:Tb and CaWO4:Eu and results in the emission of green and red light, again with comparably high QYs (17–19%).  相似文献   
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In this paper we study the multi-product lot streaming problem in a permutation flow shop. The problem involves splitting given order quantities of different products into sublots and determining their optimal sequence. Each sublot has to be processed successively on all machines. The sublots of the particular products are allowed to intermingle, that is sublots of different jobs may be interleaved. A mixed integer programming formulation is presented which enables us to find optimal sublot sizes as well as the optimal sequence simultaneously. With this formulation, small- and medium-sized instances can be solved in a reasonable time. The model is further extended to deal with different settings and objectives. As no lot streaming instances are available in the literature, LSGen, a problem generator, is presented, facilitating valid and reproducible instances. First results concerning the average benefit of lot streaming with multiple products are presented, and are based on a computational study with 160 small- and medium-sized instances.  相似文献   
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Cobalt-based materials are widely used for coronary stents, as well as bone and joint implants. However, their use is associated with high corrosion incidence. Titanium alloys, by contrast, are more biocompatible owing to the formation of a relatively inactive titanium oxide (TiO2) layer on their surface. This study was aimed at improving Co28Cr6Mo alloy cytocompatibility via sol–gel TiO2 coating to reduce metal corrosion and metal ion release. Owing to their role in inflammation and tissue remodelling around an implant, endothelial cells present a suitable in vitro model for testing the biological response to metallic materials. Primary human endothelial cells seeded on Co28Cr6Mo showed a stress phenotype with numerous F-actin fibres absent on TiO2-coated material. To investigate this effect at the gene expression level, cDNA microarray analysis of in total 1301 genes was performed. Compared with control cells, 247 genes were expressed differentially in the cells grown on Co28Cr6Mo, among them genes involved in proliferation, oxidative stress response and inflammation. TiO2 coating reduced the effects of Co28Cr6Mo on gene expression in endothelial cells, with only 34 genes being differentially expressed. Quantitative real-time polymerase chain reaction and protein analysis confirmed microarray data for selected genes. The effect of TiO2 coating can be, in part, attributed to the reduced release of Co2+, because addition of CoCl2 resulted in similar cellular responses. TiO2 coating of cobalt-based materials, therefore, could be used in the production of cobalt-based devices for cardiovascular and skeletal applications to reduce the adverse effects of metal corrosion products and to improve the response of endothelial and other cell types.  相似文献   
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Measuring interfacial friction during the manipulation of nanoparticles is becoming an increasingly important approach in nanotribology research. In this work, antimony and gold particles deposited on flat graphite surfaces have been translated by the tip of an atomic force microscope in contact mode along defined pathways. Two different manipulation techniques are discussed with respect to pathway control and friction quantification. The first technique includes pushing the particles from the side, which often results in a loss of the particle during translation due to unwanted sidewards motion. We analyze this phenomenon with an analytical model and find good agreement with experiments. An alternative approach is to move the particle while the tip remains on its top. We demonstrate that this approach allows better manipulation pathway control and that simultaneous interfacial friction measurements are in quantitative agreement with the first manipulation method.  相似文献   
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To understand the origin of the increase in critical current density of rare earth barium cuprate superconductor thin films with decreasing thickness, a series of sub‐300‐nm EuBa2Cu3O7?δ thin films deposited on SrTiO3 substrates are studied by X‐ray diffraction and electrical transport measurements. The out‐of‐plane crystallographic mosaic tilt and the out‐of‐plane microstrain both increase with decreasing film thickness. The calculated density of c‐axis threading dislocations matches the extent of the observed low‐field enhancement in critical current density for fields applied parallel to c. The in‐plane mosaic twist and in‐plane microstrain are both around twice the magnitude of the out‐of‐plane values, and both increase with decreasing film thickness. The results are consistent with the observed stronger field enhancement in critical current density for fields applied parallel to ab. The lattice parameter variation with thickness is not as expected from consideration of the biaxial strain with the substrate, indicative of in‐plane microstrain accommodation by oxygen disorder. Collectively, the results point to an enhancement of critical current by interfacial strain induced oxygen disorder which is greatest closest to the film‐substrate interface. The findings of this study have important implications for other thin functional oxide perovskite films and nanostructures where surface and interfacial strains dominate the properties.  相似文献   
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