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961.
F. -U. Gast P. S. Dittrich P. Schwille M. Weigel M. Mertig J. Opitz U. Queitsch S. Diez B. Lincoln F. Wottawah S. Schinkinger J. Guck J. Käs J. Smolinski K. Salchert C. Werner C. Duschl M. S. Jäger K. Uhlig P. Geggier S. Howitz 《Microfluidics and nanofluidics》2006,2(1):21-36
We describe a novel microfluidic perfusion system for high-resolution microscopes. Its modular design allows pre-coating of
the coverslip surface with reagents, biomolecules, or cells. A poly(dimethylsiloxane) (PDMS) layer is cast in a special molding
station, using masters made by photolithography and dry etching of silicon or by photoresist patterning on glass or silicon.
This channel system can be reused while the coverslip is exchanged between experiments. As normal fluidic connectors are used,
the link to external, computer-programmable syringe pumps is standardized and various fluidic channel networks can be used
in the same setup. The system can house hydrogel microvalves and microelectrodes close to the imaging area to control the
influx of reaction partners. We present a range of applications, including single-molecule analysis by fluorescence correlation
spectroscopy (FCS), manipulation of single molecules for nanostructuring by hydrodynamic flow fields or the action of motor
proteins, generation of concentration gradients, trapping and stretching of live cells using optical fibers precisely mounted
in the PDMS layer, and the integration of microelectrodes for actuation and sensing. 相似文献
962.
The change in the hydrogen-trapping behavior of a TiC particle accompanying its coherent to incoherent interfacial-character
transition in a 0.05C-0.20Ti-2.0Ni steel that was quenched and tempered in a partially protective argon atmosphere and in
ultrahigh vacuum (UHV) has been studied by thermal desorption spectrometry (TDS). The results indicated that (semi)coherent
TiC precipitates demonstrate distinctly different hydrogen-trapping features from that of incoherent TiC particles with respect
to hydrogen capacity, interaction energy with hydrogen, locations available for hydrogen occupation, and the capability of
hydrogen absorption from the environment. The broad (semi)coherent interface of the disc-shaped (semi)coherent TiC precipitate
does not trap hydrogen during tempering in a partially protected argon atmosphere, but traps hydrogen during cathodic charging
at room temperature. The semicoherent interface traps 1.3 atoms/nm2 of hydrogen at the core of the misfit dislocation with short-time charging (1 hour), which is characterized by a desorption
activation energy of 55.8 kJ/mol. The side interface of the (semi)coherent TiC precipitate acts like the broad interface when
the precipitate is small. As the precipitate grows, the side interface gradually loses its coherency and results in a simultaneous
increase in the trapping activation energy and the binding energy. An increase in the trapping activation energy, i.e., the energy barrier for trapping, makes hydrogen trapping more difficult in cathodic charging at room temperature, while
an increase in the binding energy enhances the capability of hydrogen absorption from the atmosphere during heat treatment.
An incoherent TiC particle is not able to trap hydrogen during cathodic charging at room temperature due to its high energy
barrier for trapping, but absorbs hydrogen during heat treatment at high temperatures. The amount of hydrogen that is trapped
by incoherent TiC particles depends on their volume, which strongly indicates that incoherent TiC particles trap hydrogen
within them rather than at the particle/matrix interface. Octahedral carbon vacancies are supposedly the hydrogen trap sites
in incoherent TiC particles. 相似文献
963.
964.
965.
The total syntheses of 9(Z),12(E)- and 9(E),12(Z)-octadecadienoic acids have been carried out. A useful intermediate in both
syntheses, 8-bromo-octanoic acid, recently has become available from commercial sources. This compound has been used to expedite
the preparation of these isomers. The remaining carbon atoms were derived from propargyl alcohol along with either 1-heptyne
or acetylene and 1-bromopentane. Because the overall yield for each sequence was roughly 15% and there were no extraordinary
reaction conditions in any of the synthetic steps, the compounds could be prepared readily in multiple gram quantities. The
syntheses of the two compounds were supported by data from a variety of spectroscopic techniques. 相似文献
966.
Alkali-metal carbonate salts meet the requirements for high-temperature solar central receiver systems, but because of their corrosiveness they present special problems in the design of storage tanks. In order to reduce corrosion and temperature sufficiently to retain strength in the storage containing wall, internal and thermal insulation is required. We present design options and operation criteria for sensible-heat, molten-salt storage with internal insulation. 相似文献
967.
Lithium-ion batteries are becoming more and more important not only for portable electronic devices, but also in prevision of high power electric vehicles. In such an optic, deep studies regarding all the components of a secondary battery are in development. In this study, high voltage cathode materials have been selected. Crystals with spinel structure have a 3D vacancy pathway suitable for Li-ions transport. The material under study was LiNi0.5Mn1.5O4 doped with magnesium replacing the nickel. Various samples were synthesized via three different routes: a solid-state method, a modified sol–gel method and a xerogel method. The structure and morphology of the powders were analyzed with HRTEM and XRD. Electrochemical tests were also performed. A wide range of particle sizes (from micro to nanosize) was the result of the different synthesis routes. Unfortunately pure materials were not always obtained. The electrochemical tests showed improvement of the material's cyclability, by reducing the particle size. The electrochemical tests further confirmed the existence of a Li1+dMn2−dO4 impurity. The results are quite promising, however, further improvement of the purity of the electrode composition are needed. 相似文献
968.
Measurements of frequencies and spatial correlations of coherent structures in rod bundle flows 总被引:2,自引:2,他引:0
Cross-wire anemometry was used to identify and characterize coherent flow pulsations in isothermal air flow near the gap regions of a five-rod bundle with a design pitch-to-diameter ratio of 1.149 and contained in a quasi-trapezoidal duct. It was confirmed that such pulsations are quasi-periodic and contribute significantly to the velocity fluctuations across the gap. The frequency of pulsations was found to decrease with diminishing rod–wall gap size in the range between 0.015D and 0.250D, where D is the rod diameter. The pulsations in a rod–wall gap and an adjacent rod–rod gap were strongly coupled and occurred at the same frequency as one rod was displaced towards the duct wall. 相似文献
969.
970.