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排序方式: 共有140条查询结果,搜索用时 46 毫秒
101.
Josiah Newton Daniel Driedger Dr. Matthew B. Nodwell Dr. Paul Schaffer Dr. Rainer E. Martin Prof. Dr. Robert Britton Prof. Dr. Chadron M. Friesen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(70):15993-15997
Herein we report the mild and rapid fluorodesulfurization of thionoesters using only silver(I) fluoride. This reaction demonstrates excellent functional group tolerance and complements existing strategies for difluoroalkyl ether synthesis, which rely on toxic and often dangerous reagents that demonstrate limited functional group compatibility. We additionally report the translation of this finding to the production of 18F-labelled difluoroalkyl ethers using fluoride-derived [18F]AgF. This new process should enable the synthesis of a wide range of difluoroalkyl ethers with applications in medicinal and materials chemistry, and radiotracer production. 相似文献
102.
Darby SG Moore MR Friedlander TA Schaffer DK Reiserer RS Wikswo JP Seale KT 《Lab on a chip》2010,10(23):3218-3226
We describe the design, fabrication, and testing of a microfabricated metering rotary nanopump for the purpose of driving fluid flow in microfluidic devices. The miniature peristaltic pump is composed of a set of microfluidic channels wrapped in a helix around a central camshaft in which a non-cylindrical cam rotates. The cam compresses the helical channels to induce peristaltic flow as it is rotated. The polydimethylsiloxane (PDMS) nanopump design is able to produce intermittent delivery or removal of several nanolitres of fluid per revolution as well as consistent continuous flow rates ranging from as low as 15 nL min(-1) to above 1.0 μL min(-1). At back pressures encountered in typical microfluidic devices, the pump acts as a high impedance flow source. The durability, biocompatibility, ease of integration with soft-lithographic fabrication, the use of a simple rotary motor instead of multiple synchronized pneumatic or mechanical actuators, and the absence of power consumption or fluidic conductance in the resting state all contribute to a compact pump with a low cost of fabrication and versatile implementation. This suggests that the pump design may be useful for a wide variety of biological experiments and point of care devices. 相似文献
103.
Schaffer B Riegler K Kothleitner G Grogger W Hofer F 《Micron (Oxford, England : 1993)》2009,40(2):269-273
Gold nanoparticles show optical properties different from bulk material due to resonance phenomena which depend on local structure and geometry. Electron energy-loss spectrometry (EELS) in scanning transmission electron microscopy (STEM) allows the spatially resolved measurement of these properties at a resolution of few nanometers. In this work, the first monochromated measurements of gold nanoparticles (spheres, rods and triangles) are presented. Due to the improved energy resolution of about 0.2 eV, surface plasmon excitations at energies below 1 eV could be accurately measured from raw experimental data. 相似文献
104.
Azulene is an aromatic molecule with interesting properties, most notably a permanent dipole moment of 1.08D. This degree of polarity in the absence of heteroatoms is quite rare and offers potential for use in unique gas chromatographic stationary phases. Here, we report the first examples of azulene-derivatized stationary phases for gas chromatographic separations. Poly(dimethyl/azulenylmethyl) siloxane polymers containing 15 and 35% of an azulene derivative were synthesized, coated on capillary columns, and evaluated. To compare the effects of increased polarity vs. the effects of polarizability, isomeric naphthalene analogues were also prepared, coated, and evaluated. The coated phases displayed efficiencies up to 2700 plates/m. For both azulene and naphthalene columns, retention increased as substitution level increased. The more polarizable naphthalene columns tended to retain analytes more strongly. Columns were also evaluated for the separation of several different mixtures of isomers against a commercial HP-5 column. All azulene and naphthalene columns exhibited separations comparable to the commercial column. The solvation thermodynamic parameters phases were measured, showing an excellent linear relationship and no change in the mechanism of interaction over the temperature range measured. 相似文献
105.
Schaffer M Bonel H Sroka R Schaffer PM Busch M Reiser M Dühmke E 《Journal of photochemistry and photobiology. B, Biology》2000,54(1):55-60
Laser therapy by low light doses shows promising results in the modulation of some cell functions. Various clinical studies indicate that laser therapy is a valuable method for pain treatment and the acceleration of wound healing. However, the mechanism behind it is still not completely understood. To explore the effect of a low-power diode laser (lambda = 780 nm) on normal skin tissue, time-dependent contrast enhancement has been determined by magnetic resonance imaging (MRI). In the examinations, six healthy volunteers (four male and two female) have been irradiated on their right planta pedis (sole of foot) with 5 J/cm2 at a fluence rate of 100 mW/cm2. T1-weighted magnetic resonance imaging is used to quantify the time-dependent local accumulation of Gadolinium-DPTA, its actual content in the local current blood volume as well as its distribution to the extracellular space. Images are obtained before and after the application of laser light. When laser light is applied the signal to noise ratio increases by more than 0.35 +/- 0.15 (range 0.23-0.63) after irradiation according to contrast-enhanced MRI. It can be observed that, after biomodulation with light of low energy and low power, wound healing improves and pain is reduced. This effect might be explained by an increased blood flow in this area. Therefore, the use of this kind of laser treatment might improve the outcome of other therapeutic modalities such as tumour ionizing radiation therapy and local chemotherapy. 相似文献
106.
Utz P. Breteau Rubener Schaffer H. Droop Richmond und Bernstein 《Fresenius' Journal of Analytical Chemistry》1902,41(9):578-579
Ohne Zusammenfassung 相似文献
107.
Complex flexible structures often are composed of simpler objects like beams joined end-to-end. We consider the case of two identical Timoshenko beams, coupled together at a typical energy-dissipating joint. The Wave Propagation Method of Keller and Rubinow is employed to compute the vibration spectrum of the system. It is found that the spectrum consists of a typical double-branched Timoshenko spectrum. In addition, however, for most combinations of energy-conserving end conditions, at least one of these branches decomposes into two sub-branches, one which is damped and one, undamped. 相似文献
108.
This paper reports the synthesis of the hydrazine-based bisphosphinito ligands (RO)2PN(Me)N(Me)P(OR)2 (R = 2-hydroxy-6-methyl-pyridyl or 3-hydroxy-6-methyl-pyridyl) and their palladium and platinum complexes whose structures were unequivocally determined by X-ray crystallography. 相似文献
109.
110.
Th. von Fellenberg F. Schaffer und E. Arbenz 《Fresenius' Journal of Analytical Chemistry》1922,61(8-9):358-359
Ohne Zusammenfassung 相似文献