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901.
[reaction: see text] Asymmetric dihydroxylation, thiyl radical mediated transfer of a silicon-tethered vinyl group to a hydrazone and an unconventional aldehyde-selective Wacker oxidation are sequenced for an efficient synthesis of methyl N-trifluoroacetyl-L-daunosaminide in 32% overall yield from crotonaldehyde. 相似文献
902.
Touaibia M Shiao TC Papadopoulos A Vaucher J Wang Q Benhamioud K Roy R 《Chemical communications (Cambridge, England)》2007,(4):380-382
Several oligomannoside clusters having a hundred-fold increase in affinities toward E. coli were synthesized by Cu(I)-catalyzed [1,3]-dipolar cycloadditions using pentaerythritol scaffolds bearing either alkyne or azide functionalities. 相似文献
903.
Lai M Kulak AN Law D Zhang Z Meldrum FC Riley DJ 《Chemical communications (Cambridge, England)》2007,(34):3547-3549
Macroporous copper with a complex hyperbolic morphology and superior mechanical properties was produced by replicating the remarkable form of a sea urchin skeletal plate using templated electrochemical deposition. 相似文献
904.
905.
906.
Generation of complex concentration profiles in microchannels in a logarithmically small number of steps 总被引:1,自引:0,他引:1
We describe the principles of design and the architecture of planar microfluidic networks producing concentration gradients with the shape of any given monotonic function. Each microfluidic network is fed by two separate source solutions and delivers to its outlet a set of N solutions that all differ in concentration. Inside the network, the source solutions flow through a series of k = log(2)(N-1) stages, where they are repeatedly split and mixed. Streams of the solutions emerging from the network are combined to create a single stream with the desired shape of the concentration profile across the direction of flow. To demonstrate the functionality of the proposed architecture, we have built and tested three networks with k = 4 and N = 17 that generate an exponential concentration profile, a linear profile, and a profile with a shape of two fused branches of a parabola. 相似文献
907.
A mass spectrometric approach for rapid and simultaneous detection of several single nucleotide polymorphisms (SNPs) is reported. Oligonucleotide single base extension (SBE) primers, labelled at the 5'-end with photocleavable, quaternised and brominated peptidic mass tags, are extended by a mixture of the four dideoxynucleotides of which one is biotinylated. The 3'-biotinylated extension products are captured by streptavidin-coated solid phase magnetic beads, whilst non-biotinylated extension products and unreacted primers are washed away. Quaternised and brominated mass tags, cleaved from captured extension products during analysis by matrix-assisted laser desorption/ionisation-time-of-flight (MALDI-TOF) MS, are detected at pmol levels. This method is applied to the analysis of mitochondrial DNA polymorphisms for the purpose of human identification. 相似文献
908.
We introduce a novel combination of boronic acid affinity chromatography with lectin affinity chromatography, dubbed as boronic
acid–lectin affinity chromatography (BLAC). Concanavalin A and wheat germ agglutinin lectins were mixed with the pesudo-lectin
boronic acid to form the BLAC affinity column and their performance was evaluated with standard glycoproteins. Optimization
of the binding and elution buffers for the BLAC system is described. The BLAC columns were employed to isolate glycoproteins
of interest using both selective and/or combined elution. 相似文献
909.
Begtrup GE Ray KG Kessler BM Yuzvinsky TD Garcia H Zettl A 《Physical review letters》2007,99(15):155901
We report a novel nanoscale thermal platform compatible with extreme temperature operation and real-time high-resolution transmission electron microscopy. Applied to multiwall carbon nanotubes, we find atomic-scale stability to 3200 K, demonstrating that carbon nanotubes are more robust than graphite or diamond. Even at these thermal extremes, nanotubes maintain 10% of their peak thermal conductivity and support electrical current densities approximately 2 x 10{8} A/cm{2}. We also apply this platform to determine the diameter dependence of the melting temperature of gold nanocrystals down to three nanometers. 相似文献
910.
Current models for ferromagnetism in diluted magnetic semiconductors, such as "p-d exchange" or "double-exchange", rely on the presence of partially filled gap states. We point out a new mechanism, not requiring partially filled states, in which ferromagnetic coupling arises from the occupation of previously unoccupied levels when two transition metal impurities form a close pair. We find from first-principles calculations that this mechanism explains strong ferromagnetic coupling between Co impurities in Cu2O, and at the same time gives rise to Co clustering. 相似文献