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991.
The reactivity of element substituted cyclopentadienes (el = Si, Ge, Sn, As, Sb) is compared by reactions with Vb-element halides and with titaniumtetrachloride. Hereby already known cp-element compounds and new cyclopentadienyl-titaniumtrichlorides with silicon, germanium, tin, arsenic and antimony substituted cp-rings are formed. The 1H-n.m.r. spectra of these complexes are described. The following row of reactivity is found for the investigated element substituted cyclopentadienes: el = AsMe2<SiMe3<GeMe3<SbMe2<SnMe3. 相似文献
992.
M. Himsworth P. Nisbet J. Dilley G. Langfahl-Klabes A. Kuhn 《Applied physics. B, Lasers and optics》2011,103(3):579-589
We investigate the feasibility of implementing an elementary building block for quantum information processing. The combination
of a deterministic single photon source based on vacuum stimulated Raman adiabatic passage (V-STIRAP), and a quantum memory
based on electromagnetically induced transparency (EIT) in atomic vapour is outlined. Both systems are able to produce and
process temporally shaped wavepackets which provide a way to maintain the indistinguishability of the photons. We also propose
an efficient and robust ‘repeat-until-success’ quantum computation scheme based on this hybrid architecture. 相似文献
993.
Linear stochastic programming provides a flexible toolbox for analyzing real-life decision situations, but it can become computationally
cumbersome when recourse decisions are involved. The latter are usually modeled as decision rules, i.e., functions of the
uncertain problem data. It has recently been argued that stochastic programs can quite generally be made tractable by restricting
the space of decision rules to those that exhibit a linear data dependence. In this paper, we propose an efficient method
to estimate the approximation error introduced by this rather drastic means of complexity reduction: we apply the linear decision
rule restriction not only to the primal but also to a dual version of the stochastic program. By employing techniques that
are commonly used in modern robust optimization, we show that both arising approximate problems are equivalent to tractable
linear or semidefinite programs of moderate sizes. The gap between their optimal values estimates the loss of optimality incurred
by the linear decision rule approximation. Our method remains applicable if the stochastic program has random recourse and
multiple decision stages. It also extends to cases involving ambiguous probability distributions. 相似文献
994.
995.
996.
Ulrich Flörke Gerald Henkel Annette Kuhn Prof. Dr. Norbert Kuhn Prof. Dr. Stefan Laufer Cäcilia Maichle‐Mößmer 《无机化学与普通化学杂志》2012,638(5):730-732
Reaction of 2, 4, 6‐tri‐tert‐butylphenol ( 1 ) with di‐n‐butylmagnesium in the molar ratio 1:1 allows the synthesis of {(nBu)Mg(μ‐OR)2Mg(nBu)} ( 2 ) (R = 2, 4, 6‐tBu3C6H2), which reacts with excess 1 to give the homoleptic alcoholate complex {(RO)Mg(μ‐OR)2Mg(OR)} ( 3 ) (R = 2, 4, 6‐tBu3C6H2). The structures of 2 and 3 were determined by X‐ray crystallography. 相似文献
997.
998.
Geng S Fang J Turner KB Daunert S Wei Y 《Analytical and bioanalytical chemistry》2012,403(8):2403-2409
Polychlorinated biphenyls (PCBs) are environmental pollutants that have been associated with numerous adverse health effects in human and animals. Hydroxylated PCBs (HPCBs) are the product of the oxidative metabolism of PCBs. The presence of hydroxyl groups in HPCBs makes these compounds more hydrophilic than the parent PCBs. One of the best approaches to break down and remove these contaminants is bioremediation; an environmentally friendly process that uses microorganisms to degrade hazardous chemicals into non-toxic ones. In this study, we investigated the cellular accumulation and toxicity of selected PCBs and HPCBs in Gram-negative bacteria, using Escherichia coli as a model organism. We found that none of the five PCBs tested were toxic to E. coli, presumably due to their limited bioavailability. Nevertheless, different HPCBs tested showed different levels of toxicity. Furthermore, we demonstrated that the primary multidrug efflux system in E. coli, AcrAB-TolC, facilitated the efflux of HPCBs out of the cell. Since AcrAB-TolC is constitutively expressed in E. coli and is conserved in all sequenced Gram-negative bacterial genomes, our results suggest that the efflux activities of multidrug resistant pumps may affect the accumulation and degradation of PCBs in Gram-negative bacteria. 相似文献
999.
Beer MV Rech C Diederichs S Hahn K Bruellhoff K Möller M Elling L Groll J 《Analytical and bioanalytical chemistry》2012,403(2):517-526
Precise determination of biomolecular interactions in high throughput crucially depends on a surface coating technique that allows immobilization of a variety of interaction partners in a non-interacting environment. We present a one-step hydrogel coating system based on isocyanate functional six-arm poly(ethylene oxide)-based star polymers for commercially available 96-well microtiter plates that combines a straightforward and robust coating application with versatile bio-functionalization. This system generates resistance to unspecific protein adsorption and cell adhesion, as demonstrated with fluorescently labeled bovine serum albumin and primary human dermal fibroblasts (HDF), and high specificity for the assessment of biomolecular recognition processes when ligands are immobilized on this surface. One particular advantage is the wide range of biomolecules that can be immobilized and convert the per se inert coating into a specifically interacting surface. We here demonstrate the immobilization and quantification of a broad range of biochemically important ligands, such as peptide sequences GRGDS and GRGDSK-biotin, the broadly applicable coupler molecule biocytin, the protein fibronectin, and the carbohydrates N-acetylglucosamine and N-acetyllactosamine. A simplified protocol for an enzyme-linked immunosorbent assay was established for the detection and quantification of ligands on the coating surface. Cell adhesion on the peptide and protein-modified surfaces was assessed using HDF. All coatings were applied using a one-step preparation technique, including bioactivation, which makes the system suitable for high-throughput screening in a format that is compatible with the most routinely used testing systems. 相似文献
1000.
We report for the first time the vertical propulsion of conducting beads in liquid filled capillaries by bipolar electrochemistry. The beads, when exposed to an external electric field, act as bipolar electrodes showing hydroquinone oxidation on one side and proton reduction on the other side. The related asymmetric bubble generation occurring at the bottom part of the beads drives their motion. The characteristic features of the propulsion can be tuned by changing parameters such as the applied electric field or the capillary shape. Using a conical capillary, we show that a Yo-Yo type motion can be induced. The quite versatile concept can then be used for cargo-lifting and is of potential interest for microfluidic applications in LOC devices. 相似文献