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排序方式: 共有654条查询结果,搜索用时 15 毫秒
411.
412.
Liquid crystals (LC) are anisotropic materials which experience a torque if an electric field is present. This field can be due to an external voltage or to the presence of a light beam. Reorientation due to light leads to non-linear behavior in the optical behavior. Due to this kind of nonlinearity therefore it is possible to generate optical spatial soliton beam in LC by bias voltage or without it and interestingly chiral nematic liquid crystals has a opportunity to generate spatial optical solitons without the need for a bias voltage. In this paper we also demonstrate that a sharp switching of the helix structure occurs when the spatial soliton is launched in the middle of two regions where soliton generation is favorable. Due to the optical nonlinearity, the helical structure becomes asymmetric and a sharp switching in one direction can be obtained. Moreover, in this paper, the torque and reorientation of the liquid crystal and the change in angular momentum of the light are discussed. 相似文献
413.
Denis V. Efimov Philip de Goey Jeroen A. van Oijen 《Combustion Theory and Modelling》2013,17(6):1103-1133
We propose a new approach to improve the accuracy of flamelet-generated manifolds (FGMs) method by extending the manifolds with additional chemically reactive degrees of freedom. Following the ideas of intrinsic low-dimensional manifold, the dimensionality of the FGM is increased by performing a local time-scale analysis of the chemical source term. A few slow characteristic directions of the reaction kinetics are used to extend the FGM, while the remaining reaction groups, characterised by fast time-scales, are assumed in steady state. The introduced method for FGM REactive Dimensionality extension is abbreviated as FGM-REDx. It is tested in one-dimensional simulations reproducing an expansion of burnt gases in an aero-engine stator. This process is characterised by a rapid change of enthalpy and pressure, altering, among others, the chemistry of pollutants CO and NO. The primary focus was on the assessment of the FGM's capability to predict the pollutants emissions. The rates of physical/thermodynamic perturbations turned out to be severe enough for the chemical species composition to go off the flamelet. The FGM extended with one additional chemically reactive dimension has been generated and successfully applied to the test cases, yielding a high accuracy gain over the standard FGM. 相似文献
414.
Jeroen Appel Sabine Akerboom Remco G. Fokkink Joris Sprakel 《Macromolecular rapid communications》2013,34(16):1284-1288
A facile method for the aqueous synthesis of monodisperse and micronmeter‐sized colloids with highly carboxylated surfaces is presented. The method is applied to three different monomers, styrene, methyl methacrylate, and 2,2,2‐trifluoroethyl methacrylate, and illustrate tuning of the size and monodispersity in the reactions. High surface density of carboxylic acids of up to 10 COOH nm−2 from potentiometric titrations, is achieved through copolymerization with itaconic acid. The versatility of this system is highlighted by creating highly fluorescent and monodisperse particles that can be index matched in aqueous solution and through surface modification via the carboxylic acid groups using standard amidation chemistry.
415.
N Lozano WT Al-Jamal A Taruttis N Beziere NC Burton J Van den Bossche M Mazza E Herzog V Ntziachristos K Kostarelos 《Journal of the American Chemical Society》2012,134(32):13256-13258
The design of liposome-nanoparticle hybrids offers a rich toolbox for the fabrication of multifunctional modalities. A self-assembled liposome-gold nanorod hybrid vesicular system that consists of lipid-bilayer-associated gold nanorods designed to allow deep tissue detection, therapy, and monitoring in living animals using multispectral optoacoustic tomography has been fabricated and characterized in vitro and in vivo. 相似文献
416.
Hogendorf WF Lameijer LN Beenakker TJ Overkleeft HS Filippov DV Codée JD Van der Marel GA 《Organic letters》2012,14(3):848-851
The use of perfluorooctylpropylsulfonylethanol as a new phosphate protecting group and fluorous linker is evaluated in the stepwise solution phase synthesis of a number of biologically relevant (carbohydrate substituted) glycerol teichoic acid fragments. Teichoic acid fragments, up to the dodecamer level, were assembled by means of phosphoramidite chemistry, using a relatively small excess of the building blocks and a repetitive efficient purification procedure of the protected intermediates by fluorous solid phase extraction (F-SPE). 相似文献
417.
Modha SG Vachhani DD Jacobs J Van Meervelt L Van der Eycken EV 《Chemical communications (Cambridge, England)》2012,48(52):6550-6552
A diversity oriented approach for the synthesis of indoloazocines is reported employing an Ugi reaction followed by a gold-catalyzed intramolecular hydroarylation. 相似文献
418.
SG Modha A Kumar DD Vachhani J Jacobs SK Sharma VS Parmar L Van Meervelt EV Van der Eycken 《Angewandte Chemie (International ed. in English)》2012,51(38):9572-9575
Caught "Spiro" handed: A diversity-oriented approach comprised of an Ugi four-component reaction and a diastereoselective gold(I)-catalyzed domino cyclization for the generation of complex spiroindolines under mild conditions has been developed. Variously substituted spiroindolines were synthesized in good to excellent yields and with complete diastereoselectivity. 相似文献
419.
We show how certain determinants of hyperelliptic periods can be computed using a generalized arithmetic-geometric mean iteration,
whose initialisation parameters depend only on the position of the ramification points. Special attention is paid to the explicit
form of this dependence and the signs occurring in the real domain. 相似文献
420.
Aqai P Peters J Gerssen A Haasnoot W Nielen MW 《Analytical and bioanalytical chemistry》2011,400(9):3085-3096
Multi-analyte binding assays for rapid screening of food contaminants require mass spectrometric identification of compound(s)
in suspect samples. An optimal combination is obtained when the same bioreagents are used in both methods; moreover, miniaturisation
is important because of the high costs of bioreagents. A concept is demonstrated using superparamagnetic microbeads coated
with monoclonal antibodies (Mabs) in a novel direct inhibition flow cytometric immunoassay (FCIA) plus immunoaffinity isolation
prior to identification by nano-liquid chromatography–quadrupole time-of-flight-mass spectrometry (nano-LC-Q-ToF-MS). As a
model system, the mycotoxin ochratoxin A (OTA) and cross-reacting mycotoxin analogues were analysed in wheat and cereal samples,
after a simple extraction, using the FCIA with anti-OTA Mabs. The limit of detection for OTA was 0.15 ng/g, which is far below
the lowest maximum level of 3 ng/g established by the European Union. In the immunomagnetic isolation method, a 350-times-higher
amount of beads was used to trap ochratoxins from sample extracts. Following a wash step, bound ochratoxins were dissociated
from the Mabs using a small volume of acidified acetonitrile/water (2/8 v/v) prior to separation plus identification with nano-LC-Q-ToF-MS. In screened suspect naturally contaminated samples, OTA and
its non-chlorinated analogue ochratoxin B were successfully identified by full scan accurate mass spectrometry as a proof
of concept for identification of unknown but cross-reacting emerging mycotoxins. Due to the miniaturisation and bioaffinity
isolation, this concept might be applicable for the use of other and more expensive bioreagents such as transport proteins
and receptors for screening and identification of known and unknown (or masked) emerging food contaminants. 相似文献