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61.
Winé G Matta J Tessonnier JP Pham-Huu C Ledoux MJ 《Chemical communications (Cambridge, England)》2003,(4):530-531
Beta zeolite supported on silicon carbide, with high thermal conductivity and high mechanical strength, was successfully used as an active and stable catalyst for Friedel-Crafts reactions in a fixed bed configuration. 相似文献
62.
A microfluidic approach for rapid bioluminescent real-time detection of single nucleotide polymorphism (SNP) is presented. The method is based on single-step primer extension using pyrosequencing chemistry to monitor nucleotide incorporations in real-time. The method takes advantage of the fact that the reaction kinetics differ between matched and mismatched primer-template configurations. We show here that monitoring the initial reaction in real time accurately scores SNPs by comparing the initial reaction kinetics between matched and mismatched configurations. Thus, no additional treatment is required to improve the sequence specificity of the extension, which has been the case for many allele-specific extension assays. The microfluidic approach was evaluated using four SNPs. Three of the SNPs included primer-template configurations that have been previously reported to be difficult to resolve by allele-specific primer extension. All SNPs investigated were successfully scored. Using the microfluidic device, the volume for the bioluminescent assay was reduced dramatically, thus offering a cost-effective and fast SNP analysis method. 相似文献
63.
We describe the operating characteristics of a new type of quantum oscillator that is based on a two-photon stimulated emission process. This two-photon laser consists of spin-polarized and laser-driven 39K atoms placed in a high-finesse transverse-mode-degenerate optical resonator and produces a beam with a power of approximately 0.2 microW at a wavelength of 770 nm. We observe complex dynamical instabilities of the state of polarization of the two-photon laser, which are made possible by the atomic Zeeman degeneracy. We conjecture that the laser could emit polarization-entangled twin beams if this degeneracy is lifted. 相似文献
64.
We describe two experiments in which we investigate the synchronization of coupled periodic oscillators. Each experimental system consists of two identical coupled electronic periodic oscillators that display bursts of desynchronization events similar to those observed previously in coupled chaotic systems. We measure the degree of synchronization as a function of coupling strength. In the first experiment, high-quality synchronization is achieved for all coupling strengths above a critical value. In the second experiment, no high-quality synchronization is observed. We compare our results to the predictions of the several proposed criteria for synchronization. We find that none of the criteria accurately predict the range of coupling strengths over which high-quality synchronization is observed. (c) 2000 American Institute of Physics. 相似文献
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66.
G. Couturier J.P. Aimé J. Salardenne R. Boisgard A. Gourdon S. Gauthier 《Applied Physics A: Materials Science & Processing》2001,72(7):S47-S50
Experiments performed using NC-AFM on a pure graphite surface suggest that the mechanical deformation of the surface under test is able to explain the observed damping signal. A simple analytical model has been built to evaluate the damping signal in terms of the mechanical properties of the surface, the amplitude of the oscillation and the tip-surface distance. Besides these experiments and a model, a virtual NC-AFM microscope has been developed, based on the Matlab language. This virtual machine allows some assumptions of the analytical model to be validated or invalidated, since no approximations are made in solving the nonlinear differential equation which controls the tip-surface interaction and the NC-AFM electronic loop is included. 相似文献
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Ohne Zusammenfassung 相似文献
70.
Marie Kjærgaard Bjørk Marie K. K. Nielsen Lotte Ø. Markussen Helene B. Klinke Kristian Linnet 《Analytical and bioanalytical chemistry》2010,396(7):2393-2401
A high-performance liquid chromatography (LC)–tandem mass spectrometry (MS/MS) method has been developed and validated for
the determination of 19 drugs of abuse and metabolites and used in whole blood. The following compounds were included: amphetamine,
methylenedioxyamphetamine, methylenedioxyethylamphetamine, methylenedioxymethamphetamine, methamphetamine, cocaine, benzoylecgonine,
morphine, 6-acetylmorphine, codeine, methadone, buprenorphine, norbuprenorphine, ketobemidone, tramadol, O-desmethyltramadol, zaleplone, zolpidem, and zopiclone. The sample pretreatment consisted of solid-phase extraction using
mixed-mode columns (Isolute Confirm HCX). Deuterated analogues were used as internal standards for all analytes, except for
ketobemidone and O-desmethyltramadol. The analytes were separated by a methanol/ammonium formate gradient using high-performance LC (Agilent
HPLC 1100) with a 3 mm × 100 mm Varian Pursuit 3 C18 column, 3-μm particle size, and were quantified by MS/MS (Waters Quattro micro tandem quadrupole mass spectrometer) using
multiple reaction monitoring in positive mode. Two transitions were used for all analytes, except for tramadol and O-desmethyltramadol. The run time of the method was 35 min including the equilibration time. For all analytes, responses were
linear over the range investigated, with R
2 > 0.99. One-point calibration was found to be adequate by validation, thereby saving analysis of multiple calibrators. The
limits of quantification (LOQs) for the analytes ranged from 0.0005 to 0.01 mg/kg. Absolute recoveries of the analytes were
from 34 to 97%, except for zaleplone (6%). Both the interday precision and the intraday precision were less than 15% (20%
at the LOQ) for all analytes, except buprenorphine, norburprenorphine, and zaleplone (less than 18%). Accuracy (bias) was
within ±15% (±20% at the LOQ) for all analytes, except MDMA and O-desmethyltramadol (within ±19%). No ion suppression or enhancement was seen nor was suppression from coeluted analytes seen.
Matrix effects were found to be less than 23% for all analytes, except zopiclone (64%). High-concentration and low-concentration
quality control samples gave acceptable values, and the method has been tried in international proficiency test schemes with
good results. The present LC-MS/MS method provides a simple, specific, and sensitive solution for the quantification of some
of the most frequent drugs of abuse and their metabolites in whole blood. The quantification by LC-MS/MS was successfully
applied to 412 forensic cases from October 2008 to mid February 2009, where 267 cases were related to zero-tolerance traffic
legislation. 相似文献