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排序方式: 共有309条查询结果,搜索用时 15 毫秒
31.
Rapid and high-performance analysis of thyreostatic drug residues in urine using gas chromatography-mass spectrometry 总被引:1,自引:0,他引:1
Peter Batjoens Hubert F. De Brabander Katia De Wasch 《Journal of chromatography. A》1996,750(1-2):127-132
A more sensitive method was developed using the hyphenated technique of gas chromatography-mass spectrometry (GC-MS) supplementary to the official high-performance thin-layer chromatography (HPTLC) method. Even combined with less efficient extraction and clean-up methods, GC-MS is able to lower the detection limit to less than 50 ppb. The powerful technique of GC-MS-MS is tried out to reduce the detection limit even more, in combination with simplified extraction methods. This time-saving approach combined with the increase in sensitivity is of great importance for a routine technique. 相似文献
32.
Neumann MG Schmitt CC Prieto KR Goi BE 《Journal of colloid and interface science》2007,315(2):810-813
A method based on the aggregate to monomol emission ratio, I(aggr)/I(monomol), was used to determine the minimal hydrotropic concentration (MHC) of aromatic hydrotropes. The main advantage of this method is that it does not require the use of probes or other additives, which might disrupt the aggregation process. Also, it relies on spectrophotometric measurements, which are more sensitive and less arduous than others, like conductivity, light scattering and surface tension. 相似文献
33.
G. Brida M. Genovese M. G. A. Paris F. Piacentini E. Predazzi E. Vallauri 《Optics and Spectroscopy》2007,102(1):90-97
The propagation of pulses of the pump and its second harmonic in a quadratically nonlinear medium whose linear properties are characterized by a negative refractive index at the pump frequency and by a positive refractive index at the harmonic frequency is considered theoretically. In the case of a low intensity of the interacting waves, the pump and second-harmonic pulses propagate in the opposite directions, but sufficiently powerful pulses can form a simulton—a solitary two-frequency wave propagating in a certain direction as a single whole. Solutions to a set of equations are found which describe the steady-state propagation of a solitary wave and of a nonlinear periodic (cnoidal) wave. 相似文献
34.
This paper focuses on a one-camera/one-shot procedure able to get the whole deformation map of hyperelastic tubular samples. A challenging application of this approach is the investigation of the highly anisotropic and inhomogeneous arterial tissue mechanical response during inflation/extension tests. To address this issue, full field optical methods based on digital correlation (DIC), fringe projection (FP) and stereo-photogrammetry (SP) have been already proposed in literature to overcome limitations of the most widely adopted 2-D video dimension analyzer (VDA) systems.In this paper, the feasibility of a very straightforward full-field procedure that uses radial metrology concepts has been studied. The rationale behind the proposed method relies on the relation existing between image deformation of a world point reflected by a 45° concave conical mirror and the relative position of this point with respect to the specular surface. Under certain assumptions reasonably true for the application of interest, by using simple relationships, it is possible to retrieve the position of markers applied onto the sample surface with great precision. This procedure has several advantages such as the retrieval of the whole 360° surface map in one shot, the ease of application, the use of one single camera, the real-time measurement capability. Conversely, the proposed approach is suitable only for geometries with smooth transversal sections, needs sample preparation and its spatial resolution is limited by the sparsity of the surface control points.The paper describes first the theoretical basis of the procedure; then results of experimental tests on calibration samples and latex tubular specimens are presented and discussed. Further set-up improvements will allow the present procedure to be implemented for in-vitro inflation/extension tests on vascular segments. 相似文献
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Paulovich FV Maki RM de Oliveira MC Colhone MC Santos FR Migliaccio V Ciancaglini P Perez KR Stabeli RG Perinoto AC Oliveira ON Zucolotto V 《Analytical and bioanalytical chemistry》2011,400(4):1153-1159
Recent advances in the control of molecular engineering architectures have allowed unprecedented ability of molecular recognition in biosensing, with a promising impact for clinical diagnosis and environment control. The availability of large amounts of data from electrical, optical, or electrochemical measurements requires, however, sophisticated data treatment in order to optimize sensing performance. In this study, we show how an information visualization system based on projections, referred to as Projection Explorer (PEx), can be used to achieve high performance for biosensors made with nanostructured films containing immobilized antigens. As a proof of concept, various visualizations were obtained with impedance spectroscopy data from an array of sensors whose electrical response could be specific toward a given antibody (analyte) owing to molecular recognition processes. In addition to discussing the distinct methods for projection and normalization of the data, we demonstrate that an excellent distinction can be made between real samples tested positive for Chagas disease and Leishmaniasis, which could not be achieved with conventional statistical methods. Such high performance probably arose from the possibility of treating the data in the whole frequency range. Through a systematic analysis, it was inferred that Sammon's mapping with standardization to normalize the data gives the best results, where distinction could be made of blood serum samples containing 10(-7) mg/mL of the antibody. The method inherent in PEx and the procedures for analyzing the impedance data are entirely generic and can be extended to optimize any type of sensor or biosensor. 相似文献
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Snégaroff K Nguyen TT Marquise N Halauko YS Harford PJ Roisnel T Matulis VE Ivashkevich OA Chevallier F Wheatley AE Gros PC Mongin F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(47):13284-13297
A series of chloro- and bromopyridines have been deprotometalated by using a range of 2,2,6,6-tetramethylpiperidino-based mixed lithium-metal combinations. Whereas lithium-zinc and lithium-cadmium bases afforded different mono- and diiodides after subsequent interception with iodine, complete regioselectivities were observed with the corresponding lithium-copper combination, as demonstrated by subsequent trapping with benzoyl chlorides. The obtained selectivities have been discussed in light of the CH acidities of the substrates, determined both in the gas phase and as a solution in THF by using the DFT B3LYP method. 相似文献
40.
Braga D Maini L de Sanctis G Rubini K Grepioni F Chierotti MR Gobetto R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(22):5538-5548
Mechanical mixing of solid dicarboxylic acids of variable chain length HOOC(CH(2))(n)COOH (n = 1-7) with solid 1,4-diazabicyclo[2.2.2]octane generates the corresponding salts or co-crystals of the formula [N(CH(2)CH(2))(3)N]-H-[OOC(CH(2))(n)COOH] (n=1-7). Preparation of the same systems from solution has been instrumental for a full characterization of the mechanochemical products by means of single-crystal and powder-diffraction X-ray analyses, as well as by solid-state NMR. The acid-base adducts, whether involving proton transfer from the COOH group to the N-acceptor, that is having ((-))O...H-N((+)) interactions, or the formation of neutral O-H...N hydrogen bonds, show a melting point alternation phenomenon analogous to that shown by the neutral carboxylic acids. The carbon chemical shift tensors of the COOH group obtained from the sideband intensity of low speed spinning NMR spectra provide a reliable criterion for assigning the protonation state of the adducts. 相似文献