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排序方式: 共有105条查询结果,搜索用时 15 毫秒
21.
Tatýana E. Glotova Nadezhda I. Protsuk Alexander I. Albanov Valentin A. Lopyrev Gennadii V. Dolgushin 《Central European Journal of Chemistry》2003,1(3):222-232
The nucleophilic addition of 2,4-dithiobiurete, 1- and 1,4-substituted 2,4-dithiobiuretes (2 a-e) with benzoylacetylene (1) has been studied. 2-(Benzoylmethyl)-4-(R1-imino)-6-(R2-imino)dihydro-4H-1,3,5-dithiazinium perchlorates (3 a-e) are obtained in glacial acetic acid (AcOH) in the presence of equimolar quantities of HClO4. The reaction of benzoylacetylene with 1,5-diphenyl-2,4-dithiobiurete in either of MeOH, C6H6, or MeCN solvents proceeds non-selectively to give a mixture of products such as 2-(benzoylmethyl)-4,6-di(phenylimino)dihydro-4H-1,3,5-dithiazine
(5), 2-(benzoylmethyl)-4-(β-benzoylvinyl)thio-3-phenyl-6-(phenylimino)-3,6-dihydro-2H-1,3,5-thiadiazine (8), 2-(benzoylmethyl)-1,3-diphenylhexahydro-1,3,5-triazine-4,6-dithione (7) and N-(β-benzoylvinyl)-N-phenylthioureas (6). 相似文献
22.
Label-free cell separation and sorting in microfluidic systems 总被引:2,自引:0,他引:2
Daniel R. Gossett Westbrook M. Weaver Albert J. Mach Soojung Claire Hur Henry Tat Kwong Tse Wonhee Lee Hamed Amini Dino Di Carlo 《Analytical and bioanalytical chemistry》2010,397(8):3249-3267
Cell separation and sorting are essential steps in cell biology research and in many diagnostic and therapeutic methods. Recently,
there has been interest in methods which avoid the use of biochemical labels; numerous intrinsic biomarkers have been explored
to identify cells including size, electrical polarizability, and hydrodynamic properties. This review highlights microfluidic
techniques used for label-free discrimination and fractionation of cell populations. Microfluidic systems have been adopted
to precisely handle single cells and interface with other tools for biochemical analysis. We analyzed many of these techniques,
detailing their mode of separation, while concentrating on recent developments and evaluating their prospects for application.
Furthermore, this was done from a perspective where inertial effects are considered important and general performance metrics
were proposed which would ease comparison of reported technologies. Lastly, we assess the current state of these technologies
and suggest directions which may make them more accessible. 相似文献
23.
Já nos Aczé l Gyula Maksa Che Tat Ng Zsolt Pá les 《Proceedings of the American Mathematical Society》2001,129(4):989-998
All strictly monotonic solutions of a general functional equation are determined. In a particular case, which plays an essential role in the axiomatization of rank-dependent expected utility, all nonnegative solutions are obtained without any regularity conditions. An unexpected possibility of reduction to convexity makes the present proof possible.
24.
25.
T. Le Tat 《Journal of Pure and Applied Algebra》2003,177(3):253-285
The postulation of a space curve is a classifying invariant which computes for any integer n the dimension of the family of surfaces of degree n containing the curve. We prove that for any integers d and g satisfying d−3?g?2d−9, there exists a smooth connected curve of degree d and genus g with the minimal postulation expected by the Riemann-Roch theorem. 相似文献
26.
[reaction: see text] An efficient and practical chemoenzymatic method was developed for the preparation of a variety of chiral secondary amines. Here, oxalamic esters were identified as unique derivatives amenable to the enzyme-catalyzed kinetic resolution of racemic secondary amines. Both enantiomers of the amines were produced in high optical purity and yields after the cleavage of the oxalamic groups. 相似文献
27.
Victor I. Maleev Tat’yana V. Skrupskaya Lidia V. Yashkina Anna F. Mkrtchyan Ashot S. Saghyan Michayl M. Il’in Denis A. Chusov 《Tetrahedron: Asymmetry》2013,24(4):178-183
A series of Co(III) anionic complexes of Schiff bases obtained from salicylaldehydes and enantiomerically pure amino acids has been synthesized. The outersphere counterion was exchanged by H+ and the novel chiral Brønsted acids were used to induce asymmetry into an aza-Diels–Alder reaction. The influence of the temperature, solvent polarity, and structural modification of the chiral anions on the enantioselectivity of the process has also been investigated. 相似文献
28.
B. S. Fedorov M. A. Fadeev A. N. Utenyshev G. V. Shilov N. P. Konovalova L. V. Tat’yanenko T. E. Sashenkova S. V. Blokhina E. N. Berseneva 《Russian Chemical Bulletin》2011,60(9):1959-1962
The chelate cadmium dichloride complex with semicarbazide was synthesized. The use of this complex in the cytostatic combination therapy together with cyclophosphamide results in 67% survival of mice and a threefold increase in the average life span of survivors with P-388 leukemia. 相似文献
29.
This paper describes the fabrication, characterisation and the application of a Nafion/2,2′-bipyridyl/bismuth composite film-coated glassy carbon electrode (NC(Bpy)BiFE) for the anodic stripping voltammetric determination of trace metal ions (Zn2+, Cd2+ and Pb2+). The NC(Bpy)BiFE electrode is prepared by first applying a 2.5 mm3 drop of a coating solution containing 0.5 wt% Nafion and 0.1% (w/v) 2,2′-bipyridil (Bpy) onto the surface of a glassy carbon electrode, while the Bi film was plated in situ simultaneously with the target metal ions at −1.4 V. The main advantage of the polymer coated bismuth film electrode is that the sensitivity of the stripping responses is increased considerably due to the incorporation of the neutral chelating agent of 2,2′-bipyridyl (Bpy) in the Nafion film, while the Nafion coating improved the mechanical stability of the bismuth film and its resistance to the interference of surfactants. The key experimental parameters relevant to both the electrode fabrication and the voltammetric measurement were optimized on the basis of the stripping signals. With a 2 min deposition time in the presence of oxygen, linear calibration curves were obtained in a wide concentration range (about 2-0.001 μM) with detection limits of 8.6 nM (0.56 μg dm−3) for Zn2+, 1.1 nM (0.12 μg dm−3) for Cd2+ and 0.37 nM (0.077 μg dm−3) for Pb2+. For nine successive preconcentration/determination/electrode renewal experiments the standard deviations were between 3 and 5% at 1.2 μM for zinc and 0.3-0.3 μM concentration level for lead and cadmium, respectively, and the method exhibited excellent selectivity in the presence of the excess of several potential interfering metal ions. The analytical utility of the stripping voltammetric method elaborated was tested in the assay of heavy metals in some real samples and the method was validated by ICP-MS technique. 相似文献
30.
Structural properties of commercial chromatographic adsorbents designated for separation of monoclonal antibodies were investigated using size-exclusion techniques. A batch technique provided the specific pore volumes distributed among small, medium and large pores. Inverse size-exclusion chromatography yielded the partition coefficients of dextran solute probes in medium pores. These data were fitted with one- and two-parametric models corresponding to different pore-size distribution functions and the suitability of the individual models for the characterization of the examined materials was then assessed. The reliability of estimation of the parameters of log-normal distribution of cylindrical pores was investigated. Large uncertainties and a strong correlation of the mean pore diameter and width of distribution function were observed. 相似文献