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排序方式: 共有120条查询结果,搜索用时 15 毫秒
31.
32.
This paper presents a preliminary structural and interfacial study of the iron chalcogenide glass [i.e., Fex(Ge28Sb12Se60)100−x] ion-selective electrode (ISE) using small angle neutron scattering (SANS) and electrochemical impedance spectroscopy (EIS). SANS detected variations in the neutron scattering as a function of iron content in the chalcogenide glass. Furthermore, a change in the chalcogenide glass structure was observed at elevated iron dopant levels. Conversely, EIS was used to show that the iron chalcogenide membrane comprises various time constants, and the interfacial charge transfer reaction depends on the membrane iron content. Equivalent circuit modeling revealed that the charge transfer resistance decreases at elevated iron levels, and this may be related to the presence of iron defects in the glass. It is proposed that the iron chalcogenide membrane comprises an iron nanostructural network embedded in the amorphous matrix, and this directly influences the electrical conductivity and concomitant electrochemical reactivity of the glass. 相似文献
33.
Clinton A. Krueger Christopher K. Hilton Mark Osgood Jianglin Wu Ching Wu 《International Journal for Ion Mobility Spectrometry》2009,12(1):33-37
Current commercially available ion mobility spectrometers are intended for the analysis of chemicals in the gas phase. Sample
introduction methods, such as direct air sampling, a GC injector or a thermal desorber, are commonly an integral part of these
instruments. This paper describes an electrospray ionization ion mobility spectrometer system that allows direct introduction
samples in solution phase. This allows direct analysis of non-volatile organic and biological samples, and avoids decomposition
of thermally liable samples, providing reliable chemical identification. In addition, the new ion mobility spectrometer allows
mobility analysis with high resolving power. Commonly used commercial IMS systems provide resolving powers between 10 and
30; this new ion mobility spectrometer has resolving power greater than 60 for routine analysis. A high resolution instrument
is necessary for many applications where a complex mixture needs to be separated and quantified. This paper demonstrates the
advantages of using a high resolution ion mobility spectrometer and an electrospray ionization source for the analysis of
non-volatile pharmaceuticals as well as dissolved explosive in solution phase. 相似文献
34.
35.
Irving M Krueger CA Wade JV Hodges JC Leopold K Collins N Chan C Shaqair S Shornikov A Yan B 《Journal of combinatorial chemistry》2004,6(4):478-486
A 4-amido-pyrrolidone library that was intentionally synthesized as pairs of diastereomers was produced by solution-phase parallel syntheses and purified by an automated high-throughput purification system. A total of 2592 4-amido-pyrrolidinones were ultimately isolated as single diastereomers from a matrix of 1920 syntheses. After the four-step synthesis and HPLC purification, the average yield of a single diastereomer was 36.6%. The average chemical purity was >90%, and the average diastereomeric purity was >87%. The choice of chiral amines used to make amides with heterocyclic acid chlorides had a dramatic effect on success. Analysis of the relationship between amines used for synthesis and the diastereomeric separation showed that amides made from chiral 1,2-amino alcohols gave superior separation to amides from chiral morpholines. The presence of a hydrogen bond donor on the amide side chain seems to be required for a better diastereomeric separation. 相似文献
36.
37.
Comins DL Kuethe JT Miller TM Février FC Brooks CA 《The Journal of organic chemistry》2005,70(13):5221-5234
Readily available N-acyl-5-vinyl-2,3-dihydro-4-pyridones undergo Diels-Alder cyclization with various dienophiles to afford novel octahydroquinolines containing synthetically useful functionality. With dihydropyridone 5 and cis-disubstituted dienophiles, the resulting cycloadducts were obtained as single diastereomers in good to excellent yield. The corresponding reaction of 5 with methyl acrylate, acrylonitrile, and phenyl vinyl sulfone showed modest preference for the endo adducts. The effect of the dihydropyridone C-2 and C-4 substituents on the degree of diastereofacial control was examined. By using this methodology, the core decahydroquinoline skeleton of gephyrotoxin was prepared in a stereocontrolled fashion. Interesting reactivity was observed with certain dienophiles leading to ring-opening of the initially formed cycloadducts. This tandem reaction provides a route to uniquely substituted beta-aminoketones, alcohols, and unnatural amino acids. 相似文献
38.
Clinton G.L. Veale Kevin A. Lobb Roya Zoraghi James P. Morrison Neil E. Reiner Raymond J. Andersen Michael T. Davies-Coleman 《Tetrahedron》2014
The public health care crisis caused by the emergence of drug resistant bacterial strains, e.g., methicillin resistant Staphylococcus aureus (MRSA) has underlined the urgent need to accelerate the discovery of new chemical entities active against antibiotic resistant bacteria. We report here the synthesis of a series thiazole containing deoxytopsentin analogues, which show moderate activity against a target MRSA pyruvate kinase enzyme: an evolutionary conserved hub protein critical for bacterial survival. A Hantzsch thiazole coupling between α-oxo-1H-indole-3-thioacetamides and 2-bromo-1-(1H-indol-3-yl)-ethanones provided facile access to the thiazole containing deoxytopsentin compounds. 相似文献
39.
Nonlinear Dynamics - Asymmetric dynamical systems sometimes admit a symmetric pair of coexisting attractors for reasons that are not readily apparent. This phenomenon is called conditional symmetry... 相似文献
40.
Clinton D. Bryan Ted A. Bryan A. Wallace Cordes Bill Durham David Y. Jeter Jason C. Yarbrough 《Journal of chemical crystallography》1997,27(7):413-415
The title complex has the NO grouptrans to the hydroxyl ligand and the chloride ion in the plane of the tripyridyl ligand. The Ru?O and Ru?N(O) distances are 1.939(5) Å and 1.764(6) Å, respectively; the Ru?N?O bond angle is 171.7(6)0. These values are consistent with previously reported shortening of Ru?O distances whentrans to a linear NO ligand. The space group of the structure isP21/c, witha=9.7213(9) Å,b=13.9318(11) Å,c=14.523(4) Å, and β=105.820(13)0. 相似文献