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51.
52.
V. Jancsik F. Bartha K. Kretschmer J. Lasch 《Applied biochemistry and biotechnology》1978,3(4):291-299
Aldolase was bound covalently to CNBr-activated Sepharose. The immobilized enzyme was investigated in a continuously stirred tank reactor (CSTR). In spite of the complexity of the system, the stationary performance of the CSTR can be described by a very simple equation. There are essentially two control parameters,V m andK eq— that govern the stationary performance of the aldolase reactor. 相似文献
53.
Contributions to Organolanthanide Chemistry. II. Cyclopentadienyllanthanide 1,3-Butadiene Complexes – Synthesis, Properties, and Reactions From cyclopentadienyllanthanide dihalides and “magnesium butadiene” Cp*La(C4H6) · MgI2 · 3 THF ( I ), Cp*Ce(C4H6) · MgBr2 · 2 THF ( II ), Cp*Nd(C4H6) · MgCl2 · 2 THF ( III ), (1,3-(t-C4H9)2C5H3)Nd(C4H6) · MgCl2 · 2 THF ( IV ), CpEr(C4H6) · MgCl2 · 2 THF ( V ) and (1,3-(t-C4H9)2C5H3)Lu(C4H6) · MgCl2 · 2 THF ( VI ) were obtained as highly air sensitive complexes which react easily with proton active compounds and molecules with multible bonds. The reaction products with diphenylamine and carbon dioxide Cp*Nd(NPh2)2 · NHPh2 ( VII ) and Cp*Ce(O2CC4H6CO2) ( VIII ) are discribed. I–VIII were characterized by elementary analysis, i.r., 1H and 13C n.m.r., and EI-MS spectra. 相似文献
54.
Contributions to Organolanthanide Chemistry. III. Synthesis and Properties of 1,4-Diaryl-1,3-butadiene Lanthanide Complexes Cyclopentadienyllanthanide halides react with 1,4-diarylbutadienes in the presence of alkali metals to give Cp*La(1,4-Ph2C4H4) · DME ( I ), Cp*La(1,4-{o-CH3O? C6H4}2 · C4H4) · 2DME ( II ), [Li(THF)3][Sm(1,4-Ph2C4H4)2] ( III ), [Li(DME)][(1,4-{p-CH3? C6H4}2C4H4)LuCl2] ( IV ) and [Li(DME)][(1,4-{o-CH3O? C6H4}2C4H4)LuCl2] ( V ). Samariumtrichloride reacts with 1,4-diphenyl-butadiene and lithium in tetrahydrofurane with formation of [Li(THF)4][Sm(1,4-Ph2C4H4)2] ( VI ). Reaction of samarium with the p-tolyl derivative in the presence of iodine gives (1,4-{p-CH3? C6H4}2C4H4)SmI · 3THF ( VII ). The compounds were characterized by elementary analysis, i.r., 1H- and 13C- n.m.r., and EI-MS spectra. 相似文献
55.
Ammonolysis of Halogeno Complexes of Tetravalent Platinum Reactions of liquid ammonia and ammonium hexahalogenoplatinates(IV) at ?40°C yield mixtures of halogenoammine complexes [Pt(NH3)6?nXn]X4?n (X = Cl, Br, I; n = 3, 2, 1, 0). Hexaammine platinum(IV) salts, [Pt(NH3)6]X4, may be isolated as main product only after several weeks of reaction. Interactions at room temperature of liquid ammonia and hexachloro or hexabromo complexes produce quantitatively the novel dinuclear di-m?-amido-bis[tetraammineplatinum(IV)] complex, [(H3N)4Pt(NH2)2Pt(NH3)4]X6. By interaction of gaseous or liquid ammonia and subsequent addition of potassium amide solution in excess potassium hexaamido platinate(IV), K2[Pt(NH2)6], is formed in good yield. 相似文献
56.
Zusammenfassung Beim Ultraschallabbau von amorphen Hochpolymeren wurden Endmolekulargewichte gefunden, die bei allen untersuchten Polymeren zwischen 20000 und 50000 lagen. Mit Hilfe elektronenmikroskopischer Methoden wurde versucht, direkt die Abnahme der Molekülgröße zu verfolgen. Als Ergebnis wurde gefunden, daß bei allen untersuchten Polymeren Feinstrukturen abgebildet wurden, die invariant gegen den Ultraschallabbau waren, und daß die Endmolekulargewichte nach Abbau mit den Molekulargewichten für die Feinstrukturen — betrachtet man diese als Einzelindividuen — gut übereinstimmen. Es wird daraus geschlossen, daß der mechanische Abbau von Polymeren nur bis zum Auftrennen in diskrete primäre Struktureinheiten führt. Diese Struktureinheiten scheinen eine grundlegende Materialkonstante zu sein.
Summary Ultrasonic degradation of amorphous high polymers results in products of defined molecular weights in the limits of 20000 to 50000. The authors try to coordinate the degradation of some polymers characterized by viscosity molecular weight and the fine structures visible at high magnification and resolution in photographs by electron microscope.The fine structures are found invariant against all kinds of mechanical degradation. The final molecular weight after degradation is the same as calculated for the weight of the structural units in the electron micrographs. These structural units are probably a real basic constant of the polymeric materials.相似文献
57.
Baldock SJ Fielden PR Goddard NJ Kretschmer HR Prest JE Treves Brown BJ 《Journal of chromatography. A》2004,1042(1-2):181-188
A microdevice design furnished with a novel sample injector, capable of delivering variable volume samples, for miniaturised isotachophoretic separations is presented. Micromachining by direct milling was used to realise two flow channel network designs on poly(methyl methacrylate) chips. Both designs comprised a wide bore sample channel interfaced, via a short connection channel, to a narrow bore separation channel. Superior injection performance was observed with a connection channel angled at 45 degrees to the separation channel compared to a device using a channel angled at 90 degrees. Automated delivery of electrolytes to the microdevice was demonstrated with both hydrostatic pumping and syringe pumps; both gave reproducible sample injection. A range of different sampling strategies were investigated. Isotachophoretic separations of model analytes (metal ions and an anionic dye) demonstrated the potential of the device. Separations of ten metal cations were achieved in under 475 s. 相似文献
58.
1,3-Dimethyl-7-deazaxanthine 2′-deoxyribofuranosides 1a and 6a and their N-3 isopropyl congeners 1b and 6b have been prepared employing the nucleobase anions 7a or 7b and 2-deoxy-3,5-di-O-(p-toluoyl)-α-D-erythropentofuranosyl chloride ( 8 ) upon glycosylation. The reaction was not stereoselective as found in case of other pyrrolo[2,3-d]pyrimidine nucleosides induced by the bulky N-3 substituent. Configuration of anomers was established by 1H-nmr nOe difference spectroscopy. Those data also indicated that the conformation around the N-glycosylic bond was locked by the bulky N-3 substituent. Contrary to the purine nucleoside such as wyosine ( 2a ) the hydrolytic stability of the N-glycosylic bond of the pyrrolo[2,3-d]pyrimidine nucleosides was increased by N-3 alkylation. Moreover, it was shown by 15N-nmr spectroscopy that different to purine nucleosides the aglycon was not protonated in acidic medium. As a result the N-glycosylic bond hydrolysis did not follow an A-1 but an A-2 mechanism. 相似文献
59.
60.
David Kretschmer 《The Journal of mathematical sociology》2018,42(2):83-112
This paper develops a dynamic model of minority labor market discrimination. Employers repeatedly decide to hire either minority or majority job candidates whose productivities are unobservable beforehand. Hiring decisions are based on productivity expectations derived from the observable productivity of employers’ previously hired workers. If employers have fewer minority workers initially—a plausible assumption for (numerical) minorities—they discriminate against minority workers over time. Discrimination results from more dispersed minority expectations across the employer population and stronger effects of additional productivity observations on minority expectations. Both effects are a direct consequence of the minority’s initial underrepresentation in firms. I demonstrate the emergence of minority discrimination formally in a two-period hiring model and show simulation results for longer time frames. 相似文献