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61.
Wolfgang A. Herrmann 《Angewandte Chemie (International ed. in English)》1982,21(2):117-130
The Fischer-Tropsch Synthesis counts among the industrial-scale processes having a versatile and broad product range, and has for decades offered the most attractive possibility for the use of coal as a source of heating oil and fuels. This conceivably simple reaction, the catalytic hydrogenation of carbon monoxide, generally leads to simple hydrocarbons as well (i.e. short chain olefins) that have been sought as chemical feedstocks since the oil crisis of the seventies, but fails to provide the large-scale, economic process required, due in large part to the minimal selectivity of traditional Fischer-Tropsch processes. In an effort to solve this problem current research in this sector is concerned not only with the optimization of old and the development of new catalytic systems, but also increasingly with the elucidation of numerous relevant reaction mechanisms. This article will discuss, from the viewpoint of an organometallic chemist, the significance of typical model reactions, both with regard to some fundamental aspects of synthesis gas chemistry, and in comparison with previous views concerning the mechanism of the Fischer-Tropsch Synthesis. The importance of various unique classes of complexes that have been studied in the context of Fischer-Tropsch chemistry is also evaluated with regard to their importance in the synthesis of hydrocarbons from carbon monoxide and hydrogen. It emerges that the primary steps of the reductive oligomerization of carbon monoxide are best described by the carbide/methylene mechanism, as originally proposed by Hans Fischer and Franz Tropsch. 相似文献
62.
The Ramanujan Journal - Let V(T) denote the number of sign changes in $$\psi (x) - x$$ for $$x\in [1, T]$$ . We show that $$\liminf _{T\rightarrow \infty } V(T)/\log T\ge \gamma _{1}/\pi +... 相似文献
63.
Sauer T 《Chaos (Woodbury, N.Y.)》1995,5(1):127-132
According to a theorem of Takens [Lecture Notes in Mathematics (Springer-Verlag, Berlin, 1981), Vol. 898], dynamical state information can be reproduced from a time series of amplitude measurements. In this paper we investigate whether the same information can be reproduced from interspike interval (ISI) measurements. Assuming an integrate-and-fire model coupling the dynamical system to the spike train, there is a one-to-one correspondence between the system states and interspike interval vectors of sufficiently large dimension. The correspondence implies in particular that a data series of interspike intervals, formed in this manner, can be forecast from past history. This capability is demonstrated using a nonlinear prediction algorithm, and is found to be robust to noise. A set of interspike intervals measured from a simple neuronal circuit is studied for deterministic structure using a prediction error statistic. (c) 1995 American Institute of Physics. 相似文献
64.
Strachan JD Adler H Alling P Ancher C Anderson H Anderson JL Ashcroft D Barnes CW Barnes G Batha S Bell MG Bell R Bitter M Blanchard W Bretz NL Budny R Bush CE Camp R Caorlin M Cauffman S Chang Z Cheng CZ Collins J Coward G Darrow DS DeLooper J Duong H Dudek L Durst R Efthimion PC Ernst D Fisher R Fonck RJ Fredrickson E Fromm N Fu GY Furth HP Gentile C Gorelenkov N Grek B Grisham LR Hammett G Hanson GR Hawryluk RJ Heidbrink W Herrmann HW Hill KW Hosea J Hsuan H Janos A Jassby DL Jobes FC 《Physical review letters》1994,72(22):3526-3529
65.
I. Wilke Y. Oppliger W. Herrmann F. K. Kneubühl 《Applied Physics A: Materials Science & Processing》1994,58(4):329-341
We report on the development of antenna-coupled thin-film nanometer Ni-NiO-Ni diodes which are used to detect 10.6 m CO2-laser radiation. The Ni-NiO-Ni diodes have a minimum contact area of 0.056 m2. This is smaller than those of any previously fabricated thin-film Metal-metalOxide-Metal (MOM) diodes. By measuring the second derivative of the dc current-voltage characteristics I(V), we demonstrate that the nonlinearity of the dc I(V) characteristics of our Ni-NiO-Ni diodes is larger than that of the dc I(V) characteristics of thin-film MOM diodes fabricated before by other authors. It is comparable to the nonlinearity of the dc I(V) characteristics of point-contact MOM diodes. Furthermore, we show that the polarisation-dependent infrared response of the Ni-NiO-Ni diodes is due to antenna coupling and that the polarisation-independent response is mainly of thermal origin. Consequently, the heating of the Ni-NiO-Ni diodes is due to the absorption of the incident CO2-laser radiation in the SiO2, and dissipation of the laser-induced ac antenna currents in the antenna. 相似文献
66.
67.
68.
B. Gutsche und R. Herrmann 《Fresenius' Journal of Analytical Chemistry》1968,242(1):13-17
Zusammenfassung Die in einer vorangegangenen Arbeit beschriebene Methode zur Bestimmung von chlorhaltigen Insecticiden in Extrakten aus tierischen und menschlichen Nahrungsmitteln wird durch folgende Maßnahmen wesentlich vereinfacht: a) Statt eines Spektralphotometers für den flammenspektrophotometrischen Nachweis wird ein einfaches Filterflammenphotometer verwandt. b) Das vorangegangene Extraktionsverfahren wird durch Weglassen eines Extraktionsschrittes wesentlich vereinfacht. Die Nachweisgrenzen der Methode und die Wiederauffindungsraten werden durch dieses Vorgehen sogar verbessert.
Die Arbeit wurde mit Mitteln der Deutschen Forschungsgemeinschaft unterstützt. 相似文献
Flame -spectrophotometric determination of pesticides with a filter-photometer
In a preceding paper a flamespectrophotometric method for the analysis of chlorinated pecticides in extracts of animal and human food-stuffs was described. Now this method was simplified by using a flame photometer with filters instead of a photometer with monochromators and by omission of one extraction step. In spite of these simplifications the detection limits are improved and a better recovery is obtained.
Die Arbeit wurde mit Mitteln der Deutschen Forschungsgemeinschaft unterstützt. 相似文献
69.
Michael MuehlhoferThomas Strassner Eberhardt HerdtweckWolfgang A Herrmann 《Journal of organometallic chemistry》2002,660(2):121-126
Novel bridged platinum(II) biscarbene complexes are reported: 1,1′-dimethyl-3,3′-methylene-4-diimidazolin-2,2′-diylidene platinum(II) (3) and 1,1′-dimethyl-3,3′-ethylene-4-diimidazolin-2,2′-diylidene platinum(II) complexes 4 are directly accessible in high yields starting from platinum halides. The one-pot synthesis obviates the need for multi-step reactions via metal precursors or free carbenes. An X-ray crystal structure of 1,1′-dimethyl-3,3′-methylene-4-diimidazolin-2,2′-diylidene platinum(II) dibromide (3b) confirmed the structural similarity to the known corresponding palladium complexes. Since free 1,1′-di-R-3,3′-methylene-4-diimidazolin-2,2′-diylidenes are only available in low yields this synthetic route provides an easy access to the corresponding carbene complexes. 相似文献
70.
Armbruster P Agarwal YK Brüchle W Brügger M Dufour JP Gaggeler H Hessberger FP Hofmann S Lemmertz P Münzenberg G Poppensieker K Reisdorf W Schadel M Schmidt K Schneider JH Schneider WF Sümmerer K Vermeulen D Wirth aG Ghiorso A Gregorich KE Lee D Leino M Moody KJ Seaborg GT Welch RB Wilmarth P Yashita S Frink C Greulich N Herrmann G Hickmann U Hildebrand N Kratz JV Trautman N Fowler MM Hoffman DC Daniels WR von Gunten HR Dornhöfer H 《Physical review letters》1985,54(5):406-409