Showing papers by "University of Duisburg-Essen published in 1986"

The Microstrip Step Discontinuity: A Revised Description

Abstract: A systematic variety of frequency-dependent numerical results hitherto unavailable are presented for the shielded microstrip impedance step. The computational method used is a rigorous full-wave spectral-domain approach developed by Jansen. The given data describe the steps for two very common groups of dielectric substrates as a function of stepwidth ratio in the range of normalized frequencies where it behaves like a two-port. They represent new MIC design information and are compared with quasi-static results and the widely used magnetic-wall waveguide approximation. Beyond this, they are validated against the sparse step-discontinuity data available from previous rigorous approaches.

Stabilisierung und Reaktionen von Iminoboranen — Kristallstruktur von (tert-Butylimino)[tris(trimethylsilyl)-silyl]boran

Abstract: Die Lithiumsalze des Tris(trimethylsilyl)methans (1) und -silans (2) reagieren mit Aminohalogenboranen zu den Substitutionsverbindungen 3–13. Chlor[tris(trimethylsilyl)-methyl](2,2,6,6-tetramethylpiperidino)boran (12) wird als THF-Addukt isoliert. Im Gegensatz zu den Methyl-, Ethyl- und Isopropyl(trimethylsilyl)amino-Verbindungen (3–7) verlieren Bis(trimethylsilyl)- (8, 9) und die tert-Butyl(trimethylsilyl)amino-Verbindungen (10, 11) thermisch Fluortrimethylsilan unter Bildung stabiler Iminoborane (14–17). – 18 wird durch Methanoladdition an 14 gebildet, 19 und 20 entstehen durch Addition von Mesitylamin an 16 und 17. Die Hydrolyse von 14 fuhrt zur Bildung des Amino(trisilylmethyl)-boranols (Me3Si)3CB(OH)–NHSiMe3 (21). Das zweite Hydrolyseprodukt von 14 (22) entsteht durch die Einwirkung von Luftfeuchtigkeit auf 21. 22 kondensiert im wasserfreien Medium nicht zum Boroxin. Die Kristallstruktur von 17 zeigt die bislang kurzeste gefundene Bor-Stickstoff-Bindungslange. Stabilisation and Reactions of Iminoboranes – Crystal Structure of (tert-Butylimino)[tris(trimethylsilyl)silyl]borane The lithium salts of tris(trimethylsilyl)methane (1) and -silane (2) react with aminohalogenoboranes to give the substitution compounds 3–13. Chloro[tris(trimethylsilyl)methyl](2,2,6,6-tetramethylpiperidino)borane (12) is isolated as THF adduct In contrast to methyl-, ethyl- and isopropyl(trimethylsilyl)amino compounds (3–7) the bis(trimethylsilyl)-(8, 9) and the tert-butyl(trimethylsilyl)amino compounds (10, 11) thermally loose fluorotrimethylsilane with formation of stable iminoboranes (14–17). – 18 is obtained by methanol addition to 14, 19 and 20 by mesitylamine addition to 16 and 17, respectively. The hydrolysis of 14 leads to the formation of the amino(trisilylmethyl)boranol (Me3Si)3CB(OH)–NHSiMe3 (21). The second product of hydrolysis of 14 (22) is obtained by atmospheric moisture from 21. 22 does not condense to the boroxine in an anhydrous medium. The crystal structure of 17 shows the shortest boron-nitrogen bond length found so far.

Joint report of the Third International Workshop on Canine Immunogenetics. I. Analysis of homozygous typing cells.

Abstract: The Third International Workshop on Canine Immunogenetics involved 80 potentially DLA-D homozygous typing cells obtained from dogs of various breeds and submitted from five laboratories in Europe and the United States. Mutual reactivity of all cells was studied in mixed leukocyte cultures, and stabilized relative responses were used for analysis. Intralaboratory and interlaboratory comparisons of results suggest that a stabilized relative response of 30% represents an acceptable parameter for "typing responses" indicating phenotypic DLA-D identity of stimulator and responder cells. Using this criterion, 10 clusters of homozygous typing cells were defined and accepted on an international level, and they were assigned the specificities Dw1 to Dw10. At least six additional (provisional) specificities were recognized that were well characterized within individual laboratories but require additional testing before workshop specificities can be assigned. These data show that DLA-D typing is feasible and represents a useful tool in the genetic analysis of the canine major histocompatibility complex. Much work is needed to confirm the present results in family studies, to determine gene frequencies, and to analyze at a molecular level the antigens responsible for mixed leukocyte culture reactivity.

Übergangsmetall-substituierte Acylphosphane und Phosphaalkene, IX. Zur Synthese von Phosphaalkenyl-, Mono- und Diacyl- phosphidokomplexen aus [Bis(trimethylsilyl)phosphido]-dicarbonyl(pentamethylcyclopentadienyl)eisen und Carbonsäurechloriden

Abstract: Die Titelverbindung (η5-C5Me5)(CO)2FeP(SiMe3)2 (4) reagiert mit 2,4,6-Trimethylbenzoylchlorid (2a) zu dem Phosphaalkenylkomplex (η5-C5Me5)(CO)2FePC(OSiMe3)(Mes) (5a). Demgegenuber fuhrt die Umsetzung von 4 mit Benzoylchlorid neben dem Phosphaalkenylkomplex 5b zu (η5-C5Me5)(CO)2FeP[C(O)Ph]2 (6b). Aus 4 und Pivaloylchlorid (2c) wird nur noch der Dipivaloylphosphidokomplex 6c gebildet. Fuhrt man die Umsetzungen von 4 mit den Saurechloriden 2a–c in Gegenwart von Ethanol durch, so erhalt man die Monoacylphosphidokomplexe (η5-C5Me5)(CO)2FePH[C(O)R] (8a–c). Komplex 8a wird von Methyllithium lithiiert und durch 2,4,6-Trimethylbenzoylchlorid in 6a ubergefuhrt. Desgleichen ergeben die Lithiierungsprodukte von 8 mit Me3SiCl die Phosphaalkenylkomplexe 5a–c. Transition-Metal-Substituted Acylphosphanes and Phosphaalkenes, IX. On the Synthesis of Phosphaalkenyl-, Mono- and Diacylphosphido Complexes from the Reaction of [Bis(trimethylsilyl)phosphido]dicarbonyl(pentamethylcyclopentadienyl)iron and Carbonyl Chlorides Reaction of the title compound (η5-C5Me5)(CO)2FeP(SiMe3)2 (4) with 2,4,6-trimethylbenzoyl chloride (2a) yields the phosphaalkenyl complex (η5-C5Me5)(CO)2FePC(OSiMe3)(Mes) (5a). Treatment of 4 with benzoyl chloride affords the phosphaalkenyl complex 5b and (η5-C5Me5)(CO)2FeP[C(O)Ph]2 (6b), whereas with pivaloyl chloride (2c) 6c is formed as the sole product. The monoacylphosphido complexes 8a–c are generated from the reaction of 4 with acyl chlorides 2a–c in the presence of ethanol. Lithiation by LiCH3 and subsequent acylation with 2,4,6-trimethylbenzoyl chloride converts compound 8a into 6a. Similarily the lithiation product of 8 is transformed into the phosphaalkenyl complexes 5a–c by treatment with Me3SiCl.

Corticotropin-Releasing Hormone (CRH) Stimulation in Nelson''s Syndrome: Response of Adrenocorticotropin Secretion to Pulse Injection and Continuous Infusion of CRH*

Abstract: Nelson's syndrome develops in 10–15% of patients with Cushing's disease who undergo bilateral adrenalectomy. Whether the pituitary tumors of Nelson's syndrome are autonomous or are regulated by hypothalamic signals or glucocorticoids is controversial. We, therefore, compared the plasma ACTH responses to synthetic ovine corticotropin-releasing hormone (CRH) in l i patients with Nelson's syndrome, 1 patient with Cushing's disease who had had bilateral adrenalectomy and did not have Nelson's syndrome, 14 patients with Cushing's disease, and 27 normal subjects. The plasma ACTH response to CRH in 10 patients with Nelson's syndrome was markedly increased and prolonged compared to the responses of normal subjects or patients with Cushing's disease. In 4 patients with Nelson's syndrome, plasma ACTH and cortisol concentrations also were determined at frequent intervals for 10–24 h during continuous infusions of 0.15 M saline or CRH (1 ¼g/kg-h). There was no desensitization of ACTH secretion during short term conti...

Dihydroazaborolyl‐Komplexe, XX. Das dynamische Verhalten BN‐gestörter Cyclopentadienyl‐Liganden — Synthese und Eigenschaften von (1‐tert‐Butyl‐2,5‐dihydro‐2‐methyl‐η5‐1H‐1,2‐azaborolyl)‐(η4‐1,5‐cyclooctadien)cobalt

Abstract: 1-tert-Butyl-2,5-dihydro-2-methyl-1H-1,2-azaborol (1) und Co2(CO)8 reagieren in Petrolether bei 60–80°C mit 40% Ausbeute zu dem Halbsandwichkomplex (1-tert-Butyl-2,5-dihydro-2-methyl-η5-1H-1,2-azaborolyl)dicarbonylcobalt (2), einer roten Flussigkeit. Die CO-Liganden in 2 konnen photolytisch durch 1,5-Cyclooctadien ersetzt werden, wobei sich der flussige organgerote Titel-Komplex 3 mit 54% Ausbeute bildet. Die behinderte Beweglichkeit der Liganden wird an Hand der temperaturabhangigen NMR-Spektren diskutiert. Dihydroazaborolyl Complexes1 , XX. The Dynamic Behavior of BN Perturbed Cyclopentadienyl Ligands — Synthesis and Properties of (1-tert-Butyl-2,5-dihydro-2-methyl-η5-1H-1,2-azaboroloyl)-(η4-1,5-cyclooctadiene)cobalt 1-tert-Butyl-2,5-dihydro-2-methyl-1H-1,2-azaborole (1) and Co2(CO)8 react in petroleum ether at 60–80°C with 40% yield to give the half sandwich complex (1-tert-butyl-2,5-dihydro-2-methyl-η5-1H-1,2-azaborolyl)dicarbonylcobalt (2), a red liquid. The CO ligands in 2 are substituted photolytically by 1,5-cyclooctadiene with formation of the liquid orangered title complex 3 in 54% yield. The hindered mobility of the ligands is discussed by means of temperature dependent NMR spectra.

Synthese und Struktur der ersten Arsaalkenylkomplexe mit FeAs‐Einfachbindung

Abstract: Preparation des complexes [Cp(CO) 2 Fe-As=C(OSiMe 3 )R]. Le squelette Fe-As=C-O est plan (R=t-Bu). Etude RX de la structure

Übergangsmetall‐induzierte CO‐Einschiebung in die PP‐Bindung von Diphosphenen unter Bildung von Diphosphinomethanonderivaten

Abstract: Preparation d'un complexe de fer carbonyle avec des unites structurales P−CO−P (complexes diphosphouree), par reaction de trans-M-P=P-aryl avec Fe 2 (CO) 9 , M=(C 5 Me 5 )(CO) 2 Fe

Solid-state photochemistry of nitro compounds: structure–reactivity correlations

Abstract: The molecular structures of 1-t-butyl-3,5-dimethyl-2,4,6-trinitrobenzene, 1-t-butyl-3,4,5-trimethyl-2,6-dinitrobenzene, and 1-t-butyl-4-acetyl-3,5-dimethyl-2,6-dinitrobenzene have been determined by single-crystal X-ray analyses with a view to establishing a structure-reactivity relationship in the photochemical intramolecular hydrogen-abstraction process in the solid state. The reactivity of these aromatic nitro compounds in the solid state has been rationalized in terms of relevant intramolecular geometrical parameters as well as intermolecular packing considerations.

Synthese und Struktur des kationischen Tetrahydrofuran‐Eisenkomplexes [C5Me5(CO)(Me3P)(THF)Fe]+

Abstract: Synthesis and Structure of the Cationic Tetrahydrofuran Iron Complex [C5Me5(CO)(Me3P)(THF)F]+ The reaction of C5Me5(CO)(Me3P)FeMe (1) with [Ph3C]PF6 in THF leads to the complex salt [C5Me5(CO)(Me3P)(THF)Fe]PF6 (2), which exchanges the THF ligand against Me3P under photochemical conditions to give [C5Me5(CO)(Me3P)2Fe]PF6 (3).