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  • Organic Chemistry  (4)
  • ASTROPHYSICS  (3)
  • 1990-1994  (7)
  • 1985-1989
  • 1945-1949
  • 1990  (7)
  • 1
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    A new class of solutions for interstellar magnetohydrodynamic shock waves (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: An analysis is presented of the equations of motion for steady MHD shock waves proopagating in interstellar clouds, for boundary conditions that preclude C shocks. In addition to J shocks, in which the neutral fluid component becomes subsonic at an adiabatic jump front, the equations admit a new class of solutions, called C-asterisk shocks, in which the transition to subsonic flow occurs continuously at a sonic point. Numerical methods are developed for computing the structure of J and C-asterisk shocks propagating in diffuse interstellar clouds. The effects of chemical, ionization, and recombination processes are included in this treatment. An alternative numerical method, which uses artificial viscosity to facilitate integration through sonic points, is analyzed and shown to be invalid. A set of exemplary solutions, computed for realistic shock parameters, shows that C-asterisk shocks occur for a broad range of conditions relevant to diffuse interstellar clouds.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 350; 700-721
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Dynamic mass exchange in doubly degenerate binaries. I - 0.9 and 1.2 solar mass stars (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The dynamic mass exchange process in doubly degenerate binaries was investigated using a three-dimensional numerical simulation of the evolution of a doubly degenerate binary system in which the primary is a 1.2-solar-mass white dwarf and the Roche lobe filling secondary is a 0.9-solar-mass dwarf. The results show that, in a little more than two orbital periods, the secondary is completely destroyed and transformed into a thick disk orbiting about the primary. Since only a very small fraction of the mass (0.0063 solar mass) escapes the system, the evolution of the binary results in the formation of a massive object. This object is composed of three parts, the initial white dwarf primary, a very hot pressure-supported spherical envelope, and a rotationally supported outer disk. The evolution of the system can be understood in terms of a simple analytical model where it is shown that the angular momentum carried by the mass during the transfer and stored in the disk determines the evolution of the system.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 348; 647-667
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    IRAS observations of a large circumstellar dust shell around W Hydrae (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: IRAS observations at 60 and 100 microns reveal a large 30-40-arcmin (about 1-pc) diameter dust shell centered on the oxygen-rich red giant W Hya. Except for SNRs, this is the largest mass-loss envelope, in apparent diameter, known around any evolved star, including PN. W Hya's radiation field, stronger than the interstellar radiation field in the outer envelope, is sufficient to heat dust grains with IR emissivity proportional to lambda exp -1.2 to temperatures of about 40 K implied by the ratio of intensities at 60 and 100 microns.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 229; 2 Ma
    Format: text
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  • 4
    Electronic Resource
    Electronic Resource
    Tetrazolverbindungen. 5. Synthese und Umaminierung von Enaminoketonen der Tetrazolreihe (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 977-994 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrazole Compounds. 5. Synthesis and Transamination of Enamino Ketones of the Tetrazole SeriesTetrazole-5-acetaldehyde enamines 5 react with aliphatic and aromatic carboxylic acid chlorides in the presence of an auxiliary base (e.g. pyridine or triethylamine) to give tetrazolylsubstituted enamino ketones 6. The latter can be modified by acid-catalyzed transamination with secondary aliphatic amines (e.g. diethylamine, pyrrolidine, piperidine, morpholine, hexamethylene imine) yielding 5-(1-acyl-2-dialkylamino-vinyl)-1-aryl-1 H-tetrazoles 7. The analogue transamination of 6 with primary alkyl, aralkyl, and aryl amines results in corresponding secondary enamino ketones 8, which exist in solution as an equilibrium mixture of the Z and E form. Acylation of secondary tetrazole-5-acetaldehyde enamines 9 does not lead to 8, but to the isomeric N-acyl derivatives 10. - Characteristic 1H-n.m.r., u.v., and i.r. spectroscopic data of the novel products are reported.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320615
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  • 5
    Electronic Resource
    Electronic Resource
    Substituierte 2-Amino-thiazole aus α-Thiocyanato-acetophenonen und DialkylaminenHerrn Prof. Dr. K. Gewald mit den besten Wünschen zum 60. Geburtstag gewidmet (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 453-460 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted 2-Amino-thiazoles from α-Thiocyanato-acetophenones and Dialkylaminesα-Thiocyanato-acetophenones 1 react with dialkylammonium salts of weak acids (acetates, propionates, benzoates) to give 2-dialkylamino-4-aryl-thiazoles 4. As reaction medium aliphatic alcohols (methanol, ethanol), dipolar-aprotic solvents (acetonitrile, dimethylformamide, dimethyl sulphoxide) or chlorinated hydrocarbons (methylene chloride, chloroform, carbon tetrachloride) can be used. In comparison to known methods for the preparation of the thiazoles 4 the synthesis via α-thiocyanato-acetophenones 1 has the advantage of the simpler accessible starting compounds. - I.r., u.v., n.m.r. and mass spectroscopic data of the thiazoles 4 are reported.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320405
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  • 6
    Electronic Resource
    Electronic Resource
    2-Dialkylamino-thiazolin-4-one aus α-Thiocyanato-carbonsäurederivatenHerrn Prof. Dr. G. Zimmermann mit den besten Wünschen zum 60. Geburtstag gewidmet (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 540-546 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Dialkylamino-thiazolin-4-ones from α-Thiocyanato-carboxylic Acid Derivativesα-Thiocyanato-acetic acid esters 1a-c or amide 1d react with dialkylamine salts of weak acids to give 2-dialkylamino-thiazolin-4-ones 2a-f. The reaction can be performed using aliphatic alcohols, dipolar aprotic solvents or halogenated hydrocarbons as reaction medium or by heating the educts at 90°C without any solvent. According to the latter method, the 5-substituted thiazolinones 2g, h are obtained from α-thiocyanatopropionic acid ethyl ester (1d) or α-thiocyanato-phenylacetic acid ethyl ester (1e) and dimethylamine acetate. - I.r., u.v. and n.m.r. data of the thiazolinones 2 are reported.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320419
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  • 7
    Electronic Resource
    Electronic Resource
    Substituierte N,N′-Bis(thiazol-2-yl)-diaminoalkane aus α-Thiocyanato-acetophenonen und N,N′-Dialkyl-diamino-alkanen (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 723-730 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted N,N′-Bis(thiazol-2-yl)-diaminoalkanes from α-Thiocyanato-acetophenones and N,N′-Dialkyl-diaminoalkanesα-Thiocyanato-acetophenones 1 react with N,N′-dialkyl-diaminoalkanes 2 in the presence of an appropriate weak acid (acetic acid, propionic acid, benzoic acid) to give the hitherto unknown N,N′-dialkyl-N,N′-bis(4-aryl-thiazol-2-yl)-diaminoalkanes 3. As reaction medium aliphatic alcohols (ethanol, methanol), halogenated hydrocarbons (methylene chloride, chloroform, carbon tetrachloride) or dipolar-aprotic solvents (acetonitrile, dimethylformamide) can be used. - I.r., u.v., n.m.r. and mass spectroscopic data of the novel bisthiazoles 3 are reported.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320522
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