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  • Chemistry  (91)
  • 61.70  (3)
  • PHYSICS, ATOMIC, MOLECULAR, AND NUCLEAR
  • 1
    Electronic Resource
    Electronic Resource
    Irradiation-induced atomic defects in SiC studied by positron annihilation (1995)
    Springer
    Applied physics 61 (1995), S. 51-53 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 61.80 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The present paper reports on positron lifetime measurements on atomic defects in SiC after low-temperature (80 K) electron irradiation of low (0.47 MeV) and high (2.5 MeV) electron energies and doses from 1.8×1017 to 1.9×1019 e/cm2 as well as after subsequent isochronal annealing up to 1900 K. For these studies the single crystals of nitrogen doped (2–3×1018 cm−3) SiC grown by a modified Lely technique with hexagonal structure (6H polytype) were used. According to the positron lifetime measurements, very different types of vacancy-like positron traps are introducted after irradiation with electrons of either low or high energy. The formation of defect agglomerates and their decay at high temperatures is studied during isochronal annealing and related to earlier studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538210
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  • 2
    Electronic Resource
    Electronic Resource
    Positron lifetimes and annihilation lineshape in Cd and au from 4.2 K to the melting points (1977)
    Springer
    Applied physics 12 (1977), S. 59-67 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract By means of an integrated source-specimen technique the temperature dependence of positron lifetimes and annihilation lineshapes has been measured, on the same specimens of gold and cadmium from 4.2K to the melting points, and also in electronirradiated and quenched gold. The anomalous temperature dependence of positron annihilation at intermediate temperatures (200 to 350 K in Cd, 270 to 750 K in Au) discovered by Lichtenberger, Schulte, and MacKenzie is confirmed. The data are incompatible with the idea that the intermediate temperature dependence is due to thermal expansion. They are well explained by an extension of the trapping model which includes the formation of metastable self-trapped positrons. From lineshape measurements after electron irradiation at 180 K and after quenching it is deduced that the trapping rate of positrons at vacancy-type defects in Au is temperature independent below room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00900069
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  • 3
    Electronic Resource
    Electronic Resource
    The positron beam at the stuttgart pelletron accelerator and its applications toβ +γ positron lifetime measurements (1987)
    Springer
    Applied physics 43 (1987), S. 261-267 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70 ; 07.77
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A slow-positron source has been installed in the therminal of an electrostatic 6.5 MeV accelerator and provides a monoenergetic positron beam in the few-MeV range. It will be used to operate a “fast” positron lifetime spectrometer based onβ + γ coincidences. The properties of the beam, the expected performance of the spectrometer, its advantages over conventionalγγ lifetime measurements, a number of intended applications, as well as recent positron-electron scattering experiments and plans for positron channelling and channelling-radiation studies are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00635181
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  • 4
    Electronic Resource
    Electronic Resource
    Cyclisierungen mit 1-Nitro-2-anilino-äthylenen (1977)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 319 (1977), S. 149-158 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclizations with 1-nitro-2-anilino-ethylenesThe reaction of 1-nitro-2-anilino-2-methylthio-ethylenes 1 with oxalyl chloride yields the substituted 4-nitropyrrol-2,3-diones 4, and with chlorocarbonyl-sulfenylchloride the 5-nitro-thiazolones 6. The methylthio group from 6 can be exchanged by amines. From 1-nitro-2,2-bis(anilino)ethylenes 2 - available from 1-nitro-2,2-bis(methylthio)-ethylene and anilines - and the same reagents, the substituted 2-nitromethylene-imidazolidine-4,5-diones 5 and the thiazolo[4,5-d]thiazoledione 9 result. The condensation of 1-nitro-2-anilino-2-hydrazino-ethylene 3 with derivatives of carboxylic acids yields 2-nitromethyl-s-triazole 12, with diacetyl the substituted 3-nitromethylene-as-triazine 13.
    Notes: 1-Nitro-2-anilino-2-methylmercapto-äthylen 1 reagiert mit Oxalylchlorid zu substituierten 4-Nitropyrroldionen-(2,3) 4 und mit Chlorcarbonyl-sulfenylchlorid zu substituierten 5-Nitrothiazolonen-(2) 6, deren Methylmercaptogruppe gegen Amine austauschbar ist. 1-Nitro-2,2-bis(anilino)-äthylene 2 - erhältlich aus 1-Nitro-2,2-bis(methylmercapto)-äthylen und Anilinen  -  liefert mit den gleichen Agenzien substituierte 2-Nitromethylenimidazolidindione-(4,5) 5 und das Thiazolo[4,5-d]thiazoldion 9. 1-Nitro-2-anilino-2-hydrazino-äthylen 3 wird mit Carbonsäurederivaten zu substituierten 2-Nitromethyl-s-triazolen 12, mit Diacetyl zum 3-Nitromethylen-as-triazin derivat 13 kondensiert.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19773190120
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  • 5
    Electronic Resource
    Electronic Resource
    3-Amino-5-nitromethylen-1,2-dithiol-4-carbonsäureester (1981)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 323 (1981), S. 133-136 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl(3-amino-5-nitromethylene-1,2-dithiol-4)carboxylate
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19813230119
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  • 6
    Electronic Resource
    Electronic Resource
    Einstufige Synthese von Pyrazino[1,2-a:4,5-a′]diindol-6,13-dionen (1987)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 745-748 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19873290428
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  • 7
    Electronic Resource
    Electronic Resource
    5-Arylamino-3-brom-1,2,4-thiadiazole und 5-Arylamino-3-bromisothiazole (1987)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 355-358 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 5-Arylamino-3-bromo-1,2,4-thiadiazoles and 5-Arylamino-3-bromo-isothiazoles
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19873290230
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  • 8
    Electronic Resource
    Electronic Resource
    Reaktion von methylenaktiven Nitrilen und Cyanamid mit acylierten Enaminen (1982)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 324 (1982), S. 933-941 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of Methylene Active Nitriles and Cyanamide with Acylated EnaminesThe addition products from enamines onto isocyanates and isothiocyanates, i.e. substituted β-aminoacrylo amides 1 and thioamides 2, react with malononitrile to yield the 6-amino-1-aryl-5-cyano-pyridin-2-ones 3 and -thiones 4 among them 5,6,7,8-tetrahydroisoquinolin-1-ones and -thiones. From ethyl cyanoacetate the 5-cyano-6-hydroxy-pyridin-2-ones 7 and from benzoyl acetonitrile the 6-phenyl-pyridin-2-ones 8 are formed. The replacement of malononitrile by cyanamide yields the 2-amino-3-aryl-pyrimidin-4-ones 5 and -thiones 6 among them 5,6,7,8-tetrahydroquinazolin-4-ones and -thiones. The not isolated β-acyl enamines derived from enamines and acid chlorides react with malononitrile or cyanamide to form the pyridin-2-ones 14 or pyrimidin-2-ones 15 caused by Dimroth-rearrangement.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19823240611
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  • 9
    Electronic Resource
    Electronic Resource
    Zur Reaktion von 1, 1-Dimethylthio- und 1-Dimethylamino-2-nitroethen mit dimerem Malononitril (1985)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 328-332 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of 1, 1-Dimethylthio- and 1-Dimethylamino-2-nitroethene with Malononitrile Dimer
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19853270218
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  • 10
    Electronic Resource
    Electronic Resource
    Neue Synthese von substituierten 4-Amino-chinazolinen und deren Heteroanalogen (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 206-213 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Synthesis of Substituted 4-Amino-quinazolines and Their HeteroanalogaN-Chloracetyl-anthranilonitriles react with potassium thiocyanate in the presence of alcohol to the (4-aminoquinazolin-2-yl-thio)-acetic acid ester (5). In the presence of water or primary amine the acetic acid derivative (6) or the acetic acid amide derivatives (7) are obtained. 2,4-Diaminoquinazolines (8) arise if vigorous reaction conditions are employed. With 2-chloracetylamino-cyclopent-1-en-carbonitrile as starting material the pyrimidines (11) are formed from the reaction with potassium thiocyanate. Analogously, (4-pyrimidyl-2-yl-seleno)-acetic acid ester (12) and (thiazolo[4,5-d]pyrimid-2-yl-seleno)-acetic acid derivatives (16) can be prepared with potassium selenocyanate. N-Chloracetyl derivatives of 5-membered heterocycles with enamino-nitrile structure (13, 15, 18, 20) react with potassium thiocyanate to yield thieno[2,3-d]-, thiazolo[4,5-d]-, pyrrolo[2,3-d]-, furo[2,3-d]- and pyrazolo[4,3-d]pyrimidines (14, 16, 19a, 19b, 21).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19963380144
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