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  • Chemistry  (91)
  • General Chemistry  (38)
  • Industrial Chemistry  (4)
  • 61.70  (3)
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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Amino-thieno[2,3-c]pyrazole und Amino-thieno[2,3-b]pyrrole (1995)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 472-477 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino-thieno[2,3-c]pyrazoles and Amino-thieno[2,3-b]pyrrolesThe synthesis of thieno[2,3-c]pyrazoles and thieno[2,3-b]pyrroles is described. From the dithioliumsalt (1) and potassium hydroxide the potassium-(2,2-dicyan-1-methylthio-ethen-1-yl)-thiolate (2) is formed. This reacts with hydrazine hydrate to form the 3-amino-5-thioxo-pyrazol-4-carbonitrile (3) S-Alkylation with α-chlorocarbonyl compounds yielding (6a-c) leads via Thorpe-Ziegler-cyclization to 3,4-diamino-thieno[2,3-c]pyrazoles (9) if the position 1 is alkylated (8). Acetyl acetone yields 2-mercapto-pyrazolo[1,5-a]pyrimidine (5). After S-alkylation (10a-d) are immediately cyclized to thieno [2′,3′:3,4]pyrazolo[1,5-a]pyrimidine (11a-d). The ketone (6a) can be cyclized to the pyrazolo [5,1-b]thiazole (12). 3 reacts with oxalyl chloride to form the 2,3-dioxo-6-thioxo-imidazo[1,2-b]pyrazole (13) of which S-phenacyl derivative (14) because the NH-proton cannot be cyclized. The 5-amino-3,4-dicyano-pyrrol-2-thiolate (16) shows the analogous behaviour. The S-alkylation is followed by cyclization, and 3,5-diamino-thieno[2,3-b]pyrroles (18a-b) arise. Reaction of 5-amino-2-alkylthio-pyrrol-3,5-dicarbonitrile (17) with acetyl acetone provides pyrrolo[1,2-a]pyrimidine (20a-c) which can be cyclized to form thieno[3′,2′:4,6]pyrimidines (21a-c) very easily.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.199533701101
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  • 5
    Electronic Resource
    Electronic Resource
    Zur Synthese von 3-Amino-pyrrolen durch Thorpe-Ziegler-CyclisierungHerrn Prof. Dr. K. Schwetlick zum 60. Geburtstag gewidmet (1992)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 334 (1992), S. 491-496 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Synthesis of 3-Amino-pyrroles by Thorpe-Ziegler-CyclizationN-Aryl and alkylaminomethylene cyanacetic acid derivatives 1 react with α-halogencarbonyl compounds 2 in the presence of potassium carbonate/sodium ethoxide to yield the substituted 3-amino-pyrroles 6. Using the same principle of cyclization pyrrole derivatives 6 can also be obtained by reaction of β-chloro- and β-alkoxymethylenemalononitriles 4 with β-aminocarbonyl compounds 5. From the malononitrile derivatives 1 containing the methylthio group in the β-position, and α-halogen ketones 7, the 2-dicyanomethylene oxazolines 8 arise which undergo alkoholysis by treatment with sodium alkoxide to form the 3-amino-5-alkoxy-pyrrole derivatives 9.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19923340608
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Hydrogels based on 2.2.3.3.4.4.4.-heptafluorobutyl methacrylate (1992)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 43 (1992), S. 335-342 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Hydrogele (vernetzte Polymere mit definiertem Wassergehalt) wurden aus hydrophilen Methacrylaten und Perfluorbutylmethacrylat durch radikalische Polymerisation und nachfolgende Quellung in gepufferter isotonischer Natriumchloridlösung hergestellt. Die erhaltenen Hydrogele wurden durch ihre lineare Quellung, den Wassergehalt, den Brechungsindex, den Gehalt an extrahierbaren Bestandteilen, ihre Transparenz für sichtbares Licht sowie durch ihre Sauerstoffpermeation charakterisiert. Derartige Hydrogele sind interessant als Materialien für Kontaktlinsen.
    Notes: Hydrogels (crosslinked polymers with a defined content of water) from hydrophilic methacrylates and perfluorobutyl methacrylate were prepared by radical polymerization, followed by swelling in buffered isotonic sodium chloride solution. The obtained hydrogel samples have been characterized by their linear expansion to hydration, weight-percent hydration, refractive index, extractables, percent transmission of visible light, and oxygen permeability. Such hydrogels are interesting as contact lens materials.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1992.010430608
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  • 8
    Electronic Resource
    Electronic Resource
    Mischorgan zum Vergleichmäßigen laminarer Strömung in engen Rohren (1966)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 38 (1966), S. 994-995 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330380912
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  • 9
    Electronic Resource
    Electronic Resource
    Darstellung von LiAl[P(CH3)2]4 und der Silylphosphine H3-x(CH3)xSi—P(CH3)2Frau Professor Margot Becke-Goehring zum 60. Geburtstage gewidmet (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 406 (1974), S. 167-170 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation of LiAl[P(CH3)2]4 and Silylphosphines H3-x(CH3)xSi—P(CH3)2By metallation of HP(CH3)2 with LiC4H9 (in diglyme, at -40°C) and the subsequent reaction of the LiP(CH3)2 with AlCl3 the compound LiAl[P(CH3)2]4 is obtained (solution in diglyme). The reactions with H3SiBr, CH3SiH2Br, (CH3(2)SiHBr, and (CH3)3)SiCl results in the formation of H3SiP(CH3)2, CH3SiH2,—P(CH32, (CH3)2)SiHP(CH3)2, and (CH3)3Si—P(CH3)2 in large quantities.
    Notes: Durch Metallierung von HP(CH3)2 mit LiC4H9 in Diglym bei -40°C und anschließende Umsetzung des gebildeten LiP(CH3)2 mit AlCl3 wird das LiAl[P(CH3)2]4 zugänglich (Lösung in Diglym). Die Umsetzung mit H3SiBr, CH3SiH2Br, (CH3)2SiHBr und (CH3)3SiCl führt zur präparativen Darstellung von H3Si—P(CH3)2, CH3SiH2—P(CH3)2, (CH3)2SiH—P(CH3)2 (CH3)3Si—P(CH3)2.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19744060207
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  • 10
    Electronic Resource
    Electronic Resource
    Reaktionen zur Bildung von Silylphosphinen des Typs X3-(n+m)(CH3)nHmSi—PH2 (X = F, Cl, Br)Vorbericht: Z. anorg. allg. Chem. 405, 337 (1974). (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 407 (1974), S. 295-304 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation of Silylphosphines of the X3-(n+m)(CH3)nHmSi—PH2 Type (X = F, Cl, Br)Reactions of halosilanes with silylphosphines containing PH2-groups are reported. CH3SiHCl—PH2 is obtained by (1) For the synthesis of Cl3Si—PH2 reactions of SiCl4 with CH3SiH(PH2)2, CH3SiH2—PH2 and (CH3)3Si—PH2 are carried out in a manner analogous to that shown in eq. (2) Side reactions are observed. Cl3Si—PH2 is isolated in mixture with SiCl4 and CH3SiHCl—PH2 when the most reactive of the above compounds, CH3SiH(PH2)2 is utilized.
    Notes: Es wird über Reaktionen zwischen Halogensilanen und PH2-haltigen Silylphosphinen berichtet. CH3SiHCl—PH2 wird nach Gl. (1) zugänglich. Zur Bildung von Cl3Si—PH2 wurden Umsetzungen von SiCl4 mit CH3SiH(PH2)2, CH3SiH2—PH2 und (CH3)3Si—PH2 durchgeführt, wobei Reaktionen entsprechend Gl. (2) eintreten. Es treten Nebenreaktionen auf. Beim reaktionsfähigeren CH3SiH(PH2)2 ist die Isolierung von Cl3Si—PH2 im Gemisch mit SiCl4 und CH3SiHCl—PH2 möglich. Unter den Reaktionsbedingungen (50°C) zerfällt Cl3Si—PH2 in PH3 und Si—P-Polymere. SiBr4 reagiert bereits bei Raumtemperatur. Durch Umsetzung mit CH3SiH(PH2)2 werden je nach Reaktionsdauer CH3SiHBr—PH2, Br3Si—PH2 und auch Br2Si(PH2)2 zugänglich. Auch die Reaktion mit CH3SiH2—PH2 führt zum Br3Si—PH2 neben CH3SiH2Br. Mit FSiBr3 bildet CH3SiH(PH2)2 das FSiBr2—PH2 neben CH3SiHBr—PH2, während bei den F-reicheren Derivaten F2SiBr2 und F3SiBr die Disproportionierung in SiF4 gegenüber der Si—P-Spaltung überwiegt. Es werden die NMR-Daten der Verbindungen angegeben.Cl3Si—PH2 decomposes into PH3 and Si—P-polymers under the reaction conditions (50°C). SiBr4 however will react at room temperature. Depending on the time of reaction CH3SiHBr—PH2, Br3Si—PH2 and even Br2Si(PH2)2 are obtained with CH3SiH(PH2)2. Also the reaction with CH3SiH2—PH2 leads to the formation of Br3Si—PH2 in addition to CH3SiH2Br. With FSiBr3, CH3SiH(PH2)2 forms FSiBr2—PH2 together with CH3SiHBr—PH2. In the reaction of the higher fluorinated derivatives F2SiBr2 and F3SiBr the disproportion into SiF4 is found to be preferred to Si—P cleavage and therefore these reactions can not be adequately used. The nmr data are reported.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19744070305
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