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  • Organic Chemistry  (8)
  • COMPUTER PROGRAMMING AND SOFTWARE  (4)
  • 1990-1994  (5)
  • 1985-1989  (7)
  • 1994  (1)
  • 1991  (4)
  • 1988  (3)
  • 1987  (4)
  • 1
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Homophthalic acid (1) undergoes reaction with 1,2-, 1,3-, and 1,4-diamines to give condensed 1(2H)-isoquinolinones like 2, 4, 13, and 25, which exhibit marked enamine character. These are attacked by electrophiles at the N or C terminus. Some notable reactions of imidazoisoquinolone 2 are those with maleic and acrylic acids to form the tetracycles 48 and 51, respectively. With propiolic acid, 5 underwent an interesting reaction to form the benzimidazonaphthyridine 53. An equally interesting behaviour was elicited from 2 in its reaction with formaldehyde, when in addition to the expected methylene-bridged molecule 59, the novel spiro derivative 60 was formed by the dimerisation of a presumed azadiene intermediate 63.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Examination of oxidation mixtures of 1-phenylprop-1-yne, 1-phenylbut-1-yne and 1-phenyl-3-methylbut-1-yne revealed the presence of hitherto not reported interesting products, especially the α-dicarbonyl compounds 1-phenylpropane-1,2-dione, 1-phenylbutane-1,2-dione and 1-phenyl-3-methylbutane-1,2-dione respectively in minor quantities. Some other typical products like benzil, benzoic anhydride and phenyl benzoate were also characterized. Although the oxidation of diphenylacetylene is very slow, benzil could be found as the main detectable product along with traces of benzoic acid. The α-diketones corresponding to the 1-phenylalk-1-ynes were oxidized at 110°C. In each case benzoic acid and the lower carboxylic acids as in the case of the autoxidation of the corresponding acetylenes were obtained. Benzil, benzoic anhydride and phenyl benzoate were also characterized in all the cases. Therefore, α-diketones are considered as intermediates responsible for the formation of the oxidative cleavage products of the C≡C triple bond.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 617-625 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: α-Diazoacetophenone, α-diazopropiophenone, α-diazobutyrophenone and α-diazodesoxybenzoin were thermally and photochemically decomposed in the presence and in the absence of oxygen using benzene, cyclohexane and chlorobenzene as solvents. The products expected from the reaction of the short-lived intermediate ketocarbenes with oxygen (α-diketones and lower carboxylic acids, especially benzoic acid) could not be detected. No substantial difference was found between the composition of the reaction mixtures formed in the presence and absence of oxygen. The results show that the oxidative cleavage of the C≡C triple bond during the autoxidation of acetylenic hydrocarbons does not proceed via the corresponding oxirenes or the valence-isomeric ketocarbenes.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 930-932 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 441-441 
    ISSN: 0899-0042
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 104-111 
    ISSN: 0899-0042
    Schlagwort(e): stereochemistry ; sulfation ; enantioselectivity ; inhibition ; chiral ; mechanism ; stereoselective ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Aryl sulfotransferase IV catalyzes the 3′-phosphoadenosine-5′-phosphosulfate (PAPS)-dependent formation of sulfuric acid esters of benzylic alcohols. Since the benzylic carbon bearing the hydroxyl group can be asymmetric, the possibility of stereochemical control of substrate specificity of the sulfotransferase was investigated with benzylic alcohols. Benzylic alcohols of known stereochemistry were examined as potential substrates and inhibitors for the homogeneous enzyme purified from rat liver. For 1-phenylethanol, both the (+)-(R)-and (-)-(S)-enantiomers were substrates for the enzyme, and the kcat/Km value for the (-)-(S)-enantiomer was twice that of the (+)-(R)-enantiomer. The enzyme displayed an absolute stereospecificity with ephedrine and pseudoephedrine, and with 2-methyl-1-phenyl-1-propanol; that is, only (-)-(1R,2S)-ephedrine, (-)-(1R,2R)-pseudoephedrine, and (-)-(S)-2-methyl-1-phenyl-1-propanol were substrates for the sulfotransferase. In the case of 1,2,3,4-tetrahydro-1-naphthol, only the (-)-(R)-enantiomer was a substrate for the enzyme. Both (+)-(R)-2-methyl-1-phenyl-1-propanol and (+)-(S)-1,2,3,4-tetrahydro-1-naphthol were competitive inhibitors of the aryl sulfotransferase-catalyzed sulfation of 1-naphthalenemethanol. Thus, the configuration of the benzylic carbon bearing the hydroxyl group determined whether these benzylic alcohols were substrates or inhibitors of the rat hepatic aryl sulfotransferase IV. Furthermore, benzylic alcohols such as (+)-(S)-1,2,3,4-tetrahydro-1-naphthol represent a new class of inhibitors for the aryl sulfotransferase.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Cubane diester crown ethers were tested as ion-selective electrodes in poly(vinyl chloride) (PVC) membranes. The four ionophores studied proved to be good K+ neutral carriers, showing Nernstian and near-Nernstian responses to this ion, in the range 10-4-10-1 M. The fixed interferences method was used to determine relative selectivity coefficients for all the electrodes. The highest selectivity for potassium relative to sodium, lithium, calcium and magnesium ions using potassium tetrakis(p-chlorophenyl)borate (KTpClPB) as a resistance modifier and NPOE as a plasticizer was obtained with the 1,4-cubyl diester-25-crown-7 ether ionophore. The effects of KTpCIPB on membrane selectivity were assessed; its removal was found to increase the selectivity of the four ionophores for potassium relative to cesium, sodium, calcium and magnesium ions with minimal effects on lithium and ammonium ions. The compounds tested exhibited a fast Nernstian response to changes in K+ concentration which was stable to within 〈100 μV h-1.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 330 (1988), S. 748-752 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Dibenzoyl peroxide, diacetyl peroxide and di-tert-butyl peroxide were thermally decomposed at 130°C in the presence of benzil, 1-phenyl-propane-1,2-dione, and 1-phenyl-butane-1,2-dione using chlorobenzene as the solvent. In all cases benzoic acid was formed. Moreover, from 1-phenyl-propane-1,2-dione and 1-phenylbutane-1,2 dione considerable amounts of benzil were obtained. The results show that reactions of the type (with X· =R′—O· or X· =R′—CO—O·), previously formulated by us to explain the course of the autoxidation of α-diketones, really take place.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2013-08-31
    Beschreibung: Any space based system, whether it is a robot arm assembling parts in space or an onboard system monitoring the space station, has to react to changes which cannot be foreseen. As a result, apart from having domain-specific knowledge as in current expert systems, a space based AI system should also have general principles of change. This paper presents a modal logic which can not only represent change but also reason with it. Three primitive operations, expansion, contraction and revision are introduced and axioms which specify how the knowledge base should change when the external world changes are also specified. Accordingly the notion of dynamic reasoning is introduced, which unlike the existing forms of reasoning, provide general principles of change. Dynamic reasoning is based on two main principles, namely minimize change and maximize coherence. A possible-world semantics which incorporates the above two principles is also discussed. The paper concludes by discussing how the dynamic reasoning system can be used to specify actions and hence form an integral part of an autonomous reasoning and planning system.
    Schlagwort(e): COMPUTER PROGRAMMING AND SOFTWARE
    Materialart: NASA, Marshall Space Flight Center, Fourth Conference on Artificial Intelligence for Space Applications; p 261-270
    Format: application/pdf
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  • 10
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2019-06-28
    Beschreibung: File systems have long been the most important and most widely used form of shared permanent storage. File systems in traditional time-sharing systems, such as Unix, support a coherent sharing model for multiple users. Distributed file systems implement this sharing model in local area networks. However, most distributed file systems fail to scale from local area networks to an internet. Four characteristics of scalability were recognized: size, wide area, autonomy, and heterogeneity. Owing to size and wide area, techniques such as broadcasting, central control, and central resources, which are widely adopted by local area network file systems, are not adequate for an internet file system. An internet file system must also support the notion of autonomy because an internet is made up by a collection of independent organizations. Finally, heterogeneity is the nature of an internet file system, not only because of its size, but also because of the autonomy of the organizations in an internet. The Jade File System, which provides a uniform way to name and access files in the internet environment, is presented. Jade is a logical system that integrates a heterogeneous collection of existing file systems, where heterogeneous means that the underlying file systems support different file access protocols. Because of autonomy, Jade is designed under the restriction that the underlying file systems may not be modified. In order to avoid the complexity of maintaining an internet-wide, global name space, Jade permits each user to define a private name space. In Jade's design, we pay careful attention to avoiding unnecessary network messages between clients and file servers in order to achieve acceptable performance. Jade's name space supports two novel features: (1) it allows multiple file systems to be mounted under one direction; and (2) it permits one logical name space to mount other logical name spaces. A prototype of Jade was implemented to examine and validate its design. The prototype consists of interfaces to the Unix File System, the Sun Network File System, and the File Transfer Protocol.
    Schlagwort(e): COMPUTER PROGRAMMING AND SOFTWARE
    Materialart: NASA-CR-189929 , NAS 1.26:189929 , TR-91-18
    Format: application/pdf
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