Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Safe bounds for the solutions of nonlinear problems using a parallel multisplitting method (1989)
    Springer
    Computing 42 (1989), S. 171-186 
    Details
    ISSN: 1436-5057
    Keywords: 65G10 ; 65H10 ; 65W05 ; CR: G. 1.0 ; G.1.5 ; Parallel methods ; nonlinear systems ; enclosures ; error bounds ; interval iterative methods ; multisplittings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Für gewisse Systeme nichtlinearer GleichungenF(x)=0 entwicklen wir ein Verfahren, welches iterativ enge untere und obere Schranken für die Nullstellen vonF berechnet. Das Verfahren beruht auf einem Multisplitting für bestimmte Matrizen und weist so in natürlcher Weise Parallelität auf. Wir geben Kriterien für die Konvergenz der Schranken gegen die Nullstellen an und untersuchen die Konvergenzgeschwindigkeit.
    Notes: Abstract For some systems of nonlinear equationsF(x)=0 we derive an algorithm which iteratively constructs tight lower and upper bounds for the zeros ofF. The algorithm is based on a multisplitting of certain matrices thus showing a natural parallelism. We prove criteria for the convergence of the bounds towards the zeros and we investigate the speed of convergence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02239746
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Enclosing the solution set of linear systems with inaccurate data by iterative methods based on incomplete LU-decompositions (1985)
    Springer
    Computing 35 (1985), S. 189-206 
    Details
    ISSN: 1436-5057
    Keywords: 65F10 ; 65G10 ; Interval arithmetic ; linear systems of equations ; iterative solution methods ; incompleteLU-decompositions ; comparison theorems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Vorgestellt wird eine Klasse von Iterationsverfahren zur Einschließung der Lösungsmenge durch einen Intervallvektor; dabei ist einen×n Intervall-H-Matrix und ein Intervallvektor. Der betrachtete Algorithmus verallgemeinert ein Iterationsverfahren von Meijerink/van der Vorst, das auf einer unvollständigenLU-Zerlegung einerM-MatrixA basiert. Es werden Aussagen über die Durchführbarkeit des Algorithmus, seiner Konvergenzgeschwindigkeit und seiner Einschließungsgüte gemacht. Da das ursprüngliche Verfahren von Meijerink/van der Vorst ein Spezialfall des vorliegenden Algorithmus ist, erhält man damit gleichzeitig seine Durchführbarkeit in der größeren Klasse derH-Matrizen. Als weitere Anwendung auf reelle Matrizen erhält man einen Zusammenhang zwischen demR 1-Faktor (Ortega/Rheinboldt [9]) des ursprünglichen Verfahrens und der zugrundeliegenden IndexmengeP.
    Notes: Abstract We present a class of iterative methods to enclose the solution set by an interval vector;A is varying in ann×n intervalH-Matrix andb is varying in an interval vector . The algorithm taken into consideration generalizes an iterative method of Meijerink/van der Vorst based on an incompleteLU-decomposition of anM-MatrixA. Theorems concerning the feasibility of the algorithm, its rate of convergence and its quality of enclosure are given. Since the original method of Meijerink/van der Vorst is a special case of our algorithm we have thus shown its applicability to the larger class ofH-matrices. Furthermore we relate theR 1-factor (as defined in Ortega/Rheinboldt [9]) of the original method to the underlying setP of indices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260505
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    On a theorem of Stein-Rosenberg type in interval analysis (1986)
    Springer
    Numerische Mathematik 50 (1986), S. 17-26 
    Details
    ISSN: 0945-3245
    Keywords: AMS(MOS): 65F10 ; 65G10 ; CR: G1.3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary In classical numerical analysis the asymptotic convergence factor (R 1-factor) of an iterative processx m+1=Axm+b coincides with the spectral radius of then×n iteration matrixA. Thus the famous Theorem of Stein and Rosenberg can at least be partly reformulated in terms of asymptotic convergence factor. Forn×n interval matricesA with irreducible upper bound and nonnegative lower bound we compare the asymptotic convergence factor (α T ) of the total step method in interval analysis with the factorα S of the corresponding single step method. We derive a result similar to that of the Theorem of Stein and Rosenberg. Furthermore we show thatα S can be less than the spectral radius of the real single step matrix corresponding to the total step matrix |A| where |A| is the absolute value ofA. This answers an old question in interval analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01389665
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Solid-state conformation of some basic sequential polypeptides (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1801-1808 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have studied the structure of solid films obtained by x-ray diffraction, from several basic polypeptides with a defined sequence. The alterating polypeptides poly(Ala-Lys), poly(Leu-Lys), poly(Val-Lys), and poly(Arg-Leu) all show a cross-β-structure in which layers of hydrophilic side chains alternate with layers containing hydrophobic side chains. The other polypeptides studied are not in the β-conformation and appear to be in the α-helical conformation. The helices obtained from poly(Lys-Ala-Ala) and poly(Lys-Ala-Ala-Lys) appear to be packed in an unusual fashion, which favors interaction between alanine side chains. Such behavior is not found in poly(Lys-Leu-Ala).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240910
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Structures and Electrical Properties of Some New Organic Conductors Derived from the Donor Molecule TMET (S,S,S,S,-Bis(dimethylethylenedithio) tetrathiafulvalene) (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 942-953 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Crystal structures and electrical properties of radical-cation salts of the chiral organic donor TMET (S,S,S,S,-bis-(dimethylethylenedithio)tetrathiafulvalene) are described. Two structural types, 2:1 with octahedral anions Pf-6, AsF-6, SbF-6, I-3 (incommensurate), and 3:2 with tetrahedral anions BF-4, CIO-4, ReO-4 are observed. Resistivity measurements between 2 and 298 K indicate that the 3:2 types are organic metals, while the other compounds are semiconductors. (TMET)3(CIO4)2 is metallic down to about 120 K at ambient pressure and remains metallic down to 2 K at 8 kbar.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700405
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    The Vinylogous Tricarbonyl Chromophore. Violerythrine End Groups and Related Six-Membered Ring Compounds. Their synthesis, Conformation, and Investigation by Photoelectron, UV, and NMR Spectroscopy and by Crystal Structure Analysis1) (1987)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1133-1149 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Der vinyloge Tricarbonyl-chromophor. Violerythrin-Endgruppen und verwandte Sechsringverbindungen. Synthese, Konformation, Untersuchung mit Photoelektronen-, UV-, NMR-Spektroskopie und Röntgenstrukturanalyse1)Die Synthese von ungesättigten Fünf- und Sechsringen, 3a, 4, 5b, 5c und 17a, die das Strukturelement des 3-Penten-1,2,5-trions enthalten, wird beschrieben. Diese vinylogen Tricarbonyle werden zusammen mit verwandten Verbindungen auf ihre chromophoren Eigenschaften hin untersucht. Die Konformation in Lösung, insbesondere der Torsionswinkel Ring-Seitenkette, wird mit Hilfe von 3JCH-Kopplungen, NOE-Differenzspektren und Kraftfeldrechnungen abgeleitet. Röntgenstrukturanalysen von 11a, 17a, 18a und 35 liefern die Geometrie im festen Zustand. Die Ionisierungsenergien werden photoelektronenspektroskopisch bestimmt. Zur Berechnung und Interpretation der Absorptionsspektren und der Farbe werden die CNDO/S-CI- und die HAM/3-Methode verwendet.
    Notes: The synthesis of five- and six-membered rings 3a, 4, 5b, 5c, and 17a, containing the structural moiety 3-pentene-1,2,5-trione, is described. The chromophoric properties of these vinylogous tricarbonyls together with related compounds are investigated. The conformation in solution, particularly the torsion angle ring/sidechain, can be derived from measurements of 3JCH coupling constants, NOE difference spectra, and force-field calculations. X-ray structure analyses of 11a, 17a, 18a, and 35 afford geometries in the solid state. Ionization energies are determined by means of photoelectron spectroscopy. The theoretical calculations and interpretation of absorption spectra and colour are carried out using the models CNDO/S-CI and HAM/3.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19871200710
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Valenzisomerisierungen, 17. Persubstituierte cis-9,10-Dihydronaphthaline und ihre Valenzisomerisierungen (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 767-779 
    Details
    ISSN: 0009-2940
    Keywords: Molecular twisting ; cis-9,10-Dihydronaphthalenes, persubstituted ; Valence isomerizations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Valence Isomerizations, 17. - Persubstituted cis-9,10-Dihydronaphthalenes and their Valence IsomerizationsThe tricyclic diester 10 is available from 2-butyne in a six-step synthesis with an overall yield of 10%. Thermolysis of 10 gives the bicyclic diester 11 which upon UV irradiation yields 12 as the first persubstituted cis-9,10-dihydronaphthalene. X-ray analysis of 12 shows the molecule considerably twisted along the central bond. In addition, the planes of the ester groups are at an angle of approximately 60° to the „planes“ of the six-membered rings so that conjugation of the diene systems with the carbonyl functions is virtually interrupted, an effect which is reflected by the unusual spectroscopic properties of 12. The same structural features can be found in decamethyl-cis-9,10-dihydronaphthalene (16). When heated slightly, 12 is converted to the tetracyclic valence isomer 34. On reduction of 12 with diisobutylaluminum hydride both, dihydronaphthalene dicarbinol 25 as well as its unexpected positional isomer 26, are formed depending on the reaction conditions. Etherification of the reduction products with CH2N2/Et2O—BF3 furnishes a mixture of the three isomeric bis(methoxymethyl) compounds 31, 32 and 33. They can be separated by chromatography in the cold, but revert to the mixture of the three isomers at room temperature. We consider diradical 38 to be the intermediate of this intriguing valence isomerization.
    Notes: Der tricyclische Diester 10 ist in sechs Stufen in einer Gesamtausbeute von 10% aus 2-Butin zugänglich. Thermolyse von 10 liefert den Bicyclus 11, bei dessen UV-Bestrahlung das erste persubstituierte cis-9,10-Dihydronaphtalin 12 gebildet wird. Eine Röntgenstrukturanalyse von 12 beweist die starke Verdrillung des Moleküls um die zentrale Bindung. Die Ebenen der Ester-Gruppen stehen ungefähr in einem 60°-Winkel zu den Sechsring-„Ebenen“, so daß die Konjugation der Dien-Systeme mit den Carbonyl-Funktionen praktisch unterbrochen ist, ein Effekt, der sich in den ungewöhnlichen spektroskopischen Eigenschaften von 12 widerspiegelt. Analoge Strukturmerkmale gelten auch für das Decamethyl-cis-9,10-dihydronaphthalin (16). Bicyclus 12 wandelt sich bei leichtem Erwärmen in den valenzisomeren Tetracyclus 34 um. Reduktion von 12 mit Diisobutylaluminiumhydrid gibt je nach den Reaktionsbedingungen das Dihydronaphthalindicarbinol 25 bzw. das unerwartete Stellungsisomere 26. Veretherung der Reduktionsprodukte mit CH2N2/Et2O—BF3 liefert ein Gemisch der drei isomeren Bis(methoxymethyl)-Verbindungen 31, 32 und 33, die chromatographisch in der Kälte trennbar sind, aber schon bei Raumtemperatur wieder das Gemisch der drei Isomeren zurückbilden, wobei das Diradikal 38 als Zwischenprodukt dieser erstaunlichen Valenzisomerisierung anzunehmen ist.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891220426
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Propiniminium-Salze: Ambifunktionelle Reaktivität gegenüber S- und N-Nucleophilen (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2311-2317 
    Details
    ISSN: 0009-2940
    Keywords: Allenes, 1,3-diamino- and 1-amino-3-thio- ; Propene iminium salts ; Propyne iminium salts ; MO calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Propyne Iminium Salts: Ambifunctional reactivity reactivity towards Sulfur and Nitrogen NucleophilesPropyne iminium ions 2a-d have been studied by both ab initio (3-21G//3-21G for 2a) and MNDO calculations (2a-d). It is found that the amino group stabilizes the propargyl cation structure at the expense of the allenyl cation structure. Furthermore, the highest positive charge density is located at the amino-substituted carbon atom.  -  Reactions of 2-propyne iminium triflates 6a, b with thiols, thiolates, morpholine, lithium morpholide, and phenylhydrazine have been investigated. C-1 attack at 6, expected under kinetically controlled conditions, is observed in a few cases only. In all other cases, products resulting from C-3 attack takes place leading either to 1,3-donorsubstituted allenes (8, 10, 12) in the absence of proton sources or to their C-2-protonated forms (9, 11, 13-15) otherwise.
    Notes: Für die Propiniminium-Ionen 2a-d werden ab-initio- (3-21G//3-21G für 2a) und MNDO-Rechnungen (2a-d) durchgeführt. Danach stabilisiert die Aminogruppe die Propargylkation- eindeutig gegenüber der Allenylkation-Struktur. Die höchste positive Ladungsdichte befindet sich am aminosubstituierten Kohlenstoffatom.  -  Umsetzungen der 2-Propiniminium-triflate 6a, b mit Thiolen, Thiolaten, Morpholin, Lithium-morpholid und Phenylhydrazin zeigen, daß nur in einigen Fällen unter kinetisch kontrollierten Bedingungen der erwartete C-1-Angriff erfolgt, ansonsten wird C-3-Angriff gefunden. Letzterer führt in Abwesenheit von Protonquellen zu 1,3-donorsubstituierten Allenen (8, 10, 12), andernfalls entstehen deren C-2-protonierte Formen (9, 11, 13-15).
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891221218
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Metabolism of carotenoids in salmonidsParts of this series were presented at the 8th Int. Symp. on Carotenoids, Boston, USA, 1987, by K. Schiedt.. Part 2Part 1 [1].. Distribution and absolute configuration of idoxanthin in various organs and tissues of one atlantic salmon (Salmo salar, L.) fed with astaxanthin (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 881-886 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The content of total carotenoids and the ratio astaxanthin/idoxanthin ( = 3,3′-dihydroxy-β,β-carotene-4,4′-dione/3,3′,4′-trihydroxy-β,β-caroten-4-one) in varoius organs and tissues of one Atlantic salmon (Salmo salar, L.) reared indoors in a tank were analyzed after feeding ‘racemic’ ((3R,3′R)/(3R,3′S; meso)/(3S,3′S) 1:2:) astaxanthin (90 mg/kg feed) during one yera. Configurational analysis of astaxanthin was carried out via the (-)-dicamphanate derivative and that of idoxanthin after reaction with (+)-(S)-l-(l-naphthyl)ethyl isocyanate. Separation of all eight optical isomers of idoxanthin-tricarbamate derivatives by HPLC is described. In salmon, enzymatic reduction of astaxanthin was found to be sterospecific leading to th (4′R)-hydroxy group irrespective of the configuration at C(3′), thus resulting in four different stereoisomers of idoxanthin formed from (3R,3′R), (3R,3′S; meso)-, and (3S3′S)-astaxanthin present in the diet.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710425
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Modelling the Metabolic Epimerization of Anti-inflammatory 2-Arylpropanoyl-coenzyme-A Conjugates: Solvent effects on the 1H/2H exchange in S-[2-(dimethylamino)ethyl] 2-phenylpropanethioate (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1225-1232 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H/2H exchange at the methine position of S-[2-(dimethylamino)ethyl] 2-phenylpropanethioate (DEPP) in solvent/D2O mixtures was taken as a model reaction for the metabolic epimerization of 2-arylpropanoyl-coenzyme-A thioesters and was monitored by 1H-NMR spectroscopy at 37°. The solvents used were (D6)acetone, (D3)acetonitrile, (D6)dimethylsulfoxide, and (D5)pyridine. In the investigated range of D2O percentage (10-50%), the exchange reaction was found to increase linearily with D2O content and with the basicity of the organic solvent, the fastest rates being close to 0.09 h-1 (t½ ca. 8 h). These rates are slower than those observed in vivo for the configurational inversion of profens, and they are elicited in totally unphysiological concentrations of bases. The hypothesis thus formulated is that the metabolic epimerization of 2-arylpropanoyl-coenzyme-A thioesters cannot occur nonenzymatically.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720606
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...