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  • 1
    Electronic Resource
    Electronic Resource
    Conversion of Light into Electricity with Trinuclear Ruthenium Complexes Adsorbed on Textured TiO2 Films (1990)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 73 (1990), S. 1788-1803 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of CN-bridged trinuclear Ru complexes of the general structure [RuL2(μ-(CN)Ru(CN)L2′)2] where L is 2,2′-bipyridine-4,4′-dicarboxylic acid and L′ is 2,2′-bipyridine (1)2,2′-bipyridine-4,4′-dicarboxylic acid (2), 4,4′-dimethyl-2,2′-bipyridine (3), 4,4′-diphenyl-2,2′-bipyridine (4), 1,10-phenanthroline (5), and bathophenanthrolinedisulfonic acid (6) have been synthesized, and their spectral and electrochemical properties investigated. The two carboxylic functions on the 2,2′-bipyridine ligand L serve as interlocking groups through which the dye is attached at the surface of TiO2 films having a specific surface texture. The role of these interlocking groups is to provide strong electronic coupling between the π* orbital of the 2,2′-bipyridine and the 3d-wave-function manifold of the conduction band of the TiO2, allowing the charge injection to proceed at quantum yields close to 100 %. The charge injection and recombination dynamics have been studied with colloidal TiO2, using laser photolysis technique in conjunction with time-resolved optical spectroscopy. Photocurrent action spectra obtained from photo-electrochemical experiments with these trinuclear complexes cover a very broad range in the visible, making them attractive candidates for solar light harvesting. Monochromatic incident photon-to-current conversion efficiencies are strikingly high exceeding 80% in some cases. Performance characteristics of regenerative cells operating with these trinuclear complexes and ethanolic triiodide/iodide redox electrolyte have been investigated. Optimal results were obtained with complex 1 which gave a fill factor of 75 % and a power conversion efficiency of 11.3% at 520 nm.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19900730624
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  • 2
    Electronic Resource
    Electronic Resource
    Einkristall-Strukturen eines Donator-Akzeptor-substituierten Cyclopentadiens, seines Kations und seines dimeren Anions: Verschiedenartige Störungen eines Kohlenstoff-FünfringesGewidmet Prof. H. G. Wagner anlässlich seines 65. Geburtstages56. Mitteilung über “Strukturen ladungsgestörter Moleküle und über Wechselwirkungen in Kristallen”; 55. Mitteilung: [1]. (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 2162-2174 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Single-Crystal Structures of a Donor-Acceptor-Substituted Cyclopentadiene, Its Cation and Its Anion Dimer: Different Distortion of a Five-Membered Carbon Ring1,4-Dimethyl-2,3,4,6-tetrahydro-1 H-cyclopentapyrazine-5,7-dicarbonitrile, its molecular cation, and its dimer dianion, generated by hydride abstraction or deprotonation, and crystallized, differ remarkably in their structures: the five-membered ring in the neutral compound is of (Z)-butadiene-type, whereas, in the tetrafluorborate salt, a peripheric NCCCCCN⊕ cyanine distortion occurs and in the sodium derivatives, solvated by either one or two 1,2-dimethoxyethane molecules, a cyclopentadienyl anion is formed. The structural perturbations induced by changing molecular charges are rationalized by extensive MNDO calculations, which on geometry optimization, reproduce the experimental structures and, in addition, provide charge distributions, further confirming the nN/π and π/π interactions already recognizable from the structural parameters.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770810
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  • 3
    Electronic Resource
    Electronic Resource
    Water penetration in nylon 6,6: Absorption, desorption, and exchange studied by NMR microscopy (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 159-168 
    Details
    ISSN: 0887-624X
    Keywords: nylon 6,6 ; water absorption ; NMR microscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The uptake of water by nylon 6,6 [42DB Adipure (trade name of Dupont Canada Inc.)] at 100°C has been monitored by a combination of one-dimensional proton NMR spectroscopy, relaxation time (T1 and T2) measurements and proton microscopic NMR imaging techniques. The relaxation times of the water absorbed into the nylon matrix are very short at room temperature, (T2 〈 1 ms and T1 ≈ 1 s) indicating that the water is located in a highly restricted environment and suggesting that strong interactions exist between the absorbed water and the polymer. The diffusion profiles measured at room temperature indicate that the diffusion of water into nylon 6,6 at 100°C is Case I Fickian diffusion. The spatial dependence of the T2 relaxation time constant and its variation with the water content was also examined. The results reveal that both T2 and T2* decrease toward the center of the sample in samples that have a concentration gradient of sorbed water. In fully saturated samples, no spatial dependence was observed. The overall values of T2 and T2* are also observed to increase as a function of exposure time. An evaluation of the desorption process at room temperature and at 100°C was performed. A continuous, exponentially decreasing solvent profile was observed for the desorption process which again indicates Case I Fickian kinetics. The exchange process of external bulk and atmospheric water with deuterium oxide (D2O) saturated nylon rods has also been studied using the microscopic imaging technique. © 1993 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310119
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  • 4
    Electronic Resource
    Electronic Resource
    Fractal Characterization of Pulverised Materials (1993)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 10 (1993), S. 1-6 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes preliminary work carried out on the applicability of fractal geometry in describing the products of comminution events.A nickel sulphide ore was subjected to two comminution events, impact shattering and ball milling. Fractal analysis was performed on samples of the resulting comminution products.Two differing fractal populations resulted, with the impact sample exhibiting particles having higher boundary fractal dimensions than the milled sample. The fractal dimension of the impact fragments increased with decreasing size, whereas the milled particles displayed a more complex distribution.The under-fractal distributions, of the two populations of fragments, generate straight lines when plotted on Gaussian probability paper. This leads to the possibility of being able to predict the distribution of fragments, in fractal terms, of a particular material when subjected to comminution.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19930100102
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  • 5
    Electronic Resource
    Electronic Resource
    Gamma-sterilization effects and influence of the molecular weight distribution on the postirradiation resistance of polypropylene for medical devices (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 313-328 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In the present study, the dose-rate effects of γ-irradiation in air on two isotactic polypropylene grades of different molecular weight distribution, used for medical devices, were investigated. The thermal, mechanical, rheological, and photometric properties of these materials were examined using DSC, stress-strain measurements, MFI, and a yellow index. At low dose rates (0.12 Mrad/h), the oxygen diffusion parameter prevailed. At high dose rates (2.84 Mrad/h), the thermal degradation became dominant. However, at high dose rates, an increase in sample temperature was monitored. This temperature rise is thought to increase the oxygen diffusion rate, peroxide decomposition, and radical migration. As a result, intermediate dose rates (in the region of 0.72 Mrad/h) gave the lowest changes in physical properties in both samples. Furthermore, it was found that the polypropylene grade of broader molecular weight distribution and lower Mn had a higher γ-irradiation and postirradiation resistance. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070510214
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  • 6
    Electronic Resource
    Electronic Resource
    The laminate-bending process for long fiber-reinforced plastics (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1085-1091 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In order to form long fiber-reinforced plastic sheets into angled parts, a new process called the Laminate-Bending Process was recently developed. The process consists of preforming a prepreg into semi-cured stable shapes having various sharp bending radii, followed by laminating the preforms into a fully cured thick angle product having high strength and rigidity. A sharp 90°V-angled product of five lay-ups of preform was test fabricated under various preforming and laminating conditions by using a continuous glass fiber reinforced epoxy resin, and it was confirmed to be excellent in delamination resistance and specific strength. Also, the process is quite practical in productivity, handling, and applicability to other advanced composite materials, and it can expand the use of such brittle materials for wider applications.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760331702
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of two distinct phenolic antioxidants in γ-sterilized NR compounds used as rubber pistons in syringes for single use (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 1737-1748 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effects of γ-irradiation and aging on pharmaceutical NR compounds have been studied mainly by DSC. The extent of aging was measured quantitatively by enthalpy changes and peak temperature shifts of the primary oxidation exotherm. Quantitative thermal evaluations were supplemented by extraction tests and mechanical testing. The NR compound formula has been kept constant and only the type and concentration of antioxidant was varied. Two distinct phenolic antioxidants, BHT and Wingstay-L at four different concentration levels, have been employed for this purpose. The most effective antioxidant package for a given elastomeric compound, subjected to γ-irradiation and aging, giving the lowest changes in physical properties, is evaluated. © 1992 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070461005
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  • 8
    Electronic Resource
    Electronic Resource
    Photon emission during deformation of glass-fiber-reinforced bisphenol-a-polycarbonateManuscript of a lecture given at the 3rd Dresden Polymer Discussion, Gaussing, Germany, April 1991. (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 2123-2133 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We give a survey on mechanically induced emission phenomena (acoustic emission [AE], neutral particle emission [NE], electron and charged particle emission [EE/PIE], radio wave emission [RE] of polymers and briefly summarize these effects in unfilled and glass-fiber-reinforced bisphenol-A-polycarbonate. A general treatment of the photon emission kinetics in terms of analysis and description, using a convolution function, is proposed. The kinetics obey a power law decay in time. By examining a model mechanism for the interfacial failure of the composite, i.e., by peeling of glass/polymer laminates, we show that the origin of the photon emission is the polycarbonate matrix after cleavage of the glass/polymer interface. Spectral characteristics of mechanically induced luminescence of glass-filled polycarbonate and of the peeling spectra of the model system of glass/polycarbonate laminates are discussed. Different brands of polycarbonate yield identical spectra. Spectra recorded during peeling in vacuum are very similar to those recorded during deformation of the composite. Polarized fluorescence spectroscopy and electronbeam luminescence were used to obtain further information about the intrinsic polycarbonate-chromophores that are available for mechanically induced photon emission. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070481207
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  • 9
    Electronic Resource
    Electronic Resource
    Verzerrte Moleküle: Störungsdesign, Synthesen und StrukturenProfessor Heinz Harnisch zum 65. Geburtstag gewidmetStrukturen ladungsgestörter und räumlich überfüllter Moleküle, 20. Mitteilung, und Moleküleigenschaften und Modelle, Essay 24. - 19. Mitteilung: H. Bock, W. Seitz. Z. Havlas, J. W. Bats, unveröffentlicht; Essay 23: [34]. (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 104 (1992), S. 564-595 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Struktur eines Moleküls kann sich mit seiner Energie und damit seiner Elektronenverteilung innerhalb der Zeitskala dynamischer Relaxation beträchtlich ändern. Ausgehend von Vergleichen geeigneter Meßdaten verwandter Verbindungen und unterstützt durch quanten-chemische Näherungsrechnungen lassen sich daher ladungsgestörte und/oder räumlich über-füllte Moleküle entwerfen, deren Synthese, Handhabung und Strukturbestimmung - unter oft extremen und vor allem weitgehend aprotischen Bedingungen - zu manchen Überraschungen führt. Dabei werden neue Strukturprinzipien deutlich und altbekannte bestätigt. So enthalten einige der bei ultraschallgeförderter Reduktion ungesättigter Kohlenwasserstoffe mit Natriummetall entstehenden Kontaktionenaggregate von Molekülanionen Dibenzolnatrium-Sandwich-Einheiten. Vicinale Dimethylaminosubstituenten bewirken wie die isoelektronischen Isopropylgruppen sterische Überfüllung und erleichtern die Oxidation zu Molekül-kationen durch energetisch günstige Delokalisierung der erzeugten positiven Ladung. Moleküle und Molekülionen, in denen sich eine gerade Anzahl von π-Elektronen über ein ungeradzahliges σ-Gerüst verteilt, bilden bevorzugt Cyanin-Untereinheiten aus; dies belegen auch die erstmals isolierten Salze von Ethen-Dikationen und Ethen-Dianionen mit C-C-Einfachbindung und gegeneinander verdrillten Molekülhälften.  -  Insgesamt konnten in zwei Jahren über 50 unbekannte Strukturen bestimmt werden. Aus ihnen haben wir viel gelernt, insbesondere über Elektronentransfer und Kontaktionenpaar-Bildung in aprotischen Lösungen. Wir mußten aber auch erkennen, daß eine Beantwortung vieler Fragen - darunter vor allem „was kristallisiert wie und warum?“ - noch in weiter Ferne liegt.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19921040507
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  • 10
    Electronic Resource
    Electronic Resource
    Ribonuclease T1: Struktur, Funktion und Stabilität (1991)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 103 (1991), S. 351-369 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In lebenden Organismen erfüllen Proteine die wichtigsten und schwierigsten Aufgaben. Hierfür müssen sie oft spezifisch mit weiteren kleinen oder großen Molekülen zusammenwirken. Dies erfordert, daß sie sich in eine globuläre Struktur falten, in der sie ihre jeweilige Funktion erfüllen können; bei Enzymen z.B. wird durch die Faltung das aktive Zentrum konstituiert. Dieser enge Zusammenhang zwischen Struktur und Funktion führte dazu, daß Faltungsweise und Faltungsstruktur der Proteine als das „Geheimnis des Lebens“ angesehen werden. Biochemiker und Chemiker haben ein großes Interesse an der Aufklärung des Mechanismus der Proteinfaltung. Wäre das „Proteinfaltungsproblem“ gelöst, könnte man aus der Aminosäuresequenz eines Proteins die bei der Faltung entstehende Struktur und ihre Stabilität voraussagen. Es ist heute möglich, Proteine herzustellen, die sich in einer oder mehreren Aminosäuren unterscheiden. Die Aufklärung ihrer dreidimensionalen Struktur durch Röntgenkristallographie und NMR-Spektroskopie trägt wesentlich zum Verständnis der Faltung und der Stabilität der Struktur von Proteinen bei. Aus diesem Grund werden gegenwärtig mehrere Proteine mit dieser Methodik eingehend untersucht. Eines davon ist das Enzym Ribonuclease T1.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19911030404
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