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  • Polymer and Materials Science  (309)
  • Wiley-Blackwell  (309)
  • American Meteorological Society (AMS)
  • PANGAEA
  • 1990-1994  (309)
  • 1980-1984
  • 1993  (309)
Collection
Publisher
  • Wiley-Blackwell  (309)
  • American Meteorological Society (AMS)
  • PANGAEA
Years
  • 1990-1994  (309)
  • 1980-1984
Year
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 1349-1355 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Although there are many studies which document high metal ion concentrations in clinically retrieved tissues surrounding total joint replacements, most investigations have remained cautious in their interpretation due to the artifactual influences of metal particulate.The possible contribution of polyethylene wear debris to artifactually high periprosthetic metal ion concentration readings has not been previously considered. This study documents the potential role of polyethylene particulate contamination in causing artifactually high metal concentration readings in tissues.The data showed metal ion contamination in the polyethylene was progressive at each stage of exposure to metal: from bar stock preparation, to manufacturing, to in vivo ambulation. The manufacturing and machining processes showed a statistically significant (P ≤ .05) increase in metal ion concentrations in the nonarticulated acetabular inserts over bar stock.The results of this study demonstrate that periprosthetic tissue and synovial fluid metal ion concentration data must be interpreted with caution due to possible artifactual problems associated with metal ion contaminated polyethylene particulate. © 1993 John Wiley & Sons, Inc.
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  • 2
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A highly potent and selective agonist to the tachykinin NK-3 receptor, [pGlu6, N-MePhe8, Aib9] substance P (6-11) (I), was synthesized via the solid phase method. The ED50 of I was 4n M in the guinea pig ileum in the absence of atropine (NK-1 + NK-3 receptors) and this agonist was 5000-fold less potent in the presence of atropine (NK-1 receptor). The analogue was virtually inactive in the rat vas deferens (NK-2 receptor). A detailed analysis of the solution conformation of this analogue in DMSO-d6 and in a DMSO-d6 H2O cryornixture was carried out by a combination of 1H-nmr 2D techniques (DQF-COSY, TOCSY, NOESY and ROESY) and model building based on empirical energy calculations. Peptide I exists as a mixture of isomers containing cis and trans Phe-N-MePhe peptide bonds. The main isomer, containing a cis Phe-N-MePhe peptide bond, shows a preferred folded conformation characterized by a type VI β-turn with Phe and N-MePhe in the i + 1 and i + 2 positions. The turn is followed by a helical segment extending to the C-terminal. This conformation is compared to previously reported conformations of other selective tachykinin agonists and may be a promising lead for the design of novel NK-3 agonists with additional conformational constraints. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 3
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Steady state fluorescence measurements in dilute solution have been performed for eight halogenated polystyrenes and for poly(2,5-dimethylstyrene). The monomers for halogenated polymers are o-X-styrene (X = F, Cl, Br), m-fluorostyrene, p-X-styrene, and p-chloro-α-methylstyrene. The position of the excimer band and the ratio of the intensities of the excimer and monomer fluorescence depend on the substitution. The results for poly(p-chloro-α-methylstyrene) and poly(2,5-dimethylstyrene) can be rationalized by a conformational analysis that examines the preferred geometries for face-to-face complexes by rings bonded to chain atoms i and i + 2. The results for the other polymers cannot be explained by a conformational analysis. They appear to arise from a combination of factors that alter the electronic properties of the chromophore.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 715-722 
    ISSN: 0887-624X
    Keywords: polypropylene ; oxidation products ; gamma ; photoinitiation ; thermal ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The detailed oxidation products have been identified and compared from the γ-, photo-, and thermally-initiated oxidation of unstabilized polypropylene films. Products were identified and quantified by a combination of iodometric analysis and infrared spectroscopy. Spectral resolution was enhanced by derivatization reactions which allow the quantification of primary, secondary, and tertiary hydroperoxide and alcohol groups as well as more reliable analysis of carbonyl species. In contrast to polyethylene oxidation which yields predominantly ketone with lesser amounts of secondary hydroperoxide and carboxylic acid, polypropylene oxidizes to give predominantly tertiary hydroperoxide and lesser quantities of secondary hydroperoxide and ketone. In addition carboxylic acid groups are a minor product except at high degrees of thermal and photoinitiated oxidation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 901-908 
    ISSN: 0887-624X
    Keywords: styrene ; free radical ; addition-fragmentation chain transfer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variety of 1,1-disubstituted ethylenes, having an electron-withdrawing (capto) and an electron-donor (dative) substituent on the same carbon, were synthesized and added to styrene polymerizations. The dative substituents investigated were alkoxy or alkylcarbonate. After the addition of a polystyryl radical to a disubstituted ethylene, the resulting alkoxy or carbonate radicals could potentially fragment, resulting in chain termination and the formation of alkyl radicals. This process is called addition-fragmentation chain transfer (AFCT). The polymers produced during this study were examined for evidence of copolymerization and AFCT. The relative stability of the radicals generated by the fragmentation process appears to be the predominant factor controlling the ratio of copolymerization versus AFCT. © 1993 John Wiley & Sons, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 24 (1993), S. 20-25 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Fundamental Investigations of Residual Stresses in Metal-Ceramic-Joints by FEMThe reduction of damages in metal-ceramic-joints caused by residual stresses is of essential significance. Therefore, a model was created to simulate the behaviour of metal-ceramic-joints under thermal stress. In this paper, results of fundamental investigations are presented.
    Notes: Eigenspannungen in Metall-Keramik-Verbunden führen häufig zu deren vorzeitigem Versagen. Im vorliegenden Beitrag werden Ergebnisse aus Grundlagenuntersuchungen vorgestellt, bei denen der Einfluß wesentlicher Werkstoffkennwerte untersucht sowie ein Vergleich der Rechenergebnisse mit Laboruntersuchungen vorgenommen wurde.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 24 (1993), S. 160-167 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: PVD-coated tribosystems at reciprocating slidingThe aim of the investigation is to increase the life time of machinery elements of steel, sliding under high contact pressure, by PVD-coating of one of the surfaces.The three-step tribological testprogram includes a fundamental test, a model test under real conditions and a suitability test with real parts. The coefficient of friction and wear depends on substrate material, deposition variance, coating structure and surrounding conditions.Hard coatings: They enlarge the life time of lubricated systems considerably (μ ≤ 0,1). Without lubrication the coefficient of friction is relatively high (μ ≥ 0,5), which results in a short life time.Coatings with low friction: Soft metals and chalchogenides on supporting hard coatings only reduce the friction for a short time. Metal carbon coatings yield the lowest coefficient of friction (μ = 0.2) and the greatest life time. In the range up to 1500 N/mm2 the pressure has a small influence on the life time. When the coated contact surface slides against an unmachined forged surface, the coating will be damaged after a short time due to local over oad at asperities.
    Notes: Das Ziel der Untersuchungen ist die Steigerung dcr Lebensdauer von unter relativ großen Pressungen gleitend beanspruchten Maschinenelementen aus Stahl durch PVD-Beschichtung eines der Kontaktpartner. Die tribologische Prüfung erfolgt dreistufig durch grundlagennahe Modellprüfung, beanspruchungsähnliche Modellversuche und Versuche am Bauteil (Steckkette) unter Praxisbedingungen. Substratwerkstoffe, Schichtsystem und Umgebungsbedingungen beeinflussen das Reibungs- und Verschleißverhalten wesentlich.Hartstoffschichten: Im geschmierten System verlängern sie die Lebensdauer erheblich (μ ≤ 0,1). Ohne Schmierung ist die Reibungszahl relativ groß (μ ≥ 0,5), was zum frühzeitigen Versagen des Tribosystems führt.Reibungsmindernde Schichten: Weichmetalle und Chalkogenide auf hartstoffbeschichteten Systemen vermindern die trockene Reibung nur kurzzeitig. Die kleinste Reibungszahl (μ = 0,2) und die größte Lebensdauer erbringen die Metall-Kohlenstoff-Schich-ten. Im Bereich bis zu 1500 N/mm2 hat die Pressung nur einen kleinen Einfluß auf die Lebensdauer. Bei Reibung gegen unbearbeitete, geschmiedete Steckkettenelemente wird die Schicht infolge lokaler Überbeanspruchung an Punktkontakten frühzeitig geschädigt.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 44 (1993), S. 345-350 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Bei der Thermogravimetrie zu berücksichtigende HinweiseKontinuierliche Thermogravimetrie ist eine verbreitete Methode, um Werkstoffe in korrosiven Gasen bei hohen Temperaturen zu prüfen und um Kinetik und Mechanismen der Hochtemperaturkorrosion aufzuklären. Hier werden Empfehlungen zur Durchführung thermogravimetrischer Tests zusammengestellt, Hinweise gegeben betreffend Probengröße und -form, Oberflächenpräparation, Reaktionsrohr, Start des Experiments, besonders empfindliche Messungen und Gasströmung und -regelung. Die Veröffentlichung ist als Grundlage und Startpunkt für zu entwickelnde Richtlinien für die Hochtemperaturkorrosionsforschung gedacht.
    Notes: Continuous thermogravimetry is a common method to test materials in gaseous corrosive environments at high temperatures and to elucidate kinetics and mechanisms of high temperature corrosion. Recommendations how to conduct thermogravimetric tests are collected here, points to be considered including sample size and form, surface preparation, reaction chamber, starting procedure, sensitive measurements, gas supply and dosing. This study is meant as a starting foundation for establishing guidelines in high temperature corrosion research.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 205 (1993), S. 177-184 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die molekulare Orientierung kreisförmiger Platten aus isotaktischem Polypropylen wurde anhand der optischen Doppelbrecung und des Infrarot-Dichroismus untersucht. Die Proben wurden zwischen vorgeheizten Pressplatten und unter Verwendung von Gleitmittel (Silikonöl) an der Pressplattenoberfläche einachsig komprimiert. Die Änderung der molekularen Anisotropie in den kristallinen Bereichen, bestimmt aus der optischen Deppelbrechung und dem Infrarot-Dichroismus, war vernachlässigbar klein über den Querschnitt der Scheiben. Der Grad der Anisotropie war relativ gering. Polfiguren, welche aus Weitwinkel-Röntgenstreuungsexperimenten bestimmt wurden, weisen auf das Entstehen einer planaren Orientierungstextur hin. Die Orientierung der Polymerketten in den kristallinen Bereichen lag hauptsächlich senkrecht zur Richtung der Kompression.
    Notes: The molecular orientation of isotactic polypropylene disks compressed uniaxially in the solid state using lubricated press platens was studied by measuring optical birefringence, infrared dichroism and wide-angle x-ray scattering. Differences in anisotropy obtained by optical birefringence and infrared dichroism were negligibly small throughout the disk at a low overall level of orientation. Pole figures obtained from WAXS measurements showed that the orientation texture developed during the deformation was essentially planar with polymer chains oriented perpendicularly to the compression direction.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 175-183 
    ISSN: 0887-6266
    Keywords: polyethylene, linear and branched, X-ray diffraction and 13 C-NMR characterization of ; x-ray diffraction of linear and branched polyethylenes ; nuclear magnetic resonance (NMR) study of linear and branched polyethlenes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: X-ray diffraction patterns of linear and branched polyethylenes typically show two sharp reflections and an amorphous halo. The position of the halo depends on branch content and temperature. A single curve describes the position of the halo maximum (2θhalo) for a range of liquid hydrocarbons and polyethylenes in the 20-140°C range. At temperatures well below their melting point, branched polymers give 2θhalo values which differ significantly from those observed for the liquid Linear polymers show a greater divergence, indicating that some of the material giving rise to the halo is much better packed than in the liquid.Parallel 13 C NMR spin-lattice relaxation studies suggest that this relatively ordered material has a trans conformation but a low average T1c value. © 1993 John Wiley & Sons, Inc.
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