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  • Polymer and Materials Science  (375)
  • 1995-1999  (375)
  • 1980-1984
  • 1970-1974
  • 1940-1944
  • 1995  (375)
  • 1940
Collection
Keywords
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Years
  • 1995-1999  (375)
  • 1980-1984
  • 1970-1974
  • 1940-1944
Year
  • 1
    Electronic Resource
    Electronic Resource
    Effect of titanium surface roughness on proliferation, differentiation, and protein synthesis of human osteoblast-like cells (MG63) (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 389-401 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effect of surface roughness on osteoblast proliferation, differentiation, and protein synthesis was examined. Human osteoblast-like cells (MG63) were cultured on titanium (Ti) disks that had been prepared by one of five different treatment regimens. All disks were pretreated with hydrofluoric acid-nitric acid and washed (PT). PT disks were also: washed, and then electropolished (EP); fine sandblasted, etched with HCl and H2SO4, and washed (FA); coarse sandblasted, etched with HCl and H2SO4, and washed (CA); or Ti plasma-sprayed (TPS). Standard tissue culture plastic was used as a control. Surface topography and profile were evaluated by brightfield and darkfield microscopy, cold field emission scanning electron microscopy, and laser confocal microscopy, while chemical composition was mapped using energy dispersion X-ray analysis and elemental distribution determined using Auger electron spectroscopy. The effect of surface roughness on the cells was evaluated by measuring cell number, [3H]thymidine incorporation into DNA, alkaline phosphatase specific activity, [3H]uridine incorporation into RNA, [3H]proline incorporation into collagenase digestible protein (CDP) and noncollagenase-digestible protein (NCP), and [35S]sulfate incorporation into proteoglycan.Based on surface analysis, the five different Ti surfaces were ranked in order of smoothest to roughest: EP, PT, FA, CA, and TPS. A TiO2 layer was found on all surfaces that ranged in thickness from 100 Å in the smoothest group to 300 Å in the roughest. When compared to confluent cultures of cells on plastic, the number of cells was reduced on the TPS surfaces and increased on the EP surfaces, while the number of cells on the other surfaces was equivalent to plastic. [3H]Thymidine incorporation was inversely related to surface roughness. Alkaline phosphatase specific activity in isolated cells was found to decrease with increasing surface roughness, except for those cells cultured on CA. In contrast, enzyme activity in the cell layer was only decreased in cultures grown on FA- and TPS-treated surfaces. A direct correlation between surface roughness and RNA and CDP production was found. Surface roughness had no apparent effect on NCP production. Proteoglycan synthesis by the cells was inhibited on all the surfaces studied, with the largest inhibition observed in the CA and EP groups. These results demonstrate that surface roughness alters osteoblast proliferation, differentiation, and matrix production in vitro. The results also suggest that implant surface roughness may play a role in determining phenotypic expression of cells in vivo.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820290314
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  • 2
    Electronic Resource
    Electronic Resource
    NMR relaxation study of thermal degradation in cured PMR polyimidesWork supported in part by NASA under grant NCC-3-164. (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1545-1557 
    Details
    ISSN: 0887-6266
    Keywords: NMR relaxation ; PMR polyimides ; thermal degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have studied cross-linking and thermal degradation of high-performance first-and second-generation PMR-15 polyimides, both thermoset and thermoplastic versions, by performing nonspectroscopic NMR solid echo T*2 relaxation measurements at temperatures up to 430°C using probes built for this purpose. We employ signal averaging and automated decomposition of the relaxation decays into two Gaussian components, the slower of which gradually appears above 300°C. Tracking the molecular mobility spectrum in terms of the relative intensity of the components and their relaxation times as temperature is cycled, we detect essentially no irreversible effects below the glass transition, measure permanent mobility reductions attributable to completion of cure, and find that exposure to temperatures above 380°C on the order of 1 h is required for substantial thermal degradation to occur. These results are closely supported by thermal and mechanical measurements on parallel specimens. Second-generation PMR resins appear to have higher microscopic rigidity and reduced viscous fraction at high temperatures. ©1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331012
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of reactive oxazolyl styrene-acrylonitrile copolymers (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 1673-1677 
    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: A series of oxazoline-modified styrene-acrylonitrile (SAN) copolymers was prepared through the reaction of amino alcohols onto preformed SAN copolymers. Consequently, a variety of reactive copolymers were synthesized. The major focus of this study was to examine the influence of reaction conditions, i.e., the nature of the catalyst and amino alcohol structure, on reactivity. The ability to incorporate oxazoline groups onto preformed polymers is dependent on whether homogeneous reaction conditions are met. For example, the use of nonreactive solubilizing agents, i.e., cosolvent, is effective. However, optimum conditions are obtained when the catalyst is completely soluble in the reaction mixture containing the amino alcohol and SAN copolymer. With these restrictions, zinc stearate is quite effective. Our results show that controlled and reproducible levels of oxazoline can be incorporated (typically at a rate of 2 mol %/h) up to high levels. These results are general and therefore are applicable to a wide variety of nitrile-containing polymers. © 1995 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070561219
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  • 4
    Electronic Resource
    Electronic Resource
    Novel polymeric alcohols by controlled catalytic polymer functionalization (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 533-543 
    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: Novel EPDM (ethylenepropylenediene monomer) and polybutadiene polyols can be synthesized by a two-step process of controlled hydroformylation and then reduction of the formyl groups to place a desired amount of pendant alcohol groups along the polymer chain. The degree of functionalization can be controlled by measuring gas uptake from a calibrated reservoir during hydroformylation. Hydroformylation can be performed in solution or under simulated melt-phase conditions using either HRh(CO)(PPh3)3 or Rh(acac) (CO)2 as catalysts. Reduction of the polyaldehyde by NaBH4 generates the polymeric alcohol without further reaction of the remaining double bonds. Polymer functionalization and further modifications were followed by H-NMR and FTIR. These unique hydrophobic polyols can be reacted further to produce other polymer systems. As an example, urethanes have been made with these polyols by reaction with diisocyanates. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070560502
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  • 5
    Electronic Resource
    Electronic Resource
    HTPB-based polyurethanes for inhibition of composite propellants (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 1151-1155 
    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: Polyurethanes were synthesized by the reaction of hydroxyterminated polybutadiene (HTPB) and diisocyanates such as toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), and isophoron diisocyanate (IPDI). A number of fillers such as carbon black, kaolin, and antimony trioxide (Sb2O3) were used in these formulations. Mechanical and thermal stability of these polyurethanes were studied. Based on its properties, HTPB-MDI derived filled polyurethane was selected and evaluated as an inhibitor for a composite propellant. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070550801
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of ageing on the dielectric behaviour of silicone-EPDM blends (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 21-35 
    Details
    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: Dielektrische Messungen an Silikon, EPDM und einem Blend aus gleichen Gewichtsteilen beider Polymerer wurden im Frequenzbereich 1-105 Hz zwischen 25 und 200°C vor und nach Alterung in Wasser, Wasserdampf und Luft durchgeführt. Für das unpolare und nahezu verlustfreie EPDM werden niedrige Werte der Dielektrizitätskonstante und des Verlustfaktors gemessen. Die für EPDM beobachtete thermische Depolarisation ist bei in Luft gealtertem EPDM aufgrund von Dipolorientierung etwas ausgeprägter. Silikon wird in zwei Stufen polarisiert. Veränderungen der dielektrischen Eigenschaften und des spezifischen Gleichstromwiderstands nach Alterung belegen, daß Ladungsträger bei niedriger Temperatur und polare Silanolgruppen bei hoher Temperatur zur Polarisation beitragen. Die Eigenschaften des Blends hängen vom Alte-rungsmedium ab. Hydrothermische Alterung bewirkt eine qualitative Verbesserung des Dielektrikums Silikon durch Entfernung von Ladungsträgern und der Unterdrückung der Silikonhydrolyse durch EPDM. Durch Alterung des Blends in Luft nimmt dessen Polarisation zu, bedingt durch die Bildung von Ladungsträgern und Dipolen sowie die zusätzliche Grenzchicht. Aus Aktivierungsenergien wird gefolgert, daß die bei niedriger Temperatur stattfindende Polarisation mit der Beweglichkeit der Ladungsträger und der Orientierung von Seitengruppen zusammenhängt. rungsmedium ab. Hydrothermische Alterung bewirkt eine qualitative Verbesserung des Dielektrikums Silikon durch Entfernung von Ladungsträgern und der Unterdrückung der Silikonhydrolyse durch EPDM. Durch Alterung des Blends in Luft nimmt dessen Polarisation zu, bedingt durch die Bildung von Ladungsträgern und Dipolen sowie die zusätzliche Grenzchicht. Aus Aktivierungsenergien wird gefolgert, daß die bei niedriger Temperatur stattfindende Polarisation mit der Beweglichkeit der Ladungsträger und der Orientierung von Seitengruppen zusammenhängt.
    Notes: Dielectric measurements in the frequency (1-105 Hz) and temperature (25-200°C) domains have been carried out for silicone, EPDM, and their 50/50 (by weight) blend before and after ageing in water, steam and air. Low values of permittivity and loss tangent for EPDM reflect its non-polar and loss-free nature. Thermal depolarisation is also observed with EPDM and the air-aged specimen shows little rising trend due to dipole orientation. Silicone is found to be polarised in two steps. Changes in dielectric properties and DC resistivity on hydrothermal weathering and air ageing confirms that charge carriers contribute in the low-temperature step and polar silanol groups contribute in the high-temperature region. The properties of the 50:50 blend are very much sensitive to the medium of ageing. Hydrothermal ageing improves the quality of the dielectric of silicone due to removal of charge carriers and the suppression of silicone hydrolysis by EPDM. Ageing of the blend in air increases the polarisation to a very high level owing to the charge carriers, the additional interface and the dipoles formed during ageing. Activation energies suggest that the low temperature polarisation step is associated with charge carrier mobility and orientation of pendent groups.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052250103
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of 1-(vinylbenzyl)thymine, a novel, versatile multi-functional monomer (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2515-2519 
    Details
    ISSN: 0887-624X
    Keywords: thymine styrene monomer ; functional styrene monomer ; multifunctional monomer ; photoresist ; photocrosslinking ; photopolymer ; 2π + 2π photocyclization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331425
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  • 8
    Electronic Resource
    Electronic Resource
    Zunderverhalten und Ausscheidungshärtung von hochkarätigen Gold-Titan-Legierungen (1995)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 26 (1995), S. 507-518 
    Details
    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: The behaviour of oxidation and precipitation hardening of very goldrich gold-titan alloysThe oxidation behavior of gold rich Au-Ti alloys with contents of titanium between 0.5 und 1.3 weight-% was investigated in synthetic and natural air in dependence on the oxidation temperature and time. A closed homogeneous layer of titanium oxid was not formed. The nucleation of TiO2 (Rutil) starts at prefered sites (grain boundaries, structure defects) below the surface of the alloys. The precipitations grow without formation a gapless cover of the grain boundaries. Between the precipitations the concentrations of titanium and oxygen are zero. The titanium is transported out of the interior of the specimen by volume diffusion. Based on an experimentally observed linear relationship between the oxygen uptake and the oxidation time the speed constants could be determined for 750°C, 825°C and 900°C. Between the natural logarithm of the speed constant and the reciprocal temperature a linear connection exists. For this reason it is possible to calculate the kinetics by a well-defined mathematical expression for the speed constant of the titanium oxidation in dependence on the titanium content and the oxidation temperature. The connection between the speed constant and the optical outfit of the surface is illustrated.Furthermore the precipitation hardening of the alloys at temperatures between 100°C and 700°C is described. A noticable increase of the hardness is already produced at relatively low temperatures. Whith increasing temperatures the hardness maximum is shifted to shorter times. With increasing titanium content the hardness maximum increases and it is obtained after shorter times. Cold working before the ageing, raises the hardness maximum and accelerates the precipitation. The precipitations are formed to little plates with high coherency to the matrix preferentialy at the grain boundaries. X-ray analysis sensitively responds to the kinetics of precipitation and gives reliable information about the concentration variations of the matrix. The results concerning the oxidation behavior and the precipitation hardening make it possible to find the conditions of an optimized heat treatment with high hardness but without negative changes of the surface.
    Notes: Das Oxydationsverhalten hochkarätiger Gold-Legierungen mit Titangehalten zwischen 0,5 und 1,3 Ma. -% Titan in synthetischer und natürlicher Luft wurde in Abhängigkeit von Oxydationstemperatur und Zeit untersucht. Es bildet sich keine geschlossene homogene Titanoxidschicht. Im oberflächennahen Bereich der Legierung entstehen TiO2-Ausscheidungen (Rutil) an bevorzugten Keimbildungsorten (Korngrenzen, Gefügedefekte), ohne jedoch eine lückenlose Belegung der Korngrenzen zu bilden. Zwischen den Ausscheidungen sind Titan- und Sauerstoffkonzentration gleich Null. Das Titan wird aus dem Probeninneren durch Volumendiffusion herantransportiert. Aus der experimentell ermittelten linearen Abhängigkeit der Sauerstoffaufnahme von der Oxydationszeit werden die Geschwindigkeitskonstanten für 750°C, 825°C und 900°C bestimmt. Zwischen dem natürlichen Logarithmus der Geschwindigkeitskonstanten und der reziproken Temperatur besteht ein linearer Zusammenhang. Damit wird die Kinetik mit einem mathematischen Ausdruck für die Geschwindigkeitskonstante in Abhängigkeit von Titangehalt und Temperatur quantifizierbar. Hieraus läßt sich der Zusammenhang Zwischen dieser Geschwindigkeitskonstanten und dem optischen Erscheinungsbild der oxydierten Legierungsoberfläche darstellen.Desweiteren wird das Aushärtungsverhalten der Legierungen bei Auslagerungstemperaturen zwischen 100°C und 700°C beschrieben. Bereits bei relativ niedrigen Temperaturen ist ein deutlicher Häteanstieg zu verzeichnen. Mit steigender Temperatur verschiebt sich das Härtemaximum zu kürzeren Zeiten. Mit zunehmendem Titangehalt werden größere Maximalhärten nach kürzeren Zeiten erreicht. Eine Kaltverformung vor der Auslagerung erhöht die maximal erreichbare Härte und beschleunigt den Ausscheidungsvorgang. Die Ausscheidungen bilden sich in Form von Plättchen mit hohem Kohärenzgrad zur Matrix bevorzugt an den Korngrenzen. Die Röntgenbeugung reagiert empfindlich auf die Kinetik des Ausscheidungsvorganges und gibt zuverlässig über die Konzentrationsänderung in der Matrix Auskunft. Die Ergebnisse über das Oxydationsverhalten und die Ausscheidungshärtung ermöglichen eine Optimierung der Wärmebehandlung mit dem Ziel der Härtesteigerung ohne störende Oberflächenveränderung.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19950260909
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  • 9
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    Electronic Resource
    Conformational mimicry: Synthesis and solution conformation of a cyclic somatostatin hexapeptide containing a tetrazole cis amide bond surrogateThe first two authors (DDB and JZ) contributed equally to the experimental work. This is the fourth in a series of articles32,35,37 detailing the conformational mimicry of the 1,5-disubstituted tetrazole. (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 181-200 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Potent, cyclic hexapeptide analogues of somatostatin are generally believed to adopt some common secondary structural features: a II′ β turn at one end of the cycle, and a type VI turn with a cis amide bond at the other. A proposed cis amide surrogate, the 1,5-disubstituted tetrazole, has been placed into a cyclic hexapeptide analog of somatostatin in order to constrain the putative cis amide bond. The final cyclization was done by either chemical or enzymatic means. The product, cyclo(Ala6-Tyr7-D-Trp8-Lys9-Val10-Phe11-Ψ[CN4]), was found to have 83% of the activity of somatostatin. Solution nmr analysis in DMSO/water revealed that the backbone as well as side chain χ1 and χ2 were well ordered. Relaxation matrix methods were used to extract distance restraints from the nuclear Overhauser effect spectroscopy data set, and these were used in a systematic search of torsional space to identify structures consistent with the nmr data. Restrained minimizations of these structures using a number of different force fields produced structures having the expected βII′ turn at D-Trp8-Lys9 and αβVIa turn in the Phe11-Ψ[CN4]-Ala6 portion of the molecule. The similarity of the minimized structures to those previously reported for cyclic hexapeptide analogues of somatostatin confirms the similarity of the tetrazole geometry to that of the cis amide in solution. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360360207
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  • 10
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    Electronic Resource
    Crystal and molecular structure of the centrosymmetric meso-valinomycin analogue - cyclo (D-Val-D-Hyi-D-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi) (C60H102N6O18) (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 615-621 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of cyclo (D-Val-D-Hyi-D-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi)-2H2O has been solved by x-ray direct methods. The crystals (grown from a mixture of octane / CH2C12) are an orthorhombic, centrosymmetric space group Pbca, cell parameters a = 11.458(2). b = 25.613(3). c = 23.691(3) Å. Z = 4; therefore the molecule lies on a center of inversion in the cell. The atomic coordinates for the C, N, and O atoms were refined in the anisotropic thermal motion approximation (allowing for II-atom contribution to Fcal) to a standard R- factor value of 0.081. In contrast to meso-valinomycin, the analogue under study does not adopt an octahedral cage bracelet conformation. It has an unusual centrosymmetric elongated form with two type II terminal β-bends formed by N—H-C=O 4 → 1 type intramolecular H bonds. Two symmetry-related water molecules reside in the elongated molecular cavity of the centrosymmetric depsipeptide ring. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360360507
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