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  • Wiley-Blackwell  (1,892)
  • 1990-1994  (1,810)
  • 1980-1984
  • 1955-1959  (82)
  • 1994  (966)
  • 1990  (844)
  • 1955  (82)
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  • 1990-1994  (1,810)
  • 1980-1984
  • 1955-1959  (82)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Poly(dimethylsiloxane)-poly(ethylene oxide)-heparin block copolymers III: Surface and bulk compositional differences (1990)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 24 (1990), S. 547-571 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Previously observed bioactivity of poly(dimethylsiloxane)-poly(ethyelene oxide)-heparin (PDMS-PEO-Hep) triblock copolymers has prompted studies of the surface and bulk character of this copolymer using angular-dependent electron spectroscopy for chemical analysis (ADESCA), static secondary mass spectroscopy (SIMS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Because the low-energy PDMS phase dominates surfaces of this copolymer when solvent cast under air or vacuum conditions, attempts were made to explain surface restructuring and rearrangements induced in hydrated or aqueous environments that permit surface accessibility and bioactivity of heparin moieties. Based on comparisons with PDMS, PEO, and heparin homopolymers, PEO/heparin blends, and an unheparinized PDMS-PEO diblock copolymer, PDMS-PEO-heparin demonstrates both phase-mixed and phase-separated regions in DSC analysis. During annealing cycles above the Tg values of the copolymer constituents, phase-mixed regions become increasingly phase separated and PEO enriched. TGA analysis confirmed the presence of block copolymer constituents and presented evidence of intermolecular segmental interactions, hence phase-mixing in the copolymers. ADESCA analysis indicates that the outer 5 Å of both the PDMS-PEO and PDMS-PEO-Hep copolymers is essentially pure PDMS. However, significant amounts of PEO are detected 5 to 20 Å below the surface. Static SIMS also detects the presence of PDMS at the surfaces of the PDMS-PEO and PDMS-PEO-Hep copolymers. Compositional models based on ADESCA, SIMS, and DSC data are presented for desiccated and hydrated copolymer surfaces.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820240503
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  • 2
    Electronic Resource
    Electronic Resource
    Melanin-concentrating hormone: A structural and conformational study based on synthesis, biological activity, high-field nmr, and molecular modeling techniques (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 609-622 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of Melanin-concentrating hormone (MCH) fragments have been synthesized and their biological activities compared with the parent peptide. The substructural units, 5-14 linear and 5-14 cyclic, have been used as models for MCH -  in 1H-nmr conformational studies. Conformational features predicted by molecular dynamics analyses find support in the nmr experiments.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290314
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  • 3
    Electronic Resource
    Electronic Resource
    Model filled polymers. I. Synthesis of crosslinked monodisperse polystyrene beads (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1909-1921 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monodisperse crosslinked polystyrene beads of varied size and crosslink density are prepared by emulsion copolymerization of styrene and divinylbenzene in the absence of emulsifier. Tumbling and internally stirred reactors were used for synthesis, with minimal agglomeration at at least 0.22 wt % potassium persulfate and up to 10% by weight of styrene in aqueous emulsion in the absence of oxygen. Particle sizes decreased from 800 to 200 nm on raising the polymerization temperature from 60 to 95°C. The glass transition temperature of the beads increased from 104.4 to 133°C by the inclusion of up to 10% by weight of divinylbenzene. The thermal stability of the beads was higher for peroxide than for persulfate initiation. The crosslink density estimated from the degree of swelling was about one third that expected from stoichiometry. The polystyrene beads are used as filler particles in polymer composites.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280722
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  • 4
    Electronic Resource
    Electronic Resource
    J-R curve calculation with the normalization method for toughened polymers (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 128-134 
    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: The method of normalization is used to develop the J-R curve fracture toughness characterization for polymeric materials. This method can develop J-R curves directly from load vs. displacement records without a need for an on-line crack monitoring system. It was used previously to develop J-R curves for metallic materials and is applied here for the first time to polymer materials. Single edge notched bend specimens of rubber toughened nylon 6/6 and rubber toughened amorphous nylon are used in this study. The J-R curves from the method of normalization are compared with the results obtained from the multiple specimen method of ASTM Standard E813. The results show that the method of normalization gives reasonable J-R curves; both methods show agreement over the early J-R curve region. In addition the JIc values are determined for each method and compared. Based on this work it is suggested that the method of normalization could be used as a general test method to develop J-R curves for polymeric materials.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760340209
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  • 5
    Electronic Resource
    Electronic Resource
    Nongenomic regulation of extracellular matrix events by vitamin D metabolites (1994)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 56 (1994), S. 331-339 
    Details
    ISSN: 0730-2312
    Keywords: 1,25-(OH)2D3 ; 24,25-(OH)2D3 ; matrix vesicles ; nongenomic regulation ; extracellular matrix ; alkaline phosphatase ; phospholipase A2 ; Protein kinase C ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Vitamin D metabolites appear to regulate chondrocytes and osteoblasts via a combination of genomic and nongenomic mechanisms. Specificity of the nongenomic response to either 1,25-(OH)2D3 or 24, 25-(OH)2D3 may be conferred by the chemical composition of the target membrane and its fluid mosaic structure, by the presence of specific membrane receptors, or by the interaction with classic Vitamin D receptors. Nongenomic effects have been shown to include changes in membrane fluidity, fatty acid acylation and reacylation, arachidonic acid metabolism and prostaglandin production, calcium ion flux, and protein kinaase C activity. Chondrocytes metabolize 25-(OH)D3 to 1,25-(OH)2D3 and 24,25-(OH)2D3; production of these metabolites is regulated by both growth factors and hormones and is dependent on the state of cell maturation. 1,25-(OH)2D3 and 24,25-(OH)2D3 may interact directly with extracellular matix vesicles to regulate their function in the matrix, including protease activity, resulting in matrix modefication and calcification. Isolated matrix vesicles, produced by growth zone chondrocytes, can activate latent transforming growth factor-β when incubated with exogenous 1,25-(OH)2D3. These observations suggest that nongenomic regulation of martix vesicle structure and function may be a mechanism by which mesenchymal cells, like osteoblasts and chndrocytes, may modulate events in the extracellular matrix at sites distant from the cell surace.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240560309
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  • 6
    Electronic Resource
    Electronic Resource
    Ionomers as charge additives (1990)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 28 (1990), S. 75-80 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Contract electrification measurements were performed on polymeric particles containing toluenesulfonate salt. Two forms of the toluenesulfonate ion pair were studied, an ionomer, poly(styrene-co-N-methyl-4-vinylpyridinium toluenesulfonate) and a molecular salt, cetyltrimethylammonium toluenesulfonate. Both types of particles charge positive, and the ionomer produces the higher charge level. XPS analysis shows that the particles containing the ionomer have a surface salt composition that resembles the formulation composition, whereas the surface salt composition of the particles containing the molecular is significantly higher than in the formulation. The variation in the surface ion concentration is used to estimate a relative charging capacity of the salts. XPS analyses of the carriers that were used with both particles shows an S 2p signal appropriate for the toluenesulfonate anion. A mechanism for charging involving the transfer of the toluenesulfonate anion from polymer particles to the carrier is proposed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1990.140280301
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  • 7
    Electronic Resource
    Electronic Resource
    The use of dynamically programmed scans to generate parent-ion tandem mass spectra with the ion-trap mass spectrometer (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 108-113 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A method is described whereby, under software control, the scan function employed to collisionally excite ions in an ion-trap mass spectrometer is regulated so as to obtain parent ion (fixed product) tandem mass spectral data. At the same time, constant neutral-loss information is also provided. Key features are the automatic ‘intelligent’ selection of parent ions from observation of the initial mass spectrum and the scanning of the applied ‘tickle’ frequency in order to locate the precise resonance points for excitation of these ions. Results for the model compounds perfluorotributylamine (‘FC43’) and n-butylbenzene are reported and complicating effects such as the unimolecular decay of the precursor ion species and charge exchange between product ions and the original sample material are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040404
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  • 8
    Electronic Resource
    Electronic Resource
    Torsional properties of healed canine diaphyseal defects grafted with a fibrillar collagen and hydroxyapatite/tricalcium phosphate composite (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 5 (1994), S. 277-283 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The need for alternatives to autogenous bone grafts is widely recognized. This study compared the torsional strength of canine femora 1 year after grafting with one of three forms of a collagen/hydroxyapatite/tricalcium phosphate bone grafting material (COLLAGRAFT15), autogenous bone, or no graft. The groups were compared to each other and to the unoperated contralateral femora. Results of torsional testing were evaluated for torsional strength, torsional displacement, total energy to fracture and White fracture mode. Data analysis showed lower torsional strength of the operated vs. unoperated femora with the exception of morsellized COLLAGRAFT15 material, which had higher strength. However, the only difference in the operated groups was that the morsellized COLLAGRAFT15 had greater strength than several groups including the autogenous bone group. There was no difference found in angular displacement between any of the groups. However, there was a difference in the energy to fracture in both strip forms of the COLLAGRAFT15. The final conclusion is that in this model, grafting with COLLAGRAFT15 provided torsional properties at one year postoperatively at least equivalent to autogenous bone. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770050402
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  • 9
    Electronic Resource
    Electronic Resource
    A detailed study of the characteristics of the ion-trap mass spectrometer using dynamically programmed scans (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 415-417 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The aims of the investigation were to use the method of dynamically programmed scans to study in detail some tandem mass spectrometric characteristics of the ion-trap mass spectrometer and then to use the programs to investigate the possibility of performing benchtop gas chromatography/tandem mass spectrometry experiments on the standard instrument. In particular we have examined the effect of applying a DC ramp during the ‘tickle’ period as a means of broadening the range of resonant frequencies, thereby facilitating the tuning required to effect excitation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290041015
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  • 10
    Electronic Resource
    Electronic Resource
    Diffusion-adsorption problems in macromolecular systems: New techniques for parameter estimationNCL Communication No. 4534. (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 39 (1990), S. 769-783 
    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: It has been shown that the techniques used for estimation of diffusion-adsorption parameters in the past have certain basic flaws. New and efficient techniques for parameter estimation have been proposed. These have many advantages such as using the full concentration-time profile (rather than part of it), time saving, etc. The validity of these techniques has been demonstrated by the analysis of the data generated in our laboratory on adsorption of polyacrylamide and also the data on adsorption of dyes on chitin reported in the literature.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070390401
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