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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1909-1921 
    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.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 29-37 
    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 formabilities of cold-rolled high molecular weight polyethylene (HMWPE) sheets have been studied by measuring their plastic anisotropy ratio (R value), strain-hardening exponent (n value), strain distribution, and the forming limit diagram (FLD). The deep drawability of the polymer is improved by rolling. After 40% or more reduction in thickness by cold rolling, the HMWPE sheet could be deep-drawn into a cylindrical cup. The results of R value measurement indicate that the R value is responsible for improved drawability. Cold rolling also increases the n value but decreases the strain gradient. Stretch forming tests have also been carried out, and the results show that cold working could also improve the stretchability of this polymer. The results of the FLD are in agreement with the other properties studied. The mechanical properties, environmental stress cracking resistance, and shape, size, and property stability of the deep-drawn HMWPE cups have also been investigated.
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 2213-2223 
    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: Deformed high molecular weight polyethylene (HMWPE) rod, produced by die drawing at 115°C, was cleaved longitudinally at liquid nitrogen temperature and the cleaved surface was etched using a permanganic etching technique. A series of etched surfaces of HMWPE sections with different draw ratios (from 1 to 13) were analyzed employing scanning electron microscopy (SEM). The change of crystalline structure in HMWPE during die drawing was observed. In undrawn HMWPE. the spherulites were made up of sheaflike lamellae and scattered within the amorphous phase. During die drawing in the first instance, the microscopically inhomogeneous deformation occurred and the spherulites aligned along the drawing direction. At a draw ratio of about 7, local melting occurred, the spherulites disintegrated, and the sheaflike lamellae oriented, followed by straininduced recrystallization and the growth of the lamellae. Finally, at a draw ratio of about 12, the plastic deformation of the lamellae occurred and microfibrils were formed. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 9-18 
    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: High-molecular-weight polyethylene (HMWPE) sheets have been cold rolled biaxially to different reductions in thickness. After 40% or more reduction in thickness by cold rolling, the stress-whitening phenomenon in HMWPE was eliminated. To find out the reason of elimination of stress whitening by cold rolling, different techniques were employed. The measurement of hardness, density, and strain distribution of the specimens were carried out for the study of the differences in mechanical and physical properties of the stress whitened and nonwhitened specimens. Recovery of density, hardness, and dimensions of the specimens due to heating were also studied. Differential scanning calorimetry (DSC) and polarized-light microscopy were used to study the melting, and recrystallization behavior and scanning electron microscopy (SEM) were used to study the surface texture of the specimens. Based on the results of the different techniques employed, it is concluded that after cold rolling, especially biaxially rolled, due to the combined forces of compression and shear acting on the specimens from different directions, the macro-and micro-imperfections of the material may be eliminated to some extent. At 40% or more rolling reduction, the imperfections were largely eliminated; hence stress whitening did not occur.
    Additional Material: 11 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 263-283 
    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 polyethylenes developed for use as high voltage electric cable insulation have been studied. All crosslinked polyethylene materials show similar thermal aging characteristics, whereas linear low-density polyethylene is susceptible to thermal aging at higher annealing temperatues. Tree-retardant additives are soluble in xylene, but some are also attached to the gel network. They function both as enhanced antioxidants and as enhancers of electric breakdown strength. Biaxially oriented film shows the greatest resistance to electric breakdown.
    Additional Material: 20 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 49 (1993), S. 15-23 
    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 comprehensive investigation of the die drawing technology of a high molecular weight polythylene (HMWPE) rod has been carried out. The effect of draw temperature, draw speed, nominal draw ratio, and exit diameter of the dies has been studied. The oriented HMWPE products were characterized mainly by the determination of the three-point bend modulus and the tensile strength. The tensile strength and the modulus of the drawn HMWPE rod could reach 700 MPa and 18 GPa, respectively. In addition, it was found that forced cooling at the die exit was essential when drawing billets with large section areas. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 138-145 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pirt's maintenance model has been widely accepted for the effects of growth rate and maintenance on growth yield. However, the interpretation of parameters in Pirt's model as biological constants is difficult for energy-sufficient culture growth. In this study, a mechanistic model for the growth energetics of energy-sufficient chemostat cultures is proposed and verified with literature data. In the model, the overutilization of the energy substrate in energy-sufficient culture growth is attributed to the defective regulation of the energy substrate metabolism and energy uncoupling. The model also uses an “energy surplus” concept to collectively represent the effects of energy excessiveness. The proposed model provides a better quantitative understanding of the maximum growth yield and maintenance of energy-sufficient cultures. It also explains the glucose concentration effect reported in the literature.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 288-291 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 622-634 
    ISSN: 0006-3592
    Keywords: endothelial cells ; contact inhibition ; cell locomotion ; growth factors ; digital time-lapse recording ; image analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Video microscopy and digital time-lapse recording were used to monitor locomotion and proliferation of bovine pulmonary artery endothelial (BPAE) cells cultured with varying concentrations of basic fibroblast growth factor (bFGF). Cell trajectories were reconstructed using a generalized nearest-neighbor algorithm and analyzed to determine how cell motility is affected by cell-cell collisions, cell divisions, and increasing cell density. The temporal evolution patterns of the average speed of locomotion for all cells in a culture were computed and the effects of varying bFGF concentrations were analyzed. Intermediate concentrations of bFGF (30 and 50 ng/mL) significantly increased the speed of locomotion above the levels we observed with 0 and 100 ng/mL concentrations of bFGF. Increases in cell density due to proliferation were immediately accompanied by a decrease in the average speed of locomotion of the cell population. Finally, the effect of bFGF concentration on the overall cell proliferation rates was assessed. With the addition of 30 or 50 ng/mL of bFGF to the culture media, the observed cell proliferation rates increased significantly. The proliferation rates decreased when the bFGF concentration increased to 100 ng/mL. These results show that bFGF concentrations that increase the motility of BPAE cells also increase the observed cell proliferation rates. © 1994 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 36 (1990), S. 530-533 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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