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  • Articles  (7)
  • Cell & Developmental Biology  (4)
  • Life and Medical Sciences  (4)
  • Polymer and Materials Science  (3)
  • Nuclear reactions
  • 1985-1989  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Flow-induced structure and rheology of a triblock copolymer (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 33 (1987), S. 1585-1600 
    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: Linear viscoelastic properties are found to be a sensitive measure of flow-induced structural changes in a block copolymer. Styrene-butadiene-styrene block copolymer (SBS) with 26% polystyrene (PS) forms a macrostructure in the quiescent state with grains of the order of 1-10 μm. Within each grain, phase separation gives rise to a regular two-phase microstructure with cylindrical PS domains with radius of the order of 200 Å. Large-amplitude oscillatory shear (γ = 4.5) at temperatures between 139 and 181°C was applied to after the grain structure with the objectives of removing the discontinuities at the grain boundaries and of aligning the domains into a continuous ultrastructure. The SBS behaved like a solid (tan δ 〈 1 at low ω) before and like a liquid (tan δ 〉 1) after shear modification. This change expressed itself in the removal of the long relaxation times from the linear viscoelastic spectrum; the intermediate and low relaxation times were not affected by the shear modification. The viscoelastic spectrum slowly recovered during annealing with recovery times of the order of the longest relaxation time of the quiescent structure. Birefringence studies showed that the SBS did not recover into its original grain structure but into a highly oriented domain structure. The discontinuities at the grain boundaries could not be removed completely.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070330514
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  • 2
    Electronic Resource
    Electronic Resource
    Comparison of physicochemical speciation procedures with metal toxicity to Chlorella pyrenoidosa. Copper complexation capacity (1989)
    Weinheim : Wiley-Blackwell
    Electroanalysis 1 (1989), S. 107-112 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A comparison was made of methods for measuring the copper complexation capacity of natural and synthetic organic ligands in freshwaters. Complexation capacity values close to theoretical were obtained for nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid, when the following separation or analysis methods were used to detect ionic copper: algal assay (Chlorella pyrenoidosa), an aluminum hydroxide resin, ion-selective electrode (ISE), and anodic stripping voltammetry (ASV) at the mercury film electrode (MFE) and Nafion-coated MFEs. No complexation capacity could be measured for Cu-NTA when the hanging mercury drop electrode (HMDE) was used.Results from the ISE and a resin with adsorbed aluminum hydroxide agreed closely with algal assay for the copper complexation capacity of solutions of fulvic acid and Fe-humic colloids. Analysis by ASV at the HMDE, MFE, and Nafion-coated MFE gave values-of more than an order of magnitude lower than the other techniques because these methods failed to detect the end point for partially labile complexes with a large complexation capacity. On the other hand, the use of differential pulse polarography (DPP) detected these labile copper complexes and yielded results comparable with those for algal assay. Comparable copper complexation capacities for pristine river water samples were obtained by algal assay (2.5-4.1 × 10-6 M Cu) and DPP (2.0-3.7 × 10-6 M Cu), with lower values for the aluminum hydroxide resin (0.8-1.1 × 10-6 M Cu). Because the ASV techniques gave much lower results (0.1-0.4 × 10-6 M Cu), they are clearly unsuitable for the determination of the complexation capacity of freshwaters.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140010204
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  • 3
    Electronic Resource
    Electronic Resource
    Electrochemical speciation analysis of metals at membrane-coated electrodes (1989)
    Weinheim : Wiley-Blackwell
    Electroanalysis 1 (1989), S. 485-491 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Speciation of model Cu complexes on the basis of size and charge was achieved by anodic stripping voltammetry (ASV) at mercury film electrodes (MFE) coated with Nafion or cellulose acetate Nafion (CANMFE). The Nafion-coated MFE effectively excludes negatively charged Cu complexes, and evidence for the containment of the diffusion layer beneath the Nafion coating is provided. The CANMFE excludes complexes with molecular weights greater than 200, including the Cu-fulvic acid complex, which is of particular interest for speciation in natural waters. Complexation titrations of fulvic acid with Cu show the unsuitability of differential pulse ASV for providing a realistic estimate of the end point (complexation capacity). Differential pulse polarography, which provides results more comparable with bioassays, can be used for the determination of complexation capacity. Results for the speciation analysis of coastal seawater and polluted fresh water are presented. The CANMFE is insufficiently sensitive for seawater analysis, but in polluted fresh water its use indicates that organic and inorganic complexes with molecular weights greater than 200 dominate the speciation for Cd (72%), Pb (96%), and Cu (〉 99.8%).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140010603
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  • 4
    Electronic Resource
    Electronic Resource
    The differential distribution of beta tubulin mRNAs in individual mammalian brain cells (1985)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 27 (1985), S. 205-214 
    Details
    ISSN: 0730-2312
    Keywords: tubulin ; mRNA ; in situ hybridization ; rat cerebellum ; development ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: It has been shown by in vitro translation of polyadenylated messenger RNAs (poly(A)+ mRNAs) that the mRNAs encoding both alpha and beta tubulin isotypes are present at much higher relative levels in the developing rat brain than they are in the adult [1], suggesting that the requirements for tubulin subunits vary with cell type and/or with the developmental stages of a particular cell type. The postnatally developing rat cerebellum, with its readily identifiable cell populations that perform the gamut of developmental tasks, is a suitable model for analyzing specific cellular mRNA distributions during development. In this report, by in situ hybridization techniques it is shown that, by comparison to total cellular poly(A)+ mRNA levels, there is relatively more of the total beta tubulin mRNAs in mitotically active external granule layer cells than in those in the internal granule layer. These results show that migration and differentiation of these granule cells is accompanied by a decrease in their beta tubulin mRNA levels relative to the levels in granule cells of the external granule cell layer. Furthermore, the relative levels of beta tubulin mRNA both in the prenatally formed Purkinje cells and the postnatally formed stellate cells are two to fourfold less than in the granule cells of the internal granule cell layer.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240270303
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  • 5
    Electronic Resource
    Electronic Resource
    Modulation of beta-adrenergic response in rat brain astrocytes by serum and hormones (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 122 (1985), S. 73-80 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Purified astrocyte cultures from neonatal rat cerebrum respond to isoproterenol, a beta-adrenergic agonist, with a transient rise in cAMP production. This astroglial property was regulated by serum, a chemically defined medium (serum-free medium plus hydrocortisone, putrescine, prostaglandin F2α, insulin, and fibroblast growth factor) and epidermal growth factor. Compared to astrocytes grown in serum-supplemented medium, astrocytes grown in the chemically defined medium were nonresponsiveto isoproterenol stimulation, and this difference did not appear to be due to selection of a subpopulation of cells by either medium. The data suggest that a decreased beta-adrenergic receptor number and an increased degradation of cAMP may account for the reduced response to beta-adrenergic stimulation. The nonresponsive state of astrocytes in the defined medium was reversible when the medium was replaced with serum-supplemented medium. An active substance(s) in serum was responsible for restoring the responsiveness of astrocytes. Each of the five components of the defined medium had little effect by itself; however, together they acted synergistically to desensitize astrocytes to beta-adrenergic stimulation. On the other hand, epidermal growth factor, a potent mitogen for astrocytes, was very competent by itself in reducing the cAMP response of astrocytes to beta-adrenergic stimulation. Thus purified astrocytes grown in the chemically defined medium appear to be a good model for the study of hormonal interactions and of serum factors which may modulate the beta-adrenergic response.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041220112
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  • 6
    Electronic Resource
    Electronic Resource
    Controlled vascular corrosion casting of the rabbit eye (1988)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 10 (1988), S. 15-26 
    Details
    ISSN: 0741-0581
    Keywords: Scanning electron microscopy ; Ocular microvasculature ; Microcorrosion cast ; Injection replica ; Batson's ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We have refined the technique of vascular corrosion casting with methacrylate to permit the reproduction of physiological states of vascular tone and to produce sturdy castings of ocular microvasculature. The method entails careful maintenance of homeostasis up to the moment of plastic perfusion, avoidance of vascular rinsing or fixation with the attendant anoxia, reduction of the viscosity of the casting resin without impairing the properties of the resultant polymer, addition of a cross-linking agent to increase the strength of the plastic, and injection at physiological temperature and pressure. This casting regimen reproduces the normal anatomical conditions of blood vessels and can be used to demonstrate altered conditions of vascular tone. In all instances, the second, untouched eye serves as a control for unilateral manipulations. Special problems of replicating the ocular vasculature are related to the intraocular pressure, which opposes the vascular perfusion pressure and constitutes an impediment to perfusion.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060100104
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  • 7
    Electronic Resource
    Electronic Resource
    Monolayer freeze-fracture - a modified procedure (1986)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 3 (1986), S. 439-451 
    Details
    ISSN: 0741-0581
    Keywords: Monolayer freeze-fracture ; Trans-membrane proteins ; Erythrocyte membrane proteins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Monolayer freeze-fracture of biological membranes is a valuable tool for integrating membrane morphology with biochemical analysis of membrane components. This correlation has been restricted by the purity of the biochemical sample. In this article, the method is reviewed, and an improved method is described. The essential modification was the use of a polysaccharide-coated microscope slide, instead of a copper plate, to cover cells attached to a polylysine-coated coverslip. It was found that proper freeze-fracture will not occur unless there is a distinct temperature gradient, with its accompanying stresses, across the cell monolayer during the freezing process. This gradient is achieved by using glass slides of different thickness to cover each side of the monolayer. Comparison of the results with those obtained when using a copper-glass system demonstrated a consistently purer sample for the glass-glass system, with whole-cell contamination of the external membrane leaflet being reduced to 0.4%. Problems associated with obtaining pure samples for biochemical analysis are discussed, and the results of freeze-fracture with the glass-glass and glass-copper systems are compared. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of polypeptides associated with the separate halves of the erythrocyte membrane demonstrated that band 3, the anion transport protein, separates with the cytoplasmic face, whereas only sialoglycoproteins and their fragments are retained in the external face. This finding, obtained with the glass-glass system, is consistent with results of our earlier freeze-fracture study that used a copper-glass system which showed that covalent bonds may be broken during this procedure.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060030407
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