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  • Chemistry  (13)
  • Polymer and Materials Science  (9)
  • Carcinogenesis  (2)
  • 1
    ISSN: 1434-0879
    Keywords: Interstitial stroma ; Carcinogenesis ; Bladder epithelium ; Neovascularization ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study describes ultrastructural alterations of the interstitial stroma in the rat bladder epithelium during N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced bladder carcinogenesis using scanning (SEM) and transmission (TEM) electron microscopy with NaOH treatment. The results obtained with SEM demonstrated the occurrence and development of stroma protrusions which exhibited pipe-like structures in the rat bladder epithelium following administration of BBN. Number and size of blood vessel sections also gradually increased both in the stroma and within the layer of the proliferated epithelial cells as examined by light microscopy (LM) and TEM. In this study stroma alterations were not only observed in malignant lesions of rat bladder, but hyperplastic lesions were also accompanied by stroma alterations. It is suggested that: (1) the interstitial stroma of the rat bladder epithelium may exhibit pathological changes in structure and these changes may correlate with the progression of epithelial cell proliferation following administration of BBN and (2) one of the most important alterations in the stroma is the occurrence of neovascularization, which may induce structural modification of the stroma in the processes of bladder tumor growth and development.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-0879
    Keywords: Zinc ; Metallothionein ; Carcinogenesis ; Rat bladder ; Transitional cell carcinoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study investigated the presence of zinc and expression of metallothionein (MT) in different pathological changes of the rat bladder induced by administration of N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Using the Timm staining method, the presence of zinc was observed in normal and benign hyperplastic epithelial cells of the rat bladder, particularly in the malignant bladder tumor, induced by the administration of BBN. Immunohistochemically, MT expression was detected only in noninvasive (30%) and invasive transitional cell carcinoma (80%) of the rat bladder where the tumor cells were rich in zinc. Our data suggest that: (1) growth and development of the rat bladder tumor, expecially malignant tumors, may have a high requirement for zinc and (2) MT synthesis may be induced by a high zinc concentration in rat bladder tumor cells.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 569-572 
    ISSN: 0887-6266
    Keywords: physical aging ; tracer diffusion coefficient ; camphorquinone ; polysulfone ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of physical aging on the tracer diffusion coefficient D of camphorquinone in polysulfone is investigated. It is shown that if the sample is sufficiently annealed and physical aging is nearly complete, the temperature dependence of D will reflect the primary α-relaxation process of the host polymer. In the temperature range between Tg (=185°C) and 165°C, D is found to be a function of time, and the time dependence of D is given by D = At-μ, with μ approximately equal to unity. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 1803-1809 
    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 hydroxyl-terminated maleopimaric acid esters (HTMAEs) and rigid polyurethane (PU) foams based on these HTMAEs were synthesized using chemically modified natural gum rosin and its derivative maleopimaric acid as raw materials. Thermal stability of these polyols and their corresponding rigid PU foams was studied by a thermogravimetric method and a dimensional stability measurement. It was shown that the thermal stability of the final foams was strongly dependent on the structure of their corresponding polyols. The thermogravimetric analysis curves of these rosin-based rigid PU foams displayed two distinct regions of weight loss. It has been shown that at the initial stage of weight loss the process was dominated by polyol component degradation; the second stage was governed by isocyanate component degradation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 1167-1171 
    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 rosin-based rigid polyurethane foams of different composition were synthesized directly from chemically modified gum rosin. The effect of the composition of these rosin-based rigid polyurethane foams on their thermal stability and compression strength was measured. It was shown that the onset temperature of weight loss and the dimensional stability at high temperature increased with increase of the molar ratio of NCO/OH. The TGA data further confirmed that the second stage weight loss in the two-stage weight loss process of these polyurethane foams was governed by thermal degradation of the isocyanate component. Although density had no significant influence on the TGA curves of the rosin-based rigid polyurethane foams, it had great influence on the dimensional stability at high temperature and compression strength of the foams. It has been shown that the inclusion of rosin in rigid polyurethane foams increases the strength and thermal stability compared with that of polyether-based ones. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1951-1956 
    ISSN: 0887-6266
    Keywords: polymer solution ; light scattering ; poly(isobornyl methacrylate) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermodynamic and hydrodynamic properties of dilute solutions of poly (isobornyl methacrylate) (PIMA) in tetrahydrofuran (THF) were characterized by using viscosity, static, and dynamic light scattering measurements. PIMA samples with different molecular weight were obtained by fractional precipitation of PIMA solution. Chain dimension parameters (Rg and RH), together with second virial coefficient A2 and intrinsic viscosity [η], were used to calculate various solution parameters characterizing polymer chains in polymer solutions. The experimental results are compared with calculation, indicating that PIMA behaves as a flexible coil in THF. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 353-365 
    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: Chitosan was chemically modified by alkylation with N-(2-bromoethyl) phthalimide, N-(3-bromopropyl) phthalimide, and N-(4-bromobutyl) phthalimide. The resulting N-(phthalidimidoalkyl) chitosans were treated with hydrazine to remove the phthalidimido group resulting in the final N-(aminoalkyl) chitosan products. For comparison purposes, poly(vinyl alcohol) (PVA) was alkylated with N-(3-bromopropyl) phthalimide, then treated with hydrazine to give the N-(3-aminopropyl) PVA product. All alkylation products were characterized by solution 1H- and 13C-NMR and by solid-state CP-MAS 13C-NMR. The above synthetic polymer derivatives, as well as chitosan, polyallyl amine, and polyethylen-imine, were used to form membrane coatings around calcium alginate beads in which blue dextran of molecular weight 7.08×104 or 26.6×104 was entrapped. These microcapsules were prepared by extrusion of a solution of blue dextran in sodium alginate into a solution containing calcium chloride and the membrane polymer. Membrane integrity and permeability were assessed by measuring the elution of the blue dextran from the capsules, spectrophotometrically. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 625-636 
    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: Polypyrrole (PPY) films having high conductivity were synthesized electrochemically in acetonitrile at low temperature and low current density. Pristine, deprotonated, and ozone-pretreated PPY films were subjected to either thermally induced or near-UV-light-induced graft copolymerization with acrylic acid (AAc), or sodium salt of 4-styrenesulfonic acid (NaSS). Surface structures and redox states of the pristine, deprotonated, reprotonated, and surface-modified polypyrrole films were studied by angle-dependent X-ray photoelectron spectroscopy (XPS). The morphology of the PPY surface after modification by graft co-polymerization was revealed by atomic force microscopy (AFM). The results showed that the density of surface grafting decreased with ozone pretreatment. Surface grafting of the two polymeric acids also gave rise to a self-protonated surface structure. A substantial proportion of the grafted protonic acid groups at the surface remained free for further surface functionalization. The surface characteristics, in particular the charge-transfer interactions and the changes in the intrinsic redox states of the substrate films, associated with the external protonation and surface self-protonation processes were also discussed. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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