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  • Polymer and Materials Science  (3)
  • chemical defense  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Physiological activity of water beetle defensive agents. II. Absorption of selected anesthetic steroids and norsesquiterpenes across gill membranes of the minnowPimephales promelas Raf. (1976)
    Springer
    Journal of chemical ecology 2 (1976), S. 131-146 
    Details
    ISSN: 1573-1561
    Keywords: minnow ; Pimephales promelas ; chemical defense ; steroids ; norsesquiterpenes ; gyrinidae ; anesthesia ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The uptake of selected steroids and norsesquiterpenes by live minnows,Pimephales promelas, was studied when the compounds were administered externally in aqueous solution. The gills of minnows absorbed 80% of the steroid removed from solution. Steroid absorption across minnow gills is apparently a nonmediated process as rate saturation could not be demonstrated. Initial absorption rates of test compounds were inversely correlated with (1) the degree of oxygenation, (2) water solubility, and (3) polarity on silica gel thin-layer chromatography. These findings support the Stein model of non-mediated transport. The majority of compounds anesthetic and toxic to minnows exerted their effects at a similar internal concentration. Anesthesia occurred at ca. 10−6–10−5 M and death at 10−4–10−3 M. Since various agents causing membrane stabilization and lysis in in vitro systems act in an identical concentration range, it is proposed that the defensive steroids and norsesquiterpenes of water beetles act via membrane stabilization and lysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00987737
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  • 2
    Electronic Resource
    Electronic Resource
    Physiological activity of water beetle defensive agents. I. Toxicity and anesthetic activity of steroids and norsesquiterpenes administered in solution to the minnowPimephales promelas Raf. (1976)
    Springer
    Journal of chemical ecology 2 (1976), S. 115-130 
    Details
    ISSN: 1573-1561
    Keywords: Dytiscidae ; Gyrinidae ; chemical defense ; 4-pregnen-3-ones ; gyrinidal ; gyrinidione ; gyrinidone ; steroids ; norsesquiterpenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract By means of a bioassay employing the minnowPimephales promelas, the anesthetic activities and toxicities of various defensive steroids and norsesquiterpenes produced by the Dytiscidae and Gyrinidae were compared with those of a wide selection of steroid standards. The most widely occurring major components of dytiscid secretions, 4-pregnen-3-ones and related derivatives, were among those compounds most active in minnow bioassays. The norsesquiterpenes gyrinidal and gyrinidione were among the most toxic compounds tested but they possessed little anesthetic action. The anesthetic activity of gyrinidone was comparable to that of testosterone. Steroid activity in the minnow bioassay was highly related to the degree of oxygenation; steroids oxygenated only at the termini of the molecule were most active. Less or additional oxygenation resulted in a loss of activity. When steroids were rapidly administered to minnows the activities of many of them were similar, suggesting they share a common mode of action.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00987736
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  • 3
    Electronic Resource
    Electronic Resource
    Composite interface analysis using voltage contrast XPS (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 977-983 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Voltage contrast x-ray photoelectron spectroscopy (XPS) was developed to characterize the interfacial bonding properties in carbon fiber-reinforced polymer matrix composites. The differing electrical properties of the fiber and matrix allow biasing of the matrix and separation of the fiber and matrix signals in the XPS spectrum. The result is a quantitative measure of the relative amount of exposed fiber and exposed matrix at the fracture surface of a failed composite specimen. A parameter used to describe the interfacial bonding is defined as the ratio of the areas of the carbon 1s peaks from the fiber and matrix components and is referred to as the interfacial bonding ratio or Cf/Cm. Typical values of Cf/Cm for polyacrylonitrile-based carbon fiber-reinforced polymer matrix composites range from zero (excellent bonding) to three (poor bonding). The voltage contrast technique was used to demonstrate the effects of matrix resin chemistry, electrolytic oxidative fiber surface treatment, fiber processing temperature, fiber modulus and hydrothermal damage on interfacial bonding.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740201208
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  • 4
    Electronic Resource
    Electronic Resource
    Cyclization of methacrylate-functional silane on particulate clay (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 2227-2242 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Physically absorbed γ-methacryloxypropyltrimethoxysilane (γ-MPS) deposited from aqueous alcohol on particulate clay exists as low-molecular-weight cyclic, caged polysilsesquioxanes. These structures are incapable of forming high-molecular-weight chains or networks because of this internal cyclization tendency. The behavior is extremely different from that found in bulk solutions or when organofunctional silanes are adsorbed on low-surface-area glass or metal substrates. Fourier-transform infrared spectroscopy and gel permeation chromatography were used to characterize the silane species deposited in bulk and on the surface of particulate clay. The cyclization tendency is postulated from analysis of the behavior of hydrolyzed γ-methacryloxypropyltrimethoxysilane upon cocondensation with other organofunctional silanes and under variable cure conditions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.180231101
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  • 5
    Electronic Resource
    Electronic Resource
    Infinite-dilution oscillatory flow birefringence properties of polystyrene and poly(α-methylstyrene) solutionsCorrected proofs received June 3, 1982 (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 1409-1425 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Oscillatory flow birefringence (OFB) measurements have been carried out for an extensive series of solutions containing narrow-distribution, atactic, linear polystyrenes PS (10, 000 or 390, 000 Mw) or poly(α-methylstyrene) PMS (400,000 Mw) in a high-viscosity solvent, Aroclor 1248. The concentration ranges examined are such that the concentration dependence is obtained in both the “dilute” and “semidilute” regimes; the data are sufficiently precise to permit extrapolation to obtain for the first time the infinite-dilution properties. Various plotting formats are explored to determine an appropriate extrapolation procedure. The infinite-dilution OFB properties are compared with the bead-spring model (Zimm) theory which predicts quantitatively the frequency dependence of the observed properties for the PS and PMS solutions studied except for the high-frequency regime. The sensitivity and precision of the OFB experiment is such that the extrapolation curves-and the resulting infinite-dilution properties-show substantially less scatter than comparable visco-elasticity (VE) data. There is no evidence of a change in the character of the concentration dependence for the range of concentrations studied.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.180200807
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