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  • Chemistry  (33)
  • Biochemistry and Biotechnology  (2)
  • arachidonic acid  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Activities and interactions among phospholipases A2 during thapsigargin-induced S49 cell death (2000)
    Springer
    Apoptosis 5 (2000), S. 389-396 
    Details
    ISSN: 1573-675X
    Keywords: arachidonic acid ; BEL ; cPLA2 ; iPLA2 ; MAFP ; sPLA2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The purpose of this study was to determine the roles of calcium-dependent phospholipase A2 (cPLA2) and calcium-independent phospholipase A2 (iPLA2) in thapsigargin-induced membrane susceptibility to secretory phospholipase A2 (sPLA2) and programmed cell death. 3H-arachidonic acid release was observed in the presence of thapsigargin. This release was inhibited partially by an inhibitor of iPLA2 (BEL) and completely by an inhibitor of both cPLA2 and iPLA2 (MAFP) suggesting that these enzymes were active during apoptosis. The process of cell death did not require the activity of either enzyme since neither inhibitor impeded the progression of apoptosis. However, both inhibitors increased the susceptibility of the membrane to sPLA2 in the presence of thapsigargin. In the case of BEL, this effect appeared to involve direct induction of apoptosis in a sub-population of the cells independent of the action of iPLA2. In conclusion, the results suggested that cPLA2 and iPLA2 are active during thapsigargin-induced apoptosis in S49 cells and that cPLA2 tempers the tendency of the cells to become susceptible to sPLA2 during apoptosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009647912056
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of different dietary arachidonic acid : docosahexaenoic acid ratios on phospholipid fatty acid compositions and prostaglandin production in juvenile turbot (Scophthalmus maximus) (1995)
    Springer
    Fish physiology and biochemistry 14 (1995), S. 139-151 
    Details
    ISSN: 1573-5168
    Keywords: turbot ; arachidonic acid ; docosahexaenoic acid ; phospholipid ; prostaglandin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Five purified diets containing AA (20:4n-6) at 0.02–0.78% dry weight and DHA (22:6n-3) at 0.93–0.17% dry weight were fed to duplicate groups of juvenile turbot (Scophthalmus maximus) of initial weight 0.87 g for a period of 11 weeks. The dietary DHA:AA ratio ranged from 62 to 0.2. Incorporation of AA into liver phospholipids increased with increasing dietary AA input. Phospholipids from fish fed diets containing 0.02, 0.06 and 0.11% of dry weight as AA generally contained less AA compared to fish fed fish oil while those fed diets containing 0.35 and 0.78% of dry weight as AA had higher AA levels in their phospholipids. The highest levels of AA were found in PI but the greatest percentage increase in AA incorporation was in PE and PC. Brain phospholipid fatty acid compositions were less altered by dietary treatment than those of liver but DHA content of PC and PE in brain was substantially lower in fish fed 0.93% pure DHA compared to those fed fish oil. This suggests that dietary DHA must exceed 1% of dry weight to satisfy the requirements of the developing neural system in juvenile turbot. In both tissues, (20:5n-3) concentration was inversely related to both dietary and tissue PI AA concentration. Similar dietary induced changes in AA, EPA and DHA concentrations occurred in the phospholipids of heart, gill and kidney. PGE2 and 6-ketoPGF1α were measured in homogenates of heart, brain, gill and kidney. In general, fish fed the lowest dietary AA levels had reduced levels of prostaglandins in their tissue homogenates while those fed the highest level of AA had increased prostaglandin levels, compared to fish fed fish oil. In brains, the PGE2 concentration was only significantly increased in fish fed the highest dietary AA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002457
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and properties of epoxy-episulfide resins (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 67-81 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Standard epoxy resins have good mechanical properties, but their prolonged low temperature curing time limits their potential use in clinical applications as well as in many industrial applications. A fast-curing epoxy-episulfide resin has been developed. The gel time of epoxy-episulfide made from EPONTrade mark of Shell Chemical Company. 828 ranges from 2 to 10 minutes by changing the ratio of the ingredients. The heat of reaction of this system is low, resulting in low cure shrinkage. Water absorption of the episulfide network is low. The epoxy-episulfide system cured with polyamide curing agent V-40 exhibits two transition temperatures, at about 85°C and 130°C, as shown in dynamic mechanical analysis data. In order to solve the long term stability problem of the above episulfides, and also the mixing problem, a lower viscosity resin, Eponex, was used to make Eponex-sulfide. Eponex-sulfide systems show promise in that they remain in a stable liquid form without epoxy. The other advantages appear to be retained.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052400106
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  • 4
    Electronic Resource
    Electronic Resource
    Fracture behavior of coated/uncoated graphite-epoxy composites (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 605-609 
    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 static delamination behavior of graphite/epoxy composite specimens subjected to mode I tensile opening (using UDCBUniform double cantilever beam. specimens), and pure mode II shear loading (using ENFEnd-notched flexural. specimens) were studied. The graphite epoxy composites for the study were made from commercially treated fibers, with and without an electropolymerized interlayer. The mode I fracture energy (GIC) was found to be significantly higher (more than 50 percent) for the coated fibers. However, this improvement was accompanied by a high reduction (more than 3 times) in the mode II fracture energy (GIIC). This effect is apparently related to poor adhesion between the interlayer and the epoxy resin, which may be corrected by use of a “top layer” of appropriate composition to form chemical bonds between the phases. The fracture toughness (KIC) of composites made with commercially treated fibers was also evaluated, using double side-notched specimens.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760280909
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  • 5
    Electronic Resource
    Electronic Resource
    Amine-cured epoxy resins: Adhesion loss due to reaction with air (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 1095-1102 
    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: The variability in adhesive bond strength and extent of cure of room-temperature, amine-cured epoxy resins has limited their applications. This paper reports the observation of microscopic crystal formation at the interface of the resin with air, resulting in a variably lower resin curing rate, extent of cure, and up to ten times lower adhesive bond strength. These crystals were identified as an amine bicarbonate salt, resulting from the reaction of the amine at the surface of the curing mixture with air. The bicarbonate formation seems to be general for the types of hardeners used in room-temperature curing. The amine-bicarbonate compound can be decomposed back to the amine by heating above 80°C. Otherwise, exposure of room-temperature systems to air before bonding is undesirable.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1977.070210423
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  • 6
    Electronic Resource
    Electronic Resource
    Matrix viscoelasticity: Controlling factor in the rubber toughening of epoxy resins (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 1875-1891 
    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: Our limited success in toughening methylene dianiline (MDA)-cured Epon 828, using varying rubber types, led to a study of the role of the matrix viscoelasticity in the toughening process. Two rubber types, with different interfacial bonding capabilities, poly(n-butyl acrylate)/15 wt % acrylonitrile/2 wt % acrylic acid and poly(n-butylacrylate)/15 wt % acrylonitrile, were incorporated into systems containing varying amine concentrations to control crosslink density. Impact strengths of controls and rubber-modified compositions increased with excess amine concentrations up to 70%. The impact strengths for the poly(n-butyl acrylate)/15 wt % acrylonitrile/2 wt % acrylic acid rubber-modified compositions were greater than their equivalent controls, with the effect being greater at a lower crosslink density. This study confirmed that the matrix viscoelasticity is the controlling parameter in the toughening process. The degree of rubber-epoxy interfacial bonding is also an important parameter to consider, if the matrix viscoelasticity permits toughening. A modified stress response model was used to explain the toughening phenomenon.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070300508
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  • 7
    Electronic Resource
    Electronic Resource
    Chemistry of epoxide-polycarbonate copolymer networks (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 247-254 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diepoxides and in-chain carbonate groups react readily in the presence of quarternary ammonium salts, although reaction is not observed without this catalyst. Two moles of epoxide react with each mole of carbonate. When diepoxides and polycarbonates are reacted, a three-dimensional network of chains crosslinked with carbonate groups is produced; the crosslink density is controlled by adjusting the epoxy/carbonate ratio. Tertiary amines and alkoxides also catalyze the epoxy/carbonate reaction, but these have the undesirable attribute of promoting epoxy polymerization. The presence of oligocarbonates accelerates the epoxy-amine reaction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080260124
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  • 8
    Electronic Resource
    Electronic Resource
    Polycarbonate-modified epoxies. I. Studies on the reactions of epoxy resin/polycarbonate blends prior to cure (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2103-2116 
    Details
    ISSN: 0887-624X
    Keywords: epoxy ; polycarbonate ; transesterification ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An epoxy resin based upon the diglycidyl ether of bisphenol-A was modified with poly(bisphenol A carbonate) (PC). Prior to aromatic amine cure, the possible reactions in the epoxy resin/PC blend were investigated using GPC and FTIR techniques. It was shown that at 150°C, the epoxy resin acted as a plasticizer and promoted the crystallization of PC. In addition, a transesterification between the secondary hydroxyl groups in the epoxy resin with the carbonate groups in PC occurred. This reaction resulted in degraded PC chains with phenolic hydroxyl end groups. There was no evidence of reaction of epoxide groups at 150°C in this blend. At 200°C, the secondary hydroxyl groups acted as a catalyst converting most of the aromatic-aromatic carbonates to the aromaticndash;liphatic and aliphaticndash;aliphatic carbonates through transesterification. At this elevated temperature, the secondary hydroxyl groups were regenerated by the addition reaction between the epoxide groups and the phenolic hydroxyl end groups, either from the transesterification or the hydrolysis of PC. This addition reaction combining the PC chains and epoxy chains eventually resulted in a crosslinked polymer if the extent of reaction was high. Thus, by using a melt blending process at high temperature, e.g., 200°C, a copolymer network structure of PC-modified epoxy could be formed. The fracture toughness should be increased by increasing the capability for plastic deformation due to the incorporation of PC chains into the network; results will be reported in a future study. © 1996 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    The continuous recovery of uranium from biologically leached solutions using immobilized biomass (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 10-17 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The potential of uranium recovery from the dilute uranium ore bioleach solutions of the Elliot Lake district of Canada was examined using immobilized microbial biomass. Batch and continuous laboratory scale pilot plant experiments were carried out. The results have shown that the immobilized microbial biomass can successfully recover all of the uranium from dilute (less than 300 mg U/L) solutions. The uranium can subsequently be eluted producing a high uranium concentration eluate perhaps exceeding 5000 mg U/L. The biomass maintained its biosorption capacity of about 50 mg U/g over 12 examined successive adsorption-elution cycles with no apparent indication of failure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340103
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  • 10
    Electronic Resource
    Electronic Resource
    Polymer science and engineering, David J. Williams, Prentice-hall, inc., Englewood cliffs, N.J. (1971). 401 pages. $17.00 (1972)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 18 (1972), S. 254-255 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690180157
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