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  • 1
    Publication Date: 1983-03-04
    Description: Six structural homologs of spermidine and five of its precursor, putrescine, were studied for their ability to prevent cytostasis of cultured L1210 leukemia cells induced by alpha-difluoromethylornithine (DFMO), a specific inhibitor of putrescine biosynthesis. High-performance liquid chromatography and competition studies with spermidine indicated that the homologs, which vary in the length of the carbon chain separating the amines, penetrated the cells. The structural specificity of the spermidine carrier was defined. Three of the six spermidine homologs supported cell growth during a 48-hour incubation in the presence of DFMO, indicating that a two-carbon extension of spermidine structure was tolerated for biological function. Two of the five putrescine homologs supported growth after being converted by the cells to their respective spermidine homologs. The central nitrogen of spermidine appears to be essential for function since diamines of chain length comparable to that of spermidine did not prevent DFMO cytostasis. No more than 15 percent of the spermidine normally present in L1210 cells was required for cell proliferation in the presence of DFMO.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Porter, C W -- Bergeron, R J -- CA-22153/CA/NCI NIH HHS/ -- CA-24538/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1983 Mar 4;219(4588):1083-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6823570" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Cell Division ; *Cell Physiological Phenomena ; Eukaryotic Cells/*physiology ; Leukemia L1210/pathology ; Mice ; Ornithine Decarboxylase Inhibitors ; Putrescine/physiology ; Spermidine/analogs & derivatives/*physiology ; Structure-Activity Relationship
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2019-06-28
    Description: Data for evaluating the effects of moisture and temperature on the integrity of fiber composite components was gathered. In particular, the static and cyclic performance of three composite laminates containing flaws was investigated at room temperature and at 422 K (300 F) in wet and dry conditions.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-165213 , NAS 1.26:165213
    Format: application/pdf
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  • 3
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    In:  Other Sources
    Publication Date: 2019-07-13
    Description: An experimental program was carried out to investigate the effects of temperature and moisture on the damage development and fracture response of graphite/epoxy composites. Fracture response data were obtained for 20-ply laminates of different layup patterns for both room temperature and immediately after the application of a temperature transient causing the specimen to attain 150 C. It is found that elevated temperature degrades the notched strength of some laminates while not degrading others. The unnotched strength of all laminates tested at elevated temperatures was degraded. The effect of preloading on damage growth and moisture absorption, the effect of autoclave pressure during the laminate cure on fracture, and the variation of interlaminar shear properties with layup, moisture exposure, laminate material, and cure pressure are also discussed.
    Keywords: COMPOSITE MATERIALS
    Type: Symposium on Test methods and design allowables for fibrous composites; Oct 02, 1979 - Oct 03, 1979; Dearborn, MI
    Format: text
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  • 4
    Publication Date: 2019-07-13
    Description: The effects of moisture and temperature on the fatigue and fracture response of composite laminates under compression loads were investigated. The structural laminates studied were an intermediate stiffness graphite-epoxy composite (a typical angle ply laimna liminate had a typical fan blade laminate). Full and half penetration slits and impact delaminations were the defects examined. Results are presented which show the effects of moisture on the fracture and fatigue strength at room temperature, 394 K (250 F), and 422 K (300 F). Static tests results show the effects of defect size and type on the compression-fracture strength under moisture and thermal environments. The cyclic tests results compare the fatigue lives and residual compression strength under compression only and under tension-compression fatigue loading.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-168023 , NAS 1.26:168023 , D180-27619-1
    Format: application/pdf
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