Biomedical subjects

JR Lee

Publications and source records attributed to JR Lee.

13 recordsLinked to original sources

PubMed2000

Effect of Fiber-Polymer Interactions on Fracture Toughness Behavior of Carbon Fiber-Reinforced Epoxy Matrix Composites.

The effect of anodic oxidation on high-strength polyacrylonitrile-based carbon fibers has been studied in terms of fiber surface energetics and fracture toughness of the composites. According to contact angle measurements based on the wicking rate of a test liquid, anodic oxidation leads to an increase in surface free energy, mainly due to the increase of its specific (or polar) component. For the carbon-fiber-reinforced epoxy resin matrix system, a direct linear relationship is shown between the specific component and the critical stress intensity factor measured by the single edge notched beam fracture toughness test. From a surface-energetic point of view, the anodic treatment may be suitable for carbon fibers incorporated in a polar organic matrix, resulting in an increased specific component of the surface free energy. Good wetting plays an important role in improving the degree of adhesion at interfaces between fibers and matrices of the resulting composites. Copyright 2000 Academic Press.

Journal Article↗

PubMed1999

Dispersive Stabilization of Liquid Crystal-in-Water with Acrylamide Copolymer/Surfactant Mixture: Nematic Curvilinear Aligned Phase Composite Film.

The effect of nonionic surfactant, (H(OCH(2)-CH(2))(8)-OC(6)H(4)-C(9)H(19)), on the dispersion stabilization of liquid crystal (LC)-in-water with acrylamide copolymer containing the related nonylphenyl groups was studied. It was observed that the addition of nonionic surfactant increases the stability of LC dispersions and improves the electrooptical properties of the nematic curvilinear aligned phase (NCAP) composite film. On the basis of the surface tension, reduced viscosity, cloud point, and coalescence time measurements, it was proposed that formation of an integrated structure induced by interactions between hydrophobic groups in the polymer chains is probably important to fabrication of a polymer composite film made of LC and polymer matrix. Copyright 1999 Academic Press.

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PubMed1998

Stabilization of Liquid Crystal-in-Water Dispersion with Polymer/Surfactant Mixture: Nematic Curvilinear Aligned Phase Composite Film

The effect of nonionic surfactant (H(OCH2-CH2)8-OC6H4-C9H19) on the stability of liquid crystal-in-water dispersions stabilized by copolymers of acrylamide with hydrophobic monomers have been studied. It was observed that the addition of surfactant increases the stability of liquid crystal (LC) dispersion and improves the electrooptical properties of the nematic curvilinear aligned phase (NCAP) system. According to the interfacial tension measurements, it was proposed that the presence of surfactant allows to form the nonpolar microenvironment in the round of LC droplet and finally reduces the anchoring effect between LC and the polymeric wall. Copyright 1998 Academic Press. Copyright 1998Academic Press

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PubMed1997

Perceptions of Species Abundance, Distribution, and Diversity:Lessons from Four Decades of Sampling on a Government-Managed Reserve

/ We examined data relative to species abundance, distribution, anddiversity patterns of reptiles and amphibians to determine how perceptionschange over time and with level of sampling effort. Location data werecompiled on more than one million individual captures or observations of 98species during a 44-year study period on the US Department of Energy's(DOE) Savannah River Site National Environmental Research Park (SRS-NERP) inSouth Carolina. We suggest that perceptions of herpetofaunal speciesdiversity are strongly dependent on level of effort and that land managementdecisions based on short-term data bases for some faunal groups could resultin serious errors in environmental management. We provide evidence thatacquiring information on biodiversity distribution patterns is compatiblewith multiyear spatially extensive research programs and also provide aperspective of what might be achieved if long-term, coordinated researchefforts were instituted nationwide.To conduct biotic surveys on government-managed lands, we recommend revisionsin the methods used by government agencies to acquire and report biodiversitydata. We suggest that government and industry employees engaged inbiodiversity survey efforts develop proficiency in field identification forone or more major taxonomic groups and be encouraged to measure the status ofpopulations quantitatively with consistent and reliable methodologies. Wealso suggest that widespread academic cooperation in the dissemination ofinformation on regional patterns of biodiversity could result byestablishment of a peer-reviewed, scientifically rigorous journal concernedwith status and trends of the biota of the United States. KEY WORDS: Abundance; Amphibian; Biodiversity; Distribution; Landmanagement; Reptile

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PubMed1996