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JW Lee

Publications and source records attributed to JW Lee.

6 recordsLinked to original sources
PubMed2000

Finite-size effects of two-particle diffusion-limited reactions

We have studied the finite-size effects of two-particle diffusion-limited reaction A+B-->0, on a one-dimensional lattice using the Monte Carlo method. The density at a finite lattice follows a power law, C(t) approximately t(-x) below the crossover time, and shows an exponential decay above the crossover time. The crossover time depends on the lattice size and the bias field. We found second-order correction terms of the density decay as C(t) approximately t(-1/4)[1+O(t(-1/8))] for the isotropic diffusion of particles and C(t) approximately t(-1/3)[1+O(t(-1/24))] for the maximum drift. We proposed the scaling function of the density given as C(t) approximately L(-1/2)f(o)(t/L(2))+L(-3/4)f(1)(t/L(2)) for the isotropic diffusion and C(t) approximately L(-1/2)f(o)(t/L(3/2))+L(-9/16)f(1)(t/L(3/2)) for the maximum drift where f(o) and f(1) are scaling functions.

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PubMed1998

Interaction of Different Types of Cells on Polymer Surfaces with Wettability Gradient.

Gradient surfaces whose properties are changed gradually along the sample length are of particular interest for basic studies of the interaction between biological species and surfaces since the effect of a selected property can be examined in a single experiment on one surface. We prepared a wettability gradient on low density polyethylene (PE) sheets by treating them in air with the corona from a knife-type electrode whose power increases gradually along the sample length. The PE surfaces oxidized gradually with the increasing corona power, and the wettability gradient was created on the surfaces as evidenced by the measurement of water contact angles, Fourier transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. The wettability gradient surfaces prepared were used to investigate the interaction of different types of cells (Chinese hamster ovary, fibroblast, and endothelial cells) as well as serum proteins in terms of the surface hydrophilicity/hydrophobicity of polymeric materials. The cells adhered and grown on the gradient surface along the sample length were counted and observed by scanning electron microscopy. It was observed that the cells were adhered, spread, and grown more onto the positions with moderate hydrophilicity of the wettability gradient surface than onto the more hydrophobic or hydrophilic positions. The maximum adhesion and growth of the cells appeared at around water contact angles of 55 degrees, regardless of the cell types used. This result seems closely related to the serum protein adsorption on the surfaces; the serum proteins were also adsorbed more onto the positions with moderate hydrophilicity of the wettability gradient surface. Copyright 1998 Academic Press.

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PubMed1998

Cross-Cultural Variations in Probability Judgment Accuracy: Beyond General Knowledge Overconfidence?

Previous studies have revealed surprising and persistent cross-cultural variations in overconfidence, whereby respondents in some Asian cultures (e.g., Chinese) exhibit markedly higher degrees of overconfidence than respondents in other cultures (e.g., in the United States and Japan). Most of those demonstrations have entailed general knowledge tasks (e.g., answering questions such as whether Europe is larger than Australia). The present studies sought to determine whether such cross-cultural variations extend to judgments about the kinds of events that bear upon more common practical decisions and to aspects of accuracy other than overconfidence. Subjects in Taiwan, Japan, and the United States made probabilistic differential diagnoses of fictional diseases in a stochastic artificial ecology. Results revealed that previously observed cross-cultural variations do indeed generalize. The data were also informative about several potential accounts for such variations, e.g., arguing against a proposal that they rest on different emphases on discrimination rather than calibration, but consistent with the influences of culture-specific cognitive customs, including responsiveness to explicitly displayed information, regardless of its presumed validity. Copyright 1998 Academic Press.

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PubMed1997

Rheology and Dynamics of Water-in-Oil Emulsions under Steady and Dynamic Shear Flow

The fundamental aspects governing the rheology of water-in-oil emulsions, such as viscosity ratio and morphology were considered. The model developed here is based on the early work of Pal and Rhodes (1989) for viscosity equation, combined with the theory of Lee and Park (1994) for the morphological contributions. Thus, the proposed conception enables us to predict not only the degree of flocculation but also viscosity ratio and morphological effects. The contribution of secondary morphology caused by the flocculation of droplets on the viscosity of dispersed emulsions has been found by using the factor, -alpha'q'xy/gamma; (where alpha' is the interfacial tension, q'xy is xy-component of anisotropy tensor, and gamma; is shear rate). However, this approach is only useful for system below the maximum random packing concentration. Experimentally, the bulk rheological properties have been examined under steady and dynamic shear flow to investigate the structure of emulsion. The flocculation-deflocculation transition was observed during the shear rate sweep, resulting in instant dilatancy of viscosity near the critical shear rate gamma; approximately 100 s-1.

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PubMed1996

Oxygenic Photoautotrophic Growth Without Photosystem I

Contrary to the prediction of the Z-scheme model of photosynthesis, experiments demonstrated that mutants of Chlamydomonas containing photosystem II (PSII) but lacking photosystem I (PSI) can grow photoautotrophically with O2 evolution, using atmospheric CO2 as the sole carbon source. Autotrophic photosynthesis by PSI-deficient mutants was stable both under anaerobic conditions and in air (21 percent O2) at an actinic intensity of 200 microeinsteins per square meter per second. This PSII photosynthesis, which was sufficient to support cell development and mobility, may also occur in wild-type green algae and higher plants. The mutants can survive under 2000 microeinsteins per square meter per second with air, although they have less resistance to photoinhibition.

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