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Search Results: 1 - 10 of 515936 matches for " M. H. Lee "
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Low molecular fucoidan and its macromolecular complex with bee venom melittin  [PDF]
G. T. Mavlonov, J. M Lee, Lee Shin, T. H. Yi, I. Y. Abdurakhmonov
Advances in Bioscience and Biotechnology (ABB) , 2011, DOI: 10.4236/abb.2011.24043
Abstract: Low molecular weight (LMW) fucoidan, obtained by free radical depolymerization of high molecular polysaccharide extract of brown algae Hizikia fusiformis, was complexed with HPLC purified bee venom melittin. Water soluble form of the LMW fucoidan – melittin complex shows increased anti-inflammatory activity, inhibiting the production of nitric oxide in murine macrophage cell line Raw 264.7. The LMW fucoidan:melitin complex obtained in this study showed good biological activities, resulting in 2-fold reduction of the melittin toxicity. The fucoidan: melittin macromolecular complex obtained should be useful in future therapeutic applications.
Optimal Estimates for the Electric Field in Two-Dimensions
H. Ammari,H. Kang,H. Lee,J. Lee,M. Lim
Mathematics , 2006,
Abstract: The purpose of this paper is to set out optimal gradient estimates for solutions to the isotropic conductivity problem in the presence of adjacent conductivity inclusions as the distance between the inclusions goes to zero and their conductivities degenerate. This difficult question arises in the study of composite media. Frequently in composites, the inclusions are very closely spaced and may even touch. It is quite important from a practical point of view to know whether the electric field (the gradient of the potential) can be arbitrarily large as the inclusions get closer to each other or to the boundary of the background medium. In this paper, we establish both upper and lower bounds on the electric field in the case where two circular conductivity inclusions are very close but not touching. We also obtain such bounds when a circular inclusion is very close to the boundary of a circular domain which contains the inclusion. The novelty of these estimates, which improve and make complete our earlier results published in Math. Ann., is that they give an optimal information about the blow-up of the electric field as the conductivities of the inclusions degenerate.
Evolution of Multi-mass Globular Clusters in Galactic Tidal Field with the Effects of Velocity Anisotropy
K. Takahashi,H. M. Lee
Physics , 1999, DOI: 10.1046/j.1365-8711.2000.03594.x
Abstract: We study the evolution of globular clusters with mass spectra under the influence of the steady Galactic tidal field, including the effects of velocity anisotropy. Similar to single-mass models, velocity anisotropy develops as the cluster evolves, but the degree of anisotropy is much smaller than isolated clusters. Except for very early epochs of the cluster evolution, nearly all mass components become tangentially anisotropic at the outer parts. We have compared our results with multi-mass, King-Michie models. The isotropic King model better fits to the Fokker-Planck results because of tangential anisotropy. However, it is almost impossible to fit the computed density profiles to the multi-mass King models for all mass components. Thus if one attempts to derive global mass function based on the observed mass function in limited radial range using multi-mass King models, one may get somewhat erratic results, especially for low mass stars. We have examined how the mass function changes in time. Specifically, we find that the power-law index of the mass function decreases monotonically with the total mass of the cluster. This appears to be consistent with the behaviour of the observed slopes of mass functions for a limited number of clusters, although it is premature to compare quantitatively because there are other mechanisms in contributing the evaporation of stars from the clusters. The projected velocity profiles for anisotropic models with the apocenter criterion for evaporation show significant flattening toward the tidal radius compared to isotropic model or anisotropic model with the energy criterion. Such a behaviour of velocity profile appears to be consistent with the observed profiles of collapsed cluster M15.
Monte Carlo Studies of the Two-Dimensional Vortex Liquid: Absence of Transition and Dynamical Properties
H. H. Lee,M. A. Moore
Physics , 1993, DOI: 10.1103/PhysRevB.49.9240
Abstract: Monte Carlo simulations are performed to study the properties of type-II superconducting films in a magnetic field in which the vortices move in the two-dimensional geometry represented by the surface of a sphere. No numerical evidence is found for any melting transition, although the correlation length over which vortex crystalline order exists grows as the temperature is reduced. At low temperatures, the relaxation timescales are of an Arrhenius form which can be associated with the creation of dislocations of a size comparable to the correlation length.
Images and nonlocal vortex pinning in thin superfluid films
H. H. Lee,J. M. F. Gunn
Physics , 1998, DOI: 10.1103/PhysRevB.57.7892
Abstract: For thin films of superfluid adsorbed on a disordered substrate, we derive the equation of motion for a vortex in the presence of a random potential within a mean field (Hartree) description of the condensate. The compressible nature of the condensate leads to an effective pinning potential experienced by the vortex which is nonlocal, with a long range tail that smoothes out the random potential coupling the condensate to the substrate. We interpret this nonlocality in terms of images, and relate the effective potential governing the dynamics to the pinning energy arising from the expectation value of the Hamiltonian with respect to the vortex wavefunction.
Effect of Ethylene Carbonate (EC) Plasticizer on Poly (Vinyl Chloride)-Liquid 50% Epoxidised Natural Rubber (LENR50) Based Polymer Electrolyte  [PDF]
M. Y. A. Rahman, A. Ahmad, T. K. Lee, Y. Farina, H. M. Dahlan
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.27111
Abstract: In this research, new thin film of a free standing electrolyte film containing poly(vinyl) chloride (PVC), 50% liquid epoxidized natural rubber (LENR50), Ethylene carbonate (EC) blends as a host for the electrolyte which was doped with lithium perchlorate (LiClO4) as the dopant salt was successfully prepared with solution casting technique. The polymer electrolyte of PVC-LENR50-EC-LiClO4 was characterized using impedance spectroscopy (EIS), scanning electron microscopy (SEM) and Fourier transform infrared (ATR-FTIR). From the EIS results shows that electrolyte exhibited the highest ionic conductivity of 2.1 × 10–7 S●cm–1 at the 30 wt.% of LiClO4. The ionic conductivity result was supported by the morphological studies which revealed the good homogeneity of the PVC-LENR50-EC blends as no phase separation was observed. The smooth surface can ease the mobility of ions in the system complexes. In addition, the formation of micro-pores by introducing lithium salts to the electrolyte also improved the transportation properties of L+ ions in the electrolyte system and hence improving its ionic conductivity. The features of complexation of the electrolytes were studied by ATR-FTIR.
Investigation of diurnal patterns in vertical distributions of pollen in the lower troposphere using LIDAR technique
Y. M. Noh,H. Lee,D. Mueller,K. Lee
Atmospheric Chemistry and Physics Discussions , 2012, DOI: 10.5194/acpd-12-31187-2012
Abstract: The diurnal patterns in pollen vertical distributions in the lower troposphere were investigated by the LIDAR remote sensing technique. Meteorological and pollen concentration data was measured at the surface using a Burkard 7 day recording volumetric spore sampler. An aerosol extinction coefficient and depolarization ratio of 532 nm was obtained from LIDAR measurements in spring (4 May–2 June) 2009 in Gwagnju, Korea. Depolarization ratios from 0.08 to 0.14 were observed only in daytime (09:00–17:00 local time (LT)) during high pollen concentration days from 4 to 9 May. Vertical distributions in the depolarization ratio with time showed a specific diurnal pattern. Depolarization ratios, which varied from 0.08 to 0.14, were measured near the surface in the morning. High depolarization ratios were detected even up to 2.0 km between 12:00 and 14:00 LT but subsequently were observed only close to the surface after 17:00 LT. Low values of depolarization ratios (≤ 0.05) were detected after 18:00 LT until next morning. During the measurement period, the daily variations in the high depolarization ratios close to the surface showed good agreement with those in surface pollen concentrations, which implies that high depolarization ratios can be attributed to high pollen concentrations. The diurnal characteristics in high values of depolarization ratios were closely associated with turbulent transport, which can be caused by increasing temperature and wind speed and decreasing relative humidity. Continuously measured diurnal and vertical characteristics of pollen data can be further used to enhance the accuracy of the pollen-forecasting model via data assimilation studies.
Prevalence and impacts of poor sleep on quality of life and associated factors of good sleepers in a sample of older Chinese adults
Catherine M Lo, Paul H Lee
Health and Quality of Life Outcomes , 2012, DOI: 10.1186/1477-7525-10-72
Abstract: This cross-sectional study used convenience sampling and gathered data during face-to-face interviews. Older community-dwelling individuals (n?=?301) were recruited in community centres in 2010. The Pittsburgh Sleep Quality Index and Medical Outcomes Study Short Form-36 were used to measure sleep quality and health-related quality of life. The Medical Outcomes Study Short Form-36 domain scores were compared between good and bad sleepers and between long and short sleepers using Hotelling’s?T-Square test. SF-36 domain scores were placed into a logistic regression model that controlled for significant demographic variables (gender, educational level, perceived health).Most (77.7%) participants were poor sleepers. Participants who had global Pittsburgh Sleep Quality Index scores <5 and slept ≥5.5?h/night had better health-related quality of life. Vitality, emotional role, physical functioning, and bodily pain domain scores were associated factors of good sleepers in different age groups.This study found a strong negative association between sleep deprivation (poor quality, short duration) and health-related quality of life. Associated factors for good sleep quality in later life differ among age groups in relation to universal age-related changes, and should be addressed by social policies and health-care programmes.
Predictions of rainfall-runoff response and soil moisture dynamics in a microscale catchment using the CREW model
H. Lee, E. Zehe,M. Sivapalan
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2007,
Abstract: Predictions of catchment hydrology have been performed generally using either physically based, distributed models or conceptual lumped or semi-distributed models. In recognition of the disadvantages of using either of these modeling approaches, namely, detailed data requirements in the case of distributed modeling, and lack of physical basis of conceptual/lumped model parameters, Reggiani et al. (1998, 1999) derived, from first principles and in a general manner, the balance equations for mass, momentum and energy at what they called the Representative Elementary Watershed (or REW) scale. However, the mass balance equations of the REW approach include mass exchange flux terms which must be defined externally before their application to real catchments. Developing physically reasonable "closure relations" for these mass exchange flux terms is a crucial pre-requisite for the success of the REW approach. As a guidance to the development of closure relations expressing mass exchange fluxes as functions of relevant state variables in a physically reasonable way, and in the process effectively parameterizing the effects of sub-grid or sub-REW heterogeneity of catchment physiographic properties on these mass exchange fluxes, this paper considers four different approaches, namely the field experimental approach, a theoretical/analytical approach, a numerical approach, and a hybrid approach combining one or more of the above. Based on the concept of the scaleway (Vogel and Roth, 2003) and the disaggregation-aggregation approach (Viney and Sivapalan, 2004), and using the data set from Weiherbach catchment in Germany, closure relations for infiltration, exfiltration and groundwater recharge were derived analytically, or on theoretical grounds, while numerical experiments with a detailed fine-scale, distributed model, CATFLOW, were used to obtain the closure relationship for seepage outflow. The detailed model, CATFLOW, was also used to derive REW scale pressure-saturation (i.e., water retention curve) and hydraulic conductivity-saturation relationships for the unsaturated zone. Closure relations for concentrated overland flow and saturated overland flow were derived using both theoretical arguments and simpler process models. In addition to these, to complete the specification of the REW scale balance equations, a relationship for the saturated area fraction as a function of saturated zone depth was derived for an assumed topography on the basis of TOPMODEL assumptions. These relationships were used to complete the specification of all of the REW-scale governing equations (mass and momentum balance equations, closure and geometric relations) for the Weiherbach catchment, which are then employed for constructing a numerical watershed model, named the Cooperative Community Catchment model based on the Representative Elementary Watershed approach (CREW). CREW is then used to carry out sensitivity analyses with respect to various combinations of climate, soil,
Pattern, process, and function in landscape ecology and catchment hydrology – how can quantitative landscape ecology support predictions in ungauged basins?
E. Zehe, H. Lee,M. Sivapalan
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2006,
Abstract: In this study we propose an uspcaling approach to derive time series of (a) REW scale state variables, and (b) effective REW scale soil hydraulic functions to test and parameterise models based on the REW approach. To this end we employed a physically based hydrological model, that represents the typical patterns and structures in the study catchment, and has previously been shown to reproduce observed runoff response and state dynamics well. This landscape- and process-compatible model is used to simulate numerical drainage and wetting experiments. The effective soil water retention curve and soil hydraulic conductivity curve are derived using the spatially averaged saturation and capillary pressure as well as averaged fluxes. When driven with observed boundary conditions during a one year simulation the model is used to estimate how the spatial pattern of soil moisture evolved during this period in the catchment. The time series of the volume integrated soil moisture is deemed as best estimate for the average catchment scale soil moisture. The approach is applied to the extensively monitored Weiherbach catchment in Germany. A sensitivity analysis showed that catchment scale model structures different from the landscape- and process compatible one yielded different times series of average catchment scale soil moisture and where not able to reproduce the observed rainfall runoff response. Hence, subscale typical heterogeneity leaves a clear fingerprint in the time series of average catchment scale saturation. In case of the Weiherbach catchment local scale heterogeneity of ks could be neglected and a simple representation of the typical hillslope scale patterns of soil types and macroporosity was sufficient for obtaining effective REW scale soil hydraulic functions. Both the effective soil hydraulic functions and time series of catchment scale saturation turned out to be useful to parameterise and test the CREW model, which is based on the REW approach and was applied to the Weiherbach catchment in a companion study Lee et al. (2006, this issue).
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