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Your search keyword '"Lee S.S."' showing total 8 results
Start Over Author "Lee S.S." Topic physics
8 results on '"Lee S.S."'

1. Nonlinear Transfer Entropy to Assess the Neurovascular Coupling in Premature Neonates

Author

Hendrikx, D, Thewissen, L, Smits, A, Naulaers, G, Allegaert, Karel, Van Huffel, S, Caicedo, A, Ryu, P.D., LaManna, J., Harrison, D., Lee, S.S., Pediatrics, and Pediatric Surgery

Subjects
Physics, medicine.diagnostic_test, Linear model, Blood flow, Oxygenation, Electroencephalography, Coupling (electronics), 03 medical and health sciences, Nonlinear system, 0302 clinical medicine, medicine, Transfer entropy, sense organs, 030212 general & internal medicine, Neurovascular coupling, Neuroscience
Abstract

In the adult brain, it is well known that increases in local neural activity trigger changes in regional blood flow and, thus, changes in cerebral energy metabolism. This regulation mechanism is called neurovascular coupling (NVC). It is not yet clear to what extent this mechanism is present in the premature brain. In this study, we explore the use of transfer entropy (TE) in order to compute the nonlinear coupling between changes in brain function, assessed by means of EEG, and changes in brain oxygenation, assessed by means of near-infrared spectroscopy (NIRS). In a previous study, we measured the coupling between both variables using a linear model to compute TE. The results indicated that changes in brain oxygenation were likely to precede changes in EEG activity. However, using a nonlinear and nonparametric approach to compute TE, the results indicate an opposite directionality of this coupling. The source of the different results provided by the linear and nonlinear TE is unclear and needs further research. In this study, we present the results from a cohort of 21 premature neonates. Results indicate that TE values computed using the nonlinear approach are able to discriminate between neonates with brain abnormalities and healthy neonates, indicating a less functional NVC in neonates with brain abnormalities.

Published
2020

2. Bottom IrMn-based spin valves by using oxygen surfactant

Author

Hwang, J.Y., Kim, M.Y., Rhee, J.R., Lee, S.S., Hwang, D.G., Kim, J.K, Lee, S.H, and Yu, S.C.

Subjects
Magnetoresistance -- Research, Surface active agents -- Usage, Metallic elements -- Magnetic properties, Nonferrous metals -- Magnetic properties, Physics
Abstract

The specularity of bottom IrMn-based spin valve (SV) with structure Ta/NiFe/IrMn/CoFe/oxidation/CoFe/Cu/CoFe/Ta was examined through exposure of part of the CoFe pinned layer to different O2 flows. The magnetoresistance ratio enhancement coupled with the lower interlayer coupling field, sheet resistance and magnetic moment of the specular SV is attributed to an enhanced specular scattering as a result of smoother interfaces after O2 exposures.

Published
2003

3. Effect of uniaxial anisotropy on anisotropic magnetoresistance: thickness dependence in bilayer NiO(30 nm)/NiFe(t)

Author

Kim, D.Y., Kim, C.G., Park, B.S., Hwang, D.G., and Lee, S.S.

Subjects
Thin films -- Magnetic properties, Thin films, Multilayered -- Research, Physics
Abstract

The anisotropy field H(sub K) and angle gamma from exchange coupling field in an anisotropic magnetoresistance sample is studied using a single domain model. Magnetoresistance profiles obtained at magnetizing angle theta = 0 degrees and 90 degrees from the exchange coupling show that H(sub K) in bilayer NiO(30nm)/NiFe(t) changes from positive to negative with increasing NiFe thickness. The anisotropy field and angle gamma also exhibit minimum values at the transition thickness.

Published
1999

4. In vitro stimulation with a strongly pulsed electromagnetic field on rat basophilic leukemia cells

Author

Choi, J.W., Shin, S.C., Kim, S., Chung, E.R., Bang, J.H., Cho, G.I., Choi, S.D., Park, Y.S., Jang, T.S., Yoo, Y.M., Lee, S.S., and Hwang, D.G.

Subjects
Biomagnetism -- Analysis, Electromagnetic fields -- Analysis, Leukemia -- Physiological aspects, Leukemia -- Genetic aspects, Physics
Abstract

Several in vitro simulation studies are conducted to explain the effects of pulsed electromagnetic field on the functioning of the rat basophilic leukemia cells. An increase in the simulation time is shown to lead to faster death of the cells of the species.

Published
2010

5. Determination of rotatable anisotropy in exchange-biased bilayers using anisotropic magnetoresistance technique

Author

Kim, J.K., Kim, S.W., Lee, K.A., Kim, B.K., Kim, J.H., Lee, S.S, Hwang, D.G., Kim, C. G., and Kim, C.O.

Subjects
Anisotropy -- Research, Nickel -- Magnetic properties, Manganese -- Magnetic properties, Iron compounds -- Magnetic properties, Magnetoresistance -- Research, Physics
Abstract

The anisotropic magnetoresistance (AMR) model is improved in order to determine the quality and direction of rotatable anisotropy in FeMn/NiFe structures independent of the thickness of the antiferromagnet layer. The properties of the rotatable anisotropies due to unstable antiferromagnet (AF) grains can be explained with the help of the values of two important parameters, magnitude and direction.

Published
2003

6. Effects of in situ magnetic field application and postdeposition magnetic annealing on sputtered Ni80Fe20/Fe50Mn50/Ni80Fe20 trilayers

Author

Chen, F.H., Ng, V., Adeyeye, A.O., Lee, J.Y., Rhee, J.R., Hwang, D.G., and Lee, S.S.

Subjects
Iron compounds -- Magnetic properties, Nickel -- Magnetic properties, Magnetic fields -- Research, Physics
Abstract

Effects of in situ magnetic field and/or postdeposition magnetic annealing on the properties of Ni80Fe20/Fe50Mn50/Ni80Fe20 trilayer structure are discussed. The annealing in the case has produced more grains with reversible moments than irreversible moments.

Published
2003

7. Mn diffusion effect in the exchange biased NiFe/FeMn/NiFe trilayers

Author

Kim, S.W., Kim, J.K., Kim, J.H., Kim, B.K., Lee, J.Y., Rhee, J.R., Hwang, D.G., and Lee, S.S.

Subjects
Iron compounds -- Research, Nickel -- Research, Manganese -- Research, Physics
Abstract

Fabrication of NiFe/Mn/FeMn/Mn/NiFe multilayers using an ion-beam deposition system is done to study the diffusion effect of the inserted Mn on exchange biasing. The abnormal tendency of bottom interface is explained by Mn atoms diffusing into the FeMn layer during film growth from XRD and AES results.

Published
2003

8. Magnetoresistance and morphology in magnetic multilayers by insertion of very thin Fe, Co layers.

Author

Hwang, D.G., Lee, S.S., Lee, K.A., Park, C.M., Kim, M.Y., Choi, K.R., Choi, S.J., Lee, Y.H., and Rhee, J.R.

Subjects
*IRON alloys, *MAGNETORESISTANCE, *COBALT alloys, *MAGNETIC multilayers, *METALLIC thin films, *MAGNETIC properties of thin films
Abstract

Dependences of magnetoresistance and morphology upon the insertion of very thin magnetic layers at interfaces between magnetic and nonmagnetic layers in Co/Cu and Ni/sub 81/Fe/sub 19//Cu multilayers have been investigated. The Co/Cu multilayers with inserted Fe thickness of 0.5/spl sim/1.0 /spl Aring/ have the MR ratio of about 18% more than the noninserted multilayers, and the MR ratio in the NiFe/Cu multilayers with inserted Co of thickness of 3 /spl Aring/ was found to be significantly increased. These results can be explained by the enhanced interlayer antiferromagnetic coupling and spin-dependent scattering phenomena at the interface. Of particular interest, the "Clustered out-growth" in the surface morphology of these multilayers was observed. [ABSTRACT FROM PUBLISHER]

Published
1996
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