S. S. Lee

Enhancement of magnetoresistance in [Pd∕Co]N∕Cu∕Co∕[Pd∕Co]N∕FeMn spin valves

The dependences of the stack number and Co and Cu thicknesses on magnetoresistance, and perpendicular exchange biasing in the [Pd∕Co]×N1∕Cu∕Co∕[Pd∕Co]×N2∕FeMn spin valves, were investigated. The magnetoresistance ratio of the spin valves with N1=4 and N2=2 was above 5% for the Cu between 1.5 and 2.5nm, and the exchange-biasing field (Hex) was increased to 600Oe. When the Co thickness over the Cu layer was increased from 0.48to1.28nm, the ratio likewise rose to 7.4% due to the strengthened spin-dependent scattering effect. Moreover, the Co thickness below the Cu layer rose to 9.1%. The maximum ratio of 10.2% was obtained in the structure of the [Pd0.8∕Co0.32]×2∕Pd0.8∕CoFe0.48∕Cu2.25∕CoFe0.6∕[Pd0.8∕Co0.48]×2∕FeMn15 (nanometer) multilayer with Hex=450Oe.

Mathematical Modeling of Vibrio vulnificus Infection in Korea and the Influence of Global Warming

Objectives To investigate the possible link between Vibrio vulnificus population size in seawater and water temperature. Methods We collected incidence and water temperature data in coastal regions of Korea and constructed a mathematical model that consisted of three classes; susceptible fish, infected fish available to humans, and infected humans. Results We developed a mathematical model to connect V. vulnificus incidence with water temperature using estimated bacterial population sizes and actual coastal water temperatures. Conclusion Increased V. vulnificus population sizes in marine environments may increase the risk of infection in people who eat at coastal restaurants in Korea. Furthermore, we estimated the near-future number of infected patients using our model, which will help to establish a public-health policy to reduce the disease burden.

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

In this study, the effects of pulsed electromagnetic field stimulation with a strong magnetic field on rat basophilic leukemia (RBL-2H3) cells were investigated to confirm the efficacy of the magnetic stimulator for biomedical applications. The maximum intensity of the magnetic field generated from the stimulation coil was 0.203 T, and the transition time was 126u2002μs. The oscillation time and frequency of the pulsed field were almost 0.1 ms and 8 kHz, respectively. The cell count as well as the mRNA expression and DNA sequence of the cytokine genes, such as the tumor necrosis factor-α (TNF-α) and interleukin-4 (IL-4), of the stimulated RBL-2H3 cells were analyzed with a hemocytometer and via reverse transcriptase polymerase chain reaction to determine the physiological response under a strong pulse field. After 12 h stimulation, cell death was observed at an increasing scale with the increase in the stimulation time. On the other hand, the cells that were stimulated for 10 min almost doubled as the interva...

Thermal stability of perpendicular exchange bias in [Pd/Ferromagnet] N /FeMn films

The dependencies of the annealing temperature and the stack number ,N on perpendicular exchange-biasing(H_ex) and coercivity(H_c) in |Pd/Co|_N and |Pd/Co (or CoFe)l_N/FeMn multilayers were investigated. The surface anisotropy was varied as a function of N with constant bulk anisotropy. It was found that H_ex does not depend on the surface anisotropy, while H_c shows a strong dependence. Therefore, it is possible to tailor wide ranges of the H_c (300 ~ 600 Oe) without varying H_ex(250 ~ 300 Oe) through the single control parameter stack number N. After annealing the H_c shows peak value at 350degC in |Pd/Co] multilayers without FeMn, but the peak temperature is down to 250degC for the exchange biased |Pd/F]_N/FeMn samples.

Local magnetization reversal of perpendicular exchange-biased multilayers by laser annealing

Partial magnetization reversal of perpendicular exchange biasing in [Pd/Colx5/FeMn multilayer with a perpendicular anisotropy using laser annealing was studied. The reversed hysteresis loop in the (Pd/Colx5/FeMn multilayer was shifted to opposite magnetic field as the laser power increases. The partial magnetization reversal of the laser-annealed multilayers was confirmed by the hysteresis loop, measured along the various positions from laser spot using MOKE. In the case of [Pd/Co]x2/Cu/[Pd/Co|x2/FelVln spin-valves Film, the reversal of magnetization was gradually increased as the illuminated region of laser annealing expands.