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Seoul, South Korea

Jeong K.,Purdue University | Jeong K.,Korea Military Academy | Turek J.J.,Purdue University | Nolte D.D.,Purdue University
Journal of Biomedical Optics | Year: 2010

Dynamic speckle from 3-D coherence-gated optical sections provides a sensitive label-free measure of cellular activity up to 1 mm deep in living tissue. However, specificity to cellular functionality has not previously been demonstrated. In this work, we perform fluctuation spectroscopy on dynamic light scattering captured using coherence-domain digital holography to obtain the spectral response of tissue that is perturbed by temperature, osmolarity, and antimitotic cytoskeletal drugs. Different perturbations induce specific spectrogram response signatures that can show simultaneous enhancement and suppression in different spectral ranges. © 2010 Society of Photo- Optical Instrumentation Engineers.

Bae S.,Korea Advanced Institute of Science and Technology | Kim D.,Korea Military Academy | Lee W.,Korea Advanced Institute of Science and Technology
Applied Catalysis B: Environmental | Year: 2013

We demonstrated that diclofenac can be rapidly and completely oxidized in Fenton reaction system using pyrite as catalyst. The pH of the solution dropped from 5.7 to 4.1-3.2 with addition of different amounts of pyrite (0.5-4.0mM) as Fe(II) concentration increased to 0.07-0.52mM. Complete degradation (100%) of diclofenac was observed by pyrite Fenton system within 120s, while only 65% of diclofenac was removed by classic Fenton system in 180s. Degradation of diclofenac was significantly inhibited (100-51%) by addition of HO scavenger (t-butanol) but not by O2 - scavenger (chloroform), indicating that diclofenac was dominantly oxidized by HO produced during pyrite Fenton reaction. It was suggested that continuous dissolution of aqueous Fe(II) by pyrite Fenton reaction supported the complete degradation of diclofenac. The rate of diclofenac degradation increased as pyrite and H2O2 concentrations increased. 2,6-dichlorophenol, 2-chloroaniline, and 2-chlorophenol were detected as major intermediates but they were rapidly degraded in 120s. Chloride ions, ammonium, and total organic carbon measurements confirmed that diclofenac finally degraded to further oxidized forms (organic acids, HCl, and CO2). © 2012 Elsevier B.V.

Kim N.-J.,University of Missouri | Kim N.-J.,Korea Military Academy | Kwon J.-H.,Seoul National University | Kim M.,Seoul National University
Journal of Physical Chemistry C | Year: 2013

We investigated a self-assembly of conjugated polymer chains resulting in crystalline one-dimensional (1D) nanostructures with a high length-to-diameter aspect ratio. Conjugate polymer 1D nanostructures were obtained via a biphase interfacial polymerization method in which aniline monomers were oxidized by metal ions dissolved in aqueous solution. High-resolution transmission electron microscopy (TEM) analyses revealed polymer chains with remarkable π-electron interchain interactions intensive enough to form long crystalline nanowires and nanobelts, which have been difficult to obtain in conjugate polymer nanostructures. The remarkably uniform nanostructures along the long axis indicate the cooperative effects of chain-end oxidative polymerization and close-packing condensation (π-electron coupling) between linear chains and the prevention of random cross-linking and coiling of polymer chains. Electrical conductance along the polymer-chain direction of nanowires forming a long ribbon was estimated to be 46 kΩ via a four-probe measurement, suggesting that stable and partially oxidized polyaniline nanostructures can be produced in the presense of Au ions as effective electron acceptors. The resulting products may find potential uses in nanoelectronics and optoelectronic devices where highly uniform and oriented conducting channels are desired. © 2013 American Chemical Society.

Lee J.,Korea Military Academy | Kapitanova K.,University of Virginia | Son S.H.,University of Virginia
Computer Networks | Year: 2010

With the increased application of wireless sensor networks (WSNs) to military, commercial, and home environments, securing the data in the network has become a critical issue. Several security mechanisms, such as TinySec, have been introduced to address the need for security in WSNs. The cost of security, however, still mostly remains an unknown variable. To provide a better understanding of this cost we have studied three aspects of WSNs security: encryption algorithms, modes of operation for block ciphers, and message authentication algorithms. We have measured and compared their memory and energy consumption on both MicaZ and TelosB sensor motes. The results of our experiments provide insight into the suitability of different security algorithms for use in WSN environments and could be used by WSN designers to construct the security architecture of their systems in a way that both satisfies the requirements of the application and reasonably uses the constrained sensor resources. © 2010 Elsevier B.V. All rights reserved.

Ko S.-G.,University of Southern California | Lee T.-H.,Korea Military Academy | Yoon H.-Y.,Korea University | Kwon J.-H.,Korea University | Mather M.,University of Southern California
Psychology and Aging | Year: 2011

People from Asian cultures are more influenced by context in their visual processing than people from Western cultures. In this study, we examined how these cultural differences in context processing affect how people interpret facial emotions. We found that younger Koreans were more influenced than younger Americans by emotional background pictures when rating the emotion of a central face, especially those younger Koreans with low self-rated stress. In contrast, among older adults, neither Koreans nor Americans showed significant influences of context in their face emotion ratings. These findings suggest that cultural differences in reliance on context to interpret others' emotions depend on perceptual integration processes that decline with age, leading to fewer cultural differences in perception among older adults than among younger adults. Furthermore, when asked to recall the background pictures, younger participants recalled more negative pictures than positive pictures, whereas older participants recalled similar numbers of positive and negative pictures. These age differences in the valence of memory were consistent across culture. © 2010 American Psychological Association.

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