Conservation Activities on Korean Rare and Endemic Plants -with a Special Reference to the Korea National Arboretum

Symposium Pape

Nanomechanical properties of hydrated organic thin films

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.Includes bibliographical references (leaves 167-171).Hydrated organic thin films are biological or synthetic molecularly thin coatings which impart a particular functionality to an underlying substrate and which have discrete water molecules associated with them. Such films exist in biology (e.g. cell membrane lipid bilayers) and have a broad array of potential engineering applications (e.g. biological implant and sensor surfaces, marine antifouling paints etc.). This doctoral thesis focuses on two important classes of hydrated organic thin films that were prepared and studied in vitro. The first model system was an oligo(ethylene oxide)-based self-assembling monolayer (OEO-SAM) which is a synthetic material that is known to exhibit exceptional resistance to nonspecific protein adsorption and, hence, it is a viable candidate for producing implant surfaces with improved biocompatibility. The second model system was the biologically relevant phosphorylcholine(PC)-supported lipid layer which mimics the structure of the cell membrane. The objective of this doctoral thesis was to quantify the functional form of the net surface interaction (force versus separation distance, F(D)), as well as the contact mechanical properties (e.g. elasticity, plasticity, fracture) of these two model systems under different solution conditions, in order to formulate a hypothesis for the molecular origins of the dominant interactions and furthermore, to gain a mechanistic understanding of their in vivo function and performance. For the OEO-SAMs, F(D) was found to exhibit the maximum monotonic repulsive functional form for intermediate surface packing densities (-70%) on loading (approach) and negligible adhesion (Fadhesion<0.3nN) on unloading (retract). Both were attributed to an electrostatic component arising from a dipole induced effective surface charge, as well as a nm-thick hydrated water layer.(cont.) For the PC lipid layers, the effect of length scale on the yield threshold force, Fy, was studied by varying the probe tip end radius, Rtip, used for the surface force measurements. Fy decreased by 20x (Force/Radius) as Rtip increased from 30 nm to 80 nm, presumably due to the fact that the contact area possessed an increased density of molecular-level defects, thereby causing stress concentrations and a reduction in mechanical stability of the layer.by Jae Hyeok Choi.Ph.D

Effect of a Non-Newtonian Load on Signature S

The quartz crystal microbalance (QCM) is increasingly used for monitoring the interfacial interaction between surfaces and macromolecules such as biomaterials, polymers, and metals. Recent QCM applications deal with several types of liquids with various viscous macromolecule compounds, which behave differently from Newtonian liquids. To properly monitor such interactions, it is crucial to understand the influence of the non-Newtonian fluid on the QCM measurement response. As a quantitative indicator of non-Newtonian behavior, we used the quartz resonator signature, S2, of the QCM measurement response, which has a consistent value for Newtonian fluids. We then modified De Kee’s non-Newtonian three-parameter model to apply it to our prediction of S2 values for non-Newtonian liquids. As a model, we chose polyethylene glycol (PEG400) with the titration of its volume concentration in deionized water. As the volume concentration of PEG400 increased, the S2 value decreased, confirming that the modified De Kee’s three-parameter model can predict the change in S2 value. Collectively, the findings presented herein enable the application of the quartz resonator signature, S2, to verify QCM measurement analysis in relation to a wide range of experimental subjects that may exhibit non-Newtonian behavior, including polymers and biomaterials

Reversible cerebral vasoconstriction syndrome without typical thunderclap headache: highresolution magnetic resonance imaging features

Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by sudden onset severe headache with or without focal neurologic deficits and is accompanied by segmental or multifocal intracranial arterial vasospasms that resolve within 3 months. The typical RCVS has thunderclap headache but patients with RCVS without this type of headache have been reported. Herein we introduce an unusual case of RCVS without thunderclap headache, together with typical high-resolution magnetic resonance imaging (HR-MRI) features of RCVS showing the possible mechanisms of this condition. The present case suggests that HR-MRI features like dynamic negative remodeling but no enhancement may be a suspicious sign for RCVS, especially in cases with atypical presentation. HR-MRI can be helpful in direct visualization of the vasoconstriction of RCVS and differential diagnosis of other diseases, possibly even without serial examinations. Further research should be performed to test the diagnostic accuracy of HR-MRI in patients with RCVS

Transparent actuator made with few layer graphene electrode and dielectric elastomer, for variable focus lens

A transparent dielectric elastomer actuator driven by few-layer-graphene (FLG) electrode was experimentally investigated. The electrodes were made of graphene, which was dispersed inN-methyl-pyrrolidone. The transparent actuator was fabricated from developed FLG electrodes.The FLG electrode with its sheet resistance of 0.45 kΩ/sq (80 nm thick) was implemented to mask silicone elastomer. The developed FLG-driven actuator exhibited an optical transparency of over 57% at a wavenumber of 600 nm and produced bending displacement performance ranging from 29 to 946 μm as functions of frequency and voltage. The focus variation was clearly demonstrated under actuation to study its application-feasibility in variable focus lens and various opto-electro-mechanical devices

Letter of Intent: Search for sub-millicharged particles at J-PARC

We propose a new experiment sensitive to the detection of millicharged particles produced at the $30$ GeV proton fixed-target collisions at J-PARC. The potential site for the experiment is B2 of the Neutrino Monitor building, $280$ m away from the target. With $\textrm{N}_\textrm{POT}=10^{22}$, the experiment can provide sensitivity to particles with electric charge $3\times10^{-4}\,e$ for mass less than $0.2$ $\textrm{GeV}/\textrm{c}^2$ and $1.5\times10^{-3}\,e$ for mass less than $1.6$ $\textrm{GeV}/\textrm{c}^2$. This brings a substantial extension to the current constraints on the charge and the mass of such particles

Polyphenolic compounds, antioxidant and anti-inflammatory effects of <i>Abeliophyllum distichum</i> Nakai extract

The present study was conducted to evaluate the antioxidant and anti-inflammatory activities of crude methanolic extract of Abeliophyllum distichum Nakai, and those of its partitioned fractions, including hexane, ethyl acetate, n-butanol, and aqueous. The antioxidant activities were analyzed by DPPH free radical scavenging and oxygen radical antioxidant capacity assay. Results showed that the BuOH fraction possessed a strong antioxidant activity through a hydrogen atom transfer reaction-based mechanism and a single electron transfer reaction-based mechanism. In lipopolysaccharide (LPS)-stimulated RAW 264.7 cells, the BuOH fraction of A. distichum methanol extract exhibited a strong inhibitory effect on the nitric oxide production and inhibited the expression of pro-inflammatory mediators, including COX-2, TNF-α, and IL-6, through the inhibition of the MEK/ERK signaling pathway. In addition, the BuOH fraction inhibited the LPS-induced ROS level through the NADPH oxidase-independent mechanism. Furthermore, HPLC analysis identified chlorogenic acid, caffeic acid, gentisic acid, rutin, ferulic acid, and quercetin, and suggested that the antioxidant and anti-inflammatory activities of the BuOH fraction should be mediated by the presence of higher amounts of caffeic acid, rutin, and ferulic acid than other fractions. Taken together, these results suggest that A. distichum extract is a source of antioxidant and anti-inflammatory compounds, and could be developed as a potential source for functional food and dietary health supplement

Direct measurement of mechanical vibrations of the 4-rod RFQ at the HLI

In this paper, we present a new haptic interface, called active skin , which is configured with a tactile sensor and a tactile stimulator in single haptic cell, and multiple haptic cells are embedded in a dielectric elastomer. The active skin generates a wide variety of haptic feel in response to the touch by synchronizing the sensor and the stimulator. In this paper, the design of the haptic cell is derived via iterative analysis and design procedures. A fabrication method dedicated to the proposed device is investigated and a controller to drive multiple haptic cells is developed. In addition, several experiments are performed to evaluate the performance of the active skin