High-performance organic semiconductors for thin-film transistors based on 2,6-bis(2-thienylvinyl)anthracene

We have synthesized two novel organic semiconductors, which have a symmetrically substituted thienylvinylene anthracene backbone. They show good electrical performances on SiO2/Si, with high field-effect mobilities of up to 0.4 cm2 V-1 s-1, and can easily be synthesized in large quantities. In addition, the high mobility of such semiconductors can be achieved at low substrate deposition temperatures.This work was supported by grants (F0004030-2007-23, F0004071-2007-23) from the Information Display R&D Center, one of the 21st Century Frontier R&D Programs funded by the Ministry of Commerce, Industry, and Energy of the Korean Government, and Seoul R&BD

Antihyperglycemic and Antioxidative Effects of Hydroxyethyl Methylcellulose (HEMC) and Hydroxypropyl Methylcellulose (HPMC) in Mice Fed with a High Fat Diet

The effect of dietary feeding of hydroxyethyl methylcellulose (HEMC) and hydroxypropyl methylcellulose (HPMC) on the glucose metabolism and antioxidative status in mice under high fat diet conditions was investigated. The mice were randomly divided and given experimental diets for six weeks: normal control (NC group), high fat (HF group), and high fat supplemented with either HEMC (HF+HEMC group) or HPMC (HF+HPMC group). At the end of the experimental period, the HF group exhibited markedly higher blood glucose and insulin levels as well as a higher erythrocyte lipid peroxidation rate relative to the control group. However, diet supplementation of HEMC and HPMC was found to counteract the high fat-induced hyperglycemia and oxidative stress via regulation of antioxidant and hepatic glucose-regulating enzyme activities. These findings illustrate that HEMC and HPMC were similarly effective in improving the glucose metabolism and antioxidant defense system in high fat-fed mice and they may be beneficial as functional biomaterials in the development of therapeutic agents against high fat dietinduced hyperglycemia and oxidative stress

TEMPERATURE DEPENDENT DIFFUSION CONSTANT AND MOBILITY OF POSITIVE ION IN BULK LIQUID HELIUM NEAR ABSOLUTE ZERO TEMPERATURES(Session I : Cross-Disciplinary Physics, The 1st Tohwa University International Meeting on Statistical Physics Theories, Experiments and Computer Simulations)

この論文は国立情報学研究所の電子図書館事業により電子化されました。Using the rate of momentum transfer through the scatterings among quasiparticles and phonons by ion, diffusion constant D(T) and the mobility of positive ion μ_+(T) are evaluated near absolute zero temperatures in bulk liquid ^4He. The diffusion constant D(T) has T^ dependence while the mobility of positive ion varies with T^, which agrees with the experimental results

Effect of Relative Humidity on the Electrospinning Performance of Regenerated Silk Solution

Recently, the electrospun silk web has been intensively studied in terms of its biomedical applications, including tissue engineering scaffolds, due to its good biocompatibility, cytocompatibility, and biodegradability. In this study, the effect of relative humidity (RH) conditions on the morphology of electrospun silk fiber and the electrospinning production rate of silk solution was examined. In addition, the effect of RH on the molecular conformation of electrospun silk web was examined using Fourier transform infrared (FTIR) spectroscopy. As RH was increased, the maximum electrospinning rate of silk solution and fiber diameter of the resultant electrospun silk web were decreased. When RH was increased to 60%, some beads were observed, which showed that the electrospinnability of silk formic acid solution deteriorated with an increase in RH. The FTIR results showed that electrospun silk web was partially β-sheet crystallized and RH did not affect the molecular conformation of silk

Silk/Rayon Webs and Nonwoven Fabrics: Fabrication, Structural Characteristics, and Properties

Silk is a naturally occurring material and has been widely used in biomedical and cosmetic applications owing to its unique properties, including blood compatibility, excellent cytocompatibility, and a low inflammatory response in the body. A natural silk nonwoven fabric with good mechanical properties was recently developed using the binding property of sericin. In this study, silk/rayon composite nonwoven fabrics were developed to increase productivity and decrease production costs, and the effect of the silk/rayon composition on the structure and properties of the fabric was examined. The crystalline structure of silk and rayon was maintained in the fabric. As the silk content increased, the porosity and moisture regain of the silk/rayon web and nonwoven fabric decreased. As the silk content increased, the maximum stress of the web and nonwoven fabric increased, and the elongation decreased. Furthermore, the silk/rayon web exhibited the highest values of maximum stress and elongation at ~200 °C. Regardless of the silk/rayon composition, all silk/rayon nonwoven fabrics showed good cytocompatibility. Thus, the silk/rayon fabric is a promising material for cosmetic and biomedical applications owing to its diverse properties and high cell viability

Preparation of Highly Crystalline Silk Nanofibrils and Their Use in the Improvement of the Mechanical Properties of Silk Films

Due to their commendable biocompatibility, regenerated silk fibroin (RSF) films have attracted considerable research interest. However, the poor mechanical properties of RSF films have limited their use in various biomedical applications. In this study, a novel, highly crystalline silk fibril was successfully extracted from silk by combining degumming with ultrasonication. Ultrasonication accelerated the development of silk nanofibrils measuring 130–200 nm on the surface of the over-degummed silk fibers, which was confirmed via scanning electron microscopy. Additionally, the crystallinity index of silk fibril was found to be significantly higher (~68%) than that of conventionally degummed silk (~54%), as confirmed by the Fourier-transform infrared (FTIR) spectroscopy results. Furthermore, the breaking strength and elongation of the RSF film were increased 1.6 fold and 3.4 fold, respectively, following the addition of 15% silk nanofibrils. Thus, the mechanical properties of the RSF film were remarkably improved by the addition of the silk nanofibrils, implying that it can be used as an excellent reinforcing material for RSF films

ROTON-LIMITED MOBILITY OF POSITIVE IONS IN BULK LIQUID ^4HE(Session I : Cross-Disciplinary Physics, The 1st Tohwa University International Meeting on Statistical Physics Theories, Experiments and Computer Simulations)

この論文は国立情報学研究所の電子図書館事業により電子化されました。It is shown that the roton-limited mobility of the positive ion in bulk liquid ^4He has the temperature variation with σ_rT^e^, where σ_r is the roton scattering cross section and is good agreement with the experiments for the roton-limited temperatures ranges from ～0.5K^ to ～1.85K^

Characteristics of TEMPO-oxidized cellulose fibril-based hydrogels induced by cationic ions and their properties

none4siCellulose microfibrils (CMFs) and cellulose nanofibrils (CNFs) were isolated from hardwood pulp by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation, which produced negatively-charged carboxylate groups on their surface. First, these CMFs and CNFs were used to prepare microgels and nanogels, respectively, at different concentrations of cellulose and trivalent Al3+ cation by inducing ionic interactions between the negatively charged carboxylates and the metal cation. Then, two other cations (i.e., divalent Ca2+ and monovalent H+ were employed to understand the structure–property relationship these hydrogels. We characterized their morphology, chemical groups, mechanical properties, surface area, and pore size, and evaluated their drug-release behaviors using theophylline. Compared to the hydrogels prepared from divalent or monovalent cations, both microgel and nanogel prepared from trivalent Al3+ showed the highest stiffness and compressive strength, which indicated that they possessed the strongest ionic cross-linking via intra- and inter-fibrillar interactions. With a decrease in the valency of the cation used, the surface area of both hydrogels decreased, while their pore radius and calculated fibril diameter increased, indicating that a higher valency cation produced a hydrogel with higher porosity and a tighter network structure. The nanogel prepared from Al3+ also showed the highest swelling ratio and the lowest release of theophylline, while that of microgel was, in contrast, consistent. The low total drug-release behavior in nanogels was attributed to their compact and highly porous structure. The Higuchi model was the best-fit model of drug release kinetics. These results indicate that the characteristics and internal structure of hydrogel has a great impact on its properties and drug-release profile, and that it may be possible to finely tune hydrogel properties and drug release profile by altering the internal structure of hydrogels during its preparation.mixedMasruchin, Nanang; Park, Byung-Dae; Causin, Valerio; Um, In ChulMasruchin, Nanang; Park, Byung Dae; Causin, Valerio; Um, In Chu

Biomimetic Electrospun Films for Effective Radiative Cooling Under Sunlight

We demonstrate that natural silk can be restructured by electrospinning into nanoscale morphology mimicking white beetle scales for enhanced radiative cooling. While natural silk cocoons exhibit strong broadband light scattering by Anderson localization, for exceptionally strong scattering, white beetle scales rely on different physics that remains largely unclear. By electrospinning regenerated silk, we create silk films where the fibers are a quarter micron in mean diameter and randomly oriented in the plane directions, similar to white beetle scale structures. Relative to raw silk films, the restructured silk films substantially increase optical scattering strength in the visible spectrum and emissivity in the atmospheric transparency window. As a result, our restructured silk film lowers the average temperature of a black substrate underneath by 7.5 °C relative to a raw silk film during the daytime of intense solar radiation. Our work suggests that scattering physics hidden in white beetle scales achieves even stronger sunlight rejection than that in natural silk cocoons which ingeniously embodies Anderson localization. Moreover, the strong scattering in our electrospun fibrous films points to highly efficient cooling fabrics that mimic nanostructures in white beetle scales with synthetic polymers