Investigating the Effects of Nitric Acid Treatments on the Properties of Recycled Carbon Fiber.

In this study, the chemical state change of recycled carbon fiber (rCF) surfaces and the mechanism of the oxygen functional groups according to nitric acid treatment at various times and temperatures were investigated to upcycle the carbon fiber recovered from used carbon composite. When treated with nitric acid at 25 °C, the carbon fiber surface demonstrated the same tensile properties as untreated carbon fiber (CF) for up to 5 h, and the oxygen functional group and polar surface energy of C-O (hydroxyl group) and C=O (carbonyl group) increased slightly compared to the untreated CF up to 5 h. On the other hand, at 100 °C, the tensile properties slightly decreased compared to untreated CF up to 5 h, and the amount of C-O and C=O decreased and the amount of O=C-O (lactone group) started to increase until 1 h. After 1 h, the amount of C-O and C=O decreased significantly, and the amount of O=C-O increased rapidly. At 5 h, the amount of oxygen functional groups increased by 92%, and the polar surface energy increased by 200% compared to desized CF. It was determined that the interfacial bonding force increased the most because the oxygen functional group, O=C-O, increased greatly at 100 °C and 5 h.

Effects of Heat Treatment Atmosphere and Temperature on the Properties of Carbon Fibers.

In this study, carbon fibers were heat-treated in a nitrogen and oxygen atmosphere according to temperature to elucidate the mechanism of chemical state changes and oxygen functional group changes on the carbon fiber surface by analyzing the mechanical and chemical properties of carbon fibers. Carbon fibers before and after heat treatment were analyzed using FE-SEM (Field Emission Scanning), UTM (Universal Tensile Testers), XPS (X-ray Photoelectron Spectroscopy), and surface-free energy. In the nitrogen atmosphere, which is an inert gas, the tensile strength was equivalent to that of the virgin up to 500 °C but decreased to 71% with respect to the virgin at 1000 °C. Furthermore, as the temperature increased from room temperature to 1000 °C, the oxygen functional group and the polar free energy gradually decreased compared with the virgin. On the other hand, in the oxygen atmosphere, which is an active gas, the tensile properties were not significantly different from those of the virgin up to 300 °C but gradually decreased at 500 °C. Above 600 °C, the carbon fibers deteriorated, and measurement was impossible. The oxygen functional group decreased at 300 °C, but above 300 °C, among the oxygen functional groups, the hydroxyl group and the carbonyl group increased. Furthermore, the lactone group formed and rapidly increased compared with the virgin, and the polar free energy increased as the temperature increased.

Poly(vinylalcohol) (PVA) Assisted Sol-Gel Fabrication of Porous Carbon Network-Na3V2(PO4)3 (NVP) Composites Cathode for Enhanced Kinetics in Sodium Ion Batteries.

Na3V2(PO4)3 is regarded as one of the promising cathode materials for next-generation sodium ion batteries, but its undesirable electrochemical performances due to inherently low electrical conductivity have limited its direct use for applications. Motivated by the limit, this study employed a porous carbon network to obtain a porous carbon network-Na3V2(PO4)3 composite by using poly(vinylalcohol) assised sol-gel method. Compared with the typical carbon-coating approach, the formation of a porous carbon network ensured short ion diffusion distances, percolating electrolytes by distributing nanosized Na3V2(PO4)3 particles in the porous carbon network and suppressing the particle aggregation. As a result, the porous carbon network-Na3V2(PO4)3 composite exhibited improved electrochemical performances, i.e., a higher specific discharge capacity (~110 mAh g-1 at 0.1 C), outstanding kinetic properties (~68 mAh g-1 at 50 C), and stable cyclic stability (capacity retention of 99% over 100 cycles at 1 C).

Fabrication of a Bending-Insensitive In-Plane Strain Sensor from a Reversible Cross-Linker-Functionalized Silicone Polymer.

A reversibly cross-linkable and transparent polymer featuring stretchability and thermal healability is prepared by introducing Diels-Alder (DA)-reactive moieties into polydimethylsiloxane (PDMS), namely, a healable PDMS (h-PDMS). Inspired by the fact that retro-DA reactions occur even at low temperatures (albeit at a low rate), we maximize the effectiveness of small reactant products, demonstrating that self-healing and self-integration realized by 1-3 min exposure of cured h-PDMS to methyl ethyl ketone (MEK) vapor is more efficient than that achieved by direct sample heating at high temperatures. This technology is first used to uniformly transfer Ag nanowires (Ag NWs) formed on a temporary substrate to the h-PDMS surface, and further MEK vapor treatment allows the transferred NWs to be impregnated below the h-PDMS surface to afford an in-plane strain sensor. Most importantly, the developed method is used to perfectly integrate two identical Ag NW/h-PDMS films and thus place NWs on a neutral plane. Consequently, because of the unique structure in which a percolated network of AgNWs is formed on the interface where the two identical h-PDMS films are chemically integrated, the fabricated sensor is transparent, self-healable, stretchable, and insensitive to bending but sensitively responds to in-plane strain induced by lateral deformation.

A comparative analysis of the impact of a positive list system on new chemical entity drugs and incrementally modified drugs in South Korea.

BACKGROUND: Medical costs in South Korea have risen, in part due to increased demand and consumption of pharmaceutical products by an aging population and also because of the introduction of newer, more expensive drugs. In an effort to stabilize the financing of health insurance and alleviate the financial burden on individuals, the government implemented a policy changing the national health insurance drug-listing system from a negative list system to a positive list system (PLS). OBJECTIVES: The goal of this study was to compare differences in drug-listing rates for new chemical entities (NCEs) and incrementally modified drugs (IMDs) after South Korea introduced the PLS in December 2006. Parameters significantly affecting NCE and IMD listings were also identified. METHODS: New drug-listing data for 2007 and 2008 were obtained from the databases of the Health Insurance Review Agency and the Ministry of Health and Welfare. Descriptive analyses on the reimbursement rate and logistic regression analysis were conducted. Statistical significance was tested for all results, and P < 0.05 was considered statistically significant. RESULTS: A total of 150 reimbursement applications (79 for NCEs, 71 for IMDs) were examined for this study. The overall drug-listing rate was lower than before the introduction of the PLS. Drug reimbursement rates for NCEs (50.6%) were lower than those for IMDs (74.6%) (P = 0.0025). However, the price negotiation rate was 85.0% for NCEs compared with 73.6% for IMDs (P = 0.1847). The time required for both reimbursement and drug pricing was significantly longer for NCE than for IMD listings (P < 0.05). Cost-effectiveness and budget impact were 2 significant variables affecting the listing of NCEs. However, no significant variable was identified for IMDs. CONCLUSIONS: The PLS challenges the drug-listing system by decreasing the drug-listing rate and lengthening the period for reimbursement determinations. These effects were more pronounced for NCE listings than for IMD listings.

Cytotoxic effects of triterpenoid saponins from Androsace umbellata against multidrug resistance (MDR) and non-MDR cells.

Cytotoxicity-guided fractionation and separation of MeOH extract from Androsace umbellata (Lour.) Merr. led to the isolation of four triterpenoid saponins. Compounds isolated from the n-BuOH soluble fraction were identified as saxifragifolin C (1), A (2), B (3), and D (4) by spectroscopic analysis. Antiproliferative effect of isolated compounds were evaluated by the sulforhodamin B assay against multidrug resistance (MDR; MES-SA/DX5 and HCT15/CLO2) and non-MDR (A549, SK-OV-3, SK-MEL-2, MES-SA, and HCT15) human tumor cell lines. All compounds exhibited strong cytotoxicity against non-MDR human tumor cell lines with IC(50) values of 0.19-2.37 muM. MDR cells and non-MDR cells had similar sensitivity to these compounds, however, MDR cells were highly resistant to doxorubicin. Compounds 1-4 induced an increase in the percentage of Annexin V-binding cells, indicating that 1-4 induced apoptosis in RAW 264.7 cells. Also, the condensation of nuclei, a characteristic morphological change of apoptosis, was observed in RAW 264.7 cells by the treatment with n-BuOH fraction, compounds 3 and 4, respectively.