Conducting Carbon Wires in Ordered, Nanometer-Sized Channels

The encapsulation of graphite-type carbon wires in the regular, 3-nanometer-wide hexagonal channels of the mesoporous host MCM-41 is reported. Acrylonitrile monomers are introduced through vapor or solution transfer and polymerized in the channels with external radical initiators. Pyrolysis of the intrachannel polyacrylonitrile results in filaments whose microwave conductivity is about 10 times that of bulk carbonized polyacrylonitrile. The MCM host plays a key role in ordering the carbon structure, most likely through the parallel alignment of the precursor polymer chains in the channels. The fabrication of stable carbon filaments in ordered, nanometer-sized channels represents an important step toward the development of nanometer electronics

Synthesis of conducting graphite-like nanometer wires via soluble precursors

Graphite - like conducting materials were encapsulated in the channels of new mesoporous MCM- 41 materials with typical channel diameters of 30-40 Ä. Acrylonitrile was introduced into the hosts via vapor transport, then polymerized with external radical initiators, K2S2O8 and HNaSOß. The polymers in the host cavities were further pyrolyzed at different temperatures under vacuum or nitrogen atmosphere. The properties of the polymer systems were studied while encapsulated or after dissolution of the host. The crystallinity of the hosts is intact after insertion of the polymer (even after pyrolysis at 800°C). The formation of conducting graphite - like materials inside the hosts was demonstrated with Raman and UV spectra. The nitrogen to carbon ratio of the pyrolyzed polymers depends on the pyrolysis temperature and the polymer environment. Most interestingly, the normalized AC absorption of pyrolyzed polyacrylonitrile in MCM-41 (at 800°C) is comparable to graphite

Evidence of ratchet effect in nanowires of a conducting polymer

Ratchet effect, observed in many systems starting from living organism to artificially designed device, is a manifestation of motion in asymmetric potential. Here we report results of a conductivity study of Polypyrrole nanowires, which have been prepared by a simple method to generate a variation of doping concentration along the length. This variation gives rise to an asymmetric potential profile that hinders the symmetry of the hopping process of charges and hence the value of measured resistance of these nanowires become sensitive to the direction of current flow. The asymmetry in resistance was found to increase with decreasing nanowire diameter and increasing temperature. The observed phenomena could be explained with the assumption that the spatial extension of localized state involved in hopping process reduces as the doping concentration reduces along the length of the nanowires.Comment: Revtex, two column, 4 pages, 10 figure

Effects of Salvianolic Acid B on Protein Expression in Human Umbilical Vein Endothelial Cells

Salvianolic acid B (Sal B), a pure water-soluble compound extracted from Radix Salviae miltiorrhizae, has been reported to possess potential cardioprotective efficacy. To identify proteins or pathways by which Sal B might exert its protective activities on the cardiovascular system, two-dimensional gel electrophoresis-based comparative proteomics was performed, and proteins altered in their expression level after Sal B treatment were identified by MALDI-TOF MS/MS. Human umbilical vein endothelial cells (HUVECs) were incubated at Sal B concentrations that can be reached in human plasma by pharmacological intervention. Results indicated that caldesmon, an actin-stabilizing protein, was downregulated in Sal B-exposed HUVECs. Proteins that showed increased expression levels upon Sal B treatment were vimentin, T-complex protein 1, protein disulfide isomerase, tropomyosin alpha, heat shock protein beta-1, UBX domain-containing protein 1, alpha enolase, and peroxiredoxin-2. Additionally, Sal B leads to increased phosphorylation of nucleophosmin in a dose-dependent manner and promotes proliferation of HUVECs. We found that Sal B exhibited a coordinated regulation of enzymes and proteins involved in cytoskeletal reorganization, oxidative stress, and cell growth. Our investigation would provide understanding to the endothelium protection information of Sal B

Association of TNF-α gene with spontaneous deep intracerebral hemorrhage in the Taiwan population: a case control study

<p>Abstract</p> <p>Background</p> <p>Genetic factors may play a role in susceptibility to spontaneous deep intracerebral hemorrhage (SDICH). Previous studies have shown that <it>TNF-α </it>gene variation was associated with risks of subarachnoid hemorrhage in multiple ethnicities. The present case-control study tested the hypothesis that genetic variations of the <it>TNF-α </it>gene may affect the risk of Taiwanese SDICH. We examined the association of SDICH risks with four single nucleotide polymorphisms (SNPs) within the <it>TNF-α </it>gene promoter, namely T-1031C, C-863A, C-857T, and G-308A.</p> <p>Methods</p> <p>Genotyping was determined by PCR-based restriction and electrophoresis assay for 260 SDICH patients and 368 controls. Associations were tested by logistic regression or general linear models with adjusting for multiple covariables in each gender group, and then in combined. Multiplicative terms of gender and each of the four SNPs were applied to detect the interaction effects on SDICH risks. To account for the multiple testing, permutation testing of 1,000 replicates was performed for empirical estimates.</p> <p>Results</p> <p>In an additive model, SDICH risks were positively associated with the minor alleles -1031C and -308A in men (OR = 1.9, 95% CI 1.1 to 3.4, p = 0.03 and OR = 2.6, 95% CI 1.3 to 5.3, p = 0.005, respectively) but inversely associated with -863A in females (OR = 0.5, 95% CI 0.2 to 0.9, p = 0.03). There were significant interaction effects between gender and SNP on SDICH risks regarding SNPs T-1031C, C-863A, and G-308A (p = 0.005, 0.005, and 0.007, respectively). Hemorrhage size was inversely associated with -857T in males (p = 0.04).</p> <p>Conclusions</p> <p>In the Taiwan population, the associations of genetic variations in the <it>TNF-α </it>gene promoter with SDICH risks are gender-dependent.</p

Plasmonic Structure Enhanced Exciton Generation at the Interface between the Perovskite Absorber and Copper Nanoparticles

The refractive index and extinction coefficient of a triiodide perovskite absorber (TPA) were obtained by fitting the transmittance spectra of TPA/PEDOT:PSS/ITO/glass using the transfer matrix method. Cu nanoplasmonic structures were designed to enhance the exciton generation in the TPA and to simultaneously reduce the film thickness of the TPA. Excitons were effectively generated at the interface between TPA and Cu nanoparticles, as observed through the 3D finite-difference time-domain method. The exciton distribution is advantageous for the exciton dissociation and carrier transport