The Integrin Ligand c(RGDf(NMe)Nal) Reduces Neointimal Hyperplasia in a Polymer‐Free Drug‐Eluting Stent System

The use of highly active and selective integrin ligands in combination with stent implantation is emerging as a promising alternative to the release of classical immunosuppressive drugs by current drug‐eluting stents (DES), which has been associated with delayed vascular healing and late stent thrombosis. Herein we present the development and biological evaluation of the integrin ligand c(RGDf(NMe)Nal) as a potent anti‐proliferative molecule that targets coronary artery smooth muscle cells (CASMCs). This peptide showed an antagonistic activity for αvβ3 and αvβ5 in the low‐nanomolar range, and selectivity against the platelet receptor αIIbβ3. In vitro, it efficiently inhibited the proliferation of CASMCs, displaying higher potency than the anti‐tumor drug candidate cilengitide. This peptide was then loaded into a polymer‐free bare metal stent (BMS), and its release studied at different time points. Up to seven days of elution, the peptide‐coated stents retained high anti‐proliferative activity toward CASMCs. Finally, the peptide was examined in vivo in a polymer‐free DES system in a rabbit iliac artery model. After 28 days of implantation, histopathological analysis revealed that the peptide clearly decreased neointimal growth and improved vessel healing and re‐endothelialization compared with the FDA‐approved Cypher DES. Our study shows that this type of lipophilic integrin ligand, when eluted from a polymer‐free stent system, has the potential to successfully decrease in‐stent restenosis in the absence of delayed vascular healing.     

Enforced one-dimensional photoconductivity in core-cladding hexabenzocoronenes

Photoconductivity in contorted hexabenzocoronene liquid crystals is found to be exclusively one-dimensional. Spectroscopic measurements and density functional theory support the existence of two pi-systems attributed to a low-energy radialene-core and higher energy out-of-plane alkoxyphenyl rings. Persistent photocurrents, measured as a function of field, channel length, and intensity, fit a stretched exponential characteristic of intracolumnar transport, restricted through the radialene-core by the alkoxyphenyl-cladding. Bimolecular recombination is enhanced with increasing carrier concentration by the system's one-dimensionality.     

Dissecting contact mechanics from quantum interference in single-molecule junctions of stilbene derivatives

Electronic factors in molecules such as quantum interference and cross-conjugation can lead to dramatic modulation and suppression of conductance in single-molecule junctions. Probing such effects at the single-molecule level requires simultaneous measurements of independent junction properties, as conductance alone cannot provide conclusive evidence of junction formation for molecules with low conductivity. Here, we compare the mechanics of the conducting para-terminated 4,4'-di(methylthio)stilbene and moderately conducting 1,2-bis(4-(methylthio)phenyl)ethane to that of insulating meta-terminated 3,3'-di(methylthio)stilbene single-molecule junctions. We simultaneously measure force and conductance across single-molecule junctions and use force signatures to obtain independent evidence of junction formation and rupture in the meta-linked cross-conjugated molecule even when no clear low-bias conductance is measured. By separately quantifying conductance and mechanics, we identify the formation of atypical 3,3'-di(methylthio)stilbene molecular junctions that are mechanically stable but electronically decoupled. While theoretical studies have envisaged many plausible systems where quantum interference might be observed, our experiments provide the first direct quantitative study of the interplay between contact mechanics and the distinctively quantum mechanical nature of electronic transport in single-molecule junctions.     

III–V Nitride semiconductors for high-performance blue and green light-emitting devices

Most of the rapid developments in (AlIn)GaN alloy system technology have occurred within the past few years, and the technology is still moving at a fast pace. New performance records for light-emitting diodes and laser diodes are constantly being reported. This article highlights the progression of the development of the (AlIn)GaN alloy system and describes the fabrication and performance of some of the light-emitting devices that have been produced to date.     

Power electronic converter technology

The present state of the art in DC-DC, AC-DC, DC-AC, and AC-AC converter technology is presented along with their typical areas of applications. Advances made in the last decade that are finding use in industrial, commercial, and military applications are emphasized. Soft switching, in which power device switching stresses are reduced due to circuit resonances, has dominated DC-DC power conversion and some high-performance DC-AC power conversion. In the higher voltage and higher power areas, the invention and improvements of gate turnoff thyristors (GTOs), insulated gate bipolar transistors (IGBTs), and integrated gate-commutated thyristors (IGCTs) have led to other unique topologies to take advantage of these devices     

Graphene oxidation: thickness-dependent etching and strong chemical doping

Patterned graphene shows substantial potential for applications in future molecular-scale integrated electronics. Environmental effects are a critical issue in a single-layer material where every atom is on the surface. Especially intriguing is the variety of rich chemical interactions shown by molecular oxygen with aromatic molecules. We find that O 2 etching kinetics vary strongly with the number of graphene layers in the sample. Three-layer-thick samples show etching similar to bulk natural graphite. Single-layer graphene reacts faster and shows random etch pits in contrast to natural graphite where nucleation occurs at point defects. In addition, basal plane oxygen species strongly hole dope graphene, with a Fermi level shift of approximately 0.5 eV. These oxygen species desorb partially in an Ar gas flow, or under irradiation by far UV light, and readsorb again in an O 2 atmosphere at room temperature. This strongly doped graphene is very different from "graphene oxide" made by mineral acid attack.     

Electrochemical effects in the chemical-mechanical polishing of copper for integrated circuits

Chemical-mechanical polishing of copper in ammonia based solutions has been studied using electrochemical techniques such as electrochemical potential, linear polarization resistance, and potentiodynamic polarization. A copper rotating disk electrode was used to simulate polishing conditions. Measurements made on sputter-coated wafers during polishing were used for comparison. The dissolution of copper is limited by transport of Cu(NH₃)₂ ⁺ from the surface, and the removal rate of copper during polishing is controlled in the solution by the formation of copper ammine complexes.     

Tolerance to discriminative stimulus effects of d-amphetamine.

Chronic administration of high doses of d-amphetamine produced time-limited, surmountable tolerance to stimulus effects of d-amphetamine. 23 male Sprague-Dawley rats discriminated saline and 0.80 mg/kg d-amphetamine under fixed ratio (FR) schedules of food delivery. Suspending training and administering saline did not alter sensitivity to d-amphetamine, indicating that neither tolerance nor sensitization developed during regular training. Acute pretreatment with 3.2 mg/kg d-amphetamine did not alter the ED50 for stimulus effects of d-amphetamine. In contrast, administration of 3.2 or 6.4 mg/kg d-amphetamine, b.i.d., for 3 days or 2 weeks increased the ED50 for stimulus effects 3- to 4-fold but did not produce consistent tolerance to rate-altering effects. Tolerance to stimulus effects was surmountable, as higher doses of d-amphetamine produced full drug-lever selection in tolerant rats. Sensitivity recovered after chronic administration ended. (PsycINFO Database Record (c) 2010 APA, all rights reserved)