Iron‐Promoted Tandem Cyclization of 1,3‐Diynyl Chalcogen Derivatives with Diorganyl Dichalcogenides for the Synthesis of Benzo[b]furan‐Fused Selenophenes

A double intramolecular 5‐endo‐dig cyclization of butyl[2‐(phenylbuta‐1,3‐diynyl)phenyl]chalcogens has been employed in a selective preparation of benzo[b]chalcogenopheno[2,3‐d]furans. Several reaction parameters were studied to determine the best reaction conditions and we observed that the reaction of butyl[2‐(phenylbuta‐1,3‐diynyl)phenyl]chalcogens (0.25 mmol) with iron(III) chloride hexahydrate (2.0 equiv.) and diorganyl diselenides (1.75 equiv.) at reflux of dichloromethane was the most appropriate to give the products in 35–89% yields. These standard reaction conditions were compatible with many functional groups in the substrates, such as methyl, chlorine, fluorine, methoxy and heteroaryl. This protocol was also efficient for diorganyl diselenides but it was ineffective with diorganyl disulfides and ditellurides. In a competition among selenium, sulfur and oxygen nucleophiles we observed that the nucleophilicity and steric effects of the competing functional groups were determinant factors for the selectivity of the cyclization. The benzo[b]chalcogenopheno[2,3‐d]furans had absorptions in the UV region (300–350 nm range) with molar absorptivity coefficient values ascribed to spin and symmetry allowed π–π* electronic transitions. An emission located in the purple region (380–440 nm range), with a Stokes shift of between 65–100 nm, is probably associated to the charge transfer character of the excited state.

     

Intimal hyperplasia following implantation of helical-centreline and straight-centreline stents in common carotid arteries in healthy pigs: influence of intraluminal flow?

Intimal hyperplasia (IH) is a leading cause of obstruction of vascular interventions, including arterial stents, bypass grafts and arteriovenous grafts and fistulae. Proposals to account for arterial stent-associated IH include wall damage, low wall shear stress (WSS), disturbed flow and, although not widely recognized, wall hypoxia. The common non-planarity of arterial geometry and flow, led us to develop a bare-metal, nitinol, self-expanding stent with three-dimensional helical-centreline geometry. This was deployed in one common carotid artery of healthy pigs, with a straight-centreline, but otherwise identical (conventional) stent deployed contralaterally. Both stent types deformed the arteries, but the helical-centreline device additionally deformed them helically and caused swirling of intraluminal flow. At sacrifice, one month post stent deployment, histology revealed significantly less IH in the helical-centreline than straight-centreline stented vessels. Medial cross-sectional area was not significantly different in helical-centreline than straight-centreline stented vessels. By contrast, luminal cross-sectional area was significantly larger in helical-centreline than straight-centreline stented vessels. Mechanisms considered to account for those results include enhanced intraluminal WSS and enhanced intraluminal blood–vessel wall mass transport, including of oxygen, in the helical-centreline stented vessels. Consistent with the latter proposal, adventitial microvessel density was lower in the helical-centreline stented than straight-centreline stented vessels.     

Modeling the sensitivity of CMOS circuits to radiation induced single event transients

An accurate and computer efficient analytical model for the evaluation of integrated circuit sensitivity to radiation induced single event transients is presented. The key idea of the work is to exploit a model that allows the rapid determination of the sensitivity of any MOS circuit to single event transients (SETs), without the need to run circuit level simulations. To accomplish this task, both single event transient generation and its propagation through circuit logic stages are characterized and modeled. The model predicts whether or not a particle hit generates a transient pulse which may propagate to the next logic gate or memory element. The electrical masking (attenuation) of the transient pulse as it propagates through each stage of logic until it reaches a memory element is also modeled. Model derivation is in strong relation with circuit electrical behavior, being consistent with technology scaling. The model is suitable for integration into CAD-Tools, intending to make automated evaluation of circuit sensitivity to SEU possible.     

Compact broadband circularly polarized slot‐patch antenna array

A simple design of circularly polarized slot‐patch antenna array with broadband operation and compact size is presented in this article. The antenna element consists of a circular slot and a semicircular patch, which are etched on both sides of a substrate. For the gain and axial ratio (AR) bandwidth enhancement, its array antennas are implemented in a 2 × 2 arrangement and fed by a sequential‐phase feeding network. The final 2 × 2 antenna array prototype with compact lateral dimension of 0.8λ_L × 0.8λ_L (λ_L is the lowest frequency within AR bandwidth) yielded a measured impedance bandwidth of 103.83% (2.76‐8.72 GHz) and a measured AR bandwidth of 94.62% (2.45‐6.85 GHz). The peak gain values within the AR bandwidth are from 2.85 to 8.71 dBi. A good agreement between the simulated and measured results is achieved. This antenna array is suitable for multiservice wireless systems covering WiMAX, WLAN and C‐band applications such as satellite communications.     

Effects of alcohol ingestion on tracking performance during angular acceleration.

Gave practice and base-line tests of tracking performance in both static (stationary) and dynamic (whole body angular acceleration) conditions to 20 male undergraduates. 10 ss then drank orange juice that contained 2 ml. Of 100-proof vodka/kg of s weight, while the others drank a control beverage. Tests, conducted 1-10 hr. After drinking, were in total darkness with the exception of the illuminated visual display. Static tracking errors for alcohol ss were significantly higher than those of controls only at the 4-hr session. However, alcohol ss made significantly more dynamic tracking errors during the 1-, 2-, and 4-hr sessions and, concomitantly, had significantly more nystagmic eye movements and higher rates of slow phase eye velocity than did controls. Results indicate that, although eye-hand coordination may show little or no impairment following alcohol ingestion in static situations, it may be seriously degraded during motion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

pKa measurements from nuclear magnetic resonance for the B1 and B2 immunoglobulin G-binding domains of protein G: comparison with calculated values for nuclear magnetic resonance and X-ray structures

Two-dimensional homo- and heteronuclear nuclear magnetic resonance (NMR) spectroscopy was used to determine pKa values for all of the acidic residues in the B1 and B2 immunoglobulin G- (IgG-) binding domains of protein G. Due to the stability of protein G over a wide pH range, estimates of ionization constants were also obtained for some basic residues. These experimentally determined ionization constants were compared with values calculated from both X-ray and NMR-derived structures of B1 and B2 using the UHBD algorithm [Antosiewicz, J., et al. (1994) J. Mol. Biol. 238, 415-436]. This algorithm has been found to be predictive for pKa measurements in proteins and, in combination with experimental measurements, allowed some evaluation of the NMR and X-ray structures. Three regions where significant differences exist between the X-ray and NMR structures are (1) the position of the E56 side chain relative to the backbone amides of K10 and D40, (2) residues 33-37 in the helix, and (3) the Y45 side-chain conformation. For all three cases, the experimental pH titration curves are notably more consistent with the X-ray structures than the NMR structures. In contrast, a number of solvent-accessible side chains have experimental pKas more in agreement with mean pKas calculated from families of NMR structures. The conformations of these side chains may be susceptible to crystal packing effects. From titration experiments under basic conditions, it is noteworthy that the chemical shift of the Y45 C epsilonH resonance is invariant up to pDcorr 12. The Y45 side-chain hydroxyl group appears to maintain a nativelike hydrogen bond with D47 at pDcorr 12, even though the protein is approximately 90% unfolded. These results suggest that this short-range (i, i + 2) interaction, located in the beta3-beta4 hairpin, is present in the high-pH denatured state and may therefore form early in the folding of protein G.     

Radiation effects on polypropylene for sterilization

In order to improve the resistance of gamma-radiation sterilization of polypropylene (PP), the formulations of the additives such as antioxidants, crosslinking agent, and trans-stilbene oxide (StO) have been carried out. The irradiated PP and ethylene-propylene copolymer samples with control and additives were characterized by mechanical tester, colorimetry, and Fourier transform infrared spectroscopy with total attenuated reflectance mode (FTIR-ATR). Crosslinking agent and StO formulated PP showed remarkable radiation resistance and minimum discoloration. Also, radiation resistance of ethylene-propylene copolymers with 3% of ethylene contents was better than that of PP homopolymers in the case of no additives. The proposed mechanisms of radiation stabilization with additives are also discussed.     

Multicenter evaluation of a second-generation assay for cardiac troponin T

We report on the evaluation of the second-generation assay for cardiac troponin T (cTnT) on the Enzymun system. This new assay is completely specific for the cardiac isoform of TnT, utilizing two cardiospecific monoclonal antibodies. The assay time is reduced to 45 min. The interassay precision shows a median CV of 5.5%; 20% interassay CV was found between 0.05 and 0.1 microg/L. The cardiosensitivity of the second-generation cTnT assay in patients with ischemic myocardial injury appears equivalent when compared with the first-generation assay. We found no falsely positive results in patients with skeletal muscle damage including multitraumas, surgery patients, and marathon runners who showed highly increased values with the unspecific first-generation assay. In Duchenne disease cTnT was still increased, but to a much lower extent. cTnT remains increased in renal failure, but to a lesser degree than with the first-generation assay. The cause of this increase remains unclear. Although a cross-reactivity of skeletal muscle TnT in the second-generation assay could be excluded by our findings, minor myocardial damage or expression of the cardiac isoform of TnT in regenerating muscles cannot be ruled out in those cases with apparently falsely increased cTnT values. The second-generation cTnT assay is a step forward in the combination of cardiosensitivity and cardiospecificity in biochemical markers for diagnosis of heart disease.