Fractional Wigner crystal in the helical Luttinger liquid

The properties of the strongly interacting edge states of two dimensional topological insulators in the presence of two particle backscattering are investigated. We find an anomalous behavior of the density-density correlation functions, which show oscillations that are neither of Friedel nor of Wigner type: they instead represent a Wigner crystal of fermions of fractional charge e/2, with e the electron charge. By studying the Fermi operator, we show that the state characterized by such fractional oscillations still bears the signatures of spin momentum locking. Finally, we compare the spin-spin correlation functions and the density-density correlation functions to argue that the fractional Wigner crystal is characterized by a non trivial spin texture.Comment: 5 pages, 2 figure

Caractérisation physique du bois de la loupe de Thuya

International audienceCe travail constitue une contribution originale à l'étude de la densité et du retrait au séchage de la loupe de thuya provenant de la forêt de Khémisset (Maroc). La densité est souvent utilisée dans les étapes de prédiction des propriétés mécaniques du bois. Quant aux retraits linéaires, l'existence ou non d'une anisotropie entre les retraits radial, tangentiel et longitudinal préfigurent du comportement mécanique du bois. Les mesures de ces propriétés physiques sont réalisées sur 77 échantillons de 2×2×2cm3 découpés selon les directions radiale, tangentielle et longitudinale. L'analyse des résultats des mesures de densité permet de classer le bois de la loupe de thuya comme un bois dense. La densité de la loupe est plus élevée que celle du bois de thuya. Cette différence s'explique par la présence d'excroissances foncées composées de cellules aux parois plus épaisses que celles du bois de thuya. L'analyse des mesures de retraits montre une faible anisotropie de retraits, expliquée à l'échelle microscopique dans un plan de référence, par une orientation très variable des cellules. Ce résultat présuppose un comportement mécanique proche d'un comportement isotrope du bois de la loupe de thuya

Cellulose oxidation and the use of carboxyl cellulose metal complexes in heterogeneous catalytic systems to promote Suzuki-Miyaura coupling and C-O bond formation reaction

This work shows the modification of microcrystalline cellulose by the selective oxidation of primary hydroxyl groups to carboxylate groups by a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated system and its application as a heterogeneous ligand by ionic exchange with catalytic metals ions such as palladium, nickel and copper. Afterwards is described the application of the synthesized material as catalyst in coupling reactions such as Suzuki-Miyaura coupling and C−O bond formation reaction in different conditions, which are of great importance for the synthesis of drugs, natural products and new materials such as dendrimers, liquid crystals and polymers with magnetic and optical properties. The carboxyl cellulose matrix shows to have superior catalytic results as a ligand for all coupling reactions. Can be also highlighted the affinity of the carboxyl cellulose ligand in polar solvents such as water and alcohols and its application in mild conditions

Production of additives with antimicrobial activity via tandem hydroformylation-amine condensation of soybean fame using an ionic liquid-based biphasic catalytic system

A biphasic catalytic system based in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate was employed for tandem hydroformylation-amine condensation reactions of soybean FAME using HRhCO(PPh3)3 as the catalyst precursor and n-butylamine. Using a tenfold excess of the ligand PPh3, the presence of the ionic liquid increased the selectivity for imine if compared to the reaction carried out under similar conditions, but in homogeneous media.The yield for imine reached 75% after 24 h. On the other hand, in the absence of a PPh3 excess, the effect of using the ionic liquid was opposite and the selectivity for imine decreased. This supposedly occurred due to the generation ofN-heterocyclics carbenes, which would coordinate to Rh to form species active for parallel and/or consecutive reactions. When an excess PPh3 is used, it suppress the carbenes coordination, maintaining the Rh complex in a form active for hydroformylation.The obtained imine products presented remarkable antimicrobial activity towards a set of fungi and bacteria commonly present in fuel storage tanks

The effect of polymer/plasticiser ratio in film forming solutions on the properties of chitosan films

In this work physical-chemical properties of chitosan/ glycerol film forming solutions (FFS) and the resulting films were analysed. Solutions were prepared using different concentrations of plasticising agent (glycerol) and chitosan. Films were produced by solvent casting and equilibrated in a controlled atmosphere. FFS water activity and rheological behaviour were determined. Films water content, solubility, water vapour and oxygen permeabilities, thickness, and mechanical and thermal properties were determined. Fourier transform infrared (FTIR) spectroscopy was also used to study the chitosan/glycerol interactions. Results demonstrate that FFS chitosan concentration influenced solutions consistency coefficient and this was related with differences in films water retention and structure. Plasticiser addition led to an increase in films moisture content, solubility and water vapour permeability, water affinity and structural changes. Films thermo-mechanical properties are significantly affected by both chitosan and glycerol addition. FTIR experiments confirm these results. This work highlights the importance of glycerol and water plasticisation in films properties.This work was supported by National Funds from FCT - Fundacao para a Ciencia e a Tecnologia, through project PEst-OE/EQB/LA0016/2011.Authors Joana F. Fundo, Andrea C. Galvis-Sanchez and Mafalda A. C. Quintas acknowledge FCT for research grants SFRH/ BD / 62176 / 2009, SFRH/BPD/37890/2007 and SFRH / BPD / 41715 / 2007, respectively

Multi-Target Drugs: The Trend of Drug Research and Development

Summarizing the status of drugs in the market and examining the trend of drug research and development is important in drug discovery. In this study, we compared the drug targets and the market sales of the new molecular entities approved by the U.S. Food and Drug Administration from January 2000 to December 2009. Two networks, namely, the target–target and drug–drug networks, have been set up using the network analysis tools. The multi-target drugs have much more potential, as shown by the network visualization and the market trends. We discussed the possible reasons and proposed the rational strategies for drug research and development in the future

The use of electric fields for edible coatings and films development and production: A review

Edible films and coatings can provide additional protection for food, while being a fully biodegradable, environmentally friendly packaging system. A diversity of raw materials used to produce edible coatings and films are extracted from marine and agricultural sources, including animals and plants. Electric fields processing holds advantage in producing safe, wholesome and nutritious food. Recently, the presence of a moderate electric field during the preparation of edible coatings and films was shown to influence their main properties, demonstrating its usefulness to tailor edible films and coatings for specific applications. This manuscript reviews the main aspects of the use of electric fields in the production of edible films and coatings, including the effect in their transport and mechanical properties, solubility and microstructure.Fundação para a Ciência e a Tecnologia (FCT), Portugal.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brasil

Asymptomatic internal carotid artery stenosis and cerebrovascular risk stratification

Background The purpose of this study was to determine the cerebrovascular risk stratification potential of baseline degree of stenosis, clinical features, and ultrasonic plaque characteristics in patients with asymptomatic internal carotid artery (ICA) stenosis. Methods This was a prospective, multicenter, cohort study of patients undergoing medical intervention for vascular disease. Hazard ratios for ICA stenosis, clinical features, and plaque texture features associated with ipsilateral cerebrovascular or retinal ischemic (CORI) events were calculated using proportional hazards models. Results A total of 1121 patients with 50% to 99% asymptomatic ICA stenosis in relation to the bulb (European Carotid Surgery Trial [ECST] method) were followed-up for 6 to 96 months (mean, 48). A total of 130 ipsilateral CORI events occurred. Severity of stenosis, age, systolic blood pressure, increased serum creatinine, smoking history of more than 10 pack-years, history of contralateral transient ischemic attacks (TIAs) or stroke, low grayscale median (GSM), increased plaque area, plaque types 1, 2, and 3, and the presence of discrete white areas (DWAs) without acoustic shadowing were associated with increased risk. Receiver operating characteristic (ROC) curves were constructed for predicted risk versus observed CORI events as a measure of model validity. The areas under the ROC curves for a model of stenosis alone, a model of stenosis combined with clinical features and a model of stenosis combined with clinical, and plaque features were 0.59 (95% confidence interval [CI] 0.54-0.64), 0.66 (0.62-0.72), and 0.82 (0.78-0.86), respectively. In the last model, stenosis, history of contralateral TIAs or stroke, GSM, plaque area, and DWAs were independent predictors of ipsilateral CORI events. Combinations of these could stratify patients into different levels of risk for ipsilateral CORI and stroke, with predicted risk close to observed risk. Of the 923 patients with <70% stenosis, the predicted cumulative 5-year stroke rate was <5% in 495, 5% to 9.9% in 202, 10% to 19.9% in 142, and <20% in 84 patients. Conclusion Cerebrovascular risk stratification is possible using a combination of clinical and ultrasonic plaque features. These findings need to be validated in additional prospective studies of patients receiving optimal medical intervention alone. Copyright © 2010 by the Society for Vascular Surgery