Strain engineering and one-dimensional organization of metal-insulator domains in single-crystal VO2 beams

Spatial phase inhomogeneity at the nano- to microscale is widely observed in strongly-correlated electron materials. The underlying mechanism and possibility of artificially controlling the phase inhomogeneity are still open questions of critical importance for both the phase transition physics and device applications. Lattice strain has been shown to cause the coexistence of metallic and insulating phases in the Mott insulator VO2. By continuously tuning strain over a wide range in single-crystal VO2 micro- and nanobeams, here we demonstrate the nucleation and manipulation of one-dimensionally ordered metal-insulator domain arrays along the beams. Mott transition is achieved in these beams at room temperature by active control of strain. The ability to engineer phase inhomogeneity with strain lends insight into correlated electron materials in general, and opens opportunities for designing and controlling the phase inhomogeneity of correlated electron materials for micro- and nanoscale device applications.Comment: 14 pages, 4 figures, with supplementary informatio

Pleiotropic effects of statins in distal human pulmonary artery smooth muscle cells

<p>Abstract</p> <p>Background</p> <p>Recent clinical data suggest statins have transient but significant effects in patients with pulmonary arterial hypertension. In this study we explored the molecular effects of statins on distal human pulmonary artery smooth muscle cells (PASMCs) and their relevance to proliferation and apoptosis in pulmonary arterial hypertension.</p> <p>Methods</p> <p>Primary distal human PASMCs from patients and controls were treated with lipophilic (simvastatin, atorvastatin, mevastatin and fluvastatin), lipophobic (pravastatin) and nitric-oxide releasing statins and studied in terms of their DNA synthesis, proliferation, apoptosis, matrix metalloproteinase-9 and endothelin-1 release.</p> <p>Results</p> <p>Treatment of human PASMCs with selected statins inhibited DNA synthesis, proliferation and matrix metalloproteinase-9 production in a concentration-dependent manner. Statins differed in their effectiveness, the rank order of anti-mitogenic potency being simvastatin > atorvastatin > > pravastatin. Nevertheless, a novel nitric oxide-releasing derivative of pravastatin (NCX 6550) was effective. Lipophilic statins, such as simvastatin, also enhanced the anti-proliferative effects of iloprost and sildenafil, promoted apoptosis and inhibited the release of the mitogen and survival factor endothelin-1. These effects were reversed by mevalonate and the isoprenoid intermediate geranylgeranylpyrophosphate and were mimicked by inhibitors of the Rho and Rho-kinase.</p> <p>Conclusions</p> <p>Lipophilic statins exert direct effects on distal human PASMCs and are likely to involve inhibition of Rho GTPase signalling. These findings compliment some of the recently documented effects in patients with pulmonary arterial hypertension.</p

Unprecedented Insulator-To-Metal Transition Dynamics by Heterogeneous Catalysis in Pd-Sensitized Single Vanadium Oxide Nanowires

Materials Science & EngineeringIn the part 1, Single crystal vanadium dioxide (VO2) nanowires were grown by physical vapor deposition (PVD) under atmospheric pressure and synthesized on a silicon dioxide (SiO2), a sapphire (Al2O3) C-plan and a sapphire R-plan as a substrate.The controllable spontaneous conversion of thin films into nanowires for large area production is investigated. The synthesis is found to depend critically on the thickness of V2O5 layer. We have controlled that the nanowires that are single crystal vanadium dioxide can be grown with thickness of V2O5 thin film and also we can synthesize VO2 nanowires to various directions on the substrate. By using the patterned substrate, we can not only control the numerous VO2 nanowire morphologies but also fabricate the guided growth of millimeter-long VO2 nanowires. In the part 2, we report the high effective hydrogen gas sensor based on the metal-to-insulator transition (MIT) by the electro-thermally induced Palladium-nanoparticles-decorated VO2 nanowire prepared by the efficient and size-controllable growth method originated from V2O5 thin film driven.We have many experiments for improved hydrogen gas detector based on the MIT. First by doping the tungsten we showed that the MIT temperature was reduced to about 40°C. Second by irradiating a well-defined electron beam into the nanowires, we could considerably increase the conductivity up to 4 times with only a modest change in the MIT temperature (< 2°C). When exposed to trace amounts of hydrogen gas in a single nanowire configuration, the enhanced conductivity gave rise to about two times as fast transition to metallic phase even near room temperature (~35°C), by reaching much faster (~3x) a critical current density at which the self-heating initiates. Last, especially Palladium-VO2 nanowire near-corshell nanostructure shows remarkably large current increase at a temperature 10 °C lower than the MIT temperature in the bulk. This current increase occurs slowly over the duration of several seconds to several tens of seconds, depending on the Pd coverage, temperature, and hydrogen concentration. This novel finding thus mentions the capability of detecting selectively hydrogen of different three gases (O2, CO2, and ethylene) and has significant implications for the effective engineering the physicochemical properties of vanadium dioxide by a heterogeneous catalytic process.ope

Estimations de l'âge de la puberté et du passage à l'âge adulte chez les jeunes Mérina et Tanala de Madagascar

Summary. — A study on the morphological characters has been conducted within young individuals Merina and Tanala of both sexes in Madagascar. Through this study, we could specify and confirm some qualitative secondary sexual characteristics on the basis of accurate quantitative characteristics such as stature, weight, biacromial and bicretal widths. These qualitative secondary sexual features include down above lips and voice breaking for boys and growth within the mammary region (breast and nipples) for girls, features which are considered as rather inaccurate. However these could be important indicators of the puberty age. Among girls, the appearance of the menarche and the monthly menstrual cycles chronologically precise these secondary sexual characters. This study leads us to define the modalities of these different characters through adulthood.Résumé. — Une étude des caractères morphologiques permettant de définir les différentes phases de la croissance a été menée chez les jeunes Merina et Tanala de Madagascar des deux sexes. Elle a permis de préciser et de confirmer grâce aux caractères quantitatifs tels que la stature, le poids, la largeur biacromiale et la largeur bicrêtale, quelques caractères sexuels secondaires qualitatifs tels que la présence du duvet au-dessus des lèvres et la mue de la voix chez les garçons, le développement de la région mammaire (mamelons et seins) chez les filles, caractères souvent considérés comme peu précis mais qui peuvent pourtant servir d'indicateurs majeurs de l'âge de la puberté. Ces derniers sont d'ailleurs accompagnés chez les filles par la ménarche et l'installation des cycles menstruels. Les modalités du passage au stade adulte pour ces différents caractères ont été précisées.Rakotosamimanana B. R., Randrianarison G., Rakotoniaina G. V., Ratsimbazafy J. H., Spiral G. J. Estimations de l'âge de la puberté et du passage à l'âge adulte chez les jeunes Mérina et Tanala de Madagascar. In: Bulletins et Mémoires de la Société d'anthropologie de Paris, Nouvelle Série. Tome 5 fascicule 1-2, 1993. pp. 175-193

Modification of Anopheles gambiae distribution at high altitudes in Madagascar

In Madagascar, Anopheles gambiae has been found below altitudes of 1,000 m. We sampled An. gambiae sensu lato (sl) between 2008 and 2010 in the Central Highlands of Madagascar at altitudes over 1,200 m. The study site consists of rainforest, rainforest edge, and an open savanna biotope. Anopheles gambiae and An. arabiensis, as well as molecular forms of An. gambiae, were identified molecularly. An. gambiae accounted for 26.7% at the edge of the rainforest and 2.3% in the open savanna biotope. One specimen of this species was caught in the forest. An. arabiensis accounted for 66.3% at the edge of the rainforest and 97.7 % in the open savanna biotope. All An. gambiae adults tested belonged to the S molecular form. An. gambiae is present at high altitudes in Madagascar, with a high prevalence at the rainforest edge. Several factors, including the appearance of new favorable biotopes, recolonization after a reduction of indoor vector control, and climate change, may contribute to its distribution. The changing distribution of An. gambiae may have consequences for the distribution and incidence of malaria in the Malagasy Highlands