1,401 research outputs found
Effects of sulfonation process on thermal behavior and microstructure of sulfonated polysulfone membranes as a material for Proton Exchange Membrane (PEM)
This paper reports the effect of sulfonation processon thermal behavior and microstrucutre of sulfonated polysulfone membrane. Various degree of sulfonation reactin has been conducted and the sulfonated membranes were characterized by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), x-ray diffraction (XRD) and scanning electron microscopy (SEM). Modifications of the origin polysulfone polymer resulted in an increment value of glass transition temperature (Tg) due to the introduction of sulfonic acid group to the polymer backbone. However, due to some hindrance such as trace amount of organic solvent left during solvent evaporation and high hydrophilicity of the produced sulfonated membranes resulted in decreasing values of Tg. The polymer membrane showed lower degradation temperature as a function of degree of sulfonation. From XRD analysis, it was found that the membrane shows slight crystalline behavior after the sulfonation reaction. Detail discussions and observation of the alteration in microstructure of the sulfonated membrane were supported by SEM micrograph
Recommended from our members
Target revaluation after failed takeover attempts - cash versus stock
Cash- and stock-financed takeover bids induce strikingly different target revaluations. We exploit detailed data on unsuccessful takeover bids between 1980 and 2008, and we show that targets of cash offers are revalued on average by +15% after deal failure, whereas stock targets return to their pre-announcement levels. The differences in revaluation do not revert over longer horizons. We find no evidence that future takeover activities or operational changes explain these differences. While the targets of failed cash and stock offers are both more likely to be acquired over the following eight years than matched control firms, no differences exist between cash and stock targets, neither in the timing nor in the value of future offers. Similarly, we cannot detect differential operational policies following the failed bid. Our results are most consistent with cash bids revealing prior undervaluation of the target. We reconcile our findings with the opposite conclusion in earlier literature (Bradley, Desai, and Kim, 1983) by identifying a look-ahead bias built into their sample construction
On Black Attractors in 8D and Heterotic/Type IIA Duality
Motivated by the study of black attractors in 8D supergravity with 16
supersymmetries, we use the field theory approach and 8D supersymmetry with non
trivial central charges to shed light on the exact duality between heterotic
string on T^2 and type IIA on real connected and compact surfaces {\Sigma}2. We
investigate the two constraints that should be obeyed by {\Sigma}2 and give
their solutions in terms of intersecting 2-cycles as well their classification
using Dynkin diagrams of affine Kac-Moody algebras. It is shown as well that
the moduli space of these dual theories is given by
SO(1,1)x((SO(2,r+2))/(SO(2)xSO(r+2))) where r stands for the rank of the gauge
symmetry G_{r} of the 10D heterotic string on T^2. The remarkable cases
r=-2,-1,0 as well as other features are also investigated.Comment: LaTex, 18 pages, 2 figures, To appear in JHE
Extremal Black Attractors in 8D Maximal Supergravity
Motivated by the new higher D-supergravity solutions on intersecting
attractors obtained by Ferrara et al. in [Phys.Rev.D79:065031-2009], we focus
in this paper on 8D maximal supergravity with moduli space
[SL(3,R)/SO(3)]x[SL(2,R)/SO(2)] and study explicitly the attractor mechanism
for various configurations of extremal black p- branes (anti-branes) with the
typical near horizon geometries AdS_{p+2}xS^{m}xT^{6-p-m} and p=0,1,2,3,4;
2<=m<=6. Interpretations in terms of wrapped M2 and M5 branes of the 11D
M-theory on 3-torus are also given.
Keywords: 8D supergravity, black p-branes, attractor mechanism, M-theory.Comment: 37 page
ActivitĂ© hypoglycĂ©mique de lâextrait aqueux dâAjuga iva L. schreber chez les rats diabĂ©tiques induite par lâalloxane
Ajuga iva (L) schreber est utilisĂ© en mĂ©decine traditionnelle dans le traitement du diabĂšte. Le but de cette étude Ă©tait d'Ă©valuer l'activitĂ© l'hypoglycĂ©mique de l'extrait aqueux de la partie aĂ©rienne de cette plante sur un modĂšle animal. Lâextrait a Ă©tĂ© prĂ©parĂ© dans de l'eau bouillante et le filtrat aqueux a Ă©tĂ© lyophilisĂ© et conservĂ©. A iva est une plante capable dâinduire une hypoglycĂ©mie chez les rats diabĂ©tiques. Alloxane a Ă©tĂ©Â administrĂ© en dose unique (150 mg poids corporel / kg) par injection intra-pĂ©ritonĂ©al. Des rats femelles Wistar (n = 30) pesant 200 ± 2g divisĂ©s en 5 groupes, ont reçu des doses diffĂ©rentes (0,05 g/mL, 0,10 g/mL, 0,15 g/mL) par voie orale. Cette opĂ©ration est rĂ©pĂ©tĂ©e tous les jours pendant 3 semaines. La glycĂ©mie a Ă©tĂ© dĂ©terminĂ©e par la mĂ©thode enzymatique colorimĂ©trique par spectrophotomĂ©trie. Seul lâextrait aqueux à forte dose a diminuĂ©e le taux du glucose sanguins de 62, 96±7, 30% comparativement au groupe control. Dans la prĂ©sente Ă©tude, le potentiel hypoglycĂ©miant de A iva est dĂ©montrĂ© chez le rat. Ces rĂ©sultats confirment l'utilisation de cette plante comme antidiabĂ©tique.Mots-clĂ©s : Ajuga iva, extrait aqueux, alloxane, activitĂ© hypoglycĂ©mique, diabĂšte.Hypoglycemic Activity of the aqueous extract of Ajuga iva L. in diabetic rats induced by alloxanAjuga iva (L) schreber is used in traditional medicine in the treatment of diabetes, The purpose of this study was to evaluate hypoglycemic effect of the aqueous extract of aerial parts of this plant on animal model. The extract was prepared in boiling water and the aqueous filtrate was lyophilized and conserved. A iva is a plant capable of inducing hypoglycemia in diabetic rats. Alloxan was administered as a single dose (150 mg body weight / kg) injection intaperitoneal injection. Female Wistar rats (n = 30) weighing 200 ± 2g divided into 5 groups received different doses (0.05 GML-1, 0.10 GML-1, 0.15 g / mL) by oral route. This is repeated every day for three weeks. Blood glucose was determined by the enzymatic and colorimetric method by spectrophotometry. Only the aqueous extract high dose rate decreased blood glucose of 62, 96 ± 7, 30% compared with the control group. In the present study, the hypoglycemic potential of the A iva was demonstrated in rats. These results give support to the traditional use of this plant as antidiabetic herbal medicine.Keywords : Ajuga iva L, aqueous extract, alloxan, diabetes, hypoglycemic activity
Fractional Statistics in terms of the r-Generalized Fibonacci Sequences
We develop the basis of the two dimensional generalized quantum statistical
systems by using results on -generalized Fibonacci sequences. According to
the spin value of the 2d-quasiparticles, we distinguish four classes of
quantum statistical systems indexed by , ,
and . For quantum gases of quasiparticles
with , , we show that the statistical weights densities
are given by the integer hierarchies of Fibonacci sequences. This is a
remarkable result which envelopes naturally the Fermi and Bose statistics and
may be thought of as an alternative way to the Haldane interpolating
statistical method.Comment: Late
Ătude comparative de lâactivitĂ© antispasmodique de lâextrait aqueux dâAjuga iva L. et de lâibuprofĂšne chez les souris
Ajuga iva (L.) Schreber, utilisĂ© dans la pharmacopĂ©e traditionnelle, pour des troubles gastro-intestinaux, le diabĂšte et comme hypocholestĂ©rolĂ©miante. LâĂ©tude pharmacologique de lâextrait aqueux dâAjuga iva (Lamiaceae) a Ă©tĂ© effectuĂ©e Ă lâaide de modĂšles animaux. LâĂ©valuation de lâactivitĂ© analgĂ©sique, montre que lâextrait aqueux Ă 0,4g/ L de cette plante induit une diminution du nombre de crampes abdominales dans le test de writhing provoquĂ© par lâacide acĂ©tique Ă 1% Ajuga iva a un effet analgĂ©sique plus efficace que celui de lâibuprofĂšne, en effet ce dernier provoque une inhibition de la douleur de 77,53±3,80 % et celui de ,lâextrait aqueux dâAjuga iva de 85,39±4,29 % pour la mĂȘme concentration (200mg/kg). Lâextrait aqueux dâAjuga iva a des propriĂ©tĂ©s analgĂ©siques qui justifient son usage traditionnel. Les effets thĂ©rapeutiques sont induits par divers composĂ©s rĂ©vĂ©lĂ©s lors du tri phyto chimique de cette plante (alcaloĂŻdes, flavonoĂŻdes, polyphĂ©nols, saponosides, et tanins catĂ©chiques) qui constituent la base scientifique de lâutilisation thĂ©rapeutique traditionnelle de la plante Ă©tudiĂ©e.Mots- clĂ©s : Ajuga iva L., extrait aqueux, effet analgĂ©sique, ibuprofĂšne, writhing test
- âŠ