Short and long-term effects of Baccharis articulata on glucose homeostasis

In this study, the in vivo effect of the crude extract and n-butanol and aqueous residual fractions of Baccharis articulata (Lam.) Pers. on serum glucose levels, insulin secretion and liver and muscle glycogen content, as well as in vitro action on serum intestinal disaccharidase activity and albumin glycation were investigated. Oral administration of the extract and fractions reduced glycemia in hyperglycemic rats. Additionally, the n-butanol fraction, which has high flavonoids content, stimulated insulin secretion, exhibiting an insulinogenic index similar to that of glipizide. Also, the n-butanol fraction treatment significantly increased glycogen content in both liver and muscle tissue. In vitro incubation with the crude extract and n-butanol and aqueous residual fractions inhibited maltase activity and the formation of advanced glycation end-products (AGEs). Thus, the results demonstrated that B. articulata exhibits a significant antihyperglycemic and insulin-secretagogue role. These effects on the regulation of glucose homeostasis observed for B. articulata indicate potential anti-diabetic properties.     

Structures and bonding in K0.91U1.79S6 and KU2Se6

The compounds K0.91U1.79S6 and KU2Se6, members of the AAn2Q6 actinide family (A = alkali metal or Tl; An = Th or U; Q = S, Se, or Te), have been synthesized from US2, K2S, and S at 1273 K and U, K2Se, and Se at 1173 K, respectively. KU2Se6 shows Curie-Weiss behavior above 30 K and no magnetic ordering down to 5 K. The value of mu(eff) is 2.95(1) mu(B)/U. Its electronic spectrum shows the peaks characteristic of 5f-5f transitions. It is a semiconductor with an activation energy of 0.27 eV for electrical conduction. Both K0.91U1.79S6 and KU2Se6 crystallize in space group Immm of the orthorhombic system and are of the KTh2Se6 structure type. Both contain infinite one-dimensional linear Q-Q chains characteristic of the AAn2Q6 family. Typical of the known AAn2Q6 compounds, in KU2Se6, there are two alternating Se-Se distances of 2.703(2) and 2.855(2) A, both much longer than an Se-Se single bond. In contrast, in K0.91U1.79S6, the first sulfide of this family to be characterized structurally, there are alternating normal S2(2-) pairs 2.097(5) A in length. In K0.91U1.79S6, the formal oxidation state of U is 4+.     

Synthesis of degradable model networks via ATRP and click chemistry

A simple scheme involving atom transfer radical polymerization (ATRP) from a bifunctional initiator, conversion of the bromine end groups of the resulting telechelic polymer to azides, and cross-linking of this azido-telechelic macromonomer with multi-acetylene functionalized small molecules via copper-catalyzed azide-alkyne cycloaddition was employed to prepare the first tert-butyl acrylate model networks. This general scheme is wide in scope, enabling synthesis of model networks possessing defined pore size from any monomer polymerizable by ATRP. Introduction of an olefin moiety into the ATRP initiator enabled degradation of the materials by ozonolysis to yield star polymer products bearing three or four arms depending on which cross-linker was employed in the parent network. Size-exclusion chromatography of the ozonolysis products confirmed the pore size of the parent network and yielded insight into the number of unreacted functionalities. Model networks derived from a trifunctional alkyne were found to be more completely cross-linked than those derived from a tetrafunctional alkyne, presumably due to less steric hindrance in the former system.     

Experimental and theoretical study of the regiospecific coordination of RuII and OsII fragments on the lacunary polyoxometalate [alpha-PW11O39]7-

New Ru(II) and Os(II) derivatives of the monovacant [alpha-PW(11)O(39)](7-) anion ([PW(11)O(39){M(DMSO)(3)(H(2)O)}](5-) (M = Ru (1), Os (2)) and [PW(11)O(39){Os(eta(6)-p-cym)(H(2)O)}](5-) (3)) have been synthesized and characterized. The binding mode of the d(6)-{M(II)L(3)(H(2)O)}(2+) moieties in these compounds is similar to that in the previously described [PW(11)O(39){Ru(eta(6)-p-cym)(H(2)O)}](5-) (4) complex: bidentate, on two nonequivalent oxygen atoms of the lacuna, leading to a loss of the C(s) symmetry of the parent anion, which thus plays the role of a prochiral bidentate ligand. The density functional theory (DFT) (B3PW91) computation of the lowest unoccupied molecular orbitals of the {ML(3)(H(2)O)}(2+) (M = Os, Ru; L(3) = fac-(DMSO)(3), eta(6)-C(6)H(6)) fragments reveals the similarities between their electrophilic properties. The origin of the regioselectivity of the grafting was investigated through a DFT (B3PW91) analysis of (i) the highest occupied molecular orbital of [alpha-PW(11)O(39)](7-) and (ii) the relative energies of the different potential regioisomers obtained by a bidentate grafting of the {ML(3)(H(2)O)}(2+) moiety onto the lacuna of [alpha-PW(11)O(39)](7-). The role of the water ligand in the stabilization of this peculiar structure was studied.     

Relationship between salt-bridge identity and 14-helix stability of beta3-peptides in aqueous buffer

[STRUCTURE: SEE TEXT] We report a systematic analysis of the relationship between salt bridge composition and 14-helix structure within a family of model beta-peptides in aqueous buffer. We find an inverse relationship between side-chain length and the extent of 14-helix structure as judged by CD. Introduction of a stabilizing salt bridge pair within a previously reported beta-peptide ligand for hDM2 led to changes in structure that were detectable by NMR.     

Diastereoselective multicomponent synthesis of dihydropyridones with an isocyanide functionality

[Structure: see text] In a search for new multicomponent strategies leading to valuable small heterocycles, a new highly diastereoselective four-component reaction (4CR) was found in which a phosphonate, nitriles, aldehydes, and isocyanoacetates combine to afford functionalized 3-isocyano-3,4-dihydro-2-pyridones. In this strategy, initially a 1-azadiene is generated, which is trapped in the same pot by an isocyanoacetate as the fourth component. Multicomponent reactions (MCRs) that lead to heterocycles containing isocyano substituents are unprecedented and offer many possibilities for further differentiation.     

Assessment of spatial BOLD sensitivity variations in fMRI using gradient-echo field maps

Clinical blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is becoming increasingly valuable in, e.g., presurgical planning, but the commonly used gradient-echo echo-planar imaging (GE-EPI) technique is sometimes hampered by macroscopic field inhomogeneities. This can affect the degree of signal change that will occur in the GE-EPI images as a response to neural activation and the subsequent blood oxygenation changes, i.e., the BOLD sensitivity (BS). In this study, quantitative BS maps were calculated directly from gradient-echo field maps obtainable on most clinical scanners. In order to validate the accuracy of the calculated BS-maps, known shim gradients were applied and field maps and GE-EPI images of a phantom were acquired. Measured GE-EPI image intensity was then compared with the calculated (predicted) image intensity (pII) which was obtained from the field maps using theoretical expressions for image-intensity loss. The validated expressions for pII were used to calculate the corresponding predicted BOLD sensitivity (pBS) maps in healthy volunteers. Since the field map is assumed to be valid throughout an entire fMRI experiment, the influence of subject motion on the pBS maps was also assessed. To demonstrate the usefulness of such maps, pBS was investigated for clinically important functional areas including hippocampus, Broca's area and primary motor cortex. A systematic left/right pBS difference was observed in Broca's area and in the hippocampus, most likely due to magnetic field inhomogeneity of the particular MRI-system used in this study. For all subjects, the hippocampus showed pBS values above unity with a clear anterior–posterior gradient and with an abrupt drop to zero pBS in the anterior parts of hippocampus. It is concluded that GE field maps can be used to accurately predict BOLD sensitivity and that this parameter is useful to assess spatial variations which will influence fMRI experiments.     

Stabilization of Solutions to a FitzHugh-Nagumo Type System

We consider a bistable reaction-diffusion system arising in the theory of phase transitions; it appears in several physical contexts such as thin magnetic films and the microphase separation in diblock copolymer melts. Mathematically it takes the form of an Allen-Cahn equation coupled to an elliptic equation. This system possesses a Lyapunov functional which represents the Gibbs free energy of the phase separation problem. We study the large time behavior of the solution orbits, and use the fact that the problem has a gradient structure to prove their stabilization by means of a version of ?ojasiewicz inequality.     

Extraction of hyperoside and quercitrin from mimosa (Albizia julibrissin) foliage

Mimosa, an excellent energy crop candidate because of its high growth yield, also contains, on a dry basis, 0.83% hyperoside and 0.90% quercitrin. Hyperoside has been documented as having anti-inflammatory and diurectic properties, whereas quercitrin may play a role in intestinal repair following chronic mucosal injury. Thus, mimosa might first be extracted for important antioxidant compounds and then used as a feedstock for energy production. This article presents results from studies aimed at determining the effect of three extraction parameters (temperature, solvent composition, and time) on the yield of these important quercetin compounds. Conditions are sought which maximize yield and concentration, whereas complementing subsequent biomass pretreatment, hydrolysis and fermentation.     

A combined finite volume–nonconforming/mixed-hybrid finite element scheme for degenerate parabolic problems

We propose and analyze a numerical scheme for nonlinear degenerate parabolic convection–diffusion–reaction equations in two or three space dimensions. We discretize the diffusion term, which generally involves an inhomogeneous and anisotropic diffusion tensor, over an unstructured simplicial mesh of the space domain by means of the piecewise linear nonconforming (Crouzeix–Raviart) finite element method, or using the stiffness matrix of the hybridization of the lowest-order Raviart–Thomas mixed finite element method. The other terms are discretized by means of a cell-centered finite volume scheme on a dual mesh, where the dual volumes are constructed around the sides of the original mesh. Checking the local Péclet number, we set up the exact necessary amount of upstream weighting to avoid spurious oscillations in the convection-dominated case. This technique also ensures the validity of the discrete maximum principle under some conditions on the mesh and the diffusion tensor. We prove the convergence of the scheme, only supposing the shape regularity condition for the original mesh. We use a priori estimates and the Kolmogorov relative compactness theorem for this purpose. The proposed scheme is robust, only 5-point (7-point in space dimension three), locally conservative, efficient, and stable, which is confirmed by numerical experiments.This work was supported by the GdR MoMaS, CNRS-2439, ANDRA, BRGM, CEA, EdF, France.