Discontinuous Galerkin methods on graphics processing units for nonlinear hyperbolic conservation laws

We present a novel implementation of the modal DG method for hyperbolic conservation laws in two dimensions on graphics processing units (GPUs) using NVIDIA's Compute Unified Device Architecture. Both flexible and highly accurate, DG methods accommodate parallel architectures well as their discontinuous nature produces element‐local approximations. High‐performance scientific computing suits GPUs well, as these powerful, massively parallel, cost‐effective devices have recently included support for double‐precision floating‐point numbers. Computed examples for Euler equations over unstructured triangle meshes demonstrate the effectiveness of our implementation on an NVIDIA GTX 580 device. Profiling of our method reveals performance comparable with an existing nodal DG‐GPU implementation for linear problems. Copyright © 2014 John Wiley & Sons, Ltd.     

Antioxidant Activity of Deferasirox and Its Metal Complexes in Model Systems of Oxidative Damage: Comparison with Deferiprone

Deferasirox is an orally active, lipophilic iron chelating drug used on thousands of patients worldwide for the treatment of transfusional iron overload. The essential transition metals iron and copper are the primary catalysts of reactive oxygen species and oxidative damage in biological systems. The redox effects of deferasirox and its metal complexes with iron, copper and other metals are of pharmacological, toxicological, biological and physiological importance. Several molecular model systems of oxidative damage caused by iron and copper catalysis including the oxidation of ascorbic acid, the peroxidation of linoleic acid micelles and the oxidation of dihydropyridine have been investigated in the presence of deferasirox using UV-visible and NMR spectroscopy. Deferasirox has shown antioxidant activity in all three model systems, causing substantial reduction in the rate of oxidation and oxidative damage. Deferasirox showed the greatest antioxidant activity in the oxidation of ascorbic acid with the participation of iron ions and reduced the reaction rate by about a 100 times. Overall, deferasirox appears to have lower affinity for copper in comparison to iron. Comparative studies of the antioxidant activity of deferasirox and the hydrophilic oral iron chelating drug deferiprone in the peroxidation of linoleic acid micelles showed lower efficiency of deferasirox in comparison to deferiprone.     

Histamine Molecule and Dianion Oxalate are Efficient Blocks for Building 2D Supramolecular Networks

Abstract  

One salt and two Cu(II) complexes (H₂hsm)(ox), 1, [Cu(hsm)(ox)], 2, and [Cu(hsm)(ox)H₂O], 3, have been synthesized and X-ray characterized (hsm is histamine and ox²⁻ is the oxalate dianion). Starting from the prochiral tetracoordinated complex 2, pentacoordinated complex 3 crystallizes as a racemic mixture of the enantiomeric Δ and Λ isomers, in space group P2₁/c. In all cases, the side chain of the hsm group is gauche, allowing the formation of strong hydrogen bonds in the salt 1, and to chelate the metal center in complexes 2 and 3. The combination hsm/ox seems to favor the formation of 2D supramolecular structures (planes or wavy planes), through efficient networks of N–H···O hydrogen bonds. Cell parameters: 1, P2₁/c, a = 6.260 (2) ?, b = 11.500 (4) ?, c = 12.525 (4) ?, β = 104.047 (17)o; 2, C2/c, a = 10.7966 (13) ?, b = 15.5622 (16) ?, c = 11.3996 (15) ?, β = 106.261 (11)o; 3, P2₁/c, a = 7.0627 (6) ?, b = 7.1323 (6) ?, c = 20.0296 (19) ?, β = 91.529 (7)o.     

Highly cytotoxic vanadium(V) complexes of salan ligands; insights on the role of hydrolysis

Vanadium(V) oxo complexes with tetradentate diamine bis(phenolato) "salan" ligands of the type LVO(OiPr) (L is salan) with different steric and electronic substitutions at the ortho and para positions to the binding phenolato moiety were synthesized and their hydrolytic stability and cytotoxicity were analyzed. With one exception bearing large steric groups, all complexes examined displayed marked cytotoxic activity, comparable to, and often higher than, that of cisplatin. While the hydrolytic stability changed significantly depending on the substituent at the ortho position relative the O-donor with little effect of para substitutions, the cytotoxic activity largely was not affected, and high cytotoxicity was recorded also for relatively unstable complexes. Additional measurements revealed that the cytotoxicity is largely maintained following pre-incubation of up to 18 hours of the complexes in the biological medium prior to cell addition, suggesting that hydrolysis products might serve as the active species. In addition, appreciable cytotoxic activity was measured for an isolated hydrolysis product that was analyzed crystallographically to exhibit a dimeric structure with bridging oxo ligand where both metal centers are bound to the salan ligand, supporting the aforementioned conclusions.     

Antitrypanosomal activity of a novel norlignan purified from Nectandra lineata

Bioactivity-guided fractionation of a MeOH-EtOAc extract from the young leaves of Nectandra lineata (Lauraceae), using a Trypanosoma cruzi bioassay resulted in the isolation of a novel norlignan 3'-methoxy-3,4-methylenedioxy-4',7-epoxy-9-nor-8,5'-neolignan-9'-acetoxy (1), together with the known compound, 3'-methoxy-3,4-methylenedioxy-4'-7-epoxy-9-nor-8,5'-neolignan-7,8'-diene (2). Compounds 1 and 2 were shown to inhibit the growth of T. cruzi epimastigotes in axenic culture.     

Enhanced ligand affinity for receptors in which components of the binding site are independently mobile

Using calmodulin antagonism as a model, it is demonstrated that, under circumstances in which binding sites are motionally independent, it is possible to create bifunctional ligands that bind with significant affinity enhancement over their monofunctional counterparts. Suitable head groups were identified by using a semiquantitative screen of monofunctional tryptophan analogs. Two bifunctional ligands, which contained two copies of the highest-affinity head group tethered by rigid linkers, were synthesized. The bifunctional ligands bound to calmodulin with a stoichiometry of 1:1 and with an affinity enhancement over their monofunctional counterparts; the latter bound with a stoichiometry of 2:1 ligand:protein. A lower limit to the effective concentrations of the domains of calmodulin relative to each other (0.2-2 mM) was determined. A comparable effective concentration was achieved for bifunctional ligands based on higher-affinity naphthalene sulphonamide derivatives.     

Michael reaction,VI. Effect of carbonyl compounds on the stereochemistry and mechanism of the reaction

Zusammenfassung Die Stereochemie einer zweistufigen Gleichgewichts-Michael-Reaktion zwischen Dialkylamiden der Phenylessigsäure und Methylestern oder Dialkylamiden der Zimtsäure wird von den neutralen Carbonylverbindungen stark beeinflußt. Dieser Effekt kann mit der Zerstörung einer intramolekularen Chelatstruktur des Addukts und der darauffolgenden Bildung einer offenen Metallform mit einem dem neutralen Addukt ähnlichenerythro-threo-Verhältnis erklärt werden. Die Zunahme der elektrischen Leitfähigkeit des Reaktionsgemisches stützt diese Vorstellung.Es wird ein über das Chelat verlaufender Mechanismus im nichtpolaren Medium postuliert. Dieser Mechanismus ist in guter Übereinstimmung sowohl mit der geringen Stereoselektivität (bei kinetischer Kontrolle) als auch mit dem Einfluß der Lösungsmittel auf die Stereochemie.

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Michael reaction, VI. Effect of carbonyl compounds on the stereochemistry and mechanism of the reaction

The equilibrium stereochemical result of the two-stepMichael reaction between phenylacetic acid dialkylamides and methyl cinnamate or cinnamic acid dialkylamides is affected by the neutral carbonyl compounds taking part in the synthesis. This effect is explained by breakdown of the intramolecular chelate structure of the reaction adduct and appearance of an open metal form with isomeric partitioning close to that of the neutral adduct. This is further supported by the increased electroconductivity of the reaction mixtures. A chelate mechanism for the reaction in nonpolar medium is postulated which is in good agreement with the low stereoselectivity under kinetic conditions as well as with the effect of the polarity of the solvent on the kinetic stereochemical result.

     

Quantification of the Effect of an Impurity Addition on the Interaction Between Unlike Molecules in Mixed Liquids: A Theoretical Study

Journal of Solution Chemistry - The aim of this work is to develop a simple theory to study the effect of the addition of an impurity on the interaction between unlike molecules in mixed liquids....