Enhanced ionic conductivity in an otherwise poorly conducting Ce0.90Ca0.10O(2-δ) system

A poorly conducting ionic material Ce(0.90)Ca(0.10)O(2-δ) was converted to a highly conducting composition by a codoping strategy with Sm(3+) and Gd(3+). A 50% replacement of Ca with either Sm or Gd has increased the conductivity at 550 °C of Ce(0.90)Ca(0.10)O(2-δ) from 0.0040 to 0.0169 S/cm for the Ce(0.90)Ca(0.05)Sm(0.05)O(2-δ) composition and to 0.0184 S/cm for the Ce(0.90)Ca(0.05)Gd(0.05)O(2-δ) composition. The enhancement in the oxide ion conductivity of these codoped samples has been related to the low ionic radii mismatch and the elastic strain. The extended X-ray absorption fine structure measurements on these systems confirmed that Gd, when coupled with Ca, introduced more disorder in the system, leading to lower activation energy and higher conductivity. In addition, a reduction in the Ce-O bond distance and coordination number has also been observed with codoping.     

Polyphenol contents and antioxidant activity of Brassica nigra (L.) Koch. leaf extract

Profound research has been done on the medicinal value of Brassica nigra (BN) seeds, and the leaves of the plant have been investigated in this study. The methanol extracts of the leaves were subjected to several in?vitro studies. The antioxidant activity of methanol extract was demonstrated with a wide range of concentration, 10-500?μg?mL(-1), and the antioxidant activity increased with the increase in concentration. Total phenol content was found to be 171.73?±?5.043 gallic acid equivalents and the total flavonoid content 7.45?±?0.0945 quercetin equivalents. Further quantification and identification of the compounds were done by HPTLC and GC-MS analyses. The predominant phenolic compounds determined by HPTLC were gallic acid, followed by quercetin, ferulic acid, caffeic acid and rutin. The free radical quenching property of BN leaf extract suggests the presence of bioactive natural compounds.     

Quantitative assessment of surface functionality effects on microglial uptake and retention of PAMAM dendrimers

Dendrimers are a promising class of polymeric nanoparticles for delivery of therapeutics and diagnostics. Polyamidoamine (PAMAM) dendrimers have shown significant efficacy in many animal models, with performance dependent on surface functionalities. Understanding the effects of end groups on biological interactions is critical for rational design of dendrimer-mediated therapies. In this study, we quantify the cellular trafficking kinetics (endocytosis and exocytosis) of generation 4 neutral (D4-OH), cationic (D4-NH₂), anionic (D3.5-COOH), and generation 6 neutral (D6-OH) PAMAM dendrimers to investigate the nanoscale effects of surface functionality and size on cellular interactions. Resting and LPS-activated microglia were studied due to their central roles in dendrimer therapies for central nervous system disorders. D4-OH exhibits greater cellular uptake and lower retention than the larger D6-OH. D4-OH and D3.5-COOH exhibit similar trafficking kinetics, while D4-NH₂ exhibits significant membrane interactions, resulting in faster cell association but lower internalization. Cationic charge may also enhance vesicular escape for greater cellular retention and preferential partitioning to nuclei. LPS activation further improves uptake of dendrimers, with smaller and cationic dendrimers experiencing the greatest increases in uptake compared to resting microglia. These studies have implications for the dependence of trafficking pathway on dendrimer properties and inform the design of dendrimer constructs tailored to specific therapeutic needs. Cationic dendrimers are ideal for delivering genetic materials to nuclei, but toxicity may be a limiting factor. Smaller, neutral dendrimers are best suited for delivering high levels of therapeutics in acute neuroinflammation, while larger or cationic dendrimers provide robust retention for sustained release of therapeutics in longer-term diseases.     

MHD flow and heat transfer of a UCM fluid over a stretching surface with variable thermophysical properties

In this paper we investigate the effects of temperature-dependent viscosity, thermal conductivity and internal heat generation/absorption on the MHD flow and heat transfer of a non-Newtonian UCM fluid over a stretching sheet. The governing partial differential equations are first transformed into coupled non-linear ordinary differential equation using a similarity transformation. The resulting intricate coupled non-linear boundary value problem is solved numerically by a second order finite difference scheme known as Keller-Box method for various values of the pertinent parameters. Numerical computations are performed for two different cases namely, zero and non-zero values of the fluid viscosity parameter. That is, 1/?? _r ??0 and 1/?? _r ??0 to get the effects of the magnetic field and the Maxwell parameter on the velocity and temperature fields, for several physical situations. Comparisons with previously published works are presented as special cases. Numerical results for the skin-friction co-efficient and the Nusselt number with changes in the Maxwell parameter and the fluid viscosity parameter are tabulated for different values of the pertinent parameters. The results obtained for the flow characteristics reveal many interesting behaviors that warrant further study on the non-Newtonian fluid phenomena, especially the UCM fluid phenomena. Maxwell fluid reduces the wall-shear stress.     

Optical absorption spectrum of Ni2+ ions doped in sodium potassium sulphate single crystal

Single crystals of nickel-doped sodium potassium sulphate were grown by slow evaporation method at room temperature. From the nature and position of the bands observed, a successful interpretation of all the observed bands could be made assuming the octahedral symmetry for the Ni^{2 +} ion in the crystal. The bands have been ascribed to transitions from the ground³A_2g(F) state to the excited³T_2g(F),¹E_g(D),³T_1g(F),¹T_2g(D) and³T_1g(P) states. The experimental and calculated energies are in good agreement. The crystal field parameters derived areDq= =880 cm^–1,B= 900cm^–1 andC=3600 cm^–1.One of the authors, Sujatha John expresses her thanks to the Secretary and the Principal, R. B. V. R. Reddy College, Hyderabad for according her permission to pursue the M. Phil. course.     

Synergistic solvent extraction of Eu(III) and Tb(III) with mixtures of various organophosphorus extractants

Synergistic solvent extraction of Eu(III) and Tb(III) from thiocyanate solutions with mixtures of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA) and di-2-ethylhexylphosphoric acid (DEHPA) or tributyl phosphate (TBP) or trioctylphosphine oxide (TOPO) or triphenylphosphine oxide (TPhPO) in benzene has been studied. The mechanism of extraction can be explained by a simple chemically based model presented in this paper. The equilibrium constants of the mixed-ligand species of the various neutral donors have been determined by non-linear regression analysis.     

Differential pulse polarographic determination of procymidone in formulations and wine

The dicarboximide fungicide procymidone was studied systematically by using direct current polarography, cyclic voltammetry, differential pulse polarography (DPP), controlled potential electrolysis, and millicoulometry in the universal buffer medium with dimethylformamide as the solvent. Procymidone exhibited a single well-defined polarographic wave in the pH range 2.0-6.0, leading to the formation of the hydroxy compound. The overall reduction process was diffusion-controlled and adsorption-free. The variation of half-wave potential with pH, the concentration of the analyte, and other experimental conditions are described. The reduction mechanism proposed is an overall 4-electron process, in which the dicarboximide group is reduced. DPP was used to determine procymidone in agricultural formulations and wine at the optimum conditions found; a detection limit of 2.4 x 10(-9) M was estimated. The results obtained by the proposed method were also compared with those obtained by other methods.     

Copper(II)-disulphide interaction: a spectroscopic and electrochemical study of the interaction of copper(II) with an imidazole-containing disulphide

Summary The interaction of copper(II) salts with the imidazole-containing disulphide 5-(1,2,5-dithiazaepan-5-ylmethylene)-4-methyl-2-ethyl imidazole (MAMI) in MeOH have been investigated. The 11 Cu(ClO₄)₂MAMI system exhibited a single ligand field band at ca. 12200cm^-1, an intense shoulder at ca. 31500 cm^-1 and a less intense split feature at 24400 and 25300cm^-1 assignable to S() Cu^II and S() Cu^II charge transfer (CT) transitions, respectively. The e.p.r. parameters suggested the presence of a CuN₂SO chromophore, however; the 11 Cu(NO₃)₂MAMI system did not exhibit a S Cu^II CT band and the g value was comparatively high. An electrochemical study of the 11 Cu(ClO₄)₂MAMI system in MeOH revealed that the copper-disulphide interaction, though weaker, would confer a high redox potential as well as reversibility, similar to the copper-thioether interaction.     

Grothendieck's theorem on non-abelian and local-global principles

A theorem of Grothendieck asserts that over a perfect field of cohomological dimension one, all non-abelian -cohomology sets of algebraic groups are trivial. The purpose of this paper is to establish a formally real generalization of this theorem. The generalization - to the context of perfect fields of virtual cohomological dimension one - takes the form of a local-global principle for the -sets with respect to the orderings of the field. This principle asserts in particular that an element in is neutral precisely when it is neutral in the real closure with respect to every ordering in a dense subset of the real spectrum of . Our techniques provide a new proof of Grothendieck's original theorem. An application to homogeneous spaces over is also given.