Charge reversal and surface charge amplification in asymmetric valence restricted primitive model planar electric double layers in the modified Poisson-Boltzmann theory

The modified Poisson-Boltzmann theory of the restricted primitive model double layer is revisited and recast in a fresh, slightly broader perspective. Derivation of relevant equations follow the techniques utilized in the earlier MPB4 and MPB5 formulations and clarifies the relationship between these. The MPB4, MPB5, and a new formulation of the theory are employed in an analysis of the structure and charge reversal phenomenon in asymmetric 2:1/1:2 valence electrolytes. Furthermore, polarization induced surface charge amplification is studied in 3:1/1:3 systems. The results are compared to the corresponding Monte Carlo simulations. The theories are seen to predict the "exact" simulation data to varying degrees of accuracy ranging from qualitative to almost quantitative. The results from a new version of the theory are found to be of comparable accuracy as the MPB5 results in many situations. However, in some cases involving low electrolyte concentrations, theoretical artifacts in the form of un-physical "shoulders" in the singlet ionic distribution functions are observed.Comment: 15 pages, 13 figure

Characterizing fruit ripening in plantain and Cavendish bananas: A proteomics approach

The fruit physiology of banana cultivars other than Cavendish is poorly understood. To study the ripening process, samples were taken daily from plantain and Cavendish bananas and the ripening stages were determined. We present data from the green to the fully mature stage. By analyzing the protein abundances during ripening we provide some new insights into the ripening process and how plantains fruits are different. Multivariate analysis of the proteins was performed correlated to the starch dynamics. A drop in sucrose synthase and a rise of acid invertase during ripening indicated a change in the balance of the sucrose fate. During ripening, sugars may no longer be available for respiration since they are stored in the vacuoles, making citrate the preferred respiratory substrate. We found significant cultivar specific differences in granule-bound starch synthase, alpha- and beta amylases and cell wall invertase when comparing the protein content at the same ripening stage. This corroborates the difference in starch content/structure between both banana types. Differences in small heat shock proteins and in the cell wall-modifying enzyme xyloglucan endotransglucosylase/hydrolase support respectively the presumed higher carotenoid content and the firmer fruit structure of plantains

Producing more rice with less water from irrigated systems

Irrigation management / Water use efficiency / Crop production / Water requirements / Water balance / Rice / Water distribution / Irrigated farming / Productivity / On-farm research / Irrigation scheduling / Groundwater / Conjunctive use / Rehabilitation / Modernization / Farmer participation / Farming systems / Irrigation systems / Crop-based irrigation / Asia / Philippines / Sri Lanka / Bangladesh / China / Malaysia / USA

Diethyl 6H,12H-5,11-methano­dibenzo[b,f][1,5]diazo­cine-1,7-dicarboxyl­ate

In the mol­ecule of the title compound, C21H22N2O4, the 1,7-diethyl ester analogue of Tröger’s base, the dihedral angle between the two benzene rings is 93.16 (3)°; the mol­ecule is C 2 symmetric

Thermodynamics of primitive model electrolytes in the symmetric and modified Poisson-Boltzmann theories. A comparative study with Monte Carlo simulations

Osmotic coefficients, individual and mean activity coefficients of primitive model electrolyte solutions are computed at different molar concentrations using the symmetric Poisson-Boltzmann and modified Poisson-Boltzmann theories. The theoretical results are compared with an extensive series of Monte Carlo simulation data obtained by Abbas et al. [Fluid Phase Equilib., 2007, 260, 233; J. Phys. Chem. B, 2009, 113, 5905]. The agreement between modified Poisson-Boltzmann predictions with the "exact" simulation results is almost quantitative for monovalent salts, while being semi-quantitative or better for higher and multivalent salts. The symmetric Poisson-Boltzmann results, on the other hand, are very good for monovalent systems but tend to deviate at higher concentrations and/or for multi-valent systems. Some recent experimental values for activity coefficients of HCl solution (individual and mean activities) and NaCl solution (mean activity only) have also been compared with the symmetric and modified Poisson-Boltzmann theories, and with the Monte Carlo simulations.Comment: 10 pages, 9 figure

Synthesis and Characterization of Homoleptic and Heteroleptic Ruthenium Polypyridine Complexes

The homoleptic ruthenium(II) complex Ru(C13H10N2)3(PF6)2, and heteroleptic ruthenium(II) complexes Ru(C13H10N2)2(C10H8N2)(PF6)2, and Ru(C13H10N2)(C10H8N2)2(PF6)2 have been prepared by following the standard synthetic procedure. These complexes were then purified by repeated column chromatography. The identity and the integrity of the complexes were confirmed by elemental analysis and mass spectroscopy. The calculated and the experimental values for the elemental analysis were in good agreement. The calculated and the experimental molar masses obtained were also identical. Ultravioletvisible absorption and emission spectroscopic methods were used to investigate the properties of these complexes. The absorption spectra of all complexes consist of a series of absorption bands in the ultraviolet and visible region. All three complexes show a strong emission band in the visible region. The emission maxima for the heteroleptic complexes are slightly redshifted

The primitive model of ionic fluids near its critical point in the Poisson–Boltzmann and modified Poisson–Boltzmann theories

The Poisson–Boltzmann (PB) and modified Poisson–Boltzmann (MPB) theories are used to investigate the primitive model of ionic fluids in the low density–large coupling regime where the liquid–vapor transition is situated. The PB and MPB spinodal curves for the restricted primitive model are calculated from the virial route and compared with those from the mean spherical approximation (energy route) and the hybrid hypernetted‐chain/mean spherical approximation (virial route). The effect of unequal ion sizes on the critical point and spinodal curves is also considered.National Sanitation Foundation (NSF) EE.UU. CHE-8907130Fondo Institucional para la Investigación (FIPI) de la Universidad de Puerto RicoComunidad Europea (beca Marie Curie)Dirección General de Investigación Científica y Técnica (DGICYT). España PBgl / 060

Effect of plasma surface treatment of poly (dimethylsiloxane) on the permeation of pharmaceutical compounds

This paper addresses the modification of poly(dimethylsiloxane), i.e. PDMS, using plasma surface treatment and a novel application of the membrane created. A set of model compounds were analysed to determine their permeation through PDMS both with, and without, plasma treatment. It was found that plasma treatment reduced permeation for the majority of compounds yet had little effect for some compounds, such as caffeine, with results indicating that polarity plays an important role in permeation, as is seen in human skin. Most importantly, a direct correlation was observed between plasma-modified permeation data and literature data through calculation of membrane permeability (Kp) values implying plasma-modified silicone membrane (PMSM) could be considered a suitable in vivo replacement to predict clinical skin permeatio