Attracting basins in ℙ2

We prove the existence of infinitely many attracting basins for some holomorphic mappings in ℙ². We also show that if a family of mappings has a complex generic homoclinic tangency, then some of the mappings in the family have an attractive periodic fixed point.     

Viscometric and volumetric behaviour of binary mixtures of sulfolane and N-methylpyrrolidone with monoethanolamine and diethanolamine in the range 303–373 K

Capillary viscometry was used to determine the kinematic viscosity of the binary systems composed of N-methylpyrrolidone + monoethanolamine and N-methylpyrrolidone + diethanolamine throughout the concentration range, at eight different temperatures in the range 303.15–373.15 K. Pure component values of viscosity were also determined in the temperature range 303.15–423.15 K. Using a rolling ball viscometer the absolute viscosity was obtained for the binary systems composed of tetramethylene sulfone (sulfolane) + monoethanolamine and tetramethylene sulfone + diethanolamine, throughout the concentration range, at three different temperatures in the range 303.15–373.15 K. Density results were obtained using a vibrating-tube densimeter for the four pure components and the four binary systems studied, in the same temperature range and the whole concentration range for the binary systems as the viscosity measurements.

The experimental viscosity results for the four pure solvents cover a broader temperature range than previously reported by other workers. The experimental results of viscosity for both pure and binary systems show a decrease with increasing temperature as expected. In the case of the binary systems the change of viscosity with concentration for the two sets of mixtures with N-methylpyrrolidone is very large in the range of 303.15–353.15 K, whereas it is small in the range 363.15–373.15 K. The observed behaviour of the change of viscosity with concentration for sulfolane with monoethanolamine is different from that shown by sulfolane with diethanolamine, at 303.15 and 323.15 K; the first system shows a minimum viscosity point in the sulfolane-rich region whereas at 373.15 K it shows values of viscosity greater than that of the pure components in the whole range of concentration; and the second system shows large variations of viscosity at low sulfolane concentration, at 303.15 and 323.15 K; whereas at 373.15 K the viscosity values change smoothly between those for the two pure components.

From the density results, molar excess volumes were derived, which were correlated using the Redlich–Kister equation; the final expression includes the functionality with both concentration and temperature.     

Dual aperture control on pH- and anion-driven supramolecular nanoscopic hybrid gate-like ensembles

The development of gate-like systems able to perform certain programmed functions is an interesting way of taking chemistry to the frontiers of nanoscience. In relation to this field, we report a complete study of the behavior of a pH-driven and anion-controlled nano-supramolecular gate-like ensemble obtained by anchoring suitable polyamines on the pore outlets of mesoporous materials of the type MCM-41 (solid N3-S). The release of an entrapped dye (Ru(bipy)3(2+)) from the pore voids into the bulk solution allows us to study the gating effect. A pH-driven open/close mechanism was observed that arises from the hydrogen-bonding interaction between amines at neutral pH (open gate) and Coulombic repulsions at acidic pH between closely located polyammoniums at the pore openings (closed gate). Molecular dynamics simulations using force field methods have been carried out to explain the pH-driven open/close mechanism. For this purpose, a mesoporous silica structure was constructed, taking as base the (111) plane of the beta-crystoballite structure on which large hexagonal nanopores and anchored polyamines were included. From these calculations, it was observed how completely unprotonated amines display poor coverage of the pore (fully open gate), whereas completely protonated amines (simulating a pH 2 or lower) result in a clear reduction of the pore aperture, in agreement with the experimental results. In additional to the pH-driven protocol, opening/closing of the gate-like ensemble can also be modulated via an anion-controlled mechanism. This study was carried out by monitoring the dye released from the pore voids of the N3-S solid at a certain pH in the presence of a range of anions with different structural dimensions and charges, including chloride, sulfate, phosphate, and ATP (C(anion) = 1 x 10(-2) mol dm(-3)). The choice of a certain anionic guest results in a different gate-like ensemble behavior, ranging from basically no action (chloride) to complete (ATP) or partial pore blockage, depending on the pH (sulfate and phosphate). The remarkable anion-controllable response of the gate-like ensemble can be explained in terms of anion complex formation with the tethered polyamines. These experimental studies are also in agreement with computational simulations with fluoride, chloride, iodide, and dihydrogen phosphate anions. In the model, larger anions push the tethered polyamines toward the pore openings more efficiently, and therefore the pore aperture decreases. The studies also show that, for anions showing a strong tendency to form hydrogen-bonding networks (e.g., phosphate), complete pore blockage was observed at acidic pH. Finally, selectivity patterns have been discussed in terms of kinetic rates of the liberation of the Ru(bipy)3(2+) dye from the amine-functionalized dye-containing material N3-S.     

Complex impure systems: Sheaves,freeways, and chains

Fundamental to the approach of Complex Impure Systems is the definition of the concept of an s‐impure set as a set of perceptual beliefs or denotative significances (relative beings) of material and/or energetic real objects (absolute beings). But any Subject not only the subject S perceives objects O as significances, and he perceives the existing relations between these significances or, alternatively, he infers them. The study of these relations, conceived not as a singular relation between singular objects, but as sheaves of relations in both directions and forming relational freeways, will be studied here. In this work, we approach the structure of the system, from a synchronous point of view, as a first approach to this class of systems. © 2016 Wiley Periodicals, Inc. Complexity 21: 387–400, 2016     

Towards a reliable molecular mass determination of intact glycoproteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Different matrices and sample-matrix preparation procedures have been tested in order to study their influence on the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra of intact glycoproteins, which present different degrees of glycosylation (human transferrin; bovine fetuin; bovine alpha(1)-acid-glycoprotein; recombinant human erythropoietin; and the novel erythropoiesis stimulating protein). Using sinapinic acid (SA) and the fast evaporation method, the studied glycoproteins became susceptible to fragmentation at any laser intensity, suggesting that this 'hot' matrix is unsuitable for a reliable molecular mass determination of glycosylated compounds. In contrast, 2,5-dihydroxybenzoic acid (DHB) and 6-aza-2-thiothymine (ATT), with an adequate sample-matrix preparation, provided improved results. Samples containing DHB after crystallization by vacuum drying demonstrated the best performance because the labile functional groups from the glycoforms were apparently fragmented to a lower extent. The average molecular masses obtained using this methodology were in all cases a better estimation than those values reported in the literature. The results were reproducible, and sensitivity was similar to that obtained with SA and the fast evaporation method. These excellent results suggest that this MALDI-TOF-MS methodology could be useful for an improved determination of the average molecular mass values of microheterogeneous compounds such as glycoproteins, glycosylated compounds or, in general, molecular mass values of molecules with similar labile functional groups.     

Comparison between Dcrit considering the abrupt variation and inflexion in the concrete mercury intrusion porosimetry curve

Experimental Techniques - Mercury intrusion porosimetry (MIP) has been widely used to evaluate the quality of concrete through the pore size distribution parameters. Two of these parameters are the...     

Voltammetric characterization of stepped platinum single crystal surfaces vicinal to the (1 1 0) pole

Platinum stepped surfaces vicinal to the (1 1 0) crystallographic pole have been investigated voltammetrically in 0.1 M HClO₄ and 0.1 M H₂SO₄ solutions. Changes in the voltammetric profile with the step density suggest the existence of two types of surface sites, that has been ascribed to linear and bidimensional domains. This result indicates the existence of important restructuring processes that separate the real surface distribution from the nominal one. The electronic properties of the surfaces have been characterized with the CO charge displacement method and the potential of zero total charge has been calculated as a function of the step density.     

Total solid-phase synthesis of the azathiocoraline class of symmetric bicyclic peptides

Thiocoraline is a potent antitumor agent isolated from the marine organism Micromonospora sp. This symmetric bicyclic depsipeptide binds the minor groove of DNA. Here we report two solid-phase strategies for the syntheses of azathiocoraline and its analogues. The thioester linkage was replaced by an amide bond to improve the compound's pharmacokinetic properties. The first strategy is based on a convergent (4+4) approach, whilst the second is a stepwise synthesis, cyclizations in both approaches occurring on the solid support. These two strategies were designed to overcome problems caused by the presence of consecutive noncommercial N-methyl amino acids, to avoid epimerization during cyclization and/or fragment condensation, and to form the disulfide bridge under solid-phase conditions. The heterocyclic moiety was added in the last step of the synthesis to assist the preparation of libraries of new compounds with potential therapeutic applications.