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     

Polarization behavior of polystyrene particles under direct current and low‐frequency (<1 kHz) electric fields in dielectrophoretic systems

The relative polarization behavior of micron and submicron polystyrene particles was investigated under direct current and very low frequency (<1 kHz) alternating current electric fields. Relative polarization of particles with respect to the suspending medium is expressed in terms of the Clausius–Mossotti factor, a parameter of crucial importance in dielectrophoretic‐based operations. Particle relative polarization was studied by employing insulator‐based dielectrophoretic (iDEP) devices. The effects of particle size, medium conductivity, and frequency (10–1000 Hz) of the applied electric potential on particle response were assessed through experiments and mathematical modeling with COMSOL Multiphysics^®. Particles of different sizes (100–1000 nm diameters) were introduced into iDEP devices fabricated from polydimethylsiloxane (PDMS) and their dielectrophoretic responses under direct and alternating current electric fields were recorded and analyzed in the form of images and videos. The results illustrated that particle polarizability and dielectrophoretic response depend greatly on particle size and the frequency of the electric field. Small particles tend to exhibit positive DEP at higher frequencies (200–1000 Hz), while large particles exhibit negative DEP at lower frequencies (20–200 Hz). These differences in relative polarization can be used for the design of iDEP‐based separations and analysis of particle mixtures.     

Dielectrophoresis for the manipulation of nanobioparticles

Dielectrophoresis (DEP) is a nondestructive electrokinetic mechanism with great potential for the manipulation of bioparticles. DEP is the movement of particles induced by polarization effects in nonuniform electric fields. Since the 1960s, this technique has been successfully used for the manipulation of microbioparticles, such as microorganisms. Moreover, due to the advances in microfabrication techniques, that allowed progressively smaller microstructures to be constructed, DEP can now be used for the manipulation of nanobioparticles. The first research studies on the DEP of nanobioparticles started in the 1990s. Since then, many research groups have carried out outstanding work with DEP of nanobioparticles such as macromolecules, virus, and spores. However, the need of a critical report that integrates these findings is evident. The aim of the present review is to depict the state-of-the-art on the use of DEP for the separation of nanobioparticles and the potential trends of novel applications of this technique. This review compiles and analyzes the significant findings obtained by many researchers. This publication is intended to provide the reader with state-of-the-art information on many research studies focused on DEP to handle nanobioparticles.     

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.     

Effect of beta-lactoglobulin hydrolysis with thermolysin under denaturing temperatures on the release of bioactive peptides

In this study, bovine beta-lactoglobulin A (beta-Lg A) was hydrolysed with thermolysin under non-denaturing and heat-denaturing conditions. The peptides released during hydrolysis were identified by HPLC-MS/MS. A total of 25 peptides were identified in the hydrolysate obtained at 37 degrees C for 5 min. Some of these peptides survived to further proteolysis even at higher incubation temperatures. Furthermore, novel cleavage sites localised in the most buried zones of beta-Lg and available for thermolysin were recognised when the incubation temperature increased in the range between 60 and 80 degrees C. Three new peptides, LDA, LKPTPEGD, and LQKW, appeared after 30 min hydrolysis at these incubation temperatures, but they were not identified in the 30-min hydrolysates obtained at 37 and 50 degrees C. Of special interest was the peptide LQKW, corresponding to the fragment f(58-61) that had been previously described as a potent angiotensin-converting enzyme-inhibitor (IC50 value of 34.7 microM).     

An activated equivalent of lactide toward organocatalytic ring-opening polymerization

The alpha-lactone equivalent lacOCA exhibits remarkable reactivity compared with lactide in nucleophile-catalyzed ROP. PLAs of controlled molecular weights and narrow polydispersities are typically obtained under mild conditions using DMAP and various protic initiators.     

Walking metals in d8···d8 hetero-bimetallic complexes: an original dynamic phenomenon

In the course of our investigations on polymetallic complexes derived from 1,3-bis(thiophosphinoyl)indene (Ind(Ph(2)P=S)(2)), we observed original fluxional behavior and report herein a joint experimental/computational study of this dynamic process. Starting from the indenylidene chloropalladate species [Pd{Ind(Ph(2) P=S)(2)}Cl](-) (1), the new Pd(II)···Rh(I) hetero-bimetallic pincer complex [PdCl{Ind(Ph(2) P=S)(2)}Rh(nbd)] (2; nbd=2,5-norbornadiene) was prepared. X-ray crystallography and DFT calculations substantiate the presence of a d(8)···d(8) interaction. According to multinuclear variable-temperature NMR spectroscopic experiments, the pendant {Rh(nbd)} fragment of 2 readily shifts in solution at room temperature between the two edges of the SCS tridentate ligand. To assess the role of the pincer-based polymetallic structure on this fluxional behavior, the related monometallic Rh complex [Rh{IndH(Ph(2) P=S)(2)}(nbd)] (3) was prepared. No evidence for a metal shift was observed in that case, even at high temperature, thus indicating that inplane pincer coordination to the Pd center plays a crucial role. The previously described Pd(II)···Ir(I) bimetallic complex 4 exhibited fluxional behavior in solution, but with a significantly higher activation barrier than 2. This finding demonstrates the generality of this metal-shift process and the strong influence of the involved metal centers on the associated activation barrier. DFT calculations were performed to shed light onto the mechanism of such metal-shift processes and to identify the factors that influence the associated activation barriers. Significantly different pathways were found for bimetallic complexes 2 and 4 on one hand and the monometallic complex 3 on the other hand. The corresponding activation barriers predicted computationally are in very good agreement with the experimental observations.