The Ground State of Certain Coulomb Systems and Feynman-Kac Exponentials

We give a lower bound for the ground state energy of certain Coulomb Hamiltonians using the Feynman-Kac formula. We show that this bound is very precise for two electron atoms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Normal subgroups of the algebraic fundamental group of affine curves in positive characteristic

Let π₁(C) be the algebraic fundamental group of a smooth connected affine curve, defined over an algebraically closed field of characteristic p > 0 of countable cardinality. Let N be a normal (respectively, characteristic) subgroup of π ₁(C). Under the hypothesis that the quotient π ₁(C)/N admits an infinitely generated Sylow p-subgroup, we prove that N is indeed isomorphic to a normal (respectively, characteristic) subgroup of a free profinite group of countable cardinality. As a consequence, every proper open subgroup of N is a free profinite group of countable cardinality. Amílcar Pacheco and Pavel Zalesskii were partially supported by CNPq research grants 305731/2006-8 and 307823/2006-7, respectively. They were also supported by Edital Universal CNPq 471431/2006-0.     

Synthesis of charged hybrid particles via dispersion polymerization in nonpolar media for color electrophoretic display application

Direct synthesis of charged hybrid particles in non‐polar media has not been widely described in the literature but can lead to many applications such as electrophoretic displays. In this work, we propose a way to synthesize charged hybrid particles within the electrophoretic medium (Toluene or Isopar G) in the presence or not of additives (Charge Control Agent, CCA). The particles synthesis was performed by Nitroxide‐mediated Radical Polymerization (NMRP) via dispersion polymerization in aliphatic hydrocarbon solvents leading to stable chargeable particles with a good size control. Hybrid particles are successfully charged by reaction with functional monomers or addition of CCA to obtain electrophoretic particles. The performance of a dual‐color red/white ink in a display was demonstrated with a test‐cell. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 338–348     

Affine interval exchange transformation without an isometric model

Contrary to the case of interval exchange transformation, we show that generalized affine interval exchange transformation (affine GIET), with or without flips and admitting dense orbits, may not be conjugated to an isometric GIET. This result is proved by constructing explicitly one such affine GIET. The author was partially supported by FAPESP – Proj. Tematico No. 03/03107-9.     

Bioanalysis of small-molecule drugs in nasal and paranasal tissues and secretions: Current status and perspectives

Over the last years, interest in intranasal administration as an alternative and promising route for the delivery of drugs withlocal, systemic, and even central nervous system action has tremendously increased. Accordingly, understanding of the propertiesand characteristics of the nasal cavity as well as the biodisposition processes of drugs into the nasal compartments is acquiringa significant prominence in the field of pharmacology. In this context, the development and validation of bioanalytical methodologies for the quantitative measurement of drugs and their metabolites in nasal and paranasal tissues and/or secretions is of the utmostimportance. However, currently, information concerning bioanalysis of drugs in nasal and paranasal tissues and/or secretionsis scattered. This review aims to provide a valuable overview of the methodologies that have been used for the collectionand preparation of nasal and paranasal samples with special emphasis placed on the review of liquid chromatographic methodsemployed for the quantitative determination of small-molecule drugs and their metabolites in such specimens.      

(C4H3SCH2NH3)2(CH3NH3)Pb2I7: non-centrosymmetrical crystal structure of a bilayer hybrid perovskite

The analysis of the crystal structure of (C4H3SCH2NH3)2(CH3NH3)Pb2I7, displaying a well-ordered acentric inorganic Pb2I7(3-) bilayer, is reported, and compared to the related monolayer hybrid perovskite.     

Unveiling the G4-PAMAM capacity to bind and protect Ang-(1-7) bioactive peptide by molecular dynamics simulations

Angiotensin-(1-7) re-balance the Renin-Angiotensin system affected during several pathologies, including the new COVID-19; cardiovascular diseases; and cancer. However, one of the limiting factors for its therapeutic use is its short half-life, which might be overcome with the use of dendrimers as nanoprotectors. In this work, we addressed the following issues: (1) the capacity of our computational protocol to reproduce the experimental structural features of the (hydroxyl/amino)-terminated PAMAM dendrimers as well as the Angiotensin-(1-7) peptide; (2) the coupling of Angiotensin-(1-7) to (hydroxyl/amino)-terminated PAMAM dendrimers in order to gain insight into the structural basis of its molecular binding; (3) the capacity of the dendrimers to protect Angiotensin-(1-7); and (4) the effect of pH changes on the peptide binding and covering. Our Molecular-Dynamics/Metadynamics-based computational protocol well modeled the structural experimental features reported in the literature and our double-docking approach was able to provide reasonable initial structures for stable complexes. At neutral pH, PAMAM dendrimers with both terminal types were able to interact stably with 3 Angiotensin-(1-7) peptides through ASP1, TYR4 and PRO7 key amino acids. In general, they bind on the surface in the case of the hydroxyl-terminated compact dendrimer and in the internal zone in the case of the amino-terminated open dendrimer. At acidic pH, PAMAM dendrimers with both terminal groups are still able to interact with peptides either internalized or in its periphery, however, the number of contacts, the percentage of coverage and the number of hydrogen bonds are lesser than at neutral pH, suggesting a state for peptide release. In summary, amino-terminated PAMAM dendrimer showed slightly better features to bind, load and protect Angiotensin-(1-7) peptides.

     

Nonequilibrium features of the association between poly(vinylamine) and sodium dodecyl sulfate: the validity of the colloid dispersion concept

The effect of different mixing protocols on the bulk and surface properties of the aqueous mixtures of linear poly(vinylamine) (PVAm) and sodium dodecyl sulfate (SDS) has been investigated using pH, electrophoretic mobility, dynamic light scattering, coagulation kinetics, and surface tension measurements. For the preparation of the solutions, two kinds of mixing protocols were applied. The so-called "stop flow mixing" enables a very rapid mixing whereas in the case of "gentle mixing" the mixing of the components is less efficient. At high surfactant concentrations a kinetically stable colloid dispersion of the PVAm/SDS particles is formed via the application of the stop flow mixing method. The mixing protocols have a significant effect on the bulk properties of the PVAm/SDS system, in particular, at the low pH range and at large PVAm concentrations. The effect of mixing can be qualitatively understood in terms of the enhanced local rate of coagulation of the PVAm/SDS complexes as well as of the appearance of polyelectrolyte/surfactant aggregates via the application of a less efficient mixing. The study also reveals that the applied methods of solution preparation do not have a major impact on the bound amount of the surfactant as well as on the surface tension isotherms of the system. This latter finding is attributed to the hindered adsorption of the large polyelectrolyte/surfactant aggregates at the air/water interface.     

Non-Selective Toxicological Effects of the Insect Juvenile Hormone Analogue Methoprene. A Membrane Biophysical Approach

The Gram-positive bacterium, Bacillus stearothermophilus, was used as a model organism to identify the non-selective toxic effects of the currently used insecticide methoprene (isopropyl(2E,4E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate). A significant decrease of the yield of bacterial cultures and a premature appearance of ultrastructural abnormalities in cells cultured in the presence of the insecticide were taken as indicators of cytotoxicity. A putative correlation of this cytotoxicity with methoprene-induced perturbations on membrane lipid organization was investigated, using differential scanning calorimetry and the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and its propionic acid derivative (DPH-PA). The membrane physical effects depended on the lipid bilayer composition and packing. The most striking effect was a progressive broadening and shifting to lower temperatures, with increasing methoprene concentrations, of the main transition phase of the dimyristoyl- or dipalmitoylphosphatidylcholine bilayers and of the lateral phase separation of liposomes reconstituted with the lipid extracts of B. stearothermophilus.     

Synthetic Studies Toward Providencin: Efficient Construction of a Furanyl-Cyclobutanone Fragment

Described is the construction of a furanyl-cylcobutanone fragment suited for incorporation into a synthesis of the naturally occurring anti-cancer agent Providencin.