Nanocomposite Polymer Electrolytes of Sodium Alginate and Montmorillonite Clay

Nanocomposite polymer electrolytes (NPEs) were synthesized using sodium alginate (Alg) and either sodium (SCa-3-Na⁺)- or lithium (SCa-3-Li⁺)-modified montmorillonite clays. The samples were characterized by structural, optical, and electrical properties. SCa-3-Na⁺ and SCa-3-Li⁺ clays’ X-ray structural analyses revealed peaks at 2θ = 7.2° and 6.7° that corresponded to the interlamellar distances of 12.3 and 12.8 Å, respectively. Alg-based NPEs X-ray diffractograms showed exfoliated structures for samples with low clay percentages. The increase of clay content promoted the formation of intercalated structures. Electrochemical Impedance Spectroscopy revealed that Alg-based NPEs with 5 wt% of SCa-3-Na⁺ clay presented the highest conductivity of 1.96 × 10⁻² S/cm², and Alg with 10 wt% of SCa-3-Li⁺ showed conductivity of 1.30 × 10⁻² S/cm², both measured at 70 °C. From UV-Vis spectroscopy, it was possible to infer that increasing concentration of clay promoted a decrease of the samples’ transmittance and, consequently, an increase of their reflectance.     

Structural and electronic properties of amorphous bismuth calcium borate from first-principle calculations

Structural Chemistry - We investigatethe electronic and structural properties of two new amorphous materials, Bi6Ca2O28B12 and Bi6Ca2 O28B11:Tm, using density functional theory with a short-range...     

Loop-quantum-gravity vertex amplitude

Spin foam models are hoped to provide the dynamics of loop-quantum gravity. However, the most popular of these, the Barrett-Crane model, does not have the good boundary state space and there are indications that it fails to yield good low-energy n-point functions. We present an alternative dynamics that can be derived as a quantization of a Regge discretization of Euclidean general relativity, where second class constraints are imposed weakly. Its state space matches the SO(3) loop gravity one and it yields an SO(4)-covariant vertex amplitude for Euclidean loop gravity.     

Large-scale Monte Carlo study of a realistic lattice model for Ga(1-x)MnxAs

Mn-doped GaAs is studied with a real-space Hamiltonian on an fcc lattice that reproduces the valence bands of undoped GaAs. Large-scale Monte Carlo (MC) simulations on a Cray XT3, using up to a thousand nodes, were needed. Spin-orbit interaction and the random distribution of the Mn ions are considered. The hopping amplitudes are functions of the GaAs Luttinger parameters. At the realistic coupling J approximately 1.2 eV the MC Curie temperature and magnetization curves agree with experiments for x = 8.5% annealed samples. Mn-doped GaSb and GaP are also briefly discussed.     

Parabolic problems in highly oscillating thin domains

Annali di Matematica Pura ed Applicata (1923 -) - In this work, we consider the asymptotic behavior of the nonlinear semigroup defined by a semilinear parabolic problem with homogeneous Neumann...     

Polymeric Membranes Containing Phosphorus in the Chain for Solid Polymer Electrolytes

Abstract

Two new series of solid polymer electrolytes (SPEs) based on phosphorus containing (co)polyesters (PPE) and Lithium triflate were obtained. PPEs are composed of phosphonate moeties (cyclohexyldichlorophosphonate (CHDP)) as linking agent and two diols: PEG (6000) and poly(tetramethylene glycol) (PTMG) in PPE I, and PEG (6000) and 4,4′-cyclohexylidenebisphenol (bisphenol Z, BZ) in PPE II. Polycondensation was carried out in solution in the presence of triethylamine (TEA) as scavenger of HCl side product (PPE I–IIa) and in the absence of any acid acceptor (PPE I–IIb). The Limiting Oxygen Index (LOI) and thermal analysis were performed both on polymers and membranes. The ionic conductivity of SPE membranes based on PPE-salt complexes, with various salt concentrations, was investigated at different temperature and ionic transference numbers were determined. Optimum composition was obtained for the polymer which contains in structure only alkyl units and 15% Lithium triflate.     

Studies on thermal,spectral, magnetic and biological properties of new Ni(II), Cu(II) and Zn(II) complexes with a bismacrocyclic ligand bearing an aromatic linker

Novel complexes of M₂LCl₄·nH₂O type (M:Ni, n = 4; M:Cu, n = 3 and M:Zn, n = 0; L: ligand resulted from 1,4-phenylenediamine, 3,6-diazaoctane-1,8-diamine and formaldehyde one-pot condensation) were synthesized and characterised by microanalytical, ESI–MS, IR, UV–Vis, ¹H NMR and EPR spectra, magnetic data at room temperature and molar conductivities as well. The electrochemical behaviour of complexes was investigated by cyclic voltammetry. Simultaneous TG/DTA measurements were performed in order to evidence the thermal behaviour of the obtained complexes. Processes such as water elimination, fragmentation and oxidative degradation of the organic ligand as well as chloride elimination occurred during thermal decomposition. The antimicrobial assays demonstrate that the compounds exhibited good antibacterial activity, especially against S. aureus and E. coli strains, the most active being the copper(II) complex, which also exhibited the most prominent anti-biofilm effect, suggesting its potential use for the development of new antimicrobial agents. The biological activity was correlated with log P _ow values. All complexes disrupt the membrane integrity of HCT 8 tumour cells.     

Influence of some sugars on the thermal,rheological and morphological properties of “pinhão” starch

When starch is incorporated into puddings, desserts, and other foods containing sugar as the main ingredient, it will have an effect on the gelatinisation temperature and pasting properties. Many studies have been undertaken to investigate the effect of several sugars in foods and starches, as well as their physicochemical and functional properties. These studies have verified the significant influence on these properties, which are dependent on the nature of sugar and of starch. In this study, pinhão starch was extracted in the laboratory and was added, stirring for 60 min, to solutions at 1 % of each of the following sugars: fructose, glucose, sucrose, and 0.5 % fructose and 0.5 % glucose. After this time, the slurry was filtered, washed, dried at 40 °C and kept in a desiccator over anhydrous calcium chloride until constant mass. The effects of each sugar on the surface of the pinhão starch granules were observed using the non-contact method of atomic force microscopy, whereby it was possible to verify a decrease in the average diameter and an increase in the average roughness. X-ray diffractometry made it possible to evaluate the degree of relative crystallinity, which was proportional to the roughness and inversely proportional to the gelatinisation enthalpy (ΔH), which was studied by differential scanning calorimetry.     

Nucleophilic Reactivity of a Copper(II)–Superoxide Complex

Metal‐bound superoxide intermediates are often implicated as electrophilic oxidants in dioxygen‐activating metalloenzymes. In the nonheme iron α‐ketoglutarate dependent oxygenases and pterin‐dependent hydroxylases, however, Fe^III–superoxide intermediates are postulated to react by nucleophilic attack on electrophilic carbon atoms. By reacting a Cu^II–superoxide complex ( 1 ) with acyl chloride substrates, we have found that a metal–superoxide complex can be a very reactive nucleophile. Furthermore, 1 was found to be an efficient nucleophilic deformylating reagent, capable of Baeyer–Villiger oxidation of a number of aldehyde substrates. The observed nucleophilic chemistry represents a new domain for metal–superoxide reactivity. Our observations provide support for the postulated role of metal–superoxide intermediates in nonheme iron α‐ketoglutarate dependent and pterin‐dependent enzymes.     

Implementation of the quality management system at the Laboratory of Radiological Protection and Safety (LPSR) in Portugal

The paper describes the activities carried out for the implementation of the quality management system (QMS) at the Laboratory of Radiological Protection and Safety (LPSR) in Portugal in order to achieve the management and technical requirements of ISO/IEC 17025:2005 and to get the accreditation for ten tests. The implementation of the QMS based on this international standard allowed LPSR to improve the methods, to identify problems, to implement preventive and corrective actions, to generate valid results and to achieve a stable level of high-quality output recognized by an independent body in the scope of waters, metrology, radiation and radiochemistry.