Argentinean prehistoric pigments’ study by combined SEM/EDX and molecular spectroscopy

Composition of the prehistoric pigments’ (from Carriqueo rock shelter, Rio Negro province, Argentina) has been analysed by means of molecular spectroscopy (Fourier transform infrared (FTIR) and micro-Raman) and scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray spectrometer (EDS). Red and yellow pigments were recognized as red and yellow ochre. The matrix of the pigments is composed of one or more substances. According to the matrix composition yellow and red pigments were also divided into two groups—i.e. those containing kaolinite or sulphates. Green pigment was detected as green earth, made up of celadonite as a chromophore.     

The Aggregation Pattern of Aβ1–40 is Altered by the Presence of N-Truncated Aβ4–40 and/or CuII in a Similar Way through Ionic Interactions

Alzheimer's disease (AD) is one of the most common of the multifactorial diseases and is characterized by a range of abnormal molecular processes, such as the accumulation of extracellular plaques containing the amyloid-β (Aβ) peptides and dyshomeostasis of copper in the brain. In this study, we have investigated the effect of Cu^II on the aggregation of Aβ_1–40 and Aβ_4–40, representing the two most prevalent families of Aβ peptides, that is, the full length and N-truncated peptides. Both families are similarly abundant in healthy and AD brains. For either of the studied peptides, substoichiometric Cu^II concentrations accelerated aggregation, whereas superstoichiometric Cu^II inhibited fibril formation, likely by stabilizing the oligomers. The addition of either Aβ_4–40 or substoichiometric Cu^II affected the aggregation profile of Aβ_1–40, by yielding shorter and thicker fibrils; amorphous aggregates were formed in the presence of a molar excess of Cu^II. The similarity of these two effects can be attributed to the increase in the positive charge on the Aβ N terminus, caused both by Cu^II complexation and N truncation at position 4. Our findings provide a better understanding of the biological Aβ aggregation process as these two Aβ species and Cu^II coexist and interact under physiological conditions.     

Symmetry breaking of solutions of non-cooperative elliptic systems

In this article we study the symmetry breaking phenomenon of solutions of non-cooperative elliptic systems. We apply the degree for G$G$-invariant strongly indefinite functionals to obtain simultaneously a symmetry breaking and a global bifurcation phenomenon.     

Study of the Porosity of Carbonaceous Materials and Organic Polymers by Thermal Analysis

The thermal desorption of benzene from rigid and swelling materials was investigated by means of a thermogravimetric technique. Pore volumes and pore size distributions were calculated from the isobars of desorption.The results are compared with those derived from nitrogen adsorption data and mercury intrusion.     

Studies of Thermal Transformations of Petrochemical Wastes For Obtaining Mineral-carbon Sorbents

In the present work an attempt was made to obtain mineral-carbon sorbents by thermal decomposition of solid waste materials containing, besides to mineral components, solid petroleum derivatives. The amount and the homogeneity of distribution of coal product formed in decomposition of organic matter on the surface of the mineral matrix, as well as the porous structure of the sorbents obtained depend largely on the conditions of calcination of the wastes used. The aim of this work was to find optimum conditions of the process. The sorptive properties of the obtained material were checked in the process of reduction of pollutants contained in industrial wastes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Multinuclear Magnetic Resonance Study of Some Mesoionic 1,2,3-Triazoles and Related Compounds

¹H, ¹³C, ¹⁴N and ¹⁵N NMR results are reported for some mesoionic 1,2,3-triazoles and related compounds. It is demonstrated that ¹⁴N NMR linewidths are dependent on the charge present on the nitrogen atom. In addition, it is shown that nitrogen NMR is of great value in the determination of the site of protonation, the ability to distinguish readily between mesoionic cyclic and non-cyclic structures and to follow the transformation between such structures.     

Swelling effects in cross-linked polymers by thermogravimetry

A Brazilian coal power plant generates a waste composed by the fly and bottom ashes produced from coal combustion and by a spent sulfated lime generated after SO₂ capture from combustion gases. This work presents a study of the early stages of the hydration of composites formed by this waste and a type II Portland cement, which will be used for CO₂ capture. The cement substitution degrees in the evaluated composites were 10, 20, 30 and 40%, and the effect of the coal power unit waste on the hydration reaction was analyzed on real time by NCDTA, during the first 40 h of hydration. The results show that the higher is the substitution degree, the higher is the retarding effect on the cement hydration process. Actually, by respective thermogravimetric (TG) and derivative thermogravimetric (DTG) analysis on initial cement mass basis, this effect is caused by double exchange reactions among Ca and Mg components of the waste, during the first 4 h of hydration, which promote a much higher exothermic effect in the NCDTA curve, simultaneously to respective induction periods. The pozzolanic reactions, due to the presence of the waste silica and alumina containing amorphous phases, consume part of the original Ca(OH)₂ content existent in the waste in the case of 30 and 40% substituted pastes, and also from part of the Ca(OH)₂ produced in cement hydration reactions, in the case of the 10 and 20% substituted pastes.