Thermal tools in the evaluation of decayed and weathered wood polymer composites prepared by in situ polymerization

This study aims to apply thermal tools in the evaluation of decayed and weathered wood polymer composites prepared by in situ polymerization with and without cross-linkers. Pinewood samples were impregnated with methyl methacrylate using glycidyl methacrylate and methacrylic acid as cross-linkers by vacuum/pressure. The polymerization was carried out in an oven at 90 °C for 10 h using benzoyl peroxide as catalyst. All samples were exposed to decay and artificial weathering tests. The characterization was performed by mass loss, color changes, optical images, wettability, thermogravimetric analysis (by means of DTG) and differential scanning calorimetry analyzes. The mass loss was higher in untreated wood in comparison with the composites, ~2.5–10 times. Cross-linked composites showed the highest resistance to fungal biodeterioration. The reduction in L*, chroma and b* confirmed loss of original yellow tones and increase in dark and dull tones of samples. The wettability was very affected by irregularities of the samples’ surface. Only DTG showed a shifting in the temperature of thermal events related to polysaccharides and lignin after exposure to decay and weathering. DTG was the best thermal technique for evaluation of decaying and weathering of wood composites.     

Battle for the bulge: directing small molecules to DNA and RNA defects

Small molecules were tailored to specifically bind bulged DNA by complementing the geometry and nucleotide size of the bulge site. The prospect of generating small molecules that influence the secondary structure of DNA and RNA holds great promise for clinical applications.     

Ionic liquids based on the bis(trifluoromethylsulfonyl)imide anion for high‐pressure Raman spectroscopy measurements

Assembling a diamond anvil cell for high‐pressure measurements involves placing in a gasket hole the sample of interest, a pressure transmitting fluid, and a material for pressure calibration. In this communication, we propose the use of ionic liquids containing the bis(trifluoromethylsulfonyl)imide anion ([Tf₂N]^‐), [(CF₃SO₂)₂ N]^‐, as a simultaneous pressure transmitting and calibrant material for high‐pressure Raman spectroscopy measurements of solid samples that are not soluble in ionic liquids. The position of the characteristic Raman band of the [Tf₂N]^‐ anion at 740 cm⁻¹ exhibits linear frequency shift for pressures up to 2.5 GPa. High‐pressure Raman spectra of different ionic liquids containing the same anion indicate that the actual magnitude of the pressure‐induced frequency shift of the [Tf₂N]^‐ normal mode depends on the counterion, the typical shift being 4.2 cm⁻¹/GPa. Ionic liquids based on the [Tf₂N]^‐ anion are also good pressure transmitting mediums because hydrostatic condition is kept at high pressure, and no crystallization is observed up to 4.0 GPa. Copyright © 2012 John Wiley & Sons, Ltd.     

New Materials for Solid‐Phase Extraction of Trace Elements

Abstract

The development of new sorbents and their application in preconcentration methods for determination of trace elements is a subject of great interest. This review summarizes and discusses several analytical methods involving the preparation and use of new solid‐phase materials. The performance and general properties of sorbents such as carbon nanotubes, imprinted ions, biosorbents, nanoparticles, and fullerene are discussed in detail. The perspective and future trends in the use of these materials are also considered.     

Bid-Based Dispatch of Hydrothermal Systems in Competitive Markets

The objective of this work is to investigate possible hydro-scheduling inefficiencies under a bidding scheme. It will be shown that the market-based dispatch of hydro-plants, under a perfect competitive market, converges to its least-cost dispatch. Besides, it will be shown that the usual spot payment scheme does not provide the correct incentive for upstream reservoirs to regulate downstream production, thus causing an operating distortion. The implementation of a Wholesale Water Market is proposed for trading stored water and so to correct such distortion. Case studies will be presented, with data taken from the Brazilian System.     

A Global Glance on Categories in Logic

We explore the possibility and some potential payoffs of using the theory of accessible categories in the study of categories of logics. We illustrate this by two case studies focusing on the category of finitary structural logics and its subcategory of algebraizable logics. Mathematics Subject Classification (2000): Primary 03B22; Secondary 18C35.     

Connected Components of Open Semigroups in Semi-Simple Lie Groups

This paper studies connected components of open subsemigroups of non-compact semi-simple Lie groups by using control sets in the flag manifolds and their coverings. The concept of recurrent component is introduced and a method is given by which their number can be computed. It is shown that the union of all recurrent components is a semigroup. The idea of mid-reversibility comes up to show that an open semigroup has just one semigroup component if the identity belongs to its closure. A necessary and sufficient condition for mid-reversibility is proved showing that e.g. in a complex group any open semigroup is mid-reversible.