Nutritive and non-nutritive attributes of washed-up seaweeds from the coast of Ceará, Brazil

This study assesses the nutritive and non-nutritive attributes of washed-up seaweeds from the Brazilian coast. It covers a broad diversity of species (24 red, nine green and four brown) with reasonable levels of proteins (10–14.8%), high ash contents (13–25%), low lipids (below 1%) and high carbohydrate contents (60%). Toxic and/or antinutritional factors were detected, such as low levels of lectins (32 and 64 HU/g of meal for chicken and rabbit trypsin-treated erythrocytes, respectively), tannins (59 mg/100 g), phytic acid (0.45%), high levels of trypsin inhibitors (99.0% inhibition) and -amylase inhibitors (70.5%). The 0/80% fraction showed moderate toxicity to mice (LD₅₀ of 63.8 mg kg⁻¹). The presence of heavy metals such as cadmium (0.29 mg/100 g), chromium (0.23 mg/100 g), nickel (0.26 mg/100 g) and vanadium (3.56 mg/100 g) was also detected. Despite moderate toxicity and antinutritional limitations, washed-up seaweeds represent a potential food alternative for humans after appropriate processing and environmental remediation to guarantee food safety.     

Strategies for an efficient indicator of structural damage

Structural health monitoring is nowadays a problem of major concern, as recent catastrophic failures of in-operation civil structures with important human losses and high costs demonstrate.A global assessment method with sufficient sensitivity and reliable enough to detect incipient damage in order to prevent unexpected failures is necessary.Pursuing this goal, in this paper some new developments of the detection and relative damage quantification indicator, concerning the detection, localization and also the relative severity of damage are presented. This method, based on the use of the frequency domain assurance criterion and of the response vector assurance criterion, seems to be an effective damage indicator. To illustrate the procedure, the authors present some numerical simulations, as well as some experimental examples taken on two beams.     

Thermal and renewable sources to sustain the growth of the Brazilian Electric System

The purpose of this article is to discuss alternative sources for the Brazilian Electric System to sustain a growth rate of 4% in its economy. From this perspective, issues like the country dependence on hydraulic energy, the potential of inserting other forms of “renewable sources” and the required modulation with thermal use, preferably internal resources, are addressed.     

Smectite organofunctionalized with thiol groups for adsorption of heavy metal ions

The structural characteristics as well as the binding capacity of the functionalized bentonite from Campina Grande (PB), Brazil, were investigated. The sample was modified by acid treatment followed by immobilization of ligands containing thiol (–SH) groups by covalent grafting with surface and interlayer silanol groups. The modification was carried out under anhydrous conditions with (3-mercaptopropyl)trimethoxysilane. The functionalization process changed the hydrophilic nature of the clay mineral into hydrophobic. X-ray diffraction indicated that their original structure had been preserved. The DRIFT spectra demonstrated the presence of organic chains and thiol groups. The BET results indicated decreased porosity and specific surface area after grafting. Organic loading, calculated from TG data was 1.76 mmol g^− 1 of bentonite. The thiol-functionalized bentonite presented binding capacity of Ag⁺ ions about ten times higher compared to the ungrafted sample. These results support a mechanism of adsorption involving primarily ion complexation by the thiol groups (specific) instead of cation exchange (unspecific). The accessibility to the reactive centers was 60–75%. Thus, the adsorption capacity of bentonite can be enhanced by surface modification using organo-functional silane coupling agents. This new hybrid organic–inorganic material may be a good alternative for separation and pre-concentration of heavy metal ions.     

Preparation of silk fibroin–poly(ethylene glycol) conjugate films through click chemistry

Azide silk fibroin (azido SF) and alkyne terminal poly(ethylene glycol) (PEG) 2000 (acetylene‐terminal PEG 2000) were synthesized. Azido SF was reacted with acetylene‐terminal PEG 2000 to produce films via a copper‐mediated 1,3‐cycloaddition (‘click’ chemistry) generating a triazole linkage as the networking forming reaction. Through click chemistry, novel silk‐based films with various weight ratios were prepared and investigated. Fourier transform infrared, X‐ray diffraction and differential scanning calorimetry analyses showed that the ordered association of the PEG molecules is strongly constrained by the presence of the SF molecules and crosslinking and that the presence of acetylene‐terminal PEG 2000 in the films induced crystallization to a β‐sheet of SF chains. Water content and contact angle measurements indicated that the hydrophilicity of the films increased compared with SF. SF–PEG films exhibited smooth and rough structures, depending on degree of crosslinking and on the weight ratio of SF and PEG, as shown by scanning electron microscopy. Copyright © 2011 Society of Chemical Industry     

Coercive field and domain wall properties in (DyχY1-χ) Fe2 and (ErχY1-χFe2 intermetallic compounds

Isothermal d.c. magnetization measurements were performed for (R_χY_1-χ)Fe₂ (RDy, Er, 0<χ<1) at several temperatures. The observed pronounced decay of the coercive field H_c with temperature was fitted with an exponential curve at low temperatures for concentrations near 30%. The coercive field H_c and the propagation field H_p showed maximum values in the concentration range 30%–40% for Dy or Er. These results can be explained by intrinsic domain wall pinning. Time relaxation effects of the remanent magnetization were detected and attributed to domain wall surface deformations.