Characterization of Amazonic White Pitch (Protium heptaphyllum) for potential use as ‘green’ adhesive

The plant species Protium heptaphyllum, widely found in the Amazon and northeast regions of Brazil, produces an oily resin commonly known as White Pitch (Breu Branco) (WP). The WP has been shown to have the characteristics to produce a sort of ‘green’ polymer. The aim of this study was to characterize commercially available WP resin for its chemical and mechanical properties and to assess its suitability for use as green adhesive. The WP obtained from typical Amazon market was purified and characterized for its chemical nature using GC/MS, TGA, DSC, and FTIR. The results also confirmed that the material used was indeed from P. heptaphyllum plant species. The mechanical and thermal properties were characterized, and its adhesion was measured. Adhesive shear and tensile strength of the WP bonded wood specimens were investigated using a small scale test method. The shear strength of the WP bonded wood specimens was always higher than the tensile strength, but this value was lower when compared with commercial adhesives.     

Effect of high energy milling on microstructure and mechanical properties of Al2O3-10 wt% Co composites consolidated by spark plasma sintering (SPS)

Al₂O₃-10 wt% Co composites were prepared by high energy milling in the presence of ethyl alcohol and with subsequent spark plasma sintering (SPS). The powders milled for 5 and 30 h were sintered by SPS at 1350 °C for 5 min. The effect of milling time on the sinterability and mechanical properties was studied. The morphology and structure of milled powders were investigated by scanning electron microscopy, dynamic light scattering and X-ray diffraction. The Co phase forms plate-like particles of different sizes, while finely fragmented Al₂O₃ particles are incorporated in the Co phase, forming composite particles. The average size of the composite particles decreases with increasing milling time, achieving 1.33 μm after 30 h. Crystallite size and micro-strain are inversely proportional. Overall, all the samples display homogeneous microstructures, high density (85.29–91.60%) and microhardness in the range 11.41–14.37 GPa.     

Investigation of the Complexes Formed between PARP1 Inhibitors and PARP1 G-Quadruplex at the Gene Promoter Region

DNA repair inhibitors are one of the latest additions to cancer chemotherapy. In general, chemotherapy produces DNA damage but tumoral cells may become resistant if enzymes involved in DNA repair are overexpressed and are able to reverse DNA damage. One of the most successful drugs based on modulating DNA repair are the poly(ADP-ribose) polymerase 1 (PARP1) inhibitors. Several PARP1 inhibitors have been recently developed and approved for clinical treatments. We envisaged that PARP inhibition could be potentiated by simultaneously modulating the expression of PARP 1 and the enzyme activity, by a two-pronged strategy. A noncanonical G-quadruplex-forming sequence within the PARP1 promoter has been recently identified. In this study, we explored the potential binding of clinically approved PARP1 inhibitors to the G-quadruplex structure found at the gene promoter region. The results obtained by NMR, CD, and fluorescence titration confirmed by molecular modeling demonstrated that two out the four PARP1 inhibitors studied are capable of forming defined complexes with the PARP1 G-quadruplex. These results open the possibility of exploring the development of better G-quadruplex binders that, in turn, may also inhibit the enzyme.     

Split-plot design optimization for trace determination of lead by anodic stripping voltammetry in a homogeneous ternary solvent system

A split-plot design has been used to simultaneously optimize reagent conditions and solvent medium for Pb²⁺ determination by anodic stripping voltammetry (ASV). Three mixture components, N,N-dimethylformamide (DMF), ethanol and water, and two process variable levels, ammonium acetate (supporting electrolyte) and hydrochloric acid concentrations, were varied. The calculations of main-plot, subplot and main-subplot interaction ANOVA sums of squares for regression and lack of fit are illustrated. These values are shown to be useful for model development. Six different models were evaluated. The bilinear-special cubic model has only a very slight lack of fit and is preferred. Standard error estimates were calculated using a method described in the literature by Cornell, and approximate critical values for t-tests on the model coefficients were investigated. Normal probability graphs seem appropriate for this analysis. The significant terms in this model are capable of describing how the mixture response surfaces change as process level conditions are varied. Optimized mixture proportions for each factorial design level are determined. Optimum conditions in the (− −) main-plot quadrant for the determination of lead by ASV in the homogeneous ternary solvent system were achieved with a solvent composition of 8.0 g of N,N-dimethylformamide (DMF), 7.0 g of ethanol and 5.0 g of water, corresponding to 40% m/m of DMF, 35% n/m of ethanol and 25% m/m of water. Water is essential since the sample and the buffer (0.1 mol kg⁻¹ ammonium acetate containing 0.00880 mol kg⁻¹ HCl) are added to the system as aqueous solutions. The other three main-plot quadrants presented optimum analytical signals for 95% aqueous solutions. The split-plot design seems to be especially appropriate for simultaneously optimizing process and mixture variables of this chemical system facilitating operational procedures by means of block randomization.     

Humus quality after eucalypt reforestations in Asturias (Northern Spain)

The impact on soil properties of recent and ancient reforestations with Eucalyptus globulus Labill. has been studied in Cambisols and Leptosols under temperate semi-oceanic climate in Asturias (Northern Spain). Eucalypt forests showed a high potential of C accumulation in soil, mainly the ancient forest, where the organic matter concentration in the uppermost horizon (up to 415 C g x kg(-1)) was greater than in all neighbouring soil formations (climacic oak forests, up to 84 C g x kg(-1); Podsol under reforested pine forests, 287 C g x kg(-1); and Ulex shrub, 70 C g x kg(-1)). Nevertheless, there was a low concentration of available bases and a very low transformation degree of the organic matter in this eucalypt forest, only comparable to that of the Podsol. In order to analyse the major features of the biogeochemical behaviour of the sites under study, the humus fractions were isolated and the humic acid fraction was studied by derivative visible and infrared spectroscopies. Incubation experiments on whole soil samples were carried out to monitor stability against biodegradation of the organic matter under comparable conditions. In general, soils under eucalypt had a CO(2) production similar to or lower than the control sites, but the soil under the ancient eucalypt forest had a high potential for CO(2) release, similar to that of the neighbouring Podsol, what might be explained by the presence in these soils of high amounts of C accumulated in readily biodegradable forms. However, the mineralisation coefficients (CO(2) released per unit of soil C) indicated that the biodegradability of the soil humus has decreased significantly in the eucalypt-reforested sites, as it could correspond to an effective control of the biogeochemical processes caused by the antimicrobial products from the eucalypt litter. Compared to the original deciduous forests, the lower values of the E(4)/E(6) ratio in the humic acids from eucalypt forests and the lignin signature in the infrared spectra point to humification mechanisms based on the selective preservation of complex macromolecular substances derived from vascular plants. The second derivative of the visible spectra of the humic acid samples under study showed conspicuous valleys, which are ascribed to fungal-derived 4,9-dihydroxyperylene-3,10-quinone pigments. These valleys were in most eucalypt forests significantly shallower than in the original deciduous forests and may also represent an indicator of the impact of introduced vegetation on the structure of the soil microbial system and the mechanisms responsible for the formation of humic acids.     

Correlation between antioxidant activity and bioactive compounds of açaí (Euterpe oleracea Mart) comercial pulps

The purpose of this work was to analyze commercial a?aí pulp and to correlate the contribution of vitamin C, total carotenoids and phenolic compounds with the antioxidant activity of there products besides the examination of the standard related to the quality of the obtained products. Analysis were made with regard to pH, acidity total, soluble solids, sugars, color, water activity, vitamin C, total anthocyanins, total carotenoids, antioxidant activity and phenolic compounds. All parameters analyzed showed significative difference among the marks not added with preservatives and sucrose. The a?aí fruit can be considered a fair source of vitamin C and good source of natural antioxidants. In regard to the correlation with the antioxidant activity only the total anthocyanins and the total carotenoids presented positive and significative correlation.     

Dielectric and dynamic-mechanical study of the mobility of poly(t-butylacrylate) chains in diblock copolymers: Polystyrene-b-poly(t-butylacrylate)

A calorimetric, dielectric and dynamic-mechanical study of the dynamics of the poly(t-butyl acrylate) (PtBa) chains has been carried out in a PtBa homopolymer and two polystyrene (PS)-b-PtBa block copolymers with different PtBa chain lengths. The DSC results show that the size of the cooperative rearranging regions is similar in the homopolymers and the copolymers, both for the PtBa rich- and the PS-rich regions. Therefore, no significant contributions are found arising from composition fluctuations in the copolymers. The relaxation map obtained from dielectric relaxation indicates that there are no differences in the temperature dependence of the α-relaxation of the PtBa block in the three samples studied. However, there are larger differences for the values obtained from DMTA experiments. Contrary to the α-relaxation, the relaxation map for the β-transition shows that the characteristic times for the PtBa blocks are smaller in the homopolymer than in the copolymers. In principle, these are unexpected results because the β-relaxations have a more local character than the α-ones. The width of the α-relaxation increases with T for all the samples, and it is slightly larger for the copolymers. The intensity of the α-relaxation is larger (between 3 and 4 times) for the homopolymer. Considering the molecular weights of the PtBa blocks, this effect has to be ascribed to the existence of frozen amorphous PtBa due to the existence of the glassy PS domains in the microphase separated copolymers.Molecular Dynamic Simulations (MDSs) for different sequences of the polymers under study were carried out. The conformational analysis was carried out between 1000 and 1700 K. The analysis of the variation of angles ?₁ and ?₂ of the ester group of PtBa points out the existence of a correlation between the conformational changes of the side group of the polymer chains and their relaxational behaviour.