Fe2+-Mg order–disorder study in orthopyroxenes from São João Nepomuceno (IVA) iron meteorite

São João Nepomuceno (SJN) is an iron meteorite belonging to IVA chemical group. It consists of Fe-Ni metal matrix and silicate inclusions made of a coarse-grained mixture of tridymite, orthopyroxene and clinopyroxene. In spite of the extensive work performed on the IVA group there is still no consensus about their origin and its thermal history is subject of ongoing debates. In this work, we report preliminary results on Fe^2?+? distribution in the non-equivalent octahedral sites in orthopyroxene crystals extracted from São João Nepomuceno in order to infer on the thermal history of this meteorite and therefore acquire more information related to the origin of the IVA iron meteorite group.     

Highly corrosion resistant siloxane-polymethyl methacrylate hybrid coatings

Siloxane-polymethyl methacrylate hybrid films were deposited on carbon steel substrates by dip-coating from a sol prepared by acid-catalyzed hydrolytic co-polycondensation of tetraethoxysilane (TEOS) and 3-methacryloxy propyl-trimethoxysilane (MPTS), followed by radical polymerization of methyl methacrylate (MMA). Structural properties of the hybrids were studied using ²⁹Si and ¹³C nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), as a function of the MMA/MPTS ratio, which ranged between 2 and 10. The efficiency of corrosion protection of hybrid-coated carbon steel was investigated by XPS, potentiodynamic polarization curves and electrochemical impedance spectroscopy after immersion of the material in acidic and neutral saline aqueous solution. The NMR and TGA results indicate a high degree of polycondensation (84%) and elevated thermal stability of 410?°C for the hybrid film with a MMA/MPTS ratio of 8, exhibiting also and excellent adhesion to the substrate. The XPS analysis confirmed the variation of the MMA phase in the hybrid, and showed that no corrosion-induced changes had occurred after 18?days immersion of the coated steel in 3.5% NaCl solution. Potentiodynamic polarization curves have shown that the hybrid coating prepared using a TEOS/MPTS ratio of 8 yielded the best anti-corrosion performance. It acts as a very efficient corrosion barrier, increasing the total impedance by almost 6 orders of magnitude and reducing the current densities by 4 orders of magnitude, compared to the bare electrode. The obtained results are discussed based on the correlation of structural information with impedance data presented for both electrolytes in the form of electrical equivalent circuits.     

Separation of isomeric disaccharides by traveling wave ion mobility mass spectrometry using CO2 as drift gas

The use of CO₂ as a massive and polarizable drift gas is shown to greatly improve peak‐to‐peak resolution (R_p‐p), as compared with N₂, for the separation of disaccharides in a Synapt G2 traveling wave ion mobility cell. Near or baseline R_p‐p was achieved for three pairs of sodiated molecules of disaccharide isomers, that is, cellobiose and sucrose (R_p‐p = 0.76), maltose and sucrose (R_p‐p = 1.04), and maltose and lactose (R_p‐p = 0.74). Ion mobility mass spectrometry using CO₂ as the drift gas offers therefore an attractive alternative for fast and efficient separation of isomeric disaccharides. Copyright © 2012 John Wiley & Sons, Ltd.     

Ultrastructure of the Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) midgut

The insect midgut has ultimately been the focus of researches tempting to control insect pests because alterations in the insect gut may affect not only its development, but also physiological events such as nutrient absorption and transformation. The objective of the present work was to describe morphologically, histochemically, and ultrastructurally the larva midgut of Alabama argillacea (Hübner) (Lepidoptera: Noctuidae), a cotton key pest in Brazil. Light and electronic transmission microscopy was used to obtain images from midgut sections of late fourth-instar larvae of A. argillacea. In general, the morphology, histochemistry, and ultrastructure characteristics of A. argillacea midgut follow that described in the literature for other lepidopteran species. However, the results showed a mitochondrial polymorphism and branched microvilli, which suggest an ultrastrucutural and physiological modification possibly associated with a high absorption and secretion activity by the columnar cells of this species. This intense activity may favor a faster response related to the action of ingested microbial agents and/or toxins, and can explain the high susceptibility of A. argillacea to the agents of control such as the toxin of Bacillus thuringiensis.     

Molecular Recognition of Acetylaminofluorene-and Aminofluorene-modified Guanosine

Abstract

New receptors based upon a carboxamidonaphthyridine unit derivatized with the polyaromatic segments [4-(1-pyrenyl)butyroylamino] and [3-(9-anthracenyl)propanoylamino] have been synthesized and studied by ¹H NMR titration in their binding interaction to the guanosine-C8 adducts from the carcinogens 2-acetylaminofluorene and 2-aminofluorene. The high binding energy, in comparison with that of the non-derivatized analogues, is rationalized in terms of a bi-site interaction (hydrogen bonding and aromatic stacking). Although many factors may contribute to the strength of the host-guest complexes described herein, it appears that in some cases π-π interaction may induce a concomitant bending in the hydrogen bond system.     

Evaluation of antioxidants on the thermo-oxidative stability of soybean biodiesel

This work shows the evaluation of three antioxidants (2,6-di-t-butyl-4-methylphenol (BHT)—synthetic antioxidant, hydrogenated cardanol (HC), and alkyl hydrogenated cardanol (AHC)—both derived from cashew nut shell liquid) on the thermo-oxidative stability of the soybean biodiesel. The antioxidants were added at concentrations of 200, 300, and 400 ppm, and the oxidative stability of the biofuel with and without antioxidants were investigated by thermogravimetric analysis (TG-DTG and IPDT) and Metrohm 743 Rancimat per the EN 14112 method. The results showed that all antioxidants contributed for the thermo-oxidative stability of the soybean biodiesel as follows: soybean biodiesel < soybean biodiesel + BHT < soybean biodiesel + HC < soybean biodiesel + AHC. In the Rancimat method, the results showed that the antioxidants influenced the biodiesel stability with an increase of at least 71 %.