Efficiency and sustainability assessment for a group of farmers in the Brazilian Amazon

The aim of this paper is to use DEA models to evaluate sustainability in agriculture. Several variables are taken into account and the resulting efficiency is measured by comparison. The performance of family farms is analysed here (variables: farmed area, work force, and production). As agricultural sustainability depends on the maintenance of systems of production for long periods of time, the models were run for the years of 1986 and 2002. Tiered DEA models were used to group farmers in sustainability categories. Non-parametric regression models were used to identify the factors affecting the efficiency measurements. All the results indicate that the majority of the farmers increased their efficiency along the time. These improvements may support the existence of sustainability.     

Electron ionisation and fast-atom bombardment mass spectrometry study of diaryl carbonates

Electron ionisation mass spectrometry studies were performed previously for p-diphenyl carbonate and some monosubstituted diphenyl carbonates. In this work, p-diphenyl carbonate and p-methoxyphenylphenyl carbonate are re-examined, and p-chlorophenyl phenyl carbonate and two disubstituted diphenyl carbonates, bis (p-chlorophenyl) carbonate and p-methoxyphenyl-p-fluorophenyl carbonate, are studied for the first time. The previously established fragmentation routes were observed for all compounds investigated. Some other different sequences were observed, and a fragmentation path, other than decarboxylation, of the molecular ion is proposed. In the fast-atom bombardment study it was observed that the M(+*)/[MH](+) ion abundance ratio increased from 0.44 for compound 1 to 2.95 for compound 5. [MH](+) is not a dominant ion in most of compounds studied, in spite of the presence of a carbonyl group, a strong proton acceptor. The presence of two oxygen atoms bonded to the carbonyl group appears to induce delocalisation of the electron pairs, thus deactivating the carbonyl site for protonation. In addition, m-nitrobenzyl alcohol (NBA) being a relatively aprotic/hydrophobic matrix reinforces the deactivation for protonation. Because the carbonate group and NBA are common features to the study, the contributions of the substituents were taken into account to explain the different behaviour of the five compounds with respect to protonation.     

Poly(methyl vinyl ether‐alt‐maleic acid)‐Functionalized Porous Silicon Nanoparticles for Enhanced Stability and Cellular Internalization

Currently, developing a stable nanocarrier with high cellular internalization and low toxicity is a key bottleneck in nanomedicine. Here, we have developed a successful method to covalently conjugate poly(methyl vinyl ether‐co‐maleic acid) (PMVE‐MA) copolymer on the surface of (3‐aminopropyl)triethoxysilane‐functionalized thermally carbonized porous silicon nanoparticles (APSTCPSi NPs), forming a surface negatively charged nanovehicle with unique properties. This polymer conjugated NPs could modify surface smoothness, charge, and hydrophilicity of the developed NPs, leading to considerable improvement in the colloidal and plasma stabilities via enhanced suspensibility and charge repulsion. Furthermore, despite the surface negative charge of the polymer‐conjugated NPs, the cellular internalization was increased in both MDA‐MB‐231 and MCF‐7 breast cancer cells. These results provide a proof‐of‐concept evidence that such polymer‐based PSi nanocomposite can be extensively used as a promising candidate for intracellular drug delivery.

     

The chemical ecology of cyanobacteria

This review covers the literature on the chemically mediated ecology of cyanobacteria, including ultraviolet radiation protection, feeding-deterrence, allelopathy, resource competition, and signalling. To highlight the chemical and biological diversity of this group of organisms, evolutionary and chemotaxonomical studies are presented. Several technologically relevant aspects of cyanobacterial chemical ecology are also discussed.     

Biosynthesis of mycobacterial methylglucose lipopolysaccharides

Mycobacterial pathogenesis is closely associated with a unique cell envelope rich in complex carbohydrates and unique lipids, among which are the mycolic acids. Mycobacteria also synthesize unique intracellular polymethylated polysaccharides (PMPSs), namely methylglucose lipopolysaccharides (MGLPs), which are acylated with short-chain fatty acids, and methylmannose polysaccharides (MMPs). Since PMPSs modulate the synthesis of long-chain fatty acids in vitro, the possibility of a similar role in vivo and the regulation of mycolic acids assembly have been anticipated. Unlike MGLPs, MMPs have been identified in M. smegmatis and other fast-growing mycobacteria but not in M. tuberculosis, implying an essential role for MGLPs in this pathogen and turning the biosynthetic enzymes into attractive drug targets. The genome of M. tuberculosis was decoded 14 years ago but only recently has the identity of the genes involved in MGLPs biosynthesis been investigated. Two gene clusters (Rv1208-Rv1213 and Rv3030-Rv3037c) containing a few genes considered to be essential for M. tuberculosis growth, have initially been proposed to coordinate MGLPs biosynthesis. Among these genes, only the product of Rv1208 for the first step in the MGLPs pathway has, so far, been crystallized and its three-dimensional structure been determined. However, recent results indicate that at least three additional clusters may be involved in this pathway. The functional assignment of authentic roles to some of these M. tuberculosis H37Rv genes sheds new light on the intricacy of MGLPs biogenesis and renewed interest on their biological role.     

Chemiluminescent Detection of Carbohydrates in the Tumoral Breast Diseases

Nowadays, there is an increase of investigations into the fibroadenoma, mainly because some studies have shown that the occurrence of fibroadenoma is linked to an increased risk of developing breast carcinoma. Currently, the chemiluminescence biomarkers are applied for validation methods and screening. Here, a lectin chemiluminescence is proposed as new histochemistry method to identify carbohydrates in mammary tumoral tissues. The lectins concanavalin A (Con A) and peanut agglutinin (PNA) conjugated to acridinium ester were used to characterize the glycocode of breast tissues: normal, fibroadenoma, and invasive duct carcinoma (IDC). The lectin chemiluminescence expressed in relative light units (RLU) was higher in fibroadenoma and IDC than in normal tissue for both lectins tested. The relationship RLU emission versus tissue area described a linear and hyperbolic curve for IDC and fibroadenoma, respectively, using Con A whereas hyperbolic curves for both transformed tissues using PNA. RLU was abolished by inhibiting the interaction between tissues and lectins using their specific carbohydrates: methyl-α-d-mannoside (Con A) and galactose (PNA). The intrinsic fluorescence emission did not change with combination of the lectins (Con A/PNA) to the acridinium ester for hydrophobic residues. These results represent the lectin chemiluminescence as an alternative of histochemistry method for tumoral diagnosis in the breast.     

Differentiation of aminomethyl corrole isomers by mass spectrometry

Two new isomeric aminomethyl corrole derivatives of [5,10,15‐tris(pentafluorophenyl)corrolato]gallium(III) were synthesized with pyridine (py) molecules as axial ligands. When investigated by electrospray ionization mass spectrometry, in the positive and the negative ion modes, these compounds showed an unusual gas‐phase behavior that could be used for their differentiation. In the positive ion mode, the differentiation was achieved through the formation of diagnostic fragment ions formed from [M‐py + H]⁺ precursors, by (CH₃)₂NH and HF losses. An unusual addition of water to the main fragment ions provides an alternative route for isomer identification. Semi‐empirical calculations were performed to elucidate the structures and stabilities of the main ionic species formed in the positive ion mode. In the negative ion mode isomer discrimination is accomplished via the fragmentation of the methoxide adduct ions [M‐py + CH₃O]^‐ through (CH₃)₂ N^. and HF losses. Copyright © 2012 John Wiley & Sons, Ltd.     

A Novel Infinite 1-D Chain of Silver(I) Bridged by trans -Azobenzene

 The self-assembly of Ag[BF₄] with trans-azobenzene in dichloromethane yields a new coordination polymer ([Ag(μ-trans-azobenzene)H₂O][BF₄])_n which was characterized by X-ray single crystal diffraction. The crystal consists of 1-D zigzag cationic chains made up from [Ag(H₂O)]⁺ units linked by trans-azobenzene bridges and BF⁻ ₄ anions. Hydrogen bonding interactions between the chains and BF⁻ ₄ anions occur via intermolecular C*H⋯F and O*H⋯F contacts, and the crystal displays a 2-D supramolecular structure.     

On generators and relations for unions of semigroups

Finite generation and presentability of general unions of semigroups, as well as of bands of semigroups, bands of monoids, semilattices of semigroups and strong semilattices of semigroups, are investigated. For instance, it is proved that a band Y of monoids S _α (α∈ Y ) is finitely generated/presented if and only if Y is finite and all S _α are finitely generated/presented. By way of contrast, an example is exhibited of a finitely generated semigroup which is not finitely presented, but which is a disjoint union of two finitely presented subsemigroups. January 21, 2000