Influence of male nutritional conditions on the performance and alimentary selection of wild females of Anastrepha obliqua (Macquart)(Diptera, Tephritidae)

Influence of male nutritional conditions on the performance and alimentary selection of wild females of Anastrepha obliqua (Macquart) (Diptera, Tephritidae). The behavior of A. obliqua females is regulated by endogenous and exogenous factors and among these the presence of males. Experiments were carried out to investigate whether the presence of males and their nutritional condition may affect the behavior of self-selection feeding and the performance of A. obliqua females. Females were sorted in groups containing yeast-deprived females and males, and non-yeast-deprived females and males. The females were maintained apart from the males by a transparent plastic screen. Several yeast and sucrose combinations were offered to the females in a single diet block or in separate blocks. Ingestion, egg production, longevity and diet efficiency were determined. The non-yeast-deprived males positively influenced the females performance when the latter were fed with yeast and sucrose in distinct diet blocks. Performance was better in the groups without males and with yeast-deprived males where the females could not select the nutrient proportions (yeast and sucrose in a single diet block).

Local-scale spatial variation in diversity of social wasps in an Amazonian rain forest in Caxiuanã, Pará, Brazil (Hymenoptera, Vespidae, Polistinae)

Polistine wasps are important in Neotropical ecosystems due to their ubiquity and diversity. Inventories have not adequately considered spatial attributes of collected specimens. Spatial data on biodiversity are important for study and mitigation of anthropogenic impacts over natural ecosystems and for protecting species. We described and analyzed local-scale spatial patterns of collecting records of wasp species, as well as spatial variation of diversity descriptors in a 2500-hectare area of an Amazon forest in Brazil. Rare species comprised the largest fraction of the fauna. Close range spatial effects were detected for most of the more common species, with clustering of presence-data at short distances. Larger spatial lag effects could also be identified in some species, constituting probably cases of exogenous autocorrelation and candidates for explanations based on environmental factors. In a few cases, significant or near significant correlations were found between five species (of Agelaia, Angiopolybia, and Mischocyttarus) and three studied environmental variables: distance to nearest stream, terrain altitude, and the type of forest canopy. However, association between these factors and biodiversity variables were generally low. When used as predictors of polistine richness in a linear multiple regression, only the coefficient for the forest canopy variable resulted significant. Some level of prediction of wasp diversity variables can be attained based on environmental variables, especially vegetation structure. Large-scale landscape and regional studies should be scheduled to address this issue.

Thermodynamic Characterization of Humic Acid-surfactant Interaction: New Insights into the Characteristics and Structure of Humic Acids

ABSTRACT Humic acids (HA) are a component of humic substances (HS), which are found in nearly all soils, sediments, and waters. They play a key role in many, if not most, chemical and physical properties in their environment. Despite the importance of HA, their high complexity makes them a poorly understood system. Therefore, understanding the physicochemical properties and interactions of HA is crucial for determining their fundamental role and obtaining structural details. Cationic surfactants are known to interact electrostatically and hydrophobically with HA. Because they are a very well-known and characterized system, they offer a good choice as molecular probes for studying HA. The objective of this study was to evaluate the interaction between cationic surfactants and HA through isothermal titration calorimetry in a thermodynamic manner, aiming to obtain information about the basic structure of HA, the nature of this interaction, and if HA from different origins show different basic structures. Contrary to what the supramolecular model asserts, HA structure is not loosely held, though it may separate depending on the conditions the HA are subjected to in their milieu. It did not show any division or conformational change when interacting with surfactants. The basic structure of the HA remains virtually the same regardless of the different sources and compositions of these HA.

Estudo microcalorimétrico da interação de tensoativos n-alquil-sulfato de sódio com tripsina a 298 k

Systematic study of the interactions of ionic surfactants with protein trypsin in buffer solution pH 3.5, 7.0 and 9.0, ionic strength 10 mM at 298 K was done using the microcalorimetric technique. In this study, anionic surfactant solutions of the sodium n-alkyl sulfates series (C8, C10, C12 and C14) were used. The enthalpy of interaction (ΔintHº) shows that the interaction of the surfactants C8, C10, C12 and C14 with trypsin in the solution pH 3.5 is an endothermic process with the value of ΔintHº decreasing linearly with increasing carbon chain length, which is attributed to the unfolding of the polypeptide chain. In the solution pH 7.0, we observed the same trend except for C14. In the solution pH 9.0, from C10 the enthapy of interaction didn't change with the increasing of the carbon chain length due to unfolding of the polypeptide. We concluded that when trypsin is folded, the enthalpy of interaction shows a linear relationship with the surfactant's hydrophobicity, in agreement with Traube's rule.

Perfil sócio-econômico dos alunos, repetência e evasão no curso de Química da UFMG

This paper describes a study about the causes for the dropout of chemistry undergraduate students at UFMG in the nineties. The students' social and economic profile was outlined. It was observed a correlation between family income and academic performance and between failure at the beginning of the course and the dropout, but it seems that family income doesn't affect markedly the dropout. The endogenous and exogenous causes contribute equally for the dropout. The authors suggest that the dropout could be significantly reduced if the endogenous causes such as large classes, inadequate curricula and programmes, poor teaching and the unapproachability on the part of the teachers were faced.

Ciência de espumas - aplicação na extinção de incêndios

The structural characteristics of foams are responsible for a broad range of applications of this system. Foams produced by aqueous solutions of surfactant concentrates are used in fire-fighting due to their special properties as extinguishing agents. In the present paper we discuss the main aspects involved in fire-fighting, based on some properties of foams. Thermal and chemical stability, good wetting of surfaces, cooling effect by water drained from the bubbles, isolation of the air from the burning surface and suppression of flammable vapors are some of the factors involved in the extinguishment of fire by foams.

Interação tensoativo/hidrótropo em sistemas aquosos, utilizando ressonância magnética nuclear de ¹H e 13C

In this work, it was studied the behavior of the nonionic surfactant aqueous solutions, containing or not a hydrotropic agent, by resonance magnetic nuclear (NMR). We have studied monofunctional diblock copolymers of poly(propylene oxide-ethylene oxide) (R-PPO-PEO-OH, where R length is linear C4) as nonionic surfactant and sodium p-toluenesulfonate (NaPTS) as hydrotropic agent. The critical micelle concentration (CMC) of the aqueous copolymer solution was obtained from ¹H-NMR. The preliminary study of the interaction between the copolymer, under the unimer and micelle forms, and the hydrotrope, in aqueous solutions, was evaluated by ¹H-NMR and 13C-NMR.

Ambientes micelares em química analítica

This review deals with the general use of the surfactants in Analytical Chemistry. Principal characteristic of the micelle is the improvement in selectivity and/or sensitivity of the analytical determination with emphasis on the catalytic reaction and "cloud point" extraction.

Biossurfactantes: propriedades e aplicações

Chemically synthesized surfactants are widely used for many purposes in almost every sector of modern industry. Surface-active compounds of biological origin (biosurfactants) have been gaining attention in recent years because of some advantages such as biodegradability, low toxicity, diversity of applications and functionality under extreme conditions. Microbial biosurfactants are useful in bioremediation of water and soil, enhanced oil recovery, and in many formulations of petrochemical, chemical, pharmaceutical, food, cosmetic and textile industries. The importance of biosurfactants, their characteristics and industrial applications are discussed.

Adaptação no método do peso da gota para determinação da tensão superficial: um método simplificado para a quantificação da CMC de surfactantes no ensino da química

The discussion based on surfactant cleaning action is commonly used in chemistry classrooms for the comprehension of theoretical concepts related to surface tension and micelle formation. The experimental quantification of surface tension of aqueous solutions of surfactants provides the practical instruments for this discussion. The present paper describes a simplification on the common apparatus employed for the drop-weight method, making the determination of surface tension accessible to any chemistry lab. The surface tension of various liquids and the critical micelle concentration, CMC, of three commercial surfactants were measured with this modified method, and proved to be consistent with literature values.

Inovação tecnológica e produção no setor químico

Innovation is the main tool for competitiveness and growth in the chemical sector and the main factors for innovation activities in industry as well as the innovation dynamics are discussed in this paper. Success indicators of innovation in Oxiteno are the following: 54% of the current production derives from RD&E projects, 11% of the gross margin in the internal market is due to new products, the company is a technology licensor, holding 17 patents and keeping a strong participation in the production and service sales in the high technology catalysts area, beyond its core petrochemicals and surfactants area.

O pKa de indicadores ácido-base e os efeitos coloidais

An experiment is proposed that can be included in undergraduate courses of chemistry. The subject is the acidity of organic compounds, which are employed as pH indicators, particularly in acid-base titrations. The indicators used are methyl orange, bromophenol blue and bromocresol green in aqueous medium. The influence of colloidal systems on the equilibrium is evaluated by the pKa. The colloids employed are surfactants like sodium dodecyl sulfate, cetyl-trimethylammonium bromide and a polymeric non-ionic F127 (pluronics). The effect of stabilization promoted by the system on the acidic or basic structureof the indicator establishes the action mechanism of the colloid on the pKa values.

Alquilbenzeno sulfonato linear: uma abordagem ambiental e analítica

The environmental impact of detergents and other consumer products is behind the continued interest in the chemistry of the surfactants used. Of these, linear alkylbenzene sulfonates (LASs) are most widely employed in detergent formulations. The precursors to LASs are linear alkylbenzenes (LABs). There is also interest in the chemistry of these hydrocarbons, because they are usually present in commercial LASs (due to incomplete sulfonation), or form as one of their degradation products. Additionally, they may be employed as molecular tracers of domestic waste in the aquatic environment. The following aspects are covered in the present review: The chemistry of surfactants, in particular LAS; environmental impact of the production of LAS; environmental and toxicological effects of LAS; mechanisms of removal of LAS in the environment, and methods for monitoring LAS and LAB, the latter in domestic wastes. Classical and novel analytical methods employed for the determination of LAS and LAB are discussed in detail, and a brief comment on detergents in Brazil is given.

Antioxidantes na manutenção do equilíbrio redox cutâneo: uso e avaliação de sua eficácia

The skin is a very complex organ, continuously exposed to physical, chemical and microbiological agents. Enzymes as well as low-molecular weight antioxidants are present in the cutaneous tissue to counterbalance the deleterious effect caused by an oxidative stress and thus maintain homeostasis. Antioxidants such as vitamins C and E, carotenoids, and extracts with these properties have been extensively used for treatment of pathologies and skin aging prevention. We review here different mechanisms that can interfere in the redox equilibrium of the skin, as well as the chemical reactions involved in these processes. Moreover, we discuss the importance of endogenous or exogenous antioxidants that can be acquired from the diet or from oral or topical administration, and methodologies that have been developed to evaluate their efficacy.

Antioxidantes dietéticos: controvérsias e perspectivas

The generation of reactive oxygen and nitrogen species (ROS and RNS) during metabolism is capable of damaging cellular biomolecules. To be protected against oxidative injury, cells evolved complex cellular defense mechanisms and the capability to use exogenous antioxidants to eliminate ROS/RNS. The potential role of micronutrients as antioxidants (vitamin C, vitamin E, carotenoids and poliphenols) has stimulated intense research efforts. In various human supplementation studies, however, these compounds presented pro-oxidant effects at high doses for most risk groups. Therefore, more studies about the bioavailability, tissue uptake, metabolism and biological activities should be performed before establishing recommendations for disease prevention.