Federal University of São Carlos

About: Federal University of São Carlos is a education organization based out in São Carlos, Brazil. It is known for research contribution in the topics: Population & Microstructure. The organization has 16471 authors who have published 34057 publications receiving 456654 citations. The organization is also known as: UFSCar & Federal University of São Carlos.

Nanoparticles Based on Chitosan as Carriers for the Combined Herbicides Imazapic and Imazapyr.

Abstract: The use of lower concentrations and fewer applications of herbicides is one of the prime objectives of the sustainable agriculture as it decreases the toxicity to non-targeted organisms and the risk of wider environmental contamination. In the present work, nanoparticles were developed for encapsulation of the herbicides imazapic and imazapyr. Alginate/chitosan and chitosan/tripolyphosphate nanoparticles were manufactured, and their physicochemical stability was evaluated. Determinations were made of the encapsulation efficiency and release kinetics, and the toxicity of the nanoparticles was evaluated using cytotoxicity and genotoxicity assays. The effects of herbicides and herbicide-loaded nanoparticles on soil microorganisms were studied in detail using real-time polymerase chain reactions. The nanoparticles showed an average size of 400 nm and remained stable during 30 days of storage at ambient temperature. Satisfactory encapsulation efficiencies of between 50 and 70% were achieved for both types of particles. Cytotoxicity assays showed that the encapsulated herbicides were less toxic, compared to the free compounds, and genotoxicity was decreased. Analyses of soil microbiota revealed changes in the bacteria of the soils exposed to the different treatments. Our study proves that encapsulation of the herbicides improved their mode of action and reduced their toxicity, indicating their suitability for use in future practical applications.

Molecular dynamics simulation of structural transformation in silicon carbide under pressure

Abstract: Pressure-induced structural transformation in cubic silicon carbide is studied with the isothermal-isobaric molecular-dynamics method using a new interatomic potential scheme. The reversible transformation between the fourfold coordinated zinc-blende structure and the sixfold coordinated rocksalt structure is successfully reproduced by the interatomic potentials. The calculated volume change at the transition and hysteresis are in good agreement with experimental data. The atomistic mechanisms of the structural transformation involve a cubic-to-monoclinic unit-cell transformation and a relative shift of Si and C sublattices in the 100 direction.

Quantum Dynamical Manifestation of Chaotic Behavior in the Process of Entanglement

Abstract: Manifestation of chaotic behavior is found in an intrinsically quantum property. The entanglement process, quantitatively expressed in terms of the reduced density linear entropy, is studied for the $N$-atom Jaynes-Cummings model. For a given energy, initial conditions are prepared as minimum uncertainty wave packets centered at regular and chaotic regions of the classical phase space. We find for short times a faster increase in decoherence for the chaotic initial conditions as compared to regular ones, which have oscillatory increase.

Solar photoelectro-Fenton degradation of paracetamol using a flow plant with a Pt/air-diffusion cell coupled with a compound parabolic collector: Process optimization by response surface methodology

Abstract: The degradation of 10 L of 157 mg L −1 paracetamol solutions in 0.05 M Na 2 SO 4 has been studied by the solar photoelectro-Fenton (SPEF) method. A solar flow plant with a Pt/air-diffusion electrochemical cell and a compound parabolic collector (CPC) photoreactor was used operating under recirculation mode at a liquid flow of 180 L h −1 with an average UV irradiation intensity of about 32 W m −2 . A central composite rotatable design coupled with response surface methodology was applied to optimize the experimental variables. Optimum SPEF treatment was achieved by applying a current of 5 A, 0.40 mM Fe 2+ and pH 3.0 at 120 min of electrolysis, being reduced total organic carbon (TOC) by 75%, with an energy cost of 93 kWh kg −1 TOC (7.0 kWh m −3 ) and a mineralization current efficiency of 71%. Initial N was partially converted into NH 4 + ion. Under these optimized conditions, paracetamol decays followed a pseudo first-order kinetics. HPLC analysis of the electrolyzed solution allowed the detection of hydroquinone, p -benzoquinone, 1,2,4-trihydroxybenzene, 2,5-dihydroxy- p -benzoquinone and tetrahydroxy- p -benzoquinone. All aromatics were destroyed by the attack of OH. Maleic, fumaric, succinic, lactic, oxalic, formic and oxamic acids were identified as generated carboxylic acids, which form Fe(III) complexes that are quickly photodecarboxylated under UV irradiation of sunlight. A reaction sequence involving all the detected byproducts was proposed for the SPEF degradation of paracetamol.

A biodiversity approach in the neotropical erythrinidae fish, Hoplias malabaricus. Karyotypic survey, geographic distribution of cytotypes and cytotaxonomic considerations.

Abstract: Hoplias malabaricus, a widely distributed neotropical freshwater fish, shows a conspicuous karyotypic diversification. An overview of this diversity is presented here comprising several Brazilian populations, and some others from Argentina, Uruguay and Surinam. Seven general cytotypes are clearly identified on the basis of their diploid number (2n=39 to 2n=42), chromosomal morphology and sex chromosome systems, which can be clustered into two major karyotypic groups. This clustering suggests that karyotype structure would be more informative than the diploid number regarding cytotype relationships in this fish group. While some cytotypes show a wide geographical distribution, some others appear to be endemic to specific hydrographic basins. Sympatric cytotypes can occur without detection of hybrid forms; this situation points to a lack of gene flow, a fact that is also reinforced by studies with genomic markers. The karyotypic data support the view that the nominal taxon H. malabaricus corresponds to a species complex comprising distinct evolutionary units, each with well-established chromosomal differences.