2-(2-Methyl-2-nitrovinyl)furan but Not Furvina Interfere with Staphylococcus aureus Agr Quorum-Sensing System and Potentiate the Action of Fusidic Acid against Biofilms

Quorum sensing (QS) plays an essential role in the production of virulence factors, in biofilm formation and antimicrobial resistance. Consequently, inhibiting QS is being considered a promising target for antipathogenic/anti-virulence therapies. This study aims to screen 2-nitrovinylfuran derivatives structurally related to Furvina (a broad-spectrum antibiotic already used for therapeutic purposes) for their effects on QS and in biofilm prevention/control. Furvina and four 2-nitrovinylfuran derivatives (compounds 1–4) were tested to assess the ability to interfere with QS of Staphylococcus aureus using bioreporter strains (S. aureus ALC1742 and ALC1743). The activity of Furvina and the most promising quorum-sensing inhibitor (QSI) was evaluated in biofilm prevention and in biofilm control (combined with fusidic acid). The biofilms were further characterized in terms of biofilm mass, viability and membrane integrity. Compound 2 caused the most significant QS inhibition with reductions between 60% and 80%. Molecular docking simulations indicate that this compound interacts preferentially with the protein hydrophobic cleft in the LytTR domain of AgrA pocket. Metabolic inactivations of 40% for S. aureus ALC1742 and 20% for S. aureus ALC1743 were reached. A 24 h-old biofilm formed in the presence of the QSI increased the metabolic inactivation by fusidic acid to 80%, for both strains. The overall results highlight the effects of compound 2 as well as the potential of combining QSI with in-use antibiotics for the management of skin and soft tissues infections.     

Polymerization and adhesion behavior of experimental dental bonding materials with different initiator systems

The use of alternative photoinitiators has been reported as a way to improve physical-mechanical characteristics of dental adhesive systems. In this way, the aim of this study was to evaluate the degree of conversion (DC) and dentin bond strength in dentin cavities of experimental simplified adhesive systems formulated with alternative photoinitiators and diphenyliodonium hexafluorophosphate (DPIHFP). A model simplified adhesive system was formulated by mixing a similar blend of monomers with different photoinitiator systems: camphorquinone (CQ), phenylpropanedione (PPD), bis-alkyl phosphine oxide (BAPO), CQ/PPD, and CQ/BAPO; with or without the addition of DPIHFP. DC was measured using Fourier Transform Infrared Spectroscopy. Bond strength was evaluated in bovine dentin cavities. DPIHFP increased DC for the CQ-based system, but did not affect the dentin bond strength. The PPD system showed the highest DC. All photoinitiator systems provided similar dentin bond strength. DPIHFP seems to increase the DC of CQ-based system, but it had no influence on PPD or BAPO systems. PPD was the most effective for to increase DC without improving bond strength of adhesive systems. Therefore, it is recommended that new adhesive systems to be formulated with phenylpropanedione to increase the DC of tooth restorations caused by traditional camphorquinone-based adhesive systems.     

Bio‐nanocomposites for food packaging applications: effect of cellulose nanofibers on morphological,mechanical, optical and barrier properties

The effect of the addition of various concentrations of cellulose nanofibers (CNF) on the thickness, solubility, morphology, mechanics, water vapor permeability and optical properties of biopolymers isolated from whey protein produced by the casting method was studied. The results show that the addition of CNF did not cause significant variation in the thickness of the films and resulted in nanocomposites with lower solubility and water vapor permeability. Scanning electron microscopy analysis showed that the films obtained with up to 4% of CNF showed good dispersion of the nanofibers in the whey protein matrix. The results of mechanical tests showed that the nanofibers acted as reinforcing material resulting in more resistant and less flexible films. © 2017 Society of Chemical Industry     

Heat transfer and drying kinetics of tomato pulp processed by cast-tape drying

Cast-tape drying (CTD) is a process to dehydrate suspensions. This study evaluated the influence of heat source and forced air convection on the drying rate and temperature of tomato pulp during CTD. To this, a pulp thin layer was spread on a flexible support with its lower surface in direct contact with a heat source. Similar drying rates and evaporative capacities were observed for both flexible supports and heating media. Steam simplifies the temperature control and equipment construction. CTD is a suitable process for producing dried tomato pulp in short drying times, resulting from high evaporative capacity.     

A Bayesian framework for the calibration of cohesive zone models

Adhesively bonded joints are used in several industrial sectors. Cohezive Zone Modes can be used to predict the adhesive mechanical behaviour. This work presents an approach to calibrate Cohesive Zone Models (CZM) by means of Statistical Inverse Analysis. The Bayesian framework for Inverse Problems is used to infer about the CZM model parameters. The solution corresponds to the exploration of the posterior probability density function of the model parameters. The exploration of the posterior density is performed by means of Markov Chain Monte Carlo (MCMC) methods mixing Population-Based MCMC with Adaptive Metropolis (AD) strategies. The assessment of the approach is performed using measured data from a single-lap shear experimental set-up. Measured data from 5 test-specimens is used for calibration and measured data from five other test-specimens is used for model validation. It is proposed a stochastic effective model for the CZM parameters. The predictions of maximum force and maximum displacement that are provided by the effective model are in accordance with measured data that is used for validation.     

An overview of reliability models and methods for distribution systems with renewable energy distributed generation

This paper presents a review of reliability models and methods for estimating renewable energy resources influence on electrical generation availability. These models and methods may be used to evaluate the impacts on the distribution systems reliability of distributed generation integration, especially when they are based on renewable energy sources. For such, the paper presents the main characteristics of renewable resources models that have been developed for wind, small hydro, solar and biomass, and presents the main methods for reliability evaluation of distribution systems with such resources integrated. These evaluation methods may be based on analytical techniques, Monte Carlo simulation or hybrid approaches. The impact of distributed generation on the reliability of electric distribution systems depends mainly on the operational mode and the energy source in which it is based. The most uncertain case is related to generation based on renewable energy of intermittent nature where the generation availability depends on the availability of the energy source and the availability of the generating unit.     

Electrospun hydroxyapatite fibers from a simple sol-gel system

This work reports the production of hydroxyapatite (HA) sub-micron fibers by combining electrospinning and a non-alkoxide sol-gel system, using cheap precursors. Phosphorus pentoxide (P₂O₅) and calcium nitrate tetrahydrate (Ca(NO₃)₂.4H₂O) were used as precursors of phosphorus and calcium, respectively. The fibers were electrospun from a mixture of the gel formed from the system Ca(NO₃)₂.4H₂O/P₂O₅ with polymeric solutions of polyvinylpyrrolidone (PVP) in water and ethanol/water mixtures. The fibers were analyzed for their morphology (Scanning Electron Microscopy, SEM), chemical composition (Fourier Transform Infrared Spectroscopy, FTIR) and structure (X-ray diffraction, XRD). The fibers obtained were composed mainly of type B carbonated HA with traces of β-tricalcium phosphate (β-TCP). SEM analysis revealed that increasing the concentration of water in the solvent system, used in the preparation of electrospinning solutions, led to fibers with smaller diameters and narrower diameter distribution.     

Poly(vinyl alcohol) films crosslinked by glutaraldehyde under mild conditions

The use of mild conditions to perform the entrapment of biomolecules in polymeric matrices is a crucial step in a broad range of applications as biosensors, biocarrier‐mediated facilitated transport membranes, and drug‐controlled release devices. In this study, we investigated the crosslinking of poly(vinyl alcohol) (PVA) by glutaraldehyde in the absence of an acid catalyst and organic solvents to improve the water resistance of the hydrophilic biocompatible polymer. Glutaraldehyde was chosen as the crosslinking agent because it favors the intermolecular reaction with PVA and is able to bind nonspecifically to proteins. The effects of the temperature and glutaraldehyde content on the thermal and structural properties of the PVA films were examined. Membranes prepared at 40°C showed a maximum crosslinking density for low glutaraldehyde content namely, 0.04 wt % in the spreading solution. Higher amounts of the crosslinker led to the branching of PVA. The increase in membrane thermal properties and reduction in crystallinity were ascribed to the crosslinking treatment, which was confirmed by Fourier transform infrared analysis. The oxygen permeability of the films was reduced up to 2.7 times, which indicated that the crosslinking of the polymer was successfully accomplished. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009