TEMPORAL POST-DISCHARGE REACTIONS IN PLASMA-CHEMICAL DEGRADATION OF SLAUGHTERHOUSE EFFLUENTS

The plasma-chemical degradation of bovine blood effluents provided by a slaughterhouse plant is achieved by exposing the dilute blood target to a gliding discharge in humid air. The several steps of the degradation were ascribed to the oxidizing and acidifying properties of the parent species formed in the discharge (e.g., mainly °OH and °NO and their derivatives). The oxidation reactions go on after the discharge is switched off and evidence Temporal Post-Discharge Reactions (TPDR). This demonstrates that less reactive moieties than °OH and °NO – tentatively H₂O₂ and ONO₂H – are concerned in TPDR and probably also involved in the main degradation process performed under plasma conditions. Industrial effluents involve large quantities of sodium citrate additive (10^?2 mol L^?1), which is first degraded according to zero order kinetics, folllowed by a 1st order kinetic step (k₁ = 0.2 min^?1) ascribed to the diffusion controlled degradation of hemoglobin (Hb).     

Influence of chlorhexidine in cavities prepared with ultrasonic or diamond tips on microtensile bond strength

This study evaluated the effect of chlorhexidine (CLX) in cavities prepared with either ultrasound-mounted CVDentUS diamond tips or conventional diamond burs on dentin bond strength after 24 h and 180 days. Forty-eight dentin surfaces from sound third molars were flattened and divided into four groups (n = 12), according to the type of cavity preparation (CVDentUS ultrasound tip or conventional diamond) and with or without 2% CLX (Consepsis) treatment. After application of the adhesive system (Clearfil SE Bond), microhybrid composite resin blocks (Charisma) were made on the dentin surface in increments. After 24 h, the specimens were sectioned into stick-shaped samples with an adhesive interface of approximately 1 mm². From each tooth, half of the sticks were evaluated after 24 h of storage in distilled water and the other half after 180 days, using a universal testing machine. Three-way analysis of variance showed no significant triple interactions (p = 0.722) or double interactions between factors. Higher bond strength values were observed with the use of ultrasonic tips (p = 0.019), irrespective of whether or not CLX was applied in either time period. No difference in bond strength values was observed in terms of CLX application (p = 0.581). No significant difference in bond strength values was shown after storage for 24 h or 180 days (p = 0.302). In conclusion, the ultrasonic tips promoted greater bond strength to dentin, irrespective of whether or not CLX was applied, and storage time.     

Incorporation of EGCG into an etch-and-rinse adhesive system: mechanical properties and bond strength to caries affected dentin

This study evaluated how a matrix metalloproteinase (MMP) inhibitor (EGCG) incorporated into an etch-and-rinse adhesive system (AS) affects the long-term microtensile bond strength (MTBS) to caries affected dentin (CAD) and flexural strength (FS) of AS. Forty CAD surfaces received acid conditioning and were randomly divided into four groups (n?=?10): EGCG-PRE – dentin treatment with 200?μg/mL EGCG solution; EGCG-INC – 200?μg/mL EGCG solution incorporated into SA; CHX-PRE – dentin treatment with 2% digluconate solution; NT – no treatment. The AS (Adper Single Bond 2, 3M ESPE) was applied and resin composite blocks were built on the dentin. Beam-shaped specimens (0.8?mm²) were obtained submitted to MTBS testing following 24?h, 6 months or 1 year of water storage (WS). Adhesive interface was analyzed by SEM. FS testing was performed by preparing specimens with the adhesive system, with or without the EGCG solution (200?μg/mL) (n?=?10). Tests were carried out in a universal machine (0.5?mm/min). MTBS data were submitted to two-way ANOVA and Tukey’s test, whereas FS data, to the Student’s t-test (α?=?0.05). MTBS values were not affected by EGCG application, either incorporated or used as a dentin treatment agent, regardless of the WS period; however, CHX negatively affected MTBS to CAD (p?<?0.001). WS significantly reduced MTBS values (p?<?0.001) from the 6-months time point. FS was not affected by EGCG incorporation into the SA (p?=?0.2527). EGCG incorporation into AS was unable to maintain bond stability to CAD over time, whereas it did not compromise adhesive’s property.     

Aerosol Retention in the Vicinity of a Breach in a Tube Bundle: An Experimental Investigation

This article summarizes the main results of a bench-scale program focused on experimentally assessing the aerosol retention near the tube breach in a tube bundle. The major variables investigated were particle nature (polydispersed TiO ₂ agglomerates vs. solid, monodisperse SiO ₂ spheres) and Re _D (0.8?2.7· 10 ⁵ ). In addition, comparisons to other data sets provided insights into the particle aerodynamic size effect on retention efficiency. Results showed that particle nature substantially affects aerosol retention in the tube bundle: mass retention efficiency was low for TiO ₂ agglomerates (less than 30%) whereas it was much higher for SiO ₂ particles (around 85%). Retention efficiency is also affected by Re _D : its sensitivity was found to follow a log-normal behavior with a maximum retention attained at Re _D near 1· 10 ⁵ . This evolution with Re _D was similar for both types of compounds. Particle size also influences retention efficiency: the bigger the TiO₂ agglomerates the lower retention efficiency (no data were available for SiO ₂ ). Among all these variables, particle nature was noted to have a prime importance for in-bundle retention, whereas Re _D and particle aerodynamic size, although also affect retention efficiency, did not play such a key role. In light of the results, the presence of retention-inhibiting mechanisms such as fragmentation, resuspension or bouncing has been discussed. The data recorded will enhance the overall understanding of the governing mechanisms involved and will serve as a database against which compare model predictions. Nevertheless, further experimental data would be desirable to set up a sound database.     

Mechanical Properties of an Extruded Wood Plastic Composite: Analytical Modeling

Abstract

The focus of this study has been to predict wood plastic composite (WPC) properties using analytical models dedicated to reinforced composites and to define their limits. Experiment tests have been realized to characterize mechanical properties of a commercial WPC. On one hand, good compressive and three points bending performances were observed in agreement with application requirements for this decking product. On the other hand, lower tensile performance and failure appearances revealed a lack of interfacial bonding between wood fiber and matrix despite the presence of a coupling agent in the composite formulation.     

Fluorescence Activation with Photochromic Auxochromes

The inherent reversibility of photochromic transformations can be exploited to switch on and off the fluorescence of appropriate organic chromophores under optical control. In turn, the photoactivation of fluorescence permits the monitoring of dynamic processes in real time as well as the reconstruction of images with spatial resolution at the nanometer level. Thus, the identification of viable structural designs to construct and operate photoactivatable fluorophores on the basis of photochromic processes can translate into the realization of valuable analytical tools for biomedical research. In this context, a strategy was designed to connect a simple photochromic oxazine to essentially any fluorescent chromophore with a pendant formyl group. In the resulting fluorophore photochrome dyads, the photoinduced interconversion of the photochromic component between its two states controls that ability of the fluorescent component to absorb exciting radiation and emit as a result. Under these conditions, the interplay of two illuminating beams, designed to operate the photochromic component and excite the fluorescent one, respectively, offers the opportunity to switch fluorescence reversibly for multiple cycles. Furthermore, the fluorophore photochrome dyads described herein can be entrapped within the hydrophobic core of polymer micelles and operated under these conditions in aqueous solutions and within the intracellular environment.     

Limitation of the Coalescence of Evolutive Droplets by the Use of Copolymers in a Thermoplastic/Thermoset Blend

Summary: Polystyrene (PS)/epoxy‐amine (DGEBA‐MDEA) is a thermoplastic/thermoset precursor blend which is miscible at high temperature (177 °C), and which phase separates under the polymerization of the epoxy‐amine system. Previous studies have shown that the morphology of this blend polymerized under shear is coarse and irregular because the dispersed epoxy‐amine domains coalesce before they gel. Several styrene‐methyl methacrylate and a styrene‐butadiene‐styrene block copolymers have been added to the PS/DGEBA‐MDEA 60/40 blend in order to limit the coalescence and thus obtain a finer morphology. Two of the copolymers used were reactive either with the epoxy or with the amine. It was shown that the addition of 15 wt.‐% of non reactive copolymer had a positive but limited effect on the size of the final epoxy‐amine particles. The copolymer remained at the interface at the early stages of the polymerization. However, it was pulled out by the shear forces around the gel point of the epoxy domains. Most of the non reactive copolymer was present in the shape of micelles at the end of the process. On the other hand, the reactive copolymers were able to establish covalent bonds with the epoxy‐amine drops and hence were not extracted at all. Consequently they allowed the decrease the size of the particles by a factor of 15. Despite this, the observation of the morphology at different stages of the polymerization has revealed that the copolymer moved at the interface of the epoxy domains during the collision of two droplets. The movements of fluids into the epoxy domains pushed the copolymer out of the inter‐droplet zone so that it could not prevent the drainage of the liquid film between the droplets and consequently their coalescence.

TEM showing that the layer of copolymer (in dark grey) has moved along the interface of epoxy‐amine drops during their successful collision in a polystyrene‐rich matrix.