Morphological study of two‐phase polymer blends during compounding in a novel compounder on the basis of elongational flows

A new laboratory‐scale mixing device based on an original concept was built and tested. This device has important technical features such as tightness to liquids and gases, the possibility of direct specimen molding after mixing, and easy handling of reactive systems. In comparison with existing laboratory mixers, the flow in this mixer is characterized by a high contribution from elongational flow. Morphological data on model polystyrene/poly(methyl methacrylate) blend systems have proved the high distributive and dispersive mixing efficiency in comparison with a classical rotational batch mixer. The influence of different experimental parameters such as the flow rate, mixing time, mixing element geometry, and viscosity ratio of blends is characterized and discussed. Much finer dispersions have been obtained with this new device versus those obtained with a conventional mixer with equivalent specific energy input. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

NOx Reduction over CeO2–ZrO2 Supported Iridium Catalyst in the Presence of Propanol

The 1-propanol assisted-reduction of NO _x was investigated over Ir/Ce_0.6Zr_0.4O₂. The catalytic performances of such a catalyst, the associated FTIR characterizations, and transient experiments suggest the formation of adsorbed R-NO _x species as intermediates of the deNO _x process; they provide the partially oxidized species required by the deNO _x model.     

Characterization of experimental complex fungal bioaerosols: Impact of analytical method on fungal composition measurements

The microbial composition of bioaerosols is an important issue to investigate to better understand occupational risks linked to exposure to airborne particles. Traditional methods are based on culture followed by colony identification by morphological, molecular biology or biochemical approaches. We have carried out a preliminary study which aims to generate reproducible complex bioaerosols and compares a high-throughput sequencing approach to the traditional culture-based approach. Mixed fungal bioaerosols containing four fungal strains (Aspergillus niger, Cladosporium cladosporioides, Penicillium brevicompactum and Wallemia melicolla) were generated in the laboratory using a bubbling aerosolizer. The fungal composition was assessed by culture and sequencing. Two genetic targets were sequenced and two assignment methods were compared. Wallemia was poorly detected by the culture-based approach, whereas Aspergillus was readily observed, in significant proportions, only by this method. The proportions in the liquid suspensions and in the bioaerosols generated were nearly identical. Sequencing of the ITS2 region provided results better reflecting the theoretical composition than 18S rDNA sequencing. The findings show that results of fungal composition investigations are strongly dependent on the analysis method used. Further studies will be required to assess the impact of these findings when considering biodiversity in complex and unknown environments.

Copyright © 2019 American Association for Aerosol Research     

Lipid Emulsions Containing Medium Chain Triacylglycerols Blunt Bradykinin-Induced Endothelium-Dependent Relaxation in Porcine Coronary Artery Rings

Lipid emulsions for parenteral nutrition are used to provide calories and essential fatty acids for patients. They have been associated with hypertriglyceridemia, hypercholesterolemia, and metabolic stress, which may promote the development of endothelial dysfunction in patients. The aim of the present study was to determine whether five different industrial lipid emulsions may affect the endothelial function of coronary arteries. Porcine coronary artery rings were incubated with lipid emulsions 0.5, 1, or 2% (v/v) for 30 min before the determination of vascular reactivity in organ chambers and the level of oxidative stress using electron paramagnetic resonance. Incubation of coronary artery rings with either Lipidem^®, Medialipid^® containing long- and medium-chain triacylglycerols (LCT/MCT), or SMOFlipid^® containing LCT, MCT, omega-9, and -3, significantly reduced the bradykinin-induced endothelium-dependent relaxation, affecting both the nitric oxide (NO) and endothelium-dependent hyperpolarization (EDH) components, whereas, Intralipid^® containing LCT (soybean oil) and ClinOleic^® containing LCT (soybean and olive oil) did not have such an effect. The endothelial dysfunction induced by Lipidem^® was significantly improved by indomethacin, a cyclooxygenase (COX) inhibitor, inhibitors of oxidative stress (N-acetylcysteine, superoxide dismutase, catalase) and transition metal chelating agents (neocuproine, tetrathiomolybdate, deferoxamine and l-histidine). Lipidem^® significantly increased the arterial level of oxidative stress. The present findings indicate that lipid emulsions containing LCT/MCT induce endothelial dysfunction in coronary artery rings by blunting both NO- and EDH-mediated relaxations. The Lipidem^®-induced endothelial dysfunction is associated with increased vascular oxidative stress and the formation of COX-derived vasoconstrictor prostanoids.     

Hydrothermal Solubilization–Hydrolysis–Dehydration of Cellulose to Glucose and 5-Hydroxymethylfurfural Over Solid Acid Carbon Catalysts

Solid acid catalysts based on graphite-like mesoporous carbon material Sibunit were developed for the one-pot solubilization–hydrolysis–dehydration of cellulose into glucose and 5-hydroxymethylfurfural (5-HMF). The catalysts were produced by treating Sibunit surface with three different procedures to form acidic and sulfo groups on the catalyst surface. The techniques used were: (1) sulfonation by H₂SO₄ at 80–250 °C, (2) oxidation by wet air or 32 v/v% solution of HNO₃, and (3) oxidation-sulfonation what meant additional sulfonating all the oxidized carbons at 200 °C. All the catalysts were characterized by low-temperature N₂ adsorption, titration with NaOH, TEM, XPS. Sulfonation of Sibunit was shown to be accompanied by surface oxidation (formation of acidic groups) and the high amount of acidic groups prevented additional sulfonation of the surface. All the Sibunit treatment methods increased the surface acidity in 3–15 times up to 0.14–0.62 mmol g^?1 compared to pure carbon (0.042 mmol g^?1). The catalysts were tested in the depolymerization of mechanically activated microcrystalline cellulose at 180 °C in pure water. The main products 5-HMF and glucose were produced with the yields in the range of 8–22 wt% and 12–46 wt%, respectively. The maximal yield were achieved over Sibunit sulfonated at 200 °C. An essential difference in the composition of main products obtained with solid acid Sibunit carbon catalysts (glucose, 5-HMF) and soluble in water H₂SO₄ catalysts (formic and levulinic acids) as well as strong dependence of the reaction kinetics on the morphology of carbon catalysts argue for heterogenious mechanism of cellulose depolymerization over Sibunit.     

Novel Shape‐Memory Materials Based on Potato Starch

Shape‐memory properties such as shape fixity and recovery ratio of amorphous starch‐based materials extruded under normal conditions were evaluated for the case of single and cyclic recovery processing. This study focused on the effect of moisture as a stimulus for the activation of recovery. A high recovery ratio (R_r > 90%) was obtained at high relative humidity, at deformation ratios up to 200%. In the case of plasticized starch with a glycerol content of 10%, the recovery ratio was close to 50% because crystallization limited the shape recovery. Results were compared to those obtained with synthetic or bio‐based shape‐memory polymers such as semi‐crystalline PU or PLAGC. Efficient shape memory properties for a non‐modified biopolymer are highlighted in this study.

     

Carbonation of CH and C-S-H in composite cement pastes containing high amounts of BFS

3:1 BFS:OPC, 9:1 BFS:OPC and 9:1 alkali activated BFS:OPC pastes cured at 20 °C and 60 °C for 90 days were submitted to accelerated carbonation under 5% CO₂, 60% relative humidity and 25 ± 5 °C for 21 days. TGA/DTG was used to quantify the amounts of carbonates formed from calcium hydroxide (CH) and calcium silicate hydrate (C-S-H), based on the CH and carbonate contents before and after carbonation. Apparent dry density, apparent porosity and gas permeability were measured before and after accelerated carbonation testing, and the phenolphthalein method used to determine the accelerated carbonation rate. The results showed that samples cured at elevated temperature, i.e. 60 °C, were initially less porous and, therefore, had decreased levels of both total carbonation and C-S-H carbonation. In addition, the carbonation of C-S-H was significantly higher in pastes that contained less CH before carbonation. In the activated 9:1 BFS:OPC, the carbonation of C-S-H was extensive, despite a lower carbonation rate than the analogous non-activated system. In the particular case of activated 9:1 BFS:OPC, a shift in the DTG decarbonation pattern was observed and XRD showed that aragonite was present as one of the calcium carbonate polymorphs.     

Fabrication of Millimeter Wave Components Via Ceramic Stereo- and Microstereolithography Processes

Complex ceramic parts, designed by 3D electromagnetic simulations for microwave devices of high performances, are difficult, even impossible, to elaborate by classical ceramic processing routes. This paper demonstrates the direct fabrication of useful complex microwave devices in millimeter and submillimeter wavelength domains, with a high dimensional resolution, by the numerical techniques of stereolithography and microstereolithography. Alumina and zirconia formulations have been developed with a powder loading >50 vol%, a suitable rheology to spread thin (25–50 μm) and homogeneous layers, and with a sufficient reactivity to UV for polymerization. Devices built with a satisfying manufacturing accuracy have presented excellent experimental electrical behaviors in good agreement with the theoretical ones.     

Charge storage in the O2(g),Pt/YSZ system

The O_2(g),Pt/YSZ system was characterized at 450 °C by using various electrochemical techniques such as single- and double-step chronoamperometry, chronocoulometry and chronopotentiometry. The response to these experiments gives evidence for the presence of pseudocapacitive processes related with charge storage. Linear sweep voltammetric measurements after prolonged anodic polarization have shown that these charges are located at three different locations.